Sources and verification

The first rule of this course is that it never invents chemistry. No formula, quantity, pH, hazard statement, capacity, shelf life, reaction, historical date or process description appears without a traceable source, and every page lists the sources it was checked against, with the date of the check. This page explains how sources are ranked and lists every one cited.

The hierarchy

Tier 1, primary and authoritative. Manufacturer technical publications and data sheets (Kodak, Ilford, Foma and the alternative-process suppliers), manufacturer safety data sheets, peer-reviewed chemistry, standard reference works, PubChem and ECHA for chemical identity and GHS classification, government and university laboratory-safety guidance, museum and conservation departments, and original historical documents: the papers, patents and manuals of the people who invented the processes. A formula in this course is a formula because a Tier 1 source states it.

Tier 2, respected specialist. Recognised authors and organisations in historical processes, photographic conservation, sensitometry, darkroom chemistry and alternative processes: the chemists and practitioners whose work is cited by the museums and the manufacturers. The course uses them for mechanism, practice and interpretation, and says when a claim rests on them.

Tier 3, community. Forums, blogs and videos. They are useful for discovering what to look into. They are never the evidence for a dangerous procedure, a chemical property, a formula, a hazard or a disposal claim. Where the course learned of something from a forum, it went and found a Tier 1 or Tier 2 source before writing it down, or it did not write it down.

!Important

A source being listed does not mean the course agrees with everything in it. Historical manuals in particular describe practices the course classifies as Level D, and manufacturer sheets describe their own products. The citation tells you where a specific claim came from so you can read it yourself.

How to read a citation

Each source line gives the title, the author or publisher, the section where the claim was found if the document is long, the web address, the tier, and the date it was last read. Manufacturer and safety documents also carry their own version or revision date where one is printed, because safety data changes and a classification read in one year may have been revised by the next.

Every source cited

758 distinct sources are cited across 848 of the course's 230 content pages. Pages that make no checkable technical, historical or safety claim — assignments and reflective pages, mainly — carry no citations, which is why the counts differ.

125px.com

Darkroom Design for Amateur Photographers, publication AK-3retrieved 2026-09-04, 2026-09-05

Sections: Checking the room for stray light; Temporary amateur darkroom; Arrangement; Permanent amateur darkroom in a small closet (storage of concentrates); Darkroom planning; Temporary amateur darkroom; Arrangement; Placement of equipment, flow of work; Safe handling of Kodak processing chemicals; Darkroom planning: the dry side and wet side separation, the five-minute dark-adaptation check with a sheet of white paper against a dark background, and sealing small leaks with black tape; Darkroom planning: staying in the room for five minutes with the lights off, the white-paper-against-a-dark-background criterion, and eliminating small light leaks with black tape; The light-tightness test - stay in the room for five minutes with every light off, then look for a sheet of white paper held against a dark background, the eyes having dark-adapted; small leaks are then sealed; The light-tightness test: five minutes in the room with every light off, then look for a sheet of white paper held against a dark background, and close small leaks with black tape and large ones with heavy cloth; Permanent amateur darkroom in a small closet - the instruction to have a licensed electrician install or inspect the wiring so that all wiring conforms to the electrical wiring code, and the double, properly grounded outlets provided for plugging in the printer, enlarger and other equipment; Location - that a damp basement without a dehumidifier is not a good location for a darkroom, because dampness causes deterioration of films and papers which can result in weak, mottled pictures, with the instruction to store chemicals, films and printing papers where it is cool and dry and to return unused paper to its original package; and the light-tightness test, five minutes in the room with every light off and then looking for a sheet of white paper held against a dark background; The light-tightness test - stay in the room for five minutes with every light off and then look for a sheet of white paper held against a dark background, the eyes having dark-adapted in that time; close small leaks with black tape and large ones with heavy cloth; Location - the statement that a damp basement without a dehumidifier is not a good location, because dampness causes deterioration of films and papers which can result in weak, mottled pictures; and the instruction to store films and printing papers where it is cool and dry and to return unused paper to its original package; Darkroom planning: the light-tightness test — five minutes in the room with every light off and then a sheet of white paper held against a dark background, the eyes having dark-adapted in that time; and the instruction to close small leaks with black tape and large ones such as a crack around a door with heavy cloth; Darkroom planning: the light-tightness test — five minutes in the room with every light off and then a sheet of white paper held against a dark background, the eyes having dark-adapted; small leaks closed with black tape and large ones with heavy cloth; Darkroom planning - the light-tightness test, staying in the room for five minutes with every light off and then looking for a sheet of white paper held against a dark background, small leaks sealed with black tape and large ones such as a crack around a door with heavy cloth; the lighttight dark drawer; the instruction to store films and printing papers where it is cool and dry, to bring them to the darkroom only when needed, and to return unused paper to its original package; The Caution preceding "Placement of Equipment, Flow of Work": some photographic chemicals, particularly acid solutions, can cause corrosion, so cold water is used to wash the sink and flush the drain after each use; Darkroom planning; Temporary amateur darkroom; Arrangement; Placement of equipment, flow of work; Darkroom planning - the light-tightness test, five minutes in the room with every light off and then a sheet of white paper held against a dark background; the lighttight dark drawer; and the instruction to return unused printing paper to its original package; Darkroom planning - chemicals, films and printing papers stored where it is cool and dry and taken to the darkroom only when needed, the attic rejected as too hot in summer and too cold in winter, unused printing paper returned to its original package, and the lighttight dark drawer; Darkroom planning, and the chemical handling area at five changes of the whole volume of air per hour; Darkroom planning: the light-tightness test, and the instruction to close small leaks with black tape and large ones such as a crack around a door with heavy cloth; The five-minute dark-adaptation check for a lighttight room, and the separation of the darkroom into a wet and a dry bench with the enlarger on the dry side; Location - a damp basement without a dehumidifier is not a good location for a permanent darkroom, because dampness causes mildew and rust on supplies and equipment and deterioration of films and papers which can result in weak, mottled pictures; the instruction to store chemicals, films and printing papers where it is cool and dry and bring them to the darkroom only when needed; the lighttight dark drawer and the instruction to return unused paper to its original package; The room must be lighttight - the five-minute dark-adaptation check, in which a sheet of white paper against a dark background must remain invisible after five minutes with all lights off; small leaks eliminated with black tape and large ones such as a crack around a door with dark heavy cloth or weather stripping; lighttight ventilators; the lighttight dark drawer with a sliding lid in a groove, painted flat black; Darkroom layout - the dry bench for enlarging and printing, and the five-minute dark-adaptation check for a lighttight room

Used by:P1 The Camera Obscura: An Image Without Chemistry · P2 Part II Overview: The Photographic Chemistry Laboratory · P2 Storage, Incompatibilities and Secondary Containment · P2 Laying Out the Laboratory: Wet Areas, Dry Areas and Contamination Control · P5 Build an Emulsion Coating Station · P6 Build the Modular Pinhole Camera · P14 Build: The Enclosure and Exposure Stage · P16 Part XVI Overview: Build the Darkroom · P16 Build: An LED Enlarger Head · P16 Break/Fix: The Room That Fogs and the Light That Is Not Even · P16 Build: Making a Room Dark and Proving It · P18 Break/Fix: The Print That Will Not Go Black · The blackout leak test · Darkroom opening and closing for a printing session · Opening and handling photographic paper in dim light · Closing the laboratory · Opening the laboratory · Loading paper and sheet film into a pinhole back · Storing unfixed prints for later fixing · Checking the ventilation before a session · The whole-room fog audit · Enlarger lamphouse or bellows leak · Paper storage fog · Room light leak, with a direction · Uneven enlargement from mixing chamber, alignment, lens falloff or mechanical vignette

Environmental Guidelines for Amateur Photographers, publication J-300retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-08

Sections: Sewer systems, which tells an amateur photographer as a domestic user that most photographic chemicals can be sent to the sewer, listing developers, stop baths, fixers after silver recovery and wash waters, and then lists what must not be sent, naming selenium toners first; Sewer systems — what an amateur may and may not send; Managing photographic chemicals: KODAK Indicator Stop Bath, its pH, and neutralisation with sodium bicarbonate; Sewer systems; Table II, silver concentrations in photoprocessing solutions; Sewer systems, and what an amateur may and may not send to one; Sewer systems; septic systems; Waste management options; septic systems; Sewer systems; septic systems; Table II, silver concentrations in photoprocessing solutions; Waste management options; Table I, General Guidelines; Managing photographic chemicals: neutralising an acidic stop bath with sodium bicarbonate before it goes to the sewer; Sewer systems — solvents and flammable materials among the materials not to be sent; Sewer systems - what may and may not be sent; Table I, General Guidelines; Municipal trash disposal — used Rapid Selenium Toner; Disposal of other Kodak products — KODAK Indicator Stop Bath; Photographic processing effluent; waste management options; septic systems; Sewer systems — the list of photographic solutions that may be sewered and the materials that may not, which names solvents and flammable materials explicitly; Table I, General Guidelines, and the municipal trash disposal entry — used Rapid Selenium Toner given no sewer, treatment-works or refuse route, and directed to household hazardous waste collection; Table I, General Guidelines, whose Rapid Selenium Toner row withholds the sewer, treatment-works and municipal-trash routes; and the Municipal Trash Disposal paragraph, that used KODAK Rapid Selenium Toner is regulated as a hazardous waste under the USEPA Resource Conservation and Recovery Act regulations for commercial users and that domestic users should not discharge this material to the sewer or discard it in the municipal trash but use a household hazardous waste collection facility; Table I, General Guidelines, the Developer unused/used row and the five route columns; Waste management alternatives for septic systems; Municipal trash disposal; and Table II, silver concentrations in photoprocessing solutions; Table I, General Guidelines, and the municipal trash disposal entry — used Rapid Selenium Toner given no sewer, treatment-works or refuse route and directed to household hazardous waste collection; Managing photographic chemicals — neutralising an acidic bath with sodium bicarbonate before it goes to the sewer; sewer systems; Reducing waste; Appendix C, resin codes; Managing waste; reducing waste; photographic effluent; sewer systems; septic systems; waste management alternatives; Table I general guidelines; Ventilation; reducing waste; Material Safety Data Sheets; obtaining MSDSs; Guidance for amateur photographers on handling used processing solutions, and on collecting silver-bearing fixer rather than discharging it; Table II, silver concentrations in photoprocessing solutions; the statement that developer solutions carry negligible silver; Managing photographic chemicals — the instruction to neutralise an acidic stop bath with sodium bicarbonate solution before it goes to the sewer, added slowly because the mixture foams, in a well ventilated area with gloves, goggles and an apron; Managing photographic chemicals — the statement that KODAK Indicator Stop Bath contains acetic acid and has a very low pH of 1.0, and the instruction to neutralise it with sodium bicarbonate solution added slowly because it foams, in a well ventilated area and with gloves, goggles and an apron; Table II, silver concentrations found in photoprocessing solutions — developer negligible, fixer and bleach-fix 3,000 to 5,000 mg/L, wash water and stabiliser 1 to 5 mg/L; Silver recovery — the statement that amateur photographers are not required to recover silver but that recovery provides environmental benefits, conserves a natural resource and may provide revenue, and that metallic replacement is usually a good method for small-volume users; Tips for recovering silver — an approximate cost of fifty United States dollars a cartridge, a life of about six months for an amateur regardless of throughput, filling the cartridge with water before use to contact the greatest surface area of steel wool and prevent channelling, and the instruction that the cartridge is for fixer and bleach-fix only because developer or any other chemical will destroy it; Table I, general guidelines, in which used Rapid Selenium Toner is the one product with every route withheld except household hazardous waste collection; Disposal of other Kodak products — neutralising indicator stop bath with sodium bicarbonate added slowly in a ventilated place with gloves, goggles and an apron; Septic systems — the recommendation against their use for photographic processing chemicals; Silver recovery — the description of the method for amateurs, in which iron metal as steel wool reacts with the silver in the fixer solution, the iron replaces the silver in solution and the less active metal settles out as a solid sludge; Tips for recovering silver — filling a cartridge with water before use so that the solution contacts the greatest surface area of steel wool and to prevent channelling, and the instruction that the cartridge is for fixer and bleach-fix only because developer or any other chemical will destroy it and inhibit the silver-recovery process; Table II, fixer and bleach-fix at 3,000 to 5,000 mg of silver per litre; Table II, silver concentrations in photoprocessing solutions, and the statement that developer solutions carry negligible silver; Table I, General Guidelines, whose columns are discharge to sewer, household hazardous waste collection, discharge to a nearby publicly owned treatment works, the KODAK RELAY programme and trash disposal, and in which Sepia Toner carries every option but trash while Rapid Selenium Toner carries household hazardous waste collection alone; and Municipal Trash Disposal, that used KODAK Rapid Selenium Toner is regulated as a hazardous waste under the USEPA RCRA regulations for commercial users and that domestic users are recommended not to discharge it to the sewer or discard it in the municipal trash, but to use a household hazardous waste collection facility or a licensed hazardous waste hauler; Table I, General Guidelines, in which Sepia Toner carries the sewer, household hazardous waste collection, nearby publicly owned treatment works and KODAK RELAY options but not trash disposal; and the surrounding text, that most communities have local household hazardous waste collection facilities available to the public for items from domestic use that should not go through municipal trash, septic or sewer systems; Sewer Systems, the list of what an amateur photographer may send to the sewer - developers, stop baths, fixers after silver recovery and wash waters - and the list headed Do NOT send, whose first entry is selenium toners; and Table I, General Guidelines, in which used Rapid Selenium Toner is the one product with every route withheld except household hazardous waste collection; The Sewer systems page, which lists what an amateur may send to the sewer and then lists what must not be sent, selenium toners first; Table I, General Guidelines, in which used Rapid Selenium Toner is the one product with every route withheld except household hazardous waste collection; and Municipal trash disposal, that used KODAK Rapid Selenium Toner is regulated as a hazardous waste under the United States Resource Conservation and Recovery Act regulations for commercial users and that domestic users should not discharge it to the sewer or discard it in the municipal trash but use a household hazardous waste collection facility or a licensed hazardous waste hauler; Table II, silver concentrations found in photoprocessing solutions; neutralisation of indicator stop bath before discharge; reducing waste at source; Managing waste; photographic effluent; sewer systems; septic systems; The table of routes for amateur photographic solutions, and the separate treatment of developers, fixers and wash waters; Reducing waste at source, including buying only the supplies you need so that chemicals are not stored past their recommended shelf life; The table of routes for amateur photographic solutions: used Rapid Selenium Toner with every route withheld but a household hazardous waste collection facility or a licensed hauler; Reducing waste at source, including buying only the supplies you need so that chemicals are not stored past their recommended shelf life and then disposed of; Managing photographic chemicals — the instruction to neutralise an acidic stop bath with sodium bicarbonate solution added slowly because it foams, in a well ventilated area and with gloves, goggles and an apron; The table of routes for amateur photographic solutions, and the entry withholding every route from used selenium toner but a hazardous waste collection facility; Ventilation, and the minimum of ten room volumes per hour exhausted to outdoors for manual sink-line or open-tray processing

Used by:P29 Capstone Stage 5: The Toned Print and the Alternative-Process Print · 6-Nitrobenzimidazole · Acetic acid (glacial) · Amidol · Ammonium bromide · Ammonium chloride · Ammonia solution (ammonium hydroxide) · Ammonium thiosulfate · Ascorbic acid · Benzotriazole · Catechol · Chloroauric acid · Chlorohydroquinone · Citric acid (anhydrous) · Dimezone S · EDTA disodium salt (anhydrous) · EDTA disodium salt dihydrate · Ethanol · Iron(II) oxalate · Gallic acid · Glycerol · Glycin · Hydrogen peroxide · Hydroquinone · Iron(II) sulfate, anhydrous · Iron(II) sulfate heptahydrate · Isopropyl alcohol · Lithium chloride · Metol · p-Aminophenol · Palladium(II) chloride · Phenidone · Potassium alum · Potassium bromide · Potassium chloride · Potassium iodide · Potassium tetrachloropalladate(II) · Potassium tetrachloroplatinate(II) · Potassium thiocyanate · Pyrogallol · Selenium · Silver selenide · Sodium ascorbate · Sodium bicarbonate · Sodium chloride · Sodium hexametaphosphate (Calgon) · Sodium selenite · Sodium selenosulfate · Sodium tetrachloropalladate(II) · Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Double-coated albumen procedure · HARMAN SELENIUM TONER · EDTA and sodium sulfite clearing sequence · KODAK Rapid Selenium Toner · KODAK PROFESSIONAL XTOL Developer · Moersch MT1 Selentoner · EDTA, citric acid and hydrochloric acid clearing sequence · Pyrocat-HD · P2 Storage, Incompatibilities and Secondary Containment · P2 Waste: Streams, Silver, and the Drain You Must Not Use · P2 Laying Out the Laboratory: Wet Areas, Dry Areas and Contamination Control · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P6 Lab: Processing Your First Film · P8 Experiment: Watching a Developer Oxidise · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P10 Experiment: Measuring Stop Bath Capacity · P10 Stop Bath Formulations and the Fixer Interaction · P12 Silver Recovery and the Responsible Darkroom · P12 Experiment: Small-Scale Metallic Replacement · P18 Experiment: Maximum Black, Base White and Dry-Down · P18 Lab: Mixing and Comparing Print Developers · P18 Break/Fix: The Print That Will Not Go Black · P20 Part XX Overview: Toning Chemistry · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Assignment: The Toned Print · The disposal caveat · Routing general chemical waste · Collecting and segregating waste across a multi-run session · Recording a batch in the inventory · Handling a selenium toner and its waste · The stock check, and retiring a chemical · Stop bath preparation · Running a toning session · Checking the ventilation before a session

Formulary, Kodak Data Booklet W.1 (June 1944)retrieved 2026-09-05, 2026-09-06, 2026-09-07

Sections: D.1 THREE-SOLUTION PYRO DEVELOPER, page 9, metric column — sodium bisulphite 9.8 grams, pyro 60 grams, potassium bromide 1.1 grams (or 11 c.c. of a 10% solution), water to make 1000 c.c.; sodium sulphite crystals 210 grams (or anhydrous 105 grams), water to make 1000 c.c.; sodium carbonate crystals 200 grams (or anhydrous 75 grams), water to make 1000 c.c.; 'Dissolve the chemicals in the order given'; the characteristics and purpose note, 'A normal-contrast pyro-soda developer for use in dish or tank for the development of films and plates — general use'; dish development at 1 + 1 + 1 + 7 for 5 to 7 minutes at 65 F. (18 C.) and tank development at 1 + 1 + 1 + 11 for about 12 minutes at 65 F. (18 C.); the index to formulae, which files D.1 under 'Developer, pyro-soda'; Notes on some chemicals mentioned in the formulary, that pyro is 1:2:3 trihydroxybenzene; D.76d Negative Developer - Buffered Borax, printed page 12: the metric and avoirdupois columns, the Characteristics and Purpose note, the instruction to dissolve in the order given and use without dilution, the borax-against-boric-acid adjustment and the potassium bromide note; D.76 and D.76R on the same page and their packed-powder asterisks; Kodak Tested Chemicals and the note that packed formulae are indicated on the formulae concerned; Notes on some chemicals mentioned in the formulary; Index to formulae, Developer - buffered borax; Printed pages 24 and 25 — HE.1's TEST FOR HYPO, a strip of an unexposed white sheet processed with the batch and immersed after the final wash in a one per cent silver nitrate solution for about three minutes, rinsed and compared while wet in subdued daylight or artificial light with the wet untreated portion, no colour difference meaning the hypo has been completely removed and a yellow-brown tint indicating its presence, with the caution that silver nitrate solution stains the skin black and the footnote that a positive test with silver nitrate may also be obtained in the absence of hypo if hydrogen sulphide or wood extracts are present in the water supply; and formula HT.1a, HYPO TEST SOLUTION, potassium permanganate 1.2 grams, sodium hydroxide 2.4 grams and distilled water to make 1000 c.c., with its directions, its blank test against oxidisable organic matter in the water, and its statement that for papers the test is not a completely reliable indication; Concentrated developer solutions - "Kodinol", a highly concentrated developer solution diluted with 16 to 40 parts; formula D.173, the substitute developer for "Velox" paper containing no "Elon"; T.9 Uranium toner, the same five weights and the same make-up volume as the 1949 handbook, the unit on the hydrochloric acid line being illegible in this copy's OCR layer so that the 1949 printing's 'c.c.' is what the course records, with the characteristics column reading 'A convenient toner for obtaining brown to red tones in slides or films. Suitable for motion picture work. It is light-sensitive, however, and should be stored in the dark. The maximum effect is produced in about 10 minutes, the tone passing from brown to red during this time' and the additional sentence 'It is convenient to keep 10 per cent stock solutions of the constituent chemicals of the above toning bath for quick compounding of a new bath'; T.11 iron toner, including the sentence that analogous results may be obtained by immersing in each solution successively for varying times; and T.17 mordanting bath for dye toning, reading uranium (uranyl) nitrate 5.0 grams, oxalic acid 4.0 grams, potassium ferricyanide 4.0 grams and water to make 1000 c.c., with the instruction to dissolve each chemical separately in a small volume of water, then add the oxalic acid solution to the uranyl nitrate solution and finally add the ferricyanide solution, and the notes that the uranyl nitrate should not contain an excess of free nitric acid, that after mixing the bath should be light yellow and perfectly clear, that the solution should not be exposed to light more than is necessary, and that prolonged washing removes some of the mordant; Notes on some chemicals — the entry for Calgon, for addition to developing solutions to prevent the precipitation of calcium salts when using hard water; and the entry for K.A.F. Kodak Antifog Tablets, for addition to developers when unfavourable circumstances tend to promote chemical fog, as when development has to be prolonged or carried out at high temperatures or when materials have deteriorated through age or incorrect storage conditions; The entry for Kodalk — the statement that it does not evolve carbon dioxide on acidifying, so that there is less tendency to precipitate aluminium sulphite sludge from fixing baths containing alum; and the entry for Kodak Wetting Agent, with the instruction that where the water is very hard and tends to deposit a scum on drying, the final rinse should be given in distilled water containing the wetting agent; Notes on some chemicals mentioned in the formulary — the entry for Kodalk, an alkali intermediate in activity between sodium carbonate and borax, with the statement that films developed in a developer in which Kodalk is used as an accelerator will not blister when placed in an acid fixing bath even at high temperatures; and the heading to the Kodalk developer formulae, which states that Kodalk does not evolve carbon dioxide on acidifying, so that the risk of blistering is eliminated while there is less tendency to precipitate aluminium sulphite sludge from fixing baths containing alum; and the entry for Kodak Wetting Agent, which states that it promotes even development, reduces any tendency to the formation of air bells and prevents drying marks or tear marks, with the instruction that for hard water a smaller amount of wetting agent should be used and that where the water is very hard and tends to deposit a scum on drying the final rinse should be given in distilled water containing the wetting agent; Notes on some chemicals — the entry for K.A.F. Kodak Antifog Tablets, for addition to developers when unfavourable circumstances tend to promote chemical fog, as when development has to be prolonged or carried out at high temperatures, or when materials have deteriorated through age or incorrect storage conditions; Notes on some chemicals — the entry for Kodak Wetting Agent, which states that it ensures uniform wetting of the material when placed in the liquid and uniform draining away when it is removed, that this promotes even development and reduces any tendency to the formation of air bells, and that with very alkaline developers the addition of any wetting agent increases appreciably the tendency to froth; Notes on some chemicals — the entry for Kodalk, an alkali intermediate in activity between sodium carbonate and borax, with the statement that films developed in a developer in which Kodalk is used as an accelerator will not blister when placed in an acid fixing bath even at high temperatures; and the heading to the Kodalk developer formulae, which states that Kodalk does not evolve carbon dioxide on acidifying, so that the risk of blistering is eliminated while there is less tendency to precipitate aluminium sulphite sludge from fixing baths containing alum; Notes on some chemicals — the entry for Kodak Wetting Agent, with the instruction that for hard water a smaller amount of wetting agent should be used and that where the water is very hard and tends to deposit a scum on drying the final rinse should be given in distilled water containing this addition of wetting agent; and the entry for Calgon, for addition to developing solutions to prevent the precipitation of calcium salts when using hard water; Notes on some chemicals — the entry for Kodak Wetting Agent, which states that it ensures uniform wetting and uniform draining, prevents drying marks or tear marks and greatly curtails drying time; with the instruction that for hard water a smaller amount of wetting agent should be used, and that where the water is very hard and tends to deposit a scum on drying the final rinse should be given in distilled water containing the wetting agent; The heading to the Kodalk developer formulae — the statement that Kodalk does not evolve carbon dioxide on acidifying, so that the risk of blistering is eliminated while there is less tendency to precipitate aluminium sulphite sludge from fixing baths containing alum; Notes on some chemicals — the entry for K.A.F. Kodak Antifog Tablets, for addition to developers when unfavourable circumstances tend to promote chemical fog, as when development has to be carried out at high temperatures or when materials have deteriorated through age or incorrect storage conditions; Notes on some chemicals — the entry for Kodalk, with the statement that films developed in a Kodalk developer will not blister when placed in an acid fixing bath even at high temperatures, and the heading to the Kodalk formulae stating that Kodalk does not evolve carbon dioxide on acidifying so that the risk of blistering is eliminated; Notes on some chemicals — the entry for Calgon, for addition to developing solutions to prevent the precipitation of calcium salts when using hard water; Notes on some chemicals — the entry for Kodalk, with the statement that films developed in a developer in which Kodalk is used as an accelerator will not blister when placed in an acid fixing bath even at high temperatures; and the heading to the Kodalk developer formulae, which states that Kodalk does not evolve carbon dioxide on acidifying so that the risk of blistering is eliminated; Notes on some chemicals — the entry for Kodak Wetting Agent, with the instruction that for hard water a smaller amount should be used, and that where the water is very hard and tends to deposit a scum on drying the final rinse should be given in distilled water containing the wetting agent

Used by:Kodak D-1 · Kodak D-76d · Kodak HT-2 · Rodinal-type p-aminophenol developer · Uranium toner · P28 Chemistry in the Bottle: Oxidation, Exhaustion, Precipitation and Contamination · P28 Fixer Faults, Washing Faults and the Stains They Leave · P28 The Emulsion Under Stress: Reticulation, Scratches, Pinholes and Drying Marks · Age fog · Air bells · Blisters · Calcium scum · Drying marks · Hardener sludge · Heat fog · Pinholes · Precipitate in a stock solution · RC blisters · Water spots

KODAK Processing Chemicals and Formulas for Black-and-White Photography, publication J-1, seventh edition 1973, updated 1977retrieved 2026-09-05, 2026-09-06, 2026-09-07

Sections: Printed page 41, TEST FOR HYPO and KODAK Hypo Test Solution HT-2 — the formula reading water 750 millilitres, KODAK 28% Acetic Acid 125.0 millilitres, KODAK Silver Nitrate Crystals 7.5 grams and water to make 1.0 litre; Testing Prints, the drop on the face of an unexposed piece of the same paper or on the extra margin of one of the prints, two minutes, rinsed, and compared with the tints shown in the KODAK Hypo Estimator; and TESTS FOR SILVER and KODAK Residual Silver Test Solution ST-1, the formula reading water 125 millilitres and Sodium Sulfide (Anhydrous) 2 grams, To Use diluted 1 part of stock with 9 parts of water, with the reading that any yellowing of the test spot other than a barely visible cream tint indicates the presence of silver. Read from the page images of the scan on 6 September 2026; Printed page 41, TEST FOR HYPO and KODAK Hypo Test Solution HT-2, including Testing the Degree of Washing of Films — a strip cut from the clear margin and immersed for about 3 minutes, well-washed films showing very little or no discoloration — and the instruction that the spot technique is not used on wet films because the reagent spreads; Printed page 41 — KODAK Hypo Test Solution HT-2, water 750 millilitres, KODAK 28% Acetic Acid 125.0 millilitres, KODAK Silver Nitrate Crystals 7.5 grams and water to make 1.0 litre, applied as a drop for two minutes and compared with the tints shown in the KODAK Hypo Estimator; and KODAK Residual Silver Test Solution ST-1, water 125 millilitres and Sodium Sulfide (Anhydrous) 2 grams, diluted 1 part to 9 for use; KODAK Fixing Bath F-24, printed page 38, and the Keeping Properties and Useful Capacities of Solutions table on printed page 25, F-24 row, quoted here only for the comparison with the bought product; Printed page 40, KODAK Fixer Test Solution, FT-1 — the formula, reading water at 26.5 degrees C (80 degrees F) 750 millilitres, Potassium Iodide 190.0 grams and water to make 1.0 litre; How to Test a Print Fixing Solution, the single-bath instruction to add to 5 drops of KODAK Fixer Test Solution FT-1 five drops of the fixing bath to be tested and 5 drops of water, to discard the fixer if a yellow-white precipitate forms instantly, and that any slight milkiness should be disregarded; the two-bath instruction, the first bath tested as for a single bath and the second bath tested by adding to 5 drops of FT-1 five drops of the fixing bath to be tested and 15 drops of water, with the rotation rule that if both tests give a yellow-white precipitate both baths are replaced, and that if only the first forms a precipitate the first is replaced by the second and the second by a fresh bath; and Storage, mixed solutions kept in brown, stoppered glass bottles for one year. Also printed page 39, KODAK Testing Solutions for Print Stop Baths and Fixing Baths — that they provide a quick and accurate method for determining when such baths should be revived or discarded, that an exhausted bath frequently leads to stains and markings in the prints and that stains produced by a fixing bath show up only after a period of time, that the appearance of a fixing bath changes very little during its useful life so that some means of determining when it is unfit for further use should be employed, and that these solutions permit a quick check on the acidity of the stop bath and the silver content of the fixing bath; the KODAK Stop Bath Test Solution SBT-1 formula and its Caution, which names sodium hydroxide and phosphoric acid and is the only caution printed for either testing solution; and the SBT-1 dosing table, which sets 1 millilitre against 1 litre in metric and 20 drops against 1 quart in US liquid measure. Also printed page 41, TESTS FOR SILVER — that an overworked fixing bath contains complex silver thiosulfate compounds retained by the films or prints which cannot be removed completely by washing and lead to stains that may not become evident for a period of time. Also printed page 8, Fixing Baths, Fixing Time, Two-Bath Method and Testing Stop Baths and Fixing Baths — twice the clearing time as the rule for films and plates, the accumulation of silver compounds slowing the bath, the five changes of the two-bath rotation before both baths are discarded, and the recommendation that one fixing bath be used for films and plates and another for papers. Also printed page 2, SAFE HANDLING OF PHOTOGRAPHIC CHEMICALS — waterproof apron and rubber gloves when mixing, safety glasses or goggles, adequate ventilation of all processing rooms, sulfur dioxide liberated by fixing baths, and chemicals and solutions kept out of the mouth. Read from the page images of the byte-identical 20,391,259-byte scan the bibliography also holds under kodak-j1-processing-chemicals-formulas, whose edition statement on the inside front cover reads SEVENTH EDITION 1973, Updated 1977; KODAK Fixing Bath F-24, printed page 38, reading water about 50 degrees C (125 degrees F) 500 millilitres, KODAK Sodium Thiosulfate (Pentahydrated) 240.0 grams, KODAK Sodium Sulfite (Anhydrous) 10.0 grams, KODAK Sodium Bisulfite (Anhydrous) 25.0 grams and cold water to make 1.0 litre, with the statement that the bath can be used for films, plates or papers when no hardening is desired and that for satisfactory use the temperature of the developer, rinse bath and wash water should not be higher than 20 degrees C (68 degrees F); the F-5, F-6, F-7 and F-9 entries on the same page and the F-6 note on sulfur dioxide odour; Keeping Properties and Useful Capacities of Solutions, printed pages 24 and 25, the preamble on the figures being estimates for solutions stored at 18.5 to 21 degrees C and proportionately less at higher temperatures, the KODAK Fixing Baths block and its F-24 row, the footnote that capacity figures apply only if a stop bath is used and the footnote that capacity can be increased by the two-bath system, and the roll-to-sheet equivalence table; Fixing Baths, Fixing Time, Two-Bath Method and Testing Stop Baths and Fixing Baths, printed page 8; Preparation of Solutions, printed pages 10 and 11, on containers and unsuitable metals, on ingredients being named in the order in which they should be dissolved, and on mixing temperature; Stop Baths, Fixing Baths & Hardeners, printed page 38: KODAK Fixing Bath F-5, reading water about 50 degrees C (125 degrees F) 600 millilitres, KODAK Sodium Thiosulfate (Pentahydrated) 240.0 grams, KODAK Sodium Sulfite (Anhydrous) 15.0 grams, KODAK 28% Acetic Acid 48.0 millilitres, KODAK Boric Acid Crystals 7.5 grams, KODAK Potassium Alum Fine Granular (Dodecahydrated) 15.0 grams and cold water to make 1.0 litre, with its statement that the bath has the advantage over the older type of fixing baths, which did not contain boric acid, of giving much better hardening and having less tendency to precipitate a sludge of aluminum sulfite, and its times of 5 to 10 minutes for films or plates in a freshly prepared bath, a discard point when the fixing time exceeds 10 minutes, and 5 to 10 minutes for prints; the sentence 'The hardener can also be mixed separately as a stock solution as follows:' and KODAK Hardener F-5a beneath it, reading water about 50 degrees C (125 degrees F) 600 millilitres, KODAK Sodium Sulfite (Anhydrous) 75.0 grams, KODAK 28% Acetic Acid 235.0 millilitres, KODAK Boric Acid Crystals 37.5 grams, KODAK Potassium Alum Fine Granular (Dodecahydrated) 75.0 grams and cold water to make 1.0 litre, with the footnote that approximately 28 per cent acetic acid is made from glacial acetic acid by adding 3 parts of glacial acid to 8 parts of water, the footnote that crystalline boric acid should be used as specified because powdered boric acid dissolves only with great difficulty and its use should be avoided, and the direction 'Slowly add 1 part of the cool stock hardener solution to 4 parts of cool 30% hypo solution (300 grams of sodium thiosulfate per liter of water), while stirring the hypo rapidly.'; KODAK Fixing Bath F-6 on the same page, the modification made by omitting the boric acid and substituting twice its weight in KODALK Balanced Alkali; KODAK Rapid Fixing Bath F-7 on the same page; Fixing Baths, printed page 8, on the alum being added to harden the gelatin of the emulsion in order to prevent excessive swelling or softening in the wash water, the acid serving to provide the best conditions for efficient hardening action, the sodium sulfite being necessary to prevent the hypo from being decomposed by the acid, and boric acid added to a bath of this type increasing the hardening power of the alum and helping to prevent the formation of aluminum sulfite sludge which might be formed if the stop bath should fail to neutralize the developer carried over by the emulsion; Preparation of Solutions, printed pages 10 and 11, on aluminum, zinc and galvanized iron not being used with either developers or fixing baths, on the addition of boric acid to an acid fixing bath up to a maximum of 15 grams per liter (2 ounces per gallon) being helpful against organic matter coagulated by the alum in the wash water, on constituents having to be dissolved in the proper sequence to avoid undesirable reactions, on most Kodak formulas being arranged so that the ingredients are named in the order in which they should be dissolved, on most packaged fixing baths being mixed at a temperature not exceeding 26.5 degrees C, and on stock solutions being best stored in small bottles because the air space in a large one increases each time a portion is used; KODAK Sulfide Sepia Toner T-7a and KODAK Polysulfide Toner T-8, printed page 47, each directing the print to be treated for 2 to 5 minutes in a hardening bath composed of 1 part KODAK Liquid Hardener and 13 parts water, or 2 parts KODAK Hardener F-5a stock solution and 16 parts water, with T-7a adding that the color and gradation of the finished print will not be affected by the use of this hardening bath, and both directing a wash of at least 30 minutes at 18.5 to 21 degrees C afterwards; KODAK Fixing Bath F-6, printed page 38, in full: in warm weather and in inadequately ventilated darkrooms the odor of sulfur dioxide given off by the KODAK Fixing Bath F-5 may be objectionable, this can be eliminated almost entirely by omitting the boric acid and substituting twice its weight in KODALK Balanced Alkali, this modification, which is known as KODAK Fixing Bath F-6, can also be used to advantage for fixing prints since it washes out of photographic papers more rapidly than the baths which have a greater hardening action, and it should be used in conjunction with a stop bath such as KODAK Indicator Stop Bath or KODAK Stop Bath SB-1 to obtain the full useful life; KODAK Fixing Bath F-5 and KODAK Hardener F-5a on the same page with their quantities and the 5 to 10 minute fixing times for films, plates and prints; KODAK Rapid Fixing Bath F-7 on the same page, which fixes much more rapidly than F-5 or F-6; Keeping Properties and Useful Capacities of Solutions, printed pages 24 and 25, its preamble on the figures being estimates for solutions stored at 18.5 to 21 degrees C and proportionately less at higher temperatures, the KODAK Fixing Baths block and its F-6 row reading stock solution in stoppered bottle 2 months, working solution tray 1 week, gallon tank 1 month and a useful capacity of 26 [100] 8 by 10-inch sheets per litre [gallon], with the footnote that capacity figures apply only if a stop bath is used and the footnote that capacity can be increased by the two-bath system; Fixing Baths, Fixing Time, Two-Bath Method and Testing Stop Baths and Fixing Baths, printed page 8, including the statement that boric acid added to a bath of this type increases the hardening power of the alum and helps to prevent the formation of aluminum sulfite sludge, and the recommendation that one fixing bath be used for films and plates and another for papers; Preparation of Solutions, printed pages 10 and 11, on ingredients being named in the order in which they should be dissolved and on packaged fixing baths being mixed at a temperature not exceeding 26.5 degrees C; Printed page 41, TEST FOR HYPO and KODAK Hypo Test Solution HT-2 — the statement that the residual hypo content of films and prints can be accurately determined only by actually testing the processed photographic material, and that this is particularly true of prints because the paper support retains hypo in its fibre structure; the formula, reading water 750 millilitres, KODAK 28% Acetic Acid 125.0 millilitres, KODAK Silver Nitrate Crystals 7.5 grams and water to make 1.0 litre, with the footnote that approximately 28% acetic acid is made from glacial acetic acid by diluting 3 parts of glacial acetic acid with 8 parts of water; the storage instruction, a screw-cap or glass-stoppered brown bottle away from strong light and no contact with hands, clothing, negatives, prints or undeveloped photographic material because it will stain them black; Testing Prints, the drop on the face of an unexposed piece of the same paper or on the extra margin of one of the prints, two minutes, rinsed, and compared with the tints shown in the KODAK Hypo Estimator; the caution that the spot test may give misleading results after washing aids other than KODAK Hypo Clearing Agent, the face showing less stain at equal hypo content, and the suggestion of measuring transmission density after total immersion instead; Testing the Degree of Washing of Films, a strip cut from the clear margin and immersed for about 3 minutes, well-washed films showing very little or no discoloration; the instruction that the spot technique is not used on wet films because the reagent spreads; and the pointer to American National Standard PH4.8-1971 for a quantitative method. Also printed page 2, SAFE HANDLING OF PHOTOGRAPHIC CHEMICALS, for the statement that formaldehyde and acetic-acid vapours are given off by solutions containing those chemicals and that sulfur dioxide may be liberated by fixing baths, that all processing rooms should be adequately ventilated, and that chemicals and solutions are kept out of the mouth and a siphon is never started by mouth. Read from the page images of the byte-identical 20,391,259-byte scan the bibliography also holds under kodak-j1-processing-chemicals-formulas, whose edition statement on the inside front cover reads SEVENTH EDITION 1973, Updated 1977; Printed page 38, the closing paragraphs of Stop Bath SB-5 — a non-hardening stop bath for use up to 26.5 degrees C (80 degrees F), films or plates treated for about 30 seconds with agitation at 18.5 to 21 degrees C between developing and fixing, the bath replaced after approximately 13 rolls per liter (quart) — followed by KODAK Stop Bath SB-5a, for photofinishing, using double the above quantities of KODAK 28 per cent Acetic Acid. Printed page 37, KODAK Stop Bath SB-1 at 48.0 mL of 28 per cent acetic acid per litre, SB-1a at 125.0 mL, and Hardening Bath SB-4 with its 30 g of potassium chrome alum and 60 g of anhydrous sodium sulfate, recommended for use with developers containing sodium sulfate and used above 24 degrees C. Printed page 25, Keeping properties and useful capacities of solutions, giving SB-5 indefinite keeping as a stock solution, 3 days in a tray, 1 month in a gallon tank and 13 [50] sheets of 8 by 10 inches per liter [gallon], against 26 [100] for SB-5a and 20 [75] for SB-1. Printed pages 7 and 8, Stop Baths and Testing Stop Baths and Fixing Baths. Printed page 19, High-Temperature Processing and its sodium sulfate table. The edition statement on the inside front cover, seventh edition 1973, updated 1977; Printed page 41, TESTS FOR SILVER and KODAK Residual Silver Test Solution ST-1 — the statement that an overworked fixing bath contains complex silver thiosulfate compounds that are retained by the films or prints and cannot be removed completely by washing, and that these salts lead to stains which may not become evident for a period of time; the formula, reading water 125 milliliters and Sodium Sulfide (Anhydrous) 2 grams, with no make-up line; the storage instruction, a small stoppered bottle for not more than 3 months; To Use, dilute 1 part of stock solution with 9 parts of water, the diluted solution keeping for a limited time and to be replaced weekly; Testing Films and Prints, a drop of the solution on the margin of a squeegeed film or print, or on an unexposed piece of photographic paper of the same type as the prints being processed and treated in the same chemicals, the solution removed with a clean white blotter after 2 or 3 minutes; the reading, that any yellowing of the test spot other than a barely visible cream tint indicates the presence of silver; the remedy, refixing in fresh hypo and rewashing for the recommended time, with the statement that prints toned in a sulfide toner or selenium toner will not yield to this treatment because the residual silver has been toned together with the image and the yellow stain so formed is permanent; Testing with KODAK Rapid Selenium Toner, a more stable reagent, diluted 1 part with 9 parts of water, the proportions not critical, used by the directions given for ST-1; and the NOTE that the test fails where a very large excess of hypo is present, as in stabilized prints. Also printed page 40, KODAK Fixer Test Solution FT-1, water at 26.5 degrees C 750 millilitres, potassium iodide 190.0 grams and water to make 1.0 litre, with How to Test a Print Fixing Solution and the one-year keeping figure for the mixed stop-bath and fixer test solutions in brown stoppered glass bottles; and printed page 2, SAFE HANDLING OF PHOTOGRAPHIC CHEMICALS, for the requirement that all processing rooms be adequately ventilated and that chemicals and solutions are kept out of the mouth. Read from the page images of the byte-identical 20,391,259-byte scan the bibliography also holds under kodak-j1-processing-chemicals-formulas, whose edition statement on the inside front cover reads SEVENTH EDITION 1973, Updated 1977; Printed page 41, TEST FOR HYPO and KODAK Hypo Test Solution HT-2 - the composition of silver nitrate in dilute acetic acid, the drop applied to an unexposed piece of the same paper or to the margin of a print for two minutes and then rinsed and compared with the printed tints, the statement that residual hypo can be accurately determined only by testing the processed material and that this is particularly true of prints because the paper support retains hypo in its fibre structure, and the storage instruction that the solution must not contact hands, clothing, negatives, prints or undeveloped material because it will stain them black; TESTS FOR SILVER and KODAK Residual Silver Test Solution ST-1 - the sodium sulfide composition and the drop on a margin for two or three minutes; Printed page 41, TEST FOR HYPO and KODAK Hypo Test Solution HT-2 - the composition of silver nitrate in dilute acetic acid, the drop applied to an unexposed piece of the same paper or to the margin of a print for two minutes and then rinsed and compared, the statement that residual hypo can be accurately determined only by testing the processed material and that this is particularly true of prints because the paper support retains hypo in its fibre structure, and the storage instruction that the solution must not contact hands, clothing, negatives, prints or undeveloped material because it will stain them black; TESTS FOR SILVER and KODAK Residual Silver Test Solution ST-1 - the sodium sulfide composition, the one-to-nine dilution, the drop on a margin for two or three minutes, and the statement that an overworked fixing bath leaves complex silver thiosulfate compounds retained in the material

Used by:P29 Capstone Stage 6: Permanence, Presentation and the Finished Portfolio · P29 Capstone Stage 3: Exposing, Processing and Measuring · P29 The Pure Silver Portfolio: The Specification · ILFORD RAPID FIXER · Iodide hypo check · Kodak F-24 · Kodak F-5a · Kodak F-6 · Kodak HT-2 · Kodak SB-5 · Kodak ST-1 · P22 Lab: Printing, Toning, Fixing and Washing a Salt Print · P22 Break/Fix: The Printed-Out Image That Faded

Measuring Silver in Photographic Processing Facilities, publication J-211retrieved 2026-09-05, 2026-09-06

Sections: Sample preparation and the three kinds of silver analysis performed at an analytical laboratory — total recoverable, dissolved and leachable silver — and the statement that testing for regulatory compliance requires sophisticated equipment, trained personnel and adherence to USEPA protocol; On-Site Techniques — silver estimating test paper usable above 1 gram per litre, and the statement that longer soaking gives an indication below that which is extremely qualitative and not reliable to quantify low levels; On-Site Techniques — qualitative test strips, of which the commonest is KODAK Silver Estimating Test Paper, a yellow strip that browns in the presence of silver and is read against a supplied colour chart, usable to estimate silver concentrations greater than 1 gram per litre; the statement that soaking a strip longer can indicate lower levels but is extremely qualitative and not reliable to quantify them; the statement that on-site techniques are qualitative and cannot typically be used to demonstrate regulatory compliance; On-Site Techniques — silver estimating test paper usable above about 1 gram per litre, and the statement that on-site techniques are qualitative and cannot typically be used to demonstrate regulatory compliance; On-Site Techniques — the statement that on-site techniques are qualitative and less accurate than analytical laboratory techniques and cannot typically be used to demonstrate regulatory compliance; On-Site Techniques — qualitative test strips, a strip of paper impregnated with a silver-sensitive material or a strip of polished copper, dipped into the sample for a short period, discoloration indicating the presence of soluble silver and varying levels of discoloration indicating different concentrations; the statement that the technique is qualitative and usable to estimate silver concentrations greater than 1 gram per litre; the statement that soaking test strips for longer can indicate silver below that level but is extremely qualitative and not reliable to quantify low levels; the statement that on-site techniques are qualitative and less accurate than analytical laboratory techniques and cannot typically be used to demonstrate regulatory compliance; the warning that nitric acid must not be used to stabilise photographic samples because it precipitates silver sulfide by decomposing the thiosulfate; On-Site Techniques — KODAK Silver Estimating Test Paper, a yellow strip read against a supplied colour chart and usable to estimate silver concentrations greater than 1 gram per litre, with the statement that soaking a strip longer is extremely qualitative and not reliable to quantify low levels, and that on-site techniques cannot typically be used to demonstrate regulatory compliance; On-Site Techniques: silver estimating test paper and the statement that on-site methods cannot typically be used to demonstrate regulatory compliance

Used by:Iodide hypo check · P11 Experiment: Clearing Time and Fixer Capacity · P11 Fixer Capacity, Exhaustion and Residual Silver · P12 Overview: Permanence and Responsibility · P12 Assignment: Your Archival Processing Sequence · P12 Experiment: Small-Scale Metallic Replacement · P12 Lab: Testing for Residual Thiosulfate and Residual Silver · Residual hypo and residual silver tests

Monitoring and Troubleshooting KODAK Black-and-White Film Processes, publication Z-133E, bound with How to Process and Print Black-and-White Film, publication AJ-3retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: KODAK Black-and-White Film Process Control Strips; determining an optimum development time for control strips; frequency of processing control strips; AJ-3: preparing a temporary darkroom; Z-133E: causes of an out-of-control process, solution contamination; Z-133E: agitation is necessary to maintain uniform solution activity by removing exhausted solution from the emulsion surface and replacing it with fresh solution; the troubleshooting table entries for streaks of non-uniform density from excessive or uneven developer agitation and mottle from inadequate agitation. AJ-3: small-tank agitation procedures, 5 to 7 inversion cycles in 5 seconds repeated at 30-second intervals; Z-133E, Causes of an Out-of-Control Process: temperature variations greater than plus or minus 0.5 degrees F (0.3 degrees C) in the developer will affect process control and image quality; agitation is necessary to maintain uniform solution activity by removing exhausted solution from the emulsion surface and replacing it with fresh solution; Troubleshooting — streaks of non-uniform density against excessive or uneven developer agitation, and mottle against inadequate developer agitation; the statement that agitation maintains uniform solution activity by removing exhausted solution from the emulsion surface; Z-133E, Causes of an Out-of-Control Process: improper solution mixing, storage and keeping, contamination, temperature and replenishment; Z-133E: the definitions of contrast index, speed and D-min as the critical sensitometric parameters, with the statement that the speed value is an arbitrary number relating only to the control strip and is not an ISO or ASA speed; aims, action limits and control limits; and the causes of an out-of-control process, including that temperature variations greater than 0.5 degrees F or 0.3 degrees C in the developer will affect process control and image quality, and that agitation is necessary to maintain uniform solution activity by removing exhausted solution from the emulsion surface; Chemicals for black-and-white films — the description of KODAK MICRODOL-X Developer as an excellent fine-grain developer designed to produce low graininess and high sharpness of image detail, available in powder and liquid forms; Z-133E — the statement that a developer temperature varying by more than 0.3 degrees Celsius affects process control and image quality; Z-133E — the statement that underdevelopment gives a decrease in density and contrast in the control strip and a loss of density, contrast and shadow detail in customers' negatives, and that overdevelopment gives an increase in both with blocked highlights; Causes of an out-of-control process, including improper solution mixing, improper storage and keeping, solution contamination, incorrect temperature and time, and improper agitation; the causes of contamination, including mixing equipment that has not been thoroughly cleaned; the troubleshooting chart entry for a developer or replenisher too old or oxidized against a contrast index and a speed both trending down; the statement that a developer temperature varying by more than 0.3 degrees Celsius affects process control and image quality; Z-133E — the statement that a developer temperature varying by more than 0.3 degrees Celsius affects process control and image quality; Causes of an out-of-control process, including improper solution mixing and solution contamination; Z-133E — the statement that a developer temperature varying by more than 0.3 degrees Celsius affects process control and image quality; the causes of solution contamination and the diagnostic entry for a developer contaminated with fixer or stop bath; Z-133E — the statement that a developer temperature varying by more than 0.3 degrees Celsius affects process control and image quality; the causes of solution contamination and the entry for a developer contaminated with fixer or stop bath; Z-133E — the statement that a developer temperature varying by more than 0.3 degrees Celsius affects process control and image quality; the statement that agitation maintains uniform solution activity by removing exhausted solution from the emulsion surface and replacing it with fresh solution; Causes of an out-of-control process, including mixing equipment that has not been thoroughly cleaned; Troubleshooting — streaks of non-uniform density against excessive or uneven developer agitation, and mottle against inadequate developer agitation; Causes of an Out-of-Control Process - the statement that temperature variations greater than plus or minus 0.5 degrees Fahrenheit, that is plus or minus 0.3 degrees Celsius, in the developer will affect process control and image quality; Determining an Optimum Development Time for Control Strips - the plus or minus 0.02 contrast-index window inside which a development time is accepted; Z-133E - How Is a Process Monitored, and the definitions of control strip, sensitometric parameters, aims, tolerances, action limits, control limits and control chart; KODAK Black-and-White Film Process Control Strips, pre-exposed neutral-density scales on T-MAX 400 with five steps D-min, TD, LD, HD and D-max, a raised dimple for orientation, and the instruction to keep the strips frozen to maintain consistency; the aims of contrast index 0.58 for a diffusion enlarger and 0.43 for a condenser, speed value 355 and D-min 0.06, with action limits of plus 0.07 to plus 0.20 and minus 0.07 to minus 0.12 on contrast index, plus 15 to plus 22 and minus 9 to minus 17 on speed, and plus 0.02 to plus 0.03 on D-min with no lower limit; Evaluating Control-Chart Plots, on random variation as process noise, on the warning against over-controlling by reacting to it, and on outliers, level shifts of four to eight consecutive points on one side of aim and trends of four to eight ascending or descending points; Seasoning Trends for Fresh Solutions, that a declining trend in speed is normal as a fresh solution seasons in systems using Developer D-76 with Replenisher D-76R; Causes of an Out-of-Control Process, including the statement that temperature variations greater than plus or minus 0.5 degrees Fahrenheit, that is 0.3 degrees Celsius, will affect process control and image quality; Determining an Optimum Development Time, the ten per cent time increments and the plus or minus 0.02 contrast-index acceptance window; Changing to a New Batch of Control Strips, the crossover of three paired runs whose averaged difference is applied to the aims; and the note that a severe magenta stain after fixing indicates a fixer near exhaustion or an inadequate fixing time; Determining an Optimum Development Time for Control Strips - the plus or minus 0.02 contrast-index window inside which a development time is accepted; Causes of an Out-of-Control Process - the statement that developer temperature variations greater than plus or minus 0.5 degrees Fahrenheit, that is plus or minus 0.3 degrees Celsius, will affect process control and image quality; Process control - the statement that agitation is necessary to maintain uniform solution activity by removing exhausted solution from the emulsion surface and replacing it with fresh solution, that it must be uniform throughout the tank, and that a developer temperature varying by more than 0.5 degrees Fahrenheit, that is 0.3 degrees Celsius, affects process control and image quality; Diagnosing and troubleshooting processing problems - streaks of non-uniform density listed against excessive or uneven developer agitation, and mottle, given as areas of non-uniform density, listed against inadequate developer agitation; Z-133E - How Is a Process Monitored, and the definitions of aim, tolerance, action limit, control limit and control chart; the contrast-index aims of 0.58 for a diffusion enlarger and 0.43 for a condenser with action limits of plus 0.07 to plus 0.20 and minus 0.07 to minus 0.12; Determining an Optimum Development Time, with its ten per cent time increments and its plus or minus 0.02 contrast-index acceptance window; Changing to a New Batch of Control Strips, the crossover of three paired runs whose averaged difference is applied to the aims; Evaluating Control-Chart Plots, on random variation as process noise and the warning against over-controlling by reacting to it; Seasoning Trends for Fresh Solutions; and the statement that a developer temperature varying by more than 0.5 degrees Fahrenheit, that is 0.3 degrees Celsius, affects process control and image quality; Z-133E - the definitions of aims, tolerances, action limits and control limits, and the statement that a plot inside the action limits is in control, that exceeding an action limit is an early warning under which customer film may still be processed, and that beyond a control limit results will be unsatisfactory for shadow density or contrast; the tolerance table for KODAK Black-and-White Film Process Control Strips, with a contrast-index aim of 0.58 for a diffusion enlarger and 0.43 for a condenser, action limits of plus 0.07 to plus 0.20 and minus 0.07 to minus 0.12 and control limits at plus 0.20 or higher and minus 0.12 or lower; a speed aim of 355 with action limits of plus 15 to plus 22 and minus 9 to minus 17; a D-min aim of 0.06 with action limits of plus 0.02 to plus 0.03, a control limit at plus 0.03 or higher and no lower limit at all; the footnote that the speed value may be slightly higher when fresh developer is used; Evaluating Control-Chart Plots - random variation as process noise, the warning against over-controlling by reacting to it, and the definitions of outliers, level shifts of four to eight consecutive points on one side of aim, and trends of four to eight ascending or descending points; Seasoning Trends for Fresh Solutions - the statement that some developer and replenisher systems are formulated so that a fresh developer solution produces a higher speed than a highly seasoned and properly replenished developer, that a declining trend in speed should be considered normal until the developer is fully seasoned, that Developer D-76 with Replenisher D-76R is one of the systems that behaves this way and that systems mixed with an appropriate starter are not; Detecting and Adjusting an Underreplenished Process - replacing 25 to 50 per cent of the tank solution with fresh solution to reduce seasoning to an acceptable level and raising the replenishment rate by 10 per cent; and Determining an Optimum Development Time, with its plus or minus 0.02 contrast-index acceptance window; Z-133E - the contrast-index aims of 0.58 for printing with a diffusion enlarger and 0.43 for a condenser; the definitions of aim, action limit and control limit; and the statement that a developer temperature varying by more than 0.5 degrees Fahrenheit, that is 0.3 degrees Celsius, affects process control and image quality; Z-133E - the contrast-index aims of 0.58 for printing with a diffusion enlarger and 0.43 for a condenser; Determining an Optimum Development Time for Control Strips - the arithmetic bracket of 4, 6, 8, 10 and 12 minutes and the acceptance rule that a contrast index within plus or minus 0.02 of aim is recorded and used, with the instruction to fine-tune from the closest strip otherwise; and the definitions of aim, action limit and control limit; Determining an Optimum Development Time for Control Strips - the bracket of 4, 6, 8, 10 and 12 minutes for dip-and-dunk processes and the acceptance rule that a contrast index within plus or minus 0.02 of aim is recorded and used; the contrast-index aim of 0.58 for printing with a diffusion enlarger and 0.43 for a condenser enlarger; the definitions of aim, tolerance, action limit and control limit; and the statement that a developer temperature varying by more than 0.5 degrees Fahrenheit, that is 0.3 degrees Celsius, affects process control and image quality; Z-133E — Causes of an Out-of-Control Process, which lists improper solution mixing, improper solution storage and keeping, solution contamination, incorrect processing temperature, incorrect processing time, improper agitation, improper solution replenishment, evaporation and equipment malfunction; Diagnosing and Troubleshooting Processing Problems, with its instruction to verify the out-of-control condition before acting on it by checking the densitometer and processing a second control strip; and Troubleshooting from the Appearance of Processed Film, the table that pairs an appearance with a possible cause and a corrective action and ends every entry with the instruction to process another control strip to confirm that the change returned the process to control; Z-133E — Causes of an Out-of-Control Process, listing improper solution mixing, improper solution storage and keeping, solution contamination, incorrect processing temperature, incorrect processing time, improper agitation, improper solution replenishment, evaporation and equipment malfunction; the four named routes by which contamination most often occurs, namely mixing equipment that has not been thoroughly cleaned, dry chemicals that become airborne during mixing and settle in an adjacent solution, pipes and tanks made of material that reacts chemically with some solutions, and solution splashed or dripped into another solution; the instruction to use separate mixing tanks for developers and fixers and to mix only the amount of solution that will be used during the recommended keeping time; and Troubleshooting from the Appearance of Processed Film, the row for Light film against a liquid concentrate developer over- or under-concentrated and against a developer contaminated with fixer or stop bath, whose corrective action is to replace the contaminated developer and wash mixing equipment thoroughly before use; Z-133E — Diagnosing and Troubleshooting Processing Problems, the instruction to verify an out-of-control condition before acting on it by checking the densitometer and processing a second control strip, and the instruction after every corrective action in the appearance table to process another control strip to confirm that the change has returned the process to control before resuming normal processing; Troubleshooting from the Appearance of Processed Film, the rows for Light film, Light fog, Streaks of non-uniform density, Mottle and Milkiness; and Causes of an Out-of-Control Process; Z-133E — Troubleshooting from the Appearance of Processed Film: the row for Milkiness, described as a pale white translucence most apparent in low-density areas, against retained silver halide due to inadequate fixing, with the corrective action of checking fixer dilution, time and temperature; the row for Graininess or mottle, white grainy particles, against a sulfurised fixer with the instruction to check the fixer for sources of oxidation such as excessive aeration or agitation and to replace it; the row for Scum, described as very fine dissolved material that dries and makes the surface cloudy, against a dirty wetting-agent solution, dirt or dust from the dryer, dirt in solutions and a sulfurised fixer; and the row for Severe magenta or pink stain against retained sensitising dye due to inadequate fixing and/or washing, with the instruction to check fixer dilution, time and temperature, wash time and flow rate, and fixer exhaustion or underreplenishment; Z-133E — Troubleshooting from the Appearance of Processed Film, the row for Light fog, described as plus density especially noticeable in low-density areas, whose listed possible causes are incorrect use of safelight, inspection during development, light leaks in the darkroom or processor together with luminescent tape, timers and indicators and fluorescent lamp afterglow, and improper film loading or handling by the customer or a camera malfunction; and the row for Dark film, abnormally high density, whose causes are overdevelopment or extreme overexposure and light fog; Z-133E — Troubleshooting from the Appearance of Processed Film: the rows for Light film (abnormally low density), whose possible causes are underdevelopment or extreme underexposure, a liquid concentrate developer over- or under-concentrated, and developer contaminated with fixer or stop bath; and for Dark film (abnormally high density), whose causes are overdevelopment or extreme overexposure and light fog; each row's corrective action beginning with checking developer time, temperature and mixing, and then the camera exposure; and Causes of an Out-of-Control Process, which names incorrect processing temperature and incorrect processing time among nine; Z-133E — Troubleshooting from the Appearance of Processed Film: the row for Scratches and abrasions, marks on emulsion or base side, against dirt or chemical build-up on rollers, squeegees or racks, stuck, misaligned or dirty rollers, processor mechanical problems, cinch marks due to excessive tension or improper handling or loading, and dirt in the camera; the row for Water marks, described as marks caused by excess water that causes differential drying, against water collecting in perforations with the instruction to check that the wetting agent is diluted correctly, water rundown from clips, water splashed on film, inadequate drying with the instruction to check that the drying temperature is adequate, and film drying too quickly with the instruction to reduce the drying temperature; the row for Pressure marks, plus-density areas such as half-moons and crescents, against poor film handling, excessive tension and camera malfunction; and the row for Static marks, described as branch-like marks, circular spots with dark centres or a row of spots, often surrounded by fogged areas, against static electricity discharges before development, with the corrective actions of maintaining moderate levels of humidity and temperature in splicing and processing areas, handling film carefully, and separating rolls and sheets slowly and carefully; Z-133E — Troubleshooting from the Appearance of Processed Film: the row for Streaks of non-uniform density against excessive or uneven developer agitation; the row for Mottle, described as areas of non-uniform density, against inadequate developer agitation; the row for Chemical splash marks, described as irregular or random density differences, against an excessively high solution level with the note that the wash level should be higher than that of the other solutions, and against excessive agitation; the row for Pressure marks, described as plus-density areas such as half-moons and crescents, against poor film handling, excessive tension and camera malfunction; and Causes of an Out-of-Control Process, which names improper agitation and states that agitation is necessary to maintain uniform solution activity by removing exhausted solution from the emulsion surface and replacing it with fresh, and that agitation must be uniform throughout the processing tank; How Is a Process Monitored, and the definitions of aim, tolerance, action limit, control limit and control chart; Evaluating Control-Chart Plots, on random variation, the warning against over-controlling by reacting to it, outliers, level shifts of four to eight consecutive points on one side of aim and trends of four to eight ascending or descending points; Seasoning Trends for Fresh Solutions; Changing to a New Batch of Control Strips, the crossover of three paired runs; the instruction to keep control strips frozen to maintain consistency; Monitoring and troubleshooting: the use of a control processed with the batch, and the reading of a fault against a known-good reference; Causes of an Out-of-Control Process: the statement that temperature variations greater than plus or minus 0.3 degrees Celsius in the developer will affect process control and image quality; Z-133E — Troubleshooting from the Appearance of Processed Film, the row for Scratches and/or abrasions, marks on emulsion or base side, whose listed causes include dirt or chemical build-up on rollers, squeegees or racks; stuck, misaligned or dirty rollers, with the corrective action of checking alignment with test film or leader and replacing worn bearings or rollers; processor mechanical problems; and dirt in the camera, whose corrective action is to notify the customer; Z-133E - agitation as the means of removing exhausted solution from the emulsion surface, and the troubleshooting table entries for streaks of non-uniform density and for mottle; Z-133E — the processing table's step 7, Wetting Agent, with the instruction that to reduce drying scum the PHOTO-FLO solution should be mixed with distilled water in areas that have hard water; and Troubleshooting from the Appearance of Processed Film, the row for Scum, described as very fine dissolved material that dries and makes the surface cloudy, whose listed causes are a dirty wetting-agent solution with the corrective action of dumping and replacing it routinely, dirt or dust from the dryer with the corrective action of changing the dryer filters routinely, dirt in solutions, and a sulfurised fixer with the corrective action of replacing the fixer; Z-133E - the list of causes of an out-of-control process, beginning with improper mixing, improper storage and keeping, and contamination; Z-133E — Troubleshooting from the Appearance of Processed Film, the row for Pressure marks, described as plus-density areas such as half-moons and crescents, whose listed causes are poor film handling with the corrective action of training operators in correct handling methods, excessive tension in continuous processors with the corrective action of checking the processor for mechanical problems, and camera malfunction with the corrective action of notifying the customer; and the row for Scratches and/or abrasions, which separately lists cinch marks due to excessive tension, improper handling or loading; Z-133E - solution contamination among the causes of an out-of-control process, with its routes: mixing equipment not thoroughly cleaned, dry chemical made airborne during mixing and settling into an adjacent solution, tanks and pipes of a reactive material, and solution splashed or dripped into another; the remedies of good housekeeping and separate mixing vessels for developers and fixers; the diagnostic entry for a developer contaminated with fixer or stop bath, whose remedy is to replace the developer and wash the mixing equipment thoroughly; the note that a severe magenta stain after fixing points at a fixer near exhaustion or an inadequate fixing time; Z-133E - contrast index and speed both trending down against the cause developer or replenisher too old or oxidised; the control-chart rules distinguishing an outlier, a level shift of four to eight consecutive points on one side of aim, and a trend of four to eight points climbing or falling in a row; the note that some developer systems are formulated so a fresh solution gives a higher speed than a properly seasoned one, D-76 with D-76R among them; Z-133E - the statement that a developer temperature varying by more than 0.3 degrees Celsius affects process control and image quality; the control-chart reading rules for random variation, outliers, level shifts and trends, and the instruction to check the measurement before changing the process; the warning against over-controlling a process by reacting to random variation; Z-133E - the causes of solution contamination: mixing equipment that has not been thoroughly cleaned, dry chemical made airborne during mixing and settling into an adjacent solution, tanks and pipes of a reacting material, and solution splashed or dripped into another; the remedies of good housekeeping and separate mixing vessels; Z-133E — Troubleshooting from the Appearance of Processed Film, the row for Dark film, abnormally high density, whose possible causes are overdevelopment or extreme overexposure and light fog, with the corrective action of checking developer time, temperature and mixing and then checking the camera exposure; Z-133E — Troubleshooting from the Appearance of Processed Film, the row for Light film, abnormally low density, which lists developer contaminated with fixer or stop bath among its causes, with the corrective action to replace the contaminated developer and wash mixing equipment thoroughly before use; Causes of an Out-of-Control Process, which names solution contamination among nine and gives its four commonest routes as mixing equipment that has not been thoroughly cleaned, dry chemicals that become airborne during mixing and settle in an adjacent solution, pipes and tanks made of material that reacts chemically with some solutions, and solution splashed or dripped into another solution, with the recommendations to use good housekeeping, to mix chemicals in a separate room, to check that tanks and pipes are of the proper material, to avoid splashing, and to use separate mixing tanks for developers and fixers; and the darkroom-layout recommendation to separate wet and dry areas and to keep a container of water for rinsing hands; Z-133E — the darkroom layout recommendation to separate the darkroom into a wet area and a dry area, to use the dry area for handling films, negatives and photographic paper, and to keep a container of water for rinsing hands to prevent contamination of the developer with other solutions, drying them on a clean towel before handling films, negatives and paper; Z-133E — Troubleshooting from the Appearance of Processed Film, the row for Water marks, described as marks caused by excess water that causes differential drying, whose five listed causes are water collecting in perforations with the corrective action of checking that the wetting agent is diluted correctly, water rundown from clips with the corrective action of checking that the wash and wetting-agent levels do not cover the clips, water splashed on film with the corrective action of eliminating the source of splashing, inadequate drying with the corrective action of checking that the drying temperature is adequate, and film drying too quickly with the corrective action of reducing the drying temperature; and the processing table's note to reduce drying scum by mixing the wetting-agent solution with distilled water in areas that have hard water; Z-133E - solution contamination among the causes of an out-of-control process, with its routes: mixing equipment not thoroughly cleaned, dry chemical made airborne during mixing and settling into an adjacent solution, and solution splashed or dripped into another; Z-133E — Troubleshooting from the Appearance of Processed Film, the row for Scratches and/or abrasions, marks on emulsion or base side, whose listed causes are dirt or chemical build-up on rollers, squeegees or racks of continuous or roller-transport processors; stuck, misaligned or dirty rollers; processor mechanical problems; cinch marks due to excessive tension, improper handling or loading; and dirt in the camera, with the corrective actions of routine cleaning, checking alignment with test film or leader, replacing worn bearings or rollers, and training operators in correct handling methods; Z-133E — Causes of an Out-of-Control Process, which names incorrect processing temperature, incorrect processing time and improper agitation among nine, with the statement that temperature variations greater than plus or minus 0.3 degrees C in the developer affect process control and image quality; and the contrast-index aims and action limits of the control-chart section; Z-133E — the darkroom-layout recommendation to separate the darkroom into a wet area and a dry area, to use the dry area for enlarging and printing and for handling films, negatives and photographic paper, to use the wet area for mixing chemicals and all processing operations, and to have a container of water for rinsing hands to prevent contamination of the developer with other solutions, with a clean towel to dry them thoroughly before handling films, negatives and paper; and Causes of an Out-of-Control Process, whose contamination routes include solution splashed or dripped into another solution; Z-133E - underdevelopment gives a decrease in density and contrast in the control strip and a loss of density, contrast and shadow detail in the negative; Z-133E — Troubleshooting from the Appearance of Processed Film, the rows for Light film and Dark film, each of which lists a camera cause alongside the processing ones and instructs the laboratory to notify the customer where the cause is in the camera or in handling; and Diagnosing and Troubleshooting Processing Problems, the instruction to verify an out-of-control condition before acting on it; Z-133E — the darkroom-layout recommendation to separate the darkroom into a wet area and a dry area, to use the dry area for enlarging and printing and for handling films, negatives and photographic paper, to use the wet area for mixing chemicals and all processing operations, and to have a container of water for rinsing hands to prevent contamination of the developer with other solutions, with a clean towel to dry them thoroughly before handling films, negatives and paper; and Causes of an Out-of-Control Process, whose contamination routes include solution splashed or dripped into another solution, with the recommendation to reduce contamination by good housekeeping and by avoiding splashing; Z-133E — Troubleshooting from the Appearance of Processed Film, the row for Chemical splash marks, irregular or random density differences, against an excessively high solution level with the note that the wash level should be higher than that of the other solutions, and against excessive agitation; and Causes of an Out-of-Control Process, which names evaporation among the nine and states that agitation must be uniform throughout the processing tank; Z-133E troubleshooting - contrast index and speed both trending down against the cause developer or replenisher too old or oxidised; the 10 per cent increments used to move contrast index towards aim and the plus or minus 0.02 acceptance window; the statement that a developer temperature varying by more than 0.3 degrees Celsius affects process control and image quality; Z-133E - the troubleshooting table entry for mottle, areas of non-uniform density, against inadequate developer agitation, and the statement that agitation maintains uniform solution activity by removing exhausted solution from the emulsion surface; Z-133E - the troubleshooting entry for developer or replenisher too old or oxidized, against a contrast index and a speed both trending down; Z-133E — Causes of an Out-of-Control Process, which names improper solution mixing and improper solution storage and keeping among nine, with the instruction to prepare each solution according to the packaged instructions, to mix all constituents well, to use the correct amounts of concentrates and water, and to mix only the amount of solution that will be used during the recommended keeping time; Z-133E — Troubleshooting from the Appearance of Processed Film, the row for Mottle, described as areas of non-uniform density, against inadequate developer agitation, with the corrective action of checking and adjusting agitation; the row for Streaks of non-uniform density against excessive or uneven developer agitation; and Causes of an Out-of-Control Process, which states that agitation is necessary to maintain uniform solution activity by removing exhausted solution from the emulsion surface and replacing it with fresh, and that agitation must be uniform throughout the processing tank; Z-133E — Troubleshooting from the Appearance of Processed Film, the row for Scratches and/or abrasions, marks on emulsion or base side, which lists cinch marks due to excessive tension, improper handling or loading among its causes with the corrective action of training operators in correct handling methods; and Causes of an Out-of-Control Process, which states that agitation is necessary to maintain uniform solution activity by removing exhausted solution from the emulsion surface and replacing it with fresh, and that agitation must be uniform throughout the processing tank; AJ-3 - the use of KODAK Photo-Flo Solution after washing to minimise water marks and streaks; storage of negatives in sleeves away from damage; Z-133E — Troubleshooting from the Appearance of Processed Film, the row for Static marks, described as branch-like marks, circular spots with dark centers, or a row of spots, often surrounded by fogged areas, against static electricity discharges before development, with the corrective actions of maintaining moderate levels of humidity and temperature in splicing and processing areas, handling film carefully, and separating rolls and sheets slowly and carefully; Z-133E - the troubleshooting table entry for streaks of non-uniform density against excessive or uneven developer agitation; AJ-3 - small-tank agitation procedures, 5 to 7 inversion cycles in 5 seconds repeated at 30-second intervals; Z-133E - underdevelopment gives a decrease in density and contrast in the control strip and a loss of density, contrast and shadow detail in the negative; the list of causes of an out-of-control process beginning with improper mixing, improper storage and keeping, and contamination; Z-133E — Causes of an Out-of-Control Process, which names solution contamination among nine and gives solution splashed or dripped into another solution as one of its four commonest routes, with the recommendation to reduce contamination by good housekeeping and by avoiding splashing when lifting and transferring; the darkroom-layout recommendation to separate the darkroom into a wet area and a dry area and to keep a container of water for rinsing hands with a clean towel; and Troubleshooting from the Appearance of Processed Film, the row for Pressure marks, plus-density areas such as half-moons and crescents, against poor film handling; Z-133E — Causes of an Out-of-Control Process, which names improper solution mixing first among nine, with the instruction to prepare each solution according to the instructions packaged with the chemicals, to be especially careful that all constituents are mixed well and that the correct amounts of concentrates and water are used, and to clean mixing tanks and equipment to avoid dirt build-up and solution contamination; and Troubleshooting from the Appearance of Processed Film, the row for Light film, which lists a liquid concentrate developer over- or under-concentrated with the corrective action of mixing the developer in the proper ratio of concentrate to water; Z-133E - agitation as a named cause of uneven development in small tanks, and the instruction to check the measurement before changing the process when a point falls outside a control limit; Z-133E — Troubleshooting from the Appearance of Processed Film, the row for Mottle, described as areas of non-uniform density, against inadequate developer agitation, and the row for Streaks of non-uniform density against excessive or uneven developer agitation, both with the corrective action of checking and adjusting agitation; and Causes of an Out-of-Control Process, which states that agitation is necessary to maintain uniform solution activity and must be uniform throughout the tank; Z-133E — Troubleshooting from the Appearance of Processed Film: the row for Water marks, described as marks caused by excess water that causes differential drying, with its five causes and corrective actions including water splashed on film, with the instruction to check and eliminate the source of splashing; the row for Surface spots that appear dark by transmitted light, whose listed causes are dirt from the wetting-agent solution with the corrective action of replacing the solution, water spotting with the corrective action of checking the dilution of the wetting-agent solution, dirt from the dryer with the corrective action of checking cleanliness and dryer filters, and a sulfurised fixer with the corrective action of replacing the fixer; and the row for Scum, very fine dissolved material that dries and makes the surface cloudy, against a dirty wetting-agent solution, dirt or dust from the dryer, dirt in solutions and a sulfurised fixer

Used by:KODAK PROFESSIONAL XTOL Developer · P2 Laying Out the Laboratory: Wet Areas, Dry Areas and Contamination Control · P3 Diffusion, Swelling and the Journey Into the Emulsion · P3 Rates, Temperature and Catalysts · P8 Acutance, Adjacency Effects and Compensating Development · P8 Alkalis, Buffers and pH · P8 Development Kinetics: Time, Temperature, Agitation and Exhaustion · P8 Solvent Action, Physical Development and Grain · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Break/Fix: The Developer That Went Wrong · P9 Experiment: Comparing Developing Agents · P9 Experimental Design for the Darkroom · P9 Lab: Preparing Standard Test Negatives · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P14 Experiment: Calibrating the Sensitometer · P14 Experiment: Process Control with Control Strips · P15 Assignment: Characterising a Film and Developer with Your Own Instruments · P27 Part XXVII Overview: From Observation to Measurement · P27 Experiment: Agitation, Stand and Semi-Stand Development · P27 Designing an Experiment That Yields a Number · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Push and Pull Processing: What Extended Development Can and Cannot Buy · P27 Assignment: The Developer Comparison, Measured and Printed · P27 Experiment: The Development Time and Temperature Series · P28 Part XXVIII Overview: Diagnosis as a Discipline · P28 Chemistry in the Bottle: Oxidation, Exhaustion, Precipitation and Contamination · P28 Break/Fix: The Film That Came Back Wrong · P28 Fixer Faults, Washing Faults and the Stains They Leave · P28 Fog and Where It Comes From · P28 Reading the Negative as Evidence: Thin, Dense, Flat and Contrasty · P28 The Emulsion Under Stress: Reticulation, Scratches, Pinholes and Drying Marks · P28 Uneven Development, Bromide Drag and Surge Marks · Control strip processing and charting · Handling and storing a deliberately faulty reference specimen · Sensitometer exposure session · Base-side scratches · Bromide drag · Calcium scum · Chemical fog · Cinch and pressure marks · Control chart: contamination · Control chart: developer exhaustion · Control chart: temperature error · Cross-contamination between alternative processes sharing a bench · Dense negative · Developer contaminated by fixer or stop · Developer stain · Drying marks · Elevated fog on a curve · Emulsion-side scratches · Excessive contrast · Fingerprints on paper · Flat negative · Frame-to-frame density variation · Hypo spots on unexposed paper · Insufficient solution volume · Low contrast index · Mottled development · Oxidised developer · Precipitate in a stock solution · Print mottle · Reel and contact marks · Drying marks and squeegee lines on prints · Static discharge marks · Surge marks · Thin negative · Tong marks · Undissolved chemical · Uneven density across a strip · Uneven print development · Water spots

Processing KODAK Motion Picture Films, Module 6: Environmental Aspects, publication H-24.06retrieved 2026-09-04, 2026-09-05

Sections: Environmental aspects — the table of selected effluent constituents, phosphate and phosphorus rows; Cleaning machines and tanks; Cleaning machines and tanks; handling of concentrated solutions; Cleaning machines and tanks; the separate collection of acid cleaning solution to prevent the emission of sulfur dioxide; Cleaning machines and tanks, and the separate collection of acid cleaning solution to prevent the emission of sulfur dioxide; Cleaning machines and tanks: collecting acid cleaning solution separately to prevent sulfur dioxide emission

Used by:Sodium hexametaphosphate (Calgon) · P2 Storage, Incompatibilities and Secondary Containment · P2 Waste: Streams, Silver, and the Drain You Must Not Use · Chemical incompatibilities · Responding to an acid spill · Routing general chemical waste

Refining Silver Recovered from Photographic Processing Facilities, publication J-213retrieved 2026-09-05

Sections: Silver-bearing materials from recovery operations — flake silver a greyish-brown solid above 90 per cent silver by dry weight, metallic replacement cartridge sludge a dark liquid sludge at 20 to 40 per cent, TMT precipitate 50 to 70 per cent, ion-exchange resin 40 to 60 per cent after in-situ regeneration and 2 to 4 per cent after elution; Refining costs — the retainment or accountability charge, the treatment or handling charge, which is higher for the more labour-intensive materials such as cartridge sludge, and the refining charge, with the statement that cartridges not operated correctly or frequently changed may contain so little silver that refining costs exceed the value of the silver; Metallic replacement cartridge sludge — the statement that an exhausted cartridge typically contains a dark liquid sludge that is a combination of degraded metallic iron and collected silver, that the amount recovered varies greatly with flow rate, pH and length of use, and that a fully exhausted cartridge should contain 20 to 40 per cent silver by dry weight; the instruction not to empty a rinsed cartridge, because wet steel wool exposed to air will rust, creating heat which may cause combustion; Silver-bearing materials from recovery operations — the table of physical appearance and typical silver content by dry weight

Used by:P12 Silver Recovery and the Responsible Darkroom · P12 Experiment: Small-Scale Metallic Replacement

Safe Handling of Photographic Processing Chemicals, publication J-98Aretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: The general handling guidance for photographic processing chemicals, cited here for the practice of assessing a whole process rather than a single bath and of keeping incompatible streams apart in storage as well as in use; Ventilation, naming acetic acid, sulfur dioxide and ammonia as common potential indoor air contaminants associated with photographic processing, stating that they may be eye- and respiratory-tract irritants depending on airborne concentration, and that significant eye- or respiratory-tract irritation during normal processing may indicate elevated levels and the need for better control; General Ventilation and Effective Covers, on dilution ventilation and on covers over tanks as a control for gases, vapours and mists; Skin contact and the instruction to wash developer from skin with a pH-balanced cleanser rather than an alkaline soap; allergic contact dermatitis from photographic developers; protecting skin abrasions and cuts; Store chemicals safely; properly dispose of photographic processing chemicals; Personal protective equipment; know first-aid in case of an emergency; General ventilation; effective covers; store chemicals safely; properly dispose of photographic processing chemicals; Personal protective equipment; contact dermatitis; know first-aid in case of an emergency; Material Safety Data Sheets; store chemicals safely; The general handling recommendations for photographic processing chemicals in a small darkroom — protective gloves and eye protection, adequate ventilation, keeping chemicals off the skin, separating mixing from processing where possible, and not eating or drinking in the work area; Properly dispose of photographic processing chemicals; the warning about drains containing chlorine-bearing cleaning agents; Know first-aid in case of an emergency; contact dermatitis; rinsing gloves before removal; Personal protective equipment — neoprene or nitrile gloves; the warning against gloves sold for household use; rinsing gloves before removal and checking them for pinholes and tears; The warning about drains containing chlorine-bearing cleaning agents, and running plenty of water before and after; Contact dermatitis, and washing after skin contact with an alkaline solution using a pH-balanced cleanser rather than ordinary soap; Know first-aid in case of an emergency, and the availability of an emergency eyewash station wherever corrosive processing chemicals are handled; Handling photographic processing chemicals: gloves, eye protection, adequate ventilation at working dilutions; Personal protective equipment; properly dispose of photographic processing chemicals; Store chemicals safely: storing processing chemicals in the containers they were delivered in and not removing their labels; Handling photographic processing chemicals: keeping solutions off the skin and no eating or drinking in the work area; Handling photographic processing chemicals: gloves, eye protection, adequate ventilation, chemicals kept off the skin; Personal protective equipment; checking gloves for pinholes, leaks and tears; rinsing gloves thoroughly with water before removing them; Handling photographic processing chemicals: gloves, eye protection, adequate ventilation, no eating or drinking in the work area; Store chemicals safely, and keep the labels that came on them; Material Safety Data Sheets, and obtaining one for a product you hold; Store chemicals safely: containers kept in a designated area, away from food, and stored in the containers they were delivered in; do not eat, drink or smoke in chemical handling areas; Properly dispose of photographic processing chemicals; know first-aid in case of an emergency; Store chemicals safely: containers positioned where they can be reached without stretching, in a designated area, away from food, and stored in the containers they were delivered in; Handling photographic processing chemicals: gloves, eye protection, adequate ventilation, chemicals kept off the skin, no eating or drinking in the work area; Handling photographic processing chemicals: gloves, eye protection and ventilation at working dilutions; General ventilation; effective covers on tanks and trays of a durable non-reactive material; Store chemicals safely - unmixed concentrates stored dry between 5 and 30 degrees Celsius, away from direct sunlight and away from sources of heat; Store chemicals safely - storing processing chemicals in the containers they were delivered in and not removing their labels

Used by:P29 Planning the Capstone: The Project Plan and Its Hazard Assessment · Kodak F-6 · KODAK PROFESSIONAL XTOL Developer · P2 Storage, Incompatibilities and Secondary Containment · P2 Lab: Commissioning Your Laboratory · P2 Laying Out the Laboratory: Wet Areas, Dry Areas and Contamination Control · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P28 Break/Fix: The Film That Came Back Wrong · The disposal caveat · First aid quick reference · Glove selection · Responding to an acid spill · Responding to an alkali spill · Checking and using the eyewash · Handling and storing a deliberately faulty reference specimen · Closing the laboratory · Labelling a container · Collecting and segregating waste across a multi-run session · Adjusting pH with a concentrated alkali · Putting protective equipment on, changing gloves and taking it off · Setting up and shutting down the print processing line · Recording a batch in the inventory · Recording a safety data sheet · Refrigerated emulsion labelling and food separation · Responding to a spill · The stock check, and retiring a chemical · Storage rotation and shelf separation · The student's project SOP · Calibrating the darkroom timer · A container found unlabelled, or a solution of unknown age · Checking the ventilation before a session · Stock solution crystallised in cold storage · Unlabelled or undated container

Sources of Silver in Photographic Processing Facilities, publication J-210retrieved 2026-09-04, 2026-09-05, 2026-09-07

Sections: Waste characterization: the toxicity characteristic leaching procedure result for processed and unprocessed films and papers; The worked examples, which estimate recoverable silver from black-and-white materials by assuming a percentage of exposure — 50 per cent for radiography and 70 per cent for graphic arts — with the statement that the higher the level of exposure the lower the amount of silver removed from the film; the area tables giving 592 square feet per 1000 black-and-white 135-36 films and 556 square feet per 1000 sheets of 8 by 10 inches; The area tables — 592 square feet per 1000 black-and-white 135-36 films, 538 per 1000 120 rollfilms and 139 per 1000 sheets of 4 by 5 inches; the worked examples, which give silver coating weights in troy ounces per 1000 square feet only for named colour and radiographic films and estimate the recoverable fraction of a black-and-white material by assuming a percentage of exposure; The area tables, giving 592 square feet per 1000 black-and-white 135-36 films and 556 square feet per 1000 sheets of 8 by 10 inches; the worked examples, which give silver coating weights in troy ounces per 1000 square feet for named colour and radiographic films — 16 to 24 for the KODAK GOLD and ROYAL GOLD films and 14.5 for T-MAT RA — and which estimate the recoverable fraction of a black-and-white material by assuming a percentage of exposure, 50 per cent for radiography and 70 per cent for graphic arts; Area of common film and papers — 592 square feet per thousand black-and-white 135-36 films; Waste characterization — representative samples of processed and unprocessed Kodak films and papers did not leach silver at 5 ppm or above under the Toxicity Characteristic Leaching Procedure; Determining the amount of silver you can potentially recover, step 3 — the instruction that for black-and-white films and papers the percentage of exposure must be estimated, because the higher the exposure the lower the amount of silver removed from the material; Variations in the silver content of photographic films and papers - the statement that silver content varies from emulsion to emulsion, that similar products from different manufacturers may vary, and that information on the amount of silver in Kodak films and papers is available from Kodak Environmental Services rather than published, typically reported in troy ounces per 1000 square feet; the medical example, in which KODAK T-MAT RA Film is given as 14.5 troy ounces per 1000 square feet and an average film exposure of 50 per cent is assumed, so that 50 per cent of the silver is removed during processing; the instruction that for black-and-white films the percentage of exposure must be estimated, and that the higher the level of exposure the lower the amount of silver removed from the film; and Area of Common Film and Papers, whose black-and-white table gives 135-36 as 592 square feet and 55.0 square metres per 1000 units; Waste characterization: processed and unprocessed films and papers

Used by:P2 Waste: Streams, Silver, and the Drain You Must Not Use · P11 Overview: Making the Image Permanent · P11 Experiment: Clearing Time and Fixer Capacity · P11 Fixer Capacity, Exhaustion and Residual Silver · P12 Silver Recovery and the Responsible Darkroom · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · Routing silver-bearing waste

The Regulation of Silver in Photographic Processing Facilities, publication J-214retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Identifying silver-bearing hazardous wastes — the 5 ppm toxicity characteristic and EPA Hazardous Waste Number D011; The 5 ppm toxicity characteristic, EPA Hazardous Waste Number D011, and the table of which photographic materials cross it; Identifying silver-bearing hazardous wastes: used fixers and the 5 ppm toxicity characteristic; photographic films and papers under the Toxicity Characteristic Leaching Procedure; Identifying silver-bearing hazardous wastes: the 5 ppm toxicity characteristic; photographic films and papers under the Toxicity Characteristic Leaching Procedure; Identifying silver-bearing hazardous wastes: the 5 ppm toxicity characteristic and EPA Hazardous Waste Number D011; The toxicity characteristic — a liquid waste containing 5 ppm or more of silver, or a solid leaching that much under the Toxicity Characteristic Leaching Procedure, is a characteristic hazardous waste with EPA hazardous waste number D011; the table of which photographic materials cross it, in which used fixers, bleach-fixes, activators and low-flow washes typically contain more than 5 ppm of silver, developers generally do not, and wash waters can through carry-over; the statement throughout that state and local agencies may impose stricter requirements

Used by:Kaolin · Silver · Silver bromide · Silver chloride · Silver iodide · Silver nitrate · Silver(I) oxalate · Silver(I) oxide · Silver sulfamate · Salted paper sensitising solution · P12 Silver Recovery and the Responsible Darkroom

The Technology of Silver Recovery for Photographic Processing Facilities, publication J-212retrieved 2026-09-05

Sections: Electrolysis — the cathode and anode half-reactions, and the statement that desilvering below 200 mg/L by longer residence or higher current density produces an inferior, black, crumbly, silver-sulfide-contaminated plate; Metallic replacement — the overview reaction written for the silver thiosulfate complex, the statement that a properly operating cartridge may reduce silver to less than 5 mg/L, channelling and premature breakthrough, and the sentence that the recovered silver frequently barely pays for the materials and equipment used to collect it; Precipitation — sulfide precipitation requiring accurate prior measurement to avoid overdosing and discharging toxic hydrogen sulfide, and TMT reaching an average below 1.5 ppm; Ion exchange — for washwaters, removing silver to about 0.1 to 0.5 ppm; Comparative silver-recovery and treatment technologies, the whole table of initial and final concentrations, capital costs, operating costs, advantages and disadvantages; Metallic replacement — the basis of the method as the reduction by metallic iron, usually present as steel wool, of the silver-thiosulfate complex to elemental silver, with the overview reaction; the statement that the silver is left behind in the cartridge while iron is solubilised and carried out by the solution; the list of factors affecting the final concentration, flow rate, iron surface area, contact time, pH, original silver concentration, thiosulfate concentration and volume passed; the statement that a properly operating cartridge may reduce silver to less than 5 mg/L; channelling and internal collapse of the steel wool causing silver breakthrough well before the iron is consumed; the statement that solutions passed through a cartridge cannot be reused for photographic processing because the dissolved iron and other reaction by-products contaminate the processor tank; Comparative table — metallic replacement final silver 0.5 to 15 mg/L, operating cost high, and the disadvantage that it discharges iron, which some sewer codes limit

Used by:P12 Silver Recovery and the Responsible Darkroom · P12 Experiment: Small-Scale Metallic Replacement

Toning Black-and-White Materials (KODAK Publication G-23, Technical Data / Reference)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-08

Sections: Page 1, that toning converts the black-and-white silver image to an inert compound and that all Kodak toners will protect the image whether or not they produce a colour shift; Fixing — that improper fixing is probably the major cause of stains in toned prints, that two-bath fixing gives the best results, and that a hardening fixer is not recommended for prints intended for toning because it makes the paper emulsion less receptive; and Guidelines for Print Processing, that toning cannot disguise poor print quality and that a good candidate has a full tonal scale with good detail in highlights and shadows; Page 1, that toning converts the black-and-white silver image to an inert compound and that all Kodak toners will protect the image whether or not they produce a colour shift; Adjusting Print Exposure and Development, that Sepia, Sepia II Warm and Brown toners reduce print densities so prints are developed fully and made slightly darker than normal while Rapid Selenium Toner tends to intensify the image; Fixing, that improper fixing is probably the major cause of stains in toned prints and that two-bath fixing gives the best results; Toning, that metal trays and tanks are not used for toning solutions, only unchipped enamel, hard rubber or plastic; and Safe handling of photographic chemicals, the instruction not to discard sulfide-type toners with stop baths or fixing baths; Page 1, the statement that toning converts the black-and-white silver image to an inert compound, reducing the harmful effects of intense light, ultraviolet radiation, oxidizing gases, extremes of temperature and humidity and fumes, and that all Kodak toners will protect the image whether or not they produce a colour shift; Hardener F-5a; Gold Toner T-21; Gold Protective Solution GP-1; Blue Toner T-26; KODAK PROFESSIONAL Sepia Toner: Bleach Stock Solution A; Hypo Alum Sepia Toner T-1a — composition, mixing and working temperature; Sulfide Sepia Toner T-7a; Safe handling of photographic chemicals; Gold Toner T-21 — Stock Solution A, its mixing instruction and the working bath temperature; KODAK PROFESSIONAL Rapid Selenium Toner — description and precautionary note; KODAK PROFESSIONAL Sepia Toner and Sepia II Warm Toner: note on the bleach bath, Solution A; KODAK PROFESSIONAL Rapid Selenium Toner — conversion of the image to silver selenide, dilutions, tones by paper type, the effect on shadow density and D-max; the introductory claim for toning as protection; Handling and Disposal; KODAK PROFESSIONAL Brown Toner, Sepia Toner and Sepia II Warm Toner — conversion of the image to silver sulfide; the introductory claim for toning as protection; Handling and Disposal — sulfide toners with stop and fixing baths; KODAK PROFESSIONAL Rapid Selenium Toner — description and precautionary note on the active ingredient; KODAK PROFESSIONAL Rapid Selenium Toner — the active ingredient described as a sulfite salt at less than 2 per cent and working solutions as less than half a per cent selenium sulfite; Blue Toner T-26 — the formula and the note that contrast and density appear to increase; Sulfide Sepia Toner T-7a; Safe handling of photographic chemicals — disposal of sulfide-type toners; Gold Protective Solution GP-1 — the formula, the mixing order and the treatment; the description of GP-1 among the toners mixed from formulas; Hypo Alum Sepia Toner T-1a; Gold Toner T-21; Blue Toner T-26; Sulfide Sepia Toner T-7a; Toners Mixed from Formulas, the footnote to Gold Protective Solution GP-1: a 1 per cent gold chloride solution is prepared by dissolving 1 gram of gold chloride in 100 mL of water, or obtained ready made from a photographic dealer; and the footnote that gold chloride is a deliquescent chemical which will liquefy rapidly in a normal room atmosphere and should be stored in a tightly stoppered bottle in a dry atmosphere; Gold Protective Solution GP-1, for the same ligand chemistry at a tenth of a gram of gold per litre; Using KODAK Professional Packaged Toners, KODAK PROFESSIONAL Rapid Selenium Toner — the conversion of the silver image to silver selenide, the active ingredient described only as a sulfite salt at a concentration of less than 2 per cent with working solutions containing less than half a per cent of "selenium sulfite", the 1:20 dilution for print protection and the 1:20 and 1:40 dilutions for increased shadow contrast and maximum density, completion in 2 to 8 minutes at 20 degrees C, the direction that toning continues to some extent in the wash, the warning that residual silver salts and traces of hypo cause stains, uneven tones and fading, round purple stains attributed to air bubbles trapped during fixing, the recommendation of print tongs and clean rubber gloves, and the general instruction against metal trays; Hardener F-5a - the footnote that powdered boric acid should be avoided because it does not dissolve easily; Hardener F-5a, page 7, printed beside Gold Toner T-21; Sulfide Sepia Toner T-7a, page 7, step 5, treating fibre-base prints in a bath made from 1 part KODAK Liquid Hardener and 13 parts water, or 2 parts Hardener F-5a and 16 parts water, for 2 to 5 minutes, with the footnote to eliminate the treatment if the prints were treated with a hardening fixer during processing; Fixing, page 2, on a hardening fixer not being recommended for prints intended for toning because it makes the paper emulsion less receptive to the toner solution, on a non-hardening fixer being used instead, and on a liquid hardener being required after toning with some toners; Toners Mixed from Formulas, Gold Protective Solution GP-1, page 8: the description 'Provides print protection while changing the image tone only slightly'; the instruction 'Prepare the solution as follows. For best results, mix it right before you use it.'; the table reading water at 20°C (68°F) 750 mL, gold chloride 1% stock solution 10 mL, sodium thiocyanate (liquid) 15.2 mL and water to make 1 L, with the footnotes that gold chloride is a deliquescent chemical which will liquefy rapidly in a normal room atmosphere and should be stored in a tightly stoppered bottle in a dry atmosphere, and that a 1 per cent gold chloride solution is prepared by dissolving 1 gram of gold chloride in 100 mL of water or obtained ready made from a photographic dealer; the mixing paragraph 'Add the 10 mL of gold chloride stock solution to the 750 mL of water. Dissolve the sodium thiocyanate solution separately in 125 mL of water. Then slowly add the sodium thiocyanate solution to the gold chloride solution while stirring rapidly.'; and the treatment, a thoroughly washed print immersed at 20°C (68°F) for 10 minutes or until a very slight change to a bluish black is visible in the image tone, then a 10-minute wash at 18 to 24°C for fibre-base prints or 4 minutes for resin-coated; Washing before toning - wash fibre-base prints for one hour in running water at 18 to 20 degrees C or use KODAK Hypo Clearing Agent to reduce the wash time, wash resin-coated papers for 4 minutes, and the statement that Hypo Clearing Agent is not recommended with resin-coated papers; the note under KODAK PROFESSIONAL Rapid Selenium Toner that a working solution of Hypo Clearing Agent may be used to dilute the toner 1 to 20 or 1 to 40 and eliminate the wash step between fixing and toning, that the prints must not be rinsed after fixing, that the bath must not be reused on untoned prints because it will contain traces of toner, and that the prints are then washed for at least 30 minutes at 18 to 20 degrees C; the Brown Toner sequence treating fibre-base prints in Hypo Clearing Agent for 1 minute; Using KODAK Professional Packaged Toners, KODAK PROFESSIONAL Rapid Selenium Toner: the active ingredient described as a sulfite salt at a concentration of less than 2 per cent, working solutions containing less than half a per cent of 'selenium sulfite', print tongs and clean rubber gloves recommended, complete toning in 2 to 8 minutes at 20 °C depending on the paper, and toning continuing to some extent in the wash; Safe handling of photographic chemicals: sulfide-type toners never discarded with stop baths or fixing baths, because the combination generates hydrogen sulfide gas; Safe handling of photographic chemicals: the direction not to discard sulfide-type toners with stop baths or fixing baths because the combination generates hydrogen sulfide gas, and that the gas fogs unexposed paper and film and oxidises unprotected silver images; Guidelines for print processing, on fixing, washing and the stains that follow from getting either wrong; Toning Black-and-White Materials, KODAK Publication G-23, May 2006, minor revision 5-06 — the opening account of what a toner does, that toning converts the black-and-white silver image to an inert compound and that all Kodak toners will protect the image whether or not they produce a colour shift; the D-max paragraph and the curve showing the increase in upper-scale contrast and D-max of KODAK PROFESSIONAL POLYMAX Fine-Art Paper (discontinued), developed in DEKTOL (1:2) at 20 °C for 2 minutes and toned in Rapid Selenium Toner diluted 1:40 for 4 minutes; the KODAK Packaged Toners entry for Rapid Selenium Toner, giving cool chocolate-brown hues with warm-tone papers, purplish brown with neutral-tone papers and very little or no change with cold-tone papers, the 1:20 dilution for print protection, the 1:20 or 1:40 dilution to increase shadow contrast and maximum density with a minimum tone change, the statement that the toner may also be used with black-and-white films, and the statement that it converts the silver image to silver selenide; the Tones Produced by Paper/Toner Combinations table, whose Rapid Selenium line reads "No Tone Shift" at 1:20; the Adjusting Print Exposure and Development paragraph, that Rapid Selenium Toner tends to intensify the image, that print development time may be shortened slightly, and that toning a fully developed print with this toner yields an increased tonal scale; the Guidelines for Print Processing sections on development, stop bath, fixing, washing, toning and drying, including the overconcentrated stop bath and mottle in the base of a toned print, the mottle from insufficient agitation in the first few seconds of the stop bath that is not evident until the print is toned, the recommendation against hardening fixers for prints intended for toning, the dark yellow stain in borders and highlights from an exhausted fixer, the round purple stains from air bubbles trapped during fixing, the yellowing from prolonged fixing, the one-hour fibre-base wash with a complete change of water every five minutes and the four-minute wash for resin-coated papers, the instruction not to use metal trays or tanks, the two-to-three-minute soak for dry prints, the instruction to keep toning times to a minimum on resin-coated papers and to leave a large border if they are toned longer than 8 to 10 minutes, and the note that drying with heat causes a shift to a cooler tone with some paper/toner combinations; the Safe Handling of Photographic Chemicals list; and the whole of Using KODAK PROFESSIONAL Packaged Toners, KODAK PROFESSIONAL Rapid Selenium Toner — the note that the active ingredient is a sulfite salt at a concentration of less than 2 percent and that working solutions generally contain less than half a per cent of "selenium sulfite", that these selenium concentrations are not considered hazardous when the solutions are handled under normal conditions, and the recommendation of print tongs and clean rubber gloves; the instruction to rewet already-dried prints in a fixing bath and rewash them; the three numbered steps, dilution according to the tone change wanted, immersion of a thoroughly washed print at 20 °C (68 °F) with agitation, complete toning in 2 to 8 minutes depending on paper type and weight, and removal when the print has almost the required tone because toning will continue to some extent in the wash; the washing instructions; the Hypo Clearing Agent combination bath, diluting the toner 1:20 or 1:40 in working-solution Hypo Clearing Agent, eliminating the wash between fixing and toning, not rinsing after fixing, toning approximately 3 minutes for print protection or longer for a tone change, not reusing that bath for untoned prints, and washing for at least 30 minutes at 18 to 20 °C with frequent agitation afterwards; and the film paragraph, dilution 1:29, four minutes at 20 °C with occasional agitation, a 20-to-30-minute wash, drying in a dust-free place, the slight increase in contrast at 1:29 and the greater increase at 1:3 or 1:9; Handling precautions — the instruction not to discard sulfide-type toners with stop baths or fixing baths, because the combination generates hydrogen sulfide gas, and to discard the solutions individually; Safe handling of photographic chemicals — the instruction not to discard sulfide-type toners with stop baths or fixing baths; Using KODAK Professional Packaged Toners, KODAK PROFESSIONAL Rapid Selenium Toner — the active ingredient described only as a sulfite salt at a concentration of less than 2 per cent, and working solutions containing less than half a per cent of selenium sulfite; Toners Mixed from Formulas, Hypo Alum Sepia Toner T-1a, page 6: water at 20°C (68°F) 2.8 L and sodium thiosulfate (pentahydrated) 480 g, mixed thoroughly; then water at 70°C (160°F) 640 mL and potassium alum (dodecahydrated) 120 g; then, added slowly to the hypo alum solution while stirring rapidly and including the precipitate, water at 20°C 64 mL, silver nitrate crystals 4 g and sodium chloride 4 g, with the footnote that the silver nitrate must dissolve completely before the sodium chloride is added; then water at 20°C to make 4 L; the note that when the solutions are combined a black precipitate may form and that it will not adversely affect the toning action of the bath with proper technique; and the working instructions, a tray in a tempered water bath heated to 49°C (120°F), a thoroughly washed print agitated occasionally and especially during the first few minutes, toning for 12 to 15 minutes depending on the paper, not longer than 20 minutes and not at a higher temperature because prints will blister or stain, a rinse in warm water with a soft sponge to remove sediment, and a one-hour wash at 18 to 24°C for fibre-base prints or 4 minutes for resin-coated; also the statement that this toner will cause a loss of print density and contrast, compensated by increasing exposure and development; Toners Mixed from Formulas, Gold Toner T-21, pages 7 and 8: Stock Solution A reading water at 50°C (125°F) 4 L, sodium thiosulfate crystals 960 g and potassium persulfate 120 g, with the instruction 'Dissolve the sodium thiosulfate in the water. While stirring vigorously, add the potassium persulfate. If the mixture does not turn milky, increase the temperature. Cool to 27°C (80°F). Then slowly add the following solution, including the precipitate, while stirring. Solutions must be cool when you combine them.' followed by water at 20°C 64 mL, silver nitrate crystals 5 g and sodium chloride 5 g, with the footnote that the silver nitrate must dissolve completely before the sodium chloride is added; Stock Solution B reading water at 20°C and gold chloride 1 g, the volume printed in the mirrored text as 250 L; the Toner Working Solution as the entire amount of Stock Solution A with 125 mL of Stock Solution B added slowly while stirring rapidly; the instruction to let the mixed solution stand for about 8 hours, during which a yellow precipitate forms, and to pour the clear solution into another container and discard the precipitate; the replenishment note that the remainder of Stock Solution B is saved to replenish the bath, with 4 mL added after every fifty 8 x 10-inch prints or equivalent when toning to a warm-brown hue; and the working instructions, a tray in a tempered water bath at 43°C (109°F) maintained during toning, a thoroughly washed print immersed for 5 to 20 minutes until it has the tone wanted, a rinse in cold water, and a one-hour wash at 18 to 24°C for fibre-base prints or 4 minutes for resin-coated; also the description of T-21 as producing a pleasing range of brown tones with most warm-tone papers by plating the silver image with gold, having little effect on cold-tone papers, and toning the highlights and the shadows at a uniform rate; Toners Mixed from Formulas, Blue Toner T-26, page 8: the description 'Produces blue tones on some papers. Warm-tone papers react well to this toner. Neutral-tone papers change slightly to soft blue-black tones. Cold-tone papers will not change.'; the note that the contrast and density of treated prints appear to increase and that exposure may be reduced slightly to compensate, that the exact tone varies with the paper and developer and that a soft gray-blue is more common than a saturated blue; the note that Blue Toner is fairly expensive to produce, that it should be prepared right before use, that if prints are toned one at a time the first few tone the most and the last few may not tone at all, and that up to five prints should be immersed simultaneously for consistent results; the table reading water at 52°C (125°F) 937 mL, gold chloride 1% stock solution 40 mL, thiourea 1 g, tartaric acid 1 g and sodium sulfate (anhydrous) 15 g, with the instruction to mix the gold chloride solution with the water and then, while stirring, add the other three, stirring until the chemicals dissolve completely; the note that a fine white precipitate may appear if the solution is stored overnight and will not interfere with toning; the treatment, a thoroughly washed print immersed at 20°C (68°F) or at 38 to 40°C (100 to 104°F) and toned with occasional agitation for 8 to 45 minutes at 20°C or 2 to 15 minutes at 38 to 40°C, with the note that the toning action is so gradual that only a small amount of agitation is needed to prevent streaking and that toning occurs in the highlights first and the shadows last, so partial toning may produce blue highlights and untoned shadows; a wash of at least 30 minutes at 18 to 24°C for fibre-base prints and 4 minutes for resin-coated; and, under Multiple Toning, the sequence of Kodak Sepia or Brown Toner followed by a thorough wash and then Blue Toner T-26, in which red or orange tones appear after approximately 15 to 30 minutes at 32°C (90°F); Toners Mixed from Formulas, Sulfide Sepia Toner T-7a, page 7: Bleach—Stock Solution A reading water at 20°C (68°F) 2 L, potassium ferricyanide (anhydrous) 75 g, potassium bromide (anhydrous) 75 g, potassium oxalate 195 g and 28% acetic acid 40 mL, with the footnote 'To make approximately 28% acetic acid from glacial acetic acid, add 3 parts of glacial acetic acid to 8 parts water'; Toner—Stock Solution B reading sodium sulfide (anhydrous) 45 g and water at 20°C 500 mL; Bleach Working Solution reading Stock Solution A 500 mL and water at 20°C 500 mL; Toner Working Solution reading Stock Solution B 125 mL and water at 20°C 375 mL; and the five working steps, bleaching until only a faint yellowish brown image remains in approximately 5 to 8 minutes, rinsing in cold running water for at least 2 minutes, toning until no further change occurs in approximately 30 seconds, rinsing immediately, and treating fibre-base prints in 1 part KODAK Liquid Hardener to 13 parts water or 2 parts Hardener F-5a to 16 parts water for 2 to 5 minutes, then washing fibre-base prints for 30 minutes at 18 to 24°C and resin-coated prints for 4 minutes; Toners Mixed from Formulas, Sulfide Sepia Toner T-7a, page 7, for the published two-solution formula and its working steps; Guidelines for Print Processing, the Stop Bath paragraph on mottle that appears only after toning, the Fixing paragraph on improper fixing as the major cause of stains in toned prints and on air bubbles producing round purple stains, and the note that prolonged fixing lets fixer into the base so that toned prints turn yellow; the Toning paragraph forbidding metal trays and tanks and allowing only unchipped enamel, hard rubber or plastic, and requiring a dry print to be soaked for 2 to 3 minutes before toning; Adjusting Print Exposure and Development, that the sepia and brown toners reduce print densities so prints should be developed fully and printed slightly darker than normal; and Safe Handling of Photographic Chemicals, the instruction not to discard sulfide-type toners with stop baths or fixing baths because the combination generates hydrogen sulfide gas, and that solutions are discarded individually; Using KODAK Professional Packaged Toners, KODAK PROFESSIONAL Rapid Selenium Toner — the conversion of the silver image to silver selenide, the active ingredient described only as a sulfite salt at less than 2 per cent, the warning that residual silver salts and traces of hypo cause stains, uneven tones and fading, round purple stains attributed to air bubbles trapped during fixing, and the general instruction against metal trays; Using KODAK Professional Packaged Toners, Sepia Toner and Sepia II Warm Toner: the note that the bleach bath, Solution A, converts metallic silver in the print to light-sensitive silver bromide, that the print may be bleached under safelight illumination to minimise the effect of light on the image, and that the effect is extremely small; Toners Mixed from Formulas, Sulfide Sepia Toner T-7a, for the bleach stock that carries potassium oxalate and acetic acid as well; Why tone a print; Toners Mixed from Formulas; Why tone a print; Toners Mixed from Formulas — T-1a, T-7a, T-21, T-26 and GP-1; Making approximately 28 per cent acetic acid from glacial acetic acid; Sepia toners: the bleach bath converts metallic silver in the print to light-sensitive silver bromide, and the toner bath converts the silver image to silver sulfide; Stop Bath — do not use an exhausted or overconcentrated stop bath; the tray and tank standing times after which evaporation may overconcentrate it; mottle in the base of a toned print from an overconcentrated bath or from insufficient agitation in the first few seconds; the instruction not to discard sulfide-type toners with stop baths or fixing baths; Stop Bath — do not use an exhausted or overconcentrated stop bath, replace it frequently or use an indicator stop bath which signals when to change the bath, and the statement that leaving stop bath in a tray for more than three days or a tank for more than one month may cause overconcentration by evaporation, which can cause mottle in the base of a toned print; Fixing — the instruction not to exceed the capacity of the fixer, the statement that an exhausted fixing bath contains insoluble silver compounds that will remain in prints and cannot be removed completely by washing, and that when these residual silver compounds meet a toner they form a dark yellow stain especially noticeable in print borders and highlights; the use of two-bath fixing for best results; Fixing — the instruction not to exceed the capacity of the fixer, the statement that an exhausted fixing bath contains insoluble silver compounds that will remain in prints and cannot be removed completely by washing, and that when these residual silver compounds meet a toner they form a dark yellow stain especially noticeable in print borders and highlights; the use of two-bath fixing for best results; the instruction not to fix prints for longer than the recommended time, approximately 10 minutes for fibre base and 2 minutes for resin-coated; Fixing — the recommendation not to use a hardening fixer for prints intended for toning because it makes the paper emulsion less receptive to the toner solution, the use of a non-hardening fixer instead, and the statement that an exhausted fixing bath contains insoluble silver compounds that remain in prints, cannot be removed completely by washing and form a dark yellow stain in borders and highlights when they meet a toner; Hardener F-5a, an acid hardener stock of sodium sulphite, 28 per cent acetic acid, boric acid crystals and potassium alum, with the footnote that 28 per cent acetic acid is made by adding 3 parts of glacial acetic acid to 8 parts of water and the note to avoid powdered boric acid because it does not dissolve easily; Fixing — the instruction not to fix prints for longer than the recommended time, approximately 10 minutes for fibre-base papers and 2 minutes for resin-coated, because prolonged fixing expands the paper and allows the solution to penetrate the base where it is difficult to remove and makes selenium- or sulfide-toned prints turn yellow, and the statement that prolonged fixing can also reduce the silver image; Why tone a print — toning extends the life of the print image during display or storage by converting the black-and-white silver image to an inert compound, which reduces the harmful effects of intense light, ultraviolet radiation, oxidizing gases, extremes of temperature and humidity, and fumes, and all Kodak toners will protect the image whether or not they produce a colour shift; KODAK PROFESSIONAL Rapid Selenium Toner, which converts the silver image to silver selenide, with the 1:20 dilution given for print protection; KODAK PROFESSIONAL Brown Toner, which converts the silver image to silver sulfide; Gold Protective Solution GP-1, which provides print protection while changing the image tone only slightly; Safe handling — sulfide-type toners are not discarded with stop baths or fixing baths because the combination generates hydrogen sulfide gas, which can fog unexposed paper and film and will oxidize unprotected silver images in negatives and prints; KODAK PROFESSIONAL Rapid Selenium Toner — wash fibre-base prints in running water at 18 to 20 degrees C for one hour, or use KODAK Hypo Clearing Agent to reduce the wash time, and wash resin-coated prints for 4 minutes; Safe handling of photographic chemicals — do not discard sulfide-type toners with stop baths or fixing baths, because the combination of these solutions will generate hydrogen sulfide gas, which can fog unexposed paper and film and will oxidize unprotected silver images in negatives and prints; discard the solutions individually; Fixing - the statement that improper fixing is probably the major cause of stains, that an exhausted fixing bath contains insoluble silver compounds that remain in prints and cannot be removed completely by washing, that these residual silver compounds form a dark yellow stain especially noticeable in print borders and highlights, that stains commonly occur when prints stick together or float and that trapped air bubbles can later produce round stains, and that prolonged fixing expands the paper and allows solution to penetrate the base, with the statement that prolonged fixing can also reduce the silver image; Development - the statement that developer contamination or exhaustion can cause image-colour variations, and the instruction not to exceed the capacity of the developer; Stop Bath - the instruction not to use an exhausted or overconcentrated stop bath, and that insufficient agitation in the first few seconds can cause mottle; Washing - that residual silver salts and traces of hypo may cause stains, uneven tones and fading; Fixing - the statement that a hardening fixer is not recommended for prints that are to be toned because it makes the paper emulsion less receptive to the toner solution, with the recommendation to use a non-hardening fixer instead, and the note that an exhausted fixing bath leaves insoluble silver compounds that washing cannot remove and that stain on contact with a toner; GUIDELINES FOR PRINT PROCESSING, Development - the instruction to use the development temperature and time recommended in the paper instructions to obtain uniform image colour, to avoid contaminating the developer with other solutions and not to exceed its capacity, and the statement that developer contamination or exhaustion can cause image-colour variations; Stop Bath - the warning not to use an exhausted or overconcentrated stop bath, the note that a bath left in a tray for more than three days or a tank for more than one month may become overconcentrated by evaporation, the statement that an overconcentrated stop bath can cause mottle in the base of a toned print, and the statement that insufficient agitation of prints especially during the first few seconds in the stop bath can also cause mottle which will not be evident until the print is toned; Fixing - the statement that improper fixing is probably the major cause of stains in toned prints, the instruction to use two-bath fixing for best results, the recommendation of a non-hardening fixer for prints intended for toning because a hardener makes the emulsion less receptive to the toner, the statement that an exhausted fixing bath contains insoluble silver compounds that cannot be removed completely by washing and that form a dark yellow stain on toning which is especially noticeable in print borders and highlights, the note that stains commonly occur when prints stick together or float in the fixer and that trapped air bubbles later produce round purple stains, and the instruction not to fix prints for longer than approximately 10 min for fibre-base and 2 min for resin-coated papers because prolonged fixing expands the paper and traps fixer in the base; Washing - one hour with agitation for fibre-base prints with a complete change of water every 5 min, 4 min in running water for resin-coated papers, and the statement that Hypo Clearing Agent is not recommended with resin-coated papers; and Drying - the note that drying with heat causes a shift to a cooler tone with some paper and toner combinations; Washing - wash fiber-base prints for one hour with agitation in a tank or tray, the wash-water flow rate providing a complete change of water every 5 minutes, with KODAK Hypo Clearing Agent used to reduce washing time and conserve water; wash resin-coated papers for 4 minutes in running water at a flow rate sufficient to change the water completely during the 4-minute wash, with the statement that Hypo Clearing Agent is not recommended with resin-coated papers; and the instruction to agitate prints and keep them separated during washing and not to overload the wash tank; Fixing - the statement that improper fixing is probably the major cause of stains in toned prints, that an exhausted fixing bath contains insoluble silver compounds which cannot be removed completely by washing, and that prolonged fixing expands the paper and allows the solution to penetrate the base so that fixer trapped in the base is difficult to remove; Drying - dry toned fiber-base prints slowly between sheets of blotting paper or on a drying rack, remove excess water from resin-coated prints and air-dry them at room temperature or with circulated warm air, and the Note that drying with heat causes a shift to a cooler tone with some paper and toner combinations so that the speed and temperature of the dryer should be set to the lowest settings; Page 1, the toning curve for KODAK PROFESSIONAL POLYMAX Fine-Art Paper (discontinued) developed in DEKTOL and toned in Rapid Selenium Toner, and the opening list of what a toner does — toning converts the black-and-white silver image to an inert compound, which reduces the harmful effects of intense light, ultraviolet radiation, oxidizing gases, extremes of temperature and humidity, and fumes, and all Kodak toners will protect the image whether or not they produce a color shift; the named conversions, Rapid Selenium Toner to silver selenide and Brown Toner and both Sepia toners to silver sulfide; Adjusting Print Exposure and Development, that the Sepia, Sepia II Warm and Brown toners reduce print densities and prints should be made slightly darker while Rapid Selenium Toner tends to intensify the image; Guidelines for Print Processing, that toning cannot disguise poor print quality and a good candidate has a full tonal scale with detail in highlights and shadows; Fixing, that improper fixing is probably the major cause of stains in toned prints and that a hardening fixer is not recommended for prints intended for toning; Toning, that metal trays and tanks are not used for toning solutions; Safe Handling, that sulfide-type toners are not discarded with stop baths or fixing baths because the combination generates hydrogen sulfide gas, which fogs unexposed paper and film and oxidises unprotected silver images; and page 6, Gold Toner T-21, which tones by plating the silver image with gold; Toners Mixed from Formulas, Sulfide Sepia Toner T-7a, page 7 - Bleach Stock Solution A of water at 20 degrees C 2 L, potassium ferricyanide (anhydrous) 75 g, potassium bromide (anhydrous) 75 g, potassium oxalate 195 g and 28 per cent acetic acid 40 mL, with the footnote that approximately 28 per cent acetic acid is made from glacial acetic acid by adding 3 parts of glacial acid to 8 parts of water; Toner Stock Solution B of sodium sulfide (anhydrous) 45 g and water at 20 degrees C 500 mL; the Bleach Working Solution of 500 mL of Stock A and 500 mL of water; the Toner Working Solution of 125 mL of Stock B and 375 mL of water; and the five working steps - bleach until only a faint yellowish brown image remains, approximately 5 to 8 minutes; rinse in cold running water for at least 2 minutes; tone until no further change occurs in the tone, approximately 30 seconds; immediately rinse the print with water; and treat fibre-base prints in 1 part KODAK Liquid Hardener to 13 parts water, or 2 parts Hardener F-5a to 16 parts water, for 2 to 5 minutes, with the footnote to eliminate that treatment if the prints were fixed in a hardening fixer and the recommendation to use a non-hardening fixer for prints that are to be toned - then wash fibre-base prints for 30 minutes at 18 to 24 degrees C and resin-coated prints for 4 minutes. Page 2, Adjusting Print Exposure and Development, that the Sepia, Sepia II Warm and Brown toners reduce print densities so prints should be developed fully and made slightly darker than normal, and that the modification also depends on the paper emulsion type and grade; Guidelines for Print Processing, that toning cannot disguise poor print quality and that a good candidate has a full tonal scale with detail in highlights and shadows; the Stop Bath paragraph, that an exhausted or overconcentrated stop bath must not be used, that a bath left in a tray for more than three days or a tank for more than a month may become overconcentrated by evaporation, that an overconcentrated stop bath can cause mottle in the base of a toned print, that insufficient agitation in the first few seconds in the stop bath can also cause mottle, and that neither is evident until the print is toned; the Fixing paragraph, that improper fixing is probably the major cause of stains in toned prints, that two-bath fixing is recommended, that a hardening fixer is not recommended for prints intended for toning because it makes the emulsion less receptive, that an exhausted fixing bath contains insoluble silver compounds that washing cannot remove and that form a dark yellow stain on meeting a toner especially in borders and highlights, and that air bubbles trapped between or under prints during fixing can later produce round purple stains in prints toned with selenium or sulfide toners. Page 3, that prolonged fixing expands the paper and allows fixer into the base which will make prints toned in selenium or sulfide toners turn yellow, and that fixing should not exceed approximately 10 minutes for fibre-base and 2 minutes for resin-coated papers; Washing, that fibre-base prints are washed for one hour with a complete change of water every 5 minutes and resin-coated papers for 4 minutes; the Toning paragraph, that metal trays and tanks must not be used and only unchipped enamel, hard rubber or plastic, that a print that is already dry is soaked in water for 2 to 3 minutes before toning, that prints toned after storage may show stains due to adverse storage conditions, that toning times for resin-coated papers are kept to a minimum to prevent the solution penetrating the edges, and that a resin-coated print toned for longer than 8 to 10 minutes should carry a large border so the edges can be trimmed off; and Drying, that toned fibre-base prints are dried slowly between blotting paper or on a rack, that resin-coated prints are air-dried at room temperature or in circulated warm air, and that drying with heat causes a shift to a cooler tone with some paper and toner combinations. Page 4, Safe Handling of Photographic Chemicals, the instruction not to discard sulfide-type toners with stop baths or fixing baths because the combination generates hydrogen sulfide gas, that hydrogen sulfide gas can fog unexposed paper and film and will oxidise unprotected silver images in negatives and prints, and that solutions are discarded individually; and the KODAK PROFESSIONAL Rapid Selenium Toner procedure, whose instruction is that prints already dried are rewetted by immersing them in a fixing bath and then rewashed, otherwise staining may occur. Page 5, the packaged Sepia Toner procedure - bleach at 18 to 21 degrees C for about 5 to 8 minutes until the print image has disappeared or turned yellow, rinse thoroughly in running water for 2 minutes, tone at 18 to 21 degrees C for approximately 60 seconds or until no further tone change occurs, and rinse thoroughly in running water for 30 seconds - and the note that the bleach bath Solution A converts metallic silver in the print to light-sensitive silver bromide, that the print may be bleached under safelight to minimise the effect of light, and that the effect is extremely small and may not be noticeable; Toners Mixed from Formulas, page 6 — the descriptions of Gold Toner T-21 as producing a pleasing range of brown tones with most warm-tone papers by plating the silver image with gold, having little effect on cold-tone papers and toning the highlights and the shadows at a uniform rate so that toning can be stopped at the hue wanted; of Gold Protective Solution GP-1 as providing print protection while changing the image tone only slightly; and of Blue Toner T-26 as producing blue tones on some papers, warm-tone papers reacting well, neutral-tone papers changing slightly to soft blue-black tones and cold-tone papers not changing; page 8, that the contrast and density of prints treated in Blue Toner T-26 appear to increase and can be compensated by reducing exposure slightly, that the exact tone varies with the paper and developer and a soft gray-blue is more common than a saturated blue, that Blue Toner is fairly expensive to produce and should be prepared right before use, that if prints are toned one at a time the first few will tone the most and the last few may not tone at all, and that up to five prints should be immersed simultaneously for consistent results, and that toning occurs in the highlights first and the shadows last so partial toning may produce blue highlights and untoned shadows; page 9, SELECTIVE AND MULTIPLE TONING — the choice of scenes with a distinct line between areas treated differently, the liquid frisket materials applied with a brush and the clear self-adhesive sheet materials cut with a frisket knife, the presoak of 10 minutes for fibre-base and 2 minutes for resin-coated prints, the instruction to let the toner flow freely over the uncoated portions and not to worry if the print buckles, the note that the reserved part should be kept out of the solution in case the toner bleeds under the frisket and that the presoak should be skipped if it does, the removal of liquid frisket by rubbing while the print is still in the wash and of Photo Maskoid by touching sticky tape to an edge, and the instruction to follow the same procedure for each toner when two or more are used sequentially; Multiple Toning, that a print may carry its original warm image tone as well as sepia, blue and red or orange tones using only Blue Toner and Sepia or Brown Toner, that cold-tone papers yield a truer red and warm-tone papers an orange hue, that the technique usually produces a density loss in the shadow areas so it is best to start with a print of higher-than-normal contrast, and that the print is treated first in Sepia or Brown Toner, washed thoroughly and then toned in Blue Toner T-26, the red or orange tones appearing after approximately 15 to 30 minutes at 32°C (90°F); and page 10, RETOUCHING TONED PRINTS, that reducers cannot be used on toned prints but an etching knife can be used to lighten dark spots; Page 1 - Rapid Selenium Toner converts the silver image to silver selenide and produces cool chocolate-brown hues with warm-tone papers, purplish brown with neutral-tone papers and very little or no change with cold-tone papers, with the 1:20 or 1:40 dilution used to increase shadow contrast and maximum density with a minimum tone change; Brown Toner and both Sepia toners convert the silver image to silver sulfide; the opening list, in which toning changes or enhances the image colour, extends the life of the print by converting the silver image to an inert compound, and enhances maximum density, with the POLYMAX Fine-Art Paper curve showing increased upper-scale contrast and D-max after 4 minutes in Rapid Selenium Toner at 1:40, the paper having been developed in DEKTOL 1:2 at 20 C for 2 minutes and the axes being log exposure in lux-seconds against density; the statement that the visual effect of a toner depends on the toner and its dilution, the paper emulsion type, surface and stock tint, the length of the treatment and the processing of the paper, and that not all toners perform the same way with all papers; Adjusting Print Exposure and Development, that Sepia, Sepia II Warm and Brown Toner will reduce print densities so prints should be developed fully and made slightly darker than normal, while Rapid Selenium Toner tends to intensify the image so print development may be shortened slightly, and that these modifications also depend on the paper emulsion type and grade; Guidelines for Print Processing, that toning cannot disguise poor print quality and a good candidate for print toning should have a full tonal scale with good detail in the highlights and shadows; Sepia Toner and Sepia II Warm Toner, the note that the bleach bath Solution A converts metallic silver in the print to light-sensitive silver bromide, that the print may be bleached under safelight illumination to minimise the effect of light, and that the effect is extremely small and may not be noticeable; Toners Mixed from Formulas, that Gold Toner T-21 produces brown tones with most warm-tone papers by plating the silver image with gold, has little effect on cold-tone papers, and tones the highlights and shadows at a uniform rate, and that Gold Protective Solution GP-1 provides print protection while changing the image tone only slightly; Blue Toner T-26, whose working solution is made from gold chloride, thiourea, tartaric acid and sodium sulfate, whose contrast and density appear to increase so that exposure may be reduced slightly, and in which toning occurs in the highlights first and the shadows last, so that partial toning may produce blue highlights and untoned shadows; Selective Toning, the use of liquid or sheet frisket material to reserve areas of a print; and Multiple Toning, that a print treated first in Sepia or Brown Toner, washed, and then toned in Blue Toner T-26 develops red or orange tones after approximately 15 to 30 minutes at 32 C, that cold-tone papers yield a truer red and warm-tone papers an orange hue, and that the technique usually produces a density loss in the shadows so a higher-than-normal contrast print is the better start; Page 1, the statement that toning enhances the maximum density in the image and that with some toners the shadow densities can be increased with little or no change in image tone, and the accompanying characteristic curve of KODAK PROFESSIONAL POLYMAX Fine-Art Paper (recorded as discontinued) developed in KODAK PROFESSIONAL DEKTOL Developer at 1:2 for two minutes at 20 degrees C and toned four minutes in KODAK PROFESSIONAL Rapid Selenium Toner at 1:40, plotted as density from 0.0 to 3.0 against log exposure in lux-seconds from 0.0 to beyond 2.0, showing an increase in upper-scale contrast and D-max; the list of factors on which the visual effect of a toner depends, namely the toner and its dilution, the paper emulsion type, surface and stock tint, the length of the treatment and the processing of the paper; and the description of Rapid Selenium Toner, that it gives cool chocolate-brown hues with warm-tone papers, purplish brown with neutral-tone papers and very little or no change with cold-tone papers, that the 1:20 dilution is used for print protection and 1:20 or 1:40 to increase shadow contrast and maximum density with a minimum tone change, and that it converts the silver image to silver selenide. Page 2, the note to the paper/toner table that those papers were developed in DEKTOL at 1:2 at 20 degrees C, and the Rapid Selenium row at 1:20 headed No Tone Shift; Adjusting Print Exposure and Development, that Rapid Selenium Toner tends to intensify the image, that development may be shortened slightly, that a fully developed print toned in it yields an increased tonal scale, and that the modification also depends on the paper emulsion type and grade; and Guidelines for Print Processing, that toning cannot disguise poor print quality and that a good candidate has a full tonal scale with detail in highlights and shadows. Page 3, the Fixing paragraph, that fixing should not exceed approximately 10 minutes for fibre-base and 2 minutes for resin-coated papers, that prolonged fixing lets the solution into the base and makes prints toned in selenium or sulfide toners turn yellow and can also reduce the silver image; the Washing paragraph, that thorough washing is especially important before toning because residual silver salts and traces of hypo may cause stains, uneven tones and fading, that fibre-base prints are washed one hour with a complete change of water every five minutes and resin-coated papers four minutes in running water, and that Hypo Clearing Agent is not recommended with resin-coated papers; the Toning paragraph, that metal trays and tanks must not be used and only unchipped enamel, hard rubber or plastic, that prints may be toned immediately after washing, that a print already dry is soaked in water for two to three minutes before toning, that toning times for resin-coated papers are kept to a minimum to prevent the solution penetrating the edges, and that a resin-coated print toned longer than 8 to 10 minutes should carry a large border so the edges can be trimmed; and Drying, that toned fibre-base prints are dried slowly between blotting paper or on a rack, that resin-coated prints are air-dried at room temperature or in circulated warm air, and that drying with heat causes a shift to a cooler tone with some paper and toner combinations, with the instruction to set a dryer to its lowest settings and the note that the amount of toning may have to be adjusted to compensate. Page 4, the Rapid Selenium Toner procedure in full - the precautionary note that the active ingredient is a sulfite salt at under 2 per cent, that working solutions generally contain less than one half of one per cent selenium sulfite, that these selenium concentrations are not considered hazardous when the solutions are handled under normal conditions, and the recommendation of print tongs and clean rubber gloves with immediate washing of any splash; the instruction that prints already dried are rewetted by immersion in a fixing bath and rewashed, otherwise staining may occur; dilution according to the tone change wanted; immersion at 20 degrees C with agitation, complete toning in 2 to 8 minutes depending on paper type and weight; the instruction to remove the print when it has almost the required tone because toning will continue to some extent in the wash; and the washing times, one hour for fibre-base and four minutes for resin-coated prints; Page 1, the opening list of what a toner does, including that toning converts the black-and-white silver image to an inert compound which reduces the harmful effects of intense light, ultraviolet radiation, oxidizing gases, extremes of temperature and humidity, and fumes, and that all Kodak toners will protect the image whether or not they produce a colour shift; the description of KODAK PROFESSIONAL Rapid Selenium Toner, that it produces several cool chocolate-brown hues with warm-tone papers, purplish brown tones with neutral-tone papers and very little or no change with cold-tone papers, that the 1 to 20 dilution is used for print protection and the 1 to 20 or 1 to 40 dilution to increase shadow contrast and maximum density with a minimum tone change, that it may also be used with black-and-white films, and that it converts the silver image to silver selenide; the POLYMAX Fine-Art Paper curve showing increased upper-scale contrast and D-max after four minutes in Rapid Selenium Toner at 1 to 40, the paper having been developed in DEKTOL 1 to 2 at 20 degrees C for two minutes; and the statement that the visual effect of a toner depends on the toner and its dilution, the paper emulsion type, surface and stock tint, the length of the treatment and the processing of the paper. Page 2, the Tones Produced by Paper/Toner Combinations table, whose Rapid Selenium row at 1 to 20 is headed No Tone Shift and whose note records that the papers were developed in DEKTOL at 1 to 2 at 20 degrees C; Adjusting Print Exposure and Development, that Rapid Selenium Toner tends to intensify the image, that print development time may be shortened slightly, that toning a fully developed print with it yields an increased tonal scale, and that exposure and development modifications also depend on the paper emulsion type and grade; Guidelines for Print Processing, that toning cannot disguise poor print quality; the Fixing paragraph, that an exhausted fixing bath leaves insoluble silver compounds which form a dark yellow stain on meeting a toner, and that air bubbles trapped during fixing can later produce round purple stains in prints toned with selenium or sulfide toners. Page 3, that prolonged fixing lets fixer into the base and makes prints toned in selenium or sulfide toners turn yellow; the Toning paragraph, that metal trays and tanks must not be used and only unchipped enamel, hard rubber or plastic; the Drying note that drying with heat causes a shift to a cooler tone with some paper and toner combinations; and Safe Handling of Photographic Chemicals. Page 4, the Rapid Selenium Toner procedure in full - the precautionary note that the active ingredient is a sulfite salt at a concentration of less than 2 per cent, that working solutions generally contain less than one half of one per cent selenium sulfite, that these selenium concentrations are not considered hazardous when the solutions are handled under normal conditions, and the recommendation of print tongs and clean rubber gloves with immediate washing of any splash; the instruction that prints already dried are rewetted by immersion in a fixing bath and rewashed before toning, otherwise staining may occur; dilution according to the tone change wanted; immersion at 20 degrees C with agitation, complete toning in 2 to 8 minutes depending on paper type and weight; the instruction to remove the print when it has almost the required tone because toning will continue to some extent in the wash; the washing times; the KODAK Hypo Clearing Agent combination method, in which working-strength Hypo Clearing Agent dilutes the toner at 1 to 20 or 1 to 40 and eliminates the wash step between fixing and toning, with the instructions not to rinse the prints after fixing, to tone for approximately three minutes for print protection or longer for a tone change, not to reuse that Hypo Clearing Agent bath to treat untoned prints because it contains traces of toner, and to wash for at least 30 minutes in running water at 18 to 20 degrees C with frequent agitation afterwards; and the film instructions, dilution 1 to 29, four minutes at 20 degrees C with occasional agitation, a 20 to 30 minute wash, and the note that a slight increase in contrast may be noticed at 1 to 29 while higher concentrations of 1 to 3 or 1 to 9 will increase the contrast; Page 1, that Brown Toner, Sepia Toner and Sepia II Warm Toner all convert the silver image to silver sulfide, that Brown Toner may also be used on negatives and slides for long-term keeping, and that Sepia Toner gives warm brown tones on cold-tone papers or yellowish brown on warm-tone ones; page 2, Adjusting Print Exposure and Development, that the Sepia, Sepia II Warm and Brown toners reduce print densities so prints should be developed fully and made slightly darker than normal, and that the modification also depends on the paper emulsion type and grade; Guidelines for Print Processing, that toning cannot disguise poor print quality and that a good candidate has a full tonal scale with detail in highlights and shadows; the Stop Bath paragraph, that an exhausted or overconcentrated stop bath must not be used, that a stop bath left in a tray for more than three days or in a tank for more than one month may become overconcentrated by evaporation, that an overconcentrated stop bath can cause mottle in the base of a toned print, and that insufficient agitation in the first few seconds in the stop bath can also cause mottle, neither being evident until the print is toned with a selenium or sulfide toner; the Fixing paragraph, that improper fixing is probably the major cause of stains in toned prints, that two-bath fixing is recommended, that a hardening fixer is not recommended for prints intended for toning because it makes the emulsion less receptive, that an exhausted fixing bath contains insoluble silver compounds that washing cannot remove completely and that form a dark yellow stain on meeting a toner, especially in borders and highlights, and that air bubbles trapped between or under prints during fixing can later produce round purple stains in prints toned with selenium or sulfide toners; page 3, that prolonged fixing expands the paper and allows fixer into the base, which will make prints toned in selenium or sulfide toners turn yellow; the Toning paragraph, that metal trays and tanks must not be used and only unchipped enamel, hard rubber or plastic, and that a dry print is soaked for 2 to 3 minutes before toning; the Drying note that drying with heat causes a shift to a cooler tone with some paper and toner combinations; Safe Handling of Photographic Chemicals, the instruction not to discard sulfide-type toners with stop baths or fixing baths because the combination generates hydrogen sulfide gas, that hydrogen sulfide gas can fog unexposed paper and film and will oxidise unprotected silver images in negatives and prints, and that solutions are discarded individually; page 4, Brown Toner used at 30 mL in 946 mL of water, toned 15 to 20 minutes at 20 degrees Celsius or 3 to 4 minutes at 38 degrees with continuous agitation, with the instruction to wear rubber gloves and use plastic tongs because the solution is quite alkaline; page 5, that the bleach bath Solution A of the packaged sepia toners converts metallic silver to light-sensitive silver bromide, that the print may be bleached under safelight to minimise the effect of light, and that the effect is extremely small and may not be noticeable; and pages 6 and 7, the T-1a and T-7a formulas with their working instructions; Page 1, the opening list of what toning does, which states that toning converts the black-and-white silver image to an inert compound, reducing the harmful effects of intense light, ultraviolet radiation, oxidizing gases, extremes of temperature and humidity and fumes, and that all Kodak toners will protect the image whether or not they produce a color shift; Adjusting Print Exposure and Development, that Sepia, Sepia II Warm and Brown toners reduce print densities so prints are developed fully and made slightly darker than normal while Rapid Selenium Toner tends to intensify the image so print development may be shortened slightly, with the note that these modifications also depend on the paper emulsion type and grade; Guidelines for Print Processing, that toning cannot disguise poor print quality and that a good candidate has a full tonal scale with good detail in highlights and shadows; Fixing, that improper fixing is probably the major cause of stains in toned prints, that two-bath fixing gives the best results, and that a hardening fixer is not recommended for prints intended for toning because it makes the paper emulsion less receptive; Toning, that metal trays and tanks are not used for toning solutions, only unchipped enamel, hard rubber or plastic; and pages 9 to 10, Selective and Multiple Toning, for liquid or sheet frisket masking and the choice of scenes with a distinct line, for sequential toning in Sepia or Brown Toner followed by a thorough wash and then Blue Toner T-26 with red or orange appearing after approximately 15 to 30 minutes at 32 C, for cold-tone papers yielding a truer red and warm-tone papers an orange, and for the warning that multiple toning usually produces a density loss in the shadow areas so the technique starts from a print of higher-than-normal contrast; Page 1, the opening list of what a toner does, that toning converts the black-and-white silver image to an inert compound which reduces the harmful effects of intense light, ultraviolet radiation, oxidizing gases, extremes of temperature and humidity, and fumes, and that all Kodak toners will protect the image whether or not they produce a color shift; and the Rapid Selenium Toner description, that the 1 to 20 dilution is used for print protection while 1 to 20 or 1 to 40 increases shadow contrast and maximum density with a minimum tone change. Page 2, the Tones Produced by Paper/Toner Combinations table, whose last row pairs the heading No Tone Shift with Rapid Selenium at 1 to 20; Guidelines for Print Processing, that toning cannot disguise poor print quality and that a good candidate for toning is a properly exposed and processed print from a high-quality negative with a full tonal scale and detail in highlights and shadows; the Stop Bath paragraph, that an overconcentrated stop bath causes mottle in the base of a toned print and that insufficient agitation in the first seconds of the stop bath does the same, neither being evident until the print is toned in a selenium or sulfide toner; and the Fixing paragraph, that improper fixing is probably the major cause of stains in toned prints, that a hardening fixer is not recommended for prints intended for toning because it makes the emulsion less receptive, that an exhausted fixing bath leaves insoluble silver compounds which washing cannot remove and which form a dark yellow stain on meeting a toner, especially noticeable in print borders and highlights, and that air bubbles trapped between or under prints during fixing can later produce round purple stains in prints toned with selenium or sulfide toners. Page 3, that prolonged fixing lets fixer into the base and makes prints toned in selenium or sulfide toners turn yellow, and that residual silver salts and traces of hypo may cause stains, uneven tones and fading. Page 4, the instruction in the Hypo Clearing Agent combination method to tone for approximately three minutes for print protection or longer for a tone change. Page 5, Gold Protective Solution GP-1, that it provides print protection while changing the image tone only slightly; Gold Toner T-21 for warm-tone papers; Gold Protective Solution GP-1 with sodium thiocyanate; Blue Toner T-26 with thiourea and tartaric acid, toning the highlights first; KODAK PROFESSIONAL Rapid Selenium Toner, which converts the silver image to silver selenide, the 1:20 dilution for print protection, the dilutions for shadow contrast, and the paper-dependent colour; Brown Toner, Sepia Toner and Sepia II Warm Toner, all converting the silver image to silver sulfide; improper fixing as the major cause of stains in toned prints; safe handling of sulfide-type toners; Why tone a print — toning converts the silver image to an inert compound and all the toners protect the image whether or not they produce a colour shift; Sulfide toners, and the direction that they are not discarded with stop baths or fixing baths; The instruction to use the development temperature and time the paper instructions recommend in order to obtain uniform image colour; Safe handling of photographic chemicals: the instruction not to discard sulfide-type toners with stop baths or fixing baths; Rapid Selenium Toner: dilution and working temperature; tongs rather than fingers; the instruction to rewet an already dried print by immersion in a fixing bath and rewash; the four-minute wash for resin-coated paper; the warning that heat drying shifts some paper and toner combinations to a cooler tone; Stop Bath — do not use an exhausted or overconcentrated stop bath, and the statement that leaving stop bath in a tray for more than three days or a tank for more than one month may cause overconcentration by evaporation; Safe handling - sulfide-type toners are not discarded with stop baths or fixing baths because the combination generates hydrogen sulfide gas, which can fog unexposed paper and film and will oxidize unprotected silver images in negatives and prints; The instruction not to discard sulfide-type toners with stop baths or fixing baths because the combination generates hydrogen sulfide gas; The instruction not to discard sulfide-type toners with stop baths or fixing baths because the combination generates hydrogen sulfide gas; toning solutions not to be put into metal trays or tanks, unchipped enamel, hard rubber or plastic only; the four-minute wash for a resin-coated print after T-7a; Improper fixing as probably the major cause of stains in toned prints; two-bath non-hardening fixing for prints to be toned; the instruction to develop fully and print slightly darker because toners reduce density; prints kept apart and moving; toning solutions not put into metal trays or tanks; the instruction to use the paper maker’s development time and temperature in order to obtain uniform image colour; Fixing: the instruction not to exceed the capacity of the fixer; the statement that an exhausted fixing bath contains insoluble silver compounds that will remain in prints and cannot be removed completely by washing; the use of two-bath fixing for best results; Hypo Alum Sepia Toner T-1a - place the tray in a tempered water bath and heat the water to 49 degrees Celsius (120 F); immerse a thoroughly washed print, agitating occasionally and especially during the first few minutes, and tone for 12 to 15 minutes depending on paper type; do not tone for longer than 20 minutes at 49 degrees Celsius and do not use a higher temperature, because prints will blister or stain at higher temperatures; rinse in warm water and wipe with a soft sponge to remove any sediment; the toner causes a loss of print density and contrast which is compensated by increasing exposure and development; the mixing procedure, in which a black precipitate may form when the solutions are combined; Drying - dry toned fibre-base prints slowly between sheets of blotting paper or on a drying rack; set the speed and temperature of a dryer to the lowest settings; Fixing - the instruction not to exceed the capacity of the fixer, and the statement that an exhausted fixing bath contains insoluble silver compounds that will remain in prints and cannot be removed completely by washing; Toning - if prints that are already dry are toned, soak them in water for 2 to 3 minutes before toning; do not use metal trays or tanks for toning solutions; residual silver salts and traces of hypo in the paper may cause stains, uneven tones and fading; Development - use the development temperature and time recommended in the paper instructions to obtain uniform image colour; avoid contaminating the developer with other solutions and do not exceed the capacity of your developer, because developer contamination or exhaustion can cause image-colour variations; Stop bath - do not use an exhausted or over-concentrated stop bath; if stop bath is left in a tray for more than three days or in a tank for more than one month, evaporation may cause over-concentration, and an over-concentrated stop bath can cause mottle in the base of a toned print; insufficient agitation of prints, especially during the first few seconds in the stop bath, can also cause mottle, and the mottle will not be evident until the print is toned with a selenium or sulfide toner; development - use the recommended temperature and time to obtain uniform image colour; Development - to obtain uniform image colour use the development temperature and time recommended in the paper instructions, and the note that development variations are among the factors that cause toning variations; Fixing - proper agitation in the fixer is important, and stains commonly occur when prints stick together or float on the surface of the fixer; for example, air bubbles trapped between or under prints during fixing can later produce round purple stains in prints toned with selenium or sulfide toners; improper fixing is probably the major cause of stains in toned prints, and two-bath fixing is recommended; Fixing - the instruction not to exceed the capacity of the fixer, the statement that an exhausted fixing bath contains insoluble silver compounds that will remain in prints and cannot be removed completely by washing, and that when these residual silver compounds meet a toner they form a dark yellow stain especially noticeable in print borders and highlights; Mixed toners - the note that a black precipitate may form when the hypo alum solutions are combined and that it will not adversely affect the toning action of the bath if the proper toning technique is used, and the separate note that a fine white precipitate may appear in a stored solution and will not interfere with its use; Drying - dry toned fibre-base prints slowly between sheets of blotting paper or on a drying rack; remove excess water from the surface of resin-coated prints and air-dry them at room temperature or use circulated warm air; drying with heat causes a shift to a cooler tone with some paper and toner combinations, so set the speed and temperature of the dryer to the lowest settings; Toning - when toning resin-coated papers keep toning times to a minimum to prevent the solution from penetrating the edges of the papers; if resin-coated prints are toned for longer than 8 to 10 minutes, leave a large border around the image so that the edges can be trimmed off if the toner penetrates them, because it is difficult to wash toner from the edges of a print; washing - wash resin-coated papers for 4 minutes in running water with a flow sufficient to change the water completely during the wash, and Hypo Clearing Agent is not recommended with resin-coated papers; Washing - thorough washing is especially important when preparing prints for toning, because residual silver salts and traces of hypo in the paper may cause stains, uneven tones and fading; wash fibre-base prints for one hour with agitation with a complete change of water every five minutes, resin-coated papers for four minutes; agitate prints and keep them separated during washing and do not overload the wash tank; Fixing - a hardening fixer is not recommended for prints intended for toning because it makes the paper emulsion less receptive to the toner solution; Toning - do not use metal trays or tanks, and if prints are already dry soak them in water for two to three minutes before toning; prints toned after storage may show stains due to adverse storage conditions; Fixing - an exhausted fixing bath contains insoluble silver compounds that remain in prints and cannot be removed completely by washing, and when these residual silver compounds come into contact with a toner they form a dark yellow stain that is especially noticeable in print borders and highlights; two-bath fixing recommended; the warning against excessive fixing, because prolonged fixing expands the paper and allows solution to penetrate the base, and fixer trapped in the base will make prints toned in selenium or sulfide turn yellow

Used by:P29 Capstone Stage 6: Permanence, Presentation and the Finished Portfolio · P29 Capstone Stage 4: The Silver Prints · P29 Capstone Stage 5: The Toned Print and the Alternative-Process Print · P29 The Pure Silver Portfolio: The Specification · Acetic acid (glacial) · Boric acid · Chloroauric acid · Gold(III) chloride · Iron(III) chloride hexahydrate · Potassium alum · Potassium bromide · Potassium ferricyanide · Potassium persulfate · Selenium · Silver bromide · Silver selenide · Silver sulfide · Sodium selenite · Sodium selenosulfate · Sodium sulfate · Sodium sulfide · Sodium thiocyanate · Sodium thiosulfate pentahydrate · Thiourea · Steigmann gold sensitiser stock · Gold-thiocyanate toner · HARMAN SELENIUM TONER · Kodak D-76d · Kodak F-5a · Kodak GP-1 · Kodak Hypo Clearing Agent and the washing accelerator Kodak patented · Kodak T-55 · Kodak T-56 · Kodak T-52 · KODAK Rapid Selenium Toner · Kodak SB-5 · Kodak ST-1 · Kodak T-1a · Kodak T-21 · Kodak T-26 · Kodak T-7a · Moersch MT3 Variotoner · Moersch MT1 Selentoner · Rehalogenating ferricyanide-bromide bleach · Comparison matrices · Toners compared · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P3 Oxidation, Reduction and the Electron That Makes the Picture · P10 Stop Bath Formulations and the Fixer Interaction · P10 Why Stopping Works · P11 Break/Fix: The Exhausted Fixer · P11 Fixer Capacity, Exhaustion and Residual Silver · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline · P11 How Fixer Works · P12 Permanence and Image Deterioration · P12 The Physics of Washing · P12 Lab: Testing for Residual Thiosulfate and Residual Silver · P18 Break/Fix: The Print That Will Not Go Black · P18 The Structure of a Printing Paper: Base, Baryta, Emulsion and Supercoat · P19 Developing the Print Consistently and Running a Printing Session · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Part XX Overview: Toning Chemistry · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Gold, Iron-Blue and the Other Metal Toners · P20 What a Toner Actually Does to a Silver Image · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P20 Assignment: The Toned Print · P20 Toning, Permanence and What the Evidence Actually Supports · Gold toned silver gelatin print · Selenium toned silver gelatin print · Sulphide (sepia) toned silver gelatin print · Silver gelatin developing-out print on fibre base · Chemical incompatibilities · Keeping the printing session log · Residual hypo and residual silver tests · Handling a selenium toner and its waste · Stop bath preparation · Storing unfixed prints for later fixing · The student's project SOP · Handling a sulphide toner and its waste · Running a toning session · Running a two-bath fixing rotation · Blistering from an over-hot hypo alum bath · Cracked emulsion from flattening a bone-dry fibre print · Exhausted fixer · The gold toner that did nothing because the first wash was omitted · Grey highlights from developer exhaustion, as distinct from fog · Mottle revealed only after toning · Muddy print from a snatched development · Round purple spots from air bubbles trapped in the fixer · Residual silver and yellow staining · Sensitiser gone cloudy in the bottle · Drying marks and squeegee lines on prints · Toner penetration at the edges of an RC print · Uneven toning · Yellow-brown highlight stain from residual silver

aber.ac.uk

Guidance for Employers on the Control of Artificial Optical Radiation at Work Regulations 2010retrieved 2026-09-04, 2026-09-05

Sections: The guidance on artificial optical radiation at work, cited for the principle that a source capable of harming the eye or skin is enclosed or interlocked rather than managed by care, and that the assessment is made on the source rather than on the operator's intentions; The guidance on artificial optical radiation at work, cited for the principle that an ultraviolet source capable of harming the eye or skin is enclosed or interlocked rather than managed by care; List 1 and the sources that can harm if used inappropriately: Class 1M, 2 or 2M lasers as defined in BS EN 60825-1, for example low-power laser pointers; List 2 hazardous sources, which begins at Class 3B; List 1 and the intermediate list - exempt and Risk Group 1 lamps and lamp systems including LEDs among safe sources, and Risk Group 2 lamps and LED systems among the sources that are safe under normal conditions but can cause harm if placed extremely close to the eyes; and the supplier's duty under section 6 of the Health and Safety at Work etc Act 1974 to provide information for safe use; List 1, safe light sources - any exempt or Risk Group 1 lamp or lamp system, including LEDs, as defined in BS EN 62471:2008; the sources that are safe under normal conditions but have the potential to cause harm if placed extremely close to the eyes, which include any Risk Group 2 lamp or lamp system including LEDs; List 2, hazardous light sources - any Risk Group 3 lamp or lamp system including LEDs; and the statement that suppliers have a duty under section 6 of the Health and Safety at Work etc Act 1974 to provide information on managing the risk; List 2 Hazardous light sources - UV curing of inks named among sources presenting a reasonably foreseeable risk to eyes and skin; List 3 Control measures to consider - an alternative safer source, filters, screens, remote viewing, curtains, safety interlocks, dedicated rooms, remote controls and time delays, training, restricted access, personal protective equipment and safety signs, with a system for dealing with potential over-exposures; List 1 Safe light sources - any exempt or Risk Group 1 lamp or lamp system, including LEDs, as defined in BS EN 62471:2008; List 2 Hazardous light sources - UV curing of inks and any Risk Group 3 lamp or lamp system, and the placing of Risk Group 2 lamps among the sources safe under normal conditions of use but capable of harm if used inappropriately; List 3 Control measures - an alternative safer source, filters, screens, remote viewing, curtains, safety interlocks, dedicated rooms, remote controls and time delays, training, restricting access, personal protective equipment and safety signs; List 1 and the sources that can harm only if used inappropriately - Class 1M, 2 or 2M lasers as defined in BS EN 60825-1, for example low-power laser pointers; List 2 hazardous light sources, which begins at Class 3B; List 3 Control measures to consider - safety interlocks, dedicated rooms, restricted access, training, personal protective equipment and safety signs, together with a system for dealing with potential over-exposures

Used by:P29 Capstone Stage 1: The Instrument, Its Calculation and Its Commissioning · P29 Capstone Stage 5: The Toned Print and the Alternative-Process Print · P6 Making and Measuring Pinholes · P14 Build: The LED Light Source and Exposure Timer · P14 Low-Voltage Electronics for the Darkroom Builder · P16 Build: The UVA Exposure Unit · P16 Ultraviolet for the Alternative Processes: Sources, Dose, Uniformity and Hazard · Measuring a pinhole with a Class 2 laser pointer · Operating the UVA exposure unit

alternativephotography.com

A Non-Silver Manual: Palladiumretrieved 2026-09-06, 2026-09-07, 2026-09-08

Sections: Development — for the account of running an ammonium citrate bath over years, "It is expensive but is used over and over, and replenished with fresh developer to make up for volume that is lost by use. Only once in my experience has this developer expired from overuse"; for the instruction that development is almost instantaneous and need not continue longer than one minute with continuous agitation, and that the print must be covered quickly to avoid lap marks; for Dana Sullivan's suggestion of diluting the developer against lap marks, offered with no ratio; for the warning that the bath becomes contaminated with ferric oxalate leaching off the prints and that its fumes give the worker a headache, so it should be used under a fume hood or outdoors; and for the studio's switch to potassium oxalate in the fume hood from the autumn of 2003. Clearing — for the three EDTA baths of about four tablespoons to 60 oz of warm water, five minutes each, and the residual-yellow sulfite bath after them; Development, for the instruction to slip the print face up and cover the surface quickly to avoid lap marks, the reuse and replenishment of the bath over years, and the report that its fumes caused headaches and that the tray belongs under a fume hood or outdoors; The account of headaches from the fumes of a reused developer carrying dissolved ferric oxalate, and the recommendation that the tray belong under a fume hood or outdoors

Used by:Ammonium citrate developer · P25 Lab: Exposing, Developing and Clearing a Palladium Print · Running a platinum or palladium session

Platinum and palladium developers and solutionsretrieved 2026-09-06

Sections: Developers for platinum and palladium — the entry for ammonium citrate in full, "This will give you more neutral gray tones when used with Palladium that will make it look more similar to Platinum"; the ranking of the five developers by contrast and tone; the anticoagulant and poison warning against potassium oxalate; and the made-up formula the article prints for the oxalate bath alone, distilled water at 100 F 48 oz and potassium oxalate 1 lb

Used by:Ammonium citrate developer

Platinum printmaking made simpleretrieved 2026-09-06, 2026-09-07

Sections: Developing — "Dam the developer (ammonium citrate) to one end of an 8x10 tray, slip your print face up into the base of the dam, and drop the tray to the level", the print left in the developer for 30 or 40 seconds, the statement that density is determined only by exposure and that development is visible instantly, and the warning that the developer "becomes slightly toxic as it builds up"; Developing, for the dammed-tray pour, the 30 to 40 second development and the statement that density of image is determined only by exposure and not by development

Used by:Ammonium citrate developer · P25 Lab: Exposing, Developing and Clearing a Palladium Print

The palladium and platinum salts, Part 2: The Techniqueretrieved 2026-09-06, 2026-09-07

Sections: Section 11.2, Developer formulae, for the bath itself — ammonium citrate 500 gr, water at 50 C or more 1500 cc, "maintain pH at 5.5 / 6", printed under the heading "Baths to be used at temperatures between 15 C and 20 C" and alongside the same figures for sodium citrate and for potassium oxalate; and for the received view Mougin quotes and then rejects, that "the developer is considered inexhaustible and can be used infinitely". Section 11.1, for the traditional oxalate method and its one to two minutes of agitation. Section 11.3, for his own practice — 50 cc of developer for a print up to 8 by 10 inches, the pH checked and kept between 5 and 6, the developer poured rapidly onto the print and agitated regularly for one minute, "Timing is not critical and doesn't cause any increase of contrast" — and for his argument for one-shot baths, that the developer loads with palladium and with ferrous oxalate which in strong concentration "eventually veils the print in an indelible way". Section 7.3.1, Personal method #2, for moving the oxidiser out of the sensitiser and into the developer, for the two oxidisers tested — a 3 per cent hydrogen peroxide solution and a 4 per cent potassium dichromate solution — and for the table of doses per 100 cc of developer against negative density range, in which the ammonium citrate bath takes half what the potassium oxalate bath takes at every step. Sections 11.4 and 11.5, for contrast rising and tone cooling as the bath gets colder, and for palladium being workable from 7 to 100 C. Section 11.6, for the ranking of developer and oxidiser combinations by image colour on Arches Platine. Section 11.7, for the instruction that the bath must be acid at pH 5 to 6 or the paper cannot be cleared. Section 12.2, for oxalic acid preferred to hydrochloric acid in the clearing baths. Section 13, for the bicarbonate neutralisation and the ten changes of wash water; Section 11.2, Developer formulae, for the ammonium citrate developer at 500 g to 1500 cc of water at 50 C or more with the pH maintained at 5.5 to 6, and for the heading that places the citrate baths at 15 to 20 C; Section 11.3, for the one-minute development, the statement that timing is not critical and does not increase contrast, the 50 cc one-shot for a print up to 8 by 10, and the argument that the bath eventually veils the print with ferrous oxalate; Section 11.7, for the statement that an acid pH of 5 to 6 is imperative because clearing is otherwise impossible; Section 11.2, Developer formulae, for the ammonium citrate developer and for the oxidiser table giving 0 cc for a negative of density range 1.8, 0.5 cc for 1.35, 1.0 cc for 1.20 and 2.0 cc for 1.05, of a 3 per cent hydrogen peroxide solution per 100 cc of developer, with twice those doses to the potassium oxalate bath; Section 11.3, for the one-minute development at 15 to 20 C, the statement that timing is not critical and does not increase contrast, and the note that palladium is allowed from 7 to 100 C with contrast rising and tone cooling as the bath gets colder

Used by:Ammonium citrate developer · P25 Lab: Exposing, Developing and Clearing a Palladium Print · P25 Experiment: Tonal Scale, Contrast and Image Colour in Palladium

The palladium and platinum salts, Part 3: The Recipes and Bibliographyretrieved 2026-09-06

Sections: Section 5, Making Ammonium Citrate, attributed in the text to "Richard S. Sullivan: Lab notes" — 120 g of citric acid dissolved in 280 cc of water in a glass or porcelain vessel, heated until it has all dissolved, 120 cc of 20 per cent ammonia added, heated to boiling, and the pH regulated between 5 and 6 by adding either citric acid or ammonia. Section 6, Making Sodium Citrate, from the same lab notes, for the parallel preparation. Section 4, Making Potassium Oxalate, whose printed reagents are sodium carbonate and oxalic acid and therefore cannot make a potassium salt. The opening warning list, for "Ammonium and sodium citrates are moderately toxic" and "Potassium oxalate is toxic"

Used by:Ammonium citrate developer

anmol.org

Calcium Nitrate Tetrahydrate: safety data sheet, Anmol Chemicalsretrieved 2026-09-08

Sections: Section 1, Product Identification, and Section 2, Hazards Identification — read beside the sheet above and found to be the same document under a different letterhead, with the same four hazard statements and signal word, the same anhydrous EC number printed against the hydrate's CAS number, and one internal inconsistency in the eye-hazard category

Used by:Calcium nitrate tetrahydrate

archive.org

A Manual of Photographic Chemistry, Theoretical and Practical, seventh editionretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Chemical Elements and their Combinations, for the equivalent-notation formula given for starch; Theory of Photography, Positive Printing, on the two principal modes of sizing paper — starch and saponified resin on the Continent, gelatine hardened by alum in English manufacture — on the alkaline reaction of the first and the acidity of the second, on Papier Rive and the German Saxe as starch-sized papers, on the photographic properties of a paper being much affected by the mode of sizing because the picture is probably formed partly upon the albumen and partly in the sizing, and on foreign starch-sized papers giving tones that are sepia-brown after fixing and purple-black under gold, for the two reasons given — that starch does not, like gelatine, redden the picture, and that an alkaline size diminishes redness where an acid one increases it; Section I, Collodion — the solution of pyroxyline in ether and alcohol, and the use of alcohol to retard evaporation; the remark on the temperature at which ether boils; Chapter VI, Section I: the solution of pyroxyline in ether and alcohol; the qualities of commercial alcohol and rectified spirit of wine; Chapter II, Section VII: the use of alcohol to retard the evaporation of collodion in hot climates; Reducing agents: (a) Protosulphate of Iron; The reduction of salts of silver by developing agents; Photographic Chemicals, Kaolin or China Clay — its preparation by careful levigation from mouldering granite and other disintegrated felspathic rocks, its being a silicate of alumina, its perfect insolubility in water and in acids, the statement that it produces no decomposition in a solution of nitrate of silver, its employment by photographers to decolorise silver solutions browned by albumen or other organic matter, the chalk that commercial kaolin may contain, the alkalinity that chalk produces in a silver nitrate solution when salts of ammonia are present, the detection of that impurity by its effervescence with acids and its removal by washing in diluted vinegar and then water; Practice of Photography, Chapter Three, Sensitizing Albuminized Paper — the bath usable until nearly black, animal charcoal as the inferior first option, the quarter of an ounce of finely pulverised kaolin to twenty ounces of bath shaken and filtered through paper, the caution that kaolin containing carbonate of lime must be purified or the bath will become alkaline and dissolve off the albumen, and freshly precipitated curdy silver chloride as the substitute that has an affinity for the brown sub-albuminate of silver but is inferior to kaolin as a decoloriser; Vocabulary — Pyroxyline: the general formula, the series of compounds obtained by the action of mixed nitric and sulphuric acids on vegetable fibres, the four varieties A to D and their solubilities, and the statement that none prepared cold is suitable for photography; The preparation of oxygen in abundance by heating chlorate of potash with manganese dioxide; Cyanide of potassium as a fixing agent; Fixing agents for positives; Fixing agents for negatives; Potash and soda, tartrate of — the formula, the equivalent weight of 282, the commercial name and the preparation from bitartrate of potash; Cyanide of potassium as a fixing agent — the energetic solvent action on the insoluble silver salts and the stability of the double salt to dilution; Practice of Photography, Chapter Three, Section I, Preparation of Sensitive Paper — Formula I, Preparation of Albuminized Paper, and specifically the sub-heading "To render the paper sensitive", which gives nitrate of silver 90 grains and distilled water 1 ounce, the direction that the operation must be conducted by the light of a candle or by yellow light, the porcelain dish, the greasy scum of dissolved albumen that forms on the surface after the bath has been a short time in use and the marbled stains it produces unless drawn off with a folded strip of blotting-paper the exact breadth of the dish, the sheet laid on convexity downwards and centre first as for the albumen, three minutes' contact for thin paper and four or five for thick "for the decomposition", the bone forceps or wax-tipped tweezers and the white mark produced by decomposition of the nitrate of silver where a pin is replaced without draining, the strip of blotting-paper hung from the lower edge to take the last drop, and the American clips on a string for drying; the statements that follow on the same pages, that a bath prepared by the above formula "is stronger than is actually necessary" but that "paper floated on weak solutions is always more or less deficient in vigour", that the strength of the bath decreases rapidly by use so that an addition of nitrate of silver must occasionally be made, the "Silver Meter" hydrometer graduated in grains per ounce and the advice to verify its scale against a freshly prepared 90-grain solution, the warning that its indications cease to be trustworthy if the bath contains alcohol or ether, the discoloration of the solution by albumen and the statement that it may be used for sensitizing until it is nearly black, the clarification of twenty ounces of bath by shaking with a quarter of an ounce of finely pulverised kaolin and filtering through paper, the requirement that kaolin which effervesces with acids be purified by washing in dilute vinegar or the bath will become alkaline and dissolve off the albumen, the inferior alternative of shaking the bath with recently precipitated curdy chloride of silver which has an affinity for the brown sub-albuminate of silver, the diagnosis of an old printing bath that has become alkaline from the reaction of the albumen so that the coagulation is imperfect and a white precipitate falls away into the bath, the remedy of ten grains of nitrate of silver and half a drop of glacial acetic acid to each ounce, and the keeping of sensitive albumenised paper for several days if protected from light before it yellows from partial decomposition, with the preservation of the sheets by drying them in a warm place and piling them under pressure in a printing frame to exclude the air; Theory of Photography, Positive Printing — Rendering the Paper Sensitive, which gives the theoretical proportion that three parts by weight of nitrate of silver will precipitate nearly one part by weight of salt with a slight excess of the nitrate remaining, the statement that for an albumenised paper with both solutions applied by floating the nitrate bath should be about six times as strong as the salting bath and should be left twice as long in contact with the paper, the twelvefold ratio where the nitrate is brushed instead, the thirtyfold ratio where the salting is by total immersion and the sensitizing by brushing, the effect of hard and soft sizing on the concentration required, the note that a glutinous salting bath containing albumen or gelatine causes more salt to be retained on the surface so that the amount of salt must be lessened, and the chlorine equivalence of 100 grains of chloride of ammonium with 109 grains of chloride of sodium and 228 grains of chloride of barium; The Nitrate Bath, which reports the author's own graded experiment — ordinary salted and albumenised paper floated two or three minutes on twenty grains to the ounce darkens but does not reach the bronzed stage, goes very pale in hyposulphite and looks cold and slaty without depth of shadow, with pale patches most abundant at the edge uppermost in drying and nearly absent at the lower edge where the excess drains and concentrates; the same weak bath with ten or fifteen minutes of floating gives an improved result because the albumen is allowed time to draw more nitrate to itself; forty grains gives deeper shadows and a warmer colour but is scarcely strong enough for the foreign papers albumenised with a ten-grain salt solution though sufficient for the English paper of the same strength; and sixty, eighty and a hundred grains all give good pictures differing very little, with the hundred-grain bath the best if the floating is cut to a single minute, the writer's own apprehension being spottiness from uneven absorption because a lengthened floating is favourable to even precipitation of the chloride; the statements on the same pages that the printing bath need not be saturated with chloride of silver as the negative bath is with iodide, that free nitric acid in the crystals is inappreciable in its retarding effect and especially so on albumenised paper which is usually slightly alkaline, that a bath containing free oxide of silver and alkaline to litmus is injurious because alkaline nitrate of silver does not properly coagulate albumen so that a white turbidity soon appears, that the weaker the bath becomes the greater the tendency to dissolve away the albumen without coagulating it so that the silver chloride formed is not retained on the surface and falls into the solution, that papers sensitised on a bath faintly acid with nitric or acetic acid are less liable to spontaneous reduction in the dark whereas papers prepared on a bath which has become alkaline soon change on keeping, that acetate of silver in a printing bath gives only a little extra bronzing in the shadows and increased difficulty of keeping the paper, that even a bath highly coloured by albumen acts nearly the same as at first, and that the brown coloration is probably a sub-albuminate of silver partially soluble in solution of nitrate of silver; the account of ammonio-nitrate of silver which increases sensitiveness and intensity and improves the colour but does not coagulate albumen, so that albumenised paper floated upon it loses its surface varnish and appears dead like plain paper; the sensitometric passages that highly salted and sensitized papers darken rapidly and pass completely into the bronze stage while papers containing less chloride darken more slowly, that a print on paper highly salted and sensitized is vigorous with great contrast, and that a print on weakly sensitized paper is unusually red after fixing and brown or mulberry when toned; and Formula I's own salting bath of chloride of ammonium 200 grains, water 5 fluid ounces and albumen 15 fluid ounces with its float of one minute and a half, together with Formula II, the plain paper, which is "sensitized on the same solution of Nitrate of Silver as the albuminized paper", and Formula III, the ammonio-nitrate paper, which "is always prepared without Albumen, which is dissolved by Ammonio-Nitrate of Silver"; Practice of Photography, Chapter Three, Section I, Preparation of Sensitive Paper — Formula I, Preparation of Albuminized Paper, and specifically the sentence that when pure albumen is used without water from 5 to 8 grains of salt to each ounce will be sufficient, that the less the quantity of salt the warmer the colour but that it must not be so far reduced as to injure the contrast and depth of shadow, the yield of about one fluid ounce of albumen per egg, the beating to a perfect froth with a bundle of quills or a fork, the skimming and subsidence, the warning that albumen not thoroughly beaten leaves flakes of animal membrane that streak the paper, the settling in a tall narrow jar and decanting of the clear upper portion, the observation that albuminous liquids are too glutinous to run through a paper filter and are better cleared by subsidence, the statement that albumen alone without any addition of water gives a more highly varnished appearance, the streaky lines that bronze under light and the single steady movement that avoids them, the ox-gall or spirituous solution of bile used to wet papers the albumen will not take, and the note that chloride of barium is contra-indicated under alkaline gold toning because the carbonate of soda would throw down carbonate of baryta in the paper; Theory of Photography, Positive Printing — the statement that albumen is not a neutral fluid but possesses an alkaline reaction due to a small quantity of soda, so that on adding chloride of ammonium to albumen a development of free ammonia takes place easily perceptible to the smell, that ammonia is a solvent of the materials used in sizing paper, and the account of deliberate evaporation of albumen in an open vessel until it becomes more limpid with a rather offensive odour and an acid reaction to litmus, which then runs on the paper easily and does not dissolve the size, together with the note that the sulfur of albumen passes into sulphuretted hydrogen during putrefaction and that the nitrate bath is soon rendered turbid by the use of stale albuminized paper; Practice of Photography, Chapter Three, The Practical Details of Photographic Printing, Section I, Positive Printing by the direct action of Light — Preparation of Sensitive Paper, which names three formulae, the Albuminized, the plain and the Ammonio-Nitrate; Formula I, Preparation of Albuminized Paper, giving chloride of ammonium 200 grains, water 5 fluid ounces and albumen 15 fluid ounces, the note that chloride of barium is sometimes used in salting paper instead of chloride of ammonium and is contra-indicated when the alkaline gold-toning process is adopted because the carbonate of soda would throw down carbonate of baryta in the paper, the statement that with pure albumen and no water from 5 to 8 grains of salt to each ounce will be sufficient, that the less the quantity of salt the warmer the colour but that it must not be so far reduced as to injure the contrast and depth of shadow, that each egg yields about one fluid ounce of albumen, the beating to a perfect froth with a bundle of quills or a fork, the skimming of the froth into a flat dish to subside, the warning that unbeaten albumen leaves flakes of animal membrane that streak the paper, the transfer of the partially subsided froth to a tall narrow jar for several hours so that membranous shreds settle, the decanting of the clear upper portion, the observation that albuminous liquids are too glutinous to run through a paper filter and are better cleared by subsidence, the alternative of shaking the salted mixture of albumen and water in a bottle for ten or fifteen minutes until it loses its glutinosity, the statement that albumen alone without any addition of water gives a more highly varnished appearance, the difficulty of streaky lines that bronze under light and the single steady movement that avoids them, the ox-gall or spirituous solution of bile formerly used and the author's replacement of it by two drachms of spirits of wine previously diluted with water to prevent coagulation to each four ounces of albumen, the finding that each quarter-sheet of 11 by 9 inches removes one fluid drachm and a half from the bath equivalent to about one grain and three quarters of salt including droppings while a quarter-sheet of plain paper takes up only one drachm so that the glutinous nature of the albumen causes a third part more of salt to be retained, the Rive and Saxe rawstocks and their different capacity for gloss, the tray filled to a depth of half an inch, the sheet bowed convexity downwards and lowered centre first, one side only wetted, one minute and a half of floating, the replacement of a sheet showing circular bubble spots for the same time again, the warning that the paper must not rest on the salting bath much longer because the solution of albumen being alkaline tends to remove the size from the paper and to sink in too deeply thus losing its surface gloss, the statement that albuminized paper will keep a long time in a dry place, that pressing with a heated iron to coagulate the layer is unnecessary because coagulation is perfectly effected by the nitrate of silver used in sensitizing, the bone spatula and the avoidance of rolling; the sensitizing solution of nitrate of silver 90 grains to 1 ounce of distilled water, the greasy scum of dissolved albumen removed with a strip of blotting-paper, three minutes for thin and four or five for thick paper, the statement that a bath prepared by that formula is stronger than is actually necessary but that paper floated on weak solutions is always more or less deficient in vigour, the discoloration of the bath by albumen and its clarification with kaolin or with recently precipitated chloride of silver which has an affinity for the brown sub-albuminate of silver, and the caution that kaolin containing carbonate of lime must be purified or the bath will become alkaline and dissolve off the albumen; Formula II, Preparation of Plain Paper — chloride of ammonium 200 grains, citrate of soda 200 grains, gelatine 20 grains, water 20 ounces, one minute of floating, sensitized on the same silver solution as the albuminized paper, and the doubt whether salted papers containing tartrate and citrate keep well because in the presence of moisture these organic salts become mouldy and absorb oxygen from the air; Formula III, Ammonio-Nitrate Paper, which is always prepared without albumen because albumen is dissolved by ammonio-nitrate of silver; Theory of Photography, Positive Printing — the pyroxyline half-sheet experiment and the conclusion that the function of the chloride is to impart sensitiveness, that of the nitrate of silver to give intensity, and that the organic matter acts by brightening the colour, so that organic compounds of silver produced by adding albumen or similar substances to the salting bath afford the warm red tone capable of yielding a full brown or black with gold and without which the picture will lack richness of effect; the passage on sizing, that papers sized with starch and saponified resin necessarily have an alkaline reaction while gelatine-sized papers are acid from the alum, that the general impression is that starch offers more mechanical advantages when albumen is to be used in the salting solution whereas gelatine gives a better surface layer of chloride of silver in plain salted paper, that Papier Rive takes a high gloss on the albumen and the more porous Saxe does not, that too strongly sized paper gives considerable gloss but prints that tone and fix with difficulty; the passage that albumen is not a neutral fluid but possesses an alkaline reaction due to the presence of a small quantity of soda, so that on adding chloride of ammonium to albumen a development of free ammonia takes place easily perceptible to the smell, and that ammonia is a solvent of the materials used in sizing paper; the account of deliberate evaporation of albumen in an open vessel until it becomes more limpid with a rather offensive odour and an acid reaction to litmus, which runs on the paper easily and does not dissolve the size, the sulfur of albumen passing into sulphuretted hydrogen during putrefaction, and the statement that the nitrate bath is soon rendered turbid by the use of stale albuminized paper and the sensitiveness to light injured; and the ranking that the reddening action of gelatine, although greater than that of starch, is less than that produced by albumen, and that the surface brilliancy is also less; Cyanide of Potassium as a Fixing Agent, pages 169 and 170 — potassium cyanide as the salt most frequently employed in fixing, sodium cyanide answering equally well, the commercial salt occurring as fused lumps contaminated with a large percentage of carbonate of potash amounting in some cases to more than half its weight, its absorption of moisture from the air, the decomposition of its solution on keeping with a change of colour and the odour of prussic acid, the statement that it is highly poisonous and must be used with caution, its description as a most energetic agent in dissolving the insoluble silver salts far more so than hyposulphite of soda, the preceding paragraph on hyposulphite of soda in which one part by weight of iodide of silver requires about twenty-four parts by weight of hyposulphite of soda in a cold solution, the conversion of the salts into cyanide existing in solution as a soluble double salt which unlike the double sulphocyanide is not decomposed by dilution with water, the statement that it is not adapted for fixing positive proofs upon chloride of silver, the attack on the image where the solution is not tolerably dilute by superficial conversion into cyanide of silver and then dissolution as a double cyanide of potassium and silver, and the increase of its solvent power on metallic silver by the addition of a little iodine to give what has been termed iodo-cyanide of potassium; The Fixing Solution, page 397, giving cyanide of potassium 10 grains and common water 1 ounce for glass positives, with the statement that the percentage of carbonate of potash in commercial cyanide is so variable that no exact directions can be given for the formula, the preference for a dilute solution such that the plate is cleared gradually in from half a minute to a minute, the slow decomposition of the solution on keeping while usually retaining its solvent power for several weeks, and the vertical bath adopted to escape the pungent odour with the warning that plates must then be carefully washed before fixing because the iron salts decompose the cyanide and produce a blue deposit; page 405, fixing solution No. 2 for negatives, cyanide of potassium 15 grains and common water 1 ounce, with the statement that it cannot be employed with safety on an iodised film developed with pyrogallic acid only because of its great tendency to weaken the half-tones, that it may be used for a bromo-iodised plate developed with iron, and that it need not be thrown away till it ceases to dissolve the iodide readily; Fixing Agents for Negatives, on cyanide lowering the intensity of a negative and whitening it by conversion into cyanide of silver, especially in strong light; the apparatus and chemicals list for negative portraiture, listing cyanide of potassium for cleaning fingers and fixing; Copying Engravings and Paintings, on cyanide weakening the half-tones even in very dilute proportions if allowed to remain on the plate, and on hyposulphite of soda being better than cyanide in all cases where albumen is employed; Appendix, Removal of Silver Stains from the Hands, Linen, etc., on removing the black stains by rubbing them with a moistened lump of cyanide of potassium and leaving it on the hands for a little time, and the energetic stain remover of cyanide of potassium 100 grains, iodine 10 grains and water 1 ounce; Appendix, paragraph g, on treating a solution of cyanide of potassium for silver recovery by diluting it largely with water and adding sulphide of potassium until no further precipitation of black sulphide ensues; "The Strengthening of the Daguerreotype Image by means of Hyposulphite of Gold", for the attribution to Fizeau subsequent to the original discovery of the process, for the plate placed on a levelling-stand after removal of the unaltered iodide of silver and covered with a solution of hyposulphite of gold containing about one part of the salt in 500 parts of water, for the flame of a spirit-lamp applied until the liquid begins to boil, for the image becoming whiter and acquiring great force, for the argument that this proves metallic mercury enters into its composition since a plain silver surface such as a collodion image is darkened by hyposulphite of gold, and for the delicate crust of metallic gold gradually forming on the surrounding silver. Also the Vocabulary entry on the thionic series, for tetrathionate of soda becoming milky within days from deposition of sulphur, for hyposulphite of soda increasing that instability so that a solution begins shortly to deposit sulphur and turns acid to test-paper, and for the statement that perchloride of iron, chloride of copper and chloride of gold decompose hyposulphite of soda and form tetrathionate among other products. Also the section on gold toning of paper prints, for the finding that the improvement of colour was due partly to a deposit of gold and partly to a communication of sulphur, since adding chloride of gold to hyposulphite of soda gives not only the double hyposulphite of gold and soda known as sel d'or but also a portion of the unstable tetrathionate of soda, so that the action of the bath is complex from the first and more so on keeping; and for the practice that followed, in which the two solutions are no longer mixed. Also the section on the fading of prints, for an old hyposulphite fixing bath becoming a toning bath without any addition of gold; Theory of Photography, Positive Printing — on papers sized with starch and saponified resin necessarily having an alkaline reaction while gelatine-sized papers are acid from the alum, on the general impression that starch offers more mechanical advantages where albumen is to be used in the salting solution whereas gelatine gives a better surface layer of chloride of silver in plain salted paper, on Papier Rive and the German Saxe as starch-sized papers, on the photographic properties of a paper being much affected by the mode of sizing because the picture is formed partly upon the albumen and partly in the sizing, on English gelatine-sized papers tending to red tones that become brown or chocolate in the finished print, on foreign papers sized with starch or resin producing tones that are sepia-brown after fixing and purple-black when treated with solution of gold, and on the two reasons given for that difference — that starch and resin do not, like gelatine, exert a marked action in reddening the picture, and that the sizing has an alkaline reaction while alkalies diminish redness and acids increase it; the passage that the reddening action of gelatine, although greater than that of starch, is less than that produced by albumen, and that the surface brilliancy is also less; the observation that a foreign starch-sized paper salted with a mixed citrate and chloride gives an agreeable effect in gold toning; and the note under the Calotype that with a foreign starch-paper, unless re-sized with some organic substance, the solutions sink in too deeply and the picture wants clearness and definition; Fixing — potassium cyanide as the salt most frequently employed, described as a most energetic agent in dissolving the insoluble silver salts, far more so than hyposulphite of soda, forming a soluble double salt that is not decomposed by dilution with water, and, four sentences later, as highly poisonous and to be used with caution; the warning that too strong a solution or too long an immersion whitens and then dissolves the middle tints; and Section I, Collodion, on the solution of pyroxyline in ether and alcohol; Cyanide of potassium as a fixing agent, pages 169 to 170 - that it is the salt most frequently employed in fixing, that the commercial salt occurs as fused lumps usually contaminated with a large percentage of carbonate of potash, and that it is a most energetic agent in dissolving the insoluble silver salts; Cyanide of potassium as a fixing agent, pages 169 to 170 — that potassium cyanide is the salt most frequently employed in fixing and that sodium cyanide will answer equally well; that the commercial salt occurs as fused lumps usually contaminated with a large percentage of carbonate of potash, in some cases more than half its weight; that it absorbs moisture from the air, that it is very soluble but that the solution decomposes on keeping, changing colour and evolving the odour of prussic acid; that it is highly poisonous and must be used with caution; that its solution is a most energetic agent in dissolving the insoluble silver salts, far more so than the hyposulphite of soda, the salts being converted into cyanide and existing in solution as a soluble double salt which, unlike the double sulphocyanide, is not decomposed by dilution with water; that unless the solution is tolerably dilute it attacks the image, converting it superficially into cyanide of silver and then dissolving that as a double cyanide of potassium and silver; and that the solvent power of cyanide on metallic silver is much increased by adding a little iodine, giving the colourless liquid termed iodo-cyanide of potassium. Also the sulphocyanides as fixing agents, immediately following. Also the outfit list under Apparatus and chemicals, around page 449, for the photographer going out to work, whose entries include "cyanide of potassium for cleaning fingers and fixing", eight ounces of glacial acetic acid, half an ounce of citric acid, four ounces of ether and alcohol mixed, and one pound of hyposulphite of soda; Comparative Sensitiveness and keeping qualities of Dry Plates, for the comparative sensitiveness of wet and dry collodion having been variously estimated at from four to forty times in favour of the former, for the two reasons Hardwich gives for the discrepancy, and for his own working comparison of twenty seconds for an ordinary wet collodion against two minutes and a half for a tannin-preserved dry plate, with the note that he has made faster dry plates only by losing intensity. General Observations on Dry Collodion Processes, for the sensitive and insensitive forms of silver iodide and their mutual conversion by soluble iodide and by nitrate of silver. Preservative Processes, for the object of the preservative and dry processes being to maintain sensitiveness after excitation, for the free nitrate of silver on a drying plate becoming concentrated by evaporation and eating away the iodide of silver to leave transparent spots, and for the statement that in proportion as the quantity of free nitrate is large, both sensitiveness and intensity are increased while the keeping qualities of the plates are diminished. Fixing, for cyanide of potassium being a most energetic agent in dissolving the insoluble silver salts, far more so than hyposulphite of soda, and for the double cyanide not being decomposed by dilution with water; Potassium cyanide as a fixing agent for collodion positives and the whiter picture it gives; the instability of hyposulphite for that purpose; Potassium cyanide as a fixing agent for collodion positives and the whiter picture it gives; Collodion — the use of alcohol to retard evaporation; the varieties of pyroxyline and their solubility; potassium cyanide as a fixing agent and its dangers to the image

Used by:Arrowroot · Diethyl ether · Ethanol · Iron(II) sulfate, anhydrous · Iron(II) sulfate heptahydrate · Kaolin · Nitrocellulose · Potassium chlorate · Potassium cyanide · Potassium sodium tartrate tetrahydrate · Sodium cyanide · Albumen sensitising solution · Albumen solution with its chloride · Albumenised salting solution · Cyanide fixing and toning · Fizeau's gilding solution · Arrowroot salting solution · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Assignment: Assessing a Historical Process for Hazard · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · Ambrotype · Tintype (ferrotype) · Wet-plate collodion negative

A Manual of Photography, 4th editionretrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: Section II, The Chromatype — the sulphate of copper and bichromate of potash sensitiser; The Calotype — Talbot's gallo-nitrate of silver; io-gallic paper; the twenty-six-to-one gallic acid and silver nitrate wash; On the paper used in photography — china clay much used by paper manufacturers to add weight and to give a smooth surface to the finer varieties, the note that the finest clays would not be likely to do much mischief in photographic papers but that the less pure Cornish clays contain the oxides of iron and other metals in a state of very fine division, and that where these come to the surface they form little centres of action from which dark circles spread; History of Photography, Section II — The Chromatype, for the process founded on Ponton's, one drachm of sulphate of copper in an ounce of distilled water with half an ounce of saturated bichromate of potash, the development with nitrate of silver, and Mr Bingham's remark that if sulphate of nickel is substituted for the sulphate of copper the paper is more sensitive and the picture is more clearly developed by nitrate of silver; and the General Summary table, which lists nitrate and iodide of nickel against Hunt and 1844; Section V, Fixing the Daguerreotype Image, for the process "as described by M. Fizeau, to whom we are indebted for its introduction" — eight grains of chloride of gold in sixteen ounces of water and thirty-two grains of hyposulphite of soda in four ounces, the gold poured into the soda a little at a time with agitation, the mixture at first slightly yellow becoming perfectly limpid, the liquid then containing a double hyposulphite of soda and gold; for the washing precautions, the drops of alcohol on the still iodised surface, the basin of water and the hyposulphite solution changed for each experiment at about one part of salt to fifteen of water; for the plate on a support, covered with the salt of gold and heated with a strong spirit-lamp, brightening and becoming of great force in a minute or two; for the translation of Fizeau's own explanation of the silver darkened by the film of gold and the mercury increased in solidity and brightness by its union with the gold; and for the washing apparatus of a narrow trough of distilled water heated by a spirit-lamp, the plate drawn out slowly and dried by blowing; History of Photography, section II, The Calotype, which reprints Talbot's specification with the two solutions; section III, Improvements in Calotype, for the nine claims of the second patent, including the hot hyposulphite bath, the warm iron behind the paper in the camera, io-gallic paper, and the twenty-six parts of saturated gallic acid to one of the usual silver solution; Pictures on Porcelain Tablets, for the third patent's albumenised porcelain sensitised with gallo-nitrate and for the alcoholic solution of gallo-nitrate of silver washed over a warm steel plate; and Practice of Photography, Mr Cundell's calotype process, reprinted from the Philosophical Magazine of May 1844 — the nitrate of silver at fifty grains to the ounce of distilled water with one-sixth part of its volume of glacial acetic acid, the saturated gallic acid, the judgement that "for many purposes these solutions are unnecessarily strong, and, unless skilfully handled, they are apt to stain or embrown the paper", the recommendation that they "may with advantage be diluted to half the strength", the gallic acid solution keeping "not more than a few days", the mixed gallo-nitrate that "speedily changes, and will not keep for more than a few minutes", the mixing in equal volumes by a graduated drachm tube, the five or ten seconds of contact at the exciting stage, the twenty-four hours' keeping of the excited sheet, the bringing-out with radiant heat from an iron held within an inch or two, and the warning that if the paper dries before the gallo-nitrate is washed off "the lights sink and become opaque"; Section II, Chrysotype, in the chapter on the history of photography, which reprints Articles 212, 213 and 218 verbatim and adds no quantity to any of them; Chapter II, "Heliography. The process of M. Niepce", for the same passage reprinted a third time, thirteen years after the first, with glass added beside plated silver as a support and with no quantity added to the varnish; Section I, Talbot's photogenic drawing, pages 18 to 20, which prints the same passage of Talbot's own words again and adds his statement that the half-second valuation is to be understood of the paper then used for taking objects by means of the solar microscope; Section I: Mr Ponton's process (bichromate of potash); History: the cost of bichromate of potash against silver nitrate

Used by:Copper(II) sulfate · Gallic acid · Kaolin · Nickel(II) sulfate · Fizeau's gilding solution · Talbot's gallo-nitrate of silver · Herschel's argentotype · Niépce's bitumen heliograph coating · Talbot's photogenic drawing paper · P1 1839 and the Many Inventors of Photography · P4 Silver and the Silver Ion · Photoglyphic engraving

A Popular Treatise on the Art of Photography, including Daguerreotype, and all the new methods of producing pictures by the chemical agency of lightretrieved 2026-09-04, 2026-09-06

Sections: Processes on metallic and glass tablets, I: Heliography — Niépce's own directions in Hunt's translation, and the account of the plate being developed with a solvent and afterwards etched with acid; Processes on metallic and glass tablets — Niepce darkening the silver by iodine in a box, and Hunt's remark that it appears to have led the way to Daguerre's process; Processes on metallic and glass tablets, I: Heliography — Niépce's own directions in Hunt's translation, in which essential oil of lavender is both the vehicle for the bitumen and, mixed with a petroleum distillate, the developing solvent; Miscellaneous processes — the action of bichloride of mercury on darkened photographic papers; Daguerreotype, "Methods of fixing the Daguerreotype Pictures", for the object of the operation given as a more perfect adhesion of the mercury and silver, for about fifteen grains of chloride of gold in a pint of pure water and thrice that quantity of hyposulphite of soda in a like quantity of water, the former poured into the latter with stirring, the liquor at first slightly yellow becoming perfectly limpid, and the product read as a double hyposulphite of soda and gold; for the plate washed in alcohol and water, placed on an iron frame, covered with the solution and heated by a powerful lamp until the impression acquires great force in a few minutes; and for the statement that the picture, when the operation is well performed, will bear rubbing with the finger; "Processes on metallic and glass tablets, I: Heliography", for Hunt's printing of the same directions, for his own note that the English oil of lavender is too expensive and that redrawn French oil answers as well, for his statement of the exposures — six to eight hours in the camera obscura and four to six hours for a copy of an engraving — and for his account of the iodine blackening as the step that "appears to have led the way to Daguerre's beautiful process"; Processes on metallic and glass tablets, I: Heliography; Processes on metallic and glass tablets, I: Heliography — Robert Hunt's translation of Niepce's own directions, including the saturation of powdered bitumen with essential oil of lavender, the warming until the oil has taken up the colouring matter, the application cold to a highly polished plate with a roll of soft skin, the drying on gently heated iron, the solvent development in a mixture of oil of lavender and oil of white petroleum, the watching of the plate by reflected light as the forms unfold, and the subsequent etching of the bared metal with acid

Used by:Bitumen of Judea · Iodine · Oil of lavender · Mercury(II) chloride · Fizeau's gilding solution · Niépce's bitumen heliograph coating · P1 Niepce and Heliography: Light That Hardens · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · Heliography on bitumen of Judea

An Account of some recent Improvements in Photography, in Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London, volume 4retrieved 2026-09-04, 2026-09-06

Sections: The preparation of Calotype paper — solutions A and B, the gallo-nitrate of silver, and the sensitiveness and development of the paper; Pages 312 to 315, which are the whole of the published account. In particular: the liquid prepared by dissolving 100 grains of crystallized nitrate of silver in two ounces of distilled water and adding to it one-sixth of its volume of strong acetic acid, called A; the saturated solution of crystallized gallic acid in cold distilled water, called B, of which "the quantity dissolved is very small"; the instruction to mix A and B in equal volumes "but only mix a small quantity of them at a time, because the mixture does not keep long without spoiling", and the naming of that mixture the gallo-nitrate of silver; the washing of the iodised sheet on the marked side by candlelight, the half minute's rest, the dip into water, the blotting and the cautious drying at a distance from the fire; the option of using the paper moist; the three months in a press against the recommendation to use it within a few hours; the tincture of galls diluted with water offered as a substitute for B and judged not altogether so satisfactory; the sensitivity "which transcends a hundred times or more that of any kind of photographic paper hitherto described" and the one second of dull winter daylight that leaves a latent and invisible impression; development by washing once more with the gallo-nitrate and warming gently before the fire, the exposed part darkening in a few seconds, the weaker impression brought out by repeating the wash and the stronger needing no heat and appearing in a minute or two; the artist watching the picture develop and stopping it with the fixing liquid; the revival of a faded negative by another wash of gallo-nitrate and a warming, with details appearing that had never been seen; and experiments 1 to 4, including the finding that the lesser quantity of gallo-nitrate darkens the paper more than the greater and that the fastest darkening is at the moment the sheet becomes nearly dry; Preparation of the Paper, pages 312 to 313, which is the whole of the published iodising procedure: the sheet of the best writing paper of smooth surface and close and even texture; the instruction to cut off the watermark lest it injure the appearance of the picture; 100 grains of crystallized nitrate of silver dissolved in six ounces of distilled water, washed on with a soft brush on one side only and that side marked; the cautious drying at a distant fire or spontaneous drying in a dark room; the dip, when dry or nearly so, into a solution of iodide of potassium containing 500 grains of that salt dissolved in one pint of water, staying two or three minutes; the dip into a vessel of water, the light drying with blotting-paper and the finish at a fire "which will not injure it even if held pretty near"; the statement that all this is best done in the evening by candlelight; the naming of the result as iodized paper "because it has a uniform pale yellow coating of iodide of silver"; that it is "scarcely sensitive to light" but ought nevertheless to be kept in a portfolio or a drawer until wanted; and that "it may be kept for any length of time without spoiling or undergoing any change, if protected from the light". Also, for what happens on either side of this page: the gallo-nitrate of silver made by mixing equal volumes of an aceto-nitrate stock with saturated gallic acid; the three months in a press against the recommendation to use the excited sheet within a few hours; the claim of a sensitivity transcending a hundred times any photographic paper hitherto described; the bromide of potassium fixing at 100 grains in eight or ten ounces of water; and experiment 4, in which the dry paper "receives a virtual instead of an actual impression"; Preparation of the paper; Use of the paper; The fixing process; the five closing experiments; The gallo-nitrate of silver and the passage on the latent and invisible impression

Used by:Gallic acid · Talbot's gallo-nitrate of silver · Talbot's calotype iodised paper · P1 Talbot: Photogenic Drawing, the Calotype and the Negative-Positive Principle · P4 The Latent Image · Calotype negative

An Account of the Processes employed in Photogenic Drawing, in a Letter to Samuel H. Christie, Esq., Sec. R.S., in The London and Edinburgh Philosophical Magazine and Journal of Science, third series, volume 14, number 88retrieved 2026-09-06

Sections: Preparation of the paper, for the opposite arrangement of the same two reagents in the earlier process — the dip into a weak salt solution first and the strong silver solution second — and Method of fixing the images, for the dilute iodide of potassium that was Talbot's first preserving process and for his warning that too strong a solution attacks the dark parts; The whole of the letter to Samuel H. Christie of 21 February 1839, pages 209 to 211: the choice of paper of good firm quality and smooth surface, with superfine writing paper named as the best he knows; the dip into a weak solution of common salt and the wiping dry, "by which the salt is uniformly distributed throughout its substance"; the solution of nitrate of silver spread on one surface only and dried at the fire, that solution "not saturated, but six or eight times diluted with water"; the statement that there is a certain proportion between the quantity of salt and the quantity of the silver solution which answers best and gives the maximum effect, and that augmenting the salt beyond that point diminishes the effect and in certain cases makes it exceedingly small; the alternate washings with saturated salt and with a liberal quantity of the silver solution, drying between times, by which he raised the sensibility to what the camera obscura required; the spontaneous darkening that shows the attempt has been carried too far and the numbered-strip test in a very weak diffused light for a quarter of an hour by which he chose the sheet to put in the camera; and both fixing methods — iodide of potassium much diluted with water, with the warning that too strong a solution attacks the dark parts of the picture, and the immersion in a strong solution of common salt followed by wiping and drying, with the pale lilac tint the highlights then take in the sun and the pale primrose yellow of the iodide-fixed highlights that turns a full gaudy yellow at the heat of a fire and recovers on cooling; Sections 1 to 11 of the paper read 31 January 1839, pages 196 to 208: the 1834 origin of the work and the quotation of Davy on Wedgwood's failure with the camera obscura; the ground colours the process could give — sky-blue, yellow, rose-colour, brown of various shades and black, with green absent — and the note that the blue variety is subject to no spontaneous change and requires no preserving process; the preserving process and the specimens exposed an hour to full summer sun without injury; the distinction between the paper he first used and the far more sensitive "Sensitive Paper"; a quarter of an hour under the solar microscope, at seventeen linear diameters; half a second as his nearest evaluation of a full-sunshine exposure on that paper; an hour or two in a large box camera at a hundred yards from a building and half an hour in the small cameras of the summer of 1835; half an hour to copy an engraving through thick paper; the unpreserved images that stayed perfect for a year or two while others grew quite dark in a tenth of that time; and the large white insensible spots of very definite outline that appeared where the preparation had failed, which Talbot read as a case of unstable equilibrium between two definite chemical compounds

Used by:Talbot's calotype iodised paper · Talbot's photogenic drawing paper · Talbot's photogenic drawing paper

Bericht uber dioptrische Untersuchungen (Fortsetzung), in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften, Mathematisch-Naturwissenschaftliche Classe, volume 26retrieved 2026-09-04, 2026-09-05

Sections: Sitzungsberichte volume 26, pp. 39-41 — the diffraction patch D = A.lambda/p, the summed blur D = 2p + A.lambda/p, and the minimisation giving p = sqrt(A.lambda/2), that is a diameter of 1.41 sqrt(f.lambda); Sitzungsberichte volume 26, pp. 39-41: the diffraction patch, the summed blur D = 2p + A.lambda/p, and its minimum; Sitzungsberichte volume 26, pp. 39-41: the diffraction patch D = A.lambda/p, the summed blur D = 2p + A.lambda/p, the minimisation giving p = sqrt(A.lambda/2) and D = 2.sqrt(2.A.lambda), the worked case A = 11 Zoll, and the one-minute-of-arc viewing criterion; Sitzungsberichte volume 26, pp. 40-41: the blur spot of about half a Linie, the one-minute-of-arc viewing criterion, and the comparison of a glassless camera obscura with a 3-inch portrait objective; Sitzungsberichte volume 26, pp. 40-41 - the one-minute-of-arc viewing criterion, used here only to convert a viewing distance into the finest detail the unaided eye can resolve at it; Sitzungsberichte volume 26, pp. 39-41 - the summed blur D = 2p + A.lambda/p and its minimisation

Used by:P29 Capstone Stage 1: The Instrument, Its Calculation and Its Commissioning · P6 Part VI Overview: Build a Pinhole Camera · P6 Diffraction and the Optimum Pinhole · P6 Pinhole Geometry: Blur, Focal Distance, Field of View and Falloff · P19 Reading the Negative and Making the Work Print · Geometric softness from an oversized hole

Cassell's Cyclopaedia of Photographyretrieved 2026-09-06, 2026-09-07

Sections: Kaolin — the synonyms china clay and white bole, the description as a native hydrated aluminium silicate which when prepared is a white powder used for clearing the silver bath, in the production of matt-surface paper, added to emulsions for the same purpose and in the manufacture of crayons; Paper, for kaolin among the silicate fillings used to render paper more opaque and give it a greater glaze while lessening its strength; China Clay, for the cross-reference; "Nickel", for an entry that is entirely about the electro-deposition of the metal in the graphic arts and mentions no photographic chemistry at all; "Cobalt, Printing with", for the pale rose cobalt ferrocyanide image and the statement that treatment with an iron salt gives a blue image and a nickel salt a red one; the printing-paper emulsion formulae, for the note that adding a small quantity of the chloride of uranium, of nickel or of cobalt shortens the scale of gradation but that calcium chromate is more satisfactory; "Hunt, Robert", for the list of metals whose salts he experimented with; "Burnisher" and "Rolling Press", for the polished nickel rollers; and the table of elements, giving Ni an atomic weight of 59; Silver Oxalate — the formula, the molecular weight of 304, the statement that it is practically insoluble in water and alcohol and soluble in nitric acid, the description as a white crystalline powder obtained by adding an alkaline oxalate to silver nitrate, and the verdict that it has been suggested for printing-out emulsions but is rarely used; Silver Oxide, for the neighbouring entry whose figures are compared here; Monochromatic Light, for the isolation of a single Fraunhofer line from the spectrum of a metal or gas "such as thallium, which gives a single isolated line at λ 5348"; Spectrometer, for photographing the lithium, sodium, thallium and blue strontium lines onto a panchromatic plate to make an interpolation chart of wavelength against distance, with a yellow or green screen for the thallium line; and the table of elements, giving Tl an atomic weight of 204; Ferrotype — the plate washed for a few seconds and then fixed with potassium cyanide, which should be kept in a saturated solution and for use diluted with double its volume of water, the note that hypo can be used instead but does not work so quickly and takes longer to wash out, the one minute of washing after cyanide against five minutes after hypo, and the reducer of iodine dissolved in methylated spirit with saturated potassium cyanide added until the red colour disappears; Potassium Sulphocyanide, page 436, giving the synonyms potassium thiocyanate, sulphocyanate or rhodanide, the formula KCNS and the statement that it is chiefly used in the sulphocyanide toning bath; Cyanides, on cyanide of potassium being the most important and highly poisonous, and on double cyanides being regarded with extreme caution because simple cyanides may readily be produced from them; Pound, page 437, for the statement that formulae are made up by apothecaries' weight, in which a pound is 5,760 grains or 12 ounces; Toning, Systematic, for the ammonium sulphocyanide and gold chloride bath; and Eburneum Process, for a collodion transparency fixed with cyanide, well washed, and toned with gold; Daguerreotype, for the treatment of the picture with a solution of gold and sodium hyposulphite which brought out the details with greater force and brilliancy, for the attribution to Fizeau of Paris in 1840, and for the quantities given there — 7 grains of gold chloride in 10 ounces of distilled water mixed with a solution of 30 grains of sodium hyposulphite in 4 ounces of water. Also, in the same article, the shadows represented by the polished silver and the lights by the adhering and very delicate film of mercury which, if fingered in any way, would be wiped off; The entry ARGENTOTYPE, "A name for bromide paper, and widely used in the early days of the bromide process", and the entry BROMO-ARGENTOTYPE; Kallitype, pages 314 and 315 — the statement that the instructions given are "practically those originally published by Nichol", the sensitiser table, the making-up procedure and the oxalic acid ceiling of 5 to 10 grains, the printing to a bluish brown on a yellow ground, the four developers with their tones, the fifteen to thirty minutes of development, the passage direct into the fixing bath without washing, the fixing bath itself, the ten-minute fixing and twenty-minute wash, the withdrawal of the commercial paper over permanence, the weak ammonia fixer, the after-treatments and the Modified, American and single-solution kallitypes; Ferric Oxalate, page 238, for Fe2(C2O4)3, molecular weight 376, the greenish glistening scales, the statement that it is the most light-sensitive of the iron salts, and the normal platinotype iron solution of 20 per cent ferric oxalate with about 1.2 per cent oxalic acid; Ferric Salts, Printing with, pages 238 and 239, for Eder's table of comparative light sensitiveness, Abney's statement of their spectral sensitiveness, and the description of kallitype as the brown-line copying process; Cerio Printing, page 111, for the commercial name. Quantities read from the page images of the Getty Research Institute scan, not from its optical character recognition; Poisons and their antidotes, the table attributed to J. V. Elsden and reprinted from the British Journal of Photography Almanac — the potassium cyanide row, giving 3 grains as fatal when taken internally, the characteristic symptoms as insensibility, slow gasping respiration, dilated pupils and spasmodic closure of the jaws, and the antidote as "no certain remedy; cold affusion over the head and neck most efficacious", with a second row for the salt applied to wounds and abrasions of the skin whose characteristic symptom is a smarting sensation and whose remedy is sulphate of iron applied immediately; and Dr R. J. Hillier's commentary that a doctor should first be sent for and that unprofessional treatment should seldom go beyond an emetic. Poisons, sale of, attributed to E. J. Wall and reprinted from the Photographic Dealer — that under the Pharmacy Act 1868 "cyanide of potassium and all metallic cyanides and their preparations" is an item in Part 1 of the schedule, so that it may be sold only to a purchaser known to the seller or introduced by somebody known to the seller, with the date, name, address, article, quantity and purpose entered and attested by the purchaser's signature and the vessel labelled with the article, the word Poison and the seller's name and address; that it is an open question whether the term includes the ferri-, ferro- and sulphocyanides but that as a matter of fact these are held not to be scheduled poisons; and the recommendation that ferro-, ferri- and sulphocyanides, bichromates, pyro and preparations of copper, uranium and cerium be labelled Poison anyway. Also the entry on destroying the photographic basis of a print worked over in ink, which specifies a mixture of iodine and potassium cyanide, "both of which are poisonous", as the best rapid non-staining solvent of the silver image; Carbon Process — the credit to Poitevin's patent of 13 December 1855, Pouncy's of 10 April 1858, the modifications of Burnett in 1858 and Fargier in 1860, Swan's 1864 patenting of carbon tissue, Johnson in 1869 and Sawyer's flexible support in 1874; the statement that the process depends on the fact that gelatine with a suitable proportion of an alkaline bichromate becomes insoluble when exposed to light but retains its solubility if kept in the dark; that no visible image is produced by exposure so that the exposure must be timed or gauged by an actinometer, with the comparison that tissue sensitised in H. W. Bennett's bath requires about half the exposure necessary for printing-out silver paper to the full depth necessary for toning; that the exposed film must be developed from the back because the whole of the face has been rendered insoluble excepting the extreme high-lights while all the surface in contact with the paper has remained soluble, that the film is so thick that the strongest shadow does not penetrate right through, and that any attempt to develop the film on its original paper would result in its floating right off as soon as the soluble gelatine commenced to dissolve; the purpose of the safe edge; and the account of double transfer and of the reversed negative that obviates it. Carbon Tissue — that it is stout paper thickly coated with soft soluble gelatine and finely ground colour, that the film must be appreciably thicker than the depth of the strongest shadow so that a thin layer of soluble gelatine remains between the insoluble shadow and the paper, that tissue was prepared in two forms, sensitive and insensitive, and that in process work the photogravure process is solely worked with a carbon resist developed on the copper plate. Continuing Action of Light — that the action occurs only in the carbon and kindred processes, that the process of rendering insoluble once begun by exposure to light continues after the print is taken from the frame even if stored in a perfectly dark place so that a partially exposed print may be completed by it, that it is very slow and uncertain, that it depends on the presence of dampness in the air and is much more rapid in wet weather than in dry, and that it may be entirely prevented by storing the print in an absolutely dry receptacle such as a calcium tube. Ammonium Bichromate — its formula and molecular weight, its use for sensitising carbon tissue, gum bichromate and some photo-mechanical processes because it has a stronger sensitising power and is more soluble than the potassium salt and in carbon printing gives richer pictures, its use with fish-glue for half-tone images on zinc and copper, and the report that it is said to be more than twice as sensitive to light as potassium bichromate. Gum-bichromate Process — that it depends on principles first laid down by Poitevin in 1855, that the bichromated colloid becomes more or less insoluble in proportion to the light action, that a print may be obtained with a single coating but that it is usual to re-coat, print and develop again almost indefinitely either to reinforce parts of the image or to print in more than one colour, that the paper must be well sized so the pigment lies on the surface, that the experienced gum worker frequently evolves his own formula, that the image is not visible so an actinometer or a piece of printing-out paper must be exposed alongside, that development is a soak in cold water in which the worker exercises control by laving, spraying, sponging or brushing, that the difficulty of registration for a second coating is compounded by the expansion and contraction of the paper, that the finished print is soaked in potash alum to remove the bichromate stain, and the closing judgement that the very existence of these variable elements precludes the possibility, even if it were desirable, of laying down any hard and fast rules for working the process. Bichromate Disease — described as a skin disease affecting some workers who use potassium bichromate extensively, said to occur only when the skin is particularly sensitive and the hands are brought much into contact with the bichromate dry or dissolved, taking the form of small ulcers or an irritating rash, with rubber gloves or finger-stalls given as the preventive and a nitrate of mercury ointment advised for very severe cases; Wothly's Process, or Wothlytype — a process of printing-out, patented by Wothly in 1864, in which the sensitive salts were a mixture of the nitrates of uranium and silver dissolved in collodion, the prints being washed after insolation with acetic or hydrochloric acid and then toned with gold chloride, and the statement that the process was practically the immediate predecessor of collodio-chloride printing-out papers. Mercuro-Uranotype — a printing process described as practically obsolete in which uranic salts are employed, they being sensitive to light, using solutions of uranium chloride and mercuric chloride, the print toned by floating on a very weak solution of gold chloride or potassium chloroplatinite, immersed in very dilute hydrochloric acid and finally washed in plain water. Uranotype — that prints made by the uranium, mercuro-uranotype and platino-uranotype processes are known as uranotypes; Wothly's Process, or Wothlytype — the 1864 patent, the nitrates of uranium and silver in collodion, the acid wash after insolation and the gold chloride toning, and the judgement that it was practically the immediate predecessor of collodio-chloride printing-out papers; Mercuro-Uranotype; Uranotype, for the term being a collective name covering the uranium, mercuro-uranotype and platino-uranotype processes

Used by:Kaolin · Nickel(II) sulfate · Silver(I) oxalate · Thallium(I) sulfate · Cyanide fixing and toning · Fizeau's gilding solution · Herschel's argentotype · Nicol's kallitype · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · P26 Uranium, Mercury and the Heavy-Metal Treatments · Uranotype and Wothlytype

Chemical Observations and Experiments on Air and Fireretrieved 2026-09-04, 2026-09-06

Sections: Experiment III, sections 63 to 66: silver solution precipitated by sal ammoniac, and the black powder redissolved and reprecipitated as horn silver; Section 63, Experiment III: horn silver blackened in sunlight, the ammonia digestion and the black residue; Section 60, "Proofs of the Existence of an Inflammable Principle in Light", for the statement that it is well known that the solution of silver in acid of nitre poured on a piece of chalk and exposed to the beams of the sun grows black, that the light of the sun reflected from a white wall has the same effect though more slowly, that heat without light has no effect on this mixture, and for the question "Should the black colour not be real silver?"; and section 61 for the burning-glass reduction of silver earth and Scheele's argument from it; Sections 60 to 66

Used by:Ammonium chloride · Silver chloride · Schulze's scotophorus mixture · P1 Niepce and Heliography: Light That Hardens · P1 Silver Salts and Light: Schulze to Ritter · P1 Wedgwood, Davy and the Problem of Permanence

Chemicals and Formulae, 3rd edition (one of a series of Kodak photographic handbooks)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: TEST FOR HYPO — process with the batch an unexposed white sheet of photographic paper of the same weight and size as the majority of prints in the batch, cut off a strip after the final wash and immerse it in a 1 per cent silver nitrate solution for about three minutes, rinse it and compare it while wet, in subdued light, with the wet untreated portion; no colour difference means the hypo has been completely removed and a yellow-brown tint indicates its presence; and the caution that silver nitrate solution stains the skin black; Kodak formula D-76, the metric column per 1000 c.c. — metol 2.0 g, sodium sulphite anhydrous 100.0 g, hydroquinone 5.0 g, borax 2.0 g, water to make 1000 c.c.; Making up solutions, for the order of dissolving, the rule for Elon and the anhydrous-versus-crystalline note, and the warning in capitals that the avoirdupois and metric columns are not exact equivalents; and Keeping properties and useful life of solutions, giving 24 hours in a dish, 1 month in a tank, 6 months in a full stoppered gallon bottle and 2 months half full; TEST FOR HYPO — an unexposed white sheet processed with the batch, a strip cut off after the final wash and immersed in a 1 per cent silver nitrate solution for about three minutes, rinsed and compared while wet in subdued light with the wet untreated portion; no colour difference meaning the hypo has been completely removed and a yellow-brown tint indicating its presence; and the caution that silver nitrate solution stains the skin black; Keeping properties and useful life of solutions — the capacity rows for D-72 diluted 1 to 1 and 1 to 2 on negatives, the absence of any print capacity row for D-72 while the same table carries print rows for D-158 and D-163, and the 24-hour figure for made-up developer standing in a dish; Kodak formula D-76 — the metric column, per 1000 c.c.: metol 2.0 g, sodium sulphite 100.0 g anhydrous, hydroquinone 5.0 g and borax 2.0 g, water to make 1000 c.c.; TEST FOR HYPO — a strip of an unexposed white sheet processed with the batch and immersed after the final wash in a 1 per cent silver nitrate solution for about three minutes, rinsed and compared while wet in subdued light with the wet untreated portion, no colour difference meaning the hypo has been completely removed and a yellow-brown tint indicating its presence; Some other 'Kodak' preparations — K.A.F. 'Kodak' Anti-Fog Powder; Formulae SB-1 and SB-1A, acid stop baths; F-5 tropical acid hardening fixing bath; F-53 liquid hardener; Notes on some of the Chemicals mentioned in this Handbook — 'Dolmi'; Kodak Formula D-170, 'Dolmi' developer for bromide papers; Kodak formula R-1, the persulphate reducer for reducing density and contrast of negative materials, page 30, metric column reading water 1000 c.c., ammonium persulphate 60.0 gm. and sulphuric acid (concentrated) 3 c.c., with the direction to take 1 part stock solution and 2 parts water and to immerse the negative in an acid fixing bath for a few minutes when reduction is complete; Kodak formula R-5, the proportional reducer for lowering contrast of negatives, page 32, Stock Solution B reading ammonium persulphate 30.0 gm. and water to make 1000 c.c., with the direction to take 1 part of A to 3 parts of B and the recommendation that distilled water or water free from iron be used in making up the stock solutions; Weights and Measures - Conversion Tables, on the avoirdupois and metric columns not being exact equivalents; Notes on some of the chemicals mentioned in this handbook, and the list of chemicals stocked, searched for ascorbate, which does not appear; Formulae: Kodak formula D-76 and Kodak formula D-76R replenisher; Fixing baths: Kodak formula F-5, tropical acid hardening fixing bath; Some "Kodak" Tested Chemicals; Notes on some of the chemicals mentioned in this handbook — 'Kodurol'; the list of chemicals stocked; Notes on some of the chemicals mentioned in this handbook ('Elon'); Making up solutions; Formula D-173; Formula D-173, an 'Elon'-free developer for 'Velox' paper; Kodak formula R-8, the modified Belitzsky reducer, a single-solution cutting reducer for tank use, page 32, metric column reading ferric chloride 25.0 gm., potassium citrate 75.0 gm., sodium sulphite (cryst.) 60.0 gm. or anhydrous 30.0 gm., citric acid 20.0 gm., sodium thiosulphate (hypo) 200.0 gm. and water to make 1000 c.c., with the instruction to dissolve the chemicals in the order given, to use full strength for maximum rate of reduction, to treat negatives 1 to 10 minutes at 65-70 °F (18-20 °C) and then wash thoroughly, and to dilute 1 part of solution with 1 part of water if a slower action is desired; and the statement that it is specially suitable for the treatment of dense negatives, by lowering the contrast and clearing the shadows; Kodak formula R-2, the permanganate reducer for reducing density of negative materials without loss of contrast, pages 30 to 31, Stock Solution A reading potassium permanganate 52.5 gm. and water to make 1000 c.c. and Stock Solution B reading cold water 1000 c.c. and sulphuric acid (concentrated) 32 c.c. added very gradually to the water with constant stirring, with the working dilution of 1 part A, 2 parts B and 64 parts water, the 2 per cent sodium bisulphite bath to remove the stain, the instruction to wash the negative thoroughly before treatment to avoid an iridescent irremovable scum, and the statement that the stock solutions keep well but the mixture should be used immediately; Kodak formula R-5, page 32, Stock Solution A reading potassium permanganate 0.3 gm. with 16 c.c. of 10 per cent sulphuric acid and water to make 1000 c.c.; Kodak formula HT-1a, the hypo test solution for checking thoroughness of washing, page 29, reading potassium permanganate 1.2 gm., sodium hydroxide 2.4 gm. and water (distilled) to make 1000 c.c., with the instruction to add 1 c.c. of it to 250 c.c. of pure water, the colour sequence violet to orange in about 30 seconds and then to yellow, and the note that oxidisable organic matter in the water reacts with the permanganate in a similar manner to hypo so that a comparison test should be made on a sample of the same water; Kodak formula R-1, the persulphate reducer, which specifies the ammonium salt; Kodak formula DK-20, the extra fine grain developer, and its replenisher DK-20R; Notes on some of the chemicals mentioned in this handbook — 'pyro is 1:2:3 trihydroxybenzene, also known as pyrogallol or pyrogallic acid'; Making up solutions; Making up solutions — sodium carbonate, anhydrous and crystals; Making up solutions - sodium carbonate, anhydrous and crystals; Some 'Kodak' tested chemicals — Calgon (sod. hexametaphosphate); Notes on some of the chemicals mentioned in this handbook: 'Kodalk'; 'Kodalk' developer formulae; formulas DK-15, DK-20, DK-20R and DK-50; Notes on some of the chemicals mentioned in this handbook: 'Kodalk'; 'Kodalk' developer formulae; formulas DK-15, DK-20, DK-20R and DK-50; Kodak formula F-5; Making up solutions - the rule that Elon is dissolved first because it is readily soluble in warm water but only slightly soluble in sulphite solutions without alkali; Storage of developer solutions - developers particularly susceptible to aerial oxidation divided into two or three solutions with the developing agent kept separate from the alkali, and the warning that a precipitate formed in the cold often contains the most important constituents; Kodak formula SB-4, chrome alum hardening bath for use in tropical processing, metric column, reading potassium chrome alum 30 g, sodium sulphate crystalline 140 g or anhydrous 60 g, and water to 1000 c.c., for use at 75 to 95 degrees F, with the directions 'Agitate negatives for 30 to 45 seconds when they are first immersed, to avoid unevenness, and leave them for 3 minutes', the capacity statement 'After the equivalent of twenty 10x8 in. films per gallon have been treated, the bath should be replaced, otherwise scum markings will result', and the keeping statement 'The freshly-made bath is a violet-blue colour and keeps indefinitely while unused. A partially used bath deteriorates on standing for a few days, the colour changing to a yellow-green'; Kodak formula SB-3, the plain chrome alum hardening bath, potassium chrome alum 30 g per litre of water, with the direction 'Agitate the negative for a few seconds immediately after immersion. Maximum hardening takes 3-5 minutes in a fresh bath'; Kodak formula SH-1, the formalin hardener, formalin 10 c.c. and sodium carbonate crystalline 13.5 g or anhydrous 5.0 g to 1000 c.c., three minutes followed by a rinse and five minutes in a fresh acid fixing bath, recommended for the treatment of negatives when the emulsion would otherwise be softened considerably by chemical treatments; Kodak formula F-16, the chrome alum acid hardening fixing bath, whose solution B is water 500 c.c., potassium chrome alum 60 g and concentrated sulphuric acid 8 c.c. made to 1000 c.c., one part of B stirred rapidly into three parts of A, to be used the same day because 'it rapidly loses its hardening properties, with or without use'; Kodak formula F-5 and the acid-hardener stock F-53 with their potassium alum; and Making up solutions, on the order of dissolving an acid hardening fixing bath and the statement that the preparation of baths containing chrome alum as the hardening agent is even more critical; Kodak formula SB-1, acid stop bath for papers, plates and films, 17 c.c. of glacial acetic acid in 1000 c.c. of water, with prints rinsed for 5 seconds; the useful-life row giving SB-1 90 sheets of 8 by 10 inches per 160 fl.oz. and indefinite keeping in a stoppered bottle; Kodak formula F-52, non-hardening acid fixing bath, metric column; and the Table of keeping properties and useful life of solutions, F-52 row, for its dish, tank and bottle lives and its 60-sheet capacity per 160 imperial fluid ounces; Kodak formula T-55, page 40 under TONERS — the stock solution of sodium sulphite, selenium powder and ammonium chloride, the instruction to boil until the selenium is completely dissolved, the dilution of 1 part stock to 5 parts water, 10 to 15 minutes at 65 degrees F (18 degrees C), and the footnote that the toner was also available as Kodak Selenium Toner; Kodak formula F-5, the tropical acid hardening fixing bath — 240 g of crystalline hypo, 15 g of anhydrous sodium sulphite, 17 mL of glacial acetic acid, 7.5 g of boric acid and 15 g of potassium alum to a litre, with its ten-minute fixing time and the keeping properties table, quoted here only for the comparison with the bought product; Kodak formula D-1, page 8, headed 'Normal-contrast pyro-soda dish or tank developer for plates and films', metric column — Stock Solution A: sodium bisulphite 9.8 gm., pyro 60.0 gm., potassium bromide 1.1 gm. (or 11 c.c. of a 10% solution), water to make 1000 c.c.; Stock Solution B: sodium sulphite, crystals 210 gm. (or anhydrous 105 gm.), water to make 1000 c.c.; Stock Solution C: sodium carbonate, crystals 200 gm. (or anhydrous 75 gm.), water to make 1000 c.c.; 'Dissolve the chemicals in the order given'; 'For Dish Development — Take 1 part A, 1 part B, 1 part C and 7 parts of water. Develop for 5 to 7 minutes 65 F. (18 C.)'; 'For Tank Development — Take 1 part A, 1 part B, 1 part C and 11 parts of water. Develop for about 12 minutes at 65 F. (18 C.)'; Making up solutions, on dissolving the constituents in the order given, on the preservative being dissolved first where there is no Elon, on sodium bisulphite being added with the sulphite, on potassium bromide having no action on the developing agents so that its position is immaterial, and on anhydrous sodium carbonate being recommended with crystals used at two and a half times the quantity; Storage of developer solutions, on the tightly corked bottle, on small bottles against large, on glass stoppers sticking, on developers particularly susceptible to aerial oxidation being divided into two or three solutions with the developing agent kept separate from the alkali, and on a precipitate from a cold stock containing the most important constituents; Keeping properties and useful life of solutions, D-1 row — 30 min. in a dish, 3 hr. in a tank, 1 month in a full stoppered gallon bottle and 2 weeks half full, both 'in 3 solutions', and 12 sheets of 8 by 10 inches in a narrow dish and 24 in a deep tank per 160 fl.oz.; Notes on some of the chemicals mentioned in this handbook, that pyro is 1:2:3 trihydroxybenzene, also known as pyrogallol or pyrogallic acid; the weights and measures warning that the avoirdupois and metric columns are not exact equivalents and that one or the other must be used exclusively; Kodak formula D-156 and its metric column, per 1000 c.c., with its dilution and its approximate development time; the list of Kodak packed developers, which describes D-156 as a normal contrast developer for Bromesko and Kodura paper giving an image of medium warm tone, and D-166 as giving warmer tones than D-156; Making up solutions; Keeping properties and useful life of solutions, whose useful-life entry for this formula is a sentence rather than a number; Kodak formula D-158 and its metric column, per 1000 c.c., with its dilution and the three development times for Velox, Kodaline films and Kodaline papers; the list of Kodak packed developers, which describes D-158 as a normal developer for Velox paper giving a blue-black image tone; Making up solutions; Keeping properties and useful life of solutions; Kodak formula D-163 and its metric column, per 1000 c.c., with its four sets of dilution and development instructions and the time-temperature chart for Kodak papers printed beneath it; the list of Kodak packed developers, which describes D-163 as a universal developer for papers giving normal or high contrast, suitable also as a dish developer for negative materials and recommended for tropical use; Making up solutions; Keeping properties and useful life of solutions; the weights and measures warning; Kodak formula D-165 and its metric column, per 1000 c.c., with its dilution and its three development times for P.300 plates, B.40 and bromide paper; Making up solutions, the rule that Elon is dissolved first and that potassium bromide may be added at any stage; Keeping properties and useful life of solutions, which carries no row for this formula; Kodak formula D-166 and its metric column, per 1000 c.c., with its dilution, its development time, its emergence time and its statement that the warmth of image tone may be varied by changing the dilution with the development time unchanged; the note that the developer sold in liquid form is double the strength of the stock made up to this formula; the list of Kodak packed developers, which describes D-166 as giving warmer tones than D-156; Keeping properties and useful life of solutions; Making up solutions; Kodak formula D-167, pyro-'Elon' staining developer for rapid dish development of press and commercial negatives giving high contrast and speed, page 18, metric column, Solution A reading 'Elon' 5.0 gm., potassium metabisulphite 10.0 gm., pyro 15.0 gm. and water to make 1000 c.c., Solution B reading sodium carbonate (cryst.) 200.0 gm. or anhydrous 75.0 gm. and water to make 1000 c.c., with the directions to dissolve the chemicals in the order given, to take 1 part of Solution A and 1 part of Solution B, that 'oxidation is very rapid and therefore solutions A and B should not be mixed until immediately before use', and to develop for 2 to 3 minutes at 65 F. (18 C.); Notes on some of the chemicals mentioned in this handbook, that pyro is 1:2:3 trihydroxybenzene, also known as pyrogallol or pyrogallic acid, and that 'Elon' is a specially purified form of monomethyl paraminophenol sulphate; Making up solutions, on dissolving the constituents in the order given, on the Elon being dissolved first because it is readily soluble in warm water but only slightly soluble in sulphite solutions without alkali, on the sulphite following the Elon and the other developing agents following that with the alkali last, and on the recommendation of anhydrous sodium carbonate with crystals used at two and a half times the quantity; Storage of developer solutions, on developers particularly susceptible to aerial oxidation being divided into two or three solutions with the developing agent kept separate from the alkali, and on stock being kept in small bottles because the air space in a large bottle increases each time it is opened; Keeping properties and useful life of solutions, D-167 row, giving 3 months in a full stoppered bottle and 2 months half full, both in 2 solutions, and 12 sheets of 8 by 10 inches per 160 fl.oz. in a narrow dish and 24 in a deep tank; the weights and measures warning that the avoirdupois and metric columns are not exact equivalents; Kodak formula D-170, the Dolmi developer for bromide papers, its metric column, its two-step make-up and its development time; Some Kodak Tested Chemicals, which gives Dolmi as pure diaminophenol hydrochloride; the list of Kodak packed developers, which describes D-170 as a developer for bromide papers and an alternative to D-163; Keeping properties and useful life of solutions; Kodak formula D-173 and its metric column, per 1000 c.c., with its heading naming metol dermatitis, its dilution and its development time; Making up solutions, which gives the general rule that the preservative is dissolved first, then the developing agents, then the alkali, and that potassium bromide may be added at any stage; Keeping properties and useful life of solutions; Kodak formula D-177, pyro-soda dish developer for general use with plates and films, page 19, metric column, Solution A described as a stock solution for storage and reading potassium metabisulphite 1.4 gm., pyro 12.5 gm., potassium bromide 1.7 gm. and water to make 150 c.c., Solution B reading Solution A 150 c.c. and water to make 1000 c.c., Solution C reading sodium sulphite (cryst.) 100.0 gm. or anhydrous 50.0 gm., sodium carbonate (cryst.) 100.0 gm. or anhydrous 37.5 gm. and water to make 1000 c.c., with the directions to dissolve the chemicals in the order given, 'For negatives of average contrast, use equal parts of Solutions B and C', 'For portraits and softer negatives, use equal parts of Solutions B and C and 2 parts of water' and 'Develop for 5-8 minutes at 65 F. (18 C.)', and the footnote that it is available as a Kodak Packed Developer Powder; the list of Kodak packed developers, which describes 'Kodak' Pyro-Soda Developer Powder D-177 as a pyro-soda dish developer for plates and films; Notes on some of the chemicals mentioned in this handbook, that pyro is 1:2:3 trihydroxybenzene, also known as pyrogallol or pyrogallic acid; Making up solutions, on dissolving the constituents in the order given and on the preservative being dissolved first where there is no Elon, and on the recommendation of anhydrous sodium carbonate with crystals used at two and a half times the quantity; Storage of developer solutions, on developers particularly susceptible to aerial oxidation being divided into two or three solutions with the developing agent kept separate from the alkali, and on stock being best kept in small bottles; Keeping properties and useful life of solutions, D-177 row, giving 30 minutes in a dish, 3 hours in a tank, 1 month in a full stoppered bottle and 2 weeks half full both in 3 solutions, and 12 sheets of 8 by 10 inches per 160 fl.oz. in a narrow dish and 24 in a deep tank; Kodak formula D-1, the normal-contrast pyro-soda dish or tank developer, for comparison; the weights and measures warning that the avoirdupois and metric columns are not exact equivalents; Kodak formula D-72, whose anhydrous parentheticals establish which salt the 1928 tables mean; Kodak formula D-19b, the later revision; Making up solutions; Kodak formula D-19b and its metric column, with its description, its dilution note and its development times; Making up solutions - the order of dissolving and the anhydrous-to-crystalline carbonate factor; Measurement of small quantities - the 10 per cent solution rule and the objection to drops; Keeping properties and useful life of solutions; Some Kodak packed developers; Kodak formula D-19bR and its metric column, with its dissolving instruction and its constant-level instruction; Making up solutions - the order of dissolving and the anhydrous-to-crystalline carbonate factor; Keeping properties and useful life of solutions; Some Kodak packed developers; Kodak formula D-23 and its metric column; Making up solutions - the order of dissolving and the rule for Elon; Keeping properties and useful life of solutions; Storage of developer solutions; Kodak formula D-25 and its metric column, with the exposure warning and the development time; Making up solutions - the instruction that sodium bisulphite is added with the sulphite; Keeping properties and useful life of solutions; Kodak formula D-25R and its metric column; Notes on some of the chemicals mentioned in this handbook - Kodalk; Keeping properties and useful life of solutions; Storage of developer solutions; Kodak formula D-32, hydroquinone caustic-soda dish developer for warm black tones on lantern slides, page 12, metric column, Stock Solution A reading sodium sulphite crystals 12.6 gm or anhydrous 6.3 gm, hydroquinone 7.0 gm, potassium bromide 3.5 gm or 35 c.c. of a 10 per cent solution, citric acid 0.7 gm and water to make 1000 c.c., Stock Solution B reading sodium carbonate crystals 81.0 gm or anhydrous 30.0 gm, sodium hydroxide (caustic soda) 4.2 gm and cold water to make 1000 c.c., with the directions to dissolve the chemicals in the order given, 'For use take I part A, I part B. For still warmer tones I part A and 2 parts B' and 'Develop for about 6 minutes at 65 F. (18 C.)'; Making up solutions, on dissolving the constituents in the order given, on the preservative being dissolved first where there is no Elon, and on the recommendation of anhydrous sodium carbonate with crystals used at two and a half times the quantity; Measurement of small quantities, on quantities under 10 grains or 0.7 gram being expressed preferably as a 10 per cent solution to avoid the uncertainty of drop counting; Storage of developer solutions, on developers particularly susceptible to aerial oxidation being divided into two or three solutions with the developing agent kept separate from the alkali; Keeping properties and useful life of solutions, D-32 row, giving 2 hours in a dish, N.R. in a tank, 2 months in a full stoppered bottle and 2 weeks half full both in 2 solutions, and 18 sheets of 8 by 10 inches per 160 fl.oz. in a narrow dish; the weights and measures warning that the avoirdupois and metric columns are not exact equivalents; Making up solutions, for the general rule that Elon is dissolved first and the alkali last and that potassium bromide may be added at any stage; the note that Kodak sodium carbonate anhydrous is recommended where a formula specifies carbonate; Kodak formula D-170, the Dolmi developer for bromide papers, which keeps the developing agent out of the stock solution; Some Kodak Tested Chemicals, giving Dolmi as pure diaminophenol hydrochloride; Keeping properties and useful life of solutions; Making up solutions, for the general rule that Elon is dissolved first and the alkali last, and the explicit statement that potassium bromide has no action on the developing agents so it is immaterial at what stage it is added; Kodak formula D-72 and its metric column, per 1000 c.c.; Making up solutions, the order of dissolving, the rule for Elon and the note that potassium bromide may be added at any stage; the anhydrous against crystalline advice and the 2 and a half times rule for carbonate crystals; the weights and measures warning that the two columns are not exact equivalents; Keeping properties and useful life of solutions; Kodak formula D-76 and its metric column; Making up solutions — the order of dissolving, the rule for Elon and the anhydrous-versus-crystalline note; Keeping properties and useful life of solutions; Some Kodak packed developers; Making up solutions - the order of dissolving, the rule for Elon, the note that potassium bromide may be added at any stage, and the recommendation of the anhydrous sulphite; Weights and measures, the capitalised warning that the two columns are not exact equivalents; Kodak formula D-76 and its metric column; Keeping properties and useful life of solutions; Kodak formula D-76R and its metric column; the instruction to use it without dilution until 25 per cent of the original developer has been replaced; Keeping properties and useful life of solutions; Some Kodak packed developers; Kodak formula D-8, single-solution hydroquinone caustic developer for maximum contrast on process materials, metric column, reading sodium sulphite crystals 180.0 gm or anhydrous 90.0 gm, hydroquinone 45.0 gm, sodium hydroxide (caustic soda) 37.5 gm, potassium bromide 30.0 gm and water to make 1000 c.c., with the directions to dissolve in the order given, to take 2 parts of stock solution and 1 part of water and to develop for 2 to 5 minutes at 70 degrees F, and the footnote that it is available as Kodak Maximum Contrast Developer Powder; Keeping properties and useful life of solutions, D-8 row, giving 4 hours in a dish, 2 months in a full stoppered bottle and 1 month half full; Storage of developer solutions, on developers particularly susceptible to aerial oxidation being divided into two or three solutions with the developing agent kept separate from the alkali; Kodak formula DK-20 and its metric column, with its description, its development time and its note on the replenisher; Notes on some of the chemicals mentioned in this handbook - Kodalk; Making up solutions; Keeping properties and useful life of solutions; Some Kodak packed developers; Kodak formula DK-20R and its metric column, with the 25 per cent replacement limit and the deep-tank rate of about 5 gallons per 1000 rolls; Weights and measures - British fluid measure to metric measure; Keeping properties and useful life of solutions; Kodak formula DK-50 and its metric column, with its description, its note on varying the Kodalk and its development time; Notes on some of the chemicals mentioned in this handbook - Kodalk; Making up solutions; Keeping properties and useful life of solutions; Making up solutions, on the hardener stock being added to the hypo solution slowly with vigorous stirring with both solutions cold; the storage advice that stock solutions are best kept in small bottles because the air space in a large one increases each time it is opened; the note that acid hardener stock solutions stored for several weeks tend to form a white incrustation of basic aluminium acetate on the inside of the container which should be ignored; Kodak formula F-52, headed non-hardening acid fixing bath for use when hardening is not desired, or must be avoided, e.g. with Transferotype and Bromoil papers, metric column reading sodium thiosulphate 250.0 g, potassium metabisulphite 25.0 g and water to make 1000 c.c.; Table of keeping properties and useful life of solutions, F-52 row; Kodak formula F-5, tropical acid hardening fixing bath for films and plates, metric column, with the instruction to dissolve the chemicals in the order given and the note that films and plates fix properly in 10 minutes in a freshly prepared bath while prolonged immersion at high temperatures is harmful; Making up solutions, on the order hypo, sulphite, acid, alum and on adding a separately made hardener slowly to cold hypo with vigorous stirring; the weights and measures warning that the avoirdupois and metric columns are not exact equivalents; Table of keeping properties and useful life of solutions, F-5 row; Kodak formula F-52, non-hardening acid fixing bath for use when hardening is not desired or must be avoided, metric column, with the footnote that Kodak Rapid Acid Fixer is available in powder form as an alternative to mixing it; Table of keeping properties and useful life of solutions, F-52 row, and its two temperature footnotes; Kodak formula F-53, acid-hardener stock solution required in Kodak formulae F-54 and F-54a, metric column, with the four-step mixing directions naming 250 c.c. of warm water at about 52 degrees C for the sulphite, the slow addition of the acetic acid with constant stirring, 500 c.c. of hot water for the alum cooled below 20 degrees C before it is added, and the make-up to 1000 c.c. with cold water; the note that Kodak Liquid Hardener as sold is two and a half times stronger than F-53; the footnote offering Kodak Hardening Powder and Kodak Liquid Hardener as alternatives; Making up solutions, on adding a separately made hardener slowly to the hypo solution with vigorous stirring with both solutions cold; Table of keeping properties and useful life of solutions, F-53 row; the weights and measures warning that the two columns are not exact equivalents; Kodak formula F-54, acid hardening fixing bath for paper, metric column, reading 500 c.c. warm water and 250 g sodium thiosulphate, and to this when cold 50 c.c. of Kodak Liquid Hardener or 125 c.c. of acid hardener stock solution formula F-53, water to make 1000 c.c.; Kodak formula F-54a, acid hardening fixing bath for films and plates, reading 500 c.c. warm water, 400 g sodium thiosulphate and 75 c.c. of Kodak Liquid Hardener or 185 c.c. of F-53; the footnotes offering Kodak Acid Fixing Salt with Hardener in powder form; the note under F-53 that Kodak Liquid Hardener as sold is two and a half times stronger than F-53; Making up solutions, on adding a separately made hardener slowly to the hypo solution with vigorous stirring with both solutions cold; Table of keeping properties and useful life of solutions, F-54 and F-54a rows; Making up solutions, the note that when some acid hardener stock solutions are stored for several weeks they tend to form a white incrustation of basic aluminium acetate on the inside of the container, which should be ignored as it usually does not impair the useful properties of the solution; and the order of mixing an acid hardening fixing bath, hypo, sulphite, acid, alum; Notes on some of the chemicals mentioned in this handbook, 'Kodalk', on films developed in a Kodalk developer not blistering when placed in an acid fixing bath even at high temperatures because the alkali does not evolve carbon dioxide on acidifying, and on there being less tendency to precipitate aluminium sulphite sludge from fixing baths containing alum; Kodak formula F-5, tropical acid hardening fixing bath for films and plates, metric column, whose acid line reads 17.0 c.c. of glacial acetic acid where the American printings read 48.0 c.c. of the 28 per cent acid; Kodak formula HE-I, hypo eliminator, metric column reading water 500 c.c., hydrogen peroxide 3 per cent solution 125 c.c., ammonia 3 per cent solution 100 c.c. and water to make 1000 c.c., with the footnotes that the peroxide is a 10 volume solution as purchased and that 3 per cent ammonia is made by diluting 9 parts of .880 ammonia to make 100 parts of solution; the statement that hypo eliminators are not usually required for negative materials, that traces of hypo are tenaciously held by paper fibres and may lead to fading on long keeping under adverse conditions, and that HE-I converts the hypo to inert sulphate and facilitates its removal; Directions for use, giving the 30 minute wash at 65 to 70 degrees F in water replaced completely every five minutes, six minutes at 70 degrees F in the eliminator and about 10 minutes final wash; Life of HE-I solution, about fifty 8 by 10 inch prints per gallon and the instruction to dilute with 10 parts of water for plates, films and lantern slides; Test for hypo, using a 1 per cent silver nitrate solution on a processed unexposed sheet; Occasional effects when using HE-I eliminator, the three items on belt driers, image colour and yellowing of whites; Kodak formula HE-I, hypo eliminator, and the third of the occasional effects listed under it, that slight yellowing of whites is avoided by bathing the prints in 1 per cent sodium sulphite for 2 minutes prior to the final wash; Kodak formula IN-4, page 34 under the heading INTENSIFIERS AND REDUCERS, headed 'Chromium intensifier for approximately proportional intensification of thin negatives whether arising from slight under-exposure or under-development.', the Stock Solution reading potassium bichromate 90.0 gm., hydrochloric acid (concentrated) 64 c.c. and water to make 1000 c.c. in the metric column and 7 oz. 90 gr., 5 fluid oz. and 80 oz. in the avoirdupois column; the directions 'For use take I part of stock solution to 10 parts of water. Bleach thoroughly, wash until the yellow stain is removed (immersing the bleached and rinsed negative in a 5% solution of sodium carbonate for a few moments quickens this stage) and then re-develop with a non-staining developer, e.g., D-72, in artificial light or diffused daylight. Wash thoroughly and dry. If greater density is required, the operation may be repeated. The degree of intensification can be controlled by varying the time of re-development.'; and the note 'N.B. Fine-grain developers of the borax type containing a high concentration of sulphite are not suitable for re-development since the sulphite tends to dissolve the silver chloride before the developing agents have time to act on it.'; Kodak formula IN-5, page 35 under the heading INTENSIFIERS AND REDUCERS, headed 'Silver intensifier for proportional intensification of positive and negative transparencies without affecting image colour and stability', the metric column reading Stock Solution No. 1 (Store in a brown bottle) as silver nitrate (cryst.) 60.0 gm. and distilled water to make 1000 c.c.; Stock Solution No. 2 as sodium sulphite (cryst.) 120.0 gm. or (anhydrous) 60.0 gm. and water to make 1000 c.c.; Stock Solution No. 3 as sodium thiosulphate (hypo) 105.0 gm. and water to make 1000 c.c.; Stock Solution No. 4 as sodium sulphite (cryst.) 30.0 gm. or (anhydrous) 15.0 gm., 'Elon' 24.0 gm. and water to make 3000 c.c.; the avoirdupois column reading 4 oz. 350 gr. to 80 oz., 9 oz. 260 gr. (4 oz. 350 gr.) to 80 oz., 8 oz. 175 gr. to 80 oz., and 2 oz. 175 gr. (1 oz. 90 gr.) with 1 oz. 405 gr. to 240 oz.; the directions 'Prepare the intensifier solution for use as follows : Slowly add I part of Solution No. 2 to I part of Solution No. I, stirring to obtain thorough mixing. The white precipitate which appears is then dissolved by the addition of I part of Solution No. 3. Allow the resulting solution to stand a few minutes until clear. Then add, while stirring, 3 parts of Solution No. 4. The intensifier is then ready for use and the film should be treated immediately. The degree of intensification obtained depends upon the time of treatment, which should not exceed 25 minutes. After intensification, immerse the film for 2 minutes, with agitation, in a plain 30% hypo solution. Then wash thoroughly.'; 'The mixed intensifier solution is stable for approximately 30 minutes at 65 F. (18 C).'; and 'All dishes used must be scrupulously clean and the operations should preferably take place in artificial light.'; the handbook's note on 'elon' being a specially purified form of monomethyl paraminophenol sulphate, also known as Metol; formulae IN-1, IN-4, IN-6 and IN-21 on the facing pages for what the alternatives are; Measurement of small quantities and The question of parts, pages 3 to 4; Kodak formula IN-I, page 33 under the heading INTENSIFIERS AND REDUCERS, headed 'Mercury intensifier : An intensifier for line and process negatives giving increased maximum density with little intensification of intermediate tones.', with the direction 'Bleach the negative in the following solution until it is white, then wash thoroughly' above a metric column reading potassium bromide 22.5 gm., mercuric chloride 22.5 gm. and water to make 1000 c.c. and an avoirdupois column reading 1 oz. 350 gr., 1 oz. 350 gr. and 80 oz.; the note that the negative can be blackened with 10% sulphite solution, a developing solution such as Formula D-72 diluted 1 to 2, or 10% ammonia, these giving progressively greater density in the order given, and that where permanence of the resulting image is essential ammonia should not be used for blackening; the alternative solution 'to increase contrast greatly' reading sodium or potassium cyanide 15.0 gm., silver nitrate (cryst.) 22.5 gm. and water to make 1000 c.c., with the preparation note about dissolving the two separately and adding the latter to the former until a permanent precipitate is just produced, standing and filtering; and the closing Warning that cyanide is a deadly poison to be handled with extreme care, that it reacts with acid to form poisonous hydrogen cyanide gas, the 1949 instruction for discarding a solution containing cyanide, and that cyanide solutions should never be used in poorly ventilated rooms; Kodak formula T-55, page 40 under the heading TONERS, headed 'Selenium toner for Bromesko and warm-tone lantern slides', the Stock Solution reading sodium sulphite (cryst.) 300.0 gm. or (anhydrous) 150.0 gm., selenium powder 6.0 gm., ammonium chloride 190.0 gm. and water to make 1000 c.c., with the avoirdupois column at 24 oz. (12 oz.), 210 gr., 15 oz. and 80 oz.; the mixing instruction 'Dissolve the sulphite in about 700 c.c. of hot water, then add the selenium powder and boil until it is completely dissolved. Allow the solution to cool; then add the ammonium chloride and stir until it is dissolved. Finally make up to the required bulk with cold water.'; the direction 'For use dilute 1 part of stock solution with 5 parts of water.'; the working instruction 'Prints should be fixed and well washed before toning in the above solution for 10 to 15 minutes at 65° F. (18° C). Finally wash well before drying.'; and the footnote 'Available as Kodak Selenium Toner'; Kodak formula T-56, page 40 under the heading TONERS, headed 'Sulphide-selenium toner for bromide, Bromesko and Kodura prints', with Solution A the Bleaching Solution reading potassium ferricyanide 50.0 gm., potassium bromide 50.0 gm. and water to make 1000 c.c.; Solution B the Stock Sulphide-Selenium Solution reading sodium sulphide (pure) 250.0 gm., selenium powder 5.7 gm. and water to make 1000 c.c.; Solution C the Toning Solution reading Stock Solution B 50 c.c. and water to make 1000 c.c.; the avoirdupois column at 4 oz., 4 oz., 20 oz., 200 gr. and 4 oz. each to 80 oz.; and the directions 'Bleach in Solution A, wash until the yellow stain is removed and tone in Solution C. Complete with brief wash in running water. Throw away Solution C after use.'; also Kodak formula T-52 on the preceding page, whose Solution A is identical and whose Solution B is the same sulphide stock without the selenium, at 200.0 gm. rather than 250.0 gm.; and Kodak formula T-55 on the same page, the direct selenium toner, whose selenium is dissolved in sodium sulphite rather than sodium sulphide; Kodak formula T-52, page 39 under the heading TONERS, headed 'Sulphide toner. A two-solution sepia toner for bromide paper and lantern slides', with Solution A the Bleaching Solution reading potassium ferricyanide 50.0 gm., potassium bromide 50.0 gm. and water to make 1000 c.c.; Solution B the Stock Sulphide Solution reading sodium sulphide (pure) 200.0 gm. and water to make 1000 c.c.; Solution C the Toning Solution reading Stock Solution B 50 c.c. and water to make 1000 c.c.; the avoirdupois column at 4 oz., 4 oz., 16 oz. and 4 oz. each to 80 oz.; the directions 'Bleach in Solution A, wash until yellow stain is removed, and tone in Solution C. Complete with brief washing in running water. Throw away Solution C after use.'; and the footnote 'A toner of this type is available as Kodak Sepia Toner'; Kodak formula IN-21, page 37 under the heading INTENSIFIERS AND REDUCERS, headed 'Uranium intensifier: a simple intensifier giving, next to Formula IN-6, maximum intensification of negatives', the metric column reading Solution A as uranium (uranyl) nitrate 20.0 gm., glacial acetic acid 10 c.c. and water to make 500 c.c. and Solution B as potassium ferricyanide 20.0 gm. and water to make 500 c.c., the avoirdupois column reading 2 oz., 1 fluid oz. and 50 oz. for A and 2 oz. and 50 oz. for B, with the directions 'Use I part A, I part B and 6 parts of water. The film or plate should be washed very thoroughly after fixing, to remove all traces of hypo. Maximum intensification will be obtained with 2-3 minutes' immersion in the above working solution : further treatment only increases fog. The intensified image should have a reddish-brown colour. Wash only briefly before drying, since the usual alkaline wash water will destroy the intensification.'; Kodak formula T-9 on page 38, the uranium toner, for the distinction between the two uranium formulas in the same handbook; Kodak formula IN-5 on page 35 for the alternative; Kodak formula R-4a, page 31, the London handbook's own Farmer's reducer at 75.0 gm. of potassium ferricyanide and 240.0 gm. of sodium thiosulphate, each to 1000 c.c., mixed 1 part A to 4 parts B to 27 parts water; the note on the avoirdupois and metric columns not being exact equivalents, in Weights and Measures - Conversion Tables; The question of parts, page 4, on parts meaning units of volume; Kodak formula R-4a, Farmer's reducer, page 31 under the heading Intensifiers and Reducers, metric column, reading Stock Solution A as potassium ferricyanide 75.0 gm. and water to make 1000 c.c., Stock Solution B as sodium thiosulphate (hypo) 240.0 gm. and water to make 1000 c.c., with the directions 'For use, take I part Solution A, 4 parts Solution B, then add water 27 parts. Pour the mixed solution at once over the negative to be reduced. Watch closely. The action is best seen when the solution is poured over the negative in a white dish. When the negative has been reduced sufficiently, wash thoroughly before drying.' and 'Solutions A and B should not be combined until they are to be used. They will not keep long when mixed.'; the avoirdupois column reading 6 oz. and 80 oz. for A and 19 oz. and 80 oz. for B; Kodak formula R-4b, the two-bath Farmer's reducer, giving Solution A as potassium ferricyanide 7.5 gm. per litre and Solution B as sodium thiosulphate 200.0 gm. per litre, with 1 to 4 minutes in A at 65-75 degrees F (18-24 degrees C) and 5 minutes in B; Kodak formulae R-1 and R-2, the persulphate and permanganate reducers, for what the alternatives are; Kodak formula R-4b, pages 31 to 32 under the heading INTENSIFIERS AND REDUCERS, headed 'Two-bath Farmer's reducer giving almost proportional reduction for lowering density and contrast of negatives', the metric column reading Solution A as potassium ferricyanide 7.5 gm. and water to make 1000 c.c. and Solution B as sodium thiosulphate (hypo) 200.0 gm. and water to make 1000 c.c., the avoirdupois column reading 260 gr. and 80 oz. for A and 16 oz. and 80 oz. for B, with the directions 'Treat the negatives in Solution A with uniform agitation for I to 4 minutes at 65-75 F. (18-24 C), depending on the degree of reduction desired. Then immerse them in Solution B for 5 minutes and wash thoroughly. The process may be repeated if more reduction is desired.' and a further sentence beginning 'For the reduction of general fog, I part of Solution A should be diluted with I part of' which breaks at the page turn in the copy read; Kodak formula R-4a on the same page for the mixed-bath comparison; Kodak formulae R-1, R-2 and R-5 on pages 30 to 32 for what the persulphate and permanganate alternatives are; Weights and Measures - Conversion Tables, on the avoirdupois and metric columns not being exact equivalents; Kodak formula T-55, page 40 under TONERS — the stock solution of sodium sulphite, selenium powder and ammonium chloride, the instruction to boil until the selenium is completely dissolved, the dilution of 1 part stock to 5 parts water, 10 to 15 minutes at 65 °F (18 °C), and the footnote that the toner was also available as Kodak Selenium Toner; Kodak formula SB-1, acid stop bath for papers, plates and films, 17 c.c. of glacial acetic acid in 1000 c.c. of water, with prints rinsed for 5 seconds; Kodak formula SB-1A; Keeping properties and useful life of solutions, whose row for SB-1 gives 3 days in a dish, 1 month in a tank, indefinite keeping in a stoppered bottle full or half full, and a useful life of 90 sheets of 8 by 10 inches per 160 fl.oz. in both a narrow dish and a deep tank; the weights and measures warning that the avoirdupois and metric columns are not exact equivalents; Kodak formula SB-1A, acid stop bath for Reflex plates, 50 c.c. of glacial acetic acid in 1000 c.c. of water; Kodak formula SB-1 for comparison; Kodak formula D-8, the single-solution hydroquinone caustic developer for maximum contrast on process materials, its metric column and its two parts stock to one part water dilution; Keeping properties and useful life of solutions, whose row for SB-1A gives 3 days in a dish, 1 month in a tank, indefinite keeping in a stoppered bottle full or half full, and a useful life of 40 sheets of 8 by 10 inches per 160 fl.oz. annotated used after D-8; Kodak formula SB-1, acid stop bath for papers, plates and films, 17 c.c. of glacial acetic acid in 1000 c.c. of water; Kodak formula SB-1A at 50 c.c.; Kodak formula SB-4, the tropical hardening bath of 30 g potassium chrome alum with 140 g crystalline or 60 g anhydrous sodium sulphate per litre; Kodak formula T-51, page 39, the hypo-alum toning bath for direct sepia toning of bromide and 'Bromesko' prints: 1 lb. (200 gm.) of hypo dissolved in 80 oz. (1000 c.c.) of hot water, 3½ oz. (44 gm.) of ordinary potassium alum added, stirred and boiled for two or three minutes, cooled to about 150°F (65°C), then a silver ripener made by dissolving 20 gr. (0.5 gm.) of silver nitrate in 1 oz. (15 c.c.) of water and adding .880 ammonia drop by drop with vigorous stirring until the precipitate first formed just re-dissolves, stirred into the hypo-alum mixture, followed by 30 gr. (1 gm.) of potassium iodide in a further 1 oz. (15 c.c.) of water; the bath used repeatedly and kept up to bulk by occasional addition of fresh solution; prints fixed as usual, briefly rinsed, soaked 10 minutes in a saturated solution of potassium alum, rinsed and toned at a temperature not exceeding 140°F (60°C), then sponged with lukewarm water to remove sediment and washed as usual; Kodak formula T-52, the London two-solution sulphide toner, for the same process at a plain ferricyanide-bromide bleach with no oxalate and no acid, and a working sulphide bath at 50 c.c. of a 200 g/L stock to the litre; Kodak formula T-55, page 40 under TONERS — the stock solution of sodium sulphite, selenium powder and ammonium chloride, the instruction to boil until the selenium is completely dissolved, the dilution of 1 part stock to 5 parts water and 10 to 15 minutes at 65 degrees F; Kodak formula T-52, Solution A, the Bleaching Solution, page 39 under the heading TONERS, metric column reading potassium ferricyanide 50.0 gm., potassium bromide 50.0 gm. and water to make 1000 c.c., with the avoirdupois column at 4 oz., 4 oz. and 80 oz.; the same Bleaching Solution printed again at the same quantities as Solution A of formula T-56, page 40; the working direction 'Bleach in Solution A, wash until yellow stain is removed, and tone in Solution C'; Formula D-173, an "Elon"-free developer for "Velox" papers; Making up solutions and the storage of developer solutions, including the warning about glass stoppers and about precipitates formed in the cold; Kodak formula HE-I, hypo eliminator, directions for use and the note on occasional effects, whose third item is that slight yellowing of whites is avoided by bathing the prints in 1 per cent sodium sulphite for 2 minutes prior to the final wash; Kodak formula T-9, page 38 under TONERS, headed 'Uranium toner for brown to red tones in slides or films', the metric column reading uranium (uranyl) nitrate 2.5 gm., potassium oxalate 2.5 gm., potassium ferricyanide 1.0 gm., ammonium alum 6.0 gm., hydrochloric acid (10% solution) 5.0 c.c. and water to make 1000 c.c., the avoirdupois column reading 90 gr., 90 gr., 35 gr., 210 gr., 190 minims and 80 oz., with the directions 'Dissolve the chemicals in the order given. The solution should be perfectly clear and pale yellow in colour. It is light-sensitive, however, and should be stored in the dark. The maximum effect is produced in about 10 minutes, the tone passing from brown to red during this time. After toning, wash for about 10 minutes, though the washing should not be prolonged, especially if the water is slightly alkaline, since the toned image is soluble in alkali.' Also Kodak formula T-11 on the same page, the iron toner, and its closing sentence that mixing the uranium (T-9) and iron (T-11) toning solutions in different proportions produces tones ranging from reddish-brown to chocolate; and Kodak formula IN-21 on page 37, the uranium intensifier; Keeping properties and useful life of solutions; the developer, fixing bath and stop bath formulas and their headers; The negative developer formulas D-76, D-23, D-25, DK-20, DK-50 and D-19b; Making up solutions; Keeping properties and useful life of solutions; Some Kodak packed developers; Kodak formulas F-5, F-52, F-53 and F-54 and their headers; Making up solutions; Table of keeping properties and useful life of solutions; Kodak formula SB-1, acid stop bath for papers, plates and films; Kodak formula SB-1A for Reflex plates; Table of keeping properties and useful life of solutions; Kodak formulas T-52 and T-55, pages 39 and 40; Making up solutions; storage of developer solutions; keeping properties and useful life of solutions; Notes on some of the chemicals mentioned in this handbook - 'Kodalk' as a new alkali intermediate in activity between sodium carbonate and borax whose developers will not blister a film in an acid fixing bath; formulas F-16 chrome alum hardening fixing bath, R-2 permanganate reducer and IN-6 quinone-thiosulphate intensifier, which are where sulphuric acid appears, with the instruction to add the sulphuric acid very gradually to the water with constant stirring; Notes on some of the chemicals mentioned in this handbook - 'Elon' defined as a specially purified form of monomethyl paraminophenol sulphate, also known as Metol; formula D-76; Formula D-76 and its replenisher D-76R; formula DK-20 and its replenisher DK-20R, with the replenishment rate of about 5 gallons per 1,000 rolls for deep-tank use and the instruction to replenish only until 25 per cent of the original developer has been replaced; Some 'Kodak' Tested Chemicals: Calgon, sodium hexametaphosphate, listed among the chemicals supplied; Formulas SB-3 and SB-4, chrome alum hardening baths, with times, agitation, capacity and the violet-blue to yellow-green keeping change; SH-1 formalin hardener; F-5, F-16, F-53, F-54 and F-54a acid hardening fixers; and the mixing-order note for acid hardening fixing baths; Formula F-5 acid hardening fixing bath for films and plates: hypo 240 g crystalline or 150 g anhydrous, sodium sulphite 30 g crystalline or 15 g anhydrous, glacial acetic acid 17 cc, boric acid 7.5 g, potassium alum 15 g, water to 1000 cc, dissolved in the order given, fixing properly in 10 minutes in a fresh bath, with prolonged immersion at high temperatures harmful; formulas SB-3 and SB-4 chrome alum hardening baths at 30 g per litre with their agitation and time instructions, SB-4's violet-blue fresh colour turning yellow-green on partial use and its capacity of twenty 10 × 8 inch films per gallon; the mixing note that hypo, sulphite, acid and alum go in that order and that chrome alum baths are even more critical; Formula F-5, acid hardening fixing bath with potassium alum, its mixing order and the warning against prolonged immersion at high temperatures; F-53 hardener stock with F-54 and F-54a; and the note that the ingredients of an acid hardening fixing bath must be dissolved in the proper order; Formula F-5 acid hardening fixing bath and the F-53 hardener stock used in F-54 and F-54a, with the mixing order of hypo, sulphite, acid and then alum, and the warning that prolonged immersion at high temperatures is harmful; Making up solutions; Kodak formula D-23; Kodak formula D-76; Making up solutions — the instruction to dissolve constituents in the order given, the warning that dissolving the developing agent first and then adding the alkali allows considerable aerial oxidation and the formation of coloured oxidation products before the sulphite is dissolved, and the rule that Elon is dissolved first because it is only slightly soluble in sulphite solutions without alkali; Storage of developer solutions — the air space in a part-used bottle and the two- and three-solution arrangement; 'Kodalk' Developer Formulae: the note that Kodalk is an alkaline accelerator intermediate in activity between sodium carbonate and borax, that it does not evolve carbon dioxide on acidifying so films do not blister in an acid fixing bath even at high temperatures, and that there is less tendency to precipitate aluminium sulphite from alum fixing baths; Kodak formula DK-50 and the note that raising or lowering the Kodalk either raises or lowers the contrast obtained in a given development time, or shortens or lengthens the time without affecting the contrast; formulas D-76, D-76R, D-23, D-25, D-25R, DK-15, DK-20, DK-20R, D-19b, D-19bR and D-72; Some Kodak tested chemicals, including Calgon (sodium hexametaphosphate) among the substances sold for darkroom use; Making up solutions; Kodak formula D-76; Kodak formula D-23; Kodak formula D-19b; Kodak formula DK-50; Kodak formula D-76; Making up solutions — the instruction to dissolve the constituents in the order given in the formula, the reason in terms of aerial oxidation and coloured oxidation products, the rule that Elon is dissolved first because it is only slightly soluble in sulphite solutions without alkali, the immateriality of when potassium bromide is added, and the advantages of anhydrous sodium sulphite; Storage of developer solutions — the tightly corked bottle, the increase in air space each time a large bottle is opened, the small air space to be left against temperature changes, and the note that glass stoppers stick; the keeping-properties table for D-76; Kodak formula D-23 with its metric quantities, the instruction to dissolve the chemicals in the order given, use without dilution, and develop about 18 minutes at 65 degrees F or 18.3 degrees C; Kodak formula D-25 and its 50 to 100 per cent exposure increase; Kodak formula D-76 with its metric quantities and the same dissolving instruction; Making up solutions — the instruction to dissolve in the order given, the reason, the rule for Elon, the immateriality of potassium bromide's position and the instruction that sodium bisulphite is added with the sulphite; the anhydrous-to-crystalline carbonate factor of two and a half; Storage of developer solutions; Kodak formula D-23; Kodak formula D-25; Kodak formula D-76 and its replenisher D-76R; Kodak formula DK-20; Developer formulae — the potassium bromide content of D-19b, D-72, DK-15, DK-20 and DK-50, and the absence of any from D-76 and D-23; Making up solutions; Kodak formula D-23; Kodak formula D-25; Kodak formula D-76; Kodak formula DK-20 and its replenisher DK-20R; Making up solutions, including the instruction that sodium bisulphite is added with the sulphite; Storage of developer solutions, including the division of readily oxidised developers into two or three solutions to keep the developing agent away from the alkali; the keeping-properties table showing formula D-1 stored in three solutions; Making up solutions, including the instruction that sodium bisulphite is added with the sulphite and the advantages of the anhydrous salt; Kodak formula D-23; Kodak formula D-25; Kodak formula D-76; Developer formulae — the Elon and hydroquinone quantities of D-76, D-72, D-19b and DK-50, and the single-agent formulas D-23 and DK-15; Kodak formula D-23, metol 7.5 g and anhydrous sodium sulphite 100 g per litre, with the instruction to dissolve in the order given and use without dilution; Kodak formula D-76 with its metric quantities; the replenisher formulae D-76R and D-25R and their alkali quantities; Kodak formula D-76, metol 2 g, sodium sulphite anhydrous 100 g, hydroquinone 5 g and borax 2 g per litre, with the instruction to dissolve in the order given; Storage of developer solutions — the tightly corked bottle, the increase in air space each time a large bottle is opened, and the small air space to be left against temperature changes; Making up solutions — the instruction to dissolve the constituents in the order given in the formula and the reason in terms of aerial oxidation; Kodak formula D-76 with its metric quantities and the borax quantity of the D-76R replenisher; Kodak formula D-23; Making up solutions — the instruction to dissolve constituents in the order given and the rule that Elon is only slightly soluble in sulphite solutions without alkali; Kodak formula D-76 with its metric quantities, metol 2 g, sodium sulphite anhydrous 100 g, hydroquinone 5 g and borax 2 g per litre; the borax quantity of the D-76R replenisher; Making up solutions — the instruction to dissolve constituents in the order given and the rule that Elon is only slightly soluble in sulphite solutions without alkali; Kodak formula D-23, metol 7.5 g and anhydrous sodium sulphite 100 g per litre; Kodak formula D-76 and the borax quantity of the D-76R replenisher; Stop and hardening baths — Kodak formula SB-1, acid stop bath for papers, plates and films, 17 c.c. of glacial acetic acid per 1000 c.c. of water; the keeping-properties table, which gives SB-1 a capacity of 90 sheets of 8 x 10 inches per 160 fl.oz.; Stop and hardening baths — Kodak formula SB-1, 17 c.c. of glacial acetic acid per 1000 c.c. of water; Kodak formula D-76, Elon 2 g, sodium sulphite anhydrous 100 g, hydroquinone 5 g and borax 2 g per litre, used without dilution; the useful-life table's capacity column, 90 sheets of 8 x 10 inches per 160 fl.oz. for SB-1; Stop and hardening baths — SB-1, an acid stop bath for papers, plates and films at 17 c.c. of glacial acetic acid per litre with prints rinsed for 5 seconds; SB-1A, an acid stop bath for Reflex plates at 50 c.c.; SB-3, a hardening bath of 30 g of potassium chrome alum per litre; SB-4, the tropical hardening bath adding 140 g of crystalline or 60 g of anhydrous sodium sulphate, with its capacity of twenty 10 x 8 inch films per gallon and its violet-blue to yellow-green colour change; the useful-life table's capacity column for SB-1, SB-1A, SB-3 and SB-4; Stop and hardening baths — Kodak formula SB-1, 1000 c.c. water and 17 c.c. glacial acetic acid, rinse prints for 5 seconds, and SB-1A at 50 c.c.; the keeping-properties and useful-life table, whose capacity column is the number of 8 x 10 inch sheets processed for the standard time in 160 fl.oz., giving SB-1 90 sheets in both dish and tank; Kodak formula D-72 and Kodak formula D-76 with their metric quantities; the Kodalk entry, which states that films developed in a Kodalk developer will not blister in an acid fixing bath even at high temperatures because the alkali does not evolve carbon dioxide on acidifying; Fixing Baths — formula F-5, which states that films and plates will be fixed properly in 10 minutes if a freshly prepared bath has been used, and that prolonged immersion at high temperatures is harmful; the keeping-properties table, giving F-5 a useful life of 120 sheets of 8 by 10 inches per 160 fluid ounces; Making up solutions — when an acid hardening fixing bath is made up the hypo is dissolved first, then the sulphite, then the acid, and finally the alum, and where the hardener is a separate stock it is added to the hypo solution slowly with vigorous stirring and both solutions must be cold; Fixing Baths — formula F-5, a tropical acid hardening fixing bath for films and plates carrying sodium thiosulphate, sodium sulphite, glacial acetic acid, boric acid and potassium alum, dissolved in the order given, fixing properly in 10 minutes in a freshly prepared bath; formula F-16, a chrome alum hardening fixing bath mixed as two solutions and used the same day, which rapidly loses its hardening properties with or without use; formula F-52, a non-hardening acid fixing bath of hypo and potassium metabisulphite for use where hardening must be avoided; formula F-53, the acid hardener stock of sodium sulphite, acetic acid and potassium alum, and formulae F-54 and F-54a which combine it with hypo for paper and for films; the keeping-properties table, which gives F-5 a useful life of 120 sheets of 8 by 10 inches per 160 fluid ounces; Making up solutions — when an acid hardening fixing bath is made up it is essential that the ingredients be dissolved in the proper order if decomposition of the hypo and precipitation of the alum are to be avoided; the hypo is dissolved first, then the sulphite, then the acid, and finally the alum; where the hardener stock is made up separately it is added to the hypo solution slowly with vigorous stirring and both solutions must be cold; the advantages of anhydrous sodium sulphite over the crystalline form. Fixing Baths — formula F-5, tropical acid hardening fixing bath for films and plates, 240.0 gm sodium thiosulphate (or 150.0 gm anhydrous), 30.0 gm sodium sulphite crystalline (or 15.0 gm anhydrous), 17.0 c.c. glacial acetic acid, 7.5 gm boric acid, 15.0 gm potassium alum, water to 1000 c.c., dissolved in the order given, films and plates fixed properly in 10 minutes in a freshly prepared bath; formula F-53, the acid hardener stock of sulphite, acetic acid and potassium alum with its own mixing directions; the keeping-properties table, which gives F-5 a useful life of 120 sheets of 8 by 10 inches per 160 fluid ounces; Hypo Eliminator and Test Solutions — TEST FOR HYPO, the unexposed white sheet processed with the batch, a strip of it immersed for about three minutes in a 1 per cent silver nitrate solution, rinsed and compared while wet in subdued light with the wet untreated portion, no colour difference meaning the hypo has gone and a yellow-brown tint meaning it has not, with the caution that silver nitrate solution stains the skin black; Kodak formula HT-1a, hypo test solution for checking thoroughness of washing; Hypo Eliminator and Test Solutions — TEST FOR HYPO, the instruction to process with the batch an unexposed white sheet of photographic paper of the same weight and size as the majority of prints in the batch, to cut off a strip after the final wash and immerse it in a 1 per cent silver nitrate solution for about three minutes, then rinse it and compare it while wet, in subdued light, with the wet untreated portion, no colour difference meaning the hypo has been completely removed and a yellow-brown tint indicating its presence; the caution that silver nitrate solution stains the skin black and direct contact is to be avoided; Hypo Eliminator and Test Solutions — hypo eliminators are not usually required in processing negative materials, but in the case of prints traces of hypo are tenaciously held by the paper fibres and may lead to fading of the image on long keeping under adverse conditions; Directions for use, a 30 minute wash at 65 to 70 degrees F in running water replaced completely every five minutes, six minutes in the eliminator and about 10 minutes' final wash, with the footnote that the washing time is increased at lower temperatures and doubled for double-weight prints; Hypo Eliminator and Test Solutions — TEST FOR HYPO, process with the batch of prints an unexposed white sheet of photographic paper of the same weight and size as the majority of prints in the batch, and after the final wash cut off a strip and immerse it in a 1 per cent silver nitrate solution for about three minutes, then rinse in water and compare, while wet, in subdued daylight or artificial light, with the wet untreated portion; if the hypo has been completely removed no colour difference should be observed and a yellow-brown tint indicates the presence of hypo; the caution that silver nitrate solution stains the skin black and direct contact is to be avoided; the footnote that the same effect can be caused if hydrogen sulphide or wood extracts are present in the water supply; KODAK FORMULA HT-1a, hypo test solution for checking thoroughness of washing, potassium permanganate 1.2 gm, sodium hydroxide 2.4 gm, water (distilled) to make 1000 c.c., with the method of adding 1 c.c. of it to 250 c.c. of pure water and draining six films or plates of 3.25 x 4.25 in into the glass, the violet colour turning orange in about 30 seconds if hypo is present, the comparison test needed because oxidisable organic matter in the water reacts with permanganate in the same way, and the statement that for papers the test is not a completely reliable indication; Kodak formula D-72 and its metric column per 1000 c.c., including the alternative of 19 c.c. of a 10 per cent solution in place of 1.9 g of potassium bromide; Making up solutions - the instruction to dissolve the constituents in the order given, the rule that Elon is dissolved first, the note that potassium bromide may be added at any stage, and the advantages of the anhydrous salts; Keeping properties and useful life of solutions - D-72 at 24 hours standing in a dish, 2 weeks in a tank, 3 months in a full stoppered bottle and 1 month in a half-full one; and the paper developer formulas D-158, D-156 and D-166 with their potassium bromide quantities; The paper developer formulas D-72, D-163, D-158, D-156, D-166, D-170 and D-173 with their metric columns per 1000 c.c., their dilutions and their development times; Keeping properties and useful life of solutions, for the dish and tank lives and the print capacities per 160 imperial fluid ounces, including the entry for D-156 that reads exhaustion affects colour of image, life depends on quality required, and the thirty-minute dish life of the amidol developer D-170; and the list of Kodak packed developers describing D-163 as a universal developer for papers; Keeping properties and useful life of solutions - D-72 at 24 hours standing in a dish and 3 months in a full stoppered bottle, and the shorter dish lives of the lower-sulfite paper formulas; Kodak formula R-4a, Farmer's reducer, page 31 under Intensifiers and Reducers - the two stock solutions, the direction to take 1 part of A, 4 parts of B and 27 parts of water and pour the mixed solution at once over the material to be reduced, watching closely, and the instruction that solutions A and B should not be combined until they are to be used because they will not keep long when mixed; Keeping properties and useful life of solutions - Keeping properties and useful life of solutions, the table column headed IN DISH, which gives 24 hours for D-72, 8 hours for D-166 and 30 minutes for the amidol developer D-170; Hypo Eliminator and Test Solutions, TEST FOR HYPO - process with the batch of prints an unexposed white sheet of photographic paper of the same weight and size as the majority of prints in the batch, and after the final wash cut off a strip of this sheet and immerse it in a 1 per cent silver nitrate solution for about three minutes, then rinse in water and compare it while wet, in subdued daylight or artificial light, with the wet untreated portion; if the hypo has been completely removed no colour difference should be observed and a yellow-brown tint indicates the presence of hypo; the caution that silver nitrate solution stains the skin black and that direct contact is to be avoided; the footnote that the same effect can be caused if hydrogen sulphide or wood extracts are present in the water supply; the directions for HE-1, which specify a wash of about 30 minutes at 65 to 70 degrees F in running water flowing rapidly enough to replace the water in the vessel completely once every five minutes, with the footnote that the washing time should be doubled when double-weight prints are treated; and the statement under HE-1 that in the case of prints traces of hypo are tenaciously held by the paper fibres; Kodak formula T-52, the London two-solution sulphide toner, whose bleaching solution A is potassium ferricyanide 50 g and potassium bromide 50 g in water to 1000 c.c. with no oxalate and no acid, whose sulphide stock B is 200 g/L and whose working toner C is 50 c.c. of B to the litre, with the instruction to throw solution C away after use; Kodak Formula T-11, Iron toner for blue tones in slides or films — the composition of ammonium persulphate 0.5 g, iron ammonium sulphate (ferric alum) 1.4 g, oxalic acid 3.0 g, potassium ferricyanide 1.0 g, ammonium alum 5.0 g and hydrochloric acid (10 per cent solution) 1 c.c., water to make 1000 c.c.; the statement that the method of compounding the bath is very important, that each solid should be dissolved separately in a small volume of water and the solutions mixed strictly in the order given before dilution to volume, and that if these instructions are followed the bath will be pale yellow and perfectly clear; the immersion of slides or films for 2 to 10 minutes at 21 °C until the desired tone is obtained and a wash of 10 to 15 minutes until the high-lights are clear; the warning that since the toned image is soluble in alkali washing should not be carried out for too long a period, especially if the water is slightly alkaline; the note that a very slight permanent yellow colouration of the clear gelatin will usually occur; the diagnosis that blue-stained high-lights mean the slide was fogged during development or the toning bath was stale or incorrectly mixed; the note that mixing the uranium T-9 and iron T-11 solutions in different proportions gives tones from reddish-brown to chocolate; and Kodak Formula T-9, the uranium toner for brown to red tones in slides or films, whose toned image is likewise soluble in alkali so that washing should not be prolonged especially if the water is slightly alkaline; Kodak formula T-55, page 40 under TONERS, the stock solution of sodium sulphite, selenium powder and ammonium chloride, and the mixing instruction to dissolve the sulphite in hot water, add the selenium powder and boil until it is completely dissolved; and the footnote that the toner was available as Kodak Selenium Toner; Kodak formula T-52, the London two-solution sulphide toner, whose bleaching solution A is potassium ferricyanide 50 g and potassium bromide 50 g in water to 1000 c.c. with no oxalate and no acid, whose stock sulphide solution B is 200 g of sodium sulphide in water to 1000 c.c., and whose toning solution C is 50 c.c. of B in water to 1000 c.c., the print being bleached in A, washed until the yellow stain is removed and toned in C, solution C being thrown away after use; formula T-51, the hypo-alum bath for direct sepia toning, used repeatedly and kept up to its original bulk by occasional addition of fresh solution, worked at a temperature not exceeding 60 degrees Celsius and sponged with lukewarm water afterwards to remove sediment; and formula T-56, the sulphide-selenium toner, which is T-52's bleach with 5.7 g of selenium powder dissolved into a 250 g/L sodium sulphide stock; Page 38 under TONERS, Kodak Formula T-9, uranium toner for brown to red tones in slides or films, its direction that the solution is light-sensitive and should be stored in the dark, that the maximum effect is produced in about 10 minutes with the tone passing from brown to red, and that washing should not be prolonged especially if the water is slightly alkaline since the toned image is soluble in alkali; the closing sentence under Kodak Formula T-11 that mixing the uranium T-9 and iron T-11 toning solutions in different proportions produces tones ranging from reddish-brown to chocolate; page 33, Kodak Formula IN-1, the mercury intensifier for line and process negatives, its blackening alternatives of sulphite solution, diluted D-72 or ammonia in order of increasing density with the note that ammonia should not be used where permanence of the resulting image is essential, the alternative silver-and-cyanide bath for greatly increased contrast, and the printed warning that cyanide is a deadly poison and should be handled with extreme care, that it reacts with acid to form poisonous hydrogen cyanide gas, and that cyanide solutions should never be used in poorly ventilated rooms; page 34, Kodak Formula IN-4, the chromium intensifier for approximately proportional intensification of thin negatives, a potassium bichromate and hydrochloric acid stock used at one part in ten, bleached, washed until the yellow stain is removed and redeveloped with a non-staining developer; page 36, Kodak Formula IN-6, the quinone-thiosulphate intensifier, whose Solution A is sulphuric acid and potassium bichromate; and page 41, Kodak Formula TC-1, the one-solution dish cleaner of potassium bichromate and sulphuric acid for removing silver and developer stains from dishes; Page 33, Kodak Formula IN-1, the mercury intensifier — the alternative silver-and-cyanide blackening bath, and the printed warning beside it that cyanide is a deadly poison and should be handled with extreme care, that it reacts with acid to form poisonous hydrogen cyanide gas, and that cyanide solutions should never be used in poorly ventilated rooms; The INTENSIFIERS AND REDUCERS pages, read as one facing group because that is how the assignment uses them - page 33, Kodak Formula IN-1, the mercury intensifier, with its blackening alternatives and its alternative silver-and-cyanide bath, printed beside the handbook's own warning that cyanide is a deadly poison, that it reacts with acid to form poisonous hydrogen cyanide gas, and that cyanide solutions should never be used in poorly ventilated rooms; page 34, Kodak Formula IN-4, the chromium intensifier for approximately proportional intensification of thin negatives, a potassium bichromate and hydrochloric acid stock used at one part in ten, bleached, washed until the yellow stain is removed and redeveloped with a non-staining developer such as D-72; page 35, Kodak Formula IN-5, the silver intensifier for proportional intensification of positive and negative transparencies without affecting image colour and stability, its four stock solutions, its fixed order of combination and its working life of approximately 30 minutes at 65 F; and Kodak Formula IN-21, the uranium intensifier; Page 33, Kodak Formula IN-1, the mercury intensifier for line and process negatives — the alternative silver-and-cyanide bath given for greatly increased contrast, with the direction to dissolve the cyanide and the silver nitrate separately and add the latter to the former until a permanent precipitate is just produced; and the warning printed beneath it, in full, that cyanide is a deadly poison and should be handled with extreme care, that it reacts with acid to form poisonous hydrogen cyanide gas, that when discarding a solution containing cyanide one should always run water to flush it out of the sink quickly, and that cyanide solutions should never be used in poorly ventilated rooms. Also the only other caution printed anywhere in the volume, under the hypo eliminator HE-1 and its test for hypo, that silver nitrate solution stains the skin black and that direct contact with the solution should be avoided. That the volume carries exactly two cautions is the course's own reading of the whole text and is stated as such; Page 33, Kodak Formula IN-1, the mercury intensifier, headed as an intensifier for line and process negatives giving increased maximum density with little intensification of intermediate tones, its bleach of potassium bromide with mercuric chloride, its three blackening alternatives of sulphite solution, diluted Formula D-72 and ammonia which the handbook says give progressively greater density in the order given, its instruction that where permanence of the resulting image is essential ammonia should not be used, its alternative silver-and-cyanide bath to increase contrast greatly, and its printed warning that cyanide is a deadly poison, reacts with acid to form poisonous hydrogen cyanide gas and should never be used in poorly ventilated rooms. Page 35, Kodak Formula IN-5, the silver intensifier for proportional intensification of positive and negative transparencies without affecting image colour and stability. Page 34, Kodak Formula IN-4, the chromium intensifier, a potassium bichromate and hydrochloric acid stock whose image is bleached, washed until the yellow stain clears and redeveloped. Page 38, Kodak Formula IN-21, the uranium intensifier, described as a simple intensifier giving, next to Formula IN-6, maximum intensification of negatives, its Solution A of uranium (uranyl) nitrate with glacial acetic acid and its Solution B of potassium ferricyanide, its statement that the film or plate should be washed very thoroughly after fixing to remove all traces of hypo, that the intensified image should have a reddish-brown colour, and that it should be washed only briefly before drying since the usual alkaline wash water will destroy the intensification. Page 38, Kodak Formula T-9, the uranium toner for brown to red tones in slides or films, its direction that the solution is light-sensitive and should be stored in the dark, that the tone passes from brown to red as the bath works, and that washing should not be prolonged especially if the water is slightly alkaline since the toned image is soluble in alkali; and the closing sentence under Formula T-11 that mixing the uranium and iron toning solutions in different proportions produces tones ranging from reddish-brown to chocolate; Kodak formula R-4a, Farmer's reducer, page 31, headed as a cutting reducer for correcting over-exposure and clearing shadow areas of negatives and high lights of prints; the two stock solutions and the instruction that they should not be combined until they are to be used because they will not keep long when mixed; and R-4b, the two-bath form, which Kodak describes as almost proportional; Fixing Baths, formula F-5: the statement that films and plates will be fixed properly in 10 minutes if a freshly prepared bath has been used; Making up solutions — the instruction to dissolve the constituents in the order given in the formula and the aerial-oxidation reason for it; Kodak formula D-76 and Kodak formula D-76R, whose borax quantity is 20 g per litre against D-76's 2 g; Hypo Eliminator and Test Solutions, TEST FOR HYPO: the unexposed control sheet of the same weight and size processed with the batch; Making up solutions: the instruction to dissolve the constituents in the order given in the formula, the aerial-oxidation reason for it, the rule that Elon is dissolved first in warm water because it is only slightly soluble in a sulphite solution without alkali, and the note that glass stoppers are undesirable for developers because the alkali tends to make them stick; Making up solutions: the instruction that when an acid hardening fixing bath is made up it is essential that the ingredients be dissolved in the proper order, and the order and quantities of formula F-5 given in both the crystalline and the anhydrous forms; Chapter III: the caustic alkalis and the instruction to dissolve them in cold water; the carbonates as a reservoir of alkali; the alkali governing the energy of the developer, too much giving chemical fog and too little being slow; alkalis softening gelatin and causing frilling or blisters in warm weather; Hypo Eliminator and Test Solutions, TEST FOR HYPO: the instruction to process with the batch an unexposed white sheet of photographic paper of the same weight and size as the majority of prints in the batch, and to cut off a strip after the final wash; Keeping properties and useful life of solutions, and the preference for the anhydrous form of sodium sulfite on grounds of stability; Hypo Eliminator and Test Solutions, TEST FOR HYPO: process with the batch an unexposed white sheet of photographic paper of the same weight and size as the majority of prints in the batch, cut off a strip after the final wash and immerse it in a 1 per cent silver nitrate solution for about three minutes, then rinse it and compare it while wet, in subdued light, with the wet untreated portion; no colour difference means the hypo has been completely removed and a yellow-brown tint indicates its presence; the caution that silver nitrate solution stains the skin black and direct contact is to be avoided; Keeping properties and useful life of solutions; the stability of anhydrous sodium sulfite over the crystalline form; Kodak formula SB-1, acid stop bath for papers, plates and films, 17 c.c. of glacial acetic acid in 1000 c.c. of water; Keeping properties and useful life of solutions, whose SB-1 row gives 3 days in a dish, 1 month in a tank, indefinite keeping in a stoppered bottle full or half full, and a useful life of 90 sheets of 8 by 10 inches per 160 fl.oz.; Keeping properties of developers; storage in small tightly corked bottles with a small air space; the crystallisation of a cold concentrated stock and the redissolving of a precipitate that contains the most important constituents; Making up solutions: dissolving the constituents in the order given, Elon first, and the note that potassium bromide may be added at any stage; Formula F-5 acid hardening fixing bath and the F-53 hardener stock used in F-54 and F-54a, with the warning that prolonged immersion at high temperatures is harmful; Storage of developer solutions - the advice to leave only a small air space, and the observation that the space grows every time a large bottle is opened; Hypo Eliminator and Test Solutions, TEST FOR HYPO - process an unexposed white sheet of the same paper with the batch, and after the final wash immerse a strip in a 1 per cent silver nitrate solution for about three minutes, rinse, and compare while wet with the untreated portion; no colour difference means the hypo has been removed and a yellow-brown tint indicates its presence; the caution that silver nitrate solution stains the skin black; the footnote that the same effect can be caused if hydrogen sulphide or wood extracts are present in the water supply; Storage of developer solutions and keeping properties - the warning that solubilities fall as temperature falls, that a concentrated stock stored cold may crystallise out, and that the precipitate often contains the most important constituents of the solution

Used by:P29 Capstone Stage 6: Permanence, Presentation and the Finished Portfolio · P29 Capstone Stage 2: Formulating and Documenting Your Chemistry · P29 Capstone Stage 3: Exposing, Processing and Measuring · P29 Capstone Stage 4: The Silver Prints · P29 Planning the Capstone: The Project Plan and Its Hazard Assessment · P29 The Pure Silver Portfolio: The Specification · 6-Nitrobenzimidazole · Acetic acid (glacial) · Amidol · Ammonium persulfate · Ascorbic acid · Benzotriazole · Borax (sodium tetraborate decahydrate) · Boric acid · Glycerol · Glycin · Metol · p-Aminophenol · Potassium citrate · Potassium permanganate · Potassium persulfate · Potassium thiocyanate · Pyrogallol · Sodium bisulfite · Sodium carbonate (anhydrous) · Sodium carbonate decahydrate · Sodium carbonate monohydrate · Sodium hexametaphosphate (Calgon) · Sodium metabisulfite · Sodium metaborate (anhydrous) · Sodium metaborate tetrahydrate (Kodalk) · Sodium sulfite · Beutler two-solution developer · Kodak SB-4 · Citric Acid Stop Bath · Foma FOMAFIX · HARMAN SELENIUM TONER · ILFORD HYPAM · Kodak D-1 · Kodak D-156 · Kodak D-158 · Kodak D-163 · Kodak D-165 · Kodak D-166 · Kodak D-167 · Kodak D-170 · Kodak D-173 · Kodak D-177 · Kodak D-19 · Kodak D-19b · Kodak D-19bR · Kodak D-23 · Kodak D-25 · Kodak D-25R · Kodak D-32 · Kodak D-49 · Kodak D-51 · Kodak D-52 · Kodak D-72 · Kodak D-76 · Kodak D-76d · Kodak D-76R · Kodak D-9 · Kodak DK-20 · Kodak DK-20R · Kodak DK-50 · Kodak F-1a · Kodak F-24 · Kodak F-5 · Kodak F-52 · Kodak F-53 · Kodak F-54 · Kodak F-5a · Kodak F-6 · Kodak HE-1 · Kodak Hypo Clearing Agent and the washing accelerator Kodak patented · Kodak IN-4 · Kodak IN-5 · Kodak IN-1 · Kodak T-55 · Kodak T-56 · Kodak T-52 · Kodak IN-21 · Kodak R-4 · Kodak R-4a · Kodak R-4b · KODAK Rapid Selenium Toner · Kodak SB-1 · Kodak SB-1a · Kodak SB-5 · Kodak T-1a · Kodak T-7a · Moersch MT1 Selentoner · Rehalogenating ferricyanide-bromide bleach · Rodinal-type p-aminophenol developer · One per cent sodium sulfite washing aid · Uranium toner · Comparison matrices · Film developers compared · Fixers compared · Stop baths compared · Toners compared · P2 Storage, Incompatibilities and Secondary Containment · P3 Acids, Bases and pH · P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P3 Buffers and Buffer Capacity · P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve · P5 Coating, Drying and Hardening · P5 Project 4: Coating Glass Dry Plates and a Lantern Slide · P5 Lab: Coating Your First Emulsion · P5 Break/Fix: Emulsion Coating Defects · P8 Overview: What a Developer Is · P8 Experiment: Watching a Developer Oxidise · P8 Alkalis, Buffers and pH · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 How Development Works · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P8 Assignment: Reading a Developer Formula · P8 Restrainers and Antifoggants · P8 Solvent Action, Physical Development and Grain · P8 Staining and Tanning Developers · P8 Sulfite: Preservative, Buffer, Silver Solvent · P8 Superadditivity: Why Two Agents Beat One · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Break/Fix: The Developer That Went Wrong · P9 Assignment: The Developer Laboratory Report · P9 Experiment: Comparing Developing Agents · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P10 Overview: Stopping Development · P10 Experiment: Measuring Stop Bath Capacity · P10 Stop Bath Formulations and the Fixer Interaction · P10 Why Stopping Works · P11 Experiment: Clearing Time and Fixer Capacity · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline · P11 Lab: Mixing Fixers from Scratch · P12 Overview: Permanence and Responsibility · P12 Assignment: Your Archival Processing Sequence · P12 The Physics of Washing · P12 Lab: Testing for Residual Thiosulfate and Residual Silver · P18 Lab: Mixing and Comparing Print Developers · P18 Print Developer Chemistry and the Developer-Paper Pair · P18 Break/Fix: The Print That Will Not Go Black · P19 Contrast Filtration and Split-Grade Printing · P19 Developing the Print Consistently and Running a Printing Session · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Gold, Iron-Blue and the Other Metal Toners · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P20 The Toners We Study and Do Not Use · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Assignment: Assessing a Historical Process for Hazard · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 Uranium, Mercury and the Heavy-Metal Treatments · P28 Reading the Negative as Evidence: Thin, Dense, Flat and Contrasty · Measuring a clearing time · Versioning a formula · Handling and storing a deliberately faulty reference specimen · Labelling a container · Mixing a developer from raw chemicals · Mixing a fixer · Adjusting pH with a concentrated alkali · Print processing: the archival sequence · Recording a batch in the inventory · Residual hypo and residual silver tests · The stock check, and retiring a chemical · Stop bath preparation · Storage rotation and shelf separation · Weighing and handling developing agents · Frilling · Oxidised developer · Residual thiosulfate · Stock solution crystallised in cold storage

Controls in Black and White Photographyretrieved 2026-09-05

Sections: The acutance chapter - the identification of the developer sold as Beutler High Definition with Altman and Henn's AH-16, and the measured result that it markedly increases the acutance of Tri-X Pan but not of Panatomic-X or Royal-X Pan

Used by:Beutler two-solution developer

Elementary Photographic Chemistryretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Fine Grain Negative Developer Formula for Motion Pictures D-76 — Elon 8.0 g, sodium sulphite 400.0 g, hydroquinone 20.0 g, borax 8.0 g, water to make 4.0 litres; and the mixing directions, dissolving the Elon in a small volume at about 52 degrees C, a quarter of the sulfite with the hydroquinone at about 71 degrees C, and the remaining sulfite with the borax at about 71 degrees C; Developing Formulas for Paper, Stock Solution D-72, its metric column and its three dilutions, and For use — Velox at 1:1 for 45 seconds at 21 degrees C, Azo at 1:2 for 45 seconds, and bromide enlarging papers at 1:4 for one and a half minutes at 21 degrees C; Chapter III, The Chemistry of Development — the commonest developing agents, reduction potential, the four ingredients of a developer, and the account of a developer's oxidation products including the statement that with sulfite present the oxidation products of hydroquinone are colourless; Chapter IV, the two compound sodium silver thiosulfates and the consequence of incomplete fixing; Chapter IX: the four ingredients of a developer, and why bromides and iodides are added; Chapter IV: the acid fixing bath, why a large quantity of a weak acid is required, and acetic acid as the best acid for the purpose; Chapter VIII: formulas SB-1, F-1 and F-1a; Chapter X: rinsing prints, the short stop, and the sludging of the fixing bath; Chapter III: reduction potential and the rule that developing agents must be in an alkaline solution, with the exception of Acrol; keeping developers — bisulphite for readily oxidizable agents such as pyro and amidol; Table of Chemical Solubilities — Diaminophenol Hydrochloride (Acrol or Amidol); Chapter II: ammonium chloride among the chlorides, bromides and iodides used in photography, and its purity test; Chapter VI, The Chemistry of Reduction and Intensification: the three classes of reducing solution; flattening reducers as those acting very much more on the heavy deposits than on the light deposits; the statement that only one such reducer is known and that it is ammonium persulphate; the oxidation of the silver to silver sulphate which dissolves in the solution; the requirement for an acid solution, the uncertain behaviour and the acceleration as reduction progresses; the boxed note that ammonium persulphate is a white crystalline salt, stable when dry, that its action was found in the Eastman Research Laboratories to depend largely on a very small quantity of iron salt as an impurity, and that its capricious behaviour is due to variations in the quantity of iron present; the derivation of a proportional reducer by mixing permanganate with persulphate. Chapter VIII, formulas R-1 and R-5; "Chapter I, the oxidation of sulphite to sulphate; Chapter II, the preservative and the affinity of sulphite for oxygen"; Chapter IV: The Chemistry of Fixation; Chapter III: the four ingredients of a developer; alkali and the energy of a developer; alkalis softening the gelatin and causing over-swelling and frilling; the preservative and the oxidation of developing agents; Chapter IX: the four ingredients of a developer, and why bromides and iodides are added; Chapter X: chemical fog and the alkali; Chapter III: borax and fine-grain development, grain clumping, sulfite as a silver halide solvent; borax or sodium tetraborate; Chapter IV: weak alkalis in gold toning baths; Chapter VIII: formulas D-76 and D-72; Chapter IV: the acid fixing bath, the decomposition of thiosulfate by acid, why a large quantity of a weak acid is required, potassium alum as hardener; Chapter X: the properties of fixing baths and sludging; Chapter III: reduction potential and the order of the developing agents; alkali and the energy of a developer; the preservative and the coloured oxidation product; Chapter IV: potassium chrome alum and ammonium chrome alum, their formulae and the loss of hardening power in the presence of sulfite; Chapter VIII: Formulas SB-3 and F-16; Chapter IX: mixing a chrome alum fixing bath and the addition of sulfuric acid; Chapter X: rinsing and hardening films or plates, the chromium scum, the colour of the bath in use, and the comparison of chrome alum with potash alum fixing baths; Chapter V, The Chemistry of Toning — the general bleach-and-replace pattern and copper citrate for red; Chapter IV: formalin as a hardening agent, its strength and its irritation of the mucous membranes; Chapter IX: the ingredients of an acid hardening fixing bath; Chapter II: making an emulsion in gelatin, and the properties of gelatin — swelling, melting, the colloid, the effect of acid and alkali, and hardening by alum; Chapter IV: the alums as tanning agents and formalin; Chapter V: whether hardening slows the washing of hypo out of the film; Chapter III: the commonest developing agents; reduction potential; alkali and the energy of a developer; the four ingredients of a developer; storage of solutions; Chapter IV: the decomposition of hypo by sulphuric or hydrochloric acid, with the precipitation of sulphur; Chapter I: oxidation and reduction — hydroquinone, quinone and sulfite; Chapter III: the commonest developing agents, reduction potential, the four ingredients of a developer, Formula D-76; storage of chemicals; Chapter VI: the iodine and potassium iodide cutting reducer; Table of Chemical Solubilities — Ferrous Sulphate; Chapter V: intensification with mercuric chloride; MERCURY BICHLORIDE; the Monckhoven intensifier; Chapter III: The Chemistry of Development — the commonest developing agents; reduction potential; Formula D-76; the four ingredients of a developer; Chapter III: The Chemistry of Development — para-aminophenol, Kodelon, methyl-para-aminophenol; reduction potential; the bases and their salts; Chapter III: The Chemistry of Development — the four ingredients of a developer, alkalis and the energy of a developer, reduction potential; Chapter IV: the alums, their general formula and the forms they are sold in; Chapter VII: direct toning with the hypo-alum bath; Chapter VIII: Formulas F-1, F-1a, F-2, F-14 and SB-1; Chapter IX: preparing an acid hardening fixing bath and the order of mixing; Chapter X: the properties of fixing baths, the measurement of hardening, useful life, sludging and fixing-bath troubles; Chapter II: making an emulsion, the excess of soluble bromide, and potassium bromide among the chlorides, bromides and iodides used in photography; Chapter III: the effect of a small quantity of bromide on hydroquinone and on Elon; Chapter VIII: paper developer D-52 and its bromide additions; Chapter IX: the four ingredients of a developer and why bromides and iodides are added; Chapter X: the accumulation of bromide with use, and developer troubles; Chapter III: potassium carbonate; Chapter VIII: formula D-11; Potassium chloride in the list of photographic chemicals; the table of chemical solubilities, ounces of chemical in 100 fluid ounces of saturated solution at 40 °F and 70 °F; Chapter VI, The Chemistry of Reduction and Intensification: the metal ferrocyanide toners, in which a metal salt whose ferrocyanide is coloured converts the silver ferrocyanide as it forms, iron citrate giving a blue image, uranium nitrate a reddish brown and copper citrate a red; Table of Chemical Solubilities, which lists Potassium Citrate among the photographic chemicals; Chapter V: the Monckhoven intensifier; Chapter V: the chromium intensifier; Potassium Bichromate; tray cleaners; Chapter VI: reduction — Farmer's Reducer; Chapter VII: toning — the ferro- and ferricyanides; Chapter VIII: formulas R-4 and T-7a; Chapter IX: mixing operations and storage of solutions; Chapter VII: toning — the ferro- and ferricyanides, potassium ferrocyanide, and the metal ferrocyanide toners; Chapter X: the storage of chemicals — deliquescence and efflorescence; Chapter VII: toning — the metal ferrocyanide toners; Chapter III: the caustic alkalis; potassium hydroxide and its equivalence to caustic soda; dissolving caustic alkalis in cold water; Chapter IX: the keeping of single-solution caustic developers; Chapter II: silver iodide in negative emulsions, and potassium iodide among the chlorides, bromides and iodides used in photography; Chapter VI: the iodine and potassium iodide cutting reducer; Chapter VIII: tropical process developer D-13; Chapter IX: the four ingredients of a developer, and the storage of chemicals that decompose in light; Chapter X: the by-products of development; Chapter II: potassium metabisulphite and sodium bisulphite; Chapter VII: blue spots from iron in the sulphide bleach and the addition of potassium oxalate; Table of Chemical Solubilities; Chapter VII: blue spots from iron in the sulphide bleach and the addition of potassium oxalate; Chapter VIII: Stock Bleaching Solution T-7a; Chapter VI, The Chemistry of Reduction and Intensification: permanganate as another cutting reducer; permanganates as very strong oxidising agents; the oxidation of the silver to silver sulphate, which is sufficiently soluble in water to be dissolved; the very weak action of a plain permanganate solution and its use at about 0.25 per cent to remove dichroic fog; the difference from ferricyanide on a pyro-developed negative, permanganate attacking the stain image in preference to the silver; permanganate with bromide as an alternative bleach; the boxed note on dark purple crystals, on impure commercial material and on Eastman Tested Permanganate; the use as a test for hypo; and manganese dioxide precipitating in the absence of excess free acid and being removed by bisulphite. Chapter VIII, formulas HE-1, R-2 and R-5, and the instruction on dissolving the permanganate crystals in a small volume of water at about 180 °F (82 °C); Chapter III: the commonest developing agents and the manufacture of pyrogallol; reduction potential; the preservative and the yellow oxidation product; Formula D-1, standard A.B.C. pyro; two-solution developers and the keeping of pyro; developer troubles — coloured solutions and scum; reduction with ferricyanide and permanganate; Chapter II: the manufacture of silver nitrate and the company's share of United States silver; Chapter V: toning and the stability of the silver sulphide image; Chapter II: making an emulsion, the precipitation of silver bromide from silver nitrate and potassium bromide, the excess of soluble bromide, negative materials as bromide with a small addition of iodide, bromide paper, and the control of sensitiveness by temperature and duration of heating; Chapter IV: the chemistry of fixation; Chapter I: double decomposition and the insolubility of the silver halides; Chapter II: the earliest photographs on silver chloride paper, chloride contact papers, Solio and its excess of silver nitrate; Chapter II: negative materials as silver bromide with a small addition of silver iodide, and the chlorides, bromides and iodides used in photography; the toning chapter: cyanide solutions as solvents for the silver halides, and the fixing of wet collodion plates; Chapter I: double decomposition and the precipitation of silver chloride; Chapter II: making an emulsion, the excess of soluble bromide, Solio and its excess of silver nitrate, the manufacture and purity of silver nitrate; Chapter VIII (Formulas): Hypo Alum Sepia Toner T-1a and Monckhoven's Intensifier; Chapter IX (Preparing Solutions): the care of chemicals and decomposition by light; Table of Chemical Solubilities, page 99; Chapter V, The Chemistry of Toning, section D — silver sulphide, its insolubility, its colour with state of subdivision, and the recommendation for permanency; Chapter X, Scum on Fixing Baths; Chapter III: the four ingredients of a developer; alkali and the energy of a developer; Chapter I: oxidation, reduction and the preservative; Chapter III: the preparation of photographic carbonate; the bisulphite and carbonate exchange and the antifogging action of the bicarbonate formed; Chapter I: acid salts of sulphurous acid; Chapter II: sodium bisulphite, the preservative and the acid fixing bath; Chapter VII: keeping developer solutions; Chapter III: the alkalis, the carbonate as a reservoir of alkali, water of crystallisation, sodium carbonate in three forms, bisulphite and carbonate, fine-grain development; Chapter VIII: formulas D-19, D-49, D-52, D-61a, D-72; Chapter III: water of crystallisation; sodium carbonate in three forms and their carbonate contents; the efflorescence of the decahydrate to the monohydrate; Chapter III: water of crystallisation; sodium carbonate in three forms; Chapter II: making an emulsion, sodium chloride among the chlorides, bromides and iodides used in photography, Solio and printing-out chloride emulsions, and silver nitrate blackening skin, wood and cloth on exposure to light; Chapter III: the quantity of alkali and the energy of the developer; the caustic alkalis; sodium hydroxide; potassium hydroxide; Chapter IX: carbon dioxide and the stoppered bottle; Chapter VIII: formulas D-9, D-32, HE-1; Chapter II: sodium metabisulphite, sodium bisulphite and the acid fixing bath; Chapter III: the quantity of alkali and the energy of the developer; the caustic alkalis; borax and fine-grain development; Chapter III: the quantity of alkali and the energy of the developer; Chapter IV: the acid fixing bath and its hardener; Chapter X: the properties of fixing baths and sludging; Chapter I and the preservative chapter: the oxidation of sodium sulphite to sodium sulphate and the difficulty of detecting it in the desiccated salt; Tropical Process Developer D-13; the table of chemical solubilities, which lists sodium sulphate anhydrous and crystal; Chapter VII: toning — sulphide toning by bleaching and redevelopment, sodium sulphide and its impurities; Chapter VIII: formulas T-1a, T-7a and the re-development intensifier; Chapter X: storage of chemicals; Chapter I: oxidation of sulphite to sulphate; Chapter II: the preservative, sodium sulphite, sodium bisulphite, fine-grain development in D-76, the acid fixing bath; Chapter V: stock solutions; Chapter VII: the useful life of developers; Chapter I: thiosulfuric acid and its sodium salt; Chapter IV: The Chemistry of Fixation; Chapter V: The Chemistry of Washing; Chapter VIII: scum on fixing baths; Chapter IV: The Chemistry of Fixation; Chapter VIII: toning — the hypo-alum bath; Fixing baths F-1, F-2 and F-14; Chapter I: acids, salts and the alums; Chapter VI: permanganate as a cutting reducer and the oxidation of silver to silver sulphate; Chapter VIII: formulas R-2, R-5 and F-16, and the instruction on mixing stock solution B; Chapter IX: the four ingredients of a developer, and why bromides and iodides are added; Chapter X: chemical fog; Chapter VIII: toning — sulfide toning by bleaching and redevelopment; "Chapter III: the four ingredients of a developer; alkali and the energy of a developer; the preservative and the graded pyrogallol experiment, in which no sulfite gives a very yellow negative whose image is partly silver and partly oxidised pyrogallol and a great deal of sulfite gives an almost blue one; the statement that pyro oxidises far more readily than Elon or para-aminophenol; the note that iron gives a dark colour in a pyro solution; Formula D-1, the standard A.B.C. pyro, with its tray dilution; Chapter VII: the keeping of pyro and the storage of readily oxidised developers in two or three solutions; Chapter X: the rule that each chemical is dissolved completely before the next is added"; Chapter IV and the note repeated under the fixing-bath formulas — glacial acetic acid freezes to a solid at moderately low temperatures, 28 per cent acetic acid is prepared by diluting three parts of pure glacial acetic acid with eight parts of water, and the warning that substituting 28 per cent acid where a formula calls for glacial gives less than one third of the required concentration of acid; Chapter on the constitution of the developer - the high concentration of sulphite in D-76 as a solvent for silver bromide and iodide that dissolves a small quantity of each grain and minimises clump formation, and the statement that adding carbonate to such a developer increases the rate of development and accentuates the graininess of the result; Chapter III, for borax introduced as the mild alkali of a fine-grain developer and for the statement that adding carbonate speeds development; Chapter IV, for weak alkalis in gold toning baths; Chapter IV, potassium chrome alum and its loss of hardening power in the presence of sodium sulfite; Chapter VIII, formulas SB-3 and F-16; Chapter X, the chrome alum hardening bath used after development and before fixation in hot weather, the instruction to agitate on immersion or a chromium scum forms, the permission to skip the water rinse where the bath is used while noting that a few seconds of rinse prolongs the hardener's life, the violet-to-yellowish-green colour of a bath in use, and the comparison of chrome alum with potash alum fixing baths; Chapter IV, potassium chrome alum: a plain aqueous solution keeps its hardening power, and the loss of that power in the presence of sodium sulfite; Chapter X, the chromium scum thrown by alkaline developer carried into a chrome alum bath, and the violet-to-yellowish-green colour change of a bath in use; Chapter IV, the design rule that the acidity of a solution depends on how much of the hydrogen is dissociated while the quantity of alkali an acid can neutralise depends on the total hydrogen present, and that acetic acid is therefore the best acid for the purpose; Rinsing Prints, the capacity of the acid rinse bath and the litmus test for whether it is still acid; Chapter IV, on cyanide solutions as solvents for the silver halides forming soluble double compounds, on potassium cyanide being employed for fixing wet collodion plates which being made from silver iodide are not easily fixed in hypo, on hydrocyanic acid and the cyanides being extremely poisonous with a few grains of cyanide swallowed causing death, and on the cyanides forming sulphocyanides with sulphur, ammonium sulphocyanide having already been referred to as used in gold toning baths; Chapter V, the Monckhoven intensifier; Chapter VI, toning: the rate at which the metal is deposited being very important, finely divided gold being red and the more pleasing blue gold coming from more rapid deposition; the statement that to ensure rapid deposition the bath must be kept alkaline, and that borax or sodium acetate is consequently added to the gold chloride to make a toning bath, while substances of weak reducing action such as sulphocyanides or formates are sometimes added; and that platinum toning baths are used in an acid condition; Chapter IV, the acid fixing bath — the decomposition of thiosulfate by acid and why a large quantity of a weak acid is required; Chapter X, the properties of fixing baths and sludging; How to Prepare Fixing Solutions and The Useful Life of Fixing Baths — that an acid hypo solution gradually becomes milky on keeping, that any considerable excess of bisulphite turns the hypo milky in warm weather through liberation of sulphur, and the frothing, milkiness and sludging of a bath at the end of its life; Chapter IX, Preparing Solutions — that as a general rule in published formulas the term "cold water to make" is always given at the end of the formula, which insures dilution to a definite volume and thus a known concentration of chemicals each time the formula is mixed, and the storage of chemicals that decompose in light; The chapter on fixing, for the account of what acid does to hypo: that a few drops of a strong acid added to a weak hypo solution decompose it and turn it milky through the precipitation of sulphur, because the acid converts the sodium thiosulphate into free thiosulphuric acid, which is unstable and decomposes into sulphurous acid and sulphur according to the equation H2S2O3 = H2SO3 + S; that the change is reversible, since boiling sulphite with sulphur re-forms thiosulphate, so that "while acids liberate sulphur from the hypo, sulphite combines with the sulphur to form hypo again" and enough sulphite present prevents acid from decomposing the hypo; and that an acid fixing bath is therefore preserved from decomposition by the sulphite, which also prevents the oxidation of developer carried over into it; How to Prepare Fixing Solutions, page 78, the three classes of fixing bath and the Bisulphite Fixing Bath printed without a formula number, reading hypo 250.0 grams, sodium sulphite 10.5 grams, sodium bisulphite 5.3 grams and water to make 1.0 liter, with the directions for class 2 baths - that the bisulphite or acid sulphite solutions must not be added to the warm hypo solution or the hypo will turn milky, that the solutions should be quite cold when mixed, that an acid hypo solution gradually becomes milky on keeping so that a bisulphite stock should be kept and added to the plain hypo stock as required, and that for general purposes 45 c.c. of a 50 per cent sodium bisulphite solution is added to 1 litre of a 35 per cent hypo solution with any considerable excess turning the hypo milky through liberation of sulphur; page 77, on a plain fixing bath being seldom used because it becomes alkaline from developer carried over, softening the gelatin and letting the image continue to develop, so that two prints sticking together develop unevenly, and on an acid bath neutralising that alkali; Chapter IV, on sodium bisulphite being the only generally available substitute when acetic acid cannot be obtained for the fixing bath, on its making a satisfactory acid fixing bath but not giving quite as good a reserve of available acid as acetic acid does, and on that mattering particularly in connection with the hardening agent; Chapter III, on sodium bisulphite being an acid salt intermediate between sodium sulphite and sulphurous acid, on a neutral solution being made by adding a small quantity of bisulphite to sulphite, on bisulphite supplying both the sulphite and the acid necessary in a fixing bath, on commercial dry bisulphite consisting chiefly of metabisulphite which is converted to bisulphite on dissolving, on the customary weight-for-weight substitution of sodium bisulphite for potassium metabisulphite, and on the difficulty of preparing bisulphite free from iron; Chapter VIII, Formulas — 'Standard A. B. C. Pyro', Stock Solution A D-1, its three stock solutions in avoirdupois and metric, 'Dissolve chemicals in order given', tray development at 1 part A, 1 part B, 1 part C and 7 parts of water for about 7 to 9 minutes at 65 F. (18 C.) and tank development at 11 parts of water for about 13 to 15 minutes; the Two Solution Pyro Tray Developer on the same page, whose Stock Solution A is identical and whose Stock Solution B carries the sulphite and carbonate together, used 1 + 1 + 8 for about 6 minutes; Chapter III, on pyrogallol being supplied in the crystal form because the powder flies about the darkroom, on the ranking of developing agents by reduction potential with hydroquinone lowest and Elon highest and pyro low among them so that the highlights come up before the shadows, on the quantity of alkali governing the energy of a developer with too much giving chemical fog and too little a slow bath and alkali softening the gelatin, on sodium sulphite crystals containing 50 per cent of dry sulphite, on the desiccated salt and Eastman Tested Sulphite, on sodium bisulphite giving a neutral preservative with sulphite and being difficult to prepare free from iron, and on the substitution of sodium bisulphite for potassium metabisulphite weight for weight; Chapter III again, the graded sulphite experiment — a pyrogallol developer without sulphite gives a very yellow negative whose image is partly silver and partly oxidised pyrogallol, sulphite gives a much less yellow image, and a great deal of sulphite gives almost as blue an image as Elon; Chapter VII, Two-Solution Developers, that a two-solution developer is a one-solution developer split so that it oxidises less readily, and that pyro is customarily kept that way because it oxidises much more readily than Elon or para-aminophenol for a given amount of preservative; Chapter VII, on a developing agent stored for a considerable time keeping best with an acid sulphite such as sodium bisulphite, on a plain sulphite solution oxidising readily below 10 per cent and very slowly above it so that sulphite stocks should be made at around 10 per cent for maximum keeping, on Elon being impossible in such a stock, and on sodium carbonate added to sodium bisulphite forming sodium sulphite and sodium bicarbonate so that a two-solution formula needs extra carbonate; Chapter VII, on storing a pyro stock with an absorption bottle of alkaline pyro at the intake; Developer Troubles, on a pyro developer mixed with iron-bearing bisulphite forming an inky substance and on the B solution of a two-solution pyro developer browning when mixed in dirty vessels; the directions for mixing, that each chemical is dissolved completely before the next and that desiccated carbonate and sulphite are added to the water and not the reverse; The reduction-potential ranking of the developing agents and the statement that a small quantity of sodium or potassium bromide affects hydroquinone and does not affect Elon nearly so much; the quantity of alkali and its effect on the energy of a developer; the relation between the colour of the black and white image and the colour a sulfide toner will give it; Chapter II, the distinction between bromide papers for enlarging and the less sensitive chloride papers used for contact printing by artificial light, and the statement that developing-out papers are chemically of the same nature as negative materials; the reduction-potential ranking of the developing agents and the effect of bromide on hydroquinone against Elon; the quantity of alkali and its effect on the energy of a developer; The reduction-potential ranking of the developing agents and the statement that a small quantity of bromide affects hydroquinone and does not affect Elon nearly so much; the quantity of alkali and its effect on the energy of a developer, on chemical fog and on the softening of gelatin; the behaviour of Elon against hydroquinone in the tray; The reduction-potential ranking of the developing agents; the statement that an Elon image comes up very quickly and gains density slowly while a hydroquinone image comes up slowly and gains density steadily and rapidly; the statement that hydroquinone has so low a potential that it is rarely used alone but is generally used with Elon; the quantity of alkali and the energy of a developer; The statement that a small quantity of sodium or potassium bromide affects hydroquinone and does not affect Elon nearly so much, and that the higher the reduction potential the more bromide is needed for a given effect; the quantity of alkali and the energy of a developer; the colour of a sulfide-toned print following the colour of the original image; Two-Solution Developers, on a two-solution developer being a one-solution developer split so that it oxidises less readily and keeps well, and on the reason for keeping a developer like pyro in two solutions being that pyro oxidises much more readily than Elon or para-aminophenol with a given amount of preservative; Chapter III, on sodium bisulphite being preferable as a preservative in a two-solution developer because oxidation progresses less readily in acid than in alkaline solution, on potassium metabisulphite being often used as a preservative and being costly against sodium bisulphite, on the quantity of alkali governing the energy of a developer and on too much alkali producing chemical fog; Chapter X, on the preservative being dissolved first, on the exception for Elon and the white precipitate of the Elon base, and on the oxidation product of pyrogallol being yellow and deposited in the film with the silver so that a pyro developer without sulphite gives a very yellow negative; Chapter III, the statement that most developing agents cannot develop at all when used by themselves and that with the exception of Acrol they must be in an alkaline solution, with the energy depending on the amount of alkali present; the table of chemical solubilities, which gives diaminophenol hydrochloride under the name Acrol; Chapter III, the reduction-potential ranking placing Kodelon between pyro and metol and the note that Kodelon can be substituted for Elon but more of it is required for a developer of the same strength; the statement that developing agents must be in an alkaline solution and that the energy of a developer follows the quantity of alkali; Two-Solution Developers, on a two-solution developer being a one-solution developer split so that it oxidises less readily and keeps well, and on the reason for keeping a developer like pyro in two solutions being that pyro oxidises much more readily than Elon or para-aminophenol with a given amount of preservative; Chapter III, on bisulphite being preferable as a preservative in a two-solution developer because oxidation progresses less readily in acid than in alkaline solution, on the quantity of alkali governing the energy of a developer, and on the carbonates as a reservoir of alkali; Chapter X, on the oxidation product of pyrogallol being yellow and deposited in the film with the silver, on a pyro developer without sulphite giving a very yellow negative and on a great deal of sulphite giving almost as blue an image as Elon, and on bromides being addable at any stage; Formula D-1, standard A.B.C. pyro, and its tray and tank dilutions; X-ray Developer Formula (Elon-Hydroquinone) D-19, its quantities per litre, its dilution instruction and its development time; formula D-72 for the anhydrous cross-check; Chapter II - sodium sulphite, the desiccated and anhydrous salts, and Eastman Tested Sulphite; sodium carbonate in its three forms; the restrainer; the statement that the quantity of alkali governs the energy of a developer; The statement that the quantity of alkali governs the energy of a developer, that too much alkali tends to produce chemical fog and too little makes it slow, and that alkalis soften the gelatin; the restrainer; sodium carbonate in its three forms; The restrainer added to compensate for chemical fog; the statement that the quantity of alkali governs the energy of a developer; sodium hydroxide as the strongest of the alkalis; Chapter II - the preservative and the behaviour of sodium sulphite; the reduction-potential ranking of the developing agents; the statement that developing agents must be in alkaline solution and that the energy of a developer follows the amount of alkali; Chapter II - sodium bisulphite and metabisulphite, the relation between them, and Eastman Kodak's dry bisulphite; the statement that developing agents must be in alkaline solution and that the energy of a developer follows the amount of alkali; Lantern Slide Formulas, Warm Black Tones, Formula D-32, page 53, metric column, Stock Solution A reading water at about 125 degrees F or 52 degrees C 500.0 c.c., sodium sulphite 6.3 grams, hydroquinone 7.0 grams, potassium bromide 3.5 grams, citric acid 0.7 gram and cold water to make 1.0 liter, Stock Solution B reading cold water 1.0 liter, sodium carbonate 30.0 grams and sodium hydroxide (caustic soda) 4.2 grams, with the directions 'For use, take 1 part of A and 1 part of B. For still warmer tones, 1 part of A and 2 parts of B' and 'Develop about 5 to 6 minutes at 70 degrees F (21 degrees C)'; Chapter III, on the quantity of alkali governing the energy of a developer, on the caustic alkalis being dissolved in cold water because of the heat evolved, and on the carbonates as a reservoir of alkali against a caustic alkali that is soon exhausted; Two-Solution Developers; Chapter X, on the four ingredients of a developer and on bromide being addable at any stage; Lantern Slide Formulas, Blue Black Tones, Formula D-34, page 52, metric column, Stock Solution A reading water at about 125 degrees F or 52 degrees C 500.0 c.c., Elon 4.2 grams, sodium sulphite 15.0 grams, hydroquinone 15.0 grams and cold water to make 1.0 liter, Stock Solution B reading water 1.0 liter, sodium carbonate 15.0 grams and potassium bromide 2.1 grams, with the directions 'For use, take equal parts of A and B', 'For softer tones, dilute with an equal amount of water' and 'Develop 1 and a half to 3 minutes at 70 degrees F (21 degrees C)'; Two-Solution Developers, on a two-solution developer being a one-solution developer split into two parts, one containing the carbonate and bromide and the other the developing agent and preservative, so that the developer oxidises less readily and keeps well; Chapter X, on the preservative being dissolved first except where Elon is present, on Elon being readily soluble in warm water but only slightly soluble in sulphite solutions without alkali, on the white Elon precipitate that appears if the sulphite is dissolved first and its redissolving on adding the carbonate, and on it being immaterial at what stage the bromide is added; Chapter III, on the quantity of alkali governing the energy of a developer and on the carbonates as a reservoir of alkali; Washing, the minimum washing time for lantern slide plates of 2 to 3 minutes; The Properties of Fixing Baths, on lantern slides clearing in 30 seconds to 1 minute; Developing Formulas for Paper, Portrait Bromide Paper Developer, Stock Solution D-49, its metric column, its dilution and its development time; the neighbouring formula D-72 for Velox, Azo and bromide papers; the reduction-potential ranking of the developing agents; the statement that the quantity of alkali governs the energy of a developer and that too much alkali tends to produce chemical fog while too little makes it slow; the distinction between chloride contact papers and bromide enlarging papers; Developing Formulas for Paper, Acrol Developer for Bromide Papers, Stock Solution D-51, its metric column, its working dilution with a 10 per cent potassium bromide addition and its warning that the developer oxidises quite rapidly when exposed to the air; Chapter III, the statement that most developing agents cannot develop at all when used by themselves and that with the exception of Acrol they must be in an alkaline solution; the grouping of amidol with pyro as readily oxidisable agents usually kept mixed with sodium bisulphite; the table of chemical solubilities, giving diaminophenol hydrochloride under the name Acrol; Developing Formulas for Paper, Vitava Paper Developer, Stock Solution D-52, its metric column, the four named papers with their dilutions and their 10 per cent potassium bromide additions, and the development time; the neighbouring formulas D-72 and D-49; the reduction-potential ranking of the developing agents and the statement that bromide affects hydroquinone and does not affect Elon nearly so much; the quantity of alkali and the energy of a developer; the note that further formulas are in the Book of Formulas for Eastman Papers; Developing Formulas for Paper, Velox, Azo and Bromide Papers, Stock Solution D-72 with its metric column and its three dilutions; the reduction-potential ranking of the developing agents and the behaviour of Elon against hydroquinone; the quantity of alkali and its effect on energy, fog and gelatin; the statement that most developing agents must be in an alkaline solution; the distinction between chloride contact papers and bromide enlarging papers; Fine Grain Negative Developer Formula for Motion Pictures D-76, its quantities per gallon and its Directions for Mixing; borax and the high sulphite of D-76 as a solvent for silver bromide; the accentuation of graininess when carbonate is substituted; the reduction-potential ranking of the developing agents; The quantity of alkali and the energy of a developer; carbonate as a reservoir of alkali that keeps the concentration nearly constant during use; borax as the alkali of the fine-grain motion picture developer; the high sulphite of D-76 as a solvent for silver bromide and the accentuation of graininess when carbonate is substituted; Developing Formulas, Process Tray Developer (Hydroquinone-Caustic), Formula D-9, page 49, metric column, Stock Solution A reading water at about 125 degrees F or 52 degrees C 500.0 c.c., sodium bisulphite 22.5 grams, hydroquinone 22.5 grams, potassium bromide 22.5 grams and cold water to make 1.0 liter, Stock Solution B reading cold water 1.0 liter and sodium hydroxide (caustic soda) 52.5 grams, with the direction 'Use equal parts of A and B and develop about three minutes at 65 degrees F (18 degrees C)' and the warnings that cold water should always be used when dissolving sodium hydroxide because considerable heat is evolved, that with hot water the solution will boil with explosive violence and may cause serious burns if the hot alkali spatters on the hands or face, and that Solution A should be stirred thoroughly when the caustic alkali is added to it or the heavy caustic solution will sink to the bottom; Chapter III, on developing agents needing an alkaline solution and on the energy depending on the amount of alkali, on hydroquinone being often used with caustic alkalis while other agents need only the weaker carbonated alkali, on too much alkali producing chemical fog and too little being slow, on alkalis softening gelatin and giving frilling or blisters in warm weather, on the caustic alkalis being dissolved in cold water because of the heat evolved, on the carbonates being a reservoir of alkali that keeps the concentration nearly constant while a proportional quantity of caustic would soon be exhausted, on sodium bisulphite being preferable as a preservative in a two-solution developer because oxidation progresses less readily in acid than in alkaline solution, and on bisulphite neutralising an equivalent quantity of carbonate and so exerting an apparent restraining action; Chapter X, on the four ingredients of a developer, on hydroquinone in water turning brown on standing and on alkali increasing the rate of oxidation so much that the solution rapidly turns dark brown and a plate developed in it is stained and fogged, and on bromides and iodides being added to compensate for chemical fog; Two-Solution Developers, on a two-solution developer being a one-solution developer split so that the developer oxidises less readily and keeps well; Chapter II - the restrainer and the reason a developer carries one; the reduction-potential ranking of the developing agents; the high sulphite of D-76 as a solvent for silver bromide; Chapter II - the statement that the quantity of alkali governs the energy of a developer, that too much alkali tends to produce chemical fog and too little makes it slow, and that alkalis soften the gelatin; the restrainer; the high sulphite of D-76 as a solvent for silver bromide; Fixing Baths, Acid Hardening Fixing Bath for Films, Plates and Papers, Formula F-1, page 55, metric column, reading hypo 480.0 grams and water to make 2.0 liters, then the direction to add the following hardener solution slowly to the cool hypo solution while stirring the latter rapidly, the hardener reading water at about 125 degrees F or 52 degrees C 160.0 c.c., sodium sulphite 30.0 grams, acetic acid 28 per cent pure 96.0 c.c. and powdered potassium alum 30.0 grams, with the instruction to dissolve in the order given and the footnote that 28 per cent acetic acid is made by diluting three parts of glacial acid with eight parts of water; the note on page 56 that if the hypo is not thoroughly dissolved before adding the hardener a precipitate of sulphur is likely to form; The Properties of Fixing Baths, on fixation time being twice the clearing time, the 30 to 40 per cent hypo optimum, portrait films fixing in 3 to 5 minutes and lantern slides clearing in 30 seconds to 1 minute, 65 degrees F as the recommended temperature and 70 degrees F as the limit, the hardening of formula F-1 being compounded to give 130 to 170 degrees F, and the 15 to 20 minute fixing time for maximum hardening; The Useful Life of Fixing Baths, giving the capacities of F-1 per gallon with a water rinse, with the SB-3 chrome alum bath and with the SB-1 acid rinse, and the exhaustion signs of frothing, milkiness and sludging with the 12 to 15 minute clearing rule; Fixing Bath Troubles, on sulphur and aluminium sulphite sludges and their causes; Fixing Baths, Deep Tank Fixing Bath for Roll Films, Formula F-14, pages 56 to 57, metric column, reading water 4.0 liters and hypo 960.0 grams, then 'When thoroughly dissolved, add the following cool hardener slowly with constant stirring to the cool hypo solution' with water 400.0 c.c., sodium sulphite 30.0 grams, acetic acid 28 per cent pure 208.0 c.c. and powdered potassium alum 60.0 grams, the footnote that 28 per cent acetic acid is made from three parts of glacial acid and eight parts of water, and the instruction to dissolve in the order given following the directions for mixing the stock hardener Formula F-1a on page 55; Fixing Bath Troubles, on the relationship between the acid content of an alum-acid bath, its tendency to precipitate aluminium sulphite and its hardening properties, and the remedy of adding about half as much acid again as soon as a slight precipitate appears; The Properties of Fixing Baths, on fixation being twice the clearing time, on the 30 to 40 per cent hypo optimum and on the recommended 65 degrees F; The Useful Life of Fixing Baths, on the signs of exhaustion and the 12 to 15 minute clearing rule; Formulas, Volumes and Weights, on the 1 gallon or 4 litre basis for tank formulas and on 'Cold water to make' being reserved for the line that fixes a definite final volume; Fixing Baths, Acid Hardener Stock Solution, Formula F-1a, page 55, metric column, reading water at about 125 degrees F or 52 degrees C 1700.0 c.c., sodium sulphite 480.0 grams, acetic acid 28 per cent pure 1500.0 c.c., powdered potassium alum 480.0 grams and cold water to make 4.0 liters, with the footnote that 28 per cent acetic acid is made by diluting three parts of glacial acid with eight parts of water and the direction 'For use, add 1 part of cool stock solution slowly with stirring, to 8 parts of a 25% cool hypo solution'; page 56, the mixing directions - dissolve the chemicals in the order given above, the sodium sulphite dissolved completely before the acetic acid is added, the potassium alum added to the thoroughly mixed sulphite-acid solution with constant stirring, and the warning that if the hypo is not thoroughly dissolved before the hardener is added a precipitate of sulphur is likely to form; Acid fixing baths, on preparing the acid hardening solution as a separate stock and adding it to the hypo solution as required, on the order of mixing and the reason the alum dissolves more readily in the acid-sulphite solution, on the alternative method of dissolving alum and sulphite separately and cooling both, on the white sludge of aluminium sulphite that follows adding alum to sulphite before the acid, and on a milky hardener indicating a relative insufficiency of acid; Fixing Baths, Motion Picture Fixing Bath, Formula F-2, page 56, metric column, reading water 4.0 liters and hypo 960.0 grams, then 'When thoroughly dissolved add the following cool hardener solution slowly with stirring to the cool hypo solution' with water 128.0 c.c., sodium sulphite 12.0 grams, acetic acid 28 per cent pure 72.0 c.c. and powdered potassium alum 24.0 grams, and the instruction to dissolve in the order given following the directions for mixing the stock hardener Formula F-1a on page 55; Formulas, Volumes and Weights, on Eastman formulas being published on a 32 ounce or 1 litre basis for tray work and a 1 gallon or 4 litre basis for tank work, on larger volumes being necessary for motion picture and photo-finishing tank formulas, and on the term 'Cold water to make' being given at the end of a formula to insure dilution to a definite volume and a known concentration; The Properties of Fixing Baths, on fixation time being twice the clearing time and on the 30 to 40 per cent hypo optimum; The Useful Life of Fixing Baths; Fixing Bath Troubles, on sulphur and aluminium sulphite sludges; How to Prepare Fixing Solutions, the three classes of fixing bath, the instruction to dissolve hypo in warm water because the temperature drops considerably while the hypo is dissolving, the account of a plain bath going alkaline so that prints sticking together develop unevenly, the direction that bisulphite or acid sulphite solutions must not be added to the warm hypo solution or the hypo will turn milky and that the solutions should be quite cold when mixed, the direction that an acid hypo solution gradually becomes milky on keeping, the general-purpose proportion of 45 c.c. of a 50 per cent sodium bisulphite solution to 1 litre of 35 per cent hypo with the warning that any considerable excess turns the hypo milky in warm weather through liberation of sulphur, and the Bisulphite Fixing Bath of hypo 250 g, sodium sulphite 10.5 g and sodium bisulphite 5.3 g per litre; The Properties of Fixing Baths, on fixation time being twice the clearing time, on the 30 to 40 per cent hypo optimum, on 65 degrees F being recommended and 70 degrees F the limit above which sulphur is apt to precipitate, and on the tropical rule that the secret lies in preventing abnormal swelling of the gelatin; The Useful Life of Fixing Baths, on frothing, milkiness and sludging and the 12 to 15 minute clearing rule; Chapter III, on sodium bisulphite as a compound of sodium sulphite with sulphurous acid, on sodium metabisulphite as a compound of sodium sulphite with sulphur dioxide, on ordinary commercial bisulphite consisting chiefly of metabisulphite converted to bisulphite on dissolving, on a neutral solution being made by adding a small quantity of bisulphite to sulphite, on bisulphite supplying both the sulphite and the acid necessary in a fixing bath, and on the customary weight-for-weight substitution of sodium bisulphite for potassium metabisulphite; Terminology and Arrangement of Formulas, on 'Cold water to make' being given at the end of a formula to insure a definite volume and known concentration, on a volume of water at about 125 degrees F being given at the beginning sufficient to dissolve all the chemicals so that the finished solution lands at 65 to 70 degrees F, and on the order of chemicals being established carefully and always to be followed; Acid fixing baths, on why an acid bath is used and what the standard hardener contains; the mixing order and the aluminium sulphite sludge that follows getting it wrong; The Properties of Fixing Baths, on the definition of fixing time as twice the clearing time, the 30 to 40 per cent hypo optimum, the 54 to 77 degree C hardening range and its melting-point test, and the preference for potash alum over chrome alum for long usage; The Useful Life of Fixing Baths, on the signs of exhaustion and the 12 to 15 minute clearing rule; Fixing Bath Troubles, on sulphur and aluminium sulphite sludges; the fixing capacities of formula F-1 with a water rinse and with an acid rinse; Acid fixing baths, on all acid fixing baths containing either sodium bisulphite, potassium metabisulphite or a mixture of sodium sulphite and a weak acid; the directions for mixing them, that bisulphite must not be added to warm hypo and that both solutions should be quite cold, that an acid hypo solution gradually becomes milky on keeping so the bisulphite is kept as a separate stock, and the general-purpose proportion of 45 c.c. of a 50 per cent sodium bisulphite solution to a litre of 35 per cent hypo; the Bisulphite Fixing Bath of hypo 250 g, sodium sulphite 10.5 g and sodium bisulphite 5.3 g per litre; and the statement that a plain bath lets development continue so that prints sticking together develop unevenly; Acid fixing baths, on the three ingredients of an acid hardening solution and on the order of mixing - sulphite in warm water, then the acid, then the alum - with the reason that the alum dissolves more readily in the acid-sulphite solution, the alternative method of dissolving alum and sulphite separately and cooling both, the white sludge of aluminium sulphite that follows adding alum to sulphite before the acid, and the statement that a milky hardener indicates a relative insufficiency of acid; the requirement that the hypo be cool and fully dissolved before the cool hardener is added; Acid fixing baths, on preparing the acid hardening solution as a separate stock and adding it to the hypo solution as required, and on the hypo needing to be cool and completely dissolved first or sulphur is precipitated; The Useful Life of Fixing Baths, on the capacities of formula F-1 for prints with a water rinse and with the acid rinse SB-1; the statement that prints fixed in a bath that has gone alkaline are likely to become stained brown; Acid fixing baths, on preparing the acid hardening solution as a separate stock solution and adding it to the hypo solution as required, on the order of mixing being sulphite first in warm water at about 125 degrees F (52 degrees C) then the acid then the potassium alum, on the alum dissolving more readily in the acid-sulphite solution, on the white sludge of aluminium sulphite that follows adding the alum before the acid, on a milky hardener indicating a relative insufficiency of acid, and on the hypo needing to be cool and completely dissolved before the cool hardener is added; Fixing Bath Troubles, on the three causes of sulphurisation, on a bath above 85 degrees F not remaining clear longer than a few days, on the relation between hardening power and the tendency to precipitate aluminium sulphite, on hardening rising with the quantity of alum and rising to a maximum and then falling with the quantity of acetic acid, on the remedy of adding about half as much acid again as the bath originally contained when a slight precipitate first appears, and on the blisters produced when carbon dioxide is evolved from carried-over carbonate; Chapter I, on sulphur dioxide dissolving in water to form sulphurous acid, SO2 + H2O = H2SO3, and on acid salts such as sodium bisulphite being equivalent to a mixture of the acid and the neutral salt; Chapter III, on acetic acid, on 28 per cent acetic acid being prepared by diluting three parts of glacial acid with eight parts of water, on thiosulphuric acid decomposing to sulphurous acid and sulphur, on the sulphite working in the opposite direction to the acid, and on the difficulty that a large quantity of acid is required in a fixing bath and yet the bath must not be strongly acid; How to Prepare Fixing Solutions, on the order of mixing, on the alum dissolving more readily in the acid-sulphite solution, on the white sludge of aluminium sulphite formed if the alum goes in before the acid, and on the hypo needing to be cool and completely dissolved before the cool hardener is added; The Properties of Fixing Baths, on fixation time being twice the clearing time, the 30 to 40 per cent hypo optimum, 65 degrees F recommended and 70 degrees F the limit above which sulphur is apt to precipitate, and the 54 to 77 degree C hardening range with its melting-point test; The Useful Life of Fixing Baths, on the acidity being reduced by the developer carried in, on hardening rising slightly during the first stages of use and then falling off rapidly, on frothing, milkiness and sludging and the 12 to 15 minute clearing rule; Fixing Bath Troubles, on a bath containing an excess of acid lasting longer before aluminium sulphite precipitates but not hardening as well, on hardening rising with acetic acid to a maximum and then decreasing until the solution does not harden at all, on the minimum acid needed for a long life usually being greater than the quantity that hardens best, on blisters from carbon dioxide evolved when the developer's carbonate meets the fixer's acid, and on dichroic fog in a bath that does not contain acid; Chapter V — following the progress of washing by removing prints at intervals and testing with the hypo test formula, and the period alternative of tasting the prints because hypo containing silver has a sweet taste; the hypo test solution of potassium permanganate 0.3 gram and sodium hydroxide 0.6 gram in distilled water to make 250 cc., used one cubic centimetre to 250 cc. of pure water; Chapter VIII — the hydrogen sulfide in the air reacting with the silver thiosulfate of a standing partially exhausted fixing bath to form a silver sulfide scum; and Chapter IX, Preparing Solutions — the statement that as a general rule in published formulas the term "cold water to make" is always given at the end of the formula, which insures dilution to a definite volume and thus a known concentration of chemicals each time the formula is mixed; Chromium Intensifier, Formula In-4, page 59 under the heading INTENSIFIERS, giving the same stock solution at the same metric quantities twenty-one years earlier - potassium bichromate 90.0 grams, hydrochloric acid concentrated 64.0 c.c., water to make 1.0 litre - with the directions to take 1 part of stock solution to 10 parts of water, bleach thoroughly, then wash five minutes and re-develop in either Nepera Solution 1:4 or in the Elon Hydroquinone developer, Formula D-72, diluted 1:2, then wash thoroughly, and the note that greater intensification can be secured by repeating the process; Chapter VI, The Chemistry of Reduction and Intensification, on intensification being performed by depositing a silver, mercury or a chromium compound upon the image, on the chromium intensifier bleaching the silver image with a solution of bichromate containing a very little hydrochloric acid, bichromate being an oxidiser of the same type as permanganate or ferricyanide, on the image then being redeveloped and found to be intensified to an appreciable extent, on the method having found increasing favour owing to the ease and certainty of its operation and the permanency of the intensified image, on mercury-intensified images being less stable than chromium-intensified ones, and on potassium bichromate forming orange-red crystals stable in air which dissolve easily to a yellow solution and are used both for bleaching negatives and for sensitising gelatin; Chapter VI, The Chemistry of Reduction and Intensification: intensification as photographically the opposite of reduction, the object being to increase contrast; that this is done by the deposition of some material on the silver image; that intensification is usually performed by depositing a silver, mercury or a chromium compound upon the image; and the account of mercury and chromium intensification against which the silver route is set; Mercury Intensifier (Monckhoven), Formula In-1, page 59 under the heading INTENSIFIERS, giving the same two solutions at the same metric quantities twenty-one years earlier, with the same blackening alternatives and the identification of the silver-cyanide bath as Monckhoven's Intensifier; Chapter VI, The Chemistry of Reduction and Intensification, on intensification as the deposition of material on the silver image, on mercury forming mercuric and mercurous salts and mercuric chloride being soluble enough for practical use, on a silver image in mercuric chloride forming a mixture of mercurous chloride and silver chloride and the bleached image appearing white, on redevelopment adding an equal part of mercury to every part of silver, on ammonia forming a black mercury ammonium chloride and a high degree of intensification, on the Eastman Intensifier as a single-solution product, on the Monckhoven intensifier as a very powerful method used chiefly by photo-engravers in which the cyanide cuts the shadows slightly while the highlights are intensified, on mercury bichloride as a virulently poisonous salt whose only use in photography is intensification, and on the finding that mercury-intensified images are not as stable as chromium-intensified ones; Chapter VII, toning: bleaching in ferricyanide and bromide and redeveloping with sodium sulphide; silver sulphide's colour varying from light brown to black according to its state of subdivision; and the warning that no photographic material should be stored in a room where sulphides are kept or sulphide toning is done; Chapter VII, toning: silver sulphide as the most popular method of toning developing-out paper prints; the two general methods, direct toning with the hypo alum bath and bleaching and redevelopment; sodium sulphide as white transparent crystals with a strong affinity for water, best kept as a strong stock solution, and the fused grade in which one part by weight is equivalent to about three parts of the crystals; iron and hypo as the impurities of commercial sulphide; the rule that a print for sulphide toning should be fully developed but not over-exposed; and the warning that no photographic material should be stored in a room where sulphides are kept or sulphide toning is done; Chapter VI, The Chemistry of Reduction and Intensification: intensification as photographically the opposite of reduction, the object being to increase contrast, done by the deposition of some material on the silver image; and the statement that a silver image can be very much intensified by toning it with uranium, the reddish-brown uranium ferrocyanide having very great printing strength and converting a weak negative into one having a great effective contrast for printing purposes; Farmer's Reducer, Formula R-4, page 58 under the heading REDUCERS, the metric column reading Solution A as potassium ferricyanide 1.0 gram and water 32.0 c.c. and Solution B as hypo 30.0 grams and water 1.0 litre, the avoirdupois column reading 15 grains in 1 ounce and 1 ounce in 32 ounces, with the directions 'Add A to B and immediately pour over the negative to be reduced. The formula should be prepared immediately before using as it decomposes rapidly after mixing together the A and B solutions. When the negative has been reduced sufficiently, wash thoroughly before drying.'; Chapter VI, The Chemistry of Reduction and Intensification, on reduction being the removal of silver from the image and the chemical action being oxidation rather than true chemical reduction, on the three classes of reducing solution, on Farmer's reducer as the typical cutting reducer consisting of a mixture of potassium ferricyanide and hypo with the ferricyanide oxidising the silver to silver ferrocyanide and the hypo dissolving the latter compound, on the mixture not keeping and decomposing rapidly, on the usual practice of making a strong ferricyanide solution and adding a few drops of it to a hypo solution when the reducer is required, on its usefulness for clearing negatives or lantern slides showing slight fog and for local reduction with a brush or a wad of absorbent cotton, and on ferricyanide removing the silver of a pyro-developed negative but not the stain; Chapter VI, Reduction, on the three classes of reducer and on Farmer's reducer as the typical cutting reducer, consisting of a mixture of potassium ferricyanide and hypo, the ferricyanide oxidising the silver to silver ferrocyanide and the hypo dissolving the latter compound, on the mixture not keeping and decomposing rapidly, on the usual practice of making a strong ferricyanide solution and adding a few drops of it to a hypo solution when the reducer is required, and on its usefulness for clearing negatives or lantern slides showing slight fog and for local reduction with a brush or a wad of absorbent cotton; formula R-4, Farmer's Reducer, giving Solution A as potassium ferricyanide 1.0 gram in 32.0 c.c. of water and Solution B as hypo 30.0 grams in 1.0 litre of water, with the direction to add A to B and immediately pour over the negative; the warning that a trace of iron in a ferricyanide bath throws blue spots; the note that ferricyanide removes the silver of a pyro-developed negative but not the stain; Chapter VI, The Chemistry of Reduction and Intensification: the three classes of reducing solution - cutting, proportional and flattening; cutting reducers removing an equal quantity of silver from all parts of the image and consequently a larger proportion from the shadows; proportional reducers acting on all parts in proportion to the quantity of silver present, so that they exactly undo the action of development, and the statement that a correctly exposed but over-developed negative should be reduced with a proportional reducer; the statement that no single substance forms an exactly proportional reducer; Farmer's reducer as the typical cutting reducer and its decomposition when mixed; Rinse Baths, Acid Rinse Bath for Paper, formula SB-1, water 1.0 litre and acetic acid 28 per cent 48.0 c.c., with the footnote that 28 per cent acid is made by diluting three parts of glacial acid with eight parts of water; Rinsing Prints, the recommendation of an acid rinse over a water rinse, the 5 to 10 second and 1 to 2 minute rinse times, the statement that no harm is done if prints are left 10 or 20 minutes, the litmus test, and the capacity of approximately seventy-five 8 by 10 prints per gallon; the fixing-bath capacities of formula F-1 with and without the acid rinse; Chapter I, the swelling and shrinking of gelatin, the statement that a small quantity of either an acid or an alkali produces a considerable increase in the swelling and that both developer and fixing bath therefore tend to swell the gelatin, especially when warm; Chapter IV, the footnote that 28 per cent acetic acid is made by diluting three parts of glacial acid with eight parts of water and the warning that this is not the same product as commercial 28 per cent acid redistilled from wood; Tropical Process Developer D-13, which carries 105.0 grams of crystalline sodium sulphate per litre; the passage on tropical processing, where the secret lies in preventing abnormal swelling of the gelatin, for once it is swollen it is almost impossible to reduce it; Rinsing Prints, the litmus test for whether the rinse bath is still acid; Chapter V, The Chemistry of Washing — the statement that it should not be necessary to wash out silver compounds but only the chemicals of the fixing bath, that if an exhausted fixing bath is used silver compounds will be present during washing and must be removed very completely, and that where work has to be hurried and the washing time cut down it is most important that fixing should be complete; the two-bath rotation given as the best way of insuring complete fixing; Chapter VII — sulphide toning by bleaching and redevelopment and the insolubility of silver sulphide as the reason the trade adopted it; Chapter IX, Preparing Solutions — the statement that as a general rule in published formulas the term cold water to make is always given at the end of the formula, which insures dilution to a definite volume and thus a known concentration of chemicals each time the formula is mixed; and Chapter X — that a very small quantity of hydrogen sulphide converts enough silver halide to sulphide to produce severe fog, so that no photographic material should be stored in a room where sulphides are kept; Chapter VIII, Toning Formulas, page 60, Sepia Toning—Hypo-Alum Bath T-1a: cold water 2800.0 cc and hypo 480.0 grams; hot water about 160°F (71°C) 640.0 cc and powdered potassium alum 120.0 grams; cold water 64.0 cc, silver nitrate crystals 4.2 grams and sodium chloride 4.2 grams; water to make 4.0 liters; the note that the silver nitrate should be dissolved completely before adding the sodium chloride and that the solution containing the milky white precipitate should then be added immediately to the hypo-alum solution, that the solution should be milky white if correctly mixed, and that if boiling water is used, or the order of mixing is changed, or the bath is not stirred while the white precipitate is added, the bath will turn a dirty grey or black; the working instruction to heat to 120°F (49°C) in a tray in a water bath, tone in 12 to 15 minutes, and never heat higher than 130°F (54°C) or blistering, staining and non-uniform toning will result; Chapter VII, on alum in water being weakly acid so that alum added to plain hypo without sulphite precipitates sulphur, on the bath at that point having free sulphur in solution, on a fresh bath weakening the print and eating out the highlights unless a little silver is added preferably as silver chloride, on a used bath working better than a fresh one, and on blue-black images giving cold chocolate tones while olive green images give warm sepia; Chapter VIII, Toning Formulas, page 60: No. 1—Stock Bleaching Solution T-7a reading potassium ferricyanide 75.0 grams, potassium bromide 75.0 grams, potassium oxalate 195.0 grams, acetic acid (28% pure) 40.0 c.c. and water 2.0 liters; No. 2—Stock Re-Developing Solution reading sodium sulphide (not sulphite) 45.0 grams and water 500.0 c.c.; the Bleaching Bath as 500 c.c. of stock No. 1 with 500 c.c. of water; the Re-Developer as 130.0 c.c. of stock No. 2 with 1.0 liter of water; the working procedure, bleaching for about one minute until only faint traces of the half-tones are left and the black of the shadows has disappeared, rinsing thoroughly in clean cold water, re-developing for about thirty seconds until original detail returns, then five minutes in 1 part of the F-1a hardener to 16 parts of water and half an hour's wash; the note not to use trays with any iron exposed; Chapter VII, on potassium oxalate reducing blue spotting because the blue iron salt is soluble in the oxalate, and on acetic acid being added to prevent possible formation of blisters; "Chapter III: the four ingredients of a developer, alkali and the energy of a developer, and alkalis softening the gelatin and causing over-swelling and frilling; Chapter VII: what happens to a developer with use and the restraining action of accumulated bromide and iodide"; Chapter VII, toning — bleaching the silver print in ferricyanide and bromide and then treating the washed print with sulphide, which converts the silver bromide directly into silver sulphide; that silver sulphide is a very insoluble compound of silver and its colour varies from light brown to black according to the state of subdivision; that the state of division of the toned image depends on that of the untoned image, so a print for toning should be fully developed but not over-exposed; and that a trace of iron in the ferricyanide-bromide bleach forms blue spots of ferric ferrocyanide, reduced by adding potassium oxalate because the blue iron salt is soluble in the oxalate; The Properties of Fixing Baths, on a plain solution of hypo being seldom used as a fixing bath and on the 30 to 40 per cent optimum; Acid fixing baths, on development continuing in a plain bath and on the uneven development where two prints stick together; the statement that a solution of alum in water is weakly acid so that alum added to plain hypo without sulphite turns the bath turbid and precipitates sulphur; Chapter IV, for the decomposition of thiosulfate by a few drops of hydrochloric or sulphuric acid with the precipitation of sulphur; Chapter VI, toning: the statement that platinum toning baths are used in an acid condition, against the alkaline condition required for gold; "Chapter III: sodium bisulphite as the preferable preservative in a two-solution developer because oxidation progresses less readily in acid than in alkaline solution, the equation by which bisulphite is converted to sulphite by carbonate and destroys an equivalent of the alkali, and the note that bisulphite is difficult to prepare free from iron and that iron gives a dark colour in a pyro solution; Chapter X: the general rule that the preservative is dissolved first, the exception for Elon, the practice of dissolving a portion of the sulphite before the Elon and the remainder after, the rule that only a low concentration of sulphite is needed to prevent Elon from dissolving, and the instruction to dissolve each chemical completely before adding the next"; The Properties of Fixing Baths, on the optimum hypo concentration for speed of fixation lying between 30 and 40 per cent and on a plain solution of hypo being seldom used as a fixing bath; Acid Fixing Baths, on a few drops of a strong acid decomposing a weak hypo solution so that it turns milky as sulfur separates; Chapter III — bisulphite as the preferable preservative in a two-solution developer because oxidation progresses less readily in acid than in alkaline solution, and the equation by which bisulphite is converted to sulphite at the expense of the carbonate; Chapter X — the rule that each chemical is dissolved completely before the next is added; Chapter VII, toning: bleaching the silver print in a bath of ferricyanide and bromide and then treating the bleached print, after washing, with sodium sulphide, which converts the silver bromide directly into silver sulphide; the warning that a trace of iron in the ferricyanide-bromide bleach, for example from a defective enamelled tray, forms blue spots of ferric ferrocyanide, and that potassium oxalate in the bleach reduces this because the blue iron salt is soluble in the oxalate; Chapter VIII, the Re-Development Intensifier, which is the same bleach used on a negative; Chapter III - the commonest developing agents, para-aminophenol and Kodelon, the bases and their salts; the reduction-potential ranking, the substitution of Kodelon for Elon and the alkali each agent requires; the quantity of alkali and chemical fog; the caustic alkalis and the rule that both are dissolved in cold water; formula D-9 and the warning that hot water makes the caustic solution boil with explosive violence; the chapter on preparing developers - "A para-aminophenol-carbonate developer is difficult to prepare in concentrated form"; Chapter II, on materials that are to be developed containing no excess of soluble silver and always an excess of bromide or chloride, against Solio paper, a printed-out chloride emulsion made with an excess of silver nitrate which causes rapid darkening in the light, and on the Eastman Kodak Company preparing its own silver nitrate; Chapter IX, Preparing Solutions, (e) on chemicals decomposed by long exposure to light, naming silver nitrate as probably the outstanding example, noting that a solution darkens quite rapidly where the crystals merely darken, and giving dark brown bottles for both as the remedy; Chapter VII, pages 43-44: that the value of ferricyanide in photography lies in the fact that ferricyanide oxidises the silver image and forms silver ferrocyanide from it; that combining with the potassium ferricyanide a salt of a metal which gives an insoluble coloured ferrocyanide yields silver ferrocyanide which is then converted into the ferrocyanide of that metal, uranium nitrate giving the reddish-brown uranium ferrocyanide, iron citrate a blue and copper citrate a red; that the operation is sometimes done in two steps instead, the silver being bleached to silver ferrocyanide first and then combined with the metal salt; and the uranium mordanting bath which transforms the image into a mixture of uranium and silver ferrocyanides for dye toning. Chapter VI, The Chemistry of Reduction and Intensification, page 39, for intensification as the deposition of some material on the silver image, for the statement that a silver image can be very much intensified by toning it with uranium, the reddish-brown uranium ferrocyanide having very great printing strength and converting a weak negative into one having great effective contrast for printing purposes, and for the cross-reference in that sentence to page 44; The chapter on preparing solutions, for Kodak's own statement of the make-up convention this formula predates: "As a general rule in published formulas the term 'Cold water to make' is always given at the end of the formula. This insures dilution to a definite volume, thus yielding a known concentration of chemicals each time the formula is mixed."; Directions for mixing D-76; borax and the high sulphite of D-76 as a solvent for silver bromide; the accentuation of graininess when carbonate is substituted; Acid fixing baths; The Properties of Fixing Baths, including the 30 to 40 per cent hypo optimum and the hardening range; The Useful Life of Fixing Baths; Fixing Bath Troubles; Sulphide toning and the colour of silver sulfide according to its state of subdivision; hypo alum toning; Chapter II: The Chemistry of Photographic Materials; Chapter II: The chemistry of photographic materials; Chapter II: printing-out and developing-out emulsions; Storage of chemicals: oxygen, carbon dioxide, deliquescence, efflorescence and light; Acetic acid: glacial and its dilutions; Formula SB-1 acid rinse bath; developing formulas D-1 and others, avoirdupois and metric columns; Chapter II: precipitation of silver chloride from silver nitrate; Chapter IV: acid decomposing hypo to sulfurous acid and sulfur; the strength of an acid depends on the proportion of hydrogen dissociated, while the alkali it can neutralise depends on the total hydrogen present; acetic acid as the acid of choice for a fixing bath; sodium bisulfite as the substitute; chrome alum baths losing their hardening properties when developer is carried over; Chapter I: air contains 20 per cent of oxygen, and sodium sulphite left exposed to it oxidises to sulphate; the quinone and sulphite cycle; Chapter III: developers are "necessarily substances which have a great affinity for oxygen", sulphite as preservative, the pyro stain, and the warning that sulphite which has effloresced is to be suspected because "the sulphate is not a preservative"; Chapter IV: developer carried into the fixing bath soon oxidises there, turning it brown and staining negatives or prints, and sulphite is added to the fixing bath as a preservative whose action is greater if the bath is kept slightly acid; Chapter VII: the water supply and the impurities that actually matter to a developer; Chapter I: An Outline of Elementary Chemistry - double decomposition and the silver nitrate plus sodium chloride precipitation; Chapter II: sodium carbonate in three commercial forms at 37, 85 and 98 per cent; potassium carbonate compared with sodium; potassium bromide; Chapter II: formula D-76 and its borax; sodium carbonate in three commercial forms; Chapter IV: the strength of an acid against the alkali it can neutralise, and the acid reserve an acid fixing bath needs against carried-over developer; Chapter IV, The Chemistry of Fixation: there are only a few substances which will dissolve silver bromide and sodium thiosulphate is the one universally used; two fixing baths as the best way of insuring complete fixing; Chapter III: the high sulphite concentration of D-76 as a solvent for silver bromide and iodide; Chapter VII: the water supply, the impurities that matter and the note that calcium salts sometimes retard the swelling of gelatin; Chapter II: gelatin as a colloid that swells rather than dissolves in cold water, the increase in swelling produced by a small quantity of acid or alkali and by warmth, hardening with alum, and reticulation from sudden expansion or contraction when solutions differ in temperature; Chapter III: the speed of development depending chiefly on the rate at which the developer diffuses into the film; Chapter V, Washing: the rate of washing depends on the rate of diffusion of hypo out of the film provided the water in contact is continuously removed, has nothing to do with solubility, is not helped by warm water because swelling hinders diffusion in about the same proportion as the rise in temperature accelerates it, is unaffected by hardening unless the gelatin has been dried after hardening, and proceeds by a constant halving time - about 15 seconds under a running faucet and 30 seconds in most trays and tanks - with successive changes of small volumes of water named as by far the most effective economical method; Chapter I: oxidation of sodium sulphite to sulphate by air, and the hydroquinone-quinone-sulphite cycle; Chapter III: the developer as a chemical reducer that must reduce exposed silver bromide and not unexposed, the reduction potential of the developing agents and its limits, sulphite as preservative, the alkali and chemical fog; Chapter VI: photographic "reduction" of a negative is chemically oxidation; Chapter III: the reduction potential of the developing agents and what it buys under adverse conditions; that a very little change in temperature affects hydroquinone greatly and Elon very little; that the speed of development depends chiefly on the rate at which the developer diffuses into the film; Chapter I: double decomposition and precipitation; Chapter II: making an emulsion, the deliberate excess of halide in a developing-out emulsion and the deliberate excess of silver in Solio printing-out paper, and speed obtained by varying temperature and duration of heating; formula D-71; Chapter II: making an emulsion, the precipitation of silver bromide, ripening by temperature and duration of heating, bromide and chloride papers; Chapter I: double decomposition; Chapter II: the thick curdy precipitate of silver bromide, and adding the silver nitrate a little at a time; Chapter II: the manufacture and purity of silver nitrate, double decomposition with potassium bromide, and the curdy precipitate; Chapter II: sensitiveness obtained by varying the temperature and duration of heating in manufacture; Chapter I: double decomposition and the precipitation of silver chloride; Chapter II: the precipitation of silver bromide from silver nitrate and potassium bromide, the thick curdy precipitate, ripening by temperature and duration of heating, negative materials as bromide with a small addition of iodide, bromide paper for enlargements and chloride papers for contact printing; Chapter II on gelatin swelling and the hardener added before coating; Chapter V on whether hardening slows the washing of hypo out of the film; Chapter II: gelatin in emulsion making, swelling in cold water, the absence of a definite solubility, melting and resetting, and the hardener added before coating; Chapter II: making an emulsion, the precipitation of silver bromide in gelatin, and ripening by temperature and duration of heating; Chapter III: the four ingredients of a developer, reduction potential and the ranking of the agents, the alkali and its effect on fog and swelling, sodium sulfite as preservative, borax and the fine-grain developer D-76; Chapter VII: the useful life of developers; Chapter III: the four ingredients of a developer, the reduction-potential ranking of the agents, the preservative and the yellow oxidation product of pyrogallol; Formula D-72, the Velox, Azo and bromide paper developer, with its metol, sodium sulphite, hydroquinone, sodium carbonate and potassium bromide quantities and its mixing water at 125 degrees F; Chapter VI: aerial fog with Elon and hydroquinone developers and the addition of about 5 per cent of old developer to prevent it; Chapter VII: the useful life of developers, the colourless mono- and disodium sulphonates of hydroquinone, and the warning that a colourless old Elon-hydroquinone developer is no indication of undiminished developing power; Chapter III: the alkali governs the energy of the developer, too much gives chemical fog and too little is slow, and alkalis soften gelatin and cause frilling or blisters in warm weather; the caustic alkalis and the instruction to dissolve them in cold water; the carbonates as a reservoir of alkali; water of crystallisation and sodium carbonate in three forms; the uselessness of bicarbonate as a photographic alkali; borax and fine-grain development; sodium acetate, dibasic sodium phosphate and borax as weak alkalis for gold toning; Chapter VIII: formula D-9, hydroquinone-caustic; Chapter III: para-aminophenol and its methylated derivative, Kodelon as the oxalate, the reduction-potential ranking, the graded sulfite experiment with pyrogallol and the colour of the resulting negative; Chapter VII: two-solution storage for readily oxidisable agents; Chapter III: the commonest developing agents, para-aminophenol and its methylated derivative, the reduction-potential ranking measured by bromide tolerance, the alkali requirement and the caustic case for hydroquinone; Chapter VII: the useful life of developers, the colourless mono- and disodium sulfonates of hydroquinone, the strong fluorescence of an oxidised Elon-hydroquinone developer, the ten per cent rule for sulfite stock solutions and the impossibility of an Elon-plus-sulfite stock, and the white sludge; Formula D-76 with its mixing directions and temperatures; Chapter III: the reduction potential of the agents, that a very little change in temperature affects hydroquinone greatly and Elon very little, and that the speed of development depends chiefly on the rate at which the developer diffuses into the film; Chapter VII: the three things that happen to a developer with use and the three reasons a deep-tank developer is discarded; Chapter XI: the temperature coefficient, its definition over 10 degrees C, its variation with the developing agent, the consequence for a mixed developer at high and low temperature, and the statement that the fog reaction has a much higher temperature coefficient than development; Chapter I: oxidation and reduction, hydroquinone and quinone; Chapter III: the narrow bounds a developing agent must sit within, the reduction-potential ranking measured by bromide tolerance, the alkali and chemical fog; Chapter VII: aerial fog with Elon-hydroquinone developers and the five per cent old-developer remedy, and dichroic or green fog from excess sulfite or hypo; Fine Grain Negative Developer Formula for Motion Pictures D-76, with the Elon, sodium sulphite, hydroquinone and borax quantities per gallon and per four litres, the Directions for Mixing — dissolve the Elon in a small volume of water at about 125 degrees F or 52 degrees C, dissolve approximately one quarter of the sulphite separately in hot water at about 160 degrees F or 71 degrees C and add the hydroquinone with stirring, then dissolve the remainder of the sulphite, add the borax, and dilute to volume with cold water — and the development time of 10 to 20 minutes at 65 degrees F; Chapter III: the four ingredients of a developer, the alkali governing the energy of a developer, borax and the fine-grain developer, and the high sulphite of D-76 as a solvent for silver bromide and iodide; Chapter III: the four ingredients of a developer; the reduction-potential ranking of the agents; the statement that the quantity of alkali governs the energy of a developer, that too much alkali tends to produce chemical fog and too little makes it slow, and that alkalis soften the gelatin; the preservative; borax and the high sulphite of D-76 as a solvent for silver bromide and iodide, and the accentuation of graininess when carbonate is added; formula D-76 with its Directions for Mixing and its Elon, sulphite, hydroquinone and borax quantities per four litres; formula D-72; Chapter VII: the useful life of developers and the colourless sulphonates; Chapter IX: the restrainer added to compensate for chemical fog; Chapter III: the four ingredients and the restrainer as the bromides and iodides of sodium or potassium, added to compensate for chemical fog produced by the developer or inherent in the emulsion; the reduction-potential ranking measured by bromide tolerance and the statement that a little bromide affects hydroquinone and does not affect Elon nearly so much; Chapter VII: what happens to a developer with use, the restraining action of accumulated bromide and iodide being analogous to cutting down the exposure, the three reasons a deep-tank developer is discarded, developer troubles and aerial fog, and the addition of about 5 per cent of old developer as a remedy; Chapter VIII: formulas D-9, D-13, D-52 and the bromide additions for the four grades of Vitava paper; Chapter III: borax and the fine-grain motion picture developer, graininess as the fusion or clumping of grains, the statement that several crystals in close proximity may develop as a clump through contact with an exposed crystal, the high sulphite of D-76 as a solvent for silver bromide and iodide, and the effect of adding carbonate to such a developer; Chapter VI: dichroic or green fog produced by a developer containing an excess of sulphite, hypo or ammonia, its appearance by reflected and transmitted light, its cause in dissolved silver salts reduced to metallic silver in a very fine state of subdivision, its concentration in the shadows where no bromide is liberated, and the susceptibility of fine-grained emulsions; Chapter IX: dichroic fog from a fixing bath that is old, exhausted or not acid; Chapter III: the commonest developing agents and the ranking by reduction potential; the preservative and the graded pyrogallol experiment — no sulfite giving a very yellow negative whose image is partly silver and partly oxidised pyrogallol, sulfite giving a much less yellow one and a great deal of sulfite giving almost as blue an image as Elon; the statement that pyro oxidises far more readily than Elon or para-aminophenol; Formula D-1, the standard A.B.C. pyro, in three stock solutions with its tray and tank dilutions and times; Chapter VII: the keeping of pyro, two-solution and three-solution storage, sodium bisulphite as the better preservative for readily oxidisable agents, and scum on standing developers; Chapter I: the oxidation of sulphite to sulphate and the reduction of quinone by sulphite; Chapter III: the four ingredients of a developer, the preservative and the graded pyrogallol experiment, borax and the fine-grain developer D-76 in which the high sulphite concentration dissolves a little of each grain, sodium sulphite and the heptahydrate; Chapter VII: the useful life of developers, the colourless mono- and disodium sulphonates, the ten per cent rule for sulphite stock solutions and the impossibility of an Elon stock, bisulphite as the better preservative in the absence of carbonate, two-solution storage, dichroic or green fog; Chapter III: the commonest developing agents, the reduction-potential ranking measured by bromide tolerance, the statement that hydroquinone has so low a potential that it is rarely used alone but is generally used with Elon, and that an Elon image comes up quickly and gains density slowly while a hydroquinone image comes up slowly and gains density steadily and rapidly; the two fates of quinone in a sulfite solution; Chapter VII: the colourless mono- and disodium sulphonates of hydroquinone and the warning that a colourless developer is no indication of undiminished power; Chapter III: the alkali governs the energy of the developer, and too much of it gives chemical fog; Chapter IX: bromides and iodides added to compensate for chemical fog; Chapter III — the alkali governs the energy of the developer, too much gives chemical fog and too little is slow, and most developing agents cannot develop at all without an alkaline solution because the energy depends upon the amount of alkali present; Chapter IX — bromides and iodides added to a developer to compensate for chemical fog produced by the developer or inherent in the emulsion; Chapter III — the statement that the energy of a developer depends upon the amount of alkali present, that too much alkali gives chemical fog and too little is slow, and that most developing agents cannot develop without an alkaline solution; Chapter VII — the colourless mono- and disodium sulphonates of hydroquinone and the warning that a colourless developer is no indication of undiminished power; Chapter IX — bromides added to compensate for chemical fog; Chapter III — the statement that the energy of a developer depends upon the amount of alkali present and that too much alkali gives chemical fog; the description of the Elon and hydroquinone image characters; Chapter III — the commonest developing agents; the statement that hydroquinone has so low a potential that it is rarely used alone but is generally used with Elon; the statement that an Elon image comes up quickly and gains density slowly while a hydroquinone image comes up slowly and gains density steadily and rapidly; the statement that the energy of a developer depends upon the amount of alkali present; the two fates of quinone in a sulphite solution; Chapter VII — the colourless mono- and disodium sulphonates of hydroquinone and the warning that a colourless developer is no indication of undiminished power; Chapter III — graininess as the fusion or clumping of grains, the statement that several crystals in close proximity may develop as a clump through contact with an exposed crystal, and the high sulphite of D-76 acting as a solvent for silver bromide and iodide; Chapter VI — dichroic or green fog produced by a developer containing an excess of sulphite, its appearance by reflected and transmitted light, its cause in dissolved silver salts reduced to metallic silver in a very fine state of subdivision, and its concentration in the shadows where no bromide is liberated; Chapter X — the life of the acid rinse bath, determined by the alkali carried over from the developer, the quantity of carbonate in it, the quantity of developer retained by the print and the time of draining, with the figure of approximately seventy-five 8 x 10 prints per gallon at a one- to two-second drain, and the blue litmus test for whether the bath is still acid; Chapter IV — acetic acid, its preparation, the 80 per cent and 28 per cent dilutions, and the footnote that 28 per cent acid is made by diluting three parts of glacial acid with eight parts of water; sodium bisulphite as the substitute when acetic acid cannot be obtained, and its poorer reserve of available acid; potassium alum as the commonest hardening agent; Chapter VIII — formula SB-1 at 48 c.c. of 28 per cent acetic acid per litre and formula SB-3, the chrome alum hardening bath; Chapter X — Rinsing and Hardening Films or Plates, the chromium scum of chromium hydroxide and the bath's blue-to-yellowish-green colour change; faults B, C, D and E covering the acid-against-hardening balance, blisters, dichroic fog and the white aluminium sulphite scum; Chapter IV — the strength of an acid against the quantity of alkali it can neutralise, and why a large quantity of a weak acid makes acetic acid the best choice; Chapter VIII — formula SB-1, an acid rinse bath for paper of 48 c.c. of 28 per cent acetic acid per litre, with the footnote that 28 per cent acid is made by diluting three parts of glacial acid with eight parts of water; Chapter X — The Importance of Rinsing, Rinsing Prints, the life of the acid rinse bath and its figure of approximately seventy-five 8 x 10 prints per gallon with a one- to two-second drain and a typical Elon-hydroquinone developer, the litmus test for an alkaline bath, and the faults B, C and D covering hardening, blisters and dichroic fog; Chapter IV — the decomposition of hypo by acid into sulphurous acid and sulphur, and the role of sulphite in preventing it; The Properties of Fixing Baths, the time for fixation taken as twice the time for the milkiness or opalescence to disappear; Fixing Bath Troubles A and D, the sulphur and aluminium sulphite sludges and dichroic fog; The Properties of Fixing Baths — the time for fixation taken as twice the time for the milkiness or opalescence of the unreduced silver salts to disappear; the dependence on the strength of the hypo, 30 to 40 per cent fixing most rapidly, on the material, portrait films 3 to 5 minutes and lantern slides 30 seconds to 1 minute, and on temperature, a film needing 95 seconds to clear at 65 degrees F (18 degrees C) taking about 60 seconds at 85 degrees F (29 degrees C), with the warning that letting the bath rise above 70 degrees F (21 degrees C) is dangerous practice because it is apt to precipitate sulphur; The Useful Life of Fixing Baths — discard when the clearing time of a slow-fixing film exceeds 12 to 15 minutes; Fixing Bath Troubles D, Dichroic Fog — if the fixing bath does not contain acid or if it is old and exhausted and contains an excess of dissolved silver salts, a stain called dichroic fog is sometimes produced; in reflected light the film appears yellowish-green and by transmitted light reddish-pink; dichroic fog never occurs in a fresh acid fixing bath, or if the film is rinsed before fixing and the temperature of the bath is kept at 65 to 70 degrees F; Chapter on reduction — dichroic fog consists of very finely divided silver, attacked by a plain permanganate solution of about 0.25 per cent which has no appreciable action on the silver of the image; The Properties of Fixing Baths — the time for fixation taken as twice the time for the milkiness or opalescence of the unreduced silver salts to disappear, and discard when the clearing time of a slow-fixing film exceeds 12 to 15 minutes; Chapter IV — developer carried into the fixing bath oxidises there, turning it brown and staining negatives or prints, which is what the sulphite is added to prevent; The Useful Life of Fixing Baths — the acidity of the bath falling as developer is carried in, the aluminium sulphite sludge that ends it, the hardening properties rising and then falling with use, the signs of exhaustion including frothing, milkiness and sludging, and the instruction to discard when the clearing time of a slow-fixing film exceeds 12 to 15 minutes; the capacity figures for formulae F-1 and F-16, seventy-five 8 by 10 inch films or plates per gallon and one hundred prints, rising to one hundred and twenty-five prints where the SB-1 acid rinse bath precedes fixation; Fixing Bath Troubles E — a partially exhausted bath left standing for several days reacts with the hydrogen sulphide usually present in the air to form a metallic-looking scum of silver sulphide on the surface; Chapter IV — the acid decomposition of hypo into sulphurous acid and sulphur, the reversibility of that change and the protective role of sulphite, and the argument that a fixing bath needs a large quantity of a weak acid because a great deal of alkaline developer is carried into it; potassium chrome alum and ammonium chrome alum, and the warning that an alkaline ammonium chrome alum bath evolves ammonia and gives dichroic fog; the loss of hardening power of a chrome alum bath in the presence of sulphite within one or two days; The Properties of Fixing Baths — a plain solution of hypo is seldom used alone, the standard hardener contains sulphite, acetic acid and either potassium or chromium alum, and the properties wanted are a fairly rapid rate of fixation, good hardening, a long sludging life and a long useful life; Fixing Bath Troubles A, B, D and E — the pale yellow sulfur precipitate and its three causes, the white gelatinous aluminium sulphite sludge and its two, the relation between excess acid, sludging life and hardening power, dichroic fog in an old or non-acid bath, and the silver sulphide scum formed on a standing partially exhausted bath; The Properties of Fixing Baths — the time for fixation taken as twice the time for the milkiness or opalescence of the unreduced silver salts to disappear; the dependence on the strength of the hypo, 30 to 40 per cent fixing most rapidly, on the material, portrait films 3 to 5 minutes against lantern slides 30 seconds to 1 minute, and on temperature, a film needing 95 seconds to clear at 18 degrees C taking about 60 seconds at 29 degrees C, with the warning that above 21 degrees C the bath is apt to precipitate sulphur; The Useful Life of Fixing Baths — discard when the clearing time of a slow-fixing film exceeds 12 to 15 minutes; Chapter on the halogens — potassium cyanide used for fixing wet collodion plates, which being made from silver iodide are not easily fixed in hypo; Chapter IV — the decomposition of hypo by acid to sulphurous acid and sulphur, its reversal by sulphite, and the argument for a large quantity of a weak acid; Chapter VIII footnote — 28 per cent acetic acid is made by diluting three parts of glacial acid with eight parts of water; The Properties of Fixing Baths — the strength of hypo, 30 to 40 per cent fixing most rapidly; Fixing Bath Troubles A — the two sludges, the pale yellow sulfur precipitate caused by too much acid, too little or impure sulphite or high temperature, and the white gelatinous aluminium sulphite sludge caused by too little acid or too little hardener, with the instruction that the hardener should only be added to the hypo solution at room temperature and the warning that adding hardener to hypo that has not fully dissolved is apt to precipitate sulphur; The washing chapter — the rate of washing depends on the rate of diffusion of the hypo out of the film and has nothing to do with solubility; the quantity of hypo remaining is continually halved in the same period of time; the half-time of about 15 seconds under a running tap and 30 seconds in most trays and tanks; the process stops unless the water in the vessel is changed; washing in cascade with two trays; six changes of water allowing five minutes for each change; and the statement that where water is to be economised by far the most effective way of washing is to use successive changes of small volumes of water; Developing Formulas for Paper, Velox, Azo and Bromide Papers - stock solution D-72 with its metric column per 1.0 litre, the direction to dissolve the chemicals in the order given in 500 c.c. of water at about 52 degrees C and make up to volume with cold water, and the three paper dilutions with their development times of 45 seconds at 1:1 and 1:2 and one and a half minutes at 1:4; the note that Azo diluted as for Velox gives colder tones; and the statement that a small quantity of bromide affects hydroquinone and does not affect Elon nearly so much; Chapter II - the statement that a slow bromide emulsion coated upon paper is known as bromide paper and is used for printing and especially for enlargements, and that the less sensitive papers commonly used for contact printing by artificial light contain silver chloride in place of silver bromide; Developing Formulas for Paper - stock solution D-72 with its three paper dilutions and their development times, the note that Azo diluted as for Velox gives colder tones, and the amidol formula D-51 for bromide papers; the reduction-potential ranking of the developing agents and the statement that a small quantity of bromide affects hydroquinone and does not affect Elon nearly so much; the quantity of alkali and its effect on the energy of a developer, on chemical fog and on the softening of gelatin; and the statement that most developing agents cannot develop at all when used by themselves and that with the exception of Acrol they must be in an alkaline solution; Chapter VIII, Toning Formulas, page 60, Stock Bleaching Solution T-7a and Stock Re-Developing Solution, whose two stock solutions are identical salt for salt and gram for gram with the 2006 printing, whose bleaching bath is likewise 500 c.c. of stock in 500 c.c. of water, but whose re-developer is 130 c.c. of stock in 1.0 litre of water and whose bleaching time is about one minute, until only faint traces of the half-tones are left and the black of the shadows has disappeared; and the note not to use trays with any iron exposed. Chapter VII, section D of the toning chapter - that potassium oxalate reduces blue spotting to a minimum because the blue iron salt is soluble in the oxalate, that acetic acid is added to prevent possible formation of blisters, that old sodium sulfide often contains hypo which dissolves silver bromide and weakens the highlights, that sodium sulfide is best kept as a strong stock solution because the crystals deliquesce, that all sulfides give off a certain quantity of hydrogen sulfide which is extremely dangerous to unexposed photographic materials because a very small quantity produces severe fog, so that no photographic materials should be stored in a room where sulfides are kept or sulfide toning is done, and that the state of division of the toned image depends on that of the untoned image so a print for sulfide toning should be fully developed but not over-exposed; Chapter VII, The Chemistry of Toning — the four principal methods, A toning by the replacement of the silver by other metals, B toning by the deposition of salts of metals, C toning by the transformation of the silver image into some substance to which dyes will attach themselves in an insoluble form, and D transformation of the silver image into a stable, strongly coloured salt of silver; under A, that when a finely divided silver image is placed in a solution of gold or platinum the silver replaces the metal in solution and goes into solution itself while the gold or platinum is deposited in the place of the silver, that the rate of deposition is very important, that finely divided gold is red while more rapid deposition gives the more pleasing blue gold, that to ensure rapid deposition the bath must be kept alkaline so borax or sodium acetate is added to the gold chloride, that substances of weak reducing action such as sulphocyanides or formates are sometimes added, and that platinum toning baths are used in an acid condition; the note on gold chloride that it forms brownish crystals which rapidly absorb water and contains 65 per cent metallic gold, sold in sealed tubes of 15 grains, and on gold sodium chloride that it contains 49 per cent metallic gold and is neither acid nor deliquescent; under B, that ferricyanide oxidises the silver image and forms silver ferrocyanide from it, that silver ferrocyanide is soluble in hypo which is Farmer's reducer, that adding bromide converts the silver ferrocyanide to silver bromide because silver bromide is the more insoluble and this operation is known as bleaching, and that combining potassium ferricyanide with a salt of a metal whose ferrocyanide is insoluble and coloured gives that metal's ferrocyanide at the image — iron citrate giving a blue iron ferrocyanide, uranium nitrate the reddish-brown uranium ferrocyanide and copper citrate the red copper ferrocyanide — the operation being run sometimes in one bath and sometimes in two; and under C, that the silver image can be transformed into silver iodide by a mixture of potassium ferricyanide and potassium iodide and that the silver iodide image will mordant basic dyes and attach them to the image, and that the Kodak Research Laboratories worked out a process using a uranium mordanting bath which transforms the image into a mixture of uranium and silver ferrocyanides onto which basic dyes are then mordanted; Chapter VII, The Chemistry of Toning - the definition of toning as the deposition on the silver image of another substance having a different colour, or the transformation of the silver image into another substance for the same purpose; the four principal methods, A replacement of the silver by other metals, B deposition of salts of metals, C transformation into a substance to which dyes will attach themselves in an insoluble form, and D transformation of the silver image into a stable, strongly coloured salt of silver; under A, that a finely divided silver image placed in a solution of gold or platinum causes the silver to replace the metal in solution, going into solution itself, while the gold or platinum is deposited in the place of the silver, that the rate of deposition matters, and that finely divided gold is red while more rapid deposition gives blue gold, alkalinity being what secures rapid deposition; under B, that the silver image is first transformed into silver ferrocyanide and the silver then substituted by another metal whose ferrocyanide is coloured, giving blue iron ferrocyanide, reddish-brown uranium ferrocyanide and red copper ferrocyanide, and that the two steps are sometimes run in one bath and sometimes in two; that ferricyanide oxidises the silver image and forms silver ferrocyanide from it, that silver ferrocyanide is soluble in hypo, which is Farmer's reducer, and that adding bromide converts the silver ferrocyanide to silver bromide because silver bromide is the more insoluble, this operation being known as bleaching; under D, that silver sulfide is a very insoluble compound whose colour varies from light brown to black according to its state of subdivision, that the transformation of the image into silver sulfide is by far the most popular method of toning developing-out paper prints, that silver sulfide is one of the most stable forms of silver where great permanency is required, and that the two general methods are direct toning with the hypo alum bath and bleaching with ferricyanide and bromide followed by sodium sulfide; that the colour of the final hypo-alum tone is related directly to the colour of the original black-and-white image, blue-black images giving cold chocolate tones and olive-green images warm sepia tones; that the state of division of the toned image depends on that of the untoned image and therefore on exposure and development, so a print for sulfide toning should be fully developed but not over-exposed; that all sulfides give off hydrogen sulfide, which fogs unexposed material, so no photographic materials should be stored where sulfide toning is done; and Chapter VI, Intensification, that a silver image can be very much intensified by toning it with uranium, the reddish-brown uranium ferrocyanide having very great printing strength; Chapter VII, section D of the toning chapter - that silver sulfide is a very insoluble compound of silver, so that a silver image or a silver halide treated with sulfur or a sulfide respectively is at once transformed into it; that silver sulfide has a colour varying from light brown to black according to its state of subdivision; that this transformation is by far the most popular method of toning developing-out paper prints; that where great permanency is required prints should preferably be toned to a silver sulfide image, experience having shown this form of silver to be one of the most stable; that there are two general methods, direct toning with the hypo alum bath and bleaching with ferricyanide and bromide followed by redevelopment in sodium sulfide; that an acid added to hypo tends to precipitate sulfur, that alum in water is weakly acid, and that alum added to plain hypo without sulfite becomes turbid and precipitates sulfur, the solution at that point being considered to have free sulfur in solution; that the hypo-alum bath works best at 49 to 52 degrees Celsius and that above 54 degrees there is danger of blistering and bleaching of the image; that a fresh bath tends to weaken the print by eating out the highlights and that a little silver must be added, preferably as silver chloride; that a used bath works better than a fresh one; that blue-black images give cold chocolate tones and olive green images warm sepia tones; that a bath which has to be heated is troublesome, so hypo-alum toning was used on the large scale while smaller quantities were bleached and redeveloped; that sodium sulfide occurs as white transparent crystals with a strong affinity for water which deliquesce unless protected, is best kept as a strong stock solution, and was supplied by Eastman Kodak in a fused grade of definite purity, one part by weight of the fused salt being equivalent to approximately three parts by weight of the crystals; that old sodium sulfide often contains hypo, which dissolves silver bromide and weakens the highlights; that all sulfides give off a certain quantity of hydrogen sulfide, which smells offensively and is extremely dangerous to unexposed photographic materials because a very small quantity converts enough silver bromide or chloride into sulfide to produce severe fog, so no photographic materials should be stored in a room where sulfides are kept or sulfide toning is done; that the state of division of the toned image depends on that of the untoned image and therefore on exposure and development, so a print for sulfide toning should be fully developed but not over-exposed; and that a trace of iron in the ferricyanide-bromide bleach, for example from a defective enamelled tray, forms blue spots of ferric ferrocyanide, a tendency reduced to a minimum by adding potassium oxalate to the bleach because the blue iron salt is soluble in the oxalate, acetic acid being added also to prevent possible formation of blisters; Chapter VI, The Chemistry of Reduction and Intensification, pages 39-40 - that intensification is the deposition of some material on the silver image; that a silver image can be very much intensified by toning it with uranium, the reddish-brown uranium ferrocyanide having very great printing strength and converting a weak negative into one having great effective contrast for printing purposes; that intensification is usually performed by depositing a silver, mercury or a chromium compound upon the image and that many intensifiers depend upon mercury, but that experience has shown that mercury intensified images are not as stable as images produced by chromium intensification; that when a silver image is placed in a solution of mercuric chloride this reacts with the silver and forms a mixture of mercurous chloride and silver chloride; that if the bleached white image is developed, both the silver chloride and the mercurous chloride are reduced to the metal so that to every part of silver an equal part of mercury has been added; that blackening with ammonia instead forms a black mercury ammonium chloride and a high degree of intensification; the note on mercury bichloride as a virulently poisonous salt whose only use in photography is intensification; the Monckhoven intensifier, bleaching with mercuric chloride and blackening with silver dissolved in potassium cyanide, the cyanide cutting the shadows very slightly while the highlights are intensified; and the chromium intensifier, in which the silver image is bleached with a solution of bichromate containing a very little hydrochloric acid, bichromate being an oxidiser of the same type as permanganate or ferricyanide, the image then redeveloped, this intensifier having found increasing favour owing to the ease and certainty of its operation and the permanency of the intensified image. Chapter VII, The Chemistry of Toning, pages 43-44, for the deposition-of-metal-salts family and the statement that uranium nitrate gives the reddish-brown uranium ferrocyanide; Chromium Intensifier, Formula In-4, page 59, printing the same stock solution at the same metric quantities twenty-one years before Kodak Limited's London handbook; Chapter VI, The Chemistry of Reduction and Intensification, on intensification being the deposition of some material on the image and being usually performed by depositing a silver, mercury or a chromium compound upon it, and on the chromium intensifier having found increasing favour owing to the ease and certainty of its operation and the permanency of the intensified image; Chapter IV, on the decomposition of hypo by sulphuric or hydrochloric acid with the precipitation of sulphur; Chapter VII, on cyanogen and the cyanides — that hydrocyanic acid and the cyanides differ from the corresponding chlorine and bromine compounds in being extremely poisonous, that a few grains of cyanide swallowed will cause death, that cyanide solutions are solvents for the silver halides forming soluble double compounds, and that potassium cyanide is employed for fixing wet collodion plates "which, being made from silver iodide, are not easily fixed in hypo"; Chapter VI, The Chemistry of Reduction and Intensification, pages 39 to 40 — that intensification is photographically the opposite of reduction and is done by the deposition of some material on the silver image; that it is usually performed by depositing a silver, mercury or a chromium compound upon the image and that many intensifiers depend upon mercury, but that experience has shown that mercury intensified images are not as stable as images produced by chromium intensification; that mercury forms mercuric and mercurous series of salts and that mercuric chloride is sufficiently soluble for practical use; that when a silver image is placed in a solution of mercuric chloride this reacts with the silver and forms a mixture of mercurous chloride and silver chloride; that if the bleached white image is developed both the silver chloride and the mercurous chloride are reduced to the metal, so that to every part of silver an equal part of mercury has been added; that blackening with ammonia instead forms a black mercury ammonium chloride and produces a high degree of intensification; the note that mercury bichloride is a virulently poisonous salt whose only use in photography is intensification; the Monckhoven intensifier, bleaching with mercuric chloride and blackening with silver dissolved in potassium cyanide; and the statement that a silver image can be very much intensified by toning it with uranium, the reddish-brown uranium ferrocyanide having very great printing strength and converting a weak negative into one having great effective contrast for printing purposes; Chapter III - the statement that the speed of development depends chiefly on the rate at which the developer diffuses into the film; Chapter VII - what happens to a developer with use, the restraining action of accumulated bromide and iodide described as analogous to cutting down the exposure, the reasons a deep-tank developer is discarded, aerial fog, and the addition of about 5 per cent of old developer as a remedy; Chapter III - the statement that if too much alkali is present the developer will tend to produce chemical fog, while if too little alkali is present it will be slow; Chapter III - the statement that the speed of development depends chiefly on the rate at which the developer diffuses into the film, and that a very little change in temperature affects hydroquinone greatly and Elon very little; Chapter XI - the temperature coefficient defined over 10 degrees C, its variation with the developing agent, the consequence for a mixed developer at high and low temperature, and the statement that the fog reaction has a much higher temperature coefficient than development; Chapter IX, Mixing Operations — the general rule that the preservative should be dissolved first, and the stated exception for Elon and Roylon, which are readily soluble in warm water at about 125 degrees F (52 degrees C) and do not oxidise rapidly: if the sulphite is dissolved before the Elon a white precipitate often appears, especially if the sulphite solution is concentrated, because Elon is a combination of an insoluble base with an acid which renders it soluble, and when the acid portion is neutralised by a weak alkali such as sodium sulphite the insoluble base is precipitated; the note that once the Elon is dissolved it takes a fairly high concentration of sulphite to bring it out of solution again though only a low concentration is required to prevent it from dissolving, and that a precipitate formed on dissolving the Elon and sulphite will usually redissolve on adding the carbonate with no harm done; the alternative practice of dissolving a portion of the sulphite first, then the Elon, then the remainder; the mixing rules that chemicals are dissolved in the order given and that each chemical is dissolved completely before the next is added, with the statement that if the alkali is added before the crystals of the developing agent are dissolved, each crystal becomes oxidised at the surface and the resulting solution will give fog; the statement that tin, copper and zinc or alloys of these metals will usually produce bad fog and stain with photographic developers and are also unsatisfactory in fixing baths; and Chapter III, the statement that the quantity of alkali governs the energy of a developer and that too much alkali tends to produce chemical fog; Chapter VIII, Fixing Bath Troubles — A, the two kinds of milkiness: a pale yellow slowly settling precipitate of sulphur from too much acid in the hardener, too little or impure sulphite, or high temperature, with the statement that above 85 degrees F (29 degrees C) an acid fixing bath will not remain clear longer than a few days even when mixed correctly and that a sulphurised bath's sulphur is apt to penetrate the gelatin and later cause fading of the image; and a white gelatinous sludge of aluminium sulphite from too little acid in the hardener or too little hardener, with the note that when fixing prints a relatively large proportion of developer is carried over unless a water or acid rinse bath is used, which soon neutralises the acid, and that an exhausted bath still containing alum and sulphite but no acid combines them into sludge; C, Blisters, from carbon dioxide evolved when the developer's sodium carbonate is neutralised by the fixing bath's acid; D, Dichroic Fog — if the fixing bath does not contain acid, or if it is old and exhausted and contains an excess of dissolved silver salts, a stain called dichroic fog is sometimes produced, appearing yellowish-green by reflected light and reddish-pink by transmitted light, and never occurring in a fresh acid fixing bath or if the film is rinsed before fixing and the bath is kept at 65 to 70 degrees F (18 to 21 degrees C); E, Scum — the metallic silver sulphide scum formed on a standing partially exhausted bath by hydrogen sulphide in the air, and the white aluminium sulphite scum on films or prints caused by insufficient rinsing after development, too low an acid concentration, or insufficient agitation on first immersion, which is soluble in alkali and may be removed by swabbing with a 10 per cent sodium carbonate solution and washing; and Chapter VI, the description of dichroic fog as consisting of very finely divided silver, attacked by a plain permanganate solution of about 0.25 per cent which has no appreciable action on the image silver; Chapter III, Development — the requirement that a developing agent must reduce exposed silver bromide but not affect unexposed silver bromide, so that its affinity for oxygen must lie within narrow bounds; the statement that the quantity of alkali governs the energy of a developer, and that if too much alkali is present the developer will tend to produce chemical fog while too little makes it slow; the statement that bromides and iodides are added to a developer to compensate for chemical fog produced by the developer or inherent in the emulsion; Chapter IX, Mixing Operations — the statement that if the alkali is added before the crystals of the developing agent are dissolved, each crystal becomes oxidised at the surface and the resulting solution will give fog, and that tin, copper and zinc or their alloys will usually produce bad fog and stain with photographic developers; Chapter VI, Reduction — the three classes of reducing solution, cutting, proportional (headed 'True scale reducers' in the list) and flattening; the definition of a cutting reducer as one that removes an equal quantity of silver from all parts of the image and consequently removes a larger proportion from the shadows than from the highlights; Farmer's reducer named as the typical cutting reducer, ferricyanide oxidising the silver to silver ferrocyanide and hypo dissolving it, the mixture not keeping, and its usefulness for clearing negatives showing slight fog and for local reduction with a brush or a wad of cotton; the definition of a proportional reducer as one acting on all parts in proportion to the silver present, so that it exactly undoes development, with the statement that no single substance forms an exactly proportional reducer and that a mixture of permanganate and persulphate approximates one (formula R-5); the definition of a flattening reducer as one acting very much more on the heavy deposits than on the light, with ammonium persulphate named as the only one known and its behaviour called somewhat uncertain, occasionally refusing to act and always acting more rapidly as reduction progresses; and the section on Intensification, that it is photographically the opposite of reduction and is done by depositing material on the silver image; Chapter II — gelatin as a colloid that swells rather than dissolves in cold water, the increase in swelling produced by a small quantity of acid or alkali and by warmth, hardening with alum, and the statement that all solutions must be kept at the same temperature in order to avoid sudden contractions or expansions of the gelatin which may result in detaching the film from its support or in the production of reticulation, a coarse wrinkling all over the film; Chapter III — the statement that alkalis soften the gelatin of the emulsion and that too alkaline a developer will produce over-swelling and give trouble with frilling or blisters in warm weather; Chapter VIII, Fixing Bath Troubles C, Blisters — the statement that when the sodium carbonate of the developer is neutralised by the acid in the fixing bath, carbon dioxide gas is evolved which produces blisters if the gelatin is too soft to withstand the disruptive action of the gas, that blisters are apt to form if the fixing bath contains an excess of acid and the films are not rinsed sufficiently or if a strongly acid rinse bath is used, that on dry film blisters appear as tiny crater-like depressions when examined by reflected light, and that the trouble is more liable to occur in hot weather and especially when the bath is not hardening sufficiently; and Fixing Bath Troubles E, the white scum of aluminium sulphite on films or prints caused by insufficient rinsing after development, too low a concentration of acid in the fixing bath, or insufficient agitation of the film on first immersing in the fixing bath; Chapter VIII, Fixing Bath Troubles G, Mottle — the statement that when processing film or plates in hangers a mottled image is occasionally found when the hanger has not been agitated enough on first immersing in the fixing bath, or if the film is insufficiently rinsed between development and fixation, because in the absence of thorough rinsing and agitation development continues locally during the first few minutes of fixing and in these spots the image has greater density; and that mottle is also produced if the ends of the hanger protrude above the surface of the fixing bath, especially during the first stages of fixation; Toning — the general ferricyanide pattern, naming iron citrate for blue, uranium nitrate for reddish brown and copper citrate for red; Toning — the sulfide sequence; silver sulfide as a very insoluble compound of silver; the colour running from light brown to black according to the state of subdivision; the permanence recommendation; Toning — the general ferricyanide pattern, naming uranium nitrate for reddish brown; Chapter IV, potassium chrome alum and ammonium chrome alum and the loss of hardening power in the presence of sulfite; Chapter X, the chrome alum fixing bath in use; Sulfurous acid and the sulfites; the decomposition of hypo by a strong acid; the ferricyanide-bromide bleach and iron contamination; the storage of photographic materials where sulfides are used; The decomposition of hypo by a strong acid, and the milkiness as sulfur precipitates; Chrome alum losing its hardening power in the presence of sulfite, and its solutions violet cold and green on warming; The Properties of Fixing Baths: the time for fixation taken as twice the time for the milkiness or opalescence of the unreduced silver halide to disappear; Fine Grain Negative Developer D-76, Directions for Mixing: the order and quantities, and the specified water temperatures of about 52 and 71 degrees C; Chapter IV: the decomposition of hypo by acid to sulphurous acid and sulphur, its reversal by sulphite, and the warning that adding hardener to hypo which has not fully dissolved is apt to precipitate sulphur; Water to make: the typography of the water line in the developing and fixing formulae; Sulphide toning: the note not to use trays with any iron exposed; Storage of chemicals: the agents that destroy a stored chemical, and the case for sealing it from the air; Storage of chemicals: deliquescence, and the difficulty of preparing a solution of definite strength from a chemical that has taken up water; Storage of chemicals: oxygen, carbon dioxide, deliquescence, efflorescence and light, and the detectability of surface sulfate on crystalline material; Chapter X, Rinsing Prints — the life of the acid rinse bath, determined by the alkali carried over from the developer, and the blue litmus test for whether the bath is still acid; Storage of chemicals: well-stoppered jars in a cool dry place; the light-sensitive cases and dark brown bottles; the caustic stopper cemented by carbonate; the solvent action of caustic alkalis on glass; Sulphide toning: the rule that no photographic materials are kept where sulphides are kept or sulphide toning is done; Sulphide toning: the rule that no photographic materials are stored where sulphides are kept or sulphide toning is done, because a very small quantity of hydrogen sulphide converts enough silver halide to sulphide to produce severe fog; the note not to use trays with any iron exposed; Storage of chemicals: the oxidation of sulfite to sulfate, and the statement that sodium sulfate is not easy to detect in desiccated sulfite except by chemical tests; the browning of developing agents; deliquescence and efflorescence; Storage of chemicals: deliquescence, and the difficulty of preparing a solution of definite percentage strength from a chemical that has deliquesced; Chapter III - the alkali governs the energy of the developer, too much gives chemical fog and too little is slow; Chapter VIII, Toning Formulas, Sepia Toning - Hypo-Alum Bath T-1a: heat to 120 F (49 C) in a tray standing in a water bath, tone in 12 to 15 minutes, and never heat higher than 130 F (54 C) or blistering, staining and non-uniform toning will result; Chapter VII, on a fresh bath weakening the print and eating out the highlights unless a little silver is added, and on a used bath working better than a fresh one; Chapter VIII, Fixing Bath Troubles C, Blisters — the statement that when the sodium carbonate of the developer is neutralised by the acid in the fixing bath, carbon dioxide gas is evolved which produces blisters if the gelatin is too soft to withstand the disruptive action of the gas; that blisters are apt to be formed if the fixing bath contains an excess of acid and the films are not rinsed sufficiently, or if a strongly acid rinse bath is used; that on dry film blisters appear as tiny crater-like depressions when examined by reflected light; and that the trouble is more liable to occur in hot weather and especially when the bath is not hardening sufficiently. Chapter III — the statement that alkalis soften the gelatin of the emulsion and that too alkaline a developer will produce over-swelling and give trouble with frilling or blisters in warm weather; Chapter III - the alkali governs the energy of the developer, too much gives chemical fog and too little is slow, and most developing agents cannot develop at all without an alkaline solution; Chapter IX - bromides and iodides added to a developer to compensate for chemical fog produced by the developer or inherent in the emulsion; Chapter III — the statement that the quantity of alkali governs the energy of a developer, so that too little alkali makes it slow in its action; and Chapter IX, Mixing Operations — the statement that tin, copper and zinc or alloys of these metals will usually produce bad fog and stain with photographic developers and are also unsatisfactory for use in fixing baths; Chapter III — the oxidation of developing agents and the coloured oxidation products that result, and the account of pyro-developed negatives in which the image consists partly of the oxidation product of the pyro associated with the silver; Chapter VI, Reduction — the note that when a pyro-developed negative is reduced with ferricyanide the silver is removed but the stain is unattacked, so that the negative appears to become yellower during reduction though the ferricyanide does not produce the colour, only making it more evident; and Chapter VIII, Fixing Bath Troubles F, Stains, naming white aluminium sulphite stain, sulphur stains and yellow silver stains as separate types; Fixing Bath Troubles D, Dichroic Fog - if the fixing bath does not contain acid or if it is old and exhausted and contains an excess of dissolved silver salts, a stain called dichroic fog is sometimes produced; in reflected light the film appears yellowish-green and by transmitted light reddish-pink; it never occurs in a fresh acid fixing bath, or if the film is rinsed before fixing and the temperature of the bath is kept at 65 to 70 degrees F; the chapter on reduction, where dichroic fog is described as consisting of very finely divided silver; The Properties of Fixing Baths - the time for fixation taken as twice the time for the milkiness to disappear, and the instruction to discard when the clearing time of a slow-fixing film exceeds 12 to 15 minutes; Chapter VIII, Fixing Bath Troubles — A, the white gelatinous sludge of aluminium sulphite, with the note that when fixing prints a relatively large proportion of the developer is carried over to the fixing bath unless a water or acid rinse bath has been used, which soon neutralises the acid and therefore increases the tendency for precipitation, and that an exhausted bath still containing alum and sulphite but no acid combines them into a sludge; C, Blisters, from carbon dioxide evolved when the developer's sodium carbonate is neutralised by the acid in the fixing bath; D, Dichroic Fog, which is produced if the fixing bath does not contain acid or is old and exhausted and carrying an excess of dissolved silver salts, and which never occurs in a fresh acid fixing bath or if the film is rinsed before fixing; and G, Mottle, found when film in hangers is insufficiently rinsed between development and fixation, because development continues locally during the first few minutes of fixing; Chapter II - gelatin as a colloid that swells rather than dissolves in cold water, the increase in swelling produced by a small quantity of acid or alkali and by warmth, and hardening with alum; Chapter VIII, Fixing Bath Troubles A — the second kind of milkiness, a white gelatinous sludge of aluminium sulphite settling on standing, caused by too little acid in the hardener (with the worked example of 28 per cent acetic acid used where the formula calls for glacial, giving less than one third of the required concentration) or by too little hardener in the fixing bath; the note that when fixing prints a relatively large proportion of developer is carried over unless a water or acid rinse bath has been used, which soon neutralises the acid and increases the tendency to precipitate; the statement that an exhausted bath still contains alum and sulphite but no acid and these combine to form a sludge; the finding that a bath containing an excess of acid may be used for a relatively long time before precipitation but does not harden as well, with the recommendation to add about half the original quantity of acid as soon as a slight precipitate appears; and Fixing Bath Troubles E — the white scum of aluminium sulphite on films or prints, caused by insufficient rinsing after development, too low a concentration of acid in the fixing bath, or insufficient agitation of the film on first immersing, with the note that since aluminium sulphite is soluble in alkali the scum may be removed by swabbing with a 10 per cent solution of sodium carbonate and then washing thoroughly; Chapter IV, fixing — the account of hypo dissolving silver halide, and Chapter VI, Reduction, on the fact that a silver image can be attacked and removed by chemical means with the density loss falling hardest on the thin parts of the image in relative terms; Chapter IV - developer carried into the fixing bath oxidises there, turning it brown and staining negatives or prints, which is what the sulphite is added to prevent; Chapter III - the two fates of the quinone that hydroquinone becomes, one route reducing it back with sulfite and the other giving hydroquinone mono- and disodium sulfonates which are colourless, and the warning that a colourless developer is no indication of undiminished power; Chapter VIII, Fixing Bath Troubles C, Blisters — the statement that carbon dioxide evolved when the developer's sodium carbonate is neutralised by the acid in the fixing bath produces blisters if the gelatin is too soft to withstand the disruptive action of the gas, that this is apt to occur when the fixing bath contains an excess of acid and films are not rinsed sufficiently or a strongly acid rinse bath is used, and that on dry film blisters appear as tiny crater-like depressions when examined by reflected light; Chapter IX, Mixing Operations — the stated exception for Elon, which is readily soluble in warm water at about 125 degrees F (52 degrees C) and does not oxidise rapidly: if the sulphite is dissolved before the Elon a white precipitate often appears, especially if the sulphite solution is concentrated, because Elon is a combination of an insoluble base with an acid which renders it soluble and the acid portion is neutralised by a weak alkali such as sodium sulphite; the note that once dissolved it takes a fairly high concentration of sulphite to bring it out again though only a low concentration prevents it from dissolving; and the statement that a precipitate formed on dissolving the Elon and sulphite will usually redissolve on adding the carbonate and no harm has been done. Chapter VIII, Fixing Bath Troubles A — the pale yellow slowly settling precipitate of sulphur from too much acid in the hardener, too little or impure sulphite, or high temperature, with the statement that above 85 degrees F (29 degrees C) an acid fixing bath will not remain clear longer than a few days even when mixed correctly, that a sulphurised bath's sulphur is apt to penetrate the gelatin and later cause fading of the image, and that the only remedy is to throw the bath away; and the white gelatinous sludge of aluminium sulphite from too little acid or too little hardener; Chapter VIII, Fixing Bath Troubles C, Blisters — the statement that when the sodium carbonate of the developer is neutralised by the acid in the fixing bath, carbon dioxide gas is evolved which produces blisters if the gelatin is too soft to withstand the disruptive action of the gas; that blisters are apt to be formed if the fixing bath contains an excess of acid and the films are not rinsed sufficiently, or if a strongly acid rinse bath is used; that on dry film blisters appear as tiny crater-like depressions when examined by reflected light; and that the trouble is more liable to occur in hot weather and especially when the bath is not hardening sufficiently; Chapter V, Washing - the rate of washing depends on the rate of diffusion of hypo out of the film provided the water in contact is continuously removed, has nothing to do with solubility, is not helped by warm water, and proceeds by a constant halving time of about 15 seconds under a running faucet and 30 seconds in most trays and tanks; Chapter II - all solutions must be kept at the same temperature in order to avoid sudden contractions or expansions of the gelatin which may result in detaching the film from its support or in the production of reticulation, a coarse wrinkling all over the film, in the context of exposure to extreme temperatures, with a hardener in the fixing bath as the control; The Properties of Fixing Baths - the time for fixation taken as twice the time for the milkiness or opalescence of the unreduced silver salts to disappear; Chapter IX, Mixing Operations — the mixing rules that chemicals are dissolved in the order given unless the directions specify otherwise and that each chemical is dissolved completely before the next is added, with the statement that if the alkali is added before the crystals of the developing agent are dissolved, each crystal becomes oxidised at the surface and the resulting solution will give fog; the statement that Elon is readily soluble in warm water at about 125 degrees F (52 degrees C); and the instruction that chemicals should be weighed and solutions prepared outside the darkroom, with care taken not to shake the finer particles of substances such as hydroquinone and potassium ferricyanide into the air; Storage of chemicals - oxygen, deliquescence and efflorescence, and the statement that sodium sulfate is not easy to detect in desiccated sulfite except by chemical tests

Used by:P29 Capstone Stage 2: Formulating and Documenting Your Chemistry · P29 Capstone Stage 4: The Silver Prints · P29 The Capstone Chemistry Report: From Photon Capture to Finished Print · 6-Nitrobenzimidazole · Acetic acid (glacial) · Amidol · Ammonium chloride · Ammonium persulfate · Ammonium sulfite · Ammonium thiosulfate · Ascorbic acid · Benzotriazole · Borax (sodium tetraborate decahydrate) · Boric acid · Catechol · Chrome alum · Copper(II) sulfate · Formaldehyde · Gelatin · Glycin · Hydrochloric acid · Hydroquinone · Iodine · Iron(II) sulfate heptahydrate · Mercury(II) chloride · Metol · p-Aminophenol · Phenidone · Potassium alum · Potassium bromide · Potassium carbonate (anhydrous) · Potassium chloride · Potassium citrate · Potassium cyanide · Potassium dichromate · Potassium ferricyanide · Potassium ferrocyanide (anhydrous) · Potassium ferrocyanide trihydrate · Potassium hydroxide (caustic potash) · Potassium iodide · Potassium metabisulfite · Potassium oxalate, anhydrous · Potassium oxalate monohydrate · Potassium permanganate · Pyrogallol · Silver · Silver bromide · Silver chloride · Silver iodide · Silver nitrate · Silver sulfide · Sodium ascorbate · Sodium bicarbonate · Sodium bisulfite · Sodium carbonate (anhydrous) · Sodium carbonate decahydrate · Sodium carbonate monohydrate · Sodium chloride · Sodium hydroxide (caustic soda) · Sodium metabisulfite · Sodium metaborate (anhydrous) · Sodium metaborate tetrahydrate (Kodalk) · Sodium sulfate · Sodium sulfide · Sodium sulfite · Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Sulfuric acid · Tetraazaindene · Thiourea · 510-Pyro · Albumen solution with its chloride · Beutler two-solution developer · Borax kallitype developer · Kodak SB-4 · Chrome alum subbing dip · Citric Acid Stop Bath · Cyanide fixing and toning · Gold-acetate toner · ILFORD HYPAM · Iodide hypo check · Dilute alkaline thiosulfate fixer for iron-silver prints · Kodak bisulphite fixing bath · Kodak D-1 · Kodak D-156 · Kodak D-158 · Kodak D-163 · Kodak D-165 · Kodak D-166 · Kodak D-167 · Kodak D-170 · Kodak D-173 · Kodak D-177 · Kodak D-19 · Kodak D-19b · Kodak D-19bR · Kodak D-23 · Kodak D-25 · Kodak D-32 · Kodak D-34 · Kodak D-49 · Kodak D-51 · Kodak D-52 · Kodak D-72 · Kodak D-76 · Kodak D-76d · Kodak D-9 · Kodak DK-20 · Kodak DK-50 · Kodak F-1 · Kodak F-14 · Kodak F-1a · Kodak F-2 · Kodak F-24 · Kodak F-5 · Kodak F-52 · Kodak F-53 · Kodak F-54 · Kodak F-5a · Kodak F-6 · Kodak HT-2 · Kodak IN-4 · Kodak IN-5 · Kodak IN-1 · Kodak T-56 · Kodak T-52 · Kodak IN-21 · Kodak R-4 · Kodak R-4a · Kodak R-4b · Kodak SB-1 · Kodak SB-5 · Kodak ST-1 · Kodak T-1a · Kodak T-7a · KODAK PROFESSIONAL XTOL Developer · Moersch MT3 Variotoner · Plain hypo fixing bath · EDTA, citric acid and hydrochloric acid clearing sequence · Platinum toner for printing-out papers · PMK pyro · Plain sodium thiosulfate fixer for printed-out papers · Pyrocat-HD · Rehalogenating ferricyanide-bromide bleach · Rodinal-type p-aminophenol developer · Salted paper sensitising solution · Uranium toner · Wedgwood and Davy's silver nitrate on leather · Film developers compared · Fixers compared · Toners compared · P1 Overview: The Three Problems Every Photograph Must Solve · P1 1839 and the Many Inventors of Photography · P1 Silver Salts and Light: Schulze to Ritter · P1 Experiment: The Image That Would Not Stay · P2 Storage, Incompatibilities and Secondary Containment · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P2 Silver Nitrate: The Reagent That Sets the Rules · P3 Acids, Bases and pH · P3 Aerial Oxidation: Why Chemistry Dies in a Half-Empty Bottle · P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P3 Buffers and Buffer Capacity · P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve · P3 Diffusion, Swelling and the Journey Into the Emulsion · P3 Oxidation, Reduction and the Electron That Makes the Picture · P3 Rates, Temperature and Catalysts · P3 Solutions, Solubility and Precipitation · P4 Part IV Overview: Silver and Light · P4 Experiment: Precipitating the Silver Halides · P4 Silver and the Silver Ion · P4 The Latent Image · P4 The Silver Halides · P5 Coating, Drying and Hardening · P5 Gelatin, the Photographic Binder · P5 Precipitation, Nucleation and Crystal Growth · P8 Overview: What a Developer Is · P8 Experiment: Watching a Developer Oxidise · P8 Alkalis, Buffers and pH · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 Development Kinetics: Time, Temperature, Agitation and Exhaustion · P8 How Development Works · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P8 Assignment: Reading a Developer Formula · P8 Restrainers and Antifoggants · P8 Solvent Action, Physical Development and Grain · P8 Staining and Tanning Developers · P8 Sulfite: Preservative, Buffer, Silver Solvent · P8 Superadditivity: Why Two Agents Beat One · P9 Overview: Experiments on Development · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Break/Fix: The Developer That Went Wrong · P9 Assignment: The Developer Laboratory Report · P9 Experiment: Comparing Developing Agents · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P10 Experiment: Measuring Stop Bath Capacity · P10 Stop Bath Formulations and the Fixer Interaction · P10 Why Stopping Works · P11 Overview: Making the Image Permanent · P11 Experiment: Clearing Time and Fixer Capacity · P11 Break/Fix: The Exhausted Fixer · P11 Fixer Capacity, Exhaustion and Residual Silver · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline · P11 How Fixer Works · P11 Lab: Mixing Fixers from Scratch · P12 The Physics of Washing · P18 Lab: Mixing and Comparing Print Developers · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · P18 Print Developer Chemistry and the Developer-Paper Pair · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Gold, Iron-Blue and the Other Metal Toners · P20 What a Toner Actually Does to a Silver Image · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P20 The Toners We Study and Do Not Use · P26 Assignment: Assessing a Historical Process for Hazard · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 Uranium, Mercury and the Heavy-Metal Treatments · P27 Experiment: Agitation, Stand and Semi-Stand Development · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Experiment: Four Curve Families, Measured · P27 Experiment: The Development Time and Temperature Series · P28 Chemistry in the Bottle: Oxidation, Exhaustion, Precipitation and Contamination · P28 Fixer Faults, Washing Faults and the Stains They Leave · P28 Fog and Where It Comes From · P28 Reading the Negative as Evidence: Thin, Dense, Flat and Contrasty · P28 The Emulsion Under Stress: Reticulation, Scratches, Pinholes and Drying Marks · P28 Uneven Development, Bromide Drag and Surge Marks · Iron-blue toned silver gelatin print · Sulphide (sepia) toned silver gelatin print · Uranium toned print · The chromium policy · Chemical incompatibilities · Responding to an acid spill · Routing chromium(III) from the coating station · Measuring a clearing time · Mixing a developer from raw chemicals · Mixing a fixer · Mixing a solution to a final volume · Dedicating tools to one process · Recording a batch in the inventory · Responding to a spilled solid · The stock check, and retiring a chemical · Stop bath preparation · Storage rotation and shelf separation · The student's project SOP · Handling a sulphide toner and its waste · A container found unlabelled, or a solution of unknown age · Weighing a solid · Base fog · Blistering from an over-hot hypo alum bath · Blisters · Chemical fog · Developer contaminated by fixer or stop · Developer stain · Dichroic fog · Exhausted fixer · Fixer contaminated by developer · Frilling · Hardener sludge · Over-fixing · Oxidation stain · Oxidised developer · Pinholes · Precipitate in a stock solution · RC blisters · Residual thiosulfate · Reticulation · Under-fixing · Undissolved chemical · Unlabelled or undated container

Elementary Photographic Chemistryretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: The chapter on fixing — the sequence of silver-thiosulfate compounds formed as fixation proceeds, and the account of why a partly fixed print retains a sparingly soluble compound that washing cannot remove; Chapter on the fixing bath: acid strength against neutralising power; ACETIC ACID; Chapter on testing chemicals: distinguishing borax from boric acid by the flame test; Chapter on testing chemicals: distinguishing borax from boric acid; Potassium chrome alum and ammonium chrome alum; the loss of hardening properties in the presence of sodium sulfite; Formalin — the commercial 40 per cent solution, its hardening power and its restriction to alkaline or neutral solutions; Chapter I: the halogens and the hydrogen halides; chromium intensifier and its bleach; gold chloride; the testing of chemicals, silver nitrate with hydrochloric acid; The four ingredients of a developer; making up solutions; mixing concentrated developers; Making up solutions — the order of dissolving, the Elon exception and the precipitation of the base; mixing concentrated developers; Gold chloride, made by dissolving gold in a mixture of hydrochloric and nitric acids; The commonest developing agents; mixing concentrated developers — the para-aminophenol-carbonate developer and caustic soda; The gelatin of the emulsion, its swelling and its hardening by alum; the composition of the acid fixing bath; Chapter III: potassium carbonate; Chapter IV: fixation and the two compound sodium silver thiosulfates; Chapter V: hydrogen sulfide and the conversion of silver bromide; Chapter IV: fixation and the two compound sodium silver thiosulfates; Chapter V: cyanide as a fixer for wet collodion plates made from silver iodide; Chapter II: the manufacture and purity of silver nitrate; Chapter III: sodium carbonate comes on the market in three forms; Chapter I: sulphite and sulphate, the one-letter difference, and the oxidation that turns one into the other; Chapter IV: the two compound sodium silver thiosulfates; Chapter VII: The Chemistry of Washing — two fixing baths; Chapter IV: manufacture and purity of hypo; the two compound sodium silver thiosulfates; Chapter IV — the two compound sodium silver thiosulfates formed in fixation, one of them almost insoluble in water while the other is very soluble, and the statement that as long as the fixing bath has any appreciable fixing power the soluble compound only is formed; the decomposition of thiosulfate by acid to thiosulfuric acid and thence to sulfurous acid and sulfur; and the entry for potassium iodide among the halides used in photography, described as similar to the bromide and very soluble; Formulae — 'STANDARD A. B. C. Pyro. (Formula D-1)', its three stock solutions in avoirdupois only, with sodium bisulphite or potassium metabisulphite 140 grains, pyro 2 ozs., potassium bromide 16 grains and water to make 32 ozs. in Stock Solution A; 'Dissolve chemicals in order given'; tray development at 1 part A, 1 part B, 1 part C and 7 parts of water and tank development at 1 part A, 1 part B, 1 part C and 25 parts of water, with no development times given; the Two Solution Pyro Tray Developer (Formula D-21) beneath it; X-ray Developer (Formula D-19), printed in avoirdupois only, and read here solely to establish that an earlier printing exists; Lantern Slide Formulae, Blue Black Tones, Formula D-34, page 48, avoirdupois only, Stock Solution A reading hot water about 125 degrees F 16 ozs., Elon 60 grains, sodium sulphite half an ounce, hydrochinon half an ounce and cold water to make 32 ozs., Stock Solution B reading water 32 ozs., sodium carbonate half an ounce and potassium bromide 30 grains, with the directions 'For use, take equal parts of A and B' and 'For softer results, dilute with an equal quantity of water'; Process Tray Developer (Hydrochinon-Caustic), Formula D-9, page 47, avoirdupois only, Solution A reading water 16 ozs., sodium bisulphite three quarters of an ounce, hydrochinon three quarters of an ounce, potassium bromide three quarters of an ounce and water to make 32 ozs., Solution B reading cold water 32 ozs. and sodium hydroxide (caustic soda) one and three quarter ozs., with the direction 'Use equal parts of A and B and develop for three minutes at a temperature of 65 degrees Fahrenheit'; Fixing Baths, Acid Fixing Bath, Formula F-1, page 49, avoirdupois only, reading 'Add the following hardener solution to 64 ozs. of plain hypo solution mixed as given before' with water 5 ozs., sodium sulphite 1 oz., acetic acid 28 per cent 3 ozs. and potassium alum 1 oz., dissolved in the order given; Plain Hypo Bath, Formula F-11, hypo 16 ozs. and water to 64 ozs.; Acid Hardener Stock Solution, Formula F-1A; Fixing Baths, Acid Hardener Stock Solution, Formula F-1A, page 49, avoirdupois only, reading water 56 ozs., sodium sulphite 16 ozs., acetic acid 28 per cent 48 ozs., potassium alum 16 ozs. and water to make 1 gallon, with the direction 'For use, add 1 part of stock solution to 8 parts of plain hypo solution as given before'; Plain Hypo Bath, Formula F-11, hypo 16 ozs. and water to 64 ozs.; Chapter IV — the two compound sodium silver thiosulfates, one almost insoluble in water and the other very soluble, and the statement that as long as the fixing bath has any appreciable fixing power the soluble compound only is formed; and the decomposition of thiosulfate by acid to thiosulfuric acid and thence to sulfurous acid and sulfur, which sulfite opposes; Chapter IV — the two compound sodium silver thiosulphates formed in fixation, one of them almost insoluble in water while the other is very soluble, and the statement that as long as the fixing bath has any appreciable fixing power the soluble compound only is formed; Fixation, on the silver bromide combining with the hypo to form a compound sodium silver thiosulphate, on the existence of two such compounds of which one is almost insoluble in water and the other very soluble, and on only the soluble one being formed while the bath retains appreciable fixing power; Washing, on two fixing baths being the best way of ensuring complete fixation; The commonest developing agents; mixing concentrated developers - the para-aminophenol-carbonate developer and the caustic soda that makes a stronger solution possible; Chapter I: An Outline of Elementary Chemistry; Chapter III: the alkalis of development; Chapter III: caustic and carbonated alkalis; the carbonate as a reservoir of alkali; too alkaline a developer over-swells gelatin; Chapter III: the caustic and carbonated alkalis; potassium carbonate more soluble and hygroscopic than sodium; Chapter III: the carbonate as a reservoir of alkali that keeps a small alkali concentration nearly constant during use; the caustic alkalis; over-alkaline developer and gelatin swelling; Chapter I: hydroquinone oxidised to quinone, quinone reduced back by sulphite, ferric salts oxidising hydroquinone and becoming ferrous; Chapter V: hydrogen sulfide and its action on photographic materials; Oxidation and reduction — the statement that when hydroquinone is oxidized we get quinone, and that adding sulphite to quinone causes the quinone to oxidize the sulphite to sulphate and be itself reduced again to hydroquinone; How to mix developing solutions — that developing solutions containing only the developing agent and alkali would be rapidly spoiled by oxidation by the air, that sodium sulphite has a very strong affinity for oxygen and protects the developer, and the graded pyrogallol demonstration of the preservative; Making up solutions: the order of dissolving, the Elon exception, and the precipitation of the free base when sulfite is dissolved first; How to mix developing solutions: the four ingredients, the browning of an unpreserved hydroquinone solution on adding alkali, and the bleaching of that colour by a little sodium bisulphite; Chapter IV — the compound sodium silver thiosulphates, one almost insoluble in water and one very soluble, and the statement that as long as the fixing bath has any appreciable fixing power only the soluble compound is formed; the washing chapter, on two-bath fixing and the invisible first insoluble compound that remains in a negative transferred to the wash as soon as it is visibly clear; Chapter IV — the two compound sodium silver thiosulphates, one almost insoluble in water and one very soluble, only the soluble one forming while the bath retains appreciable fixing power; the washing chapter — the statement that the first insoluble compound is invisible, that a negative transferred to the wash as soon as it is visibly clear keeps some of it when it dries, and that two-bath fixing ensures no material leaves the fixer until the insoluble compound has been converted to the soluble one; Chapter IV — the two compound sodium silver thiosulphates, one almost insoluble in water and one very soluble, only the soluble one forming while the bath retains appreciable fixing power; the washing chapter — two-bath fixing ensures that no material leaves the fixer until the first insoluble compound has been converted into the second soluble compound, that this first insoluble compound is invisible, and that a negative moved to the wash as soon as it is visibly clear keeps some of it when it dries; The washing chapter — the statement that material hardened in the fixing bath does not wash more slowly than unhardened material, because hardening contracts the network of the gelatin sponge without contracting the gelatin as a whole, unless the gelatin has been dried after hardening; Chapter IV — in the process of fixation silver bromide combines with hypo to form a compound sodium silver thiosulphate, two of which exist, one almost insoluble in water and one very soluble, and as long as the bath has appreciable fixing power only the soluble compound is formed; the washing chapter — two-bath fixing ensures no material leaves the fixer until the first insoluble compound has been converted into the second soluble one, and this first insoluble compound is invisible, so a negative moved to the wash as soon as it is visibly clear keeps some of it; Chapter IV and the washing chapter — the two compound sodium silver thiosulphates, one almost insoluble in water and one very soluble, only the soluble one forming while the bath retains appreciable fixing power, and the statement that this first insoluble compound is invisible; Chapter IV and the washing chapter — the two compound sodium silver thiosulphates, one almost insoluble and one very soluble, the statement that only the soluble one forms while the bath retains appreciable fixing power, and that the first insoluble compound is invisible; The corresponding passage in the 1924 printing, whose wording is "a trace of cyanide swallowed will cause death"; Chapter IV and the washing chapter: the two compound sodium silver thiosulphates, one almost insoluble in water and one very soluble; the statement that two-bath fixing ensures that no material can be removed from the fixing bath until the first insoluble compound has been converted into the second soluble one, and that this first insoluble compound is invisible; Chapter IV - the two compound sodium silver thiosulphates, one almost insoluble in water and one very soluble, only the soluble one forming while the bath retains appreciable fixing power; the washing chapter - two-bath fixing ensuring no material leaves the fixer until the insoluble compound has been converted to the soluble one; Chapter IV - the two compound sodium silver thiosulphates, one almost insoluble in water and one very soluble, only the soluble one forming while the bath retains appreciable fixing power; the washing chapter - the statement that the first insoluble compound is invisible and that a negative transferred to the wash as soon as it is visibly clear keeps some of it when it dries

Used by:P29 The Capstone Chemistry Report: From Photon Capture to Finished Print · Acetic acid (glacial) · Borax (sodium tetraborate decahydrate) · Boric acid · Chrome alum · Formaldehyde · Hydrochloric acid · Hydroquinone · Metol · Nitric acid · p-Aminophenol · Potassium alum · Potassium carbonate (anhydrous) · Silver bromide · Silver chloride · Silver nitrate · Sodium carbonate decahydrate · Sodium carbonate monohydrate · Sodium sulfate · Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Iodide hypo check · Kodak D-1 · Kodak D-19 · Kodak D-34 · Kodak D-9 · Kodak F-1 · Kodak F-1a · Kodak HT-2 · Kodak ST-1 · Plain hypo fixing bath · Rodinal-type p-aminophenol developer · P3 Part III Overview: Chemistry Foundations for Photographers · P3 Acids, Bases and pH · P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P3 Buffers and Buffer Capacity · P3 Oxidation, Reduction and the Electron That Makes the Picture · P4 Silver and the Silver Ion · P8 Experiment: Watching a Developer Oxidise · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 Sulfite: Preservative, Buffer, Silver Solvent · P11 Overview: Making the Image Permanent · P11 Break/Fix: The Exhausted Fixer · P11 Fixer Capacity, Exhaustion and Residual Silver · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline · P11 How Fixer Works · P12 Permanence and Image Deterioration · P12 Lab: Testing for Residual Thiosulfate and Residual Silver · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · Running a two-bath fixing rotation · Residual silver and yellow staining · Under-fixing

Handbook of the Practice and Art of Photography, second edition, enlarged, revised and corrected by the author and especially adapted for the United Statesretrieved 2026-09-05, 2026-09-06

Sections: The wet collodion process, fixing — the alternative baths of 1 part hyposulphite of soda to 4 or 5 parts water, or 1 part cyanide of potassium to 25 parts water; the statement that the hypo solution keeps for several days while the solution of cyanide of potassium decomposes rapidly and is transformed into potassium formate; the working rule that hyposulphite is used in the atelier where water is abundant and cyanide where the supply of water is limited or when travelling; and the warning that cyanide also dissolves the silver of the picture and destroys the delicate half-tones when it is not quickly removed by washing. The Silver Printing Process, The Fixing Bath, page 176 — the statement that hyposulphite of soda is used for fixing prints and that cyanide of potassium is not admissible as it affects the pictures very much, with the note that rhodan ammonium was never much used partly on account of its price and partly because it necessitates two fixing baths; the sulphocyanide of ammonium gold toning bath on the preceding page; and the passage on bleaching too dark prints in a solution of 1 part cyanide of potassium to 500 parts of water; Preparations — The Paper: the statement that "the water acts an important part in connection with the albumen, thick albumen producing a glossy surface and brilliant prints, therefore the thickly albumenized paper is called brilliant albumen paper", the converse that the more water is added to the albumen the duller the prepared paper, the simplest albumen recipe of 8 parts of egg white to 2 parts of a 10-in-100 ammonium chloride solution with a float of one and a half minutes, Hardwich's proportions reprinted, the observation that one sheet takes up about 6 drachms of albumen and 7 grains of salt, and the note that the salt had lately been reduced to 1 to 1.5 parts per 100 because the weak salted papers print better under thin negatives; The introductory history, for the statement that Fizeau introduced the gold toning bath, which removes the unpleasant colour and makes the pictures more permanent

Used by:Cyanide fixing and toning · Double-coated albumen procedure · Fizeau's gilding solution

Health Hazards for Photographersretrieved 2026-09-05

Sections: "PMK, Pyro-Metol-Kodalk Film Developer", with its reference line to Hutchings 1991 page 14, and the two stock solutions printed per litre and per two litres; the bibliography entry for Hutchings's The Book of Pyro; the PYROGALLOL (PYRO) hazard entry

Used by:PMK pyro

Historique et description des procedes du daguerreotype et du dioramaretrieved 2026-09-04, 2026-09-06

Sections: The five operations, in the Alphonse Giroux issue read here. Première opération, for the pumice, the olive oil, the phial of nitric acid "étendu d'eau dans la proportion d'une partie (en volume) d'acide, contre seize parties (également en volume) d'eau distillée", the three successive acidulations, the heating over a spirit lamp until a slight whitish film forms on the silver, and the instruction that at the moment of making a picture the acid must be applied at least once more. Deuxième opération, for the iodine capsule, the gold-yellow colour and the violet colour that must be avoided, the five to thirty minutes the colour takes, the requirement that the inside of the box be at the temperature of the room, and the hour beyond which the combination of iodine and silver no longer has the same property. Troisième opération, for the camera exposure of three to thirty minutes at Paris, the three or four minutes of June and July against the seven or eight of April and September, the twenty minutes a subject wholly in half-tone can take in the best months, and the hour that must not pass before the fourth operation. Quatrième opération, for the flask holding at least a kilogram of mercury, the plate carried at forty-five degrees, the thermometer with its bulb in the mercury brought to sixty degrees centigrade and forbidden to pass seventy-five, and the plate left until the thermometer has fallen to forty-five. Cinquième opération, for the stated purpose of removing the iodine that would otherwise go on decomposing in light and destroy the picture, for the wide-mouthed bottle filled to a quarter of its height with common salt and then filled with clear water, shaken until the water can dissolve no more and filtered through grey paper until perfectly limpid, for the two tinned copper dishes with the salt water about three centimetres deep and both liquids warmed without boiling, for the weak solution of pure sodium hyposulfite offered in its place as preferable because it removes the iodine entirely which the salt solution does not always do, for the plain water dip that must come first because without it the salt or the hyposulfite leaves indelible stains, for the yellow colour disappearing as the end point, for the not less than one litre of hot but unboiled distilled water poured over the inclined plate, and for the test of a drop evaporated on a burnished plate. Also the closing paragraphs of the fifth operation, for the finished plate put under glass and sealed, for the varnishes of amber, copal, rubber, wax and several resins that were tried and failed, and for the silvered plates serving several times as long as the copper is not uncovered; Rapport de M. Arago, with the notes Arago added on publishing it. Pelouze's suggestion that the useful influence of the acid may lie in its removing the last molecules of copper from the surface of the silver; Dumas's weighings, from which the thickness of the gold-yellow iodine layer does not appear to reach a millionth of a millimetre; the statement that the plate does not gain appreciable weight in taking the iodine layer but gains very noticeably under mercury vapour; Pelouze's finding that after the washing in hyposulfite the plate weighs less than before the operation began despite the amalgam now on it, and that chemical examination of the liquid shows the hyposulfite does indeed remove silver; Dumas's and Adolphe Brongniart's microscopy, which found the lights and half-tones formed of spherules very regularly one eight-hundredth of a millimetre across; the forty-five degree inclination of the plate in the mercury vapour, which Arago records as unexplained; Arago's closing sentence that thousands of fine drawings may be made with the daguerreotype before its mode of action has been completely analysed; Arago's statement of the portrait problem — that opinion is little disposed to admit that the instrument will ever serve to make portraits, the problem containing two apparently irreconcilable conditions, since for the image to be formed within the four or five minutes of immobility that may be demanded and expected of a living person the face must be in full sun; and the passage on the resources the sciences will draw from it, including the copying of the hieroglyphs of Thebes, Memphis and Karnak. Also, in the same volume, the Exposé des motifs laid before the Chamber of Deputies, for the statement that the smallest advance will suffice for Daguerre to make portraits of living persons; and the Rapport made to the Chamber of Peers by M. Gay-Lussac, for the statement that the application of the process to the portrait is nearly solved, and for the observation that coloured objects are not reproduced in their own colours and that, the various luminous rays not acting in the same way on Daguerre's reagent, the harmony of lights and shadows in coloured objects is necessarily altered — "a stopping-point traced by nature herself for the new process"; Avis de l'Éditeur, following the description of Plate VI: that on Daguerre's advice Giroux adds to his apparatus a plate brass on one side and silvered on the other as a guide for the second operation; and that when the bottle holding the hyposulfite solution is exhausted it is refilled with distilled water and the quantity of hyposulfite crystals the little silver-plated measure supplied with the apparatus will hold, filtered as the sea salt is, and that this quantity will serve to wash three plates. Also Plate VI itself, for the funnel with its grey paper filter, the two tinned copper dishes, the tinned copper hook used to raise the plate in the bath, the varnished tinplate stand on which the plate is washed, and the wide-necked kettle for heating the distilled water; "Le daguerréotype considéré sous un point de vue artistique, mécanique et pittoresque", the anonymous pamphlet of 1840 bound after the manual in the volume scanned here (Paris: Alph. Giroux et Cie, Lerebours, 1840), for its account of polishing with tripoli and pumice, of spreading the acid and pumice together as a liquid paste, of heating the plate strongly enough to vaporise the oil and reduce its residue to ash, and for the passage in which the writer records that the commercial nitric acid his supplier furnished "portait soixante degrés" and that his mixture made with sixteen parts by volume of distilled water came out stronger than the one he had been using before; "Notice sur l'héliographie", Niépce's own account of 5 December 1829, printed by Daguerre at pages 39 to 46 of the Alphonse Giroux issue with Daguerre's own footnotes to it. Read in the Internet Archive optical character recognition of the volume, which is poor in this section and is therefore checked word by word against three independent English renderings. In particular: the "principe fondamental" that light augments the natural consistency of some bodies and renders them more or less insoluble according to the duration or intensity of its action; the preparation of the varnish — "Je remplis à moitié un verre de ce bitume pulvérisé. Je verse dessus, goutte à goutte, de l'huile essentielle de lavande jusqu'à ce que le bitume n'en absorbe plus, et qu'il en soit seulement bien pénétré. J'ajoute ensuite assez de cette huile essentielle pour qu'elle surnage de trois lignes environ au-dessus du mélange" — the covering and the "douce chaleur" until the added essence is saturated with the colouring matter of the bitumen, and the evaporation "à l'air libre, dans une capsule" where the varnish has not the required consistency; the moisture that "l'altère et finit par le décomposer"; the cold application with a "tampon de peau très douce" to polished plated silver, the "belle couleur de vermeil", the hot iron under several folds of dried paper, the varnish that must cease to "poisser", and the light disc held in the mouth to condense the breath; the statement that after exposure "l'empreinte reste inaperçue" and that a solvent is needed to release it; the solvent, "composé d'une partie, non pas en poids, mais en volume, d'huile essentielle de lavande, sur dix parties, même mesure, d'huile de pétrole blanche", milky at first and clear in two or three days, exhausted when it turns opaque and very dark; the tinplate dish one inch deep, longer and wider than the plate, holding enough solvent to cover it; the washing board four feet long with two-inch battens and hinges, the lukewarm water poured above the plate rather than on it; the applications to stone, metal and glass, and the "petite quantité de cire dissoute dans l'huile essentielle de lavande" added for engraving on copper, with Daguerre's footnote that Niépce exposed those engraving copies "trois ou quatre heures aux rayons directs du soleil"; the potassium sulphide that attacks the varnish when concentrated and only reddens the metal when diluted; the iodine grains in a covered box for blackening the bared silver, and the alcohol that afterwards removes the varnish entirely; the two trials on glass, the diorama effect by transmission and the apparent local colours with the appeal to Newton's coloured rings; the Observations, with the engraving varnished on its verso, the 45-degree inclination, the damp that makes the varnish "se détache par couches de la planche" in the solvent, and the instruction that the varnish be used "en consistance assez épaisse pour former une couche compacte et aussi mince qu'il est possible" because it then resists the solvent better and is more sensitive; the Additions, with the coated plate to be kept from light as well as from damp, and the black paper and cardboard border for work on glass; the final varnish of "bitume de Judée dans l'huile animale de Dippel" left to evaporate to the degree of consistency required; and the closing line "Fait double, le 5 décembre 1829. Signé J. N. Niepce"; Cinquieme operation: removing the iodine with saturated salt solution or hyposulfite of soda; Rapport de M. Arago and the notes Arago added on publishing it: Dumas's weighings, from which the thickness of the gold-yellow iodine layer does not appear to reach a millionth of a millimetre; the statement that the plate does not gain appreciable weight in taking the iodine layer but gains very noticeably under mercury vapour; Pelouze's finding that after the hyposulfite wash the plate weighs less than before the operation began despite the amalgam now on it, and that chemical examination of the liquid shows the hyposulfite does remove silver; Dumas's and Adolphe Brongniart's microscopy, which found the lights and half-tones formed of spherules very regularly one eight-hundredth of a millimetre across; the forty-five degree inclination of the plate in the mercury vapour, which Arago records as unexplained; and Arago's closing sentence that thousands of fine drawings may be made with the daguerreotype before its mode of action has been completely analysed. Also Deuxieme operation, for the gold-yellow colour of the sensitised layer and the violet colour that must be avoided, and Troisieme operation, for the camera exposure of three to thirty minutes at Paris, the three or four minutes of June and July against the seven or eight of April and September, and the twenty minutes a subject wholly in half-tone can take in the best months; Cinquième opération: removing the iodine with saturated salt solution or hyposulfite of soda

Used by:Daguerre's 1839 process outline · Daguerre's 1839 process outline · Daguerre's 1839 process outline · Daguerre's 1839 process outline · Niépce's bitumen heliograph coating · P1 Daguerre and the Daguerreotype: A Mirror With a Memory · P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory · Daguerreotype

History and Practice of Photogenic Drawing on the True Principles of the Daguerreotype, with the New Method of Dioramic Painting, published by order of the French Governmentretrieved 2026-09-06

Sections: Fifth Operation, Fixing the Impression, and the First Operation's list of requisites: the phial of nitric acid diluted "in the proportion of one pint of acid to sixteen pints of distilled water", with the translator's own added sentence "These proportions express volume, not weight"; the bottle filled one-fourth with salt and three-fourths with pure water, shaken to saturation and filtered through paper; the solution of salt replaceable by one of hyposulphite of soda, "which is even preferable, because it removes the iodine entirely, which the saline solution does not always accomplish, especially when the sketches have been laid aside for some time"; and the "not less than a quart of distilled water" required for a design of the dimensions shown in the engraving, 8.5 by 6.5 inches. Also the preface, dated London, 13 September 1839; "Primary Material — Preparation", "Of the Solvent, and Manner of its Preparation" and "Washing — Manner of Procedure", in J. S. Memes's English translation of the same volume, preface dated 13 September 1839. The earliest English rendering of the notice, and the one in which "un verre" becomes a wine-glass: "I fill a wine-glass about half with this pulverised bitumen. I pour upon it drop by drop the essential oil of lavender till the bitumen can absorb no more, and till it be completely saturated. I afterwards add as much more of the essential oil as causes the whole to stand about three lines above the mixture". Also the solvent at one part by volume of oil of lavender to ten of oil of white petroleum, the compound that "will act several times in succession", and Daguerre's footnotes rendered as the translator gives them

Used by:Daguerre's 1839 process outline · Niépce's bitumen heliograph coating

History of Photographyretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Organic developer substances — the discovery of metol, amidol and glycin by Dr A. Bogisch at the J. Hauff works, Feuerbach; Daguerreotype portraits — Goddard's letter of 12 December 1840; Kratochwila's independent result of September 1840, published in the Wiener Zeitung on 19 January 1841, that an iodised silver plate gained at least five times in sensitivity when subjected to a mixture of bromine and chlorine vapours containing at least 50 per cent bromine, his demonstration to Liebig and Wöhler, and the eight-second portraits on cloudy days with Petzval's lens; the destruction of the latent image by the fumes of iodine, bromine or chlorine; Wet collodion process: Barreswil and Davanne 1851, Laborde 1853 and the cadmium double salts; Maddox and the gelatine emulsion; Ducos du Hauron 1878; Organic developer substances — Eder and Toth on pyrocatechin, 1880, and isomerism in the bivalent phenols; Warnerke and the tanning of gelatine; Koppmann's introduction of pyrocatechin, 1907, and the Jos-Pe method of 1925; Scheele as the first to isolate chlorine; The photochemical experiments of Berthollet, discovery of the reaction to light of chlorine water (1785), and Berthollet's discovery of bleaching by chlorine; Daguerreotype portraits — Kratochwila as the first to introduce chlorine vapour alongside bromine and his measurement of at least a fivefold gain from a mixture of bromine and chlorine vapours containing at least 50 per cent bromine, Claudet's mention of iodo-chloride in May 1841 and his Royal Society paper of 10 June 1841, the Natterer brothers' iodine-bromine-chlorine mixture, and Eder's dispute with Potonniee over the dating; Organic developer substances — Luppo-Cramer at Schering, 1899, and the naming of Adurol; Organic developer substances — the discovery of metol, amidol and glycin by Dr A. Bogisch at J. Hauff, Feuerbach; note 13 to pages 433-439; Organic developer substances — Abney 1880; Eder and Toth on isomerism in the bivalent phenols; The Discovery of Iodine (1814) — Courtois, Desormes and Clement, Gay-Lussac and Davy; Iodized Silvered Plates; the destruction of the latent image by the fumes of iodine, bromine or chlorine; Lead intensification and invention of darkening of silver with ferricyanides: Eder and Toth 1875 and 1876, and the reaction of red prussiate on metallic silver; Development with Mercury Vapors; Scientific Basis of Photography — Arago 1839, Donné 1839, Moser 1842 and Choiselat and Ratel 1843 on the origin of the developed image; the destruction of the latent image by iodine, bromine or chlorine vapour; Organic developer substances — Bogisch, metol, amidol and glycin; The wet collodion process chapter, for the 1876 report that the action of metal chlorides on silver ferrocyanide forms silver chloride and the corresponding metal ferrocyanides, with iron chloride colouring the image blue and copper chloride reddish-brown, and that colouring with cobalt and nickel salts is also referred to there; and for the summary of the ferricyanide methods as toning in blue, green, yellow, orange and brown with lead, copper, uranium, chromium, nickel and cobalt salts; Organic developer substances — Andresen, paramidophenol and German patent 60174; Eder and Toth on isomerism in the bivalent phenols; Organic developer substances — Bogisch, metol and the J. Hauff works; Talbot's bromide paper and the letter to Biot, 15 March 1839; Major C. Russell and the alkaline pyro developer, 1862-1863; Charles Bennett, 1878; Reduction of gelatine silver bromide images — the 1876 reaction of potassium ferricyanide on silver and E. Howard Farmer's 1883 bath; Talbot, silver iodide and fixing with potassium iodide, 1834-1839; Blanquart-Evrard's printing paper; Alexander Lainer and the acceleration of development by potassium iodide; Gelatine silver bromide: Berkeley 1882 and Mawson and Swan 1886; Braconnot and the reduction of silver nitrate by pyrogallic acid, 1831; Development with pyrogallic acid by Regnault and Liebig, 1851; Developer for gelatine silver bromides — pyro-ammonia and Berkeley's sodium sulphite, 1882; Mawson and Swan, 1886; Warnerke and the tanning action of pyrogallol; Utilization of tanning photographic gelatine silver bromide films by pyrogallol developers; Negatives and positives on paper: Talbot's letters to Biot of 20 February and 15 March 1839, and the announcement of the light sensitivity of silver bromide paper; From Seebeck to Daguerre: Davy's production of iodide of silver and the recognition of its sensitiveness to light (1814); Steffens, Link and Fischer, 1814; Boullay, 1827; the first use of silver iodide as a light-sensitive material; The chapter on the eighteenth-century observers — Torbern Bergman's Opuscula physica et chemica of 1779 and the statement that the rays of the sun darken the oxalate of silver, given beside his observations on the mercury oxalates; The calotype and its improvements — Parr's addition of sodium acetate as an accelerator to the iodo-bromine salt, and his later treatment of the silvered paper with sodium acetate; Printing-out processes: gold toning baths, Waterhouse of Halifax, 1858; Gelatine silver bromide: Lainer 1889 and the acid fixing bath; Andresen's eikonogen fixing bath; the acid sulphite solution of August 1889; Major C. Russell, The Tannin Process (1863): the alkaline developer and the alkaline carbonates; Negatives and positives on paper: Talbot's salted paper, the Lacock Abbey camera picture of 1835, and fixation with an excess of a strong solution of common salt; Gelatine silver bromide: Lainer 1889 and the acid fixing bath; the acid sulphite solution of August 1889; Gelatine silver bromide: Berkeley and the sulphite pyrogallol developer, 1882; Lainer and the acid fixing bath, 1889; The wet collodion process chapter, for Crookes's 1854 spectrography of the ultraviolet on wet collodion prompted by Stokes's 1852 fluorescence work, and for Crookes's investigations of 1855-1856 on the behaviour of silver bromide towards coloured light, his quinine sulphate filter and his priority in the use of light filters; Gold toning — acid thiocarbamide toning baths of Hélain and Valenta; Lead intensification and the darkening of silver with ferricyanides: Selle 1865; Eder's reaction scheme for ferricyanide on metallic silver; Warnerke and the tanning action of pyrogallol, and the utilization of tanned gelatine silver bromide films; Wet Collodion Process, page 363 — the fixation of wet collodion plates being done at first entirely with sodium hyposulphite, and the statement that it was not until 1853 that M. Gaudin published the use of potassium cyanide, which acts more rapidly and contributes to clearing up of the negative, and that it was still used at the time of writing especially with halftone negatives; the index entry "Potassium cyanide, as fixative, 363"; Photochromy, on Lippmann's interference process being fixed with potassium cyanide solution; Commercialization of Daguerreotypy: the silvered copper plate usually 6.5 by 8.6 inches, polished and subjected to iodine vapours at normal temperature to form a very thin coat of silver iodide; the wooden mercury box with its saucer-like iron bottom, its alcohol lamp and its internal thermometer; the early daguerreotypes kept in paper wrappings and Daguerre protecting his pictures under glass as early as 1839; the statement that in his early practice Daguerre knew only the imperfect fixation with a warm common salt solution, which gave the plates a mottled appearance; Herschel's discovery of the hyposulphites in 1819 and his pointing Talbot to their solvent action, Talbot acknowledging the improved fixation as early as 1 May 1839, and Daguerre abandoning salt and adopting hyposulphite of soda in 1839; and Fizeau's gilding bath of 1840 — 300 parts of hyposulphite of soda, 1,000 parts of water and one part of chloride of gold — with Fordos and Gélis identifying the double salt afterwards; Commercialization of Daguerreotypy, for daguerreotypes greatly enhanced in beauty and improved in permanence by toning in a bath of hyposulphite of soda containing gold chloride, for the invention of the gilding process attributed to Fizeau in 1840 and for the statement that the advance was generally adopted and largely increased the public demand for daguerreotypes, for Eder's own figures — "Fizeau's fixing bath contained 300 parts of hyposulphite of soda, 1,000 parts of water, and one part of chloride of gold" — and for Fordos and Gélis analysing the double salt, determining its composition and calling it hyposulphite of gold and sodium, later sodium auro-thiosulphate and in the trade Sel d'or de Fordos et Gélis. Also the later passage on toning positive silver prints, for the use of sel d'or for daguerreotypes dated there to 1841 and for Mathieu's 1847 pamphlet; Photographic tracing methods, page 543, for Herschel's use of the brown ammonium ferri-citrate, for the foundation of the "argentotype" process of 1842, for its reappearance in England as the kallitype in 1889 and in Arndt and Troost's sepia paper of 1895, and for Valenta's substitution of the green ammonium ferri-citrate in 1897; The "Notice sur l'heliographie" printed in full in the chapter on the agreement between Niépce and Daguerre, for Eder's independent English of the varnish, the developer, the washing board and the Dippel-oil varnish; for his footnote defining the ligne as a French unit of length of 2.256 millimetres; for his rendering of the developer as one part lavender oil to six of white mineral oil; and for his judgement that this notice is the earliest exact description of a photographic process and is so elaborate that satisfactory heliographic etchings can be produced by following the directions; Photographic tracing methods, page 542 — potassium ferrocyanide gives positive photographic tracings, the method Pellet used in his gum arabic iron process of 1877; Gelatine silver bromide - the history of organic developer substances, and the biography of Momme Andresen with his three patents, paraphenylendiamine 46495 of 8 January 1888, Eikonogen 50265 of 2 October 1889 and paramidophenol (rodinal) 60174 of 27 January 1891; Bogisch at J. Hauff and the introduction of metol about 1893; "Johann Heinrich Schulze discovers, in 1727, the sensitivity to light of silver salts", in the chapter on the phenomena of phosphorescence, for the biography, for the account of the accidental nitric acid containing nitrate of silver used for dissolving chalk, for "atro-rubentem et in coeruleum vergentem", for the fire control, the thread and the pasted stencils, for the shaking that made the writing disappear entirely and left the sediment ready for another light impression, and for the burning glass and the chalk-free silver nitrate solution; Lead intensification and invention of darkening of silver with ferricyanides: that the first and earliest application of a mixture of potassium ferricyanide with uranium nitrate for intensifying and brown colouring of collodion negatives was made by Selle in 1865, and that the method met with little approval and the progress of the chemical reaction was not investigated; that Eder investigated the exact chemical theory of the reaction of ferricyanides on silver and published it in 1876, stating that the same scheme operates in the darkening of silver images with uranium salts, giving a reddish brown colour; that Eder and Toth in 1876 recorded that the white ferrocyanide image turns reddish brown under uranium salts; and that Eder's 1883 second edition stated the ferricyanide methods to be applicable to gelatine silver bromide images; "Thomas Wedgwood published in 1802 his invention of the method of reproducing drawings on glass with silver nitrate or silver chloride", in From Vauquelin to Davy: the third reprint of the 1802 account consulted here, including the proportions sentence; the ages of the two men at publication, twenty-nine and about twenty-three; the judgement that although the work is routinely attributed to both, the credit belongs to Wedgwood alone; the statement that this publication contains the first account of the production of silver chloride paper by successive applications of silver nitrate and of chloride solutions on leather and paper, which served as a starting point for Talbot's later method; and the argument that Scheele's discovery that ammonia dissolves unblackened silver chloride would have given them a fixer had either man remembered it; Chapters IX-X: Schulze; Chapter XIII: Priestley to Senebier; The Life of Daguerre; Iodized Silvered Plates; Development with Mercury Vapors; Daguerre and Isidore Niepce; Commercialization of Daguerreotypy; Daguerreotype Portraits; Scientific basis of photography: Maedler and the word photography; notes to pages 254-270; Bayard's direct paper positives in the camera and analogous methods; Discovery of the photographic processes with chromates by Ponton (1839); J. B. Reade; Daguerreotype portraits: Morse; Germany: Kobell and Steinheil; Scientific basis of photography: Maedler; Joseph Nicephore Niepce: the 1816 letters to Claude; Niepce exhibits asphaltum photographs in England in 1827; the plates acquired by the Royal Photographic Society; Fabricius 1565; Sala 1614; Boyle 1667; Homberg 1694; Schulze 1727; Beccarius 1757; Senebier 1782; Herschel and Ritter 1800-1801; Bunsen and Roscoe; Negatives and positives on paper: Fox Talbot and the calotype; J. B. Reade; notes to pages 254-270 and 325-330; Chapter V: The History of the Camera Obscura, and Chapter I on Aristotle and Ibn al Haitam; From Vauquelin to Davy: Wedgwood and Davy 1802; Davy on iodide of silver 1814; Senebier 1782; Bunsen and Roscoe, Photochemische Untersuchungen; Photographic Photometry: Bunsen and Roscoe, Photochemische Untersuchungen 1855-1859; Herschel Effect; Chapter LXIV, Discovery of colour-sensitizing of photographic emulsions in 1873: Vogel, corallin in Stuart Wortley's collodion dry plates, the exhibition of 17 October 1873, the opposition of Monckhoven and Carey Lea, Becquerel's endorsement, and the azaline plates of 1884; erythrosin orthochromatic emulsions at Lowy and Plener 1884; Chapter LXV, Discovery of desensitizing: Luppo-Cramer 1901 and 1920; Development with Mercury Vapors; Negatives and positives on paper: Talbot and the calotype; Organic developer substances — Eder and Toth 1880 on isomerism in the bivalent phenols and the later extension of the rule to paramidophenol; Andresen's German patent 60174 of 27 January 1891 for paramidophenol, rodinal; Warnerke 1881 on the tanning of gelatine by pyro development; Organic developer substances: Abney 1880 for the alkaline hydroquinone developer, Eder and Toth 1880 on pyrocatechin and on the influence of isomerism in the bivalent phenols, and the later extension of the rule to paramidophenol; Alexander Lainer and the acceleration of development by potassium iodide, named in the technical literature as the Lainer effect; Braconnot and the reduction of silver nitrate by pyrogallic acid, 1831; development with pyrogallic acid by Regnault and Liebig, 1851; the pyro-ammonia developer for gelatine silver bromide plates and the yellowish or brownish stain it left; Berkeley's addition of sodium sulphite in 1882 and Mawson and Swan's potassium metabisulphite in 1886; Warnerke and the tanning action of pyrogallol, and the utilization of tanned gelatine silver bromide films; Sensitizing Emulsions and Journals, Societies and Institutions - the account of the research laboratory George Eastman installed at Rochester in 1912 under C. E. Kenneth Mees, naming L. A. Jones among the scientists gathered there, and the record that Jones contributed to the first volume of the Abridged Scientific Publications of the Research Laboratories of the Eastman Kodak Company, 1913 to 1914; and the reference to the later work of L. A. Jones, E. Huse and V. C. Hall of 1926 on the theory of photographic density; Lead intensification and invention of darkening of silver with ferricyanides - that the first and earliest application of a mixture of potassium ferricyanide with uranium nitrate for intensifying and brown colouring of collodion negatives was made by Selle in 1865, that the method met with little approval and the progress of the chemical reaction was not investigated; that in 1875 Eder with Captain Victor Toth found that mixtures of potassium ferricyanide with lead salts deposit a precipitate of silver ferrocyanide and lead ferrocyanide, reported to the Vienna Photographic Society on 14 December 1875; and that the same scheme operates in the darkening of silver images with uranium salts, giving a reddish brown colour; Development with Mercury Vapors — that Daguerre found a plate carrying an exposure far too short to darken it visibly could be made to yield a complete picture by exposing it to the vapour of mercury, and that Eder marks the received account of how he found it as hearsay reaching him through Liebig and Vogel rather than from Daguerre. Discovery of the photographic processes with chromates by Ponton (1839) — Ponton's 1839 result that paper soaked in bichromate of potash is powerfully and rapidly acted on by the sun's rays and is fixed by immersion in water, and Talbot's photoglyphic engraving patent of 29 October 1852 covering the sensitivity of dichromate mixed with gelatin or gum, from which carbon printing, gum bichromate, photogravure and dichromated gelatin descend; Chromates — Vauquelin's 1798 finding that chromic acid forms with silver a carmine-red salt that darkens in light, which Eder sets aside as silver photochemistry; Professor Suckow as the first to observe, in 1832, that chromic acid salts mixed with organic substances are light-sensitive even in the absence of silver; Ponton's 1839 report to the Royal Society of Scottish Artists, with Eder's judgement that Ponton's conception of the nature of the chemical reaction was quite incorrect and that he failed to realise the much more important light-sensitivity of mixtures of potassium bichromate with gelatine and rubber; Becquerel's starch-paste and iodine work of 1840; Hunt's chromatype and chromo-cyanotype experiments of 1843 leading to no practical result; the statement that Talbot was the discoverer of the light-sensitivity of a mixture of potassium bichromate and gelatine, his English patent of 29 October 1852 for photographic etchings on steel and his detailed publication as Gravure photographique sur l'acier in the Comptes rendus of 1853; Talbot's own description that after washing the light image appeared somewhat prominent since the water washed away the chromium salt from the parts affected by light and swelled the glue coating somewhat, his etching through the coating with platinum perchloride, and his interposition of a fine black gauze between diapositive and coating to get a halftone effect, which Eder calls the basis of the later screen process; Pretsch's English patent 2,373 of 9 November 1854 for a gravure process using the swelling property; and Poitevin discovers collotype and pigment printing (1855) — his English patent of December 1855 recommending a mixture of albumen, fibrine, gum arabic, gelatine and other similar substances with potassium bichromate, printed, dampened and rolled up with greasy ink which only adheres to the parts exposed to light, his remark in the same specification that coloured prints could be obtained by adding a pigment and washing away the portions not changed by light, his French licence of 6 August 1855, his exhibition of prints at the Paris Exposition Universelle of 1855, and his sale of the patents to the lithographer Lemercier. Photogravure and Rotogravure — the photogravure process invented by Karl Klic at Vienna in 1879, based on the pigment process, by which Klic transferred a pigment image onto a grained copperplate, developed it in warm water and then etched with iron chloride solutions of varying strength, giving particular sharpness, rich detail and halftones; the description of Klic as the creator of modern photogravure with aquatint grain on copper by means of the transfer of a pigment image and etching in iron chloride baths of various strengths to different graduated depths; and his introduction of rotogravure printing with the doctor, using the pigment process without grain and substituting a copied crossline screen; and Eder's excursus on the spelling of Klic's name — the parish register at Arnau recording Karl Klitsch, the inventor's own signature as Klic on his drawings and on his contracts with the Vienna Government Printing Office of 1881 to 1882 after his father adopted the Czech form, and the Klietsch he adopted in England because English colleagues found the Czech pronunciation difficult, which is the spelling on his tombstone at Hietzing; Development with Mercury Vapors; Commercialization of Daguerreotypy, for the wooden mercury box with its saucer-like iron bottom, its alcohol lamp and its internal thermometer, and for the imperfect fixation with warm common salt solution that gave the plates a mottled appearance; Daguerreotype Portraits, for Goddard's bromine letter of 12 December 1840, for Kratochwila's independent result of September 1840 with at least a fivefold gain, exposures of a few seconds and portraits on cloudy days in eight seconds, for Claudet's iodo-chloride of May 1841, and for Petzval's portrait objective and the boom in portraiture dated from it; Scientific Basis of Photography, for Arago's, Donne's, Moser's and Choiselat and Ratel's competing accounts of why the amalgam forms where it does, and for the destruction of an existing latent image by iodine, bromine or chlorine vapour reported by Gaudin in 1841 and by Shaw and Percy in 1843; and Fizeau's gilding bath of 1840 with Fordos and Gelis identifying the double salt afterwards; Lead intensification and invention of darkening of silver with ferricyanides — that the first and earliest application of a mixture of potassium ferricyanide with uranium nitrate for intensifying and brown colouring of collodion negatives was made by Selle in 1865, that the method met with little approval and the progress of the chemical reaction was not investigated; that in 1875 Eder with Captain Victor Toth found that mixtures of potassium ferricyanide with lead salts deposit a precipitate of silver ferrocyanide and lead ferrocyanide, reported to the Vienna Photographic Society on 14 December 1875; and that the same scheme operates in the darkening of silver images with uranium salts, giving a reddish brown colour; Bayard's direct paper positives in the camera and analogous methods; Lassaigne, Fyfe and Verignon; Development with Mercury Vapors; the red-light action on the latent image of the iodised plate found by Draper 1842, Lerebours 1846 and Claudet 1847; Negatives and positives on paper: Fox Talbot and the calotype; J. B. Reade; Poitevin 1855 and Swan 1864; the chromate processes after Ponton; Talbot's patent of 29 October 1852 on dichromate with gelatin or gum; the chromate processes after Ponton; The Life of Daguerre; Iodized Silvered Plates; Development with Mercury Vapors; Commercialization of Daguerreotypy; Daguerreotype Portraits; Joseph Nicéphore Niépce: the 1816 letters to Claude; Niépce exhibits asphaltum photographs in England in 1827; Discovery of the photographic processes with chromates by Ponton (1839); Suckow 1832; Talbot's patent of 29 October 1852 on dichromate with gelatin or gum; Talbot's patent of 29 October 1852 on dichromate with gelatin or gum; the chromate processes; Selle 1865 and the first application of potassium ferricyanide with uranium nitrate; the reaction scheme worked out in 1876; Talbot's patent of 29 October 1852 on dichromate with gelatin or gum; the chromate processes and the photomechanical family that grew from them

Used by:Amidol · Bromine · Cadmium bromide · Catechol · Chlorine · Chlorohydroquinone · Glycin · Hydroquinone · Iodine · Lead(II) nitrate · Mercury · Metol · Nickel(II) sulfate · p-Aminophenol · Phenidone · Potassium bromide · Potassium ferricyanide · Potassium iodide · Potassium metabisulfite · Pyrogallol · Silver bromide · Silver iodide · Silver(I) oxalate · Sodium acetate (anhydrous) · Sodium bicarbonate · Sodium bisulfite · Sodium carbonate (anhydrous) · Sodium chloride · Sodium metabisulfite · Sodium sulfite · Thallium(I) sulfate · Thiourea · Uranyl nitrate hexahydrate · 510-Pyro · Cyanide fixing and toning · Daguerre's 1839 process outline · Fizeau's gilding solution · Herschel's argentotype · Niépce's bitumen heliograph coating · Pellet's positive-working process · Rodinal-type p-aminophenol developer · Schulze's scotophorus mixture · Uranium toner · Wedgwood and Davy's silver nitrate on leather · P1 Overview: The Three Problems Every Photograph Must Solve · P1 Daguerre and the Daguerreotype: A Mirror With a Memory · P1 Herschel: Hypo, Prussian Blue and the Words of Photography · P1 1839 and the Many Inventors of Photography · P1 Niepce and Heliography: Light That Hardens · P1 Silver Salts and Light: Schulze to Ritter · P1 Talbot: Photogenic Drawing, the Calotype and the Negative-Positive Principle · P1 The Camera Obscura: An Image Without Chemistry · P1 Wedgwood, Davy and the Problem of Permanence · P1 Experiment: The Image That Would Not Stay · P4 Reciprocity Failure and the Life of the Latent Image · P4 Spectral Sensitivity and Colour Response · P4 The Latent Image · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 Restrainers and Antifoggants · P8 Staining and Tanning Developers · P13 Tone Reproduction: From Subject to Print · P20 The Toners We Study and Do Not Use · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory · P26 Uranium, Mercury and the Heavy-Metal Treatments · Bayard direct positive · The Becquerel variant · Calotype negative · Carbon print · Collotype · Daguerreotype · Heliography on bitumen of Judea · Photoglyphic engraving · Photogravure · Uranotype and Wothlytype · Woodburytype

Instruction in Photography, 11th edition, revised and reset throughoutretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Development — ferrous citrate dissolved in a saturated solution of ammonium citrate, with citric acid added if required; W. B. Ferguson's copper toning process — the 1900 formula, the modified formula, the range of tones and the claim of permanence; Development with glycin; Hydrokinone developer; formulae for hydrokinone; Purifying the Printing Bath — the addition of a small quantity of pure kaolin followed by shaking and filtering, the verdict that the method answers perfectly but is rather wasteful, and the two alternatives given beside it, neutralising the bath to litmus and standing it in the sun so that the organic matter is deposited with the silver oxide, and adding a small quantity of sodium chloride so that the organic matter is deposited with the silver chloride and separated by filtration; Development with metol; Metol-hydrokinone developer; The Ozotype patent specification, for the clause allowing "the cupric, cobaltus, and nickel salts, and other metallic salts capable of giving oxides on exposure to light in presence of the light sensitive compounds of chromium" in place of the manganese salts; the emulsion-coating box, for the suggestion that it could be made of metal, "nickelled iron, for instance, or silver"; and the daylight developing machine, for the note that "as the apparatus is nickel-plated throughout, it is not corroded by the solutions used, and is easily kept clean"; Platinotype — the three sensitising solutions, the statement that the effect of adding potassium chlorate is to increase contrasts because it is an oxidising agent that converts some of the platinite to a platinic salt, and the fault list entries "use more potassium chlorate in the sensitising solution" and "too much chlorate in the sensitising solution"; The wet-collodion sensitising bath, on restoring a contaminated bath by neutralising the acid with freshly precipitated silver oxide, adding it until some remains undissolved and sunning the solution; Fog on wet-plate negatives, on alkalinity of the bath by silver oxide, which is slightly soluble in water; Development, page 249 — "Ferrous citrate may be purchased and dissolved in a saturated solution of ammonium citrate, adding citric acid if required to give a clear picture", the earliest ammonium citrate developing bath read for this course and one specified by saturation rather than by weight; Formation of Gold Salts, the closing paragraph on fixing the print — the statement that hyposulphite is used because cyanide attacks the organic oxide formed by light; Manipulations in Toning, for the ammonium sulphocyanide and gold terchloride toning bath and the plain ammonium sulphocyanide bath that follows it; and the residues chapter, on old hyposulphite baths and solutions of cyanide of potassium or sodium hyposulphite used for fixing negatives being placed in a tub and treated with potassium sulphide of commerce, or a stream of sulphuretted hydrogen, until no more precipitation of silver sulphide takes place; Silver printing, on the choice of rawstock — Rives and Saxe as the two papers principally used for albumenising, both starch-sized, Saxe much more porous and consequently less glossy than Rives, Rives tender when wet and apt to tear in the large sizes so that Saxe is preferred for large prints, and the statement that "Saxe paper can be rendered nearly as glossy as Rives by doubly albumenising and rolling"; Pellet's process, pages 540 to 542 — Liesegang's account of the composition, the development, the acid bath and the note on the function of the gum; Masking the negative, which improves a picture that prints too black in the shadows before the details in the lights have printed in by shading those dark portions, either by temporarily placing a paper whilst printing or by gumming tissue-paper cut to the proper shape to the back of the negative, with two or more layers on the deepest shadows; and the passage on secondary objects under Transparent Spots, which states that where a secondary object attracts the eye by the brilliancy of its high lights, and the object of all artistic photography is to cause the eye primarily to dwell on the most important point, the bright spot should be sunned down by shading all the print except that particular part, by means of a brown-paper mask cut to the shape of the object, the negative being removed and a clean piece of glass substituted for it in the printing frame

Used by:Ammonium citrate (dibasic) · Copper(II) sulfate · Glycin · Hydroquinone · Kaolin · Metol · Nickel(II) sulfate · Potassium chlorate · Silver(I) oxide · Ammonium citrate developer · Cyanide fixing and toning · Double-coated albumen procedure · Pellet's positive-working process · P19 Lab: Dodging, Burning, Edge Work and Local Contrast

Investigations on the Theory of the Photographic Processretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: The Latent Image, section (b) The Action of Desensitisers, page 247 — uranium nitrate found to desensitise in July 1905, the attribution of the action to the metallic ion, and the list of metals whose salts "gave negative results", which begins "lead, nickel, thorium"; Reeb's determination of the reducing power of a developer from a solution of silver oxide in alkaline sulphite; the reaction of hydroxylamine with silver oxide in sulphite solution; the oxidation of p-phenylenediamine and p-aminophenol in ethereal solution with dry silver oxide, page 154; The Latent Image, section (b) The Action of Desensitisers, page 247 — uranium nitrate found to desensitise in July 1905, the attribution of the action to the metallic ion, and the list of metals whose salts "gave negative results", thallium among them; Part II Chapter I, The Chemical Dynamics of Development with Iron Salts: all developers are reducing agents but the converse does not hold, reduction potential and the Ohm-law analogy, and the Note on Fog; Chapter II, The Microscopic Study of the Photographic Image; Chapter VI, the induction period and the developability threshold at a given development energy; Part II Chapter II, The Microscopic Study of the Photographic Image: measured grain sizes for Wratten Ordinary and Imperial Special Rapid plates, Bellach's Apollo series, and the structure of developed negatives through the depth of the layer; Part II Chapter VI, The Nature and Destruction of the Latent Image: Failure of a Photo-chemical Law, Table 110; Reversal and Solarisation and the classification of reversal forms; The Decay and Destruction of the Latent Image, quoting Baekeland; Part II Chapter VI, The Decay and Destruction of the Latent Image, quoting Baekeland; and the caution that a change in a plate's rate of development is easily mistaken for decay of the latent image; Part II Chapter I, The Chemical Dynamics of Development: all developers are reducing agents but the converse does not hold, and Bredig on reduction potential with the absence of proportionality between potential and reaction velocity; Chapter VI, the induction period and the developability threshold at a given development energy; The Latent Image, the developable image after fixation and physical development as silver nitrate plus an acid reducer; Wave-length and Gradation - the statement that where the opacity of the unexposed plate is small the straight portion of the curve becomes very short, so that the slope must be taken from the tangent at the inflection rather than by producing a straight line, which is the weakness in the Hurter and Driffield inertia construction; Dynamics of Development - Iron, for the relation gamma equals gamma infinity times one minus e to the minus kt, with gamma infinity the ultimate development factor attainable with infinite development and k the velocity constant depending on the plate, the temperature and the developer; Wave-length and Gradation, for the statement that a small opacity of the unexposed plate makes the straight portion very small so that gamma must be taken from the tangent at the inflection; Dynamics of Development - Iron, for the relation gamma equals gamma infinity times one minus e to the minus kt, with gamma infinity the ultimate development factor attainable with infinite development and k a velocity constant depending on the plate, the temperature and the developer; Wave-length and gradation - the statement that where the opacity of the unexposed plate is large the gradient is nearly constant over a large part of the curve and gamma can be found by drawing a straight line through those points, as Hurter and Driffield did, but that where it is small the straight portion becomes very small and gamma must be deduced from the tangent at the inflection point; Instruments and Methods of Working - the chief objection to intensity scales being the failure of the Bunsen-Roscoe reciprocity law, with the law referenced to Poggendorff's Annalen 1855-1859; time scales impressed by continuous or intermittent exposure, the continuous being preferable and the intermittent easier; the sector wheel proposed by Claudet in 1840 and by W. B. Bolton, adopted by Hurter and Driffield with nine apertures each twice the preceding and by Scheiner at an angular ratio of 1 to 1.27; Sebert's clockwork slot apparatus of the Paris Congress of 1900 as the best theoretical form; and the objection that the angles cannot be cut accurately enough and must be calibrated afterwards. The Latent Image - the intermittency effect first shown by A. and L. Lumiere in 1881 and first investigated completely by Abney; the authors' own test of two Wratten ordinary plates exposed together for five minutes at 1520 and at 9.5 revolutions per minute, tabulated at log E from 0.20 to 2.60; and their conclusion that for practical sensitometry a sector wheel not driven above 100 revolutions per minute makes the intermittency error negligible even for slow plates; The Latent Image, pages 221 to 223 - the failure of a series of intermittent exposures to produce the same effect as the equivalent continuous exposure, first shown by A. and L. Lumiere in 1881 and investigated by Abney; the authors' own sector-wheel measurement at 1520 and 9.5 revolutions per minute showing the effect concentrated in the bottom exposures; their conclusion that below 100 revolutions per minute the intermittency error would be negligible even for slow plates; and Englisch's account of the effect as an induction loss together with a fading loss, whose reverse reaction has the greater effect the longer the pause and the more numerous the pauses; Dynamics of development, iron - the observation that values at the most dilute concentration tended to decrease, attributed to the rapid accumulation of bromide and other reaction products which do not diffuse rapidly and so influence the velocity by remaining in the reaction layer, named as one of the main causes of divergence in heterogeneous reactions

Used by:Nickel(II) sulfate · Silver(I) oxide · Thallium(I) sulfate · P4 Development as Amplification · P4 Grain, Speed and Resolution · P4 Reciprocity Failure and the Life of the Latent Image · P4 Darkroom Session: The Latent Image Made Visible · P8 How Development Works · P13 Film Speed and Exposure Index · P13 Gamma, Contrast Index and Average Gradient · P13 Assignment: Interpreting Density Data · P13 The Characteristic Curve · P14 Sensitometer Design Principles · P19 Contrast Filtration and Split-Grade Printing · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does

Kodak Reference Handbook: Materials, Processes, Techniqueretrieved 2026-09-05, 2026-09-06

Sections: Formulas page 49, Kodak Hardener F-5a, headed Stock Solution For Preparing Kodak Fixing Bath F-5, metric column reading water about 125 degrees F (50 degrees C) 600 c.c., Kodak Sodium Sulfite desiccated 75.0 grams, Kodak Acetic Acid 28 per cent 235.0 c.c., Kodak Boric Acid crystals 37.5 grams, Kodak Potassium Alum 75.0 grams and cold water to make 1.0 liter, with the same two footnotes as the later printing, the instruction 'Dissolve chemicals in order given.' and the direction 'Add one part of the cool stock hardener solution slowly to 4 parts of cool 30% hypo solution (2 1/2 pounds per gallon of solution), while stirring the hypo rapidly.'; Kodak Fixing Bath F-5 immediately above it, whose metric column reads water about 125 degrees F 600 c.c., hypo 240.0 grams, sodium sulfite desiccated 15.0 grams, acetic acid 28 per cent 48.0 c.c., boric acid crystals 7.5 grams, potassium alum 15.0 grams and cold water to make 1.0 liter, with the sentence 'The hardener may also be mixed separately as a stock solution as follows:' and fixing times of 10 to 20 minutes for films or plates and 5 to 10 minutes for prints; Kodak Hardener F-6a on Formulas page 50, identical to F-5a except that 75.0 grams of Kodalk stands where the 37.5 grams of boric acid stands; and Kodak Rapid Fixing Bath F-7 on Formulas page 50, with the alternative make-up from the stock reading water about 125 degrees F 500 c.c., Kodak Sodium Thiosulfate 360.0 grams and Kodak Ammonium Chloride 50.0 grams, then, when the hypo and ammonium chloride are dissolved completely, Kodak Hardener F-5a 200.0 c.c. and water to make 1.0 liter; and Formulas page 30, Keeping Properties and Useful Life of Solutions, its preamble that the figures are estimates based on experience intended for use only as a guide and that the keeping values are for 65 to 70 degrees F (18 to 21 degrees C) and proportionately less at higher temperatures, and its Kodak F-5 row reading tray 1 week, gallon tank 1 month, stoppered bottle full 3 months and half full 2 weeks. Read as the Internet Archive optical character recognition text of the scan, not as page images; the metric column of the formula is unambiguous there and agrees line for line with the J-1 page images this course read directly, while the avoirdupois column is corrupt in the same text and is not reproduced here, and the useful-life columns of the keeping table are interleaved by the same text extraction and are not quoted; Formulas page 50, Kodak Fixing Bath F-6, headed Odorless Bath for Films, Plates, and Papers, metric column reading water about 125 degrees F (50 degrees C) 600 c.c., Kodak Sodium Thiosulfate (Hypo) 240.0 grams, Kodak Sodium Sulfite desiccated 15.0 grams, Kodak Acetic Acid 28% 48.0 c.c., Kodalk 15.0 grams, Kodak Potassium Alum 15.0 grams and cold water to make 1.0 liter, with the footnote that 28 per cent acetic acid is made by diluting three parts of glacial acetic acid with eight parts of water, the instruction to dissolve chemicals in the order given, and the note that the bath should be used in conjunction with a stop bath such as Kodak SB-1 or SB-1a or an acid hardening bath such as Kodak SB-3 to obtain the full useful hardening life, that the hardening life equals that of Kodak F-5 provided an acid stop bath is used, and that with a water rinse the life is about one-half that of Kodak F-5; Kodak Hardener F-6a on the same page, the stock solution for preparing Kodak Fixing Bath F-6, reading water 600 c.c., sodium sulfite desiccated 75.0 grams, acetic acid 28% 235.0 c.c., Kodalk 75.0 grams and potassium alum 75.0 grams to make 1.0 liter, with the direction to add one part of the cool stock hardener solution slowly to four parts of cool 30 per cent hypo solution while stirring the hypo rapidly; Kodak Fixing Bath F-5, headed For Films, Plates, and Papers, on Formulas page 49, whose metric column reads water about 125 degrees F 600 c.c., hypo 240.0 grams, sodium sulfite desiccated 15.0 grams, acetic acid 28% 48.0 c.c., boric acid crystals 7.5 grams, potassium alum 15.0 grams and cold water to make 1.0 liter - identical to F-6 line for line except that the boric acid stands where the Kodalk does - and whose text gives 10 to 20 minutes for films or plates in a freshly prepared bath, a discard point at over 20 minutes, and 5 to 10 minutes for prints, together with the statement introducing F-6 that in warm weather and in inadequately ventilated darkrooms the odor of sulfur dioxide given off by Kodak Fixing Bath F-5 may be objectionable and can be eliminated almost entirely by omitting the boric acid and substituting twice its weight in Kodalk; Kodak Hardener F-5a on Formulas page 50; Kodak Fixing Bath F-1, For Papers, on Formulas page 49; Keeping Properties and Useful Life of Solutions, Formulas page 30, its preamble that the figures are estimates based on experience intended for use only as a guide, that the keeping values are for 65 to 70 degrees F (18 to 21 degrees C) and proportionately less at higher temperatures, and that the useful capacity figures are based on exhaustion without replenishment, the Fixing Baths block and its Kodak F-6 row reading tray 1 week, gallon tank 2 months, stoppered bottle full 3 months, half full 3 weeks and a useful life of 50 with a water rinse and 100 with SB-1 in both tray and narrow and deep tank, against the Kodak F-5 row's 100 either way, and the footnote that the double dagger marks a water rinse between development and fixing; Formulas, page 46, Kodak Stop Bath SB-5, Nonswelling Acid Rinse for Photofinishing — water 16 ounces (500 c.c.), Kodak Acetic Acid 28 per cent 1 fluid ounce (32.0 c.c.), Kodak Sodium Sulfate desiccated 1 and a half ounces (45.0 grams), water to make 32 ounces (1.0 liter), with the footnote that 28 per cent acid is made by diluting three parts of glacial acid with eight parts of water and the footnote that 3 and a half ounces per 32 ounces (105 grams per liter) of crystalline sodium sulfate may be used instead; the instruction to agitate the films when first immersed and leave them about three minutes; the replacement figure of approximately 25 rolls per quart (liter), by which point about 24 ounces (720 c.c.) of developer will have been carried into the rinse bath by the film. Formulas page 46 also carries Kodak Hardening Bath SB-4 and Kodak Special Hardener SH-1. Formulas, page 30, Keeping properties and useful life of solutions, whose stop-bath block heads its two stoppered-bottle columns 65 and 75 degrees F and gives SB-5 3 days in a tray, 1 month in a gallon tank, indefinite keeping in a stoppered bottle at both temperatures, and a useful life of 100 sheets of 8 by 10 inches per gallon in a tray and in a narrow or deep tank alike, with SB-1 marked papers only at 75 and SB-3 and SB-4 at 25; the roll-film equivalents beneath it, one roll of 620 or 135 counting as one 8 by 10 sheet. Formulas, page 31, Kodak Chemical Preparations, which lists no packaged nonswelling rinse. Processing, page 5, Stop Baths, the primary purpose of an acid rinse and the note that a hardening stop bath is desirable for films and plates in warm weather; Processing, Action of the Fixing Bath, on the developer carried in gradually neutralising the acid and finally producing a sludge of aluminium sulfite that renders the bath useless; Processing, Testing Stop Baths and Fixing Baths, on the appearance of stop baths not changing until well beyond their useful lives, and on testing solution A changing from yellow to purple when the acidity of the bath becomes too low to stop development. Processing, page 16, High Temperature Development, the precaution list and the table giving 50 grams of desiccated sodium sulfate per litre for D-11, D-19, D-61a and D-76 at 75 to 80 degrees F, 75 grams at 80 to 85 and 100 grams at 85 to 90. Formulas, page 28, Storage of Solutions, on redissolving by warming a precipitate thrown by cold storage

Used by:Kodak F-5a · Kodak F-6 · Kodak SB-5

La platinotypie : exposé théorique et pratique d'un procédé photographique aux sels de platine permettant d'obtenir rapidement des épreuves inaltérablesretrieved 2026-09-06

Sections: Partie pratique — Préparation de la dissolution sensibilisatrice, for the same 24 : 22 : 4 normal mixture and the same three variants; the preceding pages for the same 20 grammes of ferric oxalate per 100 cubic centimetres with 6 to 8 per cent of oxalic acid and the same 0.4 gramme of potassium chlorate per 100 cubic centimetres; Partie théorique, for the same 0.020 to 0.025 gramme of potassium chloroplatinite per 1,000 square centimetres

Used by:Pizzighelli and Hübl's 1886 formulations

Memorial Volume containing an account of The Photographic Researches of Ferdinand Hurter and Vero C. Driffield, being a Reprint of their Published Papers, together with a History of their Early Work and a Bibliography of Later Work on the same subjectretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: The Latent Image and its Development: the influence of bromide, Experiments 14, 15 and 16; Photochemical investigations: density proportional to the mass of silver per unit area, and the periods of the characteristic curve; The period of reversal in the characteristic curve; the bibliography entry for A. W. Clayden, Experiments on Reversal and Clayden Effect, British Journal of Photography volume 58; The Latent Image and its Development — Experiment 15, the influence of the variation of bromide in the developing solution, the densities inclusive of fog at 0, 2, 8, 32 and 128 parts of potassium bromide per thousand, and the finding that the retarding influence of bromide can be fully compensated by time of development so that the speed of the plate is not really altered; The Latent Image and its Development: Influence of the variation of bromide in the developing solution; Experiment 15, pyro-soda on plate D2, densities inclusive of fog after three minutes at 0, 2, 8, 32 and 128 parts of potassium bromide per thousand; the colour change to fawn and the silver analysis giving 2.43 times the silver for a given density; and the finding that the retarding influence of bromide can be fully compensated by time of development and that the speed of the plate is not really altered; The Latent Image and its Development — Experiment 15, the family of curves at 0, 2, 8, 32 and 128 parts of potassium bromide per thousand with the unexposed density falling from 0.160 to 0.060 and reaching its floor by 8 parts while the image was still developing strongly; the statement that the reaction is never stopped but simply retarded and that the image will appear in full force if sufficient time be allowed; and the conclusion that the speed of the plate is not really altered by the addition of bromide; The Latent Image and its Development — the statement that the reaction is never stopped by bromide but simply retarded, and that the image will appear in full force if sufficient time be allowed; The Latent Image and its Development — Experiment 15 and the conclusion that bromide retards rather than stops development, and that the speed of the plate is not really altered by its addition; Early Work — the method of giving a definite exposure through a step wedge and measuring the densities produced, and the change of view by which the inertia of the plate came to be regarded as the smallest exposure necessary to produce the slightest deposit representing the deepest shadow of the original, on the ground that very slight deposits are little altered by continued development; Contents list, which dates the paper Photochemical Investigations and a New Method of Determination of the Sensitiveness of Photographic Plates to the Journal of the Society of Chemical Industry of 31 May 1890; Photochemical Investigations, the section defining transparency, opacity and density, in which T times O equals one, density is the number of absorbing particles per unit area multiplied by the coefficient of absorption, the three quantities are related by T equals e to the minus D, and the density is stated to be directly proportional to the amount of silver deposited per unit area; Photochemical Investigations - the inertia defined as the exposure at which the produced straight line cuts the exposure axis and as the least exposure marking the beginning of the period of correct representation, the speed of the plate given as its inverse, the actinograph speed formula S equals 34 divided by i with i the inertia in candle-metre-seconds, and the worked speeds of 17, 24 and 60 for the Ilford ordinary, rapid and special rapid plates; Relation between Negatives and their Positives - the development constant, defined as the tangent of the angle of inclination of the straight portion, found by drawing a line parallel to it through 1000 on the exposure scale; Influence of the Quantitative Composition of the Developer, for the statement that altering the time of development causes the straight line to assume different angles of inclination and that the development factors can be made greater or less than one; Biographical account of Hurter as chief chemist to Gaskell, Deacon and Company of Widnes until the works were absorbed into the United Alkali Company in 1890, of Driffield joining the same firm as engineer in 1871 after half a year in Henry Sampson's Southport studio, and of music as what first brought them together; Contents list, dating the paper Photochemical Investigations and a New Method of Determination of the Sensitiveness of Photographic Plates to the Journal of the Society of Chemical Industry of 31 May 1890, and Captain Abney's paper On the Accuracy of the Grease Spot Photometer and the authors' first Reply to it, both listed at 31 July 1890, and the later paper The Sector and Grease-Spot Photometers, and their Results, which the contents list dates 31 January 1891 while the reprint header inside the volume dates it 28 February 1891, No. 2, Vol. X; Early Work, on the reading of the paper at Liverpool before the local section of the Society of Chemical Industry and on the definition of inertia; Relation between Negatives and their Positives, for the standard candle at one metre with each exposure double the previous one, the naming of the characteristic curve, the three periods of under-exposure, correct representation and over-exposure, the invariance of the point at which the produced straight line cuts the exposure scale, and the development constant; Photochemical Investigations, for the Period of Reversal and the observation that density tends to a limit; the section headed Reply to Captain Abney within that 1891 paper, for the admission that a photometer built on Abney's principle reproduced his readings and for the mutual-reflection term in the opacity of a combination; What is a Perfect Negative? - the definition of a theoretically perfect negative as one in which the opacities are directly proportional to the intensities of the light which produced them; Period of Correct Representation, for the straight portion of the curve as the region where that proportionality holds; and Relation between Negatives and their Positives, for the treatment of the negative and the print as one chain rather than two; Photochemical Investigations, Unit of Exposure - the candlemetre-second, the standard candle at one metre in a black box, the flame settled to nearly 45 mm, and the reproducibility they obtained: densities of 0.750, 0.730 and 0.720 on three separate days, and 0.490, 0.490, 0.500 and 0.480 from four different standard candles; Photochemical Investigations, Unit of Exposure - the reproducibility obtained with the standard candle, 0.750, 0.730 and 0.720 on three separate days, and 0.490, 0.490, 0.500 and 0.480 from four different standard candles; Photochemical Investigations, Unit of Exposure - the candlemetre-second defined as a standard candle at one metre for one second; the flame relied on only after it has settled to nearly 45 mm; the candle shielded in a black box with one side open; time measured with a chronograph watch or a metronome, with errors held too great below 10 seconds; shorter exposures obtained by moving the candle to two metres to quarter its intensity; the demonstration that a quarter candlemetre for 40 s and one candlemetre for 10 s are equivalent; and the reproducibility obtained - 0.750, 0.730 and 0.720 on three separate days, and 0.490, 0.490, 0.500 and 0.480 from four different standard candles; Bibliography of photographic sensitometry, entries 510 and 515 for 1909 - A. Callier, 'La diffusion de la lumiere par les cliches', Bulletin de la Societe Belge de Photographie 36, 397-99; and A. Callier, 'The Absorption and Scatter of Light by Photographic Negatives Measured by means of the Marten's Polarization Photometer', Photographic Journal 49, 200, also in Bulletin de la Societe Francaise de Photographie 23 and Zeitschrift fuer wissenschaftliche Photographie 7, 257; The Principles involved in Enlarging - the definition of the range of a bromide paper as the ratio between two exposures, one of which just falls short of producing any deposit and the other of which just suffices to produce the deepest black the paper is capable of recording when viewed by reflected light, with the worked example of five seconds against a hundred and sixty and the conversion of that ratio into the difference between two logarithms; The Principles involved in Enlarging, a lecture to the Widnes Photographic Society reprinted from the British Journal of Photography 1894 - the definition of the range of a bromide paper as the ratio between two exposures, one of which just falls short of producing any deposit and the other of which just suffices to produce the deepest black the paper is capable of recording when viewed by reflected light, worked at five seconds against a hundred and sixty; the statement that the range of gradation of the negative must coincide with the range of gradation of the paper; and the stated preference for a negative of a rather too contracted rather than a too extended range, on the grounds that it is far better to make quite sure of getting the delicate half-tones even at some loss of the deepest black tones; The Latent Image and its Development - Experiment 15, pyro-soda on plate D2 developed three minutes at 0, 2, 8, 32 and 128 parts of potassium bromide per thousand, whose unexposed densities are 0.160, 0.090, 0.065, 0.060 and 0.060 and whose densities at 40 candle-metre-seconds are 2.500, 2.020, 1.190, 0.290 and 0.100; the summary that 128 parts almost entirely prevented development in three minutes and that 2 parts reduced the highest density from 2.5 to 2.0; the statement that the reaction is never stopped but simply retarded and that the image will appear in full force if sufficient time be allowed; Experiment 14 and the conclusion that the retarding influence of bromide can be fully compensated by time of development and that the speed of the plate is not really altered by its addition; and the warning that as more bromide is added the image changes from black towards a fawn colour, after which photometric measurements are no longer a reliable indication of the amount of silver present; The Principles involved in Enlarging — the definition of the range of a bromide paper as the ratio between two exposures, one of which just falls short of producing any deposit and the other of which just suffices to produce the deepest black the paper is capable of recording when viewed by reflected light; The action of a restrainer as retarding rather than stopping development, with the image appearing in full force if sufficient time be allowed

Used by:Potassium bromide · P4 Development as Amplification · P4 Reciprocity Failure and the Life of the Latent Image · P8 Assignment: Reading a Developer Formula · P8 Restrainers and Antifoggants · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Break/Fix: The Developer That Went Wrong · P9 Assignment: The Developer Laboratory Report · P9 Experimental Design for the Darkroom · P13 Part XIII Overview: Measuring the Response of Silver to Light · P13 Exposure, Density and the Logarithm · P13 Film Speed and Exposure Index · P13 Gamma, Contrast Index and Average Gradient · P13 The Characteristic Curve · P13 Tone Reproduction: From Subject to Print · P14 Part XIV Overview: Build a Sensitometer · P14 Experiment: Calibrating the Sensitometer · P14 Sensitometer Design Principles · P15 Density Depends on How You Look: Geometry and Spectral Response · P18 Experiment: Maximum Black, Base White and Dry-Down · P19 Lab: Test Strips, Base Exposure and the Print's Black Point · P27 Experiment: Four Curve Families, Measured · P28 Print Faults: Weak Blacks, Mottle, Bronzing and the Rest · Chemical fog · Exhausted developer

Methods and Aims in Archaeologyretrieved 2026-09-04

Sections: Chapter VIII, Photographing, pp. 74-78: the fashion of wide-angle lenses distorting perspective; the sliding and rising front as about the only useful complication; a time-table of the best hours for each part of a building; Chapter VIII, Photographing, pp. 74-75: the fashion of wide-angle lenses; one small stop, say f/100, and learn exposures entirely on that basis; the pin-hole stop stuck in front of the lens; Chapter VIII, Photographing, pp. 77-78: the lighting is the most important element; revolving an object in the plane of its face to select the direction of light; dark shadows lighted with reflectors of white paper or card, or actual mirror

Used by:P7 Assignment: Architecture, Low Viewpoint and the Flat Plane · P7 Seeing Like a Pinhole: The Image, Its Makers and Previsualisation · P7 Assignment: Still Life and Controlled Light

Modern Heliographic Processes: A Manual of Instruction in the Art of Reproducing Drawings, Engravings, Manuscripts, etc., by the Action of Light; for the Use of Engineers, Architects, Draughtsmen, Artists, and Scientistsretrieved 2026-09-05, 2026-09-06

Sections: Iron Prints — Early Discoveries, page 53, 'Herschel's Processes, Discovered 1840-1842', item 2d, which gives the salt as mercurous nitrate with the formula Hg2(NO3)2 + 2H2O and states the sensitiser as equal parts, with no strength for any solution; Henri Pellet's Process, According to U. S. Patent, pages 65 to 69 — the five example liquors, the liquor commonly employed by Pellet, the four claims and Lietze's own verdict; Captain G. Pizzighelli's and L. v. Itterheim's Modification of Herschel's Positive Cyanotype Process, pages 69 to 73 — formulae 94 to 100, the paper, the coating, the exposure, the photometer strip, the development and washing, the discharging bath, Pellet's mixed-acid bath, the alum rinse, and the notes on the gum, the proportions and the red-prussiate anomaly; Collache's Direct Blue Print Process and Joltrain's Positive Blue Print Process, pages 73 to 74; Henri Pellet's Process, According to U. S. Patent, pages 65 to 69 - the five example sensitising liquors, the liquor commonly employed by Pellet, the four patent claims and Lietze's own verdict that he tried the process several times without succeeding in producing good prints; Captain G. Pizzighelli's and L. v. Itterheim's Modification of Herschel's Positive Cyanotype Process, pages 69 to 73 - the three stock solutions, the mixing order and its reason, the paper, the coating, the exposure of 3 to 10 minutes in the sun, the photometer strip, the yellow prussiate developer, the washing and brushing off of the greenish-blue surface film, the discharging bath of 1 part hydrochloric acid to 10 of water, Pellet's own recommendation from the Bulletin de la Societe francaise de photographie of 1880 to replace part of the hydrochloric acid with sulphuric in order to diminish the formation of muriatic acid vapours, the instruction to pour the acid into the water and into a bottle rather than a tray, and the alum in the final rinse

Used by:Herschel's hydrargyro-cyanotype · Pellet's positive-working process · P26 Assignment: Assessing a Historical Process for Hazard

Naturalistic Photography for Students of the Artretrieved 2026-09-04

Sections: Answers to other criticisms, I: the reply that with the aid of orthochromatic plates photography is not false in local colour; and Printing: cloud printing as "the simplest form of combination printing, and the only one admissible"; Chapter on the studio, Head-rests: "Head-rests must be entirely tabooed"; and Out-door and In-door Work: the long elastic tube to the shutter and the judgement that posing with head-rests is "feeble and archaic"; Book II, pp. 115 and 119: the great heresy of sharpness and the rule in focussing; p. 131, Pin-hole Photography, on correct drawing, one to thirty minute exposures, and a worthy field for experiment; p. 99 on diffusion circles

Used by:P7 Assignment: Landscape, Sky, Foreground and Filters · P7 Assignment: Portrait, Environmental Portrait and Self-Portrait · P7 Seeing Like a Pinhole: The Image, Its Makers and Previsualisation

Note on the Art of Photography, or the Application of the Chemical Rays of Light to the purposes of Pictorial Representation, in Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London, volume 4retrieved 2026-09-04, 2026-09-05

Sections: Note on the Art of Photography, read 14 March 1839; Abstract of the paper read 14 March 1839, pages 131-133; The note read to the Royal Society on 14 March 1839, in which hyposulphite of soda is recommended as the fixing agent and hyposulphite of ammonia is named as restoring the black colour of a photograph fixed with water alone

Used by:Ammonium thiosulfate · Sodium thiosulfate (anhydrous) · P1 Herschel: Hypo, Prussian Blue and the Words of Photography · P11 Overview: Making the Image Permanent

Note sur un moyen de fixer les images photographiques (Extrait), in Comptes rendus hebdomadaires des seances de l'Academie des sciences, tome 11 (July-December 1840), pages 237-238retrieved 2026-09-06

Sections: "Chimie appliquée — Note sur un moyen de fixer les images photographiques; par M. H. Fizeau (Extrait)", tome 11, pages 237 to 238, with the commissaires named as Arago, Dumas and Pelouze. For the statement of the double problem — fixing the proofs and giving the lights of the picture more intensity; for the preparation, "On dissout un gramme de chlorure d'or dans un demi-litre d'eau pure, trois grammes d'hyposulfite de soude dans un demi-litre d'eau pure. On verse alors la dissolution d'or dans celle de soude, peu à peu et en agitant; la liqueur mixte, d'abord légèrement jaunâtre, ne tarde pas à devenir parfaitement limpide"; for Fizeau's own reading of the product as "un hyposulfite double de soude et d'or, plus du sel marin, qui ne paraît jouer aucun rôle dans l'opération"; for the requirement that the surface be perfectly free of foreign bodies and above all of grease; for the wash sequence of a few drops of alcohol on the still iodised surface, the basin of water and then the hyposulfite solution, that solution to be renewed for each proof and to contain "environ une partie de sel pour quinze d'eau"; for the stated purpose of the alcohol, which is to make the water adhere over the whole plate and stop it withdrawing at the edges, which would infallibly produce stains; for the application — the plate on the wire frame found in every apparatus, a layer of sel d'or poured on until the plate is entirely covered, heating with a strong lamp, the proof seen to clear and take on great vigour in a minute or two, then the liquid poured off, the plate washed and dried; for the sentence that an old proof gilds as well as a new one; and for Fizeau's account of the result, that silver has dissolved and gold has precipitated on the silver and on the mercury with very different results, the silver browned by the thin layer of gold so that the blacks are strengthened, the mercury increased in solidity and brilliance by its amalgam with the gold. Also the closing sentence of the extract, that the memoir ends with considerations on the chemical reactions taking place at the different stages, which the extract does not print. Also pages 824 and 906 of the same volume, for Arago presenting a plate of Hubert's fixed by Fizeau's process more than a year after it was made, and for Fizeau asking the Académie to appoint a reporting commission

Used by:Fizeau's gilding solution

On Pin-hole Photography (Philosophical Magazine 31, 1891), article 178 in Scientific Papers, volume 3, 1887-1892retrieved 2026-09-04, 2026-09-05

Sections: Article 178, pp. 429-440 — the quarter-wave criterion and the relation 2r-squared = f.lambda, the quotation and criticism of Petzval, and the photographic determination (2r)-squared/f = 1.52 x 10^-4 cm with its back-calculated effective wavelength 4.2 x 10^-5 cm, which is the measurement behind the constant 1.90; Article 178: On Pin-hole Photography; Article 178, pp. 429-440: the geometric and diffraction blurs set against each other, and the laboratory and photographic determinations of the best aperture; Article 178, pp. 429-440: the six apertures pierced in sheet zinc from 0.0210 to 0.0366 inch, photographed against a test object, and the photographically effective wavelength of 4.2 x 10^-5 cm back-calculated from the comparison; Article 178, pp. 429-440: the six apertures pierced in sheet zinc and compared photographically against a test object, and the photographically effective wavelength of 4.2 x 10^-5 cm; Article 178, pp. 429-440: the quarter-wave criterion and the relation 2r-squared = f.lambda; the quotation and criticism of Petzval; the adaptation of Lommel 1884; the zinc apertures of 0.0210 to 0.0366 inch; the photographic determination (2r)-squared/f = 1.52 x 10^-4 cm and the back-calculated effective wavelength 4.2 x 10^-5 cm; Article 178, p. 438: six apertures perforated in a piece of thin sheet zinc and measured under the microscope, diameters 0.0210 to 0.0366 inch; Article 178, pp. 430-433: resolving power proportional to aperture and independent of focal length; brightness B proportional to lambda/f for a properly proportioned pin-hole camera; the improvement of definition with increasing f; Article 178, pp. 429-440: the six apertures pierced in sheet zinc from 0.0210 to 0.0366 inch and compared photographically; the treatment of the diffraction pattern using Lommel's results; the photographically effective wavelength of 4.2 x 10^-5 cm; On Pin-hole Photography: the optimum aperture result and the discussion of the diffraction limit for a lensless aperture; Article 178, pp. 429-440: the photographic determination of the best aperture; Article 178, pp. 429-440 - the quarter-wave criterion, the relation 2r-squared = f.lambda, and the photographic determination (2r)-squared/f = 1.52 x 10^-4 cm with the back-calculated effective wavelength; Article 178, pp. 429-440 - the quarter-wave criterion and the relation 2r-squared = f.lambda, and the photographic determination of the constant; Article 178, pp. 429-440 - the quarter-wave criterion and the relation between hole size and focal distance; Section 8, Colours of Thin Plates - the retardation of the second reflected wave given as delta = 2.mu.t.cos a', with t the thickness of the plate and a' the angle of refraction; Arago's law of the equality of reflexions and the famous loss of half an undulation, from which the reflected light vanishes whenever delta = n.lambda, so that when the first and third medium are the same 'the central spot in the system of Newton's rings is black, even though the original light contain a mixture of all wave-lengths'; the reflected and transmitted intensities given as expressions whose sum is unity, the reflected one reducing for weak reflexions to a swing between zero and four times the single-surface reflectance; Newton's twenty-fourth observation, quoted, that with the naked eye he 'could not discern above eight or nine of those rings'; the condition for the black of the nth order over a curved surface, half n lambda = a + b x squared, with a the least distance between the plates; and the note of 1900 that the rings as ordinarily observed depend upon the variable thickness of the thin plate, seen in focus, so that at high interference 'it becomes necessary to pay great attention to the perpendicularity of the incidence'; Article 178, pp. 429-440 - the quarter-wave criterion and the relation between hole radius and focal distance

Used by:P29 Capstone Stage 1: The Instrument, Its Calculation and Its Commissioning · P1 The Camera Obscura: An Image Without Chemistry · P6 Part VI Overview: Build a Pinhole Camera · P6 Commissioning the Camera: Light-Tightness, Flare and the First Negatives · P6 Curved Film Plane and Multiple-Pinhole Experiments · P6 Diffraction and the Optimum Pinhole · P6 Making and Measuring Pinholes · P6 Pinhole Geometry: Blur, Focal Distance, Field of View and Falloff · P6 Break/Fix: Unexpectedly Soft Images and Wrong Reciprocity Corrections · P7 Assignment: Panorama, Curved Plane and Multiple Pinholes · P7 Seeing Like a Pinhole: The Image, Its Makers and Previsualisation · Diffraction glow from an undersized hole · Geometric softness from an oversized hole · Near-limit softness · Newton's rings · Thick-plate vignetting

On Thallium, in the Philosophical Transactions of the Royal Society of London, volume 153retrieved 2026-09-06

Sections: Occurrence and extraction, for the recovery of the element from the flue-dust sulphur of a sulphuric-acid works; Physical characteristics, for the single green line under a nine-prism spectroscope, the standard solution of sulphate of thallium at one grain in fifteen gallons, and the monochromatic flame that turns a face corpse-green; Chemical properties, section 18, for the sulphate crystallising from the solution of the metal in sulphuric acid and for the deference to Lamy's description and solubility; Position of thallium amongst elementary bodies, section 21, for "when I discovered thallium two years ago"; section 16 and the five atomic-weight determinations made by weighing the sulphate

Used by:Thallium(I) sulfate

On the Action of the Rays of the Solar Spectrum on Vegetable Colours, and on some new Photographic Processes, in the Philosophical Transactions of the Royal Society of London, volume 132retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Article 219, the coining of cyanotype and the warning that the wash cannot be in too thin a film; Article 223, paper washed with a mixture of the solutions of ammonio-citrate of iron and ferrosesquicyanate of potash so as to contain the two salts in about equal proportions, impressed with a picture, thrown into water and dried; Articles 202 and 203, the ferrosesquicyanuret paper and its fixing in water holding a little sulphate of soda; Article 204, the spectral limits of the action; Articles 206 and 207, the substitution of ammonio-citrate of iron and the footnote on the whitening; Articles 210 and 211, the separation of the action into two stages; Article 219, the coining of cyanotype and the gum-arabic wash of Article 220; Article 223, the mixed sensitiser in about equal proportions, thrown into water and dried; Article 210, the ammonio-citric solution alone giving a paper "apparently little, but in reality highly sensitive", and the note that the ammonio- and potasso-tartrate "fully possess" the same property; Article 212, the chrysotype paper washed with "a moderately concentrated solution of ammonio-citrate of iron" whose "strength of the solution should be such as to dry into a good yellow colour, not at all brown", and the gold developer "of such strength as to have about the colour of sherry wine"; Article 213, the naming of the chrysotype and the date "June 10, 1842"; the footnote to Article 214 giving the weights of Mr Hunt's salted positive paper, which is not this formula; Article 217, the Postscript added 29 August 1842 and the hydriodate fixing of the chrysotype; Article 218 entire, which is this formula; Article 219, the coining of cyanotype; Article 223, in the Postscript added 29 August 1842 — the mixed sensitiser in about equal proportions, the wash with proto-nitrate of mercury, the total discharge of the blue, the washing out of the nitrate, the flat-iron hotter than for linen but short of scorching, the brown image, the fading in complete darkness and the revival by fresh heat; Article 224, the concentrated-spectrum experiment and the three conclusions drawn from it; Article 219, the publication of the name cyanotype for the whole class; Article 225, sunned ammonio-citrate paper as a reducing agent for other reagents; Articles 226 to 229, the photographic properties of mercury, the proto-nitrate papers and the mercurial cream of the kelainotype; the dating of the paper, received 15 June and read 16 June 1842; Article 210, in which the ferrocyanate is left out and the ammonio-citrate paper alone is shown to be highly sensitive, with the statement that the ammonio- and potasso-tartrate fully possess the same property; article 212, the chrysotype, paper washed with ammonio-citrate of iron, dried to a good yellow, exposed and then washed with a neutral gold solution; article 218, in the postscript added 29 August 1842, in which nitrate of silver is substituted for the gold and a very sharp and beautiful picture of great intensity is developed in two or three minutes and fixed with hyposulphite of soda; Articles 202 to 213 and 218 to 223: ferrosesquicyanuret paper, ammonio-citrate of iron, the two stages, chrysotype, and the naming of cyanotype; Article 219, the coining of the name cyanotype and the warning that the wash cannot be laid on in too thin a film; Article 223, paper washed with a mixture of the solutions of ammonio-citrate of iron and ferrosesquicyanate of potash so as to contain the two salts in about equal proportions, impressed with a picture, thrown into water and dried; Article 209, the positive paper made by washing ammonio-citrate of iron and then the yellow ferrocyanate over it; the footnote to Article 207, attributing the whitening to the deoxidation of the precipitated Prussian blue and the formation of the proto-ferrocyanuret of iron, the resumption of colour in the shade to its re-oxidizement, and the observation that simple Prussian blue is not whitened by the violet rays; Article 210, the experiment that leaves the ferrocyanate out, the four or five seconds in the sun with no visible effect, the blue raised afterwards by ferrosesquicyanate in the shade, and the note that the ammonio- and potasso-tartrate fully possess and the exactly neutralized perchloride partakes of the same property; Article 211, the graduated exposure series in which the blue increases and then diminishes, and the conclusion that the photographic influence is confined to the first stage, the ferrosesquicyanate acting as a mere precipitant on the nascent compounds resulting from that influence; Article 219, the coining of the word cyanotype and the warning that the wash cannot be in too thin a film; Article 223, paper washed with a mixture of the two solutions in about equal proportions, impressed with a picture, thrown into water and dried; Article 212, the chrysotype paper — a moderately concentrated solution of ammonio-citrate of iron, of such strength as to dry into a good yellow colour, not at all brown; Article 218, in the Postscript added 29 August 1842, in which nitrate of silver is washed over that paper instead of a solution of gold and a very sharp and beautiful picture of great intensity is developed, fixed with hyposulphite of soda; Article 210, for the demonstration that light alone reduces the iron in ammonio-citrate paper and that the ammonio- and potasso-tartrate fully possess the same property; Article 211, for the graduated exposure series and its reversal at long exposure; Article 212, for the chrysotype paper specified by effect — a moderately concentrated solution of ammonio-citrate of iron, of such strength as to dry into a good yellow colour, not at all brown — and for the gold solution applied after exposure; Article 218, in the Postscript added 29 August 1842, for the substitution of nitrate of silver, the delay of a few moments before the shades are touched in, the maximum of distinctness reached in two or three minutes, and the fixing by hyposulphite of soda; On the Action of the Rays of the Solar Spectrum on Vegetable Colours, and on some new Photographic Processes: the vegetable colours; Articles 218 to 223: the siderotype family and the naming of cyanotype; Articles 218 to 223: chrysotype, the siderotype family and the naming of cyanotype; Articles 202 to 213 and 218 to 223: ferrosesquicyanuret paper, ammonio-citrate of iron, the two stages, and the naming of cyanotype

Used by:Classic cyanotype sensitiser · Herschel's 1842 cyanotype · Herschel's argentotype · Herschel's hydrargyro-cyanotype · Van Dyke Brown sensitiser · P1 Herschel: Hypo, Prussian Blue and the Words of Photography · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Iron, Light and Prussian Blue · P24 Part XXIV Overview: When Iron Reduces Silver · P24 The Siderotype Principle: Iron Reduces Silver · Anthotype · Argentotype · Chrysotype · Cyanotype (classic)

On the Chemical Action of the Rays of the Solar Spectrum on Preparations of Silver and other Substances, both metallic and non-metallic, and on some Photographic Processes, in the Philosophical Transactions of the Royal Society of London, volume 130retrieved 2026-09-04

Sections: Paragraph 19 — obliteration of a picture by corrosive sublimate and its revival by a neutral hyposulphite; Sections 80 and 81 — Rochelle salt papers, their singular peculiarities and the proportion Herschel could not repeat; Paragraphs 1 to 10: recapitulation of the 1839 note, multiplied fac-similes, and the terms positive and negative; Articles 60 to 65: Chemical properties of the red end of the spectrum, the observation of 27 August 1839, and the combined action of rays of different refrangibility

Used by:Mercury(II) chloride · Potassium sodium tartrate tetrahydrate · P1 Herschel: Hypo, Prussian Blue and the Words of Photography · P4 Reciprocity Failure and the Life of the Latent Image

On the Hyposulphurous Acid and its Compounds, in the Edinburgh Philosophical Journal, volume 1retrieved 2026-09-04, 2026-09-06

Sections: Hyposulphite of ammonia; hyposulphites of ammonia and silver; Hyposulphite of soda; hyposulphites of soda and silver; On the Hyposulphurous Acid and its Compounds — the passage on newly precipitated muriate of silver being soluble in all the liquid hyposulphites, and in that of soda with great ease and in large quantity; The solvent action of the hyposulphites on the chlorides of silver, which is the property Article 218 is relying on twenty-three years later; Hyposulphite of soda; solubility of newly precipitated muriate of silver; Article II, general characters of the hyposulphites; Hyposulphite of silver

Used by:Ammonium thiosulfate · Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Daguerre's 1839 process outline · Herschel's argentotype · P1 Daguerre and the Daguerreotype: A Mirror With a Memory · P1 Herschel: Hypo, Prussian Blue and the Words of Photography · P1 Wedgwood, Davy and the Problem of Permanence

Patents for Inventions: Abridgments of Specifications, Class 98, Photography, volume 2, 1867-1876retrieved 2026-09-06

Sections: "2011. Willis, W. June 5" — the Patent Office's own abridgment of the 1873 specification, for the three coatings, for the naming of the first coating's salts as potassium platinochloride, sodium platinochloride or platinum bromide, for "For the second coating, silver or lead nitrates are used in solution", and for the third being ferric oxalate dissolved in the least possible quantity of oxalic acid. The abridgment states no quantities

Used by:Lead additions to platinum sensitisers

Patents for Inventions: Abridgments of Specifications, Class 98, Photography, volume 3, 1877-1883retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: "2800. Willis, W. July 12" — the abridgment of the 1878 specification, for the addition of a platinum, iridium or mercury salt to the oxalate developing solution and for the coating solution in which "plumbic chloride may be substituted for the mercuric chloride". No quantities are given, and the substitution is stated the opposite way round from the specification itself; Number 2800, Willis, W., July 12 — the official abridgment of the same patent, for the addition to the oxalate developing solution of a salt of platinum, iridium or mercury, for mercuric chloride named among the salts that may be added to the developing solution, and for the coating solution in which plumbic chloride and mercuric chloride are alternatives. The abridgment states no quantities; 1877, number 4632, Johnson, J. H. (Soc. Henri Pellet et Cie), 6 December — Copying drawings and the like; 1117. Willis, W. March 15 [1880], Printing-paper; developing — the official abridgment, for "A developer for these and other like papers may also consist of tartrate, citrate, or acetate of sodium potassium or ammonium, or of monammonic, diammonic or disodic orthophosphate, or a mixture of any of these alone or mixed with salts of platinum or iridium ... Sodium citrate is preferably employed"; Class 98 abridgments: bitumen and asphaltum resists on metal, 1877-1883; Class 98 abridgments: bitumen and asphaltum resists on metal, exposed under a negative, developed with a solvent and etched or built up galvanically

Used by:Lead additions to platinum sensitisers · Mercuric sepia platinotype · Pellet's positive-working process · Sodium citrate developer · P1 Niepce and Heliography: Light That Hardens · Heliography on bitumen of Judea · Photogravure

Photographic Emulsion Techniqueretrieved 2026-09-04, 2026-09-05

Sections: Page 78, quoted by Ross — a small quantity of ammonia should always be present in either the salts or the first silver solutions; Cited by Ross as the origin of the recipe, from her adaptation of his 1943 American Photography article on a homemade chloride emulsion; Chapter IX, Bromide and Chloride Papers, pages 166 to 168, of the part-two scan whose page-image index runs at printed page minus 122. Trumm's bromide paper emulsion is A, water 4000 cc, gelatin 350 g, potassium bromide 190 g and potassium iodide 2.5 g; B, distilled water 2000 cc and silver nitrate 250 g; C, water 2000 cc and gelatin 600 g. The gelatin in A is allowed to swell in the solution of bromide and iodide for half an hour and is then dissolved by heating the crock to 120 °F (49 °C). The silver solution B, heated to the same temperature, is added, poured through a funnel with a fairly fine jet - a plain or separatory funnel with a one or two inch length of barometer tubing of about 4 mm bore attached by the shortest possible piece of rubber tubing, mounted so that the jet is near one edge, leaving room for stirring. The emulsion is then further heated to 140 °F (60 °C) on a water bath and maintained there for one hour. At the end of the hour, solution C, also at 140 °F, is added, and a further one hour's digestion is given. The emulsion is then poured out to set in a cold crock placed in ice water and stirred slowly until gelling begins. It is broken into noodles and washed in about twelve changes of five minutes each. The washed noodles are put into a tared crock, remelted and made up, inclusive of finals, to a weight of 16,000 g. The finals are five per cent chrome alum solution 150 cc, spirit 1000 cc, and phenol dissolved in part of the spirit 10 g. For a matt surface, 200 g of rice starch ground up in 1000 to 1500 cc of water is stirred in prior to filtering, leaving out an equivalent quantity of water when making up. It is best set off and remelted next day or when required for coating, and an addition of an alcoholic solution of saponin or extract of quillaia bark is frequently added to give better coatings. Page 166 gives negative emulsions as usually made with forty to fifty grams of silver nitrate to the litre and paper emulsions with only fifteen to twenty-five grams per litre, and states that one litre of emulsion should coat sixty to eighty square feet of paper surface. Page 165 gives the limit that fog on a trial coating on glass should not exceed 0.02 density, states that one hundred grams of silver halide will coat eighty to one hundred feet of forty-two inch paper, and warns that too thin a coating is mistaken for poor maximum black. Immediately after Trumm's formula Baker prints an alternative bromide paper emulsion made with ammonia, attributed to E. J. Wall; Page 95: the statement that if the bromide be much in excess of the chloride the tone will be colder but the gradation will usually have a longer scale, while an excess of the chloride will tend towards higher contrast and a shorter scale but will more readily yield colour on suitable development. Page 166: paper emulsions carrying fifteen to twenty-five grams of silver nitrate to the litre against negative emulsions at forty to fifty, and one litre of emulsion coating sixty to eighty square feet; Chapter VIII, Coating Emulsions on Glass, page 140, of the part-two scan whose page-image index runs at printed page minus 122: the two cleaning options, the first being a solution of potassium dichromate two ounces to the pint with two ounces of sulphuric acid added very cautiously and slowly with stirring, applied with an old flat nailbrush and rubber gloves, and the second being to brush the glass with a hot two per cent solution of caustic soda and afterwards wash thoroughly under the tap; the substratuming instruction, 'Substratuming is done by dipping them into a dish containing a two per cent solution of chrome alum after the final rinse and racking them without further rinsing. They should be dried in a perfectly dust-free cupboard.'; the paragraph that follows on dust and bacteria as the plate maker's enemies and on mould spores travelling on dust to find an ideal medium on gelatin-coated glass; and the note attributed to Clerc that ultra-microscopic particles, probably of metallic silver in solid solution in the glass, cause the ghost of a previous image to appear on reused glass; Chapter VI, Color-sensitive Emulsions, page 108, the orthochromatic emulsion based on Eder's lines: the instruction 'Just before mixing, add two per cent erythrosin, dissolved in equal parts of alcohol and water, 25 cc' to the silver solution, which carries 500 g of silver nitrate; the finals of 100 cc of 5 per cent chrome alum, 500 cc of 5 per cent phenol in alcohol and 50 cc of 1 per cent ammonium bromide solution in a final volume of ten litres; and the self-screening instruction to introduce a yellow dye before the finals at about two per cent strength, tried out at 10 or 12 cc to a 5 by 7 plate. Page 106 for naphthol yellow, tartrazin, thiazol yellow and brilliant yellow as the recommended filtering dyes and the requirement that a filtering dye must not desensitise the silver bromide grains; Chapter IX, page 166: negative emulsions usually made with forty to fifty grams of silver nitrate to the litre and paper emulsions with only fifteen to twenty-five grams per litre, and one litre of emulsion coating sixty to eighty square feet of paper surface; page 165, fog on a trial coating on glass not exceeding 0.02 density, and the warning that too-thin coating is mistaken for poor maximum black; Chapter IX, Trumm's bromide paper and its finals; page 96, the coating weight for chloride and chlorobromide plates; page 140, glass preparation; Chapter IX, Bromide and Chloride Papers, pages 166 to 168: Trumm's bromide paper emulsion with solutions A, B and C, the funnel and barometer-tubing jet, the half-hour swell, emulsification at 120 °F (49 °C), the hour at 140 °F (60 °C), the second gelatin and second hour, setting in a cold crock in ice water, the wash in about twelve changes of five minutes, the make-up to 16,000 g inclusive of finals, the finals of 150 cc of 5 per cent chrome alum, 1000 cc of spirit and 10 g of phenol, the rice-starch matt option and the saponin or quillaia note; page 166 for negative emulsions at forty to fifty grams of silver nitrate to the litre against paper emulsions at fifteen to twenty-five, and for one litre of emulsion coating sixty to eighty square feet; page 165 for the 0.02 fog-density limit on a trial coating and the warning that too-thin coating is mistaken for poor maximum black; Page 140, the dust-free drying cupboard and the statement that dust and bacteria are the plate maker's enemies, mould spores travelling on dust; page 165, fog on a trial coating on glass not to exceed 0.02 density; page 154, the ten-day oven keeping test at 105 °F below 65 per cent relative humidity and its 0.02 extra-fog criterion; Page 166, the silver concentrations of negative and paper emulsions — forty to fifty grams of silver nitrate per litre for negatives and only fifteen to twenty-five for papers — and one litre of emulsion coating sixty to eighty square feet; page 165, fog on a trial coating on glass not exceeding 0.02 density and the warning that too-thin coating is mistaken for a poor maximum black; Page 95: the effect of bromide much in excess of chloride on tone and on the length of the scale, and of an excess of chloride on contrast and on colour with suitable development; the note that these emulsions use a very small excess only of soluble halide; page 166, paper emulsions made with fifteen to twenty-five grams of silver nitrate to the litre; Page 96: the coating weight for chloride and chlorobromide plates, not more than 25 to 40 milligrams of silver halide per square decimetre. Page 140: glass cleaning, the dichromate and sulphuric acid option and the caustic soda alternative, the two per cent chrome alum subbing dip, and the dust-free drying cupboard. Page 154: the ten-day oven keeping test at 105 °F and its 0.02 density criterion. Pages 165 to 168: fog not above 0.02 density on a trial coating on glass, the silver concentrations of negative and paper emulsions, one litre coating sixty to eighty square feet, and Trumm's finals and matt option; Chapter VIII, Coating Emulsions on Glass, page 140: negative glass obtainable in small quantities from photo-engraving suppliers or a glass merchant, Clerc on ultra-microscopic silver in reused glass and the ghost of a previous image, the potassium dichromate and sulphuric acid cleaning solution described as very corrosive chromic acid, the alternative of brushing with a hot two per cent solution of caustic soda, substratuming by dipping into a two per cent solution of chrome alum after the final rinse and racking without further rinsing, and the dust-free drying cupboard with mould spores travelling on dust; page 96 for chloride and chlorobromide plates carrying not more than 25 to 40 milligrams of silver halide per square decimetre and for Valenta's chlorobromide transparency emulsion; page 154 for the ten-day oven keeping test at 105 °F below 65 per cent relative humidity with its 0.02 extra-fog criterion; page 165 for the 0.02 fog limit on a trial coating and the warning about mistaking a thin coat for a poor maximum black; Page 96, coating weight for chloride and chlorobromide plates of not more than 25 to 40 milligrams of silver halide per square decimetre; page 165, fog on a trial coating on glass not exceeding 0.02 density and the warning that too-thin coating is mistaken for a poor maximum black; page 166, one litre of emulsion coating sixty to eighty square feet; Chapter VI, Color-sensitive Emulsions, page 108: the orthochromatic emulsion based on Eder's lines, with 25 cc of two per cent erythrosin dissolved in equal parts of alcohol and water added to the silver solution just before mixing for 500 g of silver nitrate, and the finals of 100 cc of 5 per cent chrome alum, 500 cc of 5 per cent phenol in alcohol and 50 cc of 1 per cent ammonium bromide solution in a final volume of ten litres; the self-screening instruction to introduce the yellow dye before the finals at about two per cent strength, tried out at 10 or 12 cc to a 5 by 7 plate; page 106 for naphthol yellow, tartrazin, thiazol yellow and brilliant yellow as the recommended filtering dyes and the requirement that they must not desensitise the silver bromide grains; Page 159, the pressure-mark mechanism behind black marks or streaks and the non-stress supercoat that prevents them; page 165, the warning that it is easy to mistake the effect of too-thin coating for a poor <Term id="maximum-black">maximum black</Term>, and the criterion that fog on a trial coating on glass should not exceed 0.02 density; page 140, dust and bacteria as the plate maker's enemies, mould spores travelling on dust and finding an ideal medium on gelatin-coated glass, especially where plates dry slowly in a humid warm atmosphere; page 154, the ten-day oven keeping test at 105 °F below 65 per cent relative humidity with its 0.02 extra-fog criterion; Pages 108, 140 and 166 to 168: chrome alum in the finals of an orthochromatic emulsion and of Trumm's bromide paper, phenol as a bacteriocide, and the two per cent chrome alum subbing dip; Chapter V, Slow Emulsions, pages 95 to 96: the small halide excess of the chlorobromide transparency emulsions and the addition apparatus; Chapter IX, pages 166 to 168, the funnel and jet used for Trumm's bromide paper; Page 165: the warning that it is easy to mistake the effect of too-thin coating for a poor maximum black, and the criterion that fog on a trial coating on glass should not exceed 0.02 density; page 96, chloride and chlorobromide plates carrying not more than 25 to 40 milligrams of silver halide per square decimetre; Page 108: the orthochromatic emulsion based on Eder's lines, with its erythrosin dose of 25 cc of two per cent in equal parts alcohol and water for 500 g of silver nitrate, its finals of chrome alum, phenol and 1 per cent ammonium bromide, and the self-screening yellow dye; page 106 for the named yellow dyes; pages 166 to 168 for Trumm's wash schedule and finals; Page 95, the statement that if the bromide be much in excess of the chloride the tone will be colder but the gradation will usually have a longer scale, while an excess of chloride tends towards higher contrast and a shorter scale but more readily yields colour on suitable development; page 166, paper emulsions carrying fifteen to twenty-five grams of silver nitrate to the litre against forty to fifty for negative emulsions; Trumm's bromide paper emulsion; the two per cent chrome alum dip after the final rinse; Page 95 — the effect of bromide in excess of chloride on tone and gradation; Page 140 — substratuming plates by dipping into a two per cent chrome alum solution after the final rinse and racking them without further rinsing; Chloride emulsions and the coating weights given for a chloride plate; Page 154: the ten-day oven keeping test at 105 °F below 65 per cent relative humidity, with incubated plates showing no more than 0.02 extra fog against controls; Page 165 and page 154 - the criterion that fog on a trial coating on glass should not exceed 0.02 density, and the ten-day oven keeping test at 105 degrees Fahrenheit below 65 per cent relative humidity with its 0.02 extra-fog criterion; Page 140 - dust and bacteria as the plate maker's enemies, and the conditions under which specks reach a coated surface; Page 165 - the warning that it is easy to mistake the effect of too-thin coating for a poor maximum black

Used by:Ammonium bromide · Potassium chloride · Trumm's bromide paper emulsion · Wall's soft-working gaslight paper · Chrome alum subbing dip · Erythrosin sensitising stock · KCl gaslight paper emulsion · P5 Part V Overview: Photographic Emulsions · P5 Project 3: A Bromide Enlarging Emulsion · P5 Build an Emulsion Coating Station · P5 Project 1: A Silver Chloride Contact Printing Emulsion · P5 Project 2: A Chlorobromide Paper Emulsion · P5 Coating, Drying and Hardening · P5 Project 4: Coating Glass Dry Plates and a Lantern Slide · P5 Lab: Coating Your First Emulsion · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P5 Break/Fix: Emulsion Coating Defects · P5 Gelatin, the Photographic Binder · P5 Precipitation, Nucleation and Crystal Growth · P5 Assignment: The Hand-Coated Print · P5 Washing, Digestion and Sensitisation · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · Hand-coated bromide paper · Hand-coated chlorobromide paper · Dry plate and lantern slide · Hand-coated silver chloride contact paper · Refrigerated emulsion labelling and food separation · Base fog · Comets · Thin coat

Photographic Facts and Formulasretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Development factors for the named developers; the amidol reversal and warm-tone formulas; Fixing: rapid ammonia fixing bath; Developers: fine-grain addition to a hydrochinon developer; Intensification: the mercury intensifier; Printing-out papers — Ashman's emulsion, which carries 15 g of ammonium citrate per 500 ccm; The iron processes: blueprint sensitisers using the green ammonio-citrate of iron; The iron processes: blueprint sensitisers using sodium or ammonium ferric oxalate; Reducers — Ammonium Persulphate: the particular value of the reducer being that it attacks the densest parts of a negative more than the shadows, thus considerably reducing contrasts; the complication of its action by acid, chlorides and iron salts arriving through keeping or through ordinary tap water; the 5 per cent solution in distilled water stood for three to four hours, or 15 ccm of 10 per cent sulphuric acid, or 1 ccm of 5 per cent ammonia iron alum per litre; Bennett's keeping stock; Puddy's thiocyanate variant; and the permanganate-and-persulphate pair mixed 1 part A to 3 parts B. Elimination of Hypo — potassium or ammonium persulphate in 1 per cent solution made alkaline with ammonia. Platinotype — persulphate offered in place of the bichromate as a means of shortening the scale of gradation; Printing-out papers — the normal sulphocyanide gold bath, the red-tone bath with potassium iodide, and Valenta's combined toning and fixing bath; Reducers — Puddy's persulphate and sulphocyanide mixture; Fixing and Clearing — rapid ammonia fixing bath; Developers — the alphabetical list of developing agents and their formulas, searched for ascorbate, which does not appear; Toning bromide prints: neutralising a selenium toning bath with boric acid; combined selenium toning and fixing bath; Development — the factorial method and its table of factors; Developers — Pyrocatechin or Kachin, Pyrocatechin-Potash, the rapid one-solution (Ellon), the two-solution (Vogel) and Pyrocatechin-acetone (Hanneke); Developer-fixers (Hanneke); Development of prints for warm tones; Toning bromide prints — Valenta's selenium and Schlippe's salt baths; Printing-out papers — toning baths; Defender printing-out paper; Eastman Solio paper; Development factors for the named developers; Fixing and Clearing — the acid-chrome alum bath, hardening baths, clearing baths, and the table Alums as Hardening Agents with the preparation of basic chrome alum; Orthochromatising Plates — bathing versus adding the dye in the mixing; Green and Yellow Sensitisers — erythrosine, the 1 in 5000 bath, and the spectral gap of the eosine dyes; Developers: Ferrous Oxalate — the preparation of the salt, the two-stock method, and the verdict that the developer has been completely abandoned; Fixing and Clearing — hardening baths; "Pyro-glycerine (Edwards); Platinum, Local Development; The Carbon Process, Making the Tissue, and the baryta-coated paper formula; the liquid and gelatine safelight filter formulas, including Lowy's"; Development — the factorial method and its table of factors; Stand development and the Wratten & Wainwright dilution measurements; Developers — Glycin, Glycin paste (Hübl), Glycin-soda, Glycin-potash; Printing-out papers — toning baths; Defender printing-out paper; Developers: Ferrous Oxalate; The iron processes: alternative blueprint sensitisers; Photomechanical processes: half-tone on copper, etching solutions; Fixing and clearing: dichroic fog and Abney's remedy; Reducers: Potassio-ferric oxalate (Belitzski) and its ferric chloride variant; Reducers: ferric chloride and sulphate as reducers; Toning bromide prints: vanadium and iron greens; The iron processes: the ferrogallic or ink process; "Lead Toning", for the bleach taking "lead acetate or nitrate" with glacial acetic acid and potassium ferricyanide, the verdict that the results are not very satisfactory, and the list of second baths and their colours; "Lead-iron for greenish tones (Maquenne)", for the four lead acetate stock solutions that keep in the dark; the platinotype section, for the lead-iron oxalate stock made by precipitating lead oxalate from lead acetate with oxalic acid and adding the dried precipitate to the ferric oxalate solution; the combined bath for Solio, for the gold chloride and lead acetate solution B; the enlarging section, for the gallic acid and lead acetate developers; Intensification: The Lead Intensifier; Toning bromide prints: Lead Toning; Silver printing processes, collodio-chloride paper — the choice of strontium and lithium chlorides, the instruction to dissolve the lithium chloride in alcohol as soon as it is bought, and the formulas of Hanneke, Niederstadt, Valenta, Eder and others; Intensification: The Mercury Intensifier and its blackening reagents; Metol; Metol poisoning (Beers); Elon; Toning bromide prints, for the bleach-and-tone list in which the bleached print is treated with one of a series of baths and "cobalt or nickel chloride for green" is one of them; and the selenium toner Wall credits to Namias, in which granular selenium is fused with caustic soda in a nickel or iron crucible; Intensifiers: the 5 per cent nitric acid bath after a lead intensifier; silvering glass, cleaning the glass with nitric acid; Developers: the preparation of ferrous oxalate; Reducers: the sulphite and oxalic acid bath; The iron processes: oxalic acid added to a cyanotype sensitiser; Paramidophenol — one-solution and two-solution formulas, the Ermen rodinal-type concentrate, and the list of proprietary liquid developers; Kodelon; temperature coefficients; Fixing and Clearing — hardening baths, clearing baths, and the table Alums as Hardening Agents; Developing-out papers: exposure and development for warm tones; Developers — eikonogen, the potassium carbonate equivalent; edinol two-solution developer; Reducers — Potassio-Ferric Oxalate (Belitzski), the original reducer and its make-up from ferric chloride and neutral potassium oxalate, and the statement that ferric chloride and sulphate either alone or with citric acid are extremely liable to stain the gelatine by the deposition of basic iron salts and should not be used; Ferrous Oxalate development — the potassium citrate and potassium oxalate developers for gelatino-chloride lantern plates; Copper Ferrocyanide Intensifier — the two stocks each carrying 28 g of neutral potassium citrate per litre; Printing-Out Papers — Abney's gelatino-chloride emulsion, whose salting solution carries potassium citrate with citric acid and sodium chloride; Platinum toning — Heatherly's bath; Hypo and ferricyanide (Farmer); Sulphide toning — indirect processes; Developers: hydroquinone line-work developer with caustic potash; Lainer's rapid soft-working and one-solution developers; Photomechanical processes: cleaning old collotype plates; Developing-out papers: non-abrasion developers; Reducers: iodide and hypo; Sulphide toning: indirect processes; Developers: Ferrous Oxalate; The iron processes: corrections on a blueprint; Developers: Ferrous Oxalate; Reducers: Potassio-ferric oxalate (Belitzski); The iron processes: corrections on a blueprint; Reducers — the permanganate-and-persulphate pair mixed 1 part A to 3 parts B and cleared in 1 per cent potassium metabisulphite; Elimination of Hypo — potassium permanganate in 1 per cent solution used until the colour is no longer discharged; Hypo eliminators — potassium or ammonium persulphate in 1 per cent solution made alkaline with ammonia, sold as Thioxydant and Anthion; Reducers — the ammonium persulphate reducer; flash powders, in which a persulphate is one of the oxidisers; Studio and workroom — the Rochelle salts process for silvering, and its two solutions; Printing-out papers — the normal sulphocyanide gold bath and the concentrated stock made with potassium sulphocyanide, gold chloride and strontium chloride; Developers — Pyrogallol and pyro-ammonia; Stand development, the Wratten & Wainwright pyro-soda formula; Development of prints for warm tones; Toning bromide prints — Selenium toning; Intensifiers — Namias's recommendation of silver oxalate in place of silver nitrate to avoid stains on a bleached negative, with the two solutions from which the precipitate is thrown, the decanting, the suspension in a litre of water, the shaking before each application and the subsequent hypo bath; Sulphide toning: indirect processes; Intensification: the mercury intensifier; Toning bromide prints — Selenium toning: the sodium sulfide and caustic-soda routes, which give sodium selenide rather than this compound; Fixing and Clearing — plain bath, bath strength, residues; Fixing and Clearing — plain bath, alkaline bath, making the solution, residues; Printing-out papers: the Ashman and Valenta gelatino-chloride emulsions; intensifiers, stannous tartrate; silvering glass, the sugar and tartaric acid reducing solution; Toning bromide prints: Uranium Toning; Intensification: The Uranium Intensifier; Kallitype, in The Iron Processes — the statement of the mechanism; Thomson's formulas, for the developer of equal parts 5.2 per cent Rochelle salts and 9.4 per cent borax with 0.02 to 0.8 per cent potassium bichromate described as a restrainer, and for the thirty minutes in it; Pages 24 to 25, Orthochromatising plates: the statement that ordinary or non-colour-sensitive plates may be orthochromatised by bathing in solutions of dyes, that such plates as a rule have a higher colour sensitivity than those coated with an emulsion to which the dye is added during the mixing, but that they do not keep quite as well; Green and Yellow Sensitisers, erythrosine as the dye generally used, the extra blueish kind in a 1 in 5000 aqueous solution with the addition of 0.5 per cent of ammonia; the statement that erythrosine gives a strong yellow, orange and green sensitiveness but a marked want of sensitiveness in the blue-green; the instruction that only perfectly clean glass dishes should be used for bathing plates and that old porcelain dishes and metal tanks are to be avoided because metals tend to reduce the dyes and cause fog; the note that home-bathed plates will not keep well; and the instruction that a deep red safelight may be used until the plates are covered with the dye solution, after which the work is done in darkness or by a green safelight; Fixing and Clearing — Rapid ammonia fixing bath: the addition of 2.5 to 5 per cent of ammonium chloride to a 20 per cent hypo bath increases the rapidity of fixing, 10 per cent ammonia water acts as quickly, the addition has no effect on a 40 per cent solution, and the account of ammonium hyposulphite being formed is given as a supposition; Kallitype, in The Iron Processes, for the opening statement of the mechanism — that the ferrous salts dissolve in the developer and reduce silver nitrate to the metallic state at the points where the ferric salt has been reduced by light; Fixing and Clearing, the Acid bath of hypo 150 g and potassium metabisulphite 25 g per litre with the note that this is about the correct strength for papers and that for negative work the hypo should be increased to 400 g; the statement that a 40 to 45 per cent solution of hypo is the strongest bath that should be used and the most rapid in action; that plain, alkaline, acid, and acid and alum baths may all be used, the first two generally for printing-out papers and the latter for plates, film and developed papers; Lantern Slides, Development, the Seed Hydrochinon Developer for Warm Tones - Solution A of hydrochinon, dry sodium sulphite, potassium bromide and citric acid, Solution B of dry sodium carbonate and caustic soda, mixed in equal volumes, with the instruction that for still warmer tones more B should be used; and the Seed Lantern Black Tone Transparency Plate developer of Elon, hydrochinon and sulphite against bromide and carbonate, mixed in equal volumes at about 70 degrees F; Lantern Slides, Development, the developer given for Seed Lantern Black Tone Transparency Plates - Solution A of Elon, hydrochinon and dry sodium sulphite, Solution B of potassium bromide and dry sodium carbonate, mixed in equal volumes and used at a temperature of about 70 degrees F; and the Seed Hydrochinon Developer for Warm Tones, whose Solution A carries hydrochinon, sulphite, bromide and citric acid and whose Solution B carries carbonate and caustic soda, with the instruction that for still warmer tones more B should be used; Fixing and Clearing, on a 40 to 45 per cent solution of hypo being the strongest bath that should be used and the most rapid in action, on the temperature being maintained about 18 degrees C, and on a bath used too long taking longer to fix and risking insoluble transparent silver salts difficult to wash out; Alums as Hardening Agents; Fixing and Clearing, on a bath used too long taking longer to fix and risking insoluble transparent silver salts difficult to wash out, and on the 40 to 45 per cent hypo maximum; Alums as Hardening Agents; Fixing and Clearing, on the 40 to 45 per cent hypo maximum and on the dependence of fixing rate on strength, temperature and exhaustion; Alums as Hardening Agents; Fixing and Clearing, on the rapidity of fixing depending on the strength of the bath, its temperature and the degree of exhaustion, on a 40 to 45 per cent solution of hypo being the strongest bath that should be used and the most rapid in action, on plain and alkaline baths being used for printing-out papers and acid and acid-alum baths for plates, film and developed papers, on maintaining 18 degrees C, and on a bath used too long taking longer to fix and risking insoluble transparent silver salts which are difficult to wash out; Fixing and Clearing, on the 40 to 45 per cent hypo maximum, the dependence of fixing rate on strength, temperature and exhaustion, and the warning that a bath used too long forms insoluble transparent silver salts that are difficult to wash out; Alums as Hardening Agents, the table of weights rendering 100 parts of dry gelatine insoluble; Fixing and Clearing, the Acid bath of hypo 150 g and potassium metabisulphite 25 g per litre with the note that this is about the correct strength for papers and that for negative work the hypo should be increased to 400 g; the citric acid bath given as an equally efficient alternative, with hypo 400 g, citric acid 30 g, dry sodium sulphite and hot water to 1000 ccm, and its instruction to dissolve the hypo in half the water and the acid and sulphite in one-fourth; the statement that a 40 to 45 per cent solution of hypo is the strongest bath that should be used; Fixing and Clearing, Hypo Eliminators, on whether the use of chemicals to destroy the last traces of hyposulphite of soda and of the hyposulphites of silver is justifiable if permanency is the aim, on their action probably being in most cases to convert these salts into tetrathionates, on a negative or print being practically freed from hypo in half an hour by proper washing, and on their use being only allowable in cases of great pressure of time or shortage of fresh water; the list of preparations recommended, including potassium permanganate at 1 per cent, potassium percarbonate at 1 per cent sold as Hypax and Hypono, sodium perborate, potassium or ammonium persulphate at 1 per cent made alkaline with ammonia and sold as Thioxydant and Anthion, and a 5 per cent solution of hydrogen peroxide; Intensification, The Chromium Intensifier (Eder, Welborne Piper and Carnegie): the method described as deservedly receiving considerable attention, being less liable to stain and much less poisonous than many others; that the negatives need not be absolutely free from hypo because the bleaching bath oxidises it, though the bath may need to be applied twice if much hypo is present; the two stock solutions, potassium bichromate 50 g per litre and pure hydrochloric acid 100 ccm per litre; the three bleaching baths A, B and C mixed from them in stated proportions, of which A gives the strongest and C the least intensification; the instruction to immerse until the image on the glass side appears bleached, wash until the yellow stain is removed, and develop with amidol in white light; and the variants using chromic acid with salt, and the ammonium chlorochromate prepared by evaporation; Intensification, The Mercury Intensifier: probably the most generally used of all intensifiers; the mercuric halide solution being sensitive to light and needing to be kept in the dark; the additions of salt, ammonium chloride, hydrochloric acid or potassium bromide made to increase the solubility of the mercury salt, with the bromide giving the greater increase of density; the plate needing to be free from hypo; bleaching until the image seen from the back is white; the acidulated wash that removes the mercury salt held tenaciously by the gelatine and the stains that follow if it is not removed; the ten blackening reagents lettered A to J, including the silver-potassio-cyanide of Monckhoven and its preparation, the note that negatives left too long in it are reduced, and the density ladder in which A, B, C and E give about twice the original density and ammonia about two and a half times; and the period claim about absorption of the mercury salt through the skin; Sulphide Toning: the selenium baths made by dissolving the element in sodium sulphide or by fusing it with caustic soda, and the note that better sepia tones are obtained by adding the selenium solution when cold; Sulphide Toning: the selenium toning baths made by dissolving the element in sodium sulphide or by fusing it with caustic soda, and the note that better sepia tones are obtained by adding the selenium solution when cold; Intensification, The Uranium Intensifier: the judgement that except for extremely thin and flat negatives it is not to be recommended; that the degree of intensification depends upon the ratio of the uranium to the ferricyanide; the two stock solutions, uranium nitrate 100 g with glacial acetic acid 40 ccm per litre and potassium ferricyanide 40 g with potassium oxalate 10 g and glacial acetic acid 40 ccm per litre; that equal volumes give a reddish brown image, 1 part of the first to 2 of the second a reddish image and 5 parts to 1 a brown; that the colour also depends on the duration of the action; the washing in 2 per cent citric acid or 1 per cent oxalic or glacial acetic acid, or five changes of plain water at 5 minute intervals; and that prolonged washing in running water will completely remove the intensification, generally first in patches; Reducers, Hypo and Ferricyanide (Farmer): the reducer prepared as wanted by adding a little 10 per cent solution of potassium ferricyanide to a 20 per cent plain solution of hypo, the quantity of ferricyanide depending on the result desired, the weaker solution giving the more even action and attacking the shadows less, a pale yellow coloured mixture being best, the colour disappearing rapidly in use as the sign of exhaustion, a fresh mixture being applied rather than an old one allowed to act, and the action being the conversion of some of the silver into silver ferrocyanide which dissolves in the hypo; Hypo and ferricyanide (Farmer), on the reducer being prepared as wanted by adding a little 10 per cent solution of potassium ferricyanide to a 20 per cent plain solution of hypo, on the weaker solution giving the more even action and attacking the shadows less, on a pale yellow coloured mixture being best, on the colour of the solution rapidly disappearing in use as the sign of exhaustion, and on a fresh mixture being applied rather than an old one allowed to act; Sulphide Toning, Direct Processes: the alum-and-hypo baths of Baekeland and of Artura, each ripened with a silver nitrate solution and, in Artura's case, with a salt solution too; the instruction that a hot toning bath's prints should be allowed to cool before washing or blisters are very likely to form; Platinotype, pages 274 to 285 — the normal ferric oxalate stock of 20 per cent with 1.2 per cent excess oxalic acid and the instruction that all stock solutions be kept in the dark, the 1 in 6 potassium chloroplatinite stock and the 10 per cent sodium platinum chloride, the arrowroot and gelatine sizes; Sepia Paper, Cold Bath, pages 279 to 280, for the mercuric citrate stock of 5 g yellow mercuric oxide, 25 g citric acid and 100 ccm water heated and filtered, the sensitiser of 8 ccm ferric oxalate solution, 4 ccm potassium chloroplatinite solution, 1 to 4 ccm mercuric citrate solution and 2 to 5 drops of sodium chloroplatinate solution, the two developers at 100 to 300 g and at 70 to 300 g per litre, the rules relating developer strength to mercury dose and to print softness, the five-minute minimum, the acid baths of not more than 0.5 to 1 per cent for not more than 30 minutes in all, the statement that the smaller quantities of the mercury solution give the best colours, and the agar-agar size; The Hot Bath Processes, pages 280 to 281, for the sepia sensitiser carrying 0.2 to 1 ccm of a 5 per cent mercuric chloride solution and its developer of potassium oxalate, potassium phosphate, citric acid and potassium chloride used at 70 C; The Platinum-in-Developer Process, pages 283 to 284, for sensitiser A in which 0.2 ccm of the 5 per cent mercuric chloride solution stands in place of the platinum salt; Kallitype, in The Iron Processes — the statement of the mechanism, Hall's formulas, Thomson's formulas and Thomson's later formulas, including the developer built on silver nitrate, citric acid and oxalic acid, the description of potassium bichromate as a restrainer that keeps the whites pure, and the uranium and copper variants; Pellet's or Gum-Iron Process, pages 261 to 262; Fixing and Clearing, the Plain bath of hypo 400 g in hot water to 1000 ccm; the statement that a 40 to 45 per cent solution of hypo is the strongest bath that should be used and the most rapid in action; that plain, alkaline, acid, and acid and alum baths may all be used, the first two generally for printing-out papers and the latter for plates, film and developed papers; that the temperature should be maintained about normal, 18 degrees C; that a bath used too long takes longer to fix and risks forming insoluble, transparent silver salts which are difficult to wash out; and the method of suspending the crystals in a cloth in hot water to avoid filtering; Platinotype, page 281 — develop 1 to 3 minutes, "then clear in four acid baths of hydrochloric acid, 1:60, and wash for a short time in running water", with sepia prints developed at 66 to 88 degrees C and "cleared in three acid baths of half the above strength". Palladiotype Paper, page 282 — the two developers, and the clearing bath for both papers, sodium citrate 232.5 g and citric acid 93 g in 1000 ccm, of which "for use mix 1 part with 7 parts water. Three baths should be used, with 10, 15, and 20 minutes in the first, second, and third baths respectively", followed by washing in running water for 10 or 15 minutes or in several changes of 10 minutes each. Satista Paper, pages 282 to 283 — clearing in a bath of sodium citrate alone, whose metric strength is not legible in the copy read for this page and whose imperial column reads 1 and a quarter ounces to 75 fluid ounces, in three baths of 5, 10 and 15 minutes followed by a short wash of not longer than 10 minutes; and the instruction that "the water used for the clearing bath must be free from lime", with the remedy of dissolving 0.5 g of oxalic acid in 1000 ccm, standing for some hours and decanting from the precipitate; Developers — the pyrocatechin formulas, and the eikonogen developer's note that 75 g of dry sodium carbonate may be replaced by an equivalent weight of potassium carbonate, namely 98 g; Sulphide Toning, Indirect Processes: the bleaching bath may be made with a bromide, a chloride or an iodide, each added to potassium ferricyanide and water; and the rule that if the halide salts are used in the stated quantities there is no loss in the intensity of the image, which will be the case if they are used stronger; Fixing and Clearing, on plain and alkaline baths being generally used for printing-out papers and acid and acid-alum baths for plates, film and developed papers, and on the alkaline bath of hypo with dry sodium carbonate and salt in which one quantity is illegible in the copy the course holds; Kallitype, in The Iron Processes — the statement of the mechanism; Thomson's formulas, for the developer of equal parts 5.2 per cent Rochelle salts and 9.4 per cent borax with 0.02 to 0.8 per cent potassium bichromate described as a restrainer, and for the thirty minutes in it; Hall's formulas, for a kallitype developer built on sodium acetate and tartaric acid; Developers, pages 108 and 109 - the paramidophenol one-solution and two-solution formulas, and "One solution, similar to rodinal (Ermen)" with its water, its two weighed solids, its caustic soda solution, the quantity of that solution to be added, the make-up volume and the two dilutions; the closing sentence listing the proprietary liquid developers of the type; Development, page 76 - Watkins's table of factors for various developers; page 80 - Watkins's temperature coefficients; pages 80 to 83 - stand development, the Wratten and Wainwright dilution measurements, and the Rodinal (Munkman) time-and-temperature table at 1:100; Palladiotype Paper, page 282 — the instruction that the paper gives a very visible printing image and that exposure is carried on until all details are visible; the developer of sodium citrate 232.5 g and citric acid 23.25 g to 1000 ccm, with the imperial column of 10 oz, 1 oz and 43 oz; the 7 to 16 C temperature window for black prints; the separate sepia developer of 50 g and 2.62 g to 1000 ccm and the instruction to heat it to 38 C and not beyond for warmer tones; the clearing bath of 232.5 g citrate and 93 g citric acid diluted 1 part in 7, in three baths of 10, 15 and 20 minutes; the bichromate addition for brilliant prints; the 10 to 15 minute wash; and, on pages 277 to 281, the platinotype developers this one is contrasted with. Quantities read from the page images of the Internet Archive scan, whose OCR mangles the unit letters; the arithmetic that decides them is set out in the provenance note; Kallitype, in The Iron Processes, for the statement of the mechanism and for Hall's formulas, whose clearing bath is sodium citrate with citric acid; Toning bromide prints, Uranium Toning, pages 219-220: the statement that treatment of a silver image with a mixture of a soluble uranium salt and ferricyanide of potassium results in brown to red images, the colour being dependent on the ratio of the two salts and the duration of toning; that intensification also takes place, so the prints should not be too intense at first; that the colour is dependent on the deposition of uranium ferrocyanide, which is soluble in alkalis, so that long washing in ordinary water will reduce the colour; the four baths credited to Sedlaczek, whose quantities are volumes of 10 per cent solution; and the simpler formula recorded on this page, reading 'A. Uranium nitrate 5 g / Water 500 ccm' and 'B. Potassium ferricyanide 5 g / Glacial acetic acid 14 ccm / Water 500 ccm' with the direction 'Mix just before use. Or the prints may be immersed in B until bleached, well washed, and then soaked in A until the desired colour is obtained. In this last formula, the salts are dissolved as given; that is, 10 per cent solutions are not used.' Also Intensification, The Uranium Intensifier, pages 137-138, for the two stocks, the three published ratios and their three colours, and the washing instructions; Platinotype, pages 277 to 281 — the two cold-bath developers, neutral potassium oxalate 250 g per 1000 ccm and the 100 g oxalate with 50 g potassium phosphate; the instruction to immerse one end first and draw the sheet through; development in 1 to 2 minutes with the dish rocked; the statement that dilution of the developer gives more brilliant prints; the bichromate and ammonium persulphate additions; the sepia cold-bath developers at 100 to 300 g per litre and the rule that the stronger the developer the more rapid its action and the softer the print; the hot-bath instruction to use the same developers at 50 to 75 C; Percentage solutions: the meaning of "x per cent solution" and the two tables of grains; Orthochromatic photography: the hypersensitising bath of pinaverdol, pinachrome and pinacyanol, and its 36-hour keeping; Pages 24 to 25, Orthochromatising plates: erythrosine as the dye generally used, the extra blueish kind in a 1:5000 aqueous solution with 0.5 per cent of ammonia; the statement that erythrosine gives a strong yellow, orange and green sensitiveness but a marked want of sensitiveness in the blue-green; that bathed plates as a rule have a higher colour sensitivity than those coated with an emulsion to which the dye is added during mixing but do not keep as well; that only perfectly clean glass dishes should be used because metals tend to reduce the dyes and cause fog; the panchromatic bath ceiling of not more than 1 in 75,000, the naming of pinacyanol, sensitol red and sensitol violet with the violet dyes giving the best all-round results, the statement that these dyes sensitise to about 720, and the instruction that a deep red safelight may be used until the plates are covered with the dye solution after which the work is done in darkness or by a green safelight; Pages 24 to 25, Orthochromatising plates: erythrosine as the dye generally used, the 1:5000 aqueous bath, the comparison between bathed and emulsion-dyed plates, the clean-glass-dish rule, and the panchromatic bath ceiling of 1 in 75,000; Development — Stand development, its history, its advantages and its lack of economy; the Wratten & Wainwright photometric measurements of rodinal at 1:20 and 1:200 in air-free distilled water, ordinary distilled water and tap water; Munkman's rodinal stand table at 1:100 with separate development times for portrait, architecture and landscape subjects; the stand-development formulae of Bothamley, Claudy, Harris and Munkman; Developers — the rodinal-type liquid developers and Ermen's formula with its instruction to leave some of the base undissolved; Pyrocatechin formulae; Stand development and the Wratten & Wainwright dilution measurements; Glycin, glycin-soda and glycin-potash factors; Developing-out papers: exposure and development for warm tones; non-abrasion developers and the note that the iodide is the active agent; Developers — pyrogallol and pyro-ammonia, and Wall's note that pyro-ammonia is rarely used on account of its variability; Stand development — the Wratten & Wainwright pyro-soda formula in two solutions, Bothamley's pyrocatechin in two solutions, and the pyro-soda formulae of Claudy, Harris and Munkman; Development: the Watkins factor, the estimated factors for named developers, and the rule that the factor for a combined developer with the reducing agents in equal ratios is the mean of the two; Development — stand development described as an old method, its dilute solutions and twelve to twenty-four hour times, the statement that its only advantages are fine grain and uniform results if the developer be frequently agitated, and that it is not economical because the solution is so oxidised at the end as to be useless a second time; the Wratten and Wainwright photometric test of dilution against time in rodinal, with the air-free distilled, ordinary distilled and tap water figures; Fixing and Clearing — the plain hypo bath and the statement that 40 to 45 per cent is the strongest and most rapid worth using; the alkaline fixing bath of hypo, dry sodium carbonate and a little common salt, given for silver printing-out images; the rapid ammonia fixing bath, in which 2.5 to 5 per cent ammonium chloride added to a 20 per cent hypo bath increases the rapidity of fixing, 10 per cent ammonia water does the same, and neither has any effect on a 40 per cent hypo bath; Fixing and Clearing — the rapid ammonia fixing bath, in which 2.5 to 5 per cent of ammonium chloride added to a 20 per cent hypo bath increases the rapidity of fixing, 10 per cent ammonia water does the same, and the addition has no effect at all on a 40 per cent hypo bath; the plain bath at 400 g per litre and the statement that 40 to 45 per cent is the strongest and most rapid worth using; Fixing and Clearing, Hypo Eliminators — whether the use of chemicals to destroy the last traces of hyposulphite of soda and of the hyposulphites of silver is justifiable if permanency is the aim, their action probably being to convert these salts into tetrathionates, a negative or print being practically freed from hypo in half an hour by proper washing, and their use being only allowable in cases of great pressure of time or shortage of fresh water; Bromide Paper, the entry headed FACTORIAL DEVELOPMENT FOR BROMIDE PAPER - Wall's report of Dr B. J. Glover's application of the Watkins factorial system to bromide papers using the Kodak amidol formula at 17 C, the constant of 1800 obtained from exposures of 30, 15 and 10 seconds against total development times of 60, 120 and 180 seconds, and Glover's three rules, of which the first is that development must not be for a shorter time than that required to produce the maximum black of the paper and the third that the maximum development allowable is that which just stops short of fog or stain or both; General Notes on Sulphur Toning, reporting R. Bullock of the Kodak Research Laboratory - that in the indirect process there is no advantage in increasing the bromide beyond one-third of the ferricyanide, that with 10 per cent ferricyanide the colour is more yellowish and bleaching very rapid while at 3 to 1 per cent bleaching is practically no longer and the colours normal, that about 3 per cent ferricyanide with 1 per cent ammonium bromide appears the most advisable strength, that a 3 per cent sulphide bath is best and should be unsparingly used so as not to exhaust it, that excessive bromide in the bleach leads to loss of image, and that too long washing after bleaching, weakness or too long use of the sulphide bath and the presence of hypo in it are all to be avoided; and the statement that the faster the emulsion the more purple the tone and that slow papers tend to yellowish tones; Toning Bromide and Gaslight Prints, Copper Toning — that various shades from red to violet-brown are obtainable by a process based on the deposition of red cuprous ferrocyanide on the image with the simultaneous formation of white silver ferrocyanide, that it is actually an intensification process so the primary image must not be developed too far, that Ferguson's single solution of cupric sulphate, potassium citrate and potassium ferricyanide keeps and does not stain while the colours depend on the length of immersion, that Sedlaczek's baths for particular tones will not keep well and should be mixed just before use, that a weak ammonia bath of 1 per cent will clear the whites of the bath giving red chalk or Bartolozzi tones, and that with all these baths much more transparent images may be obtained by immersion for about 5 minutes in a 5 per cent hypo solution; Iron or Cyanotype Toning — that in this process the colour is dependent on the deposition of Prussian blue on the image, that this is soluble in alkalis and therefore long washing in ordinary water is inadvisable, the two-bath route of a 5 per cent potassium ferricyanide solution with a little potassium oxalate followed by a 2 per cent solution of iron ammonium oxalate, and Sedlaczek's single-bath formulas built from 10 per cent stock solutions of ammonia iron alum, potassium citrate or potassium oxalate, ammonia alum, hydrochloric acid and potassium ferricyanide, which give respectively a deep blue, a cold blue and, with tartaric acid replacing the acid and alum, a grey blue; and Uranium Toning — that intensification takes place, that the colour depends on the deposition of uranium ferrocyanide which is soluble in alkalis, and that long washing in ordinary water will reduce the colour; Sulphide Toning - the two principal methods of obtaining warm brown or sepia to purplish brown tones, the direct in which the image is converted into silver sulphide directly and the indirect in which the silver is first converted into chloride, bromide or iodide and then into sulphide; Copper Toning - the process is based on the deposition of red cuprous ferrocyanide on the image with the simultaneous formation of white silver ferrocyanide, it is actually an intensification process and the primary image must therefore not be developed too far, and the colours depend on the length of immersion; Uranium Toning - treatment of a silver image with a mixture of a soluble uranium salt and potassium ferricyanide gives brown to red images whose colour depends on the ratio of the two salts and the duration of toning, intensification also takes place so prints should not be too intense at first, the colour depends on the deposition of uranium ferrocyanide, which is soluble in alkalis, so long washing in ordinary water will reduce the colour; Sulphide Toning, the opening definition that there are two principal methods of obtaining warm brown or sepia to purplish brown tones, the direct and the indirect, the image being converted into silver sulphide direct in the former while in the latter the silver is first converted into chloride, bromide or iodide and then into sulphide; Direct Processes, the hypo-alum baths of Baekeland and Artura, including Baekeland's alum-sugar-hypo bath of hypo 25 g, white sugar 40 g and alum 25 g in 1000 ccm of hot water, of which it is said that the bath should never be above 44 degrees Celsius, that the best results are obtained at about 32 degrees Celsius, and that toning at this temperature takes 30 minutes; and the note that when hot toning baths are used the prints should be allowed to cool before washing, otherwise blisters are very likely to form; the liver of sulphur or polysulphide process of Woodman and the ammoniacal liver of sulphur bath of Vero, 7 g of liver of sulphur in 1000 ccm of water with a few drops of ammonia, of which it is said that toning is very rapid and purplish-brown tones are obtained; and General Notes on Sulphur Toning, reporting R. Bullock of the Kodak Research Laboratory, that the character of the emulsion has considerable influence on the resulting colour, the faster the emulsion the more purple and slow papers tending to yellowish tones, that with a given paper the degree of development exerts some action although it may be masked by the character of the emulsion, that with a given paper and print the hypo-alum and liver of sulphur processes give practically identical results while the indirect methods tend to give yellowish prints, that preliminary treatment with sulphide before bleaching gives mixed direct and indirect toning whose results vary with the procedure, that in the indirect process there is no advantage in increasing the bromide beyond one-third of the ferricyanide, that with 10 per cent ferricyanide the colour is more yellowish and bleaching very rapid while at 3 to 1 per cent bleaching is practically no longer and the colours normal, that about 3 per cent ferricyanide with 1 per cent ammonium bromide appears the most advisable strength, that no advantage is found in chlorides while iodides give more yellowish tones, that a 3 per cent sulphide bath is best and should be unsparingly used so as not to exhaust it, that dipping prints for about 10 seconds in a 1 per cent solution of sodium carbonate immediately before the sulphide bath tends to give more purplish tones particularly with development papers and when a chloride bleach is used, and the final conclusions that excessive bromide in the bleach leads to loss of image and that too long washing after bleaching, weakness or too long use of the sulphide bath and the presence of hypo in it are all to be avoided; Intensification, The Mercury Intensifier, page 130 - that it is probably the most generally used of all intensifiers, that the silver image is treated with mercuric chloride or bromide until bleached, then washed and blackened by various reagents, that the mercuric halide solution is sensitive to light and should be kept in the dark, and the period safety claim that it is extremely poisonous when taken internally but that the absorption by the skin, even in the case of cuts and abrasions, is practically harmless; the purpose of the added salt, ammonium chloride, hydrochloric acid or bromide as increasing the solubility of the mercury salt, the bromide giving the greater increase of density; and the blackening reagents. Toning bromide and gaslight prints, page 243 - the mercuric chloride and potassium bromide bleach followed by second baths chosen for colour, greyish-black, grey-violet, brown to violet-black and brownish-violet, and the closing statement that all mercury toning gives intensification. Sulphide toning - that bichromate baths have been recommended as the bleach but require much longer washing to remove the yellow bichromate stain than the other baths, with Sedlaczek's and Blake-Smith's formulas named, and that too long a washing of the bleached prints causes yellow tones. Uranium toning, pages 219-220 - that intensification also takes place, that the colour depends on the deposition of uranium ferrocyanide which is soluble in alkalis, and that long washing in ordinary water will reduce the colour; Chapter VII, The Chemistry of Toning, section D - that where great permanency is required prints should preferably be toned to a silver sulfide image, experience having shown this form of silver to be one of the most stable; Kallitype, Thomson's formulas — the developer of equal parts of a 5.2 per cent Rochelle salt solution and a 9.4 per cent borax solution with the addition of 0.02 to 0.8 per cent potassium bichromate, "which keeps the whites pure and acts as a restrainer", and Hall's formulas, in which a bichromate solution is one of four components of the sensitiser and the instruction for thin and soft negatives is to increase its proportion from 30 to 50 per cent while halving the oxalic acid; Kallitype, in The Iron Processes — the statement that the ferrous salts dissolve in the developer and reduce silver nitrate to the metallic state at the points where the ferric salt has been reduced by light; Thomson's formulas, whose developer is equal parts of a 5.2 per cent Rochelle salt solution and a 9.4 per cent borax solution with 0.02 to 0.8 per cent potassium bichromate added, "which keeps the whites pure and acts as a restrainer", developed for 30 minutes; Kallitype, in The Iron Processes — the opening definition, that the process is based on the light-sensitiveness of ferric salts which are reduced to the ferrous state, and that "the ferrous salts dissolve in the developer, and reduce silver nitrate to the metallic state at the points where the ferric salt has been reduced by light"; Thomson's formulas, in which the developer is equal parts of Rochelle salt and borax solutions with a bichromate addition that "keeps the whites pure and acts as a restrainer", and Thomson's later formulas, whose developer is a silver nitrate, citric acid and oxalic acid solution; Intensification, The Mercury Intensifier, page 130 — the period claim that mercuric chloride is extremely poisonous when taken internally but that absorption by the skin, even in the case of cuts and abrasions, is practically harmless; Intensification, The Mercury Intensifier, page 130 - that it is probably the most generally used of all intensifiers, that the silver image is treated with mercuric chloride or bromide until bleached, then washed and blackened by various reagents, that the mercuric halide solution is sensitive to light and should be kept in the dark, the purpose of the added salt as increasing the solubility of the mercury salt with the bromide giving the greater increase of density; and the period statement that it is extremely poisonous when taken internally but that absorption by the skin, even in the case of cuts and abrasions, is "practically harmless", a claim the current classification does not support. Toning bromide and gaslight prints, page 243 - the mercuric chloride and potassium bromide bleach followed by second baths chosen for colour, giving greyish-black, grey-violet, brown to violet-black and brownish-violet, and the closing statement that all mercury toning gives intensification; Reduction of density — the iodo-cyanide reducer, headed "extremely poisonous, but clean acting", an iodine and potassium iodide solution to which one gram of potassium cyanide is added per litre, described as an excellent non-staining reducer for developed prints when diluted ten times; and the mercury and cyanide reducer attributed to Eder, headed "an extremely poisonous but non-staining reducer"; Intensification, The Mercury Intensifier, page 130 — that it is probably the most generally used of all intensifiers, that the silver image is treated with mercuric chloride or bromide until bleached, then washed and blackened by various reagents, that the mercuric halide solution is sensitive to light and should be kept in the dark, the purpose of the added salt as increasing the solubility of the mercury salt with the bromide giving the greater increase of density, and the period claim that the salt is extremely poisonous when taken internally but that absorption by the skin, even in the case of cuts and abrasions, is practically harmless. The Uranium Intensifier, pages 137 to 138 — that except for extremely thin and flat negatives it is not to be recommended, that the degree of intensification depends upon the ratio of the uranium to the ferricyanide and the colour also on the duration of the action of each bath, and that prolonged washing in running water will completely remove the intensification, generally first in patches. The Lead Intensifier, page 138 — that it gives very great intensification and is only suitable for black and white line work, that lead salts are rather tenaciously retained by the gelatine, and that treatment of the bleached image with a sodium sulphide solution gives the greatest increase. Uranium toning, pages 219 to 220 — that intensification also takes place, that the colour depends on the deposition of uranium ferrocyanide which is soluble in alkalis, and that long washing in ordinary water will reduce the colour; Development, Stand Development - the description of the method as a dilute developer in an upright grooved tank in which plates are left for a given time, the note that in the early days it was put forward as a cure for every error in exposure with solutions so dilute that 12 to 24 hours were required, the statement that its only advantages are fine grain and uniform results if the developer be frequently agitated, the report of Wratten and Wainwright's photometric measurements that a plate needing 3 minutes in rodinal at 1:20 needed 42 minutes at 1:200 in air-free distilled water, 46 in ordinary distilled water and 52 in tap water, the note that pyro-soda and glycin seem to be the only developers not affected by the water, and the statement that stand development is not economical because most commercial tanks require a large amount of solution which is as a rule so oxidised at the end of development as to be useless a second time; Developers, page 109 - the one-solution paramidophenol developer described as similar to rodinal after Ermen, its paramidophenol and potassium metabisulphite solution, its caustic soda solution and the instruction to add about 340 to 350 ccm with constant stirring until the precipitate of the base is nearly dissolved, leaving some undissolved; and the surrounding text on the class, for which Wall's word is energetic; The temperature coefficients determined by Watkins, printed as a list of developers with a factor each, in which a metol-hydroquinone developer is given as 1.9 and a metol-hydroquinone tabloid as 1.86, alongside pyro-soda without bromide at 1.5 and paramidophenol at 2.4; and the surrounding worked example, which defines the coefficient through a logarithmic factor applied per degree Celsius to the time of appearance in factorial development; Bichromate methods — carbon; the reach of the family by the 1920s; Collodio-chloride emulsions — the preference for strontium and lithium chlorides and the collected formulas of Hanneke, Niederstadt, Valenta, Eder and Liesegang; Bichromate methods — collotype among the photomechanical processes; Photomechanical processes: cleaning old collotype plates with a 5 per cent caustic potash solution; Bichromate methods — gum printing, and the effect of the ratio of colour to dichromate on hardness and gradation; Bichromate methods; Photomechanical processes: half-tone on copper, etching solutions; Photomechanical processes: half-tone on copper, etching solutions; the photogravure baths at 43, 40, 38, 36 and 33 degrees Baumé and the rule that the weaker the solution the stronger the etching; Uranium toning — the ratio of the two salts, the simultaneous intensification, and the solubility of the uranium ferrocyanide in alkalis; the uranium intensifier and its uneven removal; Bichromate methods — the reach of the family across the photomechanical trade; Sulphide Toning, Direct Processes - the alum-and-hypo baths of Baekeland and of Artura, and the instruction that prints from a hot toning bath should be allowed to cool before washing or blisters are very likely to form

Used by:Amidol · Ammonium chloride · Ammonium citrate (dibasic) · Ammonium iron(III) citrate · Ammonium iron(III) oxalate · Ammonium persulfate · Ammonium thiocyanate · Ammonium thiosulfate · Ascorbic acid · Boric acid · Catechol · Chloroauric acid · Chlorohydroquinone · Chrome alum · Erythrosin · Iron(II) oxalate · Formaldehyde · Glycerol · Glycin · Gold(III) chloride · Iron(II) sulfate, anhydrous · Iron(II) sulfate heptahydrate · Iron(III) chloride, anhydrous · Iron(III) chloride hexahydrate · Lead(II) acetate · Lead(II) nitrate · Lithium chloride · Mercury(II) chloride · Metol · Nickel(II) sulfate · Nitric acid · Oxalic acid · p-Aminophenol · Potassium alum · Potassium bromide · Potassium carbonate (anhydrous) · Potassium citrate · Potassium ferricyanide · Potassium hydroxide (caustic potash) · Potassium iodide · Potassium oxalate, anhydrous · Potassium oxalate monohydrate · Potassium permanganate · Potassium persulfate · Potassium sodium tartrate tetrahydrate · Potassium thiocyanate · Pyrogallol · Selenium · Silver(I) oxalate · Sodium ascorbate · Sodium chloride · Sodium selenite · Sodium selenosulfate · Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Tartaric acid · Uranyl nitrate hexahydrate · Borax kallitype developer · Erythrosin sensitising stock · ILFORD RAPID FIXER · Kallitype sensitiser · Kodak bisulphite fixing bath · Kodak D-32 · Kodak D-34 · Kodak F-1 · Kodak F-14 · Kodak F-2 · Kodak F-24 · Kodak F-5 · Kodak F-52 · Kodak HE-1 · Kodak IN-4 · Kodak IN-1 · Kodak T-55 · Kodak T-56 · Kodak IN-21 · Kodak R-4 · Kodak R-4a · Kodak T-1a · Mercuric sepia platinotype · Nicol's kallitype · Pellet's positive-working process · Plain hypo fixing bath · EDTA, citric acid and hydrochloric acid clearing sequence · Pyrocat-HD · Rehalogenating ferricyanide-bromide bleach · Alkaline plain-hypo fixing bath · Rochelle salt kallitype developer · Rodinal-type p-aminophenol developer · Sodium citrate developer · Sodium citrate kallitype developer · Uranium toner · Willis's potassium oxalate developer · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P4 Reciprocity Failure and the Life of the Latent Image · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P5 Washing, Digestion and Sensitisation · P8 Acutance, Adjacency Effects and Compensating Development · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P8 Restrainers and Antifoggants · P8 Staining and Tanning Developers · P8 Superadditivity: Why Two Agents Beat One · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline · P11 How Fixer Works · P12 The Physics of Washing · P19 Developing the Print Consistently and Running a Printing Session · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Gold, Iron-Blue and the Other Metal Toners · P20 What a Toner Actually Does to a Silver Image · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P20 The Toners We Study and Do Not Use · P20 Toning, Permanence and What the Evidence Actually Supports · P24 Contrast Control in Iron-Based Printing · P24 Lab: Printing a Kallitype · P24 The Siderotype Principle: Iron Reduces Silver · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Assignment: Assessing a Historical Process for Hazard · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 Uranium, Mercury and the Heavy-Metal Treatments · P27 Experiment: Agitation, Stand and Semi-Stand Development · P27 Assignment: The Developer Comparison, Measured and Printed · P27 Experiment: The Development Time and Temperature Series · Carbon print · Collodion print-out paper · Collotype · Gum bichromate · Photoglyphic engraving · Photogravure · Uranium toned print · Woodburytype · Blistering from an over-hot hypo alum bath

Photography with Emulsions: A Treatise on the Theory and Practical Working of the Collodion and Gelatine Emulsion Processes, 3rd editionretrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: The Paget prize emulsion and the note on the purity of ammonium bromide; Burton's process; the gelatino-bromide method using 140 grains of ammonium bromide or its equivalent in another bromide; Chapter XIII, Dr. Eder's plans of preparing gelatine emulsions with ammonia — the ammonio-nitrate of silver method, its formula, temperatures and warnings; Canon Beechey's process; M. Chardon's process; Wortley's ripening times for emulsions made with different soluble bromides; Precipitation of the emulsion by spirits of wine, and draining; Bennett's gelatino-bromide process — alcohol added before coating; the chapter on gelatine — alcohol precipitating gelatine from solution; Chapter II, Alkaline Development — the constitution of the ferrous-oxalate developer and the reaction with silver sub-bromide; Chapter XXIII, Development of Gelatine Plates with Ferrous Oxalate — preparation, dilution, bromide for density, hyposulphite for under-exposure, and storage under paraffin oil; Chapter XXV, the ferrous citro-oxalate developer; Chapter XXIV, Fixing, Intensifying and Varnishing Gelatine Negatives — peroxide of hydrogen after washing, a drachm of 20-volume solution to five ounces of water; Chapter on gelatine: alcohol and carbolic acid precipitating gelatine from solution; precipitation of the emulsion by spirits of wine; Chapter I: spectral sensitiveness of silver iodide; Chapter VII: Silver Iodide and Chloride in Emulsions; Chapter I: the emulsification of silver bromide, the molecular states of bromide of silver and their colours, and the bromine absorbent; Chapter I: emulsifying silver chloride, and the action of light on chloride of silver in the presence of moisture; Chapter I: iodide of silver in its pure state is sensitive only to the ultra-violet, violet and blue rays, and the washed iodide emulsion with and without an iodine absorbent; Chapter VII: Silver Iodide and Chloride in Emulsions; Gelatine emulsions with ammonia — keeping the dissolved emulsion: 10 grains of salicylic acid in 1 drachm of alcohol to 10 ounces of emulsion, or the same weight of thymol; the antiseptics that prevent decomposition of gelatine; Preliminary considerations: emulsions with and without extraction of the soluble salts; Cooling and washing the emulsion; Other modes of washing the emulsion, with the washing times against degree of subdivision; Chapter I: the molecular states of bromide of silver and the bromine absorbent; Chapter I: the molecular states of bromide of silver and their transmitted colours; Chapter I: the molecular states of bromide of silver and their spectral ranges; Chapter I: the molecular states of bromide of silver; the bromine absorbent; Chapter I: the equation for silver bromide, the molecular states of bromide of silver and their transmitted colours, and the spectral range of each state; Chapter VII: Silver Iodide and Chloride in Emulsions - the comparative emulsions with and without potassium iodide; Chapter VI, Introductory Remarks on Gelatine Emulsions: Maddox 1871 and Bennett's long low-temperature digestion; Chapter X, Bennett's gelatino-bromide process, first published 1878; Chapter VI, Introductory Remarks on Gelatine Emulsions: Maddox 1871 and Bennett's long low-temperature digestion; Chapter IX, the transmitted-light colour rule relating orange emulsions to finer particles and greater covering power; Chapter X, Bennett's gelatino-bromide process, first published 1878; Chapter VII, silver iodide and chloride in emulsions; Preliminary Considerations, for the statement that iodide of silver in its pure state is sensitive only to the ultra-violet, the violet and the blue rays, and that adding iodide to a bromide modifies the range of spectral sensitiveness; The sections on coating and on the substratum — the role of the substratum in preventing frilling and blistering by controlling the adhesion of the film to its support, and the observation that plates frill with certain developers; The molecular states of silver bromide and their differing sensitiveness; The sections on the substratum and on coating — the role of the substratum in controlling the adhesion of the film to its support and so in preventing frilling and blistering, and the observation that plates frill with certain developers

Used by:Ammonium bromide · Ammonia solution (ammonium hydroxide) · Cadmium bromide · Ethanol · Iron(II) oxalate · Hydrogen peroxide · Isopropyl alcohol · Potassium iodide · Silver bromide · Silver chloride · Silver iodide · Thymol · P3 Solutions, Solubility and Precipitation · P4 Development as Amplification · P4 Experiment: Precipitating the Silver Halides · P4 Spectral Sensitivity and Colour Response · P4 The Latent Image · P4 The Silver Halides · P5 Project 4: Coating Glass Dry Plates and a Lantern Slide · P5 Precipitation, Nucleation and Crystal Growth · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · P28 The Emulsion Under Stress: Reticulation, Scratches, Pinholes and Drying Marks · Dry plate and lantern slide · Blisters

Platinotyperetrieved 2026-09-06, 2026-09-07

Sections: The chapter on intensification — Willis's method of intensifying a gelatine-emulsion plate with platinum, in which ferric oxalate converts the dark silver image into a white one of silver oxalate which is then treated with dilute potassium chloroplatinite, with the equation given for the double decomposition; and the variant in which the whitened image is redeveloped with the ferrous-oxalate developer and no platinum salt at all; Production of the Platinum Image, pages 18 to 20 — the review of Willis's three patents: the three coatings of the 1873 first method given as 1 part chloro-platinate of potassium in 48 parts of water, 1 part nitrate of lead in 48 parts of water and 1 part ferric oxalate in 8 parts of water with a little oxalic acid; the second method substituting 1 part silver nitrate in 60 parts of water for the lead; the 1878 coating solution tabulated with water, potassium chloro-platinite, ferric oxalate and lead chloride, whose proportions are illegible in the scan read; the statement that Willis "is able to dispense altogether with the chloride of lead, or can substitute for it chloride of mercury"; and, for the 1880 patent, that omitting the silver or lead salt means "any fear of discolouring the white parts of the image — which so often happens when lead or silver salts are employed — is altogether avoided"; Part I, the theory — the account of Willis's patents of 1873, 1878 and 1880 and the sensitiser of patent 1117; The Salts of Iron; The Substances Suitable for the Development of the Platinum Image, for the sixteen developing substances ranked by reducing power and for the hot 80 °C concentrated condition they are used in; The Effect of the Presence of Foreign Bodies in the Sensitizing and in the Developing Solution, for the acid requirement, the reducing substances that fog, the oxidising substances that harden and the chlorate mechanism; Palladium, Iridium and Gold; On the Relative Proportions of Platinum and Iron Salt in the Sensitizing Solution, for the 0.69 g of ferrous oxalate per gramme of platinum salt, the 0.9 g of ferric oxalate, the experimental range 1 : 0.9 to 1 : 1.5, the best band 1.0 to 1.2 and the 0.02 to 0.025 g per 1,000 square centimetres. Part II, the practical details — Preparation of the Paper, for the gelatine and arrowroot baths; Preparation of the Platinum Solution, for the double salt from platinic chloride and for the 1 part in 6 normal solution; Preparation of the Ferric-Oxalate Solution, for the 20 grammes per 100 c.cm. and the 6 to 8 per cent of oxalic acid, for the ferricyanide and dilution tests and for the normal chlorate of iron solution at 0.4 gramme per 100 c.cm.; Preparation of the Sensitizing Solution, for all four mixtures; Coating the Paper, for the flannel pad, the drying limits and the footnote giving 10 cubic centimetres per 50 by 66 centimetre sheet; Printing the Picture, for the sensitiveness against silver paper and the April exposures; Developing the Picture, for the saturated cold-made potassium oxalate acidulated with oxalic acid and the water-bath tray; Finishing the Picture, for the 1 in 80 hydrochloric acid and the wash; the seven-item fault list; Using up the Platinum Residues; Value of the Platinotype Process; Finishing the Picture, pages 52 to 53 — the instruction that directly the picture is developed it must be immersed in a solution of hydrochloric acid and water, the water given as 80 parts and the acid's own figure illegible in the copy read for this page, "and left there until any of the iron-salt still present has been removed", that "this solution of hydrochloric acid must be changed (twice or three times) until it no longer turns yellow", that "we ourselves generally change the solution three times, and leave the print in it each time for about ten minutes", and that the print is then laid in a pan of water for ten to fifteen minutes, because acid left in the paper "would not have any bad effect on the print itself, but might injure the substance of the paper, so that in the course of time it would be destroyed", with the last wash water tested with litmus for neutrality; the footnote advising that the print be held with a forceps of bone or horn to keep the hands out of the liquid; and, in the fault table, the entry for whites with a yellowish tinge after drying, whose second cause is "insufficient immersion in hydrochloric acid" with the remedy that "the solution of hydrochloric acid must be changed two or three times until the last change no longer turns yellow at the end of ten minutes", and whose third cause is paper blued with ultramarine, which turns yellow when treated with hydrochloric acid

Used by:Silver(I) oxalate · Lead additions to platinum sensitisers · Pizzighelli and Hübl's 1886 formulations · EDTA, citric acid and hydrochloric acid clearing sequence

Quellenschriften zu den fruehesten Anfaengen der Photographie bis zum XVIII. Jahrhundertretrieved 2026-09-06

Sections: Pages 91 to 94, the Latin of Observatio CCXXXIII reprinted in full; pages 99 to 103, Eder's facing German; and pages 13 to 17 of the introduction, for Eder's citation of the Acta at page 528, his dating of the work, and his claim of priority for Schulze

Used by:Schulze's scotophorus mixture

Researches on Light in its Chemical Relations, embracing a consideration of all the photographic processes, 2nd editionretrieved 2026-09-04, 2026-09-06

Sections: Paragraph 262, the oxalate of the protoxide of iron with salts of platinum; The collodion process, quoted account crediting the photographic property of sulphate of iron to Robert Hunt; Chapter III, Action of the Solar Rays on Preparations of Silver — paragraphs 74 and 75, on the oxide precipitated in the dark and applied to paper, and on the oxide dissolved in ammonia and Dr Alfred Taylor's method; paragraph 76, on pure silver nitrate not being sensibly affected by light and on the smallest portion of organic matter occasioning it to blacken; paragraphs 96 to 101, on films of the oxide precipitated with baryta onto glass, their darkening under sunshine and subsequent whitening, and their behaviour with ammonia and with dilute nitric acid; Article 277, Hunt's statement that he has repeated all Herschel's published experiments with much care and has little to add; Article 278, the chrysotype transcribed; Article 280, the silver version in a single sentence; Article 281, The Cyanotype, item 3, pages 165 to 166 of the second edition, reprinting the same account word for word ten years later, again with no strengths; "Niepce's heliography", in the introductory chapter, for a fourth printing of the same passage in the same year as the Manual, and for the footnote in which Hunt names his source — "History and Practice of Photogenic Drawing, by M. Daguerre, translated from the original by T. S. Memes, LL.D. London, 1839" — which is how this page knows that his English descends from Memes's rather than from the French; Section 87, Photographic Application, which prints Talbot's own account of the preparation of ordinary photogenic paper verbatim, fifteen years after he wrote it; Chapter I, sections 31 to 33, which transcribe the 1802 memoir at length but elide the proportions sentence behind a row of asterisks; and Appendix No. II, the letter of 13 February 1854 from the Rev. J. B. Reade, who states that he was aware Wedgwood "found leather more sensitive than paper" and that it is highly probable the tanning process suggested his own application of a tanning solution to paper; Chapter I, section 32: the camera obscura image too faint to act on nitrate of silver; Chapter I, sections 31 to 33: the Wedgwood and Davy memoir of 1802, transcribed; Chapter I, sections 32 to 33: the Wedgwood and Davy memoir of 1802

Used by:Ferric oxalate · Iron(II) sulfate, anhydrous · Iron(II) sulfate heptahydrate · Silver(I) oxide · Herschel's argentotype · Herschel's hydrargyro-cyanotype · Niépce's bitumen heliograph coating · Talbot's photogenic drawing paper · Wedgwood and Davy's silver nitrate on leather · P1 The Camera Obscura: An Image Without Chemistry · P1 Wedgwood, Davy and the Problem of Permanence · P1 Experiment: The Image That Would Not Stay

Researches on Light: an examination of all the phenomena connected with the chemical and molecular changes produced by the influence of the solar rays, embracing all the known photographic processes, and new discoveries in the art, 1st editionretrieved 2026-09-05, 2026-09-06, 2026-09-07

Sections: Chapter IX, Nickel, paragraphs 251 to 255 — nitrate of nickel on paper passing into a fine light brown and giving tolerably good negative pictures; nitrate of nickel washed with ammonia, the difficulty of judging the proportion, and the preparation that "darkens quite as readily as the nitrate of silver"; the prismatic spectrum experiment finding the change entirely dependent on the rays of greatest refrangibility; iodide of nickel; nitrate of nickel with ferroprussiate of potash changing from a delicate light blue to a pea green after fifteen to thirty minutes of sunshine; and the closing sentence that many other salts of this metal give similar results; On Metallic Compounds — oxalate of silver exposed in the camera for ten minutes giving an exceedingly faint representation, beside the tartrate, phosphate, carbonate and benzoate; and the later summary that the carbonate, sulphate, acetate, citrate and oxalate of silver all undergo a considerable and tolerably rapid change under the influence of light, with the note that in some proportions the oxalate exhibits a very high degree of susceptibility; Section 75, which reprints Talbot's two solutions and the gallo-nitrate word for word three years after the Royal Society reading, adding that the excited paper "has been found to keep for two or three months" but "is often rendered useless by spontaneous change, in the dark"; section 76, on the discovery of gallic acid's effect on silver iodide as the most valuable of Talbot's contributions; section 77, on the yellow tint of the negative interrupting the rays active in producing chemical change; section 78, the period account of what the gallic acid is doing — that it separates the metallic oxides very readily from the powerful acids, that a mixture of gallic acid and nitrate of silver precipitates almost immediately in weak diffused light while the same solution "will often remain clear for many hours in the dark", that the formation of "the gallate of the oxide of silver" proceeds over the light-struck parts with an energy equal to the intensity of the light that acted on them, that warmth accelerates it, and that some experience is required to check the action at the proper time because the lights begin to darken if it runs on; and section 79, Hunt's own comparison of gallic acid development across silver nitrate, chloride, bromide, tartrate, oxalate, phosphate, carbonate, benzoate, cyanate and ferrocyanate papers; Articles 216, 217, 219, 220, 221 and 222 of the chapter on ammonia-citrate of iron; Articles 211 to 213 of the chapter on ammonia-citrate of iron, Hunt's transcription of the chrysotype and his own one-sentence report of the silver version; Article 217, the mercury cyanotype at one part by weight of the ammonia-citrate to eleven of water; Article 216 of the chapter on ammonia-citrate of iron, pages 140 to 141, restating the process with no strengths and adding that the photographs fade after a few weeks however carefully kept; Article 217, Herschel's separate improvement using corrosive sublimate; Article 220, the ammonia-citrate and protonitrate paper; Article 227, page 147 — oxalate of iron with an excess of oxalic acid, washed with nitrate of silver after exposure, giving a very intense black picture that slowly fades to a dingy grey; and the same two salts combined in the paper before exposure, giving an impression that penetrates quite through the sheet. Article 231, for all the persalts of iron being converted to protosalts by sunshine in combination with organic matter; Introductory chapter, sections 31 and 32, for the same directions printed three years later with "till the bitumen can absorb no more" restored, for the exposures given there as two or three hours from an engraving in bright sun and six or eight hours in the camera, and for Daguerre's substitution of the resin of the essential oil of lavender dissolved in alcohol; Section 75, which reprints Talbot's preparation of the iodized paper word for word three years after the Royal Society reading; section 77, on the yellow tint of the negative offering considerable interruption to the rays active in producing chemical change, and the consequent insistence on keeping the prepared sheet of as pale and uniform a tint as possible; section 78, on gallic acid separating the metallic oxides from the powerful acids and on the gallo-nitrate precipitating in weak light while it keeps in the dark; section 80, on Channing of Boston's simplification of the iodising — 60 grains of crystallized nitrate of silver to the ounce followed by 10 grains of iodide of potassium to the ounce, and a more sensitive paper from five grains of the iodide with five of common salt — with Hunt's judgement that little improvement can be made on those proportions and that a much weaker nitrate may be used on the score of economy; section 81, on Dr Ryan's warning that a sheet left too long in the iodide bath loses its silver iodide, "that salt being soluble in an excess of iodide of potassium", with Hunt's own remark that simply passing the paper through the solution answers every purpose, and on Collen's substitution of ammonio-nitrate of silver; section 82, quoting Talbot's specification on the direct positive made by darkening calotype paper and immersing it in the same 500 grains to the pint iodide solution; and Appendix number V, Improvements in the Calotype Process, which lists the second patent's hot hyposulphite bath for removing the yellow tint, the waxing, the iodo-gallic paper made by washing iodised paper with gallic acid, and the twenty-six parts of saturated gallic acid to one of the silver solution

Used by:Nickel(II) sulfate · Silver(I) oxalate · Talbot's gallo-nitrate of silver · Herschel's 1842 cyanotype · Herschel's argentotype · Herschel's hydrargyro-cyanotype · Nicol's kallitype · Niépce's bitumen heliograph coating · Talbot's calotype iodised paper

Scotophorus pro phosphoro inventus, seu Experimentum curiosum de effectu radiorum solarium, in Acta physico-medica Academiae Caesareae Leopoldino-Carolinae Naturae Curiosorum exhibentia Ephemerides, volume 1retrieved 2026-09-04, 2026-09-06

Sections: Observatio CCXXXIII, "Scotophorus pro phosphoro inventus: seu experimentum curiosum de effectu radiorum solarium", volume 1, from page 528. Read in the Internet Archive optical character recognition of the volume, and every quotation checked against Eder's 1913 reprint, which is legible where the scan is not. In particular: the aqua fortis "admodum mediocri quantitate particularum argenti imbuta, scilicet quantulo opus est ad praeparandam illam, ut separationi auri ab argento fiat idonea"; "Talem aquam fortem adhibui, ut, quod in experimento Balduiniano requiritur, cretam illa imbuerem"; the surface turning "obscure rubentem ad violaceum inclinantem" and the part of the dish the rays did not touch showing that colour "minime"; the "saturatam illam cretae portionem" divided in two; the "spissum illud magma" that had more aqua fortis poured on to make it pour, the excessive effervescence, the chalk beginning to dissolve and the "aquae portionem superfudi" that checked it; the glass darkening "vix aliquot minuta" after being set in the sun, "atro-rubentem et in coeruleum vergentem"; the friends who proposed heat and the glass held to the hearth fire "ut vix manus illum tolerare posset" with no change of colour; the shaking that erased the colour difference and reset the material; the thread drawn from mouth to bottom and left "per aliquot horas", then the horse hair, the human hair and the finest silver thread; the paper stencils with names and whole sentences cut out with a sharp knife and waxed to the glass; the dried saturated chalk that still changed colour promptly; the second glass kept in the dark that "eumdem colorem albentem retinuit"; the two null experiments, fuming spirit of nitre tempered with much water and aqua fortis as sold in the pharmacies, both giving no notable colour change; the deliberate repetition, "argenti portionem aqua forti dissolvo, dissolutum aqua tempero, et cretam, sicut antea, imbuo"; the stronger colour when "particularum argenti major copia" was in the liquor; the variant "cum aqua forti tanta argenti copia imbuto quantum solvere valet" that darkened even where no direct ray fell; the same solution diluted with water and mixed with no chalk darkening in an open glass; the plane mirror and the freshly limewashed house opposite the window; the remark that chalk was used by accident and that another white body would probably serve, with burnt hartshorn and white magnesia named and cerussa actually tried; and the burning glass held a little short of focus for an instantaneous effect; Scotophorus pro phosphoro inventus

Used by:Schulze's scotophorus mixture · P1 Silver Salts and Light: Schulze to Ritter

Sir John Herschel — Photographic Effects, a letter dated Collingwood, August 10, 1842, in The Athenaeum, number 773, page 748retrieved 2026-09-06

Sections: Page 748, the letter dated Collingwood, August 10, 1842, correcting the report of the Royal Society meeting in number 771: "The preparation of the chrysotype paper is as follows: dissolve 100 grains of crystallized ammonio-citrate of iron in 900 grains of water, and wash over with a soft brush, with this solution, any thin, smooth, even-textured paper. Dry it, and it is ready for use." Also the gold developer given only as "so dilute as to be not darker in colour than sherry wine", the fixing by "a weak solution of hydriodate of potash", and the ferrocyanate positive process in equal parts

Used by:Herschel's argentotype

Some Account of the Art of Photogenic Drawing, or the Process by which Natural Objects may be made to delineate themselves without the aid of the Artist's Pencil, in Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London, volume 4retrieved 2026-09-04, 2026-09-05

Sections: The Royal Society's abstract of the paper read 31 January 1839, including Talbot's own note of "the great variety of effects resulting from comparatively small differences in the mode of preparation of the paper"; Abstract of the paper read 31 January 1839, pages 120-121

Used by:Plain salted paper salting solution · P1 Talbot: Photogenic Drawing, the Calotype and the Negative-Positive Principle · Photogenic drawing

The "Camera Notes" Improved Glycerine Process for the Development of Platinum Prints, Camera Notes, Vol. III, No. 4, April 1900, pages 221-226retrieved 2026-09-06

Sections: "The whole article, Camera Notes Vol. III No. 4, April 1900, pages 221 to 226 - the opening paragraphs on what the method had previously been thought to be for, The Process Briefly Outlined, and Notes 1 to 5"

Used by:Glycerol

The Amateur Photographer's Handbookretrieved 2026-09-05

Sections: The developing chapter's Beutler formula - the instruction to add 50 cc of A and 50 cc of B to 500 cc of pure water and to develop slow emulsions for 7 to 10 minutes, and the statements that Beutler invented Neodyn, renamed Neofin, and that Tetenal made Neofin on his recommendations

Used by:Beutler two-solution developer

The British Journal of Photography Annual 1966retrieved 2026-09-05

Sections: Acutance formulae - The Beutler Developer with the same two stocks and a working solution of 1 part A, 1 part B and 10 parts water, the note on the Neofin Technique leaflet, and the remark that Acutol is not a Beutler-type developer

Used by:Beutler two-solution developer

The British Journal of Photography Annual 1972retrieved 2026-09-05, 2026-09-07

Sections: Acutance formulae, for maximum sharpness at some loss of fine grain - The Beutler Developer, its two stocks, the working solution of 1 part A, 1 part B and 8 parts water, and the developing times of 8 to 15 minutes at 68 degrees F and 20 degrees C, together with the note that FX-1 is fundamentally a variant of the Beutler formula; Acutance formulae - The Beutler Developer, printed with a working solution of 1 part A, 1 part B and 8 parts water and developing times of 8 to 15 minutes at 20 degrees C, and the section heading that files the formula under maximum sharpness at some loss of fine grain

Used by:Beutler two-solution developer · P27 Assignment: The Developer Comparison, Measured and Printed

The British Journal Photographic Almanac and Photographer's Daily Companionretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Epitome of progress, page 789: Boric Acid as a Restrainer; page 791: Fixing Baths Acidified with Boric Acid; Dichroic Fog and Developers (Lüppo-Cramer), page 789; Pyrocatechin formulae, page 948; Copper toning; the cupric-bromide bleacher for silver intensification; copper sulphate and potassium bromide bleaching for toning; Glycin, one-solution formulae, page 944; Stand development with Hübl's concentrated glycin solution; Developers for Reproduction (Sturenberg), page 789; Dichroic Fog and Developers (Lüppo-Cramer), page 789; Formulae and the year's abstracts, searched for ascorbate, which does not appear; Orthochromatic Flashlights, pages 750-751 — the abstract of Dr G. Krebs's English Patent No 27,267 of 1904 for non-explosive flashlights intended to make yellow, blue, green and red filters unnecessary, in which copper, zinc, lithium, strontium, barium, soda, calcium, caesium, rubidium, thallium, iridium "or other metals or their salts" are added to a magnesium or aluminium powder so that colours are correctly reproduced on ortho- or panchromatic plates; The wet collodion formulary pages, Fixing Solution, giving cyanide of potassium against water in two columns, the metric column reading 25 to 30 grammes to 1,000 cubic centimetres, printed among the collodion developers and the Eder half-tone collodion; Ferro-prussiate, etc. — Pellet Process, page 983; Formulae and their units: the basis of total bulk, "water to x ounces", the 10 per cent solution dispute, the grains-per-ounce to grammes-per-litre factor, and British weights and measures; Stand development with Hübl's concentrated glycin solution; Developers for Reproduction (Sturenberg), page 789; Dichroic Fog and Developers (Lüppo-Cramer), page 789; Hubl's directions for stand development with concentrated glycin, the bromide addition, and the instruction to add more bromide for over-exposure; Formulae and their units: the basis that the total bulk after solution of the solids is that stated in the formula, and the typographic tell "water to x ounces"; Formulae and their units - the convention that sodium carbonate and sodium sulphite name the crystallised forms unless a qualifying term is added; Formulae and their units - the basis of total bulk after solution of the solids, and the tell "water to x ounces"

Used by:Boric acid · Catechol · Copper(II) sulfate · Glycin · Sodium ascorbate · Thallium(I) sulfate · Cyanide fixing and toning · Pellet's positive-working process · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P8 Restrainers and Antifoggants · Mixing a solution to a final volume · Hydrate substituted for an anhydrous salt at the same mass · Solid added to a litre rather than made up to a litre

The Chemistry of Light and Photography (International Scientific Series)retrieved 2026-09-04, 2026-09-06

Sections: The salts of uranium — reduction of the nitrate by light in the presence of organic bodies; The opening chapter on the development of photo-chemical knowledge, for Vogel's account of bitumen of Judea as soluble in ethereal oils, of the film that does not darken but loses its solubility, and of the etching that follows on copper; The uranium printing processes — nitrate of uranium reduced by light to a sub-nitrate in the presence of organic bodies such as a paper support, giving an image so faint as to be scarcely perceptible, then made visible by plunging the sheet into a silver or gold solution where the reduced uranium precipitates the metal as a brown or violet powder; and the verdict that uranium is too rare and too dear to be employed generally in photography; Nitrate of uranium reduced by light in the presence of organic bodies; the verdict that uranium is too rare and too dear to be employed generally in photography; Nitrate of uranium reduced by light to a sub-nitrate in the presence of organic bodies; the faint image made visible in a silver or gold solution; the verdict that uranium is too rare and too dear to be employed generally in photography

Used by:Uranyl nitrate hexahydrate · Niépce's bitumen heliograph coating · P26 Uranium, Mercury and the Heavy-Metal Treatments · Uranium toned print · Uranotype and Wothlytype

The Collected Works of Sir Humphry Davy, Bart., Volume II: Early Miscellaneous Papers, from 1799 to 1805retrieved 2026-09-06

Sections: Paper XXII, pages 240 to 245: "An account of a method of copying paintings upon glass, and of making profiles by the agency of light upon the nitrate of silver. Invented by T. Wedgewood, Esq. With observations by H. Davy", reprinted from the Journals of the Royal Institution, volume I. In particular the one quantity the paper contains — "With regard to the preparation of the solution, I have found the best proportions those of one part of nitrate to about ten of water. In this case, the quantity of the salt applied to the leather or paper will be sufficient to enable it to become tinged, without affecting its composition or injuring its texture" — and the whole of the observed behaviour: no change in the dark; grey through brown to nearly black in daylight; two or three minutes in the direct beams of the sun for the full effect and several hours in the shade; red glass with very little action, yellow and green more efficacious, blue and violet the most decided and powerful; the solution applied on leather being more readily acted upon than on paper; the colour, once produced, not removable by water or by water and soap; the copy to be kept in an obscure place, examined in the shade for a few minutes only, and not sensibly affected by candles or lamps; the failure of thin varnish and of repeated washings; the woody fibres of leaves and the wings of insects received on prepared leather; prints copied by transmitted sunlight giving lights "seldom so definite as to form a distinct resemblance"; the camera obscura images "too faint to produce in any moderate time an effect upon the nitrate of silver"; Davy's own solar-microscope result with the paper placed at a small distance from the lens; the comparison in which the muriate was "the most susceptible" and both salts more readily acted upon moist than dry; the two routes to a muriate sheet, by diffusing it through water or by immersing paper moistened with the nitrate solution in very diluted muriatic acid; the warning that these salts stain the skin and the instruction to apply them with a pencil of hair or a brush; Davy's inference that a portion of the metallic oxyde abandons its acid to unite with the animal or vegetable substance in an insoluble compound, and his hope that some substance might be found to destroy it; and the closing sentence that nothing but a method of preventing the unshaded parts from being coloured is wanting to render the process as useful as it is elegant

Used by:Wedgwood and Davy's silver nitrate on leather

The Collodion Process on Glass, second edition, enlargedretrieved 2026-09-04, 2026-09-06

Sections: The solubility of pyroxylin in sulphuric ether, and the finding that gun-cotton is not soluble in pure ether free from alcohol; Chemicals: Proto-sulphate of iron; On the whitening of collodion pictures as positives, and subsequent blackening for negatives; Gun-cotton — the action of nitric acid on cotton fibre, the nascent state, and the ventilation the operation requires; The distinction between pyroxylin and xyloidin, and the discovery that gun-cotton is not soluble in ether free from alcohol; Gun-cotton — the preparation of pyroxylin from nitric and sulphuric acids; Fixing Liquids, pages 38 and 39 — cyanide of potassium possessing great power over the iodide of silver but with the one great defect that unless used with great caution it would dissolve the deposited image as well, the instruction that it should be used very weak and not left on the plate one moment longer than is necessary, the remark that pictures fixed with cyanide of potassium have a slightly whiter tone, the statement that the difference between hyposulphite of soda and cyanide of potassium in dissolving the image is only one of degree, and the fixing solution of cyanide of potassium 4 grains to water 1 ounce given as the greatest strength that should be used; Chemicals, page 89, Cyanide of Potassium, for its preparation from ferrocyanide of potassium at a strong red heat, and for the statement that it is a very poisonous salt which should be carefully handled and that in contact with a moist atmosphere it is slightly decomposed and smells of prussic acid; The preparation of cyanide of potassium by exposing dried ferrocyanide of potassium to a strong red heat in an iron vessel, and the statement that cyanide of potassium is a very poisonous salt which should be carefully handled, and that when left in contact with a moist atmosphere it is slightly decomposed and smells of prussic acid; Preparation of the Glass with Collodion, for the pour from the corner, the draining back into the bottle with the plate moved vertically to prevent the furrowed appearance, the statement that this requires a steady hand and some little practice, the five to twenty seconds that may elapse before immersion in the exciting bath, and the warning that if the drying is prolonged the sensibility and evenness of the coating are injured and the iodide of silver is liable to be thrown out from the film on to its surface, with the hot-weather case in which the plate must be immersed directly the film has set. Iodized Collodion, for the over-iodised film in which the image is formed on a layer of iodide of silver outside the collodion so that when the iodide is cleared off the picture goes with it, and the statement that the same thing happens when the film is put into the bath too dry. Development of the Latent Image, for Archer's own account of development as a continuation of the action of light reducing the iodide of silver to the metallic state; for the instruction that a decomposed developer may be poured off and a fresh supply with two or three drops of nitrate of silver solution added poured on to bring out the faint parts; for the plate having become too dry from long exposure in the camera as a cause of the developer not flowing; and for the exciting bath acquiring from constant use a large quantity of alcohol thrown out from the film, with the remedy of boiling the nitrate of silver solution to drive off the alcohol and making the volume up again with water. On the Whitening of Collodion Pictures as Positives and subsequent Blackening for Negatives, for the acid solution of corrosive sublimate described as a very corrosive compound that would destroy the remaining tenacity of a weak collodion, and for the blackening afterwards with hyposulphite of soda or, more rapidly and with more care needed, with cyanide of potassium. On the Varnishing of Collodion Pictures, for the statement that a collodion picture, positive or negative, requires varnishing to protect it from injury, that white lac varnish is the best, that the plate must be gently warmed before pouring and again after draining, and that the best backing for positives on glass is cotton velvet rather than black varnish, which is apt to penetrate and reduce the picture several tones, or paper, which is seldom of sufficient depth; The solubility of gun-cotton in ether and alcohol; the process on glass

Used by:Diethyl ether · Iron(II) sulfate, anhydrous · Iron(II) sulfate heptahydrate · Mercury(II) chloride · Nitric acid · Nitrocellulose · Sulfuric acid · Cyanide fixing and toning · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · Wet-plate collodion negative

The Darkroom Cookbook, 2nd editionretrieved 2026-09-05

Sections: Formula 53, "Gordon Hutchings' PMK Formula" — the opening sentence, Solution B in both unit columns, the mixing direction and its worked example, the note on the temperature range and on the variant Hutchings calls PMK+, and the remark on the hydrate of Kodalk

Used by:PMK pyro

The Dictionary of Photography and Reference Book for Amateur and Professional Photographers, 9th editionretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Amidol; Development and Developers — the four essential ingredients of a developer; Ammonium Chloride; Ammonium Citrate — the two formulas, the deliquescence, and the British Pharmacopoeia preparation; Ammonium Citrate, for the two formulas the entry prints, the deliquescence, the British Pharmacopoeia neutralisation and the stated uses. Cited for what the entry does not contain; Ammonium Bichromate; Gum-Bichromate Process; Bichromate Methods; Iron, Ammonio-Citrate of; Iron, Ammonio-Oxalate of (Ferric); Reduction of Density — The Persulphate Reducer: the persulphate of ammonium reducer described as most even in its action and as rather attacking the dense than the light portions; one part dissolved in twenty to fifty parts of water; a drop of sulphuric acid per 2 ozs. making the action more regular; stopping the action in a 5 per cent solution of sodium sulphite; and H. W. Bennett's keeping stock solution; Ammonium Sulphocyanide — its use in toning gelatino-chloride printing-out papers, its recommendation as a fixing agent, its deliquescence and its solubility in alcohol; Sulphocyanates or Sulphocyanides; Cyanides; Sodium Hyposulphite — solubility of the crystals, quoted for comparison; Arrowroot — the starch obtained from the tubers of Maranta arundinacea, a fine white tasteless odourless powder with a particular crepitating feel in bulk, used for sizing papers, as the vehicle for sensitive iron salts in printing papers and in a paste for mounting photographs; Plain (Salted) Papers, on the colloid in the salting solution preventing the silver solution from sinking too deeply into the paper, on arrowroot being the best and easiest size to use, and on brushes that must not be bound with metal; Kallitype, for the arrowroot sizing solution and the instruction that fresh paste be made for each batch because it will not keep; Platinum Process, on a gelatine size tending to a bluish black tone and arrowroot or starch to a brownish tinge; Development and Developers — the list of developing agents with their factors and temperature coefficients, searched for ascorbate, which does not appear; Borax; Development and Developers — the table of Watkins factors; Simultaneous Development and Fixing; Development and Developers — Adurol, the concentrated one-solution and two-solution formulas; Bromide Paper — clean-working developers and warm tones; Alum — Chrome Alum; Alcohol; Alcohol, Methylated; Drying Negatives and Prints rapidly with Spirit; Drying by Alcohol; Iron, Oxalate (Ferric); Iron, Oxalate of (Ferrous); Formalin; Aldehyde; Antipyr; Formic Aldehyde; Films, Hardening; Gallic Acid; Pyrogallic Acid; Development and Developers — chemical development defined against the depositing of silver from solution; Antiseptics; Formalin; "Glycerine, for the identity, specific gravity, hygroscopicity, the non-drying property, the use as a preservative of pyro and the suggestion of a physical restrainer; Platinum Process, the passages headed Mercury and Brush Development of Platinum Prints"; Development and Developers — Watkins factors, temperature coefficients, dilution and time, stand or tank developers; Glycin; Alpha papers; Hypo Eliminators — plain water as the best eliminator, and the oxidising agents proposed instead; Hydroquinone; Development and Developers — temperature coefficient and Watkins's table; Iron, Sulphate of; Iron, Sulphate of; Iron, Ammonio-Sulphate of; Development and Developers — Ferrous Oxalate; Iron, Perchloride of; Photo-Mechanical Processes — etching a copper plate; Iron, Perchloride of; Kaolin — the synonym china clay, the description as a very fine hydrous silicate of alumina containing about 14 per cent of water, a decomposition product from the natural decay of felspar, and the statement that it was used in the wet process as a purifier of the silver bath; "Lead, Acetate of", for the trihydrate formula and molecular weight, the synonyms Plumbic Acetate and Sugar of Lead, the preparation from litharge and excess acetic acid, the white massed crystals, intensely sweet taste and faint acetic smell, the use in combined toning and fixing baths, the doubted use as a hypo eliminator and the solubility figures; "Lead, Toning with", for the proposed bath for albumenised and gelatino-chloride papers and the statement that the toning action is due to the formation of sulphide of lead; the Toning article, for the combined bath and the explanation that the lead renders inert the sulphuretted hydrogen formed by the action of citric acid on the hypo; the solubility table entry for lead acetate; Lithium Chloride — the formula LiCl,2H2O = 78.5, the deliquescence, the solubility in cold and hot water and in alcohol and ether, and the use in collodio-chloride paper; Lithium; Lithium Bromide; Metol; Development and Developers — temperature coefficient; Skin, Effects of Chemicals on — metol poisoning; The table of elements and atomic weights, giving Nickel, Ni, 59; Skin, Effects of Chemicals on — metol poisoning; Alum; Potash Alum; Aluminium Sulphate; Potassium Bromide; Potassium Carbonate; Pearlash; Development and Developers — the Watkins factor with potassium carbonate; Development and Developers — Citrate of Potash Restrainer, 1 oz. of potassium citrate in 10 ozs. of water, and the account of what the citrate, bromide and carbonate restrainers have in common; Toning Bromide Prints — Copper Toning, the two solutions each carrying 120 grains of neutral potassium citrate in 10 ozs.; Platinotype — Inston's formula for brown tones, whose B solution carries potassium citrate with citric acid and mercuric chloride; Bichromate of Potash; Bichromate Methods; Carbon Processes; Skin, Effects of Chemicals on; Potassium Ferricyanide; Reduction of Density — Howard Farmer's Reducer; Toning — sulphide toning bleach; Potassium Ferrocyanide; Potassium Ferricyanide; Potassium Ferrocyanide; Potassium Hydrate; Potassium Iodide; Potassium Metabisulphite; Potassium Oxalate; Potassium Oxalate; Development and Developers — Ferrous Oxalate; Potassium Permanganate — the preparation by fusing potash hydrate and chlorate with black oxide of manganese, the formula as the period wrote it, the solubility of 6.3 per cent in cold water and decomposition by alcohol; Reduction of Density — Permanganate Reducer, the spontaneous decomposition of the acidified bath, the alum substitution, the manganic oxide precipitate and the bisulphite clearing bath; Anthion — persulphate of potassium, its preparation by electrolysis and its sale as a hyposulphite eliminator; Sulphocyanates or Sulphocyanides — the naming dispute and the statement that they are used as solvents of the silver haloid salts and in compounding toning solutions; Cyanides — the caution on double cyanides; Silver — extraction, purification, conductivity, malleability, the emerald-green leaf, the action of ozone and of sulphurous vapours; Caustic; Table of atomic weights (silver, 108); Silver Oxide, for the formula, the preparation with any caustic alkali except ammonia, the brownish black precipitate, the surviving uses and the impossibility of making it by heating silver in oxygen; Silver Nitrate, for ammonio-nitrate of silver prepared by dissolving silver oxide in a solution of ammonium nitrate; Development and Developers — the list of developing agents, searched for ascorbate, which does not appear; Carbonates; Sodium Bicarbonate; Potassium Carbonate; Sodium Bisulphite; Carbonates; Sodium Carbonate; Sodium Carbonate - washing soda, sal soda and soda crystals; the indefinite strength of the commercial article and its sulfate content; Sodium Chloride; Sodium Hydrate; Sodium Sulphide; Toning — sulphide toning, two important factors, failures in sulphide toning; Sodium Sulphite; Sulphocyanates or Sulphocyanides — the alkali thiocyanates as solvents of the silver haloid salts; Cyanides — the caution on double cyanides; Sodium Hyposulphite; Tannic Acid; Gelatine — the substances that render it insoluble, and the antiseptics; Spectroscope, for setting a prism at the position of minimum deviation "for a line of medium wave-length, such as the green thallium line"; and the table of elements and atomic weights, giving Thallium, Tl, 204; Thiocarbamide; Thiosinamine; Gelatine — putrefaction in the presence of water, and the substances that act as antiseptics; Albumenised Paper — the entry's own albumen and salting formula of albumen 6 ounces, chloride of ammonium or sodium 60 grains, rectified spirit 96 minims and distilled water 14 drachms, the yield of about 7 drachms of albumen per fair-sized egg, the eighty-second float on the albumen and the warning that longer sinks the albumen into the body of the paper, the double albumenising by coagulating the first layer on two volumes of alcohol to one of water, and the sensitising of the albumenised paper by floating it face downwards on a solution of silver nitrate containing about 60 grains to the ounce, three or four minutes being sufficient; Albumenised Paper — the note that absolutely fresh eggs are generally recommended but that many professional albumenisers prefer stale eggs as giving a more even and lustrous coating, the direction to crack each egg into a separate vessel before mixing with the bulk and to take out the germ, the yield of about 7 drachms of albumen from every fair-sized egg, the formula of albumen 6 ounces with chloride of ammonium or sodium 60 grains, rectified spirit 96 minims and distilled water 14 drachms, the direction to dissolve the salt in the spirit and water, add to the albumen and beat with an egg-whisk for fifteen minutes, allow to settle and filter through a tuft of well-washed cotton wool, and the double albumenised paper made by coagulating the first layer on a mixture of two volumes of alcohol and one of water before floating again; Albumenised Paper — the definition as sensitised paper prepared with albumen and salt, the note that absolutely fresh eggs are generally recommended but that many professional albumenisers prefer stale eggs as giving a more even and lustrous coating, the direction to crack each egg into a separate vessel before mixing with the bulk and to take out the germ, the yield of about 7 drachms of albumen from every fair-sized egg, the formula of albumen 6 ounces, chloride of ammonium or sodium 60 grains, rectified spirit 96 minims and distilled water 14 drachms, the direction to dissolve the salt in the spirit and water, add to the albumen and beat with an egg-whisk for fifteen minutes, allow to settle and filter through a tuft of well-washed cotton-wool, the statement that this quantity is sufficient for a quire, the recommendation of Saxe or Rive paper, the bowed sheet lowered from the middle, the puckers that reveal bubbles and the camel's-hair brush used to wet them, the float of eighty seconds and not longer or the albumen will sink into the body of the paper, the drying from two corners and the rolling between smooth rollers, the double albumenised paper made by coagulating the first layer on a mixture of two volumes of alcohol and one of water before floating again on the salted albumen, and the sensitising by floating face downwards for three or four minutes on a silver nitrate solution of about 60 grains to the ounce; Matt Albumen Paper — the statement that it gives results intermediate between albumenised and plain salted paper, Hübl's salting and sizing solution of white of egg 1 ounce, arrowroot solution 1 ounce and salt 30 grains, the whipping of the albumen to a froth and its standing for twenty-four hours to clear, the mixing of the two solutions when the arrowroot has cooled to 90 °F, the brushing on, and the sensitiser of either plain silver nitrate or the citric acid formula at half the citric acid; Alcohol — the synonymy of rectified spirit, ethylic alcohol and spirits of wine; Ammonium Citrate — the two formulas printed under one heading, NH4H2C6H5O7 and (NH4)2HC6H5O7; the statement that the salt "is usually met with in the form of solution, the salt itself being so deliquescent that it is an extremely difficult matter to keep it"; and the British Pharmacopoeia preparation, 12 parts of citric acid neutralised with 11 parts of strong ammonia solution; Kallitype, page 441 — the attribution to Nicol, the statement of the mechanism, and Developing Formulas Nos. 1 to 4 with their tones, of which No. 1 for pure black and No. 4 for purple are the two borax baths; the paragraph beneath them, for the ten to fifteen minutes and for the iron salts as a most prolific cause of failure. Borax, for the 6 per cent cold and 200 per cent hot solubilities. Quantities read from the page image of the Internet Archive scan rather than from its OCR; Alum — Chrome Alum: its use for hardening gelatine, for example in the preparation of emulsions for dry plates to prevent frilling; the deep purple crystals whose solution is purple by reflected and reddish by transmitted light; solubility of 1 part in 10 of cold water and insolubility in alcohol; Albumenised Paper — the second published account of the procedure: "Double albumenised paper is made by coagulating the first layer of albumen by floating on a mixture of two volumes alcohol and one volume of water. The paper is now dried and again floated on the salted albumen." With it, from the same entry, the formula of albumen 6 ounces, chloride of ammonium or sodium 60 grains, rectified spirit 96 minims and distilled water 14 drachms, the yield of about 7 drachms of albumen from every fair-sized egg, the float of eighty seconds and the warning that a longer one lets the albumen sink into the body of the paper, the rolling between smooth rollers when thoroughly dry, the sensitising bath of about 60 grains of silver nitrate to the ounce with three or four minutes' float, and the preference of many professional albumenisers for stale eggs as giving a more even and lustrous coating; the entry Alcohol — that the term used without qualification means common or ethylic alcohol, that rectified spirit on the old standard contains 16 per cent of water at specific gravity 0.838 and on the new British Pharmacopoeia standard 10 per cent of water at 0.834, and that proof spirit is five parts of rectified spirit diluted with three of water; the entry Alcohol, Methylated — the 10 per cent of crude wood spirit and, after the 1891 regulation, the fraction of a per cent of petroleum which separates on the addition of water and renders the liquid milky or turbid, partially unfitting it for photographic use; and the entry Ammonium Chloride — NH4Cl = 53.5, its principal use for salting albumenised paper and for preparing chloride emulsion, and its solubility as 1 in 3 of cold water and 1 in 55 of alcohol; Development and Developers, for the definition of physical development against chemical development — the wet plate covered with adherent silver nitrate solution, the nascent silver deposited on the light-affected places, the statement that "at present there is no proof that the sensitive salt is itself reduced", and the remark that the precipitation of silver from a reducing agent and silver nitrate is "delayed by the presence of organic acid such as acetic or citric"; and Gallic Acid, for the formula HC7H5O5 = 170, the solubility of 1 per cent in cold water and 33 per cent in boiling, the preparation by fermentation from powdered galls, and the use in the collodion and waxed-paper processes; Kallitype, for the attribution to Nicol, the statement of the principle, the arrowroot sizing, the appearance of the printed-out image as a faint brown image on a yellow ground, and the four developers giving black, sepia, warm maroon and purple; Sodium Hyposulphite, giving Na2S2O3.5H2O = 248, describing the commercial salt as large watery crystals which should be entirely free from acid or any yellow tinge, and giving the solubility as 1 in 2 of cold water, 1 in 1 of boiling water and insoluble in alcohol; Sulphocyanates or Sulphocyanides — the alkali thiocyanates as solvents of the silver haloid salts, also used in compounding toning solutions; Toning, Sulphide Toning (brown and sepia): the process as turning the metallic silver image into silver bromide and then into silver sulphide; the instruction to keep the bleaching bath in a yellow bottle or in the dark; the advice to make the sulphide up as a strong stock as soon as it is bought; Two important Factors in Sulphide Toning, on avoiding greenish-brown crystals and on toning a print that has been dried after fixing and washing; Failures in Sulphide Toning, on the deterioration of dissolved sodium sulphide into hypo and the three stages of failure; and the clean-up instruction to flood the measures, dishes and sink with plenty of water; Reduction of Negatives, Howard Farmer's Reducer: the bath suggested by Howard Farmer in 1883, more ferricyanide giving a stronger and quicker action, and a little ferricyanide letting the action proceed slowly without the gradation suffering while larger quantities eat away the shadows and increase the contrasts; Reduction of Negatives, Howard Farmer's Reducer, on the bath having been suggested by Howard Farmer in 1883, on more ferricyanide giving a stronger and quicker action, and on a little ferricyanide letting the action proceed slowly without the gradation suffering while larger quantities eat away the shadows and increase the contrasts; Reduction of Negatives, Howard Farmer's Reducer: more ferricyanide giving a stronger and quicker action, and a little ferricyanide letting the action proceed slowly without the gradation suffering; Toning, Failures in Sulphide Toning: the deterioration of dissolved sodium sulphide into hypo and the three stages by which a sulphide bath fails; Platinum Process — Sepia or Hot-bath Platinum Papers, and Sepia Tones on Black Platinum Paper by the Addition of Mercury, pages 571 to 573: the greater daylight sensitivity of sepia paper, the recommended developer of 10 parts normal oxalate to 1 part saturated oxalic acid at 150 to 160 F, the alternative hot-bath developer of potassium oxalate, potassium phosphate, citric acid and potassium chloride, the five or six seconds' float, the rule that a dish used for sepia is never used again for black, the table of paper, developer, temperature and colour, the account of haphazard mercury additions producing double tones with pink high values, the explanation that the oxalate acts faster than the mercury, the glycerine remedy, solution A of cold-bath developer and glycerine in equal parts, solution B of 10 per cent mercuric chloride in alcohol and the reason it is made in alcohol, the six working proportions from 40 + 1 to 20 + 4 and the colours they give, the brush and rag application, the scum, the lightening of prints from the stronger mixtures in the acid clearing bath and its remedy, the 60 F floor and the verdict that prints so made can be regarded as reasonably permanent. Page numbers read from the running heads of the Internet Archive scan; Thiocarbamide — Bogisch's proposal of thiourea as a fixing agent for silver chloride and its use in clearing baths; Toning, Failures in Sulphide Toning; Kallitype, pages 440 and 441 — the attribution to "Mr. W. W. Nicol", the statement of the principle, the Bermuda arrowroot sizing at 180 grains to 20 ounces, the sensitiser of ferric oxalate 75 grains, oxalic acid 5 grains, silver nitrate 30 grains and distilled water 1 ounce with the instruction to dissolve at about 110 °F, filter and then add the silver, the faint brown image on a yellow ground, the four developing formulas with their tones, the ten to fifteen minutes of development, the iron salts as "a most prolific cause of failure", and the ammoniacal hypo fixing bath with its ten minutes and half-hour wash. Quantities read from the page image rather than from the OCR; Cyanotype — Positive Cyanotype, or Pellet's Process, pages 212 to 213; Platinum Process, Clearing and Washing, page 570 — the instruction that developed prints "must be washed in a series of baths (not less than three) of a weak solution of hydrochloric acid. This solution is made by mixing one part of hydrochloric acid with 60 parts of water", that "the specific gravity of the acid should be not less than 1.16; if lower, more acid should be used", that "the acid should be colourless" and that "on no account should commercial hydrochloric or muriatic acid be used"; the alternative that "citric acid, in the proportion of 1 oz. to 20 ozs. of water, may be used. This softens the paper in less degree than does the hydrochloric acid"; the working test that "a white opalescence of the bath shows necessity for more acid"; the after-washing, "Platinotype papers do not require a long after-washing; three or four changes for ten or fifteen minutes are ample", with drying by suspension in preference to blotters; and, on page 571, the instruction that "black and sepia prints should never be cleared and washed together in the same dish". Also, on page 569, the note that development can be arrested by plunging the print into the acid bath directly the right depth is attained, with the warning that the result is inferior to a normal exposure and development and tends to granularity; Kallitype, page 441 — the attribution to Nicol, the statement of the mechanism, and Developing Formulas Nos. 1 to 4 with their tones; the paragraph beneath them, for the ten to fifteen minutes, for the iron salts as a most prolific cause of failure, for the assurance that prolonged immersion will not over-develop, and for the face-down immersion of a large sheet. Quantities read from the page image of the Internet Archive scan rather than from its OCR; Development and Developers - Paramidophenol, the concentrated one-solution and two-solution formulas and the note that the developer is stainless and keeps well in concentrated solution; Development and Developers - Rodinal, the dilutions for normal, under- and over-exposure; Rodinal, page 624, the composition the solution sold under that name "is said to be" compounded to; Kallitype, for the four developers of 1912, for the ten to fifteen minutes in the developer "in order to ensure that the iron salts shall be all dissolved", for the statement that the presence of the iron salts is a most prolific cause of failure, and for the face-down immersion of a large sheet; Platinum Process, pages 568 to 573 — the cold-bath developers A, B and C, the normal-strength oxalate stock of one pound in 54 ounces of water diluted one part to two, the saturated oxalic acid addition of 1 part in 20, the alternative oxalate and potassium phosphate bath, the thirty seconds at 60 F, the statement that over-development is impossible with correct exposure, the instruction to develop harsh negatives at 140 F, the bichromate addition of one grain and in no case more than two per 20 ounces, the sepia hot-bath developer of 10 parts normal oxalate to 1 part saturated oxalic acid at 150 to 160 F, the second sepia developer carrying phosphate, citric acid and potassium chloride, the developer-and-temperature table of image colours, and the mercuric chloride and glycerine sepia developers. Potassium Oxalate, for the solubility of 1 part in 3 of water. Quantities read from the page images of the Internet Archive scan; the colour table and the size of the D salts tube are legible only in part and are reported as such; Actinic; Camera; Weighing and Measuring: apothecaries, avoirdupois and fluid measure; metric equivalents; Weighing and Measuring: British weights and measures; metric equivalents in imperial units; Alpha Paper; Gaslight Paper; Blacking: the interior of all cameras, dark slides and lens tubes should be coated with a dead black to prevent the reflection of light and consequent fog on the plate; Pinhole Photography: any rectangular box which is absolutely light-tight; Pinhole Photography: the instruction that the edges of the pinhole should be quite clean and free from burr, and the rule that a prolonged exposure of about twenty or thirty times the ordinary one is required; Pinhole Photography: the description of the plain box camera, the statement that the larger the plate the wider the angle and the greater the distance the larger the image, and the instruction that the edges of the pinhole should be clean and free from burr; Blacking: the interior of all cameras, dark slides and lens tubes should be coated with a dead black to prevent the reflection of light and consequent fog on the plate; Pinhole Photography: any rectangular box which is absolutely light-tight, a very thin plate of metal, edges free from burr, and Alfred Watkins' table of needle sizes against plate distance; Pinhole Photography: a prolonged exposure is required, about twenty or thirty times the ordinary one for any given subject; Alfred Watkins' table of needle sizes, plate distances and the resulting ratios; Pinhole Photography: the instruction that the edges of the pinhole should be quite clean and free from burr; the statement that a prolonged exposure of about twenty or thirty times the ordinary one is required; and Alfred Watkins' table of needle sizes, plate distances and the resulting ratios; Pinhole Photography: the plain box camera, and the note that the larger the plate the wider the angle and the greater the distance the larger the image; Head-Rest: an apparatus for maintaining an exact position and steadiness of a sitter during exposure, and the note that its use has been abused "to such an extent as to become an absolute instrument of torture"; Aberration: the image formed by a pinhole is free from all the aberrations of a lens, and the astigmatism pinhole workers introduce by using a slot instead of a round hole; Glycin; Development and Developers — Watkins factors, temperature coefficients, dilution and time, stand or tank developers; Pyrocatechin; Metol; Hydroquinone; Development and Developers, the temperature coefficients of Watkins; Skin, Effects of Chemicals on; Development and Developers: the table of Watkins factors, including metol 30, metol-hydroquinone 14, glycin with sodium carbonate 8 and hydroquinone with bromide 5; Dichroic Fog — the plate seen by transmitted light appears tinted red or violet and by reflected light greenish or yellowish, hence the term; the plate looks foggy and suggests that it has not been properly fixed, but prolonged immersion in hypo solution does not mend matters; Lumiere and Seyewetz concluded that it is due to the presence of silver and may be caused by faulty development or fixing, its formation favoured by a solvent of silver bromide in the developer and by the presence in the fixing bath of developer containing sulphite or alkaline carbonate, hence the desirability of washing the plate between developing and fixing; three methods of treatment, of which the first, ammonium persulphate acidulated with sulphuric acid followed by a sulphite bath, is described as of special value when the fog has been formed in the fixing bath; Blacking - the interior of all cameras, dark slides and lens tubes should be coated with a dead black to prevent the reflection of light and consequent fog on the plate; Vignetting, which defines it as shading off the margins of a picture so that the subject gradually fades away, gives the methods as shaped openings in non-actinic glass, graduated thicknesses of tissue paper with serrated edges, bevelled wooden covers and, preferred, sheet lead or tinfoil with the opening cut and its edges slightly turned up or serrated so as to soften the outline, and states that the farther the vignetting shape is placed from the negative the larger the vignette and the softer the outline, and that a card or metal plate used in front of the lens is gently moved backwards and forwards an inch or two during exposure; Enlarging, which for combination printing says that to prevent too sharp a line of demarcation the mask, or a sheet of cardboard cut roughly to shape, may be gently moved up and down near the sensitive surface to shade the landscape into the sky; and Dodging Negatives, which in 1912 uses the word dodging for local intensification and reduction of the negative rather than for anything done at the printing stage; Glazing Prints - prints with a gelatine surface may be given a high glaze by squeegeeing on to prepared glass or ferrotype plates, the latter consisting of thin enamelled iron needing only careful cleaning and polishing, with French chalk, a spermaceti wax solution or paraffin named as release preparations; the method of floating the print face downwards over the glass in the water in which the prints are soaking so that air-bells between print and glass are avoided; the blotting paper, stout paper and flat squeegee passed from centre to margins; and the statement that drying must not be unduly hurried because one effect of too rapid drying is that the print dries round the edges, which peel off the glass while the centre is still damp, so that the print comes away showing a kind of oystershell mark; Mounting, Preparing the Print for Mounting - the print should first be straightened out quite flat and carefully trimmed, and creases and the tendency to curl are most easily removed by holding the dry print face downwards on a wad of clean blotting-paper on a firm, smooth table and drawing it steadily out from under the firm edge of a straight-edged wooden ruler, the stroking movement repeated once or twice from end to end and across the print; Dry Mounting - the method consists of thin sheets of tissue paper saturated with a solution of shellac, a sheet of which is tacked to the back of the print by touching it here and there with a hot iron or the back of a metal spoon heated to about 180 to 200 degrees F, the print and adherent tissue then being trimmed, laid down on the mount and placed under pressure in a dry mounting press in which metal slabs are heated to about 200 degrees F, the attraction being that it permits prints to be mounted perfectly flat on any kind of support, with the note that an ordinary flat-iron can be used but is not a satisfactory substitute; and Bromide Pencils, special pencils for retouching, spotting out and working up bromide prints and enlargements; Toning, Failures in Sulphide Toning - the deterioration of dissolved sodium sulphide into hypo and the three stages by which a sulphide bath fails, the first sign being a yellow-brown image, the next an apparent failure to act at all, and the last that the bleached image gradually disappears because the bath has become a fixing bath; Toning — Iron (blue tones), the two ferric toning baths given for bromide prints, the first compounded from 10 per cent solutions of ammonia alum, potassium ferricyanide, potassium oxalate and ammonia iron alum with hydrochloric acid, and the second reading 10 per cent solution of ferric ammonium citrate 2 ozs., 10 per cent solution of potassium ferricyanide 2 ozs. and 10 per cent solution of acetic acid 20 ozs., in which the well-washed prints are immersed until the desired tone is given and then washed until the high-lights are clear, with the statement that this bath intensifies the image; Gold Toning (blue-black or red), that a gold and sulphocyanide bath similar to that used for P.O.P. applied to a black-and-white bromide print will change the colour to a fine blue-black, and that applying a similar bath to a bromide print already toned brown in the sulphide toner will change the colour through a series of warm browns to red chalk, the print being placed in the bath dry; and Platinum Toning (sepia and black), the bromide-print formula of potassium chloroplatinite, mercuric chloride, citric acid and distilled water, in which a slight increase in the mercuric chloride renders the tone warmer and reducing it gives colder tones; Potassium Sulphide, whose synonyms are given as liver of sulphur, sulphuretted potash and potassium trisulphide, made by heating together sulphur and carbonate of potash, the resulting mass poured on slabs and broken up, and stated to be of variable composition; and Toning, Failures in Sulphide Toning, on the deterioration of dissolved sodium sulphide into hypo and the three stages by which a sulphide bath fails; Fixing - that the usual method is the solvent action of hyposulphite or thiosulphate of sodium, that cyanide of potassium, sulphocyanide of potassium or ammonium and sulphite of sodium have also been recommended, and that cyanide of potassium is more powerful than hypo but its action on the image is so great as to deteriorate the half-tones occasionally. Cyanides - that the cyanide of potassium is the most important and highly poisonous, and that double cyanides like the sulphocyanides and ferrocyanides, although apparently not actually poisonous themselves, should be regarded with extreme caution as simple cyanides may be very readily produced from them under unexpected conditions. Cyanogen soap - a soap containing potassium cyanide, sold for removing silver stains from the hands. Platinum Toning (sepia and black), the bromide-print formula of potassium chloroplatinite, mercuric chloride, citric acid and distilled water, in which a slight increase in the mercuric chloride renders the tone warmer and reducing it gives colder tones; Kallitype — the attribution to Nicol, the appearance of the printed-out image as a faint brown image on a yellow ground, and the four developers giving black, sepia, warm maroon and purple; Cyanides — that cyanide of potassium is the most important and highly poisonous, and that double cyanides such as the sulphocyanides and ferrocyanides, although apparently not actually poisonous themselves, should be regarded with extreme caution as simple cyanides may be very readily produced from them under unexpected conditions. Cyanogen soap — a soap containing potassium cyanide, sold for removing silver stains from the hands. Fixing — that cyanide of potassium is more powerful than hypo but its action on the image is so great as to deteriorate the half-tones occasionally; Bichromate Methods, for the reach of the family in 1912 across gum, carbon, photogravure, collotype, oil and bromoil and most photographic block and plate making; Carbon Processes; and Skin, Effects of Chemicals on, for bichromate poisoning through soaking the hands as in the carbon process and the aggravation where there are cuts; Uranium Nitrate — its preparation from pitchblende, its description as a brilliant yellowish-green deliquescent crystalline salt, and the statement that it is decomposed by light when in contact with organic matter into a uranous nitrate. Uranium Chloride — that it has been used for toning and as a sensitive salt for a platino-uranotype process. Uranium Printing — that the colours obtained by the use of uranium salts are decidedly pleasing, tending to a terra-cotta or copper colour which may be varied at will; Dichroic Fog — the plate seen by transmitted light appears tinted red or violet and by reflected light greenish or yellowish, the plate looks foggy and suggests that it has not been properly fixed, but prolonged immersion in hypo solution does not mend matters; and the conclusion of Lumiere and Seyewetz that it is due to the presence of silver, its formation favoured by a solvent of silver bromide in the developer and by the presence of developer in the fixing bath, hence the desirability of washing the plate between developing and fixing; Bichromate methods; Photo-Mechanical Processes; Sulphide toning — the working strengths, and the taxonomy of failure as the sulfide deteriorates in solution; Bichromate Methods; Photo-Mechanical Processes; Pinhole Photography - Alfred Watkins' table of needle sizes, plate distances and the resulting ratios; Pinhole Photography - the plate distance as the quantity that sets the geometry; Pinhole Photography - the instruction that the edges of the pinhole should be quite clean and free from burr; Dichroic Fog - the plate seen by transmitted light appears tinted red or violet and by reflected light greenish or yellowish; the plate looks foggy and suggests that it has not been properly fixed, but prolonged immersion in hypo solution does not mend matters; Lumiere and Seyewetz concluded that it is due to the presence of silver, its formation favoured by a solvent of silver bromide in the developer and by the presence in the fixing bath of developer, hence the desirability of washing the plate between developing and fixing; Pinhole Photography - the construction of the camera and the requirement that it admit light only at the hole; Dichroic Fog — the conclusion of Lumiere and Seyewetz that it is due to the presence of silver, its formation favoured by a solvent of silver bromide in the developer and by the presence in the fixing bath of developer, hence the desirability of washing the plate between developing and fixing; Pinhole Photography - the statement that a prolonged exposure of about twenty or thirty times the ordinary one is required; Condenser - that the chief use of the condenser among photographic workers is for illuminating the positive transparency in the optical lantern or the negative in the enlarging lantern, that its action is illustrated by a convex lens used as a burning-glass concentrating the light 'and also the heat' of the sun, and the instruction that 'all condensers should be so loosely mounted in thin cells that they can be turned round, otherwise the expansion by the heat may cause them to crack'; Calorific Rays - that glass is highly adiathermanous and photographic lenses therefore allow but few heat rays to pass to the sensitive film, while rock salt allows them to pass very freely; Enlarging - the opening argument that discs of confusion inappreciable to the eye on a quarter-plate negative are enlarged in the same ratio as the picture, so that a three-times enlargement makes them easily seen (the scan's optical character recognition does not resolve the two fractions of an inch the passage prints); Negatives, Defects and After-treatment of, under the running head Stains - the entry 'Iridescent Surface-marking', markings 'chiefly of a blue or greenish tinge, and usually nearer the margins than the more central parts', which 'probably consist chiefly of silver sulphide' and are 'often attributed to the plate having been kept in an atmosphere where gas is freely used', with the remedy of rubbing the dry film with a rag moistened with methylated spirit or swabbing the wetted surface with hypo and ferricyanide reducer; Enlarging - the instruction that the easel 'should be arranged so that its front, on to which the picture is projected, is perfectly vertical, and parallel to the camera back and negative, otherwise the picture will be distorted', and the opening argument that discs of confusion inappreciable to the eye on a quarter-plate negative are enlarged in the same ratio as the picture and become easily seen (the scan's optical character recognition does not resolve the two fractions of an inch the passage prints); Distortion - the rules W. Piper gave in The Amateur Photographer for 28 November 1901 for correcting converging verticals by inclining both negative and copy, including the statements that 'while a small stop will do a great deal, we cannot expect it to produce perfect focus if negative and copy are inclined in the same direction' and that 'if the negative and copy are inclined to angles proportional to their respective focal distances from the lens, perfect focus is secured without stopping down, provided we have a good flat field lens'; Pinhole Photography - the instruction that the edges of the pinhole should be quite clean and free from burr, and Alfred Watkins' table of needle sizes and plate distances

Used by:Amidol · Ammonium chloride · Ammonium citrate (dibasic) · Ammonium citrate (tribasic) · Ammonium dichromate · Ammonium iron(III) citrate · Ammonium iron(III) oxalate · Ammonium persulfate · Ammonium thiocyanate · Ammonium thiosulfate · Arrowroot · Ascorbic acid · Borax (sodium tetraborate decahydrate) · Catechol · Chlorohydroquinone · Chrome alum · Ethanol · Ferric oxalate · Formaldehyde · Gallic acid · Gelatin · Glycerol · Glycin · Hydrogen peroxide · Hydroquinone · Iron(II) sulfate, anhydrous · Iron(II) sulfate heptahydrate · Iron(III) chloride, anhydrous · Iron(III) chloride hexahydrate · Kaolin · Lead(II) acetate · Lithium chloride · Metol · Nickel(II) sulfate · Phenidone · Potassium alum · Potassium bromide · Potassium carbonate (anhydrous) · Potassium citrate · Potassium dichromate · Potassium ferricyanide · Potassium ferrocyanide (anhydrous) · Potassium ferrocyanide trihydrate · Potassium hydroxide (caustic potash) · Potassium iodide · Potassium metabisulfite · Potassium oxalate, anhydrous · Potassium oxalate monohydrate · Potassium permanganate · Potassium persulfate · Potassium thiocyanate · Silver · Silver nitrate · Silver(I) oxide · Sodium ascorbate · Sodium bicarbonate · Sodium bisulfite · Sodium carbonate (anhydrous) · Sodium carbonate decahydrate · Sodium carbonate monohydrate · Sodium chloride · Sodium hydroxide (caustic soda) · Sodium sulfide · Sodium sulfite · Sodium thiocyanate · Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Tannic acid · Thallium(I) sulfate · Thiourea · Thymol · Albumen sensitising solution · Albumen solution with its chloride · Albumenised salting solution · Ammonium citrate developer · Borax kallitype developer · Chrome alum subbing dip · Double-coated albumen procedure · Talbot's gallo-nitrate of silver · Kallitype sensitiser · Kodak F-24 · Kodak GP-1 · Kodak T-52 · Kodak R-4 · Kodak R-4a · Kodak R-4b · Kodak T-7a · Mercuric sepia platinotype · Moersch MT3 Variotoner · Nicol's kallitype · Pellet's positive-working process · EDTA, citric acid and hydrochloric acid clearing sequence · Rochelle salt kallitype developer · Rodinal-type p-aminophenol developer · Sodium citrate kallitype developer · Willis's potassium oxalate developer · P1 Silver Salts and Light: Schulze to Ritter · P1 The Camera Obscura: An Image Without Chemistry · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P2 Measuring Mass, Volume, Temperature and Density, and Knowing How Wrong You Are · P4 The Silver Halides · P5 Gelatin, the Photographic Binder · P6 Build the Modular Pinhole Camera · P6 Commissioning the Camera: Light-Tightness, Flare and the First Negatives · P6 Curved Film Plane and Multiple-Pinhole Experiments · P6 Designing the Modular Camera · P6 Pinhole Exposure and Reciprocity Correction · P6 Break/Fix: Unexpectedly Soft Images and Wrong Reciprocity Corrections · P7 Assignment: Panorama, Curved Plane and Multiple Pinholes · P7 Assignment: Portrait, Environmental Portrait and Self-Portrait · P7 Seeing Like a Pinhole: The Image, Its Makers and Previsualisation · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 Superadditivity: Why Two Agents Beat One · P11 Break/Fix: The Exhausted Fixer · P14 Build: The Enclosure and Exposure Stage · P19 Lab: Dodging, Burning, Edge Work and Local Contrast · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Gold, Iron-Blue and the Other Metal Toners · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P20 The Toners We Study and Do Not Use · P24 Lab: Printing a Kallitype · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · P26 Uranium, Mercury and the Heavy-Metal Treatments · P28 Fixer Faults, Washing Faults and the Stains They Leave · Collotype · Photogravure · Sulphide (sepia) toned silver gelatin print · Woodburytype · Bellows factor omitted · Buckled-sheet softness · Burr smear · Dichroic fog · Double image from a reflective plate · Edge leak · Fixer contaminated by developer · Flare veil · Hot spot · Light-leak fog · Motion smear · Near-limit softness · Negative popping · Newton's rings · One soft corner from misalignment · Seam leak · Shutter leak · Thick-plate vignetting

The Encyclopedia of Photography: The Complete Photographer - The Comprehensive Guide and Reference for All Photographers, Volume 6 (Cop-Dif)retrieved 2026-09-05

Sections: Developers, the acutance paragraph naming the Beutler formula as one of the best known high-acutance developers, with Solution A, Solution B in the monohydrated carbonate, the one-plus-one-plus-ten working dilution and the seven-to-ten-minute time at 65 degrees F

Used by:Beutler two-solution developer

The Manual of Modern Photographyretrieved 2026-09-05, 2026-09-07

Sections: A special developer for low-speed films, a Willi Beutler formula - the two stock solutions and their make-up water, the instruction to add 50 cc of A and 50 cc of B to 500 cc of water, the development time of 7 to 10 minutes at 65 degrees F and 18 degrees C according to gradation, the note that medium-speed films require a lesser quantity of solution B and that higher temperatures are not recommended, the definition of low-speed film as 8 to 16 ASA, the keeping statement for the two stocks, Beutler's claim of up to 141 lines per millimetre, and the note on the Tetenal Neofin red and blue developers; A special developer for low-speed films - the two stock solutions, metol 10 g and sodium sulfite 50 g in solution A and sodium carbonate 50 g in solution B, both per litre; the working instruction to add 50 cc of A and 50 cc of B to 500 cc of water and to develop low-speed films at 18 degrees C for 7 to 10 minutes according to gradation; the statement that the stocks in well-stoppered bottles will keep for a long time; and Beutler's own resolution claim of up to 141 lines per millimetre

Used by:Beutler two-solution developer · P27 Assignment: The Developer Comparison, Measured and Printed

The Silver Sunbeam: A Practical and Theoretical Text-Book on Sun Drawing and Photographic Printingretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Amylaceous or Non-Azotized Substances, and Starch — starch, arrow-root, cellulose and gum-arabic as one class of non-nitrogenous bodies, the occurrence of starch in seeds, roots, tubers and stems as very minute insoluble granules, the washing and drying by which it is prepared, its insolubility in water and in alcohol, the concentric rings by which a granule is recognised under the microscope and by which the potato granule is distinguished from that of arrow-root, arrow-root as the starch obtained from the roots of maranta arundinacea growing in the West Indies, the period model of each granule as a cell of concrete insoluble material holding a soluble pulp within, the bursting of the cells on boiling to give a thick gelatinous mass, the separation of the insoluble husks from the fluid portion, and free iodine as the best test for starch; Preparation of Arrow-Root Paper, for the period formula and the boiled-cream procedure; Iodide of Cadmium; the behaviour of cadmium-iodised and bromo-iodised collodion; The furnishing of the operating room — carbonate of lime (chalk) in the list of chemicals; Chapter XVI, The Developing Solutions: Sulphate of Iron Developer, Formulas 1 and 2; Reducing agents and developers; Chapter XVI, The Developing Solutions: Sulphate of Iron Developer, Formulas 1 and 2; Salts of silver: purifying silver by dissolving it in pure nitric acid; Collodion sensitizers: the nitrate of silver bath rendered slightly acid with nitric acid; Silver — salts of silver: manufacture, lunar caustic, properties of nitrate of silver; Silver — the separation of copper from an impure silver solution by substitution of oxide of silver, and the boiling of the crystals with well-washed oxide of silver to obtain an absolutely neutral nitrate; the reduction of the oxide of silver in solution by protosulphate of iron; The acetate toning bath, and the instruction to prepare it at least twenty-four hours before use; acetate of soda among the salts of soda; The Tannin Process of Major Russell — collodion for the tannin process; Preservative Solution of Tannin; development, fixing and the colour of the image; The Tannin and Honey Process; Nitrate of Uranium; Manipulation of Positive Printing — the division of sensitising solutions into those containing essentially nitrate of silver and those containing ammonio-nitrate of silver, subdivided by strength; the statement that the ammonio-nitrate bath is much more sensitive but blackens by use, that whichever bath is used its strength has to be maintained at its original point by the addition of fresh silver every time it is used because the bath soon becomes impoverished by the floating of paper, and that the sensitizing solution must always be slightly acid in order that the whites may be thoroughly preserved; the Formula for the Plain Silver Solution, nitrate of silver 2 ounces, rain-water 12 ounces, nitric acid 2 to 3 drops, with the paper prepared as for the salting solution, the corners turned back, the sheet bowed and lowered end by end, the bubbles removed with a glass rod, the filtering of the bath before each use, the argentometer used to hold the strength at about 70 grains to the ounce, the test paper used to check whether it is acid or alkaline, the five-minute float, and the drying on varnished steel needles with the pendent corners blotted; the account of the ammonio-nitrate bath, in which the albuminous film is not injured, the time of floating is much shortened and no more silver is consumed despite the higher strength because the picture is kept on the surface of the film; and the fuminating process, in which sheets are first floated four or five minutes on a plain bath of sixty to seventy grains of nitrate of silver to the ounce of water, dried, and then exposed to ammonia vapour in a box; Manipulation of Positive Printing — Preparation of Albumenized Paper: albumen used either pure or diluted, pure albumen giving very brilliant prints from a paper that is not so easily prepared, the whites of twenty eggs measured in a graduated measure with the germs removed by a glass rod, the addition for every ounce of ten grains of chloride of ammonium dissolved in the least quantity of distilled water, the beating to a thick white froth with an egg-beater, the ten minutes' standing, the removal of the froth with a fork onto a hair sieve, the day's standing covered from dust, the filtering through sponge, the further two days' settling, the decanting of the supernatant liquid, the greater difficulty of laying paper on salted albumen than on a plain salting solution because bubbles form more easily and are less easily removed, the failure of albumen to attach itself to dry paper in dry weather and the thin upper and thick lower coating that follows, the suspension of the sheet by its broadside to shorten the run, the removal of the accumulating bead with bibulous paper, and the salting time of two and a half to three minutes; Manipulation of Positive Printing — Preparation of Albumenized Paper, on albumen being usable either pure or diluted, on pure albumen giving very brilliant prints from a paper that is not so easily prepared, on the whites of twenty eggs measured in a graduated measure with the germs removed by a glass rod, on the addition for every ounce of ten grains of chloride of ammonium dissolved in the least quantity of distilled water, on beating to a thick white froth with an egg-beater, the ten minutes' standing, the removal of the froth with a fork onto a hair-sieve, the day's standing covered from dust, the filtering through sponge, the further two days' settling and the decanting of the supernatant liquid, on much more care being required in laying the paper on the salted albumen than on the plain salting solution because bubbles are more likely and less easily removed, on the albumen not attaching itself easily to dry paper in dry weather and the thin upper and thick lower coating that follows, on suspending the sheet by its broadside to shorten the run, and on the salting time of two and a half to three minutes; Plain Salted Paper, giving three salting formulae with chloride of ammonium, gelatine and citrate of soda in ten ounces of distilled water and the note that the object of the citrate is to give a slight rosy tinge to the middle tones; Sensitizing Bath, the plain silver solution kept at about 70 grains to the ounce; and Albumen, on solid albumen, on its precipitation by mineral acids and by metallic oxides, and on the metal in the albumen film being instrumental in producing the difference between a plain print and an albumen print; Chapter XVII, Fixing Solutions, pages 118 to 121 — the three fixing solutions then in use given as cyanide of potassium, hyposulphite of soda and sulphocyanide of ammonium; the account of cyanide of potassium as almost as poisonous as hydrocyanic acid; sulphocyanide of ammonium as the new fixing salt of Meynier said to be as powerful as cyanide of potassium without its poisonous properties, with Towler's own scepticism about that claim; the statement that cyanide of potassium is not only a solvent of the silver salts but also a reducing agent, producing in the ambrotype and the melainotype a whiteness in the silver film which cannot be effected with hyposulphite; the statement in the same chapter that chloride and bromide of silver are soluble to a greater extent than iodide of silver in hyposulphite of soda; that many photographers use it indifferently for negatives and positives because of its superior solvent properties but that it must be used dilute and watched closely or it dissolves the fine parts of the image; that it is preferred in collodion work because of the difficulty of washing hyposulphite out of the film and the eventual destruction of the film by crystallisation if any is left; Formula No. 1, fixing solution with cyanide of potassium, 1 drachm to 4 ounces of rain-water; Formula No. 3, sulphocyanide of ammonium 1 drachm to 12 ounces; the wet collodion positive process, sixth subdivision, repeating the 1 drachm to 4 ounces bath and the instruction to wash in many waters until all traces of cyanide are removed; Collodion Negatives, page 147, fixing solutions for negatives, Formula No. 2, cyanide of potassium 1 drachm to water 5 ounces, with the preceding statement that cyanide is regarded as the fixing agent proper for collodion positives and hyposulphite as the proper fixer for negatives because its solvent action is not so violent; Collodion Positives by Transmitted Light, pages 157 and 158, on the grey shadows left by iron development and the object of communicating a rich black hue to them, the saturated solution of bichloride of mercury used first, then Formula No. 1, a saturated solution of cyanide of silver in cyanide of potassium made from cyanide of potassium 100 grains and rain-water 2 ounces with nitrate of silver solution at 50 grains to the ounce added as long as the precipitate is dissolved, Formula No. 2 substituting nitrate of copper, the statement that the image assumes an intense black hue and that the solutions can be used over and over again until exhausted, the instruction to refix afterwards with hyposulphite of soda and not with cyanide because the latter reduces the silver to a white film again, and the closing note that this mode of blackening may also be used as an intensifier; the tannin dry plate, page 248, on fixing in hyposulphite and not the cyanide because the latter is apt to loosen the film; the card-picture chapter, on the health of operators being much impaired in large printing establishments and on removing silver stains with cyanide of potassium entailing the risk of incurable ulcers; the gold solution for electro-gilding, made by dissolving terchloride of gold to saturation in a saturated solution of cyanide of potassium; Positive Printing — Preparation of Arrow-Root Paper, giving the period formula and procedure: the sheet pinned to a board a trifle smaller than itself with the edges folded over, the salting mixture of 5 drachms of chloride of sodium, 4 grains of citric acid and 19 ounces of distilled water dissolved and filtered, 4 drachms of arrow-root rubbed with cold water into a cream with all lumps thoroughly broken up and saturated, the mixture boiled in a glass or porcelain dish with constant stirring, the scum removed when cold, the application with a very fine soft moist sponge worked longitudinally and laterally, the removal of ridges with a glass triangle or rod, the judgement that arrow-root paper suits large portraits and landscapes while albumenised paper is better where fineness of grain and sharpness are wanted, and the statement that all the papers so prepared will keep but are best when fresh; Sensitizing Bath, the plain silver solution of 2 ounces of nitrate of silver in 12 ounces of rain-water with 2 to 3 drops of nitric acid, the requirement that the bath always be slightly acid and filtered before use, and its strength maintained at about 70 grains to the ounce; Amylaceous or Non-Azotized Substances and Starch, on starch, arrow-root, cellulose and gum-arabic belonging to one class of non-nitrogenous bodies, on starch existing in seeds, roots, tubers and stems as very minute insoluble granules, on the washing and drying by which it is prepared, on starch being insoluble in water and in alcohol, on the concentric rings by which a starch granule is recognised under the microscope and by which the granule of the potato is distinguished from that of arrow-root, on arrow-root being the starch obtained from the roots of maranta arundinacea growing in the West Indies, on each granule being a cell of concrete insoluble material holding a soluble pulp within, on the cells being burst or broken up by boiling so that the soluble part mixes with the water to form a thick gelatinous mass, on the insoluble husks or cells being separable from the fluid portion, and on free iodine giving the violet-blue test colour which disappears on heating and returns on cooling; Nitrate of silver: lunar caustic and the blackening of the fused salt; Silver — salts of silver: nitrate of silver, lunar caustic, and the properties of the fused salt; Fixing Solutions, page 121, Formula No. 1, fixing solution with cyanide of potassium, given first of the three fixing solutions with hyposulphite of soda and sulphocyanide of ammonium following it; Cyanide of Potassium, pages 119-120, on its preparation and on the salt being almost as poisonous as hydrocyanic acid; Toning of the Prints, pages 201-203, the six gold toning formulas, all of them gold chloride or the double chloride of gold and potassium neutralised with carbonate of soda or chalk, one of them combining gold with nitrate of uranium, and none of them containing cyanide; and The Card-Picture, page 222, that stains from nitrate of silver or from the pyrogallate can be removed by washing with cyanide of potassium but that this might entail upon the operator incurable ulcers, and that the health of operators is much impaired, especially in those large printing establishments where a number of females are employed in this department, who by continual manipulation in the toning and fixing baths are frequently in a suffering condition; The Card-Picture, page 222 — that stains from nitrate of silver or from the pyrogallate can be removed by washing with cyanide of potassium, but that this might entail upon the operator incurable ulcers, and that the health of operators is much impaired, especially in those large printing establishments where a number of females are employed in this department, who by continual manipulation in the toning and fixing baths are frequently in a suffering condition; Table of contents and Chapter XVII, Fixing Solutions, page 118 onwards - the entry "Formula, No. 1, with Cyanide of Potassium, 121", which is the first of the three fixing solutions given there, with hyposulphite of soda and sulphocyanide of ammonium following it; Cyanide of Potassium, pages 119 to 120, on its preparation and on the salt being almost as poisonous as hydrocyanic acid; Toning of the Prints, page 201, with Formulas for Toning Solutions at page 202; and The Card-Picture, page 222, that stains from nitrate of silver or from the pyrogallate can be removed by washing with cyanide of potassium but that this might entail upon the operator incurable ulcers, and that the health of operators is much impaired. The page references were read from the book's own printed table of contents in the archive.org optical character recognition of this copy; the contents of the fixing and toning formulas themselves are not reproduced here and are not needed for the assessment this page sets.; Fixing solutions, page 121, Formula No. 1, the fixing solution with cyanide of potassium, given first of three with hyposulphite of soda and sulphocyanide of ammonium following it; Cyanide of potassium, pages 119 to 120, on its preparation by heating ferrocyanide of potassium in an iron bottle, and on the salt being almost as poisonous as hydrocyanic acid; and The card-picture, page 222, that stains from nitrate of silver or from the pyrogallate can be removed by washing with cyanide of potassium but that this might entail upon the operator incurable ulcers, and that the health of operators is much impaired, especially in those large printing establishments where a number of females are employed in this department, who by continual manipulation in the toning and fixing baths are frequently in a suffering condition. Also Specialties continued - dark-room, page 47, the shelf inventory of solutions kept together beneath the corner of the bench, naming protosulphate of iron, pyrogallic acid, cyanide of potassium, hyposulphite of soda, solution of iodine in iodide of potassium, tincture of iodine, nitrate of silver, bichloride of mercury and sulphide of potassium, each to be legibly labelled, always placed in the same position and always carefully corked; and the instruction on the same page not to interchange dishes, because the cyanide of potassium decomposes the iron salt into what soon becomes Prussian blue by oxidation of the iron, making the dish difficult to clean afterwards; The Card-Picture, page 222: that stains from nitrate of silver or from the pyrogallate can be removed by washing with cyanide of potassium but that this might entail upon the operator incurable ulcers, and that the health of operators is much impaired, especially in those large printing establishments where a number of females are employed in this department, who by continual manipulation in the toning and fixing baths are frequently in a suffering condition; Nitrate of uranium — that it is a yellow salt containing six equivalents of water which heat can expel, with greater heat decomposing the salt; and the identifying reactions that the alkaline carbonates all produce yellow precipitates from solutions of the salt and that ferrocyanide of potassium produces a red-brown precipitate; Ether and Alcohol, for collodion iodised with the ammonium salt being the least stable and a cadmium collodion the most permanent. Collodion Sensitizers - Iodides and Bromides, for the list of metals whose iodides and bromides were used, for the requirement that the salt be soluble in ether and alcohol so that the insoluble silver halide is produced in and on the film, for the statement that it has not yet been decided which iodide or bromide is the most appropriate, for cadmium iodide glutinising a collodion while an alkaline iodide liquefies it, for the cadmium-iodised collodion ripening slowly and keeping its sensitiveness far longer, for the practice of combining the two with the cadmium salt in excess, for the photographed solar spectrum being much broader on a bromide film than on an iodide one - violet, indigo, blue and partially green against a blue only partially represented - and for the explicit refusal to call bromides accelerators, since high authority held them to be retarders of the actinic action and the true deduction is a greater capacity for colours. Fixing, for cyanide of potassium being not only a solvent of the silver salts but also a reducing agent, producing in the ambrotype and the melainotype a whiteness in the silver film which hyposulphite cannot give, for it being regarded as the fixing agent peculiarly adapted for collodion positives by reflected light while hyposulphite is regarded as the proper fixer for negatives, for the need to use it dilute and watch it closely or it dissolves the fine parts of the image, and for the difficulty of washing hyposulphite out of a collodion film, which eventually destroys it by crystallisation. Collodion Positives - The Melainotype - The Ambrotype, for the definition of an ambrotype as a collodion positive on glass regarded by reflected light, for every part of such a picture being laterally inverted so that the application is limited to portraiture, and for the alabastrine variant in which the plate is inverted and the image beheld through the collodion in its natural position. Melainotype - Ferrotype, for the name taken from the black background and from the iron of which it is composed, for very thin sheet-iron plates covered with a rich black or brown-black polished japan, for glass and the black japan, velvet and paper being entirely dispensed with, for it being by far the easiest and quickest to take, for the exposure being exactly that of an ambrotype, for the better heat conduction of iron raising the japanned film into blisters if the varnishing flame is careless, and for the corners being cut with shears and folded into a mat for mailing in a letter; The iron developer for ambrotypes and melainotypes against the one for negatives; the acid as the throttle; The iron developer for ambrotypes and melainotypes; the acid as the throttle; The iron developer formulas for negatives and for collodion positives; the acid as the throttle; the cadmium iodide argument

Used by:Arrowroot · Cadmium bromide · Calcium carbonate · Iron(II) sulfate, anhydrous · Iron(II) sulfate heptahydrate · Nitric acid · Silver nitrate · Silver(I) oxide · Sodium acetate (anhydrous) · Tannic acid · Uranyl nitrate hexahydrate · Albumen sensitising solution · Albumen solution with its chloride · Albumenised salting solution · Cyanide fixing and toning · Arrowroot salting solution · P2 Silver Nitrate: The Reagent That Sets the Rules · P4 Silver and the Silver Ion · P20 The Toners We Study and Do Not Use · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Assignment: Assessing a Historical Process for Hazard · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory · P26 Uranium, Mercury and the Heavy-Metal Treatments · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · Ambrotype · Tintype (ferrotype) · Wet-plate collodion negative

The Stereoscope: Its History, Theory, and Construction, with its Application to the Fine and Useful Arts and to Educationretrieved 2026-09-04

Sections: Chapter VIII, pp. 136-137: images formed by a small aperture; the inflexion of light as the only conceivable error; the bust photographed by Brewster and the Rev. Mr Egerton in ten minutes through an aperture under a hundredth of an inch; the prediction of a camera with only a pin-hole

Used by:P7 Seeing Like a Pinhole: The Image, Its Makers and Previsualisation

Tom Wedgwood, the First Photographer: An Account of His Life, His Discovery and His Friendship with Samuel Taylor Coleridge, including the Letters of Coleridge to the Wedgwoods and an Examination of Accounts of Alleged Earlier Photographic Discoveriesretrieved 2026-09-06

Sections: Chapters XII and XIII, pages 185 to 201, with the complete reprint of the 1802 account at pages 189 to 194: Litchfield's statement that the extracts in the histories are "generally quotations from quotations" and that Hunt's of 1844 was the longest he had met with; the location of the paper at page 171 of volume I of the Journals of the Royal Institution; the fact that no name is appended to it and no dates are appended to any paper in the volume; the attribution to Davy on the grounds that he was then assistant editor and that the piece was included in his collected works; Leslie's letter of 18 November 1800 sending object-glasses, thin cylinders for the solar microscope and painted glasses; the Watt letter of about 1790 or 1791 thanking Josiah Wedgwood for instructions as to the "Silver Pictures"; the character of the Journals as a subscriber bulletin that ran to one volume and the absence of any evidence that the account was read at a meeting; John Davy's note in the collected works that the method had "recently" been further cultivated, especially by Mr. Talbot; and Appendix C, which sets out the collapse of Eliza Meteyard's attribution to Wedgwood of the "Breakfast Table" and "Savoyard Piper" pictures

Used by:Wedgwood and Davy's silver nitrate on leather

archivesniepce.com

Biographie de Nicephore Niepceretrieved 2026-09-04

Sections: Biographie: 1765; 1803-1807 the pyreolophore patent; 1816; 1818-1827; 1827-1828 England; 1829-1833

Used by:P1 Niepce and Heliography: Light That Hardens

Essais et realisations de Nicephore Niepce, chronologieretrieved 2026-09-04, 2026-09-06

Sections: Essais et realisations: 1816, 1822, 1826, 1827 — the sequence of Niépce's trials and the materials each used; Essais et realisations: 1822, 1826, 1827 — the trials in which the bitumen varnish and its solvent were used; "Essais et réalisations", the entries for 1822, 1824, 1825, 1826, 1827 and 1829, for the succession of supports and for the 1832 turn to the residue of distilled lavender essence dissolved in alcohol; Essais et realisations: 1816, 1818, 1822, 1824, 1825, 1826, 1827, 1829, 1832, 1833; Essais et realisations — 1818, fixed images obtained with bitumen of Judea; 1822, copies of engravings on glass plates coated with bitumen; 1823, renewed trials on stone with acid etching so that the stone could serve as a printing matrix; 1824, the discovery that under-exposure of the sensitive substance gives an image at once positive and negative, and the successful etching of camera images on copper; 1825, the finding that the whiter the support the better the effect; 1826, the move to pewter and the naming of the invention heliographie; 1827, the abandonment of etching the camera views in the face of the impossibility of rendering their half-tones; Essais et réalisations: 1816, 1818, 1822, 1824, 1825, 1826, 1827, 1829

Used by:Bitumen of Judea · Oil of lavender · Niépce's bitumen heliograph coating · P1 Niepce and Heliography: Light That Hardens · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · Heliography on bitumen of Judea

articles.adsabs.harvard.edu

On the Deviations from the Law of Reciprocity for Bromide of Silver Gelatine, Astrophysical Journal 11, pages 89-91retrieved 2026-09-04, 2026-09-05

Sections: Statement of the law of reciprocity; The statement of the reciprocity law, the exponent 0.86, the paired result at intensities 81 and 1, and the intermittent-exposure comparison; The statement of the reciprocity law as equal blackening for equal products of intensity and time, and the measured exponent of 0.86 for the gelatine plates tested

Used by:P1 Experiment: The Image That Would Not Stay · P4 Reciprocity Failure and the Life of the Latent Image · P13 Film Speed and Exposure Index

assets.nexperia.com

Understanding power MOSFET data sheet parameters, application note AN11158, revision 7.0retrieved 2026-09-05

Sections: Section on gate-source threshold voltage - VGS(th) is defined where drain and gate are shorted at a small specified current, depends on chip size, and is defined in a way that is best for routine measurement but not how the device would typically be used

Used by:P14 Low-Voltage Electronics for the Darkroom Builder · P17 Build: The Switched Output

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Waste Classification: Guidance on the classification and assessment of waste, Technical Guidance WM3 (1st edition, version 1.2.GB)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-08

Sections: Chapter 09, wastes from the photographic industry: 09 01 05* bleach solutions and bleach fixer solutions; Chapter 09, wastes from the photographic industry: the absolute hazardous entries 09 01 01*, 09 01 04* and 09 01 05*; Appendix B — legal definitions used by the list of waste: heavy metal and transition metals; step 3, mandatory group entries for chromium compounds; Appendix A, List of Waste chapter 09, wastes from the photographic industry, for 09 01 05* bleach solutions and bleach fixer solutions as an absolute hazardous entry and 09 01 99 wastes not otherwise specified as a mirror entry; Appendix B, steps 2 and 3, for the precedence of a substance-specific mandatory entry over the mandatory group entry for lead compounds, and for the rule that group entries for salts cover both anhydrous and hydrous forms unless specified otherwise; Appendix B, note 3 to the worked example, that Acute Tox. and STOT hazard classes marked with an asterisk are minimum classifications whose actual classification may be more severe and needs to be determined; note 4, that inorganic lead compounds are classified as carcinogenic by IARC and that their carcinogenic classification needs to be determined; Chapter 09, wastes from the photographic industry: 09 01 05* bleach solutions and bleach fixer solutions; the note that inorganic lead compounds are classified as carcinogenic by IARC; Chapter 16: 16 03 07* metallic mercury, an absolute hazardous entry; Chapter 20: 20 01 21* fluorescent tubes and other mercury-containing waste; Chapter 06: 06 04 04* wastes containing mercury; Appendix B, Qualifications of hazard class, category codes and statements codes, for the meaning of the single asterisk as a minimum classification whose actual classification may be higher and which IS used in waste assessment, of the double asterisk as relating to route of exposure and NOT used in waste assessment, and of the triple asterisk as assigned to reproductive toxicity hazard statements where one attribute is not applicable and also not used in waste assessment; Table 3.3 and its worked assessment in section 3, whose component of concern is nickel carbonate at 0.06 per cent, carrying the classification Carc. 1A, Muta. 2, Repr. 1B, STOT RE 1, Acute Tox. 4 *, Acute Tox. 4 *, Skin Irrit. 2, Resp. Sens. 1, Skin Sens. 1 and Aquatic Acute 1 with the codes H350i, H341, H360D***, H372**, H332, H302, H315, H334, H317 and H400, and the hazardous properties HP4, HP5, HP6, HP7, HP10, HP11, HP13 and HP14 those codes engage; and the concentration limits the worked example applies — 0.1 per cent for HP7, 0.3 per cent for HP10, 1 per cent for HP5 and HP11, 1 per cent as the cut-off for HP6 and 10 per cent for HP13; Appendix A, for the List of Waste definition of "heavy metal" as any compound of antimony, arsenic, cadmium, chromium (VI), copper, lead, mercury, nickel, selenium, tellurium, thallium and tin so far as classified as hazardous substances, and of "transition metals", which names nickel again; Chapter 09, wastes from the photographic industry: 09 01 04* fixer solutions; Appendix C12, Table C12.2: substances which may cause a waste to exhibit HP 12; Assessment of cyanide-bearing wastes — the exclusion of complex cyanides such as ferrocyanides and ferricyanides from the hazard statement for liberation of a very toxic gas on contact with acid; List of Waste chapter 09; List of Waste chapter 09 — 09 01 06*, 09 01 13* and 09 01 07; The worked assessment example: HP 6 Acute Toxicity, HP 12 Produces toxic gases in contact with water, air or acid, and HP 14 Ecotoxic, each naming sodium cyanide as a component of concern, with the EUH032 concentration limit of 0.2 per cent from Appendix C12; Chapter 09, 09 01 04* fixer solutions; Appendix C12, Table C12.2: sodium sulphide, EUH031, and the HP 12 threshold calculation; Appendix A, Legal definitions used by the list, for the List of Waste definition of "heavy metal" as any compound of antimony, arsenic, cadmium, chromium (VI), copper, lead, mercury, nickel, selenium, tellurium, thallium and tin so far as classified as hazardous substances; Appendix B, Qualifications of hazard class, category codes and statements codes, for the meaning of the asterisk as a minimum classification whose actual classification may be higher and of the double asterisk as relating to route of exposure, and for step 4's instruction to look for additional data wherever a class carries the asterisk; Chapter 09, wastes from the photographic industry: 09 01 04* fixer solutions; and the treatment of absolute hazardous entries; Appendix C12, Table C12.2 — sodium sulphide assigned EUH031, contact with acids liberates toxic gas, with the reaction written as sodium sulphide plus two hydrogen ions giving hydrogen sulphide and two sodium ions, and the HP 12 threshold calculation giving 0.4 per cent sodium sulphide for a waste to be hazardous on that ground; Chapter 09, wastes from the photographic industry, for the absolute hazardous entry 09 01 05*, bleach solutions and bleach fixer solutions; the assessment notes, for note 4, "Inorganic lead compounds are classified as carcinogenic by IARC", and the requirement that the carcinogenic classification be determined when such a waste is assessed; Appendix A, the List of Waste definition of "heavy metal" naming compounds of lead, nickel and thallium so far as classified as hazardous substances; Appendix B, the meaning of the asterisk as a minimum classification, and the worked assessment whose concentration limits are 0.1 per cent for HP7 carcinogenic and 0.3 per cent for HP10 toxic for reproduction; Chapter 09, wastes from the photographic industry, for the absolute hazardous entry 09 01 05*, bleach solutions and bleach fixer solutions; Step 1, check if the waste needs to be classified; entry types; List of Waste chapter 09, wastes from the photographic industry; List of Waste chapter 09, wastes from the photographic industry, and the statement in Step 1 that nearly all household, commercial and industrial wastes need to be classified; The classification procedure for wastes, and chapter 09, wastes from the photographic industry; List of Waste chapter 09, wastes from the photographic industry; the treatment of transition-metal compounds where they are classified as hazardous; List of Waste chapter 09, wastes from the photographic industry, and the statement in Step 1 that nearly all household, commercial and industrial wastes need to be classified, including waste from domestic households; Appendix A chapter 09, wastes from the photographic industry, entries 09 01 01*, 09 01 04*, 09 01 06* and 09 01 13*; chapter 20, sub-chapter 20 01 separately collected fractions, entry 20 01 17* photochemicals; the key point that an absolute hazardous entry always applies, must be used, and applies even where the waste displays no hazardous property; WEEE worked example - entries 20 01 21* fluorescent tubes and other mercury-containing waste, 20 01 35* discarded electrical and electronic equipment containing hazardous components and 20 01 36 for equipment containing none, with chapter 20 taking precedence over chapter 16 for household and household-type equipment; WEEE worked example - entries 20 01 35* for discarded electrical and electronic equipment containing hazardous components and 20 01 36 for equipment containing none, with chapter 20 taking precedence over chapter 16 for household and household-type equipment; WEEE worked example - list of waste entry 20 01 21* fluorescent tubes and other mercury-containing waste, an absolute hazardous entry, with the statement that the vast majority of fluorescent tubes from any source are likely to be similar to domestic types and fall under it; Appendix C12, Table C12.2, threshold limits derived for substances assigned EUH029, EUH031 or EUH032 - the row for sodium sulphide, EUH031, Na2S + 2H+ giving H2S + 2Na+, EUH031 being the supplemental statement 'contact with acids liberates toxic gas'; and the List of Waste principle that an absolute hazardous entry always applies and must be used even where the waste displays no hazardous property; Step 1 of the classification procedure, that nearly all household, commercial and industrial wastes need to be classified including waste from domestic households; and the List of Waste treatment of absolute hazardous entries, which must be used and apply even where the waste displays no hazardous property; Appendix C12, Table C12.2, threshold limits derived for substances assigned EUH029, EUH031 or EUH032 - the rows for sodium sulphide, EUH031, Na2S + 2H+ giving H2S + 2Na+, and for sodium polysulphides and potassium polysulphides, EUH031, Na2Sn + 2H+ giving H2S + 2Na+ + S(n-1) and K2S + 2H+ giving H2S + 2K+, EUH031 being the supplemental statement 'contact with acids liberates toxic gas'; Appendix C12, the assignment of the supplemental hazard statements for liberating a very toxic gas on contact with acid to cyanide salts, with the explicit exception of complex cyanides such as ferrocyanides and ferricyanides; Assessment of cyanide-bearing wastes — the exclusion of complex cyanides such as ferrocyanides and ferricyanides from the hazard statement for liberating a very toxic gas on contact with acid; Step 1 of the classification procedure, that nearly all household, commercial and industrial wastes need to be classified including waste from domestic households; the assessment of cyanide-bearing wastes, which excludes complex cyanides such as ferrocyanides and ferricyanides from the hazard statement for liberation of a very toxic gas on contact with acid; List of Waste chapter 09.; Chapter 09, wastes from the photographic industry: 09 01 04* fixer solutions and 09 01 05* bleach solutions and bleach fixer solutions; Appendix C12, Table C12.2, substances which may cause a waste to exhibit hazardous property HP 12, the release of an acute toxic gas — the entry reading "hydrogen cyanide, salts of (with the exception of complex cyanides such as ferrocyanides, ferricyanides and mercuric oxycyanide)", carrying hazard statement EUH032, the reaction written out by the regulator as NaCN + H+ giving HCN + Na+, and a concentration limit of 0.2 per cent. Also Chapter 09, wastes from the photographic industry, entry 09 01 04*, fixer solutions; Appendix B, legal definitions used by the List of Waste — 'heavy metal' means any compound of antimony, arsenic, cadmium, chromium (VI), copper, lead, mercury, nickel, selenium, tellurium, thallium and tin, as well as these materials in metallic form, as far as these are classified as hazardous substances; and step 3, the mandatory group entries, with chromium named among the examples and the instruction that a group entry must not be used where a substance-specific entry exists; Appendix B, legal definitions used by the List of Waste — heavy metal and transition metals; step 3, mandatory group entries for chromium compounds; Steps to classify the waste, step 1, that nearly all household, commercial and industrial wastes need to be classified including waste from domestic households; step 2 and Appendix A, Instructions on how to use the List of Waste, step 1 identification by waste source and the order of precedence in Table A1.1; the key point that an absolute hazardous entry always applies and that the law does not allow another entry to be applied; Appendix A chapter 09, wastes from the photographic industry; Appendix A chapter 20, municipal wastes, sub-chapter 20 01 separately collected fractions, entry 20 01 17* photochemicals; Appendix C14, the concentration limits and equations for hazardous property HP 14 Ecotoxic and its cut-off values; Appendix C, hazardous property HP 12, the release of an acute toxic gas, with the reaction of sodium sulfide with acid written out; The exclusion of complex cyanides such as ferro- and ferricyanides by name from the hazard statement for liberating a very toxic gas on contact with acid; Appendix A chapter 09, wastes from the photographic industry; the exclusion of ferro- and ferricyanides from the hazard statement about liberating a very toxic gas on contact with acid; Appendix A, identification of waste by source and the order of precedence; entry 20 01 17* photochemicals; Appendix C14, the method for hazardous property HP 14 Ecotoxic; Appendix A chapter 20, municipal wastes: entry 20 01 17* photochemicals; the rule that an absolute hazardous entry always applies; Appendix A chapter 09, wastes from the photographic industry; chapter 20 entry 20 01 17*, photochemicals; Appendix A chapter 09, wastes from the photographic industry; chapter 20, entry 20 01 17* photochemicals; The supplemental statement given to sodium sulfide for liberating a toxic gas on contact with acids; Steps to classify the waste, and the requirement to describe a waste before it is transferred

Used by:Ammonium dichromate · Cadmium bromide · Chrome alum · Lead(II) acetate · Lead(II) nitrate · Mercury · Mercury(II) chloride · Nickel(II) sulfate · Potassium cyanide · Potassium dichromate · Potassium ferricyanide · Potassium ferrocyanide (anhydrous) · Prussian blue · Silver · Sodium cyanide · Sodium sulfide · Thallium(I) sulfate · Uranyl nitrate hexahydrate · Cyanide fixing and toning · Kodak ST-1 · Lead additions to platinum sensitisers · Lead, thallium and nickel cyanotype toners · Mercuric sepia platinotype · P2 Waste: Streams, Silver, and the Drain You Must Not Use · P5 Project 3: A Bromide Enlarging Emulsion · P5 Coating, Drying and Hardening · P5 Project 4: Coating Glass Dry Plates and a Lantern Slide · P5 Assignment: The Hand-Coated Print · P12 Silver Recovery and the Responsible Darkroom · P16 Build: The UVA Exposure Unit · P16 Build: An LED Enlarger Head · P16 Ultraviolet for the Alternative Processes: Sources, Dose, Uniformity and Hazard · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Iron, Light and Prussian Blue · P21 Lab: Toning the Prussian Blue Image · P26 Assignment: Assessing a Historical Process for Hazard · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · The chromium policy · The disposal caveat · Chemical incompatibilities · The acid exclusion rule at a hexacyanoferrate or thiocyanate bench · Segregating alternative-process waste · Routing chromium(III) from the coating station · Routing general chemical waste · Collecting and segregating waste across a multi-run session · Routing silver-bearing waste · Handling a sulphide toner and its waste · A container found unlabelled, or a solution of unknown age

bergger.com

BERGGER Berfix Neutral, data sheetretrieved 2026-09-05

Sections: The description of Berfix Neutral as an alkaline-based non-acid universal fixer supplied as a liquid concentrate, its stated pH of 7, its dilutions of 1+4 for film and 1+4 or 1+9 for paper, and its fixing times of 5 to 7 minutes for film and 1 to 3 minutes for papers; Washing, recommending a rinse in a sulphite bath at 10 per cent to eliminate the chemical complexes resulting from the fixing bath and to allow full dissolution of the anti-halation layer, followed by ten washes in clear water at ten-minute intervals and a final rinse in demineralised water with wetting agent at 1+200; The whole one-and-a-half page sheet — an alkaline-based non-acid universal fixer supplied as a liquid concentrate, pH 7, diluted 1+4 for film and 1+4 or 1+9 for paper, film 5 to 7 minutes and FB paper 2 minutes at 1+4, with the claim that it requires a shorter washing time than other fixers to achieve the same archival level

Used by:Kodak F-52 · One per cent sodium sulfite washing aid · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline

BERGGER Cyanotype: datasheet, 06/2020retrieved 2026-09-05, 2026-09-06

Sections: Preparing the emulsion and Coating on the paper — 5 mL of part A plus 5 mL of part B coats approximately five 8 by 10 inch sheets and the 2 by 300 mL set approximately 300 sheets; Exposure time determination, about 10 minutes to maximum density under a cloudless Paris sky at noon in summer; Processing, Blue color intensification and Storage of solutions; The two-part premixed cyanotype kit that names its two chemicals and publishes no weights at all, cited here as the ordinary case this product is the exception to; BERGGER Cyanotype datasheet 06/2020 — Preparing the emulsion, that 5 mL of part A plus 5 mL of part B coats approximately five 8 by 10 inch sheets and that the 2 by 300 mL set coats about 300 sheets; Coating on the paper, the criss-cross pattern of horizontal then vertical strokes and the observation that a foam brush gives very even results while a splatter brush renders an interesting look along the edges, with the coating done away from sunlight but safely under artificial lighting; Exposure time determination, that the ultraviolet content of sunlight differs with latitude, season and time of day, the instruction to make a test strip by exposing in fixed increments and to choose the shortest exposure giving the highest density, and the tip that maximal density is obtained with an approximately 10 minute exposure during summer under a cloudless sky in Paris at noon; Processing, Blue color intensification by adding a few drops of hydrogen peroxide to a water bath, Washing, Drying in a dust-free location, and Storage of solutions, dry and away from natural light, with a shelf life of about one year; Coverage - the statement that the two 300 ml bottles of the set coat about three hundred sheets of 8 by 10 inch paper, used here only as the maker's own yield figure against which a project week's sensitiser consumption is checked; Preparing the emulsion — equal parts of solutions A and B, with the worked example that 5 ml of A plus 5 ml of B coats approximately five 8 by 10 inch sheets and that the complete set of two 300 ml bottles coats about 300 such sheets; Coating on the paper — the statement that BERGGER COT 320 and COT 160 papers are uniquely suitable, the choice of smooth or rag face, application with a splatter brush or foam brush in a criss-cross pattern of horizontal then vertical strokes, and the instruction that coating be done away from sunlight but may be done under artificial lighting; and Exposure time determination — the statement that the ultraviolet content of sunlight differs with latitude, season and time of day so exposure must be determined for the conditions at the time, the recommendation of a test strip in fixed increments, and the dated tip that maximum density is obtained in about 10 minutes under a cloudless summer sky in Paris at noon.

Used by:Classic cyanotype sensitiser · Photographers' Formulary cyanotype and toning kits · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Assignment: Cyanotype at Scale, on Fabric, and the Botanical Sequence · P21 What These Processes Need: The Negative, the Paper and the Light

BERGGER Pancro 400 datasheetretrieved 2026-09-04, 2026-09-05

Sections: Film composition: two emulsions differing in grain size, the layer stack including the undercoated anti-halation layer, and the base thicknesses for 135, 120 and sheet film; Long exposure corrections: the table of stop corrections against theoretical exposure time; Description - PANCRO 400 in 120 is coated on a 100 micron PET base and includes an anti-curling layer, and in sheets on a 175 micron PET base with an anti-curling layer, with the statement that the emulsion faces the user when the notch is in the upper right or lower left corner

Used by:P4 Grain, Speed and Resolution · P4 Reciprocity Failure and the Life of the Latent Image · P16 Build: The Contact Printing Frame and Its Light Source

BERGGER PMK Datasheetretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: PMK properties; preparation and conservation; use, capacity and temperature; film processing — pre-wetting, stop bath, fixing, washing; development errors; toxicity; time and temperature chart; PMK properties; Preparation; Use — capacity and working-solution life; Film processing — the pre-wetting, the non-acid stop bath, the non-tanning fixer, the extended wash and the instruction not to use a hypo eliminator; PMK properties; Preparation and Conservation; Use — capacity, working-solution life and temperature range; Film processing — pre-wetting, agitation, stop bath, fixing, washing; Development errors; Toxicity; the Time / Temp Chart; Film processing — the agitation instruction of constant stirring for the first 15 seconds and then every 15 seconds; Development errors — uneven development and uneven colouring caused by insufficient agitation, denser image edges caused by inadequate shaking and turbulence at the edges, and transverse or lateral traces of high density; PMK properties: the yellow-green tint surrounding each silver grain and the density of a pyro negative as the conjunction of two densities; capacity and temperature range; toxicity; PMK properties, preparation as two solutions A and B, the standard dilution of 1 part A, 2 parts B and 100 parts water, conservation, capacity, temperature range, film processing and the time and temperature chart with its meter settings; PMK properties — the yellow-green tint surrounding each silver grain and filling the space between them, the density of a pyro negative as the conjunction of two densities, and the claims of increased sensitivity, more pronounced definition and reduced grain; Preparation — two solutions A and B and the standard dilution of 1 part A, 2 parts B and 100 parts water; Conservation — a shelf life of up to ten years even in half-filled bottles; Use — capacity of 1000 square centimetres per litre, one hour of working-solution life in open vessels, and a temperature range of 21 to 27 degrees C with emulsion deterioration above 27 to 28; Film processing — the essential 3 to 5 minute pre-wet, agitation every 15 seconds, a non-acid stop bath, an essential non-tanning fixing bath, a 20 to 30 minute wash because the colouring intensifies during washing, and the instruction not to use a hypo eliminator; Development errors; Toxicity; the Time and Temperature chart with its meter settings; PMK Properties - a yellow-green tint surrounds each silver grain and fills the usually empty space between them and becomes an intrinsic part of the image, so that the density of a pyro negative is the conjunction of two densities, that of the silver and that of the coloration, with the result that the printing qualities of the film are increased; and Development errors, where insufficient agitation gives uneven colouring varying from olive green to yellow; Development - the instruction to agitate constantly for the first 15 seconds and then every 15 seconds, with the tank stationary between agitations, and the statement that this high stirring frequency prevents uneven development; Development errors - uneven development with areas of dissimilar density and uneven colouring listed against insufficient agitation, and denser image edges listed against inadequate shaking resulting in turbulence at the edges of the negative; and the development temperature range of 21 to 27 degrees C with the statement that emulsion damage follows above 27 to 28 degrees C; PMK properties - the statement that a yellow-green tint surrounds each silver grain and fills the usually empty space between them and becomes an intrinsic part of the image, so that the density of a pyro negative is the conjunction of two densities, that of the silver and that of the coloration; Conservation - the concentrates keeping up to 10 years including in half-filled bottles; Use - the maximum of 1,000 square centimetres of film per litre of working solution and the statement that the mixed working solution may stand one hour in an open vessel without affecting the quality of development; the recommended exposure indices of 200 for HP5 Plus, 250 for Tri-X, 80 for FP4 Plus and 32 for Pan F Plus, printed in the same document as the claim that the sensitivity of the film is increased; Development errors - uneven colouring from olive green to yellow where agitation is insufficient; and Toxicity

Used by:Pyrogallol · 510-Pyro · PMK pyro · P8 Acutance, Adjacency Effects and Compensating Development · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P8 Assignment: Reading a Developer Formula · P8 Staining and Tanning Developers · P15 Density Depends on How You Look: Geometry and Spectral Response · P27 Experiment: Agitation, Stand and Semi-Stand Development · P27 Assignment: The Developer Comparison, Measured and Printed

bonavolta.ch

KODAK Processing Chemicals and Formulas, publication J-1retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: The whole 56-page scan, which carries no extractable text layer; Seventh edition 1973, updated 1977: the imprint page; KODAK Developer D-76 and KODAK Replenisher D-76R on page 37; the keeping properties and useful capacities table on page 24; the Appendix on pages 51 to 53, its preamble and the thirteen developers it carries. Read from the page images of the scan, not from its text layer, which does not exist; The whole document — the mirror this course holds is a 56-page scan with no extractable text layer, so no formula, quantity or capacity on this page is taken from it; Printed page 41, TESTS FOR SILVER, for the ST-1 residual-silver test formula, its storage and dilution instructions and its reading procedure. The mirror the course holds carries no extractable text and a text search of the corpus found the designation nowhere; it was read from the page images on 6 September 2026 and ST-1 is set out in full in the formulary; Printed page 41, TEST FOR HYPO and TESTS FOR SILVER, for the HT-2 and ST-1 formulas and their reading procedures. The mirror the course holds carries no extractable text and a text search of the whole research corpus on 5 September 2026 found neither designation; both were read from the page images on 6 September 2026 and are set out in full in the formulary; Hardening baths SB-3 and SB-4 at 30 g of chrome alum per litre, with their agitation and time instructions

Used by:Kodak D-76 · Kodak D-76d · P10 Stop Bath Formulations and the Fixer Interaction · P11 Fixer Capacity, Exhaustion and Residual Silver · P12 Assignment: Your Archival Processing Sequence · Routing chromium(III) from the coating station

books.google.co.uk

The Darkroom Cookbook, 3rd editionretrieved 2026-09-06

Sections: Printed page 311, FORMULA #188, Fixer Test Solution, credited "Thanks to Manuel A. Garcia Maceda" — water 80.0 ml, potassium iodide 4.0 to 5.0 g, water to make 100.0 ml; printed page 312, the direction to add 10.0 ml of Fixer Test Solution to 100.0 ml of used fixer, to shake the solution, that if nothing happens or if a clear cloudiness appears the fixer is okay, and that if a white or yellow-white precipitate is formed the fixer should be thrown out; and printed page 108, Determining Fixer Capacity — that the hypo check is a reliable means to test fixer exhaustion but only if you are accurate in your measurements and testing procedure, that the potassium iodide must be 10.0 ml of a 4 to 5 per cent solution and the amount of hypo tested exactly 100.0 ml, that the combined solutions must be shaken to create a precipitate, that working dilutions of fixer should not be kept more than two months and less above 85 F / 29 C, that any fixer stock or working dilution should be discarded if it turns yellow or a white precipitate appears because sulfur is precipitating out of the solution, that as the fixer reaches its useful capacity it begins to smell like sulfur, that there are two methods for testing either film or paper and a third for film, and that when the initial clearing time has doubled it is time to mix a fresh fixing bath. Read in Google Books snippet view, which returns the publisher's own text around a searched term and never a whole page, so every sentence used here is one the returned snippets carried and the elisions are Google's. Page 311 is not among the pages the bibliography entry's own note lists as read; this page adds it; Read in Google Books snippet view. The TF-2 Alkaline Fixer entry, headed with Bill Troop's name in parentheses, running from the foot of page 273 onto page 274 and standing immediately before Formula #135, TF-3 Alkaline Rapid Fixer; its note that due to its alkalinity this fixer will wash out of negative and print materials more rapidly than will an acid fixer and that the fixer should be odorless; its quantities, water 750.0 ml, sodium thiosulfate 250.0 g, sodium sulfite 15.0 g, sodium metaborate 10.0 g, water to make 1.0 liter; and its directions, to use undiluted for either film or paper, to follow development by a 60-second plain water rinse or a minimum of 5 full changes of water, to fix films for 3 times the clearing time or a minimum of 5 minutes agitating for a full 30 seconds during each minute, to fix paper for 10 full minutes with occasional agitation, and that the capacity of TF-2 is twenty 8 by 10 inch prints or films per liter. Also the note under TF-3 that the greater concentration of Formulary TF-4 increases the fixing capacity to fifty 8 by 10 inch prints or films per liter while its slightly lower alkalinity decreases the ammonium odour; the Stop Baths and Fixers chapter, pages 103 to 110, for the disadvantages of an acid stop bath, the two thiosulfates and the statement that a 15 to 20 per cent ammonium thiosulfate solution fixes more rapidly than a 35 to 40 per cent sodium thiosulfate solution, the instruction that when using the crystalline form of sodium thiosulfate one should begin with water of at least 90 F / 32 C, the list of advantages of alkaline fixers — no hypo clearing agent required, no acid stop bath required and acid stop bath not to be used because the alkalinity of the fixer must be preserved, greater capacity than acid fixers, and both thiosulfates being more stable in alkaline solution — with the conclusion that keeping the process alkaline or neutral from developer to fixer will improve the permanence of the material as the thiosulfate will not mordant to the silver image or base, the two-bath method for paper, the clearing-time test and the rule that a bath whose clearing time has doubled should be replaced, the warning that a bath approaching capacity begins to smell of sulfur, the rule that working dilutions of fixer should not be kept more than two months and less if the ambient temperature is over 85 F / 29 C, and the statement that improper fixing is probably the major cause of stains in toned prints because an exhausted bath leaves insoluble silver compounds which cannot be washed out and which form a yellow stain on meeting a toner; page 23, the approximate relative pH scale, which places an alkaline fixer at 8.5 to 9.5; pages 164 and 169, on anhydrous, monohydrate and crystalline as hydrate names; pages 177, 193 and 194, the Pharmacopoeia entries stating that sodium metaborate is commonly sold in the octahydrate state as the most stable form, that metaborate octahydrate and Balanced Alkali (Kodalk) are for all practical purposes the same and may be substituted weight for weight, and that Balanced Alkali is more alkaline than borax and more easily soluble but less alkaline than carbonate and contains no free carbonate so that no carbonic gas bubbles form when an acid stop bath follows; page 235, that metaborate may be difficult to dissolve completely at room temperature but that any residual amount will dissolve by itself over a 24-hour period; page 273, its printing of Kodak F-24 as sodium thiosulfate 240.0 g, sodium sulfite 10.0 g and sodium bisulfite 25.0 g in 1.0 liter; and pages 312 and 351 to 358, the Hypo Clearing Agent formula and the index entries for Bill Troop, TF-2 and TF-3

Used by:Iodide hypo check · TF-2 alkaline fixer

The Film Developing Cookbook, 2nd editionretrieved 2026-09-06

Sections: The fixing chapter, in the ebook edition Google Books paginates as PT241, PT248 and PT287, which carries no printed page numbers — the passage quoting Haist's 1979 finding that sodium thiosulfate fixing "times increase when small amounts of dissolved iodide build up in solution", with the authors' emphasis and their remark that iodide levels have increased in both films and papers since Haist wrote it; the clearing-time rule, to multiply the clearing time by two (conventional advice) or three (the authors' advice) for the total fixing time, that the clearing time increases as the fixer is used, to test whenever convenient, and to discard the fixer when the clearing time doubles from the fresh test; and the recommendation to fix contemporary materials in sodium thiosulfate for three times the clearing time rather than twice; Read in Google Books snippet view. The fixers chapter, whose TF-2 ALKALINE FIXER table repeats the first edition's quantities line for line — water 750 ml, sodium thiosulfate 250 g, sodium sulfite anhydrous 15 g, sodium metaborate 10 g, water to make 1 liter — under the same "Alkaline sodium thiosulfate fixers" heading and followed by the same paragraph; the numbered advantages of alkaline fixers, of which the second reads that alkaline fixers allow much shorter washing times and therefore substantial savings in water usage, that removal of hypo is much faster even than when an ordinary fixer plus a hypo clearing agent is used, and that film fixed in an alkaline fixer does not require hypo clearing agent because hypo is down to archival levels after 40 seconds of washing, a figure the authors attribute to Haist volume II page 203, adding that film should be washed a total of two minutes to ensure all developer residue is removed and that there is little harm in extending it if running water is plentiful; the statement that although it may be more convenient to use acid fixers as they are more readily available, film processing should ideally take place in high salt solutions at or near the pH of the emulsion; the instruction, under "alkaline fixers; alkaline stop baths", that a user who wants an acid stop bath followed by an alkaline fixer should rinse the film in running water for 30 seconds after the stop bath but before the fixer; Troop's first-person account that when he formulated TF-4 for Photographers' Formulary, with the encouragement and advice of Grant Haist and Harold Russell, it was the first alkaline fixer ever offered for sale as such; the passage recording that iodide levels in films and papers increased in the 1980s when manufacturers refined the ways iodide could be used to improve speed, tone and sharpness; the remark that boric acid, at a pH of about 5, is one of the mildest of all acids and is the only acid the book commonly recommends; and the index entry "TF-2 Alkaline Fixer, 120"

Used by:Iodide hypo check · TF-2 alkaline fixer

bostick-sullivan.com

510 Pyro Developer, product pageretrieved 2026-09-05

Sections: The product description, the formulation credit and the dilution line

Used by:510-Pyro

510-Pyro Development Chartretrieved 2026-09-04, 2026-09-05

Sections: The whole seven-page chart, and specifically the paired rows for Ilford HP5 Plus, Ilford FP4 Plus, Kodak T-Max 400, Kodak Tri-X 400 and Ilford Delta 400 Professional at 1+100, the 1+500 rows for Ilford FP4 Plus and Fomapan 100, and the header line "Data Courtesy of digitaltruth.com"; The whole document — a development-time chart headed 'Data Courtesy of digitaltruth.com', carrying no composition, no ingredient list and no mixing instruction

Used by:510-Pyro · P8 Staining and Tanning Developers

Albumen Printing Kit Instructionsretrieved 2026-09-05, 2026-09-07, 2026-09-08

Sections: Kit Contents, for the 100 g of kaolin supplied "for cleaning Silver Nitrate" alongside the 1000 mL of 15 per cent silver nitrate solution; Kaolin China Clay 100 grams, for the statement that the powder maintains the freshness of the solution, that a small amount must be mixed in after every printing session, that the impurities settle with the clay after 12 to 16 hours and the solution is then decanted and filtered before each use, and that its shelf life as a powder is indefinite; Purifying the Silver Nitrate Bath after Each Session, for the half teaspoon of kaolin, the settling to a fine black precipitate and the red colour attributed to salt carried out of the albumen; Setting up to print, for the paper coffee filter used before each session and the small amount of black silver powder it catches; Your kit contains, and Kit Contents — the 1000 mL of 15 per cent silver nitrate solution shipped as the sensitising half of the kit, the statement that silver nitrate leaves a black stain on skin and almost every other surface and can cause severe burns to the eyes so that glasses or goggles are always worn, the shelf life of 10 or more years for the unused 15 per cent solution, the instruction to dispose of it with other hazardous waste, and the 100 g of kaolin supplied "for cleaning Silver Nitrate"; Setting up to print — the filtering of the silver solution through a paper coffee filter before each session and the small amount of black silver powder it catches, the red colour the bath takes on after a session from salt carried out of the albumen, the half teaspoon of kaolin shaken into the storage bottle after each session, the 12 to 16 hours of settling to a fine black precipitate and the decanting that leaves the cloudy bottom behind; Sensitizing albumenized paper — the statement that the albumen-coated paper is not light sensitive before this step, the six-minute float of the double-coated and heat-hardened sheet, the draining until there is a minimum of 20 seconds between drops, the hanging to dry over a tray or blotter, and the note that the silver nitrate solution is not itself light sensitive but becomes so on contact with organic substances; Washing the Print — the 25 to 30 minute first wash under running cold water with five complete changes, the milky blue-grey the wash turns as unexposed silver nitrate is removed, the note that municipal water high in chlorine clouds more than well water, and the warning that residual silver nitrate causes brown spots and foxing that may appear at any point in the future; Kit Contents — Albumen Solution, described as a ready-to-use salted albumen solution made from food-grade powdered egg whites containing a food-grade preservative, about sixty 8 by 10 inch prints per litre, a shelf life of 3 months unrefrigerated or 24 to 36 months refrigerated, best worked above 60 °F and removed from the refrigerator at least two hours before use because many papers resist absorbing cold albumen, and disposal by pouring down the drain with plenty of cold water; Setting up to print — filtering through cheesecloth before each session and drawing the bubbles off the tray surface with a paper spatula; Making Albumen prints — the six-minute float, the drain from a marked corner, the 60 to 90 minutes of air drying, the hardening of each coat in a dry-mount press at 250 °F or under a hot iron for two to three minutes, the second six-minute float drained from the diagonally opposite corner, and the six-minute float on a 15 per cent silver nitrate solution to sensitise; Making Albumen prints — the modern kit's double-coating procedure in full: the statement that a double coat will produce a denser, richer image and that most artists prefer to double coat to achieve a denser, glossier image; the folding and creasing of the two short ends of the sheet and the marking of the back of one corner as an orienting reference; the instruction that the first and second coats be drained from corners diagonal from each other to produce a consistent coating over the entire sheet; the float of 6 minutes per coat; the 60 to 90 minutes of air drying; Setting and Hardening The First Coat — the requirement to harden the first coat in a dry-mount press or under a clothes iron to prevent it dissolving during the second coat, the press set to 250 °F with the print flattened for 2 minutes between two clean archival sheets, and the iron at its highest setting moved slowly back and forth for 2 to 3 minutes; Floating the second coating — the re-creasing, the waves and ripples left by the press and the way the sheet relaxes flat on the albumen, and the hardening of the second coat as well once it has dried; Sensitizing albumenized paper with silver nitrate — the note that the coated paper is not light sensitive before this step and the 6-minute float on the silver nitrate solution; and Kit Contents — the ready-made salted albumen solution, its yield of about sixty 8 by 10 inch prints per litre, and the direction to work it above 60 °F because many papers resist absorbing cold albumen; Kit contents — the pre-mixed salted albumen made from food grade powdered egg whites, the 1000 mL of 15 per cent silver nitrate, the gold toning kit and the rapid fixer; Making Albumen prints — the two coats floated for 6 minutes each with heat hardening between them, the 6-minute sensitising float, the exposure by inspection, and the washing, toning and fixing sequence; Kit contents — the pre-mixed salted albumen "made from food grade powdered egg whites", its preservative, its shelf life and its working temperature, and the statement that the solution "should make approximately 60 prints on 8x10 paper"; Making Albumen prints — the two coats of six minutes each, the heat hardening between them at 250 °F, and the reason given for it; Kit contents — the pre-mixed salted albumen "made from food grade powdered egg whites", the food-grade preservative, the shelf life of 3 months unrefrigerated and 24 to 36 months refrigerated, the working temperature "above 60F (14C)" and the instruction to take it from the refrigerator at least 2 hours before use, and the statement that the solution "should make approximately 60 prints on 8x10 paper"; Setting up your workspace — the dry mount press or clothes iron used to flatten and harden the coatings, and the papers preferred, 145 to 300 gsm watercolour stock with 310 gsm Arches Platine and Bergger COT320 named; Setting up to print — filtering through folded cheesecloth in a funnel before each session, and dragging a paper spatula through the bath to pull the surface bubbles to the side; Making Albumen prints — the creased short ends, the marked reference corner, the 6-minute float, draining from diagonally opposite corners on the two coats, the 60 to 90 minute air dry, the reticulation and curl described as normal, hardening at 250 °F for 2 minutes in a dry mount press or with a clothes iron on its highest setting, and the reason given for hardening; the statement that "the albumen coated paper is not light sensitive before this step"; Safety and Handling Information — the black staining of skin, clothing and almost any surface, the apron, latex or nitrile gloves, closed-toed shoes and eye protection, the subdued lighting and red safelight, and cleanliness as the largest source of problems; Kit contents — the 15 per cent silver nitrate and its stated 10-year shelf life unused, the disposal instruction, the gold toning kit's yield and 12-hour working life, the fixer, and the kaolin; Purifying the Silver Nitrate Bath after Each Session — the red colour attributed to salt from the albumen, the half teaspoon of kaolin, the 12 to 16 hours of settling and the filtering before each session; Making Albumen prints — the six-minute sensitising float, the drip to a minimum of 20 seconds between drops, drying under safelight; Exposing The Image — 5 minutes to an hour under high-intensity ultraviolet, the split-back frame, inspection under room light for no more than 10 seconds at a time and never outdoors; Washing the Print — a minimum of 25 to 30 minutes with at least five complete changes of water, and the warning about brown spots and foxing from residual silver nitrate; Gold Toning the Print — 50 mL of 0.2 per cent gold chloride and 50 mL of 2 per cent ammonium thiocyanate in 900 mL of water, 5 minutes with agitation every 30 seconds, and replenishment after three 8 × 10 prints; Fixing The Image — 100 mL of concentrate in 900 mL of water, 6 minutes with agitation every 30 seconds, and the stated capacity; Final Wash & Drying — 30 minutes with agitation every minute, the squeegee or blot, the 2 to 3 hours to dry with the shadows deepening and the highlights taking a red or pink cast, and flattening at 200 to 225 °F; The albumen-coated paper not being light sensitive before sensitising; transferring salt and oil from the hands causing stains; the paper strip drawn through the bath to sweep bubbles to the side before every sheet; creasing the short ends upward; drying of 60 to 90 minutes with the drip corner completely dry before anything else; the heat hardening route of two minutes at 250 degrees F in a dry-mount press or an iron worked slowly for two to three minutes; draining from diagonally opposite corners on the two coats

Used by:Kaolin · Albumen sensitising solution · Albumen solution with its chloride · Double-coated albumen procedure · P23 Part XXIII Overview: Albumen Printing · P23 Egg Albumen: A Protein Binder and What It Does to Silver · P23 Lab: Preparing and Coating Albumen Paper · P23 Lab: Sensitising, Printing and Toning an Albumen Print · Preparing and coating albumen paper

Ammonium Dichromate: safety data sheet, Spectrum Chemical A1179, revision G1retrieved 2026-09-06

Sections: Spectrum Chemical A1179, revision G1 of 20 August 2015 — section 2, the longest classification in the supplier's library, with Carcinogenicity Category 1A, Germ cell mutagenicity 1B, Reproductive toxicity 1B, Acute toxicity Inhalation Category 2, Skin corrosion 1, Serious eye damage 1, Respiratory and Skin sensitization 1, STOT repeated exposure 1 and Oxidizing solids 2, signal word Danger, and the statements "Fatal if inhaled", "Causes severe skin burns and eye damage", "May cause cancer", "May cause genetic defects", "May damage fertility or the unborn child" and "May intensify fire; oxidizer"; section 8, the ACGIH TWA of 0.0002 mg/m3 as Cr against an OSHA ceiling of 0.1 mg/m3; section 9, orange-red crystals, formula weight 252.10, pH 3.95 at 1 per cent and 3.45 at 10 per cent, melting at 170 degrees C and decomposing at 180; section 10, incompatible with organic and combustible materials, powdered metals, reducing agents, acids, hydrazine, strong bases, carbides, alcohols, ethylene glycol and mercury cyanide; section 11, oral LD50 in the rat of 48, 53 and 80 mg/kg, a four-hour inhalation LC50 in the rat of 0.156 mg/L, and IARC Group 1, ACGIH A1 and NTP known human carcinogen for chromium(VI); and section 12, a freshwater fish LC50 of 136 mg/L at 96 hours.; Sections 1 and 2 of the supplier safety data sheet for ammonium dichromate, purified, CAS 7789-09-5, revision G1, preparation and revision date 20 August 2015 — the recommended use given first as "In photography", and the classification block giving Carcinogenicity Category 1A, Germ cell mutagenicity Category 1B, Reproductive toxicity Category 1B, Respiratory sensitization Category 1, Skin sensitization Category 1, Skin corrosion Category 1, Serious eye damage Category 1, acute toxicity oral Category 3 and inhalation Category 2, and specific target organ toxicity on repeated exposure Category 1

Used by:Bostick and Sullivan Ziatype kit · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes

Ammonium Ferric Oxalate: safety data sheet, Spectrum Chemical F1002, revision G1retrieved 2026-09-06

Sections: Spectrum Chemical F1002, revision G1 of 12 January 2016 — section 1, FERRIC AMMONIUM OXALATE, GRANULAR, CAS 13268-42-3, with the RTECS number annotated as belonging to the anhydrous form CAS 14221-47-7; section 2, hazardous under the 2012 OSHA standard, Acute toxicity Oral 4 and Dermal 4, Skin corrosion/irritation 2, Serious eye damage/eye irritation 2 and STOT single exposure 3, signal word Warning, with "Store locked up"; section 3, one component at 100 per cent; sections 7 and 10, room temperature in the original container, "Protect from light. Sensitive to light. Store in light-resistant containers", incompatible with oxidizing agents and strong acids; section 8, ACGIH 1 mg/m3 as Fe; section 9, formula (NH4)3Fe(C2O4)3.3H2O, formula weight 428.07, green to yellow-green, density 1.78 at 17 degrees C, decomposition at 167 to 170 degrees C, very soluble in water, no pH; section 11, every acute-toxicity field reading "No information available", the chronic note about brownish discoloration of the eyes, and "Not considered carcinogenic". Filed twice in the library, under two names, resolving to byte-identical copies of one file.

Used by:Bostick and Sullivan Ziatype kit

Cyanotype & Vandyke Brownprint Combo: product pageretrieved 2026-09-06

Sections: Cyanotype & Vandyke Brownprint Combo — the single line "250 ml Cyanotype kit - Makes 250 8"x10" prints", the supplier's third and highest figure for the same kit's yield

Used by:Bostick and Sullivan cyanotype and toning kits

Cyanotype Kit: instructionsretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Developing in Hydrogen Peroxide (optional) — the 100 mL of 3 per cent in 900 mL bath, 60 to 90 seconds, gas bubbles and the subsequent wash; Cyanotype Kit Instructions, four printed pages, re-read in full for this entry — the headline claim that the kit "will make approximately 200-250 8"x10" prints in stunning Prussian Blue"; section 1, that the solutions are sensitive to ultraviolet only, that a safelight is not necessary and normal incandescent lighting may be used throughout, that fluorescent light may be used but should be limited, that gloves are worn for handling, coating and processing, that "the solution should be considered poisonous", that it must not be kept in a food refrigerator, and that it "is stable at room temperature and will have a shelf life of approximately 1 year from the date of purchase if stored in their original separate containers"; section 2, the negative the same size as the print, the 1000 watt metal halide bulb, ultraviolet fluorescent tubes or sunlight, the split-back contact frame that allows inspection, the warning that the solutions stain wood, metal and many plastics, the dedicated brush and the shareable glass rod, the wash tray of cool steadily running water and the optional second tray of 100 mL of 3 per cent hydrogen peroxide in 900 mL of tap water, and the paper specification of 100 per cent cotton rag, unbuffered, at least 32 lb for 8.5 by 11 and hot pressed at 47 lb or more for larger work; section 3, the pencilled registration marks, the direction to mix equal parts of solutions A and B, and the drop table — 12 total for 4 by 5, 18 for 5 by 7, 24 for 6 by 9 and 40 for 8 by 10, half of each solution — with the brush method, the thirty-second and one-quarter rule, the warning about over-brushing, the coating rod method with its six-pass and ten-pass rules, the one hour of drying in a dark place and the statement that a hair dryer is not recommended because "allowing the paper to dry naturally results in a superior image"; section 4, that the image prints out, that "Cyanotypes must be over-exposed to create a permanent image", that "the blue color initially seen during exposure is non-archival and will wash away in plain water", that the correct end point is the darkest areas beginning to reverse, that a print looking faded and washed out will darken after wet processing, that judging the moment is "the most crucial part of the Cyanotype process", and the four-minute first inspection followed by inspection every few minutes; section 5, the yellow stain lifting in the first tray, the 12 to 15 minute wash with agitation and a water change every two minutes, the instruction to continue until no yellow remains in the highlights, the note that some blue pigment washing off is normal, the fifteen-second drain, air drying, the oxidation to dark Prussian blue as the paper dries, the statement that a faded print left in the dark for 2 to 4 weeks will re-oxidise, and the recommendation to flatten in a warm dry-mount press and mount on archival board; and section 6, the optional peroxide bath at 60 to 90 seconds with a further 8 to 10 minute wash, and the note that gas bubbles on the surface are normal. The sheet names no chemical anywhere and gives no composition, no pH, no exposure time for any named source and no sensitometry.; Safety and Handling Information — sensitivity to ultraviolet only, gloves, and a shelf life of about one year in the original separate containers; Preparing Your Workspace, the peroxide bath of 100 mL of 3 per cent hydrogen peroxide in 900 mL of tap water, and the choice of a 100 per cent cotton rag unbuffered paper; 4. Exposing the Image - the printing-out behaviour, the instruction to inspect after four minutes by opening one leaf spring of the hinged back, and the requirement to over-expose until the darkest areas begin to reverse; 1. Safety and Handling Information - the kit solutions are sensitive to ultraviolet light only and can be handled under normal room lighting, with incandescent lighting usable throughout and fluorescent lighting to be limited; 2. Preparing Your Workspace and Negative - exposure under a 1000 watt metal halide bulb, special ultraviolet fluorescent lights or sunlight; 4. Exposing the Image - the printing-out behaviour, the over-exposure required for a permanent image, and the instruction to watch for the darkest areas to reverse; Opening statement that the kit makes approximately 200 to 250 8 by 10 inch prints; 1. Safety and Handling Information — the solutions are sensitive to ultraviolet light only and can be handled under normal room lighting conditions, a safelight is not necessary and normal incandescent lighting can be used during the entire process, fluorescent light may be used but exposure of chemicals and coated paper to it should be limited to avoid fogging, work in a windowless room or shade the windows, always wear gloves, treat the solution as poisonous, do not store it in a refrigerator used for food, and a shelf life of about one year from purchase in the original separate containers; 2. Preparing Your Workspace and Negative — a negative the same size as the final image, printed in direct contact under intense ultraviolet light from a metal halide bulb, ultraviolet fluorescent tubes or sunlight, a split-back contact printing frame or two sheets of plate glass for registration and pressure, a brush dedicated to cyanotype alone while a glass rod may be shared if properly washed, and the choice of a 100 per cent cotton rag unbuffered paper; Cyanotype Kit Instructions, four pages, re-read in full — section 1, that the solutions are sensitive to ultraviolet only and may be handled under normal incandescent room lighting with no safelight, that fluorescent light should be limited, that gloves are worn throughout, that "the solution should be considered poisonous", that it must not be stored in a refrigerator used for food, and that it "is stable at room temperature and will have a shelf life of approximately 1 year from the date of purchase if stored in their original separate containers"; section 2, the split-back contact frame that allows inspection, the warning that the solutions stain wood, metal and many plastics, the dedicated brush against the shareable glass rod, the first tray of cool steadily running water, the optional second tray of 100 mL of 3 per cent hydrogen peroxide in 900 mL of tap water, and the paper specification of 100 per cent cotton rag, unbuffered, at least 32 lb for 8.5 by 11 inches and hot pressed at 47 lb or more for larger work; section 3, taping the upper corners, marking the four corners of the negative in pencil, the drop table of 12 drops total for 4 by 5, 18 for 5 by 7, 24 for 6 by 9 and 40 for 8 by 10 with half of each solution, the brush method with its wetted and blotted brush, its horizontal-then-vertical strokes, its rule that solution still spreading after 30 seconds means reducing the volume by a quarter, and its warning that over-brushing abrades the surface and clumps paper fibre, the rod method with its capillary loading, its rule that more than six passes means reducing the volume by a quarter and its instruction to blot with the corner of a paper towel if a line of solution remains after ten passes, and the hour of drying in a dark place with the statement that a hair dryer is not recommended because "allowing the paper to dry naturally results in a superior image"; section 4, that the image prints out, that "Cyanotypes must be over-exposed to create a permanent image", that "the blue color initially seen during exposure is non-archival and will wash away in plain water", that the end point is the darkest areas beginning to reverse and become lighter, that a print looking faded and washed out will darken after wet processing, that judging that moment is "the most crucial part of the Cyanotype process", and the first inspection at four minutes followed by inspection every few minutes; section 5, the yellow stain lifting in the first tray, the 12 to 15 minute wash with agitation and a water change every two minutes, the instruction to continue until no yellow remains in the highlights, the note that some blue pigment washing off is normal, the fifteen-second drain, air drying, the oxidation to dark Prussian blue as the paper dries, and the statement that a faded print left in the dark for 2 to 4 weeks will re-oxidise; and section 6, the peroxide bath at 60 to 90 seconds, the further 8 to 10 minute wash after it, and the note that gas bubbles on the surface are normal; Processing - the wash of 12 to 15 minutes with agitation and a change of water every two minutes, used here as the change schedule from which the volume of wash water at larger sheet sizes is scaled; and the listing of sunlight beside a 1000 W metal halide bulb and ultraviolet tubes as printing sources; Safety and Handling Information - the sensitivity to ultraviolet only, gloves, and a shelf life of about one year in the original separate containers; Preparing Your Workspace - the choice of a 100 per cent cotton rag unbuffered paper, the instruction to put newspaper or blotter under the sheet because the solutions stain the table, the brush used only for one process and the glass rod as the shareable alternative if properly washed, and the peroxide bath of 100 mL of 3 per cent hydrogen peroxide in 900 mL of tap water; Section 6, Developing in Hydrogen Peroxide (Optional) — 100 mL of 3 per cent hydrogen peroxide in 900 mL of tap water, 60 to 90 seconds with agitation, and a further 8 to 10 minute wash, given as a re-oxidation step for a finished cyanotype and not as a contrast control; Marking the negative corners in pencil; wetting and blotting the brush so the sensitiser does not wick into the bristles; the criss-cross spreading pattern; the self-tests — reduce the volume by a quarter if you are still spreading after 30 seconds or can make more than six rod passes; an hour drying in a dark place and the statement that a hair dryer is not recommended; The instruction to wash the brush thoroughly before using it again, because any solution left on it will be exposed and will contaminate the next print; 4. Exposing the Image - the instruction to inspect after four minutes by opening one leaf spring of the hinged back, and the requirement to over-expose until the darkest areas begin to reverse; Preparing your workspace - a large table with a hard smooth surface, with newspaper or blotter paper beneath because the solutions stain wood, metal and many plastic surfaces; a brush used only for cyanotype printing, avoiding a brush that has coated other alternative-process chemistry, while a glass coating rod can serve several processes if properly washed between uses; Emulsion coating and drying - marking the negative's four corners in pencil to concentrate the solution inside the image area, counting drops from a dropper into a small cup, and mixing solutions A and B thoroughly before coating; paper selection, with heavier hot-pressed papers withstanding wet processing better and producing a denser sharper image with smoother transitions; Preparing your workspace - if coating with a brush you should only use it for cyanotype printing and should avoid a brush that has been used to coat other alternative-process chemistry, while a glass coating rod can be used for multiple handcrafted processes if it is properly washed between uses; the solutions stain wood, metal and many plastic surfaces, so newspaper or blotter paper is placed on the table; Coating, exposure and washing instructions for the classic cyanotype kit, and the expected appearance at correct exposure; Washing - the wash sequence for a cyanotype and the appearance of unused sensitiser leaving the paper

Used by:Hydrogen peroxide · Bostick and Sullivan cyanotype and toning kits · Classic cyanotype sensitiser · P16 Build: The UVA Exposure Unit · P16 Ultraviolet for the Alternative Processes: Sources, Dose, Uniformity and Hazard · P21 Part XXI Overview: Photography in Prussian Blue · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Assignment: Cyanotype at Scale, on Fabric, and the Botanical Sequence · P21 Break/Fix: The Cyanotype That Went Wrong · P24 Contrast Control in Iron-Based Printing · Hand-coating a sheet with a rod and with a brush · Dedicating tools to one process · Operating the UVA exposure unit · Blotchy and streaked hand coating · Cross-contamination between alternative processes sharing a bench · Weak cyanotype maximum density · Yellow iron stain in cyanotype highlights

Cyanotype Printing Kit, 250 ml: product pageretrieved 2026-09-06

Sections: Cyanotype Printing Kit, 250 ml — the short description, "Classic cyanotype formula ( 25% Ferric Ammonium Citrate in solution A and 10% Potassium Ferricyanide in solution B) produces images rendered in brilliant Prussian Blue", with "The 250ml kit will make about 200 8"x10" prints"; the contents list, "Part A: 25% Ferric Ammonium Citrate-Green Flakes / Part B:10% Potassium Ferricyanide / 2 plastic droppers / Instructions"; and the paper recommendation of 100 per cent cotton rag, muslin or silk, with Arches Platine, Revere Platinum, Hahnemuhle Platinum Rag, Hahnemuhle Sumi-E and Rives BFK named. This is the only document in the supplier's literature that states what is in either bottle.; Cyanotype Printing Kit, 250 ml — the only document in the supplier's literature that states what is in either bottle, "Classic cyanotype formula ( 25% Ferric Ammonium Citrate in solution A and 10% Potassium Ferricyanide in solution B)", with "The 250ml kit will make about 200 8"x10" prints"

Used by:Bostick and Sullivan cyanotype and toning kits · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype

Cyanotype Toning Kit, 500 ml: product pageretrieved 2026-09-06

Sections: Cyanotype Toning Kit, 500 ml — the contents, "Cyanotype Bleaching Solution A-14% potassium carbaonate solution" and "Cyanotype Toning Solution B- 40% Tannic Acid Solution", printed twice on the page with the spelling of carbonate corrected the second time; the statement that the 500 mL kit "will tone approximately 60-75 8"x10" images", which is not the 50 to 75 of the kit's own instruction sheet; and the statement that it "Works with Classic Cyanotype and Modern Cyanotype images"; The "You receive" list, which is the only place either Bostick and Sullivan document names a chemical - "Cyanotype Bleaching Solution A-14% potassium carbonate solution" and "Cyanotype Toning Solution B- 40% Tannic Acid Solution" - together with the store page's own capacity figure of approximately 60 to 75 8 by 10 images from the 500 ml kit, which differs from the 50 to 75 printed on the instruction sheet, and the statement that the kit works with Classic Cyanotype and Modern Cyanotype images.

Used by:Bostick and Sullivan cyanotype and toning kits · P21 Lab: Toning the Prussian Blue Image

Cyanotype Toning Kit: instructionsretrieved 2026-09-06

Sections: Cyanotype Toning Kit, two printed pages — the claim that the 500 mL kit "will tone approximately 50-75 8" x 10" images with a cool, deep magenta color using a Tannic Acid toning solution"; section 1, gloves, eyewear and apron, no food refrigerator, and the statement that "the chemicals in your Cyanotype Toning Kit have a shelf life of 10 years at room temperature"; section 2, normal room lighting and three trays for bleaching, toning and a cold slow-running wash; section 3, the working dilutions of 50 mL of Bleaching Solution A in 950 mL of distilled water and 50 to 100 mL of Toning Solution B in 900 mL of distilled water, with the note that "stronger solutions tone more quickly, and give a darker image"; section 4, the bleach sequence — gentle agitation every 20 to 30 seconds, three minutes in total, the colour going from bright blue to red and then fading, the whole image reduced to a shadow after two to three minutes except in the absolute darkest areas, and the invitation to bleach for longer or shorter to obtain different colours; section 5, the toning sequence — transfer from the wash bath, agitate every 10 to 15 seconds, the shift from salmon through eggplant to a deep burnt magenta after several minutes, removal at any point for a different colour, then a fifteen-minute wash; section 6, replenishment at 5 to 10 mL of Toning Solution B per 8 by 10 image; and section 7, the instruction to store working solutions in light-tight containers for future use and the claim that depleted solutions may go down the drain with plenty of water because "Bleaching and Toning Solutions are safe for septic systems and the environment". The sheet names no chemical.; The whole two-page sheet, for the three-tray layout of bleach, toner and cold slow-running wash; the working dilutions of 50 mL of Bleaching Solution A in 950 mL of distilled water and 50 to 100 mL of Toning Solution B in 900 mL of distilled water with the note that stronger solutions tone more quickly and give a darker image; the bleaching sequence of gentle agitation every 20 to 30 seconds for 3 minutes with the colour going bright blue to red and then fading quickly, and the statement that after 2 to 3 minutes the entire image will fade to a shadow except for the absolute darkest areas which may not fade away entirely; the invitation to bleach for longer or shorter times to obtain many different colours; the toning sequence with agitation every 10 to 15 seconds and the shift from salmon to eggplant and then to a deep burnt magenta after several minutes, with the print removable at any time; the 15 minute final wash; the replenishment of 5 to 10 mL of Solution B per 8 by 10 image; the statement that toning is done under normal room lighting with no safelight; the 10 year shelf life at room temperature of the kit chemicals; the capacity of approximately 50 to 75 8 by 10 images from the 500 ml kit; and the disposal paragraph, which the course quotes in order to decline it.

Used by:Bostick and Sullivan cyanotype and toning kits · P21 Lab: Toning the Prussian Blue Image

Developers for the platinum and palladium process — store listingsretrieved 2026-09-06

Sections: Ammonium Citrate Developer (Pt/Pd Developer), SKU KDEV1_2, item no. DNTS — the identity (NH4)2HC6H5O7 and formula weight 226.19, the make-up sizes 1 L and 4 L, the description of the article as "a premeasured powder in a quart bottle" to be filled with distilled water and shaken, and the single behavioural claim, "Produces cooler tones than the traditonal potassium oxalate developer"; and the three sibling listings — sodium citrate, potassium oxalate and cold bath — none of which states a strength either

Used by:Ammonium citrate developer

EDTA: safety data sheet for EDTA Tetrasodium Salt, VWR/Amresco 0245, revision 3retrieved 2026-09-06

Sections: Sections 1, 2 and 3 — VWR/Amresco product code 0245, EDTA Tetrasodium Salt, revision 3 of 29-Sep-2016; Acute Toxicity Oral 4, Acute toxicity Inhalation (Dusts/Mists) 3, Skin Corrosion/Irritation 2, Serious Eye Damage/Eye Irritation 2 and STOT single exposure 3, signal word Danger, hazard statements H302, H315, H319 and H331 with "May cause respiratory irritation" and "May cause drowsiness or dizziness"; one component, Ethylenediaminetetraacetate tetrasodium, CAS 13235-36-4, at 95-100 per cent; VWR/Amresco 0245, revision 3 of 29 September 2016 — sections 1, 2 and 3, EDTA Tetrasodium Salt, one component, Ethylenediaminetetraacetate tetrasodium, CAS 13235-36-4, at 95 to 100 per cent, signal word Danger, with H302, H315, H319 and H331. The one sheet in the library that describes an item in this kit in the form the kit ships it, and the sheet that carries "Toxic if inhaled" against a store listing calling the same powder a "safe, easy to use clearing agent".

Used by:Bostick and Sullivan platinum and palladium kits · Bostick and Sullivan Ziatype kit

Ferric Ammonium Citrate, Green, Powder, FCC: safety data sheet, Spectrum Chemical F1001, revision G1retrieved 2026-09-06, 2026-09-07

Sections: Spectrum Chemical F1001, revision G1 of 11 December 2014 — section 1, the product name FERRIC AMMONIUM CITRATE, GREEN, POWDER, FCC and CAS 1185-57-5; section 2, the classification Serious eye damage/eye irritation Category 2B with signal word Warning and the hazard statement "Causes eye irritation", and "Causes mild skin irritation" under Other hazards; section 3, one component at 100 per cent with a trade-secret marker; sections 7 and 10, deliquescent, protect from moisture and light, sensitive to light, store in light-resistant containers, and the incompatible materials "Strong oxidizing agents. iodides. tannins. acacia preparations."; section 9, the formula field printed as "This compound is a complex salt of undetermined structure, composed of Iron, Ammonia, and Citric Acid", solubility 25 g/100 mL at 20 °C, specific gravity 1.8, no pH; section 11, LD50 oral rat greater than 2000 mg/kg, the note that prolonged eye contact may cause a brownish discoloration of the eyes, target organs eyes, skin, respiratory system, gastrointestinal tract and liver, and "Not considered carcinogenic"; Spectrum Chemical F1001, revision G1 of 11 December 2014 — section 1, FERRIC AMMONIUM CITRATE, GREEN, POWDER, FCC, CAS 1185-57-5; section 2, Serious eye damage/eye irritation Category 2B, signal word Warning, "Causes eye irritation", with "Causes mild skin irritation" under Other hazards; sections 7 and 10, deliquescent, protect from moisture and light, sensitive to light, store in light-resistant containers, incompatible with strong oxidizing agents, iodides, tannins and acacia preparations; section 9, the formula field printed as "This compound is a complex salt of undetermined structure, composed of Iron, Ammonia, and Citric Acid" with solubility 25 g/100 mL at 20 degrees C; section 11, LD50 oral rat greater than 2000 mg/kg and "Not considered carcinogenic"; Spectrum Chemical F1001, revision G1 of 11 December 2014 — section 1, ferric ammonium citrate, green, powder, FCC, CAS 1185-57-5; section 2, serious eye damage or eye irritation category 2B with the statement "Causes eye irritation" and "Causes mild skin irritation" under Other hazards; sections 7 and 10, deliquescent, protect from moisture and light, incompatible with strong oxidising agents; section 9, the formula field printed as a statement that the compound is a complex salt of undetermined structure

Used by:Bostick and Sullivan cyanotype and toning kits · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P24 Lab: Printing a Van Dyke Brown

Ferric Oxalate Powder: safety data sheet, Sigma-Aldrich 381446, version 4.5retrieved 2026-09-06

Sections: Sections 1, 2, 3.1, 8, 9, 10 and 11 — Sigma-Aldrich 381446, Iron(III) oxalate hexahydrate, CAS 166897-40-1, EC 220-951-7, Index-No. 607-007-00-3, formula C6Fe2O12 · 6H2O, molecular weight 483.84 g/mol; Acute toxicity Oral 4 and Dermal 4, signal word Warning, H302 + H312; the section 3.1 component "Diiron trioxalate hexahydrate" with the concentration column blank; "Contains no substances with occupational exposure limit values"; strong oxidizing agents as the incompatible materials; and a toxicological section in which every line reads "no data available", closing with the admission that the properties "have not been thoroughly investigated"

Used by:Bostick and Sullivan platinum and palladium kits

Gold Toning Kit for POP, Vandyke, Kallitype, Albumen and Salt Prints: instructionsretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Kit contents and mixing the toning bath — 500 mL of 2 per cent ammonium thiocyanate solution and 500 mL of 0.2 per cent gold chloride, 50 mL of each in a litre of water; Mixing the toning bath; Toning the POP print; Replenishing the toner; Gold Toning Kit for Printing Out Paper (POP) instructions, also for Van Dyke, Kallitype, Albumen and Salt Prints: the kit contents, 'A: 500ml Ammonium Thiocyanate solution 2%' and 'B: 500ml Gold Chloride solution 0.2%', described as stock solutions to be diluted; the mixing instruction 'In one tray, measure out 1000ml (1 liter or roughly 1 quart) of clean tap water or distilled water and add 50ml solution A and 50ml solution B. This is your toning bath.', with the note that the gold often momentarily turns a brown or orange colour when first mixed and should quickly redissolve; a second tray of 100 g sodium thiosulfate in 1000 ml of water as the fixer; the intermediate wash of 2 to 3 minutes in gently running water before toning, to remove excess silver and prepare the surface to absorb the toner evenly; the toning procedure, with the toner moving through the print in the shadows first, cooler and bluer tones the longer the print is left and warmer red-brown tones if it is pulled early; a 10-minute fix and a 20-minute wash afterwards; the replenishment of about 5 ml of solution B per print, or 25 ml when the bath slows to an impractical speed; and the variations for Van Dyke, kallitype, salt and albumen prints, which are toned before fixing and, in the case of Van Dykes, sometimes better after; The title page, which names kallitype prints among the processes the kit is for; The title page, which states that the kit for printing-out paper also works for Van Dyke, kallitype, albumen and salt prints; Mixing the toning bath — 50 mL of the 2 per cent ammonium thiocyanate stock and 50 mL of the 0.2 per cent gold chloride stock in a litre; Toning the POP print, and the instruction to fix after toning; The instruction for printing-out paper that prints will have a significant amount of dry-down and will get darker as they dry, cited here only as evidence that dry-down is a documented and quantified-in-words effect in the printing-out processes, where this course has found no manufacturer figure for it on a developing-out silver gelatin paper; Gold Toning Kit for Printing Out Paper — the kit as two stock solutions, 2 per cent ammonium thiocyanate and 0.2 per cent gold chloride; the observation that while toning the toner moves through the print usually in the shadows first; the instruction that for cooler, bluer tones the print is toned until no further change is observed and for redder, warmer tones it is pulled earlier; the note that with every print a portion of the gold chloride is used up and the bath must eventually be replenished, either by assuming each print uses about 5 mL of the gold stock and adding that after each print, or by watching for the bath to slow down and then adding 25 mL to bring it back to normal; and the instruction that most types of print are toned before fixing; What you get in the kit, for the 500 mL of 2 per cent ammonium thiocyanate solution A and the 500 mL of 0.2 per cent gold chloride solution B; Mixing the toning bath, for 50 mL of each in 1000 mL of water and for the gold briefly turning brown or orange before redissolving; Preparing the print, for the 2 to 3 minute rinse before toning that removes excess silver and preps the surface, and for the purple mist of excess silver reacting with chlorine in tap water; Toning the POP print, for toning until no further change for cooler blue tones and pulling earlier for warmer red-browns, for gloves and minimising exposure to the bath, and for the true colour not being seen until after fixing, rinsing and washing; Replenishing the toner, for the estimate that each print uses up approximately 5 mL of gold chloride solution and for the alternative of adding 25 mL when toning slows; Variations for Kallitype, Van Dyke, Salt prints, Albumen, for prints without gelatin toning much faster than POP paper and for adjusting accordingly; Mixing the toning bath, for 50 mL of the 2 per cent ammonium thiocyanate solution A and 50 mL of the 0.2 per cent gold chloride solution B in 1000 mL of water, for the gold momentarily turning brown or orange before redissolving, and for the separate tray of 100 g of sodium thiosulfate in 1000 mL of water; Preparing the print, for over-printing until one or two shades darker than the desired final print, for the 2 to 3 minute rinse in gently running water that removes excess silver and preps the surface, for the print lightening a shade or two and shifting towards red during that rinse, and for the purple mist of excess silver reacting with the chlorine in tap water; Toning the POP print, for handling the print by the back or edges only, for submerging it quickly and evenly and agitating at once, for the toner moving through the shadows first, for toning until no further change is observed for cooler blue tones and pulling earlier for warmer red-browns, for gloves and minimising exposure to the bath, for the true colour and density not being seen until after fixing, rinsing and washing, for fixing 10 minutes, for the 20 minute rinse, for drying on screens or clean blotter, and for the significant dry-down; Replenishing the toner, for about 5 mL of gold chloride solution being used per print and for the alternative of adding 25 mL when toning slows; Variations for Kallitype, Van Dyke, Salt prints, Albumen, for following the standard rinsing and clearing for the process but not fixing before toning, for prints without gelatin toning much faster than POP paper, and for the toning being faint on some prints until they are fully dried; Preparing the print, for the 2 to 3 minute rinse before toning that removes the excess silver and preps the surface to absorb the toner evenly; Replenishing the toner, for a portion of the gold chloride being used up with every print, for the estimate of about 5 mL per print, and for the alternative of adding 25 mL when toning slows to an impractical speed; Gold Toning Kit for Printing Out Paper, also for Van Dyke, kallitype, albumen and salt prints — the kit of 500 mL of 2 per cent ammonium thiocyanate as solution A and 500 mL of 0.2 per cent gold chloride as solution B; the toning bath of 50 mL of each in a litre of clean tap or distilled water, with the note that the gold may momentarily turn brown or orange on mixing and should redissolve; the claim that toning enhances permanency, preserves the full tonal range, prevents loss of values through the fixing stage and changes the colour to a cooler blue with maroon or purple shades possible; the toning procedure, watching the toner move through the shadows first, pulling early for warmer tones and toning to no further change for cooler ones; replenishment either by 5 mL of gold after each print or by 25 mL when the bath slows; and the Variations section for kallitype, Van Dyke, salt and albumen prints — follow the standard rinsing and clearing instructions for that process but do not fix before toning, remember that prints without gelatin tone much faster than POP paper, that some sources say Van Dykes are better toned after fixing and rinsing if staining occurs, and that on some types of print the toning will be faint until the print is fully dried; The thiocyanate gold toner: 50 mL each of 2 per cent ammonium thiocyanate and 0.2 per cent gold chloride per litre, the colour change on mixing, and replenishment; The gold thiocyanate kit as two stocks; the toner moving through the print in the shadows first; toning until no further change for cooler and bluer tones, pulled earlier for warmer; the replenishment rules; the instruction that most types of print are toned before fixing; Mixing the toning bath - 50 ml each of the 2 per cent ammonium thiocyanate and 0.2 per cent gold chloride stock solutions in 1000 ml of clean tap or distilled water, with the note that the gold often momentarily turns brown or orange when first mixed and should quickly redissolve; the fixer of 100 g sodium thiosulfate per litre, thoroughly dissolved because even very small crystals will cause stains and unevenness when they settle on the print; Preparing the print - over-print by one or two shades; step 6, rinse the print in gently running water for 2 to 3 minutes to remove the excess silver and prepare the surface to evenly absorb the toner, during which the print lightens a shade or two and shifts towards red as the excess silver reacts with chlorine in the tap water and forms a purple mist that floats off the paper; Toning - submerge the whole print quickly and evenly and begin agitating immediately, watching the toner move through the shadows first; Replenishing the toner - each print uses up approximately 5 ml of gold chloride solution, so either add 5 ml after each print or add 25 ml when toning slows to an impractical speed; the variations for Kallitype, Van Dyke, salt and albumen prints, which follow the standard rinsing and clearing for the process but are not fixed before toning, and which tone much faster than POP because they have no gelatin layer; the note that on some prints the toning will be faint until the print is fully dried; Preparing the print - over-print the image until it is one or two shades darker than the desired final print, because some density is lost in processing; the rinse of 2 to 3 minutes in gently running water to remove excess silver and prepare the surface to absorb the toner evenly, during which the print lightens a shade or two and shifts towards red; toning before fixing, and the note that the fix might bleach out some of the remaining silver and may warm up the image; the variation for Kallitype, Van Dyke, salt and albumen prints, in which the standard rinsing and clearing instructions for the process are followed but the prints are not fixed before toning

Used by:Ammonium thiocyanate · Chloroauric acid · Gold-thiocyanate toner · Kallitype sensitiser · Van Dyke Brown sensitiser · P13 Paper Sensitometry: Reflection Density, Grades and ISO(R) · P20 Gold, Iron-Blue and the Other Metal Toners · P22 Gold Toning and the Permanence of a Printed-Out Silver Image · P22 Lab: Printing, Toning, Fixing and Washing a Salt Print · P22 Break/Fix: The Printed-Out Image That Faded · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · Gold-toned and palladium-toned kallitype · The printing-out processing line · The gold toner that did nothing because the first wash was omitted · The printed-out image that bleached away in the fixer

Na2 Digital Negatives Kit Drop Count Sheet, calibrated to B&S Photoshop curvesretrieved 2026-09-06

Sections: The whole sheet, for the drop counts at nine print sizes and for the statement that they are calibrated to the supplier's own Photoshop curves — cited here for one purpose, that its 8 × 10 line of 20 drops of ferric oxalate #1, 15 of palladium #3 and 5 of the 5 per cent Na2 is not the 8 × 10 line the kit instruction sheet prints for the same kit; The whole sheet, for the drop counts of ferric oxalate #1, palladium #3 and 5 per cent Na2 at nine print sizes, and for the statement that the counts are calibrated to the supplier's own Photoshop curves for digital negatives

Used by:Bostick and Sullivan platinum and palladium kits · Three-solution drop system for platinum and palladium

Palladium Chloride: safety data sheet, Fisher Scientific P6-5, revision 1retrieved 2026-09-06

Sections: Sections 1 and 2 — Fisher Scientific P6-5, Palladium(II) chloride, revision 1 of 04-Aug-2014; Corrosive to metals 1, Serious Eye Damage/Eye Irritation 1 and Skin Sensitization 1, signal word Danger, "May cause an allergic skin reaction". Cited as the nearest thing in the library to a sheet for the palladium in these kits, and as evidence that it is not one; Fisher Scientific P6-5, revision 1 of 4 August 2014 — sections 1 and 2, Palladium(II) chloride, Corrosive to metals Category 1, Serious Eye Damage Category 1 and Skin Sensitization Category 1, signal word Danger. Cited here for what it is not: the nearest thing in the supplier's library to a sheet for the palladium in this kit, and a sheet for a red solid the company sells by the gram rather than for the dark brown lithium chloropalladite solution it makes in house.

Used by:Bostick and Sullivan platinum and palladium kits · Bostick and Sullivan Ziatype kit

Palladium Toner Kit for POP, Vandyke and Kallitype: instructionsretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Your kit includes; Preparing the toning bath; Toning your paper; Refreshing the toning bath; The title, Palladium Toner Kit for POP, Vandyke, and Kallitype; Preparing the toning bath; The title, Palladium Toner Kit for POP, Vandyke, and Kallitype; Preparing the toning bath — 10 g of citric acid to a litre of distilled water for a 1 per cent solution, with the note that the alkalinity of hard water will buffer it somewhat, plus 7 to 15 drops of sodium chloropalladite solution; Toning your paper, the rinse, and the fixing instruction of 15 per cent sodium thiosulfate for 3 minutes; Palladium Toner Kit for POP, Vandyke and Kallitype — the kit as citric acid and a sodium chloropalladite solution, the working bath being a 1 per cent citric acid solution with 7 to 15 drops of the palladium solution per litre, the note that the alkalinity of hard water will buffer the citric acid somewhat, the toning by inspection beginning in the shadows, the 5-minute rinse and the fixing in 15 per cent sodium thiosulfate afterwards in which the fix bleaches out the excess silver and reveals the final toned image, and the refreshing of the bath with 5 to 10 additional drops after 10 to 25 prints; The whole three-page sheet — the kit of 100 g citric acid making ten litres of working solution and 10 mL of palladium solution number 3, sodium chloropalladite, with the note that 10 mL is equal to 255 drops; the toning bath of 10 g citric acid in a litre of room-temperature distilled water for a 1 per cent solution, with the observation that the alkalinity of hard water will buffer the citric acid somewhat, plus 7 to 15 drops of palladium solution number 3, more drops giving faster toning and slower speeds being desirable for inspection; the instruction to pour the bath evenly over the whole print and agitate continuously front to back and side to side; the observation that toning begins in the darker shadow areas where it is hardest to see and that by the time changes are visible in the lighter zones toning is well underway; a rinse of five minutes in fresh running water to remove excess citric acid; fixing in 15 per cent sodium thiosulfate, 150 g to a litre, with 10 to 20 per cent working in practice, for three minutes with regular agitation, the fix bleaching out the excess silver and revealing the final toned image which should be a little lighter than desired because the print dries down extensively; refreshing the bath with 5 to 10 additional drops after 10 to 25 prints, with the rate depending on how much shadow area is toned; and storage for several weeks in a cool place away from direct sunlight; Your kit includes, for the 10 mL of palladium solution being 255 drops; Preparing the toning bath, for the 1 per cent citric acid and the 7 to 15 drops of palladium solution per litre; Your kit includes, for the 10 mL of palladium solution #3 being equal to 255 drops and the 100 g of citric acid making 10 litres of working solution; Preparing the toning bath, for the 1 per cent citric acid and the 7 to 15 drops of palladium solution per litre; Your kit includes, for the statement that 10 mL of palladium solution #3 is equal to 255 drops; The palladium toner for printing-out paper, Van Dyke and kallitype: 1 per cent citric acid with seven to fifteen drops of palladium solution per litre, worked by inspection, and its capacity

Used by:Sodium tetrachloropalladate(II) · Kallitype sensitiser · Van Dyke Brown sensitiser · P20 Gold, Iron-Blue and the Other Metal Toners · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P25 Part XXV Overview: Platinum and Palladium · P25 Cost, Permanence and When a Platinum Print Earns Its Price · P25 Lab: Preparing the Sensitiser and Coating for Palladium · Gold-toned and palladium-toned kallitype

Platinum and Palladium Printing Instructionsretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Kit contents and wet processing — 250 g EDTA clearing agent with sodium bisulfite, two tablespoons of each to a quart of water; Notes on the Kit Chemicals — Platinum and Palladium Solutions; Your kit will contain, and Notes on the Kit Chemicals — Potassium Oxalate Developer, for the developer the platinum and palladium kits actually ship and for the sheet's silence about any other; Making The Print, for the instruction not to develop in metal trays, to pour the developer quickly enough to break air bubbles, and for development complete within a few seconds with most printers leaving the print in for 1 to 2 minutes; The whole seven-page sheet, re-read in full for this entry — the note that "these instructions cover several Platinum/Palladium printing kits" and that a kit "may not contain all of the components discussed herein"; the claim that the kit "provides the essential chemicals in standardized form. No mixing is necessary"; *Your kit will contain a combination of the following*, for the 25 ml ferric oxalate #1, the 25 ml ferric oxalate #2 "(pt or pd)" described as belonging to the "traditional kit or classic palladium kit only", the 25 ml Palladium #3 "not in platinum printing kit", the 10 ml Platinum solution given three identities at once, the 32 oz potassium oxalate developer, the 250 g EDTA clearing agent and the 250 g sodium bisulfite; *Safety Notes*, all three sentences of it; *Notes on the Kit Chemicals* — Ferric Oxalate #1 as "the classic 27% solution", "the same for platinum and palladium" and "the only light sensitive compound in your kit"; Ferric Oxalate #2 as "also 27%" with "a small amount of potassium chlorate added as a contrast agent", the statement that the #2 solutions "have different amounts of potassium chlorate for platinum and palladium, the palladium requires twice as much chlorate to achieve contrast", the instruction to use the palladium #2 when printing a mixture, the mixing "from our exclusive yellow powder just before shipping", the shelf life "of approximately 1 year" longer if refrigerated but at room temperature when used, and "DO NOT STORE WHERE A CHILD CAN REACH IT"; Platinum and Palladium Solutions #3, for "they do not oxidize or age", the contamination warning, "always use glass containers, never metal as the platinum or palladium will plate out on the container" and the statement that refrigeration is not necessary; Sodium Platinum Na2 Solution #3, for the 5 per cent and 20 per cent dilutions, "a high contrast Platinum solution which is used in place of both the Ferric Oxalate Solution #2 and the traditional Platinum Solution #3 (Potassium Chloroplatinite)" and the instruction in bold not to use either with it; Potassium Oxalate Developer, for reuse with replenishment, the coffee filter and plastic funnel, the darkening from dissolved metal and "Many printers swear the older the developer, the better"; EDTA Clearing Agent and Sodium Bisulfite, for the two tablespoons of each to a quart and "This is not a critical measurement"; *Some Basics — Your Negative*, for the density range of 1.35 to 1.50 and the passage on the soft print; *Large Format Negatives*, for HP5, FP4, D-19, Rollo Pyro and Pyrocat-HD; *Making The Print*, steps 1 to 10, for the shot-glass mixing, the ten-minute soak, the split-back frame, the 3 to 8 minutes under a sun lamp for a 4 × 5 and the half hour for a dense negative, the prohibition on metal trays, "Development is complete within a few seconds", the developer usable "from room temperature up to the boiling point", the one or two clearing baths of five minutes each, "Fresh clearing agent will clear up to a dozen 8x10 prints", the yellow-highlight test for incomplete clearing, "Throw away the clearing bath when finished" and the half-hour wash; and all five *Drop Charts*; Notes on the Kit Chemicals, and Wet processing steps 8 and 9, for the sister kit against which this one is set — the developing-out route with its ferric oxalate at 27 per cent, its chlorate contrast bottle, its quart of potassium oxalate developer and the same EDTA and sodium bisulfite clearing powders at the same two tablespoons of each to a quart.; Kit contents, for the 250 g of EDTA clearing agent and 250 g of sodium bisulfite supplied for clearing; EDTA Clearing Agent and Sodium Bisulfite, for the instruction to use the two powders together, two tablespoons of each to a quart of water, with the remark that "this is not a critical measurement; less will just take longer to clear, more will clear faster"; and wet processing step 9, for one or two successive baths of that mixture at five minutes each, for fresh clearing agent clearing up to a dozen 8 by 10 prints, for water hardness sometimes affecting clearing time, for the statement that the clearing process removes the ferric oxalate from the print and that yellowing in the highlights means it is not being properly cleared, and for the instruction to increase the concentration or the time and to throw the bath away when finished; Your kit will contain; Notes on the Kit Chemicals; Drop Charts. Cited only as the competing supplier's version of the same three-bottle system, for its 27 per cent ferric oxalate against this supplier's 20, for its statement in words that palladium requires twice as much chlorate, and for the fact that it publishes no weight for its chlorate and no strength for either metal solution; Kit contents, for the 250 g of EDTA clearing agent and 250 g of sodium bisulfite supplied for clearing; EDTA Clearing Agent and Sodium Bisulfite, for the instruction to use the two powders together, "2 tablespoons of each to 1 quart of water. This is not a critical measurement; less will just take longer to clear, more will clear faster"; and wet processing step 9, for one or two successive baths at five minutes each, for fresh clearing agent clearing up to a dozen 8 by 10 prints, for water hardness sometimes affecting clearing time, for the statement that the clearing process removes the ferric oxalate from the print and that yellowing in the highlights means it is not being properly cleared, for the remedy of increasing the concentration or the time, for throwing the bath away when finished, and for the final wash of half an hour in gently flowing water; Your kit will contain; Safety notes; Notes on the Kit Chemicals — Ferric Oxalate #1, Ferric Oxalate #2, Platinum and Palladium Solutions #3, Sodium Platinum Na2 Solution #3, Potassium Oxalate Developer, EDTA Clearing Agent and Sodium Bisulfite; Some Basics — Your Negative; Making The Print, steps 1 to 10; Drop Charts, all five; Your kit will contain, for the ready-made potassium oxalate developer; Notes on the Kit Chemicals — Potassium Oxalate Developer, for reuse, replenishment, filtration of sludge and the divided trade opinion about an old bath; Making The Print — Development, for the pour, the one to two minutes and the statement that the developer may be used from room temperature up to boiling; Your kit will contain, for the 32 oz bottle of ready-made potassium oxalate developer whose strength the sheet does not state; Notes on the Kit Chemicals — Potassium Oxalate Developer, for the reuse, the replenishment of evaporation, the coffee-filter removal of sludge, the darkening from dissolved metal and the divided trade opinion about whether an old bath is better; Making The Print, for the place of the developer in the sequence; Large Format Negatives — the recommendation of Ilford HP5 and FP4 developed in a high contrast developer such as Kodak D-19 or a pyro developer; Inkjet Digital Negatives; Making The Print — the instruction to select a good 100 per cent rag or cotton paper, to count out the number of drops for all printing solutions into one small container, to mark the coating area from the negative, to pour the coating solution across the centre and spread it rapidly, to stop brushing when the wetness dulls, and to wash the brush thoroughly before using it again because any solution left on it will be exposed and contaminate the next print; the 10 minute soak followed by air or hair-dryer drying with the warning that an incompletely dried sheet gives splotchiness; and the Drop Charts, whose Na2 platinum-palladium kit for digital negatives gives 6 drops of palladium, 6 of ferric oxalate and 3 of Na2 5 per cent for a 4 by 5 negative, 10, 10 and 4 for 5 by 7, and 20, 20 and 4 or 5 for 8 by 10.; Notes on the Kit Chemicals — Potassium Oxalate Developer, for the indefinite life, the replenishment, the coffee-filter sludge and the darkening colour; EDTA Clearing Agent and Sodium Bisulfite, for the two tablespoons of each to a quart and the statement that this is not a critical measurement; Making The Print steps 7 to 10, for the exposure guidance, the rapid pour to break air bubbles, the development complete within a few seconds, the one-to-two minute immersion, the room-temperature-to- boiling range, the one or two clearing baths of five minutes, the dozen 8 by 10 prints per quart, the yellowing-highlights diagnostic and the half-hour wash; Notes on the Kit Chemicals, for the 27 per cent ferric oxalate, the statement that the metal solutions do not oxidise or age and plate out on metal containers, and the potassium oxalate developer that darkens with dissolved metal; Some Basics, for the negative density range of 1.35 to 1.50; Some Basics — Your Negative, for the density range of 1.35 to 1.50; Making The Print step 8, for the statement that print colour and contrast vary with developer temperature from room temperature up to boiling; Your kit will contain; Safety notes, for the dust-mask warning when drying with a hair dryer and the recommendation of supervision; Notes on the Kit Chemicals — Ferric Oxalate #1 at 27 per cent, Ferric Oxalate #2 and its chlorate, and the Platinum and Palladium Solutions #3, glass only and never metal; Some Basics — Your Negative, for the density range of 1.35 to 1.50; Making The Print, steps 1 to 5; Drop Charts, for the Na2 kit chart of 20 drops palladium and 20 drops ferric oxalate at 8 by 10, and the Classic Palladium chart of 20, 18 and 2; Kit contents and wet processing — the EDTA and sodium bisulfite clearing bath; the chlorate comparison between platinum and palladium; The drop charts for 8 by 10 and 4 by 5 coatings and the statement that 10 mL of the palladium solution equals 255 drops; One dedicated syringe per bottle plus a third for delivery; glass rather than metal for the coating implement; The drop charts for 8 by 10 and 4 by 5, the statement that 10 mL of the palladium solution equals 255 drops, and the instruction to pour the developer quickly over the print, tilting and sloshing the tray; Kit contents and processing - the potassium oxalate developer, the EDTA clearing agent and the sodium bisulfite supplied for clearing, used together at two tablespoons of each per quart of water; the instruction to drain the developer and soak in one or two successive clearing baths of five minutes each, that fresh clearing agent will clear up to a dozen 8 by 10 prints, that water hardness will sometimes affect clearing time, that the clearing process removes the ferric oxalate from the print, and that if the print shows any yellowing in the highlights it is not being properly cleared, so the concentration or the time should be increased

Used by:EDTA disodium salt (anhydrous) · Palladium(II) chloride · Potassium tetrachloropalladate(II) · Potassium tetrachloroplatinate(II) · Sodium tetrachloropalladate(II) · Ammonium citrate developer · Bostick and Sullivan platinum and palladium kits · Bostick and Sullivan Ziatype kit · EDTA and sodium sulfite clearing sequence · Photographers' Formulary platinum and palladium printing kits · EDTA, citric acid and hydrochloric acid clearing sequence · Three-solution drop system for platinum and palladium · Sodium citrate developer · Willis's potassium oxalate developer · P21 What These Processes Need: The Negative, the Paper and the Light · P25 Lab: Exposing, Developing and Clearing a Palladium Print · P25 Noble Metal Chemistry and the Platinotype · P25 Experiment: Tonal Scale, Contrast and Image Colour in Palladium · P25 Lab: Preparing the Sensitiser and Coating for Palladium · Palladiotype · Hand-coating a sheet with a rod and with a brush · Dedicating tools to one process · Running a platinum or palladium session · Platinum print stain from incomplete clearing

Platinum and palladium printing kits: the maker's own store listingsretrieved 2026-09-06

Sections: All six kit listings, for the contents and the yields the instruction sheet does not give: Platinum Printing Kit – 25 ml, 25ml Classic Palladium Printing Kit, 35 ml Traditional Platinum & Palladium Combo Kit, 35 ml Na2 Platinum & Palladium Combination Kit, Na2 Platinum/Palladium Kit For Digital Negatives and the 10 ml Na2 Student Starter Kit — including the two places where a listing names a compound the sheet does not, "10 ml Sodium Palladium Solution #3" and "Tetrasodium EDTA Clearing Agent", and the statement that the traditional kit "has largely been replaced by our Digital Negatives kit"

Used by:Bostick and Sullivan platinum and palladium kits

Platinum and palladium solutions and clearing chemicals: the maker's own store listingsretrieved 2026-09-06

Sections: Ferric Oxalate Solution # 1 and # 2, for the 27 per cent, the mixing "fresh from powdered Ferric Oxalate", the shelf life "of approximately 1-2 years before it should be tested or discarded" and the single figure "The Ferric Oxalate solution #2 has 1.2% Potassium Chlorate added as a contrast booster"; Palladium Solution #3, Platinum Solution #3 and the two Na2 solutions, for the fact that each listing carries a stock number and a list of bottle sizes and no other text at all; Potassium Oxalate (Pt/Pd Developer) 1 qt; EDTA Tetra Sodium (B+S Clearing Agent), for "Safe, easy to use clearing agent"; and Sodium Bisulfite 250 g, for "CAS No. 7681-57-4" printed beside "Other Name Sulfurous Acid Monosodium Salt"; Palladium Solution #3 and the clearing chemicals, for the 15 per cent sodium chloropalladite and the 625 drops per 25 ml bottle that the same company publishes for the developing-out palladium and does not publish for the lithium palladium in this box, and for the EDTA Tetra Sodium listing that identifies the clearing powder the Ziatype sheet leaves unnamed.

Used by:Bostick and Sullivan platinum and palladium kits · Bostick and Sullivan Ziatype kit

Potassium Carbonate, Anhydrous, Granular, Reagent, ACS: safety data sheet, Spectrum Chemical P1235retrieved 2026-09-06

Sections: Spectrum Chemical P1235, prepared 18 April 2016 — section 1, POTASSIUM CARBONATE, ANHYDROUS, GRANULAR, REAGENT, ACS, CAS 584-08-7, with pearl ash, potash and salt of tartar among the synonyms; section 2, hazardous under the 2012 OSHA standard and a dangerous substance under GHS, Acute toxicity Oral Category 4, Skin corrosion/irritation Category 2, Serious eye damage/eye irritation Category 2A and STOT single exposure Category 3, signal word Warning, with the statements "Harmful if swallowed", "Causes skin irritation", "Causes serious eye irritation" and "May cause respiratory irritation", and the storage instruction "Store locked up"; section 3, one component at 100 per cent; sections 7 and 10, deliquescent and incompatible with oxidizing agents, metals, acids, chlorine trifluoride, calcium oxide and magnesium; section 9, pH 11.6 in 10 per cent solution, solubility in water 105 g/100 mL, specific gravity 2.29

Used by:Bostick and Sullivan cyanotype and toning kits

Potassium Chlorate: safety data sheet, Spectrum Chemical P1245, revision G1retrieved 2026-09-06

Sections: Sections 1 and 2 — Spectrum Chemical P1245, POTASSIUM CHLORATE, CRYSTAL, REAGENT, ACS, CAS 3811-04-9, revision G1 of 11/18/2016; Oxidizing solids Category 1, Acute toxicity Oral Category 4, Serious eye damage/eye irritation Category 2B and Specific target organ toxicity single exposure Category 3, signal word Danger, with "May cause fire or explosion; strong oxidizer"

Used by:Bostick and Sullivan platinum and palladium kits

Potassium Chloroplatinate: the sheet published under that heading, GFS Chemicals 9418 for COLOR STANDARD SOLUTION, APHA 250retrieved 2026-09-06

Sections: Sections 1, 2 and 3 — GFS Chemicals 9418, COLOR STANDARD SOLUTION, APHA 250, version 01, issue date November-19-2015: water 97.75 per cent, hydrogen chloride 2.15 per cent, cobalt chloride hexahydrate 0.05 per cent and potassium chloroplatinate, CAS 16921-30-5, 0.05 per cent, with Skin corrosion 2, Serious eye damage 1, Carcinogenicity 1B and aquatic acute 3, signal word Danger. Cited for what the document is, which is not a sheet for anything in these kits

Used by:Bostick and Sullivan platinum and palladium kits

Potassium Ferricyanide: safety data sheet, LabChem SDS ID 75436, version 1.0retrieved 2026-09-06

Sections: LabChem SDS ID 75436, version 1.0, revised 19 August 2013 — section 1, substance name Potassium Ferricyanide, CAS 13746-66-2, formula K3FeC6N6; section 2, "Not classified" with "No labelling applicable" and no hazard statement; section 3.1, one mono-constituent at 100 per cent; sections 7.2 and 10.5, incompatible with strong oxidizers and strong acids, and 10.6, hazardous decomposition products potassium oxide, carbon monoxide and carbon dioxide, with no mention anywhere on the sheet of hydrogen cyanide; section 8.1, ACGIH TWA 1 mg/m³ as iron salts, soluble, as Fe; section 9, pH 6 in 5 per cent solution, decomposition temperature 200 °C, density 1.85 g/cm³, water solubility 33 g/100 mL; section 11, LD50 oral rat 2970 mg/kg; section 12, LC50 fishes 1869 mg/L and EC50 Daphnia 1549 mg/L; section 16, NFPA health 1, fire 0, reactivity 1; LabChem SDS ID 75436, version 1.0, revised 19 August 2013 — section 1, Potassium Ferricyanide, CAS 13746-66-2; section 2, "Not classified" with "No labelling applicable" and no hazard statement; sections 7.2, 10.5 and 10.6, incompatible with strong oxidizers and strong acids, with hazardous decomposition products given as potassium oxide, carbon monoxide and carbon dioxide and no mention of hydrogen cyanide anywhere on the sheet; section 8.1, ACGIH TWA 1 mg/m3 as soluble iron salts measured as iron; section 9, pH 6 in a 5 per cent solution and water solubility 33 g/100 mL; section 11, LD50 oral rat 2970 mg/kg; section 12, LC50 fishes 1869 mg/L and EC50 Daphnia 1549 mg/L

Used by:Bostick and Sullivan cyanotype and toning kits · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype

Potassium Oxalate Powder: safety data sheet, Spectrum Chemical P1355, revision G1retrieved 2026-09-06

Sections: Sections 1, 2 and 3 — Spectrum Chemical P1355, POTASSIUM OXALATE, MONOHYDRATE, CRYSTAL, REAGENT, ACS, CAS 6487-48-5, revision G1 of 02/11/2015; Acute toxicity Oral 4, Acute toxicity Dermal 4, Skin corrosion/irritation 2 and Serious eye damage/eye irritation 2A, signal word Warning, with "Harmful if swallowed", "Harmful in contact with skin", "Causes skin irritation" and "Causes serious eye irritation"; one component at 100 per cent

Used by:Bostick and Sullivan platinum and palladium kits

Pyrocat-HD Film Developer: kit instructionsretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Introduction — Pyrocat-HD as an alternative to PMK; development recommendations; dilution and contrast index; Introduction — the advantages over PMK that Sandy King cites for Pyrocat-HD; In your Pyrocat-HD Kit — the two supplied solutions and their preparation; the introduction and the advantages over PMK that King cites; the development recommendations and the 1:2:100 note; the film, EI and time table at 70, 75 and 80 °F; Introduction — Pyrocat-HD described as a semi-compensating, high-definition developer and the claim of no streaking or mottling with reduced agitation; the tray minimal-agitation scheme of 10 seconds every three minutes with times about 50 per cent longer; the semi-stand scheme at 1 part A to 1 part B to 200 or 400 parts water with agitation for one minute at the start and 30 seconds at the half-way point, times of 40 to 60 minutes, and the dichroic fog warning for high-speed films; Development recommendations — semi-stand agitation and the warning that dichroic fog may result from extended development of high-speed films, with the remedy of a more dilute working solution and a shorter time; Introduction — Pyrocat-HD as a semi-compensating, high-definition developer formulated by Sandy King as an alternative to PMK, and the advantages King cites; the report attributed to other users of reduced printing times with UV light sources for alt-process work because of the different stain colour, and of reduced base-plus-fog density; the development recommendations; the note that doubling the B solution takes FP4 Plus to a contrast index of 0.52 in 5 minutes 30 instead of 8 minutes; Introduction — Pyrocat-HD described as a semi-compensating, high-definition developer and the claim of no streaking or mottling with reduced agitation; the tray minimal-agitation scheme of 10 seconds every three minutes with times about 50 per cent longer; the semi-stand scheme at 1 part A to 1 part B to 200 or 400 parts water with agitation for one minute at the start and 30 seconds at the half-way point, and times of 40 to 60 minutes; Introduction - the description of Pyrocat-HD as a semi-compensating high-definition developer and the claim of no streaking or mottling with reduced agitation, listed as an advantage over PMK

Used by:Pyrogallol · PMK pyro · Pyrocat-HD · P8 Acutance, Adjacency Effects and Compensating Development · P8 Solvent Action, Physical Development and Grain · P8 Staining and Tanning Developers · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P27 Experiment: Agitation, Stand and Semi-Stand Development

Safety data sheet: Ammonium citrate dibasic (Sigma-Aldrich 247561), as filed by Bostick & Sullivanretrieved 2026-09-06

Sections: Section 1, for the product name Ammonium citrate dibasic and CAS 3012-65-5; section 2, for the GHS classification, Eye irritation Category 2A H319 and Specific target organ toxicity single exposure Category 3 H335, signal word Warning, with no skin statement; section 3.1, for the synonyms, the formula C6H14N2O7, the molecular weight 226.18 and EC 221-146-3, and for the blank concentration column; section 8, for the absence of any occupational exposure limit and for nitrile at 0.11 mm with a 480-minute breakthrough time; section 9, for the pH of 5.2 at 50 g/l at 20 C and the log Pow of -2.84; section 10.5, for the incompatibility with strong oxidising agents, strong bases and strong acids; section 6.2, "Do not let product enter drains"

Used by:Ammonium citrate developer

Safety Data Sheets: the supplier's own SDS library indexretrieved 2026-09-06, 2026-09-07

Sections: The library index, searched through the site's own REST endpoint on 7 September 2026 for "kaolin" and returning no sheet, although the same company ships 100 g of the powder in its albumen printing kit; The whole index, enumerated through the site's own /wp-json/wp/v2/sds endpoint: ninety safety data sheets, every one of them for a single substance sold by the jar or the bottle, and not one for a kit, a premixed solution or any other mixture the company sells. Cited for that negative fact, which is the reason the disclosed components on this page are sourced to a store page rather than to a sheet.; The whole index, enumerated through the site's own REST endpoint on 6 September 2026: eighty-nine sheets, every one of them a single-substance sheet for a chemical the company sells by the jar or the bottle, and not one for any kit, any premixed solution or any mixture the company sells. Cited for that negative fact, and for the presence in it of Ferric Oxalate Powder, Potassium Chlorate, Potassium Chloroplatinate, Potassium Oxalate Powder, Palladium Chloride, EDTA, Sodium (Meta)bisulfite and Sodium Platinum Chloride MSDS (Na2) — eight headings that between them cover none of the six liquids and neither of the two powders in the form the kits ship them, except one; The whole index, enumerated through the site's own /wp-json/wp/v2/sds endpoint on 6 September 2026: eighty-nine safety data sheets, every one for a single substance sold loose by the jar or the bottle, and not one for a kit, a premixed solution or any other mixture the company sells. Cited for two negative facts specific to this box — there is no sheet for the Ziatype kit, and there is no sheet anywhere in the library for gold chloride or for any chloropalladite, lithium, cesium or sodium, although the company manufactures two of them in house and sells all three.

Used by:Kaolin · Bostick and Sullivan cyanotype and toning kits · Bostick and Sullivan platinum and palladium kits · Bostick and Sullivan Ziatype kit

Salted Paper Printing Instructionsretrieved 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Section 2, Preparing Your Workspace and Negative, for the bath itself — "In the second tray prepare a fixer bath by measuring 50 grams (approximately 4 heaping teaspoons) of Sodium Thiosulfate crystals per liter of cold tap water" — and for the two trays the process needs; the kit contents list, which ships 250 g of sodium thiosulfate against a kit said to make approximately fifty 8x10 prints; section 5, Washing, for the 5 to 7 minute first wash with agitation every 20 to 30 seconds in which the unexposed silver comes off the sheet as a white milky cloud, and for the note that warm water at 90 degrees F shortens it considerably; section 6, Fixing, for 4 to 5 minutes with periodic agitation, for the print leaving the fixer at about three quarters of its final density, and for the statement that over-fixing can lead to bleaching of the image while under-fixing will cause archival permanence issues; section 7, Final Wash and Drying, for the 20 to 30 minute final wash in a slow constant stream with agitation every 5 minutes, and for the instruction that a print to be toned in gold or platinum goes straight from that wash to the toner without drying; Your kit contains, listing a 100 mL 12 per cent silver nitrate solution beside the proprietary salting solution; Safety and Handling Information, on silver nitrate not being light-sensitive while it is kept separate, on gloves and eye protection, on the staining of every surface, and on a shelf life of at least five years at room temperature; Preparing Your Workspace, on the 12 per cent solution staining wood, metal and many plastics; Coating and Drying, on equal drop counts of the two solutions, 40 drops of each for an 8 by 10 inch image, the salting coat dried before the silver coat goes over it, and the sheet being photosensitive once the silver coat has dried; Exposure, on the first inspection at about three minutes and pulling the print at one half to two thirds of the intended final density; Washing, on the white milky cloud of unexposed silver leaving the sheet in the first five to seven minutes; Coating and Drying — the instruction to mark the coating area from the negative and to count out equal amounts of the Salted Paper Sensitizer and the 12 per cent silver nitrate solution into two separate cups, with the approximate drop counts of 12 for a 4 by 5 inch image, 18 for 5 by 7, 24 for 6 by 9 and 40 for 8 by 10, the note that some papers require more and some less, the brush technique of alternating horizontal and vertical strokes, the instruction to reduce the coating volume by a quarter if spreading takes longer than 30 seconds, the requirement that the first coating be completely dry before the silver nitrate is applied, and the instruction to wash the brush in warm water and rinse it in distilled or deionised water between the two solutions.; Kit contents and opening paragraph, for the 100 mL of 12 per cent silver nitrate solution, the 250 g of sodium thiosulfate, the 25 mL of 2 per cent potassium dichromate, the approximately fifty 8 by 10 inch prints per kit and the eggplant or aubergine image colour; section 1, for the statement that silver nitrate will stain all surfaces black including skin; section 4, for stopping the exposure when the print is about one half to two thirds as dark as the intended final image; Section 4 Exposure, for the print darkening as it is exposed with no separate development stage, and for stopping when the image is about one half to two thirds as dark as the desired final image; section 5 Washing, for the white milky cloud of unexposed silver coming off the print and for washing five to seven minutes or longer while the white precipitate continues; section 6 Fixing, for the print being about three quarters as dark as wanted on leaving the fixer, for the further darkening and enrichment on drying, and for the statement that over-fixing can bleach the image while under-fixing causes archival permanence problems; Section 2, for the split-back contact printing frame, vacuum frame or two sheets of plate glass, for the two trays with slowly running tap water in the first for the first and last wash, and for the fixer of 50 g of sodium thiosulfate crystals per litre of cold tap water; section 4 Exposure, for the image darkening and developing as it is exposed with no separate development stage, for the emulsion outside the negative darkening almost immediately, for judging the moment to remove the print being the most important part of the process, for the first inspection after about three minutes with inspection indoors recommended when printing in sunlight to minimise ultraviolet exposure and fogging, for opening one leaf spring and folding back half the frame, for prints darkening considerably during washing, fixing, optional toning and drying so that exposure is stopped at about one half to two thirds of the desired final darkness, and for repeating the inspection every few minutes until the highlights begin to show detail; section 5 Washing, for agitating every 20 to 30 seconds, for the white milky cloud of unexposed silver nitrate and salted paper sensitiser floating off the print, for washing 5 to 7 minutes or longer while the white precipitate continues, and for warm water at about 32 degrees C shortening the wash considerably; section 6 Fixing, for 4 to 5 minutes with periodic agitation, for the print being about three quarters as dark as the desired final image on leaving the fixer, for further darkening and enrichment of colour in the final drying, and for over-fixing bleaching the image while under-fixing causes archival permanence problems; section 7, for the 20 to 30 minute final wash with agitation every five minutes, the 15 second drain, air drying on a line or plastic screen, flattening in a warm dry mount press, and going straight to toning after the final wash without drying if the print is to be toned; and section 4 for the dichromate contrast option this course does not use; Kit contents, for the 100 mL of 12 per cent silver nitrate and the approximately fifty 8 by 10 inch prints; section 1, for silver nitrate not being light sensitive while kept separate, for normal incandescent lighting being usable during coating, for working in a windowless room or shading the windows, for gloves and eye protection, for treating all photographic solutions as poisonous, for not storing them in a food refrigerator, for the stated shelf life of at least five years from purchase, and for the statement in capitals that silver nitrate will stain all surfaces black including skin; section 2, for the split-back frame, for the 12 per cent solution staining wood, metal and many plastics, for newspaper or blotter under the sheet, for a brush used only for salted paper and a glass rod that may be shared if properly washed, and for 100 per cent cotton rag unbuffered archival paper, hot pressed, at least 50 lb for larger images; section 3, for taping the upper corners, marking the negative's four corners in pencil, the drop table of 12, 18, 24 and 40 drops for 4 by 5, 5 by 7, 6 by 9 and 8 by 10, the equal drop counts of the two solutions, the brush method with its horizontal and vertical strokes and its rule that solution still spreading after 30 seconds means reducing the volume by a quarter, the coating rod method with its capillary loading and its rule about more than six passes, the instruction to let the first coat dry completely before the silver goes on, the washing of the brush between the two solutions, and drying the sensitised sheet in a dark room; Section 4, for stopping the exposure at about one half to two thirds of the desired final darkness; section 5, for the milky cloud of unexposed silver washing off and for continuing to wash while the white precipitate persists; section 6, for the print being about three quarters as dark as wanted on leaving the fixer, and for the statement that over-fixing can lead to bleaching of the image while under-fixing will cause archival permanence issues; Stopping when the print is one half to two thirds as dark as it should finish; the first wash of five to seven minutes with agitation every 20 to 30 seconds and longer while precipitate continues; inspecting indoors when printing in sunlight; The statement in capitals that silver nitrate will stain all surfaces black including skin; the note that the silver nitrate is not light sensitive as long as it is kept separate and can be handled under most room lighting; Exposure and fixing - stopping the exposure when the image appears about half to two-thirds as dark as the desired final image because salted paper prints darken considerably during washing, fixing, toning and drying; a fixer of about 50 g of sodium thiosulfate per litre of cold tap water with periodic agitation for 4 to 5 minutes; the statement that over-fixing can lead to bleaching of the image while under-fixing will cause archival permanence issues

Used by:Plain sodium thiosulfate fixer for printed-out papers · Salted paper sensitising solution · P21 What These Processes Need: The Negative, the Paper and the Light · P22 Part XXII Overview: The First Silver Print · P22 Printing Out: Silver Chloride Made and Darkened in the Paper · P22 Lab: Printing, Toning, Fixing and Washing a Salt Print · P22 Lab: Salting and Sensitising a Sheet of Paper · P22 Break/Fix: The Printed-Out Image That Faded · The printing-out processing line · Silver nitrate at the coating bench · The printed-out image that bleached away in the fixer

Sodium (Meta)bisulfite: safety data sheet, Esseco USA EUSA-120, issued through Univar to Bostick & Sullivanretrieved 2026-09-06

Sections: The scanned sheet in full, read from its page images because the document carries no text layer — the Univar despatch header naming Bostick & Sullivan as the customer; Esseco USA EUSA-120, SODIUM METABISULFITE, current issue date April 2017; Acute Toxicity Category 4 (Oral) and Eye Damage Category 1, signal word DANGER, "Harmful if swallowed" and "Causes serious eye damage"; section 3, one ingredient, sodium metabisulfite, CAS 7681-57-4, at 97 per cent or more; and the section 4 statements that it "may cause severe and possibly fatal allergic reactions if inhaled or swallowed by some asthmatics and other 'sulfite-sensitive' individuals", that it "reacts with acids to form toxic and irritating sulfur dioxide gas", and that it releases sulfur dioxide above 150 °C; Esseco USA EUSA-120, issue of April 2017, despatched to Bostick & Sullivan through Univar and published as a page-image scan with no text layer — sections 1, 2 and 3, SODIUM METABISULFITE, CAS 7681-57-4, one ingredient at 97 per cent or more, Acute Toxicity Category 4 oral and Eye Damage Category 1, signal word DANGER; and section 4, that it "reacts with acids to form toxic and irritating sulfur dioxide gas" and "may cause severe and possibly fatal allergic reactions if inhaled or swallowed by some asthmatics and other sulfite-sensitive individuals".

Used by:Bostick and Sullivan platinum and palladium kits · Bostick and Sullivan Ziatype kit

Sodium Platinum Chloride MSDS (Na2): the sheet published under that heading, ScienceLab.com SLP4123 for Platinum Chloride, 10%retrieved 2026-09-06

Sections: Sections 1, 2 and 3 — Sciencelab.com SLP4123, "Platinum Chloride, 10%", last updated 06/09/2012: chloroplatinic acid, CAS 16941-12-1, at 10 per cent with water at 90 per cent, chemical name and chemical formula both "Not applicable", and a hazards section calling it corrosive to skin, hazardous by inhalation and "slightly hazardous in case of skin contact (sensitizer)". Cited for what the document is, which is not a sheet for the Na2 solution the company sells

Used by:Bostick and Sullivan platinum and palladium kits

Sodium Tungstate, Dihydrate: material safety data sheet, Spectrum Laboratory Productsretrieved 2026-09-06

Sections: Spectrum Laboratory Products, undated, in the pre-GHS sixteen-section MSDS format — section 1, Sodium tungstate dihydrate, Na2WO4.2H2O, CAS 10213-10-2, NFPA health 1, fire 0, reactivity 0; section 2, one ingredient at 100 per cent with LD50 and LC50 both "Not available"; section 3, the whole hazard identification, "Slightly hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation", with carcinogenic, mutagenic, teratogenic and developmental effects all "Not available"; section 7, do not store above 25 degrees C; section 8, ACGIH TWA 5 and STEL 10 mg of tungsten per cubic metre; section 9, molecular weight 329.86, melting point 692.22 degrees C, "soluble in about 1.1 parts of water", no pH; section 10, stable, non-corrosive in presence of glass, reactive with oxidizing agents; and section 11, which goes further than section 3 and says the substance "May affect genetic material" and "May cause adverse reproductive effects based on animal data. Animal studies showed post-implantation mortality effects on fertility."

Used by:Bostick and Sullivan Ziatype kit

Tannic Acid, Powder, Reagent, ACS: safety data sheet, Spectrum Chemical T1010retrieved 2026-09-06

Sections: Spectrum Chemical T1010, prepared 4 October 2016 — section 1, TANNIC ACID, POWDER, REAGENT, ACS, CAS 1401-55-4, synonyms gallotannic acid, gallotannin and tannin; section 2, not considered hazardous under the 2012 OSHA standard and "Not a dangerous substance or mixture according to the Globally Harmonized System (GHS)", with no hazard statement; sections 7 and 10, sensitive to light, stored in light-resistant containers under inert gas, and incompatible with strong oxidizing agents, strong bases, alkalis and heavy metal salts; section 9, formula C76H52O46, molecular weight 1701.28, pH 3.5, colour light tan to light brown, melting point 218 °C; section 11, LD50 oral rat 2260 mg/kg; Sections 1, 2 and 9 - the substance identity as tannic acid CAS 1401-55-4 with the synonyms gallotannic acid, gallotannin and tannin; the statement that the chemical is not considered hazardous by the 2012 OSHA Hazard Communication Standard and is not a dangerous substance or mixture according to the Globally Harmonized System, with no hazard statement and no H-numbers; and the pH of 3.5, the molecular weight of 1701.28 and the light tan to light brown colour. Preparation date 10 April 2016, no revision.

Used by:Bostick and Sullivan cyanotype and toning kits · P21 Lab: Toning the Prussian Blue Image

The New Cyanotype Solution (Ware's Formula): product pageretrieved 2026-09-06

Sections: The New Cyanotype Solution (Ware's Formula) — "A single-solution Cyanotype emulsion from Ware's formulary", sold in 100 mL, 250 mL, 500 mL and 1 litre, with the claim that "Users report faster exposure times and a deeper intensity not seen in the traditional cyanotype process". Cited as the alternative the same supplier offers, and as a claim attributed to users rather than to a measurement.; The premixed single-solution New Cyanotype sold in 100 mL, 250 mL, 500 mL and 1 litre bottles, with speed and intensity attributed to user reports and no exposure figure, maximum density or composition published

Used by:Bostick and Sullivan cyanotype and toning kits · P21 The New Cyanotype and the Other Ways to Make a Blue Print

Traditional Kallitype Printing: Dick Stevens' Formulasretrieved 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Your Kit contains, for a third supplier's proprietary black-tone developer whose composition is not published; Printing, for kallitype prints bleaching in the fix; Developing; Clearing; Fixing; The fixing instruction — 5 per cent sodium thiosulfate, 50 g to the litre, at about 68 degrees F because warmer water accelerates bleaching, for about two minutes followed immediately by fresh water, sufficient for ten 8 by 10 prints and discarded after each session — together with the sheet's own footnote that the kallitype's silver is not enmeshed in gelatin and fixes much faster than a silver bromide print, so that even more dilute fixer and shorter times may be equally effective; the warning that kallitype prints bleach in the fix so that the only effective answers are to tone before fixing or to overprint by a stop or two, and the note that a sufficiently toned print will not bleach back; the clearing bath of tetrasodium EDTA before it; and the final wash of 15 to 20 minutes; Kit contents, for the 250 g of EDTA clearing agent shipped with the kit; Clearing (optional), for the instruction to clear for 3 to 5 minutes "in a bath of EDTA Tetrasodium of 2 tablespoons to 1 liter of water", for the note that this depends on the developer since some developers clear the print in the developing tray while the black kallitype developer supplied with the kit does require clearing, and for the capacity of about twenty 8 by 10 prints before the bath is replaced; and Toning, for the instruction that a print to be toned is toned between the clearing bath and the fixing bath; Your Kit contains; The Emulsion; Contrast; Coating; Resting; Drying; Printing; Developing; Clearing; Fixing; Final Washing; Toning; Toning Formulas; Your Kit contains; The Emulsion, for the equal parts of 10 per cent silver nitrate and 20 per cent ferric oxalate and the 20 drops of each per 8 by 10 print; Printing, for kallitype prints bleaching in the fix and for toning before fixing as one of the only two effective answers; Fixing; Toning; Kit contents, for the 250 g of EDTA clearing agent; and Clearing (optional), for the instruction to clear "in a bath of EDTA Tetrasodium of 2 tablespoons to 1 liter of water" — the one sheet from this supplier that names the salt, and the reason the platinum-palladium sheet's unnamed "EDTA clearing agent" is read as ambiguous rather than as obvious; Your Kit contains, for a third supplier's proprietary black-tone developer; Printing, for kallitype prints bleaching in the fix; Developing; Fixing; Toning; Your Kit contains; Developing; Clearing; Fixing; Toning, for the third supplier's practice, which uses a proprietary black-tone developer rather than a citrate one; Clearing, for 3 to 5 minutes in tetrasodium EDTA at two tablespoons to the litre, reusable until about twenty 8 by 10 prints have been cleared, with the note that whether clearing is needed depends on the developer and that the black tone developer supplied does require it; Toning, for the statement that kallitype prints may be toned with any of the noble metals, that toning is one way to keep them from bleaching during fixing at the cost of a colour shift, that it increases permanence, and that it is done between the clearing bath and the fixing bath; Toning Formulas, for a litre of water with 5 g of citric acid plus either 5 mL of 5 per cent gold chloride, 5 mL of standard palladium solution number 3 or 5 mL of standard platinum solution number 3, with the observation that a black deposit appears in the bottom of the tray which is silver that has been replaced by the noble metal, and that a sufficiently toned print will not bleach back; Your Kit contains, for the 25 mL of 5 per cent ammonium dichromate contrast booster; Contrast, for the instruction to adjust contrast with small additions of 5 per cent ammonium dichromate and to dilute the solution if one drop is too strong; Your Kit contains — 25 mL of 10 per cent silver nitrate, 25 mL of 20 per cent ferric oxalate, 25 mL of 5 per cent ammonium dichromate contrast booster, 250 g of EDTA clearing agent, 250 g of sodium thiosulfate and a quart of black tone developer; The Emulsion, equal parts of the two solutions with a starting point of about 20 drops of each per 8 by 10 and 12 drops each per 5 by 7, and one drop of 10 per cent Tween 20 per emulsion for an 8 by 10 as a spreading agent; Contrast, adjusted with small additions of 5 per cent ammonium dichromate; Coating, in a dimly lit room, liberally but not running wet; Resting, one to two minutes; Drying, under gentle heat, a hairdryer or natural air drying "if you are not in an extremely moist climate"; Printing, contact under sunlight or a UV source, print times about one to two stops faster than traditional palladium, little print-out image so timing must be by trial and error or test strip, and the warning that kallitype prints bleach in the fix so the only effective answers are to tone before fixing or to overprint by a stop or two; Developing, at least five minutes with standard times of 8 to 10 minutes, the image appearing immediately so the developer must be poured quickly or watermarks appear, and different developers changing the colour tone; Clearing, 3 to 5 minutes in tetrasodium EDTA at two tablespoons to the litre, reusable for about twenty 8 by 10 prints; Fixing, 5 per cent sodium thiosulfate at about 20 degrees C because warmer water accelerates bleaching, about two minutes then straight into fresh water, sufficient for ten 8 by 10 prints and discarded after each session, with the footnote that the kallitype's silver is not enmeshed in a gelatin colloid and fixes much faster than a silver bromide print; Final Washing, 15 to 20 minutes; Toning, between the clearing bath and the fixing bath; Coating, for the instruction to coat in a dimly lit room; Drying, for gentle heat or natural air drying if the climate is not extremely moist; Printing, for the warning that kallitype prints bleach in the fix so the only effective answers are to tone before fixing or to overprint by a stop or two; Developing, for the image appearing immediately so the developer must be poured quickly or watermarks may appear; Fixing, for the water being around 20 degrees C because warmer water accelerates the bleaching; Clearing for 3 to 5 minutes in tetrasodium EDTA at two tablespoons to the litre, and the rinse between the clearing bath and the fixing bath; Developing - place in the developer for at least 5 minutes with standard development times of 8 to 10 minutes, and the warning that the image will appear immediately so this must be done quickly, or else watermarks may appear; the note that different developers change the colour tone of the print; Printing - little print-out image, so timing must be found by trial and error or a test strip, and kallitype prints will bleach in the fix so tone before fixing or over-print by a stop or two

Used by:Borax kallitype developer · Dilute alkaline thiosulfate fixer for iron-silver prints · EDTA and sodium sulfite clearing sequence · Kallitype sensitiser · Nicol's kallitype · EDTA, citric acid and hydrochloric acid clearing sequence · Rochelle salt kallitype developer · Sodium citrate kallitype developer · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Contrast Control in Iron-Based Printing · P24 Lab: Printing a Kallitype · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · Clearing an iron-silver print and testing it for residual iron · Blotchy kallitype development

Vandyke Brownprinting Instructions (Argyrotype follows the same instructions)retrieved 2026-09-05, 2026-09-06, 2026-09-07

Sections: Section 2, Preparing Your Workspace and Negative, for the fixer bath of 50 grams of sodium thiosulfate crystals per litre of cold tap water; section 6, Fixing, for the five minutes with periodic agitation, for the print leaving the fixer about three-quarters as dark as the final image and darkening further as it dries, and for the statement that over-fixing can lead to bleaching of the image while under-fixing will cause archival permanence issues; and the kit contents, 250 g of sodium thiosulfate against a kit said to make approximately fifty 8 by 10 prints; The processing instructions, for a first wash of 3 to 5 minutes in plain tap water until most of the yellow stain has left the highlights, changed after eight to ten prints, with water at about 90 degrees F shortening it considerably — the whole of the iron removal that a Van Dyke kit specifies before fixing; Safety and handling information; Preparing your workspace and negative; Coating and drying, with the drop counts and both coating methods; Exposure; Washing; Fixing; Final wash and drying; The opening statement that the kit makes approximately fifty 8 by 10 inch prints; Safety and Handling Information, for ultraviolet sensitivity only and a shelf life of at least a year; Fixing, for 50 g of sodium thiosulfate crystals per litre and the warning that over-fixing bleaches the image while under-fixing costs archival permanence; Safety and Handling Information, for ultraviolet sensitivity only, normal incandescent lighting throughout, limited fluorescent exposure, a windowless or shaded room, gloves throughout, the instruction that the solution should be considered poisonous and not stored in a food refrigerator, and a shelf life of at least one year from purchase; Preparing Your Workspace and Negative, for the staining of wood, metal and many plastics, the dedicated brush against the shareable glass rod, the three trays with the fixer at 50 grams of crystals per litre of cold tap water, and the 100 per cent cotton rag unbuffered paper at a minimum of 32 lb for 8.5 by 11 inches and hot pressed at 47 lb or more for larger work; Coating and Drying, for taping the upper corners, marking the negative's four corners in pencil, the drop table of 12 drops for a 4 by 5, 18 for a 5 by 7, 24 for a 6 by 9 and 40 for an 8 by 10, the brush method with its wetted and blotted brush and its 30-second rule, the rod method with its six-pass and ten-pass rules, and the hour of drying in a dark spot with the statement that a hair dryer is not recommended because natural drying gives a superior image; Exposure, for the printing-out image that negates a separate development stage, the split-back frame, the check that the image is not reversed when viewed through the glass, the first inspection after three minutes and every few minutes thereafter, and the instruction to stop when the print appears about half as dark as the desired final image because it darkens considerably through washing, fixing, optional toning and drying; Washing, for the yellow stain lifting off the paper, the 3 to 5 minute first wash until most of it has gone from the highlights, the change of water after 8 to 10 prints, and the note that water at about 90 degrees F shortens wash times considerably; Fixing, for five minutes of periodic agitation, the print emerging about three-quarters as dark as the final image, and the warning that over-fixing bleaches while under-fixing costs archival permanence; Final Wash and Drying, for 30 minutes of slow running cool water agitated every five minutes, the fifteen-second drain, and air drying; Safety and Handling Information, for the recommendation to limit exposure of chemicals and coated paper to fluorescent light in order to limit the chances of fogging the image, and for working in a windowless or shaded room; Preparing Your Workspace, for the brush that should be used only for Vandyke printing and the warning to avoid a brush that has been used for other alternative process chemistry in order to limit contamination, and for the glass rod that may be shared if washed properly; Exposure, for minimising ultraviolet exposure while inspecting in order to prevent fogging the image; Washing, for changing the wash water after 8 to 10 prints or when washing times begin to exceed five minutes; Fixing, for the warning that over-fixing can lead to bleaching of the image while under-fixing will cause archival permanence issues; Exposure — the statement that the Vandyke image darkens and develops as it is exposed, producing a printing-out image and negating the need for a separate development stage, that judging when to remove the print is the most important part of the process, and that Vandyke prints darken considerably during washing, fixing, optional toning and drying so exposure should stop when the image is about half as dark as the desired final result; Fixing, for the further darkening in the fixer to about three-quarters of the final density

Used by:Dilute alkaline thiosulfate fixer for iron-silver prints · EDTA and sodium sulfite clearing sequence · Van Dyke Brown sensitiser · P24 Part XXIV Overview: When Iron Reduces Silver · P24 Lab: Printing a Van Dyke Brown · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · P24 The Siderotype Principle: Iron Reduces Silver

Wet Plate Collodion Kit: mixing instructionsretrieved 2026-09-04, 2026-09-06

Sections: Kit contents — the Old Workhorse bromo-iodizer, a combination of cadmium bromide, ammonium bromide and potassium iodide; Kit contents — Old Workhorse Bromo-Iodizer; Kit contents and Pouring the Plate — calcium carbonate as a non-scratching abrasive for cleaning glass; Kit contents — Wetplate Developer; Developer dilutions for tintypes, ambrotypes and glass negatives; Kit contents — calcium carbonate glass cleaner and the alcohol lamp; Disposal — rinsing the collodion bottle with isopropyl alcohol and evaporating outdoors; Kit contents — B&S Rapid Fixer; the silver bath held at pH 4 to 5 with nitric acid; Read as a manufacturer document describing present practice rather than as a procedure. The kit contents list, for the bromo-iodiser whose stated composition is cadmium bromide, ammonium bromide and potassium iodide in a half-and-half alcohol and ether solution, for the collodion and the iodiser both carrying the caution that they boil at 95 F, for the ammonium thiosulfate rapid fixer offered as an alternative to cyanide-based fixers, for the sandarac varnish in grain alcohol and oil of lavender, for the nitric acid used to adjust the silver bath, and for the alcohol lamp supplied to warm plates and varnishes. The safety precautions page, for the statement that the process requires potentially harmful or deadly chemicals, that the work produces flammable vapours, that chemicals must not be stored near a water heater or any other flame or pilot light, that a beginner should be under the supervision of an experienced wetplate photographer, and for the protective equipment list, which names safety glasses, a lab coat or heavy apron, a short-sleeved shirt, gloves, closed shoes and a gas mask marked optional. The silver bath maintenance section, for the accumulation of collodion, ether and alcohol in the bath and the two published routes for removing them, sunning in direct sunlight for days or boiling on a hotplate. The varnishing section, for the plate being warmed over an open alcohol flame, for the warning that sandarac varnish is highly flammable, and for the instruction on what to do if the plate catches fire

Used by:Ammonium bromide · Cadmium bromide · Calcium carbonate · Iron(II) sulfate heptahydrate · Isopropyl alcohol · Potassium cyanide · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That

Ziatype Printing Kit Instructionsretrieved 2026-09-04, 2026-09-06

Sections: Kit contents; 1% Ammonium Dichromate; contrast control; Kit contents and Wet Processing — the EDTA and sodium bisulfite clearing bath and its capacity; Kit contents — the lithium palladium solution; Ziatype Printing Kit Instructions, twelve printed pages, re-read in full for this entry — page 1, the kit contents, "(1) 25 ml Lithium Palladium Solution", "(1) 25 ml Ferric Ammonium Oxalate Solution (a.k.a Ammonium Ferric Oxalate, AFO, FAO)", "(1) 25 ml 40% Sodium Tungstate", "(1) 10 ml 5% Gold Chloride", "(1) 25 ml 1% Ammonium Dichromate", "(1) 250 gms EDTA clearing agent" and "(1) 250 gms Sodium Bisulfite (for clearing)", together with the list of what the buyer must supply — rag paper with a fairly hard surface, a brush or coating rod, an ultraviolet source, a negative as large as the image and a split back print frame; page 2, the history, that "The Ziatype was developed in the Labs of Bostick & Sullivan in 1997", that Richard Sullivan had tried Pizzighelli's print-out process about twenty years earlier "without much success", that "In the mid 1980's, Dr. Michael Ware developed a variation of Pizzighelli's POP process which has enjoyed a loyal but small following", that this process "is also a variation of Pizzighelli's process" and "uses lithium (or cesium) palladium chloride as the primary metal and ferric ammonium oxalate for the iron compound", and the claim that "In the Pizzighelli and Ware versions, color and contrast are interlocked and controlled largely by humidity. In the Ziatype, the color and contrast are controlled chemically as well as in part by humidity, making a more controllable and flexible printing system"; the origin of the name and Sullivan's quoted reason for it; and the five advantages claimed — a printing-out system whose images "can be evaluated as they print", "Greater printing speed when compared to platinum and palladium", "Greater color control", "No developer needed. Just water" and "Cold Neutral black made with pure palladium"; page 3, the safety notes in capitals and the dust-mask warning about hair dryers, and the notes on lithium palladium (dark brown, "will last almost indefinitely", "does not oxidize or age", never contaminate with ferric ammonium oxalate, "always use glass containers, never metal as the palladium will plate out on the container", refrigeration not necessary, "manufactured in house by our chemist Dana Sullivan"), on ferric ammonium oxalate ("the chemical in your emulsion mix that is sensitive to light. It is a green color and will last up to 2-3 years"), on the 40 per cent sodium tungstate ("a clear solution and has a shelf life of approximately 5 years.. It adds a warm tone to the print and also reduces contrast") and on the 5 per cent gold chloride ("Gold will increase contrast (increasing contrast always increases exposure time) and give you split tones"); page 4, the note on 1 per cent ammonium dichromate — "a dark orange color and has a shelf life of approximately 5 years. It darkens in color over time. It is a known carcinogenic, ALWAYS wear gloves when working with this chemical. Ammonium Dichromate increases contrast nearly twice as much as the gold does and gives a cooler tone print. Use sparingly, one drop will go a long way. Has been noted to increase grain and exposure time" — the clearing instruction "Use 2 tablespoons of each to 1 quart of water. This is not a critical measurement; less will just take longer to clear, more will clear faster", the negative's stated density range of 1.35 to 1.50, and the recommendation of HP5 and FP4 developed in D-19, Rollo Pyro or Pyrocat-HD for in-camera negatives; page 5, the workspace lighting — coat under dim fluorescent lighting with no ultraviolet and dry in the dark, because "Incipient fogging may compress the midtone values" — the base emulsion of "20 drops of ferric ammonium oxalate and 20 drops of lithium palladium" for an 8x10, the statement that this gives "a nice cool neutral black print while the emulsion is wet" and that "If the paper dries out, you will get a warmer tone print", the recommendation of a drop of Tween 20 except on Arches Platine, and the statement that "The Ziatype system was designed so that color and contrast are chemically controlled"; page 6, the three colour routes — gold "replacing any portion of the lithium palladium solution", cesium palladium or sodium tungstate or a longer dry for warmth, and 1 to 2 drops of the 1 per cent ammonium dichromate for contrast with a cool tone — the note that "Gold Chloride cannot be used with Cesium Palladium", and the drop counts per size, 10 to 15 total for a 4x5, 15 to 20 for a 5x7, 30 to 35 for a 6x9 and 40 to 45 for an 8x10; page 7, the drop count chart "courtesy of Richard Sullivan and Carl Weese", its abbreviation key including "ad- Ammonium Dichromate", its eleven rows of starting points "for a 5x7 print", and the humidity instruction that the room "needs to be around at least 50% humidity"; page 8, the statement that "The Ziatype process depends on humidity in the paper to allow the development to occur during the exposure", the One Step Drying method and its crackle test — the paper "should sound a little 'dead'" and "In no case should the paper be wet enough to transfer any emulsion to a negative" — and Sullivan's sidenote on running a darkroom at 50 to 65 per cent relative humidity at 65 degrees Fahrenheit or above, with the humidifier, the hot water in the sink, the water sprayed on the floor, Santa Fe at 7000 feet and Carl Weese's smaller humidifier in Connecticut; page 9, the two-step humidification over an ultrasonic humidifier for one to two minutes a side, the split back frame, the mylar or acetate sandwich, and the warning that "due to the necessity of the paper needing to be wet and the use of acetate sheets while exposing, that fall out spots or blurry spots in your print are much more common. The paper is basically drying and moving while exposing"; page 10, the assembly order "Glass, negative, mylar/acetate (if negative is not in Krystal Seal), coated paper, mylar/acetate, backing paper if needed, frame back", the exposure — "Ziatype is traditionally 2-3 stops faster than traditional developing out platinum and palladium", continue "until the print looks right, and there is the desired detail in your highlights", "It will appear yellow in the highlights but over all the exposure will be correct" — and the wet processing, two minutes in running water, 10 to 15 minutes in a clearing bath of 1 to 2 tablespoons of each powder to 1.5 litres of water, "The clearing bath removes the ferric ammonium oxalate from your print", and a final wash "for about 10 minutes"; and pages 11 and 12, the ten numbered steps, with the papers recommended (Bergger Cot 320, Arches Platine, Revere Platinum, Hahnemuhle Platinum Rag and Japanese Kozo), the pencilled border marks, the coating advice and its "sweet spot" — "Too little in one area and the emulsion will be too thin and overexpose too quickly. Too much and it will come off in the wash" — the timed drying advice and "Wet emulsion=cool tone, dry emulsion=warm tone", the three-minute minimum before exposure, the sun lamp taking "about 3 to 8 minutes" for a 4x5 negative with dense negatives running "a half hour or longer", the prohibition on metal developing trays, the two-minute minimum development, the clearing bath restated as 2 tablespoons of each to a litre or quart with 10 minutes in each of two baths or 10 to 15 in one, "Fresh clearing agent will clear up to a 20-25 8x10 prints", and the final wash restated as half an hour in gently flowing water. The sheet publishes no strength for the lithium palladium solution, none for the ferric ammonium oxalate solution, no pH for anything, no exposure time for a named ultraviolet source, no yield for the kit and no sensitometry of any kind.; Kit contents, for the 250 g of EDTA clearing agent and 250 g of sodium bisulfite; EDTA Clearing Agent and Sodium Bisulfite, for the same 2 tablespoons of each to a quart with the same remark that the measurement is not critical; the tray layout, "you will need at least three baths set up in your darkroom space. One for developing (water), one for clearing (EDTA and Sodium Bisulfite), and a final wash bath"; and the wet processing step giving 1 to 2 tablespoons of each to make the clearing bath and, elsewhere in the same sheet, 2 tablespoons of each to a litre or a quart for ten minutes; Kit contents and Wet Processing — the lithium palladium solution, the EDTA and sodium bisulfite clearing bath and its capacity

Used by:Ammonium dichromate · EDTA disodium salt (anhydrous) · Lithium chloride · Bostick and Sullivan Ziatype kit · EDTA, citric acid and hydrochloric acid clearing sequence · Print-out platino-palladiotype

Ziatype Printing Kit: the maker's own store listingretrieved 2026-09-06

Sections: Ziatype Printing Kit, SKU ZIa — the short description, which is the only place the maker calls the Ziatype "a palladium Printing Out Process (POP) based on the work of Pizzighelli" and dates its introduction to 1997, and the contents list printed twice, "25 ml Litihium Palladium / 25ml Ferric Ammonium Oxalate / 25ml 40% Sodium Tungstate (for a warmer tone) / 25ml 1% Ammonium Dichromate (for contrast boost) / 10ml 5% Gold Chloride / 250 gms EDTA clearing Agent / 250 Sodium Bisulfite / 5 droppers / Comprehensive printing instructions". Cited for the dropper count, for the two one-line explanations of what the tungstate and the dichromate are for, and for repeating the instruction sheet's silence about the strength of the only two bottles that make the picture.

Used by:Bostick and Sullivan Ziatype kit

Ziatype solutions and clearing chemicals: the maker's own store listingsretrieved 2026-09-06

Sections: The listings for the individual bottles and packets, read through the store's own endpoint — Lithium Palladium Solution #3, whose entire description is "Lithium Chloropalladite solution. Standard for Ziatype."; Cesium Palladium Solution #3, "Cesium Chloropalladite solution. Warm tone for Ziatype."; Palladium Solution #3, the classic developing-out bottle from the same shelf, "Sodium Chloropalladite 15% solution. Standard solution for classic Platinum and Palladium printing. One 25ml bottle equal to 625 drops of coating solution"; Ammonium Ferric Oxalate Solution #1, "Ziatype Solution No. 1", with no strength; Ammonium Ferric Oxalate Solution #2, "Formerly Ziatype Sol. No. 2. We prefer using drops of Ammonium Dichromate solution now", with the field "Chem Formula Cont. Pot. Chlorate"; the ammonium ferric oxalate solid at CAS 13268-42-3 and formula (NH4)3Fe(C2O4)3-3H2O; Sodium Tungstate Sol. 40%; Sodium Tungstate Dihydrate solid at CAS 10213-10-2 and formula weight 329.86 with the formula printed as "Na2WO4.5H2O"; 5% Gold Chloride Solution, "Hydrogen Tetrachloroaurate (III) Trihydrate"; Ammonium Dichromate 5% Solution and the solid at CAS 7789-09-5 with UN 1439 and the hazardous-shipping notice; EDTA Tetra Sodium (B+S Clearing Agent), "Safe, easy to use clearing agent"; Sodium Bisulfite at CAS 7681-57-4; and the Lithium Ferric Oxalate and Sodium Ferric Oxalate bottles, both described as Ziatype components and neither in the kit.

Used by:Bostick and Sullivan Ziatype kit

business.kodakmoments.com

Chemicals for KODAK PROFESSIONAL Black-and-White Papers, publication E-103CPretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Washing Aid - Hypo Clearing Agent at 1 to 4, 50 to 86 degrees F (10 to 30 degrees C), 2 to 3 minutes for fibre-based papers with 2 minutes for single weight and 3 minutes for double and premium weight and a footnote to consult the paper recommendations, for tray and machine use; keeping properties of NA and 3 months for the stock and 24 hours in a tray or 1 month in a tank for the working solution; useful capacity in 8 by 10 inch sheets per gallon and per litre in a tray of 80 and 21 without a pre-rinse and 200 and 50 with one; Washing Aid — Hypo Clearing Agent at 1 part stock to 4 parts water, 50 to 86 degrees F (10 to 30 degrees C), 2 to 3 minutes for fibre-base papers, and the statement that it promotes removal of fixer from films and fibre-base papers to shorten wash times and make washing at lower wash-water temperatures practical; The chemicals table for black-and-white papers - DEKTOL at a typical dilution of 1 to 2, three quarters to three minutes for RC papers and three quarters to four minutes for fibre-base papers at 20 degrees C, with a useful capacity of 120 8x10 sheets per gallon or 32 per litre, a stock keeping life of six months in a closed full container and a working-solution life in a tray of one working day; POLYMAX T at 1 to 9 with an indefinite concentrate life, the same one working day in a tray and the same 120 per gallon; and the chemical descriptions of DEKTOL as producing neutral or cold tones with cold-tone papers and warm tones with warm-tone papers, and of POLYMAX T as medium contrast, high capacity and fast acting; The chemicals table for black-and-white papers - Rapid Fixer at 2 minutes for RC papers and 5 to 10 minutes for fibre-base papers in a single bath, Indicator Stop Bath at 10 seconds for RC and 15 seconds for fibre base, and Hypo Clearing Agent at 2 minutes for single weight and 3 minutes for double and premium weight fibre papers; The chemicals matrix for black-and-white papers - DEKTOL at a typical dilution of 1 part stock to 2 of water, three quarters to three minutes for RC papers and three quarters to four minutes for fibre-base papers at 20 C, a stock keeping life of six months in a closed full container, a working-solution life of one working day in a tray and a useful capacity of 120 8 by 10 sheets per gallon or 32 per litre; POLYMAX T Developer at 1 part to 9, indefinite concentrate life, the same one working day in a tray and the same 120 per gallon or 32 per litre; Indicator Stop Bath at 1 part to 63, 18 to 24 C, 10 s for RC papers and 15 s for fibre-base, with a working-solution life of 3 days in a tray or 1 month in a tank and the instruction to discard when the colour changes to purplish blue; Rapid Fixer at 1 part to 7, 18 to 24 C, 2 min for RC papers and 5 to 10 min for fibre-base as a single bath, with a tray life of one week and a useful capacity of 100 8 by 10 sheets per gallon or 26 per litre; and Hypo Clearing Agent at 1 part to 4, 10 to 30 C, 2 to 3 min for fibre-base papers; Washing Aid — Hypo Clearing Agent is not recommended for resin-coated papers, which already have a short wash time; Black-and-white paper chemicals - keeping properties without use and useful capacity for each developer, and the note that DEKTOL offers high capacity and a uniform development rate

Used by:Kodak Hypo Clearing Agent and the washing accelerator Kodak patented · P12 The Physics of Washing · P18 Print Developer Chemistry and the Developer-Paper Pair · P18 The Structure of a Printing Paper: Base, Baryta, Emulsion and Supercoat · P19 Developing the Print Consistently and Running a Printing Session · Silver gelatin developing-out print on resin-coated base · Developer fog on paper

How to Process and Print Black-and-White Film, publication AJ-3retrieved 2026-09-03, 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Processing steps — step 7, wetting agent, and the instruction to mix PHOTO-FLO with distilled water in hard-water areas; The film processing table, step 5, Hypo Clearing Agent for 1 to 2 minutes with continuous agitation for the first 30 seconds and then at 30 second intervals, and step 6, a 5 minute water wash after the Hypo Clearing Agent or 20 to 30 minutes without it; Other Chemicals - KODAK PROFESSIONAL Hypo Clearing Agent shortens washing times and makes possible more thorough washing of films and prints, reduces the wash time to 5 minutes for films, 10 minutes for single-weight papers and 20 minutes for double-weight papers, is not recommended for water-resistant resin-coated papers which already have a short wash time of 4 minutes, and is diluted 1 to 4 for use; Other Chemicals — KODAK Rapid Selenium Toner, "For altering the image tone of black-and-white prints and prolonging print life", in a publication revised 2/16 and copyright 2016 Kodak Alaris Inc.; The film processing table — step 6, Water Wash, 5 minutes after Hypo Clearing Agent or 20 to 30 minutes without the Hypo Clearing Agent step, with the ten fill-and-dump cycles given as the rapid method for a small tank; Other Chemicals — KODAK Hypo Clearing Agent shortens washing times and reduces the wash to 5 minutes for films, 10 minutes for single-weight papers and 20 minutes for double-weight papers, is not recommended for resin-coated papers which already have a short wash time of 4 minutes, and is diluted 1+4 for use; Making a Proof Sheet - proof sheets include many images from strips of negatives at the same size as the negatives, help you choose the best negatives for enlarging and make a record to file with them; the home-made frame of a piece of window glass or clear Plexiglas and a piece of composition board of the same size, hinged with wide adhesive tape, with the remaining edges taped so that you do not cut yourself; the instruction to place the strips of negatives so that their emulsion side faces the emulsion side of the paper, with the negatives facing the light source; and the two exposures given, a bare 7 W bulb 2 ft above the frame for about 10 seconds or an enlarger with an empty carrier at f/11 for about 8 seconds, each with the instruction to double or halve the time on the evidence of the processed sheet; Making Test Exposure Strips and Prints - the rule that if the strip looks flat or muddy a higher-numbered POLYMAX filter is used to increase the contrast and if it has a very harsh, contrasty appearance a lower-numbered filter is used; and the recommendation of one final strip with very small differences in exposure time before making a full print; Making Test Exposure Strips and Prints - the definition of a test exposure strip as a 1 or 2 inch wide strip of enlarging paper cut from a larger sheet, chosen over a full test print because it is more economical, and the instruction to place the strip so that it records a good sampling of important image tones in the negative; Processing Your Proof Sheet - the tray sequence for a resin-coated paper, sliding the sheet completely into the developer emulsion side down and turning it over, rocking the tray gently throughout the development time, draining for 5 s before immersing in the stop bath for at least 10 s with thorough agitation, draining for 2 s before slipping the sheet into the fixer and agitating frequently for 2 min with the instruction not to overfix and to keep several prints separated, then 4 min of gently running water at 10 to 30 C with the instruction to avoid overwashing; and Other Chemicals, which states that Hypo Clearing Agent reduces the wash time to 10 min for single-weight and 20 min for double-weight papers and is not recommended for resin-coated papers, which already have a short wash time of 4 min; MAKING PRINTS - the statement that black-and-white photographic papers are available in a variety of sizes, speeds, contrasts, surface textures, image tones, stock tints and weights, and the suggestion to start with a resin-coated paper for both contact prints and enlargements; Making a Proof Sheet - that proof sheets help you choose the best negatives for enlarging and make a good record of your prints to file with your negatives; ENLARGING - the instruction to study the proof sheet for the images with the best composition and exposure level, neither too dark nor too light; Making Test Exposure Strips and Prints - the definition of a test print as a sheet of paper exposed and processed to find out whether the exposure and contrast estimates are correct, with the note not to be disappointed if the first one is not good enough to keep, the instruction to place a strip so that it records a good sampling of important image tones in the negative, and the rule that a flat or muddy strip calls for a higher-numbered filter and a harsh contrasty one for a lower-numbered filter; Making Test Exposure Strips and Prints - the definition of a test exposure strip as a 1 or 2 inch wide strip of enlarging paper cut from a larger sheet, chosen over a full test print because it is more economical; the instruction to place the strip so that it records a good sampling of important image tones in the negative; the five-band procedure of a 5 second exposure of the whole strip followed by covering a fifth at a time for a further 2, 3, 4 and 6 seconds, printed on the sheet as 5, 7, 10, 14 and 20 seconds and described as five exposures ranging over 2 stops about half a stop apart; the instruction to examine the processed strip under room lights and to open or close the lens if every step is too light or too dark; the rule that a flat or muddy strip calls for a higher-numbered filter and a harsh contrasty one for a lower-numbered filter; the recommendation of one final strip with very small differences in exposure time before making a full print; and the processing steps, 1 minute development for POLYCONTRAST IV RC in DEKTOL with gentle rocking throughout, at least 10 seconds in the stop bath, 2 minutes in the fixer, and a 4 minute wash at 10 to 30 degrees C; Making a print, steps 4 and 5 - transfer the print to the wash tray and wash for 4 minutes in gently running water at a temperature between 50 and 85 degrees F (10 and 30 degrees C), with the instruction to avoid overwashing; use a soft viscose sponge or a soft rubber squeegee to remove excess water from the print surfaces and dry the print on a flat surface at room temperature with good air circulation, drying being sped up with warm air from a portable hair dryer provided the temperature of the air is below 190 degrees F (88 degrees C); Other Chemicals - KODAK PROFESSIONAL Hypo Clearing Agent shortens washing times and reduces the wash time to 5 minutes for films, 10 minutes for single-weight papers and 20 minutes for double-weight papers, is not recommended for water-resistant resin-coated papers which already have a short wash time of 4 minutes, and is diluted 1:4 for use; Small-Tank Agitation Procedures — the instruction to tap the tank on the work surface to dislodge air bubbles before the initial agitation, five to seven inversion cycles in five seconds for an invertible tank and four or five reel rotations for a non-invertible one, repeated at 30-second intervals; and the processing table's note that agitation is very important for even development; Small-Tank Agitation Procedures — for an invertible tank, tap the tank on the work surface to dislodge air bubbles and provide 5 to 7 inversion cycles in 5 seconds by extending the arm and twisting the wrist 180 degrees, repeated at 30-second intervals; for a non-invertible tank, tap the tank and rotate the film reel 4 or 5 times during the first 5 to 10 seconds, repeated at 30-second intervals; and the statement that agitation is very important for even development of the film; Making a Proof Sheet — the home-made frame of window glass and composition board hinged with wide adhesive tape, and the instruction that if you use glass it is a good idea to tape the remaining edges so that you will not cut yourself; Small-Tank Agitation Procedures — for an invertible tank, tap the tank on the work surface to dislodge air bubbles and then provide 5 to 7 inversion cycles in 5 seconds; for a non-invertible tank, tap the tank on the work surface to dislodge air bubbles and rotate the film reel 4 or 5 times during the first 5 to 10 seconds; AJ-3 - the container of water kept for rinsing hands so other solutions are not carried into the developer, with a clean towel for drying them; the separation of the room into a wet area for mixing and processing and a dry area for handling film, negatives and paper; Small-Tank Agitation Procedures — the instruction to tap the tank on the work surface to dislodge air bubbles before the initial agitation, for both invertible and non-invertible tanks; Making a Proof Sheet - proof sheets are the same size as the negatives, help you choose the best negatives for enlarging and make a record to file with them; the home-made frame of a piece of window glass or clear Plexiglas and a piece of composition board of the same size, hinged with wide adhesive tape; the instruction to place the strips of negatives so that their emulsion side faces the emulsion side of the paper, with the negatives facing the light source; and the exposures given, a bare 7 W bulb 2 ft above the frame for about 10 seconds or an enlarger with an empty carrier at f/11 for about 8 seconds, each with the instruction to double or halve the time on the evidence of the processed sheet

Used by:Sodium hexametaphosphate (Calgon) · Kodak Hypo Clearing Agent and the washing accelerator Kodak patented · KODAK Rapid Selenium Toner · P12 The Physics of Washing · P16 Build: The Contact Printing Frame and Its Light Source · P19 Contrast Filtration and Split-Grade Printing · P19 Lab: Dodging, Burning, Edge Work and Local Contrast · P19 Developing the Print Consistently and Running a Printing Session · P19 Reading the Negative and Making the Work Print · P19 Lab: Test Strips, Base Exposure and the Print's Black Point · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P28 Part XXVIII Overview: Diagnosis as a Discipline · P28 Uneven Development, Bromide Drag and Surge Marks · Glass handling, cutting and breakage response · Air bells · Control chart: contamination · Pinholes · Uneven contact print from pressure, glass or source geometry

KODAK Developer D-76, technical data sheet J-78retrieved 2026-09-03, 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Storage life and capacity — 6 months in a full tightly closed bottle, 2 months half filled, 24 hours in a tray and 1 month in a tank with a floating lid; the unreplenished capacity of 16 sheets of 8 by 10 inches per US gallon with the development time raised 15 per cent after every four sheets or rolls per gallon; the 1:1 instruction to dilute just before use, discard after one batch and never replenish; and the 473 mL per 135-36 roll figure with the 10 per cent time increase for a smaller tank; Storage life and capacity; dilution; The opening description; agitation for rolls in a small tank; development-time tables at full strength and 1:1; storage life and capacity; replenishment rates and replenished capacity; Replenishment - the rate of 22.2 to 29.6 mL per roll or sheet, the replenished capacity table, and the modified replenisher for T-MAX films; Replenishment - the rate of 22.2 to 29.6 mL per 135-36 or 120 roll or 8 by 10 inch sheet; The opening description and replenishment paragraph; Storage life and capacity, the table of keeping properties and useful capacity per gallon and litre with its two footnotes; the instruction that D-76 diluted 1:1 is diluted just before use and discarded after one batch; and the modified replenishment rate of 70 mL per roll or sheet for T-MAX films. Searched for a pH figure, which the sheet does not print; The opening description; development-time tables at full strength and 1:1; storage life and capacity; replenishment rates and replenished capacity; Dilution 1:1 for one-shot use; Storage Life and Capacity: D-76 stock 6 months full and 2 months half-filled, working solution 24 hours in a tray and 1 month in a tank with a floating lid, D-76 1:1 diluted just before use and discarded after one batch; the note that partially filled bottles allow some oxidation; Development times and the note that tank development times shorter than 5 minutes may produce poor uniformity; D-76 composition and the note that a 1+1 dilution gives greater sharpness with a slight increase in graininess; The note that a 1+1 dilution gives greater sharpness with a slight increase in graininess; Opening description and the 1:1 dilution for greater sharpness with a slight increase in graininess; Agitation — the removal of the by-products of development from the surface of the film, the requirement for irregular or random movements, and the warning that solution currents flowing constantly in one direction increase film density along their paths; Storage-life table — six months in a full tightly closed bottle against two months half-filled, with the note that partially filled containers allow some oxidation; Agitation, including the small-tank procedure and the instruction to let the tank stand for the remainder of the first 30 seconds; the development-time tables for roll films in D-76 full strength and at 1:1 at 18, 20, 21, 22 and 24 degrees C; the note that tank development times shorter than 5 minutes may produce poor uniformity; the instruction to adjust the time by 10 to 15 per cent for contrast and by 10 per cent for a small tank volume; and the storage life and capacity table with its 15 per cent time compensation and its replenishment rate; The description of D-76; the small-tank agitation procedure and the instruction to let the tank stand for the remainder of the first 30 seconds; the roll-film development-time table at full strength at 18, 20, 21, 22 and 24 degrees C; the note that tank development times shorter than 5 minutes may produce poor uniformity; the storage-life and capacity table giving 6 months in a full tightly closed bottle and 2 months half-filled, and the note that partially filled bottles allow some oxidation; The opening description of D-76 and the 1:1 dilution for greater sharpness with a slight increase in graininess; the storage-life and capacity table; the instruction that the diluted developer is used once and neither reused nor replenished; Storage life and capacity: the unreplenished capacity of 16 sheets per gallon with a 15 per cent time increase after every four, and the replenished capacity of 120 per gallon at 22.2 to 29.6 mL of replenisher per roll; Opening description — full emulsion speed, excellent shadow detail, fine grain, and the 1:1 dilution for greater sharpness with a slight increase in graininess; agitation and the removal of the by-products of development from the surface of the film; the roll-film development-time tables at full strength and at 1:1; Storage-life and capacity table: six months in a full tightly closed bottle against two months half-filled, and the note that partially filled bottles allow some oxidation; Storage life and capacity — stock solution six months in a full tightly closed bottle and two months half-filled, working solution 24 hours in a tray and one month in a tank, useful capacity 16 rolls per gallon (4 per litre) with the footnote to increase development time by 15 per cent after every four rolls per gallon; the instruction that D-76 diluted 1:1 is diluted just before use and discarded after one batch; development times for roll film at stock and 1:1; the note that tank times shorter than 5 minutes may produce poor uniformity; The 1:1 dilution for greater sharpness with a slight increase in graininess; the instruction to dilute just before use and discard after one batch; the storage-life and useful-capacity table; The instruction that D-76 diluted 1:1 is diluted just before use, discarded after one batch, and neither reused nor replenished; the storage-life table for the stock solution; The opening description and the 1:1 dilution for greater sharpness with a slight increase in graininess; the instruction to dilute 1:1 just before use, to discard after one batch and neither to reuse nor to replenish it; the volumes — one 135-36 roll in 473 ml of diluted developer or two rolls in 946 ml, with a 10 per cent time increase where 237 ml is used for one roll; the storage-life and useful-capacity table; the note that tank development times shorter than 5 minutes may produce poor uniformity; the small-tank and large-tank agitation procedures and the instruction that agitation should consist of irregular movements that do not set up constant currents; The instruction that D-76 diluted 1:1 is diluted just before use, discarded after one batch, and neither reused nor replenished; The instruction that Developer D-76 diluted 1:1 is diluted just before use and discarded after processing one batch of film, and is neither reused nor replenished; Storage Life and Capacity - stock solution six months in a full tightly closed bottle and two months half-filled, working solution one month in a tank, useful capacity 16 rolls per gallon, that is 4 per litre, with a 15 per cent time increase after every four rolls per gallon; the note that solutions in full bottles have a longer shelf life because partially filled bottles allow some oxidation; the instruction that the 1:1 dilution is mixed just before use and discarded after one batch and is neither reused nor replenished; and Replenishment with Replenisher D-76R; The instruction that Developer D-76 diluted 1:1 is diluted just before use and discarded after processing one batch of film, and is neither reused nor replenished; the storage-life and useful-capacity table; and the note on 1:1 dilution giving greater sharpness with a slight increase in graininess; Agitation - the statement that agitation helps remove the by-products of development from the surface of the film so that fresh developer can act on the exposed silver halide, that agitation affects the rate of development particularly in high-density areas, and the instruction that agitation should always consist of irregular or random movements that will not cause solution currents to flow over the film constantly in any one direction because these currents increase film density along their paths and cause nonuniformity; the small-tank procedure; Development Times - the statement that the tables are starting-point recommendations and that a test should be run for critical applications; the instruction that D-76 diluted 1:1 is diluted just before use and neither reused nor replenished; the volume statement that one 135-36 roll, given as 80 square inches, is developed in 473 mL of the diluted solution, with a 10 per cent time increase where 237 mL is used instead; and the note that tank development times shorter than 5 minutes may produce poor uniformity; The instruction that D-76 diluted 1:1 is diluted immediately before use, discarded after one batch, and neither reused nor replenished; Storage Life and Capacity - the table giving Developer D-76 stock 6 months in a full tightly closed bottle and 2 months half-filled, the working solution 24 hours in a tray and 1 month in a tank with a floating lid, and a useful capacity of 16 per gallon and 4 per litre in both tray and tank, with the footnote that the figure is with time compensation and the development time is increased by 15 per cent after every four 8 x 10-inch sheets or 4 rolls per gallon processed; the statement that solutions in full bottles have a longer shelf life and that partially filled bottles allow some oxidation; the instruction that D-76 diluted 1 to 1 is diluted just before use, discarded after one batch and neither reused nor replenished, with a capacity of 8 per gallon and 2 per litre; and Replenishment - the rate of 22.2 to 29.6 mL of Replenisher D-76R per 135-36 or 120 roll or 8 x 10-inch sheet, the resulting capacity of 120 rolls of 135-36 per gallon with no increase in development time, the modified 5-to-1 replenisher for T-MAX films at 70 mL per roll which is said to help avoid a small speed loss and an increase in contrast as seasoning occurs, the instruction to discard after 9600 square inches per gallon, the instruction to discard after one month at low utilisation, and the instruction to monitor developer activity with process control strips; The instruction that D-76 diluted 1:1 is diluted just before use, not reused or replenished, and discarded after processing one batch of film; and the volume statement that one 135-36 roll, given as 80 square inches, is developed in 473 ml of the diluted solution, with a 10 per cent time increase where 237 ml is used instead; Development Times - the statement that the tables are starting-point recommendations and that a test should be run for critical applications; Storage Life and Capacity - stock 6 months in a full tightly closed bottle and 2 months half-filled, working solution 24 hours in a tray and 1 month in a tank with a floating lid, and a useful capacity of 16 per gallon and 4 per litre with a 15 per cent time increase after every four rolls per gallon; and Replenishment, whose rate of 22.2 to 29.6 mL of D-76R per roll raises the capacity to 120 rolls of 135-36 per gallon with no increase in development time; Development Times - the statement that the tables are starting-point recommendations and that a test should be run for critical applications, with the advice to change the time by 10 to 15 per cent where negatives are consistently flat or contrasty; the instruction that D-76 diluted 1:1 is diluted just before use, discarded after processing one batch and neither reused nor replenished; the volume statement that one 135-36 roll, given as 80 square inches, is developed in 473 mL of the diluted solution, with a 10 per cent time increase where 237 mL is used instead; the note that tank development times shorter than 5 minutes may produce poor uniformity; the small-tank agitation procedure with agitation at 30-second intervals; and the D-76 1:1 small-tank table at 18, 20, 21, 22 and 24 degrees C, whose TRI-X Pan row reads 11, 10, 9.5, 9 and 8 minutes and whose T-MAX 100, PLUS-X and VERICHROME Pan rows read 14.5 to 8.5, 8 to 5 and 11 to 6 across the same five temperatures; Storage Life and Capacity — the table giving D-76 stock solution 6 months in a full tightly closed bottle and 2 months in a half-filled one, 24 hours as a working solution in a tray and 1 month in a tank with a floating lid, and a useful capacity of 16 rolls of 135-36 or 120 per gallon (4 per litre) with a 15 per cent time increase after every four rolls per gallon; the instruction that solutions in full bottles have a longer shelf life while partially filled bottles allow some oxidation of the solution; and the instruction that D-76 diluted 1:1 is diluted just before use and discarded after processing one batch of film; Storage Life and Capacity — a useful capacity of 16 rolls of 135-36 or 120 per gallon (4 per litre) for D-76 at full strength, with the footnote to increase the development time by 15 per cent after every four rolls per gallon processed; and the instruction that D-76 diluted 1:1 is mixed just before use and discarded after one batch; Storage life and capacity — stock solution six months in a full tightly closed bottle and two months half-filled, working solution 24 hours in a tray and one month in a tank; the instruction that D-76 diluted 1:1 is diluted just before use, discarded after one batch, and neither reused nor replenished; D-76 keeping properties - six months in a full tightly closed bottle and two months half-filled, with the explanation that partially filled bottles allow some oxidation; capacity of 16 rolls per gallon at full strength with a 15 per cent time increase after every four rolls per gallon; the 1:1 dilution mixed just before use, discarded after one batch, neither reused nor replenished; replenishment with D-76R extending capacity to 120 8 by 10 inch sheets per gallon without increasing development times; Storage life and capacity - useful capacity 16 rolls per gallon, which is 4 per litre, with the footnote to increase development time by 15 per cent after every four rolls per gallon; Storage life and capacity - stock solution six months in a full tightly closed bottle and two months half-filled, working solution 24 hours in a tray and one month in a tank; Storage life and capacity - useful capacity 16 rolls per gallon with the footnote to increase development time by 15 per cent after every four rolls per gallon

Used by:P29 Capstone Stage 2: Formulating and Documenting Your Chemistry · Borax (sodium tetraborate decahydrate) · Kodak D-76 · Kodak D-76R · Kodak DK-20R · KODAK PROFESSIONAL XTOL Developer · Film developers compared · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P3 Aerial Oxidation: Why Chemistry Dies in a Half-Empty Bottle · P3 Rates, Temperature and Catalysts · P4 Development as Amplification · P4 Grain, Speed and Resolution · P8 Acutance, Adjacency Effects and Compensating Development · P8 Experiment: Watching a Developer Oxidise · P8 Development Kinetics: Time, Temperature, Agitation and Exhaustion · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P8 Assignment: Reading a Developer Formula · P8 Restrainers and Antifoggants · P8 Solvent Action, Physical Development and Grain · P8 Sulfite: Preservative, Buffer, Silver Solvent · P9 Break/Fix: The Developer That Went Wrong · P9 Assignment: The Developer Laboratory Report · P9 Lab: Preparing Standard Test Negatives · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P13 Lab: A Step-Wedge Exposure Series · P14 Experiment: Calibrating the Sensitometer · P14 Experiment: Process Control with Control Strips · P14 Build: The Enclosure and Exposure Stage · P15 Assignment: Characterising a Film and Developer with Your Own Instruments · P27 Experiment: Agitation, Stand and Semi-Stand Development · P27 Designing an Experiment That Yields a Number · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Experiment: Four Curve Families, Measured · P27 Assignment: The Developer Comparison, Measured and Printed · P27 Experiment: The Development Time and Temperature Series · P28 Chemistry in the Bottle: Oxidation, Exhaustion, Precipitation and Contamination · P28 Reading the Negative as Evidence: Thin, Dense, Flat and Contrasty · Versioning a formula · Control chart: developer exhaustion · Exhausted developer · Oxidised developer · Thin negative

KODAK PROFESSIONAL HC-110 Developer, publication J-24 (Technical Data / Chemicals)retrieved 2026-09-04, 2026-09-06

Sections: The dilution table, where 75 mL of stock solution and 225 mL of water is labelled 1:3 - the volumes that fix what a colon means in Kodak's notation; Preparing working solutions from stock solution: dilutions A to F with their stock and water volumes; Preparing working solutions from stock solution - dilution B given as 75 ml of stock and 225 ml of water and labelled 1 to 3

Used by:KODAK PROFESSIONAL XTOL Developer · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · Mixing a working solution from a stock · Dilution ratio misread as a fraction

KODAK PROFESSIONAL T-MAX 400 Film, publication F-4043retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Small-tank processing, the XTOL, XTOL (1:1), D-76 and D-76 (1:1) rows; Image Structure: resolving power and diffuse rms granularity for T-MAX 400; Features: high-efficiency, multi-zone T-GRAIN emulsion; Adjustments for Long and Short Exposures: no correction to 1 s, +1/3 stop at 10 s, +1 1/2 stops or 300 s at 100 s; Filter Corrections for T-MAX 400: No. 8 yellow 2/3 stop or factor 1.6 in daylight, No. 12 and No. 15 deep yellow 1 stop or factor 2, No. 25 red 3 stops or factor 8 in daylight and 2 stops or factor 4 in tungsten; Adjustments for Long and Short Exposures; Image Structure — diffuse rms granularity of 10, read at a net diffuse density of 1.00 using a 48 micrometre aperture at 12X magnification, based on development in KODAK Developer D-76 at 20 degrees C; Final steps, the Important note — fixer will be exhausted more rapidly with this film than with other films; if negatives show a magenta stain after fixing the fixer may be near exhaustion or the time may have been too short; a slight stain will not affect image stability, negative contrast or printing times and can be removed with Hypo Clearing Agent, but a stain that is pronounced and irregular over the film surface calls for refixing the film in fresh fixer; Final steps — fix 3 to 5 minutes in KODAK Rapid Fixer or 5 to 10 minutes or twice the clearing time in another fixer; the Important note that fixer will be exhausted more rapidly with this film than with other films, that a magenta stain indicates a fixer near exhaustion or too short a time, and that a pronounced and irregular stain calls for refixing in fresh fixer; Final steps, the Important note - if negatives show a magenta stain after fixing the fixer may be near exhaustion or the time may have been too short, a slight stain will not affect image stability and can be removed with Hypo Clearing Agent, but a pronounced and irregular stain calls for refixing the film in fresh fixer

Used by:KODAK PROFESSIONAL XTOL Developer · P4 Grain, Speed and Resolution · P6 Pinhole Exposure and Reciprocity Correction · P7 Assignment: Landscape, Sky, Foreground and Filters · P7 Assignment: Night, the Very Long Exposure and Solargraphy · P8 Solvent Action, Physical Development and Grain · P11 Break/Fix: The Exhausted Fixer · P11 How Fixer Works · Under-fixing

KODAK PROFESSIONAL T-MAX Developers, technical data / chemicals, publication J-86retrieved 2026-09-07

Sections: Capacity - approximately 48 rolls of 135-36 or 120 film per gallon with time compensation, its three bands of rolls 1 to 16 at the normal time, 17 to 32 at plus one minute and 33 to 48 at plus two minutes, the statement that the capacity is lower when the developer is used for push processing and that a solution used for push processing is discarded after one batch and not reused; and Storage - six months in a full tightly closed bottle, two months half-filled and one month in a covered tank; The statement that T-MAX Developer offers enhanced shadow detail in normally processed and push-processed films and that T-MAX RS produces higher image quality, described as enhanced shadow detail, than current push-processing developers when film is processed normally or pushed one, two or three stops; the statement that the published times are intended to produce a contrast index of 0.60 for T-MAX 400 Film and 0.56 for the other films and should suit a diffusion enlarger, with the instruction to reduce the development time by 20 to 30 per cent to adjust contrast for printing with a condenser enlarger; and the statement that the capacity is lower when the developer is used for push processing and that such a solution is discarded after one batch; The processing table's wetting-agent step — the instruction to provide gentle agitation for 5 seconds of the total 30, and that to reduce drying scum the PHOTO-FLO solution should be mixed with distilled water in areas that have hard water

Used by:P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Push and Pull Processing: What Extended Development Can and Cannot Buy · Calcium scum

KODAK PROFESSIONAL TRI-X 320 and 400 Films, publication F-4017retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Processing - the statement that the starting-point recommendations are intended to produce a contrast index of 0.56, and the note that tank development times shorter than 5 minutes may produce unsatisfactory uniformity; Small-tank processing, the XTOL, XTOL (1:1), D-76 and D-76 (1:1) rows at 65, 68, 70, 72 and 75 degrees F; Image Structure: diffuse rms granularity for TRI-X 400 and TRI-X 320, with the measurement conditions; Exposure, Daylight: the table of shutter speed and lens opening for average front-lit subjects from 2 hours after sunrise to 2 hours before sunset, giving 1/500 at f/16 for bright or hazy sun with distinct shadows at ISO 400; Exposure, Daylight: the table of shutter speed and lens opening for average front-lit subjects from 2 hours after sunrise to 2 hours before sunset; Exposure and Development Adjustments for Long and Short Exposures: +1 stop at 1 s with 10 per cent less development, +2 stops or 50 s at 10 s with 20 per cent less, +3 stops or 1200 s at 100 s with 30 per cent less; Filter Corrections; Tray and Large-Tank Processing, Sheets: provide continuous agitation and rotate the sheets 90 degrees as you interleave them; prewetting sheet film may improve tray process uniformity; Filter Corrections, KODAK WRATTEN Gelatin Filter, daylight and tungsten factors for TRI-X 400: No. 8 yellow 2 and 1.5, No. 11 yellowish green 4 and 3, No. 12 deep yellow 2.5, No. 15 deep yellow 2.5 and 1.5, polarising 2.5 and 2.5; Exposure, Daylight table; Exposure and Development Adjustments for Long and Short Exposures, the development reductions of 10, 20 and 30 per cent at 1, 10 and 100 metered seconds; Exposure and Development Adjustments for Long and Short Exposures: +1 stop at 1 metered second with 10 per cent less development, +2 stops or 50 s at 10 s with 20 per cent less, +3 stops or 1200 s at 100 s with 30 per cent less; and the instruction to process exposed film as soon as possible after exposure; Exposure and Development Adjustments for Long and Short Exposures: the development reductions of 10, 20 and 30 per cent at 1, 10 and 100 metered seconds; Image Structure — diffuse rms granularity of 17 for TRI-X 400 and 16 for TRI-X 320, with the statement that the data are based on development in KODAK HC-110 Developer, Dilution B; Characteristic Curves - the axes as printed, log exposure in lux-seconds running negative to about 1.0, density to 4.0, with the densitometry stated as diffuse visual and the process, temperature, agitation and four development times named on the plot; Processing - the statement that the starting-point development recommendations are intended to produce a contrast index of 0.56; Contrast Index Curves, plotting contrast index against development time for several developers; Characteristic Curves - four curves for one film at 6, 8, 10 and 12 minutes in D-76, with the axes in log exposure in lux-seconds and density, and the densitometry stated as diffuse visual; Characteristic-curve figures for D-76 and for T-MAX developer, whose axis blocks state Densitometry - Diffuse Visual; Push Processing - the statement that push processing allows the film to be exposed at higher film-speed numbers for conditions such as low-level light, stop action or existing light, but that there will be a loss of shadow detail and an increase in graininess; the statement that because of these films' exposure latitude the film may be underexposed by one stop using normal processing times, with prints showing a slight loss in shadow detail; the statements for two and three stops, each adding an increase in contrast and graininess and a further loss of shadow detail; and the instruction to expose a test roll to determine the film speed that gives the best results. Processing - the statement that the starting-point recommendations are intended to produce a contrast index of 0.56. The small-tank tables for TRI-X 400, whose D-76 row at 20 degrees C reads 6.75 minutes normal, 9.5 at EI 1600 marked a 2-stop push process and 11 at EI 3200 marked a 3-stop push process, and whose XTOL row reads 7, 9.75 and 10.5 at the same three settings; and Manual Processing, whose small-tank procedure is 5 to 7 inversion cycles in 5 seconds repeated at 30-second intervals; Processing - the statement that the starting-point recommendations are intended to produce a contrast index of 0.56 and that tests should be made to determine the best development time; the note that tank development times shorter than 5 minutes may produce unsatisfactory uniformity; the small-tank agitation procedure of 5 to 7 inversion cycles in 5 seconds repeated at 30-second intervals; and the TRI-X 400 small-tank development table at 18, 20, 21, 22 and 24 degrees C, whose D-76 row reads 8, 6.75, 6.25, 5.5 and 4.75 minutes, whose D-76 (1:1) row reads 10.75, 9.75, 9, 8.5 and 7.75, whose XTOL row reads 8, 7, 6.25, 5.75 and 4.75 and whose XTOL (1:1) row reads 10, 9, 8.5, 8 and 7.25; Storage and handling — load and unload the camera in subdued light, high temperatures or high humidity may produce unwanted quality changes, store unexposed film at 24 degrees C (75 degrees F) or lower in the original sealed package, always store film exposed or unexposed in a cool dry place, and process film as soon as possible after exposure; and the characteristic curve sheets, whose density points are stated relative to gross fog; Storage and handling — load and unload in subdued light, store unexposed film at 24 degrees C (75 degrees F) or lower in the original sealed package, always store film exposed or unexposed in a cool dry place, and process as soon as possible after exposure; the characteristic curve sheets, whose speed and contrast points are given as densities of 0.3 and 1.0 above gross fog; Storage - for best results, process film as soon as possible after exposure; Exposure, Daylight - the daylight table is given for average front-lit subjects from 2 hours after sunrise to 2 hours before sunset; Exposure, Daylight - the table is given for average front-lit subjects from 2 hours after sunrise to 2 hours before sunset, and its rows are named lighting conditions: bright or hazy sun on light sand or snow; bright or hazy sun with distinct shadows; weak, hazy sun with soft shadows; cloudy bright with no shadows; heavy overcast or open shade; Storage and handling — high temperatures or high humidity may produce unwanted quality changes, store unexposed film at 24 degrees C (75 degrees F) or lower in the original sealed package, always store film exposed or unexposed in a cool dry place, and process film as soon as possible after exposure

Used by:KODAK PROFESSIONAL XTOL Developer · P4 Grain, Speed and Resolution · P6 Commissioning the Camera: Light-Tightness, Flare and the First Negatives · P6 Pinhole Exposure and Reciprocity Correction · P6 Lab: Processing Your First Film · P7 Assignment: Landscape, Sky, Foreground and Filters · P7 Assignment: Night, the Very Long Exposure and Solargraphy · P7 Assignment: Time in the Frame, Moving Water, Clouds, People and Traffic · P8 Solvent Action, Physical Development and Grain · P13 Exposure, Density and the Logarithm · P13 Gamma, Contrast Index and Average Gradient · P13 The Characteristic Curve · P15 Density Depends on How You Look: Geometry and Spectral Response · P27 Push and Pull Processing: What Extended Development Can and Cannot Buy · P27 Experiment: The Development Time and Temperature Series · P28 Fog and Where It Comes From · P28 Reading the Negative as Evidence: Thin, Dense, Flat and Contrasty · Night exposure session · Outdoor exposure session · Recording a daylight exposure · Age fog · Heat fog

KODAK PROFESSIONAL XTOL Developer, Technical Data / Chemical, J-109retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Features and benefits; mixing instructions and the pH and specific gravity of the working tank solution; storing solutions and storage life of unused solutions; using diluted developer and the 100 mL minimum; time compensation and capacity; Features and benefits; mixing instructions and the pH of the working tank solution; storing solutions and storage life of unused solutions; Mixing instructions — the pH of the working tank solution; The whole sixteen-page sheet - the opening description and the features and benefits table; Sizes available; Mixing instructions and the specification of a correctly mixed working tank solution; Storing solutions and the storage life of unused solutions; Small-tank, tray and rotary-tube processing, using full-strength developer and the time-compensation table; Using diluted developer and the 100 mL minimum; Using seasoned developer; Agitating rolls in small tanks; Agitating sheet film in trays; Final steps in small-tank, tray and rotary-tube processing; Large-tank (replenished) processing; Starting (preseasoning) a fresh working tank solution; Converting to XTOL Developer from another developer; Replenishment; System maintenance; Disposal; and Tables 1 to 8 of development times; Mixing instructions: the specific gravity and pH of a correctly mixed working tank solution; Features and benefits: ascorbic acid-based, no hydroquinone, excellent keeping properties and high resistance to breakdown from oxidation; mixing at 18 to 30 degrees C; the working tank solution at pH 8.20; storage life six months full and at least two months partially filled; Features and benefits: ascorbic acid-based, no hydroquinone; the working tank solution at pH 8.20 plus or minus 0.05; Capacity: about fifteen 135-36 or 120 rolls per litre at full strength with time compensation, and the minimum of 100 ml of full-strength developer per roll; Features and benefits — ascorbic acid-based black-and-white film developer, no hydroquinone, two-part powder, one solution for both developer and replenisher, excellent keeping properties with six months in full bottles and high resistance to breakdown from oxidation, contrast index similar to other developers, fine grain and high sharpness, excellent emulsion speed; the specification of the mixed working tank solution at specific gravity 1.085 plus or minus 0.003 and pH 8.20 plus or minus 0.05 at 25 degrees C; mixing at 18 to 30 degrees C; the 1:1 dilution used once; capacity and the minimum-volume instruction; Mixing instructions and the specific gravity and pH of a correctly mixed working tank solution; Mixing instructions; the specific gravity and pH of a correctly mixed working tank solution, pH 8.20 plus or minus 0.05; features and benefits — ascorbic acid-based, no hydroquinone; Diluting the developer - the statement that the minimum amount of diluted developer needed to cover the film may not contain enough active ingredients to develop the film fully in the recommended time, and the recommendation to start with at least 100 mL of full-strength developer for each 135-36 or 120 roll, or the equivalent of 80 square inches (516 square centimetres), with the worked example that four rolls at 1:1 use at least 800 mL even where the equipment would allow less; Using Full-Strength Developer - the statement that the capacity of the full-strength developer with normal unreplenished processing is approximately 15 rolls of 135-36 or 120 film, or the equivalent of 80 square inches, per litre with time compensation, and the instruction to discard the developer after processing 15 rolls per litre; the time-compensation table of rolls 1 to 5 at the normal time, 6 to 10 at plus 15 per cent and 11 to 15 at a further plus 15 per cent; the footnote defining 80 square inches as one 135-36 or 120 roll, four 4 x 5-inch sheets or one 8 x 10-inch sheet, with a 220 roll counting twice; Storage Life of Unused Solutions - 6 months in a full tightly closed container, at least 2 months in a partially filled one and indefinitely in a replenisher tank with a floating lid, with the stated reason that partially filled containers allow oxidation; Replenishment at 70 mL per roll adjusted in 10 mL increments; and Starting (preseasoning) a fresh working tank solution - 6.5 mL of KODAK Developer Starting Solution per litre, with the statement that without preseasoning initial development times are about 10 per cent shorter than the tables and approach them as the tank reaches a steady state; Table 1, Processing Roll Films in Small Tanks - the table's paired EI and CI columns, in which each published development time is indexed by the contrast index it is intended to reach. KODAK PROFESSIONAL T-MAX 100 Film in full-strength XTOL at 20 degrees C reads EI 25/50 at CI 0.52 in 6.75 minutes, EI 100/200 at CI 0.56 in 7.5, EI 200 at CI 0.62 in 8, EI 400 at CI 0.72 in 9.5 and EI 800 at CI 0.82 in 10.5. KODAK PROFESSIONAL T-MAX P3200 Film reads EI 400 at CI 0.52 in 9.5 minutes, 800 at 0.56 in 10.5, 1600 at 0.62 in 11.5, 3200 at 0.72 in 13.5, 6400 at 0.82 in 15.25, 12500 at 0.92 in 17.25 and 25000 at CI 1.02 in 19. TRI-X 400 reads EI 400/800 at CI 0.56 in 7 minutes, 1600 at 0.72 in 9.75 and 3200 at 0.82 in 11.5, with the 18 degrees C cell at EI 3200 left blank. ILFORD HP-5 Plus is indexed on a different contrast ladder of 0.52, 0.58, 0.65, 0.75 and 0.85, reading EI 400 at CI 0.58 in 8.5 minutes and EI 3200 at CI 0.85 in 17.5, with the 18 degrees C cell for that row marked NR, not recommended, as determined by testing. Also the Features and Benefits table - ascorbic acid-based, no hydroquinone, full emulsion speed, excellent emulsion speed with normal and push processing, enhanced shadow contrast and improved highlight detail with some films, fine grain and high sharpness - and the statement that dilution at 1:1 provides slightly greater film speed, enhanced sharpness and shadow detail, and slightly more grain; Table 1, Processing Roll Films in Small Tanks - the ILFORD FP-4 Plus 135 rows in full-strength XTOL, indexed by EI and by the contrast index the time is intended to reach, reading EI 32/64 at CI 0.52 in 6.5 minutes at 20 degrees C, EI 125 at CI 0.58 in 8, EI 250 at CI 0.65 in 9 and EI 500 at CI 0.75 in 11; Using Full-Strength Developer - the capacity of approximately 15 rolls of 135-36 per litre with time compensation, and the definition of 80 square inches as one 135-36 or 120 roll, four 4 by 5-inch sheets or one 8 by 10-inch sheet; Storage Life of Unused Solutions - 6 months full, at least 2 months partially filled and indefinitely in a replenisher tank with a floating lid; Using Diluted Developer - the instruction that at least 100 mL of full-strength developer goes into each roll's worth of a 1:1 dilution; and the Features and Benefits table, whose only statements of composition are ascorbic acid-based and no hydroquinone

Used by:Ascorbic acid · Sodium ascorbate · 510-Pyro · KODAK PROFESSIONAL XTOL Developer · P8 Alkalis, Buffers and pH · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 How Development Works · P8 Assignment: Reading a Developer Formula · P8 Superadditivity: Why Two Agents Beat One · P9 Experiment: Comparing Developing Agents · P27 Experiment: Agitation, Stand and Semi-Stand Development · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Push and Pull Processing: What Extended Development Can and Cannot Buy · P27 Assignment: The Developer Comparison, Measured and Printed

Recovering Silver from Photographic Processing Solutions, publication J-215retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Adjustment of pH — that in practice the pH should not be increased above 7.8 to 8.0 because of the evolution of ammonia that takes place in ammonium-based fixers and bleach-fixes; Adjustment of pH; electrolytic recovery; metallic replacement cartridges; Recommendations for adjusting the pH of iron-containing solutions; Electrolytic recovery; metallic replacement cartridges; Electrolytic silver recovery — troubleshooting and solution preparation; Electrolytic recovery; metallic replacement cartridges; precipitation; Which solutions carry silver and why they are collected rather than discharged; Comparison of silver-recovery techniques; silver concentrations in various overflow solutions; Comparison of silver-recovery techniques; metallic replacement cartridges; silver concentrations in various overflow solutions; Comparison of silver-recovery techniques; metallic replacement cartridges; Comparison of silver-recovery techniques; metallic replacement cartridges for small volumes; The instruction that the pH of an ammonium-based fixer should not be raised above 7.8 to 8.0, because of the ammonia that is then evolved; Comparison of silver-recovery techniques — recovery efficiency greater than 90 per cent for electrolysis, greater than 95 for metallic replacement cartridges and greater than 99 for precipitation, with the applications column putting electrolysis in all facilities except very small ones and precipitation in very small and large ones; Silver concentrations in various overflow solutions — black-and-white fixer 3,000 to 7,000 mg/L, C-41 and E-6 tank 1 fixer 5,000 to 12,000, bleach-fix 3,000 to 10,000, low-flow washes 1,000 to 3,000 and washless-process stabilisers 100 to 1,000; Electrolysis — post-cell concentrations usually 200 to 800 mg/L and the three reasons pushing a cell below about 200 mg/L fails; Metallic replacement cartridges — the pros and cons table, the statement that dwell time is the single biggest factor, the ideal pH of 5.5 to 6.5 with too-rapid dissolution below 5.0 and slow reaction above 7, pre-conditioning with a mildly acidic solution or at least water to prevent channelling, and the note that the natural corrosivity of photographic solutions consumes steel wool even when no silver is being removed; Metallic replacement cartridges — the forms of iron used, steel wool, iron filings, steel screen wire and iron filings on a rigid support; the statement that the single biggest factor influencing performance is the residence or dwell time of the solution in the cartridge, and the instruction to use a longer residence time rather than a shorter one if in doubt; Adjustment of pH — the ideal range of 5.5 to 6.5, the statement that below pH 5.0 the steel wool is catalysed to dissolve too rapidly and the capacity can be significantly reduced, and that above pH 7 the dissolution reaction is slow and optimum silver removal may not take place; Pre-conditioning MRCs — standing with a mildly acidic solution or at the very least water to etch the steel surface and minimise channelling, and the statement that intermittent use allows the steel wool to oxidise or rust; Useful life — the statement that the natural corrosivity to steel of many photographic processing solutions consumes steel wool even when silver is not being removed; Comparison of silver-recovery techniques — recovery efficiency greater than 95 per cent for metallic replacement cartridges; Metallic replacement cartridges; silver concentrations in various overflow solutions; Silver concentrations in various overflow solutions, and the case for recovery rather than discharge

Used by:Ammonium sulfite · Ammonium thiosulfate · Potassium carbonate (anhydrous) · Silver bromide · Sodium carbonate (anhydrous) · Sodium sulfite · Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Sulfuric acid · P2 Waste: Streams, Silver, and the Drain You Must Not Use · P2 Silver Nitrate: The Reagent That Sets the Rules · P4 Experiment: Precipitating the Silver Halides · P4 Darkroom Session: The Latent Image Made Visible · P11 Overview: Making the Image Permanent · P12 Silver Recovery and the Responsible Darkroom · P12 Experiment: Small-Scale Metallic Replacement · Routing silver-bearing waste · Handling silver nitrate · Responding to a silver nitrate spill

cameochemicals.noaa.gov

CAMEO Chemicals: chemical datasheets and reactivityretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Datasheet: 6-NITROBENZIMIDAZOLE — general description, fire hazard, health hazard, reactivity profile, reactive groups, physical properties, protective clothing, first aid; Datasheet: ACETIC ACID, GLACIAL — air and water reactions, health hazard, reactivity profile; reactive group Acids, Carboxylic; Ammonium chloride datasheet — general description, reactivity profile, air and water reactions, fire hazard, health hazard; Ammonium dichromate — datasheet 2425: general description, reactivity profile, fire hazard, explosion hazard, health hazard, reactive group incompatibilities; Datasheet: AMMONIUM HYDROXIDE — general description, fire hazard, health hazard, reactivity profile, air and water reactions; Datasheet: FERRIC AMMONIUM CITRATE — general description, air and water reactions, health hazard, fire hazard, reactivity profile; reactive group Salts, Acidic; Datasheet: FERRIC AMMONIUM OXALATE — general description, air and water reactions, health hazard, fire hazard, reactivity profile; reactive groups Salts, Acidic and Reducing Agents, Weak; Datasheet: AMMONIUM PERSULFATE (chemical 105) — reactivity alert, air and water reactions, fire hazard, health hazard, reactivity profile, and the reactive group Salts, Acidic; "Ammonium sulfite — datasheet 2459: chemical identifiers, including the USCG CHRIS code AMF and the absence of a UN/NA number, an NFPA diamond, a NIOSH Pocket Guide entry and an International Chemical Safety Card; general description; air and water reactions; fire hazard; health hazard; reactivity profile; reactive groups; protective clothing; first aid; physical properties, including the chemical formula printed as (NH4)2 SO3.H2O, the molecular weight of 134.2 and the specific gravity greater than 1.1 at 68 degrees F, all attributed to USCG 1999; the Protective Action Criteria attributed to the U.S. Department of Energy, 2024; and the EPA Consolidated List of Lists entry giving a CERCLA reportable quantity of 5000 pounds"; Ammonium thiosulfate datasheet 2462 — general description, fire and health hazards, reactivity profile, air and water reactions; L-ASCORBIC ACID datasheet CH19830 — general description, reactivity alert, air and water reactions, fire hazard, health hazard, reactivity profile, physical properties; Datasheet: 1,2,3-BENZOTRIAZOLE — general description, fire hazard, health hazard, reactivity profile, air and water reactions, physical properties, protective clothing; Datasheet: BORIC ACID — health hazard, reactivity profile; reactive group datasheet 60, Acids, Weak; Cadmium bromide — datasheet 2756: general description, reactivity profile, fire hazard, health hazard, reactive group; CATECHOL datasheet CH8407 — general description, air and water reactions, fire hazard, health hazard, reactivity profile, physical properties; Datasheet: CITRIC ACID — reactivity profile, air and water reactions, health hazard; reactive groups Acids, Carboxylic and Alcohols and Polyols; Datasheet: ETHANOL — general description, fire hazard, health hazard, reactivity profile, physical properties, IDLH; FORMALDEHYDE, SOLUTIONS (FORMALIN) (CORROSIVE) datasheet 17291 — physical description, air and water reactions, reactivity alerts, fire hazard, health hazard, reactivity profile and reactive groups; FORMALDEHYDE, SOLUTION, FLAMMABLE datasheet 769 — physical description, flash point, odour threshold; GLUTARALDEHYDE SOLUTION datasheet 8707 — physical description, air and water reactions, reactivity alerts, fire hazard, health hazard, reactivity profile and reactive groups; Datasheet: HYDROCHLORIC ACID, SOLUTION — air and water reactions, health hazard, fire hazard, reactivity profile; reactive groups Acids, Strong Non-oxidizing and Water and Aqueous Solutions; HYDROQUINONE datasheet 3626 — general description, air and water reactions, fire hazard, health hazard, reactivity profile; Datasheet: FERROUS SULFATE — general description, air and water reactions, health hazard, reactivity profile; reactive group Reducing Agents, Strong; Datasheets: FERRIC CHLORIDE — general description, air and water reactions, health hazard, fire hazard, reactivity profile, reactive group Acids, Strong Non-oxidizing; FERRIC CHLORIDE, SOLUTION — reactivity profile and fire hazard; Datasheets: FERRIC CHLORIDE — general description, air and water reactions, health hazard, reactivity profile, reactive group Acids, Strong Non-oxidizing; FERRIC CHLORIDE, SOLUTION — reactivity profile; 'Datasheet: FERRIC NITRATE — general description, reactivity alerts, air and water reactions, fire hazard, health hazard, reactivity profile, protective clothing, physical properties, potentially incompatible absorbents, EPA Consolidated List of Lists; Reactive Group Datasheet: Nitrate and Nitrite Compounds, Inorganic — flammability, reactivity, toxicity; Datasheet: CITRIC ACID — reactivity profile'; Datasheet: ISOPROPANOL — general description, fire hazard, health hazard, reactivity profile, physical properties, IDLH; Lead nitrate — datasheet 3742: general description, reactivity profile, fire hazard, health hazard, reactive group and incompatible absorbents; Mercuric chloride — datasheet 3828: general description, reactivity profile, fire hazard, health hazard, reactive group assignments; P-METHYLAMINOPHENOL SULFATE datasheet 20615 — general description, fire hazard, health hazard, reactivity profile, air and water reactions; Datasheet: NITRIC ACID, OTHER THAN RED FUMING — air and water reactions, health hazard, fire hazard, reactivity profile; reactive group Acids, Strong Oxidizing; Datasheet: OXALIC ACID — reactivity profile, health hazard, fire hazard; reactive group Acids, Carboxylic; P-AMINOPHENOL datasheet 3929 — general description, air and water reactions, fire hazard, health hazard, reactivity profile; Palladium chloride — datasheet 20830: general description, reactivity profile, air and water reactions, health hazard, reactive groups, physical properties; Potassium bromide datasheet — general description, reactivity profile, health hazard; Reactive group datasheet 62 — Carbonate Salts, reactivity and flammability; Potassium cyanide — datasheet 5150: general description, reactivity profile, air and water reactions, fire hazard, health hazard, reactive group; Potassium bichromate — datasheet 4305: general description, reactivity profile, fire hazard, health hazard, reactive group incompatibilities; Datasheet: POTASSIUM HYDROXIDE, [DRY SOLID, FLAKE, BEAD, OR GRANULAR] — reactivity alerts, reactivity profile; reactive group datasheet 10, Bases, Strong; Potassium iodide datasheet — general description, reactivity profile, health hazard; Potassium metabisulfite datasheet — reactivity profile, fire hazard, health hazard; Datasheet: POTASSIUM OXALATE MONOHYDRATE — general description, health hazard, fire hazard, reactivity profile; reactive groups Salts, Basic and Reducing Agents, Weak; Datasheet: POTASSIUM OXALATE MONOHYDRATE — general description, air and water reactions, health hazard, fire hazard, reactivity profile; reactive groups Salts, Basic and Reducing Agents, Weak; Datasheet: POTASSIUM PERMANGANATE (chemical 4324) — reactivity alert, fire hazard, health hazard, the reactivity profile including the manganese heptoxide explosion with concentrated sulfuric acid, the reactive group Oxidizing Agents Strong, and the potentially incompatible absorbents; PYROGALLIC ACID datasheet CH9037 — general description, reactivity alert, air and water reactions, fire hazard, health hazard, reactivity profile, physical properties; Selenium powder — datasheet 4427: general description, fire and health hazards, reactivity profile; Silver nitrate datasheet (chemical 4443) — general description, reactivity alerts, reactivity profile, fire hazard, health hazard, physical properties, protective clothing; SODIUM ASCORBATE datasheet CH21012 — general description, air and water reactions, fire hazard, health hazard, reactivity profile, physical properties; Sodium bicarbonate datasheet (CAS 144-55-8) — physical properties, air and water reactions, health hazard, reactivity profile; Reactive group datasheet 62 — Carbonate Salts; Sodium bisulfite datasheet — reactivity profile, fire hazard, health hazard; Reactive group datasheet 62 — Carbonate Salts, reactivity; Datasheet: SODIUM HYDROXIDE, SOLID — air and water reactions, reactivity profile; reactive group datasheet 10, Bases, Strong; Sodium metabisulfite datasheet — reactivity profile, air and water reactions, fire hazard, health hazard; "Sodium selenate — datasheet 4525: chemical identifiers, including UN/NA number 2630 and the DOT hazard label Poison; general description; air and water reactions; fire hazard; health hazard; reactivity profile; reactive groups; first aid, for the signs and symptoms of acute exposure; physical properties, including specific gravity, melting and boiling point, molecular weight and water solubility; and the Protective Action Criteria attributed to the U.S. Department of Energy"; Sodium selenite — datasheet 4526: general description, fire hazard, health hazard, reactivity profile; Sodium sulfide, hydrated, with not less than 30% water — datasheet 1528: general description, fire and health hazards, reactivity profile, air and water reactions; Sodium sulfite datasheet — reactivity profile, air and water reactions, health hazard; Datasheet: SULFURIC ACID — air and water reactions, health hazard, fire hazard, reactivity profile; reactive group Acids, Strong Oxidizing; Thiourea datasheet 4635 — general description, fire and health hazards, reactivity profile; L-ASCORBIC ACID datasheet CH19830 - the reactivity alert "Strong Reducing Agent"; Potassium cyanide, datasheet 5150 — general description, reactivity profile, air and water reactions, health hazard; Nitric acid datasheet — the reactivity profile, for the attack on metals and the evolution of nitrogen dioxide with silver and copper; and the iodine datasheet, for the emission of toxic vapour at room conditions and the purple colour that becomes visible as it builds up in a confined space; Datasheet — ISOPROPANOL: the note that it is sold as a 70 per cent aqueous solution as rubbing alcohol, the vapour density of 2.07, and the reactivity profile, which records that it reacts with air or oxygen to form dangerously unstable peroxides; Datasheet — SILVER NITRATE: the formation of silver fulminate with alcohols; Ammonium thiosulfate datasheet 2462 — general description and solubility, reactivity profile, and the note that it decomposes on heating; Sodium sulfide, hydrated, with not less than 30% water, datasheet 1528 — the deliquescent yellow-pink or white crystals, flakes or lumps, alkaline and mildly corrosive to metals; the liberation of hydrogen sulfide on contact with acid; the violent reactions with strong oxidisers, carbon, charcoal and diazonium salts; and the statement that the material can explode on rapid heating or when shocked; L-ASCORBIC ACID datasheet CH19830 - the reactivity alert "Strong Reducing Agent", the air and water reactions, and the reactivity profile naming oxidisers, iron, copper and alkalis; Thiourea datasheet 4635 — reactivity profile, including violent decomposition with hydrogen peroxide and nitric acid and explosion when ground with potassium chlorate; Silver nitrate datasheet, chemical 4443 — reactivity profile, for the black precipitate of silver nitride that exploded on stirring when an ammoniacal silver nitrate solution was treated with sodium hydroxide; Datasheet, HYDROCHLORIC ACID, SOLUTION — air and water reactions, the heat generated on dilution, and the reactivity profile listing aluminium, zinc, calcium, magnesium, iron, tin and the alkali metals among the metals attacked with evolution of hydrogen; "Datasheet: CITRIC ACID — reactivity profile, on the potentially explosive reactions of citric acid with metal nitrates"; Silver nitrate datasheet (chemical 4443) — reactivity alerts and reactivity profile, for the incompatibilities listed under Incompatibilities, and for the acceleration of the burning of combustible material; Datasheet: POTASSIUM OXALATE MONOHYDRATE — general description and the note that it sinks in and mixes slowly with water; health hazard; reactivity profile and the reactive groups Salts, Basic and Reducing Agents, Weak; Acetic acid, glacial: density; Acetic acid, glacial: physical description and density; Silver nitrate: physical description; SODIUM CARBONATE datasheet — health hazard and reactivity profile; SODIUM SULFITE datasheet — the production of sulfur dioxide with acids; ASCORBIC ACID datasheet — reactivity alert Strong Reducing Agent, air and water reactions including the acceleration of oxidation by alkaline conditions, iron and copper and the degradation under anaerobic conditions; SODIUM ASCORBATE — quick air oxidation above pH 6; CATECHOL and PYROGALLIC ACID datasheets; Sodium sulfite datasheet — reactivity profile, air and water reactions and the production of corrosive material and sulfur dioxide with acids; ASCORBIC ACID datasheet — the reactivity alert Strong Reducing Agent and the statement that aqueous solutions are oxidised by air at a rate depending on pH and oxygen, accelerated by alkaline conditions, iron and copper, with degradation also under anaerobic conditions; SODIUM ASCORBATE datasheet — quick air oxidation above pH 6; Sodium sulfide, hydrated, with not less than 30 per cent water, datasheet 1528 - the reactivity profile recording that it releases toxic hydrogen sulfide gas when mixed with an acid, that aqueous solutions gradually convert to sodium hydroxide and sodium thiosulfate on exposure to air, and that the material burns skin, eyes and mucous membranes; Sodium sulfide, hydrated, with not less than 30% water, datasheet 1528 - the reactivity profile recording that it releases toxic hydrogen sulfide gas when mixed with an acid, that aqueous solutions gradually convert to sodium hydroxide and sodium thiosulfate on exposure to air, and that the material burns skin, eyes and mucous membranes; Reactivity profiles and datasheets for silver nitrate; ammonium hydroxide; sodium sulfide; sodium sulfite; sodium bisulfite; sodium metabisulfite; ethanol; oxalic acid; formaldehyde; potassium dichromate; mercury(II) chloride; thiourea; sodium selenite; Sodium hydroxide reactivity profile, including the heat liberated on dissolution, steaming and spattering, and ignition of adjacent combustible material

Used by:6-Nitrobenzimidazole · Acetic acid (glacial) · Ammonium chloride · Ammonium dichromate · Ammonia solution (ammonium hydroxide) · Ammonium iron(III) citrate · Ammonium iron(III) oxalate · Ammonium persulfate · Ammonium sulfite · Ammonium thiosulfate · Ascorbic acid · Benzotriazole · Boric acid · Cadmium bromide · Catechol · Citric acid (anhydrous) · Ethanol · Formaldehyde · Glutaraldehyde · Hydrochloric acid · Hydroquinone · Iron(II) sulfate, anhydrous · Iron(II) sulfate heptahydrate · Iron(III) chloride, anhydrous · Iron(III) chloride hexahydrate · Iron(III) nitrate nonahydrate · Isopropyl alcohol · Lead(II) nitrate · Mercury(II) chloride · Metol · Nitric acid · Oxalic acid · p-Aminophenol · Palladium(II) chloride · Potassium bromide · Potassium carbonate (anhydrous) · Potassium cyanide · Potassium dichromate · Potassium hydroxide (caustic potash) · Potassium iodide · Potassium metabisulfite · Potassium oxalate, anhydrous · Potassium oxalate monohydrate · Potassium permanganate · Pyrogallol · Selenium · Silver nitrate · Sodium ascorbate · Sodium bicarbonate · Sodium bisulfite · Sodium carbonate (anhydrous) · Sodium carbonate monohydrate · Sodium hydroxide (caustic soda) · Sodium metabisulfite · Sodium selenate · Sodium selenite · Sodium sulfide · Sodium sulfite · Sulfuric acid · Thiourea · 510-Pyro · Cyanide fixing and toning · Daguerre's 1839 process outline · Double-coated albumen procedure · ILFORD RAPID FIXER · Kodak ST-1 · KODAK PROFESSIONAL XTOL Developer · Moersch MT3 Variotoner · Nicol's kallitype · EDTA, citric acid and hydrochloric acid clearing sequence · The Simple Cyanotype (2019) · Wedgwood and Davy's silver nitrate on leather · Willis's potassium oxalate developer · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P2 Measuring Mass, Volume, Temperature and Density, and Knowing How Wrong You Are · P2 Silver Nitrate: The Reagent That Sets the Rules · P8 Experiment: Watching a Developer Oxidise · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P8 Sulfite: Preservative, Buffer, Silver Solvent · P9 Experiment: Comparing Developing Agents · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · Chemical incompatibilities · Responding to an alkali spill

canada.ca

Care of Encased Photographic Images - Canadian Conservation Institute (CCI) Notes 16/1retrieved 2026-09-06

Sections: The whole leaflet: the image as microscopic particles of silver amalgam on the silver surface; the package inside the case as four parts, plate, window mat or spacer, cover glass and pliable brass frame; the unprotected surface being sensitive to the slightest touch; handling only with protective lintless nylon or cotton gloves; loose dust removed with a soft brush or pressurized air and no other cleaning method recommended, with the glass and frame cleaned separately; relative humidity between 30 and 50 per cent and never above 60; storage temperature no higher than 24 C and ideally below 21 C, not fluctuating more than 4 C daily; and storage in individual document boxes

Used by:P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory

cdc.gov

NIOSH Pocket Guide to Chemical Hazards (DHHS (NIOSH) Publication No. 2005-149)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Entry: Acetic acid (npgd0002) — exposure limits, IDLH, chemical and physical properties, incompatibilities and reactivities, personal protection and sanitation; Index of chemical names and synonyms — searched for amidol and diaminophenol; no entry; Searched for ammonium bromide; no entry; Ammonium chloride fume: exposure limits, chemical and physical properties, personal protection and sanitation, incompatibilities and reactivities; Searched for ammonium citrate; no entry; The CAS-number index, searched for 3458-72-8, and the chemical-name index, searched for citrate; no entry for either; Chromic acid and chromates — exposure limits, IDLH, incompatibilities and reactivities, symptoms, target organs, personal protection; Ammonia — exposure limits, IDLH, chemical and physical properties, incompatibilities and reactivities; Entry: Iron salts (soluble, as Fe) — exposure limits, personal protection and sanitation; Entry: Oxalic acid — incompatibilities and reactivities, silver compounds; The CAS-number index, searched for 7727-54-0; no entry; Searched for ammonium thiocyanate and for thiocyanates; no entry; Barium sulfate (npgd0043) — REL and PEL, IDLH not determined, physical description; and the note under Barium (soluble compounds, as Ba) that its limits apply to other soluble barium compounds except barium sulfate; Borates, tetra, sodium salts (Decahydrate) and (Pentahydrate): exposure limits, properties, incompatibilities and reactivities; Bromine — exposure limits, IDLH, the ppm to mg per cubic metre conversion, chemical and physical properties, incompatibilities and reactivities, exposure routes, symptoms, target organs, personal protection and first aid; Cadmium dust (as Cd) — exposure limits, IDLH, incompatibilities and reactivities, exposure routes, symptoms, target organs; the note that the REL and PEL apply to all cadmium compounds; Catechol: exposure limits, physical description and properties, incompatibilities and reactivities, personal protection and sanitation, exposure routes, symptoms and target organs; Chlorine — exposure limits, IDLH, the ppm to mg per cubic metre conversion, relative gas density, chemical and physical properties, incompatibilities and reactivities, exposure routes, symptoms, target organs, personal protection including the frostbite entries, and first aid; Index of chemical names and synonyms — searched for chlorohydroquinone; no entry; Ethyl ether — exposure limits and the referral to Appendix D, Substances with No Established RELs; chemical and physical properties including flash point, vapour pressure and the explosive range; incompatibilities and reactivities with the note on peroxide formation; exposure routes, symptoms, target organs, personal protection and first aid; Index of chemical names and synonyms — searched for dimezone and pyrazolidone; no entry; Index of chemical names and synonyms — searched for erythrosine; no entry; Ethyl alcohol — exposure limits, IDLH, chemical and physical properties, personal protection and sanitation; Formaldehyde and Formalin (as formaldehyde): exposure limits, IDLH, chemical and physical properties, incompatibilities and reactivities, personal protection and sanitation, exposure routes, symptoms and target organs; Index of chemical names and synonyms — searched for gallic acid; no entry; Glutaraldehyde: exposure limits and Appendix C (Aldehydes), chemical and physical properties, incompatibilities and reactivities, personal protection and sanitation, exposure routes, symptoms and target organs; Glycerin (mist) - exposure limits, chemical and physical properties, personal protection and sanitation, incompatibilities and reactivities, exposure routes, symptoms and target organs; Appendix D, Substances with No Established RELs; Appendix G, Vacated 1989 OSHA PELs; the explanation of the N.R. entry in the Personal Protection and Sanitation section; Appendix A and the note on nine related low-molecular-weight aldehydes, glyoxal among them, whose carcinogenicity testing is not complete; no Pocket Guide entry for glyoxal itself; Entry: Hydrogen chloride — exposure limits, IDLH, incompatibilities and reactivities, personal protection and sanitation, symptoms and target organs; Hydroquinone (npgd0338): exposure limits, IDLH, physical properties, incompatibilities and reactivities, personal protection and sanitation; Iodine — exposure limits, IDLH, the ppm to mg per cubic metre conversion, chemical and physical properties, incompatibilities and reactivities, exposure routes, symptoms, target organs, personal protection and first aid; Entry: Iron salts (soluble, as Fe) — synonyms, exposure limits, personal protection and sanitation; Entry: Iron salts (soluble, as Fe) — synonyms including ferric chloride, exposure limits, personal protection and sanitation; Isopropyl alcohol — exposure limits, IDLH, chemical and physical properties, personal protection and sanitation, incompatibilities and reactivities; Kaolin, page 183 — CAS 1332-58-7, RTECS GF1670500, IDLH not determined, the synonyms China clay, Clay, Hydrated aluminum silicate, Hydrite and Porcelain clay, the note that the main constituent of kaolin is kaolinite, the NIOSH recommended exposure limits of 10 mg/m3 total and 5 mg/m3 respirable and the OSHA permissible limits of 15 and 5, the physical description as a white to yellowish or grayish powder that darkens and develops a clay-like odour when moistened, molecular weight given as "varies", solubility given as insoluble, specific gravity 1.8 to 2.6, noncombustible solid, incompatibilities and reactivities reported as none, exposure routes inhalation and contact, symptoms of chronic pulmonary fibrosis and stomach granuloma, and target organs the respiratory system and the stomach; Appendix C, Supplementary exposure limits: Lead — the NIOSH and OSHA definitions and limits, and the blood lead criterion; Mercury compounds [except (organo) alkyls] (as Hg) — exposure limits, IDLH, chemical and physical properties, incompatibilities and reactivities, exposure routes, symptoms, target organs, personal protection and first aid; Mercury compounds [except (organo) alkyls] (as Hg) — exposure limits, IDLH, incompatibilities and reactivities, exposure routes, symptoms, target organs, personal protection; Page 224, Nickel metal and other compounds (as Ni) — the recommended exposure limit of Ca TWA 0.015 mg/m3, the permissible exposure limit of 1 mg/m3, the note that neither applies to nickel carbonyl, the IDLH of Ca 10 mg/m3 as Ni, the symptom list beginning "Sens derm, allergic asthma, pneu" and the target-organ list "Nasal cavities, lungs, skin [lung and nasal cancer]"; Appendix G, for the vacated 1989 permissible limits of 1 mg/m3 for metal and insoluble compounds and 0.1 mg/m3 for soluble compounds; Entry: Nitric acid — exposure limits, IDLH, incompatibilities and reactivities, symptoms and target organs; Entry: Oxalic acid — exposure limits, IDLH, incompatibilities and reactivities, personal protection and sanitation, symptoms and target organs; Index of chemical names and synonyms — searched for aminophenol; no entry; Index of chemical names and synonyms — searched for phenidone, 1-phenyl-3-pyrazolidone and pyrazolidone; no entry; Searched for potassium chloride; no entry; The CAS-number index, searched for 6100-05-6 and 866-84-2; no entry for either grade; Potassium cyanide (as CN) — exposure limits, IDLH, chemical and physical properties, incompatibilities and reactivities, exposure routes, symptoms, target organs, personal protection; Chromic acid and chromates — exposure limits, IDLH, incompatibilities and reactivities, exposure routes, symptoms, target organs, personal protection; Potassium hydroxide: exposure limits, chemical and physical properties, incompatibilities and reactivities, personal protection; Sodium metabisulfite (CAS 7681-57-4), cited only as the nearest published entry; Entry: Oxalic acid — incompatibilities and reactivities, silver compounds; exposure limits; The CAS-number index, searched for 7722-64-7; no entry. Entry: Manganese compounds and fume (as Mn), npgd0379 — REL TWA 1 mg/m³ and ST 3 mg/m³, OSHA PEL ceiling 5 mg/m³, IDLH 500 mg/m³ as Mn, symptoms and target organs; Searched for potassium persulfate; no entry; Searched for potassium sodium tartrate and for tartrates; no entry; Entry: Platinum (soluble salts, as Pt) — exposure limits, IDLH, personal protection and sanitation; Searched for potassium thiocyanate and for thiocyanates; no entry; Selenium — exposure limits, IDLH, chemical and physical properties, incompatibilities and reactivities, exposure routes, symptoms, target organs, personal protection; Silver (metal dust and soluble compounds, as Ag), entry npgd0557 — exposure limits, IDLH, physical description, personal protection; Silver (metal dust and soluble compounds, as Ag), entry npgd0557 — exposure limits and IDLH; Silver (metal dust and soluble compounds, as Ag), entry npgd0557 — exposure limits, IDLH, incompatibilities and reactivities, symptoms, personal protection and sanitation; Entry npgd0557, Silver (metal dust and soluble compounds, as Ag) — the recommended exposure limit, the IDLH and the symptoms; Entry npgd0557, Silver (metal dust and soluble compounds, as Ag) — recommended exposure limit, IDLH, symptoms and target organs; Entry npgd0557, Silver (metal dust and soluble compounds, as Ag) — the recommended exposure limit, the IDLH, the symptoms and the target organs; Searched for sodium acetate; no entry; Sodium bisulfite (CAS 7631-90-5); Sodium cyanide (as CN) — exposure limits and the note that they also apply to other cyanides, IDLH, chemical and physical properties, incompatibilities and reactivities, exposure routes, symptoms, target organs, personal protection and first aid; Sodium hydroxide (npgd0565): exposure limits, IDLH, incompatibilities and reactivities, personal protection; Sodium metabisulfite (CAS 7681-57-4); Selenium — the recommended and permissible exposure limits, stated to apply to selenium compounds as Se, and the IDLH; Selenium — exposure limits and the note that they apply to selenium compounds as Se; IDLH; Searched for sodium sulfate; no entry; Hydrogen sulfide — exposure limits, IDLH, physical description and the note on olfactory fatigue; Searched for sodium thiocyanate and for thiocyanates; no entry; Index of chemical names and synonyms — searched for sodium thiosulfate, no entry; Entry: Sulfuric acid (npgd0577) — exposure limits, IDLH, incompatibilities and reactivities, symptoms and target organs; Index of chemical names and synonyms — searched for tannic acid and tannin; no entry; Index of chemical names and synonyms — searched for tetraazaindene and triazolopyrimidine; no entry; Page 305, Thallium (soluble compounds, as Tl) — recommended exposure limit and permissible exposure limit of 0.1 mg/m3 with the skin notation, IDLH 15 mg/m3 as Tl, the personal protection and sanitation column, the symptom list and the target-organ list ending in "body hair"; Index of chemical names and synonyms — searched for thiourea; only 1-naphthyl thiourea and ethylene thiourea have entries; Index of chemical names and synonyms — no entry for thymol; it appears only in the incompatibilities note of another substance, as a 0.01 per cent stabiliser against decomposition by light; Titanium dioxide (npgd0617) — the REL of Ca, the IDLH, physical properties, personal protection and sanitation, and Appendix A; Uranium (soluble compounds, as U) — exposure limits, IDLH, incompatibilities and reactivities, exposure routes, symptoms, target organs, personal protection; Borates, tetra, sodium salts (Decahydrate), for the 6 per cent solubility, the molecular weights of the hydrates and the incompatibilities; Potassium cyanide (as CN) — exposure limits, IDLH, incompatibilities and reactivities, exposure routes, symptoms, target organs, personal protection and first aid; Mercury (elemental); Iodine; Nitric acid — exposure routes, target organs and first aid; Entry for acetic acid (npgd0002) — specific gravity 1.05, and the note that the pure compound is a solid below 62 °F (16.7 °C), which is where the freezing point and the molarity arithmetic on this page come from; Mercury compounds [except (organo) alkyls] (as Hg) — the note that "other" mercury compounds include all inorganic and aryl compounds except the organo-alkyls, the recommended exposure limits for mercury vapour and for other mercury compounds, the IDLH, the exposure routes and the target organs; Uranium (soluble compounds, as U), as cited by the course's Level D policy; Hydrogen sulfide — the IDLH of 100 ppm, the recommended ceiling of 10 ppm over ten minutes, and the note that the sense of smell becomes rapidly fatigued and cannot be relied upon to warn of the continuous presence of hydrogen sulfide; Appendix C, Supplementary exposure limits — "Lead", for the definition covering metallic lead, lead oxides and lead salts, the recommended exposure limit of 0.050 mg/m3 as an 8-hour time-weighted average, and the requirement that air concentrations be maintained so that worker blood lead remains below 0.060 mg per 100 g of whole blood; Entry: Oxalic acid — incompatibilities and reactivities, silver compounds; entry: Silver (metal dust and soluble compounds, as Ag) — incompatibilities; Entry, Hydrogen chloride — the ceiling limit of 5 ppm, the IDLH of 50 ppm, and the incompatibilities and reactivities naming copper, brass and zinc; Catechol: exposure limits, the skin notation, personal protection and sanitation; Uranium (soluble compounds, as U): exposure limits, incompatibilities and personal protection, as cited by the course's Level D policy and its uranyl nitrate page; Sodium hydroxide; Hydroquinone; Acetic acid; Silver (metal dust and soluble compounds, as Ag) — incompatibilities and reactivities; Introduction: personal protection and sanitation codes; Hydroquinone; Sodium hydroxide; Acetic acid; Silver (metal dust and soluble compounds, as Ag); Silver (metal dust and soluble compounds, as Ag): exposure limits, IDLH, personal protection and sanitation, incompatibilities and reactivities, exposure routes and symptoms; Hydrogen sulfide — the physical description, the rotten-egg odour, and the note that the sense of smell is rapidly lost at higher concentrations; silver, metal dust and soluble compounds as silver, and its incompatibilities; Hydrogen sulfide, CAS 7783-06-4 - IDLH 100 ppm, NIOSH recommended exposure limit a ceiling of 10 ppm or 15 mg/m3 over 10 minutes, and the note that the sense of smell becomes rapidly fatigued and can NOT be relied upon to warn of the continuous presence of hydrogen sulfide; Selenium - the recommended exposure limit of 0.2 mg/m3 as an eight-hour average with the note that the REL also applies to other selenium compounds as Se except selenium hexafluoride, the OSHA permissible limit of 0.2 mg/m3, the IDLH of 1 mg/m3 as Se, the incompatibilities and the symptom list including garlic breath; Hydrogen sulfide, CAS 7783-06-4 - IDLH 100 ppm, NIOSH recommended exposure limit a ceiling of 10 ppm or 15 mg/m3 over 10 minutes, physical description a colourless gas with a strong odour of rotten eggs, with the note that the sense of smell becomes rapidly fatigued and can NOT be relied upon to warn of the continuous presence of hydrogen sulfide, and the symptom list of irritation of eyes, nose and throat, nausea, vomiting and diarrhoea, metallic taste, garlic breath, dizziness and lassitude; Potassium cyanide (as CN), CAS 151-50-8 - NIOSH REL ceiling 5 mg/m3 (4.7 ppm) over 10 minutes, IDLH 25 mg/m3 as CN, described as a noncombustible solid but contact with acids releases highly flammable hydrogen cyanide, incompatible with strong oxidisers such as acids, acid salts, chlorates and nitrates, exposure routes inhalation, skin absorption, ingestion and skin or eye contact. Mercury compounds [except (organo) alkyls] (as Hg) - NIOSH REL for mercury vapour TWA 0.05 mg/m3 with the skin notation and a ceiling of 0.1 mg/m3 for other mercury compounds also with the skin notation, IDLH 10 mg/m3 as Hg, the note that other mercury compounds include all inorganic and aryl mercury compounds except the organo alkyls, symptoms including tremor, insomnia, irritability, indecision, headache and lassitude, and target organs eyes, skin, respiratory system, central nervous system and kidneys. Chromic acid and chromates - NIOSH REL as Cr, carcinogen, TWA 0.001 mg/m3, OSHA PEL as CrO3 0.005 mg/m3, IDLH carcinogen at 15 mg/m3 as Cr(VI), incompatible with combustible, organic or other readily oxidisable materials named as paper, wood, sulfur, aluminium and plastics, symptoms including nasal septum perforation, liver and kidney damage, eye injury and sensitisation dermatitis, and target organs including the lung as a cancer site; Uranium, soluble compounds (as U), for the Ca marking, the 0.05 mg/m3 recommended limit, the renal symptom picture and the note attributing the cancer potential to alpha-emitting properties and decay products such as radon; mercury compounds except organo alkyls (as Hg), for the ceiling of 0.1 mg/m3 with the skin notation and the target organs; Mercury compounds [except (organo) alkyls] (as Hg) — REL for mercury vapour 0.05 mg/m3 with the skin notation, ceiling 0.1 mg/m3 for other mercury compounds, IDLH 10 mg/m3 as Hg, the symptom list beginning with tremor, insomnia, irritability, indecision, headache and lassitude, and target organs eyes, skin, respiratory system, central nervous system and kidneys. Potassium cyanide (as CN) — ceiling 5 mg/m3 over ten minutes, IDLH 25 mg/m3, the four exposure routes including skin absorption, and the note that contact with acids releases highly flammable hydrogen cyanide. Ethyl ether — flash point, vapour pressure, the explosive range and the note that it tends to form explosive peroxides under the influence of air and light. Chromic acid and chromates — REL 0.001 mg/m3 as Cr, marked carcinogen, with incompatibles named as paper, wood, sulfur, aluminium and plastics; Mercury compounds [except (organo) alkyls] (as Hg) - REL ceiling 0.1 mg/m3 with the skin notation, IDLH 10 mg/m3 as Hg, symptoms including tremor, insomnia, irritability, indecision, headache and lassitude, and target organs eyes, skin, respiratory system, central nervous system and kidneys. Potassium cyanide (as CN) - REL ceiling 5 mg/m3 (4.7 ppm) over 10 minutes, IDLH 25 mg/m3 as CN, noncombustible as a solid but contact with acids releases highly flammable hydrogen cyanide, incompatible with acids, acid salts, chlorates and nitrates, and four exposure routes including skin absorption. Chromic acid and chromates - REL as Cr, carcinogen, TWA 0.001 mg/m3, with sensitisation dermatitis among the symptoms and the lung among the cancer sites. Hydrogen chloride - a ceiling of 5 ppm. Silver, metal dust and soluble compounds (as Ag) - 0.01 mg/m3 and an IDLH of 10 mg/m3; Potassium cyanide (as CN), CAS 151-50-8 — the recommended exposure limit given as a ceiling of 5 mg/m3 (4.7 ppm) over ten minutes rather than as an eight-hour average, the immediately dangerous to life or health value of 25 mg/m3 as CN, the four exposure routes of inhalation, skin absorption, ingestion and skin or eye contact, the classification as a noncombustible solid with the note that contact with acids releases highly flammable hydrogen cyanide, the incompatibilities named as strong oxidisers such as acids, acid salts, chlorates and nitrates, the note that the solid absorbs moisture from the air forming a syrup, the faint almond-like odour, and the target organs listed as eyes, skin, respiratory system, cardiovascular system, central nervous system, thyroid and blood; Mercury compounds [except (organo) alkyls] (as Hg), which is the entry that covers elemental mercury vapour and inorganic compounds rather than the separate organo-alkyl entry: the recommended exposure limit for mercury vapour of 0.05 mg/m3 with the skin notation, the ceiling of 0.1 mg/m3 for other mercury compounds, the immediately-dangerous-to-life-or-health level of 10 mg/m3 as Hg, the specific gravity of 13.6, the vapour pressure of 0.0012 mmHg, the four exposure routes, the symptom list beginning with tremor, insomnia, irritability, indecision, headache and lassitude, and the target organs eyes, skin, respiratory system, central nervous system and kidneys; Uranium (soluble compounds, as U) — NIOSH recommended limit marked Ca with a TWA of 0.05 mg/m3, an immediately dangerous level given as Ca[10 mg/m3 (as U)], exposure routes inhalation, ingestion and contact, a symptom list of lacrimation and conjunctivitis, shortness of breath, cough and chest rales, nausea and vomiting, skin burns, red blood cells and casts in the urine, proteinuria and high blood urea nitrogen, the note that the potential for cancer is a result of alpha-emitting properties and radioactive decay products such as radon, and an incompatibility line for uranyl nitrate reading, in full, combustibles. Mercury compounds [except (organo) alkyls] (as Hg) — NIOSH recommended limit for mercury vapour TWA 0.05 mg/m3 with the skin notation and a ceiling of 0.1 mg/m3 with the skin notation for other mercury compounds, immediately dangerous level 10 mg/m3 as Hg, the note that other mercury compounds include all inorganic and aryl mercury compounds except the organo alkyls, symptoms including tremor, insomnia, irritability, indecision, headache and lassitude, and target organs eyes, skin, respiratory system, central nervous system and kidneys; Ethyl ether: the bracketed note that it is a gas above 94 F, the specific gravity of 0.71, the vapour pressure of 440 mmHg, the flash point of -49 F, the explosive range of 1.9 to 36.0 per cent in air, the Class IA flammable classification, the absence of a recommended exposure limit with the referral to Appendix D, the OSHA permissible limit of 400 ppm, the incompatibilities with strong oxidisers, halogens and sulfur compounds, and the note that the substance tends to form explosive peroxides under the influence of air and light. Cadmium: the statement that the NIOSH and OSHA limits apply to all cadmium compounds measured as cadmium, the OSHA limit of 0.005 mg/m3, the carcinogen marking and the immediately-dangerous-to-life level of 9 mg/m3; Incompatibilities and reactivities for sodium hydroxide; hydroquinone; acetic acid; silver (metal dust and soluble compounds, as Ag); potassium cyanide; chromates; oxalic acid; formaldehyde; hydrochloric acid; Uranium (soluble compounds, as U); mercury compounds; potassium cyanide; Sodium hydroxide: incompatibilities and reactivities, including water, acids and metals such as aluminium, tin and zinc; Introduction, personal protection and sanitation codes, and the basis on which an eyewash recommendation is attached to a substance; Silver (metal dust and soluble compounds, as Ag): exposure limits, personal protection and sanitation, incompatibilities and reactivities; Silver, metal dust and soluble compounds as Ag: personal protection and sanitation, incompatibilities and reactivities; Silver, metal dust and soluble compounds as Ag, and sodium hydroxide: incompatibilities and reactivities; Hydrogen sulfide: ceiling 10 ppm, IDLH 100 ppm, and the note that the sense of smell becomes rapidly fatigued and cannot be relied upon to warn of the gas

Used by:Acetic acid (glacial) · Amidol · Ammonium bromide · Ammonium chloride · Ammonium citrate (dibasic) · Ammonium citrate (tribasic) · Ammonium dichromate · Ammonia solution (ammonium hydroxide) · Ammonium iron(III) citrate · Ammonium iron(III) oxalate · Ammonium persulfate · Ammonium thiocyanate · Barium sulfate · Borax (sodium tetraborate decahydrate) · Bromine · Cadmium bromide · Catechol · Chlorine · Chlorohydroquinone · Diethyl ether · Dimezone S · Erythrosin · Ethanol · Ferric oxalate · Formaldehyde · Gallic acid · Glutaraldehyde · Glycerol · Glyoxal · Hydrochloric acid · Hydroquinone · Iodine · Iron(II) sulfate, anhydrous · Iron(II) sulfate heptahydrate · Iron(III) chloride, anhydrous · Iron(III) chloride hexahydrate · Iron(III) nitrate nonahydrate · Isopropyl alcohol · Kaolin · Lead(II) nitrate · Mercury · Mercury(II) chloride · Nickel(II) sulfate · Nitric acid · Oxalic acid · p-Aminophenol · Phenidone · Potassium chloride · Potassium citrate · Potassium cyanide · Potassium dichromate · Potassium hydroxide (caustic potash) · Potassium metabisulfite · Potassium oxalate, anhydrous · Potassium oxalate monohydrate · Potassium permanganate · Potassium persulfate · Potassium sodium tartrate tetrahydrate · Potassium tetrachloroplatinate(II) · Potassium thiocyanate · Selenium · Silver · Silver bromide · Silver chloride · Silver iodide · Silver nitrate · Silver(I) oxalate · Silver(I) oxide · Silver sulfamate · Sodium acetate (anhydrous) · Sodium bisulfite · Sodium cyanide · Sodium hydroxide (caustic soda) · Sodium metabisulfite · Sodium selenate · Sodium selenite · Sodium sulfate · Sodium sulfide · Sodium thiocyanate · Sodium thiosulfate (anhydrous) · Sulfuric acid · Tannic acid · Tetraazaindene · Thallium(I) sulfate · Thiourea · Thymol · Titanium dioxide · Uranyl nitrate hexahydrate · Ammonium citrate developer · Borax kallitype developer · Cyanide fixing and toning · Daguerre's 1839 process outline · Talbot's gallo-nitrate of silver · Herschel's hydrargyro-cyanotype · Kallitype sensitiser · Kodak IN-21 · Kodak ST-1 · Lead additions to platinum sensitisers · Nicol's kallitype · EDTA, citric acid and hydrochloric acid clearing sequence · Pyrocat-HD · Rochelle salt kallitype developer · Uranium toner · Willis's potassium oxalate developer · P2 Storage, Incompatibilities and Secondary Containment · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P2 Silver Nitrate: The Reagent That Sets the Rules · P12 Lab: Testing for Residual Thiosulfate and Residual Silver · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P20 The Toners We Study and Do Not Use · P25 The Additives We Study and Do Not Reproduce · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Assignment: Assessing a Historical Process for Hazard · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory · P26 Uranium, Mercury and the Heavy-Metal Treatments · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · Chemical incompatibilities · The Level D policy · Responding to an alkali spill · Checking and using the eyewash · Handling silver nitrate · Responding to a silver nitrate spill · Storage rotation and shelf separation · Handling a sulphide toner and its waste

chem.echa.europa.eu

ECHA CHEM record: selenium compounds with the exception of cadmium sulphoselenide and those specified elsewhere in this Annex, CLP Annex VI index 034-002-00-8retrieved 2026-09-06

Sections: Record 100.240.771 — the group name in English, the index number 034-002-00-8, the empty EC and CAS fields, the rmlType of SUBSTANCE and GROUP, and the appearance of Harmonised C&L in the list of regulatory processes. Cited for the existence and scope of the group entry, not for its content

Used by:Sodium selenate

ECHA CHEM substance record: Ammonium hydrogensulphite, EC 233-469-7, CAS 10192-30-0retrieved 2026-09-06

Sections: Substance record 100.030.414 — EC name and number, CAS number, molecular formulae, empty index number, tonnage band and submitted names. Cited only to establish that the mono-ammonium salt is a separate substance with its own identity

Used by:Ammonium sulfite

ECHA CHEM substance record: Ammonium sulphite, EC 233-484-9, CAS 10196-04-0retrieved 2026-09-06

Sections: Substance record 100.030.428 — EC name and number, CAS number, IUPAC name, molecular formula and SMILES; the empty index number; the list of regulatory processes; the tonnage band; the submitted name lists. Cited chiefly for a negative finding

Used by:Ammonium sulfite

ECHA CHEM substance record: Calcium nitrate tetrahydrate, EC 603-865-8, CAS 13477-34-4retrieved 2026-09-07

Sections: Substance record 100.117.517 — the EC name and list number, the CAS number, the molecular formulae filed, the empty index number and the three regulatory processes

Used by:Calcium nitrate tetrahydrate

ECHA CHEM substance record: Calcium nitrate, EC 233-332-1, CAS 10124-37-5retrieved 2026-09-07

Sections: Substance record 100.030.289 — the EC name and EINECS number, the CAS numbers filed against it including the tetrahydrate's, the empty index number, the REACH registration and tonnage band, the three Inland Transport of Dangerous Goods Directive annexes and the trade names

Used by:Calcium nitrate tetrahydrate

ECHA CHEM substance record: diammonium hydrate sulfite, EC 684-263-2, CAS 7783-11-1retrieved 2026-09-06

Sections: Substance record 100.209.730 — EC name and number, CAS number, molecular formula, empty index number, the two regulatory processes, and the submitted IUPAC names. Cited only to establish that ECHA holds the monohydrate as a substance separate from the anhydrous salt

Used by:Ammonium sulfite

ECHA CHEM substance record: Disilver oxalate, EC 208-568-3, CAS 533-51-7retrieved 2026-09-07

Sections: Substance record 100.007.791 — EC name and number, CAS number, molecular formula, IUPAC and Chemical Abstracts names, the empty index number and the list of regulatory processes

Used by:Silver(I) oxalate

ECHA CHEM substance record: Disilver oxide, EC 243-957-1, CAS 20667-12-3retrieved 2026-09-06, 2026-09-07

Sections: Substance record 100.039.946 — index number, regulatory processes, list participation, tonnage band, EC and CAS numbers, molecular formula and IUPAC names; Substance record 100.039.946 — identity and regulatory status of the oxide this salt is made from

Used by:Silver(I) oxide · Silver sulfamate

ECHA CHEM substance record: Dithallium sulphate, EC 231-201-3, CAS 7446-18-6retrieved 2026-09-06

Sections: Substance record 100.028.365 — index number 081-003-00-4, the regulatory-process list including Harmonised C&L, PIC and PIC Annex I, EC and CAS numbers, molecular formula, the IUPAC and process-related name lists including the Annex VI form "dithallium sulphate; thallic sulphate", and the empty tonnage-band and list-participation fields

Used by:Thallium(I) sulfate

ECHA CHEM substance record: Glycerol, EC 200-289-5, CAS 56-81-5retrieved 2026-09-06

Sections: The substance record 100.000.263 read through the public substance API - EC name and number, CAS number, IUPAC name, molecular formula, the empty index number, the list of regulatory processes and the tonnage band. Cited for a negative finding

Used by:Glycerol

ECHA CHEM substance record: Iron(III) nitrate nonahydrate, EC 616-509-1, CAS 7782-61-8retrieved 2026-09-05

Sections: Substance record 100.129.634 — index number, regulatory processes, EC and CAS numbers, molecular formulae and IUPAC names

Used by:Iron(III) nitrate nonahydrate

ECHA CHEM substance record: Kaolin, EC 310-194-1, CAS 1332-58-7retrieved 2026-09-07

Sections: Substance record 100.100.108 — the EC name and number, the principal CAS number and the sixteen others filed against the same substance, the regulator's own description of kaolin as a clay that is essentially kaolinite, the empty index number, and the list of regulatory processes

Used by:Kaolin

ECHA CHEM substance record: Lead acetate, EC 239-379-4, CAS 15347-57-6retrieved 2026-09-06

Sections: Substance record 100.035.784 — name, EC and CAS numbers, the empty index number, the four regulatory processes and the indefinite molecular formula C2H4O2.xPb

Used by:Lead(II) acetate

ECHA CHEM substance record: Lead di(acetate), EC 206-104-4, CAS 301-04-2retrieved 2026-09-06

Sections: Substance record 100.005.551 — index number 082-005-00-8, regulatory processes including Harmonised C&L and Candidate list, tonnage band, EC and CAS numbers, molecular formulae and the submitted IUPAC name list

Used by:Lead(II) acetate

ECHA CHEM substance record: Nickel sulphate, EC 232-104-9, CAS 7786-81-4retrieved 2026-09-06

Sections: Substance record 100.029.186 — index number 028-009-00-5, the regulatory-process list including Harmonised C&L, the Carcinogens and Mutagens at Work Directive and the Cosmetic Products Regulation prohibition, the EC and CAS numbers with the hexahydrate and heptahydrate filed against the same record, the molecular formula, the submitted IUPAC name list and the tonnage band

Used by:Nickel(II) sulfate

ECHA CHEM substance record: SILVER OXIDE (PREDOM. SILVER(II) OXIDE), EC 628-958-0, CAS 11113-88-5retrieved 2026-09-06

Sections: Substance record 100.157.183 — name, EC and CAS numbers, empty index number and single regulatory process

Used by:Silver(I) oxide

ECHA CHEM substance record: Sodium selenate, EC 236-501-8, CAS 13410-01-0retrieved 2026-09-06

Sections: Substance record 100.033.169 — EC name and number, CAS number, IUPAC name, molecular formula and SMILES; the empty index number; the list of regulatory processes; the tonnage band; the submitted name lists. Cited chiefly for a negative finding

Used by:Sodium selenate

ECHA CHEM substance record: Triammonium citrate, EC 222-394-5, CAS 3458-72-8retrieved 2026-09-05

Sections: The substance record 100.020.359 read through the public substance API - EC name, EC and CAS numbers, IUPAC name, molecular formula, alternate and obsolete CAS numbers, the empty index number, the list of regulatory processes and the tonnage band, and the names submitted against the record. The same public search, run on CAS 3012-65-5, returns the separate record 100.019.225, Diammonium hydrogen 2-hydroxypropane-1,2,3-tricarboxylate, EC 221-146-3, which is the evidence that the two salts are two substances in the registry and not two names for one

Used by:Ammonium citrate (tribasic)

chem.libretexts.org

6.17B: Frenkel Defect, in Map: Inorganic Chemistry (Housecroft)retrieved 2026-09-04

Sections: 6.17B: the interstitial cation and the vacancy it leaves; 6.17B: the definition of the Frenkel defect, the conditions under which it occurs, and its intrinsic character

Used by:P4 The Latent Image · P4 The Silver Halides

Analytical Chemistry 2.1, section 11.2: Potentiometric Methodsretrieved 2026-09-04, 2026-09-06

Sections: Potentiometric methods — the glass electrode, E = K + 0.05916 log a(H+) valid over about pH 0.5 to 9, two-point standardisation, the alkaline error worked at pH 12.7, and Table 11.2.6 of NIST primary standard buffer values against temperature; Table 11.2.6, NIST primary standard buffers: 0.01 molal sodium tetraborate at 9.180 at 25 degrees C, with its values at other temperatures; The glass pH electrode: construction of a combination electrode, the 50 micrometre membrane, E = K + 0.05916 log a(H+) valid over about pH 0.5 to 9, the alkaline error worked at pH 12.7, two-point standardisation, automatic temperature compensation as a slope adjustment, storage in the manufacturer buffer, junction potentials, and Table 11.2.6 of NIST primary standard buffer values against temperature; The glass pH electrode — the response equation, the constant K and its day-to-day variability, two-point standardisation, alkaline error, and the NIST primary standard buffer values against temperature; The glass pH electrode - the cell potential relation valid over roughly pH 0.5 to 9, above which the membrane also responds to sodium and potassium ions, with a worked alkaline error of minus 0.5 pH units at a true pH of 12.7 in 0.05 molal sodium; The glass pH electrode: the constant K and why it changes from day to day; two-point standardisation; storage in the manufacturer buffer; The glass pH electrode - construction of a combination electrode and the statement that the average lifetime of a typical glass electrode is several years

Used by:P29 Capstone Stage 2: Formulating and Documenting Your Chemistry · P3 Buffers and Buffer Capacity · P3 Lab: Measuring pH and Trusting the Number · P8 Alkalis, Buffers and pH · P27 Designing an Experiment That Yields a Number · Calibrating a pH meter · pH meter reading a constant value

Chapter 17.3: The Formation of Complex Ions, in General Chemistry: An Atoms First Approachretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: The formation of complex ions: the photographic example — Ksp of AgBr, the thiosulfate complex and the overall constant; 17.3 The formation of complex ions — silver bromide dissolved by thiosulfate; The formation of complex ions, the photographic example — the formation constant of 2.9 × 10¹³ for the two-coordinate thiosulfate complex of silver, and the sum of the two equilibria giving an overall constant of 15 for the dissolution of silver bromide in thiosulfate; The formation of complex ions, the photographic example — silver bromide's solubility product of 5.35 × 10⁻¹³ at 25 degrees C, the formation constant of 2.9 × 10¹³ for the two-coordinate thiosulfate complex, and the sum of the two equilibria giving an overall constant of 15 for the dissolution of silver bromide in thiosulfate; 17.3 The formation of complex ions: silver bromide dissolved by thiosulfate; 17.3 The Formation of Complex Ions: stepwise formation constants and the rule that the overall constant is their product, so that log Kf is the sum of the stepwise log K values; 17.3 Formation of Complex Ions: silver bromide solubility product and dissolved ion concentration; the tens of thousands of litres of pure water needed to fix one roll of film; The Effect of the Formation of Complex Ions on Solubility — the statement that removing unreacted silver bromide from a single roll of film with pure water would require tens of thousands of litres, and the worked addition of the dissolution and formation equilibria giving a combined constant of 15 on that compilation's values

Used by:Silver bromide · Sodium thiosulfate (anhydrous) · Daguerre's 1839 process outline · Iodide hypo check · P2 Waste: Streams, Silver, and the Drain You Must Not Use · P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve · P3 Solutions, Solubility and Precipitation · P11 How Fixer Works

General Chemistry (Petrucci et al.), section 18.8: Equilibria Involving Complex Ionsretrieved 2026-09-04

Sections: 18.8 Equilibria Involving Complex Ions: the formation-constant table attributed to Lange's Handbook of Chemistry 15th edition, giving 2.9 x 10^13 for the bis(thiosulfato)argentate ion, 1.1 x 10^7 for the diammine silver ion and 2.0 x 10^20 for the trisoxalato iron(III) ion; the worked photographic example with Ksp 5.35 x 10^-13 and a net constant of 15, and the statement that removing unreacted silver bromide with pure water would take tens of thousands of litres

Used by:P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve

Kinetics, supplemental module 9: Diffusionretrieved 2026-09-04, 2026-09-06

Sections: Fick's First Law of Diffusion: J = -D dc/dx with J the flux in mol per square metre per second; the Einstein-Smoluchowski relation D = lambda squared over 2 tau; the statement that ions at room temperature usually have a diffusion coefficient of 0.6 to 2 x 10^-9 m^2/s; that D is greater at higher temperature; and the Stokes-Einstein relation D = kT / 6 pi eta a, giving the dependence on viscosity and on molecular radius; Fick's first law stated as J equals minus D times the concentration gradient, with J the flux in mol per square metre per second; and the statement that ions at room temperature usually have a diffusion coefficient between 0.6 and 2 times 10^-9 square metres per second; Fick's First Law of Diffusion, and the diffusion coefficient's dependence on temperature and viscosity; Fick's First Law of Diffusion and the dependence of flux on the concentration gradient

Used by:P3 Diffusion, Swelling and the Journey Into the Emulsion · P27 Experiment: Agitation, Stand and Semi-Stand Development · Mottled development · Surge marks

chemicalsafety.ilo.org

International Chemical Safety Card 0063: Nickel(II) sulphateretrieved 2026-09-06

Sections: Card 0063 of April 2017 in full — physical and chemical information, chemical dangers, prevention by route of exposure, inhalation risk, effects of short-term and of long-term exposure, the occupational limits, storage, packaging, spillage disposal, environment, and all seven Notes including the read-across to the hexahydrate and heptahydrate and the instruction to anyone who has been sensitised; Card 0063 — the inhalation control "Use closed system or ventilation (not if powder)", the instruction to prevent dispersion of dust and avoid all contact, the delayed onset of asthma symptoms, the instruction to a sensitised person to avoid all further contact with nickel and with copper, chromium and cobalt compounds, the efflorescence and variable water content of the hydrates, and the storage and packaging requirements

Used by:Nickel(II) sulfate · Lead, thallium and nickel cyanotype toners

International Chemical Safety Card 0336: Thallium sulfateretrieved 2026-09-06

Sections: Card 0336 of April 2013 in full — physical and chemical information, chemical dangers, inhalation risk, effects of short-term and of long-term exposure, routes of exposure, the occupational limit, storage, packaging, spillage disposal, environment and the Notes; Card 0336 — routes of exposure including absorption through the skin, the personal protection column specifying a particulate filter respirator matched to the airborne concentration together with complete protective clothing, the instruction to prevent dispersion of dust and observe strict hygiene, the delayed effects, storage separated from food and feedstuffs and in an area without drain or sewer access, and the environmental note

Used by:Thallium(I) sulfate · Lead, thallium and nickel cyanotype toners

collections.vam.ac.uk

The Onion Field, Mersea Island, Essex - George Davison, 1890 (Royal Photographic Society Collection)retrieved 2026-09-04

Sections: Collection record RPS.2369-2017: title, artist, date photographed, place and materials and techniques

Used by:P7 Seeing Like a Pinhole: The Image, Its Makers and Previsualisation

conservation-wiki.com

Albumen, in the Photographic Materials Group section of the AIC Conservation Wikiretrieved 2026-09-04, 2026-09-05, 2026-09-07

Sections: Historical facts; Identification — image layer as photolytic silver on an albumen binder; Process overview — sizing, salting, sensitising with silver nitrate, printing out, toning, fixing and washing; Deterioration — the Fading Committee of 1855 and its findings, and the three proposed causes of highlight yellowing; Conservation and Treatment — the Fading Committee of 1855 and the causes it reported, the colloidal rather than filamentary character of a printed-out silver image and its vulnerability to oxidation and chemical attack, and the four proposed causes of yellow staining in highlight areas, among them the chemical bonding of image silver to sulfur-containing side groups of the albumen protein to form silver sulfide and the Maillard reaction between glucose in the albumen and the amino groups of the egg protein, whose yellowing is accelerated by high humidity and alkaline conditions; Conservation and Treatment — the colloidal rather than filamentary character of a printed-out silver image and its vulnerability to oxidation and chemical attack, and the proposed causes of yellow highlight staining, among them the chemical bonding of image silver to sulfur-containing side groups of the albumen protein to form silver sulfide; Historical facts; Process overview; Conservation and treatment — the Fading Committee of 1855, the colloidal silver particle size of 5 to 25 micrometres, the four proposed causes of highlight yellowing and the account of binder cracking; Housing and storage; Identification characteristics — image layer given as photolytic silver on an albumen binder; Conservation and treatment — the colloidal silver particle size of 5 to 25 micrometres and its consequence for surface area, and the four proposed causes of highlight staining, including the chemical bonding of silver to sulfur-containing side groups of the albumen protein and the Maillard protein-sugar reaction; Conservation and treatment — the Fading Committee of 1855 and the causes it reported, and the colloidal silver particle size of 5 to 25 micrometres; Process overview — the sequence of rinsing, toning, fixing and washing; Identification characteristics — photolytic silver on an albumen binder, lightweight rag support, monochrome ranging from neutral to warm depending on process and toning; Conservation and treatment — the Fading Committee of 1855 and the causes it reported, the colloidal silver particle size of 5 to 25 micrometres and its consequence for surface area, the four proposed causes of highlight staining (high humidity with high temperature; silver bonded to sulfur-containing side groups forming silver sulfide; the Maillard protein-sugar reaction accelerated by high humidity and alkaline conditions; and the oxidation of benzene-ring amino acids on absorbing light), the frequency of image fading, silver mirroring appearing along the edges, poor quality mounting materials, the vulnerability of a lightweight support to tears and abrasion, and the overall cracking of the binder attributed to humidity-driven differential dimensional change; Housing and Storage — good quality paper-board folders, and 68 °F (20 °C) plus or minus 2 degrees of drift with 50 per cent plus or minus 5 per cent variation over 24 hours; Emergency Recovery; Further Reading, including Vitale and Messier on cracking in albumen photographs; Process description; identification characteristics; deterioration and the Fading Committee of 1855; Process description; identification characteristics; Condition - most albumen prints are on a lightweight support particularly prone to structural damage such as tears, bends, creases, abrasion and losses; the frequent finding of overall cracking of the albumen binder, likely caused by variations in humidity that caused differential dimensional changes between the image layer and the support; Condition - the frequent finding of overall cracking of the binder, likely caused by variations in humidity that produced differential dimensional changes between the image layer and the support; Condition - the frequent finding of overall cracking of the binder, likely caused by variations in humidity producing differential dimensional changes between the image layer and the support

Used by:Albumen · Albumen solution with its chloride · Double-coated albumen procedure · P23 Part XXIII Overview: Albumen Printing · P23 Egg Albumen: A Protein Binder and What It Does to Silver · P23 Lab: Sensitising, Printing and Toning an Albumen Print · P23 The Albumen Print as an Object, and How It Decays · Albumen print · Matte albumen print · Albumen crazing and yellowing · Cracked emulsion from flattening a bone-dry fibre print · Mottled coating from uncontrolled humidity

Albumenized Salt Print, in the Photographic Materials Group section of the AIC Conservation Wikiretrieved 2026-09-07

Sections: The whole page as read on 7 September 2026, for the fact that every content section - Historical Facts, Identification Characteristics with Image material, Color and Support, Conservation, Housing and Storage, Exhibition, Emergency Recovery, References and Further Reading - is an empty heading, and that the page carries neither contributors nor a date initiated; The whole page, cited for what it does not contain — every content heading under Albumenized Salt Print is empty, and the page carries no contributors and no date initiated

Used by:P22 The Variants of the Salt Print and How a Conservator Identifies One · Arrowroot and albumenised salted paper

Ambrotype (Positive Collodion), in the Photographic Materials Group section of the AIC Conservation Wikiretrieved 2026-09-04, 2026-09-06

Sections: Process description — fixing in hypo or potassium cyanide; Process description — the developed plate rinsed and then fixed in hypo or potassium cyanide to dissolve the remaining unexposed silver salts; Process description and identification - a collodion positive on glass read against a dark backing, and the effect of removing the backing; The definition of an ambrotype as an under-exposed wet collodion negative on glass that appears positive because of a dark backing or a dark glass support; the common ambrotype backed with textile, metal, secondary glass, paper or paint and the ruby ambrotype on dark glass that reads red in transmitted light; James Ambrose Cutting's patents of 1854 and the name taken from the Greek for imperishable; the main period of use, 1850 to 1870 in North America; Identification Characteristics, for the image layer of collodion and physically developed silver, usually varnished, and for the analysis note that a varnish fluoresces in ultraviolet, that varnished plates show no image tarnish and that unvarnished plates exhibit white or red-yellow tarnish layers over the image; Process Overview, for the plate edges filed smooth, the occasional albumen subbing layer, the pour to the centre held by surface tension and a steady hand, the sensitising in a silver nitrate bath, the statement that the plate is only sensitive to blue and ultraviolet light so that blue sources and sunlight are effective, the laterally reversed result, fixing in hypo or potassium cyanide, and varnishes of shellac or copal or a home-brew of many components; Conservation and Treatment, for flaking backings addressed with a dark secondary support, for the fragility of an unvarnished collodion layer, for the warning that varnishes, paints and the collodion layer are sensitive to many organic solvents, that even water can dissolve weakened collodion, that non-polar solvents are preferred and that ethanol and acetone are not recommended, and for glass disease producing soft or cracking collodion and varnish with no easy fix; Housing and Storage, for the composite nature of a cased ambrotype and the recommendation of a non-fluctuating environment around 68 F and 45 per cent relative humidity, with freezing not recommended because condensation during thawing may be catastrophic; Process description; identification characteristics; the black backing and its loss; fixing in hypo or potassium cyanide; Process description and identification characteristics for the collodion positives, including the lacquered iron support

Used by:Potassium cyanide · Cyanide fixing and toning · P26 Assignment: Assessing a Historical Process for Hazard · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · Ambrotype · Tintype (ferrotype)

Collodion Negative, in the Photographic Materials Group section of the AIC Conservation Wikiretrieved 2026-09-04, 2026-09-06

Sections: Varnishing — the aqueous pre-coat of gum arabic, dextrin, albumen or gelatin applied to protect the collodion binder from the alcohol in the varnish; Process description — collodion as pyroxylin dissolved in alcohol and ether; the disadvantages of the wet plate, in which the collodion becomes impervious to the processing solution once the alcohol and ether have dried, and the weight of equipment and materials a photographer had to transport to work away from a studio; Process description — collodion as pyroxylin dissolved in alcohol and ether, and pyroxylin as cellulose from cotton or wood treated with nitric and sulfuric acids; the debated invention of the wet collodion process; the disadvantages of the wet plate, in which the collodion becomes impervious to the processing solution once the alcohol and ether have dried, and the weight of equipment and materials needed to work away from a studio; Historical Facts, for the disputed attribution between Gustave Le Gray and Frederick Scott Archer, for the ten-minute window before the collodion becomes impervious to the processing solution once the alcohol and ether have dried, for the roughly 250 kilograms of equipment and materials needed to make a negative away from a studio, and for the replacement of the process in the 1880s by the gelatin silver process, described as equally sensitive but with long lasting, portable plates. Dry Plate Method, for the hygroscopic materials and preservatives - sugar, tannin, glycerin, dextrin - and Taupenot's albumen sealing of 1856 which kept plates sensitised for weeks, with the note that these early experiments often reduced sensitivity and that development sometimes took up to twelve hours. Identification Characteristics, for pyroxylin made by treating cellulose from cotton or wood with nitric and sulfuric acids, for varnishes of natural resins in solvents applied over an aqueous pre-coat of gum arabic, dextrin, albumen or gelatin so that the alcohol in the varnish does not dissolve the binder, for the range of image colours from creamy white through neutral grey to olive green and dark brown, for the ease of confusing a collodion negative with a gelatin one, for soda lime silicate glass of 3.175 to 6.35 mm hand-cut with rough edges and slightly irregular shapes, and for the photographer's fingerprints in one corner and the absence of binder at the four corners where the plate touched the holder. Contemporary Practice, for the list of present-day practitioners the wiki names. Conservation and Housing, for the condition list including silver mirroring, weeping glass, crystalline deposits and moist droplets, and for individual envelopes in custom boxes stored vertically in a cool dry place; Collodion as nitrocellulose dissolved in alcohol and ether; the imperviousness of the dried film; Collodion as pyroxylin dissolved in alcohol and ether; the imperviousness of the dried film; the weight of equipment needed to make a negative away from the studio; the Le Gray and Archer attributions

Used by:Albumen · Diethyl ether · Gum arabic · Nitrocellulose · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · Collodion print-out paper · Wet-plate collodion negative

Daguerreotype, in the Photographic Materials Group section of the AIC Conservation Wikiretrieved 2026-09-04, 2026-09-06

Sections: Process description — the note that the Becquerel process needs no bromine or chlorine sensitising and is about ten times slower in consequence; Plate coating materials — isinglass, gum arabic, albumen, gelatine, shellac, waxes and dextrose among others; Process description — sensitising the polished silvered plate with the vapour of elemental iodine in a sealed fuming box, and the note that the plate slides in so the photographer is not exposed; Image layer — silver and mercury amalgam, image particle size, gilding; Process description — mercury vapour development, the fuming box and the Becquerel alternative; Process description — mercury vapour development and the Becquerel alternative; Process description: iodine fuming of the silvered plate, and the plate's sensitivity to blue and ultraviolet light; Identification and process description: the copper plate electroplated with pure silver and polished on a series of grinding wheels; sensitisation by the vapour of elemental iodine in a fuming box, creating silver iodide on the surface; sensitivity confined to blue and ultraviolet; highlights of silver and mercury amalgam against dark areas of metallic silver; image particles of 0.1 to 50 micrometres; gold toning with gold chloride introduced in 1841; the image usually laterally reversed; a single-exposure direct positive; and the statement that ungilded plates are very prone to abrasion and the image can easily be wiped off; Identification and process description, for the image layer of silver and mercury amalgam highlights against dark areas of metallic silver, for image particles of 0.1 to 50 micrometres, for the plate often gold toned with gold chloride in a process that changes the composition of the image layer and was introduced in 1841, and for the statement that ungilded plates are very prone to abrasion and the image can easily be wiped off; Historical facts; identification characteristics; process overview; Historical facts and process overview — the Becquerel process of 1840, in which the exposed plate is brought out by red light rather than by mercury vapour, needing no mercury and no bromine or chlorine sensitising, at the cost of plates around ten times slower, which makes portraiture difficult; Identification characteristics, including the mirror-like specular surface, the cased package of plate, mat, cover glass and case, applied colour, and the instruction that the surface must not be touched; Identification and process description: the copper plate electroplated with pure silver; sensitisation by the vapour of elemental iodine in a fuming box, creating silver iodide on the surface; sensitivity confined to blue and ultraviolet; highlights of silver and mercury amalgam against dark areas of metallic silver; image particles of 0.1 to 50 micrometres; gold toning with gold chloride introduced in 1841; the statement that ungilded plates are very prone to abrasion and the image can easily be wiped off; the sealing of a cover glass over a spacer because the exposed surface is itself the image and tarnishes; and the Becquerel process, listed as a process variation of 1840, which needs no mercury and no bromine or chlorine sensitising and is about ten times slower; Historical facts; process variants, the Becquerel process of 1840

Used by:Bromine · Chlorine · Gum arabic · Iodine · Mercury · Mercury(II) chloride · Silver iodide · Daguerre's 1839 process outline · Fizeau's gilding solution · P1 Daguerre and the Daguerreotype: A Mirror With a Memory · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Assignment: Assessing a Historical Process for Hazard · P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory · The Becquerel variant · Daguerreotype

Gelatin Dry-plate Negative, Photographic Materials Conservation Catalogretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Condition — silver mirroring as a very common deterioration of dry-plate negatives, a bluish metallic sheen starting from the edges and visible under reflected light, against improperly washed processing chemistry which appears instead as yellow or brown stains in transmitted light; the note that areas with silver mirroring are extremely susceptible to abrasion; Identification Characteristics — that a very common deterioration of dry plate negatives is silver mirroring, a blueish metallic sheen starting from the edges and visible under reflected light, and that improperly washed processing chemicals can be present as yellow or brown stains visible in transmitted light; and that some dry plate negatives exhibit an intense yellow colour throughout their surface or locally, which is characteristic of negatives that lacked density or contrast and were therefore chemically intensified in a post-processing step with a mercuric iodide or mercuric chloride solution, the mercuric halide having usually reacted over time with the silver making up the image to form silver iodide or silver chloride, which are yellow and light sensitive. Conservation — that it is essential to note whether original retouching media are present before attempting any treatment, and that areas with silver mirroring are extremely susceptible to abrasion. Bibliography — Lavedrine and Garnier, Analysis and Restoration of Negatives Intensified with Mercuric Iodide, Topics in Photographic Preservation 3 (1989), 12-21; Condition — silver mirroring as a very common deterioration of dry-plate negatives, described as a bluish metallic sheen starting from the edges and visible under reflected light, set against improperly washed processing chemistry which appears instead as yellow or brown stains in transmitted light; and the note that areas with silver mirroring are extremely susceptible to abrasion; Condition — silver mirroring as a very common deterioration of dry-plate negatives, a bluish metallic sheen starting from the edges and visible under reflected light, against improperly washed processing chemistry which appears instead as yellow or brown stains in transmitted light; Condition - silver mirroring as a very common deterioration of dry-plate negatives, a bluish metallic sheen starting from the edges and visible under reflected light, against improperly washed processing chemistry which appears instead as yellow or brown stains in transmitted light; the note that areas with silver mirroring are extremely susceptible to abrasion

Used by:P12 Permanence and Image Deterioration · P26 Uranium, Mercury and the Heavy-Metal Treatments · P28 Fixer Faults, Washing Faults and the Stains They Leave · Dry plate and lantern slide · Silver mirroring

Photogenic Drawings, Salted Paper Prints, and Calotype Prints, in the Photographic Materials Group section of the AIC Conservation Wikiretrieved 2026-09-06, 2026-09-07

Sections: Identification Characteristics, for the image layer of silver deposited directly in the paper support and the range of image colour across photogenic drawings, salted paper prints and calotypes; and Conservation, Housing and Storage Considerations; Identification Characteristics — image layer, colour and support; and Conservation, Housing and Storage Considerations, for the stable temperature between 18 and 30 degrees C and 30 to 50 per cent relative humidity. Not cited for chronology; see the entry's own note; Identification Characteristics, for the image being silver deposited directly in the paper support and for the colour range from warm brown to cool grey; Analysis, for non-destructive XRF identifying the silver image and detecting sulfur where the print was fixed in sodium thiosulfate; Housing and Storage Considerations, for a stable temperature between 18 and 30 degrees C to avoid embrittlement and a relative humidity between 30 and 50 per cent; Identification Characteristics, for the image being silver deposited directly in the paper support; Analysis, for non-destructive XRF identifying the silver image and detecting sulfur where the print was fixed in sodium thiosulfate; Support, for later wove papers able to withstand prolonged water immersion; Historical Facts, for photogenic drawings as the name Talbot gave his earliest 1830s experiments, for the first viable paper negative process in the late 1830s and the positive salted-paper prints made from those negatives, for Blanquart-Evrard's simplified version of Talbot's formula published in France in 1847, for the calotype as an improved photogenic drawing process invented and then patented by Talbot in 1841, and for the list of historic practitioners; Identification Characteristics, for the image being formed by silver deposited directly in the paper support, for the colour range from warm brown to cool grey tones, and for the support being paper, initially stationery and later wove papers that can withstand prolonged water immersion; Analysis, for non-destructive XRF identifying the silver image and detecting sulfur where the print was fixed in sodium thiosulfate, and for destructive GC-MS identifying coating materials; Analysis, for non-destructive XRF identifying the silver image and also detecting sulfur if the image has been fixed in sodium thiosulfate; Housing and Storage Considerations, for a stable temperature between 18 and 30 degrees C to avoid embrittlement and a relative humidity between 30 and 50 per cent

Used by:Talbot's gallo-nitrate of silver · Talbot's calotype iodised paper · P22 Gold Toning and the Permanence of a Printed-Out Silver Image · P22 Lab: Printing, Toning, Fixing and Washing a Salt Print · P22 The Variants of the Salt Print and How a Conservator Identifies One · P22 Break/Fix: The Printed-Out Image That Faded

Photographic Materials Group Wiki: Gelatin Printing-Out Paper (POP)retrieved 2026-09-04, 2026-09-05

Sections: Historical facts; Identification characteristics - the image formed by metallic silver in a gelatin binder; the range of sepia tones to rich browns and creamy whites depending on the toner used; a high-quality heavyweight paper support coated with a baryta layer, often with a smooth glossy surface; the historical note that the image appears gradually on exposure and is then stabilised through toning and fixing

Used by:P1 Experiment: The Image That Would Not Stay · Silver mirroring and sulfiding in an untoned printed-out print

Platinum, Palladium (Photographic Materials Group Wiki)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Identification characteristics: process description and elements detectable by XRF; Identification characteristics: process description; Contemporary Process Overview, for the image coming up instantly in the developer, for contrast being achieved mostly by exposure rather than by the developer, and for the process being inherently acidic; Colour, for the effect of pH on the lightness of the print; Identification Characteristics, for the image colours of platinum, palladium and their mixtures and the factors that modulate them; and the process summary, for the sensitiser mixed in a shot glass and for the statement that image contrast is achieved mostly by exposure rather than in the developer; Identification, for the elements detectable in a platinum or palladium print by X-ray fluorescence — platinum, palladium, iron, sometimes silver, and mercury, lead and uranium from toning; Contemporary Process Overview, for contrast being achieved mostly by exposure rather than by the developer; Colour, for mercury development giving warmer tones and for oxidising chemicals and more acidic processing doing the same; Identification, for the elements detectable by XRF including mercury; Contemporary Process Overview, for mercury toner being described as a developer, prepared by mixing mercury chloride with water and added to the sensitizer, the developing solution, or both; Preservation, for the statement that mercury-developed photographs can reduce in colour over time and appear lighter brown; Color, for the matte deep warm black of platinum, the wider grey scale and lower contrast than silver, and for the statement that gelatin sizing, oxidising chemicals and more acidic processing all produce browner tones; Contemporary Process Overview, for the sequence "development is followed by acid clearing baths followed by water washing of the print" and the statement that the process is inherently acidic; and Housing and Storage Considerations, for the recommendation of neutral pH enclosures passing the Photographic Activity Test; Identification Characteristics, for the image colours of platinum, palladium and their mixtures and for the factors that modulate them; the process summary, for the sensitiser made in a shot glass and the statement that image contrast is achieved mostly by exposure rather than by the developer, although contrasting agents can be applied; Colour, for the effect of pH on the lightness of the print and for more acidic processing giving browner tones; Contemporary Process Overview, for contrast being achieved mostly by exposure rather than by the developer and for the process being inherently acidic; Identification Characteristics, for the image colours of platinum, palladium and their mixtures and the factors that modulate them; the process summary, for contrast being achieved mostly by exposure rather than by the developer; Colour, for the effect of pH on the lightness of the print and for mercury development giving warmer tones; Contemporary Process Overview, for the image coming up instantly in an oxalate developer, for contrast being achieved mostly by exposure rather than by the developer, and for the process being inherently acidic; Identification Characteristics, for the image layer embedded in the top fibre structure of the support and the colours of the two metals; Contemporary Process Overview; Housing and Storage Considerations; Treatment, for the brittleness and yellowing of the paper support; Historical Facts, for the list of historic practitioners; Identification Characteristics, for the colours and the image-transfer observation; Housing and Storage Considerations, for the neutral-pH paper-board folders, the Photographic Activity Test and the environment of 68 degrees Fahrenheit plus or minus 2 degrees of drift with 50 per cent relative humidity varying by not more than 5 per cent over 24 hours; Treatment, for the brittleness and yellowing from the acidic processing, the 2014 X-ray fluorescence confirmation that platinum prints can mirror in maximum-density areas, the caution about strong de-acidification unless pure platinum content is confirmed, the acid transfer to contacting cellulosic materials, and the statement that mercury-developed photographs can reduce in colour over time; Contemporary Process Overview, for the statement that the image comes up instantly and that the process is inherently acidic; Treatment, for the brittleness and yellowing of the paper support; Identification Characteristics, for the image layer embedded in the top fibre structure of the support, the image colours of platinum and palladium and the factors that modulate them, and the image-burn and image-transfer observations; Contemporary Process Overview, for the shot-glass sensitiser and the statement that contrast is achieved mostly by exposure rather than by the developer; Treatment, for the brittleness and yellowing of the paper support; Identification Characteristics — Color, for the matte deep rich warm black of platinum, the warmer yellower brown of palladium, the statement that both metals provide a wider scale of grey tones and less contrast than silver, and the list of factors that modulate the colour including pH, relative humidity, processing temperature and the colour of the paper support; Contemporary Process Overview, for the sensitiser made in a shot glass from ferric oxalate with a few drops of the metal salt, applied to paper and dried; Identification Characteristics — Analysis, for the statement that platinum, palladium, iron and sometimes silver, mercury, lead and uranium are detectable by X-ray fluorescence, the last three from toning; Contemporary Process Overview, for the description of mercury toner as mercury chloride in water added to the sensitiser, the developer or both; Treatment, for the statement that mercury-developed photographs can reduce in colour over time and appear lighter brown; Identification Characteristics, for the image layer embedded in the top fibre structure of the support and for the colours of platinum and palladium; Housing and Storage Considerations, for the neutral pH paper-board folders, the Photographic Activity Test and the environmental figures; Process overview; identification characteristics; deterioration; Condition and deterioration of platinum and palladium prints, including yellow staining associated with residual iron

Used by:Ferric oxalate · Potassium oxalate monohydrate · Potassium tetrachloropalladate(II) · Potassium tetrachloroplatinate(II) · Sodium tetrachloropalladate(II) · Ammonium citrate developer · Bostick and Sullivan platinum and palladium kits · Lead additions to platinum sensitisers · Mercuric sepia platinotype · Pizzighelli and Hübl's 1886 formulations · EDTA, citric acid and hydrochloric acid clearing sequence · Three-solution drop system for platinum and palladium · Sodium citrate developer · Ware's print-out platino-palladiotype · Willis's potassium oxalate developer · P25 Part XXV Overview: Platinum and Palladium · P25 Cost, Permanence and When a Platinum Print Earns Its Price · P25 Lab: Exposing, Developing and Clearing a Palladium Print · P25 Noble Metal Chemistry and the Platinotype · P25 Experiment: Tonal Scale, Contrast and Image Colour in Palladium · P25 Lab: Preparing the Sensitiser and Coating for Palladium · P25 The Additives We Study and Do Not Reproduce · P25 Assignment: The Process Comparison Atlas · Palladiotype · Platinotype · Platinum print stain from incomplete clearing

Silver Gelatin, Photographic Materials Conservation Catalogretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: The condition and deterioration account for silver gelatin prints, cited for the description of silver mirroring as a bluish metallic sheen beginning at the edges and visible under reflected light, and for the warning that mirrored areas are extremely susceptible to abrasion so that rubbing may move or remove image material; Identification characteristics — the image within the emulsion layer, on top of the baryta layer in developing-out papers; the 1894 and 1900 dates for baryta on commercial papers; baryta layers absent, thinly or thickly applied; Chronology - baryta layers added to commercial developing-out papers in 1894 and introduced to Kodak papers in 1900; and the statement that in a developing-out print the image sits on top of a baryta layer rather than partly within the paper structure, with the note that baryta layers may be absent, thinly or thickly applied; Identification Characteristics, Color - pristine silver gelatin printing-out photographs range in colour from warm browns to cool purples because of the nature of the development of the photolytic silver strand, pristine silver gelatin developing-out photographs are generally monochromatic, blue-black and white in appearance, and both processes can be toned to different colours using other minerals such as selenium or gold; The identification section's account of colour, that pristine silver gelatin printing-out photographs range in colour from warm browns to cool purples because of the nature of the photolytic silver strand, that pristine silver-gelatin developing-out photographs are generally monochromatic, blue-black and white in appearance, and that both can be toned to different colours using selenium or gold; Identification - that pristine silver gelatin printing-out photographs range from warm browns to cool purples while pristine developing-out photographs are generally monochromatic, blue-black and white, and that both processes can be toned to different colours with the addition of a toning process, using other minerals such as selenium or gold; Identification characteristics — the image within the emulsion layer, on top of the baryta layer in developing-out papers; the 1894 and 1900 dates for baryta on commercial papers; Identification characteristics — supports and layer structure

Used by:P29 Capstone Stage 6: Permanence, Presentation and the Finished Portfolio · Barium sulfate · P18 The Structure of a Printing Paper: Base, Baryta, Emulsion and Supercoat · P20 What a Toner Actually Does to a Silver Image · P20 Experiment: Selenium Toning and the Print Curve · P20 Toning, Permanence and What the Evidence Actually Supports · Silver gelatin developing-out print on fibre base · Silver gelatin developing-out print on resin-coated base

VanDyke Brown, Kallitype, Brown Print, Sepia Print, Ferro-Gallic, Argentotype, Agyrotype (Photographic Materials Group Wiki)retrieved 2026-09-07

Sections: The whole page, read on 7 September 2026 and found to carry its section headings and no text under any of them; The whole page, read on 7 September 2026 for the conservation, housing, storage and exhibition guidance a completed Photographic Materials Group entry would carry, and found to have its headings and no text under any of them; The whole page, read on 7 September 2026 for the conservators' account of how these prints deteriorate, and found to carry its section headings with no text under any of them; The whole page, read for the conservators' account of image material, colour and support, and found to carry those headings with no text beneath them; Identification characteristics and deterioration, for the conservators' account of the two iron-silver processes against which a student's own prints are compared

Used by:P24 Part XXIV Overview: When Iron Reduces Silver · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · P24 The Siderotype Principle: Iron Reduces Silver · P25 Assignment: The Process Comparison Atlas

cool.culturalheritage.org

The Albumen & Salted Paper Book: The History and Practice of Photographic Printing, 1840–1895retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Chapter Two, Binder Materials Used in Printing Papers — Albumen: the pH of native egg white, why fresh alkaline albumen is used only for matte papers, the three denaturing treatments (beating, chlorides and acidification), the settling and refrigerated ageing, and the aged odour that signals readiness; Chapter Three — the fermentation technique, its use as a substratum on glass by the mid-1850s, the Dresden factories and the paper stock they needed; Chapter 3: the chlorides added to albumen, beating and denaturation, the sample albumen preparation, hardening in isopropanol; Chapter 6: the sensitising reaction; Ammonia fuming; Ammonia and other additives to the silver bath; Theory of the fixation process — the list of substances with fixing or stabilizing action; Chapter 6, Fixation and Washing: theory of the fixation process; Chapter Two, Starches — starch as microscopic white grains insoluble in alcohol, ether and cold water, the bursting of the grains and the turbid paste formed on heating in water, the pastes preferred for photographic use being pure white, very viscous, odourless and of low turbidity, arrowroot from the West Indian plant maranta arundinacea as the most important with tapioca and sago also useful, the dried layer that does not swell in water and withstands the processing solutions, and the statements that starches do not react with silver salts and have no effect on the reduction of silver chloride; The Role of Organic Binders, on the "active" organic substances and on starch as the most useful of those that are not active but keep the light-sensitive material on the surface and prevent a dull sunken-in appearance; Chapter Three, Arrowroot Papers and Preparation of Arrowroot Paper, for the formula and its procedure, the surface running from very matte to a dull gloss, the longer density range and more delicate detail against a plain salted paper, DeBrébisson's first starch papers of 1854 in tapioca, the rise and fall of the trade and the disappearance of the last arrowroot papers after the First World War, the skin removed from the cooled liquid as the residue of the hulls of the burst grains, and the sensitising of arrowroot paper on 12 per cent silver nitrate containing 4 to 5 per cent citric acid with floating times of half a minute to a minute and a half; Chapter Seven, Tone Reproduction and Print Exposure, on matte papers needing relatively more reduced silver and a longer negative density range and on matte salted papers such as arrowroot being the fastest of these materials; Chapter Eight, on porous surfaces such as arrowroot taking much less gold than glossy albumen; Chapter Ten, Step 1, Preparing the Starch Paste, on the boiled wheat starch mounting paste, the requirement that no iron or steel touch the starch solution at any stage of its preparation or use, the dependence of the gel and its adhesive properties on the length and method of cooking, thymol as the fungicide and refrigerated storage for up to a week; Toning: gold toner formulae, the Borax Bath; Chapter 5, Alkaline gold toning — neutralising the gold chloride stock solution with calcium carbonate; Chapter 8: Theory of Noble Metal Toning; The Practice of Gold Toning; Gold Chloride; Strength of Gold Toning Solutions; Gold Toner Formulae; Chapter Two, Binder Materials Used in Printing Papers — Gelatin: the effect of alum and of potassium chrome alum on gelatin gels; Chapter 2, the role of organic binders and "active" organic substances; Chapter 3, arrowroot paper; Chapter 5, sensitization and the preservative effect of citric acid; replenishment of the silver bath; Chapter Two, Binder Materials Used in Printing Papers — Gelatin: manufacture, swelling and melting, the effect of alum, chrome alum and formaldehyde, and the reddish colour gelatin lends a salted paper print; Chapter 8: Gold Chloride; Theory of Noble Metal Toning; Chapter 3, hardening the albumen layer: the 70 per cent isopropyl alcohol immersion and the chloride matching rule; Chapter Six, Decolorizing the Silver Solution — the bath beginning clear and colourless and turning brown and eventually almost black with use, organic matter from the sizing or the binder always partially dissolving into it, the reaction of that organic matter with some of the silver causing spontaneous reduction to the metallic state, the metallic silver being responsible for the coloration, the rule that the bath may be used slightly discoloured but not when it is nearly black, kaolin as a finely powdered white clay that absorbs the organic matter and settles to the bottom of the bottle, about 15 grams being sufficient to clear one litre repeatedly, the kaolin being left in the storage container and shaken up with the bath after each use, the settling overnight, the two-hole stopper and glass tubing siphon that empties the bottle without disturbing the layer on the bottom, filtering through medium filter paper as the alternative when there is no time to let it settle, and filtering being necessary rather than optional once a surface scum appears because scum shows as a metallic marbled sheen on exposed prints; Chapter Six, Preserving Sensitized Paper, for the same reduction happening on the sheet; Chapter 5, sensitization: silver nitrate formed by the action of nitric acid on silver metal; the Volhard titration of a silver bath; ammoniated silver baths neutralised with nitric acid; Salted Papers: contrast enhancement with potassium bichromate; Chapter 8: Platinum Toning — History of Platinum Toning; The Practice of Platinum Toning; Chapter 1, Characteristics of printing-out papers — image colour, colloidal aggregates against filaments, refractive index and the colour change on fixing and drying; Chapter 6, Sensitization — argyria, and Reclamation of Silver Wastes, page 64, for the 6 to 8 per cent figure and the first two changes of wash water; Chapter 1: Silver chloride, the role of excess silver nitrate and of active organic binders; Chapter 6: Sensitization — salting and silvering strengths, distilled water, the first wash; Chapter 1, Silver chloride and the role of excess silver nitrate; Chapter 6, Sensitization — composition of the sensitizing solution, cautions on eye protection and argyria, reclamation of silver wastes, the danger of fulminating silver in ammoniacal baths; Chapter 5, Sulfur toning and the "old hypo" method; Chapter 7, The question of permanence — highlight yellowing, silver albumenate and the irreversibility of the sulfide stain; Gold toner formulae — the sodium acetate bath; the ripening of the bath and the decolorization that signals it; strength of gold toning solutions; Alkaline gold toning — neutralising the gold chloride stock solution; Fixation, washing and drying of albumen paper; Chapter 9: The practice of fixation; Reclamation of silver wastes; Chapter 1: silver chloride and the need for excess silver nitrate; Chapter 2: plain salted paper, salting solutions and floating; Chapter 3: chloride content of albumen; Chapter 6: the sensitising reaction and chemical grades; Plain salted paper - the variant salting formula containing sodium citrate, and what the addition does to image colour; Gold toner formulae — the thiocyanate toner; strength of gold toning solutions; the decolorization of the gold bath as the guide to its state; Chapter 6, Fixation and Washing: theory of the fixation process; chemical reactions involved in fixation; washing aids; Chapter 6, Fixation and Washing: history of fixation with thiosulfates; the practice of fixation; fixer exhaustion; colour changes during fixation; Mounting — the starch paste, with 0.4 mL of a saturated solution of thymol in methyl alcohol added as a fungicide; Chapter Six, Sensitization — silver nitrate as the one invariable ingredient of a sensitising solution and its manufacture by the action of nitric acid on silver metal, the sufficiency of a technical or ACS grade, the double replacement reaction and its equation, the requirement that the bath both react with all the chloride present and leave a considerable excess of silver nitrate in the light-sensitive layer, the four-times rule with its worked example of a 3 per cent salting solution answered by approximately 12 per cent silver, the requirement for distilled or de-ionised water and the cloudy precipitate of silver chloride and silver carbonate that tap water throws, the identification of that same reaction as the clouding of the first wash water, the simplest sensitising solution of 120 g of silver nitrate to a made-up litre, the recommendation of 2 to 2.5 per cent chloride with a 10 to 12 per cent bath for most salted papers, the special case of albumen paper in which the glossy surface compensates for a lack of heavy silver deposit so that 1 to 1.5 per cent chloride with an 8 to 9 per cent bath was common practice from 1880 to 1900 for the thinner negatives of the gelatin dry plate, the judgement that modern albumen practice is best conducted at 1.5 per cent chloride or above with a bath of 10 per cent or above and that the small loss of unprintable thin negatives is repaid in better and more permanent prints, the contrast with starch binders which are not coagulated by the silver solution and therefore require strong baths and short floats, the regulation of silver chloride grain size by bath strength with stronger solutions producing larger grains less likely to be absorbed into the paper fibres, the dependence of albumen float time on bath strength through the coagulating action of silver nitrate, the dissolution of the albumen off a sheet floated too long on a weak or freshly made bath, the coagulating contribution of the sodium or ammonium nitrate that accumulates in an older bath and the old advice to add it deliberately to silver-poor baths of 5 to 8 per cent with his statement that the advice does not apply at 10 per cent, the eye-protection and glove requirements and the argyria warning, the floatation method with its timing from the moment all bubbles are broken and the sheet lies flat, the three-minute egg timer, the glass tray and the rejection of stainless steel, the slow peeling of the sheet and the 5 to 7 degree drying line with the runoff blotted, the warning against over-drying, the brush and Blanchard's brush methods for matte papers but not glossy albumen with the metal ferrule that stains, the slightly stronger solutions used for brushing, the two applications needed where shadow density is insufficient, the "measles" and its causes, the paper-white round spots with hard definite edges left by air bubbles, the exhaustion of the bath by reaction and by mechanical carry-out, the preference for starting at 12 per cent and holding 10 to 12 per cent, the estimate of two or three batches or about thirty 11 by 14 prints from a 12 per cent litre before a determination is needed, the rule-of-thumb replenishment of the lost volume with a solution twice as strong with its worked example of 150 mL of 24 per cent restoring 850 mL of 12 per cent, the volume-basis replenishment of citric acid, the recommendation of Volhard titration with sodium thiocyanate and a ferric ammonium sulfate indicator for serious work and the note that the method was used for albumen sensitising baths as early as 1875, the browning and blackening of the bath by dissolved organic matter spontaneously reduced to metallic silver, the statement that the bath may be used slightly discoloured but not nearly black, the 15 g of kaolin per litre left in the storage bottle and shaken up after each use with overnight settling and the siphon, the necessity of filtering when a surface scum appears, the one to two day usable life of sensitized albumen and salted papers with yellowing in 8 to 12 hours in hot and humid conditions, the yellow colour as spontaneously reduced metallic silver in a very finely divided state and the progression to reddish brown and to a bronzed black over months in dark storage, the instruction to sensitize, print and process on the same day, the addition of 5 per cent citric acid to the silver bath for the maximum preservative effect with 1 per cent giving a noticeable extension, the effect of citric acid in the silver bath on the colour of a glossy albumen print which becomes more brownish than when the acid is in the albumen, the improved pre-processing stability and greater sensitivity and maximum density in both cases, the difficulty of purple tones in its presence, the 2 per cent citric acid brushed on before salting or after sensitizing as an alternative, Adolf Ost's publication of the idea in 1869 and the first ready-sensitized albumen paper of the Sensitized Paper Co. of Portsmouth, Ohio, in 1872, the guarding of manufacturers' methods as secrets and the professionals' two reasons for continuing to sensitize at home; Chapter Four, Albumen Paper — Sensitizing Albumen Paper, giving the float of 2 1/2 to 3 minutes on a 10 to 12 per cent silver nitrate solution, the statement that no additives to the sensitizing bath are required in the ordinary course of printing, the conditioning of sheets that are too dry by a night in a damp basement, the air bubbles that prevent sensitization and leave white circles, the slow lifting so that no silver reaches the back of the sheet and the runoff does not streak, the unnecessary glass rod, the mild heat permitted for drying and the prohibition on excessive dryness at the time of printing, the blotting of the drops, and the following section on ammonia fuming, which reports that fuming for 5 to 10 minutes was common in the United States and hardly practised in Europe, that it produces a more sensitive and contrasty paper in some circumstances, that much of its value may be had by simply increasing the strength of the silver bath or aiming at a different negative density range, that its value was greatest where a paper of low chloride content was sensitized on a relatively weak bath, and that for modern practice the troublesome and unpleasant process seems unnecessary; the statement that sensitized albumen paper remains in good condition for 24 to 48 hours depending on environmental conditions and should be exposed and processed within that period, and that white light must be excluded from all operations in sensitizing and subsequent handling; Chapter One, Basic Principles — the two-step definition of a salted paper, Talbot's finding that papers were hardly sensitive when chloride and silver were present in equal amounts and that about six times more nitrate was necessary, his 2 to 4 per cent salting solution against a 12 per cent silver bath, Vogel's explanation that the chlorine liberated by light unites with the free silver nitrate to form new silver chloride so that the cycle repeats and more image silver is formed where excess silver nitrate is available, the statement that pure silver chloride paper gives grey and flat images and that successful printing depends on active organic substances and excess silver nitrate together, the naming of albumen, gelatin and the organic acids citric, tartaric and oxalic as the active substances which facilitate the more complete reduction of silver chloride and themselves form light-sensitive silver salts such as silver albumenate, the classification of starch as an inactive binder which only keeps the image on the surface, the colloidal size of the print-out silver particles and the dependence of their colour on the refractive index of the medium, and the colour changes on fixing and on drying; Chapter Two, Binder Materials — the coagulation of albumen by contact with salts of metals, by alcohol and by temperatures above 65 °C, the coagulation by silver nitrate in the sensitizing bath and the formation of the insoluble and itself light-sensitive silver albumenate, and the pH of native egg white as 7.8; Chapter Three, Processing — Step 1, the initial wash of usually about 10 minutes in running water whose purpose is to remove the excess silver nitrate, with the statement that if it were not removed at this stage the silver nitrate would retard or completely prevent any toning from taking place and that if it were still present when the print is fixed black stains would be the result, and the saving of the first wash water in large-scale operations because the majority of the silver used to sensitize the paper is recovered from it; Step 2, the performance of toning before fixing because toning forms silver chloride as a by-product which would re-sensitise a print already fixed, and the conduct of all steps up to and including fixing in yellow light; Step 3, the short wash of 3 to 5 minutes before fixing; Chapter Seven, Tone Reproduction and Print Exposure — the self-masking property by which density built up in the shadows of a printing-out print acts as a mask on the lowest densities of the negative, delaying maximum density and preventing the loss of shadow detail before the highlights print in, with the net effect of good shadow density and delicate light tones and far less tendency to soot and chalk than a developing-out paper; Hubl's finding that the scale length of glossy albumen paper equalled that of platinum paper while salted papers exceeded platinum by a considerable margin, and his finding that albumen paper has a slow progression from shadows to middletones and a relatively abrupt jump from middletones to white where platinum does the opposite; and Exposure Time, giving the speed of albumen and salted papers as exceedingly slow with matte salted papers such as arrowroot the fastest, plain salted papers next and albumen the slowest of the lot, an average exposure for albumen paper of 5 to 10 minutes in direct sunlight and from half an hour to several days in shade, the requirement to print past the point where the print looks right because density is lost in the toning and fixing solutions, and the beginner's starting point of overprinting one and a half stops for albumen paper and two for salted papers; Chapter Two, Binder Materials Used in Printing Papers — Albumen: the specific gravity of 1.040, the brittle transparent dried layer, the 15 per cent solution of powdered albumen that approximates native egg white, the insolubility of albumen in alcohol and its coagulation by alcohol, by temperatures above 65 °C and by contact with salts of metals, the coagulation by silver nitrate in the sensitising bath and the formation of the insoluble and itself light-sensitive silver albumenate, the pH of native egg white as 7.8, the use of fresh alkaline albumen only for matte papers where it is always mixed with starch or other substances, the preparation of glossy papers from partially decomposed acidic albumen because in that condition it creates a glossier surface and a more even coating and has less tendency to yellow after sensitisation, the statement that albumen is never used in the strictly native condition, and the account of beating as the step that denatures proteins of differing viscosity into a homogeneous liquid that will form an even layer; Chapter Four, Albumen Paper — Blanquart-Evrard's communication to the French Academy of Sciences on 27 May 1850 and his original recipe of white of egg beaten to a froth with 25 per cent by weight of a saturated salt solution, settled overnight and floated for one minute; the account of the search for gloss, the finding by many independent experimenters that partially decomposed albumen gave a glossier and more even coating, the passage of decomposed albumen into an acid condition, the deliberate fermentation at elevated temperatures for several days, its use as a collodion substratum by the mid-1850s, its adoption as standard procedure in the Dresden factories from the early 1870s and the smell by which Dresden paper could be identified, and the statement that other European and American producers made good paper from aged but not fermented albumen; the separation of the eggs without the slightest contamination by yolk, blood or chalazae and the yield of about one ounce of albumen per large egg; the relation of chloride content to sensitivity and to a small extent contrast, papers of 1 to 1.5 per cent chloride being less sensitive and slightly more contrasty from thin negatives at the expense of a rich dense image against the normal 1.5 to 2.5 per cent, the statement that more chloride than is necessary only raises silver consumption without conferring any benefit, the judgement that it is best in ordinary circumstances to keep the chloride at 1.5 per cent or above, the interchangeability of ammonium and sodium chloride for colour and contrast, ammonium chloride being the commonest of the nineteenth century, the direction to dissolve the chloride in a minimum of water and add it to the egg white before beating and the note that this is unnecessary if a blender is used, the three denaturing treatments of beating, chlorides and acidification, the statement that the chemical forces which bind together the enormous molecules of protein grow weaker as the pH is lowered, the reduction of froth volume caused by the chlorides, the sample preparation of 15 g of ammonium chloride and 2 mL of glacial acetic acid in 30 mL of water combined and added to 1 litre of albumen, three minutes of beating in an electric mixer or blender until the entire mixture has been converted to froth, 24 hours of settling in a covered container, straining through muslin under pressure, a week of covered refrigeration, the several weeks of further usefulness and the smell, colour and sedimentation that reveal decomposition; the tray filled to a depth of approximately two thirds to three quarters of an inch, the conditioning of paper and solution to the working temperature, the filtering through muslin immediately before coating, the 4 mL of Kodak Photo-Flo per litre added immediately before a batch and its two purposes of bubble control and improved runoff, the float of 1 to 1.5 minutes timed from the moment all bubbles are broken and the sheet lies flat, the coating of one side only, the drying temperatures of 30 to 50 °C used in the nineteenth-century factories and the gloss they buy, the blotting of the runoff bead, the flattening under weights; the double-coating section — the gravity-driven difference in gloss between the top and bottom of a hung sheet, the greater ease of toning and fixing a thin coat, the three hardening routes of a six-month warm loft, a current of steam and a 70 per cent isopropyl alcohol immersion, the reason 70 per cent is chosen, the requirement that whatever chloride the albumen contains be added to the alcohol as well, the marking of the lowest edge and its reversal for the second float, and the greater curl, brittleness and toning difficulty of double-coated paper; the storage of albumenised sheets cool and dry, rolled albumen side out, and the conditioning of over-dry sheets before sensitising; the Dresden figures of 9 litres of albumen solution per ream of 480 sheets 46 by 58 cm obtained from 27 dozen eggs, and the 18,674 reams of the Dresdener Albuminfabriken in 1888; Chapter Five, Alternative and Hybrid Papers — pure albumen giving the familiar glossy paper, 1 to 1 dilutions with water giving a half-matte paper and 1 to 6 a paper almost indistinguishable from other matte salted papers; Chapter Six, Sensitization — the double replacement reaction written out, the rule that the silver solution be approximately four times as strong as the salting solution with the worked example of 3 per cent against 12, the recommendation of 2 to 2.5 per cent chloride with a 10 to 12 per cent bath for most salted papers, the special case of albumen paper in which the glossy surface compensates for a lack of heavy silver deposit so that 1 to 1.5 per cent chloride with an 8 to 9 per cent bath was common practice in 1880 to 1900 for the thinner negatives of the gelatin dry plate, the judgement that modern albumen practice is best conducted at 1.5 per cent chloride or above with a bath of 10 per cent or above and that the small loss of unprintable thin negatives is repaid in better-looking and more permanent prints, the dependence of float time on bath strength through the coagulating action of silver nitrate on albumen, the dissolution of the albumen off a sheet floated too long on a weak or freshly made bath, the coagulating contribution of the sodium or ammonium nitrate that accumulates in an older bath and the old advice to add it deliberately to silver-poor baths of 5 to 8 per cent, the float of 2.5 to 3 minutes, the requirement for distilled or de-ionised water in the silver bath and the clouding of the first wash, the argyria warning and the eye protection and gloves required for silver nitrate; the preservation chapter — the maximum preservative effect of 5 per cent citric acid in the silver bath and the noticeable extension given by 1 per cent, the effect of citric acid in either the albumen or the silver bath on the colour of a glossy albumen print, the greater brownness when it is in the silver rather than in the albumen, the improved pre-processing stability and greater sensitivity and maximum density in both cases, the difficulty of purple tones in its presence, Adolf Ost's 1869 publication and the 1872 appearance of ready-sensitised paper, and the instruction to sensitise, print and process on the same day; Chapter Seven, Tone Reproduction and Print Exposure — the effect of a transparent binder on diffuse reflection and on the scattering of light by paper fibres, the ranking of required negative density range with plain salted paper greatest and glossy albumen lowest, Hübl's finding that glossy albumen equalled platinum paper in scale length while salted papers exceeded it by a considerable margin, his finding that albumen paper has a slow progression from shadows to middletones and an abrupt jump from middletones to white so that a negative for albumen should emphasise highlight detail, the self-masking property of printing-out papers, the ranking of speed with matte salted papers such as arrowroot fastest, plain salted papers next and albumen the slowest of the lot, and the average exposure of albumen paper of 5 to 10 minutes in direct sunlight and from half an hour to several days in shade; and the yolk economy of the nineteenth century, in which yolks were salted and sold to bakeries and to tanners who used them to finish kid leathers; Chapter One, Basic Principles — the two-step nature of a salted paper, Talbot's finding that about six times more nitrate than chloride is necessary and his 2 to 4 per cent salting solution against a 12 per cent silver bath, Vogel's explanation of the recycling of liberated chlorine, The Role of Organic Binders naming albumen, gelatin and the organic acids citric, tartaric and oxalic as the "active" organic substances which facilitate the more complete reduction of silver chloride and themselves form light-sensitive silver salts such as silver albumenate and silver citrate, the effect of confining the image to the surface on maximum density and on the scattering of light in the whites, and the statement that albumen may be applied in pure form to produce a glossy paper or may be diluted to any strength with a corresponding loss of gloss, detail and brilliance; Chapter Two, Binder Materials Used in Printing Papers — Albumen: the specific gravity of 1.040, the brittle transparent dried layer, the 15 per cent solution of powdered albumen that approximates native egg white, the insolubility of albumen in alcohol and the coagulation of albumen by alcohol, by temperatures above 65 °C and by contact with salts of metals, the coagulation by silver nitrate in the sensitizing bath and the formation of the insoluble and itself light-sensitive silver albumenate, the pH of native egg white as 7.8, the use of fresh alkaline albumen only for matte papers where it is always mixed with starch or other substances, the preparation of glossy papers from partially decomposed acidic albumen because in that condition it creates a glossier surface and a more even coating and has less tendency to yellow after sensitization, and the statement that albumen is never used in the strictly native condition; Chapter Three, Salted Papers — the plain salting solution of 20 g of sodium chloride and 2 g of gelatin in a litre and its citrate variant, floating for three minutes, and the sensitised keeping of one or two days; Chapter Four, Albumen Paper — the 1839 letter of "H.L." to The Athenaeum proposing equal parts white of egg and water, Blanquart-Evrard's communication to the French Academy of Sciences on 27 May 1850 and his original recipe of white of egg beaten to a froth with 25 per cent by weight of a saturated salt solution, the relation of chloride content to sensitivity and to a small extent contrast, papers of 1 to 1.5 per cent chloride being less sensitive and slightly more contrasty from thin negatives at the expense of a rich dense image against the normal 1.5 to 2.5 per cent, the uselessness of more chloride than is necessary, ammonium chloride being the commonest chloride of the nineteenth century, the direction to dissolve the chloride in a minimum of water and add it to the egg white before beating, the reduction of froth volume caused by the chlorides, the three denaturing treatments of beating, chlorides and acidification, the sample preparation of 15 g of ammonium chloride and 2 mL of glacial acetic acid in 30 mL of water added to 1 litre of albumen with three minutes of beating, 24 hours of settling, straining through muslin and a week of refrigerated ageing, the tray filled to two thirds or three quarters of an inch, the float of 1 to 1.5 minutes timed from the moment all bubbles are broken, the 4 mL of surfactant per litre added immediately before coating and its two purposes of bubble control and even runoff, the drying temperatures of 30 to 50 °C used in the nineteenth-century factories and the gloss they buy, the blotting of the runoff bead, the hardening of a first coat in 70 per cent isopropyl alcohol carrying the same chloride content as the albumen, the keeping of albumenized sheets stored cool and dry and the direction to roll them albumen side out, and the float of 2.5 to 3 minutes on a 10 to 12 per cent silver nitrate solution; Chapter Five, Alternative and Hybrid Papers — the statement that pure albumen produces the familiar glossy albumen paper, that 1 to 1 dilutions with water result in a half-matte paper, that a dilution of 1 to 6 produces a paper almost indistinguishable from other matte salted papers and that even a 2 per cent solution of albumen causes a significant improvement in depth and contrast over a paper with no organic binder at all, the account of the salting step becoming a salting-sizing step, the dates of gelatin about 1850, albumen 1850 and starch 1854, the preference of most leading photographers after 1855 for a salting-sizing solution based on albumen in some dilution, gelatin, starch or whey, and the Preparation of Matte Albumen Paper after Hübl — fresh albumen used at most 24 hours after settling, 100 mL of it combined with 100 mL of arrowroot solution containing 4 g of sodium chloride, Hübl's original formula of equal volumes of albumen and a 2 per cent arrowroot solution first published in Photographische Rundschau for February 1895, and the sensitiser of 120 g of silver nitrate and 15 g of citric acid in a litre; Chapter Six, Sensitization — the double replacement reaction, the requirement that the silver solution be approximately four times as strong as the salting solution, the worked example of a 3 per cent salting solution calling for approximately 12 per cent silver, the direction to keep the chloride at about 2 to 2.5 per cent with a 10 to 12 per cent bath for most salted papers, the special case of albumen paper where the glossy surface compensates for a lack of heavy silver deposit so that 1 to 1.5 per cent chloride with an 8 to 9 per cent bath was common practice in 1880 to 1900 for the thinner negatives of the gelatin dry plate, the recommendation that modern practice keep the chloride at 1.5 per cent or above and the bath at 10 per cent or above, the coagulating action of a strong silver bath on the albumen layer and the longer float it therefore requires, the dissolution of the albumen off the sheet on a weak or freshly made bath before coagulation is complete, the coagulating contribution of the sodium or ammonium nitrate that accumulates in an older bath, the argyria warning and the eye-protection and glove requirements for silver nitrate, the necessity of distilled or de-ionised water, the citric acid preservative effect with its maximum at 5 per cent and a noticeable extension at 1 per cent, the effect of citric acid in either the albumen or the silver bath on the colour of a glossy albumen print, the direction to sensitize, print and process on the same day, the tendency of an ammonia-nitrate bath to dissolve the albumen off the paper, and the danger of fulminating silver if an ammoniacal silver bath is boiled down; Chapter Seven, Tone Reproduction and Print Exposure — the Effect of Binder Materials on Tone Reproduction, that a glossy paper calls for a negative of shorter density range because a transparent binder minimises diffuse reflection and the scattering of light by the paper fibres so that whites appear whiter and shadows denser, that matte papers need relatively more reduced silver and therefore longer exposures and a longer negative density range, the ranking of plain salted paper greatest, matte papers like arrowroot and matte albumen slightly less and albumen paper lower again, the 21-step gray scale method of measuring scale length, Hübl's finding that glossy albumen equalled platinum paper in scale length while salted papers exceeded it by a considerable margin, his finding that albumen paper has a slow progression from shadows to middletones and an abrupt jump from middletones to white so that a negative for albumen should emphasise highlight detail, the self-masking property of printing-out papers, and the ranking of speed with matte salted papers fastest, plain salted papers next and albumen slowest; Chapter Ten, The Question of Permanence, under Causes of Highlight Yellowing in Albumen Prints, page 108 — the first published notice of residual silver in the non-image areas of albumen prints, made in December 1859 by Alphonse Davanne and Jules Girard in a communication on the fixation of positive prints to the French Photographic Society, in which a 2 per cent solution of potassium cyanide did remove all traces of silver from albumen prints while strong solutions of hypo did not, with the quoted passage on the difficulty of obtaining albumenised proofs whose whites are pure and well preserved, and the two drawbacks the same authors recorded as virtually ruling cyanide fixation out as a practical technique — that it attacked and severely bleached the silver image, and that it was highly poisonous; footnote 10, giving the source as Bulletin de la Société Française de Photographie, 5, 347 (1859); the paragraph on silver bonded during sensitisation to sulfur-containing side groups on the albumen protein, held so tightly that treatment in hypo does not remove it; Chapter Nine, Fixation and Washing, Theory of the Fixation Process, for the list of substances with some fixing or stabilising action — ammonia, potassium cyanide, strong chloride solutions, thiocyanates, thiourea, sodium sulfite and sodium and ammonium thiosulfate — and the judgement that of all of them sodium thiosulfate has the fewest drawbacks for printing-out papers and has been in almost exclusive use for that task since the earliest days; Chapter Eight, on the alkaline gold toners of the separate toning-and-fixing method and on the 1867 discovery of gold toning baths based on the combination of gold chloride with thiocyanates, with the note that thiocyanate was formerly called sulphocyanide in the old style chemical nomenclature and that thiocyanate toners are definitely not a substitute for fixer; Theory of Noble Metal Toning, on the image of a printing-out paper being composed of very small, very highly dispersed particles of metallic silver whose small particle size gives a very large surface area relative to mass, so that a large portion of the total mass is on the surface and readily accessible to destructive chemical agents; and Chapter Ten, on highlight yellowing being so prevalent in albumen prints that it often serves as an important clue in their identification; Chapter Four, Albumen Paper — Double Coating of Albumen Paper, which is the whole of the published procedure: the gravity-driven difference in gloss and thickness between the top and the bottom half of a hung sheet and the statement that it is usually not pronounced enough to spoil a batch; the dependence of the ultimate colour of the prints, their brilliance and "depth", and the ease of toning and fixing on the thickness and glossiness of the coating; the statement that toning and fixing are more difficult with thicker coatings because the albumen becomes increasingly less permeable as the coating thickness increases; the search for gloss and "depth" that led to experiments with multiple coatings; the finding that some form of hardening or coagulating step was necessary between coatings to render the first coating insoluble, because otherwise there was no gain in thickness or amount of albumen on the sheet, the second coating step having dissolved off the albumen remaining from the first; the three approaches to hardening — six months in a warm loft, which Reilly calls the simplest and most widely used method of the nineteenth century and attributes in his footnote 20 to Henry C. Stiefel, Sensitized Papers, How Made and Used, The Adams Press, New York, 1894, page 29; a current of steam, which in effect cooks the albumen and renders it insoluble; and brief immersion in a 70 per cent solution of isopropyl alcohol, with the reason for that strength stated at both ends, pure alcohol being too strong and coagulating the layer unevenly while too dilute a solution is not strong enough to coagulate the albumen before it partially dissolves into the water, and the judgement that experience has shown 70 per cent to be the most effective; the requirement that whatever chloride content is present in the albumen itself should also be added to the alcohol solution, to prevent leaching out of the chlorides from the albumen, with the worked illustration that if the albumen contains 2 per cent ammonium chloride so should the alcohol solution; the working method of placing the alcohol solution in a tray and slowly pulling the sheets of albumenised paper through it, hanging them to dry and then piling and flattening them under weights so that they can be manipulated during the second float; the instruction to mark the edge of each sheet that was lowest when the sheets were hung to dry the first time and to hang that marked edge as the top after the second floating, in order to even out the coating and compensate for the runoff effect; and the summary of what two coatings buy and cost — papers that are quite glossy and may be so heavily coated that they are brittle and hard to tone, that usually produce better prints from thin negatives than single-coated paper does, that made up a large portion of the albumen paper sold after 1880, and that have a greater tendency to curl and are harder to manipulate in sensitisation and printing. With it, Chapter Two, Binder Materials Used in Printing Papers — Albumen: the specific gravity of 1.040, the drying to a brittle transparent mass at room temperature, the statement that albumen is insoluble in alcohol and that alcohol will coagulate albumen, "a property that is useful to obtain multiple coatings of albumen on a single sheet", the coagulation by temperatures above 65 °C and by contact with salts of metals, the coagulation by silver nitrate in the sensitising bath into an insoluble and itself light-sensitive silver albumenate that makes an important contribution to image formation, and the pH of native egg white as 7.8; Chapter Four, Coating Paper with Albumen — the tray filled to a depth of approximately two thirds to three quarters of an inch, the float of 1 to 1.5 minutes timed from the moment all bubbles are broken and the sheet lies flat, the coating of one side only and the statement that albumen paper cannot be immersed, the 4 mL of Kodak Photo-Flo per litre added immediately before a batch for bubble control and improved runoff, the drying-room temperatures of 30 to 50 °C maintained in the nineteenth-century factories and the gloss and depth they buy on a single-coated paper, the collection of albumen along the bottom edge of a hung sheet and the thick rind that forms if the runoff is allowed to dry, the remedy of blotting it off with a cloth several times during drying, and the flattening under weights that makes the sheets supple and easy to handle in the further floating operations to come; Chapter Four, Sensitizing Albumen Paper — the keeping of albumenised sheets in a cool dry place, the rolling albumen side out to minimise cracking, the conditioning of an over-dry sheet overnight in a damp place because a sheet that is too dry will not properly absorb the silver nitrate solution, and the float of 2.5 to 3 minutes on a 10 to 12 per cent silver nitrate solution with no additives required in the ordinary course of printing; Chapter Four, Ammonia Fuming — the statement that fuming is not necessary for good results, that its value was greatest where a paper of low chloride content was sensitised on a relatively weak bath, and that much of its value may be had instead by increasing the strength of the silver bath or aiming for negatives of a slightly different density range; Chapter Four, Printing and Processing Albumen Paper — the 24 to 48 hours for which a sensitised sheet remains in good condition, the requirement that a print appear too dark when it leaves the printing frame, and the statement that albumen prints require slightly less overprinting than salted paper prints and that double-coated albumen papers need less overprinting than single-coated sheets; Chapter Four, Toning Albumen Paper — the need for a much stronger and more effective toning solution than salted papers require because albumen is less permeable and the silver particles are more protected, the consequent slowness of toning even with a stronger bath, and the statement that any variations in the thickness of the albumen coating, especially in the case of double-coated papers, will be immediately apparent in the toning step because less heavily coated areas will tone more quickly and deeply; Chapter Four, Fixation, Washing and Drying of Albumen Paper — the alkaline 15 per cent sodium thiosulfate fixer, the two baths of four minutes each both freshly made on the day of use, and the statement that both fixation and washing are made more difficult by the nature of albumen itself since coagulated albumen is resistant to penetration by solutions; Chapter Six, The Floatation Method of Sensitization — the average float of 2.5 to 3 minutes, which "insures adequate sensitization of even doubly albumenized paper"; Chapter Seven, Effect of Binder Materials on Tone Reproduction — the rule that a glossy paper calls for a negative of shorter density range because a transparent binder minimises diffuse reflection and the scattering of light by the paper fibres, so that the same amount of reduced silver that gives a deep shadow on a glossy paper gives a much paler one on a matte surface, and the resulting ranking of required negative density range with plain salted papers greatest, matte arrowroot and matte albumen slightly less and glossy albumen lowest; Chapter Seven, Using a Gray Scale to Measure Gradation and Contrast — the 21-step tablet method of measuring a paper's scale length, the requirement that the step-1 patch match the density of the margin outside the tablet, and Hübl's findings that glossy albumen equals platinum paper in scale length and has a slow progression from shadows to middletones with an abrupt jump from middletones to white; and Appendix C, part III — the statement that albumen prints of 1850 to 1870 are usually less glossy than those of 1870 to 1890 because of the use of burnishing and rolling machines and the increased use after 1870 of double-coated paper, and the characteristic crackled or crazed surface texture of albumen paper; Chapter Eight, Toning, "Gold Toning", for the idea of gold toning paper prints borrowed from daguerreotypists who used a mixture of gold chloride and sodium thiosulfate called sel d'or to intensify and tone their daguerreotypes, for the modification discovered in 1840 by Fizeau and soon becoming standard practice, for P. F. Mathieu applying it to paper in 1847 and Le Gray popularising it after 1850, for sel d'or constituting what would now be called a toning-fixing bath since it is formed by mixing a solution of gold chloride into an excess of sodium thiosulfate and so retains its power to dissolve silver chloride, and for the image colour it gave, from yellowish-brown to cool brown, purple or bluish-black. Also "Strength of Gold Toning Solutions", for 0.1 to 0.2 g of gold chloride per litre for matte salted papers and 0.4 to 0.5 g for glossy albumen, and for the warning that a gold toning solution is ruined by even a trace of fixer; Chapter Eight, Toning, Gold Toner Formulae: the Sodium Acetate Bath, reading fused sodium acetate 20 g, 1% gold chloride solution 40 to 50 ml and water to make 1 liter; the Borax Bath at borax 10 g and 1% gold chloride 40 ml to the litre and the Thiocyanate Toner at sodium thiocyanate 15 to 20 g and 1% gold chloride 60 to 80 ml, for comparison; the account of alkaline toning practice, in which the stock gold solution retains a yellow colour while in the relatively inactive acidic state and becomes colourless when it has passed into the more active state through contact with alkaline substances, so that decolorization is the best guide to the state of the toning bath; the statement that some baths in the older literature take hours or even days to decolorize and become usable, the most common of these being the sodium acetate toner, which generally requires 24 hours to ripen before it can be used; the warning that a toner made too alkaline tones more quickly but loses its activity much more rapidly, that too active toners do not produce pleasant tones and are harder to control, and that making the toner too alkaline results in baths that still contain a great deal of gold but no longer tone prints; the note that most alkaline baths are intended for one-use toning and become inactive spontaneously after a few hours, with no clue other than the cessation of toning action to indicate exhaustion, but that baths made with sodium acetate can be used repeatedly if strengthened with additions of gold stock solution; the two approaches in the older literature, one neutralising the gold stock with calcium carbonate before compounding and the other relying on the alkaline substances of the formula, with the modern recommendation to use the gold stock in its acid condition; Strength of Gold Toning Solutions, giving 0.1 to 0.2 g of gold chloride per litre for matte salted papers and 0.4 to 0.5 g for glossy albumen, toning by inspection over 3 to 15 minutes at 17 to 20 °C with constant agitation and in weak incandescent light, toning continued well past the first visible change in image colour, and for glossy albumen until only the shadows retain their original warm colour by transmitted light; the warning that the toner solution is ruined by even a trace of fixer; and the instruction to give the toned prints a 5-minute wash in running water before fixing; Chapter Eight, Toning, Gold Toner Formulae: the Borax Bath, reading borax (sodium borate) 10 g, 1% gold chloride solution 40 ml and water to make 1 liter; Strength of Gold Toning Solutions, giving 0.1 to 0.2 g of gold chloride per litre for matte salted papers and 0.4 to 0.5 g for glossy albumen, with toning by inspection over 3 to 15 minutes at 17 to 20 °C and constant agitation; the ripening of an alkaline gold bath, the sodium acetate toner generally requiring 24 hours; the decolorization of the bath from yellow to colourless as the best guide to its state; the warning that a bath made too alkaline tones more quickly but loses activity much faster and can end up holding a great deal of gold while toning nothing; the note that most alkaline baths are one-use and go inactive spontaneously after a few hours; the warning that the toner is ruined by even a trace of fixer; and the warning that too strong a bath deposits gold superficially so that the layer is largely removed in the fixer; Gold toning: the strength rule of 0.1 to 0.2 g of gold chloride per litre for matte salted papers and 0.4 to 0.5 g for glossy albumen; the thiocyanate toner in weights; and the decolorization of the bath as the guide to its state, as summarised on the course's chloroauric acid and sodium thiocyanate pages; Chapter Nine, Fixation and Washing, the paragraph on the pH of the fixing bath: that albumen and salted paper prints are best fixed in an alkaline solution of sodium thiosulfate to which no hardeners have been added, and that alkaline thiosulfate solutions are necessary for two reasons — "first, the slight alkalinity prevents any acids which might be inadvertently introduced into the fixing bath from decomposing the sodium thiosulfate and liberating sulfur. Second, an acid fixing bath would tend to attack the finely divided metallic silver of the image, causing excessive bleaching of the highlights and middletones in the print. This attack on the image silver itself is minimized when the pH of the fixer is kept on the alkaline side"; the Theory of Fixation immediately above it, on thiosulfate ions needing to be present in excess or insoluble complexes form that cannot be washed from the image layer, on the consequent need for two baths, and on the fixing process being completed fairly rapidly so that prolonged fixation is much more injurious to prints than is generally believed because thiosulfate that penetrates the paper fibres becomes almost impossible to remove; The Practice of Fixation, for the 15 per cent bath of 150 g of the pentahydrate with 2 g of sodium carbonate in a litre, the 18 to 20 degrees C working temperature and the two baths of four minutes each; and the History of Fixation with Thiosulfates, on thiosulfate solutions being unstable so that fixers for these papers should be made up just before use; Gold toner formulae — the thiocyanate toner given in weights as sodium thiocyanate 15 to 20 g, 1 per cent gold chloride 60 to 80 mL and water to 1 litre; strength of gold toning solutions, 0.1 to 0.2 g of gold chloride per litre for matte salted papers and 0.4 to 0.5 g for glossy albumen; and the decolorization of the gold bath as the guide to its state, as summarised on the course's sodium thiocyanate and chloroauric acid pages; Chapter 9, Washing Aids, on the removal of thiosulfate not being achievable by washing in water alone if a print of optimum stability is desired, and on washing aids working by displacing absorbed thiosulfate ions and replacing them with less harmful and more soluble ions; Chapter 9, Washing Aids - these treatments displace the absorbed thiosulfate ions and replace them with less harmful and more soluble ions of various salts, and the best washing aid for albumen and salted papers is a 1 per cent sodium sulfite solution; the 2 to 4 minute running-water wash before it, which avoids overloading the mechanism of ion exchange, and the exhaustion figure of no more than 20 prints of approximately 8 by 10 inches per litre; Gold toning: bath strengths of 0.1 to 0.2 g of gold chloride per litre for matte salted papers and 0.4 to 0.5 g per litre for glossy albumen, toning by inspection, and the warning that too strong a bath deposits gold superficially so that the layer is largely removed in the fixer, as summarised on the course's chloroauric acid page; Chapter 9, The Theory of Fixation, on thiosulfate ions needing to be present in excess or insoluble complexes are formed that cannot be washed from the image layer, on the consequent need for two baths, and on prolonged fixation being more injurious to prints than is generally believed; Chapter Eight, Toning, Platinum Toning: the useful platinum toning formula, reading potassium chloroplatinite 1% sol. 50 ml, citric acid 4 g and water 750 ml; the history, in which M. De Caranza recommended toning with an acidified platinic chloride solution in 1856, such a toner having only a very slight toning action and a strong tendency to bleach the silver image, all platinic chloride formulae having so little toning energy that at best they are restricted to matte papers and are totally ineffective with albumen paper, while the platinous chloride salts, chiefly potassium chloroplatinite, are very active toners when combined with acids and have a smaller tendency to attack the silver image; potassium chloroplatinite remaining obscure until 1879, when Willis began to market the platinotype process; J. Reynolds discovering in 1886 that it was a very energetic toner of silver prints, yielding brown and brownish-black tones instead of the purplish and bluish-black tones obtained with gold toners; Alfred Stieglitz publishing in 1889 a pioneering platinum toner formula consisting simply of nitric acid, potassium chloroplatinite and water; the widespread use of platinum toning between 1895 and 1925 on matte collodion and matte gelatin printing-out papers, with matte gelatin papers often toned only with platinum and therefore brown in hue, and matte collodion papers generally toned with both gold and platinum, producing the olive-black colour of studio portraits of 1895 to 1920; the practice, in which gold toning goes on best in an alkaline environment while platinum toning requires a neutral or acidic condition; the tendency to produce yellowish highlights if toning is carried on too long, or if the solution is too strong or too acidic; the tendency of impurities such as silver nitrate or sodium thiosulfate to rob the toning bath of its activity by altering the platinum to an irreducible condition, for which reason prints must be well washed and treated in a 5% sodium chloride solution for 2 minutes and then washed again for 5 minutes in running water before toning; the instruction to wash the prints well after toning so that none of the acidic platinum toner is carried into the fixing bath; and the combined gold and platinum route, toning in the Borax gold bath until the print is lilac in colour and then long enough in the platinum toner to achieve a neutral colour, with the note that the absolutely neutral black characteristic of the platinum print itself cannot consistently be attained; Chapter Nine, Fixation and Washing — the opening statement that because of the extremely small size of the silver image particles in these papers the image is considerably more vulnerable to chemical attack, especially from the residual products of fixation; the Theory of the Fixation Process, on the unexposed salts being primarily silver chloride with silver citrate, silver chromate or others present depending on what was added to the salting or sensitising solutions, on the list of substances with some fixing or stabilising action and the judgement that of all of them sodium thiosulfate has the fewest drawbacks, on there being probably at least three different kinds of silver-thiosulfate complex, on thiosulfate ions needing to be present in excess or insoluble complexes form that cannot be washed from the image layer, on one of the complexes being soluble only in fresh thiosulfate, on the consequent need for two baths, and on prolonged fixation being much more injurious than is generally believed because thiosulfate penetrates the paper fibres; the paragraph on the pH of the fixing bath, giving the two reasons albumen and salted paper prints are best fixed in an alkaline thiosulfate solution to which no hardeners have been added; The Practice of Fixation, for the 18 to 20 degrees C working temperature, the instruction to make the bath with slightly warmer water because heat is consumed in dissolution, the warning that too great a temperature differential against the other trays can blister albumen paper, the requirement that prints be washed free of other substances and especially of acidic platinum toning baths first, and the two baths of 4 minutes each with constant agitation and a 5 second drain between them; Fixer Exhaustion, for the literature estimate of no more than 150 8 by 10 prints per litre of a 15 per cent solution against Reilly's own conservative 10 to 15 prints per litre, and for the reasons — the silver content of printing-out papers being very high relative to develop-out materials and the colloidal silver image being vulnerable; Color Changes During Fixation, for the loss of density and the shift from brilliant purple or brown to a duller yellower brown, for the packing of the silver particles into aggregates and the fall in refractive index as the silver chloride is removed, for the reddening of prints in the first wash and for the gain in density and neutrality on drying; the History of Fixation with Thiosulfates, on Herschel's application of hypo to silver chloride paper on 29 January 1839 out of his 1819 discovery, on Talbot and Daguerre having until then merely stabilised with strong sodium chloride, and on thiosulfate solutions being unstable so that fixers for these papers should be made up just before use; and Washing of Prints, on washing being harder for prints than for film because thiosulfate is absorbed into the paper fibres, on the base paper becoming a reservoir of image-threatening substances if fixation is prolonged, on the best washing aid for these papers being a 1 per cent sodium sulfite solution, and on the wash sequence of 2 to 4 minutes running water, 3 to 4 minutes in the sulfite, and 30 minutes of washing; Chapter 9, Fixation and Washing, The Practice of Fixation, giving sodium thiosulfate (pentahydrate) 150 g, sodium carbonate 2 g and water to make 1 litre, the 18 to 20 degree C working temperature, the instruction to make the bath with water slightly warmer than that because heat is consumed in dissolution, the two-bath procedure of 4 minutes with constant agitation, a 5 second drain and 4 minutes more, and the requirement that prints be washed free of acidic toning baths first; Fixer Exhaustion, giving the literature estimate of no more than 150 8 by 10 prints per litre of 15 per cent solution against Reilly's own conservative 10 to 15 prints per litre and the reasons for the difference; the theory of fixation, on thiosulfate needing to be in excess, on the two-bath requirement and on prolonged fixation being more injurious than is generally believed; Color Changes During Fixation; Chapter 3, Step 4 Fixing, giving the total fixing time as 8 to 10 minutes and requiring a fresh batch for each printing session; Chapter 5, on adding 2 grams of sodium carbonate per litre to promote more effective fixation and prevent blistering of heavily albumenised papers; Chapter Three, Arrowroot Papers, on the binder being a paste of boiled arrowroot starch, the surface running from very matte to a dull gloss according to the amount of starch and the smoothness of the rawstock, arrowroot prints being considerably more brilliant and richer-looking than plain salted papers with a longer density range and more delicate detail preserved, DeBrébisson's first starch papers of 1854 using tapioca, the displacement of plain salted papers for matte work, the rise and fall of the trade and the disappearance of the last arrowroot papers after the First World War; Preparation of Arrowroot Paper, giving the whole formula and procedure — 35 g of arrowroot rubbed to a creamy paste with a little cold water in a mortar, enough further cold water to make a fairly runny cream with no lumps, the warning that the cream separates and must be stirred to the moment of use, 35 g of sodium chloride and 3 g of citric acid dissolved separately in 950 mL of water, that solution brought to the boil in a porcelain container, the cream added in small amounts with constant stirring using a glass rod or wooden spoon, a few minutes of gentle boiling, cooling before use, the removal of the skin of burst starch hulls from the cooled liquid, and the statement that tapioca or rice starch may be used in the same manner; the paragraph that the formula is essentially that of plain salted paper except for the citric acid, that starch is not an "active" organic substance and so has no effect on the reduction of silver chloride, that without the citric acid the prints would be grey and flat, and that with both citric acid and starch present the prints take a warm purple colour after exposure and change to yellowish-brown after fixation if they are not toned; the note that arrowroot pastes must be absorbed into the paper fibres to a certain extent in order to adhere, so that porous papers need a binder of higher starch content, and that highly calendered plate finishes are harder to coat evenly; Coating of Papers with Arrowroot Salting Solution, on marking the back in pencil first, on solutions of 2 per cent arrowroot or less being fluid enough to float, on heavier coatings obtained by immersion and drawing out over one or two glass rods, on the method most recommended in the old manuals — a 3 to 4 per cent starch paste brushed on with a thin flat brush in one direction then crossed perpendicular, allowed to sink in for a minute or two, then evened out with a round dry brush until a uniform matte surface is obtained — on the sponge-and-squeegee alternative with its 1 to 2 minute wait, on brushing the paste into the crevices of a textured paper and on hanging to dry; the sensitising of arrowroot paper by floating on a 12 per cent silver nitrate solution that also contains 4 to 5 per cent citric acid, the half minute that may suffice for a light coating against the minute and a half at most for a heavy one, the loss of brilliance and the grey flat print that follow too long a floatation especially on porous papers, the option of applying the silver with a wide brush, the several weeks the sensitised paper then keeps, and the direction to tone with any of the formulae of Chapter Eight; the Resume of Processing Steps, on the initial wash of about 10 minutes in running water, the short 3 to 5 minute wash before fixing, the alkaline 15 per cent sodium thiosulfate fixer used as two baths of 4 minutes each with a fresh batch for each session, the 2 to 4 minute wash before hypo clearing, the 3 to 4 minutes in 1 per cent sodium sulfite and the final wash; Chapter One, Basic Principles, on silver chloride having to be formed in place from a soluble chloride and silver nitrate, on pure silver chloride paper giving grey and flat images, on Talbot's finding that about six times more nitrate was necessary with a salting solution of 2 to 4 per cent against a 12 per cent silver bath, and on Vogel's explanation of the recycling of liberated chlorine; The Role of Organic Binders, naming albumen, gelatin and the organic acids citric, tartaric and oxalic as the "active" organic substances that facilitate the more complete reduction of silver chloride and themselves form light-sensitive silver salts such as silver albumenate and silver citrate, naming starch as the most useful of the substances that are not active in that way but do keep the light-sensitive material on the surface and prevent a dull sunken-in appearance, and on the location of the image layer deciding maximum density and surface; Chapter Two, Starches, on starch existing as microscopic white grains insoluble in alcohol, ether and cold water, on the grains bursting and a turbid paste being created when starch is heated in water, on the pastes preferred for photographic use being pure white, very viscous, odourless and of low turbidity, on arrowroot from the West Indian plant maranta arundinacea being the most important with tapioca and sago also useful, on the dried layer not swelling in water and withstanding the processing solutions, on starches not reacting with silver salts and having no effect on the reduction of silver chloride, and on most starch-bound salted papers therefore also carrying an active organic substance, usually citric acid; Chapter Six, Sensitization, on the double replacement reaction and the fate of sodium nitrate, on there having to be enough silver nitrate to react with all the chloride and to leave a considerable excess besides, on the sensitising solution having in practice to be approximately four times as strong as the original salting solution with the worked example that a 3 per cent salting solution calls for approximately 12 per cent silver depending in part on the binder, on the simplest sensitiser of 120 g of silver nitrate in a litre of distilled water, on distilled or de-ionised water being required because tap water throws a cloudy precipitate that robs the bath of strength, on that same reaction being what clouds the first wash, on keeping the chloride content at about 2 to 2.5 per cent with a 10 to 12 per cent silver bath because lowering the chloride tends to produce prints lacking brilliance and density, and on starch-bound papers requiring strong silver baths and short floating times because starch, unlike albumen, is not coagulated or rendered insoluble by the silver solution, the starch layer being very permeable to water so that prolonged floating drives fine silver chloride particles down into the fibres, with stronger solutions producing larger grains less likely to be absorbed; the passage on organic acids added to the silver bath or applied separately, citric acid being the most effective, its marked effect on papers such as arrowroot and resin-arrowroot which contain no active organic binder, the redder and more brilliant print it produces there and the longer keeping it incidentally confers, and the maximum preservative effect at 5 per cent with as little as 1 per cent extending usable life noticeably; Chapter Seven, Tone Reproduction and Print Exposure, on glossy papers needing a lower negative density range because a transparent binder minimises diffuse reflection and scattering, on matte papers needing relatively more reduced silver and therefore longer exposures and a longer negative density range, on plain salted papers requiring the greatest density range with matte papers like arrowroot and matte albumen slightly less and albumen lower again, on the 21-step gray scale method of measuring the scale length of a paper once it has been fabricated, and on matte salted papers like arrowroot being the fastest of these materials followed by plain salted papers with albumen the slowest; Chapter Eight, Strength of Gold Toning Solutions, on porous surfaces such as arrowroot and plain salted paper requiring much less gold than glossy albumen because they tone more quickly and would rapidly become overtoned, on 0.1 to 0.2 g of gold chloride per litre for matte salted papers against 0.4 to 0.5 g for glossy albumen, on toning by inspection for 3 to 15 minutes at 17 to 20 °C with constant agitation, and on a trace of fixer ruining the toner; Chapter Nine, Theory of the Fixation Process, on the image layer of an exposed but unprocessed print consisting of the metallic silver, the binder — starch, gelatin, albumen — and unexposed silver salts which may include silver citrate and silver chromate as well as silver chloride, on the extremely small size of the image particles making these prints more vulnerable to chemical attack from the residual products of fixation, and on sodium thiosulfate having the fewest drawbacks among the complexing agents; Chapter Five, Alternative and Hybrid Papers, on the resin-arrowroot paper made with ammonia-shellac added to a 2.5 per cent arrowroot solution prepared as in Chapter Three, and on the arrowroot-albumen paper made from equal volumes of fresh albumen and Chapter Three arrowroot solution; Chapter Ten, Step 1 Preparing the Starch Paste, on thymol as a fungicide added to a starch paste; Chapter Three, Salted Papers — Photographic Printing Before 1850, on Talbot's two-step paper, the adoption of hypo in 1839 and Davanne and Girard's explanation of the difference between English and French papers; Plain Salted Paper, giving sodium chloride 20 g, gelatin 2 g and water to make 1 litre, the swelling of the gelatin in 250 mL of cold water, the dissolution of the salt in the heated remainder, the cooling to approximately 80 degrees F, the three-minute float, the statement that the gelatin is only enough to slightly inhibit the sinking of the image into the paper fibres, the warning about porous rawstocks, and the citrate variant of 20 g sodium chloride with 20 g sodium citrate and 2 g gelatin; Floating the Paper on the Salting Solution, on choosing the smoother side, marking the back in pencil, curling and its remedies, bubbles, hanging to dry by the long edge, pressing flat, the indefinite keeping of the salted sheet and the fact that salting is done in white light; the sensitising of paper made to these two formulae for 3 minutes on a 12 per cent silver nitrate solution and the one or two days the sensitised sheet then keeps; Contrast Control in Salted Papers, on the chloride content of the salting solution affecting contrast, on chromates as the only route to large increases and the judgement that the best prints are made without them, and on Hrdliczka in the mid-1890s; Arrowroot Papers and Preparation of Arrowroot Paper, giving 35 g arrowroot, 35 g sodium chloride and 3 g citric acid in 950 mL, and the reason citric acid is present where starch is the binder; Chapter One, Silver Chloride and The Role of Organic Binders, on silver chloride formed in situ, on Talbot's finding that six times more nitrate was necessary, on Vogel's account of the recycling of liberated chlorine, on "active" organic substances and on the location of the image layer; Chapter Two, Binder Materials Used in Printing Papers — Gelatin, on swelling in cold water, melting above 32 degrees C, the effect of alum and formaldehyde, and the reddish colour gelatin lends a salted paper print; Starches, on starch having no effect on the reduction of silver chloride; Chapter Four, Albumen Paper, on the chloride content of albumen — 1 to 1.5 per cent being less sensitive and slightly more contrasty from thin negatives at the expense of a rich dense image, and more chloride than necessary conferring no benefit beyond higher silver consumption, both stated of albumen and not of salted paper; Chapter Six, Sensitization, on the double replacement reaction, on the sensitising solution needing to be approximately four times as strong as the salting solution, on keeping the chloride content at 2 to 2.5 per cent with a 10 to 12 per cent silver bath, on distilled water for the silver bath and on the clouding of the first wash; Chapter Seven, Tone Reproduction and Print Exposure — Characteristics Required in Negatives and Effect of Binder Materials on Tone Reproduction, on matte papers requiring the longest density range, on scale length measured with a 21-step scale, on Hübl's comparison with platinum paper and on the self-masking property of printing-out papers; Chapter Ten, Step 1 Preparing the Starch Paste, on thymol as a fungicide added to a starch paste; Chapter Six, Sensitization, which is the whole of this page's provenance: the opening account of silver nitrate as the one invariable ingredient of a sensitising solution, its manufacture from nitric acid on silver metal, the sizes it is sold in and the statement that a technical or ACS grade is sufficient; the double replacement reaction and its equation; the requirement that the bath both react with all the chloride present and leave a considerable excess of silver nitrate in the light-sensitive layer; the rule that the sensitising solution must be approximately four times as strong as the salting solution, worked as 3 per cent against 12 per cent; the requirement of distilled or de-ionised water and the reason, that tap water throws a cloudy precipitate of silver chloride and silver carbonate which robs the bath of strength; Composition of the Sensitizing Solution, giving silver nitrate 120 g and distilled water to make 1 litre, the caution to wear eye protection whenever silver nitrate is compounded or handled, the recommendation to keep the chloride at 2 to 2.5 per cent and the silver bath at 10 to 12 per cent for most salted papers because lowering the chloride costs brilliance and density, the different case of albumen paper at 1 to 1.5 per cent chloride with an 8 to 9 per cent bath and the judgement that modern albumen work is better at 1.5 per cent and above with a 10 per cent bath or stronger, and the effect of the binder — strong baths and short floats for starch papers, because starch is not coagulated by silver nitrate and because stronger solutions produce larger grains of precipitated silver chloride that are less likely to be absorbed into the paper fibres; the dependence of albumen float time on bath strength, the coagulating effect of accumulated sodium and ammonium nitrate in an older bath, and the note that the old advice to add those nitrates pertained to silver-poor baths of 5 to 8 per cent; Techniques of Sensitization, with the caution on eye protection and tightly fitting gloves, the account of argyria, the requirement of safelight illumination, the average 2.5 to 3 minute float for albumen paper, the care needed to keep silver from the back of the sheet, the timing from the moment all bubbles are broken, the preference for glass vessels, the rejection of stainless steel and of second-hand plastic trays, and the slow lift and the hanging by two corners of the long edge; Brush Sensitization, on its economy of solution, its freedom from back-of-sheet contamination, its liability to streaks, the wide flat thread-bound Japanese brush and the reason a metal ferrule stains, the Blanchard's brush, the slightly stronger solutions used for brushing, the two applications sometimes needed for shadow density, and the diagnosis of the "measles" as insufficient sensitisation against paper-white hard-edged spots as trapped bubbles; Exhaustion of the Silver Solution, on the two mechanisms of loss, the advice to start at 12 per cent and hold the bath between 10 and 12, the false economy of a 10 per cent bath, the capacity of perhaps two or three batches or some 30 prints of 11 by 14 inches before a determination of strength is needed, the rule of thumb of replenishing the lost volume with a solution twice as strong with its worked example of 150 mL of 24 per cent, the matching rule for citric acid replenished strictly on volume lost, and the warning that the rule of thumb is unsuitable for continuous use; Decolorizing the Silver Solution, on organic matter dissolving off the paper, its reduction to metallic silver, the browning and blackening of the bath, 15 g of kaolin per litre shaken up and left to settle overnight, filtering, and surface scum shown as a marbled metallic sheen on the print; Preserving Sensitized Paper, on the one or two day life of sensitised sheets, the 8 to 12 hours in extreme heat and humidity, the yellow to reddish brown to bronzed sequence of spontaneous reduction, storage in a tightly closed container in a cool dry place, and citric acid at 5 per cent for maximum preservative effect with 1 per cent noticeable; Ammonia and Other Additives to the Silver Bath, on the 1840 discovery of the ammonia-nitrate bath, its rapid yellowing and discolouration, its tendency to dissolve albumen, the doubtful utility of neutralising it with nitric acid, the danger of fulminating silver if such a bath is boiled down, and the judgement that most nineteenth century additives are superfluous if not potentially harmful; Reclamation of Silver Wastes, giving 6 to 8 per cent of the silver in a sensitised sheet as the part that forms the image, the first and second wash waters and the fixer as the recoverable streams, precipitation with sodium chloride or sodium carbonate, and the 60 per cent typically recovered in a gallery; Chapter One, Basic Principles, on colloidal photolytic silver and its colour, on silver chloride having to be formed in place, on Talbot's discovery of the critical ratio and the six times more nitrate he found necessary with a 2 to 4 per cent salting solution and 12 per cent silver, on Vogel's recycling explanation, and on active organic substances; Chapter Two, Working Environment, on yellow bug-lite safelights, on the wet and dry areas, and on trays reserved by operation; Chapter Three, Plain Salted Paper, giving the 3 minute float on a 12 per cent silver nitrate solution for paper salted to his two plain formulae and the one or two day keeping that follows, and Contrast Control in Salted Papers, giving the bichromated salting solution sensitised for 3 minutes on a 10 per cent silver bath containing 5 per cent citric acid; Preparation of Arrowroot Paper, giving the 12 per cent bath with 4 to 5 per cent citric acid, the half minute to one and a half minute float for starch papers, the grey flat prints that follow too long a float, and the several weeks a citric-acid-sensitised arrowroot paper keeps; Chapter Five, Alternative and Hybrid Papers, giving Hübl's matte albumen sensitiser of 120 g silver nitrate and 15 g citric acid in a made-up litre with a 1 to 2 minute float, and his resin-arrowroot sensitiser of 120 g silver nitrate and 80 g citric acid in a litre with a 4 to 5 minute float; Appendix B, the Volhard titration for silver bath strength worked out by Irving Pobboraysky, with its 0.2 N thiocyanate, its saturated ferric ammonium sulfate indicator, its 6 M nitric acid, its standardisation against 0.1 N silver nitrate made as 4.25 g in 250 mL, and the multiplication of the found normality by 170 to give grams per litre; Chapter 9, Fixation and Washing, Washing Aids, giving the 1 per cent sodium sulfite solution as the best washing aid for albumen and salted papers and explaining that such treatments displace absorbed thiosulfate ions and replace them with less harmful and more soluble ions; Method for Washing Albumen and Salted Papers, giving sodium sulfite (anhydrous) 10 g and water to make 1 litre, the 2 to 4 minute running-water wash before it, the 3 to 4 minutes with constant agitation in it, the single use and discard, the exhaustion figure of no more than 20 prints of approximately 8 by 10 inches per litre, and the 30 minute final wash with 40 to 50 minutes for heavy stocks; Washing Time, on thicker base paper needing both a longer wash and a longer washing-aid treatment, and on some papers being injured by prolonged washing; Chapter 3, Step 5 and Step 6, giving the short wash before the clearing agent and the 3 to 4 minute treatment in 1 per cent sodium sulfite; Chapter One, Silver Chloride and The Role of Organic Binders, on silver chloride having to be formed in situ because it cannot be dissolved and coated, on Talbot's finding that six times more nitrate was necessary, on Vogel's account of the recycling of the liberated chlorine, and on the enormous exposure a printing-out image costs against a developed one; Chapter Three, Salted Papers, on Talbot's two-step paper and on the adoption of hypo in 1839; Chapter Two, Binder Materials — Gelatin and Starches, on gelatin lending a characteristic reddish colour to salted paper prints, on Talbot's own prints being reddish brown because the gelatin was already there as the manufacturer's sizing rather than because he added any, and on French photographers finding that their papers did not behave like English ones because French mills sized with starch; Chapter Six, Sensitization, on the rule that the sensitising solution be approximately four times as strong as the salting solution and on the 2 to 2.5 per cent chloride with a 10 to 12 per cent silver bath recommended for salted papers; Chapter Seven, on the self-masking of printing-out papers; Chapter One, Printing-Out Papers, for the statement that a printing-out image needs more light energy than a develop-out one, "in some cases 100,000 times more"; Silver Chloride and The Role of Organic Binders, for silver chloride always being formed in situ by double replacement because it cannot be dissolved and coated, for Talbot's finding that about six times more nitrate was necessary, for the 2 to 4 per cent salting and 12 per cent silver nitrate that follow from it, and for Vogel's account of the liberated chlorine being recycled by the excess silver nitrate; Chapter One, Printing-out papers; Chapter Eight, Toning; Chapter 9, Fixation and Washing; Chapter 9, Fixation and Washing, The Practice of Fixation; Chapter One, Printing-out papers and their self-masking behaviour; Chapter 3, preparing and coating albumen; Chapter 9, fixation and washing; Chapter One: Printing-out papers; Chapter One: Printing-out papers; Classification of printing-out papers; Additives to the silver bath; ammonia in the silver bath; Sensitizing albumen paper: caution on eye protection, skin staining and argyria; Chapter Two, Binder Materials Used in Printing Papers, Gelatin: manufacture in a pH-controlled vat, melting point of a swollen mass, and the effect of alum, chrome alum and formaldehyde; Chapter 6, Fixation and Washing — the slightly alkaline print fixer of sodium thiosulfate with sodium carbonate, which prevents acid carried in from decomposing the thiosulfate and keeps the bath from attacking the finely divided silver of a printing-out image; the instruction to make a fixing bath with water slightly warmer than the working temperature since some heat is always consumed in the formation of the solution; the decomposition of dissolved sodium thiosulfate in part to sodium sulfite and elemental sulfur; Chapter 6, Fixation and Washing — the instruction to make a fixing bath with water slightly warmer than the working temperature, since some heat is always consumed in the formation of the solution, and the warning that too great a difference between a cold fixer and the other baths can blister albumen paper; Chapter 9, Washing of Prints — the by-products of fixation must be removed because they are unstable and will cause yellowing and fading of the image if allowed to remain, and because of the extremely small size of the silver image particles the image is considerably more vulnerable to chemical attack, especially from the residual products of fixation; Theory of Noble Metal Toning — toning provides a measure of protection against oxidation and sulfiding of the image silver by partially replacing and enclosing it with metallic gold or platinum, the small particle size meaning the silver has a very large surface area relative to its mass so that a large portion of its total mass is on the surface and readily accessible to destructive chemical agents, and gold and platinum reacting much less readily with sulfur and being much more difficult to oxidise; Chapter 11, Causes of Highlight Yellowing in Albumen Prints — the presumed mechanism of the yellowing is the formation of silver sulfide by reaction of the albumen-bound silver with labile sulfur supplied by residual fixer or atmospheric pollution, this kind of yellow staining can and does occur in gelatin and collodion as well as albumen prints, the onset time depends primarily on the moisture level and temperature of the storage environment and the amount of residual thiosulfate and silver-thiosulfate complexes present, and Spiller's 1868 detection of retained silver by the brown stain produced on moistening the white surface with sulphide of ammonium; Chapter 9, Washing of Prints — the purpose of washing is to remove the sodium thiosulfate and silver thiosulfate complexes that remain after fixation; washing prints is more difficult than washing films primarily because of the absorption of thiosulfate into the paper fibres; with prints the rate of washing slows down tremendously at the lower levels of thiosulfate concentration and in practice it is impossible to remove every trace of thiosulfate simply by washing in water; Washing Aids — these treatments displace the absorbed thiosulfate ions and replace them with less harmful and more soluble ions, and the best washing aid for albumen and salted papers is a 1 per cent sodium sulfite solution; Washing Conditions and Apparatus — sufficient flow over the entire print surface and the entire volume of water changed at least every 5 minutes, with hand agitation absolutely necessary where the apparatus is imperfect; Washing Time — the thicker the base paper the longer the wash and the longer the washing-aid treatment, and some papers may be injured by prolonged washing; Chapter 9, Washing of Prints — with prints the rate of washing slows down tremendously at the lower levels of thiosulfate concentration and in practice it is impossible to remove every trace of thiosulfate simply by washing in water; Washing Aids — the treatments displace absorbed thiosulfate ions and replace them with less harmful and more soluble ions, and the 1 per cent sodium sulfite solution with its 3 to 4 minute treatment and its exhaustion figure of no more than 20 prints of approximately 8 by 10 inches per litre; Chapter 11 — Spiller's 1868 report that retained silver in an albumen print was found by the brown stain produced on moistening the white surface with sulphide of ammonium; Chapter 9, Washing of Prints - the statement that with prints the rate of washing slows down tremendously at the lower levels of thiosulfate concentration and that in practice it is impossible to remove every trace of thiosulfate simply by washing in water, and the statement that with imperfect apparatus hand agitation of the prints is absolutely necessary; Washing Aids - the treatments displace absorbed thiosulfate ions and replace them with less harmful and more soluble ions; Theory of Noble Metal Toning — that toning with noble metals improves the colour and density of the image and provides a measure of protection against oxidation and sulfiding by partially replacing and enclosing the image silver with metallic gold or platinum; that the printed-out image is composed of very small, highly dispersed particles whose small size means a very large surface area relative to mass, so that a large portion of the total mass is on the surface and accessible to destructive chemical agents, and that a layer of gold or platinum on a silver particle shields the silver inside, especially from oxidising agents; that the colour of a print depends on the size and shape of the image particles, the distance between them and the refractive index of the medium, and that replacement of silver atoms by gold or platinum enlarges the metal aggregates so the print appears colder and more neutral; that the rate of substitution is greater for gold ions than for platinum ions although the rate may be modified by other substances in the bath; that in an acid bath such as a simple gold chloride solution one atom of gold replaces three atoms of silver, so that toning lags far behind bleaching of the silver and the result would be a flat, lifeless image with a reddish colour, while in an alkaline toner the gold exists in a different ionic form and there is a more favourable substitution of one atom of gold for one atom of silver; that platinum toning goes on much more effectively in an acid environment; that in either gold or platinum toning the substitution creates silver chloride as a by-product so toning must always be followed by a fixing step; The Practice of Gold Toning, that toning is an inexact process and the factors influencing the outcome include the pH of the binder, the pH of the silver solution, the amount of silver deposited, the thoroughness of the initial wash, the pH, strength, temperature and age of the toning solution and the time of immersion, with the recommendation to leave prints untoned as a basis of comparison; and Gold Chloride, that the gold chloride bought from suppliers is always an acidic substance technically called chlorauric acid, that true gold chloride is not usually commercially available, that the dry chemical is very deliquescent and is packed in small hermetically sealed glass tubes, that solutions are fairly stable if kept out of light and out of contact with organic materials, that the stock gold solution retains a yellow colour in the relatively inactive acidic state and becomes colourless when it has passed into the more active state through contact with alkaline substances so that decolorization is the best guide to the state of the bath, that the sodium acetate toner generally requires 24 hours to ripen, and that the toning solution should not be made too alkaline because although it tones more quickly in that condition it also loses activity much more rapidly, too-active toners being difficult to control; Theory of Noble Metal Toning, that toning with noble metals provides a measure of protection against oxidation and sulfiding of the image silver by partially replacing and enclosing it with metallic gold or platinum, that the small particle size of a printed-out image gives it a very large surface area relative to its mass so a large portion of the mass is on the surface and readily accessible to destructive chemical agents, and that a layer of gold or platinum on a silver particle will tend to shield the silver inside from attack, especially from oxidising agents; the historical review, that the new technique of separate toning in alkaline gold chloride solutions followed by fixation in fresh strong sodium thiosulfate allowed albumen paper to attain a much better record of resistance to fading than plain salted paper, that the new alkaline gold toners deposited more gold than the other toning methods and that this contributed to the resistance of albumen prints to oxidative fading, and that in addition to the protection offered by the gold the albumen layer itself made a significant difference in protecting the silver image from oxidising gases; Highlight Yellowing in Albumen Prints, that approximately 85 per cent of extant albumen prints made after 1860 display moderate to severe yellowing and probably 95 per cent of those made in the 1850s, followed by the author's statement that these figures are not based on any formal statistical sampling but merely on his accumulated experience in examining prints and on discussions with curators and collectors, and that a statistical study of a large collection would be a most welcome addition to the literature of photographic preservation, with his proposal that such a monitoring programme measure reflection densities in image and non-image areas through red, green, blue and visual filters and recheck the same prints at two, five and ten year intervals; and the closing note that much research has been done concerning the permanence of gelatin-based printing papers but that there is no certainty of the applicability of those results to albumen-based materials; Chapter 7, Tone Reproduction and Print Exposure — the general rule that all printing-out papers require negatives with a greater density range than develop-out papers do; Effect of Binder Materials on Tone Reproduction, that a glossy binder such as albumen minimises diffuse reflection and scattering by the paper fibres so that a shorter density range is required than for a matte surface, that a matte print needs relatively more reduced silver for a dense black and therefore longer exposure and therefore more highlight density in the negative, and the resulting order in which plain salted papers require the greatest density range, matte papers such as arrowroot and matte albumen slightly less, and glossy albumen paper least; Using a Gray Scale to Measure Gradation and Contrast, the explicit statement that because of the variation in binder materials no exact density ranges can be specified for negatives intended for these different papers, and the substitute method of sensitising a sample sheet, printing a 21-step gray scale to full maximum density verified against the unmasked margin, counting the resolved steps as the scale length of that paper, and taking the appropriate negative density range as approximately the density difference between the highest and lowest discernible steps, with the practical qualification that detail is always lost at both extremes so slightly shorter ranges are used; Hübl's finding that the scale length of glossy albumen paper equalled that of platinum paper while salted papers exceeded platinum by a considerable margin, and that albumen and platinum papers of the same total scale length differ in the distribution of their contrast, albumen having a slow progression from shadows to middletones and an abrupt jump to white while platinum is the reverse, so that a negative for albumen should emphasise highlight detail; the account of self-masking, in which density built up in the shadows of a printing-out paper acts as a mask on the lowest densities of the negative, delaying maximum density and preserving shadow detail while the highlights print in; and the instruction that modern printers can measure print densities on a reflection densitometer and plot them against the gray scale densities under their own normal exposure and processing conditions.; Preface, for the statement that the salted paper print dominated photographic practice from 1840 to 1855 and the albumen print from 1855 to 1895, and that albumen accounts for about 85 per cent of surviving nineteenth-century photographic prints; Chapter One, Printing-Out Papers, for the first 65 years of photographic history being the era of printing out, for printing-out papers needing in some cases 100,000 times more light energy than develop-out materials, for the impossibility of enlargement onto them, and for the long tonal range that reproduces detail from negatives too contrasty for the softest develop-out grade; Classification of Printing-Out Papers, for the two-step definition of a salted paper against the one-step emulsion paper; Characteristics of Printing-Out Papers, for the colloidal aggregate size of the photolytic particles and for the colour change on fixing and on drying; Silver Chloride, for Talbot's finding that about six times more nitrate than chloride is needed and his 2 to 4 per cent salting and 12 per cent silver figures; Chapter Two, Work Areas, for the yellow 60 W incandescent working light and the statement that there is no need to work in the dim light of a modern safelight; Chapter Three, Resume of Processing Steps, steps 1 to 8, for the sequence of initial wash, toning, wash, fixing, wash, hypo clearing, final wash and drying; Chapter Six, Reclamation of Silver Wastes, for only about 6 to 8 per cent of the silver on a sensitised sheet ending up in the image; Chapter Seven, Exposure Time, for the recommendation to overprint about two stops for salted papers; Chapter Eight, History of Toning Methods, for heat toning with a hot iron as probably the oldest method and Talbot's use of it, for sulfur toning by the deliberate decomposition of the hypo bath and the prints that faded within weeks, for Blanquart-Evrard's 1847 suggestion of instant ageing by adding silver nitrate and his proposal of acetic acid, and for the survival in good condition of many sulfur-toned prints including those of Hill and Adamson; Gold Toning, for the borrowing of the idea from the daguerreotypists' sel d'or, for Fizeau's discovery in 1840, for Mathieu's 1847 pamphlet, for Le Gray's publicity after 1850, for sel d'or being a toning-fixing bath that can liberate sulfur if over-used or acidified, for separate toning and fixing being established in the late 1850s and the evidence against sel d'or being conclusive by 1860, for Waterhouse's alkaline gold toning proposed around 1855, for the 1867 discovery of thiocyanate-based baths, for thiocyanate toners achieving a more complete substitution and a colder deep purple tending to black, for the bleach-then-intensify appearance a thiocyanate toner gives, for thiocyanates consuming more gold than the alkaline varieties, and for thiocyanate toners not being a substitute for fixer; Theory of Noble Metal Toning, for the two benefits of colour and protection, for the small particle size giving a large surface area relative to mass so that a large portion of the mass is accessible to destructive agents, for gold and platinum reacting much less readily with sulfur and being harder to oxidise, for a layer of gold or platinum shielding the silver inside especially from oxidising agents, for the four factors that set image colour, for toning changing the size and shape of the particles by replacement and for the enlargement of the aggregates making the print colder, for the acid bath in which one gold atom replaces three of silver giving a flat lifeless reddish image because toning lags behind bleaching, for the alkaline bath giving a more favourable one-for-one substitution, for platinum toning going on better in acid, and for silver chloride being created as a by-product so that toning must always be followed by fixing; The Practice of Gold Toning, for the eleven factors that influence the outcome, for the recommendation to leave prints untoned as a basis of comparison, and for rubber gloves; Gold Chloride, for the commercial material being the acidic chlorauric acid rather than true gold chloride, for true gold chloride being made by passing chlorine over gold leaf and not usually being available, for the commercial forms of an amorphous orange mass or a 1 per cent solution, for the 15 grain hermetically sealed tubes and the deliquescence, for stock solutions being made with distilled water and kept out of light and away from organic material, for the 1 per cent stock most formulae assume, and for the nineteenth-century practice of dissolving gold coins in mixed acids with Reilly's judgement that the fumes and concentrated acids make it unsuitable for a home laboratory; the same section for the two approaches to alkaline toning, for the yellow to colourless decolorisation being the best guide to the state of the bath, for the sodium acetate bath needing 24 hours to ripen, for a too-alkaline bath toning quickly and losing activity quickly, for too active a toner giving unpleasant tones and being hard to control, for most alkaline baths being one-use and going inactive spontaneously after a few hours with no clue other than the cessation of toning, and for acetate baths being reusable if strengthened; Strength of Gold Toning Solutions, for porous papers such as arrowroot and plain salted paper requiring 0.1 to 0.2 g of gold chloride per litre against 0.4 to 0.5 for glossy albumen, for toning by inspection taking 3 to 15 minutes, for carrying toning well past the first visible change, for 17 to 20 degrees C and constant agitation, for the ruin of a toner by a trace of fixer, for weak incandescent light to judge by, and for the five-minute wash before fixing; Gold Toner Formulae, for the borax, sodium acetate and thiocyanate formulations; Platinum Toning, for De Caranza's 1856 acidified platinic chloride with its slight toning action and strong tendency to bleach, for platinic chloride formulae being restricted to matte papers and useless on albumen, for potassium chloroplatinite being very active with acids and less prone to attack the image, for its obscurity before Willis marketed the platinotype in 1879, for Reynolds's 1886 discovery and Stieglitz's 1889 formula, for the 1895 to 1925 popularity with matte collodion and matte gelatin papers, for the olive-black of combined gold and platinum toning, for platinum toning requiring neutral or acid conditions, for yellow highlights from over-toning or too strong or acid a bath, for silver nitrate or thiosulfate impurities robbing the bath by making the platinum irreducible, for the 5 per cent sodium chloride bath and washes before toning, and for the combined gold-then-platinum sequence to a neutral black; Chapter Nine, The Practice of Fixation and Fixer Exhaustion, for the alkaline fixer and the two reasons for the carbonate and for the conservative capacity estimate; Washing of Prints, for the image being in much more intimate contact with the paper fibres than in a modern baryta paper and for the base paper becoming a reservoir of image-threatening substances, and for experimental evidence on the washing of these papers being almost nonexistent; Chapter Ten, Preparing Prints for Display or Storage, for flattening between acid-free blotters under weights while slightly damp, for heat making plain salted papers colder and darker and for Talbot's hot iron, and for most salted papers needing only matting rather than mounting; Mounting Adhesives Used in the 19th Century, for starch being the usual adhesive with gelatin, gum arabic, dextrine and albumen also used, for conservators' agreement that pure fresh starch is the best mountant, and for impure glue being known as a cause of trouble by the 1850s; the same chapter for nineteenth-century mounts of good paper over a lignin-loaded pulp core, for the acidification, brittleness, yellowing and foxing that follow, and for very little barrier existing between the silver image and the mount; Print Storage, for boxes and sleeves, for avoiding wooden cabinets and painted or varnished containers, for automobile exhaust and copier ozone as destructive atmospheric agents, and for 18 to 20 degrees C at 35 to 45 per cent relative humidity with the statement that temperature and humidity govern the rate of every destructive reaction; Chapter Eleven, The Era of Salted Papers, for the 1855 Photographic Society committee's finding that the most ordinary cause of fading is sulfur, intrinsic from hyposulphite left in the print or extrinsic from the atmosphere and much faster in the presence of moisture, and for its two recommendations of thorough washing and gold toning; Albumen Prints After 1860, for more image silver giving improved resistance to fading and for the alkaline gold toners depositing more gold and contributing to resistance to oxidative fading; Generalized Image Fading, for the internal causes of residual thiosulfate and silver-thiosulfate complexes and the external causes of atmospheric sulfur compounds and oxidising gases such as ozone; Deterioration Caused by Defective Mounts and Mounting Adhesives, for approximately 95 per cent of albumen prints having been mounted, for lignin decomposition products migrating through the board, for putrefied starch or gelatin adhesives, and for remounting being the only preservation treatment that has proven itself; The Need for Restoration Research, for the statement that no research into these problems had been done since the days of Haddon and Grundy; Chapter One, Printing with Silver Salts and Printing-Out Papers, for the two evolutionary strains of silver printing paper, for printing-out needing in some cases 100,000 times more light energy, for the visual check on the progress of exposure, for the long tonal range that renders negatives too contrasty for the softest develop-out grade, and for the impossibility of enlargement; Classification of Printing-Out Papers, for the definition of a salted paper as any handmade silver chloride printing-out paper made in a salting step and a sensitising step; Characteristics of Printing-Out Papers, for the dissociation of silver chloride into silver and chlorine, for the aggregate particles being of colloidal size and much smaller than the filaments of developed silver, for the colour depending in part on the refractive index of the medium, and for the colour change on fixing being caused by removal of the silver chloride and the closer packing of the particles, and the further change to darker and colder on drying; Silver Chloride, for the in-situ formation by treating the paper with a soluble chloride and then silver nitrate, for sodium nitrate taking no part and washing away, for pure silver chloride paper giving grey and flat images, for Talbot's finding that equal amounts of chloride and silver nitrate give a paper hardly light-sensitive at all and that about six times more nitrate is needed, for his 2 to 4 per cent salting and 12 per cent silver figures, and for Vogel's explanation that the liberated chlorine unites with the silver nitrate present to form new silver chloride in a repeated cycle; The Role of Organic Binders, for the "active" organic substances albumen, gelatin and the organic acids citric, tartaric and oxalic which facilitate more complete reduction of silver chloride and themselves form light-sensitive substances such as silver albumenate and silver citrate, for starch and the other inactive substances that only keep the sensitive material on the surface, and for the effect of the depth of penetration on maximum density, matte surface and sharpness; Relating Theory to Practice, for the statement that printing-out papers are far more subject to damage from careless handling and contamination than modern papers because of the excess silver nitrate; Chapter Three, Plain Salted Paper, for the necessity of some organic material and the flatness of a paper without it; Contrast Control in Salted Papers, for the chloride content of the salting solution affecting contrast, for large increases being possible only with chromates, for the discovery of the chromate effect by Hrdliczka in the mid-1890s, and for the judgement that the best salted paper prints are made in sunlight with optimum negatives and without contrast-enhancing additions; Arrowroot Papers, for starch not being an active substance and for citric acid being what keeps an arrowroot print from being grey and flat; Resume of Processing Steps, Step 1 Initial Wash, for the ten minutes in running water, for the excess silver nitrate retarding or preventing toning and causing black stains in the fixer if it is not removed, and for the first wash water being saved for silver recovery; Chapter Four, The Early History of Albumen Paper, for the first published notice of albumenised paper in The Athenaeum of 11 May 1839; Chapter Five, for gelatin about 1850, albumen 1850, starch 1854 and whey in the early 1850s, and for the shift after 1855 to salting-sizing solutions; Chapter Six, Sensitization, for the double replacement reaction written out, for the sensitising solution needing to be approximately four times as strong as the salting solution, for distilled or de-ionised water because tap water's chloride and carbonate ions throw down a precipitate that robs the bath of strength, and for the clouding of the initial wash water being that same reaction between the excess silver nitrate left in the paper and the ions in tap water; Reclamation of Silver Wastes, for only about 6 to 8 per cent of the silver on a sheet forming the image; Chapter Seven, Characteristics Required in Negatives, for the need to match the negative to the paper because there is no contrast grade, and for plain salted paper requiring the greatest density range; Effect of Binder Materials on Tone Reproduction, for the reason a matte paper needs a longer-scale negative than a glossy one; Using a Gray Scale to Measure Gradation and Contrast, for the 21-step method of measuring scale length, for Hubl's finding that glossy albumen equals platinum paper in scale length while salted paper exceeds platinum by a considerable margin, and for the self-masking explanation of long scale length; Print Exposure and Exposure Time, for albumen and salted papers being primarily sensitive to ultraviolet and only much less to visible blue, for the loss of sensitivity below 5 degrees C, for a very intense source lowering print contrast while a weaker light raises it slightly, and for overprinting one and a half stops for albumen and two stops for salted papers; Chapter Nine, Theory of the Fixation Process, for the inventory of what is in an exposed unprocessed print and for thiosulfate having the fewest drawbacks among the possible complexing agents; Chemical Reactions Involved in Fixation, for the requirement of an excess of thiosulfate and for prolonged fixation being much more injurious than is generally believed; The Practice of Fixation, for the alkaline bath and the two reasons for the carbonate; Color Changes During Fixation, for the shift to a yellower duller brown with loss of density, for the solid-solution account of the unfixed image, for the packing of the particles and the fall in refractive index, for the reddening on first meeting wash water being caused by swelling, and for the gain in density and colder colour on drying; Washing of Prints, General Considerations, for the image being in much more intimate contact with the paper fibres than in a modern paper with a baryta and gelatin substratum and for the base paper becoming a reservoir of image-threatening substances, and for the statement that experimental evidence on the washing of albumen and salted paper prints is almost nonexistent; Chapter Eleven, The Era of Salted Papers 1840-1855, for the fading that threatened to discredit photography on paper, for Henneman's statement that of twenty-five Pencil of Nature prints made in one batch with only three washings some remained perfect and others totally failed, for the 1855 Photographic Society committee's conclusion that the most ordinary cause of fading is sulfur, intrinsic from hyposulphite left in the print or extrinsic from the atmosphere and much faster in the presence of moisture, and for Davanne and Girard's 1855 analyses; Highlight Yellowing in Albumen Prints and its Causes, for the silver bound to sulfur-containing side groups of the protein, for Davanne and Girard's 1859 finding that 2 per cent potassium cyanide removed all silver where strong hypo did not, for Spiller's 1868 argentic organic compound detected with ammonium sulfide, and for Haddon and Grundy's measurement that an unexposed, thoroughly fixed and washed albumen print still contained nearly 5 per cent of the silver left after sensitisation; Chapter One, Printing-Out Papers, for the advantage that the image appears during exposure so that progress can be checked visually and stopped at the right moment, and for the impossibility of enlargement; Chapter Two, Printing Frames, for the hinged two-part back so that one spring may be loosened and half the back opened while the closed half maintains registration, for the felt or chamois pad that distributes pressure and ensures contact, for the frame being at least one format larger than the negative, and for double-thickness picture glass rather than window glass; Chapter Three, Resume of Processing Steps for Albumen and Salted Papers, steps 1 to 8 in full - the initial wash of about ten minutes in running water to remove the excess silver nitrate, with the warning that leaving it retards or prevents toning and causes black stains in the fixer and the note that in large operations this water was saved for silver recovery; toning before fixing because toning forms silver chloride which would resensitise a fixed print, with toning done in weak white light if by inspection and everything up to and including fixing otherwise in yellow light; a three to five minute wash before fixing because interaction between fixer and toner damages colour and permanence; fixing in an alkaline 15 per cent sodium thiosulfate solution for 8 to 10 minutes, or two baths of 4 minutes each with at least 5 seconds draining between them, with a fresh batch made for each session because the extra silver in these papers quickly exhausts a fixing bath and even unused fixer breaks down rapidly; a two to four minute wash before the hypo clearing agent to avoid overloading it; 3 to 4 minutes in 1 per cent sodium sulfite; a final wash of at least 30 minutes in an effective washer with longer for heavier stock; and drying by blotting and air drying face up on fibreglass screens; Chapter Seven, Print Exposure, for exposure and development being simultaneous and inseparable in a printing-out paper and the image being affected by the colour and intensity of the exposing light and the duration; Effect of the Light Source on Print Contrast, for an intense source lowering contrast and a weaker light raising it slightly, for the old rule of printing dense negatives in sunlight and thin ones in the shade meaning open sky rather than direct sun, for covering frames with tissue or ground glass, and for the effect of the colour of the light; Exposure Time, for the speed of these papers being exceedingly slow with matte salted papers fastest and albumen slowest, for an average albumen exposure of 5 to 10 minutes in direct sunlight and half an hour to several days in shade, for exposure being carried past the point where the print looks right because density is lost in toning and fixing, for the degree of overprinting depending on binder, negative and toning bath, and for the starting point of one and a half stops for albumen and two stops for salted papers; the same section for watching the margins and making a first check shortly after they appear to have reached maximum density, for bronzing as the guide to maximum density with its greenish lustre and the explanation that silver has migrated to the surface and formed a coherent shiny film, and for the old advice to print until the shadows are just bronzed; Some Precautions in Printing, for neither paper nor frame being excessively dry because moisture is needed for good sensitivity and contrast, for the paper never being damp because silver nitrate transferred to the negative causes red stains, for the 1 mil Mylar spacer, for the doubled image at the edges when a cold frame is put in sunlight and paper and negative expand unequally, and for the instruction never to open the frame to check exposure in sunlight or open shade but to bring it inside to a room lit by a low-wattage white incandescent lamp; Chapter Eight, The Practice of Gold Toning, for the eleven factors that influence the outcome and for the recommendation to leave prints untoned as a basis of comparison; Strength of Gold Toning Solutions, for porous papers such as arrowroot and plain salted paper requiring 0.1 to 0.2 g of gold chloride per litre against 0.4 to 0.5 for glossy albumen because porous papers tone more quickly and would over-tone in the stronger baths, for toning by inspection taking 3 to 15 minutes, for carrying toning well past the first visible change, for 17 to 20 degrees C with constant agitation, for the toner being ruined by even a trace of fixer, for judging in weak incandescent light, for the deceptiveness of judging a print lying flat in a tray, and for the five-minute running-water wash after toning and before fixing; Gold Toner Formulae, for the borax, sodium acetate and thiocyanate baths; Chapter Nine, Theory of the Fixation Process, for the inventory of what is present in an exposed unprocessed print and for thiosulfate having the fewest drawbacks; History of Fixation with Thiosulfates, for Herschel's application of sodium thiosulfate on 29 January 1839 and for the distinction between fixing and Talbot's stabilising with strong sodium chloride; Chemical Reactions Involved in Fixation, for at least three different silver-thiosulfate complexes, for the requirement that thiosulfate be present in excess or insoluble complexes form which cannot be washed out, for one of the complexes being soluble only in fresh thiosulfate, for two baths being necessary in consequence, and for fixation being completed rapidly while prolonged fixation is much more injurious than is generally believed because thiosulfate penetrating the fibres becomes almost impossible to remove; The Practice of Fixation, for the alkaline bath of 150 g of sodium thiosulfate pentahydrate and 2 g of sodium carbonate per litre, for the two reasons the alkalinity is needed - preventing any acid introduced from decomposing the thiosulfate and liberating sulfur, and preventing an acid bath from attacking the finely divided image silver and excessively bleaching highlights and middletones - for the working temperature of 18 to 20 degrees C, for making the bath with slightly warmer water because heat is consumed in dissolving, for the risk of blistering albumen if the temperature differential is too great, for the two trays and the four plus four minutes with constant agitation and the five-second drain, and for the statement that this procedure is applicable to all silver printing-out papers; Fixer Exhaustion, for the difficulty of establishing the exhaustion point, for the literature estimate of no more than 150 8 by 10 prints per litre of 15 per cent solution, for Reilly's own far more conservative figure of no more than 10 to 15 such prints per litre where longest life is wanted, for the high silver content of printing-out papers relative to develop-out materials as the reason, and for fixer being cheap relative to the other costs; Color Changes During Fixation, for the dramatic change from brilliant purple or brown to a much yellower duller brown with loss of density, for the solid-solution account of the unfixed image, for the packing of the particles and the fall in refractive index on removal of the silver chloride, for the reddening on first meeting wash water being caused by swelling of the image layer, and for prints becoming more neutral and gaining slightly in density as they dry and the layer contracts; Washing of Prints, for the absorption of thiosulfate into the paper fibres making print washing harder than film washing, for the rate slowing tremendously at low concentrations, for the impossibility in practice of removing every trace by water alone, for the image being in much more intimate contact with the fibres than in a modern paper with a baryta and gelatin substratum so that the base paper can become a reservoir of image-threatening substances, and for the statement that experimental evidence on the washing of albumen and salted paper prints is almost nonexistent so that the factors known for gelatin prints are assumed to hold; Washing Aids, for water being such a poor remover of low levels of thiosulfate that an extra step is needed, for the displacement of absorbed thiosulfate by more soluble ions, and for 1 per cent sodium sulfite being the best washing aid for these papers; Washing Conditions and Apparatus, for sufficient flow over the entire print surface, for the whole volume being changed at least every five minutes, for hand agitation being absolutely necessary where more than two prints share a tray with a siphon, and for nineteenth-century practice ranging from twelve hours according to Abney to fifteen minutes according to Haddon and Grundy; Washing Time, for thicker base paper needing longer, for albumen probably needing substantially longer than arrowroot or plain salted paper because of its less porous image layer, for the recommended times being safe for glossy albumen and all other salted papers, and for some papers being injured by prolonged washing; Method for Washing Albumen and Salted Papers, for the 2 to 4 minute wash then 3 to 4 minutes with constant agitation in 10 g of anhydrous sodium sulfite per litre used once and discarded at no more than 20 prints per litre, then 30 minutes of washing with 40 to 50 for extremely heavy stock and very thick albumen; Drying the Prints, for gentle squeegeeing face-down on clean glass or blotting with photographic blotters and air drying face up on clean fibreglass screens or blotters, for the degree of curl depending on base thickness and binder, and for drying under weights or in a book press with silicone release paper against the coated side; Chapter Ten, Preparing Prints for Display or Storage, for flattening between acid-free blotters under weights or in a book press while the prints are slightly damp rather than bone dry, for patience and against excessive pressure, for heat making plain salted papers colder in image colour and somewhat darker with Talbot's finishing hot iron as the historical case, and for most salted papers being matted rather than mounted because they are made on relatively heavy paper and carry little binder; Chapter One, The Role of Organic Binders, for the division into "active" organic substances - albumen, gelatin and the organic acids citric, tartaric and oxalic, which facilitate more complete reduction of silver chloride and themselves form light-sensitive compounds - and the others, of which starch is the most useful, which are not active but keep the light-sensitive material on the surface and prevent a dull sunken-in appearance; the same section for the location of the light-sensitive layer being one of the most basic dynamics of any photographic paper, for deep penetration lowering the maximum density and giving a matte surface because light reflected from the paper is scattered by the fibres, for a compact layer on top of the fibres minimising that scattering and greatly increasing maximum density, for a smooth transparent binder minimising scattering in the whites so the paper looks more brilliant and more contrasty, for the gain in sharpness and resolution that follows from keeping the image on the surface, and for albumen being applicable pure for a glossy paper or diluted to any strength with a corresponding loss of gloss, detail and brilliance; Chapter Three, Photographic Printing Before 1850, for Talbot's prints being reddish brown because of the gelatin sizing used by English paper makers while French papers used starch sizing and gave different results, for Davanne and Girard investigating and explaining that difference, and for no organic binder being used in salting solutions until the late 1840s; Plain Salted Paper, for plain salted papers having little or no organic binder and being matte-surfaced and of relatively low maximum density, for some organic material being necessary even so, for the sizing already in the paper usually being insufficient, for the porosity of the rawstock being the largest single factor, for watercolour paper giving very flat prints and early photographers choosing the smoothest stocks available, and for the neutral citrate variant making prints more reddish and slightly more brilliant; Contrast Control in Salted Papers, for each paper having a characteristic gradation, for plain salted papers being very soft-working and requiring negatives of far greater density range than any modern develop-out paper, for the more matte a paper is the lower its contrast is likely to be, for albumen therefore requiring a less contrasty negative than plain salted paper, for the chloride content of the salting solution affecting contrast, for large increases being possible only with chromates, for Hrdliczka's mid-1890s discovery of the chromate effect and the late-1890s introduction of chromated papers with small sales, for nineteenth-century photographers depending mainly on negative density for contrast control which is why so many intensifier formulae appear in period manuals, and for the judgement of many writers that the best salted paper prints are always made in sunlight with optimum negatives and without contrast-enhancing additions; Arrowroot Papers, for the binder being boiled arrowroot starch, for surface qualities from very matte to a dull gloss according to the amount of starch and the smoothness of the rawstock, for arrowroot prints being considerably more brilliant and richer-looking than plain salted papers with a longer density range and more delicate detail, for DeBrebisson's first starch papers of 1854 using tapioca, for arrowroot emerging as the most suitable starch and starch papers almost completely displacing plain salted papers for matte prints, for the mid-1850s rise of businesses selling salted and sized photographic papers, for albumen's ascent to unchallenged dominance during the last half of the 1850s, for starch papers continuing among a small number of photographers and arrowroot remaining an article of commerce well into the twentieth century, for the carte de visite making maximum detail necessary, for the renewed interest in matte papers from the 1880s and the public regarding matte papers as more artistic by 1900, for platinum toning helping the acceptance of arrowroot papers, and for the economics of printing-out papers driving the last arrowroot and plain salted papers off the market after the First World War; Preparation of Arrowroot Paper and Coating of Papers with Arrowroot Salting Solution, for the formula, the boiled-cream method, the skin of burst grain hulls, tapioca and rice starch as alternatives, the presence of citric acid because starch is not an active substance and without it the prints would be grey and flat which are the hallmarks of a pure chloride image, the warm purple after exposure changing to yellowish brown after fixation in the absence of toning, the floating of solutions containing 2 per cent arrowroot or less, the heavier coatings obtained by immersion and drawing out over glass rods, the pinned sheet and 3 to 4 per cent paste applied with a flat brush then evened with a dry round brush, the sponge and squeegee alternative, and the sensitising of arrowroot paper on 12 per cent silver nitrate with 4 to 5 per cent citric acid for half a minute to a minute and a half with the warning that too long a float gives grey and flat prints especially on porous papers; Chapter Five, Alternative and Hybrid Papers, for whey, casein, agar-agar, carrageenin, Iceland moss and resins as alternative binders, for each having a characteristic effect and for combinations being possible, for a whole range of effects from varying the dilution of one binder, for pure albumen giving glossy paper, 1 plus 1 dilution a half-matte paper, 1 plus 6 a paper almost indistinguishable from other matte salted papers, and even a 2 per cent albumen solution significantly improving depth and contrast over a paper with no organic binder at all, for many early prints being made with diluted albumen as a conscious choice, for gelatin about 1850, albumen 1850, starch 1854 and whey in the early 1850s with lactose as its active sizing ingredient, for fewer and fewer prints being made with plain salt water during 1850 to 1855, for most leading photographers after 1855 using a salting-sizing solution based on albumen in some dilution, gelatin, starch or whey, for the majority of mid-1850s prints being matte but not the very deep matte of simple salted paper, and for paper manufacturers beginning to offer specially sized and salted papers; the same chapter for the difficulty this creates for identification, for matte salted papers presenting the difficulty more often than glossy papers because there is less binder to display its characteristics, for materials in smaller quantities tending to resemble each other, for differences in toning obscuring the clues image colour might provide, for matte salted paper prints of the early period often being the ones most in need of attention, for glossy albumen being distinguishable from gelatin printing-out paper fairly easily, for factory albumenising being dominant by 1865, for matte salted papers becoming the province of artistic amateurs and select professionals in the last third of the century, for the 1880s appearance of Algeinpapiere from Iceland moss, resin papers with mixed resin-gelatin and resin-starch binders, and matte albumen papers of albumen and starch, mainly produced in Europe, for the popularity of true platinum prints and the soaring platinum price making a platinum-toned silver print cheaper than a platinotype so that papers were sold as "silver-platinum paper", for matte albumen being the most popular commercial article among these papers though a small percentage of the market, and for all matte salted papers being out of commercial production by the end of the 1920s; Resin Papers, for resins as paper sizing through the century, for thick resin deposits being impermeable so that toning, fixing and washing are difficult, for the yellow colour of some resins and the discoloration of some rosin batches keeping resin papers from wide use, for Henry Cooper's 1880s mixture of resin and gelatin giving a matte paper with soft results similar to platinum prints especially with combined gold and platinum toning, and for the resin soap being precipitated and made insoluble when the paper meets the silver solution, analogously to albumen; Resin-Arrowroot Paper, for von Hubl's 1896 method; Matte Albumen Paper, for its being a matte salted paper prepared with a mixture of albumen and starch, for Hubl's invention and his 1896 Der Silberdruck auf Salzpapier, for the original formula of equal volumes of albumen and a 2 per cent arrowroot solution first published in Photographische Rundschau in February 1895, for E. Just's ready-sensitized paper of 1898 and Trapp and Munch's of 1902, for the half-matte paper of 1913 made by increasing the proportion of albumen, for Trapp and Munch's eighteen base stocks, for the colour being brownish red untoned, purplish black with gold alone and warm brown to black with combined gold and platinum, for matte gelatin printing-out papers being confusable with matte albumen and matte albumen usually having a slightly rougher more matte surface, for Trapp and Munch ceasing production in 1929 as the last maker, and for the last glossy albumen paper being made about 1926; Chapter Seven, Using a Gray Scale to Measure Gradation and Contrast, for the 21-step method, for Hubl's finding that glossy albumen equalled platinum paper in scale length while salted papers exceeded platinum by a considerable margin, for plain salted papers having the longest scale and albumen the shortest, and for Hubl's comparison of the shape of the three curves; Effect of Binder Materials on Tone Reproduction, for glossy papers needing a shorter-range negative because a transparent binder minimises diffuse reflection and scattering by the fibres, and for the ranking of plain salted, matte, and albumen papers by the negative density range each wants; Appendix C, Guidelines for the Identification of Albumen and Salted Paper Prints, in full - for the difficulty of setting out guidelines for hand-crafted products, for identification depending almost wholly on experience and judgement, for the guidelines being intended to narrow the range of possibilities rather than to make a positive identification, for the necessity of seeing and handling original prints, for tipped-in specimens in period journals as labelled examples, for making prints oneself as a way to learn identification, for the advice not to rely on reproductions or descriptions; Guideline I, for silver prints of the era generally showing deterioration or chemical blemishes and for a perfectly intact unblemished image usually indicating a photomechanical process or a gelatin or collodion printing-out paper; Guideline II, for image colour being one of the most important factors but requiring experience, for the complications of fading, yellowing, photomechanical mimicry and hand colouring, for prints in original condition being usually warm brown, purplish-brown, purple or purplish-black, seldom black, never green though severely faded albumen prints sometimes have a faint greenish tinge, and for about 85 per cent of albumen prints showing noticeable yellow or yellowish-brown stain in the whites and highlights; Guideline III, for surface characteristics alone being little help without corroborating indicators, for salted paper prints being rough or matte-surfaced while albumen prints are smooth with a greater or lesser gloss, for salted papers being made on both smooth and porous stocks of various weights while albumen prints after 1860 were generally on very smooth lightweight stock, for albumen prints of 1850 to 1870 being usually less glossy than those of 1870 to 1890 because of burnishing and double coating, for albumen paper having no baryta and gelatin substratum so that emulsion-type gelatin and collodion papers are generally smoother, and for albumen's characteristic crackled or crazed surface texture; Guideline IV, for internal evidence in the image and on the mount, for the assumption that negative and print are contemporary, for the chart of most common types of photographic paper - salted papers 1840-1855, albumen 1855-1895, gelatin and collodion printing-out papers 1895-1905 - for transition periods making dates unhelpful, for prints of 1840 to 1850 being plain salted paper prints except in rare calotype cases, for 1850 to 1860 being a transition with unprecedented variety at mid-decade and no possibility of differentiating the matte salted papers at a glance, for 1860 to 1885 being a time of reasonable certainty in which studio portraits and stereo views are especially likely to be albumen and a print of any kind not on albumen is unusual, and for the mid-1880s beginning a thirty-year period of great diversity ended by the First World War, after which develop-out bromide and chlorobromide papers dominated until the early 1960s; Chapter Two, Work Areas, for the separate wet and dry areas, for 18 to 20 degrees C and 45 per cent relative humidity, for the requirement to be able to eliminate white light from all work areas, for yellow bug-lite 60 W incandescent bulbs and the statement that there is no need to work in the dim light of the safelights required for modern papers, and for sensitised papers not being hung where people pass underneath; Equipment, Trays, for new trays labelled for each operation, for the silver tray ideally being glass and for a stainless steel tray not being recommended; Paper, for all-rag pure cellulose papers, for their wet strength, for the effect of a coarse porous surface, and for the diagnostic that a print looking better by transmitted than by reflected light means the solution sank too deep; Chapter Three, Plain Salted Paper, for the formula approximating the materials of the 1840s and its neutral-citrate variant, for the need of some organic material, for the effect of rawstock porosity, for examining the sheet for a front and back side and marking the back in pencil, and for the three-minute float and the three-minute sensitisation on a 12 per cent silver solution; Floating the Paper on the Salting Solution, for floating being preferred because it prevents the blotchy patches caused when silver solution reaches the back, for the temperature match that prevents curling, for the remedy of misting the back or folding a half-inch flap on all four sides, for the two folded corners used as handles, for bowing the sheet and lowering it corner to corner rather than from the middle, for piercing bubbles with a toothpick, for timing from the moment all bubbles are broken, for peeling the sheet off slowly, for hanging by the two corners of the long edge, for pressing the dried sheets flat under weights, for salted paper keeping indefinitely in a cool dry place, and for the salting being done in white light; Contrast Control in Salted Papers, for the chloride content affecting contrast, for large increases requiring chromates, and for the judgement that the best prints are made without contrast-enhancing additions; Arrowroot Papers and their preparation and coating, for the boiled starch method, for starch not being an active substance, for the citric acid, and for the shorter float on a 12 per cent silver bath containing 4 to 5 per cent citric acid; Chapter Six, Sensitization, for silver nitrate being sold as colourless crystals and technical or ACS grade being sufficient, for the double replacement reaction, for the sensitiser needing to be about four times the strength of the salting solution, for distilled or de-ionised water and the cloudy precipitate tap water causes, for the simplest sensitising solution of 120 g per litre, for keeping the chloride at about 2 to 2.5 per cent and the silver bath at 10 to 12 per cent, for stronger solutions making larger grains less likely to be absorbed into the fibres, and for starch papers needing strong baths and short floats; Techniques of Sensitization, for the caution to wear approved eye protection and tightly fitting gloves, for silver nitrate causing permanent irreversible eye damage, for skin staining and argyria on repeated absorption, for washing hands immediately, for sheets dripping silver solution posing a special hazard to the eyes, for sensitising and drying under proper safelight illumination, for the two-and-a-half to three minute float, for conditioning the paper so it is not excessively dry, for the glass tray and the three-minute egg timer, for lifting slowly so hardly a drop leaves the sheet, for hanging at 5 to 7 degrees and blotting the lower corner, and for not over-drying; Brush Sensitization, for the advantages of less made-up solution and no sensitiser on the back, for the risk of streaks, for the wide flat Japanese brush bound with thread rather than a metal ferrule because silver nitrate reacts with the metal and stains the print, for slightly stronger solutions being used in brush coating, for washing the brush in distilled water and reserving it, for the Blanchard's brush, for two applications where shadow density is insufficient, for the measles caused by insufficient sensitisation, and for paper-white round spots with hard edges being air bubbles under the sheet while light brown stained spots are bubbles under the salting solution; Exhaustion of the Silver Solution, for the bath losing both strength and volume, for starting at 12 per cent and maintaining 10 to 12 per cent, for a 12 per cent bath remaining satisfactory for perhaps two or three batches, say thirty 11 by 14 prints, before a determination is needed, for the rule of thumb of replenishing the lost volume with a solution twice as strong, for the worked example of 150 mL of 24 per cent restoring a litre that has fallen to 850 mL, for citric acid being replenished on volume lost, and for the rule of thumb not being suitable for continuous use; the titration section and Appendix B, for Volhard's method with sodium thiocyanate and a ferric ammonium sulfate indicator acidified with nitric acid, worked out by Irving Pobboraysky, and for its use on albumen sensitising baths as early as 1875; Decolorizing the Silver Solution, for the bath turning brown and eventually almost black, for the cause being organic matter dissolving from the sizing or binder and reducing some of the silver to the metallic state, for about 15 g of kaolin per litre clearing it repeatedly, for shaking and letting it settle overnight, for filtering as the alternative, and for filtering being necessary when a surface scum appears; Preserving Sensitized Paper, for one or two days of useful life, for yellowing in 8 to 12 hours in extremely humid and warm conditions, for the yellow being spontaneously reduced metallic silver, for the progression to deep reddish brown and finally to a black bronzed surface over several months in dark storage, for slowing it by a tightly closed container in a cool dry place, for slightly yellowed paper still being usable because the fixer removes some of the finely divided silver from the highlights, and for the recommendation to sensitize, print and process on the same day; Techniques for Preserving Sensitized Albumen and Salted Papers, for 5 per cent citric acid in the sensitising bath giving the maximum preservative effect while as little as 1 per cent extends usable life noticeably, for the alternative of brushing a 2 per cent citric acid solution on before salting or after sensitising, for preserved papers having to be scrupulously kept out of white light because the slightest actinic exposure forms metallic silver that catalyses further reduction, and for Adolf Ost's 1869 publication of the idea; Ammonia and Other Additives to the Silver Bath, for the ammonia-nitrate process of 1840 to 1860 and its rapid yellowing, and for the danger of fulminating silver if an ammoniacal silver bath is boiled down; Reclamation of Silver Wastes, for only 6 to 8 per cent of the silver forming the image, for most of the recoverable silver being in the first and second changes of wash water, for precipitating it with sodium chloride or sodium carbonate, for fixing solutions being evaporated to a sludge, for print trimmings and spoiled prints being a source, for 60 per cent recovery being typical in a nineteenth-century gallery, and for the judgement that recovery is usually not worth the trouble for a small user because of refiners' minimum charges; Chapter Three, Resume of Processing Steps, Step 1 Initial Wash, for the excess silver nitrate retarding or completely preventing toning if it is not removed and for black stains being the result if it is still present when the print is fixed; Chapter Six, Brush Sensitization, for the "measles" - blotches or light spots in dense areas caused by insufficient sensitisation from a too-weak silver solution or insufficient residual sensitiser - for nothing being possible for prints already exposed while unexposed sheets may be re-floated or re-brushed with a stronger solution, for paper-white round spots with hard definite edges being air bubbles under the sheet during sensitising, and for similar spots with a light brown stain being bubbles under the sizing-salting solution; Exhaustion of the Silver Solution, for the bath losing strength to the chloride and volume to the paper and for the consequences of insensitive flat prints or the measles; Chapter Seven, Characteristics Required in Negatives, for these papers requiring negatives of far greater density range than develop-out papers and for a compromise negative printing well on neither kind; Effect of Binder Materials on Tone Reproduction, for a matte surface needing relatively more reduced silver to produce a deep black; Exposure Time, for exposure being carried past the point where the print looks right, for the two-stop starting figure for salted papers, and for bronzing as the guide to maximum density; Chapter Eight, The Practice of Gold Toning, for the eleven factors influencing the outcome including the thoroughness of the initial wash, the pH of the toning solution, the strength, temperature and age of the gold solution and the time of immersion; Gold Chloride, for the yellow to colourless decolorisation being the best guide to the state of an alkaline bath, for the sodium acetate bath needing 24 hours to ripen, for a too-alkaline bath toning quickly and losing activity quickly so that a bath can contain a great deal of gold and no longer tone at all, and for most alkaline baths being one-use and going inactive spontaneously after a few hours with no clue other than the cessation of toning; Strength of Gold Toning Solutions, for the toner being ruined by even a trace of fixer; Theory of Noble Metal Toning, for the acid gold(III) bath in which one gold atom replaces three of silver so that toning lags far behind bleaching and the result is a flat lifeless reddish image; Chapter Nine, Chemical Reactions Involved in Fixation, for the requirement of excess thiosulfate or insoluble complexes form that cannot be washed out, for one complex being soluble only in fresh thiosulfate, and for prolonged fixation being much more injurious than is generally believed because thiosulfate penetrating the fibres becomes almost impossible to remove; The Practice of Fixation, for the two reasons an alkaline bath is specified - preventing acid from decomposing the thiosulfate and liberating sulfur, and preventing an acid bath from attacking the finely divided image silver and excessively bleaching highlights and middletones; Fixer Exhaustion, for the conservative capacity of no more than 10 to 15 prints of about 8 by 10 inches per litre against the literature's 150, and for the high silver content of printing-out papers being the reason; Color Changes During Fixation, for the shift to a yellower duller brown with loss of density and its physical explanation; Washing of Prints, for the image being in much more intimate contact with the fibres than in a modern baryta paper so that the base paper becomes a reservoir of image-threatening substances, for the rate of washing slowing tremendously at low thiosulfate concentrations and the impossibility of removing every trace by water alone, and for experimental evidence on washing these papers being almost nonexistent; Chapter Eleven, The Era of Salted Papers 1840-1855, for the fading and staining that threatened to discredit photography on paper, for Henneman's statement that of twenty-five Pencil of Nature prints made in one batch with only three washings some remained perfect and others totally failed, for many amateur salt prints of the same period surviving much better than the Reading prints and the observation that mass-produced images get poorer fixing and washing than individual efforts, and for the 1855 committee's finding that the most ordinary cause of fading is sulfur, intrinsic from hyposulphite left in the print or extrinsic from the atmosphere, and much more rapid in the presence of moisture; Highlight Yellowing in Albumen Prints and Causes of Highlight Yellowing, for the silver bound to sulfur-containing side groups of the protein, for Davanne and Girard's 1859 finding that 2 per cent potassium cyanide removed all silver where strong hypo did not, for Spiller's 1868 argentic organic compound detected by moistening the white surface with ammonium sulfide and watching a brown stain appear, for Haddon and Grundy's measurement that a thoroughly fixed and washed but unexposed albumen print still contained nearly 5 per cent of the silver left after sensitisation, and for the presumed mechanism of yellowing being formation of silver sulfide by reaction of bound silver with labile sulfur from residual fixer or atmospheric pollution; Assessing the Rate of Yellowing and Fading, for the human visual system pegging the lightest area in a print as a reference white so that stained highlights cannot be judged without a side-by-side comparison with a true white; Generalized Image Fading, for residual thiosulfate and silver-thiosulfate complexes as the principal internal causes and atmospheric sulfur compounds and oxidising gases such as ozone as the external ones, and for albumen prints not responding to bleach-and-redevelop restoration because the residual silver in the highlights redevelops with the image, the redevelopment gives insufficient density and the restored colour is out of character; Deterioration Caused by Defective Mounts and Mounting Adhesives, for about 95 per cent of albumen prints having been mounted, for the thin good-quality top and bottom sheets over a lignin-loaded pulp core, for the decomposition products of lignin migrating through the top layer and attacking the photograph causing staining and brittleness and accelerating fading and yellowing, for putrefied starch or gelatin adhesives doing the same, for foxing from mould, fungus or metallic salts in the board, for the danger being especially acute where the print is on thin stock because very little barrier exists between the silver image and the mount, and for removal from a defective mount and careful remounting being the only preservation technique that has proven itself in practice; Preface — the salted paper print dominant 1840 to 1855 and the albumen print 1855 to 1895, and the statement that the albumen print "accounts for approximately 85 % of the total number of surviving 19th-century photographic prints"; Chapter One, The Role of Organic Binders — the "active" organic substances, the location of the light-sensitive layer and its effect on maximum density and on gloss; Chapter Four, Albumen Paper — the early history and the letter signed "H.L." of 11 May 1839, the invention of the process by Blanquart-Evrard and his communication of 27 May 1850, the disappearance of albumen paper as a commercial article in 1929, the preparation of the albumen solution, the coating by floating, double coating, sensitising on a 10 to 12 per cent silver bath for 2½ to 3 minutes, ammonia fuming and Reilly's judgement of it, and the toning, fixing and washing of albumen paper; Chapter Six — the keeping time of sensitised paper and the citric acid preservative; Chapter Ten — mounting, and the storage range of 18 to 20 °C at 35 to 45 per cent relative humidity; Chapter Eleven, Highlight Yellowing in Albumen Prints — the 85 per cent and 15 per cent figures for moderate to severe yellowing and the explicit statement that they rest on the author's accumulated experience rather than on a formal statistical sample; Chapter One, The Role of Organic Binders — the "active" organic substances albumen, gelatin and the organic acids, the statement that they facilitate more complete reduction of silver chloride and themselves form light-sensitive substances such as silver albumenate, the contrast between an image confined to the surface and one penetrating the fibres, and the effect of dilution on gloss, detail and brilliance; Characteristics of Printing-Out Papers — the colloidal size of the aggregate silver particles, the dependence of colour on the refractive index of the medium, and the colour changes on fixing and on drying; Chapter Two, Binder Materials Used in Printing Papers, Albumen — the specific gravity of 1.040, the brittle transparent dried mass, the 15 per cent solution of powdered albumen approximating native egg white, insolubility in alcohol and coagulation by alcohol, coagulation above 65 °C and by contact with salts of metals, the coagulation by silver nitrate and the formation of silver albumenate, the pH of 7.8, the use of fresh alkaline albumen only for matte papers, and the beating that denatures proteins of different viscosities into a homogeneous liquid; Chapter Four, Albumen Paper — the letter of "H.L." in The Athenaeum of 11 May 1839, Hunt's 1841 suggestion, the rediscoveries of 1865 and 1866, Blanquart-Evrard's invention and his communication of 27 May 1850, his original recipe, the discovery that partially decomposed albumen coats more evenly and glossier, the fermentation technique and the Dresden factories, the separation of the whites and the chalazae, the chloride percentages and their effect, the sample preparation of albumen, the coating by floating, drying temperature and gloss, and Double Coating of Albumen Paper in full; Chapter Seven, Effect of Binder Materials on Tone Reproduction and Using a Gray Scale to Measure Gradation and Contrast — Hübl's finding that glossy albumen paper has the same scale length as platinum paper and that salted paper exceeds both, and his comparison of the shape of the three curves; Chapter Eleven, Causes of Highlight Yellowing in Albumen Prints — Davanne and Girard in December 1859, Carey Lea in 1866, Spiller's paper of 14 January 1868 and Haddon and Grundy's measurement of nearly 5 per cent retained silver; Chapter Two, Binder Materials Used in Printing Papers, Albumen — the specific gravity of 1.040, the brittle transparent dried mass, the 15 per cent solution of powdered albumen approximating native egg white, insolubility in and coagulation by alcohol, coagulation above 65 °C and by salts of metals, the pH of 7.8, and the beating that denatures proteins of different viscosities; Chapter Two, Paper — the smooth heavily sized stock, and the two mills; Chapter Four, Preparation of the Albumen Solution — only the freshest eggs, about one ounce of albumen per large egg, the complete separation without yolk, blood or chalazae, the egg separator and the two-bowl method, the sale of the yolks, the chloride percentages of 1 to 1.5, 1.5 to 2.5 and above, the choice between ammonium and sodium chloride, the chloride dissolved in a minimum of water and added before beating, the exemption where a blender is used, the sample preparation of 15 g ammonium chloride, 2 mL glacial acetic acid and 30 mL water added to 1 litre of albumen, beating for 3 minutes or until wholly frothed, settling covered for 24 hours, straining through muslin under pressure, one week refrigerated, several weeks of usable life afterwards, and the sensory test for a spoiled batch; Chapter Four, Coating Paper with Albumen — the tray filled to a depth of two thirds to three quarters of an inch, the float of 1 to 1½ minutes timed from the moment all bubbles are broken, conditioning the paper and the solution to room temperature, filtering through muslin immediately before use, the surfactant at 4 mL per litre and its two purposes, coating one side only and never by immersion, the light circles on a dark background caused by trapped air and the need to lift thicker sheets to inspect the underside, the 10 × 12 inch starting size, hanging by two corners of the long edge, the effect of drying temperature on gloss and the 30 to 50 °C of the factory drying rooms, the rind of albumen that forms if the runoff is not blotted, and flattening the dried sheets under weights; Chapter Four, Double Coating of Albumen Paper — the gravity gradient between the top and bottom of a hanging sheet, the effect of coating thickness on colour, brilliance, toning and fixing, the discovery that a hardening step is needed between coats, the six-month warm loft, the current of steam, the 70 per cent isopropyl alcohol with the reasons for that strength, the rule that the alcohol must carry the same chloride as the albumen, pulling the sheets slowly through the tray, marking the lowest edge and reversing it for the second float, and the characteristics of double-coated paper; Chapter Four, Sensitizing Albumen Paper — that albumenised sheets "will keep very well if stored in a cool and dry place", that a rolled sheet is rolled albumen side out to minimise cracking, and that a sheet must not be excessively dry when it is sensitised; Chapter Five, Preparation of Matte Albumen Paper — Hübl's method, fresh albumen used at most 24 hours after settling, and coating by distributing the mixture on a pinned sheet rather than by floating; Chapter Six, Techniques of Sensitization — that brush sensitising suits matte salted papers "but not glossy albumen paper"; Chapter Four, Sensitizing Albumen Paper — albumenised sheets keep very well stored cool and dry, rolled albumen side out, must not be excessively dry at the time of sensitising and are conditioned overnight in a damp place, floated on a 10 to 12 per cent silver nitrate solution for 2½ to 3 minutes with no additives required, the bubble check, the slow lift with no silver reaching the back, the glass rod that Reilly calls unnecessary if the sheet is peeled slowly, mild heat to accelerate drying and the warning against over-drying, and the blotting of the runoff; Chapter Four, Ammonia Fuming — the closed box, the dish of strong ammonia, the usual 5 to 10 minutes, the purpose, the American and European practice, the resolution that a stronger silver bath or a different negative density range achieves the same end, and the judgement that for modern practice fuming "seems unnecessary"; Chapter Four, Printing and Processing Albumen Paper — the 24 to 48 hour life of sensitised paper, white light excluded with a low-wattage incandescent for inspection and the reason yellow light will not do, felt pads and the risk to a glass negative, printing too dark in every case, albumen needing slightly less overprinting than salted paper and double-coated less than single, the purple-to-brown colour out of the frame, the exposed prints kept in the dark until all are ready, and the first wash continued past the disappearance of the cloudy precipitate but not past 10 minutes in running water because excessive washing removes the last traces of silver nitrate some toners need; Chapter Four, Toning Albumen Paper — the stronger bath needed because albumen is less permeable and the silver particles more protected, the slower toning, variations in coating thickness showing immediately, full strength for ordinary glossy albumen, the untoned control print, gold toners used almost exclusively for glossy albumen, toning by inspection under weak incandescent light, the prints ending darker and colder than they look in the bath, the 10 to 15 minutes, the slate blue of over-toning and the loss of density, the judgement by transmitted light, and "redding up" in 3 per cent acetic acid; Chapter Four, Fixation, Washing and Drying of Albumen Paper — the alkaline 15 per cent sodium thiosulfate, the two fresh baths made up the day of use, 4 minutes and a 5-second drain and 4 minutes more, the reason two baths are used, the 2 g of sodium carbonate per litre that promotes fixation and helps prevent blistering, the other cause of blistering being rapid temperature change, all solutions at about 70 °F (21 °C), the 2 to 4 minute wash, the hypo clearing agent, the 30 minute final wash, and blotting and air drying face up; Chapter Six, Composition of the Sensitizing Solution — the 120 g per litre simplest bath, the eye-protection caution, the four-times rule, distilled water and why, the chloride and bath strengths for salted papers against albumen, the 8 to 9 per cent baths of 1880 to 1900 and the modern recommendation of 1.5 per cent chloride and 10 per cent or above; Chapter Six, Techniques of Sensitization — the eye and glove caution, argyria, the 2½ to 3 minute average float, conditioning the paper, the timing from the moment all bubbles are broken, blowing on bubbles, the glass tray and the rejection of stainless steel, the glass rod, the slow peel, the 5 to 7 degree line and the blotting, the warning against over-drying, brush sensitising for matte salted papers but not glossy albumen, the metal ferrule, the "measles" and the white spots from bubbles; Chapter Six, Exhaustion and Decolorizing — the 12 per cent starting bath held at 10 to 12, the two or three batches or 30 11 × 14 prints, the replenishment rule of twice-strength solution and the citric acid replenished on volume, the Volhard titration, the browning of the bath and the 15 g of kaolin per litre; Chapter Six, Preserving Sensitized Paper — one or two days of usable life, 8 to 12 hours in extreme heat and humidity, the yellow being spontaneously reduced silver, 5 per cent citric acid for maximum preservative effect and 1 per cent for a noticeable one, the effect of citric acid on print colour in albumen, Adolf Ost in 1869 and the ready-sensitised paper of 1872; Chapter Six, Ammonia and Other Additives — the ammonia-nitrate bath dissolving albumen off the paper and the fulminating silver warning; Chapter Six, Reclamation of Silver Wastes — only 6 to 8 per cent of the silver forms the image, most of the recoverable silver being in the first and second changes of wash water; Chapter Seven, Print Exposure and Exposure Time — sensitivity primarily to ultraviolet, 5 to 10 minutes in direct sunlight and half an hour to several days in shade, sensitivity considerably lowered below 5 °C, the intense source lowering contrast, overprinting by about one and a half stops for albumen and two for salted papers, bronzing as the guide to maximum density, the doubled image from a cold frame in sunlight, and the 1 mil polyester spacer; Chapter Eight, Strength of Gold Toning Solutions and Gold Toner Formulae — 0.4 to 0.5 g of gold chloride per litre for glossy albumen against 0.1 to 0.2 for matte salted papers, 3 to 15 minutes by inspection, 17 to 20 °C with constant agitation, the toner ruined by a trace of fixer, the 5 minute wash before fixing, and the borax and thiocyanate formulae; Chapter Eight, Theory of Noble Metal Toning — one gold atom for three silver in acid and one for one in alkali, and silver chloride as the by-product that fixation must remove; Chapter Nine, The Practice of Fixation and Washing — the conservative capacity of 10 to 15 8 × 10 prints per litre against the 150 that the literature suggests, the colour and density change during fixation and its physical explanation, the reddening in the first wash caused by swelling, the difficulty of washing an image in intimate contact with the paper fibres, the 1 per cent sodium sulfite washing aid and its 20-print capacity, the Method for Washing Albumen and Salted Papers in full, and the warning that prolonged washing may begin to dissolve some image layers; Chapter Ten — the mounting of albumen prints while damp, the force a thick albumen layer exerts, the caption to Figure 42, "Trimming prints using a rotary blade trimming knife and brass templates. A rotary knife made it easier to follow the outlines of curved templates", and the rolling and burnishing that followed mounting, starch as the adhesive conservators prefer, the rejection of dry mounting, window mats of museum board and the cream or ivory tint museums choose, corners and Japanese paper hinges, and Kolody's method with its cautionary note; Chapter Eleven — the sel d'or method, in which the acidity of the gold solution decomposed the thiosulfate and liberated sulfur; Chapter Eleven, Highlight Yellowing in Albumen Prints — the statement that no albumen print survives from the 19th century without some degree of staining in non-image areas, the approximately 85 per cent of extant post-1860 prints showing moderate to severe yellowing and 15 per cent apparently white, the 95 and 5 per cent figures for the 1850s, the explicit statement that these rest on the author's accumulated experience and discussions with curators and collectors rather than on formal statistical sampling, and the call for such a study; Causes of Highlight Yellowing — the chemical bonding of silver to sulfur-containing side groups, Davanne and Girard in December 1859, Carey Lea in 1866, Spiller on 14 January 1868, Haddon and Grundy's measurement of nearly 5 per cent retained silver and their printed-out demonstration, and the presumed mechanism of silver sulfide formation from labile sulfur; Assessing the Rate of Yellowing and Fading — the reference-white adaptation of human vision, the proposed monitoring programme, and the statement that silver sulfide is more chemically stable than the colloidal silver of the image so that no known treatment removes the stain; Generalized Image Fading — the internal causes of residual thiosulfate and silver-thiosulfate complexes, the external causes of atmospheric sulfiding and oxidative fading by ozone and organic solvents, and the three reasons bleach-and-redevelopment fails on albumen; Deterioration Caused by Defective Mounts and Mounting Adhesives — approximately 95 per cent of albumen prints mounted at production, the lignin core and its migrating decomposition products, foxing and mould, and remounting as the only preservation technique proven in practice; The Need for Restoration Research; Albumen Prints After 1860 — the 2 to 3 per cent chloride of the 1860s against the weaker salting of the 1880s and 1890s, more image silver giving improved resistance to fading, and the better average durability of prints of the 1860s and 1870s; Introduction of Albumen Paper 1850-1860 — the sel d'or method, the alkaline gold toners depositing more gold, and the albumen layer itself protecting the image from oxidising gases; Albumen Versus Emulsion-Type Printing-Out Papers — the 1890s mistrust, the yellowing that seemed intrinsic, and the erroneous view that all albumen prints must fade; Chapter Ten — mounting while damp, the force of the albumen layer, starch as the adhesive conservators prefer, the rejection of dry mounting, polyester sleeves and window mats of museum board in cream or ivory, Kolody's mounting method and its cautionary note about severely cracked layers, print storage boxes and enclosures, and the temperature and humidity range of 18 to 20 °C at 35 to 45 per cent relative humidity; Chapter Four — burnishing and rolling, the horny surface of a heavy albumen layer, "French Enamel", and the tinted papers from 1863 with their buff or chamois cast; Appendix C, Some Guidelines for the Identification of Albumen and Salted Paper Prints, in full; Chapter One: Printing-out papers; Classification of printing-out papers; Gold toning; Chapter 2, the role of organic binders; Chapter 3, preparing and coating albumen; Chapter 5, sensitization; Chapter 9, fixation and washing; the three denaturing treatments; Chapter 2, the role of organic binders and "active" organic substances; Chapter 3, arrowroot paper; Chapter 5, sensitization and the preservative effect of citric acid; the platinum toning of matte surfaces; Chapter 11, Causes of Highlight Yellowing in Albumen Prints — the statement that this kind of yellow staining can and does occur in gelatin and collodion as well as albumen prints; the platinum toning of matte collodion; Gold toning — the three families of bath, the decolorisation of the stock as the guide to readiness, bath strength matched to the paper, and the consequences of over-toning; Chapter 2, the role of organic binders; Chapter 3, preparing albumen and the use of fresh alkaline albumen for matte papers; the platinum toning of matte surfaces; Chapter One: Printing-out papers; Classification of printing-out papers; salting solutions and the effect of a neutral citrate; Gold toning: alkaline against acid baths, bath strength matched to the paper, and the consequences of over-toning; Albumen preparation: the eggs separated completely with no contamination of yolk, blood or chalazae; the chloride dissolved in a minimum of water and added before the beating; three minutes of beating or until the whole mixture is froth; twenty-four hours to settle; straining through muslin, squeezed if necessary; conditioning paper and solution to the temperature of the work room; floating with the centre down first, lifting a thick sheet to inspect for bubbles, drawing the sheet off slowly by one corner, hanging on an inclined line and blotting the runoff repeatedly because a dried rind makes the sheets hard to work with; the alcohol hardening bath carrying the same chloride, with no immersion time published; drying rooms at 30 to 50 degrees C; The proportion of the silver put on a sensitised sheet that ends in the image, and the recognition of print trimmings and spoiled prints as a recoverable silver source; The brush bound with thread rather than a metal ferrule; conditioning the paper and the solution to the temperature of the work room; drawing a floated sheet off slowly by one corner; Chapter 6, Fixation and Washing: the instruction to make a fixing bath with water slightly warmer than the working temperature, since dissolving the salt cools it; The brush bound with thread rather than a metal ferrule, because silver nitrate reacts with the ferrule and stains the print; the advice against a stainless steel tray; a wet fabrication area and a dry printing area with rigorous cleanliness where they share one room; Exposure by inspection and the bronzing end point; overprinting about two stops for salted papers and one and a half for albumen; the first wash of about ten minutes and the clouding as silver chloride and carbonate precipitate; gold toning at 17 to 20 degrees C for 3 to 15 minutes by inspection, judged by lifting the print; the wash of 3 to 5 minutes before fixing because interaction between fixer and toner damages colour and permanence; two four-minute baths of fresh alkaline 15 per cent thiosulfate drained at least five seconds between them; the warning that prolonged fixation is much more injurious than is generally believed and that an acid bath attacks the finely divided image silver; the short wash then 1 per cent sodium sulfite for 3 to 4 minutes at no more than 20 prints per litre; the final wash of at least 30 minutes, 40 to 50 for the heaviest stock, with hand agitation absolutely necessary; The warning that silver nitrate can cause permanent, irreversible eye damage and that sheets dripping silver solution pose a special hazard to the eyes; argyria from repeated absorption and the instruction to wash immediately after contact; the brush bound with thread rather than a metal ferrule and the advice against a stainless steel tray; the drying line not over a walkway; the proportion of coated silver that ends in the image; the refusal to recommend boiling down an ammoniacal silver bath; Highlight yellowing in albumen prints - the most common form of deterioration; approximately 85 per cent of extant prints made after 1860 showing moderate to severe yellowing and about 95 per cent of those from the 1850s; highlight yellowing being peculiar to albumen paper and not occurring in quite the same way in otherwise similar gelatin and collodion papers, so that it often serves as an identification clue; severe yellowing accompanied in most cases by a colour shift and density loss in the image, loss of highlight detail, and sometimes a greenish tinge; the time to onset affected primarily by the moisture level and temperature of storage and the amount of residual thiosulfate and silver-thiosulfate complexes; Double coating - two coatings producing papers so heavily coated that they may be brittle and hard to tone, thicker coatings becoming increasingly less permeable so that toning and fixing are more difficult, and double-coated papers having a greater tendency to curl; Sensitizing - the instruction that sheets rolled for storage are better rolled albumen side out so that cracking of the albumen is minimised; no presently known treatment removing the highlight yellowing without completely altering the character of the print; Working environment, equipment and materials - the reason albumen does not dissolve off the sheet during processing being that contact with silver nitrate in the sensitizing bath coagulates it and forms a new insoluble silver-albumen complex called silver albumenate, which is itself light sensitive and contributes to image formation; Double coating of albumen paper - the need for a hardening or coagulating step between coatings to render the first insoluble, because otherwise the second coating step dissolved off the albumen remaining from the first; the three approaches of storing the paper in a warm loft for six months, subjecting the albumen to a current of steam, and briefly immersing the sheets in a 70 per cent solution of isopropyl alcohol, with pure alcohol too strong and unevenly coagulating the layer while too dilute a solution is not strong enough to coagulate it before it partially dissolves; the instruction to add to the alcohol whatever chloride content the albumen itself carries, to prevent leaching; the pulling of sheets slowly through the alcohol tray and flattening under weights; marking the lowest edge so it hangs as the top after the second floating, to even out the runoff; Sensitizing albumen paper - sheets kept cool and dry keep well, rolled albumen side out to minimise cracking; sheets must not be excessively dry at sensitization or they will not properly absorb the silver nitrate solution, so an overnight rest in a damp place is advised, which also makes them more supple; floating on a 10 to 12 per cent silver nitrate solution for two and a half to three minutes, with no additives required in the ordinary course of printing; the care needed to avoid air bubbles trapped under the sheet, which prevent sensitization and cause white circles on the finished print, and to lift the sheet very slowly so that no silver solution reaches the back and the runoff does not mark the coating; the note that thicker coatings become increasingly less permeable, making toning and fixing more difficult, and that double-coated papers curl more and are harder to manipulate; Deterioration caused by defective mounts and mounting adhesives - approximately 95 per cent of albumen prints were mounted at the time of production; many nineteenth-century boards had thin top and bottom layers of relatively good paper laminated to a thick core of pulp with a high percentage of lignin, whose decomposition products migrate through the top layer and attack the photograph, causing staining and brittleness and accelerating fading and yellowing of the silver image; putrefied starch or gelatin adhesives producing the same kinds of deterioration; the reddish stains known as foxing and stains caused by mould or fungus growth; the removal of prints from obviously defective mounts and careful remounting with safe adhesives as the only preservation technique that has proven itself in practice, and the note that remounting does nothing to reverse deterioration that has already occurred; The characteristics of printing-out papers - a toning process usually carried out prior to fixing, which alters the colour from the yellowish or reddish brown of a fixed printing-out image to brown, purplish brown, purple or black; Generalized image fading - the principal internal causes being residual thiosulfate and silver-thiosulfate complexes left by inadequate fixing and washing; the external causes of sulfiding of the image from atmospheric sulfur compounds such as sulfur dioxide, and oxidation fading caused by oxidising gases such as ozone and organic solvents; Generalized image fading - the principal internal causes being residual thiosulfate and silver-thiosulfate complexes left through inadequate fixing and washing; the external causes of sulfiding of the image from atmospheric sulfur compounds such as sulfur dioxide and oxidation fading caused by oxidising gases such as ozone and organic solvents; the finding that albumen prints do not respond to bleach-and-redevelopment methods that have restored sulfided gelatin-based develop-out materials, because the residual silver in the highlights redevelops along with the image, the redevelopment does not provide sufficient density and the restored colour is out of character; Highlight yellowing - the conversion of albumen-bound silver to silver sulfide as the immediate cause of yellowing, with labile sulfur supplied by residual fixer or atmospheric pollution; The characteristics of printing-out papers - the colour after fixation usually being yellowish or reddish brown, so that a toning process is usually carried out prior to fixing; the explanation that dissolving the unreduced silver chloride changes the refractive index of the system and packs the silver particles more closely, which is why prints with a rich purple or brown colour after exposure change to a reddish or yellowish brown in the fixing bath; Highlight yellowing in albumen prints - the most common form of deterioration, a yellow or yellowish-brown stain in non-image areas, with approximately 85 per cent of extant prints made after 1860 showing moderate to severe yellowing and about 95 per cent of those from the 1850s; Causes of highlight yellowing - the probable origin being the chemical bonding of silver to sulfur-containing side groups on the albumen protein, so tightly held that treatment in hypo does not remove it, with the conversion of that silver to silver sulfide as the immediate cause; Davanne and Girard's 1859 finding that 2 per cent potassium cyanide removed all traces of silver while strong hypo did not, and the two drawbacks that ruled cyanide out; Spiller's 1868 report of the metal retained as a colourless argentic organic compound comparatively insoluble in hyposulphites, detected by a brown stain on moistening with sulphide of ammonium; Haddon and Grundy's measurement that an unexposed, thoroughly fixed and washed print still contained nearly 5 per cent of the silver present after sensitization, and their demonstration of printing out an image on such a sheet; the presumed mechanism of silver sulfide formation from labile sulfur supplied by residual fixer or atmospheric pollution; the human visual system pegging the lightest area as a reference white, which conceals the problem; the statement that no presently known treatment can remove the highlight yellowing without completely altering the character of the print, because silver sulfide is much more chemically stable than the colloidal silver of the image

Used by:Albumen · Ammonium chloride · Ammonia solution (ammonium hydroxide) · Ammonium thiosulfate · Arrowroot · Borax (sodium tetraborate decahydrate) · Calcium carbonate · Chloroauric acid · Chrome alum · Citric acid (anhydrous) · Gelatin · Gold(III) chloride · Isopropyl alcohol · Kaolin · Nitric acid · Potassium alum · Potassium dichromate · Potassium tetrachloroplatinate(II) · Silver · Silver chloride · Silver nitrate · Silver sulfide · Sodium acetate (anhydrous) · Sodium bicarbonate · Sodium carbonate (anhydrous) · Sodium chloride · Trisodium citrate dihydrate · Sodium thiocyanate · Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Thymol · Albumen sensitising solution · Albumen solution with its chloride · Albumenised salting solution · Cyanide fixing and toning · Double-coated albumen procedure · Fizeau's gilding solution · Gold-acetate toner · Gold-borax toner · Gold-thiocyanate toner · Dilute alkaline thiosulfate fixer for iron-silver prints · Kodak GP-1 · Kodak HE-1 · Kodak Hypo Clearing Agent and the washing accelerator Kodak patented · Kodak T-21 · Plain hypo fixing bath · Platinum toner for printing-out papers · Plain sodium thiosulfate fixer for printed-out papers · Alkaline plain-hypo fixing bath · Arrowroot salting solution · Plain salted paper salting solution · Salted paper sensitising solution · One per cent sodium sulfite washing aid · Talbot's photogenic drawing paper · Wedgwood and Davy's silver nitrate on leather · Comparison matrices · Fixers compared · Printing processes compared · P1 1839 and the Many Inventors of Photography · P1 Talbot: Photogenic Drawing, the Calotype and the Negative-Positive Principle · P2 Storage, Incompatibilities and Secondary Containment · P2 Silver Nitrate: The Reagent That Sets the Rules · P5 Gelatin, the Photographic Binder · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline · P11 Lab: Mixing Fixers from Scratch · P12 Permanence and Image Deterioration · P12 The Physics of Washing · P12 Lab: Testing for Residual Thiosulfate and Residual Silver · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Gold, Iron-Blue and the Other Metal Toners · P20 Toning, Permanence and What the Evidence Actually Supports · P21 What These Processes Need: The Negative, the Paper and the Light · P22 Part XXII Overview: The First Silver Print · P22 Gold Toning and the Permanence of a Printed-Out Silver Image · P22 Printing Out: Silver Chloride Made and Darkened in the Paper · P22 Lab: Printing, Toning, Fixing and Washing a Salt Print · P22 The Variants of the Salt Print and How a Conservator Identifies One · P22 Lab: Salting and Sensitising a Sheet of Paper · P22 Break/Fix: The Printed-Out Image That Faded · P23 Part XXIII Overview: Albumen Printing · P23 Egg Albumen: A Protein Binder and What It Does to Silver · P23 Lab: Preparing and Coating Albumen Paper · P23 Lab: Sensitising, Printing and Toning an Albumen Print · P23 The Albumen Print as an Object, and How It Decays · Process atlas · Albumen print · Arrowroot and albumenised salted paper · Calotype negative · Collodion print-out paper · Gold toned silver gelatin print · Matte albumen print · Photogenic drawing · Salted paper print · Gold-toned and palladium-toned kallitype · Preparing and coating albumen paper · Segregating alternative-process waste · Hand-coating a sheet with a rod and with a brush · Mixing a fixer · Dedicating tools to one process · The printing-out processing line · Silver nitrate at the coating bench · Albumen crazing and yellowing · Albumen layer dissolving during sensitising · Edge fading from mount and adhesive · The gold toner that did nothing because the first wash was omitted · The iron-silver print that faded within weeks · Silver mirroring and sulfiding in an untoned printed-out print · The printed-out image that bleached away in the fixer · Yellow-brown highlight stain from residual silver

corporate.kodakalaris.com

Safety Data Sheets, Regulatory Shipping Information and Article Information Sheets - Kodak Alaris Environment, Health and Safetyretrieved 2026-09-06

Sections: The whole page, and the four bookmarking steps that replace it

Used by:KODAK PROFESSIONAL XTOL Developer

d-nb.info

Meine Dunkelkammer-Praxis - Deutsche Nationalbibliothek catalogue recordsretrieved 2026-09-05

Sections: The four catalogue records for Meine Dunkelkammer-Praxis, W. Knapp of Duesseldorf, 1958, 1961, 1972 and 1978

Used by:Beutler two-solution developer

Willi Beutler - Gemeinsame Normdatei (GND) authority record 1152352989retrieved 2026-09-05

Sections: The authority record giving the dates and occupation, and the identifier the catalogue record for Meine Dunkelkammer-Praxis carries in its author field

Used by:Beutler two-solution developer

data.rijksmuseum.nl

Introduction Information and Data Policyretrieved 2026-09-06

Sections: The rights position on collection data and images - Public Domain or the Creative Commons Zero (CC0) Public Domain Dedication where the material is free of copyright or the museum has waived its rights, Creative Commons BY 4.0 where indicated, and the items that remain restricted with a copyright holder identified separately

Used by:P26 Assignment: Assessing a Historical Process for Hazard

datasheets.raspberrypi.com

Raspberry Pi Pico Datasheet: An RP2040-based microcontroller boardretrieved 2026-09-05

Sections: Section 4.2, general purpose IO - GPIO powered from the on-board 3.3 V rail and fixed at 3.3 V, GPIO0 to GPIO22 digital only, GPIO26 to 28 ADC-capable, and the reverse diode to the 3.3 V rail that limits the input voltage on those pins; section 4.3, using the ADC - the reference filtered from the switching regulator through 201 ohms into 2.2 microfarads, the inherent offset of about 30 mV varying chip to chip, and the recommendation to tie a second channel to ground as an offset measurement; section 2.3 and the pin descriptions - VBUS 5 V plus or minus 10 per cent, VSYS 1.8 to 5.5 V, and the 3V3 pin load kept below 300 mA; section 3.1, current tables; Section 1, key features - 26 multi-function 3.3 V GPIO, 12-bit 500 ksps ADC, 16 PWM channels, one timer with four alarms, and the Abracon ABM8-272-T3 crystal; section 2.3, recommended operating conditions - VBUS 5 V plus or minus 10 per cent, VSYS 1.8 to 5.5 V; the pin descriptions for VBUS, VSYS and 3V3, including the recommendation to keep the 3V3 load below 300 mA; section 4.2, general purpose IO; section 4.3, using the ADC, including the reference filter and the roughly 30 mV offset; section 3.1.2 and 3.1.3, BOOTSEL and DORMANT current tables; Section 2.3 and the pin descriptions - the 3V3 pin is an output whose external load is to be kept below 300 mA, and VBUS is the 5 V from the USB connector; section 4.2, general purpose IO - the GPIO are powered from the on-board 3.3 V rail and are fixed at 3.3 V, with a reverse diode to that rail limiting the voltage that may be applied to a pin; Section 4.3, using the ADC - the ADC reference is filtered from the switching regulator through 201 ohms into 2.2 microfarads, the converter has an inherent offset of about 30 mV that varies from chip to chip, and a second channel may be tied to ground and read as an offset measurement; Section 1, key features - 26 multi-function 3.3 V GPIO and one timer with four alarms; section 2.3, recommended operating conditions; Section 1, key features - 26 multi-function 3.3 V GPIO; section 2.3 and the pin descriptions - VBUS is the 5 V from the USB connector and the 3V3 pin is an output whose external load is to be kept below 300 mA; section 4.2, general purpose IO, powered from the on-board 3.3 V rail and fixed at 3.3 V; Section 1, key features - a dual-core Cortex-M0+ at up to 133 MHz, 26 multi-function 3.3 V GPIO and one timer with four alarms; section 4.2, general purpose IO; Section 1, key features - 26 multi-function 3.3 V GPIO of which 0 to 22 are digital only and 26 to 28 may also be ADC inputs, 16 PWM channels; section 2.3 and the pin descriptions - VBUS is the 5 V from the USB connector, VSYS accepts 1.8 to 5.5 V, and the 3V3 pin is an output whose external load is to be kept below 300 mA; section 4.2, general purpose IO, powered from the on-board 3.3 V rail and fixed at 3.3 V; Section 1, key features - a 12-bit 500 ksps analogue-to-digital converter and 26 multi-function 3.3 V GPIO of which 26 to 28 may also be ADC inputs

Used by:P14 Build: The LED Light Source and Exposure Timer · P14 Low-Voltage Electronics for the Darkroom Builder · P15 Build: The Densitometer Electronics and Firmware · P15 Photodiodes, ADCs and Measuring Light Over Three Decades · P17 Part XVII Overview: Build the Pure Silver Timer · P17 Build: The Switched Output · P17 Build: The Timer Firmware · P17 Build: The Timer Hardware · P17 Experiment: Calibrating the Timer

RP2040 Datasheet: A microcontroller by Raspberry Piretrieved 2026-09-05, 2026-09-08

Sections: Section 5.5.3.5, interpreting GPIO output voltage specifications - the 2, 4, 8 and 12 mA drive strengths are not hard limits, and the limits on the total current sourced and sunk by the IO bank; section 2.16.1.1, recommended crystals; Section 2.16.1.1, recommended crystals - Abracon ABM8-272-T3 at 12.000 MHz, frequency tolerance plus or minus 30 ppm at 25 C, frequency stability plus or minus 30 ppm, ageing plus or minus 5 ppm in the first year; section 5.5.3.5, interpreting GPIO output voltage specifications - the 2, 4, 8 and 12 mA drive strengths are not hard limits and describe how far the output voltage falls at a stated load; Section 4.9.3, ADC ENOB - characterisation at 250 ksps across silicon lots giving SINAD 53.6 to 54.6 dB and an effective number of bits of 8.6 minimum, 8.7 typical and 8.8 maximum for the nominally 12-bit converter, with the note that testing used a board carrying a low-noise external voltage reference. Section 4.9.4, INL and DNL - the integral nonlinearity error is a sawtooth rather than the expected curve, the differential nonlinearity is mostly flat and below 1 LSB but peaks at codes 512, 1536, 2560 and 3584, and the cause is a mismatch in internal capacitors of only tens of femtofarads; Section 2.19, GPIO - output drive strength settable to 2 mA, 4 mA, 8 mA or 12 mA; and the pad's behaviour as an input when the pin is not driven; Section 2.19, GPIO - output drive strength can be set to 2 mA, 4 mA, 8 mA or 12 mA, with the pad control register's DRIVE field defaulting to 0x1; section 5.5.3.5, interpreting GPIO output voltage specifications, where those figures are stated not to be hard limits but to describe how far the output voltage falls at a stated load; section 2.9.1, digital IO supply, which asks for a 100 nF decoupling capacitor close to each IOVDD pin; Section 2.16.1.1, recommended crystals - the Abracon ABM8-272-T3 at 12.000 MHz, with a frequency tolerance of plus or minus 30 ppm at 25 C, a stability of plus or minus 30 ppm and ageing of plus or minus 5 ppm in the first year; Section 2.16.1.1, recommended crystals: frequency tolerance, stability and first-year ageing of the specified 12 MHz part

Used by:P14 Build: The LED Light Source and Exposure Timer · P14 Low-Voltage Electronics for the Darkroom Builder · P15 Photodiodes, ADCs and Measuring Light Over Three Decades · P17 Build: The Timer Firmware · P17 Build: The Timer Hardware · P17 Experiment: Calibrating the Timer · Calibrating the darkroom timer

dbc.wroc.pl

Numerical investigation of sharpness in photographic layers containing DIR compounds, Optica Applicata volume XXIX number 3, pages 275 to 283retrieved 2026-09-04, 2026-09-06

Sections: Introduction: at a knife-edge exposure, development-inhibiting by-products diffuse laterally from the heavily exposed region into the lightly exposed one while fresh developer diffuses the other way, so the edge of the dense area develops faster and gives a local density maximum (the border effect) and the edge of the thin area develops more slowly and gives a local minimum (the fringe effect); acutance as a measure taken from the density trace across a knife-edge exposure; Introduction: the line spread function defined as the distribution of illuminance in the image of a slit of negligible width, and the border and fringe effects; Section 1, Introduction — the lateral diffusion of development-inhibiting by-products from the high-exposure region and of fresh developer from the low-exposure region, and the definitions of the border effect and the fringe effect; Section 2, Model — the line spread function, the chemical spread function, the effective spread function and the ratio R of border to fringe; Section 3, Experimental — the fitted values of K and Kc for three Kodak Gold colour negative films developed in C-41, and the definition of acutance as a measure related to the average square gradient of the knife-edge density profile, with Higgins and Jones's smallest visible density gradient of 0.005 density units per micrometre; Introduction - the adjacency-effect mechanism at a knife-edge exposure, in which development-inhibiting by-products diffuse laterally from the high-exposure region into the low-exposure region while fresh developer diffuses the other way, so that development runs faster at the edge of the dense area and gives a local density maximum called the border effect and slower at the edge of the thin area and gives a local density minimum called the fringe effect; Experimental - the edge measurements made by scanning across knife edges with a microdensitometer, with the distance axis in micrometres; and the acutance definition, in which the starting and stopping points are set by the smallest visible density gradient, which Higgins and Jones found to be 0.005 density units per micrometre; Introduction - development-inhibiting by-products diffusing laterally from a heavily exposed region into a lightly exposed one, giving the border and fringe effects

Used by:P3 Diffusion, Swelling and the Journey Into the Emulsion · P4 Grain, Speed and Resolution · P8 Acutance, Adjacency Effects and Compensating Development · P27 Experiment: Agitation, Stand and Semi-Stand Development · Bromide drag

digitaltruth.com

510-Pyro, in the Photographic Chemical Formulas and Technical Data database (FormulaID 161)retrieved 2026-09-05

Sections: The whole entry — the five composition lines, the mixing instruction, the dilution, the starting-point development time, and the two notes on extended development and on the phenidone revision

Used by:510-Pyro

Photographers' Formulary Palladium Printing Kit, catalogue number 07-0007: instructionsretrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: PALLADIUM SALTS; clearing with dilute citric acid; PALLADIUM SALTS; the function of potassium chlorate in Sensitizer B; clearing with dilute citric acid; The older eight-page printing of the palladium sheet, mirrored by Digitaltruth. Cited for the corroboration of the two printing defects the current sheet still carries — the "15-ml 20% palladium solution" and the "1.67 drops" — and for its 50 °C/120 °F ceiling on heating, where the platinum sheet of the same house prints 50 °C/122 °F; The opening description and the warning that "palladium metal can be etched from the print if the clearing solution contains too much citric acid"; Chemicals contained in this kit, for the same 30 g of citric acid; Mixing the solutions needed for palladium printing, Dilute Citric Acid, for "place 1000 ml of water at 120 degrees F in a storage container with a plastic cap and add 30 grams of citric acid ... When dissolved add 1000 ml of cold water to bring the final solution to 2000 ml", followed by "this dilute citric acid is much weaker than that used to clear platinum prints. Palladium metal can be etched from a print by a more concentrated solution of acid"; and Etching, for the identical three-tray procedure at five minutes a tray with the same rotation; Directions, for the statement that palladium is less sensitive to contrast control with potassium chlorate and that twice as much is therefore used; Chemicals contained in this kit; Palladium Salts; Mixing the solutions — Sensitizer B, Dilute Citric Acid and Potassium Oxalate Developer; Mixing the sensitizer, the five drop tables; Development and Clearing; Chemicals contained in this kit and Mixing the solutions needed for palladium printing — Potassium Oxalate Developer, for what a palladium kit sold today actually supplies, and for the anticoagulant and poison warning that goes with it; Chemicals contained in this kit, for the same 227 g of potassium oxalate as the platinum kit; For your chemical safety, for the anticoagulant and poison warning; Mixing the solutions needed for palladium printing — Potassium Oxalate Developer, for the 227 g into 700 mL rather than 500 mL and for the statement that the developer has an indefinite life and may be replenished with fresh solution to maintain volume; Development, for room temperature or 90 to 100 F, the two-minute minimum and the statement that a palladium print cannot be over-developed; Mixing the solutions needed for palladium printing — Dilute Citric Acid at 30 g to 2000 mL and Potassium Oxalate Developer; Development and Clearing, for the statement that the dilute citric acid is much weaker than that used for platinum because palladium metal can be etched from a print by a more concentrated acid; Chemicals contained in this kit; Palladium Salts; Mixing the sensitizer, for the drop tables; and the statement that palladium is less sensitive to contrast control with potassium chlorate than is platinum; Mixing the sensitizer, for the five drop tables and the parts columns, and the statement that palladium is less sensitive to contrast control with potassium chlorate than is platinum; Chemicals contained in this kit; Palladium Salts; Mixing the solutions needed for palladium printing — Sensitizer B and Dilute Citric Acid; Sensitizing the paper, for the area covered; Mixing the sensitizer, for the five drop tables and the parts columns; and the statement that palladium is less sensitive to contrast control with potassium chlorate than is platinum; Kit contents; the division of labour between ferric oxalate and the palladium salt; the potassium chlorate contrast agent and its mechanism

Used by:Palladium(II) chloride · Potassium tetrachloropalladate(II) · Sodium tetrachloropalladate(II) · Photographers' Formulary platinum and palladium printing kits · EDTA, citric acid and hydrochloric acid clearing sequence · Three-solution drop system for platinum and palladium · Sodium citrate developer · Willis's potassium oxalate developer · P25 Lab: Exposing, Developing and Clearing a Palladium Print · P25 Noble Metal Chemistry and the Platinotype · P25 Experiment: Tonal Scale, Contrast and Image Colour in Palladium · P25 Lab: Preparing the Sensitiser and Coating for Palladium · Palladiotype

Photographers' Formulary Platinum Printing Kit, catalogue number 07-0001: instructionsretrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: PLATINUM SALTS; FOR YOUR CHEMICAL SAFETY; The older eight-page printing of the same platinum sheet, mirrored by Digitaltruth. Cited for the three places where the two printings differ: it prints the dilute citric acid as "1000 ml of water at 120 ° C" where the current printing has 120 °F, it gives the 15 mL kit's coverage as 12.5 sheets of 8 × 10 where the current printing gives 12, and it lists Thomas Shillea's Instruction Manual For The Platinum Printing Process among the resource materials, which the current printing drops; The opening description, that the paper "is then exposed by contact printing, developed in potassium oxalate, and finally cleared with a solution of citric acid to remove the iron salts"; Chemicals contained in this kit, for the 30 g of citric acid supplied; Mixing the solutions needed for platinum printing, Dilute Citric Acid, for "place 1000 ml of water at 120 degrees in a storage container with a plastic cap and add 30 grams of citric acid. Stir the solution (or cap and shake the container) until citric acid has dissolved. When dissolved add 500 ml of cold water to bring final solution to 1500 ml"; and Etching, for the three trays, five minutes in each with intermittent agitation, the first tray becoming "cloudy and yellowed in appearance ... due to any remaining Ferric Oxalate being etched from the paper", the rotation by which the first tray is discarded and the second and third move up so that "the third tray should always contain a clear acid solution", the warning that this step "is a critically important part of the process and is usually passed over too casually" and that a print not properly etched "will darken with age and in this way can be destroyed", the warning not to leave a print unattended to float, because air bubbles cause uneven etching, and Washing the finished platinum print, for a complete exchange of water every five minutes for an hour, water no colder than 68 degrees F, and distilled water recommended; Chemicals contained in this kit; For your chemical safety; Ferric Oxalate, including the trihydrogen and tripotassium forms and the ferricyanide spot test; Platinum Salts; Mixing the solutions needed for platinum printing — Sensitizer B, Dilute Citric Acid and Potassium Oxalate Developer; Sensitizing the paper — Area covered; Mixing the sensitizer, the five drop tables and the worked example for a 55-drop mixture; Exposure; Processing the exposed print — Development, Etching and Washing; Chemicals contained in this kit, for the 227 g of potassium oxalate supplied; For your chemical safety, for the anticoagulant and poison warning and the instruction to use tongs or gloves; Mixing the solutions needed for platinum printing — Potassium Oxalate Developer, for the 227 g into 500 mL, the statement that not all of the solid will dissolve and the naming of the result as the saturated developer; Processing the exposed print — Development, for room temperature or 90 to 100 F, for the two-minute minimum, for the streaking risk with a heated bath and for the statement that a platinum print cannot be over-developed; Mixing the solutions needed for platinum printing — Potassium Oxalate Developer, for the 227 g in 500 mL saturated bath; Processing the exposed print — Development, for the 90 to 100 degree Fahrenheit bath, the "at least two minutes", the statement that you cannot overdevelop a platinum print and the streaking warning; Etching, for the three trays of five minutes with the rotation and the warning that a print not properly etched will darken with age; Washing the finished platinum print, for the hour with a complete exchange every five minutes; Ferric Oxalate, for the trihydrogen and tripotassium forms, the statement that the potassium salt is not recommended, the 50 degree drying ceiling and the ferricyanide spot test for photoactivity and excess ferrous ions; Platinum Salts, for the near-saturation of the 20 per cent solution and the red precipitate; Mixing the sensitizer, for the worked example that rounds 55 drops to 56 and the assumption of 20 drops per millilitre; Kit contents and the division of labour between ferric oxalate and the platinum salt; the potassium chlorate contrast agent

Used by:Potassium tetrachloroplatinate(II) · Photographers' Formulary platinum and palladium printing kits · EDTA, citric acid and hydrochloric acid clearing sequence · Three-solution drop system for platinum and palladium · Willis's potassium oxalate developer · P25 Lab: Exposing, Developing and Clearing a Palladium Print · P25 Lab: Preparing the Sensitiser and Coating for Palladium · Platinotype

Photographers' Formulary Salted (Plain) Paper P.O.P. Printing Kit, catalogue number 07-0110: instructionsretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Kit contents; Solution A, the gelatin-salt solution; Photographers' Formulary Salted (Plain) Paper P.O.P. Printing Kit 07-0110, Mixing the Solutions, Solution D (The Gold-borax Toning Bath): distilled water at 38°C/100°F 500 ml, borax 4 g, gold chloride 1% solution 8 ml, with the instruction 'Place the warm water in the mixing bowl and add the borax. Stir the solution to dissolve the solid. Add the entire contents in the gold chloride-solution bottle. Stir the solution to ensure it is homogeneous then transfer it to the storage container.' and the direction to use a 500 ml brown glass storage container; the TONING section, describing the kit's chemicals as being for alkaline gold toning which will cause a shift in print colour towards the blue, directing that the toning bath be used at 21°C/70°F with the print immersed for 6 to 12 minutes, that the print edges be trimmed to conserve the gold toner, that it is difficult to judge the end result until the print is fixed, washed and dried, and that in general the print develops a colder tone the longer it is in the toning bath, with the cold tone increasing on fixing and drying; the INTERMEDIATE WASH section, requiring the free silver nitrate to be washed from the print in a tray rather than under running water before toning and fixing; Solution E, the fixer, as sodium thiosulfate pentahydrate 50 g in distilled water at 52°C 500 ml, used for 10 minutes; and the final wash of at least one hour, with the note that the chemical treatments weaken the paper fibres; Mixing the Solutions, Solution E (The Fixer), reading distilled water at 52 degrees C / 125 degrees F 500 ml and sodium thiosulfate pentahydrate 50 g, with the instruction to place the hot water in the bowl, add the thiosulfate, stir, let it stand about five minutes and stir again because the large crystals dissolve slowly and will not dissolve unless the solution is stirred; the FIXING section, immersing and agitating the untoned or toned print for 10 minutes to remove all silver salts, with the note that the print need not be washed between the toning bath and the fixer but that the toning bath must not be contaminated with fixer; the INTERMEDIATE WASH section, requiring the free silver nitrate to be washed from the print in a tray rather than under running water before toning and fixing; the EXPOSURE section, on the lightest step of a step table that shows darkening and usually four more steps being lost on washing, toning and fixing; and FINAL WASHING, at least one hour, with the warning that the chemical treatments weaken the paper fibres so that prints abrade easily; Chemicals contained in this kit, and Solution B (The Silver Nitrate Solution), giving 13 g of silver nitrate in 100 mL of distilled water at 20 °C, the instruction to place the water in the mixing bowl and add the silver nitrate to it, the statement that silver nitrate itself is not light sensitive but decomposes in strong light to a black precipitate, and the direction to store the solution in a dark place; Sensitizing the Paper, on brushing solution B onto the dry salted sheet under a red light; Solution D, the gold-borax toning bath of 4 g of borax and 8 mL of 1 per cent gold chloride in 500 mL of water at 38 degrees C; TONING, for the untoned print's reddish brown cast, for toning being optional and normally done before fixing though it may follow the final wash, for the bath at 21 degrees C and 6 to 12 minutes, for the difficulty of judging the result until the print is fixed washed and dried, for the colder tone with longer toning and for that coldness increasing on fixing and drying, and for trimming the print's edges to conserve gold; Opening description of the process and the self-masking paragraph, for silver chloride being converted to silver metal which shields the unreacted silver chloride remaining on the paper with the greatest effect in the shadows; EXPOSURE, for the step-table method and the instruction to mark the lightest step showing darkening immediately after exposure, and for the statement that this step and usually four more are lost upon washing, toning and fixing; INTERMEDIATE WASH, for washing in a tray rather than under running water, for the first tray turning cloudy, for washing until a tray full is not cloudy, for the warning not to over-wash because the image can be lost, and for the print lightening and becoming reddish during that wash; Solution D, the gold-borax toning bath of 4 g of borax and 8 mL of 1 per cent gold chloride in 500 mL of distilled water at 38 degrees C; Solution E, the fixer of 50 g of sodium thiosulfate pentahydrate in 500 mL of water at 52 degrees C, with the note that the large crystals dissolve slowly and will not dissolve unless stirred; EXPOSURE, for the paper being sensitive only to the ultraviolet, for sunlight, a UV light box or a mercury vapour yard lamp, for 10 to 20 minutes at 18 inches from a mercury vapour lamp not being unusual, for the paper needing to be dry or it will stain the negative and the thin acetate sheet that prevents it, for the recommendation to calibrate by exposing a step table alone before printing a negative, for marking the lightest step showing darkening immediately after exposure, and for that step and usually four more being lost upon washing, toning and fixing so that exposure can be increased to compensate; INTERMEDIATE WASH, for washing in a tray rather than under running water, for the first tray turning cloudy and washing until a tray is not cloudy, for the warning not to over-wash because the image can be lost, for the print lightening and becoming reddish, and for the print remaining light sensitive until fixing so that work continues in subdued light; TONING, for the untoned print's reddish brown cast after fixing, for toning normally before fixing though it may follow the final wash, for trimming the print's edges to conserve gold, for the bath at 21 degrees C and 6 to 12 minutes, for the difficulty of judging the result until the print is fixed washed and dried, and for the colder tone with longer toning increasing further on fixing and drying; FIXING, for 10 minutes with agitation to remove all silver salts and for no wash being needed between toner and fixer provided the toning bath is not contaminated with fixer; FINAL WASHING, for at least an hour, for the print being no longer light sensitive after fixing, and for the chemical treatments having weakened the paper fibres so that they abrade easily; Contrast Control and Chemical Safety, for the potassium dichromate solution this course does not use; Chemicals contained in this kit, for the 11 g each of soft gelatin, sodium citrate and ammonium chloride and the 13 g of silver nitrate; Chemical Safety, for silver nitrate being both an oxidiser and a caustic that can cause skin burns, for the brown to brown-black stain being silver metal bound to the protein of the skin which cannot be washed off, and for the recommendation of rubber gloves; Mixing the Solutions, Solution A, for the gelatin softened in 180 mL of water at 20 degrees C and dissolved in 320 mL at 38 degrees C before the citrate and the chloride are added, and Solution B, for 13 g of silver nitrate in 100 mL of distilled water stored in a brown glass container in a dark place because silver nitrate decomposes in strong light forming a black precipitate; Preparation of the POP Paper, for a good quality single-ply paper of minimal porosity, for sizing being unnecessary because the salting solution contains gelatin, for arrowroot sizing where a porous paper is used, for salting by soaking about 30 seconds with air bubbles removed, for drying evenly by air or hair drier, for returning the excess to the storage container, for the dry salted paper storing in a dry place, and for the paper being hygroscopic and stored interleaved with soft tissue; Sensitizing the Paper, for brushing Solution B on and drying, for the statement that while Solution B can be applied under a tungsten lamp the makers do not recommend it, for pinning the sheet to a board and coating horizontally then vertically under a red light, and for streaks resulting from uneven coating; INTERMEDIATE WASH, for washing in a tray until a trayful is not cloudy and for the warning not to over-wash because the image can be lost; EXPOSURE, for the step table calibration in which the lightest step showing darkening and usually four more are lost upon washing, toning and fixing; Washing in additional trays of water until a trayful is not cloudy, and the warning not to over-wash because the image can be lost; the single fixing bath at 5 per cent for four to five minutes with periodic agitation; the difficulty of judging the result until the print is fixed, washed and dried

Used by:Trisodium citrate dihydrate · Gold-borax toner · Plain sodium thiosulfate fixer for printed-out papers · Salted paper sensitising solution · P22 Gold Toning and the Permanence of a Printed-Out Silver Image · P22 Printing Out: Silver Chloride Made and Darkened in the Paper · P22 Lab: Printing, Toning, Fixing and Washing a Salt Print · P22 Lab: Salting and Sensitising a Sheet of Paper · P22 Break/Fix: The Printed-Out Image That Faded · The printing-out processing line

docs.arduino.cc

Arduino UNO R3 (A000066) datasheetretrieved 2026-09-05

Sections: Description and section 3.2, Processor - an ATmega328P running at up to 20 MHz, fourteen digital pins and six analogue inputs, with IOREF connected to the 5 V rail

Used by:P14 Low-Voltage Electronics for the Darkroom Builder

docs.micropython.org

class ADC, analog to digital conversion, MicroPython library documentationretrieved 2026-09-05

Sections: ADC.read_u16 - one reading returned as an integer from 0 to 65535 scaled across the input range, whatever the converter's real resolution; ADC.read_u16 - one reading returned as an integer from 0 to 65535, scaled so the minimum reading is 0 and the maximum 65535; ADC.read_uv, whose calibration is left to the port

Used by:P14 Build: The LED Light Source and Exposure Timer · P14 Low-Voltage Electronics for the Darkroom Builder · P15 Photodiodes, ADCs and Measuring Light Over Three Decades

class PWM, pulse width modulation, MicroPython library documentationretrieved 2026-09-05

Sections: Constructor and methods - freq in hertz, duty_u16 setting the duty cycle as the ratio of the given value to 65535, and duty_ns setting the pulse width directly; and the note that on the rp2 port there are eight independent PWM blocks each with two outputs and a 16-bit counter, so setting the frequency of one object may affect another sharing the same generator

Used by:P14 Build: The LED Light Source and Exposure Timer

class Timer, control hardware timers, MicroPython library documentationretrieved 2026-09-05

Sections: Timer Types - most ports support hardware timers except Zephyr and RP2, which support only virtual timers, and soft-interrupt callbacks are prone to garbage-collection jitter; Timer Types - hardware timers may be more accurate for very fine sub-millisecond timing, but most ports support them except Zephyr and RP2, which support only virtual timers; class Timer - the distinction between virtual and hardware timers, the note that most ports support hardware timers except Zephyr and RP2 which support only virtual timers, and the hard keyword, where False schedules the callback as a soft interrupt allowing allocation but possibly introducing garbage-collection delays and jitter

Used by:P14 Build: The LED Light Source and Exposure Timer · P14 Low-Voltage Electronics for the Darkroom Builder · P17 Build: The Timer Firmware

Quick reference for the RP2, MicroPython documentationretrieved 2026-09-05

Sections: Timers - the RP2040 system timer provides a global microsecond timebase but only the software timer is available; ADC - four 12-bit SAR channels on GP26 to GP29, standard range 0 to 3.3 V, read_u16 across that range, and the note that after a hard reset an unconfigured pin sinks about 60 microamps and can give wrong readings; Pins and GPIO - internal pull-up on an input; Timers - the RP2040 system timer provides a global microsecond timebase but only the software timer is available, with callbacks as soft interrupts unless hard=True; ADC - four 12-bit SAR channels on GP26 to GP29, standard range 0 to 3.3 V, read_u16 across that range, and the warning that an unconfigured pin sinks about 60 microamps after a hard reset; PWM - eight slices of two channels each; Hardware I2C bus - machine.I2C(0) takes the default assignment for the Pico of scl on Pin 5 and sda on Pin 4, with the same read and write methods as the software bus, and i2c.scan() returning the addresses that answer; Pins and GPIO - the internal pull-up on an input; Timers - the RP2040's hardware timers are not exposed and machine.Timer provides virtual timers whose callbacks are prone to garbage-collection jitter and delays unless hard=True is passed; Delay and timing, with time.ticks_ms and time.ticks_diff; WDT, the watchdog timer, enabled with a timeout of which 1 s is the minimum and 8388 ms the maximum; Pins and GPIO, the internal pull-up and Pin.irq; hardware I2C, where machine.I2C(0) takes the port default of scl on Pin 5 and sda on Pin 4; Pins and GPIO - the internal pull-up on an input, and Pin.irq with its trigger constants; PWM - eight slices of two channels each, sixteen channels in total; hardware I2C, where machine.I2C(0) takes the port's default assignment of scl on Pin 5 and sda on Pin 4

Used by:P14 Build: The LED Light Source and Exposure Timer · P14 Low-Voltage Electronics for the Darkroom Builder · P15 Build: The Densitometer Electronics and Firmware · P17 Build: The Timer Firmware · P17 Build: The Timer Hardware

time, time related functions, MicroPython library documentationretrieved 2026-09-05

Sections: time.ticks_us and time.ticks_diff - counters from an arbitrary reference that wrap at an unexposed value, on which only ticks_diff and ticks_add are valid; time.sleep_us, documented as delaying for at least the requested interval; time.sleep_ms and time.sleep_us - delay for at least the given interval and may take longer; time.ticks_ms, time.ticks_us and time.ticks_diff - increasing counters from an arbitrary reference that wrap at an unexposed value, on which only ticks_diff and ticks_add are valid; ticks_ms, ticks_us and ticks_cpu - the values wrap around and only ticks_diff and ticks_add are valid on them, with the documented patterns for polling with a timeout and for scheduling events against a deadline

Used by:P14 Build: The LED Light Source and Exposure Timer · P14 Low-Voltage Electronics for the Darkroom Builder · P17 Build: The Timer Firmware

doi.org

The nature and formation of the photographic latent image, Philosophical Magazine 2 (21), pages 1149-1170retrieved 2026-09-04

Used by:P4 Part IV Overview: Silver and Light · P4 The Latent Image

The Theory of the Photolysis of Silver Bromide and the Photographic Latent Image, Proceedings of the Royal Society of London Series A 164 (917), pages 151-167retrieved 2026-09-04

Used by:P4 Part IV Overview: Silver and Light · P4 The Latent Image

download.luminus.com

SST-10-UV product datasheetretrieved 2026-09-05

Sections: The SST-10-UV datasheet: the emitter's radiant flux, its thermal derating and the maker's handling notes, cited as the class of manufacturer data a high-brightness or ultraviolet build has to be assessed against rather than against a general claim; Optical characteristics table - peak wavelength ranks at 370, 385, 395, 405 and 415 nm typical with a 10 nm spectral half width at every rank, typical radiometric flux 875 to 1015 mW, viewing angle 130 degrees, thermal resistance 1.4 C/W; and the footnote that typical radiometric flux is for reference only while minimum flux is guaranteed by the bin ordered

Used by:P29 Capstone Stage 1: The Instrument, Its Calculation and Its Commissioning · P16 Ultraviolet for the Alternative Processes: Sources, Dose, Uniformity and Hazard

downloads.cree-led.com

XLamp XP-E2 LEDs, product family data sheet CLD-DS56 rev 25Bretrieved 2026-09-05

Sections: Relative Flux vs. Junction Temperature and Relative Chromaticity vs. Current and Temperature, cited for their existence and axes as evidence that both the output and the mixture of a phosphor white LED move with temperature; and the absence of any switching or rise-time figure in the document; Characteristics - forward voltage 2.84 V minimum to 3.1 V maximum for white at 350 mA and 85 C and 3.12 V at 1000 mA; maximum DC forward current 1500 mA for white; maximum junction temperature 150 C; thermal resistance junction to solder point 5.8 C/W for white; temperature coefficient of voltage -1.5 mV/C for white; Relative Flux vs. Current, whose axes run to 1500 mA against a flux axis drawn to 300 per cent; and the absence of any switching or rise-time figure in the document; Characteristics tables - thermal resistance junction to solder point 5.8 C/W white and 9 C/W green; temperature coefficient of voltage -1.5 mV/C white, -1.2 green, -1.9 blue, -2.1 amber; maximum DC forward current 1500 mA white and green, 1200 mA royal blue and blue; maximum junction temperature 150 C; forward voltage 2.84 to 3.1 V for white at 350 mA and 85 C and 3.12 V at 1000 mA; Relative Flux vs. Current chart axes, running to 1500 mA against a flux axis drawn to 300 per cent for white; Relative Flux vs. Junction Temperature chart axes, 25 to 150 C; Relative Spectral Power Distribution - the white parts plotted from 380 to 780 nm as a narrow short-wavelength peak with a broad longer-wavelength hump, and the coloured parts as single narrow bands; Characteristics - thermal resistance junction to solder point 5.8 C/W white and 9 C/W green, viewing angle 110 degrees white and 135 green, forward voltage 2.7 V typical for green at 350 mA; Relative Chromaticity vs. Current and Temperature, cited for its existence and axes as evidence that a phosphor white LED's mixture is not fixed; and the absence of any switching or rise-time figure anywhere in the document; Characteristics - viewing angle 110 degrees for the white parts and 135 degrees for green, quoted as the angle within which half the flux is emitted; and the absence of any near-field intensity distribution in the document; Characteristics - forward voltage 2.7 V typical for green at 350 mA, viewing angle 135 degrees for green, thermal resistance junction to solder point 9 C/W for green; and Relative Spectral Power Distribution, where the coloured parts are plotted as single narrow bands. Cited as the worked example of the datasheet figures to look for on whatever emitter is bought, not as a specified part; Relative Flux vs. Junction Temperature and Relative Chromaticity vs. Current and Temperature, cited for their existence and their axes as evidence that both the output and the mixture of an LED move with junction temperature; the document gives no figure that may be transferred to another manufacturer's emitter; Characteristics - thermal resistance junction to solder point of 5.8 C/W for white, 5.7 for blue and 9 C/W for green; maximum DC forward current of 1500 mA for white and green and 1200 mA for blue; maximum LED junction temperature of 150 C; viewing angle at half maximum of 110 degrees for white and 135 degrees for blue and green; forward voltage of 2.99 V typical for white at 700 mA and 85 C, 3.14 V for blue and 3.01 V for green at 1000 mA and 25 C; temperature coefficient of forward voltage of -1.5 mV per C for white; Performance Groups - Luminous Flux, the table of flux groups measured at 350 mA, running from group K2 at 30.6 to 35.2 lm up to group S6 at 180 to 188 lm, cited as the structure of a flux specification rather than as the output of any particular part; Characteristics - maximum LED junction temperature of 150 C, thermal resistance junction to solder point, temperature coefficient of forward voltage, and viewing angle at half maximum; and the existence and axes of the relative spectral power distribution chart, the relative flux against forward current chart, the relative flux against junction temperature chart and the relative chromaticity against current and temperature charts, cited as the figures to look for on whatever emitter is bought rather than as values the course reads off; Characteristics and charts - the existence and axes of the relative spectral power distribution chart from 380 to 780 nm and of the relative chromaticity charts against forward current and against junction temperature, cited as the figures to look for on any emitter's datasheet rather than as values the course reads off; and the temperature coefficient of forward voltage of -2.1 mV per degree C for amber; Characteristics - maximum DC forward current of 1500 mA for white and green and 1200 mA for blue, forward voltage of 2.99 V typical for white at 700 mA and 85 C, thermal resistance junction to solder point of 5.8 C/W for white; Relative flux against junction temperature, plotted from 25 to 150 degrees Celsius, read here for its direction and deliberately not for its ordinates; relative chromaticity against current and temperature; thermal resistance junction to solder point of 5.8 C/W for white and 9 C/W for green; Performance groups - dominant wavelength, giving the royal blue bins from 450 to 465 nm, the blue bins from 465 to 485 nm and the green bins from 520 to 535 nm at 350 mA, used here for the wavelengths a two-channel head would actually be built from; Characteristics - thermal resistance junction to solder point of 5.8 degrees Celsius per watt for white, maximum LED junction temperature of 150 degrees Celsius, forward voltage of 2.99 V typical for white at 700 mA and 85 degrees Celsius, and the plot of relative luminous flux against junction temperature; cited here for the size of the waste-heat term in an LED head, not for any claim about a negative; Characteristics and charts - the relative spectral power distribution plotted from 380 to 780 nm, cited here only for the span over which the course's own emitter datasheets plot visible output; Relative flux against junction temperature, plotted from 25 to 150 degrees Celsius; relative flux against forward current, with the current axis to 1500 mA and the flux axis to 300 per cent of the 350 mA value; thermal resistance junction to solder point of 5.8 degrees per watt for white and 9 for green; relative chromaticity against current and temperature

Used by:P14 Experiment: Calibrating the Sensitometer · P14 Build: The LED Light Source and Exposure Timer · P14 Low-Voltage Electronics for the Darkroom Builder · P14 Sensitometer Design Principles · P14 Build: The Enclosure and Exposure Stage · P15 Build: The Densitometer Optical Head (Transmission and Reflection) · P15 Break-Fix: Diagnosing a Misbehaving Densitometer · P16 Build: An LED Enlarger Head · P16 Build: An LED Safelight · P16 Safelight: Spectra, Distance, Duration and the Fog Limit · P17 Build: The Switched Output · P17 Break/Fix: The Timer That Lies · P18 Variable-Contrast Papers: Three Emulsions, One Sheet · Negative popping · Newton's rings · Session exposure drift

drytac.com

Dry Mount Film, clear heat-activated acrylic mounting adhesive, product technical pageretrieved 2026-09-06

Sections: Technical specifications on the product page - an activation temperature of 185 to 210 degrees F (85 to 99 degrees C) and an acrylic adhesive on a thin PVC carrier, with photo framing and plaquing among the applications

Used by:P19 Lab: Washing, Drying, Flattening and Mounting the Print

Trimount Permanent Dry Mounting Tissue, product technical pageretrieved 2026-09-06, 2026-09-08

Sections: Technical specifications on the product page - an activation temperature of 194 to 210 degrees F (90 to 99 degrees C), a thickness of 3 mil (75 micrometres), the adhesive described as a heat activated solvent adhesive and as pH neutral, the applications given as photo framing and plaquing, and the statement that the product will not negatively impact any compatible substrate or media in long-term applications under normal storage conditions; the page states no dwell time, no pressure and nothing about resin-coated photographic papers; Activation temperature band published for permanent dry-mounting tissue

Used by:P19 Lab: Washing, Drying, Flattening and Mounting the Print · Mounting a print and putting it in an enclosure

ecfr.gov

40 CFR Part 459, Photographic Point Source Categoryretrieved 2026-09-04, 2026-09-05

Sections: 459.10 Applicability; 459.12 Effluent limitations guidelines; Section 459.10, applicability and the exclusion of facilities processing 150 square metres per day or less; section 459.12, the best practicable control technology limitation for silver; Section 459.10, applicability and the exclusion of facilities processing 150 square metres per day or less; section 459.12, best practicable technology limitations for silver

Used by:P2 Waste: Streams, Silver, and the Drain You Must Not Use · P12 Silver Recovery and the Responsible Darkroom · The disposal caveat

echa.europa.eu

Classification and Labelling (C&L) Inventoryretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Searched on 7 September 2026 through the public ECHA CHEM substance API for "silver sulfamate", "silver sulphamate" and CAS 14325-99-6, and no substance record was returned for any of them; Notified and harmonised classifications under CLP; Notified and harmonised classifications under CLP, and the aggregation of notifier disagreement; Notified and harmonised classifications; the number of notifiers and reports behind an aggregated entry

Used by:Silver sulfamate · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P26 Assignment: Assessing a Historical Process for Hazard · Reading GHS and CLP · Recording a safety data sheet

ehs.princeton.edu

Photography, in the Environmental Health and Safety guidance for arts and studio workretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Toning, hazards and precautions — that toning solutions are used with local exhaust ventilation, that sulphide toners must not be contaminated with acid, that a print is rinsed thoroughly after an acid bleach before it enters the toner, and that thiourea is a probable human carcinogen because it causes cancer in animals, with the advice to avoid it wherever possible; General precautions — adding acid to water and never the reverse; Developing Baths — hazards and precautions; Mixing photochemicals; Fixing baths and stop baths — hazards and precautions; Mixing photochemicals; Developing Baths — precautions; Mixing photochemicals — the instruction to use a glove box, local exhaust ventilation or a NIOSH-approved toxic dust respirator when mixing powders; Other hazards — hypochlorite bleaches releasing chlorine gas on contact with acid; Mixing photochemicals — powders, and the request for extraction or an enclosure; Color Processing: Bleaching, Fixing, and Other Steps — hazards and precautions; Color Processing: Bleaching, Fixing, and Other Steps — prehardeners and stabilizers; Cleaning acids; the instruction not to add acid to, or heat, hypochlorite bleaches; adding acid to water; Intensification and reduction — discarded intensifiers; General precautions — adding acid to water and never the reverse; storing concentrated acids; Intensifiers and reducers — hazards and precautions; Colour processing — bleaching, hazards and precautions; Disposal of photochemicals; Disposal of photochemicals; Toning — the release of hydrogen selenide from selenium salts treated with acid; Mixing photochemicals; Toning — the release of hydrogen selenide from selenium salts treated with acid, and selenium as a skin and eye irritant that can cause kidney damage; Toning — hazards and precautions; Disposal of photochemicals; Hazards — hypochlorite bleach releasing chlorine gas when acid is added; adding acid to water and never the reverse; Mixing photochemicals — powders; Toning — hazards and precautions; Intensification and reduction — the older intensifiers and reducers now discarded, cyanide among them; Toning: hazards and precautions, on sulphide toners and acid contamination, and on rinsing a print thoroughly after an acid bleach before it enters the toner; Reducers and intensifiers: potassium ferricyanide releasing hydrogen cyanide gas if heated, if hot acid is added or on exposure to strong ultraviolet light, and the record of cyanide poisoning from treating Farmer's reducer with acid; Toning — hazards and precautions for sulfide toners, and the requirement that a print be rinsed thoroughly after an acid bath before it enters a sulfide bath; Disposal of photochemicals; Photographic chemicals and their hazards: sodium thiosulfate on heating or long standing in solution decomposing to form sulphur dioxide, and darkroom ventilation as the control for it; Toning: hazards and precautions, on sulphide toners not being contaminated with acid and on rinsing a print thoroughly after an acid bleach before it enters the toner; Mixing photochemicals - the preference for liquid concentrates over powders and the dust controls where powders must be mixed; Toning — hazards and precautions; thiourea described as a probable human carcinogen with local exhaust ventilation required for toning solutions and the advice to avoid it wherever possible; sulphide toners not to be contaminated with acid; Cleaning acids — the rule that acid is added to water and never the reverse; Intensifiers and Reducers: uranium nitrate among the older, now discarded intensifiers; the hazards paragraph stating that uranium intensifiers are radioactive and especially hazardous to the kidneys; the precaution not to use mercury, cyanide or uranium intensifiers because of their high or extreme toxicity; and the statement that potassium ferricyanide will release hydrogen cyanide gas if heated, if hot acid is added, or if exposed to strong ultraviolet light, with cases of cyanide poisoning having occurred through treating Farmer's reducer with acid; Mixing photochemicals; stop baths and fixer; other hazards; Mixing photochemicals; stop baths and fixer; Mixing photochemicals; other hazards; Mixing photochemicals; developing baths; Mixing photochemicals - always add acid to the water when diluting; Developing Baths — hazards and precautions; Mixing photochemicals, and the request for a glove box, local exhaust or an approved dust respirator whenever powdered developers are mixed; Toning, hazards and precautions - that toning solutions must be used with local exhaust ventilation, that sulphide toners must not be contaminated with acid, and that a print must be rinsed thoroughly after an acid bleach before it enters the toner; Intensifiers and reducers, that potassium ferricyanide will release hydrogen cyanide gas if heated, if hot acid is added, or if exposed to strong ultraviolet light such as a carbon arc, with the record that cases of cyanide poisoning have occurred through treating Farmer's reducer with acid; and Disposal of photochemicals, which lists ferricyanide solutions among the photographic solutions to be treated as hazardous waste; Toners - that selenium is a skin and eye irritant and can cause kidney damage, that treatment of selenium salts with acid may release highly toxic hydrogen selenide gas and that selenium toners also give off large amounts of sulfur dioxide gas; and Precautions, that toning solutions must be used with local exhaust ventilation and that precautions must be taken to ensure sulfide or selenium toners are not contaminated with acids; Toners - the statement that selenium is a skin and eye irritant and can cause kidney damage, that treatment of selenium salts with acid may release highly toxic hydrogen selenide gas, and that selenium toners also give off large amounts of sulfur dioxide gas; and Precautions, that toning solutions must be used with local exhaust ventilation and that precautions must be taken to make sure sulfide or selenium toners are not contaminated with acids; Toning, hazards and precautions - that toning solutions must be used with local exhaust ventilation, that sulphide toners must not be contaminated with acid, that a print must be rinsed thoroughly after an acid bleach before it enters the toner, and that thiourea is a probable human carcinogen because it causes cancer in animals, with the advice to avoid it wherever possible; Intensifiers and Reducers - uranium nitrate among the older, now discarded intensifiers; the hazards paragraph stating that uranium intensifiers are radioactive and especially hazardous to the kidneys; the precaution not to use mercury, cyanide or uranium intensifiers because of their high or extreme toxicity; and the statement that potassium ferricyanide will release hydrogen cyanide gas if heated, if hot acid is added, or if exposed to strong ultraviolet light, with cases of cyanide poisoning having occurred through treating Farmer's reducer with acid; Intensifiers and reducers, that potassium ferricyanide will release hydrogen cyanide gas if heated, if hot acid is added, or if exposed to strong ultraviolet light such as a carbon arc, with the record that cases of cyanide poisoning have occurred through treating Farmer's reducer with acid; and Disposal of photochemicals, which lists ferricyanide solutions among the photographic solutions to be treated as hazardous waste; The photographic chemicals guidance, for the instruction to treat ferricyanide solutions as hazardous waste without qualification by dilution, recorded here as the position that disagrees with Ware's environmental argument.; Intensifiers and Reducers — the precaution not to use mercury, cyanide or uranium intensifiers because of their high or extreme toxicity, the statement that uranium intensifiers are radioactive and especially hazardous to the kidneys, and the statement that potassium ferricyanide will release hydrogen cyanide gas if heated, if hot acid is added, or if exposed to strong ultraviolet light, with cases of cyanide poisoning having occurred through treating Farmer's reducer with acid; Intensifiers and Reducers - the precaution not to use mercury, cyanide or uranium intensifiers because of their high or extreme toxicity, and the statement that potassium ferricyanide will release hydrogen cyanide gas if heated, if hot acid is added, or if exposed to strong ultraviolet light, with cases of cyanide poisoning having occurred through treating Farmer's reducer with acid; Intensifiers and reducers — that sodium or potassium cyanide is extremely toxic by inhalation and ingestion and moderately toxic by skin contact, that adding acid to cyanide forms extremely toxic hydrogen cyanide gas which can be rapidly fatal, that potassium ferricyanide will release hydrogen cyanide gas if heated, if hot acid is added, or if exposed to strong ultraviolet light, and that cases of cyanide poisoning have occurred through treating Farmer's reducer with acid; Intensifiers and Reducers — uranium nitrate among the older, now discarded intensifiers; the hazards paragraph stating that uranium intensifiers are radioactive and especially hazardous to the kidneys; the precaution not to use mercury, cyanide or uranium intensifiers because of their high or extreme toxicity; and the statement that potassium ferricyanide will release hydrogen cyanide gas if heated, if hot acid is added, or if exposed to strong ultraviolet light, with cases of cyanide poisoning having occurred through treating Farmer's reducer with acid; Intensifiers and reducers — the statement that potassium ferricyanide will release hydrogen cyanide gas if heated, if hot acid is added, or if exposed to strong ultraviolet light such as a carbon arc, and the record that cases of cyanide poisoning have occurred through treating Farmer's reducer with acid; The older, discarded intensifiers, including uranium nitrate and the mercury ones; The older, discarded intensifiers, including uranium nitrate; Stop baths and fixer; other hazards — hypochlorite bleaches and acid; potassium ferricyanide, heat, acid and ultraviolet; sulfide toners and acid carry-over; adding acid to water; Potassium ferricyanide with heat or acid; the record of cyanide poisoning from treating Farmer’s reducer with acid; ferricyanide solutions among the photographic solutions to treat as hazardous waste; Stop baths and fixer; hypochlorite bleaches and acid; potassium ferricyanide with heat or acid; sulfide toners and acid carry-over; Ferricyanide solutions among the photographic solutions to treat as hazardous waste; toning solutions and local exhaust ventilation; Mixing photochemicals from dry chemicals, and the recommendation to buy liquid chemistry where it is available; Toning solutions and local exhaust ventilation; the warning that treating selenium salts with acid may release highly toxic hydrogen selenide; Mixing photochemicals from dry chemicals; other hazards; Storage of concentrated acids and other corrosive chemicals on low shelves to reduce the chance of face or eye damage from a breakage; Toning solutions and local exhaust ventilation; ferricyanide solutions among the photographic solutions to treat as hazardous waste

Used by:P29 Capstone Stage 5: The Toned Print and the Alternative-Process Print · Acetic acid (glacial) · Amidol · Ammonium thiosulfate · Ascorbic acid · Barium sulfate · Catechol · Chlorine · Erythrosin · Formaldehyde · Gallic acid · Glutaraldehyde · Glycin · Hydrochloric acid · Hydroquinone · Mercury(II) chloride · Metol · Nitric acid · p-Aminophenol · Phenidone · Potassium cyanide · Potassium ferricyanide · Potassium ferrocyanide (anhydrous) · Potassium ferrocyanide trihydrate · Pyrogallol · Silver selenide · Sodium ascorbate · Sodium selenosulfate · Sodium sulfide · Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Sulfamic acid · Sulfuric acid · Tannic acid · Tetraazaindene · Thiourea · Thymol · Titanium dioxide · Uranyl nitrate hexahydrate · Cyanide fixing and toning · Kodak T-52 · Kodak R-4 · Kodak R-4b · Kodak ST-1 · Kodak T-1a · Kodak T-7a · KODAK PROFESSIONAL XTOL Developer · Moersch MT3 Variotoner · EDTA, citric acid and hydrochloric acid clearing sequence · Uranium toner · P2 Part II Overview: The Photographic Chemistry Laboratory · P2 Storage, Incompatibilities and Secondary Containment · P2 Waste: Streams, Silver, and the Drain You Must Not Use · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P2 Laying Out the Laboratory: Wet Areas, Dry Areas and Contamination Control · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P3 Acids, Bases and pH · P9 Experiment: Comparing Developing Agents · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P20 The Toners We Study and Do Not Use · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Experiment: The Exposure Scale, Maximum Density and Contrast of a Cyanotype · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Assignment: Assessing a Historical Process for Hazard · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 Uranium, Mercury and the Heavy-Metal Treatments · P28 Reading the Negative as Evidence: Thin, Dense, Flat and Contrasty · Uranium toned print · Uranotype and Wothlytype · Chemical incompatibilities · The acid exclusion rule at a hexacyanoferrate or thiocyanate bench · Responding to an acid spill · Segregating alternative-process waste · Adjusting pH with a concentrated alkali · Handling a selenium toner and its waste · Responding to a spilled solid · Responding to a spill · Stop bath preparation · Storage rotation and shelf separation · Running a toning session · Weighing a solid · Weighing and handling developing agents

electrical.theiet.org

BS 7671, Requirements for Electrical Installations, IET Wiring Regulations, 18th editionretrieved 2026-09-05

Sections: Cited by number only, for the publisher's statement that BS 7671 is the national standard for electrical installations in the United Kingdom; no requirement is reproduced or paraphrased

Used by:P17 Switching Lamps Safely: Isolation, Certified Modules and the Mains Boundary

electricalsafetyfirst.org.uk

Plugs and fuses, Electrical Safety Firstretrieved 2026-09-05

Sections: Check the plug meets British Standard BS 1363, marked on the back; the fuse is the correct size and meets BS 1362, marked on the fuse body; and appliances should come with a standard UK plug or a conversion adaptor rather than a travel adaptor, since otherwise they may not meet UK safety requirements; Check your plugs - the plug meets British Standard BS 1363, marked on the back; the fuse is the correct size and meets British Standard BS 1362, marked on the fuse body, and check the manufacturer's instructions if you are not sure which fuse to use; the note that a fuse blows if an appliance draws too much current and that the blown fuse stops the cable and appliance overheating; Checking the plug and cable, and Checking inside the plug - check the plug meets British Standard BS 1363, marked on the back, and that the fuse is the correct size and meets British Standard BS 1362, marked on the fuse body; appliances other than shavers and hardwired items should come with a standard UK plug or a conversion adaptor rather than a travel adaptor, and otherwise may not meet UK safety requirements; the signs of overheating and the instruction not to ignore burn marks or arcing sounds; and the standardisation of plug fuses on 3 A and 13 A

Used by:P16 Build: An LED Safelight · P17 Build: The Switched Output · P17 Switching Lamps Safely: Isolation, Certified Modules and the Mains Boundary

en-standard.eu

ISO 18915:2000 and BS ISO 18915:2000 catalogue records, European Standards online storeretrieved 2026-09-06

Sections: The two catalogue records from which the above was read - ISO 18915:2000, edition 1, released 2000-12-14, 16 pages in English; and the BSI adoption BS ISO 18915:2000, released 2001-03-15, 26 pages, ISBN 0 580 37029 1, status given as Standard, ICS 37.040.20 Photographic paper, films and plates, cartridges. Both reproduce the same scope clause word for word

Used by:P20 Toning, Permanence and What the Evidence Actually Supports

en.wikisource.org

Archer, Frederick Scott, in the Dictionary of National Biography 1885-1900, volume 2retrieved 2026-09-06

Sections: The whole entry: Archer's dates of 1813 to May 1857; Schoenbein's discovery of gun-cotton in 1846 and Maynard of Boston preparing collodion, an ethereal solution of gun-cotton, for surgical purposes in 1847; Archer applying collodion to photography in 1850 by adding an iodide to it and immersing the coated glass plate while wet in a solution of nitrate of silver; the first account published in the Chemist in March 1851; the priority sentence that Archer does not seem to have been the first to suggest the application but that there appears no doubt whatever that he was the first to carry it into effect; that he did not patent it, possibly because he did not realise its value, though he patented a development of no practical value in 1855; that the process was at first employed only for positives and that its greater suitability for negatives was found later; and the subscription and crown pension granted to his children on the ground that their father had reaped no benefit from an invention which had been a source of large profits to others

Used by:P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That

Herschel, Sir John Frederick William, in the Dictionary of National Biography 1885-1900, volume 26retrieved 2026-09-04

Sections: Herschel, Sir John Frederick William: photography, the actinometer, and the photograph on glass; Herschel, Sir John Frederick William: photography

Used by:P1 Herschel: Hypo, Prussian Blue and the Words of Photography · P1 1839 and the Many Inventors of Photography

Leather, in the Encyclopaedia Britannica, eleventh edition, volume 16retrieved 2026-09-06

Sections: The opening division of leather into tanned, tawed and chamoised, and the section headed Tawing: that tawing means conversion of skins into leather by mineral salts such as alum, that the tawing paste is "a mixture of alum, salt, flour, egg yolk and water" with quantities that "diverge widely, every dresser having his own recipe", one worked example being 9 lb alum and 5 lb salt to 100 lb of skin, and that calf kid and glove kid are treated on these lines

Used by:Wedgwood and Davy's silver nitrate on leather

Photography, in the Encyclopaedia Britannica, eleventh edition, volume 21retrieved 2026-09-04, 2026-09-06

Sections: Action of the Spectrum on Chromic Salts; The collodion process — the iodising and bromising of collodion; Development — the later organic developers and the colour of their silver deposit; Action of Light on Uranium; The Daguerreotype, for gilding described as the next improvement in the process after the accelerating vapours, for the practice introduced by H. L. Fizeau in which gold chloride is mixed with hyposulphite of soda and the levelled plate bearing a sufficient quantity of the fluid is warmed by a spirit-lamp until the required vigour is given, and for the statement that nearly all the daguerreotypes extant have been treated in this manner and that their permanence is in great measure due to the operation; The paragraphs on Nicéphore de Niepce, for the summary that the asphaltum is powdered and the oil of lavender dropped upon it in a wine-glass and the whole gently heated, for the developer at ten parts by volume of white petroleum, and for the statement that Niepce was the first to found a process giving pictures subsequently unaffected by light; Halation: Abney's 1875 investigation of reflection from the back surface of the plate, and the practice of backing a plate; Effect of Hydrogen Peroxide on Sensitive Plates: W. J. Russell on fog from vapours and the destruction of the light image; Orthochromatic and panchromatic plates: pinaverdol, pinachrom and pinacyanol, Konig's isocyanines, and the practice of screening off blue and violet with yellow or orange screens; Action of the Spectrum on Chromic Salts — that the result of spectrum action is confined to the most refrangible end, commencing in the ultra-violet, that a solution of potassium bichromate absorbs those rays alone which are effective in altering it, and that the change is only possible in the presence of organic matter of some kind such as gelatin or albumen. Action of the Spectrum on Asphaltum — that the action seems to be continued into and below the red while the blue rays are the most effective, and that the action of light on this body is to render it less soluble in its usual solvents. Printing with Chromates, Carbon Prints — Ponton's May 1839 report that paper saturated with the salt and dried, then exposed through a drawing, gives a yellow picture on an orange ground requiring nothing to fix it but washing in water; Becquerel's 1840 announcement that paper sized with iodide of starch and soaked in the dichromate was more sensitive than unsized paper; Dixon's gum arabic and dichromate on lithographic stone; the ranking of Dixon's method after Talbot's photo-engraving process published in 1852; Poitevin's English patent of 13 December 1855 for a direct carbon print by rendering gelatin insoluble; Pouncy's publication of 1 January 1859 and the absence of halftones; Abbe Laborde's 1858 diagnosis quoted in full, that in the sensitive film however thin two distinct surfaces must be recognised, that the action of light commences on the outer surface, and that in the washing the half-tones therefore lose their hold on the paper and are washed away; Burnett's 1858 paper to the Photographic Society of London quoted at length on printing through the unprepared side and on why printing from the prepared side prevents the attainment of half-tones by washing; Fargier's 1860 collodion-coating patent; Swan's 1864 patent and carbon tissue of gelatin, sugar and colouring matter sensitised with potassium or ammonium bichromate; Johnson's 1869 patent on swelling adhesion and the use of soap against brittleness; Sawyer's 1874 flexible support and the reason a metal plate made the dark parts contract away from the lighter; and the statement that as the tissue is coloured it is not possible to ascertain by inspection whether printing is sufficient, so that an actinometer or a strip of silvered paper is used alongside. Photo-mechanical Printing Processes — Poitevin's claim that a dichromated gelatin film after exposure and damping receives greasy ink on the parts affected by light; Tessie de Motay and Marechal of Metz in 1865 as the first to produce halftones from gelatin films by greasy ink, with the note that Paul Oreloth seems to have made the discovery previous to 1854 since his patent of that year states that his designs were inked with printing ink before being transferred to stone or zinc; A. Albert of Munich, who found that the hardening action of light itself, applied to the surface next the plate, could give the film the durability that added hardeners could not, adopted a transparent plate, and took over a thousand impressions where fewer than a hundred had been possible; the name Lichtdruck; and Edwards's heliotype. Photo-lithography — Asser of Amsterdam in 1859 and Osborne of Melbourne in 1860; The spectral action of a dichromate solution and the requirement for organic matter; The spectral action of a dichromate solution, and the requirement for organic matter; Uranium salts acted on only by the light they absorb, the nitrate absorbing in the green-blue

Used by:Ammonium dichromate · Cadmium bromide · Chlorohydroquinone · Potassium dichromate · Uranyl nitrate hexahydrate · Fizeau's gilding solution · Niépce's bitumen heliograph coating · P4 Grain, Speed and Resolution · P4 Reciprocity Failure and the Life of the Latent Image · P4 Spectral Sensitivity and Colour Response · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · Carbon print · Collotype · Gum bichromate · Photoglyphic engraving · Uranotype and Wothlytype

Talbot, William Henry Fox, in the Dictionary of National Biography 1885-1900, volume 55retrieved 2026-09-04, 2026-09-06

Sections: Talbot, William Henry Fox; The patent history: that in 1852, at the request of the presidents of the Royal Society and the Royal Academy, Talbot threw his discoveries open while keeping portrait-taking for sale to the public; and that in December 1854 he tried and failed in the courts to enforce his patent against a photographer the entry names Sylvester Laroche, whose collodion development he held to infringe it

Used by:P1 1839 and the Many Inventors of Photography · P1 Talbot: Photogenic Drawing, the Calotype and the Negative-Positive Principle · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · Calotype negative

Wedgwood, Thomas, in the Dictionary of National Biography 1885-1900, volume 60retrieved 2026-09-04, 2026-09-06

Sections: Wedgwood, Thomas, by Leonard Darwin: born at Etruria Hall, Staffordshire, 14 May 1771, died at Eastbury, Dorset, 10 July 1805; the full title of the 1802 paper; the statement that the primary end of the experiments was a camera picture and that he was unsuccessful in it, no effect being obtainable in any moderate time; that he failed to find any method of fixing his picture and the copies had to be kept in the dark; and the dismissal of Meteyard's attempt to connect Josiah Wedgwood's Paris agent Daguerre with the inventor of the daguerreotype; Wedgwood, Thomas

Used by:Wedgwood and Davy's silver nitrate on leather · P1 Wedgwood, Davy and the Problem of Permanence

epa.gov

Household Hazardous Waste (HHW)retrieved 2026-09-04

Sections: Safe management of household hazardous waste; regulating HHW; What household hazardous waste is; improper disposal, including pouring products down the drain or into storm sewers; contacting the local environmental, health or solid waste agency

Used by:P2 Waste: Streams, Silver, and the Drain You Must Not Use · The disposal caveat

RCRA in Focus: Photo Processingretrieved 2026-09-05

Sections: Waste minimisation for the fixing step — follow manufacturers recommendations for pH levels and stop bath use, keep fixer covered when not in use to prevent oxidation, replenish the strength of the fixer by adding ammonium thiosulfate, and add ammonium thiosulfate to silver-contaminated baths to extend the allowable buildup of silver; Silver recovery methods — photo processing produces silver-bearing waste streams ranging from less than 5 mg/L to 12,000 mg/L, the concentration depending on the stage the waste comes from and the material being processed, and the silver existing predominantly as the soluble silver-thiosulfate complex with small amounts of silver sulfide; Silver recovery from rinsewater — up to 10 per cent of the recoverable silver lost by carry-over into the rinse tank even with an efficient recovery system and an effective squeegee, spent rinsewater typically 1 to 50 mg/L and too low for economical recovery by electrolysis or metallic replacement, with the iron by-product of metallic replacement precluding reuse of the rinsewater; Ion exchange recovering as much as 98 per cent of the silver and reaching effluents as low as 0.1 ppm; Chemical precipitation — the statement that photo processors no longer use sulfide, borohydride or amine borate precipitation because of the hazards associated with their use; Silver recovery methods — metallic replacement described as an active solid metal contacting a solution containing dissolved ions of a less active metal, with the more active metal going into solution as an ion and iron in the form of steel wool used most often for its economy and convenience; the statement that the silver in photographic waste streams exists predominantly as the soluble silver-thiosulfate complex with small amounts of silver sulfide

Used by:P11 Fixer Capacity, Exhaustion and Residual Silver · P12 Silver Recovery and the Responsible Darkroom · P12 Experiment: Small-Scale Metallic Replacement

espressif.com

ESP32 series datasheetretrieved 2026-09-05

Sections: Features - 12-bit SAR ADC of up to 18 channels; section 5.3, DC characteristics tabulated at 3.3 V

Used by:P14 Low-Voltage Electronics for the Darkroom Builder

fau.edu

Safety and Disposal Guidelines for the Use of Photographic Chemicalsretrieved 2026-09-04, 2026-09-05

Sections: Developers — hazards and safe work practices; Hardeners — hazards, precautions and disposal; Section IX, Hardeners — the hazards, the precautions, and the disposal instruction that spent and unused or concentrated hardener be collected and containerised with a hazardous waste label; Section VI, Intensifiers — the extremely hazardous components, naming mercuric chloride, mercuric iodide, potassium cyanide, sodium cyanide and uranium nitrate; Developers — the instruction to avoid pyrogallol and catechol and to substitute phenidone; Section III, Stop Baths — the precaution to purchase dilute solutions of acetic acid rather than concentrated ones, and to use a water rinse step between developer and stop bath to reduce the formation of sulfur dioxide gas; Section III, Stop Baths — the common ingredients, the precaution to purchase dilute solutions of acetic acid rather than concentrated ones, and the precaution to use a water rinse step between developer and stop bath to reduce the formation of sulfur dioxide gas; Section IV, Fixer — the statement that fixer solutions release sulfur dioxide more rapidly when contaminated with acid from the stop bath; Section III, Stop Baths — the precaution to purchase dilute solutions of acetic acid rather than concentrated ones

Used by:Catechol · Formaldehyde · Glutaraldehyde · Glyoxal · Pyrogallol · Sodium cyanide · 510-Pyro · Pyrocat-HD · P8 Staining and Tanning Developers · P10 Experiment: Measuring Stop Bath Capacity · P10 Stop Bath Formulations and the Fixer Interaction · Stop bath preparation

fda.gov

FDA to Revoke Authorization for the Use of Red No. 3 in Food and Ingested Drugsretrieved 2026-09-04, 2026-09-05

Sections: HFP Constituent Update, 15 January 2025 — the revocation, the Delaney Clause, the two male-rat studies, the statement on human relevance, and the reformulation deadlines; HFP Constituent Update, 15 January 2025: the revocation, the Delaney Clause, the two male-rat studies, the agency's own statement on human relevance, and the reformulation deadlines; HFP Constituent Update, 15 January 2025: the revocation as a matter of law under the Delaney Clause following two studies showing cancer in laboratory male rats by a rat-specific hormonal mechanism, together with the agency's statements in the same notice that the mechanism does not occur in humans, that relevant human exposure levels are typically much lower, and that claims of human risk are not supported by the available scientific information; the reformulation deadlines of 15 January 2027 for food and 18 January 2028 for ingested drugs; The revocation under the Delaney Clause, the rat-specific hormonal mechanism, and the agency's statement on human relevance

Used by:Erythrosin · Erythrosin sensitising stock · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P5 Washing, Digestion and Sensitisation

firstcall-photographic.co.uk

Firstcall Photographicretrieved 2026-09-05

Sections: Darkroom chemistry, paper, film, tanks, dishes, safelights and raw chemicals

Used by:The Pure Silver laboratory planner

Firstcall Photographic — search results for "gold toner"retrieved 2026-09-06

Sections: Moersch MT10 Gold Toner 250 ml working solution at 32.99 pounds and Fotospeed Blue Toner 150 ml at 23.99 pounds, reduced from 34.00; and, on the parallel search for gold chloride, no listing for the raw salt

Used by:P20 Gold, Iron-Blue and the Other Metal Toners

Firstcall Photographic — search results for "potassium ferricyanide"retrieved 2026-09-06

Sections: Jacquard Cyanotype Potassium Ferricyanide 113 g at 10.99 pounds, 230 g at 17.99 pounds reduced from 22.99, and 450 g at 31.99 pounds; and Moersch Bleach Concentrate Hexacyanoferrat/Bromide 100 ml at 7.99 pounds

Used by:P20 Part XX Overview: Toning Chemistry

Firstcall Photographic — search results for "selenium toner" and "sepia toner"retrieved 2026-09-06

Sections: Kodak Rapid Selenium Toner 946 ml at 21.95 pounds, reduced from 26.90; Ilford Selenium Toner 1 L at 51.52 pounds, reduced from 57.24; Fotospeed ST20 Sepia Toner 150 ml, making 1.5 L, at 11.87 pounds, reduced from 16.99; Foma Fomatoner Sepia Toner, 2 x 250 ml, at 23.99 pounds; Moersch MT10 Gold Toner 250 ml working solution at 32.99 pounds; Fotospeed Blue Toner 150 ml at 23.99 pounds, reduced from 34.00; Kodak Rapid Selenium Toner 946 ml at 21.95 pounds, reduced from 26.90, in stock; Ilford Selenium Toner 1 L at 51.52 pounds, reduced from 57.24, in stock; Ilford Multigrade Warmtone RC Glossy 8 by 10 in, 25 sheets, at 37.42 pounds, in stock, and 100 sheets at 129.41 pounds; and Ilford Multigrade Cooltone RC Glossy 8 by 10 in, 25 sheets, at 35.58 pounds, in stock, and 100 sheets at 135.24 pounds. Recorded as a magnitude for items the course's price file does not hold, not as planner data; Read on 6 September 2026 for a current United Kingdom supply route. Kodak Rapid Selenium Toner 946 ml at 21.95 pounds reduced from 26.90, in stock; Ilford Selenium Toner 1 L at 51.52 pounds reduced from 57.24, in stock; Fotospeed ST20 Sepia Toner 150 ml making 1.5 L at 11.87 pounds reduced from 16.99, in stock; Foma Fomatoner Sepia 2 x 250 ml at 23.99 pounds; Moersch MT10 Gold Toner 250 ml working solution at 32.99 pounds; Moersch MT2 Carbontoner 100 ml at 14.99 pounds; Fotospeed Blue Toner 150 ml at 23.99 pounds reduced from 34.00; Ilford Multigrade FB Warmtone S-Matt 8 x 10 in at 58.50 pounds for 25 sheets reduced from 65.00 and 191.60 pounds for 100 reduced from 212.89. The same retailer's mount-board search returned foam-centred board, slide mounts and copystands, and no board whose listing mentions conservation quality, buffering or ISO 18902

Used by:P20 Part XX Overview: Toning Chemistry · P20 Experiment: Selenium Toning and the Print Curve · P20 Assignment: The Toned Print

Firstcall Photographic — search results for "sepia toner" and "potassium ferricyanide"retrieved 2026-09-06

Sections: Fotospeed ST20 Sepia Toner 150 ml, making 1.5 L, at 11.87 pounds, reduced from 16.99; Foma Fomatoner Sepia Toner, 2 x 250 ml, at 23.99 pounds; Jacquard Cyanotype Potassium Ferricyanide 113 g at 10.99 pounds, 230 g at 17.99 pounds and 450 g at 31.99 pounds; and Moersch Bleach Concentrate Hexacyanoferrat/Bromide 100 ml at 7.99 pounds

Used by:P20 Lab: Bleaching and Redeveloping a Sepia Print

foma.cz

Bezpecnostni list: FOMAFIX (safety data sheet, in Czech)retrieved 2026-09-06

Sections: Section 1.1 and 1.2, product identifier and identified use; section 2.1, 2.2 and 2.3, classification, label elements and other hazards; section 3.2, composition of the mixture; section 5.1 and 5.2, extinguishing media and the evolution of oxides of sulphur; section 6, accidental release; section 7.2, storage; section 8.1, the Czech workplace limit for acetic acid, and 8.2, personal protection; section 9.1, physical and chemical properties; section 10, stability, hazardous reactions, conditions to avoid and decomposition products; section 11 and 12, toxicology and ecotoxicology; section 13, waste codes and disposal; section 14, transport; section 15.2, the absence of a chemical safety assessment; and section 16, the classification method and the revision history

Used by:Foma FOMAFIX

Bezpecnostni list: FOMAFIX H (safety data sheet, in Czech)retrieved 2026-09-06

Sections: Section 1.2, identified use as a hardening solution added to the fixer for machine processing of X-ray film; section 2.1 and 2.2, classification and the label sentence naming sulphuric acid and aluminium sulphate; section 3.2, composition of the mixture

Used by:Foma FOMAFIX

Bezpecnostni list: FOMATOL LQN (safety data sheet, in Czech)retrieved 2026-09-06

Sections: Section 1.2, identified use; section 2.1 and 2.2, classification and label elements; section 2.3, other hazards; section 3.2, composition of the mixture; section 5.2 and 10.6, evolution of sulphur dioxide; section 7.2, storage; section 8.1, Czech workplace limits; section 8.2, personal protection; section 9.1, physical and chemical properties; section 10, stability, hazardous reactions and incompatible materials; section 11 and 12, toxicology and ecotoxicology; section 13, waste codes and disposal; section 14, transport classification; section 16, the classification method and the revision history

Used by:Foma FOMATOL LQN developer

Bezpečnostní list: FOMATONER SEPIA, díl A (safety data sheet, FOMATONER Sepia part A)retrieved 2026-09-06

Sections: Section 2.1, the mixture classified Eye Irrit. 2 H319; section 3.2, the composition table naming a ferricyanide, CAS 13746-66-2, at less than 15 per cent and a bromide, CAS 7758-02-3, at less than 15 per cent; section 9.1, pH 5.8 to 6.2; and section 13.1, the waste codes 09 01 01*, 20 01 17* and 15 01 10* and the instruction not to flush the product into the sewer

Used by:P20 Lab: Bleaching and Redeveloping a Sepia Print

Bezpečnostní list: FOMATONER SEPIA, díl B (safety data sheet, FOMATONER Sepia part B)retrieved 2026-09-06

Sections: Section 2.1, the mixture classified Eye Irrit. 2 H319, Skin Irrit. 2 H315 and STOT SE 3 H335; section 3.2, the composition table naming CAS 584-08-7 at less than 40 per cent, disodium dihydrogen ethylenediaminetetraacetate at less than 5 per cent, a bromide at less than 3 per cent, and index number 612-082-00-0, CAS 62-56-6, EC 200-543-5 at less than 1 per cent carrying Carc. 2 H351, Repr. 2 H361d, Acute Tox. 4 H302 and Aquatic Chronic 2 H411, which is thiourea; section 9.1, pH about 11.5; and section 13.1, the waste codes and the instruction not to flush the product into the sewer; The document header, version 8.0, revision date 4 February 2016, replacing version 7.1; and section 2.1, the classification Eye Irrit. 2 H319, Skin Irrit. 2 H315 and STOT SE 3 H335. Cited here for the document's date, as the currency of the sheet for the packaged sepia kit sold in the United Kingdom

Used by:P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Assignment: The Toned Print

Developers for black-and-white negative films (Fomadon)retrieved 2026-09-04, 2026-09-05

Sections: FOMADON LQN; FOMADON LQR; FOMADON P; FOMADON P; FOMADON R09; FOMADON LQN; FOMADON LQR; FOMADON R 09 - the general description, the two dilutions, the developing capacity per package, and the development-time table for Fomapan 100, 200, 400 and Foma Ortho 400 at 1+25 and 1+50; FOMADON R09 — a liquid concentrate of a fine-grain normal-working para-aminophenol negative developer, at 1+25 or 1+50; FOMADON R09, a liquid concentrate of a fine-grain normal-working para-aminophenol negative developer at 1+25 or 1+50 with a stated capacity of 25 films per package; FOMADON LQN and its capacity of 12 films per package; FOMADON R09 — a liquid concentrate of a fine-grain, normal-working para-aminophenol negative developer at 1+25 or 1+50 with a capacity of 25 films per package; FOMADON LQN and LQR as phenidone-hydroquinone concentrates; FOMADON P as a two-component metol-hydroquinone powder developer

Used by:Hydroquinone · Metol · p-Aminophenol · Phenidone · Rodinal-type p-aminophenol developer · P8 Acutance, Adjacency Effects and Compensating Development · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P8 Assignment: Reading a Developer Formula

Developers for black-and-white photographic papers (Fomatol)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: FOMATOL P; FOMATOL LQN; FOMATOL P; FOMA GD-L; FOMA UNIVERSAL DEVELOPER; FOMATOL LQN — In general, Use, Dilution, Developing capacity, Packaging; the Development times for FOMA photo papers table at 20 °C, FOMATOL LQN column; the closing note referring the reader to the safety data sheet for disposal, transport, storage and handling; the sheet foot, FOMA 04/23; FOMATOL P: a two-component phenidone and isoascorbate paper developer in powder form; FOMATOL P, a two-component phenidone-isoascorbate normal-working positive developer in powder form; FOMATOL LQN, a phenidone-hydroquinone liquid concentrate for all black-and-white papers at 1+7 for manual processing, with one litre of working solution sufficient for 1.5 square metres of fibre paper and 3 square metres of resin-coated paper; FOMATOL P, a two-component phenidone-isoascorbate powder developer; FOMATOL PW, formulated for the Fomatone papers, with slower developing kinetics, lower speed utilisation and a warm image tone; and FOMA GD-L, a contrast-working phenidone-hydroquinone concentrate; FOMA GD-L - the description of a single-component liquid concentrate for the preparation of a contrasting phenidone-hydroquinone developer intended for manual and automatic processing of graphic materials and black-and-white photographic papers, cited here as a maker's own statement that a developer can be sold as a contrast choice; FOMATOL LQN - a phenidone-hydroquinone liquid concentrate diluted 1 part to 7 for manual processing and 1 part to 4 for automatic processing, with the statement that one litre of ready-to-use developer at 1+7 is sufficient to develop 1.5 square metres of fibre-base and 3 square metres of resin-coated paper, and a recommended replenishment rate given only for automatic processing of 200 mL of ready-to-use developer at 1+4 per square metre of paper; and FOMATOL P, a two-component phenidone-isoascorbate powder developer making 2.5 litres and sufficient for 3.75 square metres of fibre-base and 7.5 square metres of resin-coated paper

Used by:Ascorbic acid · Phenidone · Sodium ascorbate · Foma FOMATOL LQN developer · P3 Aerial Oxidation: Why Chemistry Dies in a Half-Empty Bottle · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P18 Print Developer Chemistry and the Developer-Paper Pair · P19 Contrast Filtration and Split-Grade Printing · P19 Developing the Print Consistently and Running a Printing Session

FOMABROM VARIANT, black-and-white variable-contrast enlarging FB photographic paper, product datasheetretrieved 2026-09-05, 2026-09-06

Sections: Processing — the same fixing recommendation, and the manual processing in trays table giving Fomafix at 1+5 for 3 minutes against 5 minutes for the powder fixer at 20 °C, with washing at 30 and 45 minutes; Processing — the manual processing in trays table giving Fomatol LQN at 1+7 for 100 to 130 seconds at 20 °C; the recommendation of Fomatol LQN, Fomatol P or Universal developer FOMA for common work over all contrast grades and a neutral image tone; and the list of foreign developers named beside them, which is ILFORD Multigrade, Kodak Polymax T, Adox MCC Developer and Rollei Print Neutral rather than the list the graded-paper sheets give; The two technical-data tables, one for ILFORD MULTIGRADE filters and one for Foma Variant filters, each giving ISO P speed, ISO R range and a lengthening factor for every filter on the same paper; the filtration table for Agfa, Kodak, Durst and Meopta heads; the statement that the paper is orthochromatically sensitised and needs safelight illumination of 625 nm and higher; and the statement that exposure for filters 0 to 3 is the same and for 4 to 5 should be doubled; Technical data (Ilford Multigrade filters for contrast control) - the table giving ISO P speed, ISO R range and a lengthening factor for each filter, reading a lengthening factor of 2.4 at filters 00 to 3 and 4.8 at filters 4 and 5 against an unfiltered row with no factor and a speed of P500, with the note that exposure for filters 0 to 3 is the same and for filters 4 to 5 should be doubled; Technical data (Foma Variant filters for contrast control) - the second table for the same paper under Foma's own filters, giving speeds of 310, 360, 500, 360, 240, 190 and 110 and lengthening factors of 1.6, 1.4, none, 1.4, 2.1, 2.6 and 4.6; Contrast control - the statement that exposing only the blue-sensitised part under magenta raises contrast and exposing the green-sensitised part under yellow reduces it

Used by:Foma FOMAFIX · Foma FOMATOL LQN developer · P18 Variable-Contrast Papers: Three Emulsions, One Sheet · P19 Contrast Filtration and Split-Grade Printing

FOMABROM, product datasheetretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Processing — the sentence recommending a common acid fixer, for example the powder Fomafix P, or Fomafix rapid fixer; and the manual processing in trays table giving the stop bath, Fomafix at 1+5 for 3 minutes against Fomafix P or an acid fixer for 5 minutes, both at 20 °C, and washing in running water for 30 minutes and 45 minutes respectively; Processing — the recommendation of Fomatol LQN or Fomatol P for common work and a neutral image tone, the list of foreign developers recommended alongside them, and the manual processing in trays table giving Fomatol LQN at 1+7 for 90 to 120 seconds at 20 °C; Safelighting: indirect illumination of wavelength 575 nm and higher, yellow, yellow-green, amber or orange; Sensitometric values by contrast grade - ISO range R 80 for normal and 60 for hard, ISO speed P 400 for both, and a maximum density of 2.1 for both; and the statement that the curves are valid for the glossy surface and that any other surface, namely the matt one, causes a decrease in the maximum density value; In general - the description of FOMABROM as a universal paper on a baryta base manufactured using silver chlorobromide emulsion giving a neutral-to-medium warm tone; Safelighting - indirect illumination at 575 nm and higher; and the statement that the resulting image tone is influenced by the developers used; Sensitometric values by contrast grade, giving Dmax 2.1 for both grades, with the statement that the curves are valid for the glossy surface and that any other surface, namely the matt one, causes a decrease in the maximum density value; and the description of the paper as being on a double-weight baryta paper base; Sensitometric values by contrast grade for the graded FOMABROM - normal at ISO range R80 and hard at R60, both at ISO speed P400 - and the safelighting recommendation of 575 nm and higher, used here as the graded counterpart of the variable-contrast FOMABROM VARIANT; Manual processing in trays - development in Fomatol LQN at 1+7 for 90 to 120 s at 20 C, a stop bath of acetic acid published as 2 per cent without a stated basis, or Fomacitro at 1+19, for 20 to 30 s at 20 C, fixing in Fomafix at 1+5 for 3 min or in Fomafix P acid fixer for 5 min at 20 C, and washing in running water for 30 min above 12 C or 45 min below 12 C; Processing table - washing in running water for 30 minutes above 12 degrees C and 45 minutes below it; Drying - FOMABROM is recommended to be dried freely laid at room temperature, or by hot air at a maximum of 85 degrees C and subsequently pressed, or dried stretched at a maximum temperature of 35 degrees C; Sensitometric values by contrast grade — ISO range R 80 for normal and 60 for hard, ISO speed P 400 for both, and a maximum density of 2.1 for both; and the statement that the curves are valid for the glossy surface and that any other surface, namely the matt one, causes a decrease in the maximum density value

Used by:Foma FOMAFIX · Foma FOMATOL LQN developer · P4 Spectral Sensitivity and Colour Response · P18 Experiment: Maximum Black, Base White and Dry-Down · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · P18 The Structure of a Printing Paper: Base, Baryta, Emulsion and Supercoat · P18 Variable-Contrast Papers: Three Emulsions, One Sheet · P19 Developing the Print Consistently and Running a Printing Session · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P28 Print Faults: Weak Blacks, Mottle, Bronzing and the Rest

FOMAFIX and FOMAFIX P — fixers for black-and-white films and photopapersretrieved 2026-09-05, 2026-09-06

Sections: FOMAFIX — In general, Use, Dilution, Fixing capacity and Packaging; the Manual processing at 20 °C table, FOMAFIX and FOMAFIX P columns, for all eleven materials; the FOMAFIX P entry beside it, its two-bag preparation in 600 mL of water at 40 °C made up to 750 mL for films and 1 litre for papers, its capacity and its packaging; and the closing note referring the reader to the safety data sheet for ecological disposal and for the principles of safe use in transport, storage and handling; the sheet foot, FOMA 04/23; FOMAFIX — the description as a liquid concentrate of a rapid fixer with high efficiency, strong buffer ability and long-term stability; the dilutions, 1 part concentrate to 5 parts water for manual processing and 1 to 4 for automatic; and the fixing capacity of 1 litre of working solution at 1+5, 17 perforated films of 135-36 or rollfilms of 120, or 2 square metres of baryta-base papers and 4 square metres of RC papers; FOMAFIX, described as a liquid concentrate rapid fixer with high efficiency, strong buffer ability and long-term stability, diluted 1+5 for manual and 1+4 for automatic processing, with the capacity per litre at 1+5 of 17 films of 135-36 or 120, up to 40 sheets of 13 by 18 cm, 2 square metres of baryta-base paper and 4 of resin-coated, and the manual processing table giving 3 minutes for the Fomapan films against 10 minutes in the powder fixer FOMAFIX P; the datasheet names no fixing agent; FOMAFIX — dilution 1 part concentrate to 5 parts water for manual processing, a capacity per litre of 17 films of 135-36 or 120, and manual processing times of 3 minutes for the Fomapan films; FOMAFIX — a liquid concentrate rapid fixer described as having high efficiency, strong buffer ability and long-term stability, diluted 1+5 for manual processing, with a capacity per litre of working solution of 17 films of 135-36 or 120, 2 square metres of baryta paper or 4 square metres of resin-coated paper, and manual processing times of 3 minutes for the Fomapan films and 1.5 to 3 minutes for the papers

Used by:Foma FOMAFIX · ILFORD RAPID FIXER · Kodak F-52 · P11 Experiment: Clearing Time and Fixer Capacity · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline

FOMAPAN 100 Classic, product datasheetretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Processing — the stop step given as a short rinse in distilled water or 10 seconds in 2 % acetic acid; Fixing, at 18 to 25 °C for 10 minutes in any common type of acid fixing bath or for at least 3 minutes in Fomafix rapid fixer; and Washing, 30 minutes in running water below 15 °C and 15 minutes above it; Schwarzschild effect: the table of exposure lengthening against metered time; Storage: unexposed films stored in the original packaging in a cool dry place, out of reach of harmful vapours, gases and ionizing radiations; Schwarzschild effect: exposure 1/1000 to 1/2 s, 1 s, 10 s and 100 s against lengthening factors of 1, 2, 8 and 16 times, and aperture corrections of 0, -1, -3 and -4 stops; Speed ISO 100/21 degrees; Speed ISO 100/21 degrees; Processing, safelighting infrared or total darkness; Development, the table of recommended times for a spiral developing tank with agitation continuous for the first 30 seconds then for the first 10 seconds of every minute, giving Ilford ID-11 and Kodak D-76 stock at 6 to 7 minutes at 20 degrees C; Fixing, 18 to 25 degrees C for 10 minutes in a common acid fixing bath or at least 3 minutes in Fomafix; Washing, running water for 30 minutes below 15 degrees C and 15 minutes above; Packaging, the statement that the orientation of the emulsion side is determined by a notch located on the right upper corner of the short side of the film format; Schwarzschild effect: metered exposures of 1/1000 to 1/2 s, 1 s, 10 s and 100 s against lengthening factors of 1, 2, 8 and 16 times, with aperture corrections of 0, -1, -3 and -4 stops; Speed ISO 100/21 degrees; Schwarzschild effect: exposures of 1/1000 to 1/2 s, 1 s, 10 s and 100 s against lengthening factors of 1, 2, 8 and 16 times; Processing — the safelighting instruction of infrared light or total darkness; development, Ilford ID-11 and Kodak D-76 stock at 6 to 7 minutes at 20 degrees C; In general and Speed - a nominal speed rating of ISO 100/21 degrees with the claim of good results when overexposed by 1 EV as ISO 50/18 or underexposed by 2 EV as ISO 400/27 without any change in processing; the Schwarzschild effect table giving exposure lengthening factors of 1, 2, 8 and 16 times at metered times of one five-hundredth to a half second, 1 second, 10 seconds and 100 seconds; Processing - the safelighting instruction of infrared light or total darkness for this panchromatic film; Schwarzschild effect - the exposure-lengthening table against metered time, giving a factor of 1x from 1/1000 to 1/2 second and 2x at 1 second, with the equivalent aperture corrections; Storage - the instruction that unexposed film be kept out of reach of harmful vapours, gases and ionizing radiations; Processing - the safelighting instruction of infrared light or total darkness for this panchromatic film; Storage and handling - unexposed film to be stored away from harmful vapours and gases, cited as a manufacturer's statement that vapours can damage sensitised material; Base - the statement that 120 roll film uses a clear polyester base 0.1 mm thick with an antihalation colour layer, that 35 mm film uses a grey or grey-blue cellulose triacetate base 0.125 mm thick, and that sheet film uses a clear polyester base 0.175 mm thick with an antihalation colour layer. Cited as a manufacturer's own statement that the base of one emulsion differs between formats, and that no single base density figure exists to be quoted; Sheet film - orientation of the emulsion side of the film is determined by a notch located on the right upper corner of the short side of the film format; Development, the table for a spiral developing tank with agitation continuous for the first 30 seconds then for the first 10 seconds of every minute; Washing, running water for 30 minutes below 15 degrees C and 15 minutes above; Packaging, the notch at the right upper corner of the short side of the sheet format; Packaging - the statement that the orientation of the emulsion side is determined by a notch located on the right upper corner of the short side of the film format; Processing - safelighting infrared or total darkness; Schwarzschild effect - metered exposures of 1 s, 10 s and 100 s against lengthening factors of 2, 8 and 16 times

Used by:Foma FOMAFIX · P4 Reciprocity Failure and the Life of the Latent Image · P6 Build the Modular Pinhole Camera · P6 Pinhole Exposure and Reciprocity Correction · P6 Lab: Processing Your First Film · P6 Break/Fix: Unexpectedly Soft Images and Wrong Reciprocity Corrections · P7 Assignment: Night, the Very Long Exposure and Solargraphy · P9 Lab: Preparing Standard Test Negatives · P13 Film Speed and Exposure Index · P13 Lab: A Step-Wedge Exposure Series · P14 Sensitometer Design Principles · P14 Build: The Enclosure and Exposure Stage · P15 Build: The Densitometer Optical Head (Transmission and Reflection) · P15 Break-Fix: Diagnosing a Misbehaving Densitometer · P16 Build: The Contact Printing Frame and Its Light Source · Processing a film · Loading paper and sheet film into a pinhole back · Thin negative from wrong reciprocity data

FOMAPAN R 100 reversal film data sheetretrieved 2026-09-04

Sections: Composition of working solutions — the reversal bath; Composition of working solutions — Bleaching FB-2; Composition of working solutions — the reversal bath, and the note on water for preparing processing solutions; Composition of working solutions — reversal bath; Composition of working solutions: the reversal bath contains Calgon 1.5 g or Chelaton III 5.0 g per litre

Used by:EDTA disodium salt dihydrate · Potassium dichromate · Sodium hexametaphosphate (Calgon) · Sodium hydroxide (caustic soda) · P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve

FOMASPEED, variable contrast RC paper, technical dataretrieved 2026-09-05, 2026-09-06

Sections: Processing — the manual processing in trays table giving Fomafix at 1+5 for 90 seconds against 3 minutes for the powder fixer at 20 °C, with washing at 2 and 4 minutes; and the machine processing table giving Fomafix at 1+5 for 25 to 35 seconds at 30 °C with a 60 second wash; In general — the statement that developing agents incorporated into the emulsion layer shorten manual development to 60 to 90 seconds at 20 °C; Processing — the recommendation of Fomatol LQN or Fomatol P for common work and a neutral image tone with Kodak Dektol, ILFORD PQ UNIVERSAL and BROMOPHEN among the foreign developers named beside them, the manual processing in trays table giving Fomatol LQN at 1+7 for 60 to 90 seconds at 20 °C with the stop-bath and fixing times beside it, and the machine processing table giving Fomatol LQN at 1+4 for 25 to 35 seconds at 30 °C; Sensitometric values by contrast grade - normal at ISO range R80 and hard at R60, both at ISO speed P400 and Dmax 2.1 on the glossy surface; In general - the statement that developing agents incorporated into the emulsion layer facilitate rapid machine processing and shorten development times in manual processing to 60 to 90 seconds at 20 degrees C; the description of the emulsion as silver chlorobromide giving a neutral-to-medium warm tone; and the safelighting recommendation of indirect illumination at 575 nm and above; Manual processing in trays - development in Fomatol LQN at 1+7 for 60 to 90 s at 20 C, a stop bath of acetic acid published as 2 per cent without a stated basis for 10 s, or Fomacitro at 1+19 for 10 to 20 s, at 20 C, fixing in Fomafix at 1+5 for 90 s or in Fomafix P acid fixer for 3 min at 20 C, and washing in running water for 2 min above 12 C or 4 min below 12 C; Processing table - washing in running water for 60 seconds; Drying - FOMASPEED should not be glazed, only dried, either left to dry naturally at room temperature or using warm air at temperatures up to a maximum of 85 degrees C

Used by:Foma FOMAFIX · Foma FOMATOL LQN developer · P17 F-Stop Timing and the Mathematics of Print Exposure · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · P19 Developing the Print Consistently and Running a Printing Session · P19 Lab: Washing, Drying, Flattening and Mounting the Print

FOMATONE MG Classic, black-and-white variable-contrast enlarging photographic paper working in a warm tone, product datasheetretrieved 2026-09-05, 2026-09-06, 2026-09-07

Sections: Processing — the statement that stopping development before fixing is very important with this paper and that neglecting it can cause non-homogeneities in the grey areas; and the manual processing in trays table giving Fomafix at 1+5 for 1.5 minutes against 3 minutes for the powder fixer at 20 °C, with washing at 30 and 45 minutes; Processing — the recommendation of Fomatol LQN, Fomatol P and Fomatol PW for their brown-green and warm-brown image tone, the statement that Fomatol PW was formulated for this paper, and the manual processing in trays table giving Fomatol LQN at 1+7 for 1 to 3 minutes at 20 °C; Technical data, both the Ilford Multigrade filter table and the Foma Variant filter table - a maximum density of 2.0 at every contrast grade, each followed by the statement that the data are valid for the glossy surface and that for the matt surface Dmax = 1.6; and the note under the sensitometric curves that any surface other than the semi-glossy, namely the matt one, causes a decrease in the maximum density value; In general - the description of a special silver chlorobromide emulsion giving the silver image a brown-green to warm-brown tone that can be further influenced by the type of developer used, with the paper base coloured in compliance with the tone of the developed silver; Safelighting - orange illumination at 610 nm and higher, with the note that the paper's low sensitivity permits longer exposure to it than other papers; Exposure - the note that the speed is considerably lower than other Foma papers and that the Schwarzschild effect appears particularly above 15 minutes; Processing - the recommendation of Fomatol PW, formulated for this paper, and the note that further dilution with lengthened development gives a stronger warm tone; Processing - the recommendation of Fomatol PW, and the note that further dilution of the developer with proportionally lengthened development times gives even warmer image tones, doubling the time at 1+1 and quadrupling it at 1+3; The two technical-data tables and the sentence printed beneath each of them, that the data are valid for the glossy surface and that for the matt surface Dmax = 1.6, against the glossy figure of 2.0 given in the tables themselves; and the statement that the paper base is coloured in compliance with the tone of the developed silver; Contrast control - the statement that the paper is sensitised in the blue and green spectral areas and that its contrast is controlled with yellow and magenta filters, exposure of the blue-sensitised part alone under magenta raising contrast and exposure of the green-sensitised part under yellow reducing it, with grade 2 obtained unfiltered; and the filtration table for Durst and Meopta colour mixing heads; Technical data (Ilford Multigrade Filters for contrast control) - the table giving ISO R figures of 140, 120, 105, 90, 90, 75, 70 and 55 for filters 00, 0, 1, unfiltered, 2, 3, 4 and 5 and lengthening factors of 3.4, 3.4, 3.0, none, 2.4, 2.0, 2.4 and 3.0, with Dmax 2.0 on the glossy surface; Technical data (Foma Variant Filters) - ISO R figures of 120, 105, 90, 80, 75, 65 and 55 and lengthening factors of 2.0, 1.5, none, 1.5, 1.8, 2.0 and 3.0; Contrast control - the statement that the paper is sensitised in the blue and green spectral areas, that magenta raises and yellow lowers contrast, and that with no colour filtration the contrast grade equals 2; Exposure - the warning that the Schwarzschild effect shows particularly at long exposures above 15 minutes and at the low light intensity characteristic of this paper; Processing - the statement that developers giving more expressed images usually reduce contrast and the yield of speed, and that the paper base is coloured in compliance with the tone of the developed silver; Processing - the note that selected emulsion batches of the FOMATONE MG Classic papers can also be used for the lith process and that, considering the specific processing conditions and the various interactive effects of special lith developers, it is necessary to test each emulsion lot separately, especially the modification of the exposure and developing time; Note on the lith process, which states that selected emulsion batches of the paper can be used for it and that it is necessary to test each emulsion lot separately, especially the modification of the exposure and developing time; Technical data — a maximum density of 2.0 at every contrast grade, followed by the statement that the data are valid for the glossy surface and that for the matt surface Dmax = 1.6; Technical data — a maximum density of 2.0 at every contrast grade with the statement that the data are valid for the glossy surface and that for the matt surface Dmax = 1.6, and the note under the sensitometric curves that any surface other than the semi-glossy causes a decrease in the maximum density value; Technical data — a maximum density of 2.0 at every contrast grade, with the statement that the data are valid for the glossy surface and that for the matt surface Dmax = 1.6

Used by:Foma FOMAFIX · Foma FOMATOL LQN developer · P18 Experiment: Maximum Black, Base White and Dry-Down · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · P18 Print Developer Chemistry and the Developer-Paper Pair · P18 The Structure of a Printing Paper: Base, Baryta, Emulsion and Supercoat · P18 Variable-Contrast Papers: Three Emulsions, One Sheet · P19 Contrast Filtration and Split-Grade Printing · P19 Lab: Dodging, Burning, Edge Work and Local Contrast · P19 Assignment: The Exhibition Print and Its Critique · P28 Print Faults: Weak Blacks, Mottle, Bronzing and the Rest · Dry-down error · Poor maximum black

fotoimpex.com

ADOX RODINAL datasheetretrieved 2026-09-04, 2026-09-05

Sections: The whole two-page datasheet, which carries no extractable text layer; The whole document, which carries no extractable text layer and from which this course therefore quotes nothing

Used by:Rodinal-type p-aminophenol developer · P8 Acutance, Adjacency Effects and Compensating Development · P8 Assignment: Reading a Developer Formula

fotoimpex.de

ADOX FX-39 II datasheet (Technische Beschreibung)retrieved 2026-09-04, 2026-09-05

Sections: The opening technical description, stating that FX-39 is based on Willi Beutler's Neofin Rot and has been improved in every parameter; Technische Beschreibung — the statement that FX-39 is based on Willi Beutler's Neofin Rot and has been improved in every parameter; that contrast is influenced through the dilution, 1+9 for normal contrast with an increase in speed utilisation and 1+19 for high-contrast subjects, acting to reduce contrast with the speed utilisation falling to nominal; the agitation scheme; the film time table; Technische Beschreibung — contrast influenced through the dilution, 1+9 for normal contrast with increased speed utilisation and 1+19 for high-contrast subjects acting to reduce contrast with the speed utilisation falling to nominal; Technische Beschreibung - the development-time table, whose times for every listed film are given against a stated contrast figure of 0.65; the statement that the 1+9 dilution gives normal contrast with a speed increase and the 1+19 dilution acts to reduce contrast for high-contrast subjects while the speed utilisation falls, which is the published statement that a dilute high-acutance developer trades speed against compensating ability

Used by:Beutler two-solution developer · P8 Acutance, Adjacency Effects and Compensating Development · P8 Assignment: Reading a Developer Formula · P13 Assignment: Interpreting Density Data

freepatentsonline.com

GB 635,841, Photographic emulsions: the British Patent Office abridgment of the Davey and Knott specification, as reproduced in the FreePatentsOnline record for United States Patent 2,592,250retrieved 2026-09-06

Sections: The whole abridgment: the emulsion is formed in the absence of ammonia; the colloid binder contains little or no sulphur sensitizers, e.g. inert gelatin, cellulose esters or ethers, and resins; the pH of the emulsion may be between 4.5 and 7.0; the iodide content of the final emulsion may be 10 per cent, 20 per cent, or more, calculated by weight on the total silver halide; the emulsions, after exposure, may be developed in an internal developer; and, of example 1, that aqueous solutions of KCl and AgNO3 are simultaneously run into an aqueous solution of inert gelatin and KCl

Used by:Davey and Knott's double-jet iodobromide emulsion

freestylephoto.com

Photographers' Formulary Cyanotype Kit, catalogue number 07-0090: instructionsretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Hydrogen Peroxide Oxidation Bath — 50 mL of 3 per cent in 500 mL, degassing, loss of potency and the instruction to use it fresh; Permanence — restoring a faded print; Toning, "Violet Tones": the borax solution or the warm lead acetate solution, used until the desired colour is achieved and then washed for fifteen minutes; Chemical Safety — the cyanide groups bound to iron, and the conditions under which hydrogen cyanide can be released; Chemical safety — why potassium ferricyanide is not the poison sodium cyanide is, and the conditions under which a ferricyanide will release hydrogen cyanide; Mixing the Stock Solutions — Stock Solution A, ferric ammonium citrate 100 g with distilled water to make 500 mL, and Solution B, potassium ferricyanide 40 g with distilled water to make 500 mL; the optional 1 per cent potassium dichromate solution; Washing, the five-minute wash in soft water and the warnings about hard and alkaline water; Contrast Increase by a 0.2 per cent potassium ferricyanide first bath; Peroxide After-bath; After Treatment, the 5 per cent oxalic acid spot clearing; Page 5, Toning Solutions, "Violet Tones", offering either a mild borax solution or a warm 5 per cent lead acetate solution, each used until the desired colour is achieved and then washed for fifteen minutes; The older printing of the same 07-0090 sheet, mirrored by Freestyle — the CHEMICALS CONTAINED IN THIS KIT table with its footnote that ferric ammonium citrate (green) is somewhat light sensitive and should be stored in the dark; the statement that the kit contains chemicals to make approximately twenty-four 8 by 10 prints; the higher-contrast sensitiser table giving total volumes of 11.5 mL and 28 mL from 5 mL and 12 mL of each stock with 30 drops and 4 mL of dichromate solution and the note that twenty drops is approximately 1 mL; THE NEGATIVE FOR CYANOTYPE PRINTING, that a negative printing well on grade 0 paper will give an excellent cyanotype with the standard sensitiser and that a negative of smaller density range printing on grade 1 or 2 calls for the higher contrast sensitiser; PAPER, that almost any paper can be used and that sizing is not imperative; the sizing account, that it fills the pores of the paper with starch and provides a uniform surface; and TONING SOLUTIONS, brown to black from ammonia 28 per cent 10 mL in 100 mL of distilled water followed by tannic acid 10 grams in 500 mL — the tenfold stronger ammonia bath that the supplier's later printings do not carry; Photographers' Formulary Cyanotype Kit 07-0090, page 5, TONING SOLUTIONS, Brown to Black Tones: 'Ammonia 28% 10 ml, Distilled Water 100 ml, AND Tannic Acid 10 grams, Distilled Water 500 ml', with the direction 'Mix both solutions separately. This is a two-step immersion process. Immerse the print in the ammonia solution until the color has been bleached-out. Wash in cool water for 10 minutes. Then immerse the print in the tannic acid solution until the desired color is achieved. Wash under running water for 15 minutes and dry.'; the introduction to the section, which credits the ideas to Jan Arnow's A Handbook of Alternative Photographic Processes and states that the process is done as a toning after the cyanotype process has been completed entirely; and the two further toners on the same page, Green Tones by a 1 per cent sulphuric acid solution made by adding 2 mL of the kit's 48 per cent acid to water, and Violet Tones by either a mild borax solution or a warm 5 per cent lead acetate solution, each used until the desired colour is achieved and then washed for 15 minutes; Chemical Safety, on potassium ferricyanide's bound cyanide groups and on the release of hydrogen cyanide only in strong acid, and on potassium dichromate as toxic, an oxidiser and a potential carcinogen; Higher Contrast Sensitizer, the 1 per cent potassium dichromate solution at six drops per 2 mL of standard sensitiser and the expected loss of two steps on a Kodak No. 2 step tablet; Cyanotype Kit 07-0090 instructions — Mixing the Stock Solutions, Stock Solution A of 400 mL of distilled water at 20 degrees C plus 100 g of ferric ammonium citrate made up to 500 mL and Stock Solution B of 40 g of potassium ferricyanide made up the same way, giving 20 and 8 per cent w/v, with three dark brown storage containers specified; the mixing in subdued light, the use "as soon as feasible" and the statement that "the sensitizer solution is stable for about 2-4 hours after mixing"; the diagnostic that "The dry sensitized paper should appear greenish-yellow. If it is blue, ferrous salts are present either by exposure or through chemical contamination"; the exposure by sunlight or a 275 to 300 watt sunlamp at 12 to 18 inches for ten to twenty minutes, the olive-green appearance before washing, and the instruction to expose until the high values carry considerably more tone than wanted and the shadows have begun to reverse, "therefore an apparent overexposure is necessary"; WASHING, the about five minutes in running soft water, the statement that a short washing period leaves ferric salts in the paper causing the print to fade and that prolonged washing lightens the image "particularly if the wash water is slightly alkaline", and that the iron salts in hard water can alter the appearance of the print; Contrast Increase, the initial wash bath of 0.2 per cent potassium ferricyanide; the Peroxide After-bath of 50 mL of 3 per cent hydrogen peroxide added to 500 mL of water, not supplied with the kit and obtainable from a chemist; and After Treatment, the 5 per cent oxalic acid solution used to clear blue from the whites followed by a wash; The Negative for Cyanotype Printing — the statement that the cyanotype process has a long exposure scale so the best prints are obtained when the negative has a large density range, the rule that a negative giving a good print on grade 0 paper will give an excellent cyanotype with the Standard Sensitizer, and the recommendation of the Higher Contrast Sensitizer for a negative of smaller density range that prints well on grade 1 or 2; and Paper, the statement that almost any paper can be used, the suggestion of Crane's papers, and the note that although not imperative the paper should be sized for best results, followed by an arrowroot starch sizing procedure.; Chemical Safety — the statement that the cyanide groups are chemically bound to the iron atom and are not free to act as a poison, and the conditions under which hydrogen cyanide can be released; Washing - the five-minute wash in soft water and the warnings about hard and alkaline water; Contrast Increase by a 0.2 per cent potassium ferricyanide first bath; Peroxide After-bath; and After Treatment, the 5 per cent oxalic acid spot clearing; Page 5, Toning Solutions, for the Brown to Black Tones pair of 10 mL of 28 per cent ammonia in 100 mL of distilled water and 10 g of tannic acid in 500 mL of distilled water with the two-step immersion direction and the 10 and 15 minute washes; for the introduction crediting the ideas to Jan Arnow's A Handbook of Alternative Photographic Processes and stating that the process is done as a toning after the cyanotype process has been completed entirely; and for the Green Tones and Violet Tones entries on the same page.; Cyanotype Kit 07-0090, page 5, Toning Solutions, Brown to Black Tones; the Green Tones and Violet Tones entries on the same page; the introduction crediting the ideas to Jan Arnow's handbook

Used by:Hydrogen peroxide · Lead(II) acetate · Prussian blue · Sodium cyanide · Classic cyanotype sensitiser · Lead, thallium and nickel cyanotype toners · Photographers' Formulary cyanotype and toning kits · Tannic acid toner for cyanotype · Ware's improved Classic cyanotype · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 What These Processes Need: The Negative, the Paper and the Light · P21 Iron, Light and Prussian Blue · P21 Break/Fix: The Cyanotype That Went Wrong · P21 Lab: Toning the Prussian Blue Image · Toned cyanotype

Photographers' Formulary Kallitype Printing Kit, catalogue number 07-0070: instructionsretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Ferric oxalate; Chemical test for photo-activity and excess ferrous ions in ferric oxalate; Chemicals contained in this kit; Chemicals contained in this kit; Chemical safety; Kit contents; Stock Developer Solution A and its mixing note; the three development formulas and their times and temperatures; the note on how the proportion of A to B moves the image colour; The Sensitizer — the addition of 2 g of solid silver nitrate to 30 mL of 20 per cent ferric oxalate solution, the statement that it is very common for a precipitate of silver oxalate to form, that the precipitate does no harm, and the instruction to make sure it is not transferred to the paper; the two to three days of ripening with occasional stirring, and the note that the stirring matters especially if a precipitate formed during mixing; Chemicals contained in this kit, for the 75 g of borax supplied; Mixing the solutions — The Developer Stock Solutions and Stock developer solution B, for the 75 g in 400 mL of distilled water at 52 °C, for the instruction to mix it as Solution A is mixed, and for the statement that the borax dissolves slowly and residual solid commonly remains; Development, for the rule connecting the proportion of A and B to the image colour, for the black-tone and brown-tone make-ups and their five minutes, for the 38 °C/100 °F, and for the dichromate contrast control; The Negative, for the density range of 1.85; Sizing, for arrowroot against gelatin; Final Steps, for clearing, the five-minute fixing limit and the warning against a standard photographic fixing bath; Mixing the Solutions, Fixing Bath, reading distilled water at 52 degrees C / 125 degrees F 1000 ml, sodium thiosulfate pentahydrate 50 g and ammonia 28 per cent 12 ml, with the instruction to dissolve the thiosulfate in the warm water first and then to add the ammonia in a well-ventilated area and stir to homogeneity; the kit contents list, which ships 50 g of sodium thiosulfate pentahydrate and 15 ml of 28 per cent ammonia; the Chemical Safety section on ammonia, that concentrated ammonia is also called ammonium hydroxide, that the liquid releases extremely choking ammonia gas when opened, that the container must be kept well capped, that it is used in the kallitype fixing bath and that the bath must be mixed in a well-ventilated area; and the Processing section, Clearing and Fixing Soak, giving five minutes in potassium oxalate then a quick water rinse, then "Soak the print for not more than 5 minutes in the sodium thiosulfate fixing bath, a longer soak will cause the print to fade. Do not use a standard photographic fixing bath; the finely divided, unprotected silver metal will be etched from the print", followed by 40 minutes of running water, or 2 to 4 minutes of running water then Hypo-Clear and a 15 to 20 minute wash; Mixing the Solutions, Clearing Bath, reading distilled water at 20 degrees C / 68 degrees F 500 ml and potassium oxalate 60 g, with the instruction to stir until the solid dissolves and to store in a pint container; the Chemical Safety section, that potassium oxalate is rather toxic, that the solution should be mixed in a sink with the utensils cleaned before they leave it, that rubber gloves should be worn, and that because it is used as the clearing bath it can easily come into contact with the skin; and the Processing section, Clearing, for the five-minute soak at 20 degrees C followed by a quick water rinse before the fixing bath; Chemicals contained in this kit; Chemical safety; Ferric Oxalate; Chemical test for photo-activity and excess ferrous ions in ferric oxalate; Mixing the solutions — The Sensitizer; Sensitizing the Paper; Exposure; Final Steps; Chemicals contained in this kit; Ferric Oxalate, and the chemical test for photo-activity and excess ferrous ions; Mixing the solutions — The Sensitizer, for the one-bottle modern sensitiser of 30 mL of 20 per cent ferric oxalate carrying 2 g of solid silver nitrate, for the silver oxalate precipitate that "does no harm", and for the two to three days of ripening in the darkroom before use; Sensitizing the Paper; Final Steps, for clearing, the five-minute fixing limit and the warning against a standard photographic fixing bath; The section on ferric oxalate, cited for one purpose only: the supplier prints the same paragraphs about the misnomer, the two forms and its own 20 per cent trihydrogen solution in a third kit sheet, which is what makes those paragraphs the company's standing account of the material rather than a remark about one product; Chemicals contained in this kit; Mixing the solutions — The Developer Stock Solutions, Stock Developer Solution A and Stock Developer Solution B, for the 100 g in 200 mL at 52 °C, the endothermic dissolving and the cloudiness that clears; 10% Potassium Dichromate Solution for Contrast Control; The Negative, for the density range of 1.85; Sizing, for arrowroot against gelatin and the colour each gives; Development, for the three working developers, their make-up volumes, their times, the 38 °C for the two warm ones and the rule connecting the proportion of A and B to the image colour; Final Steps, for clearing, the five-minute fixing limit and the warning against a standard photographic fixing bath; Chemicals contained in this kit; The Developer Stock Solutions; Development, for the three Rochelle salt and borax developers this one replaces and their times and temperatures; The Negative — the statement that kallitype is capable of an extremely long tonal range and that negatives with a density range up to 1.85 can be used, with contrast increased to some extent by adding potassium dichromate to the developer; and Sensitizing the Paper, brush coating with the note that it is not necessary to measure the amount of sensitiser used.; Clearing bath, 60 g of potassium oxalate in 500 mL of distilled water, with the safety paragraph describing potassium oxalate as an anticoagulant and a poison, the instruction to use tongs or rubber gloves and to mix the solution in a sink; Final steps, for the print soaked in the potassium oxalate clearing bath for five minutes at 20 degrees C, drained, given a quick water rinse and transferred to the fixing bath, and for the statement that for the print to be stable the iron salt, the excess silver salt and all the thiosulfate must be removed; The negative, for the statement that print contrast can to some extent be increased by adding potassium dichromate to the developer and not to the sensitizer; Development, for 5 to 20 drops of 10 per cent potassium dichromate per 500 mL of mixed developer; the 10 per cent potassium dichromate solution for contrast control and its safety paragraph, which states that all chromium compounds are potential carcinogens and that a dichromate spillage on skin causes a chemical burn appearing as ulceration; Chemicals contained in this kit — arrowroot starch 20 g, ferric oxalate 30 mL, silver nitrate 2 g, Rochelle salt 100 g, borax 75 g, potassium oxalate 60 g, sodium thiosulfate pentahydrate 50 g, ammonia 28 per cent 15 mL and potassium dichromate 5 g; Chemical safety, naming silver nitrate, potassium oxalate, ammonia and potassium dichromate as the four needing special attention, and describing potassium oxalate as an anticoagulant and a poison to be handled with tongs; Ferric Oxalate, for the misnomer, the two forms, the statement that only the acidic tri-hydrogen form is sufficiently photosensitive, the recommendation against the green tripotassium solid, the kit's own 20 per cent solution prepared by the iron alum-oxalic acid procedure with a slight excess of oxalic acid, the sensitivity in the 460-nm region, the red safelight and the 50 degrees C ceiling on heating the solution or the sensitised paper; Chemical test for photo-activity and excess ferrous ions in ferric oxalate; Mixing the solutions — The sensitizer, 2 g of silver nitrate stirred into the 30 mL of ferric oxalate under a red safelight, the common precipitate of silver oxalate which does no harm but must not be transferred to the paper, and the ripening of two to three days with occasional stirring; The developer stock solutions, Stock A of 100 g Rochelle salt in 200 mL of water at 52 degrees C and Stock B of 75 g borax in 400 mL, with the note that Rochelle salt dissolves endothermically and that residual borax is common; Clearing bath, 60 g potassium oxalate in 500 mL; Fixing bath, 50 g sodium thiosulfate and 12 mL of 28 per cent ammonia in a litre; the 10 per cent potassium dichromate solution for contrast control; Sizing, for arrowroot giving a brown colour and gelatin a blue tone; The negative, for a density range up to 1.85; Sensitizing the paper, for about 1 mL for a 4 by 5 and 4 mL for an 8 by 10 and about seven 8 by 10 prints from the kit; Exposure, for 10 to 20 minutes under a 275 or 300 watt sunlamp at 12 to 18 inches; Development, for the three developers — black tone 72 mL A plus 128 mL B to 500 mL developed 5 minutes and working best warm at around 38 degrees C or higher, brown tone 96 mL A plus 64 mL B to 500 mL developed 5 minutes and likewise best warm, and sepia tone 48 mL A alone to 500 mL developed 10 minutes at room temperature — with the rule that more Stock A increases the sepia tone and more Stock B increases the blackness, and contrast raised by 5 to 20 drops of 10 per cent dichromate per 500 mL of mixed developer; Final steps, clearing five minutes in potassium oxalate at 20 degrees C, a quick rinse, not more than five minutes in the thiosulfate fixing bath because a longer soak fades the print, the instruction not to use a standard photographic fixing bath because the finely divided unprotected silver metal will be etched from the print, and a final wash of 40 minutes or 2 to 4 minutes plus Hypo-Clear plus 15 to 20 minutes; Ferric Oxalate, for the statement that the solid tri-potassium form is destroyed and turns from green to brown when exposed to ultraviolet light, that tri-hydrogen ferric oxalate is probably heat-sensitive but the exact extent is not known, that neither the solution nor the sensitised paper should be heated above 50 degrees C, and that the solution has a yellow to yellow-green appearance in room light; Chemical test for photo-activity and excess ferrous ions in ferric oxalate, for the three readings of the test and the statement that a blue cast indicates poor quality with the depth of the blue proportional to how poor; Mixing the solutions, for the common precipitate of silver oxalate which does no harm provided it is not transferred to the paper, and for the ripening of two to three days with occasional stirring; Development, for the three developers, their temperatures and the note that the black and brown developers work best warm at around 38 degrees C or higher; Final steps, for the statement that if the iron salt, the excess silver salt and the thiosulfate are not all removed the print will not be stable; Ferric Oxalate — the statement that the photographic term is a misnomer that has caused considerable confusion, the two forms tri-potassium and tri-hydrogen ferric oxalate, the statement that only the acidic form is sufficiently photosensitive to be useful, the recommendation against the green solid tripotassium salt, the kit's own product as a 20 per cent solution of the tri-hydrogen form prepared by the iron alum-oxalic acid procedure with a slight excess of oxalic acid, the statement that it is photosensitive to light in the 460-nm region, and the instruction not to heat the solution or the sensitised paper above 50 degrees C; Chemical test for photo-activity and excess ferrous ions in ferric oxalate; Sensitizer - the note that it is very common for a precipitate of silver oxalate to form, that the precipitate does no harm, and that if the sensitizer forms one you must be sure not to transfer it to the paper you are coating; the requirement that the sensitizer ripen for two to three days before use; Coating - brushing the solution onto the paper first across and then up and down until the paper is completely wet, then working the surface with a second clean brush until it loses its gloss, and allowing the paper to dry hung or pinned; drying the sensitized paper in the dark, which may be speeded with a hand-held hair dryer without over-heating the print; Development - three developers from two stock solutions, with more of Stock A (Rochelle salts) increasing the sepia tone and more of Stock B (borax) increasing the blackness; black-tone development for 5 minutes, with the note that this developer works best if it is warm, around 38 degrees Celsius (100 F) or higher; brown-tone development for 5 minutes, likewise best warm; sepia-tone development for 10 minutes at room temperature; contrast increased by adding 5 to 20 drops of 10 per cent potassium dichromate per 500 ml of mixed developer, added to the developer and not to the sensitizer; Final steps - clearing for 5 minutes in the potassium oxalate clearing bath at 20 degrees Celsius, then a quick rinse, then not more than 5 minutes in the thiosulfate fixing bath; Sensitizer and processing - the ripening requirement; the clearing instruction that whether clearing is needed depends on the developer used, that some developers clear instantly in the developing tray, that the black kallitype developer supplied does require clearing, and that clearing takes three to five minutes in a bath of EDTA tetrasodium at two tablespoons to a litre of water, reusable until about twenty 8 by 10 prints have been cleared; the instruction to tone between the clearing bath and the fixing bath; Toning - the instruction to tone between the clearing bath and the fixing bath, and the statement that toning will also increase the permanence of the kallitype print; Final steps - for the print to be stable the iron salt, the excess silver salt and all the thiosulfate must be removed; Fixing soak - soak the print for not more than 5 minutes in the sodium thiosulfate fixing bath, because a longer soak will cause the print to fade, and do not use a standard photographic fixing bath because the finely divided, unprotected silver metal will be etched from the print; the final wash of 40 minutes in running water, or 2 to 4 minutes followed by a hypo-clearing agent and a 15 to 20 minute wash; Sensitizer - the note that it is very common for a precipitate of silver oxalate to form, that this precipitate does no harm, and that if the sensitizer forms one you must be sure not to transfer it to the paper you are coating; the requirement that the sensitizer ripen for two to three days before use, kept in the darkroom and stirred

Used by:Ferric oxalate · Potassium oxalate monohydrate · Potassium sodium tartrate tetrahydrate · Silver(I) oxalate · Borax kallitype developer · Dilute alkaline thiosulfate fixer for iron-silver prints · EDTA and sodium sulfite clearing sequence · Kallitype sensitiser · Nicol's kallitype · Photographers' Formulary platinum and palladium printing kits · Rochelle salt kallitype developer · Sodium citrate kallitype developer · P21 What These Processes Need: The Negative, the Paper and the Light · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Contrast Control in Iron-Based Printing · P24 Lab: Printing a Kallitype · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · P24 The Siderotype Principle: Iron Reduces Silver · Kallitype · Blotchy and streaked hand coating · Blotchy kallitype development · Iron-silver highlights that will not clear · The iron-silver print that faded within weeks · The printed-out image that bleached away in the fixer · Sensitiser gone cloudy in the bottle

Photographers' Formulary Liquid Cyanotype Kit, catalogue number 07-0091: instructionsretrieved 2026-09-04, 2026-09-06

Sections: Chemical Safety; Higher Contrast Sensitizer; Liquid Cyanotype Kit 07-0091 — the statement that the kit contains solutions to make approximately twenty-four 8 by 10 prints; the contents table giving arrowroot starch 20 g, potassium ferricyanide solution (Sol B) 40 g in 500 mL water, ferric ammonium citrate (green) (Sol A) 100 g in 500 mL water and potassium dichromate 1 g; the sizing solution from 20 g of arrowroot starch in a litre; and the sensitising, exposure, washing and toning instructions, which are the dry kit's with the stock-mixing pages removed

Used by:Potassium dichromate · Photographers' Formulary cyanotype and toning kits

Photographers' Formulary Van Dyke Brown Printing Kit, catalogue number 07-0080: instructionsretrieved 2026-09-05, 2026-09-06, 2026-09-07

Sections: THE FIXING SOLUTION, reading water at 52 degrees C / 125 degrees F 2000 ml and sodium thiosulfate pentahydrate 100 grams, with the instruction to add the solid to the warm water and stir until it dissolves; the Initial Wash and Development section, that if the wash water is slightly alkaline the iron salts will not be removed and that hard water usually carries dissolved iron salts which contaminate the print; the Fixing Bath section, that the fixer is a dilute solution of sodium thiosulfate which removes the excess silver ions, that the print is soaked at 20 degrees C for five minutes and will fade if a longer period is used, that the print darkens and becomes brown during fixing, that just enough fixer to cover the print should be used and discarded after two or three prints, and that "Do not use a standard photographic fixing bath; the very finely divided silver metal of the Van Dyke print will be etched off the paper"; and the FINAL WASH section, 40 minutes of running water at 20 degrees C, or 24 minutes of running water followed by Hypo-Clear and a 15 to 20 minute wash; The Initial Wash and Development section, for the wash of about one minute in running soft water at 20 degrees C / 68 degrees F, for the statement that the water quality is important because "if your wash water is slightly alkaline, the iron salts will not be removed" and that "hard water is not satisfactory; it usually contains dissolved iron salts, which will contaminate the print", and for the remedy where the supply is a problem, three separate trays of distilled or demineralised water at about a minute in each; and the observation that the print darkens and becomes yellowish during that wash; Chemicals contained in this kit; Chemical safety; Mixing the solutions — the sensitizer, Solution A, Solution B, Solution C; The working solution; The 10% potassium dichromate solution for contrast control; The fixing solution; Paper; Sizing of the paper; The negative; Sensitizing the paper; Exposure; Final steps; Contrast increase; Initial wash and development; Fixing bath; Final wash; The Negative — the statement that Van Dyke Brown is capable of an extremely long tonal range and that negatives with a density range up to 1.85 can be used, with contrast increased to some extent by adding potassium dichromate to the developer rather than to the sensitiser.; Chemicals contained in this kit; The negative, for the statement that Van Dyke Brown is capable of an extremely long tonal range and that negatives with a density range up to 1.85 can be used; Exposure, for the optimum in the 10 to 30 minute range under a photoflood; Final steps, for the statement that if the iron salts and the silver salts are not both removed the print will fade with time; Contrast increase — about 9 to 10 drops of a 10 per cent potassium dichromate solution added to 500 mL of the initial wash and development water, giving an increase in contrast equal to about the loss of one step of a Kodak No 2 Step Table, with the exact amount to be determined by trial and error; The negative, for a density range up to 1.85 and for the statement that the final print contrast can to some extent be increased by adding potassium dichromate to the developer and not to the sensitizer; Chemicals contained in this kit; Chemical safety; Mixing the solutions — the sensitizer, Solution A, Solution B and Solution C, and The working solution, for the three 33 mL solutions, the order of combination A then B then C with C added slowly and with stirring, the statement that the separate solutions are not light sensitive and the combined one is, the precipitate that may or may not form and is to be disregarded, and the brown bottle in which the result "will remain active for months"; Paper; Sizing of the paper; The negative, for the extremely long tonal range and the density range up to 1.85; Sensitizing the paper, for the brush strokes top to bottom and side to side and for about 1 mL for a 4 by 5 and 4 mL for an 8 by 10, so that the kit's 100 mL makes about a hundred 4 by 5 or twenty-five 8 by 10 prints; Exposure, for ultraviolet sensitivity, the 500 or 1000 watt photoflood at 24 to 30 inches, the optimum in the 10 to 30 minute range and the instruction to expose until the shadows and middle tones show detail; Initial wash and development, for about one minute in running soft water at 20 degrees C during which the print darkens and becomes yellowish, and for the three trays of distilled or demineralised water where the supply is alkaline or hard; Fixing bath, for the dilute sodium thiosulfate solution made as 100 g in 2000 mL of water at 52 degrees C, used at 20 degrees C for five minutes, with the statements that a longer period fades the print, that only enough to cover the print should be used and it should be discarded after two or three prints, and that a standard photographic fixing bath must not be used because the very finely divided silver metal of the Van Dyke print will be etched off the paper; Final wash, for 40 minutes in running water at 20 degrees C or 24 minutes followed by Hypo-Clear and a further 15 to 20 minutes; Final steps, for the statement that if the iron salts and the silver salts are not both removed the print will fade with time; Initial wash and development, for the statement that if the wash water is slightly alkaline the iron salts will not be removed, that hard water is not satisfactory because it usually contains dissolved iron salts which will contaminate the print, and for the remedy of three trays of distilled or demineralised water; Fixing bath, for the five minutes at 20 degrees C with the warning that a longer period fades the print, for using just enough fixer to cover the print and discarding it after two or three, and for the instruction not to use a standard photographic fixing bath because the very finely divided silver metal will be etched off the paper; Final steps, for the statement that if the iron salts and the silver salts are not both removed the print will fade with time; Mixing the solutions, for the sensitiser remaining active for months in a brown bottle in a darkroom; Chemicals contained in this kit, for the note that ferric ammonium citrate is somewhat light sensitive and should not be stored in bright light

Used by:Dilute alkaline thiosulfate fixer for iron-silver prints · EDTA and sodium sulfite clearing sequence · Van Dyke Brown sensitiser · P21 What These Processes Need: The Negative, the Paper and the Light · P24 Part XXIV Overview: When Iron Reduces Silver · P24 Contrast Control in Iron-Based Printing · P24 Lab: Printing a Van Dyke Brown · P24 Break/Fix: The Iron-Silver Print That Would Not Clear

Van Dyke Brown Printing Kit 07-0080: instructions and safety data sheetsretrieved 2026-09-04, 2026-09-05, 2026-09-07

Sections: Chemicals contained in this kit; Mixing the solutions — the sensitizer; Van Dyke Brown Printing Kit 07-0080 instructions: chemicals contained in this kit; mixing the solutions, Solution B; L-(+)-tartaric acid safety data sheet, sections 1 to 3; The kit instructions bundled at the front of the safety-data PDF, which carry the same quantities and the same mixing order as the standalone sheet; the Fluka ammonium iron(III) citrate sheet, sections 2 and 3, for the GHS classification, the CAS number 1185-57-5 and the statements that the solid is light sensitive and hygroscopic; the L-(+)-tartaric acid sheet, sections 2 and 3; the silver nitrate sheet from Columbus Chemical Industries, for the oxidising and corrosive classification and the incompatibilities; Chemical safety (silver nitrate); mixing the solutions; Silver Nitrate, Crystal, ACS safety data sheet revised 31 August 2012, sections 2, 3, 6, 7, 8, 9, 10, 11 and 14; Kit instructions, chemical safety: the brown to brown-black skin stain as silver metal bound to the protein of the skin; The sodium thiosulfate safety data sheet bundled with the kit, Univar MSDS ESS82056 for Esseco USA product covering both the anhydrous salt and the pentahydrate — Emergency overview, odourless clear to white crystals or granules which may irritate the skin and respiratory tract, may cause irritation and burns to the eyes, and react with acids to form toxic and irritating sulfur dioxide and hydrogen sulfide gas; Normal handling, the statement that with anhydrous material the reaction of dissolution is exothermic and the solution retains heat while with the hydrate the reaction is endothermic and the solution will cool; Engineering controls, the instruction to provide local exhaust if dusty or misty conditions exist or if there is a release of sulfur dioxide or hydrogen sulfide; Storage, in a cool dry well-ventilated area away from acids and oxidising agents; The silver nitrate sheet bundled in the kit's safety-data PDF — Silver Nitrate, Crystal, ACS, product 4730, Columbus Chemical Industries, revised 31 August 2012: oxidising solids category 2, acute oral toxicity category 4, skin corrosion 1B, serious eye damage 1, with H272, H302, H314 and H400; incompatible materials strong reducing agents, alcohols, ammonia, magnesium and strong bases; the ACGIH TLV, OSHA PEL and NIOSH REL of 0.01 mg/m3; and the accidental-release instruction to prevent spillage entering drains and to pick up without creating dust. The kit instructions bundled in the same document, for the statement that a dilute silver nitrate solution spilled on skin gives a brown to brown-black stain of silver metal bound to skin protein which cannot be washed off; Silver Nitrate, Crystal, ACS safety data sheet revised 31 August 2012, sections 4, 6, 7, 8 and 10; Silver Nitrate, Crystal, ACS safety data sheet revised 31 August 2012, section 6, accidental release measures, including picking the solid up without creating dust and preventing spillage from entering drains; Silver Nitrate, Crystal, ACS safety data sheet revised 31 August 2012, section 6, accidental release measures, and the direction to pick the solid up without creating dust; Silver Nitrate, Crystal, ACS safety data sheet revised 31 August 2012, section 6: accidental release measures, and the environmental precaution to prevent spillage entering drains; Chemicals contained in the kit and the mixing of the sensitizer from ferric ammonium citrate, tartaric acid and silver nitrate

Used by:Ammonium iron(III) citrate · Tartaric acid · Van Dyke Brown sensitiser · P2 Silver Nitrate: The Reagent That Sets the Rules · P4 Silver and the Silver Ion · P11 Lab: Mixing Fixers from Scratch · P24 Lab: Printing a Van Dyke Brown · Van Dyke Brown · Handling silver nitrate · Responding to a silver nitrate spill · Responding to a spilled solid · Responding to a spill · Iron-silver highlights that will not clear

getty.edu

Hippolyte Bayard: A Persistent Pioneerretrieved 2026-09-04

Sections: Exhibition announcement, April 2024

Used by:P1 1839 and the Many Inventors of Photography · Bayard direct positive

The Atlas of Analytical Signatures of Photographic Processes: Silver Gelatinretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Selenium Toning, which states that properly done archival selenium toning did not cause any major colour changes and that the high sensitivity of the XRF instrument allows detection of selenium even in photographs toned very briefly; and the sulfur-toning passage, which states that even when sulfur is clearly visible in the XRF spectrum the main source of the signal is not the Ag2S of the toned image but the sulfur of the BaSO4 of the baryta layer, which makes differentiating the source extremely difficult; The development of the baryta layer and its introduction in 1866; the historical timeline; the three-layer structure and the microplatelets of the baryta layer under magnification; XRF — barium and strontium; resin-coated papers and the overlap of the titanium and barium peaks; Identification: POP silver gelatin photographs — XRF, the attribution of chromium to chromium alum hardening of the gelatin binder of the baryta layer; Copper Toning — X-ray fluorescence of a copper-toned developing-out print and the identification of the copper ferricyanide precipitate; Identification: POP silver gelatin photographs — the absence of a hardened gelatin supercoat on early prints, and the attribution of chromium in the XRF spectrum to chromium alum hardening of the baryta layer's gelatin; Iron Toning; Copper Toning; Iron Toning; Selenium Toning; Printing-out and developing-out silver gelatin — particle size and image colour; Historical timeline (Joseph Swan, English Patent 2,968, 22 July 1879); Identification: POP silver gelatin photographs — the colour of silver bromide print-out images; Identification: POP silver gelatin photographs — visual characteristics and image colour; Identification: DOP silver gelatin photographs — the greenish tonality of prints on papers containing a large concentration of silver iodide; Selenium Toning — the change of purpose from colour to stability, and detection by X-ray fluorescence; Sulfur Toning — brown sulfur toning as the commonest treatment of the early twentieth century, the matte portrait papers it was used on, and why X-ray fluorescence cannot easily identify it; Sulfur Toning; Resin-coated papers — the polyethylene layer filled with titanium dioxide; XRF of RC paper and the overlap of the titanium and barium peaks; Selenium Toning — the change of purpose from a dark brown-orange tone to chemical and environmental stability, and detection by X-ray fluorescence long afterwards; Sulfur Toning — the conversion of image silver to silver sulfide and its appearance; Sulfur Toning — brown sulfur toning as the commonest treatment of the early twentieth century and why X-ray fluorescence cannot easily identify it; Selenium Toning — the change of purpose from a dark brown-orange tone to chemical and environmental stability, the slight increase in image contrast and brilliance when toning is done for permanence, and detection by X-ray fluorescence long afterwards; Uranium Toning: that treatment of a silver image with a mixture of a soluble uranium salt and ferricyanide of potassium yields brown to dark orange-red images, the colour depending on the ratio of the two salts and the duration of toning; the 1960s uranium-toned developing-out photograph and its X-ray fluorescence spectrum, with the two major uranium peaks at 13.64 and 17.22 keV; and the non-contact radioactivity measurement of about 117 micro-REM per hour about 1 cm above the print against a natural background of about 10, with the statements that the uranium is well embedded in the gelatin layer, that handling can be carried out using standard conservation procedures, and that the level is well above background but not high enough to cause health issues in occasional handling; The development of the baryta layer; the three-layer structure; Identification: POP silver gelatin photographs; POP silver gelatin process; RC photographs; Identification: printing-out against developing-out silver gelatin, and the statement that photogenically formed silver particles are much smaller than chemically developed ones; POP silver gelatin process: the note that printing-out papers require deliberate overprinting because the image intensity falls during processing; The printing-out and developing-out silver gelatin processes compared — photogenically formed silver particles are much smaller than chemically developed ones and their colour follows their size; The historical background, for the statement that many so-called gaslight photographic papers could be exposed in-house rather than by sun exposure; Identification of POP silver gelatin photographs - the statement that photogenically developed silver particles are much smaller than chemically developed ones and that the colour of a POP silver chloride image relates to the size of the silver particles, ranging from light yellow-brown to red and darker brown, while silver bromide POP images are cooler and greyer; the account of warm-tone DOP papers, whose emulsion chemistry was slightly modified to restrict the growth of silver particles during development, the smaller developed particles creating the warmer tonality, with the note that there is no chemical signature distinguishing them; the note that greenish portrait papers contained a large concentration of silver iodide and that no iodide remains in the processed image; and the statement that graded papers were manufactured with silver halide particles of different sizes, uniform sizes giving high contrast and mixed sizes lower contrast; Historical background and timeline - the baryta layer traced to its introduction by Jose Martinez-Sanchez and Jean Laurent in 1866, and Kodak introducing baryta coating about 1900; the schematic cross section of a typical baryta-coated fibre-based DOP photograph and the statement that papers of this structure were first used in the 1890s and were still being produced in 2012; the account of the paper stock, originally rag-based, modified after the 1920s by processed wood cellulosic material and by synthetic resins introduced as internal binders and sizes to increase wet strength and hot process stability; RC photographs - the origin of resin-coated paper in a military requirement for material that would not absorb processing solutions, the first commercial RC paper from Kodak in 1968, the paper base sealed on both sides by extruded polyethylene with the verso made matte to resemble ordinary paper that can be written on and the recto filled with titanium dioxide, and the emulsion overcoated by a topcoat or supercoat of hardened gelatin; surface finish produced with matting agents and by calendering or texturing the paper or the baryta; base tints from pure white to buff, made with coloured stock or colourants in the baryta; Other analytical signatures - optical brightening agents added to the paper base, baryta layer or emulsion, dated to industrial production about 1953 and general use after 1955 on Paul Messier's research, and the statement that their concentration can be reduced by extensive washing or quenched by later treatment; Variable Contrast Photographic Material - graded papers manufactured with silver halide particles of different sizes, uniform sizes giving high contrast and mixed sizes lower contrast; Rudolph Fisher's 1911 German patent for a paper with variable response to different colours of light, never marketed; the US Defender Company, later acquired by DuPont, introducing the first variable contrast paper in 1940 under the name the atlas prints as Varigram; Ilford Ltd introducing the first Multigrade paper at about the same time in England, commercially available only in 1950 and exported to the United States from 1956; Kodak's Polycontrast papers in the spring of 1957; variable contrast papers becoming dominant only in the 1990s; and the description of VC papers as coated with a mixture of two or three silver halide emulsions, all of equal contrast and of the same sensitivity to blue light but each sensitised in different proportions to green; Gold Toning — that special gold-toning formulas produced very pleasing bright-red DOP photographs and also beautiful bright-blue tonality, both confirmed as gold by X-ray fluorescence; Uranium Toning — brown to dark orange-red images from a soluble uranium salt with potassium ferricyanide; Iron Toning — that a number of toning formulas were published for blue toning of silver images based on converting silver particles to silver salts and then forming a blue image by reaction with a solution of an iron salt, that different chemical mechanisms of these reactions often yield blue images composed of Prussian blue pigments, that the presence of Prussian blue can be determined by XRF showing a higher concentration of iron in the Dmax area than in the Dmin area, and that blue toning was also known as cobalt toning, the name indicating the colour of the image rather than the presence of any cobalt in the bath; and Copper Toning — a DOP photograph toned using a copper sulfate–potassium ferricyanide formula whose XRF spectrum shows the presence of both copper and iron from the precipitate of the copper ferricyanide complex responsible for the red colour of the image; Identification of POP silver gelatin photographs - the colour of a POP silver chloride image relates to the size of the silver particles; most silver gelatin POP photographs were gold toned, the toning process increases the size of silver particles, the growth is not straightforward because there is some deposition of gold onto the silver particles while analysis of the gold bath during toning shows a growing concentration of silver in it, and toning usually shifts the image colour to red-violet or dark black-violet; the XRF signature of POP silver gelatin photographs showing both silver and gold as imaging metals; Post-Process-Treated DOP Silver Gelatin Photographs - brown sulfur toning as the most common toning of the early twentieth century, used on the matte-surface portrait papers in vogue between the wars, and the warning that the sulfur seen in the XRF spectrum of such a print comes mainly from the barium sulfate of the baryta layer rather than from the toned image, which makes the source of the signal extremely difficult to separate; Gold Toning, that special gold-toning formulas produced bright-red DOP images and also bright-blue ones, both confirmed as gold by XRF; Uranium Toning, that a soluble uranium salt with potassium ferricyanide yields brown to dark orange-red images whose colour depends on the ratio of the two salts and the duration of toning; Iron Toning, that blue toning formulas work by converting silver particles to silver salts and then forming a blue image by reaction with an iron salt, often yielding Prussian blue, confirmed by a higher iron concentration in the Dmax area than in the Dmin area, and that blue toning was also known as cobalt toning after the colour rather than any cobalt in the bath; Copper Toning, a DOP photograph toned with a copper sulfate and potassium ferricyanide formula whose XRF spectrum shows both copper and iron from the precipitate of the copper ferricyanide complex responsible for the red colour of the image; and Selenium Toning, first used to give a dark brown-orange tone and later recognised for increasing the chemical and environmental stability of silver particles, with the note that properly done archival selenium toning caused no major colour change, the only perceivable visual effect being a slight increase in image contrast and brilliance, and that selenium is detectable by XRF even after very short toning; Selenium Toning - that selenium toning was first used to give silver gelatin photographs a dark brown-orange tone and that selenium was later recognised for increasing the chemical and environmental stability of silver particles; that properly done, archival selenium toning did not cause any major colour changes or shifts, the only perceivable visual effect being a slight increase in image contrast and brilliance; and that even when archival selenium toning cannot be recognised visually the presence of selenium can be detected by X-ray fluorescence, the instrument's sensitivity allowing detection even in photographs toned for a very short period. Also the introduction to warm-tone papers, that their emulsion chemistry was modified to restrict the growth of silver particles during development and that the smaller developed particles created the warmer tonality; Selenium Toning - that selenium toning was first used to give a dark brown-orange tone and later recognised for increasing the chemical and environmental stability of silver particles, that properly done archival selenium toning caused no major colour change with the only perceivable visual effect being a slight increase in image contrast and brilliance, and that selenium is detectable by X-ray fluorescence even after very short toning; Post-Process-Treated DOP Silver Gelatin Photographs, that brown sulfur toning was the most common toning of the early twentieth century and was used on the matte-surface portrait papers in vogue between the wars, and the warning that the sulfur seen in the X-ray fluorescence spectrum of such a print comes mainly from the barium sulfate of the baryta layer rather than from the toned image, which makes the source of the signal extremely difficult to separate; Selenium Toning, which states that properly done archival selenium toning did not cause any major colour changes or shifts, that the only perceivable visual effect was a slight increase in image contrast and brilliance, and that the high sensitivity of the XRF instrument allows the detection of selenium even in photographs toned for a very short period of time as part of archival processing; and the sulfur-toning passage, which states that even when sulfur is clearly visible in the XRF spectrum the main source of the signal is not the Ag2S of the toned image but the sulfur of the BaSO4 of the baryta layer, which is almost always present and makes differentiating the source of the sulfur signal extremely difficult; Uranium Toning - that treatment of a silver image with a mixture of a soluble uranium salt and ferricyanide of potassium yields brown to dark orange-red images, the colour depending on the ratio of the two salts and the duration of toning; the 1960s uranium-toned developing-out photograph and its X-ray fluorescence spectrum, with the two major uranium peaks at 13.64 and 17.22 keV; and the noncontact radioactivity measurement of about 117 micro-REM per hour about 1 cm above the print against a natural background of about 10, with the statements that the uranium is well embedded in the gelatin layer, that handling can be carried out using standard conservation procedures, and that the level is well above background but not high enough to cause health issues in occasional handling; Post-Process-Treated DOP Silver Gelatin Photographs - Sulfur Toning, that brown sulfur toning was the most common toning of the early twentieth century, and that in interpreting XRF spectra of sulfur-toned photographs the main source of the sulfur signal is not the silver sulfide of the toned image but the barium sulfate of the baryta layer, which makes the source of the sulfur signal extremely difficult to distinguish; Gold Toning, that gold-toning formulas produced red and even bright-blue images whose XRF spectra clearly show gold; Uranium Toning, that a soluble uranium salt with potassium ferricyanide yields brown to dark orange-red images, that uranium is confirmed by two major XRF peaks at 13.64 and 17.22 keV and quickly by a sensitive radiation meter, and that the measured radioactivity of the example print was about 117 micro REM per hour at about 1 cm against a natural background of about 10, well above background but not high enough to cause health issues in occasional handling; Iron Toning, that blue toning formulas yield images composed of Prussian blue pigments identified by a higher iron concentration in the Dmax than the Dmin area; Copper Toning, that a copper sulfate and potassium ferricyanide formula gives a red image whose spectrum shows copper and iron from the copper ferricyanide precipitate; and Selenium Toning, that selenium was first used for a dark brown-orange tone, was later recognised for its ability to increase the chemical and environmental stability of silver particles, entered archival processing of photographs for the art and museum market during the second half of the twentieth century, that properly done archival selenium toning caused no major colour change and only a slight increase in image contrast and brilliance, and that even when it cannot be recognised visually the presence of selenium toning can be detected by XRF spectrometry, the instrument being sensitive enough to detect selenium in photographs toned for a very short period; Process description and identification characteristics; The analytical signatures by which a silver gelatin object is distinguished from the processes that preceded it, and the instrumental methods that settle a contested attribution; Uranium Toning — that treatment of a silver image with a mixture of a soluble uranium salt and ferricyanide of potassium yields brown to dark orange-red images, the colour depending on the ratio of the two salts and the duration of toning; the 1960s uranium-toned developing-out photograph and its X-ray fluorescence spectrum, with the two major uranium peaks at 13.64 and 17.22 keV; and the noncontact radioactivity measurement of about 117 micro-REM per hour about 1 cm above the print against a natural background of about 10, with the statements that the uranium is well embedded in the gelatin layer, that handling can be carried out using standard conservation procedures, and that the level is well above background but not high enough to cause health issues in occasional handling; The development of the baryta layer; the three-layer structure; resin-coated papers; Iron Toning — a blue-toned silver gelatin photograph showing Prussian blue, identified by a higher iron concentration in the maximum-density areas than in the highlights; The development of the baryta layer and its introduction in 1866; the three-layer structure and the microplatelets of the baryta layer under magnification; XRF — barium and strontium; Resin-coated papers — the polyethylene layers, the titanium-dioxide-pigmented layer under the emulsion and the hardened gelatin supercoat; the overlap of the titanium and barium peaks in XRF; POP silver gelatin process, step 2 - POP requires some level of overprinting because the image intensity is decreased during processing; Printing-out paper process - POP requires some level of overprinting because the image intensity is decreased during processing

Used by:P29 Capstone Stage 6: Permanence, Presentation and the Finished Portfolio · Barium sulfate · Chrome alum · Copper(II) sulfate · Gelatin · Potassium ferrocyanide (anhydrous) · Potassium ferrocyanide trihydrate · Selenium · Silver · Silver bromide · Silver chloride · Silver iodide · Silver selenide · Silver sulfide · Sodium selenite · Sodium sulfide · Titanium dioxide · HARMAN SELENIUM TONER · KODAK Rapid Selenium Toner · Kodak ST-1 · Moersch MT3 Variotoner · Moersch MT1 Selentoner · Uranium toner · Printing processes compared · P1 Silver Salts and Light: Schulze to Ritter · P1 Experiment: The Image That Would Not Stay · P4 Silver and the Silver Ion · P7 Assignment: Night, the Very Long Exposure and Solargraphy · P12 Permanence and Image Deterioration · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · P18 The Structure of a Printing Paper: Base, Baryta, Emulsion and Supercoat · P18 Variable-Contrast Papers: Three Emulsions, One Sheet · P20 Gold, Iron-Blue and the Other Metal Toners · P20 What a Toner Actually Does to a Silver Image · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P20 Assignment: The Toned Print · P20 The Toners We Study and Do Not Use · P20 Toning, Permanence and What the Evidence Actually Supports · P25 Assignment: The Process Comparison Atlas · P26 Assignment: Assessing a Historical Process for Hazard · P26 Uranium, Mercury and the Heavy-Metal Treatments · Process atlas · Iron-blue toned silver gelatin print · Selenium toned silver gelatin print · Sulphide (sepia) toned silver gelatin print · Silver gelatin developing-out print on fibre base · Silver gelatin developing-out print on resin-coated base · Solargraph camera placement and retrieval · Storing unfixed prints for later fixing

github.com

IUPAC Digitized pKa Dataset, high-confidence subset v2.3retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Acetic acid (Ethanoic acid), pKa at 25 degrees C; Citric acid, pKa3, at 20 degrees C in 0.1 mol/L sodium perchlorate; Entry serjeant2861: l-ascorbic acid, pKa1 and pKa2 at 0.4, 25 and 40 °C; Benzotriazole — pKa1 8.64 and 8.2 (Perrin) and 8.37 and 8.11 (Serjeant); pKaH1 1.6; Entry serjeant2826: 1,2-benzenediol, pKa1 and pKa2, with the note that the dianion oxidises readily in air; Entry serjeant2828: 1,4-benzenediol (hydroquinone), pKa1 and pKa2; searched for 2-chlorobenzene-1,4-diol and found no entry; Citric acid, pKa1 to pKa3 at 20 degrees C in 0.1 mol/L sodium perchlorate; Entry serjeant3410: benzoic acid, 3,4,5-trihydroxy- (gallic acid) — pKa1, pKa2 and pKa3 across several determinations; Entry serjeant2828: 1,4-benzenediol, pKa1 and pKa2; Entry perrin556: aniline, 4-hydroxy-N-methyl-, pKaH1; Oxalic acid, pKa1 and pKa2 at 25 degrees C in 0.1 mol/L sodium perchlorate; Entry serjeant3097: phenol, 4-amino-, pKa1; Entry serjeant2832: 1,2,3-benzenetriol, pKa1, pKa2 and pKa3; Entry serjeant2861: l-ascorbic acid, pKa1 and pKa2 at 25 °C; Tartaric acid, pKa1 and pKa2 for the optically active and meso forms; Entry serjeant5041: phenol, 2-isopropyl-5-methyl- (thymol), pKa1 10.62 at 20 °C, assessed approximate; Entry serjeant2043, acetic acid, pKa1 4.76 at 25 degrees C; entry serjeant2865, citric acid, pKa1 2.87, pKa2 4.35 and pKa3 5.68 at 20 degrees C at ionic strength 0.1 in sodium perchlorate; Acetic acid (Ethanoic acid), pKa at 25 degrees C; Citric acid, pKa1 to pKa3 at 20 degrees C in 0.1 mol/L sodium perchlorate; Entry serjeant2043, acetic acid, pKa 4.76 at 25 degrees C; Entry serjeant2861: l-ascorbic acid, pKa1 and pKa2 at 25 degrees C; Citric acid, pKa1 2.87, pKa2 4.35 and pKa3 5.68 at 20 degrees C in 0.1 mol/L sodium perchlorate, all assessed as approximate; Entry serjeant2826: 1,2-benzenediol, pKa1 and pKa2, and the note that the dianion oxidises readily in air; Tartaric acid — pKa1 3.17 and pKa2 4.91 for the meso form at 25 °C, assessed reliable, and the approximate 3.03 and 4.46 for the D form, in the high-confidence dataset v2.3; Entry serjeant3097, phenol 4-amino-, pKa1: 10.46 and 10.44 at 25 C; Entry serjeant2043, acetic acid; entry serjeant2865, citric acid; High-confidence dataset v2.3, Serjeant entry for citric acid at 20 degrees C in 0.1 mol/L sodium perchlorate; Entry perrin: 4-aminophenol pKa; entry serjeant2830 and neighbours: 1,2-benzenediol pKa1 and pKa2; entry serjeant2832: 1,2,3-benzenetriol pKa1, pKa2 and pKa3; L-ascorbic acid pKa1 and pKa2; Entry serjeant2828: 1,4-benzenediol pKa1 and pKa2; entry perrin556: aniline, 4-hydroxy-N-methyl-, pKaH1; Benzotriazole: pKa1 at 20 degrees C and ionic strength 0.05 mol/L, and the second determination at 0.4 mol/L; Benzotriazole pKa1 8.64 at 20 degrees C at 0.05 mol/L, assessed approximate; Entry serjeant2828: 1,4-benzenediol pKa1 9.88; entry perrin556: aniline, 4-hydroxy-N-methyl-, pKaH1; L-ascorbic acid pKa1 4.04; searched for 1-phenyl-3-pyrazolidone and phenidone, no entry; Entry serjeant2043, acetic acid, pKa1 4.76 at 25 degrees C; entry serjeant2865, citric acid, pKa1 2.87, pKa2 4.35 and pKa3 5.68 at 20 degrees C at I = 0.1 in sodium perchlorate; Entry serjeant2043, acetic acid (ethanoic acid), pKa1 4.76 at 25 degrees C; entry serjeant2865, citric acid, pKa1 2.87, pKa2 4.35 and pKa3 5.68 at 20 degrees C at I = 0.1 in sodium perchlorate

Used by:Acetic acid (glacial) · Ammonium citrate (tribasic) · Ascorbic acid · Benzotriazole · Catechol · Chlorohydroquinone · Citric acid (anhydrous) · Gallic acid · Hydroquinone · Metol · Oxalic acid · p-Aminophenol · Pyrogallol · Sodium ascorbate · Tartaric acid · Thymol · Citric Acid Stop Bath · Foma FOMAFIX · Kodak HT-2 · Kodak SB-5 · KODAK PROFESSIONAL XTOL Developer · EDTA, citric acid and hydrochloric acid clearing sequence · Pyrocat-HD · Rochelle salt kallitype developer · Rodinal-type p-aminophenol developer · Sodium citrate developer · Sodium citrate kallitype developer · Stop baths compared · P3 Acids, Bases and pH · P3 Buffers and Buffer Capacity · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 Restrainers and Antifoggants · P8 Superadditivity: Why Two Agents Beat One · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Experiment: Comparing Developing Agents · P10 Experiment: Measuring Stop Bath Capacity · P10 Why Stopping Works

gml.noaa.gov

General Solar Position Calculationsretrieved 2026-09-04, 2026-09-05

Sections: Solar hour angle ha = (tst / 4) - 180 and the solar zenith angle from cos(zenith) = sin(lat)sin(decl) + cos(lat)cos(decl)cos(ha); the declination series in the fractional year; The solar zenith angle from cos(zenith) = sin(lat)sin(decl) + cos(lat)cos(decl)cos(ha), and the declination series in the fractional year; The solar zenith angle from cos(zenith) = sin(lat)sin(decl) + cos(lat)cos(decl)cos(ha), which at an hour angle of zero reduces to a solar-noon elevation of 90 degrees minus latitude plus declination

Used by:P7 Assignment: Architecture, Low Viewpoint and the Flat Plane · P7 Assignment: Night, the Very Long Exposure and Solargraphy · Solargraph camera placement and retrieval

gov.uk

Advice on safe storage, handling and use of eggs for cateringretrieved 2026-09-07, 2026-09-08

Sections: The handling advice — hands washed and dried before and after handling eggs, surfaces and equipment cleaned and disinfected afterwards, cracked, damaged or dirty eggs not used, eggs kept away from other foods, and the statement that no egg can be guaranteed free from Salmonella whatever the source or brand; The handling advice in full — store eggs in a cool dry place, ideally keep refrigerated until use; do not use eggs that are cracked, damaged or dirty; wash and dry hands thoroughly before and after handling eggs; clean and disinfect surfaces and equipment after handling eggs; keep eggs away from other foods; and the statement that "No egg can be guaranteed to be free from Salmonella, whatever the source or brand", with British Lion and Laid in Britain eggs presenting "a very low risk of Salmonella"; No egg can be guaranteed free from Salmonella whatever the source or brand; hands washed and dried before and after; surfaces and equipment cleaned and disinfected afterwards; cracked, damaged or dirty eggs rejected; eggs kept away from other foods

Used by:P23 Part XXIII Overview: Albumen Printing · P23 Lab: Preparing and Coating Albumen Paper · Preparing and coating albumen paper

Find a local hazardous waste disposal serviceretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Find a local hazardous waste disposal service; Hazardous waste from households — what counts and where the council takes it; Hazardous waste from households — what counts and where it goes; Hazardous waste from households — what counts, that councils may offer a collection service, and the note that the service is available in England and Wales only; Hazardous waste from households — what counts and where it goes, England and Wales; Hazardous waste from households, England and Wales; Hazardous waste from households, and where it goes; Hazardous waste from households, and the note that council collection services are available in England and Wales only; What you need to know; availability; Find a local hazardous waste disposal service, and the statement on the page that it is available in England and Wales only; Hazardous waste from households - what counts as hazardous household waste and the direction to use the local council's household waste and recycling centre or its collection service, England and Wales; Hazardous waste from households — the direction to use the local council's household waste and recycling centre or its collection service, England and Wales; Hazardous waste from households, for the household waste and recycling centre route; Hazardous waste from households — what counts as hazardous, and the routing of it to the council's collection service rather than to the bin or the drain; Hazardous waste from households - what counts, and that it goes to the council's collection service rather than to the bin or the drain; The council hazardous waste service finder, and its scope statement that the service is available in England and Wales only; Hazardous waste from households — what counts as hazardous waste, and the direction to the local authority collection service rather than to the bin or the drain, with the note that the service differs between authorities; The household hazardous waste route, which directs hazardous waste from a home to a local authority collection service rather than to the bin or the drain, and which differs between authorities; Household hazardous waste: what a household waste and recycling centre accepts and the requirement to check with the authority

Used by:Amidol · Barium sulfate · Bitumen of Judea · Bromine · Cadmium bromide · Catechol · Chlorine · Chloroauric acid · Chlorohydroquinone · Chrome alum · Diethyl ether · Dimezone S · Erythrosin · Formaldehyde · Gallic acid · Glutaraldehyde · Glycin · Glyoxal · Gold(III) chloride · Hydroquinone · Iodine · Oil of lavender · Lead(II) acetate · Lead(II) nitrate · Mercury · Mercury(II) chloride · Metol · Nickel(II) sulfate · Nitrocellulose · p-Aminophenol · Palladium(II) chloride · Phenidone · Potassium alum · Potassium chlorate · Potassium cyanide · Potassium ferricyanide · Potassium ferrocyanide (anhydrous) · Potassium ferrocyanide trihydrate · Potassium tetrachloropalladate(II) · Potassium tetrachloroplatinate(II) · Pyrogallol · Selenium · Sodium cyanide · Sodium selenite · Sodium selenosulfate · Sodium sulfide · Sodium tetrachloropalladate(II) · Tannic acid · Tetraazaindene · Thallium(I) sulfate · Thiourea · Thymol · Titanium dioxide · Uranyl nitrate hexahydrate · Cyanide fixing and toning · Kodak Hypo Clearing Agent and the washing accelerator Kodak patented · Lead additions to platinum sensitisers · Lead, thallium and nickel cyanotype toners · Mercuric sepia platinotype · Moersch MT3 Variotoner · Rodinal-type p-aminophenol developer · P1 Assignment 1: A Botanical Cyanotype Photogram, After Atkins · P2 Waste: Streams, Silver, and the Drain You Must Not Use · P12 Silver Recovery and the Responsible Darkroom · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Experiment: Selenium Toning and the Print Curve · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Lab: Toning the Prussian Blue Image · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Lab: Printing a Van Dyke Brown · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Assignment: Assessing a Historical Process for Hazard · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · P26 Uranium, Mercury and the Heavy-Metal Treatments · The disposal caveat · Segregating alternative-process waste

Hazardous waste: Overviewretrieved 2026-09-06

Sections: Overview — the duty of care on a business that produces, holds, carries or receives hazardous waste in England, the separate signposts to the rules in Northern Ireland, Scotland and Wales, and chemicals and solvents among the listed examples of hazardous waste

Used by:P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide

Laser radiation: safety adviceretrieved 2026-09-04, 2026-09-05

Sections: Standards for laser products: Class 2; Consumer laser products, on pointers marked Class 2 that measure as Class 3B or 4; Standards for laser products: Class 2, visible 400-700 nm, safe for short exposures but hazardous on deliberate staring; Consumer laser products: pointers marked Class 2 or under 1 mW measured as Class 3B or Class 4, and the eye injuries that followed; UKHSA advice: never point a consumer laser beam at people; Standards for laser products - Class 2, visible 400 to 700 nm, safe for short exposures through the natural aversion response but hazardous for deliberate staring, with dazzle, flash-blindness and afterimages particularly under low ambient light; Laser consumer products - red 630 to 670 nm, green 532 nm, blue about 445 nm, and the common faults of higher than stated output power, additional often invisible emission wavelengths and incorrect labelling, with pointers marked Class 2 or under 1 mW measured as Class 3B or Class 4; UKHSA advice - beams up to Class 3R should never be pointed at people, there is no simple test for non-specialists to determine output power, medical attention only if afterimages persist for hours or reading vision is disturbed, and the Laser Misuse (Vehicles) Act 2018

Used by:P6 Part VI Overview: Build a Pinhole Camera · P6 Making and Measuring Pinholes · Measuring a pinhole with a Class 2 laser pointer

The Highway Code: rules for pedestrians (1 to 35)retrieved 2026-09-04, 2026-09-05

Sections: Rules 1 and 2, pavements and footways and keeping to the right-hand side where there is none; Rule 3, being seen at night: reflective materials in the dark and light-coloured or fluorescent clothing in poor daylight; Rules 1 and 2, pavements and keeping to the right-hand side where there is none; Rules 1 and 2: pavements and footways, and keeping to the right-hand side where there is none; Rules 1, 2 and 7: pavements and footways, keeping to the right-hand side where there is none, and crossing without running; Rule 1 - pavements and footways should be used if provided; Rule 2 - where there is no pavement, keep to the right-hand side of the road so that you can see oncoming traffic; Rule 3 - wear or carry something light-coloured, bright or fluorescent in poor daylight, and when it is dark use reflective materials such as armbands, sashes, waistcoats, jackets and footwear

Used by:P7 Assignment: Architecture, Low Viewpoint and the Flat Plane · P7 Assignment: Night, the Very Long Exposure and Solargraphy · P7 Assignment: Panorama, Curved Plane and Multiple Pinholes · P7 Assignment: Time in the Frame, Moving Water, Clouds, People and Traffic · Night exposure session

graphicsatlas.org

Graphics Atlas guided tour: Salted Paper (process_id 269)retrieved 2026-09-07

Sections: The guided tour's six named views for a salted paper print - Image Tones, Paper Fibers, Matte Surface, Retouching, Tears and Layer Structure - and its four worked examples, Gore Hall at Harvard College, a photograph on silk, a tinted carte de visite and a yearbook portrait; with the caveat that the mirrored text carries the navigation and these labels but none of the descriptive prose the live site shows beside each view; The guided-tour markup of a salted paper print

Used by:P22 The Variants of the Salt Print and How a Conservator Identifies One · P25 Assignment: The Process Comparison Atlas

Graphics Atlas: Guided Tour - Albumen (Blue Tinted CDV)retrieved 2026-09-07

Sections: The note on the object — an albumen print mounted to a thick 2½ × 4 inch paper card with rounded corners, and the blue tint introduced in the 1860s; The note on the object — an albumen print mounted to a thick 2½ × 4 inch paper card, the sitter framed in an oval, the card with rounded corners, and the blue tint added to the albumen layer, a technique introduced in the 1860s and popular in pink, yellow and blue; The guided-tour markup of an albumen print, including surface and layer structure

Used by:P23 Lab: Sensitising, Printing and Toning an Albumen Print · P23 The Albumen Print as an Object, and How It Decays · P25 Assignment: The Process Comparison Atlas

Graphics Atlas: Guided Tour - Ambrotype (Cutting Method)retrieved 2026-09-06

Sections: The note on the Cutting-method ambrotype: that in 1854 James Ambrose Cutting developed a method of adhering two pieces of glass with Canada balsam, meant as a hermetic seal but ultimately unnecessary because the varnish layer alone worked well as a protectant; that ambrotypes made under Cutting's patent are known to exhibit deterioration caused by the technique, visible here as a yellowish-green hue; and that Cutting's lasting contribution was the name. Also the marked features, which include ruby glass, drip lines, milky-white highlights and hand colouring

Used by:P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That

Graphics Atlas: Guided Tour - Carbonretrieved 2026-09-06

Sections: The guided-tour feature list for a carbon carte de visite — baryta layer, image tone, image relief, pigment particles and deterioration as the five things the atlas marks up on the object; and the note on the view, recording that the photographer Achilles Sacre-Smits of Ghent printed the words charbon inalterable on the mount, that the tendency of silver-based photographs to fade was well known, and that by writing those words he is boasting that his carbon prints will not fade

Used by:P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes

Graphics Atlas: Guided Tour - Platinum (Amateur Portrait, ca. 1900)retrieved 2026-09-07

Sections: The process note that platinum printing was exalted as more artistic and beautiful than other printing processes for the softness and subtlety of tone it offered, and that platinum was about three times faster than silver chloride printing-out papers; The process note that platinum was about three times faster than silver chloride printing-out papers and could be printed in diffused light, and that several varieties of platinum paper were commercially available at the turn of the twentieth century; The guided-tour headings under which a platinum print is marked up — contact print, retouching, image tone, tonal range, paper fibres visible, matte surface, layer structure — and the statement that platinum was about three times faster than silver chloride printing-out papers

Used by:P25 Cost, Permanence and When a Platinum Print Earns Its Price · P25 Noble Metal Chemistry and the Platinotype · P25 Assignment: The Process Comparison Atlas

Graphics Atlas: Guided Tour - Silver Gelatin DOPretrieved 2026-09-06

Sections: The silver gelatin developing-out section of the guided-tour index, which catalogues toned prints as object types of their own, among them a polysulfide-toned postcard, a selenium-toned stereoview, a sulfur-toned studio portrait and a dye-toned metallic postcard

Used by:P20 Toning, Permanence and What the Evidence Actually Supports

Graphics Atlas: Guided Tour - Tintype (Cased Object)retrieved 2026-09-06

Sections: The note on the cased tintype: that early tintypes were presented in cases like those used for ambrotypes and daguerreotypes, that the package is photograph, brass mat, cover glass and preserver in a case of wood covered in embossed paper or leather and lined with velvet, that in this example the cover glass is in direct contact with the plate, and that a detached lid is a common form of deterioration for cased objects. Also the marked features, which include discoloured highlights, black spots and a broken preserver

Used by:P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That

Graphics Atlas: Guided Tour - Wet Plate Collodionretrieved 2026-09-06

Sections: The features the atlas marks up on its example wet plate collodion negative - glass support, glass side, image tone, developer sweeps, artifacts, varnish lines, surface abrasions, silver image particles and layer structure - read as evidence of what a conservator is taught to look at on such an object

Used by:P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That

gsrs.ncats.nih.gov

Substance record for ACACIA, UNII 5C5403N26O, in the Global Substance Registration Systemretrieved 2026-09-04

Sections: Substance record for ACACIA, UNII 5C5403N26O — preferred name, substance class structurallyDiverse, source material class ORGANISM, type PLANT, part resin, CAS 9000-01-5, ECHA (EC) 232-519-5, the food-additive codes 21 CFR 172.780 and 184.1330, JECFA and Codex INS-414 and GRAS notification GRN 58; Registry entry for acacia — structurally diverse, the part named as resin

Used by:Gum arabic · Gum bichromate

Substance record for EGG WHITE, UNII 3E0I92Z2GR, in the Global Substance Registration Systemretrieved 2026-09-04

Sections: Substance record for EGG WHITE, UNII 3E0I92Z2GR — preferred name, substance class structurallyDiverse, source material class ORGANISM, type BIRD, part egg white, CAS 9006-50-2, and the registry's own name list, which includes ALBUMEN and GALLUS GALLUS EGG WHITE

Used by:Albumen

Substance record for GELATIN, UNII 2G86QN327L, in the Global Substance Registration Systemretrieved 2026-09-04

Sections: Substance record for GELATIN, UNII 2G86QN327L — preferred name, substance class, definition type, and the code list including CAS 9000-70-8 and ECHA 232-554-6; the registry's component substances distinguished by species, cure and Bloom number; Substance record for GELATIN, UNII 2G86QN327L: substance class Mixture, CAS 9000-70-8, EC 232-554-6, and the component substances named by species, cure and Bloom number; Registry entry for gelatin — identity and description

Used by:Gelatin · P5 Gelatin, the Photographic Binder · Carbon print

Substance record for LAVENDER OIL, UNII ZBP1YXW0H8, in the Global Substance Registration Systemretrieved 2026-09-04

Sections: Substance record for LAVENDER OIL, UNII ZBP1YXW0H8 — preferred name, substance class structurallyDiverse, source material class ORGANISM, type PLANT, parts flower, leaf and stem, CAS 8000-28-0, and the separate registry entries for SPIKE LAVENDER OIL and LAVANDIN OIL

Used by:Oil of lavender

Substance record for MARANTA ARUNDINACEA ROOT, UNII FVN346W31A, in the Global Substance Registration Systemretrieved 2026-09-05

Sections: Substance record for MARANTA ARUNDINACEA ROOT, UNII FVN346W31A — substance class structurallyDiverse, source material class ORGANISM, type PLANT, part root, and the name list carrying ARROWROOT ROOT, WEST INDIAN ARROWROOT ROOT and ST. VINCENT ARROWROOT ROOT alongside the botanical synonyms Maranta indica, Maranta ramosissima and Maranta sylvatica

Used by:Arrowroot

Substance record for PYROXYLIN, UNII KYR8BR2X6O, in the Global Substance Registration Systemretrieved 2026-09-04

Sections: Substance record for PYROXYLIN, UNII KYR8BR2X6O — preferred name NITROCELLULOSE, substance class polymer, definition type PRIMARY, the polymer classification (homopolymer, linear, substituted, biosynthetic source type), CAS 9004-70-0, and the registry's own note that this is an incomplete polymer record

Used by:Nitrocellulose

Substance record for STARCH, CORN, UNII O8232NY3SJ, in the Global Substance Registration Systemretrieved 2026-09-05

Sections: Substance record for STARCH, CORN, UNII O8232NY3SJ — substance class Mixture, definition type PRIMARY, and the code list carrying CAS 9005-25-8 with the type GENERIC (FAMILY); the registry's practice of filing a separate mixture record for each botanical source

Used by:Arrowroot

gutenberg.org

The Pencil of Natureretrieved 2026-09-04, 2026-09-06

Sections: Brief Historical Sketch of the Invention of the Art, for Talbot's own retrospective account of the calotype and of the sensitiveness of the paper, and for the proviso that a negative will yield an almost unlimited number of copies "provided that every portion of iodine has been removed from the picture before the copies are made"; Brief Historical Sketch of the Invention of the Art, for the 1834 Geneva finding that silver iodide was not sensitive at all; for the proviso that the number of copies a negative will yield is almost unlimited "provided that every portion of iodine has been removed from the picture before the copies are made"; and for Talbot's own retrospective verdict that the fixing process by iodine "must be considered as not sufficiently certain to be retained in use as a photographic process"; Brief Historical Sketch of the Invention of the Art: the uneven brush strokes whose borders blackened faster, the conjecture that those portions had absorbed a lesser quantity of salt, the experiment that established "that a lesser quantity of salt produced a greater effect", Talbot's reading of the result as an imperfect chloride or subchloride, the observation that abundance of salt almost destroyed the action so that a bath of salt water was afterwards used as a fixing process, the leaves and lace covered with a glass pressed down tightly, the hour or two in the camera obscura that gave the roofline and left the shadows blank, the 1834 Geneva finding that silver iodide was not sensitive at all, the fixation by iodide of potassium and the whitening fading that followed it, and the repeated alternate washes of salt and silver with the paper used moist that brought a bright-day camera exposure down to ten minutes; Brief Historical Sketch of the Invention of the Art; Brief Historical Sketch of the Invention of the Art; Plate VI The Open Door; Plate VII Leaf of a Plant; Plate XXIV A Fruit Piece; Brief Historical Sketch of the Invention of the Art; Plate XXIV A Fruit Piece; Brief Historical Sketch of the Invention of the Art; Plate VII Leaf of a Plant; Plate VI The Open Door; Plate VII Leaf of a Plant; the remarks preceding the plates

Used by:Talbot's gallo-nitrate of silver · Talbot's calotype iodised paper · Talbot's photogenic drawing paper · P1 1839 and the Many Inventors of Photography · P1 Talbot: Photogenic Drawing, the Calotype and the Negative-Positive Principle · Calotype negative · Photogenic drawing · Salted paper print

hamamatsu.com

Si photodiodes, technical note KSPD9001Eretrieved 2026-09-04, 2026-09-05

Sections: 2-3 Spectral response; Cut-off wavelength: lambda equals 1240 divided by the threshold energy in electronvolts; Cut-off wavelength: the relation lambda equals 1240 divided by the threshold energy in electronvolts, and the band picture of a semiconductor detector; Cut-off wavelength and band gap: the relation lambda equals 1240 divided by the threshold energy in electronvolts; Section 2-3 - the threshold relation between photon energy and wavelength, the cut-off wavelength in nanometres being 1240 divided by the threshold energy in electronvolts, which places silicon's long-wavelength limit beyond the visible; Section 2-2, linearity - the photocurrent of a silicon photodiode is linear over more than nine orders of magnitude between 10 to the minus 12 and 10 to the minus 2 watts, the lower limit set by the noise equivalent power and the upper by load and series resistance; Section 2-2, linearity - the photocurrent is linear over more than nine orders of magnitude for incident power between 10 to the minus 12 and 10 to the minus 2 watts, the lower limit set by the noise equivalent power and the upper by the load and series resistances; section 2-4, noise characteristics - Johnson noise from the shunt resistance and shot noise from the dark and photo currents; Section 2-1 - an op amp connected to the photodiode presents an equivalent load of the feedback resistance divided by the open-loop gain, several orders of magnitude smaller, which is what allows the short-circuit current to be measured; section 2-2, linearity - the photocurrent is linear over more than nine orders of magnitude for incident power between 10 to the minus 12 and 10 to the minus 2 watts, with the lower limit set by the noise equivalent power and the upper by the load and series resistances, and the linearity degrading as the series resistance rises; Section 2-3, dark current, and section 2-4, noise characteristics - dark current rises with temperature and contributes shot noise alongside the photocurrent, and Johnson noise arises from the shunt resistance; cited as the physical basis for the temperature behaviour of the detector's dark term; Section 1, operating principle, and section 2-1, current versus voltage characteristics - the short-circuit current is proportional to the light level while the open-circuit voltage changes logarithmically with it and varies greatly with temperature, making it unsuitable for measurement of light level; the series resistance is a few ohms and the shunt resistance 10 to the 7th to 10 to the 11th ohms, so their terms stay negligible over a wide range; an op-amp connected to the photodiode presents an equivalent load of the feedback resistance divided by the open-loop gain, several orders of magnitude smaller, enabling ideal measurement of the short-circuit current. Section 2-2, linearity - the photocurrent is linear over more than nine orders of magnitude for incident light between 10 to the minus 12 and 10 to the minus 2 watts, the lower limit set by the noise equivalent power and the upper by load resistance and reverse voltage, degrading as series resistance rises; reverse bias raises the upper limit but increases dark current and noise. Section 2-3, dark current, and section 2-4, noise - Johnson noise from the shunt resistance and shot noise from the dark and photo currents, combined into the noise equivalent power; Silicon photodiode characteristics - photocurrent linear over more than nine orders of magnitude for incident light between 10 to the minus 12 and 10 to the minus 2 watts, with the lower limit set by noise equivalent power

Used by:P1 Silver Salts and Light: Schulze to Ritter · P4 Spectral Sensitivity and Colour Response · P4 The Latent Image · P4 The Silver Halides · P14 Experiment: Calibrating the Sensitometer · P15 Part XV Overview: Build a Densitometer · P15 Experiment: Calibrating the Densitometer in Both Modes · P15 Build: The Densitometer Electronics and Firmware · P15 Break-Fix: Diagnosing a Misbehaving Densitometer · P15 Photodiodes, ADCs and Measuring Light Over Three Decades · Densitometer: drifting zero

hrc.utexas.edu

The Niepce Heliographretrieved 2026-09-04, 2026-09-06

Sections: The Niepce Heliograph — the object record, "[View from the Window at Le Gras], 1827. Heliograph on pewter, 16.7 x 20.3 x .15 cm"; The Niépce Heliograph, exhibition text and object record, for the dissolving of light-sensitive bitumen in oil of lavender, the thin coating on polished pewter, the several days of exposure and Niépce's own December 1827 judgement of his process; The Niepce Heliograph, exhibition text and object record; The Niepce Heliograph, exhibition text; The Niepce Heliograph object record — that Niepce dissolved light-sensitive bitumen in oil of lavender and applied a thin coating over a polished pewter plate, that after several days of exposure to sunlight the plate yielded an impression of the courtyard, and the object dimensions, 16.7 by 20.3 by 0.15 cm; The Niépce Heliograph, exhibition text and object record

Used by:Bitumen of Judea · Niépce's bitumen heliograph coating · P1 Niepce and Heliography: Light That Hardens · P1 The Camera Obscura: An Image Without Chemistry · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · Heliography on bitumen of Judea

hse.gov.uk

Choosing the right gloves to protect skin: a guide for employersretrieved 2026-09-04

Sections: Identify the substances handled; consider the type and duration of contact; Identify the substances handled; consider the type and duration of contact; manufacturers' data are for pure chemicals rather than mixtures

Used by:P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · Glove selection

Classification, labelling and packaging of chemicals (CLP) in GB or NIretrieved 2026-09-04

Sections: Supplying chemicals to the Great Britain market; supplying chemicals to the Northern Ireland market; CLP in Great Britain and in Northern Ireland since 1 January 2021

Used by:P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · Reading GHS and CLP

Controlling airborne contaminants at work: A guide to local exhaust ventilation (LEV), HSG258retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: What makes a good LEV system; the hierarchy of control; Introduction — the purpose of local exhaust ventilation in reducing exposure from the inhalation of airborne contaminants, and what the guidance covers; Chapter 3, paragraph 52 and the list of controls preceding LEV; The list of controls that come before extraction, and paragraph 93, that some bench-mounted fan and filter units commonly used for solder fume control are ineffective and that a supplier should show the proposed system provides adequate control; Table of contaminant types, which lists solder fume among fumes; the controls that come before extraction - eliminate, substitute, reduce the size of the source, modify the process to emit less; and paragraph 93, that some bench-mounted fan and filter units commonly used for solder fume control are ineffective and that suppliers should ensure a proposed system provides adequate control; The order of controls, in which elimination and substitution come before extraction; and paragraph 93, that some bench-mounted fan and filter units commonly used for solder fume control are ineffective and that a supplier should be asked to show the proposed system provides adequate control; The section on general ventilation, that the usual approach is to capture the main sources with local exhaust ventilation and to use general ventilation for minor sources or for any loss of contaminant from large sources, general ventilation being the replacement of contaminated air with clean air; Chapter 3, paragraph 52, on containing and capturing a vapour-air mixture before it mixes with the workroom air

Used by:Formaldehyde · Glutaraldehyde · Glyoxal · P2 Laying Out the Laboratory: Wet Areas, Dry Areas and Contamination Control · P14 Build: The LED Light Source and Exposure Timer · P14 Low-Voltage Electronics for the Darkroom Builder · P15 Build: The Densitometer Electronics and Firmware · P20 Lab: Bleaching and Redeveloping a Sepia Print · Opening the laboratory · Checking the ventilation before a session

COSHH essentials for Printing: Manual film and plate development, sheet P1retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Personal protective equipment — gloves, other equipment; Hazards; Equipment and procedures; Personal protective equipment; Gloves; Equipment and procedures; personal protective equipment; Equipment and procedures; Personal protective equipment; Personal protective equipment - gloves and other equipment; Personal protective equipment; ventilation; Personal protective equipment; Ventilation; personal protective equipment; Personal protective equipment; Gloves; Equipment and procedures - general ventilation of more than five air changes an hour with a through draught; Gloves - single-use nitrile 0.2 mm where the safety data sheet gives no specific advice; Other equipment - eye protection and cotton overalls; the impervious apron and new 0.4 mm nitrile gloves for a spill; Hazards; Equipment and procedures; Personal protective equipment; Equipment and procedures - general ventilation of more than five air changes an hour with a through draught; Respiratory protective equipment - not normally needed for routine operations; Gloves - single-use nitrile, 0.2 mm; Other equipment - eye protection and cotton overalls; Cleaning and housekeeping - the apron and 0.4 mm gloves for a spill; Equipment and procedures; personal protective equipment — gloves and eye protection; Cleaning and housekeeping; Equipment and procedures; cleaning and housekeeping; Gloves; other equipment; respiratory protective equipment; cleaning and housekeeping; Equipment and procedures; Personal protective equipment for manual film and plate development; Personal protective equipment for manual film and plate development: single-use nitrile gloves as splash protection; Equipment and procedures, and Personal protective equipment for manual film and plate development; Control approach and personal protective equipment for manual development; Hazards; Equipment and procedures, including general ventilation at greater than five air changes per hour with a through draught and the instruction to keep developing solutions in shallow trays to contain spillage; Personal protective equipment; Gloves — single-use nitrile gloves 0.2 mm thick where the safety data sheet gives no specific information; Cleaning and housekeeping; Equipment and procedures, including general ventilation greater than five air changes per hour with a through draught and shallow trays to contain spillage; Personal protective equipment; Gloves — single-use nitrile gloves 0.2 mm thick; Cleaning and housekeeping; Equipment and procedures; Personal protective equipment; Gloves — single-use nitrile gloves 0.2 mm thick; Equipment and procedures, including general ventilation greater than five air changes per hour with a through draught; Personal protective equipment; Gloves — single-use nitrile gloves 0.2 mm thick; Equipment and procedures — general ventilation of more than five air changes per hour with a through draught; Personal protective equipment; Gloves — single-use nitrile gloves 0.2 mm thick; Equipment and procedures — general ventilation greater than five air changes per hour with a through draught; Gloves, single-use nitrile gloves 0.2 mm thick; Equipment and procedures — general ventilation greater than five air changes per hour with a through draught; Gloves, single-use nitrile gloves 0.2 mm thick as splash protection; Equipment and procedures — general ventilation greater than five air changes per hour with a through draught; Personal protective equipment; Gloves, single-use nitrile gloves 0.2 mm thick as splash protection where the safety data sheet gives no more specific advice; Equipment and procedures, including general ventilation greater than five air changes per hour with a through draught; Personal protective equipment; Gloves - single-use nitrile gloves 0.2 mm thick as splash protection where the safety data sheet gives no more specific advice; Equipment and procedures - general ventilation greater than five air changes per hour with a through draught, and shallow trays to contain spillage; Personal protective equipment; Gloves - single-use nitrile gloves 0.2 mm thick; Cleaning and housekeeping; Equipment and procedures - the instruction to provide a good standard of general ventilation, using powered wall- or window-mounted fans to supply fresh air, greater than five air changes per hour, with a through draught; to provide easy-to-clean work surfaces with lipped edges for liquid handling; and to keep developing solutions in shallow trays to contain spillage. Respiratory protective equipment, that RPE is not normally needed for routine operations but may be needed for cleaning up spills; Equipment and procedures - the instruction to provide a good standard of general ventilation using powered wall- or window-mounted fans to supply fresh air, greater than five air changes per hour, with a through draught; to provide easy-to-clean work surfaces with lipped edges for liquid handling; and to keep developing solutions in shallow trays to contain spillage; Equipment and procedures, the instruction to provide a good standard of general ventilation with a through draught and easy-to-clean lipped work surfaces for liquid handling; and Personal protective equipment, single-use nitrile gloves 0.2 mm thick as splash protection where the safety data sheet gives no more specific advice; The general ventilation specification for manual photographic processing and the glove guidance, for the through draught this session works in and for single-use nitrile at 0.2 mm as splash protection where the safety data sheet gives nothing more specific.; Personal protective equipment - single-use nitrile gloves 0.2 mm thick as splash protection where no more specific advice exists; ventilation; Equipment and procedures, for general ventilation with a through draught and lipped wipeable work surfaces; Personal protective equipment, for single-use nitrile gloves at 0.2 mm as splash protection; Equipment and procedures, for a good standard of general ventilation with a through draught and easy-to-clean lipped work surfaces; Personal protective equipment, for single-use nitrile gloves 0.2 mm thick as splash protection where the safety data sheet gives no more specific advice; Personal protective equipment for manual film and plate development — single-use nitrile gloves 0.2 mm thick as splash protection where the safety data sheet gives no specific advice; Equipment and procedures, including general ventilation greater than five air changes per hour with a through draught; Personal protective equipment, single-use nitrile gloves as splash protection for manual film and plate development; Mixing from powders and concentrates; single-use nitrile at 0.2 mm as splash protection where the safety data sheet gives no more specific advice; general ventilation greater than five air changes per hour with a through draught; General ventilation greater than five air changes per hour with a through draught from powered wall- or window-mounted fans; easy-to-clean lipped surfaces and shallow trays; Gloves; other equipment; Other equipment, including new 0.4 mm nitrile gloves and the disposal of loaded absorbent as hazardous waste; Cleaning and housekeeping; other equipment, including absorbent granules and mats and new 0.4 mm nitrile gloves; respiratory protective equipment for clearing spills; Other equipment: absorbent granules and mats, impervious apron, new 0.4 mm nitrile gloves; respiratory protective equipment for clearing spills; disposal of loaded absorbent as hazardous waste; Equipment and procedures — general ventilation of more than five air changes per hour with a through draught; Personal protective equipment, single-use nitrile gloves 0.2 mm thick; Cleaning and housekeeping, including putting lids on containers immediately after use, even empty ones; General ventilation greater than five air changes per hour with a through draught; lipped easy-to-clean surfaces and shallow trays for spillage; Equipment and procedures, and powered wall or window fans at more than five air changes per hour with a through draught; Respiratory protective equipment: not normally needed for routine operations, and where it may be needed; Mixing from powders; single-use nitrile at 0.2 mm as splash protection where the safety data sheet gives no more specific advice; respiratory protection not normally needed for routine operations and where it may be needed

Used by:Acetic acid (glacial) · Amidol · Ammonium bromide · Ammonium chloride · Ammonium citrate (dibasic) · Ammonium citrate (tribasic) · Ammonium iron(III) citrate · Ammonium iron(III) oxalate · Ammonium sulfite · Ammonium thiocyanate · Ammonium thiosulfate · Ascorbic acid · Benzotriazole · Borax (sodium tetraborate decahydrate) · Boric acid · Calcium carbonate · Chlorohydroquinone · Chrome alum · Citric acid (anhydrous) · Copper(II) sulfate · Dimezone S · EDTA disodium salt (anhydrous) · EDTA disodium salt dihydrate · Erythrosin · Ethanol · Ferric oxalate · Iron(II) oxalate · Gallic acid · Gelatin · Glycerol · Glycin · Hydrochloric acid · Hydrogen peroxide · Hydroquinone · Iron(II) sulfate, anhydrous · Iron(II) sulfate heptahydrate · Iron(III) chloride, anhydrous · Iron(III) chloride hexahydrate · Iron(III) nitrate nonahydrate · Isopropyl alcohol · Lithium chloride · Metol · Oxalic acid · p-Aminophenol · Phenidone · Potassium alum · Potassium bromide · Potassium carbonate (anhydrous) · Potassium chloride · Potassium hydroxide (caustic potash) · Potassium iodide · Potassium metabisulfite · Potassium oxalate, anhydrous · Potassium oxalate monohydrate · Potassium sodium tartrate tetrahydrate · Potassium thiocyanate · Prussian blue · Pyrogallol · Silver bromide · Silver chloride · Silver iodide · Silver nitrate · Silver(I) oxide · Silver selenide · Silver sulfamate · Silver sulfide · Sodium acetate (anhydrous) · Sodium ascorbate · Sodium bicarbonate · Sodium bisulfite · Sodium carbonate (anhydrous) · Sodium carbonate decahydrate · Sodium carbonate monohydrate · Sodium chloride · Trisodium citrate dihydrate · Sodium hexametaphosphate (Calgon) · Sodium hydroxide (caustic soda) · Sodium metabisulfite · Sodium metaborate (anhydrous) · Sodium metaborate tetrahydrate (Kodalk) · Sodium sulfate · Sodium sulfite · Sodium thiocyanate · Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Sulfamic acid · Sulfuric acid · Tannic acid · Tartaric acid · Tetraazaindene · Thymol · Ammonium citrate developer · Borax kallitype developer · Kodak Hypo Clearing Agent and the washing accelerator Kodak patented · KODAK PROFESSIONAL XTOL Developer · Nicol's kallitype · Rochelle salt kallitype developer · Rodinal-type p-aminophenol developer · Willis's potassium oxalate developer · P2 Storage, Incompatibilities and Secondary Containment · P2 Laying Out the Laboratory: Wet Areas, Dry Areas and Contamination Control · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P4 Experiment: Precipitating the Silver Halides · P4 Darkroom Session: The Latent Image Made Visible · P6 Commissioning the Camera: Light-Tightness, Flare and the First Negatives · P6 Lab: Processing Your First Film · P7 Assignment: Still Life and Controlled Light · P8 Overview: What a Developer Is · P8 Experiment: Watching a Developer Oxidise · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P8 Sulfite: Preservative, Buffer, Silver Solvent · P9 Overview: Experiments on Development · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Break/Fix: The Developer That Went Wrong · P9 Experiment: Comparing Developing Agents · P9 Lab: Preparing Standard Test Negatives · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P10 Experiment: Measuring Stop Bath Capacity · P11 Experiment: Clearing Time and Fixer Capacity · P11 Break/Fix: The Exhausted Fixer · P11 Lab: Mixing Fixers from Scratch · P12 Experiment: Small-Scale Metallic Replacement · P13 Lab: A Step-Wedge Exposure Series · P18 Lab: Mixing and Comparing Print Developers · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Experiment: Selenium Toning and the Print Curve · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Experiment: The Exposure Scale, Maximum Density and Contrast of a Cyanotype · P21 Lab: Toning the Prussian Blue Image · P24 Lab: Printing a Kallitype · P24 Lab: Printing a Van Dyke Brown · Glove selection · Closing the laboratory · Opening the laboratory · Mixing a developer from raw chemicals · Adjusting pH with a concentrated alkali · Handling a selenium toner and its waste · Handling silver nitrate · Responding to a silver nitrate spill · Responding to a spilled solid · Responding to a spill · Stop bath preparation · Storage rotation and shelf separation · Handling a sulphide toner and its waste · Checking the ventilation before a session · Weighing a solid · Weighing and handling developing agents

COSHH essentials: Selecting protective gloves, sheet S101retrieved 2026-09-04, 2026-09-05

Sections: Selection of chemical-protective gloves; maintenance; training and supervision; Selection of chemical-protective gloves; maintenance; the eight-hour ceiling; single-use gloves; Selection of chemical-protective gloves; maintenance; Selection of chemical-protective gloves; maintenance; the designated place where gloves are put on and taken off

Used by:P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · Glove selection · Closing the laboratory · Putting protective equipment on, changing gloves and taking it off · Responding to a spill

EH40/2005 Workplace exposure limits, containing the list of workplace exposure limits for use with COSHHretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Table 1 — searched for benzimidazole compounds and found no entry; introduction, paragraph 6; Table 1 — acetic acid, CAS 64-19-7; The list itself, which carries no entry for albumen or egg white; the introductory note that absence from the list does not indicate that a substance is without risk; Table 1 — searched for amidol and for diaminophenol; no entry. Introduction, paragraph 6, on substances absent from the list; Table 1, searched for ammonium bromide and for bromides; introduction, paragraph 6; Table 1 — ammonium chloride, fume; introduction, paragraph 6; Table 1, searched for ammonium citrate and for citrates; introduction, paragraph 6; Table 1, searched for citrate, for ammonium citrate and for triammonium citrate; no entry. Introduction, paragraph 6; Table 1: Chromium (VI) compounds (as Cr); Table 1 — Ammonia, anhydrous, CAS 7664-41-7; introduction, paragraph 6; Table 1 — Iron salts (as Fe); Table 1, searched for persulphates, peroxodisulphates and ammonium salts; introduction, paragraph 6; "Table 1 — Sulphur dioxide, CAS 7446-09-5, 0.5 ppm or 1.3 mg/m3 over eight hours and 1 ppm or 2.7 mg/m3 over fifteen minutes; Ammonia, anhydrous, CAS 7664-41-7, 25 ppm or 18 mg/m3 over eight hours and 35 ppm or 25 mg/m3 over fifteen minutes; Sodium hydrogen sulphite, CAS 7631-90-5, 5 mg/m3 over eight hours; Disodium disulphite, CAS 7681-57-4, 5 mg/m3 over eight hours. A search of Table 1 found no entry for ammonium sulphite or for any ammonium sulfite salt. Paragraph 6 of the introduction, that the absence of a substance from the list does not indicate that it is safe"; Table 1, searched for thiocyanates; introduction, paragraph 6; Table 1 — sulphur dioxide; introductory note on substances absent from the list; Table 1, the entry for Starch, CAS 9005-25-8, at 10 mg/m³ total inhalable and 4 mg/m³ respirable over the eight-hour reference period with no short-term limit and no Carc, Sen or Sk notation; Table 1, Flour dust and Grain dust, both at 10 mg/m³ with the Sen notation, quoted only as the comparison the entry for starch does not carry; and the introductory note that absence from the list does not indicate that a substance is without risk; Introduction, paragraph 6 — substances absent from the list of workplace exposure limits; Table 1 — Barium sulphate, CAS 7727-43-7, inhalable and respirable dust; Barium compounds, soluble (as Ba); the synonym index entries Barite, Barytes, Blanc fixe and Heavy spar; introduction paragraph 6; Table 1 — searched for benzotriazole and found no entry; introduction, paragraph 6; Table 1: Asphalt, petroleum fumes, CAS 8052-42-4 — long-term and short-term limits; the introductory note that absence from the list does not indicate that a substance is without risk; Table 1: Disodium tetraborate, anhydrous, decahydrate and pentahydrate; Table 1: Bromine, CAS 7726-95-6 — long-term and short-term limits in ppm and mg per cubic metre; the introductory note that absence from the list does not indicate that a substance is without risk; Table 1: Cadmium and cadmium compounds except cadmium oxide fume, cadmium sulphide and cadmium sulphide pigments (as Cd); Table 1 — Calcium carbonate (1317-65-3), inhalable and respirable dust; introduction, paragraph 6; Table 1 — searched on 7 September 2026 for calcium nitrate and for nitrates generally and found no entry, the calcium entries being carbonate, cyanamide, hydroxide, oxide, silicate and sulphate; and the introduction, on absence from the list not indicating that a substance is without risk; Table 1: Pyrocatechol; Synonyms list — 1,2-Benzenediol and 1,2-Dihydroxybenzene as Pyrocatechol; introduction paragraph 6 on substances absent from the list; Table 1: Chlorine, CAS 7782-50-5 — short-term limit only; the introductory note that absence from the list does not indicate that a substance is without risk; Table 1 — searched for chlorohydroquinone and chlorhydroquinone; no entry. Introduction, paragraph 6, on substances absent from the list; Table 1 — Chromium (III) compounds (as Cr) and Chromium (VI) compounds (as Cr); paragraphs 53 to 56 on substances that can cause occupational asthma; introductory note on substances absent from the list; Table 1 — searched for citric acid; introductory note on substances absent from the list; Table 1 — Copper and compounds, dust and mists (as Cu); Copper fume (as Cu); introduction, paragraph 6; Table 1: Diethyl ether, CAS 60-29-7, long-term and short-term limits in ppm and mg per cubic metre; the introductory note that absence from the list does not indicate that a substance is without risk; Table 1 — searched for dimezone, pyrazolidone and pyrazolidinone; no entry. Introduction, paragraph 6, on substances absent from the list; Table 1 — searched for EDTA and edetate and found no entry; introduction, paragraph 6; Table 1 — searched for erythrosine, erythrosin and tetraiodofluorescein; no entry. Introduction, paragraph 6, on substances absent from the list; Table 1 — Ethanol, CAS 64-17-5; introduction, paragraph 6; Table 1 — Iron salts (as Fe); introduction, paragraph 6; Table 1 — Formaldehyde; paragraphs 48 to 51 on carcinogenic and mutagenic substances; the note that the Carc, Sen and Sk notations are not exhaustive; Table 1 — searched for gallic acid and trihydroxybenzoic acid; no entry. Introduction, paragraph 6, on substances absent from the list; Introductory note that the absence of a substance from the list does not indicate that it is without risk; Table 1 — Glutaraldehyde, with the Sen notation; paragraphs 53 to 56 on substances that can cause occupational asthma; the foreword on the legal standing of Table 1; "Table 1 - Glycerol, mist, CAS 56-81-5; the table's column headings and the note on the Carc, Sen and Sk annotations; paragraph 14 on substances with no listed short-term limit; introduction, paragraph 6"; Table 1 — searched for glyoxal, ethanedial and oxalaldehyde; no entry. Introduction, paragraph 6, on substances absent from the list; The list itself, which carries no entry for gum arabic or gum acacia; Table 1, Flour dust and Grain dust with the Sen notation, quoted only as a comparison the course declines to transfer; the introductory note that absence from the list does not indicate that a substance is without risk; Table 1 — hydrogen chloride, gas and aerosol mists, CAS 7647-01-0; Table 1 — Hydrogen peroxide (7722-84-1); introduction, paragraph 6; Table 1: Hydroquinone, CAS 123-31-9; introduction paragraph 6 on substances absent from the list; Table 1: Iodine, CAS 7553-56-2 — short-term limit only; the introductory note that absence from the list does not indicate that a substance is without risk; Table 1 — Propan-2-ol, CAS 67-63-0; introduction, paragraph 6; Table 1 — Kaolin, respirable dust, CAS 1332-58-7, long-term limit 2 mg/m3 with no short-term limit and no Carc, Sen or Sk notation; the synonym list, which maps the entry onto itself; and the introduction, on absence from the list not indicating that a substance is without risk; The list itself, which carries no entry for lavender oil or for essential oils as a class; Table 1, Turpentine, CAS 8006-64-2, quoted only as a comparison the course declines to transfer; the introductory note that absence from the list does not indicate that a substance is without risk; Paragraph 52, "Asbestos and lead", stating that asbestos and lead are regulated separately, and the approval notice referring to the occupational exposure limit for lead in regulation 2(1) of the Control of Lead at Work Regulations 2002; The note that asbestos and lead are regulated separately, and the reference to the occupational exposure limit for lead in regulation 2(1) of the Control of Lead at Work Regulations; Table 1 — searched for lithium chloride and found no entry; lithium hydride and lithium hydroxide are listed; introduction, paragraph 6; Table 1: Mercury and divalent inorganic compounds including mercuric oxide and mercuric chloride (measured as mercury); Table 3, biological monitoring guidance values; the introductory note that absence from the list does not indicate a substance is without risk; Table 1: Mercury and divalent inorganic compounds including mercuric oxide and mercuric chloride (measured as mercury); Table 3 biological monitoring guidance value for mercury; Table 1 — searched for metol and 4-methylaminophenol sulfate, not listed; introduction paragraph 6 on substances absent from the list; Table 1 — "Nickel and its inorganic compounds (except nickel tetracarbonyl)", split into water-soluble nickel compounds (as Ni) at a long-term limit of 0.1 mg/m3 and nickel and water-insoluble nickel compounds (as Ni) at 0.5 mg/m3, neither with a short-term limit, and the comments column reading "Sk, Carc (nickel oxides and sulphides) Sen (nickel sulphate)"; and the table heading's own statement that the Carc, Sen and Sk notations are not exhaustive; Table 1 — nitric acid, CAS 7697-37-2; The introductory note that the absence of a substance from the list does not indicate that it is without risk; the list itself, which carries no entry for nitrocellulose; Table 1 — oxalic acid, CAS 144-62-7; Table 1 — searched for aminophenol, not listed; introduction paragraph 6 on substances absent from the list; Table 1 — Halogeno-platinum compounds (as Pt); introduction, paragraph 6, on substances absent from the list; Table 1 — searched for phenidone and 1-phenyl-3-pyrazolidone, not listed; introduction paragraph 6 on substances absent from the list; Table 1 — Aluminium salts, soluble; introductory note on substances absent from the list; Table 1 — searched for potassium carbonate; introductory note on substances absent from the list; The list itself, which carries no entry for potassium chlorate or for chlorates as a group; the introductory note that absence from the list does not indicate that a substance is without risk; Table 1, searched for potassium chloride; introduction, paragraph 6; Table 1, searched for citrates and for potassium salts; introduction, paragraph 6; Table 1: Cyanides, except HCN, cyanogen and cyanogen chloride (as CN); Potassium cyanide (as cyanide); Table 1: Chromium (VI) compounds (as Cr); the January 2020 list of substances whose limits were reduced; Table 1: Cyanides, except HCN, cyanogen and cyanogen chloride (as CN); Hydrogen cyanide; Table 1: Potassium hydroxide, CAS 1310-58-3; Table 1 — sulphur dioxide; disodium disulphite; introductory note on substances absent from the list; Table 1 — Manganese and its inorganic compounds (as Mn), 0.2 mg/m³ inhalable fraction and 0.05 mg/m³ respirable fraction over eight hours, with no short-term limit and no notation; the list of substances searched for permanganate under its own name; introduction, paragraph 6; Table 1, searched for persulphates and for peroxodisulphates; introduction, paragraph 6; Table 1, searched for tartrates; introduction, paragraph 6; Table 1 — Halogeno-platinum compounds (as Pt) and Platinum compounds, soluble (as Pt); paragraphs 25-26; paragraphs 53-56, substances that can cause occupational asthma; Table 1 — Cyanides, except hydrogen cyanide, cyanogen and cyanogen chloride (as CN); Iron salts (as Fe); introduction, paragraph 6; Table 1: Selenium and compounds, except hydrogen selenide (as Se); Dihydrogen selenide (as Se); Table 1 — Silver, metallic (7440-22-4) and Silver (soluble compounds as Ag); introduction, paragraph 6; Table 1 — Silver (soluble compounds as Ag) and Silver, metallic; introductory note on substances absent from the list; Table 1 — Silver (soluble compounds as Ag) and Silver, metallic; Table 1 — Silver (soluble compounds as Ag) and Silver, metallic; and the introduction's statement that absence from the list does not indicate that a substance is without risk; Table 1 — Selenium and compounds, except hydrogen selenide (as Se); Dihydrogen selenide (as Se); Silver, metallic and Silver (soluble compounds as Ag); introduction, paragraph 6; Table 1 — Silver (soluble compounds as Ag) and Silver, metallic; searched for sulphamic and sulfamic acid and their salts and found no entry; introduction, on absence from the list not indicating that a substance is without risk; Table 1 — Silver, metallic and Silver (soluble compounds as Ag), searched for an insoluble-silver entry and none found; introduction, paragraph 6; Table 1, searched for sodium acetate and for acetates; introduction, paragraph 6; Table 1 — sodium hydrogen sulphite; sulphur dioxide; Table 1 — searched for sodium carbonate; introductory note on substances absent from the list; Table 1, searched for sodium carbonate in any grade; introduction, paragraph 6; Table 1, searched for citrates; introduction, paragraph 6; Table 1: Sodium cyanide (as cyanide); Potassium cyanide (as cyanide); Cyanides, except HCN, cyanogen and cyanogen chloride (as CN); Hydrogen cyanide; the Sk notation in the annotations; Table 1 — no entry for sodium hexametaphosphate; tetrasodium pyrophosphate; introduction, paragraph 6; Table 1: Sodium hydroxide, CAS 1310-73-2; Table 1 — disodium disulphite; sulphur dioxide; Table 1: Disodium tetraborate, anhydrous, decahydrate and pentahydrate; introductory note on substances absent from the list; "Table 1 — Selenium and compounds, except hydrogen selenide (as Se); Hydrogen selenide; and the introduction's statement that the absence of a substance from the list does not indicate that it is safe"; Table 1: Selenium and compounds, except hydrogen selenide (as Se); Table 1 — Selenium and compounds, except hydrogen selenide (as Se); Dihydrogen selenide (as Se); introduction, paragraph 6; Table 1, searched for sodium sulfate; introduction, paragraph 6; Table 1: Hydrogen sulphide; Table 1 — searched for sulphamic and sulfamic acid and found no entry; introduction, paragraph 6; Table 1 — sulphuric acid (mist), CAS 7664-93-9, and the note that the mist is defined as the thoracic fraction; Table 1 — searched for tannic acid and tannin; no entry. Introduction, paragraph 6, on substances absent from the list; Table 1 — searched for tartaric acid; introductory note on substances absent from the list; Table 1 — searched for tetraazaindene, tetrazaindene and triazolopyrimidine; no entry. Introduction, paragraph 6, on substances absent from the list; Table 1 — "Thallium, soluble compounds (as Tl)", with no CAS number, a long-term exposure limit of 0.1 mg/m3, no short-term limit and the Sk notation for skin absorption; Table 1 — searched for thiourea, not listed; introductory note on substances absent from the list; Table 1 — searched for thymol; no entry. Introduction, paragraph 6, on substances absent from the list; Table 1 — Titanium dioxide, CAS 13463-67-7: total inhalable and respirable dust limits, with no short-term limit and no notation; Table 1, disodium tetraborate anhydrous, decahydrate and pentahydrate; introduction, paragraph 6; Table 1, the entry for halogeno-platinum compounds (as Pt) at 0.002 mg/m³ with the Sen notation and paragraphs 25 and 26 defining them; the entry for oxalic acid at 1 mg/m³ long-term and 2 mg/m³ short-term; and the absence of any entry for palladium compounds or for chlorates, together with the introductory statement that absence from the list does not indicate that a substance is without risk; Table 1, chromium(III) compounds as Cr at 0.5 mg/m3 against chromium(VI) as Cr at 0.01 mg/m3 with the Carc and Sen notations; aluminium salts, soluble, at 2 mg/m3; Table 1 — cyanides, except HCN, cyanogen and cyanogen chloride (as CN); potassium cyanide (as cyanide); hydrogen cyanide, with the Sk notation; Table 1 — mercury and divalent inorganic compounds (as Hg), long-term 0.02 mg/m³; iodine, short-term 0.1 ppm; bromine, 0.1 ppm long-term and 0.2 ppm short-term. Introduction, paragraph 6, on substances absent from the list; Table 1, searched for erythrosine, erythrosin and tetraiodofluorescein with no entry found; the introduction's statement that the absence of a substance from the list does not indicate that it is safe; Table 1 — mercury and divalent inorganic compounds, measured as mercury, long-term 0.02 mg/m³ and no short-term figure, with the biological monitoring guidance value. Introduction, paragraph 6, on substances absent from the list; Table 1 — dihydrogen selenide at 0.02 ppm over eight hours and 0.05 ppm over fifteen minutes; selenium and compounds except hydrogen selenide (as Se); Table 1, mercury and divalent inorganic compounds including mercuric oxide and mercuric chloride (measured as mercury); Table 3, the biological monitoring guidance value for mercury; the introductory note that absence from the list does not indicate that a substance is without risk; Table 1 — sodium hydrogen sulphite, long-term 5 mg/m3; acetic acid, long-term 10 ppm (25 mg/m3) and short-term 20 ppm (50 mg/m3); and the introductory note on substances absent from the list; Table 1 — acetic acid, long-term 10 ppm (25 mg/m3) and short-term 20 ppm (50 mg/m3); sodium hydrogen sulphite, long-term 5 mg/m3; sulphur dioxide; and the introductory note on substances absent from the list; Table 1 - sulphur dioxide, CAS 7446-09-5, long-term exposure limit 0.5 ppm or 1.3 mg per cubic metre over 8 hours and short-term limit 1 ppm or 2.7 mg per cubic metre over 15 minutes; sodium hydrogen sulphite, CAS 7631-90-5, long-term limit 5 mg per cubic metre with no short-term limit; the list of synonyms giving sodium bisulphite as sodium hydrogen sulphite; Table 1, chromium (VI) compounds (as Cr), with the Carc and Sen notations and the biological monitoring guidance value, as cited by the course's chromium policy; Table 1, mercury and divalent inorganic compounds of mercury (as Hg), and hydrogen cyanide with the Sk notation, as cited by the course's Level D policy; Table 1, acetic acid, CAS 64-19-7, long-term exposure limit 10 ppm or 25 mg/m3 and short-term limit 20 ppm or 50 mg/m3; Table 1, acetic acid, long-term exposure limit 10 ppm or 25 mg/m3 and short-term limit 20 ppm or 50 mg/m3; Table 1: hydrogen sulphide, 5 ppm over eight hours and 10 ppm over fifteen minutes; Introduction, paragraph 6 - substances absent from the list of workplace exposure limits; Paragraph 52, "Asbestos and lead", for the statement that asbestos and lead are regulated separately, and the glossary entry referring to the occupational exposure limit for lead specified in regulation 2(1) of the Control of Lead at Work Regulations; Paragraph 52, that lead is regulated separately under the Control of Lead at Work Regulations rather than by a workplace exposure limit; Table 1, "Thallium, soluble compounds (as Tl)" at 0.1 mg/m3 with the Sk notation, and the nickel rows with their Sk, Carc and "Sen (nickel sulphate)" notations; Table 1, the entry "Mercury and divalent inorganic compounds including mercuric oxide and mercuric chloride (measured as mercury)", long-term exposure limit 0.02 mg/m3 as an 8-hour time-weighted average with no short-term limit listed; Table 3, the biological monitoring guidance value for mercury of 20 micromoles of mercury per mole of creatinine in urine, random sampling; Table 1 — searched for thiourea, not listed, and the introductory note that absence from the list does not indicate that a substance is without risk; Table 1, the entry for halogeno-platinum compounds (as Pt) at 0.002 mg/m³ with the Sen notation, against 5 mg/m³ for platinum metal; paragraphs 25 and 26, which define the class as coordination compounds in which the platinum atom is directly coordinated to halide ions; the entry for oxalic acid at 1 mg/m³ long-term and 2 mg/m³ short-term; and the absence of any entry for chlorates, together with the introductory statement that absence from the list does not indicate that a substance is without risk; Table 1 — hydrogen chloride, gas and aerosol mists, CAS 7647-01-0, 1 ppm long-term and 5 ppm short-term; Table 1, the entry for halogeno-platinum compounds (as Pt) at 0.002 mg/m³ with the Sen notation, and paragraphs 25 and 26 defining them; the entry for oxalic acid at 1 mg/m³ long-term and 2 mg/m³ short-term; the absence of any entry for palladium compounds or for chlorates, together with the introductory statement that absence from the list does not indicate that a substance is without risk; Table 1, searched for citrates and for citric acid; introduction, paragraph 6; Table 1, chromium(VI) compounds as Cr, with the Carc and Sen notations and the biological monitoring guidance value, as cited by the course's chromium policy; Table 1, the entry for halogeno-platinum compounds (as Pt) at 0.002 mg/m³ with the Sen notation and paragraphs 25 and 26 defining them; the entry for oxalic acid at 1 mg/m³ long-term and 2 mg/m³ short-term; the absence of any entry for palladium compounds, with the introductory statement that absence from the list does not indicate that a substance is without risk; Table 1, oxalic acid at 1 mg/m3 long-term and 2 mg/m3 short-term, and halogeno-platinum compounds as Pt at 0.002 mg/m3 with the Sen notation; introduction, paragraph 6, that absence from the list does not indicate that a substance is without risk; Table 1: mercury and divalent inorganic compounds; bromine; iodine; Table 1: acetic acid; ammonia, anhydrous; Table 1: acetic acid; hydroquinone; sodium hydroxide; silver (soluble compounds as Ag). Annotations paragraph; Table 1: acetic acid; hydroquinone; sodium hydroxide; silver. Annotations paragraph; Table 1: mercury and divalent inorganic compounds, as mercury; Table 1: chromium(III) against chromium(VI); formaldehyde; glutaraldehyde; and silver compounds; Table 1: silver, soluble compounds as Ag, 0.01 mg/m3 long-term; metallic silver 0.1 mg/m3; and the statement that absence from the list does not indicate that a substance is safe; Table 1: chromium(III) compounds as Cr, 0.5 mg/m3 long-term with no notation, against chromium(VI) compounds as Cr, 0.01 mg/m3 with the Carc, sen and BMGV notations; Table 1: chromium(III) compounds as Cr 0.5 mg/m3 against chromium(VI) 0.01 mg/m3 with the Carc and Sen notations; aluminium salts, soluble, 2 mg/m3; glutaraldehyde 0.05 ppm with the Sen notation; formaldehyde 2 ppm with the Carc notation; and the statement that absence from the list does not indicate that a substance is safe; Table 1: chromium(III) compounds as Cr, 0.5 mg/m3 long-term with no notation, against chromium(VI) compounds as Cr, 0.01 mg/m3 with Carc, sen and BMGV; aluminium salts, soluble, 2 mg/m3; The statement that the absence of a substance from the list does not indicate that it is safe; searched for erythrosine and for glyoxal under all their names with no entry found; Table 1: formaldehyde 2 ppm with the Carc notation; glutaraldehyde 0.05 ppm with the Sen notation; chromium(III) compounds as Cr 0.5 mg/m3 against chromium(VI) 0.01 mg/m3; aluminium salts, soluble, 2 mg/m3; and the introductory statement that absence from the list does not indicate that a substance is safe; The introductory statement that the absence of a substance from the list does not indicate that it is safe; Table 1: disodium tetraborate anhydrous, decahydrate and pentahydrate; introduction paragraph 6 on substances absent from the list; Table 1: hydroquinone, CAS 123-31-9; introduction paragraph 6 on substances absent from the list; Table 1 — the workplace exposure limits for borates, 5 mg/m3 for the decahydrate and 1 mg/m3 for the anhydrous and pentahydrate forms; Introduction, paragraph 6 — that the absence of a substance from the list does not indicate that it is safe; Table 1 — sulphur dioxide; introduction paragraph 6 on substances absent from the list; Table 1 — workplace exposure limits for borates; Table 1 — sulphur dioxide, CAS 7446-09-5, long-term exposure limit 0.5 ppm or 1.3 mg/m3 and short-term limit 1 ppm or 2.7 mg/m3; acetic acid, CAS 64-19-7, 10 ppm long-term and 20 ppm short-term; Table 1 — acetic acid, CAS 64-19-7, long-term exposure limit 10 ppm or 25 mg/m3 and short-term limit 20 ppm or 50 mg/m3; sulphur dioxide, CAS 7446-09-5, 0.5 ppm or 1.3 mg/m3 long-term and 1 ppm or 2.7 mg/m3 short-term; Table 1 — soluble aluminium salts, 2 mg/m3 as aluminium averaged over eight hours; the introductory note that absence from the list does not indicate that a substance is without risk; Table 1 — sulphur dioxide, 0.5 ppm over eight hours and 1 ppm over fifteen minutes; soluble aluminium salts, 2 mg/m3 as aluminium over eight hours; acetic acid, 10 ppm over eight hours and 20 ppm over fifteen minutes; the introductory note that absence of a substance from the list does not indicate that it is without risk; Table 1 — hydrogen sulphide, 5 ppm over eight hours and 10 ppm over fifteen minutes; the introductory note that absence of a substance from the list does not indicate that it is without risk; Table 1 - rosin-based solder flux fume, CAS 8050-09-7, 0.05 mg/m3 over eight hours and 0.15 mg/m3 over fifteen minutes, annotated Sen; Annotations - Sen means capable of causing occupational asthma; Table 1 - rosin-based solder flux fume, CAS 8050-09-7, long-term exposure limit 0.05 mg/m3 over eight hours and short-term limit 0.15 mg/m3 over fifteen minutes, annotated Sen; Annotations - Sen means capable of causing occupational asthma; paragraph 6 of the introduction, that absence from the list does not indicate that a substance is safe; Table 1 - rosin-based solder flux fume, CAS 8050-09-7, at 0.05 mg/m3 over eight hours and 0.15 mg/m3 over fifteen minutes; Annotations - Sen, capable of causing occupational asthma; Table 1 — hydrogen sulphide, CAS 7783-06-4, long-term exposure limit 5 ppm or 7 mg/m3 and short-term limit 10 ppm or 14 mg/m3; and selenium and compounds except hydrogen selenide (as Se), long-term exposure limit 0.1 mg/m3 with no short-term limit listed; Table 1, List of approved workplace exposure limits - hydrogen sulphide, CAS 7783-06-4, long-term exposure limit 5 ppm or 7 mg/m3 as an 8-hour time-weighted average and short-term exposure limit 10 ppm or 14 mg/m3 over a 15-minute reference period; Table 1 - Selenium and compounds, except hydrogen selenide, as Se, at 0.1 mg/m3 over eight hours, and dihydrogen selenide, as Se, at 0.02 ppm over eight hours and 0.05 ppm over fifteen minutes; Table 1 - Selenium and compounds, except hydrogen selenide, as Se, at 0.1 mg/m3 over eight hours; Dihydrogen selenide, as Se, at 0.02 ppm over eight hours and 0.05 ppm over fifteen minutes; Hydrogen sulphide at 5 ppm over eight hours and 10 ppm over fifteen minutes; and the introduction, paragraph 6, that the absence of a substance from the list of workplace exposure limits does not indicate that it is safe; Table 1, List of approved workplace exposure limits, the entry for hydrogen sulphide, CAS 7783-06-4, long-term exposure limit 5 ppm or 7 mg/m3 as an 8-hour time-weighted average and short-term exposure limit 10 ppm or 14 mg/m3 over a 15-minute reference period, with no skin, sensitisation or carcinogen notation; Table 1 - thallium, soluble compounds (as Tl), long-term exposure limit 0.1 mg/m3 with the Sk notation for skin absorption and no short-term limit listed; selenium and compounds except hydrogen selenide (as Se), long-term exposure limit 0.1 mg/m3; and the statement in the introductory text that the absence of a substance from the list does not indicate that it is without risk; Table 1 — Cyanides, except hydrogen cyanide, cyanogen and cyanogen chloride (as CN); Hydrogen cyanide; and the introduction, paragraph 6, that absence from the list does not indicate that a substance is safe; Table 1 — Chromium(VI) compounds at 0.01 mg/m3 as chromium over eight hours, with the Carc, Sen and BMGV notations and the separate 0.025 mg/m3 entry for exposure generated by a work process; Table 1 — ammonia, anhydrous, CAS 7664-41-7, 25 ppm (18 mg/m³) over eight hours and 35 ppm (25 mg/m³) over fifteen minutes; Table 1 — ammonia, anhydrous, CAS 7664-41-7, 25 ppm (18 mg/m³) over eight hours and 35 ppm (25 mg/m³) over fifteen minutes; the introduction's paragraph 6, that absence from the list does not indicate that a substance is without risk; Table 1 — chromium(VI) compounds as Cr at 0.01 mg/m3 over eight hours with a separate process-generated entry at 0.025 mg/m3, annotated Carc, Sen and BMGV; Table 2, the biological monitoring guidance value for chromium(VI); the foreword, for the 2020 revision of the chromium(VI) limit; Table 1, the entry for halogeno-platinum compounds (as Pt) at 0.002 mg/m3 with the Sen notation, the entry for platinum metal at 5 mg/m3 and the entry for oxalic acid at 1 mg/m3 long-term; paragraphs 53 to 56 on occupational asthma; and the absence of any entry for palladium compounds together with the introductory statement that absence from the list does not indicate that a substance is without risk; Table 1, the entry for oxalic acid at 1 mg/m3 long-term and 2 mg/m3 short-term, and the introductory statement that absence from the list does not indicate that a substance is without risk; Table 1, the entry for halogeno-platinum compounds (as Pt) at 0.002 mg/m3 with the Sen notation and the entry for platinum metal at 5 mg/m3; paragraphs 25 and 26 defining halogeno-platinum compounds; paragraphs 53 to 56 on occupational asthma; and the introductory statement that absence from the list does not indicate that a substance is without risk; Table 1, the entry for halogeno-platinum compounds (as Pt) at 0.002 mg/m3 with the Sen notation and paragraphs 25 and 26 defining them; the entry for oxalic acid at 1 mg/m3 long-term and 2 mg/m3 short-term; paragraphs 53 to 56 on occupational asthma; and the introductory statement that absence from the list does not indicate that a substance is without risk; Table 1 — mercury and divalent inorganic compounds (as Hg) at 0.02 mg/m3 with a biological monitoring guidance value; thallium, soluble compounds (as Tl) at 0.1 mg/m3 with the Sk notation; chromium(VI) compounds (as Cr) at 0.01 mg/m3 with the Carc, Sen and BMGV annotations; halogeno- platinum compounds (as Pt) at 0.002 mg/m3 with the Sen notation; the absence of uranium and of palladium compounds from the list; paragraph 52, that lead is regulated separately under the Control of Lead at Work Regulations 2002; and the introductory statement that absence from the list does not indicate that a substance is without risk; Table 1 — mercury and divalent inorganic compounds (as Hg), long-term limit 0.02 mg/m3 with a biological monitoring guidance value and no short-term figure; cyanides other than hydrogen cyanide, cyanogen and cyanogen chloride (as CN), 5 mg/m3 long-term, with potassium cyanide listed by name and a skin notation; hydrogen cyanide, 0.9 ppm long-term and 4.5 ppm over fifteen minutes with the Sk notation; chromium (VI) compounds (as Cr), 0.01 mg/m3 long-term, annotated Carc, Sen and BMGV; cadmium and cadmium compounds (as Cd), 0.025 mg/m3, annotated Carc; diethyl ether, 100 ppm long-term and 200 ppm over fifteen minutes; and the introductory statement that the absence of a substance from the list does not indicate that it is without risk; Table 1 - mercury and divalent inorganic compounds (as Hg) at 0.02 mg/m3 long-term with no short-term figure; chromium (VI) compounds (as Cr) at 0.01 mg/m3 with the Carc and Sen notations and a biological monitoring guidance value; silver, soluble compounds (as Ag) at 0.01 mg/m3 against 0.1 mg/m3 for the metal; hydrogen chloride, gas and aerosol mists, at 1 ppm (2 mg/m3) long-term and 5 ppm (8 mg/m3) over fifteen minutes; hydrogen cyanide at 0.9 ppm long-term and 4.5 ppm over fifteen minutes with the Sk notation. Table 3, biological monitoring guidance values. The introductory text, for the statement that the absence of a substance from the list does not indicate that it is without risk, and the Annotations, for the meaning of Carc, Sen, Sk and BMGV; Table 1 — hydrogen cyanide, 0.9 ppm long-term and 4.5 ppm over fifteen minutes with the Sk notation for skin absorption; cyanides other than hydrogen cyanide, cyanogen and cyanogen chloride (as CN), 5 mg/m3 long-term with potassium cyanide listed by name and a skin notation; and the introductory statement that the absence of a substance from the list does not indicate that it is without risk; Table 1 — Chromium (VI) compounds (as Cr) at 0.01 mg/m3 over eight hours with the Carc and Sen annotations and a biological monitoring guidance value; benzene at 1 ppm with Carc and Sk; asphalt, petroleum fumes, CAS 8052-42-4; and the introductory statement that absence from the list does not indicate that a substance is without risk; Table 1: mercury and divalent inorganic compounds (as Hg), long-term exposure limit 0.02 mg/m3 with no short-term figure; iodine, short-term limit 0.1 ppm; bromine, 0.1 ppm long-term and 0.2 ppm short-term. Table 3, biological monitoring guidance values, for the mercury entry of 20 micromoles per mole of creatinine in urine. And the introductory statement that the absence of a substance from the list does not indicate that it is without risk; Table 1 — thallium, soluble compounds (as Tl), long-term exposure limit 0.1 mg/m3 with the Sk notation for skin absorption and no short-term limit listed; cadmium and cadmium compounds except cadmium oxide fume, cadmium sulphide and cadmium sulphide pigments (as Cd), long-term exposure limit 0.025 mg/m3 annotated Carc; mercury and divalent inorganic compounds (as Hg), long-term limit 0.02 mg/m3 with a biological monitoring guidance value and no short-term figure. Paragraph 52, under the heading Asbestos and lead, that asbestos and lead are regulated separately, and the notice of approval referring to the occupational exposure limit for lead specified in regulation 2(1) of the Control of Lead at Work Regulations 2002. And the introductory statement that the absence of a substance from the list does not indicate that it is without risk; Table 1: diethyl ether, 100 ppm (310 mg/m3) long-term and 200 ppm (620 mg/m3) over fifteen minutes; cadmium and cadmium compounds (as Cd), 0.025 mg/m3 long-term with the Carc notation; ethanol, 1000 ppm long-term; silver compounds, soluble (as Ag), 0.01 mg/m3; and the introductory statement that the absence of a substance from the list does not indicate that it is without risk; Table 1: iodine; mercury and divalent inorganic compounds; Table 1 — halogeno-platinum compounds (as Pt) and platinum compounds, soluble (as Pt), with the Sen notation; paragraphs 25 and 26; paragraphs 53 to 56 on occupational asthma; Table 1 — Chromium; Chromium (II) compounds (as Cr); Chromium (III) compounds (as Cr); Chromium (VI) compounds (as Cr) and its process-generated entry. Annotations, for Carc, Sen, Sk and BMGV; Table 2, biological monitoring guidance values, chromium VI; paragraphs 53 to 56 on occupational asthma; foreword, the 2020 revision of the chromium (VI) limit; Annotations, for Carc, Sen, Sk and BMGV; the note that the Carc, Sen and Sk notations are not exhaustive; the statement that absence from the list does not indicate that a substance is safe; Table 1 — sulphur dioxide; hydrogen sulphide; hydrogen cyanide; chlorine; ammonia, anhydrous; acetic acid; Table 1 — mercury and divalent inorganic compounds (as Hg); hydrogen cyanide; cadmium and cadmium compounds (as Cd); halogeno-platinum compounds (as Pt) and platinum compounds, soluble (as Pt); chromium (VI) compounds (as Cr); benzene; diethyl ether; sulphur dioxide; hydrogen sulphide. Annotations, for the meaning of Carc, Sen, Sk and BMGV; paragraphs 25 and 26 on halogeno-platinum compounds; paragraphs 53 to 56 on substances that can cause occupational asthma; Table 1, sulphur dioxide, hydrogen sulphide, chlorine and acetic acid, with their long-term and fifteen-minute limits; Table 1, ammonia anhydrous, at 25 ppm long-term and 35 ppm over fifteen minutes; Table 1, chromium(III) compounds as Cr at 0.5 mg/m3 with no notation, against chromium(VI) compounds at 0.01 mg/m3 with Carc, Sen and a biological monitoring guidance value; Table 1: the workplace exposure limits for borates, 5 mg/m3 for the decahydrate and 1 mg/m3 for the anhydrous and pentahydrate forms; Table 1: halogeno-platinum compounds at 0.002 mg/m3 with the Sen notation; oxalic acid at 1 mg/m3 long-term and 2 mg/m3 short-term; and the paragraphs on preventing exposure to an asthmagen; Table 1: selenium and compounds except hydrogen selenide at 0.1 mg/m3 as Se; dihydrogen selenide at 0.02 ppm over eight hours; Table 1: hydrogen sulphide at 5 ppm (7 mg/m3) over eight hours and 10 ppm (14 mg/m3) over fifteen minutes

Used by:6-Nitrobenzimidazole · Acetic acid (glacial) · Albumen · Amidol · Ammonium bromide · Ammonium chloride · Ammonium citrate (dibasic) · Ammonium citrate (tribasic) · Ammonium dichromate · Ammonia solution (ammonium hydroxide) · Ammonium iron(III) citrate · Ammonium persulfate · Ammonium sulfite · Ammonium thiocyanate · Ammonium thiosulfate · Arrowroot · Ascorbic acid · Barium sulfate · Benzotriazole · Bitumen of Judea · Borax (sodium tetraborate decahydrate) · Bromine · Cadmium bromide · Calcium carbonate · Calcium nitrate tetrahydrate · Catechol · Chlorine · Chlorohydroquinone · Chrome alum · Citric acid (anhydrous) · Copper(II) sulfate · Diethyl ether · Dimezone S · EDTA disodium salt (anhydrous) · EDTA disodium salt dihydrate · Erythrosin · Ethanol · Iron(II) oxalate · Formaldehyde · Gallic acid · Gelatin · Glutaraldehyde · Glycerol · Glycin · Glyoxal · Gum arabic · Hydrochloric acid · Hydrogen peroxide · Hydroquinone · Iodine · Iron(II) sulfate, anhydrous · Iron(II) sulfate heptahydrate · Iron(III) chloride, anhydrous · Iron(III) chloride hexahydrate · Iron(III) nitrate nonahydrate · Isopropyl alcohol · Kaolin · Oil of lavender · Lead(II) acetate · Lead(II) nitrate · Lithium chloride · Mercury · Mercury(II) chloride · Metol · Nickel(II) sulfate · Nitric acid · Nitrocellulose · Oxalic acid · p-Aminophenol · Palladium(II) chloride · Phenidone · Potassium alum · Potassium bromide · Potassium carbonate (anhydrous) · Potassium chlorate · Potassium chloride · Potassium citrate · Potassium cyanide · Potassium dichromate · Potassium ferricyanide · Potassium hydroxide (caustic potash) · Potassium iodide · Potassium metabisulfite · Potassium permanganate · Potassium persulfate · Potassium sodium tartrate tetrahydrate · Potassium tetrachloropalladate(II) · Potassium tetrachloroplatinate(II) · Potassium thiocyanate · Prussian blue · Pyrogallol · Selenium · Silver · Silver bromide · Silver chloride · Silver iodide · Silver nitrate · Silver(I) oxalate · Silver(I) oxide · Silver selenide · Silver sulfamate · Silver sulfide · Sodium acetate (anhydrous) · Sodium ascorbate · Sodium bisulfite · Sodium carbonate (anhydrous) · Sodium carbonate decahydrate · Sodium carbonate monohydrate · Sodium chloride · Trisodium citrate dihydrate · Sodium cyanide · Sodium hexametaphosphate (Calgon) · Sodium hydroxide (caustic soda) · Sodium metabisulfite · Sodium metaborate (anhydrous) · Sodium metaborate tetrahydrate (Kodalk) · Sodium selenate · Sodium selenite · Sodium selenosulfate · Sodium sulfate · Sodium sulfide · Sodium sulfite · Sodium tetrachloropalladate(II) · Sodium thiocyanate · Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Sulfamic acid · Sulfuric acid · Tannic acid · Tartaric acid · Tetraazaindene · Thallium(I) sulfate · Thiourea · Thymol · Titanium dioxide · Ammonium citrate developer · Borax kallitype developer · Bostick and Sullivan platinum and palladium kits · Kodak SB-4 · Cyanide fixing and toning · Daguerre's 1839 process outline · Erythrosin sensitising stock · Fizeau's gilding solution · HARMAN SELENIUM TONER · Herschel's hydrargyro-cyanotype · ILFORD HYPAM · ILFORD RAPID FIXER · Kodak Hypo Clearing Agent and the washing accelerator Kodak patented · Kodak IN-4 · Kodak IN-1 · KODAK Rapid Selenium Toner · Kodak SB-1 · Kodak SB-1a · Kodak SB-5 · Kodak ST-1 · KODAK PROFESSIONAL XTOL Developer · Lead additions to platinum sensitisers · Lead, thallium and nickel cyanotype toners · Mercuric sepia platinotype · Moersch MT3 Variotoner · Moersch MT1 Selentoner · Pizzighelli and Hübl's 1886 formulations · EDTA, citric acid and hydrochloric acid clearing sequence · Three-solution drop system for platinum and palladium · Rochelle salt kallitype developer · Sodium citrate developer · Sodium citrate kallitype developer · Ware's improved Classic cyanotype · Ware's print-out platino-palladiotype · Wedgwood and Davy's silver nitrate on leather · Willis's potassium oxalate developer · P1 Daguerre and the Daguerreotype: A Mirror With a Memory · P2 Laying Out the Laboratory: Wet Areas, Dry Areas and Contamination Control · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P4 Reciprocity Failure and the Life of the Latent Image · P5 Part V Overview: Photographic Emulsions · P5 Project 1: A Silver Chloride Contact Printing Emulsion · P5 Project 2: A Chlorobromide Paper Emulsion · P5 Coating, Drying and Hardening · P5 Project 4: Coating Glass Dry Plates and a Lantern Slide · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P5 Gelatin, the Photographic Binder · P5 Washing, Digestion and Sensitisation · P8 Alkalis, Buffers and pH · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P8 Staining and Tanning Developers · P8 Sulfite: Preservative, Buffer, Silver Solvent · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P10 Experiment: Measuring Stop Bath Capacity · P10 Stop Bath Formulations and the Fixer Interaction · P11 Overview: Making the Image Permanent · P11 Lab: Mixing Fixers from Scratch · P12 Lab: Testing for Residual Thiosulfate and Residual Silver · P14 Build: The LED Light Source and Exposure Timer · P14 Low-Voltage Electronics for the Darkroom Builder · P15 Build: The Densitometer Electronics and Firmware · P17 Build: The Timer Hardware · P20 Part XX Overview: Toning Chemistry · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P20 The Toners We Study and Do Not Use · P21 Iron, Light and Prussian Blue · P21 The New Cyanotype and the Other Ways to Make a Blue Print · P23 Part XXIII Overview: Albumen Printing · P23 Lab: Sensitising, Printing and Toning an Albumen Print · P24 Contrast Control in Iron-Based Printing · P25 Part XXV Overview: Platinum and Palladium · P25 Lab: Exposing, Developing and Clearing a Palladium Print · P25 Noble Metal Chemistry and the Platinotype · P25 Lab: Preparing the Sensitiser and Coating for Palladium · P25 The Additives We Study and Do Not Reproduce · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Assignment: Assessing a Historical Process for Hazard · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory · P26 Uranium, Mercury and the Heavy-Metal Treatments · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · The Becquerel variant · Daguerreotype · Platinotype · The chromium policy · Reading GHS and CLP · Chemical incompatibilities · The Level D policy · Responding to an acid spill · Responding to an alkali spill · Routing chromium(III) from the coating station · Mixing a developer from raw chemicals · Running a platinum or palladium session · Handling a selenium toner and its waste · Handling a sulphide toner and its waste

Electrical safety and you: A brief guide, INDG231(rev1)retrieved 2026-09-05

Sections: Reducing the risk, Reduce the voltage - limit the supply voltage to the lowest needed to get the job done; What are the hazards - normal mains voltage, 230 volts AC, can kill; Reducing the risk, Reduce the voltage - limit the supply voltage to the lowest needed to get the job done; What are the hazards - 230 volts AC can kill, and the risk is greatest in wet surroundings; What are the hazards - contact with live parts causing shock and burns, normal mains voltage 230 volts AC can kill, and the note that risks are greatest in wet surroundings; Reducing the risk, Reduce the voltage - limit the supply voltage to the lowest needed to get the job done, with 12, 25, 50 and 110 volts given as examples and battery-operated tools named as safest; Reducing the risk - limit the supply voltage to the lowest needed to get the job done; and What are the hazards, that normal mains voltage of 230 V AC can kill and that risks are greatest in wet surroundings; Reducing the risk - limit the supply voltage to the lowest needed to get the job done, with 12, 25, 50 and 110 volts given as examples; and What are the hazards - normal mains voltage of 230 V AC can kill and the risk is greatest in wet surroundings; Reducing the risk - the definition of competent as having suitable training, skill and knowledge for the task to prevent injury to themselves and others; Reduce the voltage - limit the supply voltage to the lowest needed to get the job done, with 12, 25, 50 and 110 volts given as examples; the instruction that damaged or defective equipment should be removed from use and either repaired by someone competent or disposed of to prevent its further use; Work safely - that equipment is switched off and unplugged before cleaning or making adjustments, that even simple tasks such as wiring a plug can lead to danger, and that more complicated tasks such as equipment repairs or alterations to an electrical installation should only be carried out by people with knowledge of the risks and the precautions needed; Reducing the risk - one of the best ways of reducing the risk of injury from electrical equipment is to limit the supply voltage to the lowest needed to get the job done, with 12, 25, 50 and 110 volts given as examples for temporary lighting and battery-operated tools named as the safest choice; What are the hazards - normal mains voltage of 230 V AC can kill and the risk is greatest in wet surroundings; What are the hazards - normal mains voltage of 230 V AC can kill, and risks are greatest in wet surroundings; Reducing the risk - limit the supply voltage to the lowest needed to get the job done; Reducing the risk, Reduce the voltage - limit the supply voltage to the lowest needed to get the job done; What are the hazards - normal mains voltage of 230 V AC can kill and the risks are greatest in wet surroundings; Reducing the risk - limit the supply voltage to the lowest needed to get the job done, with 12, 25, 50 and 110 volts given as examples; What are the hazards - normal mains voltage of 230 V AC can kill and the risk is greatest in wet surroundings; Reducing the risk, Reduce the voltage - limit the supply voltage to the lowest needed to get the job done, with battery-operated equipment named as the safest choice; What are the hazards - normal mains voltage of 230 V AC can kill and the risks are greatest in wet surroundings; Reducing the risk - limit the supply voltage to the lowest needed to get the job done; What are the hazards - contact with live parts causes shock and burns, normal mains voltage of 230 volts AC can kill, and the risks are greatest in wet surroundings; Reducing the risk, Reduce the voltage - limit the supply voltage to the lowest needed to get the job done; What are the hazards — normal mains voltage of 230 V AC can kill, and the risks are greatest in wet surroundings

Used by:P14 Part XIV Overview: Build a Sensitometer · P14 Build: The LED Light Source and Exposure Timer · P14 Low-Voltage Electronics for the Darkroom Builder · P15 Part XV Overview: Build a Densitometer · P15 Build: The Densitometer Electronics and Firmware · P16 Part XVI Overview: Build the Darkroom · P16 Build: The UVA Exposure Unit · P16 Build: An LED Enlarger Head · P16 Build: An LED Safelight · P16 Build: Making a Room Dark and Proving It · P17 Part XVII Overview: Build the Pure Silver Timer · P17 Build: The Switched Output · P17 Build: The Timer Hardware · P17 Experiment: Calibrating the Timer · P17 Switching Lamps Safely: Isolation, Certified Modules and the Mains Boundary · Darkroom opening and closing for a printing session

First aid at work: frequently asked questionsretrieved 2026-09-04, 2026-09-05

Sections: First-aid equipment — provision for eye irrigation; Eye irrigation where mains tap water is not readily available; sterile water and sterile normal saline in sealed disposable containers; expiry dates on sterile items; First-aid equipment, and the provision for eye irrigation where mains tap water is not readily available

Used by:P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · First aid quick reference · Checking and using the eyewash

L74: First aid at work. The Health and Safety (First-Aid) Regulations 1981. Guidance on Regulationsretrieved 2026-09-06

Sections: Table 3, examples of additional first-aid training needs identified by a first-aid needs assessment — management of a casualty suffering from cyanide poisoning, listed against the work setting of chemical manufacture, and oxygen administration listed against settings including those where there is a risk of exposure to hydrogen cyanide

Used by:P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide

Managing skin exposure risks at work, HSG262retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Allergic contact dermatitis (paragraph 11); Why gloves alone are not a control strategy; Sensitisation, and why gloves alone are not a control strategy; Substances that damage the skin; sensitisation; Substances that damage the skin; sensitisation and the principle that once a person has reacted, further exposure is prevented rather than managed; Allergic contact dermatitis, paragraph 11; What health problems can occur through skin contact; allergic contact dermatitis; The avoid, protect, check hierarchy for skin exposure, and the guidance that gloves are the last resort rather than the first control and must be selected against the substance and checked before use; Corrosives, irritants and sensitisers; what happens at the point of contact; What health problems can occur through skin contact; allergic contact dermatitis; the avoid, protect, check framing; Sensitisation, and why the only remedy once a person is sensitised is to prevent further exposure; Allergic contact dermatitis, and the point in the task at which exposure usually happens; The hierarchy that puts gloves after the controls that prevent contact, rather than first

Used by:Amidol · Ammonium bromide · Ammonium persulfate · Catechol · Chloroauric acid · Chlorohydroquinone · Dimezone S · Glycin · Glyoxal · Gold(III) chloride · Hydroquinone · Metol · p-Aminophenol · Palladium(II) chloride · Potassium persulfate · Potassium tetrachloropalladate(II) · Potassium tetrachloroplatinate(II) · Sodium tetrachloropalladate(II) · Thiourea · Moersch MT3 Variotoner · Rodinal-type p-aminophenol developer · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P22 Lab: Salting and Sensitising a Sheet of Paper · First aid quick reference · Glove selection · The Level D policy · Putting protective equipment on, changing gloves and taking it off · Silver nitrate at the coating bench

Memorandum of guidance on the Electricity at Work Regulations 1989, HSR25, third editionretrieved 2026-09-05

Sections: Paragraph 142, use of reduced voltages, which are particularly appropriate for portable equipment and in highly conducting locations where the body may be damp; paragraph 143, which gives an extra-low-voltage system as one operating at or below 50 V ac or 120 V dc and notes that such systems are earth-referenced special cases; paragraph 146, current limitation, where a current limited preferably to 1 mA and certainly to no more than 3 mA in a conventional dry environment will not usually present a risk of injury but may still give a perceptible shock and a consequential injury such as a fall; paragraph 147, separated or isolated systems, that all systems are to some extent referenced to their environment by capacitive or inductive coupling or by leakage

Used by:P17 Switching Lamps Safely: Isolation, Certified Modules and the Mains Boundary

Safe use of knives in the kitchenretrieved 2026-09-04, 2026-09-05

Sections: General principles for safe knife use; Ways to minimise the risk; Ways to minimise the risk: keep the blade sharp, cut on a stable surface, store the knife securely after use, never try to catch a falling one; Ways to minimise the risk: keep the blade sharp, cut on a stable surface, store the knife securely after use, never leave it loose on a worktop, never try to catch a falling one; General principles: keep the blade sharp, cut on a stable surface, store the tool securely after use, never leave it loose on a worktop, never try to catch a falling one; Safe working practices for hand-held cutting; The general principles - keep the blade sharp, cut on a stable surface, store the knife securely after use, never leave it loose where it can be knocked off, never try to catch a falling one

Used by:P1 Assignment 1: A Botanical Cyanotype Photogram, After Atkins · P1 The Camera Obscura: An Image Without Chemistry · P5 Build an Emulsion Coating Station · P6 Build the Modular Pinhole Camera · P6 Making and Measuring Pinholes · P9 Lab: Preparing Standard Test Negatives · P14 Build: The Enclosure and Exposure Stage

Selecting protective gloves for work with chemicals: Guidance for employers and health and safety specialists, INDG330retrieved 2026-09-04, 2026-09-05

Sections: Choosing the right glove; The law, and Chemical resistance of protective gloves — the requirement that gloves be selected to withstand exposure to the chemical agent and be compatible with the wearer, the work to be done and the other PPE worn; Chemical resistance of protective gloves; selecting suitable protective gloves; Choosing gloves for the chemicals in use; the limits of manufacturers' data; Chemical resistance of protective gloves; permeation, penetration and degradation; selecting suitable protective gloves; Permeation, penetration and degradation; the limits of manufacturer data; single-use gloves

Used by:Chloroauric acid · Chlorohydroquinone · Gold(III) chloride · Palladium(II) chloride · Potassium tetrachloropalladate(II) · Sodium tetrachloropalladate(II) · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P4 Experiment: Precipitating the Silver Halides · Glove selection · Putting protective equipment on, changing gloves and taking it off

Wood dust: Controlling the risks, Woodworking Information Sheet 23retrieved 2026-09-04

Sections: Why is it necessary to control wood dust?: all wood dust hazardous to health, causing asthma, dermatitis and irritation of eyes, nose and throat, hardwood dust also a rare nasal cancer, and wood dust flammable; What causes high wood dust exposures?: sawing, routing, turning and powered sanding, and compressed air and dry sweeping to be avoided; What the law says: workplace exposure limits of 3 mg/m3 hardwood and 5 mg/m3 softwood as 8-hour time-weighted averages, and reduction to as low as reasonably practicable; RPE: an assigned protection factor of at least 20, disposable respirators described as FFP3, CE or UKCA marked and fit tested; Why is it necessary to control wood dust? and What causes high wood dust exposures?: all wood dust hazardous to health, hardwood and softwood workplace exposure limits, sawing and sanding as the high-exposure operations, dry sweeping to be avoided, and the FFP3 respirator with an assigned protection factor of at least 20

Used by:P6 Build the Modular Pinhole Camera · P6 Designing the Modular Camera

Working with substances hazardous to health: A brief guide to COSHH, INDG136retrieved 2026-09-04

Sections: Choosing control measures; Assessing risk; Assessing risk; choosing control measures; Assessing risk; what are exposure control measures; choosing control measures; Assessing risk; Choosing control measures: eliminate the harmful substance and use a safer one; use a safer form of it; Choosing control measures, and the order of priority that places personal protective equipment last

Used by:P2 Part II Overview: The Photographic Chemistry Laboratory · P2 Lab: Commissioning Your Laboratory · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P2 Measuring Mass, Volume, Temperature and Density, and Knowing How Wrong You Are · P2 Silver Nitrate: The Reagent That Sets the Rules · P3 Lab: Measuring pH and Trusting the Number · P6 Build the Modular Pinhole Camera · P6 Making and Measuring Pinholes · Glove selection

icnirp.org

Guidelines on Limits of Exposure to Ultraviolet Radiation of Wavelengths Between 180 nm and 400 nm (Incoherent Optical Radiation)retrieved 2026-09-05, 2026-09-06

Sections: Exposure limits - within an 8-hour period the total unweighted radiant exposure of the unprotected eye over 315 to 400 nm not to exceed 10^4 J/m2, alongside the 30 J/m2 spectrally weighted limit over 180 to 400 nm; Table 1 - relative spectral effectiveness of 0.00011 at 365 nm and a monochromatic limit of 2.7 x 10^5 J/m2 there; Appendix, UVA radiation effects - the recommendation that people without ultraviolet-absorbing intraocular lenses wear UVA protective eyewear when working with UVA sources, and the statement that experimental threshold data for chronic ocular UVA exposure are lacking; Basic concepts - the CIE band designations, UVA 315 to 400 nm, UVB 280 to 315 nm and UVC 100 to 280 nm, with the note that some specialists take the UVA/UVB divide at 320 nm; Exposure limits - within an 8-hour period, radiant exposure of the unprotected eye not to exceed 30 J/m2 spectrally weighted over 180 to 400 nm and, separately, the total unweighted radiant exposure over 315 to 400 nm not to exceed 10^4 J/m2, with the same 30 J/m2 weighted figure for melano-compromised skin; Table 1 - the relative spectral effectiveness S(lambda), 1.000 at 270 nm, 0.003 at 315 nm, 0.00011 at 365 nm and 0.000030 at 400 nm; Table 2 - permissible daily exposure durations against effective irradiance; Appendix, UVA radiation effects - the lack of evidence that the 1 to 3 mW/cm2 of UVA met in sunlight or indoor work harms skin or eye, the cataract hypothesis that nonetheless justifies caution about chronic ocular exposure, the absence of experimental threshold data, and the recommendation that people without ultraviolet-absorbing intraocular lenses wear UVA protective eyewear when working with UVA sources; and the note that very intense UVC sources, particularly below 230 nm, may produce hazardous concentrations of ozone and nitrogen oxides, which is why many germicidal lamps now use envelopes blocking below about 230 nm; Exposure limits, Exposure of the eyes — that ultraviolet radiant exposure between 180 and 400 nm incident on the unprotected eye should not exceed 30 J/m2 effective spectrally weighted over an 8-hour period, and that the total unweighted radiant exposure between 315 and 400 nm should not exceed 10^4 J/m2; and Exposure of the skin, the same 30 J/m2 effective limit for melano-compromised skin with the statement that it is difficult to achieve in sunlight and that judgment must be used in its practical application; The exposure limits for incoherent ultraviolet radiation, cited here only as the basis for the rule that the enclosure and its interlock, and not personal protection, are the controls that matter around a printing source.; Exposure limits - the total unweighted radiant exposure of the unprotected eye over 315 to 400 nm within an 8-hour period not to exceed 10^4 J/m2; Appendix, UVA radiation effects - the recommendation that people with no intraocular lens, or one not designed to absorb ultraviolet, be fitted with UVA protective eyewear when working with sources of UVA radiation

Used by:P16 Build: The UVA Exposure Unit · P16 Ultraviolet for the Alternative Processes: Sources, Dose, Uniformity and Hazard · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Experiment: The Exposure Scale, Maximum Density and Contrast of a Cyanotype · Operating the UVA exposure unit

Protecting Workers from Ultraviolet Radiation, ICNIRP 14/2007retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: 9.2.4 Work hours; 9.3 Personal protective measures for outdoor workers; 9.2.3 Simple tips for sun avoidance; 9.2.4 Work hours; 9.3 Personal protective measures for outdoor workers; 9.2.3 Simple tips for sun avoidance; 9.2.4 Work hours; 9.3 Personal protective measures; materials and UVR; 9.3 Personal protective measures; eye and skin protection against ultraviolet sources; 9.2.3 Simple tips for sun avoidance, including the shadow rule and the four hours around midday; 9.2.3 Simple tips for sun avoidance, the shadow rule and the four hours around midday; 9.3 Personal protective measures for outdoor workers; 9.2.3 Simple tips for sun avoidance, the shadow rule and the four hours around midday; 9.3 Personal protective measures; 9.2.3 Simple tips for sun avoidance, the shadow rule and the four hours around midday; 9.2.1 and the shade discussion: glass strongly attenuates UVB and some shorter wavelengths of UVA, and window glass transmits some radiation down to 310 nm; 9.1 Engineering controls, materials - window glass transmits some radiation down to 310 nm, within the UVB, whereas most plastics such as polymethyl methacrylate (Perspex, Lucite) and polycarbonate normally do not transmit below about 370 nm; 10.2 Engineering controls - light-tight cabinets and enclosures, absorbing shields and baffles as the key engineering control, observation ports only of suitably tested absorbing material such as certain grades of acrylic, PVC and window glass, fail-safe interlocks manufactured, installed, tested and used to agreed relevant technical standards where direct access to the source is required, with the worked example of a door switch that removes power from the lamps when the door is opened, non-reflective interior surfaces to eliminate reflected ultraviolet, and ventilation needed to exhaust ozone produced by UVC; 5.3.4 Banking and commerce - colourless inks and banknote features fluorescing under UVA; 9.1 - polymethyl methacrylate and polycarbonate normally do not transmit below about 370 nm; 2.3.1 and 2.3.2 - the low-pressure mercury discharge lamp as an efficient emitter of 254 nm, with some quartz envelopes also transmitting 185 nm, and the fluorescent lamp as the same discharge with a phosphor converting that 254 nm emission to longer wavelengths; 7.4 CIE Risk Groups for Lamps and Table 8 - the exempt, Risk Group 1, 2 and 3 definitions by the exposure duration at which a limit is exceeded, with the unweighted UVA lens limit exceeded beyond 1000 s for exempt, 300 s for Risk Group 1 and 100 s for Risk Group 2, measured at 20 cm for non-general-lighting lamps, and the note that the CIE exempt group used a 1000 s integration where ICNIRP uses 8 hours; 9.1 - window glass transmits some radiation down to 310 nm while polymethyl methacrylate and polycarbonate normally do not transmit below about 370 nm; 10.2 Engineering controls - light-tight cabinets and enclosures, absorbing shields and baffles, observation ports of tested absorbing material, fail-safe interlocks to agreed technical standards where direct access to the source is required, non-reflective interior surfaces, and ventilation to exhaust ozone produced by UVC; 10.2 Engineering controls - fail-safe interlocks manufactured, installed, tested and used to agreed relevant technical standards where direct access to the source is required, with the worked example of a door switch that removes power from the lamps when the door is opened; The control hierarchy for artificial ultraviolet sources — enclosure and interlocking of the source before personal protection, and the placing of protective eyewear last; 9.2.3 Simple tips for sun avoidance, 9.2.4 Work hours and 9.3 Personal protective measures for outdoor workers - shade, clothing, headwear and the avoidance of the hours around solar noon, as the administrative controls that are all an outdoor printing session has; The control hierarchy for artificial ultraviolet sources — enclosure and interlocking of the source before personal protection, and protective eyewear placed last; 9.2.3 Simple tips for sun avoidance - the shadow rule, and the statement that breaks in variable cloud can raise ultraviolet to clear-sky levels or above; 9.2.4 Work hours - outdoor work in the four-hour midday period carries the greatest risk and rest periods are best taken in the shade; 9.3.1 Clothing and hats - most summer clothing gives protection factors above 10 and more than 85 per cent of fabrics 20 or higher; 9.5 UV risk management for outdoor workers - shade between 11:00 and 15:00 for a local solar noon near 13:00, SPF 15 to 30 reapplied every two hours, and the shadow rule as the simple test for a UV Index above 4; 8.7 Tables 9 and 10, hazard assessment factors for skin and ocular exposure - 0.02 for sunglasses or spectacles with a brimmed hat against 0.5 for sunglasses alone, 1.5 for partial cloud sometimes covering the sun against 1 for clear sky, and the ground reflectance rows for snow, dry sand, surf and concrete; 3.2.2.1 Sunburn - the minimum erythemal dose defined as producing just perceptible erythema 8 to 24 hours after irradiation; 9.5 UV risk management for outdoor workers - the shadow rule as the simple test for a UV Index above 4; 10.2 Engineering controls - light-tight cabinets and enclosures as the key engineering control, observation ports only of suitably tested absorbing material, non-reflective interior surfaces, and fail-safe interlocks where direct access to the source is required, with the worked example of a door switch that removes power from the lamps when the door is opened

Used by:P1 Overview: The Three Problems Every Photograph Must Solve · P1 Assignment 1: A Botanical Cyanotype Photogram, After Atkins · P1 The Camera Obscura: An Image Without Chemistry · P1 Experiment: The Image That Would Not Stay · P4 Experiment: Precipitating the Silver Halides · P7 Part VII Overview: The Art of Pinhole Photography · P7 Assignment: Architecture, Low Viewpoint and the Flat Plane · P7 Assignment: Landscape, Sky, Foreground and Filters · P7 Assignment: Panorama, Curved Plane and Multiple Pinholes · P7 Assignment: Portrait, Environmental Portrait and Self-Portrait · P7 Assignment: Still Life and Controlled Light · P7 Assignment: Time in the Frame, Moving Water, Clouds, People and Traffic · P16 Build: The Contact Printing Frame and Its Light Source · P16 Build: The UVA Exposure Unit · P16 Ultraviolet for the Alternative Processes: Sources, Dose, Uniformity and Hazard · P17 Build: The Switched Output · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Assignment: Cyanotype at Scale, on Fabric, and the Botanical Sequence · P24 Lab: Printing a Van Dyke Brown · Outdoor exposure session · Recording a daylight exposure · Operating the UVA exposure unit · Uneven contact print from pressure, glass or source geometry

ilfordphoto.com

An Introduction to Film Process Controlretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Specific gravity — the worked note that since 1 litre of water weighs 1000 g, a litre of HYPAM at 1+4 with an SG of 1.08 to 1.09 weighs 1080 to 1090 g; and the recommendation that appropriately sized measuring cylinders be used; Lab equipment - basic: thermometer, measuring cylinders; lab equipment - advanced: hydrometer, and the weight of a litre of water; Lab equipment - basic: thermometer, containers and mixing vessels, measuring cylinders; lab equipment - advanced: pH meter, hydrometer; Lab equipment - advanced: pH meter or pH sticks; monitoring the pH of solutions; Lab equipment - advanced: pH meter or pH sticks, and why monitoring pH is useful; Lab equipment - advanced: pH meter or pH sticks; the ranges of sticks useful for developers and for fixers; monitoring pH as process control; The general argument for plotting a control result over time rather than judging a single result, and for separating a change in the process from the scatter of the measurement; Stop bath — the statement that a stop bath between developer and fixer stops development in a matter of seconds and helps to prolong the activity and life of a fixer bath, that fixer baths are mildly acidic and become less efficient as they become neutral, and that the carry over from stop bath into the fixer is acidic; Process control - the three monitored variables given as speed (LD), contrast (HD minus LD) and minimum density (Dmin); Process control - the three variables a control system measures, given as speed (LD), contrast (HD minus LD) and minimum density (Dmin), plotted on a control chart with action and control lines; The advice that a good-quality liquid-in-glass thermometer is useful for checking the calibration of built-in sensors, its advantage over an electronic probe being that very little can go wrong with it; The statement that a densitometer is essential and that a visual assessment of density cannot be used for accurate process control because it is not a measurement; the three variables an FPC system measures, speed as LD, contrast as HD minus LD and minimum density as Dmin, plotted against action and control lines; and the advice that a good-quality liquid-in-glass thermometer is useful for checking the calibration of a built-in sensor because very little can go wrong with it; Why a film process control system is important - the statement that every film processed changes the condition of the developer and that the major effects of processing a film are that the pH changes, making the developer more acidic, that developing agents are used up, and that waste products, mainly bromide, are introduced into the developer; the additional statement that age and temperature affect a developer, that developers react with air in oxidation that causes some of the active ingredients to break down and reduce activity, and that high temperatures speed that up; the statement that there will always be a difference in performance between a tank of fresh developer and a tank of used or seasoned developer, and that a well set up replenishment system holds the tank stable for many months; the statement that a densitometer is essential and that a visual assessment of density cannot be used for accurate process control because it is not a measurement; the three variables measured, speed as LD, contrast as HD minus LD and minimum density as Dmin; and the escalation rule that a plot inside the action lines is in control, a plot between the action and control lines allows processing to continue while the cause is found, and a plot beyond the control line stops processing; A densitometer - the statement that it is essential for measuring the density of the steps and that a visual assessment of density cannot be used for accurate process control because it is not a measurement; and Process Control, which names the three variables a control system measures as speed, contrast as HD minus LD, and minimum density; The statement that a densitometer is essential and that a visual assessment of density cannot be used for accurate process control because it is not a measurement; the three variables a film process control system measures, speed as LD, contrast as HD minus LD and minimum density as Dmin; and the advice that a good-quality liquid-in-glass thermometer is useful for checking the calibration of a built-in sensor because very little can go wrong with it; Lab equipment - basic: measuring cylinders, and the weight of a litre of water; Lab equipment - advanced: pH meter or pH sticks; monitoring pH as process control; Lab equipment - basic and advanced, and what each instrument is for

Used by:ILFORD HYPAM · P2 Lab: Commissioning Your Laboratory · P2 Measuring Mass, Volume, Temperature and Density, and Knowing How Wrong You Are · P3 Part III Overview: Chemistry Foundations for Photographers · P3 Acids, Bases and pH · P3 Lab: Measuring pH and Trusting the Number · P7 Pinhole Portfolio Review and the Exposure Record as Data · P10 Why Stopping Works · P13 Gamma, Contrast Index and Average Gradient · P13 The Characteristic Curve · P27 Part XXVII Overview: From Observation to Measurement · P27 Designing an Experiment That Yields a Number · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Experiment: Four Curve Families, Measured · P27 Experiment: The Development Time and Temperature Series · Checking the balance and verifying the thermometer · Verifying volumetric glassware by weighing water · Calibrating a pH meter · Balance drifting, or reading below its minimum weighable mass

Comparing the new MGRC with MGIVRC, technical informationretrieved 2026-09-04, 2026-09-05, 2026-09-07

Sections: Physical Characteristics compared - the table giving a maximum density of 2.15 for the new MULTIGRADE RC DELUXE and 2.05 for MULTIGRADE IV RC DELUXE on the same 190 gsm resin-coated base, with the statement that the higher maximum density gives more depth to the prints and a slightly extended tonal range; Exposure - the statement that the new paper is approximately one stop faster and no longer has a large step change in exposure between grade 3.5 and grade 4; Contrast Control - the statement that the new paper has a smoother characteristic curve with no steps and a more consistent contrast response through the tonal range, with low to mid grades offset up to one grade harder; Development - the note that the induction time is slower so images take longer to appear while overall development times are unchanged; and the ISO Range (R) and ISO Speed (P) tables of the two papers side by side; Physical Characteristics compared - the table giving a maximum density of 2.15 for the current MULTIGRADE RC DELUXE and 2.05 for the MULTIGRADE IV RC DELUXE it superseded, with the statement that the higher maximum density gives more depth to the prints and a slightly extended tonal range; Physical characteristics compared - the table giving a maximum reflection density of 2.15 for MULTIGRADE RC DELUXE and 2.05 for MULTIGRADE IV RC DELUXE on the same 190 gsm resin-coated base, with the statement that the higher maximum density gives more depth to the prints and a slightly extended tonal range; Physical characteristics compared - the table giving a maximum reflection density of 2.15 for MULTIGRADE RC DELUXE and 2.05 for MULTIGRADE IV RC DELUXE on the same 190 gsm resin-coated base; Physical characteristics compared - the table giving a maximum reflection density of 2.15 for MULTIGRADE RC DELUXE and 2.05 for MULTIGRADE IV RC DELUXE on the same 190 gsm resin-coated base, and the statement that the newer paper's higher maximum density gives more depth and a slightly extended tonal range; EXPOSURE - the statement that the current MULTIGRADE RC DELUXE is approximately 1 stop faster than MGIVRC and no longer has a large step change in exposure between grade 3.5 and grade 4, so that only fine tuning of the exposure is required when switching between grades; Contrast - the statement that in the fifth-generation MULTIGRADE RC DELUXE the low to mid grades are offset up to 1 grade harder than in MULTIGRADE IV RC DELUXE and the large speed difference between grade 3.5 and grade 4 is reduced; and the two ISO range tables printed side by side, reading 160, 130, 110, 90, 70, 60, 50 for the new paper and 180, 160, 130, 110, 90, 60, 40 for the one it superseded; Physical Characteristics compared - the table giving Dmax 2.15 for MULTIGRADE RC DELUXE and 2.05 for MULTIGRADE IV RC DELUXE on the same 190 gsm base, with the statement that the higher maximum density gives more depth to the prints and a slightly extended tonal range; and EXPOSURE, which states that the new paper is approximately 1 stop faster than MGIVRC and no longer has a large step change in exposure between grade 3.5 and grade 4, so that only fine tuning of the exposure is required when switching between grades; Physical characteristics compared — the table giving a maximum reflection density of 2.15 for MULTIGRADE RC DELUXE and 2.05 for MULTIGRADE IV RC DELUXE on the same 190 gsm resin-coated base, with the statement that the newer paper's higher maximum density gives more depth and a slightly extended tonal range; The comparison of the two generations of resin-coated multigrade paper; Physical characteristics compared — a maximum reflection density of 2.15 for MULTIGRADE RC DELUXE and 2.05 for MULTIGRADE IV RC DELUXE, figures published for the dry paper; Physical characteristics compared — a maximum reflection density of 2.15 for MULTIGRADE RC DELUXE and 2.05 for MULTIGRADE IV RC DELUXE on the same 190 gsm resin-coated base

Used by:P13 Paper Sensitometry: Reflection Density, Grades and ISO(R) · P13 Tone Reproduction: From Subject to Print · P16 Experiment: Commissioning the Enlarger · P16 Enlarger Optics: Condenser, Diffusion, Lens, Alignment and Falloff · P16 Break/Fix: The Room That Fogs and the Light That Is Not Even · P18 Experiment: Maximum Black, Base White and Dry-Down · P18 Lab: Mixing and Comparing Print Developers · P19 Contrast Filtration and Split-Grade Printing · P19 Reading the Negative and Making the Work Print · P19 Lab: Test Strips, Base Exposure and the Print's Black Point · P28 Print Faults: Weak Blacks, Mottle, Bronzing and the Rest · Silver gelatin developing-out print on resin-coated base · Dry-down error · Poor maximum black

Contrast Control for ILFORD MULTIGRADE Variable Contrast Papers, technical informationretrieved 2026-09-04, 2026-09-05

Sections: Contrast range: all chloro-bromide emulsions are blue sensitive with a slight sensitivity to green; MULTIGRADE as a mixture of three emulsions carrying different amounts of green sensitising dye; the action of magenta and yellow filters; Contrast range: MULTIGRADE as three blended emulsions carrying different amounts of green sensitising dye, and the action of magenta and yellow filters; How MULTIGRADE papers work — the emulsions and their differing sensitivity to green light, the statement that exposure to blue light gives a high-contrast image and exposure to green light a low-contrast one, and that a magenta filter absorbs green and transmits blue while a yellow filter absorbs blue and transmits green; The two emulsion diagrams, whose horizontal axis is labelled relative log exposure with no absolute scale; Diffuser v condenser enlargers - the statement that condenser enlargers give about an extra grade of contrast compared with a diffuser enlarger, and that the difference depends on the amount of silver left in the negative; Contrast range - the account of MULTIGRADE as an emulsion mixed from three separate blue-sensitive emulsions carrying different amounts of green sensitising dye, all of the same contrast and the same blue speed; the explanation that blue light makes all three react and add, giving a narrow exposure range and high contrast, while green light is answered first by the most heavily dyed part only, giving a much wider exposure range and low contrast; the statement that a magenta filter absorbs green and transmits blue while a yellow filter does the reverse; MULTIGRADE FILTERS - twelve filters numbered 00 to 5 in half steps with the exposure time the same for 00 to 3 and a half and double for 4 to 5; DIFFUSER v CONDENSER ENLARGERS - condenser enlargers giving about an extra grade of contrast, the difference depending on the amount of silver left in the negative and being small for very pale flat negatives and for dye images; DIFFUSER v CONDENSER ENLARGERS - the statement that condenser enlargers give about an extra grade of contrast compared with a diffuser enlarger, that the difference depends on the amount of silver left in the negative, and that there is little change between the enlarger types for very pale flat negatives and for the dye image of an XP2 SUPER negative; Contrast control - MULTIGRADE papers described as a mixture of three blue-sensitive emulsions carrying different amounts of green sensitising dye, all of the same inherent contrast and the same blue speed but with very different green speeds, so that blue exposure gives high contrast and green exposure low contrast; Diffuser v condenser enlargers - the statement that condenser enlargers give about an extra grade of contrast compared with a diffuser enlarger, and that the difference depends on the amount of silver left in the negative; Contrast control - MULTIGRADE described as a mixture of three blue-sensitive emulsions carrying different amounts of green sensitising dye, so that blue exposure gives high contrast and green exposure low contrast; MULTIGRADE FILTERS - that the twelve filters may be used above or below the lens and cut to fit an enlarger filter drawer, that a kit of twelve mounted filters, a mounted safelight filter and a holder exists for below-lens use, and that exposure is unchanged from filter 00 to 3 and a half and doubles for 4 and 5; Contrast control - that all chloro-bromide black-and-white emulsions are blue sensitive with a slight sensitivity to green light and that sensitising dyes are needed to extend them; that MULTIGRADE papers are coated with a mixture of three separate blue-sensitive emulsions carrying different amounts of green sensitising dye, all of the same inherent contrast and the same blue speed but with very different green speeds; that blue exposure therefore gives a narrow exposure range and high contrast while green exposure gives a much wider exposure range and low contrast; MULTIGRADE filters - the exposure time for filters 00 to 3 and a half is the same, and that for filters 4 to 5 is double; and Dual colour filter settings, where dual filtration usually needs longer exposures but less adjustment between contrast steps; Contrast range - the statement that all chloro-bromide black-and-white emulsions are blue sensitive with a slight sensitivity to green light, and that to make an emulsion sensitive to colours in addition to blue, sensitising dyes need to be added; Contrast range - the account of MULTIGRADE papers as coated with an emulsion which is a mixture of three separate emulsions, each a basic blue-sensitive emulsion carrying a different amount of green sensitising dye, all parts having the same contrast and the same speed to blue light and differing only in green speed; the explanation that blue light makes all three react together over a narrow exposure range giving high contrast while green light is answered first by the most heavily dyed part alone, giving a much wider exposure range and low contrast; the statement that a magenta filter absorbs green and transmits blue and a yellow filter the reverse; MULTIGRADE FILTERS - twelve filters 00 to 5 in half steps, exposure the same for 00 to 3.5 and double for 4 to 5; MULTIGRADE 600 equipment - motorised filters giving contrast control in tenth-grade steps over grades 0 to 5; USE OF COLOUR HEADS - the single and dual filter tables for Durst, Kodak, Meopta and Leitz heads with the statement that maximum contrast is slightly lower because colour-head filters are optimised for colour paper, that the tables are a guide only and the actual filtration must be determined by trial, and that yellow and magenta filters are not arranged to equalise exposures; EXPOSING LIGHT SOURCES - cold cathode heads designed for variable contrast papers giving a full range that may not be evenly spaced, the Aristo W45 exposure-factor matrix showing the grade intervals bunched at the hard end, and the statement that cold cathode heads not designed for variable contrast papers and pulsed xenon sources may give a reduced contrast range; DIFFUSER v CONDENSER ENLARGERS - condenser enlargers giving about an extra grade of contrast with most negatives, depending on the amount of silver left in the negative; Contrast range - MULTIGRADE papers are coated with a mixture of three emulsions of the same inherent contrast and the same speed to blue light, each carrying a different amount of green sensitising dye, so that exposure to blue light gives a narrow-latitude high-contrast combined curve and exposure to green light a much wider, lower-contrast one; Contrast range - MULTIGRADE papers coated with a mixture of three separate emulsions, each a blue-sensitive emulsion carrying a different amount of green sensitising dye, all of the same contrast and the same speed to blue light and differing only in green speed, so that blue light makes all three react together over a narrow exposure range and green light is answered first by the most heavily dyed part alone over a much wider one; the statement that a magenta filter absorbs green and transmits blue and a yellow filter the reverse, and that varying the proportion of blue to green light gives any contrast between the two extremes; MULTIGRADE FILTERS - the twelve filters 00 to 5 in half steps with the statement that the exposure time for filters 00 to 3.5 is the same and that for filters 4 to 5 is double; MULTIGRADE 600 equipment - motorised filters giving contrast control in tenth-grade steps over grades 0 to 5; USE OF COLOUR HEADS - the statement that the suggested filtration tables can only be a guide because individual enlargers vary and that the actual filtration for a particular enlarger must be determined by trial, and that the yellow and magenta filters have not been arranged to equalise exposures so new exposure times have to be recalculated when contrast is changed; Contrast range - MULTIGRADE papers coated with a mixture of emulsions differing only in green sensitivity, so that a magenta filter which absorbs green raises contrast and a yellow filter which absorbs blue lowers it; and MULTIGRADE FILTERS, which states that the exposure time for filters 00 to 3.5 is the same and that for filters 4 to 5 is double; DIFFUSER v CONDENSER ENLARGERS - the statement that MULTIGRADE papers suit both, that in practical terms with most negatives condenser enlargers give about an extra grade of contrast compared with a diffuser enlarger, and that the size of the difference depends on the amount of silver left in the negative; Contrast control - that all chloro-bromide black-and-white emulsions are blue sensitive with a slight sensitivity to green light; that MULTIGRADE papers are coated with a mixture of three separate blue-sensitive emulsions carrying different amounts of green sensitising dye, all of the same inherent contrast and the same blue speed but with very different green speeds; and that blue exposure therefore gives a narrow exposure range and high contrast while green exposure gives a much wider exposure range and low contrast

Used by:P4 Spectral Sensitivity and Colour Response · P4 Darkroom Session: The Latent Image Made Visible · P8 Staining and Tanning Developers · P13 Exposure, Density and the Logarithm · P13 Gamma, Contrast Index and Average Gradient · P13 Paper Sensitometry: Reflection Density, Grades and ISO(R) · P13 Tone Reproduction: From Subject to Print · P16 Build: An LED Enlarger Head · P16 Enlarger Optics: Condenser, Diffusion, Lens, Alignment and Falloff · P16 Safelight: Spectra, Distance, Duration and the Fog Limit · P17 F-Stop Timing and the Mathematics of Print Exposure · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · P18 Variable-Contrast Papers: Three Emulsions, One Sheet · P19 Part XIX Overview: Fine Printing · P19 Contrast Filtration and Split-Grade Printing · P19 Lab: Dodging, Burning, Edge Work and Local Contrast · P19 Reading the Negative and Making the Work Print · Newton's rings

Film Development Time / Temperature Compensation Chartretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Film development time and temperature compensation chart; Film development time and temperature compensation chart, 18 to 27 degrees Celsius; The whole chart: development times at 18, 19, 20, 21, 22, 24, 25 and 27 degrees C against each recommended time at 20 degrees C, rounded to the nearest 15 seconds; the worked example of 8 minutes at 20 degrees C becoming 5 minutes 30 seconds at 24; the statement that it is a useful guide for all film and developer combinations; and the warning that times below 5 minutes are not recommended because of the risk of uneven development; Film development time / temperature compensation chart, April 2002: the columns for 18, 19, 20, 21, 22, 24, 25 and 27 degrees C; the worked example that 8 minutes at 20 degrees C becomes 5 minutes 30 seconds at 24 degrees C; the note that times are rounded to the nearest 15 seconds; and the instruction that development times below 5 minutes are not recommended because of the risk of uneven development; The whole chart, and the statement that it is a useful guide for all film and developer combinations, with the warning that times below 5 minutes are not recommended; The 8-minute row of the time-temperature table, giving 9:45, 8:45, 8:00, 7:15, 6:30, 5:30, 5:00 and 4:15 at 18, 19, 20, 21, 22, 24, 25 and 27 degrees C, and the warning that times below 5 minutes are not recommended because of the risk of uneven development; The single-sheet lookup chart offered as a guide for all film and developer combinations, giving the development time at 18 to 27 degrees C corresponding to each recommended time at 20 degrees C; The whole chart - a guide for adjusting development times to processing temperatures other than 20 degrees C, useful for all film and developer combinations, with the worked example that a recommended 8 minutes at 20 degrees C becomes 5 minutes 30 seconds at 24 degrees C, times rounded to the nearest 15 seconds, and the warning that development times below 5 minutes are not recommended because of the risk of uneven development; The whole sheet, whose title and opening paragraph state that it is a film development time and temperature compensation chart and a useful guide for all film and development combinations, its worked example that 8 min at 20 C becomes 5 min 30 s at 24 C, and its warning in capitals that development times below 5 min are not recommended because of the risk of uneven development; The tabulated 8-minute row, which reads 9:45, 8:45, 8:00, 7:15, 6:30, 5:30, 5:00 and 4:15 at 18, 19, 20, 21, 22, 24, 25 and 27 degrees C, from which the course takes the figure that 1 degree C near 20 is worth about 9 per cent of development time; and the warning that times below 5 minutes are not recommended because of the risk of uneven development; The tabulated 8-minute row, which reads 9:45, 8:45, 8:00, 7:15, 6:30, 5:30, 5:00 and 4:15 at 18, 19, 20, 21, 22, 24, 25 and 27 degrees C, from which the course takes the figure of about 9 per cent of development time per degree near 20 degrees C; The tabulated 8-minute row, which reads 9:45, 8:45, 8:00, 7:15, 6:30, 5:30, 5:00 and 4:15 at 18, 19, 20, 21, 22, 24, 25 and 27 degrees C; the statement that the chart is a useful guide for all film and development combinations; the rounding of every entry to the nearest 15 seconds; and the warning that development times below 5 minutes are not recommended because of the risk of uneven development; The printed warning that development times below 5 minutes are not recommended due to the risk of uneven development; and the tabulated 8-minute row, reading 9:45, 8:45, 8:00, 7:15, 6:30, 5:30, 5:00 and 4:15 at 18, 19, 20, 21, 22, 24, 25 and 27 degrees C; Film development time / temperature compensation chart: the worked example that 8 minutes at 20 degrees C becomes 5 minutes 30 seconds at 24 degrees C, and the instruction that development times below 5 minutes are not recommended because of the risk of uneven development; The published time-temperature compensation chart, from which a 1 degree Celsius error is worth about 9 per cent of development time; The tabulated 8-minute row, reading 9:45, 8:45, 8:00, 7:15, 6:30, 5:30, 5:00 and 4:15 at 18, 19, 20, 21, 22, 24, 25 and 27 degrees C, from which the course takes about 9 per cent of development time per degree C near 20 degrees C; The tabulated rows, from which the course takes the figure of about 9 per cent of development time per degree C near 20 degrees C, and the printed warning that development times below 5 minutes are not recommended due to the risk of uneven development

Used by:P2 Lab: Commissioning Your Laboratory · P2 Measuring Mass, Volume, Temperature and Density, and Knowing How Wrong You Are · P3 Rates, Temperature and Catalysts · P6 Lab: Processing Your First Film · P8 Development Kinetics: Time, Temperature, Agitation and Exhaustion · P9 Experimental Design for the Darkroom · P14 Experiment: Process Control with Control Strips · P15 Assignment: Characterising a Film and Developer with Your Own Instruments · P19 Developing the Print Consistently and Running a Printing Session · P27 Part XXVII Overview: From Observation to Measurement · P27 Designing an Experiment That Yields a Number · P27 Experiment: The Development Time and Temperature Series · P28 Reading the Negative as Evidence: Thin, Dense, Flat and Contrasty · P28 Uneven Development, Bromide Drag and Surge Marks · Checking the balance and verifying the thermometer · Control strip processing and charting · Processing a film · Control chart: temperature error · Dilution ratio misread as a fraction · Excessive contrast · Low contrast index · Uneven print development

Film Reciprocity Failure Compensation, technical information (version 2)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: How to allow for low intensity reciprocity failure — the relation Tc = Tm^P, the worked HP5 Plus example of 10 seconds becoming 20.4 seconds at P = 1.31, the statement that exposures of one second or less need no compensation, the factor table for eleven films, and the note that contrast is increased with long exposures and that pulling the development may be required; The compensation tables and the statement of when reciprocity law failure begins to matter for ILFORD films, cited here for the claim that at very long durations the correction becomes the larger part of the exposure rather than a trim on it; How to allow for low intensity reciprocity failure — the relation Tc = Tm^P, the statement that exposures of one second or less need no compensation, and the note that contrast is increased with long exposures and that pulling the development may be required; Low Intensity Reciprocity Failure: the cause given, the equation Tc = Tm to the power P, the worked HP5 Plus example and the note that exposures of one second or less need no compensation; How to allow for low intensity reciprocity failure: the relation Tc = Tm^P, the worked HP5 Plus example of 10 seconds becoming 20.4, the statement that exposures of one second or less need no compensation, the factor table for eleven films, and the note that contrast is increased with long exposures and that pulling the development may be required; How to allow for low intensity reciprocity failure: the relation Tc = Tm^P; the published exponents, including 1.26 for FP4 PLUS and 1.31 for HP5 PLUS; the worked HP5 Plus example of a metered 10 seconds becoming 20.4; the statement that exposures of one second or less need no compensation; and the note that contrast is increased with long exposures so that pulling the development may be required; How to allow for low intensity reciprocity failure: Tc = Tm^P, with P = 1.26 for FP4 Plus and 1.31 for HP5 Plus; the statement that exposures of one second or less will not require any compensation; the note that contrast is increased with long exposures and that pulling the development may be required; How to allow for low intensity reciprocity failure: the relation Tc = Tm^P, the table of P per film including 1.26 for FP4 Plus and 1.31 for HP5 Plus, the statement that exposures of one second or less will not require any compensation, the caution that for very long exposures at very low light levels other variables such as the accuracy of the light measurement come into play so that some trial and error may be required, and the note that contrast is increased with long exposures; The relation Tc = Tm^P and the table of P per film; the statement that the sheet covers films, no paper appearing on it; the caution that some trial and error may be required at very long exposures; How to allow for low intensity reciprocity failure: the relation Tc = Tm^P, the exponent 1.31 for HP5 Plus, and the statement that exposures of one second or less will not require any compensation; How to allow for low intensity reciprocity failure; the note that contrast is increased with long exposures and that pulling the development may be required; The statement that exposures of one second or less need no compensation, the per-film exponents, and the note that contrast may rise on long exposures; The relation that corrected time equals metered time raised to the power P, the exponent 1.26 for FP4 Plus and 1.25 for ORTHO Plus, the statement that exposures of one second or less need no compensation, and the note that contrast may rise on long exposures; The whole sheet - low intensity reciprocity failure described as lower density for the same total exposure given over a longer time, the statement that exposure times of one second or less will not require any compensation, the equation Tc equals Tm to the power p with the worked example of 10 seconds becoming 20.4 for HP5 Plus, the factor table giving SFX 1.43, Pan F+ 1.33, D100 1.26, D400 1.41, D3200 1.33, FP4+ 1.26, HP5+ 1.31, XP2 1.31, Ortho+ 1.25, K100 1.26 and K400 1.30, and the note that contrast is increased with long exposures so that pulling development may be required; The statement that exposure times of one second or less will not require any compensation; the relation that corrected time equals metered time raised to the power P, with 1.26 for FP4 Plus; and the note that contrast is increased with long exposures so that pulling development may be required; The note that contrast is increased with long exposures so that pulling development may be required, cited here as the manufacturer statement that a change of exposure conditions can change the slope the development has to deliver; How to allow for low intensity reciprocity failure - exposure times of one second or less will not require any compensation, and the corrected time is the metered time raised to a film-specific power above that; How to allow for low intensity reciprocity failure - corrected time equals metered time raised to the power P, with 1.26 for FP4 Plus and 1.31 for HP5 Plus; and the statement that exposure times of one second or less will not require any compensation; How to allow for low intensity reciprocity failure - the mechanism given as reduced efficiency in forming stable development centres at low light levels; the correction as corrected time equals metered time raised to the power P; the table of factors, FP4 Plus 1.26 and HP5 Plus 1.31; the statement that exposure times of one second or less will not require any compensation; the worked HP5 Plus example of 10 s becoming 20.4 s; and the note that contrast may rise on long exposures; Low intensity reciprocity failure described as a reduced efficiency in forming stable development centres at lower light levels; the correction given as corrected time equals metered time raised to the power P, with a table of P per film; and the statement that exposure times of one second or less need no compensation. A film document throughout, with no paper figure anywhere in it; How to allow for low intensity reciprocity failure during long exposures with ILFORD black and white films - the correction is published per camera film as an exponent in Tc = Tm to the power P, and exposure times of one second or less need no compensation; The correction given as an exponent per film, with the statement that exposure times of one second or less need no compensation. A film document, with no paper figure anywhere in it; The statement that for very long exposures at very low light levels other variables come into play, such as the accuracy of the light measurement, so that some trial and error may be required; and that contrast is increased with long exposures, for which pulling the development may be required; How to allow for low intensity reciprocity failure - the relation Tc = Tm^P, the statement that exposures of one second or less need no compensation, the factor table for eleven films, and the note that contrast is increased with long exposures and that pulling the development may be required; How to allow for low intensity reciprocity failure - the correction applied to the total metered time; How to allow for low intensity reciprocity failure - the relation Tc = Tm^P and the statement that exposures of one second or less need no compensation; How to allow for low intensity reciprocity failure - the relation Tc = Tm^P applied to the metered time, the exponent 1.26 for FP4 PLUS, and the note that contrast is increased with long exposures so that pulling the development may be required; How to allow for low intensity reciprocity failure - the relation Tc = Tm^P, the published exponents including 1.26 for FP4 PLUS and 1.31 for HP5 PLUS, and the statement that exposures of one second or less need no compensation

Used by:P29 Capstone Stage 3: Exposing, Processing and Measuring · P29 The Assignment Path: Fourteen Pictures That Build One Photographer · P29 The Capstone Chemistry Report: From Photon Capture to Finished Print · P4 Reciprocity Failure and the Life of the Latent Image · P6 Pinhole Exposure and Reciprocity Correction · P6 Break/Fix: Unexpectedly Soft Images and Wrong Reciprocity Corrections · P7 Assignment: Landscape, Sky, Foreground and Filters · P7 Assignment: Night, the Very Long Exposure and Solargraphy · P7 Pinhole Portfolio Review and the Exposure Record as Data · P7 Assignment: Portrait, Environmental Portrait and Self-Portrait · P7 Assignment: Time in the Frame, Moving Water, Clouds, People and Traffic · P9 Experimental Design for the Darkroom · P9 Lab: Preparing Standard Test Negatives · P13 Film Speed and Exposure Index · P13 Lab: A Step-Wedge Exposure Series · P13 Tone Reproduction: From Subject to Print · P14 Part XIV Overview: Build a Sensitometer · P14 Experiment: Calibrating the Sensitometer · P14 Sensitometer Design Principles · P17 Experiment: Calibrating the Timer · P17 F-Stop Timing and the Mathematics of Print Exposure · P17 Break/Fix: The Timer That Lies · Night exposure session · Recording a daylight exposure · Bellows factor omitted · Empty shadows · Dense negative from double correction · Thin negative from wrong reciprocity data

FP4 Plus Technical Informationretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Choosing the best ILFORD developer for the job: the Maximum film speed row; The speed rating of ISO 125/22 measured in ID-11; Choosing the best ILFORD developer for the job, the Finest grain row; the development-time table, PERCEPTOL rows; the Manual processing, accidental exposure only table, whose PERCEPTOL row gives 8 and a half minutes at EI 25/15 and below; Developer recommendations: the maximum sharpness and fine grain columns; Storage, Exposed film: process as soon as practical and store exposed films in cool, dry conditions; Spectral sensitivity given as a wedge spectrogram to tungsten light at 2850 K; the note on through-the-lens metering with deep red and orange filters; Speed rating ISO 125/22 degrees; Development times, 35mm and Roll Film, ID-11 stock 8.5 minutes at EI 125 and 20 degrees C; the note that times for manual spiral and deep tanks assume intermittent agitation and that continuous agitation as in a dish or tray should reduce them by up to 15 per cent, and that a pre-rinse is not recommended; Safelight recommendations, handle in total darkness; Agitation, four inversions in the first 10 seconds then four again in the first 10 seconds of each further minute, and continuous agitation by rocking the dish for sheet film; Stop, fix, wash and rinse, with the instruction that all solutions be within 5 degrees C of the developer; Wash 5 to 10 minutes; Rinse with ILFOTOL at 1+200; Drying at 30 to 40 degrees C in a cabinet or at room temperature in a clean dust-free area; the statement that sheet film is coated on 0.180 mm polyester and that the emulsion faces the user when the sheet is held in the position shown; Making long exposures: no adjustment needed between half a second and one ten-thousandth, and the graph based on the formula Ta = Tm^1.26 for longer exposures; Speed rating ISO 125/22 degrees; Speed rating ISO 125/22 degrees; Filter factors, including the warning that automatic exposure cameras can under-expose by as much as one and a half stops with deep red and orange filters; Making long exposures, the relation Ta = Tm^1.26; Recommended developers table and the development-time table across ID-11 stock, 1+1 and 1+3; Development times — Kodak D-76 at stock for FP4 Plus at EI 50, 125 and 200, spiral tank at 20 degrees C; the agitation basis and the 15 per cent reduction for continuous agitation; Recommended developers table; the development-time table in which PERCEPTOL is listed at EI 50/18 and 125/22 and ID-11 at 50, 125 and 200; Development times, 35 mm and roll film, spiral tank at 20 degrees C with intermittent agitation — Kodak D-76 at stock 8 minutes and at 1+1 11 minutes at EI 125; Development times, 35 mm and roll film, spiral tank at 20 degrees C — Kodak D-76 at stock 8 minutes and at 1+1 11 minutes for a meter setting of EI 125; Development times, 35 mm and roll film, spiral tank at 20 degrees C — Kodak D-76 at stock 8 minutes, 1+1 11 minutes and 1+3 16 minutes at EI 125; the recommended-developer table; Development times, 35 mm and roll film, spiral tank at 20 degrees C with intermittent agitation — Kodak D-76 at stock 8 minutes and at 1+1 11 minutes for a meter setting of EI 125; Development times, 35 mm and roll film, spiral tank at 20 degrees C with intermittent agitation — Kodak D-76 at stock 6, 8 and 9 minutes and at 1+1 9, 11 and 15 minutes for meter settings EI 50, 125 and 200; the instruction to reduce spiral-tank times by up to 15 per cent where continuous agitation is used; and the statement that a pre-rinse is not recommended because it can lead to uneven processing; Development times, 35 mm and roll film, spiral tank at 20 degrees C with intermittent agitation — Kodak D-76 at stock 8 minutes, at 1+1 11 minutes and at 1+3 16 minutes for a meter setting of EI 125; the instruction to reduce spiral-tank times by up to 15 per cent where continuous agitation is used; the recommended-developer table giving PERCEPTOL stock for finest grain and ID-11 at 1+3 for maximum sharpness; Exposure rating - a speed rating of ISO 125/22 to daylight, with the statement that the ISO speed rating was measured using ILFORD ID-11 developer at 20 degrees C with intermittent agitation in a spiral tank, and that the recommended EI range of 50/18 to 200/24 is a practical evaluation rather than foot speed; Development times, 35 mm and roll film, spiral tank at 20 degrees C with intermittent agitation - Kodak D-76 at stock 6, 8 and 9 minutes and at 1+1 9, 11 and 15 minutes for meter settings EI 50, 125 and 200; the spectral sensitivity given as a wedge spectrogram to tungsten light at 2850 K; and the storage instruction to process exposed film as soon as practical; Development times, 35 mm and roll film, spiral tank at 20 degrees C with intermittent agitation - Kodak D-76 at 1+1 for 11 minutes at EI 125; the storage instruction to process exposed film as soon as practical; and the spectral sensitivity given as a wedge spectrogram to tungsten light at 2850 K; Development times, 35 mm and roll film, spiral tank at 20 degrees C with intermittent agitation - Kodak D-76 at 1+1 for 11 minutes at EI 125; and the storage instruction to process exposed film as soon as practical; Development times, 35 mm and roll film, spiral tank at 20 degrees C with intermittent agitation - Kodak D-76 at 1+1 for 11 minutes at a meter setting of EI 125; and the storage instruction to process exposed film as soon as practical; Film base - 35 mm coated on 0.125 mm acetate base, roll film on 0.110 mm clear acetate base with an anti-halation backing, sheet film on 0.180 mm polyester with an anti-halation backing. Cited for the fact that the base is specified by material, thickness and treatment and that no density value is given for it; Development times, 35 mm and roll film, spiral tank at 20 degrees C - ID-11 at stock 8.5 minutes, 1+1 11 minutes and 1+3 20 minutes at the middle meter setting of EI 125; Kodak D-76 at stock 8 minutes, 1+1 11 minutes and 1+3 16 minutes at the same setting; the recommended-developer table and the base descriptions by material and thickness; Film base - FP4 Plus roll film coated on 0.110 mm / 4-mil clear acetate and sheet film on 0.180 mm / 7-mil polyester, both with an anti-halation backing which clears during development; and the statement that the emulsion faces the user when sheet film is held in the position shown; Development times - Kodak D-76 at stock 6, 8 and 9 minutes, at 1+1 9, 11 and 15 and at 1+3 14, 16 and 20 minutes for meter settings EI 50, 125 and 200 in a spiral tank at 20 degrees C, and Rodinal at 1+25 9 minutes and at 1+50 15 minutes at EI 125; the statement that the times produce negatives of average contrast suitable for printing in all enlargers and are intended as a guide that may be altered if a different result is needed; the instruction that where continuous agitation is used for manual processing the times are reduced by up to 15 per cent, and that a pre-rinse is not recommended because it can lead to uneven processing; the Agitation section, which recommends intermittent agitation for spiral and deep tanks and specifies inverting the tank four times during the first 10 seconds and four times again during the first 10 seconds of each further minute, with continuous agitation recommended for sheet film in dishes; the instruction to keep all process solutions within 5 degrees C of the developer; the spiral-tank wash of five, ten and twenty inversions in three changes of water; ILFOTOL at 5 mL per litre with the note that too little or too much wetting agent can lead to uneven drying; and the instruction to handle the film in total darkness; Storage and handling - the instruction to process exposed film as soon as practical; Development times, 35 mm and roll film, spiral tank at 20 degrees C with intermittent agitation - Kodak D-76 at stock 6, 8 and 9 minutes at meter settings EI 50, 125 and 200, and ID-11 at stock 6.5, 8.5 and 10; the statement that the times produce negatives of average contrast suitable for printing in all enlargers and are intended as a guide; the agitation scheme of four inversions during the first 10 seconds and four more during the first 10 seconds of each further minute; and the instruction to keep all process solutions within 5 degrees C of the developer; Storage and handling - the instruction that once exposed, FP4 Plus is processed as soon as practical; the base description, 35 mm film coated on 0.125 mm acetate and sheet film on 0.180 mm polyester, which decides which of the conservation guidance rows applies to a 35 mm archive; and the development-time table for Kodak D-76, spiral tank at 20 degrees C with intermittent agitation, giving 8 minutes at stock and 11 minutes at 1+1 at EI 125; Exposure rating - the ISO speed rating of 125/22 to daylight, with the statement that it was measured using ILFORD ID-11 developer at 20 degrees C with intermittent agitation in a spiral tank, and that the recommended EI range is a practical evaluation of film speed rather than foot speed; and Development times - the agitation scheme of four inversions during the first 10 seconds and four more during the first 10 seconds of each further minute, with the instruction to reduce the times by up to 15 per cent where continuous agitation is used; Development times, 35 mm and roll film, spiral tank at 20 degrees C with intermittent agitation - Kodak D-76 at stock 6, 8 and 9 minutes at EI 50, 125 and 200, ID-11 at stock 6.5, 8.5 and 10, and Rodinal at 1+25 giving 9 minutes at EI 125 and at 1+50 giving 15; the statement that the times produce negatives of average contrast suitable for printing in all enlargers and are a guide that may be altered; the note that times for other manufacturers' developers are included for convenience and are only a general guide; the agitation scheme of four inversions during the first 10 seconds and four more during the first 10 seconds of each further minute; the ISO speed rating of 125/22 to daylight measured in ILFORD ID-11 at 20 degrees C with intermittent agitation in a spiral tank; and the instruction to keep all process solutions within 5 degrees C of the developer; Development times, 35 mm and roll film, spiral tank at 20 degrees C with intermittent agitation - Kodak D-76 at stock 6, 8 and 9 minutes and at 1+1 9, 11 and 15 minutes at meter settings EI 50, 125 and 200, and ID-11 at stock 6.5, 8.5 and 10 and at 1+1 8, 11 and 15; the statement that the table produces negatives of average contrast suitable for printing in all enlargers and is intended as a guide that may be altered if a different result is needed; the instruction to reduce spiral-tank times by up to 15 per cent where continuous agitation is used and that a pre-rinse is not recommended because it can lead to uneven processing; the note that development times may need adjusting to suit individual processing systems and working practices; the agitation scheme, four inversions during the first 10 seconds and four more during the first 10 seconds of each further minute; the statement that the ISO 125/22 speed was measured in ILFORD ID-11 at 20 degrees C with intermittent agitation in a spiral tank; the worked temperature example that 4 minutes at 20 degrees C becomes 3 minutes at 23 and 6 minutes at 16; the instruction to keep all process solutions within 5 degrees C of the developer; and the instruction to handle the film in total darkness; Storage — for immediate use store the film in a cool (10-20 degrees C / 50-68 degrees F) dry place in its original packaging; it may be stored in a fridge or freezer but with plenty of time allowed to acclimatise before use; once exposed, process as soon as practical, and exposed films should always be stored in cool dry conditions; and store processed negatives in a cool dry place in the dark; The storage instruction to process exposed film as soon as practical; Development times, 35mm and Roll Film; the note that tabulated times assume intermittent agitation and that continuous agitation should reduce them by up to 15 per cent, and that a pre-rinse is not recommended; Safelight recommendations, handle in total darkness; Drying at 30 to 40 degrees C in a cabinet or at room temperature in a clean dust-free area; Safelight recommendations - handle in total darkness; and the statement that sheet film is coated on 0.180 mm polyester and that the emulsion faces the user when the sheet is held in the position shown; Development times at 20 degrees C with intermittent agitation; and the storage instruction to process exposed film as soon as practical; Storage — for immediate use store FP4 Plus in a cool (10-20 degrees C / 50-68 degrees F) dry place in its original packaging; it may be stored in a fridge or freezer but with plenty of time allowed for the film to acclimatise before use; once exposed, process as soon as practical, and exposed films should always be stored in cool dry conditions; Published characteristic curves and the development times that generate them; Storage — for immediate use store the film in a cool (10-20 degrees C / 50-68 degrees F) dry place in its original packaging, and store processed negatives in a cool dry place in the dark; Film base - FP4 Plus 35 mm film coated on 0.125 mm / 5-mil acetate base; roll film on 0.110 mm / 4-mil clear acetate base with an anti-halation backing which clears during development; sheet film on 0.180 mm / 7-mil polyester base, also with an anti-halation backing, and the note that the emulsion faces the user when the sheet is held in the position shown; Film base - FP4 Plus roll film coated on 0.110 mm / 4-mil clear acetate and sheet film on 0.180 mm / 7-mil polyester, both with an anti-halation backing which clears during development; Making long exposures - the graph based on the formula Ta = Tm^1.26 for exposures longer than half a second

Used by:ILFORD MICROPHEN developer · ILFORD PERCEPTOL developer · P4 Grain, Speed and Resolution · P4 Reciprocity Failure and the Life of the Latent Image · P4 Spectral Sensitivity and Colour Response · P6 Pinhole Exposure and Reciprocity Correction · P6 Lab: Processing Your First Film · P6 Break/Fix: Unexpectedly Soft Images and Wrong Reciprocity Corrections · P7 Assignment: Landscape, Sky, Foreground and Filters · P8 Acutance, Adjacency Effects and Compensating Development · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P8 Solvent Action, Physical Development and Grain · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Break/Fix: The Developer That Went Wrong · P9 Assignment: The Developer Laboratory Report · P9 Experiment: Comparing Developing Agents · P9 Lab: Preparing Standard Test Negatives · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P13 Film Speed and Exposure Index · P13 Lab: A Step-Wedge Exposure Series · P14 Experiment: Calibrating the Sensitometer · P14 Experiment: Process Control with Control Strips · P14 Build: The Enclosure and Exposure Stage · P15 Break-Fix: Diagnosing a Misbehaving Densitometer · P15 Assignment: Characterising a Film and Developer with Your Own Instruments · P16 Build: The Contact Printing Frame and Its Light Source · P27 Experiment: Agitation, Stand and Semi-Stand Development · P27 Designing an Experiment That Yields a Number · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Experiment: Four Curve Families, Measured · P27 Push and Pull Processing: What Extended Development Can and Cannot Buy · P27 Assignment: The Developer Comparison, Measured and Printed · P27 Experiment: The Development Time and Temperature Series · P28 Fog and Where It Comes From · Control strip processing and charting · Processing a film · Loading paper and sheet film into a pinhole back · Sensitometer exposure session · Age fog · Blocked shoulder · Heat fog · Negative popping · Newton's rings · Dense negative from double correction · Thin negative from wrong reciprocity data · Uneven contact print from pressure, glass or source geometry

General health and safety adviceretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Waste disposal for photographic products, domestic users; Waste disposal for photographic products — domestic users; Waste disposal for photographic products, domestic users; pregnant and breastfeeding women; Waste disposal for photographic products — domestic users, the Household Waste and Recycling Centre chemical cupboard and the instruction that chemicals be bottled separately and appropriately labelled; business users, the instruction that different waste chemicals should not be mixed but kept in separate, appropriately labelled containers; Waste disposal for photographic products — domestic users, the Household Waste and Recycling Centre chemical cupboard and the instruction that chemicals should be bottled separately and appropriately labelled; business users, the instruction that different waste chemicals should not be mixed but kept in separate, appropriately labelled containers; Waste disposal for photographic products — domestic users, the Household Waste and Recycling Centre chemical cupboard, the instruction that chemicals should be bottled separately and appropriately labelled, and the note that a few authorities collect on request; business users, the instruction that different waste chemicals should not be mixed but kept in separate, appropriately labelled containers; Waste disposal for photographic products - domestic users, and business and trade users; Waste disposal for photographic products — domestic users, and business and trade users; Waste disposal for photographic products — domestic users and business users; Waste disposal for photographic products - domestic users; Waste disposal for photographic products — domestic users and the instruction that chemicals be bottled separately and appropriately labelled; business users and the instruction that different waste chemicals should not be mixed; General health and safety advice; waste disposal for photographic products; Safe working practices; waste disposal for photographic products; Waste disposal for photographic products: domestic users; business and trade users; Safe working practices; Safety data sheets for photochemistry as sold; general health and safety advice; Safe working practices, including the use of tongs and gloves; Waste disposal for photographic products, domestic users in the UK; Safe working practices, including gloves, eye protection and an apron for handling and mixing all chemicals; Waste disposal for photographic products, domestic users in the UK; Waste disposal for photographic products — domestic users in the United Kingdom; Waste disposal for photographic products — domestic users in the United Kingdom, used chemistry to a household waste and recycling centre and small quantities of scrap film and paper as normal household waste; Waste disposal for photographic products — domestic users in the United Kingdom, used chemistry to a household waste and recycling centre; Waste disposal for photographic products — the advice to domestic users in the United Kingdom to bottle wastes separately, label them and take used chemistry to a household waste and recycling centre; Waste disposal for photographic products — the advice to domestic users in the United Kingdom to bottle wastes separately, label them and take used chemistry to a household waste and recycling centre, and to treat small quantities of scrap film and paper as normal household waste; Waste disposal for photographic products — the advice to domestic users in the United Kingdom to take used chemistry to a household waste and recycling centre; Waste disposal for photographic products - the direction that United Kingdom domestic users take used chemistry to a household waste and recycling centre; Waste disposal for photographic products - the advice to domestic users in the United Kingdom; Waste disposal for photographic products - the advice to domestic users in the United Kingdom to take used chemistry to a household waste and recycling centre rather than to the drain; Waste disposal for photographic products - the advice to domestic users in the United Kingdom to take spent photographic chemistry to a household waste and recycling centre rather than to a drain; Waste disposal for photographic products — the advice to domestic users in the United Kingdom to take spent photographic chemistry to a household waste and recycling centre rather than to a drain; General health and safety advice — disposal of used chemistry and of scrap film and paper for domestic users in the United Kingdom; General health and safety advice, on gloves and eye protection whenever chemicals are handled or mixed; Waste disposal for photographic products, domestic users: bottling wastes separately, labelling them and taking them to a household waste and recycling centre; recovery of silver from used fixer; Safe working practices, including an apron or overall and suitable gloves with eye or face protection whenever chemicals are handled or mixed; Safety data sheets for photochemistry as sold, and general health and safety advice; Safe working practices: not using utensils meant for preparing food to make up and store photochemicals, keeping foodstuffs away from where photographic chemicals are prepared and used, keeping chemicals out of reach of children and animals, and not storing chemicals in soft-drink bottles; Waste disposal for photographic products: domestic users; recovery of silver from used fixer, film and paper; Safe working practices; storing chemicals out of reach of children and animals; Safe working practices, including keeping processing chemicals out of reach of children and animals, and not storing chemicals in soft-drink bottles; Waste disposal for photographic products, domestic users: bottling wastes separately, labelling them and taking them to a household waste and recycling centre

Used by:6-Nitrobenzimidazole · Acetic acid (glacial) · Albumen · Amidol · Ammonium bromide · Ammonium chloride · Ammonium citrate (dibasic) · Ammonium citrate (tribasic) · Ammonia solution (ammonium hydroxide) · Ammonium iron(III) citrate · Ammonium iron(III) oxalate · Ammonium persulfate · Ammonium thiocyanate · Ammonium thiosulfate · Arrowroot · Ascorbic acid · Barium sulfate · Benzotriazole · Borax (sodium tetraborate decahydrate) · Boric acid · Calcium carbonate · Calcium nitrate tetrahydrate · Chloroauric acid · Chlorohydroquinone · Chrome alum · Citric acid (anhydrous) · Copper(II) sulfate · Dimezone S · EDTA disodium salt (anhydrous) · EDTA disodium salt dihydrate · Erythrosin · Ethanol · Ferric oxalate · Iron(II) oxalate · Gallic acid · Gelatin · Glycerol · Glycin · Gold(III) chloride · Gum arabic · Hydrochloric acid · Hydrogen peroxide · Hydroquinone · Iron(II) sulfate, anhydrous · Iron(II) sulfate heptahydrate · Iron(III) chloride, anhydrous · Iron(III) chloride hexahydrate · Iron(III) nitrate nonahydrate · Isopropyl alcohol · Kaolin · Lithium chloride · Metol · Nitric acid · Oxalic acid · p-Aminophenol · Palladium(II) chloride · Phenidone · Potassium alum · Potassium bromide · Potassium carbonate (anhydrous) · Potassium chloride · Potassium citrate · Potassium hydroxide (caustic potash) · Potassium iodide · Potassium metabisulfite · Potassium oxalate, anhydrous · Potassium oxalate monohydrate · Potassium permanganate · Potassium persulfate · Potassium sodium tartrate tetrahydrate · Potassium tetrachloropalladate(II) · Potassium tetrachloroplatinate(II) · Potassium thiocyanate · Prussian blue · Pyrogallol · Silver · Silver bromide · Silver chloride · Silver iodide · Silver nitrate · Silver(I) oxalate · Silver(I) oxide · Silver sulfamate · Silver sulfide · Sodium acetate (anhydrous) · Sodium ascorbate · Sodium bicarbonate · Sodium bisulfite · Sodium carbonate (anhydrous) · Sodium carbonate decahydrate · Sodium carbonate monohydrate · Sodium chloride · Trisodium citrate dihydrate · Sodium hexametaphosphate (Calgon) · Sodium hydroxide (caustic soda) · Sodium metabisulfite · Sodium metaborate (anhydrous) · Sodium metaborate tetrahydrate (Kodalk) · Sodium sulfate · Sodium sulfite · Sodium tetrachloropalladate(II) · Sodium thiocyanate · Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Sulfamic acid · Sulfuric acid · Tannic acid · Tartaric acid · Tetraazaindene · Thiourea · Thymol · Ammonium citrate developer · Borax kallitype developer · HARMAN SELENIUM TONER · ILFORD BROMOPHEN developer · ILFORD HYPAM · ILFORD ILFOSTOP · ILFORD MICROPHEN developer · ILFORD MULTIGRADE developer · ILFORD PERCEPTOL developer · ILFORD PQ UNIVERSAL developer · ILFORD RAPID FIXER · ILFORD WASHAID · EDTA and sodium sulfite clearing sequence · KODAK PROFESSIONAL XTOL Developer · Moersch MT3 Variotoner · Nicol's kallitype · EDTA, citric acid and hydrochloric acid clearing sequence · Rochelle salt kallitype developer · Sodium citrate developer · Sodium citrate kallitype developer · Willis's potassium oxalate developer · P1 Overview: The Three Problems Every Photograph Must Solve · P1 Experiment: The Image That Would Not Stay · P2 Part II Overview: The Photographic Chemistry Laboratory · P2 Waste: Streams, Silver, and the Drain You Must Not Use · P2 Lab: Commissioning Your Laboratory · P2 Laying Out the Laboratory: Wet Areas, Dry Areas and Contamination Control · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P2 Silver Nitrate: The Reagent That Sets the Rules · P3 Lab: Measuring pH and Trusting the Number · P4 Experiment: Precipitating the Silver Halides · P4 Darkroom Session: The Latent Image Made Visible · P6 Commissioning the Camera: Light-Tightness, Flare and the First Negatives · P6 Curved Film Plane and Multiple-Pinhole Experiments · P6 Lab: Processing Your First Film · P8 Experiment: Watching a Developer Oxidise · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Break/Fix: The Developer That Went Wrong · P9 Experiment: Comparing Developing Agents · P9 Lab: Preparing Standard Test Negatives · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P11 Experiment: Clearing Time and Fixer Capacity · P11 Break/Fix: The Exhausted Fixer · P11 Lab: Mixing Fixers from Scratch · P12 Assignment: Your Archival Processing Sequence · P12 Silver Recovery and the Responsible Darkroom · P12 Experiment: Small-Scale Metallic Replacement · P12 Lab: Testing for Residual Thiosulfate and Residual Silver · P13 Lab: A Step-Wedge Exposure Series · P18 Experiment: Maximum Black, Base White and Dry-Down · P18 Lab: Mixing and Comparing Print Developers · P18 Break/Fix: The Print That Will Not Go Black · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Lab: Bleaching and Redeveloping a Sepia Print · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Lab: Toning the Prussian Blue Image · The disposal caveat · Glove selection · Routing general chemical waste · Closing the laboratory · Opening the laboratory · Labelling a container · Collecting and segregating waste across a multi-run session · Putting protective equipment on, changing gloves and taking it off · Recording a safety data sheet · Refrigerated emulsion labelling and food separation · Routing silver-bearing waste · The stock check, and retiring a chemical · Storage rotation and shelf separation · The student's project SOP

HARMAN Direct Positive Paper, technical informationretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: The recommendation that a print made for display or requiring optimum life expectancy be protected from oxidising gases, and that prints be toned using HARMAN SELENIUM TONER, which has little effect on the colour of an image but does help to protect it; Processing summary — PQ UNIVERSAL at 1+9 for 1 minute 30 seconds to 3 minutes at 20 degrees C; Processing: process as soon as possible after exposure to minimise any risk of latent image regression; Key features: slow ISO speed between ISO 1 and 3; Section 5, Exposure for pinhole camera applications, method 1: guide times of 1 to 2 minutes in bright summer sunshine and 2 to 3 minutes in bright but not direct sun; Key features: slow ISO speed between ISO 1 and 3; Section 5, Exposure for pinhole camera applications, method 1: the guide times of 1 to 2 minutes in bright summer sunshine, 2 to 3 minutes in bright but not direct sun, 4 to 5 minutes in overcast mixed sun and cloud, 6 to 10 minutes dull or cloudy and 1 hour for a lit interior; The instruction that the paper should be processed as soon as possible after exposure to minimise any risk of latent image regression; Section 5, Exposure for pinhole camera applications, the guide times including about 1 hour for a lit interior; Section 5, Exposure for pinhole camera applications: the guide times of 1 to 2 minutes in bright summer sunshine through to about 1 hour for a lit interior; Section 5, Exposure for pinhole camera applications, method 1: the guide time of about 1 hour for a lit interior; Key features, slow ISO speed between ISO 1 and 3; Key features - a fixed grade high contrast paper on a 255 g/m2 baryta fibre base, of a contrast similar to ILFORD MULTIGRADE grade 3.5 to 4, with a slow ISO speed between 1 and 3, compatible with ortho deep red safelights only; and the note that increasing the exposure reduces density; Key features and Section 5 method 2, the pre-flash technique - the instruction to make a test strip in the same manner as with standard photo paper such as ILFORD MULTIGRADE, and the parenthetical statement that with conventional photo paper one would select the white which is just showing the slightest indication of highlight detail, which is the reverse of the direct-positive case; the instruction that the sheet then receives an overall pre-flash exposure of that exact time; and the alternative method of pre-flashing with a desk lamp where the time is likely to be only 1 or 2 seconds and the correct time has to be found by pre-exposing whole small sheets; Processing - the instruction that paper should be processed as soon as possible after exposure to minimise any risk of latent image regression; Section 5, Exposure for pinhole camera applications, method 1 - guide times of 1 to 2 minutes in bright summer sunshine and 6 to 10 minutes dull or cloudy

Used by:HARMAN SELENIUM TONER · ILFORD PQ UNIVERSAL developer · P4 Reciprocity Failure and the Life of the Latent Image · P4 Darkroom Session: The Latent Image Made Visible · P6 Commissioning the Camera: Light-Tightness, Flare and the First Negatives · P6 Pinhole Exposure and Reciprocity Correction · P7 Assignment: Night, the Very Long Exposure and Solargraphy · P7 Pinhole Portfolio Review and the Exposure Record as Data · P7 Assignment: Still Life and Controlled Light · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · P19 Contrast Filtration and Split-Grade Printing · P27 Designing an Experiment That Yields a Number · Recording a daylight exposure

HARMAN SELENIUM TONER: technical informationretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-08

Sections: Mixing Instructions — 1+3 for normal toning and 1+20 where the primary reason is protection of the image with minimal tone change, at 20 degrees C plus or minus 1 C; the statement that protection of the image at 1+20 will be complete in 2 to 4 minutes; User Instructions, for the three-dish arrangement with plain water either side of the toner and the holding dish about 4 C warmer, and the suggestion that a first-time toner makes two identical prints and keeps one to refer to; the stop and wash instruction of 30 to 40 seconds in the second holding dish, then 2 minutes for RC prints and at least 30 minutes for fibre prints, or the ILFORD optimum permanence wash sequence; Capacity, that as the solution is used and ages the rate of tonal change becomes slower; and Additional Safety Information, that the product is a toxic chemical, that the maker strongly recommends always working in a well-ventilated area preferably with some form of air extraction, and wearing rubber gloves in all use and disposal; User instructions; Mixing instructions; Health and safety information; Additional safety information; Health and safety information; Additional safety information; Mixing instructions; HARMAN SELENIUM TONER technical information, page footer dated June 2010 — the description as a liquid concentrate toner designed for the dish/tray toning of all black and white photographic papers both resin coated and traditional fibre based, at ambient room temperatures nominally 20 degrees C/68 degrees F; the statement that the toner enhances the archival stability and maximum density of prints and that the colour and degree of tonal change vary according to the type of paper, ranging from cool chocolate-brown through purplish brown to little discernable change, with warm tone papers usually producing the most visible effects; the mixing instructions giving 1+3 for normal toning applications and 1+20 where the primary reason is protection of the image with minimal tone change, the instruction always to stir process solutions thoroughly before use, and the working temperature of 20 degrees C/68 degrees F plus or minus 1 degree C/2 degrees F; the preparation instructions giving three dishes with the toner in the centre and plain water approximately 4 degrees C warmer either side, and the guideline that 3 litres of working solution is sufficient for a dish measuring 12 by 16 inches (30.5 by 40.6 cm); the develop, stop and fix paragraph; the user instructions on the holding dish and the reference print; the toning instructions on lifting the print by its top corners, sliding it in quickly and agitating for the whole period by gently rocking the dish, and on not continually observing the print in the toner; the statement that protection of the image at 1+20 will be complete in 2 to 4 minutes; the instruction to agitate for 30 to 40 seconds in the second holding dish to stop the toning action and that the print may be returned for more; the washing instruction of 2 minutes for RC prints and at least 30 minutes for fibre prints in fresh running water above 5 degrees C/41 degrees F, or the ILFORD optimum permanence wash sequence; the Capacity paragraph, that capacity is in practical terms limited by the time it takes for the toning effect to be completed, that the rate of tonal change becomes progressively slower as the solution is used and ages, and that at 1+3 the capacity is at least the equivalent of 25 sheets of 20.3 by 25.4 cm per litre; the Working Solution Life paragraph giving up to 6 months in full tightly capped bottles, 1 month in half tightly capped bottles and up to 7 days in an open tray; the Storage paragraph giving 2 years for full unopened bottles stored at 5 to 20 degrees C (41 to 68 degrees F) and use completely within 6 months once opened, keeping all bottles tightly sealed; and the Health and Safety Information and Additional Safety Information paragraphs; The instruction that when the desired level of toning has been achieved RC prints are washed a further 2 minutes and fibre prints for at least 30 minutes in fresh running water above 5 degrees C, and that alternatively for fibre base prints the ILFORD optimum permanence wash sequence may be used; HARMAN SELENIUM TONER technical information, June 2010 — the two dilutions and their two purposes, the capacity figure of at least 25 sheets of 20.3 by 25.4 cm per litre at 1+3, the working solution life of up to 6 months in full tightly capped bottles, 1 month half full and up to 7 days in an open tray, and the storage figures of 2 years for a full unopened bottle at 5 to 20 °C and complete use within 6 months once opened; Mixing instructions, Toning, Capacity, Working Solution Life and Storage — the two dilutions of 1+3 and 1+20, the working temperature of 20 degrees C plus or minus 1 degree, the capacity of at least 25 sheets of 20.3 by 25.4 cm per litre at 1+3, and the keeping figures of 2 years unopened, 6 months once opened and 6 months, 1 month or 7 days at working strength; User instructions and Mixing instructions — a liquid concentrate diluted 1+3 for normal toning and 1+20 where the primary reason is protection of the image, used at 20 C, with colour ranging from cool chocolate-brown through purplish brown to little discernible change according to paper type; Health and Safety Information, toxic if swallowed, may cause sensitisation by skin contact, do not empty into drains, dispose of this material and its container at a hazardous or special waste collection point; and Additional Safety Information, that the product is a toxic chemical and the maker strongly recommends working in a well-ventilated area, preferably with some form of air extraction system; User instructions - the toner enhances the archival stability and maximum density of prints and the colour and degree of tonal change vary with the paper, ranging from cool chocolate-brown through purplish brown to little discernible change, warm-tone papers usually producing the most visible effects; and the recommendation, for a first experience of toning, to make two identical prints and leave one in a holding dish of water as a reference during toning so that changes in density and colour can be identified; The whole of the two-page technical information sheet dated June 2010 - the description as a liquid concentrate for dish or tray toning of all black and white papers, resin coated and fibre based, at a nominal 20 degrees C plus or minus 1 degree C; the statement that the toner enhances the archival stability and maximum density of prints and that the colour and degree of tonal change vary with the paper, from cool chocolate-brown through purplish brown to little discernable change, warm tone papers usually producing the most visible effects; the mixing instructions giving 1+3 for normal toning applications and 1+20 where the primary reason is protection of the image with minimal tone change; the guideline that 3 litres of working solution is sufficient for a dish measuring 12 by 16 inches; the three-dish arrangement with the toner in the centre and plain water approximately 4 degrees C warmer either side; the instruction to make two identical prints for a first toning session and keep one in the holding dish as a reference; the instruction not to observe the print continually in the toner because it makes the subtle changes harder to see, and to compare it regularly with the reference print instead; the statement that protection of the image at 1+20 will be complete in 2 to 4 minutes; the instruction to agitate for 30 to 40 seconds in the second holding dish to stop the toning action and that the print may be returned to the toner if it needs more; the washing instruction of 2 minutes for RC and at least 30 minutes for fibre prints in fresh running water above 5 degrees C, or the ILFORD optimum permanence wash sequence; the Capacity paragraph, that capacity is in practical terms limited by the time the toning effect takes to complete, that the rate of tonal change becomes progressively slower as the solution is used and ages, and that at 1+3 the capacity is at least the equivalent of 25 sheets of 20.3 by 25.4 cm per litre; the Working Solution Life paragraph, up to 6 months in full tightly capped bottles, 1 month in half-full ones and up to 7 days in an open tray; the Storage paragraph, two years unopened at 5 to 20 degrees C and six months once opened; and the Health and Safety and Additional Safety Information paragraphs, which call the product a toxic chemical, strongly recommend working in a well-ventilated area preferably with some form of air extraction system, require rubber gloves in all use and disposal, ask for gloves, glasses and an apron while preparing and using chemicals, and instruct that it must not be emptied into drains but disposed of with its container at a hazardous or special waste collection point; The whole of the two-page technical information sheet dated June 2010 - the description as a liquid concentrate for dish or tray toning of all black and white papers, resin coated and fibre based, at a nominal 20 degrees C; the statement that the toner enhances the archival stability and maximum density of prints and that the colour and degree of tonal change vary with the paper, from cool chocolate-brown through purplish brown to little discernable change, warm tone papers usually producing the most visible effects; the mixing instructions giving 1+3 for normal toning applications and 1+20 where the primary reason is protection of the image with minimal tone change; the three-dish arrangement with the toner in the centre and plain water approximately 4 degrees C warmer either side; the instruction to make two identical prints for a first toning session and keep one in the holding dish as a reference; the instruction not to observe the print continually in the toner; the statement that protection of the image at 1+20 will be complete in 2 to 4 minutes; the instruction to agitate for 30 to 40 seconds in the second holding dish to stop the toning action and that the print may be returned to the toner if it needs more; the washing instruction of 2 minutes for RC and at least 30 minutes for fibre prints in fresh running water above 5 degrees C, or the ILFORD optimum permanence wash sequence; the Capacity paragraph, that capacity is in practical terms limited by the time the toning effect takes to complete and that the rate of tonal change becomes progressively slower as the solution is used and ages; the Working Solution Life and Storage paragraphs; and the Health and Safety and Additional Safety Information paragraphs, which call the product a toxic chemical, strongly recommend working in a well-ventilated area preferably with some form of air extraction system, require rubber gloves in all use and disposal, ask for gloves, glasses and an apron while preparing and using chemicals, and instruct that it must not be emptied into drains but disposed of with its container at a hazardous or special waste collection point; User Instructions, for the holding dish of water about 4 C warmer than the working solution, the suggestion that a first-time toner makes two identical prints and leaves one in the holding dish to refer to during toning, the instruction not to observe the print continuously in the toner because it makes subtle changes harder to see, and the three-dish arrangement with plain water either side of the toner; Mixing Instructions, for 1+3 for normal toning and 1+20 where the primary reason is protection of the image with minimal tone change, at 20 C plus or minus 1 C, and 3 litres of working solution to fill a 12 by 16 inch dish; the statement that colour and degree of tonal change vary with paper type from cool chocolate-brown through purplish brown to little discernible change, with warm-tone papers usually producing the most visible effects; the statement that protection of the image at 1+20 will be complete in 2 to 4 minutes; the stop and wash instruction of 30 to 40 seconds in the second holding dish, then 2 minutes for RC prints and at least 30 minutes for fibre prints, or the ILFORD optimum permanence wash sequence; Capacity, that as the solution is used and ages the rate of tonal change becomes slower; Health and Safety Information, toxic if swallowed, may cause sensitisation by skin contact, do not empty into drains, dispose of this material and its container at a hazardous or special waste collection point; and Additional Safety Information, that the product is a toxic chemical and the maker strongly recommends always working in a well-ventilated area, preferably with some form of air extraction system, and wearing rubber gloves in all use and disposal; Health and Safety Information and Additional Safety Information - toxic if swallowed, may cause sensitisation by skin contact, do not empty into drains, dispose of this material and its container at a hazardous or special waste collection point, and the maker's own statement that the product is a toxic chemical with the strong recommendation to work in a well-ventilated area, preferably with some form of air extraction system; Mixing Instructions, that the concentrate is diluted 1+3 for normal toning applications and 1+20 where the primary reason is protection of the image with minimal tone change; the statement that the toner enhances the archival stability and maximum density of prints; and the Toning paragraph, that protection of the image at the 1+20 dilution will be complete in 2 to 4 minutes; Dilutions of 1+3 for a tone change and 1+20 where the purpose is protection of the image; completion in two to four minutes; The product described as a toxic chemical; the recommendation to work in a well-ventilated area preferably with some form of air extraction; rubber gloves in all use and disposal; the instruction not to empty into drains but to dispose of material and container at a hazardous or special waste collection point; working-solution life of six months in a full capped bottle against seven days in an open tray; the note that the rate of tonal change slows as a solution ages; Making two identical prints and keeping one in a holding dish of plain water for comparison; the instruction not to watch the print continuously in the toner; toning continuing into the wash, so the print is removed at almost the required tone; the allowance for returning a print for more; Working dilutions and times for selenium toning of fibre and resin-coated papers, and the requirement for thorough washing before toning; Working dilutions and times, and the requirement that prints be thoroughly fixed and washed before toning; Recommended dilutions and toning times for resin-coated and fibre-base papers; Recommended dilutions and times for fibre and resin-coated papers, with the requirement that prints be thoroughly fixed and washed, and the instruction to agitate throughout

Used by:P29 Capstone Stage 5: The Toned Print and the Alternative-Process Print · Selenium · Sodium selenite · HARMAN SELENIUM TONER · ILFORD WASHAID · KODAK Rapid Selenium Toner · Moersch MT1 Selentoner · P20 Part XX Overview: Toning Chemistry · P20 What a Toner Actually Does to a Silver Image · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Assignment: The Toned Print · P20 The Toners We Study and Do Not Use · P20 Toning, Permanence and What the Evidence Actually Supports · Selenium toned silver gelatin print · Handling a selenium toner and its waste · Running a toning session · Mottle revealed only after toning · Round purple spots from air bubbles trapped in the fixer · Toner penetration at the edges of an RC print · Uneven toning

Health and safety FAQs: what ventilation do I need in my darkroom?retrieved 2026-09-04, 2026-09-05

Sections: What ventilation do I need in my darkroom? (quoting CIBSE Guide B, section 2.3.24.4); What ventilation do I need in my darkroom - extract in the room or opening the room up between processes, a light-trapped extract fan for longer sessions, and CIBSE Guide B section 2.3.24.4, which gives photographic darkrooms 6 to 8 air changes per hour and says small darkrooms for occasional use may often be ventilated naturally through a suitable light trap; What ventilation do I need in my darkroom — extract in the room or opening the room up between processes, and a light-trapped extract fan for longer sessions; What ventilation do I need in my darkroom, quoting CIBSE Guide B section 2.3.24.4 at six to eight air changes per hour

Used by:P2 Laying Out the Laboratory: Wet Areas, Dry Areas and Contamination Control · P16 Build: Making a Room Dark and Proving It · Darkroom opening and closing for a printing session · Checking the ventilation before a session

HP5 Plus Technical Informationretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: The opening statement that HP5 Plus can be exposed at meter settings up to EI 3200/36 given extended development in named developers including MICROPHEN; Choosing the best ILFORD developer for the job, the powder column; the development-time table for MICROPHEN stock, 1+1 and 1+3 against ID-11 at the same meter settings; The speed rating of ISO 400/27; Choosing the best ILFORD developer for the job, the Finest grain row; the development-time table, PERCEPTOL rows at stock, 1+1 and 1+3; the Manual processing, accidental exposure only table, whose PERCEPTOL row gives 9, 9 and 11 minutes at EI 50/18, 100/21 and 200/24; Wash: running water for 5 to 10 minutes at a temperature within 5 degrees C of the process temperature, or the fill-and-invert method for spiral tanks; Processing at Different Temperatures: if 6 minutes at 20 degrees C is recommended, the time at 23 degrees C is 4.5 minutes and at 16 degrees C is 9 minutes; Film base and anti-halation backing thicknesses for roll and sheet film; Speed rating ISO 400/27 degrees; Speed rating ISO 400/27 degrees; Filter factors, which give no table and instead refer the reader to the filter manufacturer, with the warning about deep red and orange filters and through-the-lens metering; Speed rating ISO 400/27 degrees; the instruction to process exposed film as soon as is practical; Speed rating ISO 400/27 degrees; Spectral sensitivity, a panchromatic wedge spectrogram to tungsten light at 2850 K; Recommended developers table — the maximum sharpness row naming ILFOSOL 3 at 1+9 and ID-11 at 1+3, against the finest grain row naming PERCEPTOL stock; the development-time table across dilutions; the agitation instruction and the 15 per cent reduction for continuous agitation; Processing at different temperatures — the worked example that 6 minutes at 20 degrees C becomes 4.5 minutes at 23 and 9 minutes at 16; Development times — Kodak D-76 at stock for HP5 Plus at EI 400, 800 and 1600, spiral tank at 20 degrees C; the agitation basis; Recommended developers table — finest grain, maximum sharpness, maximum film speed and economy rows; the development-time table with its meter-setting columns across ID-11, MICROPHEN and PERCEPTOL at stock, 1+1 and 1+3, and for Agfa Rodinal at 1+25 and 1+50 and Kodak D-76 at stock, 1+1 and 1+3; Recommended developers table, including finest grain and maximum sharpness; the development-time table with its meter-setting columns, in which PERCEPTOL stock appears only at EI 250/25 and at 1+1 and 1+3 only at EI 320/26, while ID-11 and MICROPHEN appear at EI 400/27 and above; The note that times for manual spiral and deep tanks assume intermittent agitation and that continuous agitation as in a dish or tray should reduce them by up to 15 per cent; Fixing table — ILFORD RAPID or HYPAM fixers at 1+4, 18 to 24 degrees C, 2 to 5 minutes at 20 degrees C, capacity 24 films of 135-36 per litre unreplenished; Exposure rating - the statement that the recommended exposure index range is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard; Exposure rating - rated ISO 400/27 degrees, with good image quality claimed from EI 400/27 to EI 3200/36 given extended development in named developers, and the statement that the recommended exposure index range is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard; Spectral sensitivity - the wedge spectrogram published to tungsten light at 2850 K; Exposure rating - the statement that the recommended exposure index range is based on a practical evaluation of film speed and is not based on foot speed as the ISO standard is; Development times, 35 mm and roll film, spiral and deep tank at 20 degrees C - ID-11 at stock 7.5 minutes, 1+1 13 minutes and 1+3 20 minutes at a meter setting of EI 400; the statement that the table's times produce negatives of average contrast suitable for printing in all enlargers and are intended as a guide that may be altered if a different result is needed; that the manual times are based on intermittent agitation, that continuous agitation calls for a reduction of up to 15 per cent, that rotary processing without a pre-rinse calls for the same reduction and that a pre-rinse is not recommended because it can lead to uneven processing. Agitation - invert the tank four times during the first 10 seconds, then four times again during the first 10 seconds of each further minute. Stop, fix, wash and rinse - all process solutions kept at the same temperature or at least within 5 degrees C of the developer. Safelight - handle in total darkness; The statement that although rated at ISO 400/27 degrees, HP5 Plus can produce high quality prints when exposed at meter settings up to EI 3200/36 and given extended development in ILFOTEC DD-X, ILFOTEC HC, MICROPHEN or ILFOTEC RT RAPID; Exposure rating - that best results are obtained at EI 400/27 but good image quality will also be obtained from EI 400/27 to EI 3200/36, and that the recommended exposure index range is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard; the choosing table naming ILFOTEC DD-X and MICROPHEN stock for maximum film speed at EI 3200/36; the statement that the times are based on intermittent agitation and that continuous agitation calls for reducing them by up to 15 per cent; the spiral-tank development table at 20 degrees C, whose ILFOTEC DD-X 1+4 row reads 9, 10, 13 and 20 minutes at EI 400, 800, 1600 and 3200, whose MICROPHEN stock row reads 6.5, 8, 11 and 16, whose ID-11 stock row reads 7.5, 10.5 and 14 with no figure at EI 3200, and whose ILFOSOL 3 at 1+9 row reads 5 at EI 200, 6.5 at EI 400 and 13.5 at EI 800; and the separate table headed accidental exposure only, for film inadvertently exposed at settings below EI 250/25, giving PERCEPTOL stock as 9 minutes at both EI 50 and EI 100 and 11 minutes at EI 200, with the note that the quality of negatives processed in this way will not be so high as conventionally processed ones; Development times — the table's 20 degrees C column for ID-11 and D-76, giving 7 and a half minutes in ID-11 stock at EI 400 and 14 minutes at EI 1600; Agitation — four inversions during the first 10 seconds and four again during the first 10 seconds of each further minute; and Exposure rating, best results at EI 400/27 with good image quality also obtained from EI 400 to EI 3200; Making long exposures — no adjustment for reciprocity law failure between one half and one ten-thousandth of a second, and for exposures longer than half a second the relation Ta = Tm to the power 1.31, where Ta is the adjusted time and Tm the metered time; Agitation — four inversions during the first 10 seconds and four again during the first 10 seconds of each further minute; Development times, the table's 20 degrees C column for ID-11 and D-76; Stop, fix, wash and rinse — the recommendation that all process solutions are kept at the same temperature or at least within 5 degrees C (9 degrees F) of the developer temperature; Rinse — ILFOTOL wetting agent at 5 mL per litre of rinse water (1+200), with the statement that the amount may need adjustment depending on local water quality and drying method and that too little or too much wetting agent can lead to uneven drying, and the instruction to remove excess rinse solution before drying; Drying — the instruction to use a clean squeegee or chamois cloth to wipe the film before hanging it, to avoid drying marks, and to dry at 30 to 40 degrees C in a drying cabinet or at room temperature in a clean dust-free area; Agitation — with spiral tanks, invert the tank four times during the first 10 seconds, then invert four times again during the first 10 seconds of each further minute, with continuous agitation recommended in dishes or trays by rocking; Development times — the note that times are based on intermittent agitation, that continuous agitation should reduce them by up to 15 per cent, that rotary processors without a pre-rinse should reduce spiral-tank times by up to 15 per cent, and that a pre-rinse is not recommended as it can lead to uneven processing; and Stop, fix, wash and rinse — all process solutions kept at the same temperature or at least within 5 degrees C of the developer; The published base specifications — 35 mm film coated on 0.125 mm / 5 mil acetate base, roll film on 0.110 mm / 4 mil clear acetate base with an anti-halation backing which clears during development, and sheet film on 0.180 mm / 7 mil polyester base with an anti-halation backing; Stop bath — the recommendation of ILFOSTOP at 1+19 for 10 seconds at 20 degrees C, with the statement that a stop bath immediately stops development and reduces carry over of excess developer into the fixer bath, helping to maintain the activity and prolong the life of the fixer; and Stop, fix, wash and rinse, all process solutions at the same temperature or at least within 5 degrees C of the developer; The published base specifications — 35 mm film on 0.125 mm acetate base, roll film on 0.110 mm acetate base, sheet film on 0.180 mm polyester base; and Handling, the instruction to handle the film in total darkness; Development times — the table's 20 degrees C column, from which the effect of an over-long time can be read directly; and Agitation, four inversions in the first 10 seconds of each minute; Rinse — ILFOTOL at 5 mL per litre of rinse water (1+200), with the instruction to remove excess rinse solution from the film before drying; and Drying — the instruction to use a clean squeegee or chamois cloth to wipe the film before hanging it to avoid drying marks, and to dry at 30 to 40 degrees C in a drying cabinet or at room temperature in a clean dust-free area; Drying — the instruction to use a clean squeegee or chamois cloth to wipe the film before hanging it to dry, in order to avoid drying marks, and to dry at 30 to 40 degrees C in a drying cabinet or at room temperature in a clean dust-free area; Development times — 7 and a half minutes in ID-11 stock at EI 400 against 14 minutes at EI 1600, the note that the times are based on intermittent agitation and that continuous agitation should reduce them by up to 15 per cent, and the four-inversions-per-minute agitation scheme; Filter factors — the warning that with some automatic exposure cameras the correction given for deep red and orange filters can produce negatives under exposed by as much as one and a half stops; and Making long exposures, the statement that no reciprocity adjustment is needed between one half and one ten-thousandth of a second and the relation Ta = Tm to the power 1.31 beyond half a second; Agitation — continuous agitation is recommended in dishes and trays by rocking the dish or tray, against intermittent agitation for spiral and deep tanks; Agitation — intermittent agitation for spiral and deep tanks with four inversions in the first 10 seconds of each minute, and continuous agitation recommended in dishes and trays by rocking; The published base specifications — 35 mm film coated on 0.125 mm acetate base, roll film on 0.110 mm clear acetate base, and sheet film on 0.180 mm polyester base; and Handling, the instruction to handle the film in total darkness

Used by:ILFORD MICROPHEN developer · ILFORD PERCEPTOL developer · P3 Diffusion, Swelling and the Journey Into the Emulsion · P3 Rates, Temperature and Catalysts · P4 Grain, Speed and Resolution · P6 Pinhole Exposure and Reciprocity Correction · P7 Assignment: Landscape, Sky, Foreground and Filters · P7 Assignment: Night, the Very Long Exposure and Solargraphy · P7 Assignment: Portrait, Environmental Portrait and Self-Portrait · P8 Acutance, Adjacency Effects and Compensating Development · P8 Development Kinetics: Time, Temperature, Agitation and Exhaustion · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P8 Assignment: Reading a Developer Formula · P8 Solvent Action, Physical Development and Grain · P9 Experimental Design for the Darkroom · P11 Experiment: Clearing Time and Fixer Capacity · P11 How Fixer Works · P13 Part XIII Overview: Measuring the Response of Silver to Light · P13 Film Speed and Exposure Index · P14 Sensitometer Design Principles · P15 Assignment: Characterising a Film and Developer with Your Own Instruments · P27 Push and Pull Processing: What Extended Development Can and Cannot Buy · P28 Break/Fix: The Film That Came Back Wrong · P28 Reading the Negative as Evidence: Thin, Dense, Flat and Contrasty · P28 The Emulsion Under Stress: Reticulation, Scratches, Pinholes and Drying Marks · P28 Uneven Development, Bromide Drag and Surge Marks · Base-side scratches · Blisters · Cinch and pressure marks · Dense negative · Drying marks · Emulsion-side scratches · Excessive contrast · Frame-to-frame density variation · Print mottle · Reel and contact marks · Static discharge marks

ILFOBROM GALERIE FB, technical informationretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Product description, which states that the paper has a bright white base tint that will not yellow with prolonged washing and a neutral image colour in all viewing conditions, and that these qualities can be relied upon from print-to-print and batch-to-batch; Optimum permanence sequence with selenium toner, the toner diluted with working strength ILFORD WASHAID instead of water; and the recommendation that display prints be toned against oxidising gases, with selenium toner recommended as it has little effect on the image colour of ILFOBROM GALERIE FB and laminating named among the alternatives; Development — BROMOPHEN at 1+3 for 1 minute 30 seconds to 3 minutes at 20 degrees C; Development — the statement that GALERIE FB is developed in PQ UNIVERSAL or MULTIGRADE diluted 1+9 for 2 minutes at 20 degrees C; the characteristic curve captions for glossy grades 1 to 4 and matt grades 1 to 3, both developed in PQ UNIVERSAL or MULTIGRADE at 1+9 for 2 minutes; Processing summary — PQ UNIVERSAL 1+9 for 1 minute 30 seconds to 3 minutes at 20 degrees C; Optimum permanence sequence — the same two sequences on a different paper's sheet, with the fix given as ILFORD RAPID FIXER or HYPAM (1+4) for 1 minute with intermittent agitation, a 5 minute first wash, a 10 minute ILFORD WASHAID (1+4) rinse with intermittent agitation and a 5 minute final wash, and the selenium variant ending in a 30 minute final wash; A traditional graded paper in four glossy grades; safelight recommendations of SL1 or 902 with a 15 W bulb at not less than 1.2 m and no more than 4 minutes of direct illumination; The product description of a traditional graded black-and-white paper on a double-weight fibre base, available glossy in four equally spaced grades 1 to 4 and matt in three, used here as the comparison against a variable-contrast paper; ISO range - four equally spaced grades at range figures 130, 110, 90 and 70, with the worked example matching an effective density range of 1.22 to the nearest figure; Product description - a graded paper on a double weight 255 g/m2 fibre base with a bright white base tint stated not to yellow with prolonged washing, available glossy in four equally spaced grades 1 to 4 and matt in three grades 1 to 3; The description of a graded paper on a double weight fibre base, glossy in four equally spaced grades 1 to 4 and matt in three, the instruction that when using colour enlargers the paper must be exposed with white light without filtration, the ISO range table giving R130, R110, R90 and R70 for grades 1 to 4, and the single ISO speed of P400 for all four grades; Product description - the statement that the paper's deep rich blacks, brilliant whites, bright white base tint and neutral image colour can be relied upon from print-to-print and batch-to-batch, cited here as the only manufacturer statement in this corpus about consistency between coatings, and as a qualitative claim rather than a published tolerance; Contrast range - ILFOBROM GALERIE FB in four equally spaced grades at ISO range figures of 130, 110, 90 and 70, and the worked example taking an effective density range of 1.22 log exposure units to a figure the sheet prints as 120 and then to grade 1, whose tabulated range figure is 130; Safelight recommendations of SL1 or 902 with a 15 W bulb at not less than 1.2 m, and no more than 4 minutes of direct illumination

Used by:P29 Capstone Stage 4: The Silver Prints · HARMAN SELENIUM TONER · ILFORD BROMOPHEN developer · ILFORD PQ UNIVERSAL developer · ILFORD WASHAID · P4 Darkroom Session: The Latent Image Made Visible · P13 Paper Sensitometry: Reflection Density, Grades and ISO(R) · P17 F-Stop Timing and the Mathematics of Print Exposure · P18 The Structure of a Printing Paper: Base, Baryta, Emulsion and Supercoat · P18 Variable-Contrast Papers: Three Emulsions, One Sheet · P19 Lab: Dodging, Burning, Edge Work and Local Contrast · P19 Assignment: The Exhibition Print and Its Critique · P19 Reading the Negative and Making the Work Print · Testing a safelight

ILFORD Chemical Sundries: ILFOSTOP, ILFOTOL and WASHAID, technical informationretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: ILFOSTOP — why an acid stop bath is recommended, and what a water rinse costs instead; ILFOSTOP — a low odour citric acid stop bath; dilution, time, capacity, pH and specific gravity; the indicator dye; substituting a water bath; ILFOSTOP described as a low odour citric acid stop bath containing a pH-sensitive indicator dye; dilution 1+19, temperature range 18 to 24 degrees C, 10 seconds at 20 degrees C; capacities per litre unreplenished; concentrate pH 2.1; storage and solution life, five years in full airtight bottles and seven working days at working strength; ILFORD WASHAID — the dilution of 1+4, the standard processing sequence for FB paper and the description of the product as designed to be used with the ILFORD optimum permanence sequences; WASHAID at 1+4, the ten-minute immersion between two five-minute washes that the HYPAM sheet refers to for fibre-based paper; ILFOSTOP at 1+19, 18 to 24 degrees C, 10 seconds at 20 degrees C; ILFOSTOP — the product description as a low odour citric acid stop bath; the pH-sensitive indicator dye changing from yellow to purple as the bath becomes exhausted; the recommendation for dish/tray processing of paper and deep tank processing of film and the statement that it is not recommended for machine processing; mixing instructions and use; the ILFOSTOP table giving dilution 1+19, a temperature range of 18 to 24 degrees C and 10 seconds at 20 degrees C, with capacities per litre unreplenished of 15 films of 135-36, 60 and 30 sheets of 20.3 x 25.4 cm on RC and FB paper; pH and specific gravity, concentrate pH 2.1 and SG 1.101 to 1.111 at 20 degrees C; the process-time paragraph and the residual dye stain; the water-bath substitution; storage and solution life; availability; the opening health and safety and pH-and-specific-gravity paragraphs of the sheet; WASHAID — the 1+4 dilution and the ten-minute immersion between two five-minute washes that the RAPID FIXER sheet refers to for fibre-based paper; ILFORD WASHAID — the description as a hypo-eliminator formulated to aid the efficient removal of the thiosulphate by-products of fixation by ion exchange, particularly useful in speeding up the washing of fibre based papers, designed to be used with the ILFORD optimum permanence sequences, usable to aid the rapid washing of all ILFORD films and fibre papers saving both time and water, and particularly useful if a hardening fixer has been used; the pH and specific gravity table giving ILFORD WASHAID 1+4 at pH 7.00 to 7.20 and SG 1.020 at 20 degrees C; the mixing instructions and use; the WASHAID table giving dilution 1+4, a temperature range of 18 to 24 degrees C, 10 minutes for FB paper and 2 to 3 minutes for film at 20 degrees C, a film capacity per litre of 2 square metres (11 square feet) or 40 films of 135/36, and an FB paper capacity per litre of 40 sheets of 20.3 by 25.4 cm; the standard processing sequence table giving, for FB paper and film in minutes, a first wash in fresh running water of 5 and 1, WASHAID 1+4 of 10 and 2 to 3, and a final wash in fresh running water of 20 and 5; the water-temperature paragraph; the Optimum permanence for fibre based papers section and its two sequences, the plain one of a 1 minute fix in ILFORD RAPID FIXER 1+4, a 5 minute first wash, a 10 minute WASHAID rinse and a 5 minute final wash, and the selenium one in which the toner is diluted with working strength ILFORD WASHAID instead of water and the final wash is 30 minutes; the warning not to exceed the capacity of the fixer and not to extend the fixing time because both make washing more difficult; storage and solution life, 4 years in full airtight bottles, 6 months in half full tightly capped bottles and 7 working days at working strength; availability in 1 litre bottles making enough working strength solution for 200 sheets of 20.3 by 25.4 cm fibre based paper or 200 films of 135/36; and the sheet's opening health and safety and pH-and-specific-gravity paragraphs; ILFORD WASHAID - described as a hypo-eliminator formulated to aid the efficient removal of the thiosulphate by-products of fixation by ion exchange and as particularly useful if a hardening fixer has been used; the 1+4 dilution, pH 7.00 to 7.20 and specific gravity 1.020 at 20 degrees C; the temperature range 18 to 24 degrees C, 10 minutes for fibre-base paper and 2 to 3 minutes for film at 20 degrees C; capacities of 40 sheets of 20.3 by 25.4 cm or 40 135/36 films per litre; the optimum permanence sequences of 5, 10 and 5 minutes for paper and 1, 2 to 3 and 5 minutes for film; the selenium sequence in which the toner is diluted with working-strength WASHAID instead of water; the warning not to exceed the capacity of the fixer and not to extend the fixing time because both make washing more difficult; and the keeping figures of 4 years for a full airtight bottle of concentrate, 6 months half full, and 7 working days at working strength; ILFORD WASHAID, described as a hypo-eliminator formulated to aid the efficient removal of the thiosulphate by-products of fixation by ion exchange, particularly useful in speeding up the washing of fibre based papers and where a hardening fixer has been used; its dilution of 1+4, pH 7.00 to 7.20, times of 10 minutes for fibre-base paper and 2 to 3 minutes for film at 20 degrees C, capacities of 40 sheets of 8 by 10 inches or 40 135/36 films per litre, and the optimum permanence sequences in which it replaces most of the final wash; Mixing instructions: rinsing the measuring cylinder into the mixing vessel and making up to the final working volume; pH and specific gravity; ILFOSTOP as a low odour citric acid stop bath, its concentrate pH and specific gravity, and its purpose; ILFOTOL concentrate; ILFORD WASHAID at 1+4; ILFORD WASHAID Storage and solution life: concentrate 4 years in full airtight bottles and 6 months in half full tightly capped bottles; working strength 7 working days; ILFOSTOP: a low odour citric acid stop bath containing a pH-sensitive indicator dye that changes from yellow to purple as the bath becomes exhausted; dilution 1+19; 10 seconds at 20 degrees C; capacity per litre unreplenished of 15 films, 60 RC prints and 30 fibre-base prints; concentrate pH 2.1; working-strength life of 7 working days; ILFORD WASHAID: a hypo-eliminator formulated to aid the efficient removal of the thiosulphate by-products of fixation by ion exchange; dilution 1+4, 10 minutes for fibre-base paper and 2 to 3 minutes for film at 20 degrees C; wash water 18 to 24 degrees C for paper and within 5 degrees C of the process temperature for film; ILFOSTOP: the pH-sensitive indicator dye changing yellow to purple as the bath exhausts; concentrate pH 2.1; capacity per litre; ILFOSTOP described as a low odour citric acid stop bath, and its dilution and time; ILFOSTOP: a low odour citric acid stop bath, dilution 1+19, 18 to 24 degrees C, 10 seconds for film and paper, and the indicator dye that turns from yellow to purple as the bath exhausts; ILFOSTOP, a low odour citric acid stop bath at 1+19, 10 seconds at 20 degrees C; ILFOSTOP: a low odour citric acid stop bath at 1+19, 18 to 24 degrees C, 10 seconds for film and paper, capacity 15 films per litre, with the indicator dye that turns yellow to purple, and the statement that a water rinse may be substituted but increases the risk of processing marks and stains; ILFOTOL: a non-ionic wetting agent used at 5 ml per litre (1+200), with the warning that either too little or too much can lead to uneven drying and that foaming occurs with excessive agitation; ILFORD WASHAID at 1+4, 2 to 3 minutes for film at 20 degrees C, and the film sequence of a one-minute first wash, WASHAID, and a five-minute final wash; ILFOSTOP dilution and time; The statement that a water rinse may be substituted for the stop bath but increases the risk of processing marks and stains; ILFOTOL at 5 ml per litre in the final rinse; ILFOSTOP at 1+19 for 10 seconds and the statement that a water rinse may be substituted but increases the risk of processing marks and stains; ILFOTOL at 5 ml per litre in the final rinse, with the warning that either too little or too much can lead to uneven drying; ILFOSTOP described as a low odour citric acid stop bath containing a pH-sensitive indicator dye that changes from yellow to purple as the bath becomes exhausted; dilution 1+19; 10 seconds at 20 degrees C; capacities per litre unreplenished of 15 films of 135-36, 60 RC and 30 FB sheets of 20.3 x 25.4 cm; ILFOSTOP — a citric acid stop bath at 1+19 with a pH-sensitive indicator dye changing from yellow to purple; concentrate pH 2.1; capacities per litre unreplenished of 15 films of 135-36, 60 RC and 30 FB sheets of 20.3 x 25.4 cm; working strength life of seven working days; ILFOSTOP — a low odour citric acid stop bath containing a pH-sensitive indicator dye changing from yellow to purple as the bath becomes exhausted; concentrate pH 2.1 and specific gravity 1.101 to 1.111; dilution 1+19, 18 to 24 degrees C, 10 seconds at 20 degrees C; capacities per litre unreplenished; the note that it is not recommended for machine processing because short fix and wash times may leave a residual dye stain; storage and solution life, five years in full airtight bottles and seven working days at working strength; the water-bath substitution and its costs; ILFOSTOP — a low odour citric acid stop bath containing a pH-sensitive indicator dye that changes from yellow to purple as the bath becomes exhausted; concentrate pH 2.1; dilution 1+19 and 10 seconds at 20 degrees C; capacities per litre unreplenished of 15 films of 135-36, 60 RC and 30 FB sheets of 20.3 x 25.4 cm; the statement that a water bath may be substituted but increases the risk of processing marks and stains; ILFORD WASHAID — a hypo-eliminator formulated to aid the efficient removal of the thiosulphate by-products of fixation by ion exchange, particularly useful in speeding up the washing of fibre based papers and where a hardening fixer has been used; dilution 1+4, pH 7.00 to 7.20, 10 minutes for fibre-base paper and 2 to 3 minutes for film at 20 degrees C, capacity 40 sheets of 20.3 x 25.4 cm or 40 films of 135/36 per litre; ILFOSTOP at 1+19 for 10 seconds, with the statement that a water rinse may be substituted but increases the risk of processing marks and stains; ILFOTOL at 1+200 in the final rinse, with the warning that too little or too much both give uneven drying; ILFORD WASHAID - a hypo-eliminator formulated to aid the efficient removal of the thiosulphate by-products of fixation by ion exchange, particularly useful in speeding up the washing of fibre based papers and designed to be used with the ILFORD optimum permanence sequences, and particularly useful if a hardening fixer has been used; dilution 1+4, temperature range 18 to 24 degrees C, 10 minutes for fibre-base paper at 20 degrees C and 2 to 3 minutes for film, with a capacity of 40 sheets of 20.3 by 25.4 cm fibre-base paper per litre; the sequence table giving a 5 minute first wash, 10 minutes in WASHAID and a 20 minute final wash for fibre-base paper; the optimum permanence sequence of a 5 minute first wash, 10 minutes in WASHAID and a 5 minute final wash; storage life of 4 years in full airtight bottles, 6 months half full, and 7 working days at working strength, with 1 litre of concentrate enough for 200 sheets of 8 by 10 inch fibre-base paper; ILFORD ILFOTOL - a non-ionic wetting agent used as a final rinse to aid rapid, even drying and reduce the risk of drying marks, used for fibre based prints at 1+200 by immersing the print completely for a few seconds, draining and squeegeeing both sides before air-drying, heat-drying or glazing, with the warning that either too little or too much wetting agent can lead to uneven drying and that foaming occurs with excessive agitation; ILFORD WASHAID — described as a hypo-eliminator formulated to aid the efficient removal of the thiosulphate by-products of fixation by ion exchange, with its pH and specific gravity table giving pH 7.00 to 7.20 and SG 1.020 at 20 °C for WASHAID at 1+4, a temperature range of 18 to 24 °C, 10 minutes for fibre-base paper and 2 to 3 minutes for film at 20 °C; The statement that a water rinse may be substituted for the stop bath but increases the risk of processing marks and stains; and ILFOTOL at 5 mL per litre in the final rinse; The general instruction that to avoid problems due to cross-contamination of photochemicals all utensils and measuring and mixing vessels must be thoroughly washed after use, and that wherever possible dedicated equipment should be used for making up developer solutions; and the storage lives given for ILFOSTOP concentrate, 5 years in full airtight bottles against 12 months in half full tightly capped bottles, and for ILFOTOL concentrate, 3 years against 12 months; ILFORD WASHAID — a hypo eliminator formulated to aid the efficient removal of the thiosulphate by-products of fixation by ion exchange, particularly useful in speeding the washing of fibre-based papers and designed for use with the ILFORD optimum permanence sequences, and particularly useful if a hardening fixer has been used; the dilution of 1+4, the temperature range of 18 to 24 degrees C, 10 minutes for FB paper and 2 to 3 minutes for film, and the capacities of 40 films of 135/36 or 2 square metres and 40 sheets of 20.3 x 25.4 cm FB paper per litre; and the general instruction that to avoid problems due to cross-contamination of photochemicals all utensils and mixing vessels must be thoroughly washed after use, with dedicated equipment used for developer solutions wherever possible; ILFORD ILFOTOL — a non-ionic wetting agent used as a final rinse before drying films, which aids rapid even drying and so greatly reduces the risk of drying marks, can be used as a final rinse before drying fibre-based prints, and can additionally be used to clean glass and plastic lenses and filters and as an anti-static treatment; the recommended starting dilution of 5 mL per litre (1+200) with the note that the dilution needed depends on local water quality, the processor and the drying method; the instruction that ILFOTOL be measured and dispensed accurately because either too little or too much wetting agent can lead to uneven drying; and the note that foaming will occur if excessive agitation is given; ILFORD WASHAID — dilution 1+4, ten minutes for fibre-base paper, capacity; the fibre-base optimum-permanence wash sequence; Mixing instructions: rinsing the measuring cylinder into the mixing vessel and making up to the final working volume; Mixing instructions: rinsing the measuring cylinder into the mixing vessel and adding the remainder of the water to make up to the final working volume; ILFOSTOP — dilution 1+19, 18 to 24 degrees C, 10 seconds at 20 degrees C; capacities per litre unreplenished of 15 films of 135-36, 60 RC and 30 FB sheets of 20.3 x 25.4 cm; the mixing instruction to rinse the measuring cylinder into the mixing vessel and make up to the final working volume; solution life of seven working days at working strength; ILFORD ILFOTOL — the instruction that the wetting agent be measured and dispensed accurately because either too little or too much can lead to uneven drying, and the note that foaming will occur if excessive agitation is given to ILFOTOL solutions; ILFORD ILFOTOL — the recommended starting dilution of 5 mL per litre (1+200), with the statement that the dilution needed depends on a number of factors and may need adjustment for a particular set of circumstances, performance varying with local water quality, the type of processor and the drying method; and the instruction that it be measured and dispensed accurately because either too little or too much can lead to uneven drying; The general instruction that to avoid problems due to cross-contamination of photochemicals all utensils and measuring and mixing vessels must be thoroughly washed after use, and that wherever possible dedicated equipment should be used for making up developer solutions; and the ILFOSTOP entry's instruction not to let developer become contaminated with stop bath solution; ILFOSTOP — the statement that after development films and papers should be rinsed in an acid stop bath to stop development immediately and neutralise the developer, that the dilution is 1+19 and the time for film and paper 10 seconds at 20 degrees C, and that where a stop bath cannot be included a water bath or rinse can be substituted but using a water bath increases the risk of seeing processing related marks and stains, so the water must be completely changed at very frequent intervals; ILFORD ILFOTOL — a non-ionic wetting agent used as a final rinse before drying films, which aids rapid even drying and so greatly reduces the risk of drying marks; the recommended starting dilution of 5 mL per litre (1+200) with the note that the dilution needed depends on local water quality, the processor in use and the drying method; and the instruction that ILFOTOL be measured and dispensed accurately because either too little or too much wetting agent can lead to uneven drying; ILFOSTOP — the statement that after development films and papers should be rinsed in an acid stop bath to stop development immediately and neutralise the developer to help maintain the activity of the fixer bath; that ILFOSTOP helps to maintain the activity and prolong the life of the fixer solution by reducing carry over of excess developer (alkaline) into the fixer bath (acidic); the dilution of 1+19 and the time of 10 seconds at 20 degrees C for film and paper; and the statement that where a stop bath cannot be included a water bath can be substituted but increases the risk of processing related marks and stains, so the water must be completely changed at very frequent intervals and fewer fixing problems will be seen if the fixer's activity is monitored; ILFOSTOP, Mixing instructions and use — the instruction to make sure the amount of solution is enough to fill a dish or tray to a depth of about half full, or to cover the films in a spiral tank completely, or to fill a deep tank; and the capacity figures per litre; ILFOSTOP dilution, capacity and the indicator that signals exhaustion; recommended immersion time for prints; ILFOTOL wetting agent - recommended dilution and its purpose in promoting even draining and drying; ILFORD ILFOTOL — the statement that in addition to its use as a final rinse the wetting agent can be used to clean glass and plastic lenses and filters and as an anti-static treatment; The general instruction that to avoid problems due to cross-contamination of photochemicals all utensils and measuring and mixing vessels must be thoroughly washed after use and that dedicated equipment should be used wherever possible; and the ILFOSTOP entry's instruction not to let developer become contaminated with stop bath solution; ILFORD WASHAID - the reduction of wash times for fibre-base prints and the recommended sequence between fixing and washing; ILFORD ILFOTOL — the recommended starting dilution of 5 mL per litre (1+200), the note that the dilution needed depends on local water quality, the processor and the drying method, and the instruction that it be measured and dispensed accurately because either too little or too much can lead to uneven drying

Used by:Acetic acid (glacial) · Citric acid (anhydrous) · Citric Acid Stop Bath · HARMAN SELENIUM TONER · ILFORD HYPAM · ILFORD ILFOSTOP · ILFORD RAPID FIXER · ILFORD WASHAID · Kodak Hypo Clearing Agent and the washing accelerator Kodak patented · One per cent sodium sulfite washing aid · P2 Measuring Mass, Volume, Temperature and Density, and Knowing How Wrong You Are · P3 Acids, Bases and pH · P3 Aerial Oxidation: Why Chemistry Dies in a Half-Empty Bottle · P3 Buffers and Buffer Capacity · P3 Diffusion, Swelling and the Journey Into the Emulsion · P3 Lab: Measuring pH and Trusting the Number · P4 Darkroom Session: The Latent Image Made Visible · P6 Commissioning the Camera: Light-Tightness, Flare and the First Negatives · P6 Curved Film Plane and Multiple-Pinhole Experiments · P6 Lab: Processing Your First Film · P7 Assignment: Still Life and Controlled Light · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Experiment: Comparing Developing Agents · P9 Lab: Preparing Standard Test Negatives · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P10 Overview: Stopping Development · P10 Experiment: Measuring Stop Bath Capacity · P10 Stop Bath Formulations and the Fixer Interaction · P10 Why Stopping Works · P12 The Physics of Washing · P13 Lab: A Step-Wedge Exposure Series · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Gold, Iron-Blue and the Other Metal Toners · P27 Experiment: Agitation, Stand and Semi-Stand Development · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Experiment: Four Curve Families, Measured · P27 Experiment: The Development Time and Temperature Series · P28 Chemistry in the Bottle: Oxidation, Exhaustion, Precipitation and Contamination · P28 Fixer Faults, Washing Faults and the Stains They Leave · P28 The Emulsion Under Stress: Reticulation, Scratches, Pinholes and Drying Marks · Silver gelatin developing-out print on fibre base · Mixing a working solution from a stock · Mixing a solution to a final volume · Stop bath preparation · Air bells · Calcium scum · Developer contaminated by fixer or stop · Developer stain · Drying marks · Fixer contaminated by developer · Insufficient solution volume · Mottle revealed only after toning · Drying marks and squeegee lines on prints · Static discharge marks · Tong marks · Uneven toning · Water spots

ILFORD DELTA 100 PROFESSIONAL, technical informationretrieved 2026-09-05, 2026-09-06

Sections: The fixing table, which gives ILFORD RAPID or HYPAM fixers at 1+4, 18 to 24 degrees C, 2 to 5 minutes at 20 degrees C and a capacity of 24 films of 135-36 per litre unreplenished; Choosing the best ILFORD developer for the job: the Maximum film speed row at EI 200/24, and the Finest grain row, which goes to PERCEPTOL; Choosing the best ILFORD developer for the job — the two Finest grain rows, one at EI 100/21 giving PERCEPTOL (1+1) and one at EI 50/18 giving PERCEPTOL (stock); the development-time table, PERCEPTOL rows at stock, 1+1 and 1+3; Fixing table — ILFORD RAPID or HYPAM fixers at 1+4, 2 to 5 minutes at 20 degrees C and a capacity of 24 films of 135-36 per litre, the same figures the sheets for the conventional-grain films give

Used by:ILFORD HYPAM · ILFORD MICROPHEN developer · ILFORD PERCEPTOL developer · P11 How Fixer Works

ILFORD DELTA 3200 PROFESSIONAL, technical informationretrieved 2026-09-06, 2026-09-07

Sections: The statement that the recommended developers are ILFOTEC DD-X, MICROPHEN and ID-11; the developer-selection table naming MICROPHEN stock for maximum sharpness, rapid processing and maximum film speed up to EI 25000/45; the ISO speed rating of 1000/31 measured in ILFORD ID-11 at 20 degrees C; the development-time table to EI 12500/42; the separate EI 25000/45 table giving MICROPHEN stock 22 minutes at 20 degrees C and 17 and a half at 24 degrees C; The ISO speed rating of 1000/31 and the statement that it was measured in ID-11; Choosing the best ILFORD developer for the job — PERCEPTOL (stock) named as the best overall image quality powder at EI 400/27 and EI 800/30 and in the Finest grain row; the development-time table, PERCEPTOL stock row from EI 400/27 to EI 3200/36; Exposure rating - the statement that DELTA 3200 Professional is designed to be exposed at EI 3200/36 and given extended development, that the recommended meter setting is EI 3200/36 but good image quality can also be obtained from EI 400/27 to EI 6400/39, that it is particularly recommended in the range EI 1600/33 to EI 6400/39, and that it can be exposed at ratings up to EI 25000/45 provided test exposures are made first; the statement that DELTA 3200 Professional has an ISO speed rating of 1000/31 degrees to daylight, measured using ILFORD ID-11 developer at 20 degrees C with intermittent agitation in a spiral tank; and the statement that the recommended EI range is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard. Development times, 35 mm and roll film at 20 degrees C - ILFOTEC DD-X 1+4 at 6, 7, 8, 9.5, 12.5 and 17 minutes for EI 400, 800, 1600, 3200, 6400 and 12500; ID-11 stock at 7, 8, 9.5, 10.5, 13 and 17; MICROPHEN stock at 6, 7, 8, 9, 12 and 16.5; PERCEPTOL stock at 11, 13, 15 and 18 for EI 400 to 3200; and the separate EI 25000/45 table giving ILFOTEC DD-X 1+4 as 25 minutes at 20 degrees C and MICROPHEN stock as 22; Handling — the statement, on a sheet whose page footers are dated June 2025, that DELTA 3200 Professional is a very fast film, that it should always be loaded and unloaded in subdued light, and the advice that the film is not subjected to airport scanners, but that if it is it should always be carried as hand luggage

Used by:ILFORD MICROPHEN developer · ILFORD PERCEPTOL developer · P27 Push and Pull Processing: What Extended Development Can and Cannot Buy · P28 Fog and Where It Comes From

ILFORD DELTA 400 PROFESSIONAL, technical informationretrieved 2026-09-05, 2026-09-06

Sections: The speed rating of ISO 400/27 to daylight and the statement that it was measured using ILFORD ID-11 developer at 20 degrees C with intermittent agitation in a spiral tank; Choosing the best ILFORD developer for the job, the Maximum film speed row; The speed rating of ISO 400/27 and the statement that it was measured using ILFORD ID-11 developer at 20 degrees C; Choosing the best ILFORD developer for the job, the Finest grain row; the development-time table, PERCEPTOL rows; Development times - the note that the times in bold will produce negatives of normal contrast, given as Gbar 0.62

Used by:ILFORD MICROPHEN developer · ILFORD PERCEPTOL developer · P13 Gamma, Contrast Index and Average Gradient

ILFORD Film Processing Chart, version January 2025retrieved 2026-09-06

Sections: Page 1 headings - the poster's version date of January 2025, its statement that times are given at 20 degrees C in minutes and seconds, its note that a temperature compensation table is also available separately, and its exception of XP2 SUPER as a C-41 film. The table of times is not present in the PDF's text layer and no development time is quoted from this document

Used by:P27 Experiment: The Development Time and Temperature Series

ILFORD HYPAM FIXER, technical informationretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Opening description of the product and its fixing agent; Opening description — when a fix hardener is and is not recommended; The whole seven-page sheet — the opening description as a non-hardening rapid fixer supplied as a liquid concentrate whose fixing agent is ammonium thiosulphate and which contains no sodium thiosulphate, the 18 to 40 degrees C range, and the hardener paragraph with its four remaining circumstances and the instruction never to mix hardener with concentrated fixer; the mixing instructions, the warning that fixer concentrates do not readily mix with water, the order of addition and the ten-minute recirculation before a processor is used; the pH and specific gravity table, 5.0 to 5.5 at both dilutions with SG 1.080 to 1.090 at 1+4 and 1.040 to 1.050 at 1+9 at 20 degrees C, and the paragraph on pH sticks covering pH 4 to 6 and a hydrometer covering 1.000 to 1.200; the fixing time table with its two columns, without hardener and with, for general purpose film, specialist, X-ray and graphic arts materials, RC paper and FB paper at 1+4 and 1+9, and the film and paper agitation regimes; the washing instructions for film, RC and FB paper, the spiral-tank fill-and-invert method and the WASHAID sequence; the section on the use of a fix hardener and its effect on film fix and wash times, including the statement that ILFORD PHOTO no longer produces a fix hardener and the extended 4 to 10 minute fix and 10 to 20 minute wash; the capacity table per litre of working strength solution and the note that the paper figures may be exceeded where print stability is not critically important; the paragraph on what exhausts an unreplenished bath; replenishment, the four rates, the machine RC range, the silver-recovery reduction and the deep-tank method; two bath fixing; Checking and maintaining fixer activity — the stop bath recommendation with the full ILFOSTOP and ILFOSTOP PRO table, adjusting fixer pH with 50 per cent acetic acid and adjusting specific gravity in both directions; the film clearing time test and the discard rule; silver concentration limits for film, FB and RC papers and the sodium sulphide test with its reference tint; silver recovery, sulphiding, the hydrogen sulphide warning and the achievable silver levels; working solution life; storage; and availability and capacity; Checking and maintaining fixer activity — Stop Bath: the recommendation of an acid stop bath such as ILFORD ILFOSTOP with indicator dye, the sentence stating that ILFOSTOP is also recommended for all machine processing applications, the note that the indicator can be ignored for replenished machine processors, and the ILFORD Stop Bath table, which carries a capacity row the other sheets do not — other specialist, X-ray and graphic art materials, 0.75 square metres (8 square feet) per litre for ILFOSTOP against 1 square metre (11 square feet) for ILFOSTOP PRO; The opening description of HYPAM as a non-hardening rapid fixer supplied as a liquid concentrate whose fixing agent is ammonium thiosulphate and which contains no sodium thiosulphate, the 18 to 40 degrees C range, and the hardener paragraph — that a fixer hardener can be used to turn working strength HYPAM into a hardening fixer for films, that modern camera films are sufficiently hardened when manufactured so that the general use of a fix hardening agent is no longer recommended, the four circumstances in which one is still recommended, the statement that a hardener is not recommended for paper processing, and the instruction never to mix hardener with concentrated fixer; Washing FB paper — the same 60 minute figure and the same WASHAID paragraph, 5 minutes running water, 10 minutes in 1+4 WASHAID at 18 to 24 degrees C and a 5 minute final wash; the following section on the use of a fix hardener and its effect on film fix and wash times; The opening description of HYPAM as a non-hardening rapid fixer supplied as a liquid concentrate whose fixing agent is ammonium thiosulphate and which contains no sodium thiosulphate, with the note that a fix hardener is no longer generally recommended because modern camera films are sufficiently hardened at manufacture; Silver concentration — the same testing solution, 2 g of sodium sulphide in 125 ml of water diluted 1+9 for use, the same reference spot on a print known to be well fixed and thoroughly washed, the same barely visible cream tint as the reference colour, the same remedy of a five-minute soak followed by the recommended fixing and washing sequence in fresh fixer, and the same two conditions on when the test is valid; pH and specific gravity at 1+4 and 1+9; Opening description: HYPAM is a non-hardening rapid fixer whose fixing agent is ammonium thiosulphate and which contains no sodium thiosulphate; usable temperature range 18 to 40 degrees C; the note that modern camera films are sufficiently hardened when manufactured for most processing circumstances; The opening description — a non-hardening rapid fixer, ammonium thiosulphate as the fixing agent, and the statement that a fix hardener is no longer generally recommended because modern camera films are sufficiently hardened at manufacture; The opening description — a non-hardening rapid fixer whose fixing agent is ammonium thiosulphate, and the statement that a fix hardener is no longer generally recommended because modern camera films are sufficiently hardened at manufacture; The opening description — HYPAM is a non-hardening rapid fixer supplied as a liquid concentrate whose fixing agent is ammonium thiosulphate and which contains no sodium thiosulphate, and the statement that a fix hardener is no longer generally recommended because modern camera films are sufficiently hardened at manufacture; The opening description — HYPAM is a non-hardening rapid fixer whose fixing agent is ammonium thiosulphate, and the statement that a fix hardener is no longer generally recommended because modern camera films are sufficiently hardened at manufacture; The opening description — HYPAM is a non-hardening rapid fixer whose fixing agent is ammonium thiosulphate, with the statement that a fix hardener is no longer generally recommended because modern camera films are sufficiently hardened at manufacture

Used by:Ammonium thiosulfate · Potassium alum · ILFORD HYPAM · ILFORD ILFOSTOP · ILFORD RAPID FIXER · ILFORD WASHAID · Kodak F-52 · Kodak ST-1 · P3 Acids, Bases and pH · P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve · P10 Stop Bath Formulations and the Fixer Interaction · P10 Why Stopping Works · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline · P28 The Emulsion Under Stress: Reticulation, Scratches, Pinholes and Drying Marks · Hardener sludge

ILFORD ILFOTEC DD film developer and replenisher for dip and dunk (hanger) processors, technical informationretrieved 2026-09-07

Sections: Mixing - ILFOTEC DD concentrate diluted 1+4 to make working strength replenisher, and ILFOTEC DD STARTER added at 1+250, that is 4 mL of starter per litre, to turn replenisher into machine tank developer, with the warning that adding more or less than the calculated amount significantly affects the development time recommendations; Development times - the statement that the table is for seasoned replenished developer with starter, and the instruction that without starter the given times are reduced by 20 per cent and then progressively increased as batches of film are processed and the developer becomes seasoned; pH and specific gravity of 8.50 and 1.070 at 20 degrees C for the fresh 1+4 working strength, with the advice that users make their own control measurements; Deep tank batch processing without replenishment - the capacity of up to 10 films of 135-36 or 120 per litre, the 10 per cent time increase per successive film and the tank-volume tables, the worked example of five unequal batches, the statement that it is more inconsistent to reuse developer with time compensation than to replenish, and the discard rule that the developer goes when the theoretical capacity has been reached or the times have become impractical; Replenishment - the instruction to find the optimum rate with a process control system; and the stop bath and fixer capacities of 15 and 24 films of 135-36 per litre

Used by:P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does

ILFORD ILFOTEC DD-X film developer, technical informationretrieved 2026-09-04, 2026-09-07

Sections: pH and specific gravity: ILFOTEC DD-X at 1+4; Working Solution Life and Storage: concentrate 24 months in full tightly capped bottles and 4 months in half full ones; working strength not kept more than 24 hours; the statement that the developer oxidises with reuse and storage and the case for one-shot processing; Stop, fix, wash and rinse: all process solutions kept at the same temperature or at least within 5 degrees C of the developer temperature; Overview - the statement that ILFOTEC DD-X is supplied as a liquid concentrate diluted 1+4 for one-shot use when the highest image quality is required and that it can be reused for greater economy but image quality will be reduced slightly; Reusing developer - the capacity of up to 10 films of 135/36 or 120 per litre when reused, the 10 per cent time increase per successive film, the requirement that the 250 to 300 mL used for one film be poured back and mixed with the unused part, and the statement that reusing lowers image quality slightly and increases the risk of contamination, precipitates and suspended emulsion particles; the recommendation against reusing developer for push processing; Working solution life of not more than 24 hours; Storage - the concentrate keeping 24 months in full tightly capped bottles and 4 months in half full ones; and Availability and capacity - 16 films of 135/36 one-shot from a 1 litre bottle at 1+4, or up to 50 with reuse techniques; Overview - the statement that ILFOTEC DD-X gives full film speed and produces negatives that are easy to print, with depth in the shadows, a smooth transition through the mid-tones and bright detailed highlights, that it is particularly recommended for DELTA 3200 Professional rated at EI 3200/36, and that it is highly recommended when fast films need to be push processed; and the statement that push processing using reused developers is not recommended

Used by:P3 Acids, Bases and pH · P3 Aerial Oxidation: Why Chemistry Dies in a Half-Empty Bottle · P3 Diffusion, Swelling and the Journey Into the Emulsion · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Push and Pull Processing: What Extended Development Can and Cannot Buy

ILFORD ILFOTEC LC29 film developer, technical informationretrieved 2026-09-04, 2026-09-06

Sections: Reusing developer; films per litre at 1+9 and 1+19; Table of dilutions; note on minimum quantity of concentrate; pH and specific gravity; development times at 1+9, 1+19 and 1+29; reusing developer; pH and specific gravity: ILFOTEC LC29 at 1+9; Dilutions and reuse — only 1+9 and 1+19 are suitable for reuse, giving 10 and 5 films per litre respectively with a 10 per cent time increase per successive film, and the statement that for the highest image quality the developer should be used one-shot; Table of dilutions; note on minimum quantity of concentrate; Table of dilutions - a 600 ml tank at 1+9 taking 60 ml of concentrate and 540 ml of water

Used by:P2 Waste: Streams, Silver, and the Drain You Must Not Use · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P3 Acids, Bases and pH · P27 Part XXVII Overview: From Observation to Measurement · Mixing a working solution from a stock · Dilution ratio misread as a fraction

ILFORD MULTIGRADE FB CLASSIC technical informationretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Optimum permanence, the sequence in which selenium toner diluted with working-strength WASHAID replaces the water at the toning step and the final wash is 30 minutes, with the instruction not to add a hardener to the fixer and not to extend the fixing time; and Prints, under Storage, which states that it is recommended that prints made for display are toned to protect them from the oxidising gases found in many environments; Optimum permanence, the sequence in which selenium toner diluted with working-strength WASHAID replaces the water at the toning step and the final wash is 30 minutes; Optimum permanence sequence with selenium toner — fixation in ILFORD RAPID FIXER (1+4) or HYPAM (1+4) with intermittent agitation for 1 minute, toning in selenium toner diluted with working strength ILFORD WASHAID instead of water for an unstated time printed as an asterisk, washing aid for 10 minutes with intermittent agitation and a final wash in fresh running water for 30 minutes; and the recommendation that prints made for display are toned to protect them from the oxidising gases found in many environments, with selenium toner recommended as it has little effect on the image colour of MULTIGRADE FB CLASSIC; Processing summary — BROMOPHEN at 1+3 for 1 minute 30 seconds to 3 minutes at 20 degrees C; Processing summary — MULTIGRADE developer at 1+9 for 1 minute 30 seconds to 3 minutes and at 1+14 for 2 to 5 minutes, both at 20 degrees C; Development — the image begins to appear at approximately 20 seconds on a correctly exposed print, and development can be extended to 6 minutes without any noticeable change in contrast or fog; the sensitometric curves, exposed and developed in MULTIGRADE at 1+9 for 2 minutes at 20 degrees C; Processing summary — PQ UNIVERSAL at 1+9 for 1 minute 30 seconds to 3 minutes at 20 degrees C; OPTIMUM PERMANENCE — the statement that the standard fixing and washing recommendations give excellent print permanence for all commercial needs and that when optimum permanence is needed, perhaps for archival storage of prints, the following sequences at 18 to 24 degrees C including wash water are recommended using ILFORD WASHAID; the instruction not to add a hardener to the fixer; the warning not to exceed the capacity of the fixer and not to extend the fixing time; the sequence of a 1 minute fix, a 5 minute first wash, 10 minutes of ILFORD WASHAID (1+4) with intermittent agitation and a 5 minute final wash; and the selenium sequence in which the toner is diluted with working strength ILFORD WASHAID instead of water and the final wash is 30 minutes; OPTIMUM PERMANENCE — the statement that the standard fixing and washing recommendations give excellent print permanence for all commercial needs and that the following sequences are recommended when optimum permanence is needed, at 18 to 24 degrees C including wash water, using ILFORD WASHAID; the instruction not to add a hardener to the fixer; the instruction to be careful not to exceed the capacity of the fixer and not to extend the fixing time, as both make washing more difficult; the optimum permanence sequence itself, fixation in RAPID FIXER or HYPAM at 1+4 for 1 minute, first wash in fresh running water 5 minutes, WASHAID at 1+4 with intermittent agitation 10 minutes, final wash in fresh running water 5 minutes; the optimum permanence sequence with selenium toner, in which WASHAID replaces water after toning and the final wash is 30 minutes; Processing summary — washing in fresh running water above 5 degrees C for 30 to 45 minutes; OPTIMUM PERMANENCE — the standard fixing and washing recommendations will give excellent print permanence for all commercial needs, and the optimum permanence sequences are recommended when optimum permanence is needed, perhaps for archival storage of prints, with the instruction not to add a hardener to the fixer; Processing summary — washing in fresh running water above 5 degrees C for 30 to 45 minutes; Fixing — the use of a hardening fixer is not recommended as it reduces washing efficiency, and exceeding the capacity of the fixer or extending the fixing time both make washing more difficult; Optimum permanence sequence — 1 minute's fixation, a 5 minute first wash, 10 minutes in WASHAID at 1+4 with intermittent agitation and a 5 minute final wash; Processing summary — washing in fresh running water above 5 degrees C for 30 to 45 minutes; OPTIMUM PERMANENCE — the sequence and the instruction not to add a hardener to the fixer; ISO range - MULTIGRADE FB CLASSIC reads 170, 140, 110, 95, 80, 60 and 50 through filters 00 to 5, and R95 unfiltered; Product description - a variable contrast paper on a 255 g/m2 baryta coated fibre base; Processing summary, giving developer, stop, fixer and a wash of 30 to 45 minutes in running water; and Optimum permanence, the fixing and washing sequence recommended for archival storage; Product description - a variable contrast paper on a 255 g/m2 baryta coated fibre base with a white base tint and a neutral image colour, available in glossy 1K and matt 5K surfaces; ISO range and ISO paper speed by filter; and the processing summary with its development recommendation and its wash of 30 to 45 minutes in fresh running water; Spectral Sensitivity - the wedge spectrogram to tungsten light at 2856 K and the instruction to use a safelight with a cut-off no lower than 580 nm, of a dark brown or red type; ISO speed - a paper speed of ISO P500 unfiltered and P230 across filters 00 to 3, with the note that ISO paper speed is different from film speed and that a suggested start value for pinhole use is about ISO 6; the description of a white base tint and a neutral image colour; Storage - a cool dry place below 20 degrees C, high temperature and humidity to be avoided, and excellent condition for up to three years stored as recommended; Development - the statement that with MULTIGRADE developer 1+9 the image begins to appear at approximately 20 seconds on a correctly exposed print, and that development can be extended up to 6 minutes without any noticeable change in contrast or fog; and the offer of the 1+14 dilution for greater control during development and for economy; Processing summary and the fixing recommendation for fibre base at 1+4; the statement that a hardening fixer is not recommended; and OPTIMUM PERMANENCE, the instruction to be careful not to exceed the capacity of the fixer or to extend the fixing time; Product description - a variable contrast paper on a 255 g/m2 baryta coated fibre base, white base tint, neutral image colour, double weight, glossy surface 1K and matt surface 5K; Fixation - the statement that a hardening fixer is not recommended because it reduces washing efficiency and that RAPID FIXER and HYPAM are non-hardening, and that there is no benefit in extending fixation because of image etching; Processing summary - the fixing, washing and drying times; Optimum permanence - the fixing and washing sequence with WASHAID, with the instruction not to add a hardener and not to exceed the fixer capacity or extend the fixing time because both make washing more difficult; Drying - squeegee both sides, clip back-to-back to minimise curl, air-dry, glaze or heat-dry; Finishing - the statement that the glossy 1K surface responds more favourably to toning than the matt 5K surface; Storage - up to three years when stored as recommended; Contrast range - the ISO range table by filter and the unfiltered figure of R95; ISO speed - the table by filter and the unfiltered figure of P500; Contrast control - the statement that guide exposure times for filters 00 to 3.5 are generally the same but filters 4 to 5 need typically between 1.5 times and double the time; Exposing light sources - suitability for tungsten and tungsten halogen and for cold cathode sources designed for variable contrast papers, with other cold cathode and pulsed xenon sources possibly giving a reduced contrast range; Characteristic curves, plotted for filters 00 to 5 with grades 4 and 5 shown separately because of their increased exposure; Processing summary, giving development of 1:30 to 3:00 at 20 C in MULTIGRADE developer 1+9, stop and fixer at 18 to 24 C, and a wash of 30 to 45 minutes; Development, where the image begins to appear at approximately 20 seconds on a correctly exposed print and development can be extended up to 6 minutes without any noticeable change in contrast or fog; and Finishing, which states that the paper can be mounted using the standard techniques for fibre base papers; Contrast range - the ISO range table reading 170, 140, 110, 95, 80, 60 and 50 at filters 00 to 5 and the unfiltered figure of R95; ISO speed - the table reading 230 at filters 00 to 3 and 210 at filters 4 and 5, with an unfiltered speed of P500; Contrast control - the statement that guide exposure times for filters 00 to 3.5 are generally the same but that filters 4 to 5 will need additional exposure, typically between 1.5 times and double the time; Development - the statement that development may be extended to 6 minutes without any noticeable change in contrast or fog; Processing summary (intermittent agitation) - MULTIGRADE developer 1+9 for 1:30 to 3:00 at 20 C, ILFOSTOP 1+19 for 0:10, ILFORD RAPID FIXER 1+4 for 1:00, wash 30 to 45 minutes; and Development, where development can be extended up to 6 minutes without any noticeable change in contrast or fog; Base and image colour, giving a white base tint and a neutral image colour; and Prints, which recommends that prints made for display are toned to protect them from the oxidising gases found in many environments, and names selenium toner as having little effect on the image colour of this paper, with sulphide toning and silver image stabilisers as other protection methods; Contrast range, whose ISO range table to ISO 6846-1992 gives R95 at filter 2; Processing summary, giving MULTIGRADE developer at 1+9 for 1 min 30 s to 3 min at 20 C, at 1+14 for 2 to 5 min, BROMOPHEN at 1+3 and PQ UNIVERSAL at 1+9 for 1 min 30 s to 3 min, ILFOSTOP at 1+19 for 10 s at 18 to 24 C, ILFORD RAPID FIXER or HYPAM at 1+4 for 1 min at 18 to 24 C and a wash of 30 to 45 min in fresh running water above 5 C; Development, where the image begins to appear at approximately 20 s on a correctly exposed print with MULTIGRADE developer at 1+9 and development can be extended to 6 min without any noticeable change in contrast or fog; Stop bath, where a stop bath is strongly recommended because it stops development immediately, reduces the risk of staining and extends the life of the fixer bath; Fixation, where a hardening fixer is not recommended because it reduces washing efficiency, there is no benefit in extending fixation and long fixing times can cause image etching; and Drying, which recommends a final rinse in ILFOTOL at 1+200; Contrast range - the ISO range table for MULTIGRADE FB CLASSIC with MULTIGRADE filters, reading 170, 140, 110, 95, 80, 60 and 50 at filters 00 to 5, the unfiltered figure of R95, the statement that the values are representative of those obtained when dish or tray processing to ILFORD recommendations, and the same note that the range meant is that of the image projected on the baseboard and read with a photometer; Processing summary (intermittent agitation) - MULTIGRADE developer 1+9 for 1:30 to 3:00 at 20 C, 1+14 for 2:00 to 5:00, BROMOPHEN 1+3 and PQ UNIVERSAL 1+9 for 1:30 to 3:00, ILFOSTOP 1+19 for 0:10, ILFORD RAPID FIXER or HYPAM 1+4 for 1:00, wash 30 to 45 minutes in fresh running water above 5 C; and Development, where the image begins to appear at approximately 20 seconds on a correctly exposed print and development can be extended up to 6 minutes without any noticeable change in contrast or fog; OPTIMUM PERMANENCE - the sequence recommended when optimum permanence is needed, at 18 to 24 degrees C including the wash water: fixation in ILFORD RAPID FIXER or HYPAM at 1+4 for 1 minute, a first wash in fresh running water for 5 minutes, ILFORD WASHAID at 1+4 with intermittent agitation for 10 minutes, and a final wash in fresh running water for 5 minutes, with the instruction not to add a hardener to the fixer and the warning not to exceed the capacity of the fixer or to extend the fixing time because both make washing more difficult; the selenium-toned variant, in which WASHAID replaces water during toning and the final wash is 30 minutes; Processing summary - washing in fresh, running water above 5 degrees C for 30 to 45 minutes; Fixation - the statement that a hardening fixer is not recommended because it reduces washing efficiency, and that there is no benefit in extending fixation because of image etching; Drying - a final rinse in ILFOTOL diluted 1+200 aids even and rapid drying, prints are squeegeed on both sides after washing and can be clipped back-to-back to minimise curl and air-dried at room temperature, glazed, or heat-dried; FINISHING - the paper responds as other fibre base papers to toning, chemical reduction and retouching, the glossy 1K surface responding more favourably to toning than the matt 5K, and it can be mounted using the standard techniques for fibre base papers; STORAGE - prints processed as recommended have a more than adequate storage life for most purposes, print life is shortened in adverse storage conditions or on exposure to oxidising gases, and prints made for display are recommended to be toned; The optimum permanence sequence with selenium toner - fixation in ILFORD RAPID FIXER at 1+4 or HYPAM at 1+4 with intermittent agitation for 1 minute, toning in selenium toner diluted with working strength ILFORD WASHAID instead of water for a time printed as an asterisk and explained as the appropriate time to achieve the depth of colour needed, washing aid with intermittent agitation for 10 minutes and a final wash in fresh running water for 30 minutes, against the plain optimum permanence sequence whose final wash is 5 minutes; the processing summary, MULTIGRADE developer at 1+9 for 1 minute 30 seconds to 3 minutes at 20 degrees C and a plain wash of 30 to 45 minutes; the characteristic curve caption, that the published curves are of glossy paper exposed through filters 00 to 5 and developed in MULTIGRADE at 1+9 for 2 minutes at 20 degrees C; the note under Finishing that the glossy 1K surface responds more favourably to toning than the matt 5K surface; and the recommendation that prints made for display are toned to protect them from oxidising gases, with selenium toner recommended as it has little effect on the image colour of MULTIGRADE FB CLASSIC; The optimum permanence sequence with selenium toner - fixation in ILFORD RAPID FIXER at 1+4 or HYPAM at 1+4 with intermittent agitation for 1 minute, toning in selenium toner diluted with working strength ILFORD WASHAID instead of water for a time printed as an asterisk and explained as the appropriate time to achieve the depth of colour needed, washing aid with intermittent agitation for 10 minutes and a final wash in fresh running water for 30 minutes, against the plain optimum permanence sequence whose final wash is 5 minutes; and the recommendation that prints made for display are toned to protect them from the oxidising gases found in many environments, with selenium toner recommended as it has little effect on the image colour of MULTIGRADE FB CLASSIC and sulphide toning and silver image stabilisers named as other protection methods; Prints, under Storage, which states that print life will be shortened in adverse storage conditions or if the print is exposed to oxidising gases, that it is recommended that prints made for display are toned to protect them from the oxidising gases that are found in many environments, and that selenium toner is recommended as it has little effect on the image colour of this paper while other protection methods including sulphide toning and silver image stabilisers can be used; Finishing, that the glossy 1K surface responds more favourably to toning than the matt 5K surface; and Optimum permanence, the sequence in which selenium toner diluted with working-strength WASHAID replaces the water at the toning step and the final wash is 30 minutes, with the instruction not to add a hardener to the fixer and not to extend the fixing time; Storage, Prints - that prints processed as recommended will have a more than adequate storage life for most purposes, that print life will be shortened in adverse storage conditions or if the print is exposed to oxidising gases, that it is recommended that prints made for display are toned to protect them from the oxidising gases found in many environments, that selenium toner is recommended as it has little effect on the image colour of MULTIGRADE FB CLASSIC, and that other protection methods can be used including sulphide toning and silver image stabilisers; OPTIMUM PERMANENCE, that the standard fixing and washing recommendations give excellent print permanence for all commercial needs and that the sequences below are recommended when optimum permanence is needed, perhaps for archival storage of prints, with the instruction not to add a hardener to the fixer; and the optimum permanence sequence with selenium toner - ILFORD RAPID FIXER or HYPAM at 1+4 for 1 minute, toning in selenium toner diluted with working strength washing aid for the time needed to reach the depth of colour wanted, ILFORD WASHAID instead of water with intermittent agitation for 10 minutes, and a final wash in fresh running water for 30 minutes; Processing summary at 20 degrees C — MULTIGRADE developer 1+9 for 1 minute 30 seconds to 3 minutes, ILFOSTOP 1+19 for 10 seconds, RAPID FIXER 1+4 for 1 minute; Development — the image begins to appear at approximately 20 seconds and development can be extended up to 6 minutes without any noticeable change in contrast or fog; Fixation — no benefit in extending fixation beyond the recommended time, with some loss of print quality from image etching when long fixing times are given; and Safelight recommendations, a 15 W bulb at a minimum of 1.2 m with a filter cut-off no lower than 580 nm; Fixation — the statement that the use of a hardening fixer is not recommended as it reduces washing efficiency, that ILFORD RAPID FIXER and HYPAM are non-hardening fixers, and that there is no benefit in extending fixation beyond the recommended time because some loss of print quality might be seen when long fixing times are given due to image etching; Optimum permanence — the instruction not to add a hardener to the fixer and to be careful not to exceed the capacity of the fixer and not to extend the fixing time, as both these make washing more difficult; and the optimum permanence sequence of 1 minute fixation at 1+4, a 5 minute first wash, WASHAID and a final wash; Safelight recommendations — dark orange, dark brown or red filters, a 15 W bulb, safelights positioned a minimum of 1.2 m (4 ft) from the paper, and a filter cut-off no lower than 580 nm; and Development, the statement that development can be extended up to 6 minutes without any noticeable change in contrast or fog; Processing summary at 20 degrees C — MULTIGRADE developer at 1+9 for 1 minute 30 seconds to 3 minutes, or 1+14 for 2 to 5 minutes, BROMOPHEN at 1+3 for 1 minute 30 to 3 minutes, ILFOSTOP 1+19 for 10 seconds, RAPID FIXER or HYPAM 1+4 for 1 minute, and 30 to 45 minutes washing in fresh running water; Development — the image begins to appear at approximately 20 seconds with MULTIGRADE developer 1+9, and development can be extended up to 6 minutes without any noticeable change in contrast or fog; Fixation — the statement that there is no benefit in extending fixation beyond the recommended time because some loss of print quality might be seen when long fixing times are given due to image etching, and that a hardening fixer is not recommended as it reduces washing efficiency; and Safelight recommendations — dark orange, dark brown or red filters, a 15 W bulb, a minimum of 1.2 m (4 ft) from the paper, and a filter cut-off no lower than 580 nm; Processing summary at 20 degrees C — MULTIGRADE developer 1+9 for 1 minute 30 seconds to 3 minutes with intermittent agitation; and Development, the statement that development can be extended up to 6 minutes without any noticeable change in contrast or fog; Toning — the warning that metal replacement toners such as blue (iron) and red (copper) may give no extra protection and the image might fade; Paper structure and finishes; processing times and the recommendation for optimum permanence; Drying and finishing: air drying, clipping prints back to back to minimise curl, glazing, and the response of the paper to retouching; OPTIMUM PERMANENCE: the sequences recommended when optimum permanence is needed, at 18 to 24 degrees C including wash water; fixation in RAPID FIXER or HYPAM at 1+4 for 1 minute, first wash in fresh running water 5 minutes, WASHAID at 1+4 with intermittent agitation 10 minutes, final wash in fresh running water 5 minutes; the instruction not to add a hardener to the fixer and to be careful not to exceed the capacity of the fixer or to extend the fixing time; Processing summary, washing in fresh running water above 5 degrees C for 30 to 45 minutes; Development times at 1+9 and the approximately 20 second emergence on fibre base; the instruction that every bath is within 1 degree C of the working temperature before starting; The instruction not to add a hardener, not to exceed the capacity of the fixer and not to extend the fixing time; the optimum-permanence washing sequence; OPTIMUM PERMANENCE: fixation in RAPID FIXER or HYPAM at 1+4 for 1 minute; the instruction not to add a hardener to the fixer and to be careful neither to exceed the capacity of the fixer nor to extend the fixing time, as both make washing more difficult; Stop bath — the statement that the use of a stop bath is strongly recommended because it stops development immediately, reduces the risk of staining, and extends the life of the fixer bath; Drying — a final rinse in ILFOTOL diluted 1+200 with water will aid even and rapid drying; after washing, squeegee prints on both sides to remove surplus water, and prints can be clipped back-to-back to minimise curl and air-dried at room temperature, or glazed, or heat-dried; Fixation — the statement that the use of a hardening fixer is not recommended as it reduces washing efficiency, and that ILFORD RAPID FIXER and HYPAM are non-hardening fixers; and Optimum permanence, the instruction not to add a hardener to the fixer; Fixation — the statement that there is no benefit in extending fixation beyond the recommended time and that some loss of print quality might be seen when long fixing times are given due to image etching, and that the use of a hardening fixer is not recommended as it reduces washing efficiency; and Optimum permanence — the instruction to be careful not to exceed the capacity of the fixer and not to extend the fixing time, as both these make washing more difficult; Processing summary at 20 degrees C — MULTIGRADE developer 1+9 for 1 minute 30 seconds to 3 minutes, or 1+14 for 2 to 5 minutes, BROMOPHEN 1+3 for 1 minute 30 to 3 minutes, ILFOSTOP 1+19 for 10 seconds, RAPID FIXER or HYPAM 1+4 for 1 minute; Development — the image begins to appear at approximately 20 seconds with MULTIGRADE developer 1+9 and development can be extended up to 6 minutes without any noticeable change in contrast or fog; Fixation — no benefit in extending fixation beyond the recommended time, with some loss of print quality from image etching; and Safelight recommendations, a 15 W bulb at a minimum of 1.2 m with a filter cut-off no lower than 580 nm; Stop bath — the statement that the use of a stop bath is strongly recommended because it stops development immediately, reduces the risk of staining and extends the life of the fixer bath; and the processing summary, ILFOSTOP 1+19 for 10 seconds at 18 to 24 degrees C; Development times and the instruction to agitate continuously; Processing summary — MULTIGRADE developer 1+9 for 1 minute 30 seconds to 3 minutes at 20 degrees C with intermittent agitation; and Development, the statement that development can be extended up to 6 minutes without any noticeable change in contrast or fog; Safelight recommendations — dark orange, dark brown or red filters, a 15 W bulb, safelights positioned a minimum of 1.2 m (4 ft) from the paper, and a filter cut-off no lower than 580 nm; Development, the statement that development can be extended up to 6 minutes without any noticeable change in contrast or fog; and the Contrast range and ISO range figures, which give a guide to selecting the appropriate grade for a given effective negative density range

Used by:P29 Capstone Overview: What the Pure Silver Portfolio Asks · P29 Planning the Capstone: The Project Plan and Its Hazard Assessment · HARMAN SELENIUM TONER · ILFORD BROMOPHEN developer · ILFORD MULTIGRADE developer · ILFORD PQ UNIVERSAL developer · ILFORD WASHAID · P12 Assignment: Your Archival Processing Sequence · P12 Permanence and Image Deterioration · P12 The Physics of Washing · P12 Lab: Testing for Residual Thiosulfate and Residual Silver · P17 F-Stop Timing and the Mathematics of Print Exposure · P18 Part XVIII Overview: Printing Chemistry · P18 Experiment: Maximum Black, Base White and Dry-Down · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · P18 Print Developer Chemistry and the Developer-Paper Pair · P18 Break/Fix: The Print That Will Not Go Black · P18 The Structure of a Printing Paper: Base, Baryta, Emulsion and Supercoat · P18 Variable-Contrast Papers: Three Emulsions, One Sheet · P19 Part XIX Overview: Fine Printing · P19 Contrast Filtration and Split-Grade Printing · P19 Lab: Dodging, Burning, Edge Work and Local Contrast · P19 Assignment: The Exhibition Print and Its Critique · P19 Developing the Print Consistently and Running a Printing Session · P19 Reading the Negative and Making the Work Print · P19 Lab: Test Strips, Base Exposure and the Print's Black Point · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Assignment: The Toned Print · P20 Toning, Permanence and What the Evidence Actually Supports · P28 Break/Fix: The Film That Came Back Wrong · P28 Fixer Faults, Washing Faults and the Stains They Leave · P28 Fog and Where It Comes From · P28 Print Faults: Weak Blacks, Mottle, Bronzing and the Rest · P28 Uneven Development, Bromide Drag and Surge Marks · Iron-blue toned silver gelatin print · Silver gelatin developing-out print on fibre base · Mounting a print and putting it in an enclosure · Print processing: the archival sequence · Keeping the printing session log · Running a toning session · Running a two-bath fixing rotation · Developer stain · Dry-down error · Hardener sludge · Over-fixing · Poor maximum black · Print mottle · RC blisters · Uneven f-stop test-strip bands · Uneven print development · Weak or grey blacks

ILFORD MULTIGRADE FB COOLTONE: technical informationretrieved 2026-09-05, 2026-09-06

Sections: Optimum permanence sequence with selenium toner, and the recommendation of selenium toner for display prints as it has little effect on the image colour of MULTIGRADE FB COOLTONE, with sulphide toning and silver image stabilisers named as alternative protection methods; Processing summary — PQ UNIVERSAL at 1+9 for 1 minute 30 seconds to 3 minutes at 20 degrees C; The description of a cool white base tint and a cool-of-neutral image colour on a 255 g/m2 baryta coated fibre base; ISO speed - P250 across filters 00 to 3 and P590 unfiltered, with a suggested pinhole start value of about film ISO 6; Contrast range and ISO speed - the range table reading 130, 115, 100, 85, 70, 55 and 50 at filters 00 to 5 with an unfiltered figure of R85, and the speed table reading 250 at filters 00 to 3 and 225 at filters 4 and 5 with an unfiltered speed of P590; Contrast control - the statement that guide exposure times for filters 00 to 3.5 are generally the same but that filters 4 to 5 will need typically between 1.5 times and double the time; The description of the paper as having a cool white base tint and a cool-of-neutral image tone, supplied in gloss 1K surface, with good toning characteristics; the processing summary, a plain wash of 60 minutes; the optimum permanence sequence with selenium toner, fixation 1 minute, toning in selenium toner diluted with working-strength washing aid, ILFORD WASHAID 10 minutes and a final wash of 30 minutes; and the recommendation of selenium toner for display prints as it has little effect on the image colour of MULTIGRADE FB COOLTONE; The statement that the paper responds favourably to toning, and the recommendation of selenium toner for display prints as it has little effect on the image colour of MULTIGRADE FB COOLTONE, with sulphide toning and silver image stabilisers named as alternative protection methods

Used by:HARMAN SELENIUM TONER · ILFORD PQ UNIVERSAL developer · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · P19 Contrast Filtration and Split-Grade Printing · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim

ILFORD MULTIGRADE FB WARMTONE: technical informationretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: The note beneath the optimum permanence sequences, that for optimum permanence with other toners that give a protective effect — sulphide, polysulphide and some metal replacement toners such as gold and platinum — the optimum permanence sequence is used first and the print toned afterwards, while other metal replacement toners such as blue (iron) and red (copper) may not give extra protection and the image might fade, and dye toners do not give extra protection; Toning — the note that metal replacement toners such as blue (iron) and red (copper) may not give extra protection; Toning; Optimum permanence; Toning — the statement that MULTIGRADE FB WARMTONE is receptive to a wide range of toners, that subtle colour changes or more dramatic effects are readily achieved, and that polysulphide toners and selenium toners are especially recommended, with the instruction to follow the instructions supplied with the toner; and the optimum permanence sequence with selenium toner, in which the toner is diluted with working strength ILFORD WASHAID instead of water; Development — the statement that from the ILFORD range of developers the warmest results on MULTIGRADE FB WARMTONE are achieved with the HARMAN warm-tone developer and ILFORD BROMOPHEN; Characteristic Curves — the curves exposed through filters 00 to 5 and developed in MULTIGRADE diluted 1+9 for 2 minutes at 20 degrees C; Processing summary — ILFORD BROMOPHEN at 1+3 for 1 minute 30 seconds to 3 minutes at 20 degrees C; Processing summary — ILFORD PQ UNIVERSAL at 1+9 for 1 minute 30 seconds to 3 minutes at 20 degrees C, listed beside the HARMAN warm-tone developer and BROMOPHEN; The description of a warm black image tone on a warm white base; ISO Range and ISO Speed - P100 across filters 00 to 3 and P50 at 4 and 5, P200 unfiltered, with an approximate film ISO equivalent of 3; Development - the statement that the choice of developer affects the image colour and that the warmest results are achieved with HARMAN WARMTONE and ILFORD BROMOPHEN developers; Washing - the statement that short washing times give a cooler image colour and that prints should be washed for at least 30 minutes for the warmest results; Fixing - the statement that a hardening fixer gives a cooler image tone and that long fixing times affect the image colour; Fixing - the statement that a hardening fixer is not recommended because it reduces washing efficiency, may impair toning performance and gives a cooler image tone; Washing - the statement that short washing times give a cooler image colour and that thirty minutes or more is wanted for the warmest result; Drying - the warning that belt print dryers and photographic blotters are not recommended because prints may stick, and that a hardening fixer would be needed if a belt dryer must be used; The description of the paper as having a warm black image tone on a warm white base and as especially suitable for toning; the footnote that filters originally designed for older Multigrade II and III paper are not suitable and should be replaced; and the combined ISO Range and ISO Speed table, giving range figures of 170, 160, 130, 110, 90, 70 and 50 and speeds of 100 at filters 00 to 3 and 50 at filters 4 and 5, with an unfiltered range of R110 and an unfiltered speed of P200; Fixing, which states that long fixing times will affect the image colour of the paper; and Washing, which states that short washing times, for example when using a washing aid, give a cooler image colour than longer washing times, and that prints should be washed for at least 30 minutes for the warmest results; ISO Range and ISO Speed - the range table reading 170, 160, 130, 110, 90, 70 and 50 at filters 00 to 5, the unfiltered figure of R110, and the worked example stating that a negative of effective density range 1.32 log exposure units gives the range figure 130 and should be tried with MULTIGRADE filter 1 on this paper; Optimum permanence sequence, in which selenium toner diluted with working-strength ILFORD WASHAID replaces the water at the toning step; and the note beneath it, that for optimum permanence with other toners that give a protective effect, for example sulphide (sepia), polysulphide and some metal replacement toners (gold and platinum), the optimum permanence sequence is used first and the print toned afterwards, and that other metal replacement toners such as blue (iron) and red (copper) toner may not give extra protection and the image might fade, while dye toners do not give extra protection; Optimum permanence — the note that for optimum permanence with other toners that give a protective effect, for example sulphide (sepia), polysulphide and some metal replacement toners (gold and platinum), the optimum permanence sequence is used first and the print toned afterwards; and the note beneath it, that other metal replacement toners such as blue (iron) and red (copper) toner may not give extra protection and the image might fade, and that dye toners do not give extra protection; The note beneath the optimum permanence sequence, that sulphide (sepia), polysulphide and some metal replacement toners such as gold and platinum give a protective effect, while other metal replacement toners such as blue (iron) and red (copper) toner may not give extra protection and the image might fade, and that dye toners do not give extra protection; The description of the paper as having a warm black image tone on a warm white base and as especially suitable for toning, available in double weight 1K glossy and 24K semi-matt; the processing summary, a plain wash of 60 minutes; the statement that the choice of developer affects the image colour and that the warmest results come from HARMAN WARMTONE and ILFORD BROMOPHEN developers; the Washing paragraph, that short washing times, for example when using a washing aid, give a cooler image colour than longer washing times and that for the warmest results prints should always be washed for at least 30 minutes; the Toning paragraph, that the paper is receptive to a wide range of toners and that polysulphide and selenium toners are especially recommended; and the optimum permanence sequence with selenium toner, identical in structure to MULTIGRADE FB CLASSIC's, whose plain-sequence final wash carries the footnote to extend it to 30 minutes if the warmest image colour is needed; Toning - the statement that MULTIGRADE FB WARMTONE is receptive to a wide range of toners, that subtle colour changes or more dramatic effects are readily achieved, and that polysulphide toners and selenium toners are especially recommended, with the instruction to follow the instructions supplied with the toner; Toning, that the paper is receptive to a wide range of toners and that polysulphide and selenium toners are especially recommended; and Optimum permanence, the instruction that for optimum permanence with other toners that give a protective effect, for example sulphide (sepia), polysulphide and some metal replacement toners such as gold and platinum, the optimum permanence fixing and washing sequence is used first and the print is then toned as desired, with the note that other metal replacement toners such as blue (iron) and red (copper) toner may not give extra protection and the image might fade, and that dye toners do not give extra protection; Toning, that toning creates an aesthetic effect and in some cases can help to protect the print from external contaminants, and that polysulphide and selenium toners are especially recommended for this paper; and the note beneath the optimum permanence sequences, that for optimum permanence with other toners that give a protective effect, for example sulphide (sepia), polysulphide and some metal replacement toners (gold and platinum), the optimum permanence sequence is used first and the print toned afterwards, while other metal replacement toners such as blue (iron) and red (copper) toner may not give extra protection and the image might fade, and dye toners do not give extra protection; Toning and Optimum permanence - that toning creates an aesthetic effect and in some cases can help to protect the print from external contaminants; that for optimum permanence with other toners that give a protective effect, for example sulphide (sepia), polysulphide and some metal replacement toners such as gold and platinum, the optimum permanence sequence is used first and the print toned afterwards; and the note that other metal replacement toners such as blue (iron) and red (copper) toner may not give extra protection and the image might fade, and that dye toners do not give extra protection; The toners named as especially suitable, including polysulphide, and the protective effect of sulphide (sepia) toning

Used by:P29 Capstone Stage 6: Permanence, Presentation and the Finished Portfolio · Copper(II) sulfate · Potassium ferrocyanide (anhydrous) · Sodium sulfide · HARMAN SELENIUM TONER · ILFORD BROMOPHEN developer · ILFORD PQ UNIVERSAL developer · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · P18 The Structure of a Printing Paper: Base, Baryta, Emulsion and Supercoat · P19 Contrast Filtration and Split-Grade Printing · P19 Assignment: The Exhibition Print and Its Critique · P19 Reading the Negative and Making the Work Print · P20 Part XX Overview: Toning Chemistry · P20 Gold, Iron-Blue and the Other Metal Toners · P20 What a Toner Actually Does to a Silver Image · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P20 Assignment: The Toned Print · P20 Toning, Permanence and What the Evidence Actually Supports · Sulphide (sepia) toned silver gelatin print

ILFORD MULTIGRADE FILTERS, product leaflet i24retrieved 2026-09-05

Sections: Filter description - grades 00 to 3.5 are speed matched and little or no adjustment to exposure time is necessary between them, while grades 4 to 5 will generally require more exposure, in practice between 0.5 and 1 stop depending on the product; Introduction - twelve evenly spaced speed-matched grades 00 to 5 in half steps, usable above or below the lens or cut for a filter drawer; the statement that grades 00 to 3.5 are speed matched and little or no exposure adjustment is needed between them, while grades 4 to 5 will generally require more exposure, in practice between 0.5 and 1 stop depending on the product; Care of filters - the statement that dust, rough handling and finger marks on a filter reduce print contrast and degrade the image; Introduction - twelve evenly spaced speed-matched grades numbered 00 to 5 in half steps, the lowest number the softest; the statement that grades 00 to 3.5 are speed matched and little or no adjustment to exposure time is necessary when changing between these grades, that grades 4 to 5 will generally require more exposure, in practice between 0.5 and 1 stop depending on the product, and that the change may be made either with the exposure time or with the lens aperture; Care of filters - the statement that marks caused by dust, rough handling or finger marks reduce print contrast and degrade the image; Introduction - twelve evenly spaced speed-matched grades numbered 00 to 5 in half steps, with the statement that grades 00 to 3.5 are speed matched and little or no adjustment to exposure time is necessary when changing between them, that grades 4 to 5 will generally require more exposure, in practice between 0.5 and 1 stop depending on the product, and that the change may be made either with the exposure time or with the lens aperture; and Care of filters, which states that marks caused by dust, rough handling or finger marks reduce print contrast and degrade the image; Introduction - twelve evenly spaced speed matched grades numbered 00 to 5 in half-step increments; the statement that grades 00 to 3.5 are speed matched and little or no adjustment to exposure time is necessary when changing between them, that grades 4 to 5 will generally require more exposure, in practice between 0.5 and 1 stop depending on the product, and that the change may be made either with the exposure time or with the lens aperture

Used by:P17 F-Stop Timing and the Mathematics of Print Exposure · P18 Variable-Contrast Papers: Three Emulsions, One Sheet · P19 Contrast Filtration and Split-Grade Printing · P19 Lab: Dodging, Burning, Edge Work and Local Contrast · P19 Lab: Test Strips, Base Exposure and the Print's Black Point

ILFORD MULTIGRADE, PQ UNIVERSAL and BROMOPHEN paper developers, technical informationretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: PROCESSING PAPER, dish or tray processing — the recommended developing temperature of 20 degrees C plus or minus 1 C, the instruction to prepare the volume of every solution before starting and to check that every solution is within 1 C of the working temperature, and the statement that to maintain print-to-print consistency when batch processing a large number of either RC or FB prints it may be advantageous to reduce exposure slightly and extend development; Developer capacities, per litre of working strength solution, giving 100 RC and 50 FB 8 by 10 inch prints for MULTIGRADE at 1+9, 70 and 40 at 1+14, 70 and 45 for PQ UNIVERSAL at 1+9 and 70 and 45 for BROMOPHEN at 1+3; and WORKING SOLUTION LIFE, that working strength developer left in an open dish should not be kept for more than one working day; PROCESSING PAPER — the statement that for a correctly exposed fibre-base print the image begins to appear after about 35 seconds, and the recommended development temperature of 20 degrees C plus or minus 1 C; ILFORD BROMOPHEN developer; pH and specific gravity table; ILFORD MULTIGRADE developer; ILFORD PQ UNIVERSAL developer; ILFORD BROMOPHEN developer; the pH and specific gravity table; ILFORD BROMOPHEN developer; ILFORD MULTIGRADE and PQ UNIVERSAL developers; pH and specific gravity table; ILFORD BROMOPHEN developer, the pH and specific gravity table; Developer capacities, quoted here only for the comparison of a published print capacity with Foma's published area capacity; ILFORD BROMOPHEN developer, the product description; Preparing BROMOPHEN stock developer; Preparing working strength BROMOPHEN; pH and specific gravity; Dish/tray processing and the interleaving method; Development times, RC paper and FB paper; Developer capacities; Working solution life; Storage; Availability and capacity; ILFORD MULTIGRADE developer, the product description; Preparing MULTIGRADE and PQ UNIVERSAL developer; pH and specific gravity; Dish/tray processing and the interleaving method; Development times, RC paper and FB paper; Developer capacities; Working solution life; Storage; Availability and capacity; ILFORD PQ UNIVERSAL developer, the product description; Preparing MULTIGRADE and PQ UNIVERSAL developer; pH and specific gravity; Dish/tray processing and the interleaving method; Development times, RC paper and FB paper; Developer capacities; Processing sheet film, including the film development times, exposure indices and Gbar figures and the film capacity; Working solution life; Storage; Availability and capacity; Washing FB paper — the 60 minute wash for double weight paper in fresh running water above 5 degrees C; the statement that a washing aid is not needed when conventionally processing fibre base papers but that its use does reduce the final wash times thus saving time and water; the statement that if a hardening fixer has been used a washing aid is recommended as hardened prints take longer to wash; the instruction that when using ILFORD WASHAID prints are washed for at least 5 minutes in running water before the washing aid and then washed in running water for 20 minutes; and the Washing aid table giving ILFORD WASHAID as a liquid at 1+4, 18 to 24 degrees C, 10 minutes; pH and specific gravity table: MULTIGRADE at 1+9, PQ UNIVERSAL at 1+9 and BROMOPHEN stock; pH and specific gravity of MULTIGRADE, PQ UNIVERSAL and BROMOPHEN at working strength; Working Solution Life: BROMOPHEN stock 6 months full and 3 months half full, working-strength paper developer in an open dish not more than one working day; Storage: unopened concentrate 2 years at 5-20 degrees C, used up within six months once opened; high temperatures reduce the effective solution life considerably; pH and specific gravity of MULTIGRADE, PQ UNIVERSAL and BROMOPHEN; Processing paper: fibre-base papers absorb far more liquid than resin-coated ones and go limp when wet; recommended development temperature 20 degrees C plus or minus 1 degree C; Processing paper: recommended development temperature 20 degrees C plus or minus 1 degree C; on correctly exposed fibre-base prints the image begins to appear after 35 seconds and development may be extended to 6 minutes without any noticeable change in contrast or fog; development times of 1 to 2 minutes at 20 degrees C for the four developers; Development times: the image begins to appear after 35 seconds on fibre-based prints, and development may be extended to 6 minutes without noticeable change in contrast or fog; the pH and specific gravity table; developer capacities; MULTIGRADE described as a dimezone-s/hydroquinone developer; the pH and specific gravity table; development times and capacities; the note that fibre prints may be developed to 6 minutes without noticeable change in contrast or fog; MULTIGRADE developer described as a dimezone-s and hydroquinone paper developer; dilutions, times and capacities; MULTIGRADE developer: dilution 1+9 and development of 60 seconds at 20 degrees C for RC papers; MULTIGRADE developer dilution and development time for RC paper; pH and specific gravity table for MULTIGRADE at 1+9, PQ UNIVERSAL at 1+9 and BROMOPHEN stock; ILFORD MULTIGRADE and PQ UNIVERSAL described as dimezone-s/hydroquinone developers; ILFORD BROMOPHEN as a phenidone-hydroquinone developer; the pH and specific gravity table; Processing paper: the statement that on a correctly exposed fibre-base print the image begins to appear after 35 seconds and that development may be extended to 6 minutes without noticeable change in contrast or fog; ILFORD BROMOPHEN described as a phenidone/hydroquinone developer and MULTIGRADE and PQ UNIVERSAL as dimezone-s/hydroquinone developers; The image tone ILFORD claims for MULTIGRADE, PQ UNIVERSAL and BROMOPHEN, and the pH and specific gravity table; ILFORD BROMOPHEN described as a phenidone/hydroquinone developer and MULTIGRADE and PQ UNIVERSAL as dimezone-s/hydroquinone developers; the pH and specific gravity table; ILFORD BROMOPHEN described as a phenidone/hydroquinone developer and MULTIGRADE and PQ UNIVERSAL as dimezone-s/hydroquinone developers; the pH and specific gravity table, Bromophen stock at 10.30 to 10.50; The published pH and specific gravity table at 20 degrees C, MULTIGRADE developer at 1+9 reading pH 10.45 to 10.55; the recommended development temperature of 20 degrees C plus or minus 1 degree; and the statement that high temperatures reduce solution life considerably; Dilutions and processing times for MULTIGRADE paper developer with resin-coated and fibre-based papers at 20 degrees C; Developer capacity in 8 by 10 inch prints per litre of working strength solution, tabulated at each dilution for MULTIGRADE, PQ UNIVERSAL and BROMOPHEN; the recommended development temperature of 20 C plus or minus 1 C; and the statement that high temperatures reduce solution life considerably; Developer capacities - the number of 8x10 inch prints a litre of working solution will develop, given separately for RC and FB paper; and the published pH and specific gravity table for fresh working solutions; Development times, RC and FB paper, with MULTIGRADE at 1+9 and the statement that on correctly exposed FB prints the image begins to appear after 35 seconds and that development may be extended to 6 minutes without any noticeable change in contrast or fog; the temperature recommendation of 20 degrees C plus or minus 1 with the warning that high temperatures reduce solution life considerably and may give very short development times leading to uneven processing; ILFORD MULTIGRADE developer described as a rapid liquid concentrate dimezone-s/hydroquinone developer used at 1+9 or 1+14; Development times, RC paper - MULTIGRADE 1+9 for 1 minute and PQ UNIVERSAL 1+9 and BROMOPHEN 1+3 for 2 minutes, all at 20 degrees C; the statement that on correctly exposed FB prints the image begins to appear after 35 seconds and that development may be extended to 6 minutes without any noticeable change in contrast or fog; Developer capacities - 100 RC and 50 FB 8x10 prints per litre for MULTIGRADE 1+9; the temperature recommendation of 20 degrees C plus or minus 1; the instruction to prepare working solutions directly before they are needed and to draw off mains water and let it stand because it is highly aerated; the interleaving method of agitation and the instruction to remove the paper 10 seconds before the end of the development time and let it drain; and Working solution life - not more than one working day in an open dish; Development times - the note that approximately double the RC times are recommended with MULTIGRADE RC COOLTONE paper to obtain the coolest image colour; Developer capacities - the note that approximately half the stated capacities are achieved if only COOLTONE is processed, because of the longer development times; and the statement that BROMOPHEN is particularly recommended for dish processing MULTIGRADE Warmtone RC and FB papers to get the warmest image tone; The product descriptions - MULTIGRADE and PQ UNIVERSAL as liquid concentrate dimezone-s/hydroquinone developers and BROMOPHEN as a phenidone/hydroquinone powder developer, with their dilutions of 1+9 or 1+14, 1+9, and 1+3 from stock; pH and specific gravity - MULTIGRADE 1+9 at pH 10.45 to 10.55, PQ UNIVERSAL 1+9 at 10.48 to 10.58 and BROMOPHEN stock at 10.30 to 10.50, with the note that the figures were obtained under controlled laboratory conditions and that users should make their own control measurements; Development times for RC and FB paper; Developer capacities - the number of 8x10 inch prints one litre of working solution will develop, 100 RC and 50 FB for MULTIGRADE 1+9, 70 and 40 at 1+14, 70 and 45 for PQ UNIVERSAL, 70 and 45 for BROMOPHEN, with approximately half those figures if only COOLTONE is processed; the instruction to prepare working solutions directly before they are needed and to draw off mains water and let it stand because it is highly aerated; and the recommendation of BROMOPHEN for the warmest image tone on MULTIGRADE Warmtone papers; Working solution life - working strength MULTIGRADE, PQ UNIVERSAL and BROMOPHEN developer left in an open dish should not be kept for more than one working day, and if stored in a tightly capped bottle may last up to 24 hours; Developer capacities - 100 RC and 50 FB 8x10 prints per litre for MULTIGRADE at 1+9, 70 and 40 at 1+14, 70 and 45 for PQ UNIVERSAL and BROMOPHEN, and approximately half those figures where only COOLTONE is processed; the recommended developing temperature of 20 degrees C plus or minus 1, with the note that slightly lower temperatures need development extended slightly; the instruction to prepare working solutions directly before they are needed; and the instruction not to contaminate developer solutions with either stop bath or fixer solutions; The product descriptions of MULTIGRADE developer as giving a neutral image tone with most papers, PQ UNIVERSAL as giving a slightly warm to neutral image tone, and BROMOPHEN as giving a slightly warm to neutral tone and being particularly recommended for dish or tray developing MULTIGRADE Warmtone RC and FB papers to get the warmest image tone; the RC and FB processing tables giving MULTIGRADE developer at 1+9 and 1+14 and BROMOPHEN at 1+3; the note that approximately double these times are recommended with MULTIGRADE RC COOLTONE paper to obtain the coolest image colour; and the statement that on correctly exposed FB prints development may be extended to 6 minutes without any noticeable change in contrast or fog; The published pH and specific gravity table at 20 C, in which MULTIGRADE at 1+9 reads pH 10.45 to 10.55; PROCESSING PAPER, dish or tray processing - the recommended developing temperature of 20 C plus or minus 1 C, with the statement that slightly lower temperatures need slightly extended development and slightly higher temperatures need reduced times, that these developers are not designed for high temperature processing, and that high temperatures will reduce the effective solution life considerably and may give very short development times that can lead to uneven processing; the instruction to prepare the volume of every solution before starting, to fill the dish about half full and to check that every solution is within 1 C of the working temperature; the interleaving method for developing multiple sheets at once, slipping them in one at a time emulsion side down; the statement that to maintain print to print consistency when batch processing a large number of either RC or FB prints it may be advantageous to reduce exposure slightly and extend development; the note that approximately double the development times are recommended with MULTIGRADE RC COOLTONE paper to obtain the coolest image colour and that approximately half the published capacities are then achieved; Developer capacities, giving per litre of working strength solution 100 RC and 50 FB 8 by 10 inch prints for MULTIGRADE at 1+9, 70 and 40 at 1+14, 70 and 45 for PQ UNIVERSAL at 1+9 and 70 and 45 for BROMOPHEN at 1+3; and WORKING SOLUTION LIFE, which states that working strength MULTIGRADE, PQ UNIVERSAL and BROMOPHEN left in an open dish should not be kept for more than one working day; Working solution life — BROMOPHEN stock solution lasts up to 6 months in full capped containers and 3 months in a half full tightly capped container, while working strength MULTIGRADE, PQ UNIVERSAL and BROMOPHEN left in an open dish should not be kept for more than one working day and may last up to 24 hours in a tightly capped bottle; Storage — full unopened bottles of MULTIGRADE and PQ UNIVERSAL concentrate stored at 5 to 20 degrees C keep for 2 years, and once opened the concentrate should be used completely within six months with all bottles kept tightly sealed; and unopened packets of BROMOPHEN powder in cool dry conditions at 5 to 20 degrees C keep indefinitely, with stock solution to be prepared immediately once opened; Developer capacities — per litre of working strength solution, 100 sheets of 20.3 x 25.4 cm (8 x 10 inch) RC paper or 50 of FB for MULTIGRADE at 1+9, 70 RC or 40 FB at 1+14, 70 RC or 45 FB for PQ UNIVERSAL at 1+9, and 70 RC or 45 FB for BROMOPHEN at 1+3, with the note that approximately half these capacities are achieved if only MULTIGRADE RC COOLTONE is processed because of the longer development times; and Working solution life, that working strength MULTIGRADE, PQ UNIVERSAL and BROMOPHEN left in an open dish should not be kept for more than one working day; Developer capacities — the table giving, per litre of working strength solution, 100 sheets of 20.3 x 25.4 cm (8 x 10 inch) RC paper or 50 of FB for MULTIGRADE at 1+9, 70 RC or 40 FB for MULTIGRADE at 1+14, 70 RC or 45 FB for PQ UNIVERSAL at 1+9, and 70 RC or 45 FB for BROMOPHEN at 1+3; and the instruction that the volume made up must be enough to fill a dish or tray to a depth of about half full; The published pH of fresh working solutions, and the instruction that users make their own control measurements from their own accurately mixed fresh solutions; Working-strength capacity in 8 by 10 prints per litre at 1+9 and 1+14; the instruction that working solution in an open dish is not kept more than one working day; Working-strength capacity in 8 by 10 prints per litre, and the one-working-day life of a solution left in an open dish; MULTIGRADE, PQ Universal and BROMOPHEN - recommended dilutions, development times and temperatures for fibre and resin-coated papers, and the developing capacity table giving 8 by 10 inch prints per litre of working strength solution at each dilution; Developer capacities - 1 litre of MULTIGRADE developer at 1+9 develops 100 eight-by-ten inch RC prints or 50 fibre-base prints, at 1+14 seventy and forty, PQ Universal at 1+9 seventy and forty-five, BROMOPHEN at 1+3 seventy and forty-five; approximately half these capacities for MULTIGRADE RC COOLTONE because of its longer development times; on correctly exposed FB prints the image begins to appear after 35 seconds and development may be extended to 6 minutes without noticeable change in contrast or fog; Mixing instructions and use — the instruction to determine the amount of solution needed for the processing session and to make sure it is enough to fill a dish or tray to a depth of about half full, or to cover the films in a spiral tank completely, or to fill a deep tank; and the developer capacity table per litre of working strength solution; Recommended development times and temperatures for RC and FB papers at each dilution; the statement that on correctly exposed FB prints the image will begin to appear after 35 seconds with these developers, and that development may be extended to 6 minutes without any noticeable change in contrast or fog; the advice that to maintain print-to-print consistency when batch processing it may be advantageous to reduce exposure slightly and extend development; Developer capacities — per litre of working strength solution, 100 sheets of 20.3 x 25.4 cm RC paper or 50 of FB for MULTIGRADE at 1+9, 70 RC or 40 FB at 1+14, and 70 RC or 45 FB for PQ UNIVERSAL at 1+9 and BROMOPHEN at 1+3; and Working solution life, that working strength developer left in an open dish should not be kept for more than one working day; Developer capacities — per litre of working strength solution, 100 sheets of 20.3 x 25.4 cm (8 x 10 inch) RC paper or 50 of FB for MULTIGRADE at 1+9, 70 RC or 40 FB at 1+14, and 70 RC or 45 FB for PQ UNIVERSAL at 1+9 and BROMOPHEN at 1+3, with the note that approximately half these capacities are achieved if only MULTIGRADE RC COOLTONE is processed because of the longer development times; and Mixing instructions and use, the instruction that the volume made up must be enough to fill a dish or tray to a depth of about half full; Developer capacity tables in 8 by 10 inch prints per litre of working strength solution at each dilution, for MULTIGRADE, PQ Universal and BROMOPHEN; Storage — unopened packets of BROMOPHEN powder stored in cool and dry conditions at 5 to 20 degrees C will keep indefinitely, and once opened the stock solution should be prepared immediately; Developer capacities — per litre of working strength solution, 100 sheets of 20.3 x 25.4 cm (8 x 10 inch) RC paper or 50 of FB for MULTIGRADE at 1+9, 70 RC or 40 FB at 1+14, 70 RC or 45 FB for PQ UNIVERSAL at 1+9 and for BROMOPHEN at 1+3; the instruction that the volume made up must be enough to fill a dish or tray to a depth of about half full; and Working solution life, that working strength developer left in an open dish should not be kept for more than one working day

Used by:P29 Capstone Stage 4: The Silver Prints · P29 The Capstone Chemistry Report: From Photon Capture to Finished Print · Ascorbic acid · Dimezone S · Hydroquinone · Phenidone · 510-Pyro · Foma FOMATOL LQN developer · ILFORD BROMOPHEN developer · ILFORD MULTIGRADE developer · ILFORD PQ UNIVERSAL developer · ILFORD WASHAID · P3 Acids, Bases and pH · P3 Aerial Oxidation: Why Chemistry Dies in a Half-Empty Bottle · P3 Buffers and Buffer Capacity · P3 Diffusion, Swelling and the Journey Into the Emulsion · P3 Rates, Temperature and Catalysts · P4 Development as Amplification · P4 Darkroom Session: The Latent Image Made Visible · P6 Commissioning the Camera: Light-Tightness, Flare and the First Negatives · P7 Assignment: Panorama, Curved Plane and Multiple Pinholes · P7 Assignment: Portrait, Environmental Portrait and Self-Portrait · P7 Assignment: Still Life and Controlled Light · P8 Alkalis, Buffers and pH · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 Development Kinetics: Time, Temperature, Agitation and Exhaustion · P8 Assignment: Reading a Developer Formula · P8 Restrainers and Antifoggants · P8 Superadditivity: Why Two Agents Beat One · P9 Experiment: Comparing Developing Agents · P13 Paper Sensitometry: Reflection Density, Grades and ISO(R) · P16 Experiment: Commissioning the Enlarger · P16 Experiment: The Safelight Fog Test · P17 Break/Fix: The Timer That Lies · P18 Part XVIII Overview: Printing Chemistry · P18 Experiment: Maximum Black, Base White and Dry-Down · P18 Lab: Mixing and Comparing Print Developers · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · P18 Print Developer Chemistry and the Developer-Paper Pair · P18 Break/Fix: The Print That Will Not Go Black · P19 Contrast Filtration and Split-Grade Printing · P19 Developing the Print Consistently and Running a Printing Session · P28 Chemistry in the Bottle: Oxidation, Exhaustion, Precipitation and Contamination · P28 Print Faults: Weak Blacks, Mottle, Bronzing and the Rest · P28 Uneven Development, Bromide Drag and Surge Marks · Adjusting pH with a concentrated alkali · Setting up and shutting down the print processing line · Keeping the printing session log · Developer fog on paper · Grey highlights from developer exhaustion, as distinct from fog · Insufficient solution volume · Muddy print from a snatched development · Poor maximum black · Print mottle · Session exposure drift · Undissolved chemical · Uneven print development

ILFORD Powder Film Developers: PERCEPTOL, ID-11 and MICROPHEN, technical informationretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: The same August 2024 nine-page sheet reached by a second URL on ILFORD's own site: the mixing instruction, the 1+1 and 1+3 working solutions, and the pH and specific gravity table; Preparing stock developer solutions: dissolving in three-quarters of the volume and making up to the final volume; Preparing stock developer solutions: dissolving in three-quarters of the total volume and making up to the final volume; preparing 1+1 and 1+3 working solutions; Preparing stock developer solutions; pH and specific gravity table for PERCEPTOL, ID-11 and MICROPHEN; pH and specific gravity table for PERCEPTOL, ID-11 and MICROPHEN stock solutions, with the note that the figures were obtained under controlled laboratory conditions; pH and specific gravity of ID-11, PERCEPTOL and MICROPHEN stock solutions; pH and specific gravity table, and the note that the figures were obtained under controlled laboratory conditions and that users should make their own control measurements; Development times - the statement that the published times are for films rated at an appropriate exposure index for each developer and should produce negatives of normal contrast, typically around a Gbar of 0.62, and that they are only a guide to be adjusted for individual processing systems and preferences; Development times - the statement that the times are for films rated at an appropriate exposure index for each developer and should produce negatives of normal contrast, typically around a Gbar of 0.62; the development-time table itself, whose meter settings differ between developers for the same film, HP5 Plus being listed at EI 250/25 in PERCEPTOL stock against EI 400/27 in ID-11 stock, and DELTA 400 at EI 200/24 in PERCEPTOL against EI 400/27 in ID-11; the product descriptions of PERCEPTOL as an extra fine grain developer designed for use when a decrease in film speed is not important and of MICROPHEN as a fine grain developer giving an effective increase in film speed; Preparing stock developer solutions: dissolving in three-quarters of the total volume and making up to the final volume; Preparing stock developer solutions: dissolving the powders in about three-quarters of the total solution volume of warm water and adding cold water to make up to the final volume; The pH and specific gravity table, and the note that the published figures were obtained under controlled laboratory conditions and that users should make their own control measurements; Preparing stock developer solutions - dissolving in three-quarters of the total volume and making up to the final volume

Used by:ILFORD MICROPHEN developer · ILFORD PERCEPTOL developer · P2 Lab: Commissioning Your Laboratory · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P2 Measuring Mass, Volume, Temperature and Density, and Knowing How Wrong You Are · P3 Acids, Bases and pH · P3 Buffers and Buffer Capacity · P3 Lab: Measuring pH and Trusting the Number · P13 Gamma, Contrast Index and Average Gradient · P13 Assignment: Interpreting Density Data · Mixing a working solution from a stock · Mixing a solution to a final volume · Weighing a solid · pH meter reading a constant value · Solid added to a litre rather than made up to a litre

ILFORD RAPID FIXER, technical informationretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Silver concentration — below 2 g/L when fixing FB papers where a high level of image permanence is required, approximately 40 prints of 20.3 by 25.4 cm per litre, and below 0.5 g/L for prints needing maximum stability for long-term storage, approximately 10 such prints; the sodium sulphide testing solution, 2 g in 125 ml diluted 1+9, read against a reference spot on a print known to be well fixed and thoroughly washed; and the note that silver estimator papers are usually not sensitive enough to test the very low silver levels suitable for optimum permanence, so that for important prints the paper itself is tested; Film clearing time — fixing for twice the clearing time and discarding the bath when the clearing time in used fixer exceeds twice that in fresh; Capacity without replenishment, 24 films of 135-36 per litre at 1+4; and Silver concentration, 8 to 10 g/L tolerable in a film bath; Silver concentration — below 2 g/L when fixing FB papers where a high level of image permanence is required, approximately 40 prints of 20.3 by 25.4 cm per litre, and below 0.5 g/L for prints needing maximum stability for long-term storage, approximately 10 such prints; the statement that print throughput can only be a guide because it depends on the proportion of exposed to unexposed areas; and Two bath fixing; Film clearing time, fixing for twice the clearing time and discarding the bath when the clearing time in used fixer exceeds twice that in fresh; Silver concentration, below 2 g/L for fibre-base prints where a high level of image permanence is required, approximately forty 20.3 by 25.4 cm prints per litre, and below 0.5 g/L for prints needing maximum stability for long-term storage, approximately ten such prints; and the sodium sulphide testing solution, 2 g in 125 ml diluted 1+9, read against a reference spot on a print known to be well fixed and thoroughly washed; Mixing instructions; pH and specific gravity; fixing times and capacity; two bath fixing; film clearing time; silver concentration; silver recovery; The statement that the fixing agent is ammonium thiosulphate and that the product contains no sodium thiosulphate; the pH and specific gravity table; the capacity table and the residual-silver limits of 8 to 10 g/L for film, below 2 g/L for commercially permanent fibre prints and below 0.5 g/L for maximum stability; and the four keeping figures — quoted here only for the comparison of what one maker publishes about a rapid fixer against what another does; The pH and specific gravity table, giving SG 1.070 to 1.080 at 1+4 and 1.030 to 1.040 at 1+9, against HYPAM's 1.080 to 1.090 and 1.040 to 1.050; the fixing times, capacities, replenishment rates, working solution life and storage figures, which agree with HYPAM's throughout; and the statement that RAPID FIXER must not be used with fix hardeners; Checking and maintaining fixer activity — Stop Bath: the recommendation of ILFOSTOP with indicator dye or ILFOSTOP PRO without it, the statement that ILFOSTOP PRO is recommended for all machine processing applications, the yellow-to-purple description, the ILFORD Stop Bath table giving ILFOSTOP and ILFOSTOP PRO at 1+19 and 18 to 24 degrees C with 10 seconds at 20 degrees C and capacities of 15 against 22 films, 60 against 90 RC sheets and 30 against 45 FB sheets per litre, the minimum-time paragraph, and Adjusting fixer pH; The whole five-page sheet — the opening description as a non-hardening rapid fixer supplied as a liquid concentrate, the 18 to 40 degrees C working range, the prohibition on fix hardeners and the statement that the fixing agent is ammonium thiosulphate and that the product contains no sodium thiosulphate (hypo); mixing instructions, the warning that fixer concentrates do not readily mix with water, the order of addition and the ten-minute recirculation before a processor is used; the pH and specific gravity table, 5.0 to 5.5 at both dilutions with SG 1.070 to 1.080 at 1+4 and 1.030 to 1.040 at 1+9 at 20 degrees C, and the paragraph on pH sticks covering pH 4 to 6 and a hydrometer covering 1.000 to 1.200; the fixing time table for general purpose film, RC paper and FB paper at 1+4 and 1+9 with the film and paper agitation regimes; the capacity table per litre of working strength solution and the note that the paper figures may be exceeded where print stability is not critically important; the paragraph on what exhausts an unreplenished bath; the washing instructions for film, RC paper and FB paper and the WASHAID sequence; two-bath fixing; the replenishment table and rates, the machine RC range and the reduction available with silver recovery, and the deep-tank replenishment method; Checking and maintaining fixer activity — the stop bath recommendation, adjusting fixer pH with 50 per cent acetic acid and adjusting specific gravity; the film clearing time test and the discard rule; silver concentration limits for film, FB and RC papers and the sodium sulphide test with its reference tint; silver recovery, sulphiding, the hydrogen sulphide warning and the achievable silver levels; working solution life; storage; and availability and capacity; Washing FB paper — wash FB papers for 60 minutes in fresh running water at a temperature above 5 degrees C, and the paragraph stating that using ILFORD WASHAID reduces the washing time thus saving time and water, with prints washed 5 minutes in running water above 5 degrees C, drained of excess water, immersed 10 minutes in a dish/tray of 1+4 WASHAID at 18 to 24 degrees C and finally washed 5 minutes in running water above 5 degrees C; Washing RC paper, 2 minutes, or 30 seconds vigorously when a print is wanted in the shortest possible time; the average minimum fixing times table giving FB paper at 1+4 as 1 minute and at 1+9 as 2 minutes, and general purpose film at 1+4 as 2 to 5 minutes; the capacity table giving FB paper 40 sheets of 20.3 by 25.4 cm or 2 square metres per litre; Silver concentration — the level in a film fixing bath may be allowed to rise to 8 to 10 g/L without serious effect; below 2 g/L when fixing FB papers where a high level of image permanence is required for commercial use, approximately 40 prints of 20.3 by 25.4 cm per litre, above which compounds may remain in the paper base after washing and over time possibly contribute to print staining; below 0.5 g/L for prints needing maximum stability for long-term storage, approximately 10 such prints; 4 to 6 g/L tolerated for RC papers because the base is protected on both sides by an impervious polythene coating; the statement that print throughput can only be a guide because it depends on the proportion of exposed to unexposed areas; the statement that silver estimator papers are usually not sensitive enough to test the very low silver levels suitable for optimum permanence; and the sodium sulphide test on the paper itself, 2 g in 125 ml diluted 1+9 for use; The statement that the fixing agent is ammonium thiosulphate and that the product contains no sodium thiosulphate, that it is non-hardening and must not be used with fix hardeners; the dilutions of 1+4 and 1+9 with pH 5.0 to 5.5 and specific gravity 1.070 to 1.080 and 1.030 to 1.040 at 20 degrees C; the table of minimum fixing times at 20 degrees C, 2 to 5 minutes for general purpose film at 1+4 and half a minute to two minutes for papers; the capacities per litre of 24 films of 135-36, 80 sheets of 8 by 10 inch RC paper and 40 of FB paper; the clearing-time test and the silver limits of 8 to 10 g/L for film, below 2 g/L for commercially permanent fibre-base prints and below 0.5 g/L for maximum long-term stability; Silver concentration — the level in a film fixing bath may rise to 8 to 10 g/L without serious effect; below 2 g/L when fixing FB papers where a high level of image permanence is required for commercial use, approximately 40 prints of 20.3 by 25.4 cm per litre, above which compounds may remain in the paper base after washing and over time possibly contribute to print staining; and below 0.5 g/L for prints needing maximum stability for long-term storage, approximately 10 such prints; the statement that print throughput can only be a guide because it depends on the proportion of exposed to unexposed areas, and that silver estimator papers are usually not sensitive enough to test the very low silver levels suitable for optimum permanence, so that for important prints the paper itself is tested; the testing solution, prepared by dissolving 2 g of sodium sulphide in 125 ml of water, with the note to follow the health and safety information supplied by the sodium sulphide manufacturer, and diluted 1+9 with water for use; the reference procedure, a drop of the diluted solution on a white area of a print known to be well fixed and thoroughly washed by the two-bath method, excess removed with clean blotting paper or absorbent tissue, leaving a barely visible cream tint that is the reference colour for that type of paper; the reading, that any subsequent prints showing a yellowing of the test spot are not properly fixed; the remedy, soaking the prints in water for 5 minutes then repeating the recommended fixing and washing sequence in fresh fixer; and the two conditions, that prints must be well washed before using the test and that it is not effective on prints direct from the fixer bath; Dilutions 1+4 and 1+9 with their pH and specific gravity; Dilution, pH and specific gravity at 1+4 and 1+9; pH and specific gravity at 1+4; the instruction to correct a drifted pH with 50 per cent acetic acid; Working Solution Life and Storage: 6 months in full tightly capped bottles, 1 month in a half full one, and two years for full unopened concentrate at 5-20 degrees C; pH at 1+4; correcting a drifted pH with 50 per cent acetic acid; the clearing-time test and the capacity figures per litre; Opening description: the fixing agent is ammonium thiosulphate and it contains no sodium thiosulphate (hypo); Film clearing time: fix for twice the time the emulsion takes to clear, and discard the fixer when the clearing time in used fixer exceeds twice that in fresh; Silver concentration: up to 8-10 g/L in a film bath, below 2 g/L for fibre-base papers where high permanence is required (about 40 8x10 prints) and below 0.5 g/L for maximum stability (about 10 prints), with the warning that above those levels compounds may remain in the paper base after washing and over time possibly contribute to print staining; Two bath fixing; Adjusting specific gravity: efficiency is reduced and poor fixing experienced if the concentration is too high or too low; Washing films: after fixing, films are washed to remove the residual thiosulphate and other by-products of the process; pH at 1+4; correcting a drifted pH with 50 per cent acetic acid; An ammonium thiosulphate rapid fixer containing no sodium thiosulphate; dilution 1+4 for paper; the pH and specific gravity table; Fixing times: RC paper at 1+4, half a minute; Washing RC paper, 2 minutes in fresh running water above 5 degrees C; Capacity without replenishment; the note that RC papers can be processed in fixers containing 4 to 6 g/L of silver; Fixing times, RC paper at 1+4 for half a minute; Washing RC paper, 2 minutes in fresh running water above 5 degrees C; Film clearing time: the drop-on-a-scrap method, the instruction to fix for twice the clearing time, and the rule that fixer is discarded when the clearing time in used fixer exceeds twice the clearing time in fresh fixer; Fixing times, general purpose film at 1+4 for 2 to 5 minutes with the same agitation as development, against RC paper at 1+4 for half a minute; the statement that for all film fixing applications the fixer is diluted 1+4; Washing films, 5 to 10 minutes at within 5 degrees C of the process temperature, and the spiral-tank sequence of five, ten and twenty inversions; Capacity without replenishment; Silver concentration, 8 to 10 g/L tolerable in a film fixing bath; Dilution 1+4 and fixing time for RC paper; Dilution 1+4 and fixing times for RC paper and for film; Dilution 1+4 and fixing times for RC paper; Film clearing time and the instruction to fix for twice the clearing time; fixing times for general purpose film at 1+4; washing films; Film clearing time — the drop-on-a-scrap method, the instruction to fix for twice the clearing time, and the rule that the bath is discarded when the clearing time in used fixer exceeds twice that in fresh; Film clearing time and the instruction to fix for twice the clearing time; washing films, 5 to 10 minutes within 5 degrees C of the process temperature; Film clearing time — the drop-on-a-scrap method, the instruction to fix for twice the clearing time, and the rule that the bath is discarded when the clearing time in used fixer exceeds twice that in fresh; fixing times for general purpose film at 1+4; washing films, 5 to 10 minutes within 5 degrees C of the process temperature; Film clearing time and the instruction to fix for twice the clearing time; fixing times for general purpose film at 1+4; washing films, 5 to 10 minutes within 5 degrees C of the process temperature; The ILFORD stop bath table giving ILFOSTOP at 15 films, 60 RC and 30 FB sheets per litre and ILFOSTOP PRO at 22, 90 and 45 at the same 1+19 dilution; pH and specific gravity, 5.0 to 5.5 at 1+4 and at 1+9; the ILFORD stop bath table giving ILFOSTOP and ILFOSTOP PRO capacities at the same 1+19 dilution; the statement that where a stop bath cannot be included there should be no process problems provided fixer activity is monitored and adequate replenishment rates are used; Adjusting fixer pH; pH and specific gravity table, 5.0 to 5.5 at both 1+4 and 1+9; the ILFORD stop bath table giving ILFOSTOP and ILFOSTOP PRO capacities side by side; capacity without replenishment, which names solutions carried over from the preceding baths as a cause of dilution and of the pH being raised; Adjusting fixer pH, the instruction to add a few drops of 50 per cent acetic acid gradually and with thorough stirring if a stop bath is not used; The opening description — a non-hardening rapid fixer whose fixing agent is ammonium thiosulphate and which contains no sodium thiosulphate; dilution 1+4 for all film applications; fixing times of 2 to 5 minutes for general purpose film at 1+4; capacity per litre of 24 films of 135-36; Film clearing time, the instruction to fix for twice the time the emulsion takes to clear and to discard the bath when the clearing time in used fixer exceeds twice that in fresh; Silver concentration, 8 to 10 g/L in a film bath and below 2 g/L for fibre-base prints of commercial permanence; Film clearing time — the drop-on-a-scrap method, the instruction that film should remain in the fixer for twice the time the emulsion takes to clear, and the rule that fixer should be discarded when the clearing time in used fixer exceeds twice the clearing time in fresh; Fixing times, general purpose film 2 to 5 minutes at 1+4; Capacity without replenishment, 24 films of 135-36 per litre at 1+4, with the statement that an unreplenished bath is exhausted by the build-up of silver and halides and by carried-over solutions that dilute it and raise its pH; the pH and specific gravity table, pH 5.0 to 5.5 with SG 1.070 to 1.080 at 1+4; Adjusting specific gravity, the statement that if the concentration is too high or too low efficiency is reduced and poor fixing can be experienced; Silver concentration, 8 to 10 g/L tolerable in a film bath; Film clearing time — the drop-on-a-scrap method, fixing for twice the clearing time, and discarding the bath when the clearing time in used fixer exceeds twice that in fresh; Two bath fixing; Silver concentration — the sodium sulphide test for prints, 2 g in 125 ml diluted 1+9, with the instruction that any print showing a yellowing of the test spot is not properly fixed and should be soaked in water for 5 minutes and then given the recommended fixing and washing sequence again in fresh fixer; Capacity without replenishment; Capacity without replenishment — an unreplenished bath is eventually exhausted by the build-up of silver and halides in it and by solutions carried over from the preceding baths, which dilute it and raise its pH; the capacity table, 24 films of 135-36 per litre at 1+4, 80 sheets of 20.3 x 25.4 cm RC paper or 4 square metres, and 40 sheets of the same size on fibre base or 2 square metres, with the note that the paper figures may be exceeded whenever print stability is not critically important; Two bath fixing; Replenishment, 45 ml per 135-36 film and 855 ml/m2 for film, 250 ml/m2 for RC and 500 ml/m2 for FB paper; Film clearing time, fixing for twice the clearing time and discarding the bath when the clearing time in used fixer exceeds twice that in fresh; Silver concentration, 8 to 10 g/L tolerable in a film bath, below 2 g/L for fibre-base prints of commercial permanence which is about forty 8 by 10 inch prints, below 0.5 g/L for maximum long-term stability which is about ten, 4 to 6 g/L for RC paper because the base is protected on both sides by polythene, the statement that above the fibre-base level compounds may remain in the paper base after washing and over time possibly contribute to print staining, the note that silver estimator papers are usually not sensitive enough to test the very low silver levels suitable for optimum permanence, and the sodium sulphide test for prints, 2 g in 125 ml diluted 1+9, read against a reference spot on a known well-fixed print; Working solution life, 6 months in full tightly capped bottles, 2 months in a tank or dish with a floating lid, 1 month in a half-full bottle and 7 days in an open dish; The opening description — a non-hardening rapid fixer whose fixing agent is ammonium thiosulphate, containing no sodium thiosulphate, which must not be used with fix hardeners; the pH and specific gravity table giving pH 5.0 to 5.5 at both 1+4 and 1+9; fixing times and capacities per litre for film, RC and FB paper; Adjusting fixer pH, the instruction to add a few drops of 50 per cent acetic acid gradually with stirring if a stop bath is not used and the pH has risen; Fixing times, general purpose film 2 to 5 minutes at 1+4, RC paper half a minute at 1+4 and 1 minute at 1+9, FB paper 1 minute at 1+4 and 2 minutes at 1+9, and capacity 24 films of 135-36 per litre; Film clearing time — the drop-on-a-scrap method, the instruction to fix for twice the clearing time and to discard the bath when the clearing time in used fixer exceeds twice the fresh clearing time; pH and specific gravity, 5.0 to 5.5 with SG 1.070 to 1.080 at 1+4 and 1.030 to 1.040 at 1+9; Adjusting specific gravity, the statement that if the solution concentration is too high or too low efficiency is reduced and poor fixing can be experienced; Mixing instructions — fixer concentrates do not readily mix with water, so it is very important to stir thoroughly during mixing, the mixing vessel must be large enough, and the concentrate is poured into the vessel with the water added gradually while stirring; the recommendation that gloves, eye protection and an apron or overall are worn when handling and mixing all chemicals; dilution 1+4 for all film applications and 1+4 or 1+9 for manual paper fixing; the pH and specific gravity table, pH 5.0 to 5.5 at both dilutions with SG at 20 degrees C of 1.070 to 1.080 at 1+4 and 1.030 to 1.040 at 1+9; the statement that users should make their own control measurements from their own accurately mixed fresh solutions for later comparison, and that pH measurement sticks covering pH 4 to 6 are sufficient where a meter is not available; Film clearing time, the drop-on-a-scrap method; Working solution life; Silver concentration — the sodium sulphide test for prints, 2 g in 125 ml diluted 1+9 for use, read against a reference spot placed on a print known to be well fixed and thoroughly washed, with the note that silver estimator papers are usually not sensitive enough to test the very low silver levels suitable for optimum permanence; Film clearing time — the drop-on-a-scrap method and the instruction that the fixing time needed is double the clearing time; Silver concentration — the level in a film fixing bath may rise to 8 to 10 g/L without serious effect, but for a high level of image permanence in commercial use it should be kept below 2 g/L when fixing FB papers, approximating to 40 prints of 20.3 by 25.4 cm per litre, and for prints needing maximum stability for long-term storage it should not rise above 0.5 g/L, approximately 10 such prints; the statement that print throughput can only be a guide because it depends on the proportion of exposed to unexposed areas; the sodium sulphide test, 2 g in 125 ml diluted 1+9 for use, read against a reference spot on a print known to be well fixed and thoroughly washed, with the instruction that prints must be well washed before using the test and that it is not effective on prints direct from the fixer bath; Silver concentration — above 2 g/L compounds may remain in the paper base after washing and over time possibly contribute to print staining; the sodium sulphide test for prints and its reference spot; Silver concentration — the level of silver in a film fixing bath may be allowed to rise to 8 to 10 g/L without serious effect; for a high level of image permanence in commercial use the concentration should be kept below 2 g/L when fixing FB papers, approximating to 40 prints of 20.3 by 25.4 cm per litre, and for prints needing maximum stability for long-term storage it should not rise above 0.5 g/L, approximately 10 such prints; RC papers may be processed in fixers containing 4 to 6 g/L because the base is protected on both sides by polythene; Silver recovery — the recommendation of the electrolytic method for maximum efficiency because the treated fixer can be recycled or reused, the warning that too large a current causes sulphiding and that vigorous electrolysis may release hazardous hydrogen sulphide, concentrations of around 50 to 100 ppm commonly achieved by a properly set-up electrolytic system, and around 3 ppm after secondary and tertiary treatment by ion exchange and metal exchange; Capacity without replenishment, 24 films of 135-36 per litre at 1+4; Silver concentration — the level of silver in a film fixing bath may rise to 8 to 10 g/L without serious effect; Capacity without replenishment, 24 films of 135-36 per litre at 1+4; the pH and specific gravity table, pH 5.0 to 5.5 at 1+4; Silver recovery — the warning that vigorous electrolysis may lead to hazardous hydrogen sulphide gas being released, and that silver estimator papers are usually not sensitive enough to test the very low silver levels suitable for optimum permanence; Capacity without replenishment — an unreplenished bath is eventually exhausted by the build-up of silver and halides in it and by solutions carried over from the preceding baths; Silver concentration — above 2 g/L compounds may remain in the paper base after washing and over time possibly contribute to print staining; Silver concentration — the recommendation that paper be tested to ensure adequate fixing; prepare the testing solution by dissolving 2 g of sodium sulphide in 125 ml of water, take care to follow the health and safety information supplied by the sodium sulphide manufacturer, and for use dilute the testing solution 1+9 with water; to establish a permanent reference for a particular type of paper place a drop of the diluted testing solution on a white area of a print that is known to be well fixed and thoroughly washed using the two bath fixing method, remove any excess solution with clean blotting paper or absorbent tissue and a barely visible cream tint should be left, which is the reference colour for that type of paper; any subsequent prints that show a yellowing of the test spot are not properly fixed, and should be soaked in water for 5 minutes and then given the recommended fixing and washing sequence again in fresh fixer; prints must be well washed before using the test, which is not effective on prints direct from the fixer bath; the statement that silver estimator papers are usually not sensitive enough to test the very low silver levels suitable for optimum permanence; Film clearing time - the drop-on-a-scrap method, the instruction to fix for twice the clearing time, and the rule that the bath is discarded when the clearing time in used fixer exceeds twice that in fresh; fixing at 1+4 for general purpose film; Film clearing time - the drop-on-a-scrap method, the instruction to fix for twice the clearing time, and the rule that the bath is discarded when the clearing time in used fixer exceeds twice that in fresh; Dilution and fixing times for prints, and the capacity figures that govern how many sheets one working-strength bath will take; Silver concentration - the level to be kept below 2 g/L when fixing FB papers for a high level of image permanence, approximating to 40 prints of 20.3 by 25.4 cm per litre, and the statement that print throughput can only be a guide; Silver concentration - the level to be kept below 2 g/L when fixing FB papers for a high level of image permanence, approximating to 40 prints of 20.3 by 25.4 cm per litre, and below 0.5 g/L for prints needing maximum stability, approximately 10 such prints; the statement that print throughput can only be a guide; Capacity - the statement that the figures for paper may be exceeded whenever print stability is not critically important, cited here for what a published capacity figure is a claim about; Silver concentration - the recommendation that paper be tested to ensure adequate fixing, the testing solution of 2 g of sodium sulphide in 125 ml of water diluted 1+9 for use, the reference spot made on a white area of a print known to be well fixed and thoroughly washed by the two bath method and blotted to leave a barely visible cream tint, the statement that any subsequent print showing a yellowing of the test spot is not properly fixed and should be soaked in water for 5 minutes and given the recommended fixing and washing sequence again in fresh fixer, and the statement that prints must be well washed before using the test, which is not effective on prints direct from the fixer bath; Silver concentration - the level to be kept below 2 g/L when fixing fibre-base papers for a high level of image permanence, approximating to 40 prints of 20.3 by 25.4 cm per litre, with the statement that print throughput can only be a guide; The description of the product as a non-hardening rapid fixer whose fixing agent is ammonium thiosulphate, and the pH and specific gravity table giving pH 5.0 to 5.5 at both 1+4 and 1+9; The pH and specific gravity table, giving pH 5.0 to 5.5 at both 1+4 and 1+9, and the description of the product as a non-hardening rapid fixer whose fixing agent is ammonium thiosulphate; Film clearing time and the instruction to fix for twice the clearing time; fixing times for general purpose film at 1+4; Fixing times — the average minimum times at 20 degrees C with fresh fixer, 30 seconds for RC paper at 1+4, 1 minute for FB paper at 1+4 and 2 to 5 minutes for general purpose film at 1+4; capacities per litre of 80 sheets of 20.3 x 25.4 cm RC paper and 40 of FB; the two-bath fixing technique; and washing, 2 minutes for RC paper and 60 minutes for FB paper in fresh running water above 5 degrees C; Fixing times — the average minimum times at 20 degrees C with fresh fixer, 2 to 5 minutes for general purpose film at 1+4, half a minute for RC paper at 1+4 and 1 minute at 1+9, 1 minute for FB paper at 1+4 and 2 minutes at 1+9; Capacity per litre of working strength fixer — 24 films of 135-36 at 1+4, 80 sheets of 20.3 x 25.4 cm RC paper or 4 square metres, and 40 sheets of FB paper or 2 square metres, with the note that the paper figures may be exceeded whenever print stability is not critically important; Capacity without replenishment, the statement that an unreplenished bath is eventually exhausted by the build-up of silver and halides and by the action of solutions carried over from preceding baths, which can cause dilution and raise the pH; the two-bath fixing technique, fixing for half the recommended time in the first bath and the remainder in the second, discarding the first when its capacity is reached and promoting the second; and the washing recommendations, 2 minutes for RC paper and 60 minutes for FB paper in fresh running water above 5 degrees C, or 5 minutes wash, 10 minutes in WASHAID 1+4 and a 5 minute final wash; Fixing times — half a minute for RC paper at 1+4, 1 minute at 1+9, 1 minute for FB paper at 1+4 and 2 minutes at 1+9, against 2 to 5 minutes for general purpose film at 1+4; and capacities per litre of 80 sheets of 20.3 x 25.4 cm RC paper and 40 of FB paper, with the note that the paper figures may be exceeded whenever print stability is not critically important; Dilution and fixing times for film and for fibre-base and resin-coated paper; capacity without replenishment; silver concentration limits for print stability; Dilution and fixing times for fibre-base and resin-coated paper; capacity without replenishment; the 4 to 6 g/L silver figure for resin-coated paper; Film clearing time: the drop-on-a-scrap method, the instruction that film should remain in the fixer for twice the time the emulsion takes to clear, and the rule that the bath is discarded once the clearing time in used fixer exceeds twice the clearing time in fresh fixer; Fixing times, general purpose film at 1+4 for 2 to 5 minutes; Film clearing time: the drop-on-a-scrap method, the instruction to fix for twice the clearing time, and the rule that fixer is discarded when the clearing time in used fixer exceeds twice the clearing time in fresh; Fixing times, general purpose film at 1+4 for 2 to 5 minutes with the same agitation as development; Washing films, 5 to 10 minutes at within 5 degrees C of the process temperature, and the spiral-tank sequence of five, ten and twenty inversions; Paper fixing times at 1+4: one minute for fibre base and thirty seconds for resin-coated; Mixing instructions: fixer concentrates do not readily mix with water, so it is very important to stir thoroughly during mixing; dilution 1+4 for all film applications and 1+4 or 1+9 for manual paper processing; Paper fixing times at 1+4, and the silver concentration limits for prints of high and maximum permanence; Silver concentration: the level to be kept below 2 g/L when fixing FB papers for a high level of image permanence, approximating to 40 prints of 20.3 by 25.4 cm per litre, and below 0.5 g/L for prints needing maximum stability, approximately 10 such prints; the statement that print throughput can only be a guide; Silver concentration limits for fibre prints of high and maximum permanence, and the statement that print throughput can only be a guide; Silver concentration: prepare the testing solution by dissolving 2 g of sodium sulphide in 125 ml of water and for use dilute it 1+9; place a drop on a white area of a print known to be well fixed and thoroughly washed by the two bath method, remove excess with clean blotting paper, and a barely visible cream tint is the reference colour for that paper; any subsequent prints showing a yellowing of the test spot are not properly fixed and should be soaked in water for 5 minutes and given the recommended fixing and washing sequence again in fresh fixer; prints must be well washed before using the test, which is not effective on prints direct from the fixer bath; Paper fixing times at 1+4 and the silver concentration limits for prints of high and maximum permanence; Two bath fixing; Capacity without replenishment; Silver concentration, the level tolerable in a film fixing bath against the much lower levels for fibre-base prints of commercial permanence and for maximum long-term stability; Film clearing time and the discard rule; Film clearing time - the drop-on-a-scrap method, fixing for twice the clearing time, and discarding the bath when the clearing time in used fixer exceeds twice that in fresh; Capacity without replenishment; Silver concentration; Fixing times — half a minute for RC paper at 1+4 and 1 minute for FB paper at 1+4, which is the measure of how quickly a rapid fixer clears a paper emulsion when it has access to it; Capacity without replenishment — the statement that an unreplenished fixer bath is eventually exhausted by the build up of silver and halides in it and the action of solutions carried over from the preceding baths that can cause some dilution and the pH to be raised; and Adjusting fixer pH, the instruction to add a few drops of 50 per cent acetic acid gradually with stirring if a stop bath is not used and the pH has risen; The opening description — a liquid rapid fixer for black and white films and papers whose fixing agent is ammonium thiosulphate; and the fixing times, half a minute for RC paper at 1+4 and 1 minute for FB paper at 1+4, which is the measure of how quickly this chemistry acts on a paper emulsion; Fixing times — the average minimum times at 20 degrees C using fresh fixer: general purpose film 2 to 5 minutes at 1+4, RC paper half a minute at 1+4 and 1 minute at 1+9, FB paper 1 minute at 1+4 and 2 minutes at 1+9; and the note that a longer fixing time may be given automatically by some film processing machines and, provided it is not excessive, should not cause process problems; The composition and working life of the bath, and the instruction to rinse or use a stop bath before fixing; Recommended dilution, fixing times and capacity for prints, and the requirement for agitation; Silver concentration - above 2 g/L compounds may remain in the paper base after washing and over time possibly contribute to print staining; the sodium sulphide test for prints, 2 g in 125 ml diluted 1+9, with the instruction that any print showing a yellowing of the test spot is not properly fixed; Film clearing time - the drop-on-a-scrap method and fixing for twice the clearing time; Two bath fixing

Used by:P29 Capstone Stage 6: Permanence, Presentation and the Finished Portfolio · P29 Capstone Stage 3: Exposing, Processing and Measuring · P29 Capstone Stage 4: The Silver Prints · P29 The Pure Silver Portfolio: The Specification · Ammonium thiosulfate · Foma FOMAFIX · ILFORD HYPAM · ILFORD ILFOSTOP · ILFORD RAPID FIXER · ILFORD WASHAID · Iodide hypo check · Kodak F-52 · Kodak ST-1 · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P2 Measuring Mass, Volume, Temperature and Density, and Knowing How Wrong You Are · P3 Acids, Bases and pH · P3 Aerial Oxidation: Why Chemistry Dies in a Half-Empty Bottle · P3 Buffers and Buffer Capacity · P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve · P3 Diffusion, Swelling and the Journey Into the Emulsion · P3 Lab: Measuring pH and Trusting the Number · P4 Darkroom Session: The Latent Image Made Visible · P6 Commissioning the Camera: Light-Tightness, Flare and the First Negatives · P6 Curved Film Plane and Multiple-Pinhole Experiments · P6 Lab: Processing Your First Film · P7 Assignment: Architecture, Low Viewpoint and the Flat Plane · P7 Assignment: Landscape, Sky, Foreground and Filters · P7 Assignment: Night, the Very Long Exposure and Solargraphy · P7 Assignment: Panorama, Curved Plane and Multiple Pinholes · P7 Assignment: Portrait, Environmental Portrait and Self-Portrait · P7 Assignment: Still Life and Controlled Light · P7 Assignment: Time in the Frame, Moving Water, Clouds, People and Traffic · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Break/Fix: The Developer That Went Wrong · P9 Experiment: Comparing Developing Agents · P9 Lab: Preparing Standard Test Negatives · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P10 Experiment: Measuring Stop Bath Capacity · P10 Stop Bath Formulations and the Fixer Interaction · P10 Why Stopping Works · P11 Overview: Making the Image Permanent · P11 Experiment: Clearing Time and Fixer Capacity · P11 Break/Fix: The Exhausted Fixer · P11 Fixer Capacity, Exhaustion and Residual Silver · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline · P11 How Fixer Works · P11 Lab: Mixing Fixers from Scratch · P12 Overview: Permanence and Responsibility · P12 Assignment: Your Archival Processing Sequence · P12 Permanence and Image Deterioration · P12 Silver Recovery and the Responsible Darkroom · P12 Experiment: Small-Scale Metallic Replacement · P12 The Physics of Washing · P12 Lab: Testing for Residual Thiosulfate and Residual Silver · P13 Lab: A Step-Wedge Exposure Series · P14 Experiment: Process Control with Control Strips · P16 Experiment: Commissioning the Enlarger · P16 Experiment: The Safelight Fog Test · P18 Lab: Mixing and Comparing Print Developers · P18 Break/Fix: The Print That Will Not Go Black · P19 Developing the Print Consistently and Running a Printing Session · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P27 Experiment: Agitation, Stand and Semi-Stand Development · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Experiment: Four Curve Families, Measured · P27 Assignment: The Developer Comparison, Measured and Printed · P27 Experiment: The Development Time and Temperature Series · P28 Break/Fix: The Film That Came Back Wrong · P28 Fixer Faults, Washing Faults and the Stains They Leave · P28 Print Faults: Weak Blacks, Mottle, Bronzing and the Rest · Silver gelatin developing-out print on fibre base · Silver gelatin developing-out print on resin-coated base · Measuring a clearing time · Processing a film · Handling and storing a deliberately faulty reference specimen · Mixing a fixer · Setting up and shutting down the print processing line · Print processing: the archival sequence · Keeping the printing session log · Residual hypo and residual silver tests · Running a toning session · Running a two-bath fixing rotation · Exhausted fixer · Fingerprints on paper · Fixer contaminated by developer · Hypo spots on unexposed paper · Over-fixing · Oxidation stain · Round purple spots from air bubbles trapped in the fixer · Residual silver and yellow staining · Tong marks · Under-fixing

ILFORD SIMPLICITY film sachets: film developing solutions in sachets, technical informationretrieved 2026-09-07

Sections: Making up the solutions — the instruction that to minimise problems with cross contamination the solutions should be made in the order developer, then stop, then fixer, and that measuring cylinders and stirrers should be washed in between each make and after use

Used by:P28 Chemistry in the Bottle: Oxidation, Exhaustion, Precipitation and Contamination · Developer contaminated by fixer or stop

ILFOSOL 3: liquid concentrate developer for low volume black and white film processing, technical informationretrieved 2026-09-07

Sections: Storage — under cool conditions at 4 to 20 degrees C, ILFOSOL 3 developer concentrate keeps in good condition for 24 months in full tightly capped bottles and 4 months in half full tightly capped bottles; and Working solution life, that working strength solutions should not be kept for more than 24 hours and that fresh developer should be made up each time and discarded after the session

Used by:P28 Chemistry in the Bottle: Oxidation, Exhaustion, Precipitation and Contamination

Making your first black and white print, information sheetretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-08

Sections: The statement that ILFOSTOP and ILFORD RAPID FIXER can be made up and used for more than one printing and processing session; the process summary for MULTIGRADE IV RC DeLuxe giving ILFOSTOP at 1+19 for 10 seconds at about 20 degrees C, preferably no warmer than 24 degrees C and no cooler than 18 degrees C; the worked dilution of 30 mL of ILFOSTOP in 570 mL of water; The processing table — ILFORD MULTIGRADE developer diluted 1+9 for 1 minute at 20 degrees C; the worked dilution of 60 mL of concentrate into 540 mL of water, and the statement that it gives enough solution for about 40 8x10 inch MULTIGRADE RC prints; The statement that ILFOSTOP and ILFORD RAPID FIXER can be made up and used for more than one printing and processing session; the note that photographic chemicals are not hazardous when used correctly and the recommendation that gloves, eye protection and an apron or overall are worn when handling and mixing all chemicals; the process summary for MULTIGRADE IV RC DeLuxe giving RAPID FIXER at 1+4 for 30 seconds at about 20 degrees C; and the worked dilution of 120 mL of RAPID FIXER in 480 mL of water, with the statement that the three solutions so made give enough to process about 40 sheets of 20.3 by 25.4 cm MULTIGRADE RC paper; Equipment; the three-step process; Process summary for MULTIGRADE RC paper; the recommendation to wear gloves, eye protection and an apron; the warning that a trace of fixer or stop bath in the developer gives inconsistent results or blank prints; Exposing a test print - with the safelight on and the room lights off, put a sheet of MULTIGRADE paper into the easel shiny side up, and reseal the packet; and Paper negatives, which presses a washed and dried print face to face with a fresh sheet under a sheet of glass; Setting the aperture - turning the aperture ring from full aperture to f/8 to increase edge sharpness and give more even illumination, and aiming for an exposure of about ten seconds because shorter times are hard to time accurately and longer ones are tedious; Focusing your image - the lens at full aperture, an easel loaded with a spare piece of paper, and a focus finder placed in the centre of the image to focus on the negative grain; Setting the aperture - turning the aperture ring from full aperture to f/8 to increase edge sharpness and give more even illumination, counting the clicks so it can be done without looking, and aiming for an exposure of about ten seconds; Setting up your darkroom - the division of the room into a dry area for the enlarger and negative handling and a wet area for processing; Focusing your image - the lens at full aperture, an easel loaded with a spare piece of paper, and a focus finder placed in the centre of the image to focus on the negative grain; Setting the aperture - turning the aperture ring from full aperture to f/8 to increase edge sharpness and give more even illumination, counting the clicks so it can be done without looking, and aiming for an exposure of about ten seconds because shorter times are hard to time accurately and longer ones are tedious; Setting the aperture - turning the aperture ring from full aperture to f/8 to increase edge sharpness and give more even illumination; One dish per solution, each marked developer, stop or fix, with chemistry stored in matching coloured containers because a trace of fixer or stop bath in the developer leads to inconsistent results or completely blank prints; and a separate pair of tongs per dish; Exposing a test print, which builds a strip in exposures of 2, 4, 8 and 16 seconds and describes the result as four strips each one stop darker than the one next to it; Setting the aperture, which asks for a working aperture giving about 10 seconds because shorter times are hard to time accurately; and the introduction, which defines dodging and burning and states that print-making needs only a room that can be blacked out and no running water, because the washing stage takes place in daylight; The introduction, which describes dodging and burning as using your hands or pieces of card to hold back light from or give extra light to selected areas of your print so that you can emphasise key elements of the picture, and names as a further technique using different contrasts for different areas of the print; Setting the aperture, which asks for f/8 for edge sharpness and even illumination and for an aperture giving about 10 seconds because shorter times are hard to time accurately and longer ones are tedious; Mixing your chemicals, which states that 600 ml each of MULTIGRADE developer at 1+9, ILFOSTOP at 1+19 and RAPID FIXER at 1+4 is enough to process about forty 8 x 10 inch MULTIGRADE RC prints; and the introduction's statement that print-making needs just a room that can be blacked out and no running water; The chemicals you need, which instructs mixing only as much developer as fills the dish about half full and discarding the working solution at the end of the session; Setting up, which lays out three dishes labelled DEV, STOP and FIX, two pairs of print tongs and a clock, and mixes at about 23 C so that the baths settle at 20 C plus or minus 1 C; Mixing your chemicals, which makes 600 mL each of developer at 1+9, ILFOSTOP at 1+19 and ILFORD RAPID FIXER at 1+4 and states that this is enough to process about 40 8 by 10 inch MULTIGRADE RC prints; Developing a print, which slides the paper in quickly and smoothly with no air bubbles on the emulsion, rocks the dish continuously, lifts the sheet with tongs at 50 s and drains it; Stopbath, which transfers the print to the stop as one minute shows on the timer, warns against contaminating the developer tongs with the stop bath and uses the second pair of tongs, kept with the fixer, to move the print onward; and Fixing, which gives 30 s in fresh solution, warns against leaving prints in the fixer for minutes on end and directs that a print not being washed straight away is stored in a dish of clean water; Setting the aperture - the instruction to stop down to f/8 for edge sharpness and more even illumination, to choose an aperture giving an exposure of about 10 seconds because shorter times are hard to time accurately and longer ones tedious, and to use MULTIGRADE filter 2 because it produces a good range of print tones with an average negative; the introduction, which defines dodging and burning as using hands or pieces of card to hold back light from or give extra light to selected areas; Examining the test print - the instruction to rinse the test print and examine it under a bright light, the four strips at 2, 4, 8 and 16 seconds described as each one stop darker than the one next to it, and the instruction to note those times and the aperture for reference; Exposing a test print, which exposes the whole sheet for 2 seconds and then covers a quarter at a time for a further 2, 4 and 8 seconds; Examining the test print, which describes the result as four strips at 2, 4, 8 and 16 seconds, each one stop darker than the one next to it, instructs the reader to rinse the strip and examine it under a bright light, to note the times and the aperture for reference, and to open up by two stops if every band is too light or close down by one if every band is too dark; Setting the aperture, which asks for f/8 for edge sharpness and even illumination and for an aperture giving about 10 seconds because shorter times are hard to time accurately and longer ones are tedious; Mixing your chemicals, which states that 600 ml each of MULTIGRADE developer at 1+9, ILFOSTOP at 1+19 and RAPID FIXER at 1+4 is enough to process about forty 8 x 10 inch MULTIGRADE RC prints; Developing a print, which rocks the dish continuously backward and forward; and the introduction, which states that print-making needs just a room that can be blacked out and no running water; Setting the aperture - turning the ring from full aperture to f/8 to increase edge sharpness and give more even illumination, counting the clicks so it can be done without looking, which is the published basis for printing at a stopped-down working aperture rather than wide open; The tray sequence and its dishes; the two pairs of tongs with fixed jobs; solutions mixed at about 23 degrees C to settle at 20; the dish of clean water for prints not washed straight away; The warning that a trace of fixer or stop bath can contaminate the developer, leading to inconsistent results or, at worst, completely blank prints; the recommendation of differently coloured dishes for each solution, or dishes clearly marked developer, stop and fix, with chemicals stored in matching colour containers; Processing MULTIGRADE IV RC DeLuxe - MULTIGRADE developer diluted 1+9 for one minute at 20 degrees Celsius, or PQ Universal 1+9 for two minutes; the instruction to mix only as much developer as will half fill the dish and to discard it after the session; the warning that a trace of fixer or stop bath can contaminate the developer, leading to inconsistent results or at worst completely blank prints; The instruction to mix only as much developer as will half fill the dish and to pour the used solution away after the session; MULTIGRADE developer at 1+9 for one minute at 20 degrees Celsius on MULTIGRADE IV RC DeLuxe; Processing MULTIGRADE IV RC DeLuxe - MULTIGRADE developer at 1+9 for one minute at 20 degrees Celsius, or PQ Universal at 1+9 for two minutes, followed by ILFOSTOP for 10 seconds; the safelight set at least 1.2 metres from the developing dish; Focusing your image - with the lens at full aperture, a focus finder placed in the centre of the image to focus on the negative grain for the sharpest possible image; Setting the aperture - turn the aperture ring from full aperture to f8 to increase edge sharpness and give more even illumination, counting the clicks so it can be done without looking, and aiming for an exposure time of about ten seconds because shorter times are hard to time accurately and longer ones are tedious; Equipment - the digital thermometer with an LED display that gives a stabilised reading fifteen seconds after immersion in the developer, stop bath or fixer, listed among the recommended darkroom equipment; Exposing a test print - a sheet of MULTIGRADE paper goes into the easel shiny side up; and Paper negatives, which presses a washed and dried print face to face with a fresh sheet under a sheet of glass

Used by:ILFORD ILFOSTOP · ILFORD MULTIGRADE developer · ILFORD RAPID FIXER · P2 Laying Out the Laboratory: Wet Areas, Dry Areas and Contamination Control · P4 Darkroom Session: The Latent Image Made Visible · P16 Build: The Contact Printing Frame and Its Light Source · P16 Build: An LED Enlarger Head · P16 Experiment: Commissioning the Enlarger · P16 Enlarger Optics: Condenser, Diffusion, Lens, Alignment and Falloff · P16 Break/Fix: The Room That Fogs and the Light That Is Not Even · P16 Experiment: The Safelight Fog Test · P19 Part XIX Overview: Fine Printing · P19 Lab: Dodging, Burning, Edge Work and Local Contrast · P19 Developing the Print Consistently and Running a Printing Session · P19 Reading the Negative and Making the Work Print · P19 Lab: Test Strips, Base Exposure and the Print's Black Point · Enlarger alignment and uniformity check · Setting up and shutting down the print processing line · Control chart: contamination · Developer fog on paper · Grey highlights from developer exhaustion, as distinct from fog · Muddy print from a snatched development · Negative popping · Timer display fog · Uneven contact print from pressure, glass or source geometry

MULTIGRADE RC Papers, technical informationretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Processing — the development, stop, fix and wash sequence and times for resin-coated papers at 20 degrees C, which govern the commissioning sheets processed on this page; The recommendation that prints made for display are toned to protect them from oxidising gases, and the statement that selenium toner is recommended but that there may be some change in image colour depending on the dilution and the amount of toning applied; Processing summary — ILFORD BROMOPHEN at 1+3 for 2 minutes at 20 degrees C, with ILFOSTOP 1+19 for 10 seconds, ILFORD Rapid Fixer 1+4 for 30 seconds and a 2 minute wash; Processing summary — ILFORD MULTIGRADE at 1+9 for 1 minute and at 1+14 for 1 minute 30 seconds at 20 degrees C; Development — the image begins to appear after approximately 10 seconds, and prints developed for shorter times may be underdeveloped and lacking in contrast and density; Processing summary — ILFORD PQ UNIVERSAL at 1+9 for 2 minutes at 20 degrees C; Safelight recommendations; spectral sensitivity; ISO speed; storage; Processing: the image begins to appear after approximately 10 seconds with MULTIGRADE developer at 1+9, and the processing summary; Latent Image Stability: no significant change in picture quality over 24 hours between exposure and processing; Spectral sensitivity, given as a chart; safelight recommendations; ISO speed and ISO range tables; Processing summary: MULTIGRADE developer 1+9 for 1 minute at 20 degrees C, ILFOSTOP 1+19 for 10 seconds, ILFORD Rapid Fixer 1+4 for 30 seconds, wash 2 minutes; Safelight recommendations; Latent Image Stability; ISO speed and the note that paper speeds are roughly equivalent to a film ISO of 3 to 6; ISO Speed (P): an equivalent film ISO of approximately 3 to 6; Storage: store unused papers in a cool dry place in the original packaging; Processing summary: MULTIGRADE developer 1+9 for 1 minute at 20 degrees C, ILFOSTOP 1+19 for 10 seconds, ILFORD Rapid Fixer 1+4 for 30 seconds, wash 2 minutes in fresh running water above 5 degrees C; the warning against wet times longer than 15 minutes; Safelight recommendations, no more than 4 minutes of direct illumination at not less than 1.2 m; ISO Speed (P) and the note that MULTIGRADE RC papers have approximately an equivalent film ISO of 3 to 6; Latent Image Stability; Processing summary: MULTIGRADE developer 1+9 for 1 minute at 20 degrees C, ILFOSTOP 1+19 for 10 seconds, ILFORD Rapid Fixer 1+4 for 30 seconds, wash 2 minutes in fresh running water above 5 degrees C, and the warning against wet times longer than 15 minutes because prolonged immersion causes edge penetration and curl in resin-coated papers; ISO Speed (P), the note that MULTIGRADE RC papers have approximately an equivalent film ISO of 3 to 6; Safelight recommendations; ISO Speed (P): MULTIGRADE RC papers have approximately an equivalent film ISO of 3 to 6; Spectral Sensitivity; Spectral sensitivity, published as a chart without a wavelength scale; the paper as a blue-sensitive material; ISO Speed (P): the note that ISO paper speeds are not the same as film ISO speeds and that MULTIGRADE RC papers have approximately an equivalent film ISO of 3 to 6; Spectral Sensitivity; Safelight recommendations: no more than 4 minutes of direct illumination at not less than 1.2 m; ISO Speed (P) and the note that MULTIGRADE RC papers have approximately an equivalent film ISO of 3 to 6; Processing summary; ISO Speed (P), including the note that MULTIGRADE RC papers have approximately an equivalent film ISO of 3 to 6; ISO Range (R); ISO Speed (P) and the equivalent film ISO of 3 to 6; ISO Range (R); Spectral Sensitivity; Spectral Sensitivity; ISO Speed (P) and the equivalent film ISO of 3 to 6; Safelight recommendations; ISO Speed (P) and the equivalent film ISO of 3 to 6; ISO Range (R); Spectral Sensitivity; Storage; ISO Speed (P) and the equivalent film ISO of 3 to 6; ISO Range (R); the warning against wet times over 15 minutes for RC papers; ISO Speed (P), including the note that ISO paper speeds are not the same as film ISO speeds and that MULTIGRADE RC papers have approximately an equivalent film ISO of 3 to 6; ISO Range (R); Storage; ISO Speed (P), including the note that MULTIGRADE RC papers have approximately an equivalent film ISO of 3 to 6; Spectral Sensitivity; ISO Range (R); ISO Speed (P), including the equivalent film ISO of 3 to 6; Spectral Sensitivity; ISO Range (R); ISO Range (R), the table of range figures against filter grade including the unfiltered column; ISO Speed (P) and the note on an equivalent film ISO of 3 to 6; Exposing light sources, including LED exposing heads; Spectral Sensitivity; ISO Range (R), the unfiltered column; ISO Speed (P) and the equivalent film ISO of 3 to 6; ISO Range (R) - the table of range figures by filter for six Multigrade RC products, whose values run from 190 at the softest filtration down to 40 at the hardest; the instruction that these figures guide the choice of grade for a given effective negative density range; the worked example of an effective density range of 1.32 log exposure units multiplied by 100 to give 130 and the corresponding filter; and the note that the range meant is that of the image as projected on the enlarger baseboard; ISO Range (R) - the table of range figures by filter for six MULTIGRADE RC products; the instruction to take the effective negative density range, multiply it by 100 and choose the nearest range figure; the worked example of 1.32 log exposure units giving 130; and the note that the range meant is that of the image as projected on the enlarger baseboard; ISO Range (R) - the table of range figures by filter for six MULTIGRADE RC products, attributed on the sheet to ISO standard 6846-1992, with the instruction that they guide the choice of grade for a given effective negative density range, the worked example taking an effective density range of 1.32 log exposure units to the range figure of 130, and the note that the range meant is that of the image as projected on the enlarger baseboard; ISO Speed (P) - the table by filter and the note that ISO paper speeds are not the same as film ISO speeds and that MULTIGRADE RC papers have approximately an equivalent film ISO of 3 to 6; Contrast range - seven full grades in half-grade steps with the speed-matched filters; Characteristic Curves, plotted for four emulsions exposed through filters 00 to 5 and developed in MULTIGRADE developer at 1+9 for one minute at 20 degrees C; Processing summary and the note that prints developed for shorter times may be underdeveloped and lacking in contrast and density; Safelight, no more than four minutes of direct illumination at not less than 1.2 m; ISO Range (R) - the table of range figures by filter for MULTIGRADE RC papers, attributed on the sheet to ISO standard 6846-1992, with the instruction to multiply the effective negative density range by 100 and choose the nearest range figure, and the note that the range meant is that of the image as projected on the enlarger baseboard; ISO Speed (P) - the note that these papers are roughly equivalent to a film ISO of 3 to 6; Processing summary, intermittent agitation - ILFORD MULTIGRADE developer at 1+9 for 1 minute at 20 degrees C, at 1+14 for 1 minute 30 seconds, PQ Universal at 1+9 for 2 minutes and Bromophen at 1+3 for 2 minutes; the note that prints developed for shorter times may be underdeveloped and lacking in contrast and density; the recommendation of a stop bath; and the statement that a hardening fixer is not recommended because it reduces washing efficiency; ISO Range (R) - the table of range figures by filter grade running from 190 at the softest to 40 at the hardest, and the note that the range meant is that of the image as projected on the enlarger baseboard rather than as read from the negative on a light box; Storage - unused papers in a cool dry place in the original packaging, keeping in excellent condition for up to two years; ISO Range (R) - the table of range figures by filter grade, running from 190 at the softest filtration to 40 at the hardest, and the note that the range meant is that of the image as projected on the enlarger baseboard rather than as read from the negative on a light box; Storage - unused MULTIGRADE RC papers in a cool dry place in the original packaging, avoiding high temperature and high humidity, keeping in excellent condition for up to two years when stored as recommended; ISO Range (R) - the range figures by filter grade and the note that the range meant is that of the image as projected on the enlarger baseboard; Safelight recommendations - no more than 4 minutes of direct illumination at a minimum distance of 1.2 m; and the note that the papers are roughly equivalent to a film ISO of 3 to 6; Safelight recommendations - no more than 4 minutes of direct illumination at a minimum distance of 1.2 m; the ISO range figures for each filter grade; and the note that the papers are roughly equivalent to a film ISO of 3 to 6; ISO Range (R) - the table of range figures to ISO 6846:1992 for MULTIGRADE RC papers, in which MULTIGRADE RC DELUXE reads 160, 130, 110, 90, 70, 60 and 50 through filters 00 to 5 and 90 unfiltered; ISO Range (R) - the table of range figures to ISO 6846:1992, used here only to convert a rounding error into the fraction of a paper's scale it represents; ISO Range (R) - the table of range figures to ISO 6846:1992, in which MULTIGRADE RC DELUXE reads 160, 130, 110, 90, 70, 60 and 50 through filters 00 to 5 and 90 unfiltered; ISO paper speeds of 240 through filters 00 to 3 and 220 through 4 and 5; and the note that these papers are roughly equivalent to a film ISO of 3 to 6; ISO Range (R) - the table of range figures to ISO standard 6846:1992, in which MULTIGRADE RC DELUXE (NEW) reads 160, 130, 110, 90, 70, 60 and 50 through filters 00 to 5 and 90 unfiltered, with the worked example that a negative of effective density range 1.32 is multiplied by 100 and matched to the nearest figure; and ISO Speed (P), where the same paper reads 240 through filters 00 to 3, 220 through 4 and 5, and 500 unfiltered, with the note that paper speeds are not film speeds; Exposing light sources - designed for enlargers with tungsten or tungsten-halogen sources, also suitable for cold cathode sources and for LED exposing heads designed for variable contrast papers, while other cold cathode and pulsed xenon sources may give a reduced contrast range; ISO Range (R) - the table of range figures to ISO 6846:1992, in which MULTIGRADE RC DELUXE reads 90 through filter 2; ISO paper speeds of 240 through filters 00 to 3 and 220 through 4 and 5; Handling - no more than four minutes of direct safelight illumination at not less than 1.2 metres; Processing summary, giving a fix of 30 seconds and a wash of 2 minutes; and the note that prolonged immersion causes edge penetration and curl, so wet times longer than 15 minutes are to be avoided; Processing summary at 20 degrees C - MULTIGRADE developer 1+9 for 1 minute, ILFOSTOP 1+19 for 10 seconds, ILFORD Rapid Fixer 1+4 for 30 seconds, wash 2 minutes in fresh running water above 5 degrees C; Development - the image begins to appear after approximately 10 seconds and prints developed for shorter times may be underdeveloped and lacking in contrast and density; Drying - a final rinse in ILFOTOL at 1+200 aids even and rapid drying, prints dry in 10 to 20 minutes at room temperature, and resin-coated papers must not be glazed, ferrotyped or dried on a drum or flatbed glazer; ISO Speed (P) by filter; and the statement that prolonged immersion causes edge penetration and curl so wet times longer than 15 minutes are to be avoided; Processing summary at 20 degrees C - MULTIGRADE developer 1+9 for 1 minute, ILFOSTOP 1+19 for 10 seconds, ILFORD Rapid Fixer 1+4 for 30 seconds and a wash of 2 minutes in fresh running water above 5 degrees C; Development - the image begins to appear after approximately 10 seconds and prints developed for shorter times may be underdeveloped and lacking in contrast and density; Fixing - a hardening fixer is not recommended because it reduces washing efficiency, and there is no benefit in extending fixation, with image etching and a change of image colour named as the penalties; Drying - prints dry in 10 to 20 minutes at room temperature and must not be glazed or ferrotyped; Safelight recommendations - not more than 4 minutes of direct safelight at a minimum distance of 1.2 metres; ISO Range (R) and ISO Speed (P) tables by filter; and Storage - up to 2 years in the original packaging in cool dry conditions; The product table giving base tone and image tone for each product - neutral, cool/neutral, warm and cool; ISO Speed (P) by filter for six products with the note that ISO paper speeds are not the same as film ISO speeds and that MULTIGRADE RC papers have approximately an equivalent film ISO of 3 to 6; Latent Image Stability - no significant change in picture quality when papers are left for 24 hours after exposure before processing; Storage - up to two years when stored as recommended; Development - the statement that the image begins to appear after approximately 10 seconds with MULTIGRADE developer 1+9, and the note that prints developed for shorter times may be underdeveloped and lacking in contrast and density; Development - the statement that on correctly exposed prints with MULTIGRADE developer 1+9 the image begins to appear after approximately 10 seconds, and that prints developed for shorter times may be underdeveloped and lacking in contrast and density; Fixing - that a hardening fixer is not recommended because it reduces washing efficiency, that there is no benefit in extending fixation beyond the recommended time, that some loss of print quality might be seen from image etching with long fixing times, and that long fixing times will affect the image colour of the paper; Processing summary at 20 degrees C; Storage - a cool dry place in the original packaging, avoiding high temperature and high humidity, keeping in excellent condition for up to two years when stored as recommended; The product table giving base weights of 190 gsm coded M and 250 gsm coded K, base tone and image tone by product, and surface codes 1 glossy, 25 satin, 44 pearl, with the note that base weights are quoted excluding the polythene coating and emulsion and that about 70 gsm should be added for total weight; Processing summary - fix 30 seconds, wash 2 minutes; Washing - the statement that prolonged immersion can cause edge penetration and print curl and that wet times longer than 15 minutes are to be avoided; Drying - the note that RC papers should not be glazed or dried on a drum or flatbed glazer because the polyethylene can stick; Storage - up to two years; ISO Range (R) - the table of range figures by filter for six MULTIGRADE RC products including the unfiltered column, attributed to ISO standard 6846-1992, with the worked example converting an effective density range of 1.32 to the range figure 130; ISO Speed (P) - the table by filter; Contrast control - the note that the exposure time for filters 00 to 3.5 is typically the same and filters 4 to 5 require increased exposure; Exposing light sources - the statement that the papers suit tungsten and tungsten-halogen sources, cold cathode sources and LED exposing heads designed for variable contrast papers, and that other cold cathode and pulsed xenon sources may give a reduced contrast range; ISO Range (R) - the range table by filter for six MULTIGRADE RC products including the unfiltered column, attributed to ISO standard 6846-1992; ISO Speed (P) - the speed table by filter for the same six products, giving 240 at filters 00 to 3 and 220 at filters 4 and 5 for the current RC DELUXE and RC PORTFOLIO, 200 and 100 for MULTIGRADE IV RC DELUXE and RC COOLTONE, 100 and 50 for RC WARMTONE, and an unfiltered speed of 500 for all but RC WARMTONE, whose unfiltered speed is 200; Latent Image Stability - the statement that no significant change in picture quality will be seen when MULTIGRADE RC papers are left for a period of 24 hours after exposure and before processing; Latent Image Stability - the statement that no significant change in picture quality will be seen when MULTIGRADE RC papers are left for a period of 24 hours after exposure and before processing; Processing summary (intermittent agitation) - MULTIGRADE developer 1+9 for 1:00 at 20 C, ILFOSTOP 1+19 for 0:10, ILFORD Rapid Fixer 1+4 for 0:30, wash 2:00; and Drying, where a final rinse in ILFOTOL at 1+200 aids even and rapid drying and prints dry in 10 to 20 minutes at room temperature; Processing summary for dish or tray processing, giving MULTIGRADE developer at 1+9 for 1 min and at 1+14 for 1 min 30 s at 20 C, PQ UNIVERSAL at 1+9 and BROMOPHEN at 1+3 for 2 min, ILFOSTOP at 1+19 for 10 s, ILFORD RAPID FIXER or HYPAM at 1+4 for 30 s and a wash of 2 min; Development, where the image begins to appear after approximately 10 s and prints developed for shorter times may be underdeveloped and lacking in contrast and density; Fixing, where long fixing times will affect the image colour of the paper; Washing, where prolonged immersion can cause edge penetration and print curl so wet times longer than 15 min are to be avoided; the note that resin-coated papers should not be glazed or ferrotyped; and MACHINE PROCESSING, whose ILFORD 2000RT developer table gives development times including transfer of 46 s at 20 C, 32 s at 25 C, 22 s at 30 C, 15 s at 35 C and 12 s at 40 C, with a suggested developer replenishment rate of 150 to 250 mL per square metre of paper processed and a maximum paper throughput of 4 square metres per litre for a non-replenished fixer; ISO Range (R) - the range table for six MULTIGRADE RC products attributed to ISO standard 6846-1992; the statement that these figures guide the choice of grade for a given effective negative density range; the note that the range meant is that of the image as projected on the enlarger baseboard and that a photometer is the instrument for reading it; and the worked example taking an effective density range of 1.32 log exposure units to the nearest tabulated range figure of 130 and then to the corresponding MULTIGRADE filter for the paper type in use. ISO Speed (P) - the table by filter, with the note that paper speeds are not film speeds; Processing summary (intermittent agitation) - MULTIGRADE developer 1+9 for 1:00 at 20 C, 1+14 for 1:30, PQ UNIVERSAL 1+9 for 2:00, BROMOPHEN 1+3 for 2:00, ILFOSTOP 1+19 for 0:10 at 18 to 24 C, ILFORD Rapid Fixer 1+4 for 0:30 at 18 to 24 C, wash 2:00 in fresh running water above 5 C; Development, where the image begins to appear after approximately 10 seconds on a correctly exposed print and prints developed for shorter times may be underdeveloped and lacking in contrast and density; Washing, where a 30 second vigorous wash is offered when speed matters and wet times beyond 15 minutes are to be avoided because of edge penetration and curl; and Drying, where a final rinse in ILFOTOL at 1+200 aids even and rapid drying, prints dry in 10 to 20 minutes at room temperature, and these papers must not be glazed, ferrotyped or dried on a drum or flatbed glazer; Processing summary - washing in fresh running water above 5 degrees C for 2 minutes; Washing - the statement that when a print is needed in the shortest possible time the paper may be washed vigorously for 30 seconds in running water, and that prolonged immersion can cause edge penetration and print curl with resin coated papers so that wet times longer than 15 minutes are to be avoided; Drying - a final rinse in ILFOTOL at 1+200, a machine dryer for optimum quality, prints drying in 10 to 20 minutes at room temperature otherwise, and the NOTE that MULTIGRADE RC papers as with other resin coated papers should not be glazed or ferrotyped or dried on a drum or flatbed glazer because this can cause the polyethylene in the paper to stick to the glazing surface; Washing times and Hot air drying under machine processing - at least 15 seconds above 5 degrees C with the water flow set to fill the wash tank in 4 minutes or less, and drying air temperatures up to 85 degrees C / 185 degrees F; FINISHING - prints can be mounted using the standard techniques for resin coated papers; Processing summary, intermittent agitation - MULTIGRADE developer 1+9 for 1 minute at 20 degrees C, ILFOSTOP 1+19 for 10 seconds at 18 to 24 degrees C, ILFORD Rapid Fixer 1+4 for 30 seconds at 18 to 24 degrees C and a wash in fresh running water above 5 degrees C for 2 minutes; Development, that on a correctly exposed print in MULTIGRADE developer at 1+9 the image begins to appear after approximately 10 seconds and that prints developed for shorter times may be underdeveloped and lacking in contrast and density; Fixing, that a hardening fixer is not recommended because it reduces washing efficiency, that ILFORD Rapid Fixer and Hypam are non-hardening, and that there is no benefit in extending fixation because image etching and a change of image colour follow; Washing, that prolonged immersion in water can cause edge penetration and print curl with resin coated papers and that for this reason wet times longer than 15 minutes should be avoided; Drying, that a final rinse in ILFOTOL at 1+200 aids even and rapid drying, that prints left to dry at room temperature dry in 10 to 20 minutes, and that resin coated papers should not be glazed or ferrotyped; Finishing, that MULTIGRADE RC papers respond in the same way as other resin coated papers to the usual techniques of toning; and Prints, that prints made for display should be toned to protect them from the oxidising gases found in many environments, that selenium toner is recommended, and that other protection methods include sulphide toning; The paper range table, which lists MULTIGRADE RC DELUXE with a cool/neutral base tone and a cool/neutral image tone, MULTIGRADE RC WARMTONE at 190 g/m2 with a warm base tone and a warm image tone, and MULTIGRADE RC COOLTONE at 190 g/m2 with a cool base tone and a cool image tone, all in glossy and pearl surfaces; the Processing summary for intermittent agitation, ILFORD MULTIGRADE developer at 1+9 for 1 minute at 20 degrees C or 1+14 for 1 minute 30 seconds, ILFOSTOP at 1+19 for 10 seconds at 18 to 24 degrees C, ILFORD RAPID FIXER or HYPAM at 1+4 for 30 seconds at 18 to 24 degrees C and a wash in fresh running water above 5 degrees C for 2 minutes; Development, that on a correctly exposed print in MULTIGRADE developer at 1+9 the image begins to appear after approximately 10 seconds and that prints developed for shorter times may be underdeveloped and lacking in contrast and density; Fixing, that a hardening fixer is not recommended because it reduces washing efficiency, that ILFORD RAPID FIXER and HYPAM are non-hardening, and that there is no benefit in extending fixation because image etching and a change of image colour follow; Washing, that prolonged immersion in water can cause edge penetration and print curl with resin coated papers and that for this reason wet times longer than 15 minutes should be avoided; Drying, that a final rinse in ILFOTOL at 1+200 aids even and rapid drying and that prints left to dry at room temperature dry in 10 to 20 minutes; the exposure and filtration tables giving separate relative exposure figures for each paper at each MULTIGRADE filter grade; and Prints, that prints made for display should be toned to protect them from the oxidising gases found in many environments, that selenium toner is recommended and that there may be some change in image colour depending on the dilution and the amount of toning applied; The ISO Range table for the MULTIGRADE RC family, for the current MULTIGRADE RC DELUXE figures of R90 at filter 2, R70 at filter 3 and R160 at filter 00, used here only as the comparison the manifest asks for between a cyanotype's exposure scale and an enlarging paper's.; ISO Range (R) — the table of range figures by filter for six MULTIGRADE RC products, attributed on the sheet to ISO standard 6846-1992, reading 160, 130, 110, 90, 70, 60 and 50 at filters 00 to 5 for MULTIGRADE RC DELUXE, with the instruction that the figures guide the choice of grade for a given effective negative density range, the note that the range meant is that of the image as projected on the enlarger baseboard and that a photometer is the instrument for reading it, and the worked example taking an effective density range of 1.32 log exposure units to the range figure 130.; Latent Image Stability - the statement that no significant change in picture quality will be seen when MULTIGRADE RC papers are left for a period of 24 hours after exposure and before processing; ISO Range and filtration - the instruction to multiply the effective negative density range by 100 and choose the nearest range figure, and the published range figures for MULTIGRADE RC DELUXE of 160, 130, 110, 90, 70, 60 and 50 for filters 00 to 5, with 90 unfiltered; ISO Range and filtration - the instruction to multiply the effective negative density range by 100 and choose the nearest range figure, and the published range figures for MULTIGRADE RC DELUXE of 160, 130, 110, 90, 70, 60 and 50 for filters 00 to 5, with 90 unfiltered; and the development times and temperature range for the paper in ILFORD paper developers; Processing summary — MULTIGRADE developer 1+9 for 1 minute and ILFORD Rapid Fixer 1+4 for 30 seconds at 20 degrees C; Development — the image begins to appear after approximately 10 seconds and prints developed for shorter times may be underdeveloped and lacking in contrast and density; and Washing, 2 minutes in fresh running water above 5 degrees C; Development — the image begins to appear after approximately 10 seconds with MULTIGRADE developer 1+9, with the note that to ensure the best quality the development guidelines should be followed and that prints developed for shorter times may be underdeveloped and lacking in contrast and density; Processing summary — MULTIGRADE developer 1+9 for 1 minute and ILFORD Rapid Fixer 1+4 for 30 seconds at 20 degrees C; Fixing — the statement that there is no benefit in extending fixation beyond the recommended time, that some loss of print quality might be seen when long fixing times are given due to image etching, and that long fixing times will affect the image colour; Safelight recommendations — a minimum of 1.2 m between the paper and the safelight for direct lighting; Drying — the note that RC papers should not be glazed, ferrotyped or dried on a drum or flatbed glazer as this can cause the polyethylene in the paper to stick to the glazing surface, and that at room temperature prints dry in 10 to 20 minutes; and Machine processing, Hot air drying, temperatures up to 85 degrees C (185 degrees F); Drying — a final rinse in ILFOTOL diluted 1+200 aids even and rapid drying; at room temperature prints will dry in 10 to 20 minutes; and the note that MULTIGRADE RC papers, as with other resin-coated papers, should not be glazed or ferrotyped or dried on a drum or flatbed glazer, as this can cause the polyethylene in the paper to stick to the glazing surface; Machine processing, Hot air drying — use temperatures up to 85 degrees C (185 degrees F); Paper structure and finishes; processing times, including the four-minute wash and the warning against over-washing; The note that the papers are roughly equivalent to a film ISO of 3 to 6; Safelight recommendations — no more than 4 minutes of direct illumination at a minimum distance of 1.2 m; Storage - unused papers kept in a cool dry place in the original packaging, which is what makes one check comparable with the next; Safelight recommendations - no more than 4 minutes of direct illumination at a minimum distance of 1.2 m; Storage - unused papers in a cool dry place in the original packaging, avoiding high temperature and high humidity; Safelight recommendations - no more than 4 minutes of direct illumination at a minimum distance of 1.2 m; Storage - unused papers in a cool dry place in the original packaging; The instruction that resin-coated papers must not be glazed, ferrotyped or dried on a drum or flatbed glazer, and the 85 degree C ceiling for hot-air drying; Processing summary at 20 degrees C: developer 1+9 for 1 minute, ILFOSTOP 1+19 for 10 seconds, Rapid Fixer 1+4 for 30 seconds; the warning against prolonged immersion, edge penetration and wet times over 15 minutes; Processing summary at 20 degrees C: MULTIGRADE developer 1+9 for 1 minute, ILFOSTOP 1+19 for 10 seconds, ILFORD Rapid Fixer 1+4 for 30 seconds, wash 2 minutes; Processing summary at 20 degrees C, and the emergence of the image at approximately 10 seconds on a correctly exposed print at 1+9; ISO Speed (P) - the note that ISO paper speeds are not the same as film ISO speeds and that MULTIGRADE RC papers have approximately an equivalent film ISO of 3 to 6; Safelight recommendations; Processing summary at 20 degrees C, MULTIGRADE developer 1+9 for 1 minute, ILFOSTOP 1+19 for 10 seconds, ILFORD Rapid Fixer 1+4 for 30 seconds, wash 2 minutes; Storage - store unused MULTIGRADE RC papers in a cool, dry place in the original packaging, avoiding high temperature and high humidity; STORAGE - store unused MULTIGRADE RC papers in a cool, dry place in the original packaging, avoiding high temperature and high humidity; and the separate paragraph on print keeping, which is given for papers processed as recommended in that document; Processing summary at 20 degrees C, and the ISO(R) figures published for the filter range; Storage — store unused papers in a cool dry place in the original packaging, avoid conditions of high temperature and high humidity, and the statement that the papers will keep in excellent condition for up to 2 years when stored as recommended; Speed rating and the short-scale, high-contrast character of the paper; The resin-coated base and its handling; speed rating ISO 3 to 6 determined under a daylight illuminant; Spectral sensitivity, published as a chart without a wavelength scale, and the paper as a blue-sensitive material; Drying — a final rinse in ILFOTOL diluted 1+200 aids even and rapid drying, and at room temperature prints will dry in 10 to 20 minutes; and the Processing summary, MULTIGRADE developer 1+9 for 1 minute at 20 degrees C; Speed rating ISO 3 to 6 determined under a daylight illuminant, and the paper as a blue-sensitive material; Storage — store unused papers in a cool dry place in the original packaging and avoid conditions of high temperature and/or high humidity, with the statement that the papers will keep in excellent condition for up to 2 years when stored as recommended; Storage — store unused MULTIGRADE RC papers in a cool dry place in their original packaging, avoiding conditions of high temperature and high humidity, with the statement that they will keep in excellent condition for up to 2 years when stored as recommended; Fixing — the statement that there is no benefit in extending fixation beyond the recommended time, that some loss of print quality might be seen when long fixing times are given due to image etching, and that long fixing times will affect the image colour of the paper; Storage - unused MULTIGRADE RC papers in a cool dry place in the original packaging, avoiding high temperature and high humidity; two years in excellent condition when stored as recommended; the note that print life is shortened in adverse storage conditions or where the print is exposed to oxidising gases; Development — the image begins to appear after approximately 10 seconds with MULTIGRADE developer 1+9, with the note that prints developed for shorter times may be underdeveloped and lacking in contrast and density; Processing summary, MULTIGRADE developer 1+9 for 1 minute and Rapid Fixer 1+4 for 30 seconds at 20 degrees C; and Storage, that the papers keep in excellent condition for up to 2 years when stored cool and dry in the original packaging; Drying — a final rinse in ILFOTOL diluted 1+200 aids even and rapid drying, optimum quality results are obtained with a machine dryer suitable for RC papers, at room temperature prints dry in 10 to 20 minutes, and the note that MULTIGRADE RC papers, as with other resin-coated papers, should not be glazed or ferrotyped or dried on a drum or flatbed glazer as this can cause the polyethylene in the paper to stick to the glazing surface; and Machine processing, Hot air drying, use temperatures up to 85 degrees C (185 degrees F); Storage - unused MULTIGRADE RC papers stored in a cool dry place in the original packaging, with high temperature and high humidity avoided; two years of excellent condition when stored as recommended; Handling recommendation for MULTIGRADE RC - no more than four minutes of direct safelight illumination at not less than 1.2 metres; Handling - no more than four minutes of direct safelight illumination at not less than 1.2 metres, and the storage recommendation of a cool dry place in the original packaging; MULTIGRADE RC construction and processing - the resin-coated base, recommended fixing and washing times for RC papers, and the note that RC papers wash quickly because the base does not absorb solutions; Washing - that prolonged immersion in water can cause edge penetration and print curl with resin-coated papers and that for this reason wet times longer than 15 minutes should be avoided; Safelight recommendations — for direct lighting, a minimum of 1.2 m between the paper and the safelight; and Storage, that the papers keep in excellent condition for up to 2 years when stored cool and dry in the original packaging, avoiding high temperature and humidity

Used by:P29 Capstone Stage 1: The Instrument, Its Calculation and Its Commissioning · HARMAN SELENIUM TONER · ILFORD BROMOPHEN developer · ILFORD MULTIGRADE developer · ILFORD PQ UNIVERSAL developer · P1 Experiment: The Image That Would Not Stay · P4 Development as Amplification · P4 Reciprocity Failure and the Life of the Latent Image · P4 Spectral Sensitivity and Colour Response · P4 Darkroom Session: The Latent Image Made Visible · P6 Build the Modular Pinhole Camera · P6 Commissioning the Camera: Light-Tightness, Flare and the First Negatives · P6 Curved Film Plane and Multiple-Pinhole Experiments · P6 Designing the Modular Camera · P6 Diffraction and the Optimum Pinhole · P6 Pinhole Exposure and Reciprocity Correction · P6 Break/Fix: Unexpectedly Soft Images and Wrong Reciprocity Corrections · P7 Part VII Overview: The Art of Pinhole Photography · P7 Assignment: Architecture, Low Viewpoint and the Flat Plane · P7 Assignment: Landscape, Sky, Foreground and Filters · P7 Assignment: Night, the Very Long Exposure and Solargraphy · P7 Assignment: Panorama, Curved Plane and Multiple Pinholes · P7 Pinhole Portfolio Review and the Exposure Record as Data · P7 Assignment: Portrait, Environmental Portrait and Self-Portrait · P7 Seeing Like a Pinhole: The Image, Its Makers and Previsualisation · P7 Assignment: Still Life and Controlled Light · P7 Assignment: Time in the Frame, Moving Water, Clouds, People and Traffic · P13 Gamma, Contrast Index and Average Gradient · P13 Assignment: Interpreting Density Data · P13 Paper Sensitometry: Reflection Density, Grades and ISO(R) · P13 Tone Reproduction: From Subject to Print · P14 Experiment: Process Control with Control Strips · P14 Sensitometer Design Principles · P15 Assignment: Characterising a Film and Developer with Your Own Instruments · P16 Experiment: Commissioning the Enlarger · P16 Enlarger Optics: Condenser, Diffusion, Lens, Alignment and Falloff · P16 Break/Fix: The Room That Fogs and the Light That Is Not Even · P16 Build: Making a Room Dark and Proving It · P16 Safelight: Spectra, Distance, Duration and the Fog Limit · P16 Experiment: The Safelight Fog Test · P17 Part XVII Overview: Build the Pure Silver Timer · P17 Build: The Timer Firmware · P17 Experiment: Calibrating the Timer · P17 F-Stop Timing and the Mathematics of Print Exposure · P17 Switching Lamps Safely: Isolation, Certified Modules and the Mains Boundary · P17 Break/Fix: The Timer That Lies · P18 Part XVIII Overview: Printing Chemistry · P18 Experiment: Maximum Black, Base White and Dry-Down · P18 Lab: Mixing and Comparing Print Developers · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · P18 Print Developer Chemistry and the Developer-Paper Pair · P18 Break/Fix: The Print That Will Not Go Black · P18 The Structure of a Printing Paper: Base, Baryta, Emulsion and Supercoat · P18 Variable-Contrast Papers: Three Emulsions, One Sheet · P19 Contrast Filtration and Split-Grade Printing · P19 Lab: Dodging, Burning, Edge Work and Local Contrast · P19 Developing the Print Consistently and Running a Printing Session · P19 Reading the Negative and Making the Work Print · P19 Lab: Test Strips, Base Exposure and the Print's Black Point · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Experiment: Selenium Toning and the Print Curve · P21 Experiment: The Exposure Scale, Maximum Density and Contrast of a Cyanotype · P21 What These Processes Need: The Negative, the Paper and the Light · P27 Designing an Experiment That Yields a Number · P27 Push and Pull Processing: What Extended Development Can and Cannot Buy · P27 Assignment: The Developer Comparison, Measured and Printed · P28 Break/Fix: The Film That Came Back Wrong · P28 Print Faults: Weak Blacks, Mottle, Bronzing and the Rest · P28 The Emulsion Under Stress: Reticulation, Scratches, Pinholes and Drying Marks · Silver gelatin developing-out print on resin-coated base · The blackout leak test · Darkroom opening and closing for a printing session · Enlarger alignment and uniformity check · Opening and handling photographic paper in dim light · Loading paper and sheet film into a pinhole back · Mounting a print and putting it in an enclosure · Setting up and shutting down the print processing line · Print processing: the archival sequence · Keeping the printing session log · Recording a daylight exposure · Testing a safelight · Solargraph camera placement and retrieval · Storing unfixed prints for later fixing · Calibrating the darkroom timer · Age fog · Blocked highlights · Buckled-sheet softness · Diffraction glow from an undersized hole · Double image from a reflective plate · Dry-down error · Edge leak · Flare veil · Heat fog · Hot spot · Hypo spots on unexposed paper · Light-leak fog · Motion smear · Over-fixing · Paper storage fog · Poor maximum black · RC blisters · Room light leak, with a direction · Safelight-fogged control strip · Seam leak · Shutter leak · Timer display fog · Toner penetration at the edges of an RC print · Weak or grey blacks

ORTHO Plus Technical Informationretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: The blue and green sensitivity and handling in deep red safelight; The statement that blue and green sensitivity enables the film to be handled in deep red safelight, with the 906 filter, a 15 W bulb and a distance of not less than 1.2 m; Choosing the best ILFORD developer for the job — the Pictorial Contrast time table, whose PERCEPTOL stock row gives 13:00 to a G-bar of 0.62 and 16:00 to a G-bar of 0.70 at 20 degrees C, where the powder sheet's ORTHO PLUS row leaves all three PERCEPTOL columns blank; Development times — the Intermediate Contrast band, PQ Universal at 1+9 and 20 degrees C giving 4 minutes for Gbar 0.80 and 12 minutes for Gbar 1.00, and the note that dish or tray development with continuous agitation should be 15 per cent shorter; Base and anti-halation properties for 35 mm, 120 and sheet film; Making long exposures: the graph and the formula Ta = Tm to the power 1.25; Blue and green sensitivity, handling in deep red safelight, reds appearing much darker than normal; spectral sensitivity given as a wedge spectrogram to tungsten light at 2850 K; filter factors in daylight and tungsten; Technical information: the blue and green sensitivity allowing the film to be handled in deep red safelight, with the 906 filter, a 15 W bulb and not less than 1.2 m; Technical information: the statement that blue and green sensitivity enables the film to be handled in deep red safelight, with the ILFORD 906 filter, a 15 W bulb and not less than 1.2 m; the filter factor table giving separate daylight and tungsten columns for yellow, deep yellow, tricolour blue and tricolour green; Handling under deep red safelight with the 906 filter, a 15 W bulb and not less than 1.2 m; The statement that the film has no red sensitivity so reds appear much darker than normal, offered as a usable effect rather than a defect; Introduction and spectral sensitivity: the statement that the film has no red sensitivity, so reds appear much darker than normal, offered as a usable effect; The statement that blue and green sensitivity allows handling under a deep red safelight; the ILFORD 906 deep red safelight recommendation with a 15 W bulb at not less than 1.2 m; Exposure rating - the two figures for one film developed to normal contrast in ILFORD ID-11, ISO 80/20 degrees to daylight sources and ISO 40/17 degrees to tungsten sources, with the note that 135 cassettes are DX coded for ISO 80 and that a manual setting of 40 or a one-stop correction should be used for tungsten; Choosing the best ILFORD developer for the job - a development-time table indexed by target contrast, with the statement that Gbar 0.62 to 0.70 would be considered normal for in-camera use, and further tables at Gbar 0.80 to 1.00 and above for other work; Exposure rating - ISO 80/20 to daylight and ISO 40/17 to tungsten; the statement that blue and green sensitivity allows handling under a deep red safelight, with the ILFORD 906 filter and a 15 W bulb at not less than 1.2 m; Safelight recommendations - either total darkness or an ILFORD 906 dark red safelight with a 15 W bulb at not less than 1.2 m; and the statement that blue and green sensitivity allows the film to be handled in deep red safelight; Safelight recommendations - either total darkness or an ILFORD 906 dark red safelight with a 15 W bulb at not less than 1.2 m, and the statement that blue and green sensitivity allows the film to be handled in deep red safelight while reds appear much darker than normal; Safelight recommendations — either total darkness or an ILFORD 906 dark red safelight with a 15 W bulb at not less than 1.2 m

Used by:Erythrosin · Erythrosin sensitising stock · ILFORD PERCEPTOL developer · ILFORD PQ UNIVERSAL developer · P4 Grain, Speed and Resolution · P4 Reciprocity Failure and the Life of the Latent Image · P4 Spectral Sensitivity and Colour Response · P5 Build an Emulsion Coating Station · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P5 Washing, Digestion and Sensitisation · P7 Assignment: Landscape, Sky, Foreground and Filters · P7 Assignment: Portrait, Environmental Portrait and Self-Portrait · P9 Lab: Preparing Standard Test Negatives · P13 Film Speed and Exposure Index · P13 Gamma, Contrast Index and Average Gradient · P13 Lab: A Step-Wedge Exposure Series · P16 Build: Making a Room Dark and Proving It · P16 Safelight: Spectra, Distance, Duration and the Fog Limit · The blackout leak test

PAN F Plus Technical Informationretrieved 2026-09-05, 2026-09-06

Sections: Choosing the best ILFORD developer for the job, which carries no Maximum film speed row at all; The speed rating of ISO 50/18 measured in ID-11; Choosing the best ILFORD developer for the job, the Finest grain row; the development-time table, PERCEPTOL rows at stock, 1+1 and 1+3; Exposure rating - a speed rating of ISO 50/18 degrees given as 50ASA, 18DIN, EI 50/18 degrees, measured in ILFORD ID-11 at 20 degrees C with intermittent agitation in a spiral tank

Used by:ILFORD MICROPHEN developer · ILFORD PERCEPTOL developer · P13 Film Speed and Exposure Index

PERCEPTOL, ID-11 and MICROPHEN film developers (ILFORD technical information)retrieved 2026-09-03, 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: The pH and specific gravity table for fresh stock solutions measured under controlled laboratory conditions, ID-11 given as pH 8.60 to 8.70 with a specific gravity of 1.090, together with the advice that users make their own control measurements rather than relying on the published figures; pH and specific gravity of fresh stock solutions; pH and specific gravity — ID-11 stock at pH 8.60 to 8.70 with a specific gravity of 1.090 at 20 degrees C, quoted here only for the comparison with a paper developer's alkalinity; The MICROPHEN product description and its speed, grain and low-alkalinity claims; Mixing instructions and Preparing stock developer; Preparing working strength developer solutions; pH and specific gravity; Manual processing, spiral tanks; Dish (tray) processing, sheet film only; Deep tank processing and manual agitation; Rotary tube processors; Development times, ILFORD and Kentmere films; Stop, fix, wash and rinse; Reusing developer without replenishment; Working solution life; Storage; Availability; The PERCEPTOL product description and its extra-fine-grain, high-resolution-lens and film-speed statements; Mixing instructions and Preparing stock developer; Preparing working strength developer solutions; pH and specific gravity; Manual processing, spiral tanks; Dish (tray) processing, sheet film only; Deep tank processing and manual agitation; Rotary tube processors; Development times, ILFORD and Kentmere films; Stop, fix, wash and rinse; Reusing developer without replenishment; Working solution life; Storage; Availability; The pH and specific gravity table for ID-11, PERCEPTOL and MICROPHEN at stock, 1+1 and 1+3; the two-part powder mixing instruction at about 40 degrees C; films per litre; The pH and specific gravity table: ID-11 stock at pH 8.60 to 8.70; Reusing developer without replenishment - the films-per-litre table and the N, N+10%, N+20%, N+30%, N+40%, N+90% time-compensation schedule; The pH and specific gravity table for ID-11, MICROPHEN and PERCEPTOL stock solutions; pH and specific gravity of fresh stock solutions; Working Solution Life: 6 months full, 1 month half full, 4 months in a deep tank with a floating lid, 1 month in a deep tank without one, and 24 hours at 1+1 or 1+3; Storage: unopened powder keeps indefinitely at 4-20 degrees C and stock is prepared immediately once a packet is opened; Manual processing, spiral tanks: four inversions during the first 10 seconds of development and of each subsequent minute, with the tank tapped afterwards to dislodge air bubbles, and all process solutions adjusted to within 1 degree C of the temperature in use; Dish processing: continuous agitation reduces the recommended development times by about 15 per cent; Machine processing: the same 15 per cent reduction for rotary tube processors, and the recommendation against a pre-rinse because it can lead to uneven development; Development Times: the instruction to increase the given development times by 10 per cent for each 1 degree C drop in temperature and decrease them by 10 per cent for each 1 degree C rise, with the worked example of 6 minutes at 20 degrees C becoming 4.5 minutes at 23 and 9 minutes at 16; the statement that the times target a Gbar of about 0.62; the times for DELTA 100 Professional at EI 100 in ID-11 at stock, 1+1 and 1+3; Dish processing: continuous agitation reduces the recommended development times by about 15 per cent; Manual processing: recommended temperature 20 degrees C, usable range 20 to 24 degrees C, all process solutions within 1 degree C of the temperature being used, and the four-inversions-in-ten-seconds agitation cycle repeated each minute; Preparing working strength developer solutions and the one-shot instruction for 1+1 and 1+3; the spiral-tank agitation cycle; the statement that continuous agitation in a dish reduces development times by about 15 per cent; pH and specific gravity of fresh stock solutions; development times for ILFORD and Kentmere films at 20 degrees C targeting a Gbar of about 0.62; the descriptions of PERCEPTOL, ID-11 and MICROPHEN and the note that the low alkalinity of MICROPHEN reduces grain size and grain clumping; the instruction that users make their own control measurements from their own accurately mixed fresh solutions; pH and specific gravity of fresh stock solutions; mixing instructions for the two-bag powders; the description of MICROPHEN and its low alkalinity; Development times and the instruction to change them by 10 per cent per degree C; the spiral-tank agitation cycle of four inversions in the first ten seconds of each minute; the statement that continuous agitation in a dish reduces times by about 15 per cent and that rotary processing needs the same reduction; the Gbar target of about 0.62; reusing developer without replenishment, the films-per-litre figures and the 10 per cent per film schedule; working solution life; and the passage on one-shot processing; Mixing instructions — the instruction to make up the stock solution to the volume stated on the pack and not to prepare smaller quantities from fractional parts of each powder, dissolving part A in about three quarters of the volume of warm water at about 40 degrees C and then adding part B; the pH and specific gravity table giving ID-11 stock at pH 8.60 to 8.70 and specific gravity 1.090, with the advice that users make their own control measurements; the instruction to draw off mains water and let it stand because it is highly aerated; The descriptions of PERCEPTOL, ID-11 and MICROPHEN, including the attribution of MICROPHEN's grain behaviour to the low alkalinity of the developer and the claimed speed increase of up to half a stop; the pH and specific gravity table for all three at stock, 1+1 and 1+3; the two-part powder mixing instructions at about 40 degrees C; working solution life and the films-per-litre figures; Reusing developer without replenishment: the statement that each film processed releases halides and other by-products that act as a restrainer on subsequent films, the films-per-litre figures, and the tables of 10 per cent time increases per film and per batch; The description of PERCEPTOL as an extra fine grain developer for use when a decrease in film speed is not important, and of ID-11 as a fine grain developer without loss of emulsion speed; the pH and specific gravity table for stock, 1+1 and 1+3; pH and specific gravity of fresh stock solutions; the description of PERCEPTOL as an extra fine grain developer for use when a decrease in film speed is not important; The descriptions of PERCEPTOL, ID-11 and MICROPHEN, the speed increase claimed for MICROPHEN and the attribution of its grain behaviour to low alkalinity; the pH and specific gravity table; working solution life; the films-per-litre figures for reuse without replenishment; The pH and specific gravity table for fresh stock solutions, giving ID-11 at 8.60 to 8.70, and the advice that users make their own control measurements; The statement that each film processed releases halides and other by-products into the developer that act as a restrainer on the development of subsequent films; the reuse table giving a 10 per cent time increase for each successive film in 1 litre of stock, to a maximum of ten films at plus 90 per cent, and the note that 250 to 300 ml is used for one film; working solution life, six months in a full capped container and one month half full; the pH and specific gravity table for ID-11 stock, pH 8.60 to 8.70 and SG 1.090; The pH and specific gravity table for fresh stock solutions, ID-11 at 8.60 to 8.70, and the advice that users make their own control measurements from their own accurately mixed fresh solutions for later comparison; the statement that by-products released by each film act as a restrainer on subsequent films; MICROPHEN described as a fine grain developer giving an effective increase in film speed, with its grain behaviour attributed to low alkalinity; the mixing instruction to dissolve part A in about three quarters of the volume of warm water at about 40 degrees C and the note that a few undissolved grains are normal; the pH and specific gravity table, ID-11 stock at 8.60 to 8.70 and MICROPHEN stock at 8.67 to 8.93; the spiral-tank agitation recommendation; The description of PERCEPTOL as an extra fine grain developer designed for use when a decrease in film speed is not important; the spiral-tank agitation recommendation of four inversions in the first ten seconds and again in the first ten seconds of each subsequent minute; the pH and specific gravity table for stock, 1+1 and 1+3; the instruction that 1+1 and 1+3 solutions are prepared directly before use, are not reused and are not kept more than 24 hours; the reuse table giving a 10 per cent time increase per successive film and 250 to 300 ml of solution for one film; The pH and specific gravity table — ID-11 stock solution published at pH 8.60 to 8.70; the instruction that users make their own control measurements from their own accurately mixed fresh solutions; Reusing developer without replenishment - ten 135/36 films per litre of stock ID-11, the statement that each film released halides and other by-products that act as a restrainer on the development of subsequent films, and the table of ten per cent time increases per successive film; Working solution life - six months in full capped containers, one month in a half full tightly capped container, four months in a deep tank with a floating lid and one month without; the statement that reusing developer lowers image quality slightly and increases the risk of contamination and precipitates; and the recommendation of one-shot processing where image quality, reliability and consistency matter more than economy, with the instruction never to reuse the 1+1 and 1+3 dilutions; The pH and specific gravity table for fresh stock solutions, ID-11 at pH 8.60 to 8.70, and the advice that users make their own control measurements from their own accurately mixed fresh solutions for later comparison; the statement that by-products released by each film act as a restrainer on subsequent films; The table of pH and specific gravity for fresh stock solutions measured under controlled laboratory conditions, ID-11 given as pH 8.60 to 8.70, together with the advice that users make their own control measurements rather than relying on the published figures; Manual processing, spiral tanks - the agitation scheme of four inversions during the first 10 seconds repeated during the first 10 seconds of each subsequent minute, with the tank tapped afterwards to dislodge air bubbles, and the instruction to drain the developer 10 seconds before the end of the development time; the statement that dish processing with continuous agitation reduces the recommended times by about 15 per cent; the warning that very short development times with some films may lead to uneven processing; the instruction that all process solutions be within 1 degree C of the temperature being used; the stated usable range of 20 to 24 degrees C; the statement that the published times should produce negatives of normal contrast, typically around a Gbar of 0.62, and are only a guide; the instruction that 1+1 and 1+3 dilutions are prepared directly before use, are not reused and are not kept more than 24 hours; and the reuse figures of 10 films per litre of ID-11 stock with a 10 per cent time increase per successive film and 250 to 300 mL of solution for one film; The table of pH and specific gravity for fresh stock solutions measured under controlled laboratory conditions, ID-11 given as pH 8.60 to 8.70, with the advice that users make their own control measurements from their own accurately mixed fresh solutions; and the statement that PERCEPTOL, ID-11 and MICROPHEN diluted 1+1 or 1+3 should not be kept for more than 24 hours; Reusing developer without replenishment - the statement that each film or batch released halides and other by-products into the developer that act as a restrainer on the development of subsequent films, that a tally must be kept, and the requirement that used developer be poured back into the stock bottle and mixed with the unused part before the next film; the table of stock films per litre giving PERCEPTOL 4, ID-11 10 and MICROPHEN 10; the ladder of 10 per cent time increases per successive film, reaching N+90 per cent at the tenth; the deep-tank tables for 5, 13.5 and 25 litres; the statement that reusing developer lowers image quality slightly, increases the risk of physical damage and of precipitates and suspended emulsion particles, and that there is a risk of miscounting; the recommendation of one-shot processing where image quality, reliability and consistency matter more than economy; the statements that diluted 1+1 and 1+3 developers are not recommended for reuse and that push processing in reused developers is not recommended; the working solution life of 6 months in full capped containers, 1 month in a half full tightly capped container, 4 months in a deep tank with a floating lid and 1 month without one, with 1+1 and 1+3 dilutions not to be kept more than 24 hours; the ILFOSTOP capacity of 15 films of 135-36 per litre at 1+19 and the RAPID and HYPAM fixer capacity of 24 at 1+4; and the pH table for fresh stock solutions with its advice that users make their own control measurements; The product descriptions - PERCEPTOL as an extra fine grain developer designed for use when very fine grain negatives are required and a decrease in film speed is not important; ID-11 as a fine grain developer for general film processing where fine grain negatives are required without loss of emulsion speed; and MICROPHEN as a fine grain developer which gives an effective increase in film speed, with the statement that a speed increase of up to half a stop can be achieved with most films but that with faster films such as HP5 Plus, Delta 400 Professional and Delta 3200 Professional it is more, that many developers giving a speed increase produce a corresponding increase in grain size while MICROPHEN is formulated to overcome that disadvantage through its low alkalinity, and that MICROPHEN is particularly useful when using extended development times to push process fast films. Also the statement that push processing using reused developers is not recommended; Development Times - the statement that the published times should produce negatives of normal contrast, typically around a Gbar of 0.62, and that they are only a guide; the instruction to increase the times by 10 per cent for each 1 degree C drop and decrease them by 10 per cent for each 1 degree C rise, with the worked example that 6 minutes at 20 degrees C becomes 4.5 minutes at 23 and 9 minutes at 16; the stated usable temperature range of 20 to 24 degrees C for these three developers; the instruction that all process solutions be within 1 degree C of the temperature being used; the spiral-tank agitation scheme of four inversions in the first 10 seconds repeated each minute, with the tank tapped afterwards to dislodge air bubbles; the instruction to drain the developer 10 seconds before the end of the development time; the note that dish processing with continuous agitation reduces the times by about 15 per cent; and the table of pH for fresh stock solutions with the advice that users make their own control measurements; Working solution life — PERCEPTOL, ID-11 and MICROPHEN stock solutions last up to 6 months in full capped containers, 1 month in a half full tightly capped container, 4 months in a deep tank with a floating lid and 1 month in a deep tank without one, while the same developers diluted 1+1 or 1+3 should not be kept for more than 24 hours; Preparing stock developer — part A dissolved in about three-quarters of the total volume of warm water at about 40 degrees C, stirred until most of it has dissolved, part B added gradually while stirring, cold water added to the final volume, and the note that it is normal for a few grains of powder to remain undissolved and that discoloured or darker particles in the white powders are normal; the advice that because most water drawn from pressure mains is highly aerated, users should draw off the water they need and leave it to stand for a few minutes before making up developers; the pH and specific gravity table for fresh stock solutions, giving PERCEPTOL 7.68 to 7.82, ID-11 8.60 to 8.70 and MICROPHEN 8.67 to 8.93, with the advice that users make their own control measurements from their own accurately mixed fresh solutions for later comparison; and the account of reusing stock solutions, that as the developer oxidises with reuse and storage the risk of contamination increases, precipitates may be formed and tiny particles of emulsion from previously processed films may be held in suspension, so that one-shot processing is recommended when image quality, reliability and consistency matter more than economy, and diluted 1+1 and 1+3 solutions should not be reused at all; and Storage, that unopened powder packets in cool dry conditions at 4 to 20 degrees C keep indefinitely and that once opened stock solutions should be prepared immediately; Working solution life — six months in a full capped container, one month half full, and the statement that PERCEPTOL, ID-11 and MICROPHEN diluted 1+1 or 1+3 should not be kept for more than 24 hours; the advice that users make their own control measurements from their own accurately mixed fresh solutions for later comparison; Mixing instructions: the instruction to make up the stock solution to the volume stated on the pack and not to prepare smaller quantities from part of a pack; ID-11 stock keeping - six months in a full capped container, one month in a half-full one, four months in a deep tank with a floating lid and one month without; capacity of ten 135/36 films per litre with a 10 per cent development time increase for each successive film; the statement that each film processed releases halides and other by-products that act as a restrainer on subsequent films; the caveat that the compensation can only be an approximation; the withdrawal of the 2.5 litre ID-11 Replenisher pack in September 2012; The three-quantity control chart - speed as LD, contrast as HD minus LD, and minimum density Dmin; The three-quantity film process control system - speed as LD, contrast as HD minus LD, and minimum density Dmin - each carried on a control chart with action and control lines; Capacity and the instruction that each film processed releases halides and other by-products into the developer that act as a restrainer on the development of subsequent films, with 10 per cent more time for each successive film in a litre to a maximum of ten films at plus 90 per cent; ID-11 keeping properties - six months in a full capped container against one month in a half-full one; the ten films per litre capacity with a 10 per cent time increase for each successive film, and the statement that each film processed releases halides and other by-products that act as a restrainer on subsequent films; Preparing stock developer — part A dissolved in about three-quarters of the total volume of warm water at about 40 degrees C, part B added gradually while stirring, cold water added to the final volume, with the note that it is normal for a few grains of powder to remain undissolved and that discoloured or darker particles in the white powders are perfectly normal and will not affect the final development; and the account of reusing stock solutions, that as the developer oxidises with reuse and storage precipitates may be formed and tiny particles of emulsion from previously processed films may be held in suspension; The three-quantity control chart - speed as LD, contrast as HD minus LD, and minimum density Dmin, each with action and control lines; Preparing stock developer — the instruction to dissolve part A in about three-quarters of the total solution volume of warm water at about 40 degrees C, stirring until most of the part A powder has dissolved, then to continue stirring while gradually adding part B, keeping stirring until no more powder dissolves, then adding cold water to the final volume and allowing to cool to 20 degrees C; the note that it is normal for a few grains of powder to remain un-dissolved; the note that discoloured or darker particles in the white powders are perfectly normal and will not affect the final development; the instruction always to make up the stock to the volume stated on the pack and not to prepare smaller quantities using fractional parts of each powder; and the advice that because most mains water is highly aerated, users should draw off the water they need and let it stand for a few minutes before making up developers

Used by:P29 Capstone Stage 2: Formulating and Documenting Your Chemistry · Borax (sodium tetraborate decahydrate) · ILFORD BROMOPHEN developer · ILFORD MICROPHEN developer · ILFORD PERCEPTOL developer · Kodak D-76 · Kodak D-76d · Kodak D-76R · KODAK PROFESSIONAL XTOL Developer · P3 Aerial Oxidation: Why Chemistry Dies in a Half-Empty Bottle · P3 Diffusion, Swelling and the Journey Into the Emulsion · P3 Rates, Temperature and Catalysts · P8 Overview: What a Developer Is · P8 Acutance, Adjacency Effects and Compensating Development · P8 Alkalis, Buffers and pH · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 Development Kinetics: Time, Temperature, Agitation and Exhaustion · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P8 Assignment: Reading a Developer Formula · P8 Restrainers and Antifoggants · P8 Solvent Action, Physical Development and Grain · P8 Sulfite: Preservative, Buffer, Silver Solvent · P8 Superadditivity: Why Two Agents Beat One · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Break/Fix: The Developer That Went Wrong · P9 Assignment: The Developer Laboratory Report · P9 Experiment: Comparing Developing Agents · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P10 Experiment: Measuring Stop Bath Capacity · P14 Experiment: Process Control with Control Strips · P15 Assignment: Characterising a Film and Developer with Your Own Instruments · P27 Part XXVII Overview: From Observation to Measurement · P27 Experiment: Agitation, Stand and Semi-Stand Development · P27 Designing an Experiment That Yields a Number · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Push and Pull Processing: What Extended Development Can and Cannot Buy · P27 Experiment: The Development Time and Temperature Series · P28 Chemistry in the Bottle: Oxidation, Exhaustion, Precipitation and Contamination · Versioning a formula · Mixing a developer from raw chemicals · Control chart: developer exhaustion · Control chart: temperature error · Elevated fog on a curve · Exhausted developer · Low contrast index · Precipitate in a stock solution · Safelight-fogged control strip · Undissolved chemical

Processing your first black and white film, information leafletretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: The chemicals paragraph — ILFOSTOP brings development to an end and prolongs the life of the fixer, the solution must completely cover the processing spiral, and after processing it can be stored and used again; the process summary giving ILFOSTOP at 1+19 for 10 seconds at about 20 degrees C, preferably no warmer than 25 degrees C and no cooler than 15 degrees C; the worked dilution of 15 mL of ILFOSTOP plus 285 mL of water; step 12, pour in the stop bath at 20 degrees C, agitate by turning the tank upside down twice, pour it out after 10 seconds, and the statement that the time is not critical but must be at least 10 seconds; The chemicals paragraph — ILFORD RAPID FIXER makes the developed image permanent, the solution must completely cover the processing spiral, it works quickly and after processing it can be stored and used again; the process summary giving RAPID FIXER at 1+4 for 3 minutes at about 20 degrees C; the worked dilution of 60 mL of RAPID FIXER plus 240 mL of water for a one-reel tank; step 12, pour in the fixer at 20 degrees C, start the clock as you finish pouring, agitate as during development until fixation is complete, and the statement that the time is not critical provided it is over 3 minutes, then pour the fixer into a storage bottle; Using chemicals; Using chemicals; the equipment you need; Process summary and step-by-step, October 2003 leaflet with a March 2017 revision date: ILFOTEC DD-X 1+4 for 12 minutes at 20 degrees C for DELTA 100 Professional; ILFOSTOP 1+19 for 10 seconds at about 20 degrees C, preferably no warmer than 25 and no cooler than 15; ILFORD RAPID FIXER 1+4 for 3 minutes; wash in running water for 5 to 10 minutes or in ten changes of water each lasting one minute; the instruction that the two later steps should be within 5 degrees C of the developer temperature; the mixing volumes 60 ml of DD-X into 240 ml of water, 15 ml of ILFOSTOP into 285 ml, 60 ml of fixer into 240 ml; the water-bath instruction; the agitation scheme of four inversions in the first 10 seconds and four again at the start of every further minute with the tank tapped to dislodge bubbles; starting to pour the developer out 15 seconds before the mark; ILFOTOL at 5 ml per litre in the final rinse; squeegee, weighted clip, still dust-free air, hair dryer on low kept moving 30 cm away; the recommended development times table at 20 degrees C for 35 mm films; the practice-loading instruction and the requirement that the spiral be completely dry; the five-minute darkroom light-tightness check; the different-coloured beakers and the warning that a trace of fixer can contaminate the developer; and the description of a correctly exposed and processed negative; Process summary and step-by-step — the agitation scheme of four inversions in the first ten seconds and four again at the start of every further minute with the tank tapped to dislodge bubbles; the instruction that the later steps are within 5 degrees C of the developer temperature; the wash of 5 to 10 minutes running or ten changes of one minute; the wetting agent in the final rinse; and the warning that a trace of fixer in the developer gives inconsistent results or blank film; Examining the negative — the statement that a correctly exposed and processed negative has a full range of tones, with some parts almost clear like the rebates and other parts so dense you can only just read print through them; Examining the negative — a correctly exposed and processed negative has a full range of tones, with some parts almost clear like the rebates and other parts so dense you can only just read print through them; Process summary — wash in running water for 5 to 10 minutes, or in ten changes of 20 degrees C water each lasting one minute; the statement that temperature is not as critical during washing but should be within 5 degrees C of the developer temperature; The instruction to use different-coloured beakers for each solution, and the warning that a trace of fixer can contaminate the developer; the agitation scheme of four inversions in the first ten seconds and four again at the start of every further minute with the tank tapped to dislodge bubbles; The five-minute darkroom light-tightness check before loading; the instruction that the spiral be completely dry; the practice-loading instruction; and the warning that a trace of fixer can contaminate the developer; Step 17, Examining the negative — the film edges (rebates) should be clear, with legible frame numbers along the bottom, and a correctly exposed and processed negative should have a full range of tones with some parts almost clear like the rebates and other parts so dense you can only just read print through them; step 10, Agitation, and the instruction to tap the tank on the bench at each inversion to dislodge air bubbles; Using chemicals — the advice to buy plastic beakers or bottles in different colours so that a different colour can be used for each solution, with the statement that even a trace of fixer can contaminate the developer and possibly ruin your next film; Step 17, Examining the negative — the film edges (rebates) should be clear with legible frame numbers along the bottom, and a correctly exposed and processed negative should have a full range of tones; step 10, Agitation, four inversions in the first 10 seconds of each minute with the tank tapped on the bench at each inversion to dislodge air bubbles; and the working volumes for one 35 mm film; Step 17, Examining the negative — the film edges (rebates) should be clear, with legible frame numbers along the bottom, and a correctly exposed and processed negative should have a full range of tones, with some parts almost clear like the rebates and other parts so dense you can only just read print through them; Step 10, Agitation — turn the tank upside down four times during the first 10 seconds and again for 10 seconds at the start of every further minute, and each time you invert the tank tap it on the bench to dislodge any air bubbles which may have formed on the film; step 6, the working volumes for one 35 mm film, 60 mL of ILFOTEC DD-X and 240 mL of water for the developer, 15 mL of ILFOSTOP and 285 mL of water for the stop bath, and 60 mL of ILFORD RAPID FIXER and 240 mL of water for the fixer; Process summary and step-by-step: the water bath a couple of degrees warmer than the working temperature; the instruction that the later solutions be within 5 degrees C of the developer; the agitation scheme of four inversions in the first 10 seconds and four again at the start of every further minute with the tank tapped to dislodge bubbles; starting to pour the developer out 15 seconds before the mark; ILFOSTOP 1+19 for 10 seconds; wash in running water for 5 to 10 minutes or in ten changes of water each lasting one minute; ILFOTOL at 5 ml per litre in the final rinse; squeegee, weighted clip, still dust-free air; the practice-loading instruction and the requirement that the spiral be completely dry; the five-minute darkroom light-tightness check; Using chemicals: labelling containers and not using soft-drink bottles; The practice-loading instruction and the requirement that the spiral be completely dry; and the five-minute darkroom light-tightness check; Using chemicals: labelling containers clearly, and not storing chemicals in soft-drink bottles; Step 10, Agitation — turn the tank upside down four times during the first 10 seconds and again for 10 seconds at the start of every further minute, and each time you invert the tank tap it on the bench to dislodge any air bubbles which may have formed on the film; Examining the negative - a correctly exposed and processed negative has a full range of tones, with some parts almost clear like the rebates and other parts so dense you can only just read print through them; Loading the development tank — the instruction to wind the film all the way onto the spiral and give a few extra turns before putting the spiral into the tank and screwing on the lid; Step 17, Examining the negative — the film edges (rebates) should be clear, and a correctly exposed and processed negative should have a full range of tones, with some parts almost clear like the rebates and other parts so dense you can only just read print through them; Step 15, Squeegee — hang the film and slowly unwind it from the spiral, then carefully run squeegee tongs or a clean piece of chamois cloth down the length of the film to remove excess water, with the warning to take care as any grit caught up here will scratch the whole film; Using chemicals — the advice to use a different coloured vessel for each solution, with the statement that even a trace of fixer can contaminate the developer; and step 17, Examining the negative, the instruction to handle negatives by the edges only; Examining the negative - the full range of tones a correctly exposed and processed negative shows; Step 17, Examining the negative — the rebates should be clear with legible frame numbers along the bottom, and a correctly exposed and processed negative should have a full range of tones; Step 6 — the working volumes for one 35 mm film, 60 mL of ILFOTEC DD-X and 240 mL of water for the developer, 15 mL of ILFOSTOP and 285 mL of water for the stop bath, and 60 mL of ILFORD RAPID FIXER and 240 mL of water for the fixer, that is 300 mL of each; Step 10, Agitation — the instruction to tap the tank on the bench at each inversion to dislodge any air bubbles which may have formed on the film; and step 16, Drying, in a still dust-free atmosphere; Loading the development tank — the instruction to continue winding the film all the way on to the spiral and to give a few extra turns, with the spiral then placed in the tank; and the working volumes for one 35 mm film, 300 mL of solution in a spiral tank; Using chemicals — the advice to use a different coloured vessel for each solution, with the statement that even a trace of fixer can contaminate the developer; and step 15, Squeegee, the instruction to run squeegee tongs or a clean chamois down the film with care because any grit caught up will scratch it; Using chemicals - labelling containers clearly and not storing chemicals in soft-drink bottles

Used by:ILFORD ILFOSTOP · ILFORD RAPID FIXER · P2 Storage, Incompatibilities and Secondary Containment · P2 Laying Out the Laboratory: Wet Areas, Dry Areas and Contamination Control · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P6 Lab: Processing Your First Film · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P9 Break/Fix: The Developer That Went Wrong · P11 Break/Fix: The Exhausted Fixer · P12 The Physics of Washing · P14 Experiment: Process Control with Control Strips · P14 Build: The Enclosure and Exposure Stage · P28 Part XXVIII Overview: Diagnosis as a Discipline · P28 Chemistry in the Bottle: Oxidation, Exhaustion, Precipitation and Contamination · P28 Break/Fix: The Film That Came Back Wrong · P28 Reading the Negative as Evidence: Thin, Dense, Flat and Contrasty · P28 Uneven Development, Bromide Drag and Surge Marks · Processing a film · Labelling a container · Loading paper and sheet film into a pinhole back · A container found unlabelled, or a solution of unknown age · Air bells · Blocked highlights · Cinch and pressure marks · Dense negative · Developer contaminated by fixer or stop · Empty shadows · Emulsion-side scratches · Fingerprints on paper · Flat negative · Frame-to-frame density variation · Hypo spots on unexposed paper · Insufficient solution volume · Pinholes · Reel and contact marks · Thin negative · Tong marks · Unlabelled or undated container

Product Withdrawal: ILFORD ID-11 Replenisherretrieved 2026-09-03, 2026-09-04, 2026-09-05, 2026-09-07

Sections: The September 2012 notice discontinuing the 2.5 litre ID-11 Replenisher pack and the three alternatives it offers; Product withdrawal notice, September 2012: the alternatives offered, including compensating for developer exhaustion by increasing development time, and the improvised replenisher made from two part A sachets and one part B; The one-page notice of September 2012 discontinuing the 2.5 litre ILFORD ID-11 Replenisher pack, with ID-11 Developer itself unaffected, and the alternatives it offers; The September 2012 withdrawal notice for ILFORD ID-11 Replenisher in the 2.5 litre pack, its three offered alternatives - compensating for developer exhaustion by increasing development time, making a replenisher-like solution from two packs by dissolving both part A sachets and one part B and discarding the other part B, or converting to ILFOTEC DD - the instruction that process control is needed to find the optimum replenishment rate for the improvised solution, and the note that as the volume of film passed through the developer reduces, the replenishment rate should be increased in order to compensate for oxidation of the developer

Used by:Kodak D-76R · P8 Restrainers and Antifoggants · P14 Experiment: Process Control with Control Strips · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does

Reversal Processing: using ILFORD black & white films to make monochrome transparencies, technical informationretrieved 2026-09-04, 2026-09-05

Sections: Chemicals required; Solution preparation — clearing solution; processing table; Chemicals required; solution preparation — the bleach, solutions A and B; processing notes — bleach and clearing bath; the health and safety information at the head of the sheet; Health and safety information; solution preparation — the bleach, solutions A and B; processing notes — bleach and clearing bath

Used by:Potassium metabisulfite · Potassium permanganate · Sodium metabisulfite · Sulfuric acid

Safelight Filters and Darkroom Lamps, technical informationretrieved 2026-09-04, 2026-09-05, 2026-09-07, 2026-09-08

Sections: The safelight test — a pale grey of approximately 0.2 to 0.3 in density, the four steps of about 0, 1, 2 and 4 minutes made with a card, and the criteria that no density change between the 0 and 4 minute areas means the conditions are adequate and that a change of about 0.04 in density after one minute means they are inadequate; The filter-to-material table: 906 dark red for orthochromatic materials and recording materials, 915 light red for orthochromatic graphic arts materials, and 904 dark brown for fast blue-sensitive materials; Testing safelights: the after-exposure strip described as checking for latensification and the before-exposure strip as checking for hypersensitisation; Applications of ILFORD filters: the table matching filter SL1, 902, 904, 906, 907, 908, 914, 915, 916 and 917 to material class; the definition of a safelight; the testing procedure and its pass criterion; Testing safelights: the four-step 0, 1, 2 and 4 minute method, the before and after enlarger exposures, the pass criterion, and the general recommendation of an SL1 or 902 filter with a 15 W bulb at not less than 1.2 m; The filter-to-material table, including 904 dark brown for fast blue-sensitive materials and 906 dark red for orthochromatic materials; the general recommendation of a 15 W bulb at not less than 1.2 m; and the four-step safelight test at 0, 1, 2 and 4 minutes with its pass criterion; The filter-to-material table and the four-step safelight test at 0, 1, 2 and 4 minutes with its pass criterion of no density change out to four minutes; Filter table: 906 dark red for orthochromatic materials and recording materials, 915 light red for orthochromatic graphic arts materials, 904 dark brown for fast blue-sensitive materials; the four-step safelight test at 0, 1, 2 and 4 minutes and the pass criterion of no density change out to 4 minutes; Testing safelights: the four-step 0, 1, 2 and 4 minute method with a pre-exposed sheet, the pass criterion of no density change out to 4 minutes, and the warning that low-level fogging may show not as visible safelight fog but as a general loss of contrast; Applications of ILFORD filters: 906 dark red for orthochromatic materials, 915 light red for orthochromatic graphic arts materials, 904 dark brown for fast blue-sensitive materials; Testing safelights: the four-step 0, 1, 2 and 4 minute method with a pre-exposed sheet; the general recommendation of an SL1 or 902 filter with a 15 W bulb at not less than 1.2 m, safe for up to 4 minutes; Testing safelights: the four-step 0, 1, 2 and 4 minute method with a pre-exposed sheet, and the warning that low-level fogging may show not as visible safelight fog but as a general loss of contrast; The definition of a safelight, and the filter table matching filters 902 and 906 to blue-sensitive and orthochromatic materials; The definition of a safelight as illumination that does not cause a significant visible change to the material during use, with the note that the word safe is relative; and the safelight test procedure in four steps of 0, 1, 2 and 4 minutes, in which the safelight exposure is given after the enlarger exposure so that the test measures the material in the state it is actually handled in; Applications of ILFORD filters - a safelight is the illumination that does not cause a significant visible change to a material during use, and the word safe is relative; Safelight test procedure - the pass criterion of no density change out to 4 minutes, and the statement that a change of about 0.04 in density after one minute means the conditions are inadequate; borrowed here as the course's only published indication of what a detectable density difference on paper is; Darkroom lamps - the SL1 bench and wall lamp taking a 15 W E14 bulb, the DL10 taking 8 by 10 inch filters and a 15 W bulb, and the DL20 hanging lamp carrying a lower 8 by 10 inch filter and an upper 10 by 12 inch filter to give direct and reflected light at once; Filter construction - glass coated with coloured gelatin bound up with a diffuser; Using darkroom safelighting - the nine factors including the shape and size of the lamp, direct or indirect lighting, the distance between lamp and work place, and whether the filter is clear or diffused; and the general recommendation of an SL1 or 902 with a 15 W bulb at not less than 1.2 m for up to 4 minutes; Testing safelights - the criteria that no density change between the zero and four minute areas means the conditions are safe, and that a change of about 0.04 in density after one minute means they are inadequate, cited here as the only published figure this course has for what counts as a detectable density difference on paper; Using darkroom safelighting - the nine factors affecting effectiveness and safety, the instruction to change a filter each year and record the installation date, and the warning that low-level fogging shows as reduced contrast and a lack of clear highlights rather than as visible fog; Testing safelights - the criteria that no density change between the zero and four minute areas means the conditions are safe and that a change of about 0.04 in density after one minute means they are inadequate; and the instruction to wait about fifteen minutes for the eyes to adapt before checking a room for leaks; Using darkroom safelighting - the nine factors that influence the effectiveness and safety of darkroom lighting, including the colour of the walls and ceiling and the age of the filter; and the instruction that the only satisfactory way of checking for light leaking into the room is to wait until the eyes have adapted to the dark, which can take about fifteen minutes; Applications of ILFORD filters - the definition of a safelight as illumination that does not cause a significant visible change to a material during use, the note that the word safe is relative, and the filter table matching SL1, 902, 904, 906, 907, 908, 914, 915, 916 and 917 to material classes; Filter construction - one piece of glass coated with coloured gelatin and one piece of clear glass bound up with a diffuser; Using darkroom safelighting - the nine factors affecting effectiveness and safety, the instruction to change a filter each year and record the installation date, the warning that low-level fogging shows as reduced contrast and a lack of clear highlights rather than as visible fog, and the general recommendation of an SL1 or 902 with a 15 W bulb at not less than 1.2 m and up to 4 minutes; Testing safelights - the statement that paper is more sensitive to safelight fogging after it has been exposed in the enlarger than before, that the after strip checks for latensification and the before strip for hypersensitisation, and the criteria of no density change out to 4 minutes and of about 0.04 in density after one minute as inadequate; Testing safelights - the pale grey tone of approximately 0.2 to 0.3 in density; the four steps of about 0, 1, 2 and 4 minutes made with a card; the After exposure checking for latensification, described as the more critical because paper is more sensitive to safelight fogging after it has been exposed in the enlarger than before, and the Before exposure checking for hypersensitisation; processing in total darkness to the standard sequence; the criteria that no density change between the 0 and 4 minute areas means the conditions are safe and that a change of about 0.04 in density after one minute means they are inadequate; the remedies of a weaker bulb, a greater distance and a replaced filter; and the instruction to wait about fifteen minutes for the eyes to adapt before checking a room for leaks; Testing safelights — the full stepped procedure with its before-exposure and after-exposure patches, the instruction to determine the place of most safelight exposure rather than assume it, the cumulative step series of 0, 1, 2 and 4 minutes, the pass criterion that no density change between the 0-minute and 4-minute areas means the conditions are safe while a change of about 0.04 in density after one minute means they are inadequate, and the general recommendation of an SL1 or 902 safelight with a 15 W bulb at not less than 1.2 m (4 ft), which should be safe for up to 4 minutes; and the instruction to check for light leaking into the room only after the eyes have adapted to the dark, which takes about 15 minutes; Using darkroom safelighting — the nine factors that influence effectiveness and safety, the instruction that a filter in use for several hours a day gradually fades and should be changed each year with the date of installation recorded, and the warning that safelighting can appear safe while causing low-level fogging seen not as fog but as a general loss of photographic quality, particularly reduced contrast and lack of clear highlights; the instruction to check for light leaking into the room only after the eyes have adapted to the dark, which takes about 15 minutes; Testing safelights, the full stepped procedure with its before-exposure and after-exposure patches and its 0, 1, 2 and 4 minute steps; the pass criterion that no density change between the 0-minute and 4-minute areas means the conditions are safe and that a change of about 0.04 in density after one minute means they are inadequate; and the general recommendation of an SL1 or 902 safelight with a 15 W bulb at not less than 1.2 m (4 ft), safe for up to 4 minutes; Using darkroom safelighting — the warning that it is possible for safelighting to appear safe but be causing low level fogging, which may not be seen as safelight fog but only as a general loss of photographic quality, particularly reduced contrast and lack of clear highlights; and the general recommendation of an SL1 or 902 safelight with a 15 W bulb at not less than 1.2 m, safe for up to 4 minutes; Using darkroom safelighting — the instruction that the only satisfactory way of checking for light leaking into the room is to wait until the eyes have adapted to the dark, which can take about fifteen minutes; and the criterion that a change of about 0.04 in density after one minute means safelight conditions are inadequate; Using darkroom safelighting — the nine factors that influence whether darkroom lighting is effective and safe, the instruction to change a filter each year and record its installation date, and the statement that the only satisfactory way of checking for light leaking into the room is to wait until the eyes have adapted, which can take about fifteen minutes; Testing safelights - a change of the order of 0.04 in density taken as the threshold of a detectable difference on paper, which is the only such published figure this course has and is used here as a detectability threshold rather than as a quality standard; The statement that an SL1 or 902 safelight at 15 W and 1.2 m should be safe for up to four minutes; Using darkroom safelighting - the general recommendation of an SL1 or 902 filter with a 15 W bulb at not less than 1.2 m and up to 4 minutes, the nine factors affecting whether safelighting is effective and safe, and the warning that low-level fogging shows as reduced contrast and a lack of clear highlights rather than as visible fog; Testing safelights: the four-step 0, 1, 2 and 4 minute method, the before and after enlarger exposures, the pass criterion that no density change between the 0 and 4 minute areas means the conditions are safe while a change of the order of 0.04 in density after one minute means they are inadequate, and the general recommendation of an SL1 or 902 filter with a 15 W bulb at not less than 1.2 m; Testing safelights: the pale grey tone of approximately 0.2 to 0.3 in density, the four steps of about 0, 1, 2 and 4 minutes made with a card, the After exposure checking for latensification and described as the more critical because paper is more sensitive to safelight fogging after it has been exposed in the enlarger than before, and the criterion that a change of about 0.04 in density after one minute means the conditions are inadequate; Testing safelights - the four-step 0, 1, 2 and 4 minute method with a pre-exposed sheet, and the warning that low-level fogging may show not as visible safelight fog but as a general loss of contrast; Testing safelights - the warning that low-level fogging may show not as visible safelight fog but as a general loss of contrast; Testing safelights - the pass criterion of no density change out to 4 minutes, and the statement that a change of about 0.04 in density after one minute means the conditions are inadequate; borrowed here, as on the contact printer build page and the uneven contact print entry, as the only published indication in this course of what counts as a detectable density difference on paper; Using darkroom safelighting — the warning that it is possible for safelighting to appear safe but be causing low level fogging, which may not be seen as safelight fog but only as a general loss of photographic quality, particularly reduced contrast and lack of clear highlights; Testing safelights - the four-step 0, 1, 2 and 4 minute method with a pre-exposed sheet, the pass criterion of no density change out to 4 minutes, and the warning that low-level fogging may show not as visible safelight fog but as a general loss of contrast; Safelight definition as illumination that does not cause a significant visible change to the material during use, with the note that safe is relative; recommended filters and lamp distances; Safelight test procedure - the pass criterion of no density change out to 4 minutes, and the statement that a change of about 0.04 in density after one minute means the conditions are inadequate; borrowed here, as on the contact printer build page, as the only published indication in this course of what a detectable density difference on paper is; Using darkroom safelighting — the nine factors that influence effectiveness and safety, the warning that it is possible for safelighting to appear safe but be causing low level fogging which may not be seen as safelight fog but only as a general loss of photographic quality, particularly reduced contrast and lack of clear highlights, the instruction that a filter in use for several hours a day gradually fades and should be changed each year with the date of installation recorded, and the general recommendation of an SL1 or 902 safelight with a 15 W bulb at not less than 1.2 m, safe for up to 4 minutes; and the instruction to check for light leaking into the room only after the eyes have adapted to the dark, which takes about 15 minutes

Used by:P29 Capstone Stage 1: The Instrument, Its Calculation and Its Commissioning · Erythrosin sensitising stock · P4 Reciprocity Failure and the Life of the Latent Image · P4 Spectral Sensitivity and Colour Response · P4 Darkroom Session: The Latent Image Made Visible · P5 Build an Emulsion Coating Station · P5 Lab: Coating Your First Emulsion · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P5 Break/Fix: Emulsion Coating Defects · P5 Washing, Digestion and Sensitisation · P6 Commissioning the Camera: Light-Tightness, Flare and the First Negatives · P6 Break/Fix: Unexpectedly Soft Images and Wrong Reciprocity Corrections · P7 Assignment: Landscape, Sky, Foreground and Filters · P13 Lab: A Step-Wedge Exposure Series · P16 Part XVI Overview: Build the Darkroom · P16 Build: The Contact Printing Frame and Its Light Source · P16 Build: An LED Safelight · P16 Experiment: Commissioning the Enlarger · P16 Break/Fix: The Room That Fogs and the Light That Is Not Even · P16 Build: Making a Room Dark and Proving It · P16 Safelight: Spectra, Distance, Duration and the Fog Limit · P16 Experiment: The Safelight Fog Test · P28 Break/Fix: The Film That Came Back Wrong · P28 Fog and Where It Comes From · P28 Print Faults: Weak Blacks, Mottle, Bronzing and the Rest · The blackout leak test · Darkroom opening and closing for a printing session · Enlarger alignment and uniformity check · Handling and storing a deliberately faulty reference specimen · Opening and handling photographic paper in dim light · Testing a safelight · The whole-room fog audit · Base fog · Flat negative · Newton's rings · Poor maximum black · Safelight fog · Safelight-fogged control strip · Uneven contact print from pressure, glass or source geometry · Weak or grey blacks

Safety data sheet: Bromophen Developer (Part A)retrieved 2026-09-05

Sections: Section 1, product identifier and product code; section 2, classification, label elements and other hazards; section 3.2, composition of the mixture; section 6, accidental release; section 7, handling and storage; section 8, exposure controls and personal protection; section 9, physical and chemical properties; section 10, stability and reactivity; section 13, disposal considerations; section 15, regulatory information; section 16, the legend and the disclaimer

Used by:ILFORD BROMOPHEN developer

Safety data sheet: Bromophen Developer (Part B)retrieved 2026-09-05

Sections: Section 1, product identifier and product code; section 2, classification, label elements and other hazards, including 2.3; section 3.2, composition of the mixture; section 7, handling and storage; section 8, exposure controls and personal protection; section 9, physical and chemical properties; section 10, stability and reactivity; section 12.6, other adverse effects; section 13, disposal considerations; section 15, regulatory information

Used by:ILFORD BROMOPHEN developer

Safety data sheet: HARMAN Selenium Tonerretrieved 2026-09-06, 2026-09-08

Sections: Document header, date of issue 18 July 2024, revision 1, product code 1143207; and section 2, the classification Acute Tox. 4, Skin Sens. 1 and Aquatic Chronic 3 with pictogram GHS07, signal word Warning and hazard statements H302, H317 and H412; Section 3.2, the composition table, cited for the contrast: HARMAN declare Sodium Sulphite, CAS 7757-83-7, EC 231-821-4, at 10-30 per cent and Not classified, where Moersch declare the ammonium salt at 10 per cent and classify it; Section 1.1, product identifier and product code 1143207; section 1.2, identified use; sections 2.1 and 2.2, classification, pictogram, signal word, hazard and precautionary statements; section 2.3, other hazards; section 3.2, composition of the mixture; section 4, first aid and most important symptoms; sections 5.2 and 5.3, special hazards and advice for firefighters; section 6, accidental release; section 7, handling and storage; section 8, exposure controls and personal protection; section 9, physical and chemical properties; section 10, stability and reactivity; section 11, toxicological information and the calculation method; section 12, ecological information; section 13, disposal considerations; section 14, transport; section 15.1, UK REACH Annex XVII and the lists recorded as Not listed; section 16, the legend and the disclaimer; Section 3.2, composition of the mixture — Ammonium Thiosulphate at 10-30 %, Sodium Sulphite at 10-30 % and sodium selenite, CAS 10102-18-8, at 1-5 %; section 9, in which appearance is given as Liquid and colour, odour, pH, density and every other physical property are recorded as Not known; Section 3.2, composition of the mixture — ammonium thiosulphate at 10-30%, sodium sulphite at 10-30% and sodium selenite CAS 10102-18-8 at 1-5%; section 9, in which every physical property of the liquid other than that it is a liquid is recorded as Not known; and sections 7.2 and 10.5, incompatible materials none known and not known; Sections 2.1 and 2.2, the mixture classified Acute Tox. 4, Skin Sens. 1 and Aquatic Chronic 3 with pictogram GHS07, signal word Warning and hazard statements H302, H317 and H412; section 3.2, the composition table naming Ammonium Thiosulphate CAS 7783-18-8 at 10 to 30 per cent w/w, Sodium Sulphite CAS 7757-83-7 at 10 to 30 per cent w/w and sodium selenite CAS 10102-18-8 at 1 to 5 per cent w/w; and section 8, which records no occupational exposure limit assigned, asks for use with ventilation, local exhaust ventilation or breathing protection and for a washing facility for eye and skin cleaning, specifies eye protection with side protection to EN ISO 16321-1 and impervious gloves to EN 374, and states that a suitable mask with filter type A to EN14387 or EN405 may be appropriate. Date of issue 18 July 2024; Sections 2.1 and 2.2, the mixture classified Acute Tox. 4, Skin Sens. 1 and Aquatic Chronic 3 with pictogram GHS07, signal word Warning and hazard statements H302, H317 and H412; section 3.2, the composition table naming Ammonium Thiosulphate CAS 7783-18-8 at 10 to 30 per cent w/w, Sodium Sulphite CAS 7757-83-7 at 10 to 30 per cent w/w and sodium selenite CAS 10102-18-8 at 1 to 5 per cent w/w, the last classified Acute Tox. 2 H300, Skin Irrit. 2 H315, Skin Sens. 1 H317, Eye Irrit. 2 H319, Acute Tox. 2 H330, Aquatic Acute 1 H400 and Aquatic Chronic 1 H410, and naming nothing else; section 8, which records no occupational exposure limit assigned, asks for use with ventilation, local exhaust ventilation or breathing protection, specifies eye protection with side protection to EN ISO 16321-1 and impervious gloves to EN 374, and states that a suitable mask with filter type A to EN14387 or EN405 may be appropriate; section 9, in which appearance is recorded as Liquid with colour, odour, pH, density and every other physical property recorded as Not known; section 12.1, harmful to aquatic life with long lasting effects, with the aquatic figures all Not known; and section 13, disposal to a hazardous or special waste collection point. Date of issue 18 July 2024, revision 1; The document header, date of issue 18 July 2024, revision 1, product code 1143207, written to REACH (EC) No 1907/2006 as amended by the UK REACH Regulations SI 2019/758 and SI 2020/1577; and section 2, the classification Acute Tox. 4, Skin Sens. 1 and Aquatic Chronic 3 with pictogram GHS07, signal word Warning and hazard statements H302, H317 and H412. Cited here only as evidence that a current maker-published GB safety data sheet exists for this product and carries this date; Composition — sodium selenite at 1 to 5 per cent w/w with ammonium thiosulphate and sodium sulphite each at 10 to 30 per cent w/w; Composition, sodium selenite at 1 to 5 per cent w/w; Acute Tox. 4 with H302 and H317; impervious gloves to EN 374; eye protection with side protection to EN ISO 16321-1; ventilation, local exhaust ventilation or breathing protection

Used by:P29 Capstone Stage 5: The Toned Print and the Alternative-Process Print · Ammonium sulfite · HARMAN SELENIUM TONER · KODAK Rapid Selenium Toner · Moersch MT1 Selentoner · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Assignment: The Toned Print · Selenium toned silver gelatin print · Handling a selenium toner and its waste

Safety data sheet: Hypam Rapid Fixerretrieved 2026-09-06

Sections: Section 1.1, product identifier and product code 1758285; section 1.2, identified use; sections 2.1, 2.2 and 2.3, the Repr. 1B classification, pictogram GHS08, signal word Danger, hazard statements H360FD and EUH210, and the precautionary statements including P405, store locked up; section 3.2, composition of the mixture, its three components and the two bands printed as single figures to four decimal places; section 4, first aid; sections 5.2 and 5.3; section 6, accidental release; sections 7.1 and 7.2, handling and storage; section 8.1.1, occupational exposure limits, and 8.2, exposure controls and personal protection; section 9, physical and chemical properties, including colour yellow-green, odour slightly pungent, pH 5.1 and relative density 1.34 at 20 degrees C; section 10, stability and reactivity; section 11, toxicological information and the calculation method; section 12, ecological information; section 13, disposal considerations; section 14, transport; section 15.1, the UK REACH Candidate List line naming boric acid and the Annex XVII restrictions line; section 16, the legend and the disclaimer

Used by:ILFORD HYPAM

Safety data sheet: Ilfostopretrieved 2026-09-06, 2026-09-08

Sections: Section 1.1, product identifier and product code; section 1.2, identified use; section 2.1 and 2.2, classification, pictogram, signal word and label elements; section 2.3, other hazards; section 3.2, composition of the mixture; section 4, first aid; section 5.2, special hazards; section 6, accidental release; section 7, handling and storage; section 8, exposure controls and personal protection; section 9, physical and chemical properties; section 10, stability and reactivity; section 11, toxicological information and the calculation method; section 12, ecological information; section 13, disposal considerations; section 14, transport; section 15.1, UK REACH Annex XVII and the lists recorded as Not listed; section 16, the legend and the disclaimer; Section 2.1, which classifies the mixture Eye Irrit. 2 and nothing else, and 2.2, giving pictogram GHS07, signal word Warning and hazard statement H319 alone; section 3.2, the composition table, which names citric acid at 10-30 per cent and 2-phenoxyethanol at 1-5 per cent and names no dye; section 8, which records no occupational exposure limit assigned

Used by:ILFORD ILFOSTOP · P10 Overview: Stopping Development

Safety data sheet: Microphen Developer (Part A)retrieved 2026-09-06

Sections: Section 1.1, product identifier and product code; section 2, classification, label elements including EUH031 and the unknown-toxicity line, and 2.3 other hazards; section 3.2, composition of the mixture; section 6, accidental release; section 7, handling and storage; section 8, exposure controls and personal protection; section 9, physical and chemical properties; section 10, stability and reactivity; section 13, disposal considerations; section 15.1, the Candidate List, Annex XVII and CoRAP lines; section 16, the legend and the disclaimer

Used by:ILFORD MICROPHEN developer

Safety data sheet: Microphen Developer (Part B)retrieved 2026-09-06

Sections: Section 1.1, product identifier and product code; section 2.1 and 2.2, the Repr. 1B classification and label; section 3.2, composition of the mixture; section 7, handling and storage; section 8, exposure controls; section 9, physical and chemical properties; section 12.1, ecological toxicity; section 13, disposal considerations; section 15.1, the Candidate List and Annex XVII lines; section 16, the disclaimer

Used by:ILFORD MICROPHEN developer

Safety data sheet: Multigrade Paper Developerretrieved 2026-09-05

Sections: Section 1, product identifier and identified use; section 2, classification, label elements and other hazards; section 3.2, composition of the mixture; section 7, handling and storage; section 8, exposure controls and personal protection; section 9, physical and chemical properties; section 10, stability and reactivity; section 13, disposal considerations; section 15, regulatory information; section 16, the legend and the disclaimer

Used by:ILFORD MULTIGRADE developer

Safety data sheet: Perceptol Developer (Part A)retrieved 2026-09-06

Sections: Section 1.1, product identifier and product code; section 2, classification, label elements and the signal word; section 2.3, other hazards; section 3.2, composition of the mixture; section 6, accidental release; section 7, handling and storage; section 8, exposure controls and personal protection; section 9, physical and chemical properties; section 10, stability and reactivity; section 11, the acute toxicity estimate; section 12.1, ecological toxicity; section 13, disposal considerations; section 15.1, the Candidate List, Annex XVII and CoRAP lines; section 16, the legend and the disclaimer

Used by:ILFORD PERCEPTOL developer

Safety data sheet: Perceptol Developer (Part B)retrieved 2026-09-06

Sections: Section 1.1, product identifier and product code; section 2.1 and 2.2, the Not classified statement and the label; section 3.2, composition of the mixture; section 6.2 and 6.3, environmental precautions and clean-up; section 7, handling and storage; section 8, exposure controls; section 9, physical and chemical properties; section 11, toxicological information; section 12.1, ecological toxicity; section 13, disposal considerations; section 15.1, the regulatory lines; section 16, the disclaimer

Used by:ILFORD PERCEPTOL developer

Safety data sheet: PQ Universal Developerretrieved 2026-09-06

Sections: Section 1, product identifier and product code; section 2, classification, label elements and other hazards, including 2.3; section 3.2, composition of the mixture; section 6, accidental release; section 7, handling and storage; section 8, exposure controls and personal protection; section 9, physical and chemical properties; section 10, stability and reactivity; section 11, toxicological information and the calculation method; section 12.6, other adverse effects; section 13, disposal considerations; section 15.1, UK REACH Annex XVII and the CoRAP line; section 16, the legend and the disclaimer

Used by:ILFORD PQ UNIVERSAL developer

Safety data sheet: Rapid Fixerretrieved 2026-09-06

Sections: Section 2.1 and 2.2, which classify the sibling product as not dangerous for supply or use with no pictogram, no signal word and no hazard statement; section 3.2, whose composition table names ammonium thiosulphate at 35-50%, sodium hydrogensulphite / sodium bisulphite at 1-5% and acetic acid at <2%, and names no boric acid; section 9, which records colour, odour, pH and density as not known — all quoted here only for the comparison between two sheets issued by the same maker on the same day; Section 1.1, product identifier and product codes; section 1.2, identified use; sections 2.1, 2.2 and 2.3, the classification, the absence of pictogram, signal word and hazard statement, the precautionary statements and other hazards; section 3.2, composition of the mixture; section 4, first aid; section 5.2, special hazards; section 6, accidental release; section 7.1 and 7.2, handling and storage; section 8.1.1, occupational exposure limits, and 8.2, exposure controls and personal protection; section 9, physical and chemical properties; section 10, stability and reactivity; section 11, toxicological information and the calculation method; section 12, ecological information; section 13, disposal considerations; section 14, transport; section 15.1, UK REACH Annex XVII and the lists recorded as Not listed; section 16, the legend, the acronyms and the disclaimer

Used by:ILFORD HYPAM · ILFORD RAPID FIXER

Safety data sheet: Washaidretrieved 2026-09-06

Sections: Section 1.1, product identifier; section 1.2, identified use; section 2.1 and 2.2, classification and label elements; section 2.3, other hazards; section 3.2, composition of the mixture; section 4, first aid; section 5, firefighting; section 6, accidental release; section 7, handling and storage; section 8, exposure controls and personal protection; section 9, physical and chemical properties; section 10, stability and reactivity; section 11, toxicological information and the calculation method; section 12, ecological information; section 13, disposal; section 14, transport; section 15.1, UK REACH Annex XVII and the lists recorded as Not listed; section 16, the legend and the disclaimer

Used by:ILFORD WASHAID

SFX 200 Technical Informationretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Choosing the best ILFORD developer for the job: the Maximum film speed row; Choosing the best ILFORD developer for the job, the Finest grain row; the development-time table, PERCEPTOL rows at stock and 1+1; Coated on a grey acetate base which gives good halation protection; Extended red sensitivity up to 740 nm; the wedge spectrogram; the filter factor table; total darkness for handling, and the distinction from true infrared film; Filter factors: 8 yellow 2, 12 deep yellow 2.3, 21 orange 2.4, 25 red 2.8, 29 deep red 3, 89B very deep red 16; and the statement that with a very deep red filter skies can be rendered almost black and most green vegetation almost white; The heading rating of ISO 200/24 degrees, used here only as one of the seven published arithmetic and degree pairs against which the course checks its own derivation of the logarithmic speed scale

Used by:ILFORD MICROPHEN developer · ILFORD PERCEPTOL developer · P4 Grain, Speed and Resolution · P4 Spectral Sensitivity and Colour Response · P7 Assignment: Landscape, Sky, Foreground and Filters · P13 Film Speed and Exposure Index

Washing Photographic Film and Papers: instructions for minimum water usageretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: FB Papers — the optimum permanence sequence of 1 minute's fixation, a 5 minute first wash, 10 minutes in WASHAID at 1+4 and a 5 minute final wash; RC Papers — a minimum of 30 seconds in vigorous fresh running water and the warning not to over-wash; Films, the spiral-tank method of fill and invert five, ten and twenty times; Films, spiral tank processing method — fill with water at the same temperature plus or minus 5 degrees C, invert five times, drain and refill and invert ten times, drain and refill and invert twenty times, then a final rinse with ILFOTOL at 1+200; FB Papers — the optimum permanence sequence of 1 minute's fixation, a 5 minute first wash, 10 minutes in WASHAID at 1+4 and a 5 minute final wash; and RC Papers — a minimum of 30 seconds in vigorous fresh running water and the warning not to over-wash; FB Papers — the optimum permanence sequence of 1 minute's fixation, a 5 minute first wash, 10 minutes in WASHAID at 1+4 and a 5 minute final wash; RC Papers — a minimum of 30 seconds in vigorous fresh running water, or three trays of still water for 15 seconds each with agitation, and the warning not to over-wash because water ingress at the edge can swell and damage the print; FB Papers — the optimum permanence sequence of 1 minute's fixation, a 5 minute first wash, 10 minutes in WASHAID at 1+4 and a 5 minute final wash; RC Papers — a minimum of 30 seconds in vigorous fresh running water and the warning not to over-wash; Notes — the statement that the fill-and-invert wash method is validated for ILFORD films, papers and non-hardening fixers, and that hardening fixers can significantly increase the required wash time; Purpose of washing, that washing removes residual chemicals and in particular thiosulphate from the fix process which can cause long-term image degradation if not effectively removed; FB Papers, the statement that fibre based papers absorb processing solutions more readily into the paper base and therefore need longer washing, that it is possible to use ILFORD WASHAID to more effectively remove residual fixer, and the sequence of fixation in ILFORD RAPID FIXER or HYPAM (1+4) for 1 minute, a 5 minute first wash in fresh running water, 10 minutes in ILFORD WASHAID (1+4) with intermittent agitation and a 5 minute final wash; the note that an archival print washer with discrete slots increases wash efficiency and allows a reduced flow rate; the note that the guidance is for non-hardening ILFORD fixers and that hardening fixers can significantly increase the required wash time; and the fill-and-invert film wash whose water is at the processing temperature plus or minus 5 degrees C (9 degrees F); Purpose of washing; films, spiral tank processing method for minimum water usage; Purpose of washing - removal of residual thiosulphate, which can cause long-term image degradation; the spiral tank fill-and-invert method of five, ten and twenty inversions at a temperature within 5 degrees C of the processing solutions; resin-coated papers waterproofed by their polythene coating against fibre-based papers which absorb processing solutions into the base and need longer; a minimum of 30 seconds in vigorous running water for RC in a dish, or three still trays for 15 seconds each; the fibre-base optimum permanence sequence with WASHAID; and the warning not to over-wash RC papers; FB Papers — the archival sequence for dish-processed fibre prints, one minute of fixation in RAPID FIXER or HYPAM at 1+4, a five-minute first wash, ten minutes in WASHAID at 1+4 and a five-minute final wash; the statement that fibre-based papers absorb processing solutions more readily into the paper base and therefore need longer washing times; Notes — the statement that the instructions are suitable for use with ILFORD non-hardening fixers, either HYPAM or RAPID, and that using hardening fixers can significantly increase the required wash time; FB Papers — the archival sequence, one minute of fixation at 1+4 followed by a 5 minute wash, 10 minutes in WASHAID and a 5 minute final wash; FB Papers — the archival sequence for dish-processed fibre prints, fixation in ILFORD RAPID FIXER or HYPAM at 1+4 for 1 minute, a 5 minute first wash, 10 minutes in WASHAID at 1+4 and a 5 minute final wash; Purpose of washing — washing removes residual chemicals from the photographic process, in particular thiosulphate from the fix process, which can cause long-term image degradation if not effectively removed; Films, the spiral-tank method of fill and invert five times, ten times and twenty times; FB Papers, the optimum permanence sequence; Purpose of washing — the removal of residual chemicals, in particular thiosulphate, which can cause long-term image degradation if not effectively removed; Films, the spiral-tank method of filling with water at the same temperature as the processing solutions and inverting the tank five times, draining and refilling and inverting ten times, draining and refilling and inverting twenty times; RC Papers, a minimum of 30 seconds in vigorous fresh running water; FB Papers, the optimum permanence sequence of a 5 minute first wash, 10 minutes in WASHAID at 1+4 and a 5 minute final wash; Purpose of washing — washing removes residual chemicals, in particular thiosulphate from the fix process, which can cause long-term image degradation if not effectively removed; Notes — the instructions are for non-hardening fixers and using hardening fixers can significantly increase the required wash time; Films, spiral tank processing method — fill with water at the same temperature plus or minus 5 degrees C, invert five times, drain and refill and invert ten times, drain and refill and invert twenty times, then a final rinse with ILFOTOL at 1+200; RC Papers — a minimum of 30 seconds in vigorous fresh running water, or three trays of still water for 15 seconds each with agitation, and the warning not to over-wash because water ingress at the edge can swell and damage the print; FB Papers — fibre-based papers absorb processing solutions more readily into the paper base and therefore need longer washing times, and the optimum permanence sequence of 1 minute's fixation, a 5 minute first wash, 10 minutes in WASHAID at 1+4 and a 5 minute final wash; the note that an archival print washer with discrete slots increases wash efficiency and allows a reduced flow rate; Films, spiral tank processing method — fill, invert five times, drain and refill and invert ten times, drain and refill and invert twenty times; RC Papers — a minimum of 30 seconds in vigorous fresh running water; FB Papers — the optimum permanence sequence of a 5 minute first wash, 10 minutes in WASHAID at 1+4 and a 5 minute final wash; Purpose of washing, the removal of residual chemicals and in particular thiosulphate; RC Papers, a minimum of 30 seconds in vigorous fresh running water; FB Papers, the optimum permanence sequence of a 5 minute first wash, 10 minutes in WASHAID at 1+4 and a 5 minute final wash; Purpose of washing - removal of residual thiosulphate, which can cause long-term image degradation; the spiral tank fill-and-invert method of five, ten and twenty inversions; RC papers a minimum of 30 seconds in vigorous fresh running water; FB papers the optimum permanence sequence of a 5 minute first wash, 10 minutes in WASHAID at 1+4 and a 5 minute final wash; Wash water within 5 degrees Celsius of the process temperature for film, and the fill-and-invert method

Used by:P29 Capstone Overview: What the Pure Silver Portfolio Asks · P29 Capstone Stage 3: Exposing, Processing and Measuring · P29 Capstone Stage 4: The Silver Prints · P29 Planning the Capstone: The Project Plan and Its Hazard Assessment · P29 The Pure Silver Portfolio: The Specification · ILFORD HYPAM · ILFORD WASHAID · P2 Waste: Streams, Silver, and the Drain You Must Not Use · P3 Diffusion, Swelling and the Journey Into the Emulsion · P11 Fixer Capacity, Exhaustion and Residual Silver · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline · P11 How Fixer Works · P12 Overview: Permanence and Responsibility · P12 Assignment: Your Archival Processing Sequence · P12 The Physics of Washing · P12 Lab: Testing for Residual Thiosulfate and Residual Silver · Print processing: the archival sequence · Residual thiosulfate · Reticulation

inchem.org

Concise International Chemical Assessment Document 61: Hydrogen cyanide and cyanides - human health aspectsretrieved 2026-09-06

Sections: Section 7.9, mode of action — that free cyanide inhibits cytochrome oxidase by binding haem iron, the terminal enzyme of the mitochondrial electron transport chain, so that tissue utilisation of oxygen is impaired and a state of histotoxic anoxia follows, and that cyanide can also inhibit approximately forty enzymes, mostly metalloenzymes containing iron, copper or molybdenum; that the central nervous system is particularly vulnerable because of its high dependency on oxidative metabolism and limited anaerobic capacity, and that death is believed to result from central nervous system depression subsequent to inhibition of brain cytochrome oxidase activity. Section 6.3, metabolism — that the major detoxification route is the mitochondrial enzyme rhodanese, which transfers the sulfane sulfur of thiosulfate to the cyanide ion to form thiocyanate, that about 80 per cent of cyanide is detoxified by this route, that the rate-limiting step is the amount of thiosulfate, and that the rate of spontaneous detoxification in humans is about 1 microgram per kilogram of body weight per minute. Section 6.1, absorption — that an ingested cyanide salt meets the highly acidic medium of the stomach so that essentially all of it forms hydrogen cyanide, and section 6.2, that hydrogen cyanide has a pKa of 9.22 so that at physiological pH it is distributed as the molecule rather than as the free ion. Section 7.1, that symptoms can occur within seconds of inhaling hydrogen cyanide or within minutes of ingesting a cyanide salt, and the rabbit dermal LD50 figures of 0.343 mmol/kg for potassium cyanide on intact skin with the note that dermal toxicity is markedly greater on abraded skin. Section 8.1, the human acute dose-effect estimates, described in the document itself as crude average exposure estimates. Section 8.2, the Egyptian electroplating study in which 20 of 36 exposed workers showed thyroid enlargement, the 1983 questionnaire study of 36 former workers of a silver-reclaiming facility in the USA that had been closed after the death of a worker from cyanide poisoning, and the statement that thiocyanate prevents the uptake of iodine and acts as a goitrogenic agent. Section 2, the table of cyanide compounds, which lists potassium silver cyanide, CAS 501-61-6, KAg(CN)2, relative molecular mass 198.01, under the synonym potassium dicyanoargentate. Section 4, that potassium ferricyanide is used chiefly for blueprints, in photography, for staining wood, in calico printing and in electroplating. Section 5.1, that at former manufactured gas plant sites the most prevalent cyanide compounds are iron-complexed forms such as ferric ferrocyanide rather than the highly toxic free cyanide forms, iron-complexed cyanides comprising over 97 per cent of total cyanides in the soils studied

Used by:P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide

Environmental Health Criteria 58: Seleniumretrieved 2026-09-06

Sections: Section 3, the chemistry of the oxidation states — that selenium in the +6 or selenate state is stable under both alkaline and oxidizing conditions, occurs in alkaline soils where it is soluble and easily available to plants, is the most common form of the element found in alkaline waters and may potentially be the most environmentally dangerous form of the element; that selenium in the +4 state tends to oxidize slowly to the +6 state in alkaline solution if oxygen is present but not in an acid medium, is readily reduced to elemental selenium by reagents such as ascorbic acid or sulfur dioxide, and binds tightly to iron and aluminium oxides so that it is quite insoluble in soils; section 6.1.1.2, human gastrointestinal absorption, for the 94 per cent absorption of 1 mg of selenate-selenium in solution against about 60 per cent for selenite and for the correction of the earlier 92 per cent figure; section 6.1.3, absorption through the skin, for the statement that apart from one 1972 rat study on sodium selenite there are no quantitative data on the dermal absorption of water-soluble selenium compounds; section 6.3.2 and Table 14, urinary and faecal excretion of one-milligram doses by human volunteers; Section 9.1, that the Task Group concluded selenium meets the criteria of essentiality for man, that as is true for all essential elements not only deficient but also excessive exposure results in adverse health effects, and that between these extremes is a range of safe and adequate exposures free from toxicity and adequate to meet nutritional requirements; section 9.2, that extreme mean values for calculated selenium intake from food by adults varied from 11 to 5000 micrograms per day while dietary intakes usually fall within the range of 20 to 300 micrograms per day; Table 7, adapted from Yang et al. (1983), giving average daily intakes of 4990 micrograms in a high-selenium area of China with a history of intoxication reported as chronic selenosis, 750 in a high-selenium area reported as without selenosis, 116 in a moderate-selenium area at Beijing and 11 in a low-selenium area with Keshan disease, with the observation that the intakes of the selenosis and non-selenosis high-selenium areas did not overlap; and section 9.5.2, the three blood-selenium situations used to estimate a dose-response, together with the Task Group's caution about how signs and symptoms were searched for and how control populations were selected

Used by:Sodium selenate · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim

International Chemical Safety Card 0044: Ethanol (anhydrous)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Physical properties; physical and chemical dangers; routes of exposure and inhalation risk; effects of short-term and long-term exposure; occupational exposure limits; storage; Physical properties — flash point and explosive limits; physical dangers; storage; Physical and chemical information: the boiling point of 78 C, the flash point of 12.0 C and the explosive limits of 3.1 to 27.7 volume per cent in air; Chemical dangers, on violent reaction with strong oxidants including silver nitrate

Used by:Ethanol · Double-coated albumen procedure · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · Chemical incompatibilities

International Chemical Safety Card 0163: Hydrogen chlorideretrieved 2026-09-04, 2026-09-06

Sections: Physical and chemical dangers; effects of short-term and long-term exposure; occupational exposure limits; prevention; storage; Physical and chemical dangers; effects of short-term exposure; prevention; storage

Used by:Hydrochloric acid · EDTA, citric acid and hydrochloric acid clearing sequence

International Chemical Safety Card 0183: Nitric acid (more than 70% in water)retrieved 2026-09-04

Sections: Physical properties; chemical dangers; effects of short-term and long-term exposure; occupational exposure limits; prevention; storage; the dilution instruction

Used by:Nitric acid

International Chemical Safety Card 0215: Ammonium hydroxide (10%-35% solution)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Physical properties; chemical dangers; occupational exposure limits; routes of exposure and inhalation risk; effects of short-term and long-term exposure; storage; environmental data; Physical and chemical information, for the description as a very volatile solution and the boiling point of 38 degrees C for the 25 per cent reagent; the UN GHS criteria block, for the signal word and the five hazard statements; Chemical dangers; Storage. Cited for the reagent this formula exists in order not to use; The card for the 10 to 35 per cent solution, read to establish the controls the ammonia route would require and which this session avoids by not taking it

Used by:Ammonia solution (ammonium hydroxide) · Mike's Cyanotype · P21 Lab: Toning the Prussian Blue Image

International Chemical Safety Card 0357: Potassium hydroxideretrieved 2026-09-04

Sections: Physical and chemical information; chemical dangers; effects of short-term exposure; occupational exposure limits; storage; notes

Used by:Potassium hydroxide (caustic potash)

International Chemical Safety Card 0360: Sodium hydroxideretrieved 2026-09-04, 2026-09-05

Sections: Physical and chemical information; chemical dangers; effects of short-term exposure; occupational exposure limits; storage; notes; ICSC 0360: corrosive to eyes, skin and respiratory tract; a harmful concentration of airborne particles can be reached quickly when dispersed; the instruction never to pour water into the substance but always to add it slowly to the water; Chemical dangers, on corrosion of metals with the evolution of hydrogen

Used by:Sodium hydroxide (caustic soda) · P5 Project 4: Coating Glass Dry Plates and a Lantern Slide · Responding to an alkali spill

International Chemical Safety Card 0362: Sulfuric acid, concentrated (more than 51% and less than 100%)retrieved 2026-09-04

Sections: Physical properties; chemical dangers; effects of short-term and long-term exposure; occupational exposure limits; prevention; storage; the dilution instruction

Used by:Sulfuric acid

International Chemical Safety Card 0363: Acetic acidretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Physical properties; chemical dangers; effects of short-term and long-term exposure; occupational exposure limits; storage; environmental data; Physical properties; chemical dangers; effects of short-term exposure; storage; Physical properties and chemical dangers — the solution in water is a weak acid, and it attacks many metals forming flammable hydrogen gas; Physical properties and chemical dangers — the solution in water is a weak acid, it attacks many metals forming flammable hydrogen gas, and the substance is corrosive to the eyes, the skin and the respiratory tract; Flash point 39 degrees C, explosive limits 6.0 to 17 vol per cent, and the statement that a harmful contamination of the air can be reached rather quickly on evaporation at 20 degrees C; occupational exposure limits; Flash point 39 degrees C, explosive limits 6.0 to 17 vol per cent, and the statement that a harmful contamination of the air can be reached rather quickly on evaporation at 20 degrees C; Flash point 39 degrees C and the statement that a harmful contamination of the air can be reached rather quickly on evaporation at 20 degrees C; Occupational exposure limits, EU-OEL 25 mg/m3 or 10 ppm as an eight-hour TWA and 50 mg/m3 or 20 ppm as a STEL; the statement that a harmful contamination of the air can be reached rather quickly on evaporation at 20 degrees C; Physical properties including the flash point of 39 degrees C and explosive limits of 6.0 to 17 vol per cent; chemical dangers; routes of exposure and the statement that a harmful contamination of the air can be reached rather quickly on evaporation at 20 degrees C; short-term and long-term exposure; the occupational limits, EU-OEL 25 mg/m3 or 10 ppm as an eight-hour TWA and 50 mg/m3 or 20 ppm as a STEL; storage; Chemical dangers and short-term exposure - the corrosive action on eyes, skin and respiratory tract, the flash point of 39 degrees C, and the note that a harmful contamination of the air can be reached rather quickly on evaporation at 20 degrees C. Card dated May 2010.; Chemical dangers and spillage disposal

Used by:Acetic acid (glacial) · Albumen solution with its chloride · Talbot's gallo-nitrate of silver · ILFORD HYPAM · ILFORD RAPID FIXER · Kodak SB-1 · Kodak SB-1a · Kodak SB-5 · P10 Experiment: Measuring Stop Bath Capacity · P10 Stop Bath Formulations and the Fixer Interaction · P21 Lab: Toning the Prussian Blue Image · Responding to an acid spill

International Chemical Safety Card 0529: Oxalic acidretrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: Chemical dangers — explosive silver oxalate with certain silver compounds; Physical properties; chemical dangers; inhalation risk; effects of short-term and long-term exposure; occupational exposure limits; storage; Chemical dangers, for the formation of explosive silver oxalate on contact with certain silver compounds; Storage, for the requirement that oxalic acid be kept separated from silver compounds; Chemical dangers — explosive silver oxalate with certain silver compounds; storage; Chemical dangers — explosive silver oxalate with certain silver compounds; effects of exposure; storage; Chemical dangers, for explosive silver oxalate formed with certain silver compounds; Chemical dangers, for the formation of explosive silver oxalate on contact with silver compounds; Effects of short-term exposure and Effects of long-term or repeated exposure, for the kidney as the target organ; Storage, separated from silver compounds; Chemical dangers, for the formation of explosive silver oxalate on contact with silver compounds; Storage, separated from silver compounds; Chemical dangers, on the formation of explosive compounds with certain silver compounds

Used by:Ammonium iron(III) oxalate · Ferric oxalate · Oxalic acid · Potassium oxalate, anhydrous · Potassium oxalate monohydrate · Silver(I) oxalate · Kallitype sensitiser · Nicol's kallitype · Willis's potassium oxalate developer · P24 Lab: Printing a Kallitype · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · Chemical incompatibilities

International Chemical Safety Card 0554: Isopropyl alcoholretrieved 2026-09-04, 2026-09-05

Sections: Physical properties; physical and chemical dangers; routes of exposure and inhalation risk; effects of short-term and long-term exposure; occupational exposure limits; storage; Physical properties — boiling point, relative density, vapour pressure at 20 °C, flash point, auto-ignition temperature and explosive limits; physical and chemical dangers, including the line that the vapour mixes well with air and that explosive mixtures are easily formed; effects of short-term exposure on the central nervous system; storage, "fireproof, separated from strong oxidants, cool, well closed"

Used by:Isopropyl alcohol · Double-coated albumen procedure

International Chemical Safety Card 0565: Sodium acetate (anhydrous)retrieved 2026-09-04

Sections: Physical and chemical information; chemical dangers; storage; classification and labelling according to UN GHS criteria; effects of short-term exposure; inhalation risk

Used by:Sodium acetate (anhydrous)

International Chemical Safety Card 0567: Sodium borate, decahydrate (borax)retrieved 2026-09-04, 2026-09-06

Sections: Physical and chemical information; effects of short-term and long-term exposure; occupational exposure limits; environment; notes; storage; Environment — harm to aquatic organisms; Effects of short-term and long-term exposure; environment; Physical and chemical information, for 5.1 g per 100 mL at 20 °C and for the weak base; effects of short-term and long-term exposure; environment; storage

Used by:Borax (sodium tetraborate decahydrate) · Boric acid · Sodium metaborate (anhydrous) · Sodium metaborate tetrahydrate (Kodalk) · Borax kallitype developer

International Chemical Safety Card 0612: Asphaltretrieved 2026-09-04, 2026-09-06

Sections: Whole card: classification and labelling, physical and chemical information, routes of exposure, effects of short-term and long-term exposure, inhalation risk, and the occupational exposure limits quoted from ACGIH and the German MAK list; Classification and labelling according to UN GHS criteria, which is empty; Effects of long-term or repeated exposure, for absorption by inhalation of fume, irritation of the eyes and respiratory tract, burns from the heated substance, and fumes possibly carcinogenic to humans. The card is for petroleum asphalt, which is a related material and not bitumen of Judea; The whole card for petroleum asphalt, CAS 8052-42-4 — the empty UN GHS classification block, the combustibility, the statement that the substance can be absorbed into the body by inhalation of fume, that evaporation at 20 degrees is negligible but a harmful concentration of airborne particles can be reached quickly when dispersed, that fumes of the substance are possibly carcinogenic to humans, and the ACGIH and MAK exposure limits

Used by:Bitumen of Judea · Niépce's bitumen heliograph coating · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes

International Chemical Safety Card 0624: Glycerolretrieved 2026-09-06

Sections: Physical state and appearance; physical and chemical dangers; fire and explosion; symptoms, prevention and first aid for inhalation, skin, eyes and ingestion; inhalation risk; occupational exposure limits; storage; spillage disposal; physical and chemical information. Cited also for the blank short-term and long-term exposure rows

Used by:Glycerol

International Chemical Safety Card 0632: Ammonium persulfateretrieved 2026-09-05

Sections: Physical and chemical information; chemical dangers; fire and explosion; storage; spillage disposal; effects of short-term and long-term exposure; inhalation risk; occupational exposure limits; the notes on asthma and on working clothes

Used by:Ammonium persulfate

International Chemical Safety Card 0672: Potassium permanganateretrieved 2026-09-05

Sections: Physical and chemical information; chemical dangers; fire and explosion; storage; spillage disposal; the classification under UN GHS criteria; effects of short-term and long-term exposure; inhalation risk; occupational exposure limits; the note on rinsing contaminated clothing

Used by:Potassium permanganate

International Chemical Safety Card 0675: Sodium thiocyanateretrieved 2026-09-04, 2026-09-07, 2026-09-08

Sections: Chemical dangers and storage for the sodium salt, applied here as an inference and labelled as one; Physical and chemical information; chemical dangers; storage; effects of short-term and long-term exposure; inhalation risk; spillage disposal; the EC classification quoted in the additional information; Chemical dangers and the old EC classification quoted on the card, for the violent reaction with acids and for R32, contact with acids liberates very toxic gas; Storage, for keeping it separated from acids, bases, oxidants and foodstuffs; Chemical dangers and the old EC classification quoted on the card, for the violent reaction with acids and for R32, contact with acids liberates very toxic gas; Storage, for separation from acids, bases, oxidants and foodstuffs; Chemical dangers and the old EC classification quoted on the card, for the violent reaction with acids and R32, contact with acids liberates very toxic gas; Chemical dangers: violent reaction with acids, and the old EC entry R32, contact with acids liberates very toxic gas; storage away from acids, bases, oxidants, food and feedstuffs; Chemical dangers: violent reaction with acids; storage away from acids, bases, oxidants, food and feedstuffs; Chemical dangers: violent reaction with acids, and the old EC entry R32, contact with acids liberates very toxic gas

Used by:Ammonium thiocyanate · Sodium thiocyanate · P22 Gold Toning and the Permanence of a Printed-Out Silver Image · P22 Lab: Printing, Toning, Fixing and Washing a Salt Print · P22 Break/Fix: The Printed-Out Image That Faded · The acid exclusion rule at a hexacyanoferrate or thiocyanate bench · Segregating alternative-process waste · The printing-out processing line

International Chemical Safety Card 0698: Sodium seleniteretrieved 2026-09-04, 2026-09-06

Sections: Physical properties; Chemical dangers; Occupational exposure limits; Effects of short-term and long-term exposure; Prevention and storage; Environmental data; Chemical dangers, that the solution in water is a weak base and that reaction with strong acids generates a toxic hazard; occupational exposure limits; effects of short-term and long-term exposure; prevention and storage, separated from strong acids and from food and feedstuffs and stored in an area without drain or sewer access; environmental data; Chemical dangers, that the solution in water is a weak base and that reaction with strong acids generates a toxic hazard; occupational exposure limits; effects of short-term and long-term exposure; prevention and storage, separated from strong acids and from food and feedstuffs and stored in an area without drain or sewer access; and the environmental data on bioaccumulation along food chains

Used by:Sodium selenite · HARMAN SELENIUM TONER · KODAK Rapid Selenium Toner

International Chemical Safety Card 0772: Tartaric acidretrieved 2026-09-04, 2026-09-07

Sections: Physical properties; chemical dangers; inhalation risk; effects of short-term exposure; occupational exposure limits; storage; environmental data; Chemical dangers, for the reaction with silver; Routes of exposure and Inhalation, Skin and Eyes

Used by:Tartaric acid · P24 Lab: Printing a Van Dyke Brown

International Chemical Safety Card 0808: Quartz (crystalline silica)retrieved 2026-09-07

Sections: Card 0808, November 2016 — Classification and labelling, for the signal word Danger and the statements that it may cause cancer if inhaled and causes damage to the lungs, the immune system and the kidneys through prolonged or repeated exposure if inhaled; Occupational exposure limits, for the TLV of 0.025 mg/m3 as TWA for the respirable fraction with the A2 notation, the EU-OEL of 0.1 mg/m3 for the respirable fraction and MAK carcinogen category 1; Effects of long-term or repeated exposure, for silicosis

Used by:Kaolin

International Chemical Safety Card 0855: Citric acidretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Physical properties; physical and chemical dangers; effects of short-term and long-term exposure; occupational exposure limits; storage; Storage — separated from strong oxidants, strong bases, metal nitrates and metals; Molecular mass 192.1; solubility 59 g per 100 mL of water at 20 degrees C; flash point 100 degrees C; the statement that a dust explosion is possible if the powder or granules are mixed with air, with explosive limits of 0.28 to 2.29 vol per cent; chemical dangers, that the solution in water is a medium strong acid and attacks metals; negligible evaporation at 20 degrees C; MAK 2 mg/m3 for the inhalable fraction; Physical properties — solubility 59 g per 100 mL of water at 20 degrees C; chemical dangers, that the solution in water is a medium strong acid and attacks metals; inhalation risk, negligible evaporation at 20 degrees C; physical dangers, the possibility of a dust explosion from the powder; Chemical dangers; Storage, for the instruction to keep it separated from strong oxidants, strong bases, metal nitrates and metals; Physical and chemical information, for the molecular mass and the water solubility; Physical and chemical information, for the solution being a medium strong acid and for the substance attacking metals; effects of short-term exposure; prevention; Molecular mass; solubility; negligible evaporation at 20 degrees C; the dust explosion statement and its explosive limits; Physical properties — solubility 59 g per 100 mL of water at 20 degrees C; physical dangers, dust explosion possible when the powder is mixed with air; chemical dangers, a medium strong acid in water that attacks metals; short-term exposure, irritating to eyes, skin and respiratory tract; Physical properties including solubility of 59 g per 100 mL of water at 20 degrees C and a flash point of 100 degrees C; physical dangers, the possibility of a dust explosion and the explosive limits of 0.28 to 2.29 vol per cent; chemical dangers, that the solution in water is a medium strong acid and that it attacks metals; inhalation risk and the negligible evaporation at 20 degrees C; short-term and long-term exposure; MAK of 2 mg/m3 for the inhalable fraction; Physical properties — solubility 59 g per 100 mL of water at 20 degrees C; physical dangers, a dust explosion is possible if the powder or granules are mixed with air; chemical dangers, the solution in water is a medium strong acid and it attacks metals

Used by:Citric acid (anhydrous) · Iron(III) nitrate nonahydrate · Citric Acid Stop Bath · ILFORD ILFOSTOP · Mike's Cyanotype · Sodium citrate developer · Stop baths compared · P10 Experiment: Measuring Stop Bath Capacity · P10 Stop Bath Formulations and the Fixer Interaction · Stop bath preparation

International Chemical Safety Card 0952: Sodium sulfate (anhydrous)retrieved 2026-09-04, 2026-09-05

Sections: Physical and chemical information; chemical dangers; effects of short-term exposure; inhalation risk; the empty classification and labelling and occupational-exposure-limit boxes; Physical and chemical information; the empty classification and labelling and occupational-exposure-limit boxes; the note that a nuisance-causing concentration of airborne particles is reached quickly

Used by:Sodium sulfate · Kodak SB-5

International Chemical Safety Card 0991: Boric acidretrieved 2026-09-04, 2026-09-06

Sections: Physical and chemical information; chemical dangers; effects of short-term and long-term exposure; occupational exposure limits; storage; Effects of short-term and long-term exposure; occupational exposure limits and the pregnancy risk group; storage — separated from strong bases; Prevention of dust dispersion; inhalation, skin and eye protection; reproductive hazard

Used by:Boric acid · ILFORD HYPAM · P11 Lab: Mixing Fixers from Scratch

International Chemical Safety Card 1037: Calcium nitrateretrieved 2026-09-07

Sections: Card 1037, August 2003 — the identifiers CAS 10124-37-5, EC 233-332-1 and UN 1454; the Notes, for the statement that the recommendations on the card also apply to calcium nitrate hydrate and tetrahydrate, CAS 13477-34-4, and for the instruction to rinse contaminated clothing with plenty of water because of the fire hazard; Fire and explosion, for the substance being not combustible but enhancing the combustion of other substances and for the risk of fire and explosion on contact with combustible substances; Chemical dangers, for the substance being a strong oxidant that reacts with combustible and reducing materials; Storage, separated from combustible substances and reducing agents, dry; Transportation, UN hazard class 5.1 and packing group III; Physical and chemical information, for the colourless-to-white hygroscopic crystals, the anhydrous formula and molecular mass, the melting point of 560 degrees C, the density of 2.50 g/cm3 and the solubility of 121.2 g per 100 mL; Routes of exposure and Effects of short-term exposure, for absorption by inhalation of the aerosol and by ingestion, mechanical irritation of the eyes and respiratory tract and the formation of methaemoglobin on ingestion with effects that may be delayed; Inhalation risk, for a nuisance-causing concentration of airborne particles being reached quickly when dispersed; and Spillage disposal

Used by:Calcium nitrate tetrahydrate

International Chemical Safety Card 1044: Sodium bicarbonateretrieved 2026-09-04

Sections: Physical properties; chemical dangers; routes of exposure; storage; Physical properties and effects of exposure

Used by:Sodium bicarbonate · P3 Lab: Measuring pH and Trusting the Number

International Chemical Safety Card 1088: Potassium thiocyanateretrieved 2026-09-04

Sections: Physical and chemical information; chemical dangers; storage; routes of exposure; effects of short-term and long-term exposure; inhalation risk; the EC classification quoted in the additional information

Used by:Potassium thiocyanate

International Chemical Safety Card 1132: Potassium ferricyanideretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Physical properties; Chemical dangers; Prevention and storage; Environment; Physical and chemical information, for the formula, molecular mass, density and water solubility; Chemical dangers, for the decomposition on heating and the reaction with acids; Storage; Effects of short-term exposure; Environment; Physical and chemical dangers; effects of short-term exposure; the decomposition on heating and on contact with acids; Chemical dangers - the statement that potassium ferricyanide decomposes on heating and on contact with acids, producing toxic gases, cited here for why a print bleach is kept away from every acid bath in the darkroom; Chemical dangers - that the substance decomposes on heating and on contact with acids, producing toxic gases including hydrogen cyanide; and Physical dangers and Storage, that it is kept separated from acids; Chemical dangers, that the substance decomposes on heating and on contact with acids producing toxic gases including hydrogen cyanide; Storage, that it is kept separated from acids; and the inhalation entry, for the P2 dust filter; Card ICSC 1132, dated August 2002 — Chemical dangers, decomposition on heating and on contact with acids producing toxic gases including hydrogen cyanide; Prevention and storage, separated from acids; Chemical dangers, for decomposition on heating and on contact with acids producing toxic gases including hydrogen cyanide; Storage, for separation from acids; Chemical dangers — that the substance decomposes on heating, producing toxic gases including hydrogen cyanide, and that it reacts with acids, which generates a toxic hazard; Storage, "separated from acids, dry"; and the statements that the temperature of decomposition is unknown in the literature and that the health effects of exposure have not been investigated adequately; Chemical dangers — the statement that potassium ferricyanide reacts with acids, generating a toxic hazard, and that the solid decomposes on heating producing toxic gases including hydrogen cyanide; Chemical dangers: the solid decomposes on heating and on contact with acids, producing toxic gases including hydrogen cyanide; personal protection, a P2 filter where dust cannot be avoided; Chemical dangers: decomposition on heating and on contact with acids, producing toxic gases including hydrogen cyanide; Chemical dangers: decomposition on contact with acids producing toxic gases including hydrogen cyanide

Used by:Potassium ferricyanide · Mike's Cyanotype · The Simple Cyanotype (2019) · P19 Contrast Filtration and Split-Grade Printing · P20 Lab: Bleaching and Redeveloping a Sepia Print · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Iron, Light and Prussian Blue · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P28 Reading the Negative as Evidence: Thin, Dense, Flat and Contrasty · The acid exclusion rule at a hexacyanoferrate or thiocyanate bench · Segregating alternative-process waste · Clearing an iron-silver print and testing it for residual iron

International Chemical Safety Card 1133: Potassium persulfateretrieved 2026-09-04

Sections: Physical and chemical information; chemical dangers; fire and explosion; storage; effects of short-term and long-term exposure; inhalation risk; occupational exposure limits; the notes on asthma and on working clothes

Used by:Potassium persulfate

International Chemical Safety Card 1135: Sodium carbonate (anhydrous)retrieved 2026-09-04, 2026-09-06

Sections: Physical properties; chemical dangers; effects of short-term and long-term exposure; storage; Chemical dangers; storage; effects of short-term and long-term exposure - the card covers the anhydrous salt and is applied here as an inference; Chemical dangers; storage; effects of short-term and long-term exposure — the card covers the anhydrous salt; Physical properties; chemical dangers; effects of short-term exposure; inhalation of the dispersed powder; Short-term effects and hazardous reactions: severe eye irritation; violent reaction with acids generating heat and carbon dioxide; Chemical dangers, that the aqueous solution is a medium-strong base which reacts violently with acids generating heat and carbon dioxide; short-term exposure effects; solubility of 30 g per 100 mL of water at 20 degrees C. Card dated April 2024.

Used by:Sodium carbonate (anhydrous) · Sodium carbonate decahydrate · Sodium carbonate monohydrate · Dilute alkaline thiosulfate fixer for iron-silver prints · P3 Lab: Measuring pH and Trusting the Number · P21 Lab: Toning the Prussian Blue Image

International Chemical Safety Card 1144: Kaolinretrieved 2026-09-07

Sections: Card 1144, November 2016 — the identifiers CAS 1332-58-7 and EC 310-194-1, the synonyms hydrated aluminium silicate, china clay and argilla; Classification and labelling, for the statement that there is no hazard classification according to GHS criteria; Fire and explosion, for not combustible; Physical and chemical information, for the white powder, the formula H2Al2Si2O8 H2O, the approximate molecular mass of 258, the relative density of 2.6 and insolubility in water; Physical dangers and Chemical dangers, both recorded as no data; Routes of exposure, mainly inhalation; Effects of short-term exposure, mechanical irritation; Inhalation risk, a harmful concentration of airborne particles reached quickly when dispersed; Effects of long-term or repeated exposure, the lungs affected by repeated or prolonged exposure to dust particles resulting in fibrosis (kaolinosis); Occupational exposure limits, TLV 2 mg/m3 as TWA for the respirable fraction with the A4 notation and MAK carcinogen category 3; Spillage disposal, for the particulate filter respirator, sweeping into covered containers and moistening first to prevent dusting; and the Notes, for the statement that the card applies to kaolin containing less than 1 per cent crystalline silica and that ICSC 0808 Quartz should also be consulted above that

Used by:Kaolin

International Chemical Safety Card 1219: Sodium citrate dihydrateretrieved 2026-09-04, 2026-09-06

Sections: Physical and chemical information; chemical dangers; effects of short-term exposure; inhalation risk; the note on the apparent melting point; the empty classification and occupational-exposure-limit boxes; Physical and chemical information, for solubility and for the aqueous solution being a weak base; chemical dangers; effects of short-term exposure; the empty classification and occupational-exposure-limit boxes; Physical and chemical information, for solubility and for the solution being a weak base; chemical dangers; effects of short-term exposure; the empty classification and occupational-exposure-limit boxes

Used by:Trisodium citrate dihydrate · Sodium citrate developer · Sodium citrate kallitype developer

International Chemical Safety Card 1450: Potassium chlorideretrieved 2026-09-04

Sections: Physical and chemical information; effects of short-term exposure; inhalation risk; spillage disposal; the empty classification and labelling and occupational-exposure-limit boxes

Used by:Potassium chloride

International Chemical Safety Card 1560: Nitrocellulose, dry, less than 12.6% nitrogenretrieved 2026-09-04, 2026-09-06

Sections: Whole card: classification and labelling under UN GHS criteria; fire and explosion; chemical and physical dangers; physical and chemical information; storage; spillage disposal; the notes on damped commercial products, on nitrogen content above 12.6 per cent and on the absence of human health data; Fire and explosion, for the substance being highly flammable with a risk of explosion on friction or shock and when exposed to heat, flame, sparks or electrostatic discharges; fire fighting, for water in large amounts with no foam and no carbon dioxide; storage, for the requirement to store only if damped; spillage disposal, for keeping a spill wet and not allowing it to dry out; and the note that the formulation with more than 12.6 per cent nitrogen is used exclusively for the manufacture of explosives; Physical dangers and the 12.6 per cent nitrogen threshold above which the material is used exclusively for explosives; Physical dangers; the 12.6 per cent nitrogen threshold above which the material is used exclusively for explosives

Used by:Nitrocellulose · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · Collodion print-out paper · Wet-plate collodion negative

International Chemical Safety Card 1588: Potassium carbonate (anhydrous)retrieved 2026-09-04, 2026-09-06

Sections: Physical properties; chemical dangers; effects of short-term exposure; storage; Chemical dangers, that the solution in water is a medium strong base which reacts violently with acids; solubility of 112 g per 100 mL of water at 20 degrees C; storage separated from strong acids. Card dated April 2005.

Used by:Potassium carbonate (anhydrous) · P21 Lab: Toning the Prussian Blue Image

infineon.com

IRLZ44NPbF HEXFET Power MOSFET, data sheet PD-94831retrieved 2026-09-05

Sections: Electrical Characteristics at TJ = 25 C - gate threshold voltage 1.0 to 2.0 V at VDS = VGS and ID = 250 microamps; on-resistance 0.022 ohm at 10 V, 0.025 ohm at 5.0 V and 0.035 ohm at 4.0 V of gate drive, with no figure at 3.3 V; input capacitance 1700 pF; Absolute Maximum Ratings - 55 V drain-source, 47 A continuous drain current at 25 C case, gate-source plus or minus 16 V, junction-to-ambient thermal resistance 62 C/W; Front page summary and Absolute Maximum Ratings; Electrical Characteristics at TJ = 25 C - gate threshold voltage 1.0 V minimum and 2.0 V maximum at VDS = VGS and ID = 250 microamps; on-resistance 0.022 ohm at VGS = 10 V, 0.025 ohm at VGS = 5.0 V and 0.035 ohm at VGS = 4.0 V, with no figure at 3.3 V; input capacitance 1700 pF; total gate charge 48 nC; thermal resistance 62 C/W junction-to-ambient; Front page - logic-level gate drive, VDSS 55 V, RDS(on) 0.022 ohm, ID 47 A at a case temperature of 25 C and 33 A at 100 C, power dissipation 110 W at a case temperature of 25 C with a linear derating factor of 0.71 W per degree, gate-to-source voltage plus or minus 16 V, operating junction and storage temperature range minus 55 to plus 175 C; Thermal Resistance - junction-to-case 1.4, case-to-sink 0.50 and junction-to-ambient 62 C/W; Electrical Characteristics at TJ = 25 C - on-resistance 0.022 ohm at VGS = 10 V, 0.025 ohm at 5.0 V and 0.035 ohm at 4.0 V with no figure at 3.3 V, gate threshold 1.0 V minimum and 2.0 V maximum at VDS = VGS and ID = 250 microamps, drain-to-source leakage current 25 microamps at VDS = 55 V and VGS = 0 V and 250 microamps at VDS = 44 V and a junction temperature of 150 C, input capacitance 1700 pF, turn-on delay 11 ns, rise time 84 ns, turn-off delay 26 ns and fall time 15 ns, all four measured at VGS = 5.0 V with a 3.4 ohm gate resistor; Electrical Characteristics at TJ = 25 C - turn-on delay 11 ns, rise time 84 ns, turn-off delay 26 ns and fall time 15 ns, all measured at VGS = 5.0 V with a 3.4 ohm gate resistor; input capacitance 1700 pF; Electrical Characteristics at TJ = 25 C - drain-to-source leakage current 25 microamps maximum at VDS = 55 V with VGS = 0 V, rising to 250 microamps at VDS = 44 V and a junction temperature of 150 C

Used by:P14 Build: The LED Light Source and Exposure Timer · P14 Low-Voltage Electronics for the Darkroom Builder · P17 Build: The Switched Output · P17 Experiment: Calibrating the Timer · P17 Break/Fix: The Timer That Lies

iso.org

ISO 18915:2000, Imaging materials - Methods for the evaluation of the effectiveness of chemical conversion of silver images against oxidation, first edition, 2000-12-14retrieved 2026-09-06

Sections: Published scope, clause 1.1, which states that the standard describes methods for evaluating the effectiveness of chemical conversion treatments intended to increase the resistance of wet-processed silver images to oxidation, that it does not recommend general or specific treatments, and that treatment temperature, times and replenishment rates are outside its scope. Read as the catalogue scope only; Published scope, clause 1.1, which states that the standard describes methods for evaluating the effectiveness of chemical conversion treatments intended to increase the resistance of wet-processed silver images to oxidation, that it does not recommend general or specific treatments, and that treatment temperature, times and replenishment rates are outside its scope; Published scope, clause 1.1, which states that the standard describes methods for evaluating the effectiveness of chemical conversion treatments intended to increase the resistance of wet-processed silver images to oxidation, that it does not recommend general or specific treatments, and that treatment temperature, times and replenishment rates are outside its scope. Read as the catalogue scope only; the course does not purchase the ISO standards and quotes no part of the normative text; Clauses 1.1 and 1.2, the published scope - that the standard describes methods for evaluating the effectiveness of chemical conversion treatments intended to increase the resistance of wet-processed silver images to oxidation, that the treatment may be applied as part of the original processing or as a post-processing treatment, that the standard does not recommend general or specific treatments for silver images, that treatment temperature, times and replenishment rates are outside its scope, that factors to be considered in a stabilizing treatment are discussed in informative annex B, that two test methods are described, the dichromate bleach test and the hydrogen peroxide incubation test, whose significance is discussed in informative annex C, and that the standard applies to silver-gelatin images coated on supports of either plastic, paper or glass. The normative text was not read

Used by:P29 Capstone Stage 6: Permanence, Presentation and the Finished Portfolio · P29 The Capstone Chemistry Report: From Photon Capture to Finished Print · P29 The Pure Silver Portfolio: The Specification · P20 Assignment: The Toned Print · P20 Toning, Permanence and What the Evidence Actually Supports

ISO 3664:2009, Graphic technology and photography - Viewing conditions, third edition, 2009-04 (withdrawn)retrieved 2026-09-06, 2026-09-07

Sections: Catalogue record for the withdrawn third edition, published 2009-04-14, confirmed on systematic review in 2015 and 2020, marked to be revised in 2021 and withdrawn on 2025-07-11, revised by ISO 3664:2025; The specification of viewing conditions for graphic technology and photography, cited here only as the existence of a standard that defines the illumination under which a reflection print is to be judged

Used by:P19 Assignment: The Exhibition Print and Its Critique · Dry-down error

ISO 3664:2025, Graphic technology and photography - Viewing conditions, fourth edition, 2025-07retrieved 2026-09-06

Sections: Catalogue record for the fourth edition, July 2025, and its published abstract, which states that the document specifies viewing conditions for images on reflective and transmissive media and applies to critical evaluation and comparison of reflection prints. Cited by number only; no value from its normative text appears here; Catalogue record for the fourth edition, July 2025, 29 pages, ISO/TC 42, and the published abstract, which states that the document specifies viewing conditions for images on reflective and transmissive media and applies to critical evaluation and comparison of reflection prints, to appraisal of tone reproduction and colourfulness at illumination levels similar to those for practical use including routine inspection, and to critical appraisal of projected transparencies. Cited by number only; no value from the normative text appears here

Used by:P29 Capstone Stage 4: The Silver Prints · P19 Assignment: The Exhibition Print and Its Critique

ISO 5-2:2009, Photography and graphic technology - Density measurements - Part 2: Geometric conditions for transmittance density, fifth edition, 2009-12-01retrieved 2026-09-05, 2026-09-06

Sections: Cited by number only, as the standard that separates diffuse from projection transmittance density and specifies a geometry for each; consulted in the publisher's free preview for title, edition and contents, and quoted nowhere; Cited by number only, as the standard separating diffuse from projection transmittance density; consulted in the publisher's free preview for title, edition and contents, and quoted nowhere; Cited by number only, as the standard that specifies the geometric conditions for transmittance density; consulted in the publisher's free preview, whose introduction records that the 1985 edition replaced the integrating-sphere method with a diffuser, typically opal glass; Cited by number only, as the standard that specifies geometric conditions for transmittance density; consulted in the publisher's free preview, whose introduction records that the 1985 edition replaced the integrating-sphere method with a diffuser, typically opal glass, and notes that inter-reflection between diffuser and specimen slightly lowers the density obtained; Cited by number only, for the fact that transmittance density is defined under stated geometric conditions and that the standard distinguishes diffuse from projection density; and for the foreword's list of the four parts of ISO 5, which is where the course takes the title of Part 4 from; Cited by number only, consulted in the publisher's free preview: the introduction's account of diffuse transmittance density as the quantity relevant to contact printing, the opal diffuser that replaced the integrating sphere, and the sampling aperture defining the area measured; and the foreword's list of the four parts of ISO 5, from which the title of Part 4, geometric conditions for reflection density, is taken. Part 4 itself has not been read by this course and nothing is claimed of its content; Cited by number only; consulted in the publisher's free preview, whose introduction records that diffuse transmittance density is the quantity relevant to contact printing and to viewing on a light box, that a diffuser typically of opal glass replaced the integrating sphere in 1985 because inter-reflection between diffuser and specimen is part of what a contact print experiences, and that the area measured is defined by a small opening called the sampling aperture. Also cited for the foreword's list of the four parts of ISO 5, from which the title of Part 4, geometric conditions for reflection density, is taken; Cited by number only, as the standard specifying geometric conditions for transmittance density; consulted in the publisher's free preview, whose introduction records that the second edition of 1985 replaced the integrating-sphere method with a diffuser, typically opal glass, that slightly smaller density values result because of inter-reflection between the diffuser and the specimen, that diffuse transmittance density is the quantity relevant to contact printing and to viewing on a light box, that the standard also describes two types of projection density identified by f-number because the f-number is what is marked on a projection lens, that the f/4.5 type is representative of microfilm readers and the f/1.6 type of motion-picture projectors, and that the area measured is defined by a small opening called the sampling aperture. Also cited for the foreword's list of the four parts of ISO 5 and their titles; Cited by number only, as the geometric condition the Part XV densitometer's transmission head is modelled on; conformance is neither claimed nor tested; Density measurement, part 2 - geometric conditions for transmission density, which determine what quantity a given instrument reports; Density measurement, part 2 - geometric conditions for transmission density, and the influence of the measuring aperture

Used by:P13 Exposure, Density and the Logarithm · P13 The Characteristic Curve · P14 Experiment: Calibrating the Sensitometer · P14 Sensitometer Design Principles · P14 Build: The Enclosure and Exposure Stage · P15 Part XV Overview: Build a Densitometer · P15 Experiment: Calibrating the Densitometer in Both Modes · P15 Build: The Densitometer Optical Head (Transmission and Reflection) · P15 Density Depends on How You Look: Geometry and Spectral Response · P27 Experiment: Four Curve Families, Measured · Densitometer: scale error · Uneven density across a strip

ISO 6:1993, Photography - Black-and-white pictorial still camera negative film/process systems - Determination of ISO speed, second edition, 1993-02-01retrieved 2026-09-05, 2026-09-06, 2026-09-07

Sections: Catalogue record for the standard governing the determination of ISO speed for black-and-white pictorial still camera negative film and process systems. Named here only as the standard the course models its own speed criterion on; the course holds no part of its normative text; Catalogue record for the standard governing determination of ISO speed for black-and-white pictorial still camera negative film and process systems. Named by number as the standard the course's own speed criterion is modelled on; no part of its normative text is held or quoted; Cited by number only, as the standard the course's own speed criterion is modelled on; no part of it is quoted anywhere in the course; Cited by number only, as the standard that fixes the photographic convention of exposure H in lux-seconds and its logarithm as the horizontal axis of a sensitometric curve; no part of it is quoted; Cited by number only, as the standard the course's speed criterion is modelled on and as the standard that treats speed as a property of a film and process together; no threshold, formula or table from it is printed anywhere in this course; Cited by number only, as the standard the course's contrast and speed conventions are modelled on; no threshold, geometry or value from it is printed anywhere in this course; Cited by number only, as the standard the course's own speed criterion is modelled on; no threshold, formula or table from it is printed anywhere in this course; Cited by number only, as the standard the course's own speed criterion is modelled on; no threshold, geometry, density value or clause is reproduced; Cited by number only, as the standard the course's own speed criterion is modelled on, and for the fact that it refers the sensitometric illuminant to ISO 7589; no threshold, geometry, density value or clause is reproduced anywhere in this course; Cited by number only, as the standard the course's own speed criterion is modelled on; no threshold, geometry or density value is reproduced; Cited by number only, as the standard the course's speed criterion is modelled on; no threshold, formula or table from it appears anywhere in this course; Cited for its scope and for two of its own statements, not for any threshold, formula or table, none of which appears anywhere in this course. Introduction - the statement that the speed of a film depends on the process used, that the standard therefore specifies a method for determining the speed of film and process combinations, that a particular film may have several ISO speeds associated with it depending on the processes used, and that this conflicts with the tradition of associating a specific speed value with a particular product; and the note that manufacturers usually take advantage of the overexposure tonal latitude of a film and give it a conservative speed value to protect users from underexposure. Foreword - that the second edition of 1993 eliminated the first edition's restriction that speed be determined in a specified developer and fixing bath. Clause 5.4.2, Processing specifications - the statement that speeds obtained using various processing procedures can differ significantly, that other sensitometric and physical changes can accompany the speed changes, and that generally, processes which yield higher ISO speed will also increase the graininess of the negative and the final print; Cited by number only, as the standard the course's own speed criterion is modelled on; no threshold, formula or table from it appears anywhere in this course; Cited by number only, as the standard the course's own speed criterion is modelled on; Determination of ISO speed for black-and-white pictorial still camera negative film - the criterion density above base plus fog and the fixed development contrast at which the speed point is read

Used by:P29 Capstone Overview: What the Pure Silver Portfolio Asks · P29 Capstone Stage 3: Exposing, Processing and Measuring · P29 The Pure Silver Portfolio: The Specification · P13 Part XIII Overview: Measuring the Response of Silver to Light · P13 Exposure, Density and the Logarithm · P13 Film Speed and Exposure Index · P13 Gamma, Contrast Index and Average Gradient · P13 Assignment: Interpreting Density Data · P13 Lab: A Step-Wedge Exposure Series · P13 Tone Reproduction: From Subject to Print · P14 Experiment: Calibrating the Sensitometer · P14 Experiment: Process Control with Control Strips · P14 Sensitometer Design Principles · P15 Assignment: Characterising a Film and Developer with Your Own Instruments · P27 Experiment: Four Curve Families, Measured · P27 Push and Pull Processing: What Extended Development Can and Cannot Buy · P27 Experiment: The Development Time and Temperature Series · Sensitometer exposure session · Cut-off toe

jacquardproducts.com

Cyanotype Detailed Instructionsretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Cyanotype Formula, Mixing and Exposing Instructions, steps 1 to 7 — 40 g potassium ferricyanide in 400 mL water and 100 g ferric ammonium citrate in 400 mL water, 24 hours to dissolve, equal parts mixed, the sensitiser stable 2 to 4 hours, exposure of 1 to 30 minutes in sunlight, a wash of at least 5 minutes; and the Notes on distilled water, mould in the citrate stock, six-month storage of coated material, and yellowing by phosphates and high pH; The maker's sensitiser strengths, 40 g of potassium ferricyanide in 400 mL and 100 g of ferric ammonium citrate in 400 mL mixed in equal parts, cited for comparison with this kit's 40 g and 100 g in 500 mL each; Cyanotype formula, mixing and exposing instructions; Creating images; Troubleshooting; Notes; Cyanotype Detailed Instructions, steps 1 to 7 and the Notes — 40 g of potassium ferricyanide in 400 mL of water labelled STOCK SOLUTION A and 100 g of ferric ammonium citrate in 400 mL of water labelled STOCK SOLUTION B, which is the reverse of every other sheet read for this page; 24 hours allowed for each powder to dissolve fully; equal parts mixed in subdued lighting with the instruction to mix only the amount immediately needed "as the sensitizer is stable just 2-4 hours"; coating and air drying in the dark, with double coating offered for denser prints; exposure of 1 to 30 minutes in sunlight or under a UV source with the note that over-exposure is almost always preferred to under-exposure and that fabric looks bronze when fully exposed; a wash of at least 5 minutes in cool water, changing the water periodically until it runs clear, with no soap; and the Notes, that distilled water is used where the tap water is hard, that "The stock solutions are stable long term", that mould growth may occur in the ferric ammonium citrate solution over time, that sensitised paper and fabric may be stockpiled and stored with six months for best results in a sealed bag, that coated material which has darkened is not necessarily expired, that yellowing may occur on exposure to phosphates or high pH and that cyanotype fabrics should be laundered in cold water with non-phosphate detergent, and that nothing should be wet before or during exposure; Document dated 08.17.21. The instruction that fabric may be coated or dipped in the sensitizer while paper may be double-coated for denser prints; exposures in sunlight of 1 to 30 minutes depending on conditions or under a UV light source, with the note that over-exposure is almost always preferred to under-exposure and that the fabric will look bronze in colour once fully exposed; processing in a tray or bucket of cool water for at least 5 minutes with the water changed periodically until it runs clear, and the instruction not to use soap; air-drying on a clean clothesline or on newsprint or blotting paper; the note that sensitized paper or fabric may be stockpiled and stored, used within 6 months for best results, in a cool dry environment preferably in a sealed bag to avoid oxidation; the instruction not to wet fabric or paper before or during exposure and to keep hands, printing surface and objects dry; the note that cyanotype fabric may be ironed before exposure with a dry iron that does not spit or leak water, working on the backside; and the troubleshooting entries for water spots from damp hands, from moisture produced by leaves or design elements during exposure and from splashing before the wash, for discoloration to brown or yellow if the print is exposed to phosphates, soap or dirty objects including an unclean drying line and clothes pins, for blurry or out-of-focus prints from imperfect contact, and for prints that darken during drying because they were not thoroughly washed; Cyanotype formula, mixing and exposing instructions - the mixed sensitizer stable just 2 to 4 hours, the note that over-exposure is almost always preferred to under-exposure, the statement that the fabric will look bronze in colour once fully exposed and that with wetting the print will change from a bronze to a blue colour, and the wash of at least five minutes with the water changed periodically until it runs clear and no soap; and the Notes - use distilled water if your tap water is hard, mould growth may occur in the ferric ammonium citrate stock over time, sensitized paper or fabric stored in a sealed bag in a cool dry environment and used within six months, coated paper that darkens over time being not necessarily expired, yellowing where prints are exposed to phosphates or high pH solutions, the instruction to launder cyanotype fabrics in cold water with non-phosphate detergents, the warning that sweat and hand oils may cause discoloration, and the instruction to keep hands, printing surface and objects dry and not to wet the paper before or during exposure; Cyanotype formula, mixing and exposing instructions, step 5 - exposures in sunlight of 1 to 30 minutes depending on conditions, and the note that over-exposure is almost always preferred to under-exposure; Cyanotype formula, mixing and exposing instructions, step 5 - exposures in sunlight of 1 to 30 minutes depending on conditions; Cyanotype formula, mixing and exposing instructions - the note that over-exposure is almost always preferred to under-exposure, that the fabric will look bronze in colour once fully exposed, and that with wetting the print will change from a bronze to a blue colour; processing in cool water for at least five minutes with the water changed periodically until it runs clear, no soap; the optional hydrogen peroxide step and rinse; stock solutions stable long term while the mixed sensitizer is stable just two to four hours; Processing - wash for at least five minutes in cool water, changing the water periodically until the water runs clear, and do not use soap; the recommendation to use distilled water if the tap water is hard; Mixing - allow 24 hours for each powder to dissolve fully in making the stock solutions; the stock solutions are stable long term while the mixed sensitizer is stable just two to four hours; mix only the amount you immediately need

Used by:Classic cyanotype sensitiser · Photographers' Formulary cyanotype and toning kits · P1 Assignment 1: A Botanical Cyanotype Photogram, After Atkins · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Assignment: Cyanotype at Scale, on Fabric, and the Botanical Sequence · P21 Break/Fix: The Cyanotype That Went Wrong · Outdoor exposure session · Recording a daylight exposure · Bronzing and reversal from cyanotype over-exposure · Prussian blue bleeding into the highlights by peptisation · Sensitiser gone cloudy in the bottle

Cyanotype Fabric Sheets, product pageretrieved 2026-09-04, 2026-09-06

Sections: Product description and exposure guidance; Product description - pre-sensitized cotton sateen fabric sheets, and the statement that exposure time depends on conditions but is generally 3 to 10 minutes; and the mural fabric listing, on which a person can lie during exposure to make a full-body print

Used by:P1 Assignment 1: A Botanical Cyanotype Photogram, After Atkins · P21 Assignment: Cyanotype at Scale, on Fabric, and the Botanical Sequence

Cyanotype FAQsretrieved 2026-09-04, 2026-09-06

Sections: Is it permanent?; How should I wash my cyanotype fabric prints?; What is the cyanotype formula?; Can I paint or print on top of a cyanotype print?; Document dated 02.08.19. Is it permanent - the statement that yellowing may occur if prints are exposed to phosphates or alkaline environments, that cyanotype fabrics must be laundered in cold water using non-phosphate detergents, that over-washing may also cause the print to fade, that sweat and hand oils may cause discoloration, and that washing a faded print in a dilute bath of hydrogen peroxide can usually restore it to its original intensity. Can I make cyanotype prints on paper and fabric - the list of natural surfaces that can be treated with the sensitizer, naming silk, cotton, wool, hemp, linen, canvas, paper, leather and wood, and the statement that polyester, not being a natural fibre, generally cannot be used. How should I wash my cyanotype fabric prints - keep washing to a minimum if possible, hand-washing in cold water with a non-phosphate detergent, and the instruction not to use Synthrapol or SolarFast Wash. What is the difference between cyanotype and SolarFast - the maker's own statement, item 3, that cyanotype is not as washable and permanent as SolarFast is on fabric. Can I paint or print on top of a cyanotype print - the warning that a paint or dye of high pH may fade or entirely remove the blue beneath it. Can cyanotype prints be made on colored fabric or paper - the statement that like a dye the image is transparent, so printing on a coloured substrate has an additive effect and prints made on black substrates will not show up

Used by:P1 Assignment 1: A Botanical Cyanotype Photogram, After Atkins · P21 Assignment: Cyanotype at Scale, on Fabric, and the Botanical Sequence

kaiser-fototechnik.de

'digital timer' Electronic Exposure Timer for enlargers, article 4030retrieved 2026-09-05

Sections: Specification - exposure times 0.1 to 99 seconds, maximum switching capacity 500 W, focusing light switch, 2 m power cable, and no external trigger input listed; Specification - exposure times 0.1 to 99 seconds, maximum switching capacity 500 W, focusing light switch and 2 m power cable, with no external trigger input listed

Used by:P17 Build: The Switched Output · P17 Switching Lamps Safely: Isolation, Certified Modules and the Mains Boundary

keyesphoto.com

Photographic Emulsions: their preparation and coating on glass, celluloid and paper, experimentally and on the large scaleretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Printing paper emulsions, for the note that greater contrasts can be obtained by adding small quantities of uranium, nickel or copper salts but that they are not as satisfactory as calcium chromate, and for the later passage recommending calcium chromate or small additions of uranyl, copper or nickel chlorides for hardening the contrasts in chloride emulsions, credited to Valenta; Chapter III, chemical sensitising — sodium thiosulphate, sodium selenosulphate (Na2SeSO3), potassium tellurotellurate and potassium isoselenocyanate as sensitisers, the 1:1,000,000 to 1:300,000 range, and the maximum beyond which fog increases; Pages 99 and 151 to 152 — Wratten's tannin ratio of 1 to 286 of gelatine, the rule that a hardener is dosed on the gelatin and not on the bulk of the emulsion, and the warning about yellow stain during development; Page 101, the division that bromide papers are always washed emulsions while the gaslight papers are usually unwashed; pages 95 to 96, the statement that the more bromide an emulsion contains in comparison to the chloride the faster it is as a rule, the longer the scale of gradation and the less easy to obtain warm tones, and the controlled series establishing that the rate of deposition of the silver and not the composition of the emulsion determines the colour of the image; page 103, the practice of pouring bromide emulsions into ice-cold pans immediately after digestion to set quickly and stop the ripening; pages 151 to 152, the rule that the quantity of hardener depends on the total quantity of the gelatine and not on the bulk of the emulsion, and the range of one of chrome alum to two hundred and fifty or three hundred of dry gelatine; Chapter VI, Printing Paper Emulsions, pages 103 to 105. The framing on page 103 reads 'GASLIGHT OR DEVELOPMENT PAPERS. These are as a rule unwashed emulsions containing varying ratios of bromide and chloride of silver ... the formulas are given as used commercially', and page 101 sets the division that bromide papers are always washed emulsions, the gaslight being usually unwashed. The soft-working paper on page 104 is A, potassium bromide 25 g, sodium chloride 200 g, citric acid 50 g, gelatine 625 g, alcohol 250 ccm and water 5000 ccm, at 50 °C (122 °F); B, silver nitrate 500 g and water 1660 ccm; digest seventy-five minutes at 50 °C; finals, chrome alum 3 g and water to 11,000 g. The contrast paper printed beside it is potassium bromide 13 g, strontium chloride cryst. 433 g, gelatine 625 g, sodium acetate 100 g, alcohol 160 ccm, hydrochloric acid 25 ccm and water 5000 ccm, with silver nitrate 500 g in 1650 ccm, an hour at 60 °C, and finals of chrome alum 3 g, hydrochloric acid 25 ccm, cupric chloride 5 g and water to 11,000 g, with the note that the control of the contrast is determined by the quantity of the acid and copper solution and that reduction of these reduces the contrasts. Page 105 adds that both papers contain a fairly high ratio of gelatine in mixing and are then diluted down to the required bulk, to prevent the formation of a coarse grain, and that with all paper emulsions saponin or the quillaia tincture should be added, referring to page 152. Pages 95 to 96 carry Wall's own series from pure chloride through 5, 10 and 20 per cent bromide to pure bromide, exposed under a test plate of densities 1 to 3.01 to magnesium ribbon, a Nernst lamp and incandescent gas and developed in one metol-hydroquinone developer, in which 'in every case the same colored image was obtained from the lightest to the deepest deposit', with his conclusion that it is the rate of deposition of the silver which is the determining factor of the color of the image and not the composition of the emulsion, and his separate statement that the more bromide an emulsion contains in comparison to the chloride, the faster it is as a rule, the longer the scale of gradation and the less easy to obtain warm tones. Pages 151 to 152 give the rule that the quantity of hardener used depends on the total quantity of the gelatine and not on the bulk of the emulsion, the range of one of chrome alum to two hundred and fifty or three hundred parts of dry gelatine, and the prohibition on formaldehyde; Chapter V and chapter VI, pages 91 to 94 and page 113: the great advantage of the chloride and bromo-chloride emulsions being the ease with which warm tones can be obtained and the extremely fine-grained image they give, more like a stain than the normal silver image, and their suitability for lantern slide and transparency work; the statement that the slow chloride emulsions given there may be considered to be practically of the same type as the slow gaslight lantern plates on the market; the pepper defect, a characteristic coarse grain distributed through a chloride emulsion and reduced to the metallic state without exposure to light, sometimes too fine to see by eye, with the instruction that test plates should always be examined with an eyepiece particularly in the parts protected from light, and the two avoidances of reducing the quantity of water during the mix or adding the silver nitrate dry to the chlorized gelatine; the finals set for a washed commercial chloride emulsion, per 45,000 ccm, of gelatine 900 g, alcohol 2500 ccm, basic chrome alum solution 100 ccm and hydrochloric acid 5 ccm; and the division that bromide papers are always washed emulsions while gaslight papers are usually unwashed; Chapter VI, printing paper emulsions, and the division between washed bromide papers and unwashed gaslight papers; pages 95 to 96, the controlled series on image colour; Page 101: bromide papers are always washed emulsions where the gaslight papers are usually unwashed, and the practice of pouring bromide emulsions into ice-cold pans immediately after digestion to set quickly and stop the ripening; page 92 for pepper, the coarse grain reduced to metallic silver without exposure that may be too fine to see without an eyepiece, and its avoidances; Pages 92 to 94, the slow chloride gaslight emulsions and their finals set of gelatine, alcohol, basic chrome alum solution and hydrochloric acid per 45,000 ccm; page 92, the "pepper" defect and its two avoidances; pages 101 and 113, the division between always-washed bromide papers and usually-unwashed gaslight papers; Chapter VI, Printing Paper Emulsions: page 103, gaslight or development papers as a rule unwashed emulsions containing varying ratios of bromide and chloride, with the formulas given as used commercially; page 104, the "Soft-working paper" formula, its 50 °C emulsification, its seventy-five-minute digestion, its chrome alum finals and its made-up weight of 11,000 g; page 105, the high gelatine ratio in mixing to prevent a coarse grain, and saponin or quillaia tincture for all paper emulsions; page 101, bromide papers always washed and gaslight usually unwashed, and the practice of pouring bromide emulsions into ice-cold pans to stop ripening; pages 95 to 96, the controlled series across pure chloride, 5, 10 and 20 per cent bromide and pure bromide, exposed under a 1 to 1024 test plate to three light sources and developed in one metol-hydroquinone developer, with Chapman Jones cited on particle size; pages 97 to 100, the five chlorobromide plate emulsions and their stated characters; page 152, the rule that the chrome alum quantity depends on the total gelatine and not on the bulk of the emulsion; Pages 151 to 152: the basic chrome alum solution and the rule that the dose depends on the total gelatine and not on the bulk of the emulsion; Wratten's tannin and its yellow-stain warning; the prohibition on formaldehyde. Page 92, the pepper defect. Page 94 and page 104, the finals sets and the saponin or quillaia surfactant; Pages 91 to 92: the pure bromide lantern emulsion and the note that lantern plates of that type were much in favour in England because almost any colour can be obtained by suitable variation of the exposure and developer; the advantage of chloride and bromo-chloride emulsions being the ease of warm tones and an extremely fine-grained image more like a stain than the normal silver image, specially suitable for lantern slide and transparency work; pepper, the coarse grain reduced to the metallic state without exposure, sometimes too fine to see without an eyepiece, with the instruction that test plates should always be examined with an eyepiece; page 94 for the slow chloride emulsions being practically of the same type as the slow gaslight lantern plates on the market; Page 92: pepper, a characteristic coarse grain distributed throughout the emulsion and reduced to the metallic state without exposure to light, sometimes so fine it cannot be seen by visual examination, with the instruction that test plates should always be examined with an eyepiece particularly in the parts protected from light action, and the two avoidances of reducing the quantity of water during the mix or adding the silver nitrate dry to the chlorized gelatine; Pages 151 to 152: the basic chrome alum solution, the rule that the dose depends on the total gelatine and not on the bulk of the emulsion, Wratten's tannin, and the prohibition on formaldehyde as an emulsion hardener; Pages 91 to 105: the slow chloride emulsions and the gaslight papers; the chlorobromide plate emulsions across the halide-ratio range; the pepper defect on page 92; and the high gelatine ratio during mixing used to prevent coarse grain; Pages 95 to 96: the controlled series across pure chloride, 5, 10 and 20 per cent bromide and pure bromide, developed in one metol-hydroquinone developer, giving the same coloured image in every case, with the conclusion that it is the rate of deposition of the silver rather than the composition of the emulsion that determines the colour of the image, and Chapman Jones cited on the colour depending on the size of the silver particles; the statement that the more bromide an emulsion contains in comparison with the chloride the faster it is as a rule, the longer the scale of gradation and the less easy to obtain warm tones; pages 91 to 92 on the extremely fine-grained image of chloride and bromo-chloride emulsions, more like a stain than the normal silver image; Pages 101 to 105: bromide papers always washed and gaslight papers usually unwashed; page 99 and pages 151 to 152 for the finals sets and the gelatin-relative hardener rule; Chapter VI, Printing Paper Emulsions, page 103, the framing of gaslight or development papers as a rule unwashed emulsions containing varying ratios of bromide and chloride of silver, and page 101, the division that bromide papers are always washed emulsions while the gaslight is usually unwashed; pages 95 to 96, the series from pure chloride through 5, 10 and 20 per cent bromide to pure bromide, exposed to three sources and developed in one metol-hydroquinone developer, in which the same coloured image was obtained in every case, with the conclusion that it is the rate of deposition of the silver which determines the colour of the image and not the composition of the emulsion, and the separate statement that the more bromide an emulsion contains relative to the chloride the faster it is as a rule, the longer the scale of gradation and the less easy to obtain warm tones; Bromide papers as washed emulsions and gaslight papers as usually unwashed; commercial emulsion making at scale; The controlled series from pure chloride through 5, 10 and 20 per cent bromide to pure bromide, developed in one metol-hydroquinone developer; the effect of halide ratio on speed and gradation; Chloride and chlorobromide emulsions; the division between washed bromide papers and unwashed gaslight papers; Page 101: bromide papers are always washed emulsions where the gaslight papers are usually unwashed; the named defect of pepper and the two avoidances given for it; Page 92 - pepper as a characteristic coarse grain distributed throughout the emulsion and reduced to the metallic state without exposure to light, sometimes too fine to be seen by visual examination, with the instruction that test plates should always be examined with an eyepiece particularly in the parts protected from light action, and the two avoidances of reducing the quantity of water during the mix or adding the silver nitrate dry to the chlorized gelatine

Used by:Nickel(II) sulfate · Sodium selenosulfate · Tannic acid · Trumm's bromide paper emulsion · Wall's soft-working gaslight paper · KCl gaslight paper emulsion · P5 Part V Overview: Photographic Emulsions · P5 Project 3: A Bromide Enlarging Emulsion · P5 Project 1: A Silver Chloride Contact Printing Emulsion · P5 Project 2: A Chlorobromide Paper Emulsion · P5 Coating, Drying and Hardening · P5 Project 4: Coating Glass Dry Plates and a Lantern Slide · P5 Break/Fix: Emulsion Coating Defects · P5 Gelatin, the Photographic Binder · P5 Precipitation, Nucleation and Crystal Growth · P5 Assignment: The Hand-Coated Print · P5 Washing, Digestion and Sensitisation · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · Hand-coated bromide paper · Hand-coated chlorobromide paper · Hand-coated silver chloride contact paper · An emulsion preparation session · Black spots

kodak.com

Basic Photographic Sensitometry Workbook, publication H-740retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Family of Curves and the Time-Contrast Index Curve — the stated purpose of the curve being to find the development time for a desired contrast index, and the answer that the four factors affecting contrast index are time, temperature, agitation and developer; The Time-Contrast Index Curve, its stated purpose of finding the development time for a desired contrast index, and the four factors affecting contrast index given as time, temperature, agitation and developer; Contrast Index — the marked-straightedge construction with marks at 0.0, 0.2 and 2.2; Film Speed, for the average gradient of 0.62 implied by the speed condition and the 0.58 to 0.65 range the plus or minus 0.05 tolerance allows; and the family of curves, whose toe remains basically the same while the straight line and shoulder steepen with development; Family of Curves and the Time-Contrast Index Curve — the stated purpose of the curve being to find the development time for a desired contrast index, which is the quantity the developer-comparison milestone matches its four developers on; Contrast Index and the family of curves — the marked-straightedge construction, the four factors affecting contrast index given as time, temperature, agitation and developer, and the statement that with longer development most of the change is in the straight line and the shoulder while the toe remains basically the same; Contrast Index — the marked-straightedge construction with marks at 0.0, 0.2 and 2.2, the 0.0 mark placed on the D-min line and the 0.2 and 2.2 marks on the curve; Film Speed, for the average gradient of 0.62 implied by the speed condition and the 0.58 to 0.65 range that the plus or minus 0.05 tolerance allows; and the Time-Contrast Index Curve, whose stated purpose is to find the development time for a desired contrast index; Contrast Index and the straightedge construction that measures it; the family of curves at 5, 8 and 13 minutes and its contrast indices of 0.51, 0.62 and 0.73; the additional data giving 0.55 at 6 minutes, 0.67 at 10 and 0.72 at 12; the four factors that affect contrast index; the Time-Contrast Index curve and its purpose; and the note that different developers yield different film speeds and that the developer specified by the standard method is similar to KODAK Developer D-76; Contrast Index and the straightedge construction; the family of curves at 5, 8 and 13 minutes with contrast indices of 0.51, 0.62 and 0.73, and the further data giving 0.55 at 6 minutes, 0.67 at 10 and 0.72 at 12; the four factors affecting contrast index; the Time-Contrast Index curve; Contrast Index and the Time-Contrast Index Curve; the answer that the four factors affecting Contrast Index are time, temperature, agitation and developer; The characteristic curve and its axes; contrast index as a measure of development; the worked family of curves for an unnamed film in an unnamed developer at 20 degrees C with agitation at 30-second intervals, and the answer key giving the contrast index of each; Contrast Index — the marked-straightedge construction with its 0.0, 0.2 and 2.2 marks, the 0.0 mark on the D-min line and the other two on the curve, and the statement that the toe therefore influences Contrast Index where it does not influence gamma; the family of curves for film XYZ in developer A at 20 degrees C with intermittent agitation at 30-second intervals, whose contrast indices the answer key gives as 0.51 at 5 minutes, 0.62 at 8 and 0.73 at 13, with the additional data of 0.55 at 6 minutes, 0.67 at 10 and 0.72 at 12; the observation that most of the change with development time is in the straight line and the shoulder and that the toe remains basically the same; the Time-Contrast Index Curve and its stated purpose of finding the development time for a desired Contrast Index, with the answer-key read-offs of 11 minutes for CI 0.70 and 7 minutes for CI 0.58; and the answer that the four factors affecting Contrast Index are time, temperature, agitation and developer; Introduction and Names of Units - sensitometry as the numerical description of light in, development, and degree of darkening out; the worked sample curve and its tabulated densities, which this part uses as its published example dataset; Names of Units - Exposure equals Illuminance times Time, with the worked example of 75 millilux for one fifteenth of a second giving 5 millilux-seconds; Density - transmission, opacity as the reciprocal of transmission, and density as the base-ten logarithm of opacity; Why Logs - compaction of the scale and the claim that the eye works logarithmically; Step Tablets - the 11-step and 21-step tablets, both about 0.05 to 3.05, at increments of 0.30 and 0.15; Figuring Exposure - the subtraction of filter and step-tablet densities from the log exposure of the source; Constructing the Curve - the rule that 0.30 in density must match 0.30 in log exposure on the paper; Glossary - the preference for step over stop as the general term for a factor of two in exposure; Film Speed - the two-step method printed in full: point A at 0.10 density units above D-min, point B at 1.30 log exposure units further along, the film taken as properly developed when the density at B is 0.80 plus or minus 0.05 above that at A, and the speed formula given as 800 divided by the antilog of A in millilux-seconds or 0.8 divided by the antilog of A in lux-seconds; the worked example placing A at log exposure 0.90 for a speed of 100; the statement that the developer specified by the standard method is similar to KODAK Developer D-76 and that different developers yield different film speeds; Standard Film-Speed Tables, with the rows 32 40 50, 64 80 100, 125 160 200, 250 320 400, 500 650 800, the note that 650 and 1250 do not follow the general pattern, and the explanation that a one-third-step change is 0.1 in log exposure because the log of 2 is roughly 0.3; Family of Curves and Exposure Latitude, for the placement of the subject range from the speed point; Gamma - defined as the slope of the straight-line portion, with the worked example giving 0.94 over 1.5 log exposure units for a gamma of 0.63; Contrast Index - the marked-straightedge construction with marks at 0.0, 0.2 and 2.2, the 0.0 mark placed on the D-min line and the 0.2 and 2.2 marks on the curve, and the statement that the minimum point falls on the toe so that the shape of the toe influences the result, unlike gamma; Average Gradient - defined between any two points with the two densities written as subscripts, worked as 1.52 over 3.0 for 0.51 on the same curve; Family of Curves at 5, 8 and 13 minutes with contrast indices given in the answer key as 0.51, 0.62 and 0.73; the four factors affecting contrast index given as time, temperature, agitation and developer; the Time-Contrast Index Curve, its purpose of finding the development time for a desired contrast index, and the readings of 11 minutes for 0.70 and 7 minutes for 0.58; Film Speed, for the average gradient of 0.62 implied by the speed condition and the 0.58 to 0.65 range that the plus or minus 0.05 tolerance allows; Family of Curves - three curves at 5, 8 and 13 minutes for one film in one developer, with the note that the longer the development the steeper the slope, that most of the change is in the straight line and the shoulder, and that the toe remains basically the same; the Time-Contrast Index Curve and its stated purpose of finding the development time for a desired contrast index; Film Speed, for the two-step construction and for the 0.80 plus or minus 0.05 condition over 1.30 log exposure units; Exposure Latitude, for placing a subject range on the curve from the speed point; Paper Curves - the statement that paper densities are read on a reflection densitometer, that papers are slower than films, that paper speed is not figured in the same way as film speed, and the typical family of black-and-white paper curves for grades 1 to 4 plotted as reflection density against relative log exposure on an axis running to 2.4; Step Tablets - the 11-step tablet at a 0.30 density increment and the 21-step tablet at 0.15, both covering about 0.05 to 3.05; Figuring Exposure, for the arithmetic by which a step's density is subtracted from the log exposure delivered by the source to give the log exposure at that step; Constructing the Curve, for the instruction to make the scales equal so that every 0.30 of density change matches every 0.30 of log exposure change; Film Speed, for the two-step criterion construction; Contrast Index, for the straightedge construction; The Parts of a Curve - toe, straight line and shoulder, with shadows falling on the toe and highlights on the shoulder; D-min, described as base plus fog and as gross fog, and attributed to the transparent base plus a slight chemical fog from crystals that develop although unexposed; D-max, with the note that a black-and-white curve may not show it; Constructing the Curve and the tabulated eleven densities of the sample film; Family of Curves at 5, 8 and 13 minutes, whose contrast indices the answer key gives as 0.51, 0.62 and 0.73, with the observation that most of the change is in the straight line and the shoulder and the toe remains basically the same; Exposure Latitude, worked for a brightness range of 60 to 1; Exposure Latitude - the construction that places a subject luminance range as a bar on the log exposure axis from the speed point, and the worked example of a scene spanning 60 to 1, which is 1.8 in log terms, on a curve covering 3.0, leaving 1.2 of slack that divides into under- and over-exposure latitude; Family of Curves, for the statement that the toe remains basically the same while development changes the straight line and the shoulder; Paper Curves, for reflection density and the family of paper grades; Sensitometers - the block diagram of light, shutter, filter, holder, step tablet and film sample, and the worked exposure of 100,000 millilux for one-fifth of a second read with a lux meter; Step Tablets - the 11-step at 0.30 increments and the 21-step at 0.15, both spanning about 0.05 to 3.05; Exposure - illuminance measured with a lux meter and multiplied by time, with the worked example of 100,000 millilux for one-fifth of a second giving 20,000 millilux-seconds and a log exposure of 4.3; Figuring Exposure - the filter density and then the step tablet's own density subtracted from the log exposure; Step Tablets - the 21-step at 0.15 spanning about 0.05 to 3.05; Contrast Index - the straightedge construction and the definition as the slope of the line between two points on the D-log E curve; Step Tablets - the 21-step at a 0.15 increment spanning about 0.05 to 3.05; Sensitometers - the sensitometer diagrammed as light, shutter, filter, holder, step tablet and film sample, read afterwards on a densitometer; Exposure - illuminance measured with a lux meter, the worked example of 100,000 millilux for one-fifth of a second giving 20,000 millilux-seconds and a log exposure of 4.3; Figuring Exposure - the 0.95 filter subtracted from the log exposure before the step tablet's own density; Step Tablets - the 11-step at 0.30 and the 21-step at 0.15, both spanning about 0.05 to 3.05, with the full list of step densities; Step Tablets - the 21-step tablet spanning about 0.05 to 3.05 in increments of 0.15; Density - density as the logarithm of the reciprocal of transmittance, and the arithmetic of reading a step tablet; Family of curves - the statement that the longer the development time the steeper the slope of the curve, that most of the change is in the straight line and the shoulder and that the toe remains basically the same, with the worked family at 5, 8 and 13 minutes for one film in one developer at 20 degrees C with intermittent agitation at 30-second intervals; Time-Contrast Index Curve - contrast index plotted against development time for a developer, temperature and agitation combination, whose purpose is to make it easy to find the development time for any desired contrast index; Contrast Index - the straightedge construction with marks at 0.0, 0.2 and 2.2 log exposure units; Base plus fog and gross fog defined as the density of the base plus the density of the fog in the emulsion, with D-min the preferred term; the account of chemical fog as a few silver halide crystals developing without having been exposed; The treatment of paper curves - that paper densities are read on a reflection densitometer, that papers are much slower than films, and that paper speed is not figured in the way film speed is; Paper Sensitometry - negatives and printing paper treated as one system, negative curves of slope typically around 0.45 to 0.65 given more exposure latitude and paper slopes from about 1.5 to 3.5 depending on grade to compensate, and the statement that paper densities require a reflection densitometer; The Parts of a Curve - D-min described as base plus fog and attributed to the transparent base plus a slight chemical fog from crystals that develop although unexposed; Step Tablets, for the 21-step tablet at a 0.15 density increment covering about 0.05 to 3.05; Figuring Exposure, for the arithmetic by which a step's density is subtracted from the log exposure delivered by the source to give the log exposure at that step; and Constructing the Curve, for the instruction to make the two scales equal so that every 0.30 of density change matches every 0.30 of log exposure change; Family of Curves and the Time-Contrast Index Curve — contrast indices given in the answer key as 0.51 at 5 minutes, 0.55 at 6, 0.62 at 8, 0.67 at 10, 0.72 at 12 and 0.73 at 13, the stated purpose of the curve being to find the development time for a desired contrast index, and the readings taken from it of 11 minutes for 0.70 and 7 minutes for 0.58; the answer that the four factors affecting contrast index are time, temperature, agitation and developer; and the workbook's practice of naming neither the film nor the developer of its worked example, calling them XYZ and A; Family of Curves and the Time-Contrast Index Curve - the answer key's six contrast indices of 0.51 at 5 minutes, 0.55 at 6, 0.62 at 8, 0.67 at 10, 0.72 at 12 and 0.73 at 13 for a film and developer the workbook declines to name, calling them XYZ and A; the stated purpose of the curve, which is to read a development time off a chosen contrast index; and the answer that the four factors affecting contrast index are time, temperature, agitation and developer; Contrast Index - the marked-straightedge construction with marks at 0.0, 0.2 and 2.2, the 0.0 mark laid on the D-min line and the other two on the curve, and the statement that the minimum point falls on the toe so that the shape of the toe influences the result, unlike gamma; Family of Curves - one film in one developer at 20 degrees C with intermittent agitation at 30-second intervals, developed 5, 8 and 13 minutes, whose contrast indices the answer key gives as 0.51, 0.62 and 0.73, with the observation that most of the change is in the straight line and the shoulder and that the toe remains basically the same; the answer to question 71, that the four factors affecting contrast index are time, temperature, agitation and developer; the Time-Contrast Index Curve and its stated purpose of finding the development time for a desired contrast index; and the eleven tabulated densities of the sample film used on this page only as a worked table for the uncertainty arithmetic; Film Speed - the two-step speed construction the course's own criterion is taken from, and the statement that different developers yield different film speeds; Family of Curves and the Time-Contrast Index Curve - the six published contrast indices of 0.51 at 5 minutes, 0.55 at 6, 0.62 at 8, 0.67 at 10, 0.72 at 12 and 0.73 at 13 for a film and developer the workbook declines to name, the stated purpose of the curve being to find the development time for a desired contrast index, and the answer that the four factors affecting contrast index are time, temperature, agitation and developer; Family of Curves and the Time-Contrast Index Curve - the six published contrast indices of 0.51 at 5 minutes, 0.55 at 6, 0.62 at 8, 0.67 at 10, 0.72 at 12 and 0.73 at 13 for a film and developer the workbook declines to name, and the stated purpose of the curve, which is to read a development time off a chosen contrast index; and the answer that the four factors affecting contrast index are time, temperature, agitation and developer; Contrast Index and the Family of Curves - one film in one developer at 20 degrees C with intermittent agitation at 30-second intervals, developed 5, 8 and 13 minutes, whose contrast indices the answer key gives as 0.51, 0.62 and 0.73, with the additional data of 0.55 at 6 minutes, 0.67 at 10 and 0.72 at 12; the Time-Contrast Index Curve, whose stated purpose is to make it easy to find the development time for any desired contrast index, and the two values read back off it, 11 minutes for 0.70 and 7 minutes for 0.58; the answer that the four factors affecting contrast index are time, temperature, agitation and developer; the answer that a 0.1 log exposure interval is one third of a step; and the workbook's practice of naming neither the film nor the developer of its worked example, calling them XYZ and A; Figuring Exposure: the step tablet's own density subtracted from the log exposure reaching bare film; Step Tablets, the 21-step at a 0.15 increment spanning about 0.05 to 3.05; The shoulder as the region where the slope falls away and further exposure buys less density, ending at D-max; the note that a black-and-white curve often does not reach D-max at all because a step tablet's three log units of range run out first and because in normal use a film never gets that much light; The toe as the region where density has begun to rise but the slope is still climbing; the speed point defined as a fixed density above base plus fog, and the consequence that it moves with base plus fog; Base plus fog, also written D-min, as the density of a piece of film processed but never exposed; the two contributions - the support and its dye, and chemical fog - and the older term gross fog; the note that a black-and-white curve often does not reach D-max within a step tablet's three log units; Contrast index as the slope of a line drawn between two points on the curve, and its use in place of gamma for pictorial black-and-white films; the gamma-time and contrast-index-time relationships, in which slope rises with development time towards a limit; Sensitometric exposure - the requirement that the exposing field be uniform over the area of the strip, and that the modulator be in intimate contact with the emulsion

Used by:P29 Capstone Overview: What the Pure Silver Portfolio Asks · P29 Capstone Stage 2: Formulating and Documenting Your Chemistry · P29 Capstone Stage 3: Exposing, Processing and Measuring · P29 The Assignment Path: Fourteen Pictures That Build One Photographer · P29 The Capstone Chemistry Report: From Photon Capture to Finished Print · P29 The Pure Silver Portfolio: The Specification · P8 Development Kinetics: Time, Temperature, Agitation and Exhaustion · P8 Assignment: Reading a Developer Formula · P9 Overview: Experiments on Development · P9 Assignment: The Developer Laboratory Report · P9 Experimental Design for the Darkroom · P13 Part XIII Overview: Measuring the Response of Silver to Light · P13 Exposure, Density and the Logarithm · P13 Film Speed and Exposure Index · P13 Gamma, Contrast Index and Average Gradient · P13 Assignment: Interpreting Density Data · P13 Paper Sensitometry: Reflection Density, Grades and ISO(R) · P13 Lab: A Step-Wedge Exposure Series · P13 The Characteristic Curve · P13 Tone Reproduction: From Subject to Print · P14 Part XIV Overview: Build a Sensitometer · P14 Experiment: Calibrating the Sensitometer · P14 Experiment: Process Control with Control Strips · P14 Sensitometer Design Principles · P15 Experiment: Calibrating the Densitometer in Both Modes · P15 Assignment: Characterising a Film and Developer with Your Own Instruments · P18 Experiment: Maximum Black, Base White and Dry-Down · P19 Reading the Negative and Making the Work Print · P20 Experiment: Selenium Toning and the Print Curve · P27 Part XXVII Overview: From Observation to Measurement · P27 Designing an Experiment That Yields a Number · P27 Experiment: Four Curve Families, Measured · P27 Push and Pull Processing: What Extended Development Can and Cannot Buy · P27 Assignment: The Developer Comparison, Measured and Printed · P27 Experiment: The Development Time and Temperature Series · Sensitometer exposure session · Blocked shoulder · Cut-off toe · Elevated fog on a curve · Low contrast index · Uneven density across a strip

How Safe Is Your Safelight? A Guide to Darkroom Illumination, publication K-4retrieved 2026-09-04, 2026-09-05, 2026-09-07

Sections: The safelight test — a light grey test area of reflection density 0.25 to 0.50, the safelight steps of 0, 1, 3 and 7 minutes made with a moving card, and the criterion that no density change between the unexposed and the longest-exposed area means the conditions are adequate; Safelight filter table — filter 1A (light red) for slow orthochromatic materials, filter 2 (dark red) for fast orthochromatic materials, at 15 or 25 watts; Test for black-and-white papers, preparing the darkroom; Important facts about safelights; Black-and-White Papers: safelight exposure before or after the printing exposure, the definition of safe time, and the warning that a coin test checks only for fog; Important facts about safelights; the total-darkness materials list; the definition of safe time as half the time to a detectable change; the test for black-and-white papers; Test for Black-and-White Papers: the light grey tone of reflection density 0.25 to 0.50, the 0, 1, 3 and 7 minute steps, the definition of safe time, and the warning that a coin test checks only for fog; Important facts about safelights: the ideal that a filter transmits only light outside the colour-sensitivity range of the material, and the statement that colour sensitivity does not end abruptly, so most papers and films have some sensitivity even to their own recommended safelight; Blue-Sensitive and Orthochromatic Black-and-White Films: handling under red safelights; the definition of safe time as half the time at which a detectable change first appears; The statement that blue-sensitive and orthochromatic black-and-white films can be handled under red safelights, and that most emulsions retain some sensitivity to the colours a recommended filter transmits so safelight exposure should always be minimised; The statement that the colour sensitivity of most emulsions does not end abruptly at a wavelength, that most papers and films retain some sensitivity to the colours a recommended safelight filter transmits, and that safelight exposure should therefore always be minimised; Blue-sensitive and orthochromatic black-and-white films may be handled under red safelights; Important facts about safelights: that the colour sensitivity of most emulsions does not end abruptly at a wavelength and that some sensitivity remains to the colours a recommended filter transmits; Important facts about safelights - no safelight protects a sensitised material indefinitely, filters fade with use, and poor safelight conditions can produce a loss in photographic quality before actual fogging is visible; and the definition of safe time as an exposure less than or equal to half the time at which a detectable change appears; A safelight has three basic parts - the lamp housing, which keeps the white light emitted by the bulb from escaping, the filter, and the bulb; Placement of safelight lamps - direct illumination no closer than 1.2 m, no more than one utility lamp per 6 square metres of ceiling, lamps at least 2.5 m apart, the instruction not to put a direct safelight where it will shine on an enlarging easel, and the warning against pools of relatively bright light against a dark background; Safelight precautions - unsafe illumination from an incorrect or faded filter, too high a bulb wattage, lamp location or too many safelights, and fogging from light escaping an enlarger head or from lighted dials on equipment controls; and the note that a red filter often has less effect on paper than the recommended amber, which is preferred because most workers judge print density better under it; Important facts about safelights - the statement that poor safelight conditions can produce a loss in photographic quality before actual fogging is visible; Safelight precautions - light escaping from an enlarger head and lighted dials on equipment controls named as sources of fog; and the five-minute wait in a darkened room with the eyes adapting before looking for leaks; Important facts about safelights - that no safelight protects a sensitised material indefinitely, that filters fade with use, and that poor safelight conditions can produce a loss in photographic quality before actual fogging is visible; Black-and-White Papers - the term super-additive exposure for a low-level overall exposure given before or after the printing exposure, the statement that virtually all exposures are cumulative, and that excessive exposure degrades highlights and lowers print contrast before fogging is visible in the borders; Safelight precautions - light escaping from an enlarger head, lighted dials on equipment controls, pinholes, and plywood that appears opaque but may admit infrared, each named as a source of fog; Placement of safelight lamps - the instruction not to place a direct safelight where it will shine on an enlarging easel; Test for Black-and-White Papers, Before starting the test - turn off the white lights, wait at least five minutes for a fluorescent tube's residual glow to dissipate, check that no white light enters through doorways or pass-throughs, and remember that it takes at least ten minutes for the eyes to become fully adjusted to the dark; Safelight precautions - light escaping from an enlarger head, lighted dials on equipment, pinholes between the darkroom and lighted areas, and plywood that appears opaque but may admit infrared; Placement of safelight lamps - flat white ceilings for indirect safelights, walls in a light colour similar to that transmitted by the filter, flat black immediately behind each enlarger and around light locks, direct illumination no closer than 1.2 m, and the instruction not to put a direct safelight where it will shine on an enlarging easel; Total-darkness materials, panchromatic black-and-white films and plates among them; and the definition of safe time as an exposure less than or equal to half the time at which a detectable change appears; Important facts about safelights, and the following text - no safelight protects a sensitised material indefinitely, filters are designed for specific materials, filters fade with use, and poor safelight conditions can produce a loss in photographic quality before actual fogging is visible; the statement that the colour sensitivity of most emulsions does not end abruptly at a wavelength so that most papers and films retain some sensitivity to the colours a recommended filter transmits; the three parts of a safelight; the note that the apparent colour of a filter is only a partial indication of its transmission and that coloured bulbs and improvised safelights may emit light or other radiant energy that fogs an emulsion; Black-and-White Papers - the definition of safe time as an exposure less than or equal to one half of the time required to produce a detectable change, the term super-additive exposure for a low-level overall exposure before or after the printing exposure, the statement that virtually all exposures are cumulative, and that excessive exposure degrades highlights and lowers print contrast before fogging is visible in the borders; Total-darkness materials; Placement of safelight lamps - no more than one utility lamp per 6 square metres of ceiling, lamps spaced at least 2.5 m apart, direct illumination no closer than 1.2 m, and the instruction not to place a direct safelight where it will shine on an enlarging easel; Safelight precautions - light escaping from an enlarger head, lighted dials on equipment controls, pinholes, and plywood that appears opaque but may admit infrared; and the statement that Kodak's safelight-filter recommendations are based on test procedures similar to those described in ANSI Standard PH2.22-1998; Test for Black-and-White Papers - the preparation steps of a new bulb, a five-minute wait for a fluorescent tube's residual glow and at least ten minutes for the eyes to adapt; the grey-tone exposure targeted at a reflection density of 0.25 to 0.50, that is 0.15 to 0.40 above the paper density; the safelight steps of 0, 1, 3 and 7 minutes made with a moving card; the two enlarger exposures labelled After and Before at opposite ends of the sheet; processing in total darkness; the three evaluations A, B and C, of which C is described as typical and gives 7 minutes before and 3 after; the definition of safe time as an exposure less than or equal to one half of the time required to produce a detectable change; the term super-additive exposure and the statement that virtually all exposures are cumulative; the warning that a coin test checks only for fog and not for the added effects of safelight and enlarger exposure together; and Tests for Other Photographic Materials, with steps of 0, 4, 7 and 13 minutes for sheet film read against the film's gross fog; Black-and-White Papers - the term super-additive exposure, the statement that virtually all exposures are cumulative, and that excessive exposure degrades highlights and lowers print contrast before fogging is visible in the borders; Safelight precautions - lighted dials on equipment controls named as a source of fog; Test for Black-and-White Papers - the grey-tone pre-exposure targeted at a reflection density of 0.25 to 0.50, the stepped exposure made with a moving card, the After and Before enlarger exposures at opposite ends of the sheet, processing in total darkness, the term super-additive exposure with the statement that virtually all exposures are cumulative, and the definition of safe time as an exposure less than or equal to one half of the time required to produce a detectable change; Black-and-White Papers - the term super-additive exposure, the statement that virtually all exposures are cumulative, and that excessive exposure degrades highlights and lowers print contrast before fogging becomes visible in the borders; Important facts about safelights - that no safelight protects a sensitised material indefinitely and that filters fade with use; Safelight precautions - lighted dials on equipment controls named as a fog source; The definition of safe time as any exposure time less than or equal to one half of the time required for a safelight to produce a detectable change in a particular material; the statement that the colour sensitivity of most emulsions does not end abruptly at a wavelength so that safelight exposure should always be minimised; and the recommendation of a 15-watt bulb kept at least 4 feet (1.2 metres) from the paper; The definition of safe time as any exposure time less than or equal to one half of the time required for a safelight to produce a detectable change in a particular material; the statement that the colour sensitivity of most emulsions does not end abruptly at a wavelength and that most papers and films retain some sensitivity to the colours a recommended safelight filter transmits, so safelight exposure should always be minimised; and the recommendation of a 15-watt bulb kept at least 4 feet (1.2 metres) from the paper; Before starting the test — waiting at least five minutes for a fluorescent tube's residual glow to dissipate, checking that no white light enters through doorways or pass-throughs, and the statement that it takes at least ten minutes for the eyes to become fully adjusted to the dark; Safelight precautions — light escaping from an enlarger head, lighted dials on equipment controls, pinholes between the darkroom and lighted areas, and plywood that appears opaque but may admit infrared; Total-darkness materials, panchromatic black-and-white films and plates among them; and the definition of safe time as an exposure less than or equal to half the time at which a detectable change appears; Before starting the test — waiting at least five minutes for a fluorescent tube's residual glow to dissipate and at least ten minutes for the eyes to become fully adjusted to the dark; Safelight precautions — light escaping from an enlarger head, lighted dials on equipment controls and pinholes between the darkroom and lighted areas; Placement of safelight lamps — direct illumination no closer than 1.2 m, and the instruction not to put a direct safelight where it will shine on an enlarging easel; Safelight precautions - the instruction to keep safelight exposure to a minimum, to store paper in lighttight containers and to handle paper emulsion side down away from the safelights, and the list of other emitters in the room, light escaping from an enlarger head, lighted dials on equipment controls and pinholes; Black-and-White Papers - the statement that virtually all exposures are cumulative and that excessive exposure degrades highlights and lowers print contrast before fogging is visible in the borders; Placement of safelight lamps - direct illumination no closer than 1.2 m; The word 'safe' is relative, and the colour sensitivity of most emulsions does not end abruptly at a wavelength, so most papers and films keep some sensitivity to the colours a recommended safelight filter transmits; therefore always minimise the exposure of photographic materials to safelight illumination; Safelight precautions - store paper in lighttight containers; Test for Black-and-White Papers: the light grey tone of reflection density 0.25 to 0.50, the 0, 1, 3 and 7 minute steps, the definition of safe time as any time less than or equal to half the time at which a detectable change first appears, and the warning that a coin test checks only for fog and not for the added effects of safelight and enlarger exposure together; Test for Black-and-White Papers: the light grey tone of reflection density 0.25 to 0.50, the 0, 1, 3 and 7 minute steps made with a moving card, the definition of safe time as an exposure less than or equal to half the time required to produce a detectable change, and the statement that virtually all exposures are cumulative; Safelight precautions: light escaping from an enlarger head, lighted dials on equipment controls, and pinholes between the darkroom and lighted areas; and the five-minute wait for a fluorescent tube's residual glow to dissipate; Safelight precautions - an incorrect or faded filter, too high a bulb wattage, safelight location and too many safelights; light escaping from an enlarger head, lighted dials on equipment controls and non-opaque construction materials; the warning that excessive safelight exposure may show up only in the image area because it receives additional exposure from the enlarger; Safelight precautions - light fogging from sources other than the safelight, specifically light escaping from an enlarger head, lighted dials on equipment controls and non-opaque darkroom construction materials; the note that excessive fogging may show up only in the image area because that area receives additional exposure from the enlarger, and that a coin test is therefore misleading; The instruction to store paper in lighttight containers and to handle it emulsion side down away from the safelights; Safelight precautions - light fogging from sources other than the safelight, including light escaping from an enlarger head, lighted dials on equipment controls and non-opaque darkroom construction materials; the specific examples of pinholes between the darkroom and lighted areas admitting visible light, and plywood that appears opaque admitting infrared; Safelight precautions - an incorrect filter, a faded or cracked filter, incorrect bulb wattage, safelight location and too many safelights; light escaping from an enlarger head, lighted dials on equipment controls and non-opaque darkroom construction materials; the warning that excessive safelight exposure may show up only in the image area because that area receives additional exposure from the enlarger; the caution that a coin test checks only for fog and not for the added effects of safelight and enlarger exposure together; Safelight precautions - light fogging from sources other than the safelight, specifically lighted dials on equipment controls listed alongside light escaping from an enlarger head and non-opaque construction materials; the instruction to keep safelight exposure to a minimum, store paper in lighttight containers and handle paper emulsion side down away from the safelights

Used by:P29 Capstone Stage 1: The Instrument, Its Calculation and Its Commissioning · Erythrosin · P1 The Camera Obscura: An Image Without Chemistry · P1 Experiment: The Image That Would Not Stay · P4 Reciprocity Failure and the Life of the Latent Image · P4 Spectral Sensitivity and Colour Response · P4 Darkroom Session: The Latent Image Made Visible · P4 The Silver Halides · P5 Build an Emulsion Coating Station · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P5 Break/Fix: Emulsion Coating Defects · P5 Washing, Digestion and Sensitisation · P7 Assignment: Landscape, Sky, Foreground and Filters · P13 Paper Sensitometry: Reflection Density, Grades and ISO(R) · P13 Lab: A Step-Wedge Exposure Series · P16 Part XVI Overview: Build the Darkroom · P16 Build: An LED Safelight · P16 Experiment: Commissioning the Enlarger · P16 Break/Fix: The Room That Fogs and the Light That Is Not Even · P16 Build: Making a Room Dark and Proving It · P16 Safelight: Spectra, Distance, Duration and the Fog Limit · P16 Experiment: The Safelight Fog Test · P17 Build: The Switched Output · P17 Build: The Timer Hardware · P17 Break/Fix: The Timer That Lies · P28 Break/Fix: The Film That Came Back Wrong · P28 Fog and Where It Comes From · The blackout leak test · Darkroom opening and closing for a printing session · Opening and handling photographic paper in dim light · Night exposure session · Testing a safelight · The whole-room fog audit · Elevated fog on a curve · Enlarger lamphouse or bellows leak · Paper storage fog · Room light leak, with a direction · Safelight fog · Safelight-fogged control strip · Timer display fog · Weak or grey blacks

Safelight Recommendationsretrieved 2026-09-04, 2026-09-05

Sections: Safelight filter table; The filter-to-material table with bulb wattages and the 1.2 m minimum distance for direct illumination; The table's two illumination columns - 15 W frosted bulbs for direct illumination no closer than 1.2 m and 25 W for indirect, with 7.5 W where the material is more sensitive; The whole one-page table - filter OC light amber for contact and enlarging papers, 1 red for some blue-sensitive materials, 1A light red for slow orthochromatic materials, 2 dark red for fast orthochromatic materials, 3 dark green and 7B green, 10 dark amber and 13 amber for panchromatic papers and colour negative materials, and GBX-2 red; with 15 W frosted bulbs for direct illumination no closer than 1.2 m and 25 W for indirect; The filter table - the OC light amber filter recommended for contact and enlarging papers, at 15 W and 25 W

Used by:P1 Experiment: The Image That Would Not Stay · P4 Spectral Sensitivity and Colour Response · P16 Build: An LED Safelight · P16 Safelight: Spectra, Distance, Duration and the Fog Limit · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed

kodakprofessional.com

Chemicals for KODAK PROFESSIONAL Black-and-White Films, Publication No. E103CFretrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: XTOL Developer: features and benefits; Washing Aid - Hypo Clearing Agent at 1 part stock solution to 4 parts water, 65 to 70 degrees F (18 to 21 degrees C), 1 to 2 minutes, for small or large tank, tray, rotary-tube and rack-and-tank use; keeping properties without use of 3 months for the stock solution in a full closed container and 24 hours in a tray or 1 month in a tank for the working solution; useful capacity in 8 by 10 inch sheets per gallon and per litre of 50 to 60 (12 to 15) without a pre-rinse and 150 to 200 (35 to 50) with one; the description promoting removal of fixer from films and fibre-base papers to shorten wash times and make washing at lower wash-water temperatures practical, the note that it is available as a powder, and the instruction to mix the full volume marked on the package; The XTOL Developer row of the chemicals table - typical dilution, uses, keeping properties without use and useful capacity - read against the Developer D-76 row of the same table; and the XTOL Developer entry in the features and benefits list; The keeping properties and useful capacity columns for Developer D-76 at full strength and at 1:1; Developer descriptions table and its footnote — for greater sharpness you can use D-76 diluted 1:1, which requires longer development times and may result in a slight increase in graininess; The description of XTOL Developer as an ascorbic acid developer giving very high image quality at full emulsion speed, with stable performance across a range of temperatures, dilutions and agitation methods; The one-page table of chemicals for KODAK PROFESSIONAL black-and-white films, revised 12-18 - keeping properties without use and useful capacity in 8 x 10 sheets per gallon and per litre, in a tray and in a tank, giving Developer D-76 full strength 6 months, 24 hours in a tray and 1 month in a tank, and 16 per gallon and 4 per litre; D-76 at 1 to 1 not applicable and not recommended for a tank, 24 hours in a tray; XTOL Developer 6 months, 24 hours and 2 months, and 19 per gallon and 5 per litre; T-MAX Developer at 1 to 4, 8 per gallon and 2 per litre; HC-110 dilution A 20 per gallon and 5 per litre in a tray and 40 and 10 in a tank, dilution B half of each; Indicator Stop Bath discarded when the colour changes; Rapid Fixer 120 per gallon and 32 per litre and Fixer 100 and 26; and Hypo Clearing Agent 50 to 60 per gallon without a pre-rinse and 150 to 200 with one

Used by:Ascorbic acid · Kodak Hypo Clearing Agent and the washing accelerator Kodak patented · KODAK PROFESSIONAL XTOL Developer · P8 Development Kinetics: Time, Temperature, Agitation and Exhaustion · P8 Solvent Action, Physical Development and Grain · P8 Superadditivity: Why Two Agents Beat One · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does

KODAK PROFESSIONAL POLYMAX T Developer and KODAK PROFESSIONAL POLYMAX T Fixer, publication J-5retrieved 2026-09-06, 2026-09-08

Sections: PROCESSING RECOMMENDATIONS, Development - the instruction to adjust the printing exposure so that the print develops to the correct density within the recommended time, and the statement that overexposed and underdeveloped prints often have a muddy-looking appearance, with low contrast and weak blacks, because they are pulled from the developer in much less than the recommended time, and that these images are often mottled from uneven development; Print Agitation - covering the emulsion side with solution as quickly as possible, rocking the tray or keeping the print in motion, adding several prints one at a time and agitating by continuously moving the bottom print to the top, and draining each print briefly on removal; Fixing - the two-bath rotation of half the single-bath time in each of two baths, discarding the first at two hundred 8 by 10 prints per gallon, promoting the second and mixing a fresh second, repeating four times and then replacing both, replacing both after one week of use regardless of the number of prints, with the reason that the first bath does most of the work while the second stays relatively fresh and that the procedure enhances the conditions necessary for complete washing and effective toning, and the warning that fixing times longer than recommended may reduce the silver image especially in the highlights and cause fixer and silver retention in the paper fibres; and Tray Processing, whose tables give the developer 0:45 to 4:00 at 20 C for fibre-base and 0:45 to 3:00 for resin-coated papers, the fixer 5:00 to 10:00 as a single bath or 3:00 to 5:00 in two baths for fibre-base and 2:00 or 1:00 for resin-coated, and a useful capacity of 120 8 by 10 sheets per gallon for the developer and 100 for the fixer; Two-bath fixing: the first bath run to twice the single-bath rating and discarded, the second promoted, and both replaced after a week of use whatever the count

Used by:P19 Developing the Print Consistently and Running a Printing Session · Setting up and shutting down the print processing line

KODAK PROFESSIONAL T-MAX 100 Film, publication F-4016retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Small-tank processing, the XTOL, XTOL (1:1) and D-76 rows; Tray processing, sheets; the replenishment rate for XTOL Developer of 70 mL per 135-36 or 120 roll or 8 x 10-inch sheet; the footnote that more dilute solutions than the table gives are not recommended, and that dilute developers need longer times and give slightly higher film speed and a slight increase in graininess; and the Contrast Index Curves plotted for XTOL and XTOL 1:1 alongside D-76; Image Structure: resolving power and diffuse rms granularity for T-MAX 100, with the measurement conditions; Features: KODAK T-GRAIN Emulsion; Adjustments for Long and Short Exposures: +1/3 stop at 1 s, +1/2 stop or 15 s at 10 s, +1 stop or 200 s at 100 s; Filter Corrections, daylight and tungsten; Filter Corrections, daylight and tungsten: No. 8 yellow 1.5, No. 15 deep yellow 2, No. 25 red 8 and 4; the note that filter factors for other Kodak black-and-white films are different; Image Structure — resolving power quoted at two test-object contrasts, 63 lines per millimetre at 1.6:1 and 200 at 1000:1, and the modulation transfer function curve; Image Structure — diffuse rms granularity of 8 and resolving power figures, with the footnote giving the reading conditions and the statement that the data are based on development in KODAK Developer D-76 at 20 degrees C; Characteristic Curves - the same axes as the Tri-X sheet, log exposure in lux-seconds against density, with the densitometry stated as diffuse visual; Exposure - the statement that the nominal speed of the film is EI 100, that it was determined in a manner published in ISO standards, and the advice to use the rated speed or make tests to determine a speed rating that meets your needs; Processing - the statement that the starting-point recommendations are intended to produce negatives with a contrast appropriate for printing with a diffusion enlarger, and the instruction to reduce development time for a condenser enlarger; the development-time adjustment table with the note to shift one column to the left for a condenser enlarger; Contrast Index Curves for small tank, large tank, rotary tube and tray at 20 degrees C, densitometry diffuse visual, with contrast index plotted from 0.3 to 0.9 against development time for D-76, D-76 1:1, T-MAX, T-MAX RS, XTOL, XTOL 1:1 and HC-110 dilution B; Features and benefits - the T-GRAIN emulsion claims of improved sharpness, expanded exposure latitude giving quality prints from moderately under- or overexposed negatives, and better highlight separation; Contrast Index Curves, plotted for seven developer and dilution combinations in four processing arrangements at 20 degrees C with the densitometry stated as diffuse visual; Features and Benefits - the T-GRAIN emulsion claims of improved sharpness, expanded exposure latitude with better highlight separation, and improved reciprocity at long and short exposure times; Characteristic Curves, a family of four curves at 6, 7, 9 and 11 minutes in T-MAX developer at 20 degrees C with small-tank agitation at 30-second intervals, densitometry stated as diffuse visual; Characteristic-curve and modulation-transfer figures, whose axis blocks state Densitometry - Diffuse visual, alongside the exposure and process conditions; Processing - the statement that the starting-point development recommendations are intended to produce negatives with a contrast appropriate for printing with a diffusion enlarger, and the development-time adjustment table with its instruction to shift one column to the left for a condenser enlarger

Used by:KODAK PROFESSIONAL XTOL Developer · P4 Grain, Speed and Resolution · P6 Pinhole Exposure and Reciprocity Correction · P7 Assignment: Landscape, Sky, Foreground and Filters · P8 Acutance, Adjacency Effects and Compensating Development · P8 Solvent Action, Physical Development and Grain · P13 Exposure, Density and the Logarithm · P13 Film Speed and Exposure Index · P13 Gamma, Contrast Index and Average Gradient · P13 Assignment: Interpreting Density Data · P13 The Characteristic Curve · P15 Density Depends on How You Look: Geometry and Spectral Response · P16 Enlarger Optics: Condenser, Diffusion, Lens, Alignment and Falloff

Processing KODAK PROFESSIONAL Black-and-White Films, publication ED-BWFretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: The processing table - a 30 second rinse under running water, 1 to 2 minutes of wash aid with continuous agitation for the first 30 seconds and then at 30 second intervals, and a 5 minute wash run fast enough to give a complete change of water in the container in 5 minutes; Roll films, small-tank film processing - the 20 degrees C XTOL column for T-MAX 100, T-MAX 400 and TRI-X 400; Sheet films, tray processing - the 20 degrees C XTOL column for T-MAX 100, T-MAX 400 and TRI-X 320; and Final steps in processing black-and-white film; Starting-point development times for roll films in small tanks at 20 and 24 degrees C, and the note that development times shorter than 5 minutes may produce unsatisfactory uniformity; Fix — 2 to 4 minutes with a liquid-concentrate fixer or 5 to 10 minutes with a powder fixer, and the instruction to fix for twice as long as it takes the film to clear; Fix — the instruction to fix for twice as long as it takes the film to clear, and the standing note that a pronounced and irregular magenta stain calls for refixing the film in fresh fixer; Fix — 2 to 4 minutes with a liquid-concentrate fixer or 5 to 10 minutes with a powder fixer, fixing for twice as long as it takes the film to clear, and the standing note that with T-MAX films fixer will be exhausted more rapidly than with other films; The processing table for black-and-white films — develop with continuous agitation, rinse with a stop bath, fix 2 to 4 minutes with a liquid-concentrate fixer or 5 to 10 minutes with a powder fixer agitating continuously for the first 30 seconds and at 30-second intervals thereafter, with the instruction to fix for twice as long as it takes the film to clear; rinse 30 seconds under running water; wash aid 1 to 2 minutes with KODAK PROFESSIONAL Hypo Clearing Agent; wash 5 minutes with the water running fast enough to change the container completely in 5 minutes, or for rapid washing in a small tank fill to overflowing and dump ten times; final rinse in wetting agent 30 seconds; dry in a dust-free place; the note that with T-MAX films fixer exhausts more rapidly and a magenta stain after fixing means the fixer is near exhaustion or the fixing time too short; The processing table — a 30 second rinse under running water, 1 to 2 minutes in KODAK PROFESSIONAL Hypo Clearing Agent with continuous agitation for the first 30 seconds and then at 30 second intervals, and a 5 minute wash run at least fast enough to give a complete change of water in the container in 5 minutes, with the alternative for a small tank of filling to overflowing with fresh water and dumping it all out, ten times; Fix: 2 to 4 minutes with a liquid-concentrate fixer or 5 to 10 minutes with a powder fixer, and the instruction to fix for twice as long as it takes the film to clear

Used by:Kodak Hypo Clearing Agent and the washing accelerator Kodak patented · KODAK PROFESSIONAL XTOL Developer · P8 Development Kinetics: Time, Temperature, Agitation and Exhaustion · P11 Experiment: Clearing Time and Fixer Capacity · P11 Break/Fix: The Exhausted Fixer · P11 How Fixer Works · P12 Assignment: Your Archival Processing Sequence · P12 The Physics of Washing · Measuring a clearing time

led-ld.nichia.co.jp

Specifications for UV LED, part number NVSU233B(T), U365x / U385x / U395xretrieved 2026-09-05

Sections: Initial electrical and optical characteristics at 1000 mA - U365 at 1450 mW and 3.85 V with a 9.0 nm half width, U395 at 1650 mW and 3.65 V; Absolute maximum ratings - forward current 1400 mA, power dissipation 5.88 W, junction temperature 130 C, operating temperature -10 to 85 C; and thermal resistance junction to solder point of 3.9 C/W typical and 5.7 C/W maximum; Initial electrical and optical characteristics at 1000 mA - U365 at 1450 mW and 3.85 V with a 9.0 nm spectral half width, U385 at 1730 mW and 3.70 V with 11 nm, U395 at 1650 mW and 3.65 V with 11 nm; and Absolute maximum ratings - junction temperature 130 C, thermal resistance junction to solder point 3.9 C/W typical, operating temperature -10 to 85 C; Initial electrical and optical characteristics at 1000 mA - U365 at 1450 mW and 3.85 V, U395 at 1650 mW and 3.65 V; Absolute maximum ratings - forward current 1400 mA, junction temperature 130 C

Used by:P16 Build: The UVA Exposure Unit · P16 Ultraviolet for the Alternative Processes: Sources, Dose, Uniformity and Hazard · P17 Build: The Switched Output

legislation.gov.uk

Highways Act 1980, section 137: Penalty for wilful obstructionretrieved 2026-09-04, 2026-09-05

Sections: Section 137(1), wilful obstruction of the free passage along a highway; Section 137(1) - a person who without lawful authority or excuse in any way wilfully obstructs the free passage along a highway is guilty of an offence; subsection (1B), which adds that a temporary restriction already in place makes no difference. England and Wales only

Used by:P7 Assignment: Architecture, Low Viewpoint and the Flat Plane · P7 Assignment: Night, the Very Long Exposure and Solargraphy · P7 Assignment: Panorama, Curved Plane and Multiple Pinholes · P7 Assignment: Time in the Frame, Moving Water, Clouds, People and Traffic · Night exposure session

The Environmental Permitting (England and Wales) Regulations 2016 (S.I. 2016/1154)retrieved 2026-09-06

Sections: Regulation 8, the list of regulated facilities, whose paragraph (e) is a radioactive substances activity; regulation 12(1), that a person must not, except under and to the extent authorised by an environmental permit, operate a regulated facility or cause or knowingly permit a water discharge activity or groundwater activity, and 12(3), that the requirement does not apply to a person holding a radioactive substances exemption for that activity; and Schedule 23, paragraph 11(1) and 11(2), that subject to paragraphs 13 and 14 a radioactive substances activity means, among other things, an activity in which a person who uses premises for the purposes of an undertaking keeps or uses radioactive material on those premises, disposes of radioactive waste on or from those premises, or accumulates radioactive waste on those premises; Regulation 8, the list of regulated facilities, whose paragraph (e) is a radioactive substances activity; regulation 12(1), that a person must not, except under and to the extent authorised by an environmental permit, operate a regulated facility, and 12(3), that the requirement does not apply to a person holding a radioactive substances exemption for that activity; and Schedule 23, paragraph 11(2), that a radioactive substances activity means, among other things, an activity in which a person who uses premises for the purposes of an undertaking keeps or uses radioactive material on those premises, disposes of radioactive waste on or from those premises, or accumulates radioactive waste on those premises

Used by:P20 The Toners We Study and Do Not Use · P26 Uranium, Mercury and the Heavy-Metal Treatments

The Hazardous Waste (England and Wales) Regulations 2005 (S.I. 2005/894)retrieved 2026-09-04

Sections: Regulation 5, the definition of domestic waste; regulation 14, separated domestic fractions, in particular paragraph (2) on obligations of an occupier of domestic premises and paragraphs (3) and (4) on when Part 4 begins to apply and who is then treated as the producer

Used by:The disposal caveat

UK General Data Protection Regulation, Article 2: Material scoperetrieved 2026-09-04

Sections: Article 2(2)(a), processing by an individual in the course of a purely personal or household activity

Used by:P7 Assignment: Portrait, Environmental Portrait and Self-Portrait · P7 Assignment: Time in the Frame, Moving Water, Clouds, People and Traffic

Water Industry Act 1991, section 111: restrictions on use of public sewersretrieved 2026-09-04

Sections: Subsection (1), the prohibition addressed to any person on emptying into a public sewer, or a drain communicating with one, matter likely to injure it or to affect prejudicially the treatment and disposal of its contents, or a prohibited chemical refuse; subsection (2), what makes chemical refuse a prohibited substance; subsection (3), the offence

Used by:The disposal caveat

Water Industry Act 1991, section 118: consent required for discharge of trade effluent into public sewerretrieved 2026-09-04, 2026-09-05

Sections: Section 118: consent required for discharge of trade effluent into public sewer; Subsection (1), consent required for the discharge of trade effluent from trade premises; subsection (5), the offence of discharging without consent

Used by:P2 Waste: Streams, Silver, and the Drain You Must Not Use · P12 Silver Recovery and the Responsible Darkroom · The disposal caveat

littlehouseofpyro.com

510-Pyro, product pageretrieved 2026-09-05

Sections: The product description, with the bottle capacity and shelf-life claims

Used by:510-Pyro

loc.gov

Care, Handling, and Storage of Photographsretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Storage enclosures, which recommends paper made to ISO specifications buffered to a pH of 7 to 9.5, states that buffered paper may be used for acetate and nitrate films, platinum prints, silver prints, chromogenic prints and prints mounted on acidic boards, and that unbuffered paper tending to have a pH of 6 to 7 is recommended for cyanotypes and architectural drawings; Environment, for the 30 to 50 per cent relative humidity set point for a mixed collection without cycling more than 5 per cent a day, 30 to 40 per cent where only photographs are stored, and the 18 degrees C extended-term storage temperature taken from ISO 18920 with daily fluctuations greater than plus or minus 2 degrees C avoided; Light, for the 30 to 100 lux exhibit range, ultraviolet not exceeding 75 microwatts per lumen and the statement that permanent display is not recommended; and the account of oxidant gases, acidic and sulfiding gases and environmental fumes; Light, which states that light levels in exhibits should be kept as low as possible but high enough to allow for viewing and should be in the range of 30 to 100 lux, and that ultraviolet light levels should not exceed 75 microwatts per lumen; and Handling, for freshly washed hands, lint-free cotton or inert plastic gloves and no contact with the image surface; Handling; Environmental factors: the highest recommended extended-term storage temperature of 18 degrees C for black-and-white prints and negatives on polyester film base, with daily fluctuations greater than plus or minus 2 degrees C to be avoided; Handling; Handling — freshly washed hands, clean lint-free cotton or inert plastic gloves, and not touching the image surface; Environmental Factors — relative humidity and temperature, air pollution, light and housekeeping; high RH softens the gelatin binder and low RH cracks it; mould above 60 per cent RH and 75 to 80 degrees F; an ideal set point between 30 and 50 per cent RH without cycling more than plus or minus 5 per cent a day, and 30 to 40 per cent where only photographs are stored; the highest recommended extended-term storage temperature for black-and-white prints and negatives on polyester base of 18 degrees C with daily fluctuations greater than plus or minus 2 degrees C avoided, citing ISO 18920, and the ISO definition of extended-term as when it is desired to preserve information for as long as possible; Air Pollution — the four forms, oxidant gases, particulate matter, acidic and sulfiding gases and environmental fumes, with nitrogen oxides and ozone named as the two main oxidant gases, ozone produced by some electrostatic copiers and printers, nitrogen and sulfur dioxide reacting with atmospheric water to give nitric and sulfuric acids that cause silver images to fade, and peroxides from untreated wood, paints and varnishes causing images to oxidise and fade; the instruction to insist that photographic chemical processing and development be done to ISO standards, ISO 18901, and the statement that the use of chemical toners also helps to protect silver images from deterioration; Handling - freshly washed hands, clean lint-free cotton or inert plastic gloves, and not touching the image surface; The storage-enclosure recommendation that paper have an alpha cellulose content of 87 per cent, cited here as the context in which the term is actually used in the conservation literature - enclosures rather than photographic base stock; Handling - hands freshly washed, clean lint-free cotton or inert plastic gloves such as nitrile, no contact with the photograph surface, and an auxiliary support of Plexiglas or rag board when a print must be moved or turned over; Light, which states that permanent display of photographs is not recommended, that damage from light is cumulative and depends on intensity, length of exposure and wavelength, that blue light from 400 to 500 nm and ultraviolet from 300 to 400 nm are especially damaging, that light levels in exhibits should be kept as low as possible but high enough to allow for viewing and in the range of 30 to 100 lux, and that ultraviolet levels should not exceed 75 microwatts per lumen; and Handling, for freshly washed hands, lint-free cotton or inert plastic gloves, and no contact with the image surface; Handling - the instruction that when handling photographs and negatives hands are freshly washed, clean lint-free cotton gloves or inert plastic gloves such as nitrile are worn, and the photograph surface is not touched; Paper or Plastic? - paper sleeves and envelopes should be made to ISO specifications, which recommend an alpha cellulose content of 87 per cent, no lignin, groundwood or alum-rosin sizing, and buffering to a pH of 7 to 9.5; buffered paper may be used for acetate and nitrate films, platinum prints, silver prints, chromogenic prints and prints mounted on acidic boards, while unbuffered paper, tending to have a pH of 6 to 7, is recommended for cyanotypes and architectural drawings; the plastics recommended by ISO standards, namely polyester, polyethylene, polypropylene, spun-bonded polyolefins and polystyrene, and the instruction to avoid adhesives or fasteners that may cause chemical or physical damage such as rubber cement, pressure-sensitive tape, paper clips or rubber bands; Suggested Storage Methods, Prints - an excellent storage method is to place the print in a mat, which provides a great deal of protection from physical damage and some degree of protection from pollutants and environmental fluctuations, though mats are expensive, time consuming to make and greatly increase the storage space needed, and prints larger than 8 by 10 inches should be shelved horizontally; Oversized prints - rolling of photographs should be avoided since the photograph may crack when it is unrolled; Albums, scrapbooks and mounted photographs - historical print mountings were often made of acidic, unstable materials and when acidic paper mounts become brittle the photographic image itself is at risk because of breakage; Handling - be sure that hands are freshly washed, wear clean lint-free cotton gloves or inert plastic gloves such as nitrile, avoid touching the photograph surface, and use an auxiliary support such as a piece of Plexiglas, 2- or 4-ply rag board or folder stock if a photograph must be moved a short distance or turned over, together with the statement that repair of photos with pressure-sensitive tape and marking original prints with ink or felt-tip pens are examples of negligence; Storage enclosures, which recommends paper made to ISO specifications buffered to a pH of 7 to 9.5, states that buffered paper may be used for acetate and nitrate films, platinum prints, silver prints, chromogenic prints and prints mounted on acidic boards, and that unbuffered paper tending to have a pH of 6 to 7 is recommended for cyanotypes and architectural drawings; and Light, which states that light levels in exhibits should be kept as low as possible but high enough to allow for viewing and should be in the range of 30 to 100 lux, and that ultraviolet light levels should not exceed 75 microwatts per lumen; Air Pollution, the four forms - oxidant gases, particulate matter, acidic and sulfiding gases and environmental fumes - with nitrogen oxides and ozone named as the two main oxidant gases, ozone also produced by some electrostatic copiers and printers, nitrogen and sulfur dioxide reacting with atmospheric water to give nitric and sulfuric acids that make silver images fade, and peroxides from untreated wood, paints and varnishes; Light, that permanent display is not recommended, that damage is cumulative and depends on intensity, duration and wavelength, that blue light from 400 to 500 nm and ultraviolet from 300 to 400 nm are especially damaging, and that exhibition light levels should be in the range 30 to 100 lux with ultraviolet not exceeding 75 microwatts per lumen; Chemical Processing and Image Stability, that major silver deterioration occurs when photographs are not correctly processed and washed, the instruction to insist that processing be done to ISO 18901, and the statement that use of chemical toners also helps to protect silver images from deterioration; and Enclosures, that many commercially available enclosures are labelled archival or acid-free and that the requirements to look for are those in the latest revision of ISO 18902 including the Photographic Activity Test, ISO 18916; Storage enclosures - the recommendation of paper made to ISO specifications and buffered to a pH of 7 to 9.5 for acetate and nitrate films, platinum prints, silver prints, chromogenic prints and prints mounted on acidic boards, and the separate recommendation of unbuffered paper tending to have a pH of 6 to 7 for cyanotypes and architectural drawings; and Light, which states that permanent display is not recommended, that damage from light is cumulative and depends on intensity, length of exposure and wavelength, that blue light from 400 to 500 nm and ultraviolet from 300 to 400 nm are especially damaging, that exhibition light levels should be in the range of 30 to 100 lux and that ultraviolet levels should not exceed 75 microwatts per lumen; The process date chart, giving albumen prints as 1850 to about 1900; Relative Humidity and Temperature — the highest recommended extended-term storage temperature for black-and-white prints as 18 °C with daily fluctuations greater than plus or minus 2 °C to be avoided, and relative humidity of 30 to 50 per cent; Enclosures — the ISO specification of 87 per cent alpha cellulose, no lignin, groundwood or alum-rosin sizing, paper buffered to pH 7 to 9.5, the statement that buffered paper may be used for silver prints and prints mounted on acidic boards, and that unbuffered paper is recommended for cyanotypes and architectural drawings; Suggested Storage Methods — the mat, the polyester sleeve with two-ply board, and the warning against plastic for flaking or sensitive surfaces; Storage and enclosures — adverse environments causing paper to yellow and become brittle, especially where the paper is acidic; air pollution producing nitric and sulfuric acids which attack all components of photographs and cause supports to discolour and become brittle; the recommendation of stiff card supports beneath brittle photographs and the advice against rolling; Handling; Handling; and Storage and enclosures — adverse environments causing paper to yellow and become brittle, especially where the paper is acidic; Handling: freshly washed hands, clean lint-free cotton or inert plastic gloves, and not touching the image surface; Handling — the instruction that when handling photographs and negatives, hands should be freshly washed, clean lint-free cotton gloves or inert plastic gloves such as nitrile should be worn, and the photograph surface should not be touched; the instruction to use an auxiliary support such as Plexiglas or rag board when a photograph must be moved or turned over; and the listing of repair with pressure-sensitive tape and marking originals with ink or felt-tip pens among examples of negligence; Suggested Storage Methods, Glass plate negatives — intact plates in individual paper enclosures arranged vertically on their long edges, shelving strong enough for the weight, boxes clearly labelled fragile/glass and heavy, and filler board used to stop partly filled boxes jostling; Broken glass plates, or those with deteriorated image layers — cracked plates supported with a piece of glass or lignin-free ragboard inside their sleeves, broken plates housed between good quality 4-ply or corrugated board inside a four-flap enclosure and stored flat, and the recommendation that the work be done in consultation with a conservator; Handling and storage: enclosures, and keeping materials that can migrate away from finished work; Handling - freshly washed hands, clean lint-free cotton or inert plastic gloves, holding by the edges, and no contact with the image surface; Handling: freshly washed hands, clean lint-free cotton or inert plastic gloves, no contact with the image surface, an auxiliary support under a print that is moved; buffered paper with silver prints, unbuffered at pH 6 to 7 with cyanotypes; pigment-ink pens that pass the Photographic Activity Test; Handling - freshly washed hands, holding by the edges, and no contact with the image surface; Handling: freshly washed hands, clean lint-free cotton or inert plastic gloves such as nitrile, and no contact with the image surface. Storage, Glass plate negatives: intact plates housed individually in seamed or seamless paper enclosures and arranged vertically on their long edges, boxes labelled fragile/glass and heavy, and filler board used to stop partly filled boxes jostling. Storage environment: glass plate negatives kept at 30 to 40 per cent relative humidity; Handling - hands freshly washed, clean lint-free cotton or inert plastic gloves such as nitrile, and avoid touching the photograph surface; Storage Systems and Enclosures, Materials - never use enclosures made from unprocessed woodpulp paper, glassine or polyvinyl chloride, avoid coloured papers whose dyes migrate, and the requirement that an enclosure meet ISO 18902 including the Photographic Activity Test ISO 18916; Design - envelope adhesives may stain and fade the silver image, so the emulsion side is placed away from the seam and seams run along the sides rather than down the centre, and the layered housing of sleeve, then folder, then box; Paper or Plastic? - paper sleeves buffered to pH 7 to 9.5, buffered paper acceptable for silver prints and unbuffered recommended for cyanotypes, acceptable plastics, and the instruction to avoid rubber cement, pressure-sensitive tape, paper clips and rubber bands; Deterioration - the 30 to 50 per cent relative humidity set point without cycling more than 5 points a day, mould growth above 60 per cent, the 18 degree Celsius extended-term figure for black-and-white prints with daily fluctuation under 2 degrees, and peroxides given off by untreated wood, paints and varnishes; Handling - freshly washed hands, lint-free cotton or inert plastic gloves, no contact with the image surface, and the marking of original prints with ink or felt-tip pens named as negligence; Relative humidity - high RH causing a gelatin binder to become soft and sticky and vulnerable to mechanical damage, low RH causing the binder to shrink and crack and the secondary support to curl; the advice against rolling photographs because they may crack when unrolled for use; Handling — the instruction that hands should be freshly washed and clean lint-free cotton or inert plastic gloves such as nitrile worn, that the photograph surface should not be touched, and that an auxiliary support should be used when an item must be moved or turned over; and the listing of repair with pressure-sensitive tape and marking originals with ink or felt-tip pens among examples of negligence; Relative humidity and photographs - high RH causes a gelatin binder to become soft and sticky, making it vulnerable to mechanical damage; low RH causes the binder to shrink and crack and the secondary support to curl; Relative humidity - high RH causes a gelatin binder to become soft and sticky, making it vulnerable to mechanical damage and image deterioration, while low RH causes the binder to shrink and crack and the secondary support to curl; storage - rolling of photographs should be avoided since the photograph may crack when it is unrolled for use; the recommendation of stiff card supports beneath brittle or broken photographs; adverse environments causing paper to yellow and become brittle, especially if the paper is acidic; Storage and enclosures - adverse environments causing paper to yellow and become brittle, especially where the paper is acidic; air pollution producing nitric and sulfuric acids which attack all components of photographs and cause silver images to fade and supports to discolour and become brittle; the recommendation of stiff card supports beneath brittle photographs, and the advice against rolling; Handling — the instruction that hands should be freshly washed and clean lint-free cotton or inert plastic gloves such as nitrile worn, that the photograph surface should not be touched, and that an auxiliary support such as Plexiglas or rag board should be used when an item must be moved or turned over; Handling — the instruction that when handling photographs and negatives hands should be freshly washed, clean lint-free cotton gloves or inert plastic gloves such as nitrile should be worn, and the photograph surface should not be touched; and the instruction to use an auxiliary support such as Plexiglas or rag board when a photograph must be moved a short distance or turned over, to protect it from damage caused by unnecessary touching, bending and flexing

Used by:P29 Capstone Stage 6: Permanence, Presentation and the Finished Portfolio · P29 Capstone Stage 4: The Silver Prints · P1 Assignment 1: A Botanical Cyanotype Photogram, After Atkins · P1 Experiment: The Image That Would Not Stay · P7 Pinhole Portfolio Review and the Exposure Record as Data · P9 Lab: Preparing Standard Test Negatives · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P12 Permanence and Image Deterioration · P13 Lab: A Step-Wedge Exposure Series · P18 The Structure of a Printing Paper: Base, Baryta, Emulsion and Supercoat · P19 Part XIX Overview: Fine Printing · P19 Assignment: The Exhibition Print and Its Critique · P19 Reading the Negative and Making the Work Print · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Assignment: The Toned Print · P20 Toning, Permanence and What the Evidence Actually Supports · P21 Assignment: Cyanotype at Scale, on Fabric, and the Botanical Sequence · P23 The Albumen Print as an Object, and How It Decays · P25 Cost, Permanence and When a Platinum Print Earns Its Price · P25 Assignment: The Process Comparison Atlas · P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory · P28 The Emulsion Under Stress: Reticulation, Scratches, Pinholes and Drying Marks · Glass handling, cutting and breakage response · Handling and storing a deliberately faulty reference specimen · Opening and handling photographic paper in dim light · Loading paper and sheet film into a pinhole back · Mounting a print and putting it in an enclosure · Outdoor exposure session · Plate coating and drying · Solargraph camera placement and retrieval · Storing unfixed prints for later fixing · Albumen crazing and yellowing · Base-side scratches · Blistering from an over-hot hypo alum bath · Cracked emulsion from flattening a bone-dry fibre print · Edge fading from mount and adhesive · Emulsion-side scratches · Fingerprints on paper

Copyright and Other Restrictions that Apply to Publication/Distribution of Images: Assessing the Risk of Using a P&P Imageretrieved 2026-09-06

Sections: Can I use an image that I have found in the P&P collections, which states that in all cases it is the researcher's obligation to determine and satisfy copyright or other use restrictions when publishing or otherwise distributing material, and that the division conveys what it knows through catalogue records and rights statements using the wordings public domain and no known restrictions; and How should I credit the Library, which asks for the Library of Congress, the specific collection and the image reproduction number; Can I use an image that I have found in the P and P collections - the statement that in all cases it is the researcher's obligation to determine and satisfy copyright or other use restrictions when publishing or otherwise distributing material, and that the division conveys what it knows through catalogue records and rights statements using the wordings public domain and no known restrictions. Cited here as the standard the course applies to any reproduction it does not publish; Assessing the copyright and other restrictions that apply to publication and distribution of images from a collection, and why a catalogue record's rights field is the field to read

Used by:P19 Assignment: The Exhibition Print and Its Critique · P21 Assignment: Cyanotype at Scale, on Fabric, and the Botanical Sequence · P26 Assignment: Assessing a Historical Process for Hazard

Preservation FAQs: Photographsretrieved 2026-09-04, 2026-09-06, 2026-09-08

Sections: The instruction that all products for storing photographs and all materials in direct contact with a photograph should pass the photographic activity test (PAT), ISO 18916; the marking-pen guidance; and the named sleeving plastics polyester, polyethylene and polypropylene; Is it okay to use self-stick tape if it is marked archival? - once applied, self-stick or pressure-sensitive tape can be extremely difficult to remove and often creates condition problems over time, and photo corners are named as the alternative; What kind of photograph album should I use - the statement that all products for storing photographs should pass the photographic activity test, ISO 18916; What kind of pen should be used for marking or signing photographs - permanent ink pens that pass the photographic activity test can be used on semi-gloss inkjet papers, films and polyester, polyethylene and polypropylene sleeves and should not fade, bleed or transfer when used properly, and can be purchased from preservation suppliers; How can I safely frame my photographs - all materials in direct contact with the photograph should pass the photographic activity test, the frame should be designed so that the surface of the photograph does not touch the glazing by means of a window mat or spacers, and over time all photographs exposed to light even behind UV-filtering glass will undergo irreversible light damage, so that framing a facsimile should be considered for a photograph of personal, monetary or historic value; A rolled photograph may crack when it is unrolled

Used by:P7 Pinhole Portfolio Review and the Exposure Record as Data · P19 Lab: Washing, Drying, Flattening and Mounting the Print · Mounting a print and putting it in an enclosure

Standards: Care, Handling, and Storage of Photographsretrieved 2026-09-05, 2026-09-06

Sections: The standards list, for the 1985 revision of the American national standard for photography (chemicals) — residual thiosulfate and other chemicals in films, plates and papers, determination and measurement, ANSI PH4.8-1985; The standards bibliography — ANSI PH4.8-1985, photography (chemicals), residual thiosulfate and other chemicals in films, plates and papers, determination and measurement; ANSI IT9.1-1988, imaging media (film), silver gelatin type, specification for stability; ANSI IT9.2-1991, filing enclosures and containers for storage; ANSI PH4.32-1986, methods for evaluating processing with respect to the stability of the resultant image, black-and-white papers; The standards bibliography, cited only for the designation and title of the American National Standard that preceded the ISO residual-thiosulfate method - ANSI PH4.8-1985, photography (chemicals), residual thiosulfate and other chemicals in films, plates and papers, determination and measurement; The standards bibliography, which lists ANSI PH4.32-1986, American national standard for photography (processing), methods for evaluating processing with respect to the stability of the resultant image, black-and-white papers; and ANSI PH4.8-1985, residual thiosulfate and other chemicals in films, plates and papers, determination and measurement

Used by:Kodak HT-2 · Kodak ST-1 · P12 Permanence and Image Deterioration · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Toning, Permanence and What the Evidence Actually Supports

look.ams-osram.com

BPW 34 silicon PIN photodiode, data sheet version 1.5retrieved 2026-09-05

Sections: Characteristics at 25 C - spectral sensitivity 80 nA/lx measured under standard light A at 2856 K, wavelength of maximum sensitivity 920 nm, spectral range of sensitivity 420 to 1120 nm at the ten per cent points, radiant sensitive area 7.02 square millimetres, half angle 60 degrees; Characteristics at 25 C - short-circuit current 80 microamps at 1000 lux under standard light A, spectral sensitivity 80 nA/lx, wavelength of maximum sensitivity 920 nm, spectral range 420 to 1120 nm, radiant sensitive area 7.02 square millimetres, half angle 60 degrees, dark current 2 nA typical and 30 nA maximum, rise and fall times 0.02 microseconds; Maximum Ratings - reverse voltage 32 V, total power dissipation 150 mW; Characteristics - spectral sensitivity 80 nA/lx under standard light A at 2856 K, wavelength of maximum sensitivity 920 nm, spectral range of sensitivity 420 to 1120 nm at the ten per cent points; Characteristics at 25 C - radiant sensitive area 7.02 square millimetres, half angle 60 degrees, wavelength of maximum sensitivity 920 nm, spectral range 420 to 1120 nm, dark current 2 nA typical and 30 nA maximum at a reverse voltage of 10 V; Maximum Ratings - reverse voltage 32 V; Characteristics at 25 C - radiant sensitive area 7.02 square millimetres with a typical active chip area of 2.65 by 2.65 mm, half angle 60 degrees, wavelength of maximum sensitivity 920 nm and spectral range 420 to 1120 nm; Characteristics at 25 C - wavelength of maximum sensitivity 920 nm, spectral range of sensitivity 420 to 1120 nm at the ten per cent points, radiant sensitive area 7.02 square millimetres, dimensions of the active chip area typically 2.65 by 2.65 mm, half angle 60 degrees, and spectral sensitivity 80 nA/lx quoted under standard light A; Characteristics at 25 C - wavelength of maximum sensitivity 920 nm, spectral range of sensitivity 420 to 1120 nm at the ten per cent points, radiant sensitive area 7.02 square millimetres with a typical active chip area of 2.65 by 2.65 mm, half angle 60 degrees, spectral sensitivity 80 nA/lx under standard light A, short-circuit current 80 microamps at 1000 lx, dark current 2 nA typical and 30 nA maximum at a reverse voltage of 10 V, rise and fall times 0.02 microseconds; Maximum Ratings - reverse voltage 32 V, total power dissipation 150 mW; Spectral characteristics - maximum sensitivity at 920 nm and a spectral range of 420 to 1120 nm at the ten per cent points, so that infrared reaches the detector more efficiently than visible measuring light; Spectral characteristics - maximum sensitivity at 920 nm and a spectral range of 420 to 1120 nm at the ten per cent points; dark current of 2 nA typical and 30 nA maximum at 10 V reverse bias

Used by:P14 Experiment: Calibrating the Sensitometer · P14 Build: The LED Light Source and Exposure Timer · P14 Sensitometer Design Principles · P15 Build: The Densitometer Electronics and Firmware · P15 Build: The Densitometer Optical Head (Transmission and Reflection) · P15 Density Depends on How You Look: Geometry and Spectral Response · P15 Photodiodes, ADCs and Measuring Light Over Three Decades · Densitometer: ambient leak · Densitometer: high-density compression

TSL2591 high dynamic range digital light sensor, datasheet DS000338retrieved 2026-09-05

Sections: Features - a stated 600 000 000 to 1 dynamic range. ALS characteristics at a 3 V supply - two channels, full-spectrum and infrared; gain scaling nominally 1, 24.5, 400 and 9200 times; integration times of 100 to 600 ms in 100 ms steps; maximum ADC count 36863 at 100 ms and 65535 from 200 ms upward; dark count typically 20 at maximum gain; and irradiance responsivity quoted only for a nominally 4000 K white LED and an 850 nm infrared LED

Used by:P15 Photodiodes, ADCs and Measuring Light Over Three Decades

macodirect.de

macodirectretrieved 2026-09-05

Sections: ILFORD chemistry, for the European equivalents

Used by:The Pure Silver laboratory planner

Safety Data Sheet: KODAK Rapid Selenium Tonerretrieved 2026-09-06

Sections: Section 1, product identifier KODAK Rapid Selenium Toner, product code 1464486, synonym PCD 2667, supplier Kodak Alaris Inc., and the identified use "Toner. For industrial use only."; section 2, the 29 CFR 1910.1200(d) classification, signal word, hazard and precautionary statements, the other-hazards note that dried product residue can act as a reducing agent, and the HMIS III and NFPA ratings; section 3, the composition table and its Weight percent column; section 4, first aid; section 5, hazardous combustion products and the reducing-agent behaviour of dried residue; section 6, accidental release; section 7, handling and storage; section 8, the ACGIH and OSHA time-weighted averages and the engineering and personal controls; section 9, physical and chemical properties; section 10, incompatible materials and hazardous decomposition products; section 11, toxicological information including the selenium overexposure symptoms, the sulphite note and the acute toxicity data; section 12, the estimated ecological figures; section 13, disposal considerations; section 14, transport; section 15, the notification status and other-regulations tables; and section 16, the label statements, the line "Additional Components Include: Water (7732-18-5)." and the closing note on the working solution; Section 3, the composition table and its Weight percent column; section 16, the line "Additional Components Include - Water (7732-18-5)" - cited only as the shape of the document that does not exist for this product; The document header, Kodak Alaris product code 1464486, document reference Z17000000763 version 4.2, revision date 31 July 2014, print date 27 May 2015. Cited here only for the document's date, as evidence of how old the most recent maker-published sheet for this product is

Used by:KODAK Rapid Selenium Toner · KODAK PROFESSIONAL XTOL Developer · P20 Assignment: The Toned Print

media.getty.edu

The Atlas of Analytical Signatures of Photographic Processes: Introductionretrieved 2026-09-07

Sections: Purpose of the Atlas and the founding meeting, for the agreement among the participating experts that identification based solely on visual and microscopic inspection can be used to answer more than 75 per cent of identification questions successfully, and for the working strategy of collecting visual and microscopic signatures first, then XRF for the imaging metal, toning metals and inorganic elements of the substrate, then FTIR for an organic binder with the warning that a surface coating may shield the binder's signal, then comparison against the interpretation guide, with microsampling rare and only with a conservator's and curator's approval; and for the reason identification matters at all - that without it the environmental conditions and maximum display light levels for an object cannot be determined

Used by:P22 The Variants of the Salt Print and How a Conservator Identifies One

metmuseum.org

Open Access at The Metretrieved 2026-09-06

Sections: What is Open Access, which states that the Open Access Initiative introduced in February 2017 makes all images of public-domain artworks and basic data on all accessioned works available for unrestricted use under Creative Commons Zero, and the browsing note that Open Access works carry an OA icon and an Open Access filter in the online collection; The Met's open-access policy for images and data of works in its collection, and the fields its object records carry

Used by:P19 Assignment: The Exhibition Print and Its Critique · P26 Assignment: Assessing a Historical Process for Hazard

mikeware.co.uk

Alternative Photographic Processes: Argyrotype — workshop handoutretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: The introduction, on an image colour fine-tuned by humidity and by the incorporation of a humectant; the sensitiser formula, which gives glycerol as 1 cc per 100 cc and names it glycerine, 1,2,3-trihydroxypropane and 1,2,3-propanetriol; preparation step 4; the note headed Image Colour Improved by Glycerol; Coating and Drying, for the ambient relative humidity range, the warm-air drying that shifts colour towards warmer tones, and the warning that very humid paper may damage a silver-gelatin negative; Image Colour Improved by Glycerol — particle size, humidity and print colour; Chemicals for Preparing and Processing Argyrotype Sensitizer; Preparation of Argyrotype Sensitizer, steps 1 to 3 and the closing note on the 20 per cent excess of sulphamic acid, the stoicheiometric 5.87 g and the pH of about 3.5; Alternative Preparation of Silver(I) Oxide, steps a to f; Overview of Argyrotype, for the 1991 version employing the unusual silver salt to avoid the image loss caused by silver nitrate and to enable mildly acidic working at pH 3.5, and for the single-bottle sensitizer with a long shelf life whose contrast is controlled by added acid; Chemicals for Preparing and Processing Argyrotype Sensitizer, for the quantities per 100 cc; Preparation of Argyrotype Sensitizer, steps 1 to 6 and the closing note on the 20 per cent excess of sulphamic acid, the stoicheiometric 5.87 g, the pH of about 3.5 and the extra 1 g for contrast; Alternative Preparation of Silver(I) Oxide, steps a to f; Introduction — the 1991 formulation using silver sulphamate at pH 3.5, its single-bottle sensitiser and contrast control by added acid; Overview of Argyrotype, for the argentotype of 1842 as the first iron-based silver printing process and for the clearing difficulty its descendants inherited; Processing Solutions, for the 2.5 per cent w/v sodium thiosulphate bath, about 25 g to the litre, sufficient to process about ten 10 by 8 inch prints, and for the note that the hydrated form may be used; Wet Processing Procedure step 2, Clear, for the de-chlorinated water bath acidified with about 25 g of citric acid per 10 litres to scavenge chlorine and give a pH of about 4; step 3, Tone and Fix, for the two minutes, the capacity, the instruction not to store and re-use the bath, the intensification and the red-to-brown colour shift, and the warning that overlong treatment loses image density especially in the highlights; step 4, the 15 to 30 minute wash; and Permanence and Toning, for the argument that an argyrotype becomes partially sulphide-toned in the thiosulphate bath — the yellow silver nanoparticles acquiring a coating of silver sulphide perhaps only a monolayer deep, which changes their colour profoundly through its effect on the surface plasmon resonance — that silver sulphide is very insoluble and stable and should therefore improve the image's resistance to hostile chemicals, but that "overlong immersion in thiosulphate completely transforms the silver nanoparticles into silver sulphide, causing the image to become badly faded", with the supporting energy-dispersive X-ray evidence of sulphur in the image, and for the statement that gold, platinum or palladium toning, if wanted, should be done before the thiosulphate bath; Wet Processing Procedure step 2, Clear, for the de-chlorinated water bath acidified with about 25 g of citric acid per 10 litres to scavenge chlorine and give a pH of about 4, which is Ware's own clearing bath for an iron-silver print and the comparison this page is measured against; Overview of Argyrotype; Chemicals for preparing and processing; Preparation of Argyrotype sensitizer, with the note on the 20 per cent excess of sulphamic acid, the pH of about 3.5 and what the excess acid does; Notes on the Argyrotype process — choice of paper, addition of surfactant, image colour improved by glycerol, coating, drying, printing exposure and negatives; Wet processing procedure, steps 1 to 5; Permanence and toning; Overview of Argyrotype; Chemicals for Preparing and Processing Argyrotype Sensitizer, with the strengths of the two processing solutions and the note on the meaning of per cent w/v and v/v; Apparatus for Preparing Argyrotype Sensitizer; Preparation of Argyrotype Sensitizer, steps 1 to 6 and the closing note on the 20 per cent excess of sulphamic acid, the stoicheiometric 5.87 g, the pH of about 3.5 and what more or less acid does; Alternative Preparation of Silver(I) Oxide, steps a to f; Notes on the Argyrotype Process — Choice of Paper, Addition of Surfactant to the Sensitizer, Image Colour Improved by Glycerol, Coating, Drying, Printing Exposure and Negatives; Wet Processing Procedure, steps 1 to 5; Permanence and Toning; Summary of Argyrotype Procedure, steps 1 to 11; Permanence and Toning — the statement that modern makers of kallitypes and Van Dykes seem to agree that toning with platinum, palladium or gold is essential to their preservation, that like all print-out silver images the toning should be done before the thiosulphate bath, and the account of partial sulphide toning in the thiosulphate bath with the energy-dispersive X-ray evidence of sulphur in the image and the warning that overlong immersion converts the nanoparticles completely to silver sulphide and badly fades the print; Preparation of Argyrotype sensitizer, the note on the excess of sulphamic acid — that the deliberate 20 per cent excess over the stoicheiometric 5.87 g gives a pH of about 3.5 which suppresses hydrolysis of the iron(III), keeps the silver in solution and is the optimum for photosensitivity, and that even more sulphamic acid can be added to increase print contrast because "it tends to dissolve silver in the highlights", with an extra 1 g per 100 cc making a more contrasty sensitiser that can be mixed with the standard one to fine-tune contrast; Printing Exposure and Negatives, for a required negative density range of at least 2 and as much as 2.4 in the ultraviolet; Wet Processing Procedure, steps 1 to 5 — the optional post-hydration over water, the clearing bath of de-chlorinated water with about 2.5 g of citric acid per 10 litres to scavenge chlorine and give a pH of about 4, the 2.5 per cent sodium thiosulphate bath of about two minutes with a capacity of about ten 10 by 8 prints and the instruction not to store and re-use it, the 15 to 30 minute wash and the strong dry-down of at least one Zone; Permanence and Toning, for the partial sulphide toning in the thiosulphate bath, the colour change from yellowish-red to mahogany brown, the energy-dispersive X-ray evidence of sulphur in the image, and the statement that overlong immersion converts the nanoparticles completely to silver sulphide and badly fades the print; Coating, for about 1.5 cc of sensitiser for a 10 by 8 inch area by rod and more by brush, and for blotting off excess sensitiser that may crystallise and damage negatives; Permanence and Toning, for the account of partial sulphide toning in the thiosulphate bath and the statement that overlong immersion transforms the silver nanoparticles completely into silver sulphide, causing the image to become badly faded; Wet Processing Procedure step 1, for the warning that overlong steaming causes highlight fog; Overview of Argyrotype, for the process being devised in 1991 and for the statement that the difficulty with the traditional iron-silver processes lies in clearing the print of iron salts without dissolving the image silver in the presence of the oxidizing nitrate ion; Chemicals for preparing and processing, for the green ammonium iron(III) citrate at about 16 per cent iron; Preparation of Argyrotype sensitizer, for the deliberate 20 per cent excess of sulphamic acid over the 5.87 g stoicheiometrically needed, the resulting pH of about 3.5, the suppression of iron(III) hydrolysis, the prevention of silver citrate precipitating, and the statement that this pH is also the optimum for the photosensitivity; Image Colour Improved by Glycerol, for the colour being determined by the size of the metal particles and that in turn by the humidity of the coating during the printing-out exposure; Permanence and Toning, for the partial sulphide-toning in the thiosulphate bath, the colour change from yellowish-red to mahogany-brown, the energy-dispersive X-ray evidence of sulphur in the image, and the statement that overlong immersion transforms the silver nanoparticles completely into silver sulphide and badly fades the image; Coating, exposure and wet processing; the effect of humidity on image colour

Used by:Glycerol · Lithium chloride · Silver(I) oxide · Silver sulfamate · Sulfamic acid · Herschel's argentotype · Dilute alkaline thiosulfate fixer for iron-silver prints · EDTA and sodium sulfite clearing sequence · Van Dyke Brown sensitiser · Ware's argyrotype · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Contrast Control in Iron-Based Printing · P24 Lab: Printing a Van Dyke Brown · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · P24 The Siderotype Principle: Iron Reduces Silver · Argentotype

An Algorithm for the Six Most Probable Causes of Foggingretrieved 2026-09-06, 2026-09-07

Sections: The whole one-page handout - the six numbered causes of fogging, the instruction to compare a border region of the sensitized area that was coated but masked during exposure with the margin of uncoated paper, the six questions answered in sequence and the causes each branch reaches, and the three notes: that fog is unwanted residual image substance and reads grey while stain is unwanted other residual chemicals and especially ferric salts and reads yellow, that fault four can be detected by including a small area of high ultraviolet blocking such as Rubylith for comparison with the maximum density of the negative, and that some tests depend on whether the process is print-out or development, since fogging from a faulty safelight may not be visible until wet processing is complete; The whole one-page handout, header "Mike Ware 2012" — the six most probable causes of fogging in their published numbering, the instruction to compare a border region of the sensitized area that was coated but masked during exposure with the margin of uncoated paper, the six questions asked in sequence and the causes each branch reaches, the note distinguishing fog as unwanted residual image substance and usually grey from stain as unwanted other residual chemicals and especially ferric salts and usually yellow, the recommendation to include a small area of high ultraviolet blocking such as Rubylith for comparison with the negative's maximum density, and the note that some tests depend on whether the process is print-out or development because fogging from a faulty safelight may not be visible until wet processing is complete, especially for development processes. Cause (6) is given as "The clearing procedure is inadequate, leaving residual iron, etc.", which is a siderotype fault rather than a cyanotype one; The whole one-page handout, headed 'Mike Ware 2012' — the six numbered causes of fogging in a siderotype print, the instruction to compare a border region of the sensitised area that was coated but masked during exposure with the margin of uncoated paper and to answer the questions in sequence, the note distinguishing fog as unwanted residual image substance reading grey from stain as unwanted other residual chemicals reading yellow, and the note that some tests depend on whether the process is print-out or development, since fogging from a faulty safelight may not be visible until wet processing is complete, especially for development processes

Used by:P21 Break/Fix: The Cyanotype That Went Wrong · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · P28 Fog and Where It Comes From

Argyronomicon: Silver Photographs on Paper — Chemical History of their Invention, Deterioration, and Conservationretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: The Gurney-Mott account of latent-image formation set out in four numbered steps — photon absorption freeing an electron, its trapping at a sensitivity centre, the arrival of an interstitial silver ion at the trapped charge, and the alternation of electronic and ionic steps at the same site — with the threshold of about four atoms given as what the minimum is thought to be; The list of paper additives and protecting agents used in the salted-paper and printing-out processes, which includes egg white; 7.4 Talbot's ammonio-nitrate of silver — the two equations for the diammine complex and the cautionary note on silver nitride; Chapter 2, on Mungo Ponton's dichromate prints of 1839 and the sizing agent or the paper itself, probably gelatin or starch, providing the oxidisable component; the account of Guillot-Saguez's iodizing method, in which free iodine formed by slight oxidation of the potassium iodide coating turned French papers blue because of their starch sizing, and the colour served as an indicator because it was discharged when the exciting solution had penetrated the sheet; 23.1, on silver nitrate becoming photosensitive only in the presence of readily oxidisable substances, the oxidisable component on a silver-nitrate-only paper being the cellulose of the paper or the starch or gelatin sizing agent; 23.3 Significance of Halogen Acceptors, listing the cellulose substrate and probably an organic sizing agent of gelatine or starch among the potential acceptors around a Talbot sensitiser, proposing water and silver(I) ions as the major acceptor, and concluding that the sizing agent is not essential to the photochemistry of print-out but retains the sensitiser and therefore the image in the surface fibres and possibly protects the colloidal silver particles by surface adsorption, influencing colour and stability; 2.6 Bitumen — the 1822 contact prints, photohardening and washing away the soluble asphalt with lavender oil and petroleum, the 3 to 4 hour contact exposure, and the ancient Egyptian use of the same material; 3.8 — the estimated speed of the bitumen process and the practical camera exposure; 3.9 Niépce in England 1827 — the Getty Conservation Institute and National Media Museum examination of the four surviving plates, the XRF composition of the pewter, and the infrared identification of hardened bitumen, of a photoresist, and of one plate that is not bitumen at all; 9.7.3 Alkaline gold chloride toning (Molard 1851; Waterhouse 1855); 9.7.5 Hypo alum sulphiding toner — the hydrolysis of the hexaaquaaluminium ion and the liberation of colloidal sulfur from thiosulfate; 23.3 Significance of Halogen Acceptors — the halogen released by latent-image formation and what accepts it; Section 1.3, Schulze's Serendipitous 'Scotophorus' — the preparation as a suspension of chalk in an aqueous solution of silver nitrate, the reading that the intended product was Balduin's phosphor and the necessary salt calcium nitrate, and section 1.2 on the eighteenth-century interest in luminous minerals; Collodion and its flammable solvent, diethyl ether mixed with ethanol; 23.3 Significance of Halogen Acceptors — gelatin in development emulsions against print-out levels of exposure, and the sizing agent as a protecting agent for colloidal silver; note 503 on Sheppard's Photographic Gelatin, Photographic Journal 65 (1925); The list of paper additives and protecting agents used in the salted-paper and printing-out processes — milk, isinglass, rice water, honey, gum arabic, sugar candy and egg white; 2.6 Bitumen — photohardening and washing away the soluble asphalt with lavender oil and petroleum, and the note that solvent oils derived from lavender and cloves were known in ancient Egypt; 3.8 — the physautotype exposure; 3.9 Niépce in England 1827 — the identification of Un Clair de Lune as a photohardened resinous gum resembling the physautotype process, rediscovered by Marignier using the residue from distilling oil of lavender; 9.7.5 'Hypo Alum' Sulphiding toner — the hydrolysis of alum and the liberation of colloidal sulfur; Chapter 10, Photography in Scotland 1842-1846 — the sizing of British and French photographic papers; The printing-out papers — a halogen absorber such as citrate deliberately added to the emulsion; 22 Colours of Silver Images — 22.1 surface plasma resonance, 22.2 size and colour of nanoparticle silver, 22.3 refractive index of the environment, 22.5 effect of aggregation; 7.2 particle size of print-out against developed images; 9.3 coating weight and particle size; 7.5.3 Bromide fixation; 7.6 Waterloo paper; 22 Colours of silver images; 2.1 Silver salts — chlorargyrite; 7.2 Silver print-out processes — the photolysis equation and the halogen acceptor; 7.5 Talbot's halide fixation; 18.6 Demonstrating the Becquerel effect; 21.6 Quantum yields from silver halide photolysis; 22 Colours of silver images; 7.5.1 Iodide fixation; 7.5 Talbot's halide fixation and the calotype; 2.1 Silver salts — silver nitrate is not light-sensitive per se; 7.2 Silver print-out processes; Section 7.4, Talbot's ammonio-nitrate of silver — the formulation credited to Alfred Swaine Taylor, the two equations for the precipitation of the oxide and its redissolution as the diammine silver complex, and the cautionary note on silver nitride; The printing-out papers — a halogen absorber such as citrate deliberately added to the emulsion, and albumen acting as a scavenger for chlorine; 7.5.4 Thiosulphate fixation; 9.5 sulphiding and the fading of salted paper prints; 9.6 Sparling's iron toner — tetrathionate; 9.7.5 hypo-alum sulphiding toner; 7.5.4 Thiosulphate fixation; 9.2 Reciprocity law and its failure — the ca. 1855 advice to overprint against loss in the fixer; 9.7.5 Hypo-alum sulphiding toner; Smee's letter of 10 May 1842 offering the ammonio-citrate and ammonio-tartrate of iron, and Herschel's reply of 15 June 1842; 9.7.1 Sel d'or and the gold displacement reaction; endnote 503 on Sheppard and allyl thiourea; 22.1 to 22.3 Colours of Silver Images, for surface plasma resonance, for Wiegel's table of particle diameter against transmitted colour, and for the effects of departure from spherical shape and of the refractive index of the matrix; 23.5, for a more neutral image colour being consistent with a larger silver particle size in a sensitiser buffered against the acid generated during exposure; 1.6 Ambivalent Daguerreotypes, for the differential between the specular reflection of the polished silver and the diffuse scattering by the microscopic globules of silver amalgam, for virtually none of the incident light being absorbed by the object, and for the process enjoying widespread success by the end of 1839 "having adopted Herschel's method of fixation with thiosulphate"; 1.7, for a direct image being a mirror of reality that must be re-photographed to restore its chirality; and the chapter on the tropics, for the daguerreotype halogenated with the aggressively corrosive vapours of elemental iodine and bromine and developed over hot mercury whose vapour is notorious for its insidious neurotoxicity; 9.7.1 Sel d'Or, aka Fordos and Gélis' Salt, for the earliest method of gold toning attributed to Himly in 1839 and more often to Fizeau in 1840, for the formula of the salt as Na3[Au(S2O3)2]·2H2O and the alternative name sodium aurothiosulphate, for the two ways of working it described in Sutton's 1855 Calotype Handbook — an approximately 0.1 per cent solution of the pure salt giving "the French violet tints", and Fizeau's original method of preparing the bath in situ by adding gold chloride slowly to hyposulphite of soda — for the toning reaction written as the displacement of gold by silver in the complex, and for the tetrathionate by-product and its sulphiding of silver metal. Also 9.6, for tetrathionate being produced by the oxidation of thiosulphate by almost any oxidising agent through the removal of two electrons; 7.8.2 Exciting, for the readings that put numbers on Talbot's grains and ounces — the exciting solution containing 4.9 per cent w/v (0.288 M) silver nitrate, 7 per cent v/v acetic acid and 0.5 per cent w/v gallic acid, made by mixing equal volumes of an aceto-nitrate of silver stock of 9.8 per cent w/v (0.577 M) silver nitrate and 14 per cent v/v strong acetic acid with a saturated gallic acid solution of approximately 1 per cent w/v; the statement that the silver iodide already in the paper is made sensitive by the excess silver ions, that the gallic acid increased the sensitivity further but was not essential, that the acetic acid inhibited spontaneous decomposition, and that even so the excited paper "remained critically unstable" and had to be exposed within an hour or two before it fogged. 7.8.3 and 7.8.4 for the exposure and for development being physical rather than chemical, for the deposition of more silver upon the image to build density, and for the revival of under-exposed or faded negatives. 7.8.5 and 7.8.6 for the fixing, the larger image silver particles that follow from physical development, and Talbot's testing in notebook Q of an exciting solution without gallic acid and a developer of gallic acid alone, neither of which he published. 6.2 for the discovery in the days following 20 September 1840 and the hundredfold gain; 6.7 for patent No. 8,842 of 8 February 1841 and No. 9,753 of 1 June 1843; the chronology table for 23 September 1840. 10.5 for Cundell's published objection that Talbot's solutions were "unnecessarily strong", for the further dilution of ten to forty times proposed in the Philosophical Magazine of August 1846, for John Adamson's advice that stability was greatly increased by excluding the gallic acid, and for the consequent adoption after 1846 of aceto-nitrate of silver alone as the exciting solution. 11.1 for Blanquart-Evrard's claims; 11.2 for Guillot-Saguez's 7.1 per cent aceto-nitrate with no gallic acid; 13.1 for Flacheron's developer of saturated gallic acid alone; 14 for Greenlaw's 1 per cent gallic acid with 0.2 per cent aceto-nitrate and for the base fog attributed to physical development; 15 and Table 1 for the two categories of exciting and the two means of development. 23.1 to 23.6 for the chemical model: the Ag+ + e– = Ag half-reaction that has no accompanying oxidation in pure silver nitrate, the role of halogen acceptors, the adsorption of impurity ions that makes a silver halide "sensitized" or "fixed", and the disproportionation equilibria that are extensive for chlorine, slight for bromine and negligible for iodine until free silver ions drive them, with the consequence that fixed silver iodide "is completely insensitive even to direct sunlight"; 5.4, Herschel's use of engravings and the caption calling an 1839 silver negative print an argentotype; 5.9 and Table 5.3, Herschel's etymology for the new processes; 5.10, the siderotype processes, the argentotype's brown nanoparticle silver, its poor stability and the derivative family it fathered at the end of the century; 7.5.4, the three pitfalls of thiosulphate fixation of a print-out silver image; Section 7.5.4, Thiosulphate fixation, for the complexation equation, for the statement that there should be no residual silver halide in a properly thiosulphate-fixed photograph, and for the three pitfalls of applying thiosulphate fixation to a print-out paper — that excess silver nitrate must be washed out with water first or the image is seriously stained with brown silver sulphide, that the colloidal silver of the image "is easily oxidised by air in the presence of thiosulphate ions" so that over-long immersion, too concentrated a solution or oxidising impurities in the water cause serious loss of image density if the print has access to the air, and that insufficient washing after fixation leads to extensive fading by sulphiding; section 23.8, Significance of Redox Potentials, for the tabulated standard potentials used on this page — Ag+/Ag +0.7991 V, [Ag(S2O3)2]3-/Ag,2S2O32- +0.01 V, Ag2S/2Ag,S2- -0.71 V and the pH-dependent oxygen couple O2,4H+/2H2O at +1.229 - 0.059pH — and for the general principle that any involvement of highly insoluble products or complex ions in the redox equilibrium greatly increases the ease of oxidising metallic silver; and section 20.9 to 20.10, on the collection environment, for the statement that "it is chemically certain that molecular oxygen of the air is a more potent oxidising agent under acidic, than under alkaline conditions" and that image silver is correspondingly less susceptible to aerial oxidation under alkaline conditions; Section 23.8, Significance of Redox Potentials, for the standard potential of the silver couple Ag+/Ag at +0.7991 V, for the pH-dependent oxygen couple O2,4H+/2H2O at +1.229 minus 0.059 pH, and for the general principle that any involvement of highly insoluble products or complex ions in the redox equilibrium greatly increases the ease of oxidising metallic silver; and sections 20.9 to 20.10, for the statement that "it is chemically certain that molecular oxygen of the air is a more potent oxidising agent under acidic, than under alkaline conditions"; 7.5.4 Thiosulphate fixation, for the three pitfalls of fixing a plain-paper silver image; 9.3 Coating Weight and Particle Size, for the 2 per cent survival of applied silver, the 0.1 g per square metre coating weight, the 10 nm particle radius, the thirtyfold density loss on complete conversion to silver sulphide and the yellow-orange colour of pure nanoparticle silver; 9.5 — residual thiosulphate left in the paper after washing slowly attacking the image silver and converting it to silver sulphide, the colour drastically weakened from a rich brown to a pale buff, and the experimental finding that oxidation by air promotes the sulphiding action of residual thiosulphate; 9.5 — residual thiosulphate left in the paper after washing slowly attacking the image silver and converting it to silver sulphide, the colour drastically weakened from a rich brown to a pale buff, and the finding that oxidation by air promotes the sulphiding action; 7.5.4 Thiosulphate fixation, for the three pitfalls — unwashed silver nitrate staining the image with silver sulphide, oxidation of colloidal silver in the fixer, and incomplete washing afterwards; 9.3 Coating Weight and Particle Size, for the 2 per cent survival of applied silver, the 0.1 g per square metre image coating weight, the 10 nm particle radius, the thirtyfold density loss on complete conversion to silver sulphide, the yellow-orange colour of pure nanoparticle silver, and John Adamson's ammonia-fixed prints; Section 2.6 Bitumen, for the 1822 contact prints on glass, the photohardening and the washing away of the soluble asphalt with lavender oil and petroleum, and the three to four hour contact exposure in sunlight; section 3.8, for Marignier's reconstruction of the camera and lens, the estimated speed of less than 10⁻⁶ ISO and the practical exposure of about five days; and section 3.9, for the 2010 Getty Conservation Institute and National Media Museum examination of the surviving plates; Section 23.8, Significance of Redox Potentials, for the pH-dependent oxygen couple O2,4H+/2H2O at +1.229 minus 0.059 pH, and for the general principle that any involvement of highly insoluble products or complex ions in a redox equilibrium greatly increases the ease of oxidising the metal; Section 9.3, Coating Weight and Particle Size, for the 1855 analyses finding that only about 2 per cent of the silver taken up by the sensitised paper remained in the final image, for the image coating weight of about 0.1 g per square metre, for the whole-plate print containing typically 3.3 mg of silver in total against about ten times that in a modern silver-gelatin print, for the colloidal silver of a salt print having a particle size perhaps one hundredth of that in a modern image and so a surface area a hundred times larger, for the statement that complete conversion of nanoparticle silver to silver sulphide drops the optical density by a factor of about 30, for silver sulphide forming directly by the reaction of thiosulphate ions with nanoparticle silver especially under acidic conditions, and for the account of the surface coating of sulphide that deepens the colour of 10 nm silver from yellow-orange to a satisfying brown while complete sulphiding weakens it to a drab buff; section 7.5, Fixation - Chemistry and Etymology, for the distinction between Talbot's halide stabilisation and Herschel's removal of the halide by complexation, for Herschel having called the latter "washing out", and for residual thiosulphate left in the paper slowly converting image silver to silver sulphide; section 9.5, Old Hypo Colouring Baths, for Blanquart-Evrard's observation about 1850 that much-used hypo baths coloured prints richly, for the artificial ageing of baths with acid, silver nitrate and oxidising agents, and for the drastic fading of the prints so treated being acknowledged by about 1858; section 9.6, Sparling's Iron Toner, for the statement that oxidation of thiosulphate with almost any oxidising agent — iron(III) chloride, silver nitrate, iodine, nitric acid are the ones named — first produces tetrathionate by removing two electrons, and that tetrathionate is an effective sulphide toner of silver metal, with the equation 4Ag + S4O6(2-) + H2O giving 2Ag2S + HSO3(-) + HSO4(-); and section 23.10, Sulphiding of Silver Images, for silver sulphide having one of the smallest solubility products known for any binary salt at about 6 x 10^-50 and a redox potential of -0.71 V, so that in the presence of sulphide ions metallic silver is quite a powerful reducing agent comparable with metallic zinc, for the two disproportionations of thiosulphate — 5S2O3(2-) + 6H(+) giving 2S + 2S4O6(2-) + 3H2O under acid conditions, or 2S2O3(2-) giving 2S + 2SO3(2-), depending on the pH — for the colloidal sulphur so released being a mild oxidant towards silver that forms the sulphide as 2Ag + S giving Ag2S, and for sulphide-faded images being unrestorable by redevelopment in conventional photographic developers whose redox potentials are insufficiently negative, unlike iodide-faded ones; 23.1, on silver nitrate becoming photosensitive only in the presence of readily oxidisable substances and on the oxidisable component in a silver-nitrate-only paper being the cellulose or the starch or gelatin sizing agent; 23.2 Photolytic Silver, on the exposure needed to build a colloidal particle being of the order of a million times that needed for a latent image, on the limit imposed by the crystal lattice, on photolytic silver particles in pure crystals not growing beyond about 10 nm and on the corresponding optical density of the order of 0.02; 23.3 Significance of Halogen Acceptors, listing the potential acceptors around a Talbot sensitiser as excess silver(I) ions, water molecules, the cellulose substrate and probably an organic sizing agent of gelatine or starch, proposing that the combined action of water and silver(I) ions is the major halogen acceptor contributing the greater part of the image silver, and stating that although gelatin may be the important acceptor in development emulsions it is known not to be an effective scavenger of halogen at print-out levels of exposure, so that the paper sizing agent is not essential to the photochemistry of print-out — which may be demonstrated experimentally — but does serve to retain the sensitiser and therefore the image in the surface fibres and possibly to protect the hydrophobic colloidal silver particles by surface adsorption, thereby influencing colour and stability; 23.4 Impurity Adsorption onto Silver Halide Crystals, on precipitated silver halides being non-stoicheiometric with the adsorbed impurity ion depending on the solution in contact, and on the distinction between "sensitized" silver halide with silver ions in excess and "fixed" silver halide with halide in excess; 23.5 "Sensitized" Silver Halide, on the excess positive charge attracting photoelectrons to the crystal surface so that silver specks form and grow free of the constraint of the lattice while positive holes diffuse out to form halogen molecules, and on the four fates of those halogen molecules — reversal in the absence of an acceptor, trapping by the substrate or another organic component of the sensitiser by addition to unsaturated compounds, substitution in saturated aliphatic compounds or oxidation of functional groups such as alcohols, which completes the photolysis of the crystal but does not promote photolysis of the excess silver ions because the halide is taken out of circulation, and reaction with the water normally present in the paper, cellulose holding about 8 per cent water by weight at 60 to 70 per cent relative humidity, with disproportionation to halide ion and hypohalous acid; 7.2 Photogenic Drawing, on the reversible photolysis of silver chloride and the need for a chemical absorber of chlorine, and on the particle size of a printed-out image; 7.3 Photogenic Drawing Paper, on Talbot's 1834 discovery that a strong response to light depends on the halide being substantially less than chemical equivalence, on the salting strengths recorded in Notebook P (0.6 to 2.3 per cent w/v, with a customary trough at 1.1 per cent) and on his silver solutions of 11 to 23 per cent; 23.2 Photolytic Silver; 23.3 Significance of Halogen Acceptors, on water and silver(I) ions as the major halogen acceptor, on gelatin not being an effective scavenger of halogen at print-out levels of exposure, and on the sizing agent retaining the sensitiser in the surface fibres and protecting the colloidal silver; 23.4 to 23.6, on "sensitized" silver halide with adsorbed silver ions against "fixed" silver halide with adsorbed halide ions, the disproportionation equations, and the acidity generated during exposure; 22 Colours of Silver Images, and 22.1 to 22.3, for photolytic silver at 10 to 100 nm, surface plasmon resonance, Wiegel's table of particle diameter against transmitted colour, and the effect of departure from spherical shape and of the refractive index of the matrix; 23.5, for a more neutral image colour being consistent with a larger silver particle size in a sensitiser buffered against the acid generated during exposure; 23.1 Explanation of the Phenomena, on Talbot's sensitizers differing from modern development sensitizers principally in their large excess of free silver nitrate, and on silver nitrate in isolation not being photosensitive because the reduction of silver(I) has no accompanying oxidation half-reaction available to it; 23.2 Photolytic Silver, on the millionfold exposure needed over that for a latent image, on the 10 nm limit to particles formed inside a pure crystal and the optical density of about 0.02 that follows; 23.3 Significance of Halogen Acceptors, on the combined action of water and silver(I) ions as the major halogen acceptor and on gelatin not being an effective scavenger at print-out levels of exposure; 23.4 to 23.6, on adsorbed impurity ions making "sensitized" silver halide where silver is in excess and "fixed" silver halide where halide is, on the excess positive charge drawing photoelectrons to the crystal surface so that silver specks grow free of the lattice, on the disproportionation of halogen in water and its equilibrium constants, on the calculation showing all three halogens totally disproportionated in the presence of free silver(I), and on the hydrogen ions generated during exposure; 7.3 Photogenic Drawing Paper, on Talbot's 1834 discovery that a strong response to light depends on the halide being substantially short of chemical equivalence, on the salting concentrations implied by Notebook P and by Malone's account of the Reading Establishment, and on Talbot's silver solutions of 23 to 18 per cent w/v with Notebook P values of 20 and 11 per cent; 7.4 Ammonio-Nitrate of Silver Paper, on Alfred Swaine Taylor's 1839 formulation, the ca. 20 per cent silver nitrate it starts from, the equations for the oxide and the diammine complex, the colder image colour and greater resistance to fading Talbot recorded, and the cautionary note that such solutions can deposit silver nitride, a contact explosive, so that storing them is not recommended; Section 1.3, "Schulze's Serendipitous 'Scotophorus'", for the description of the preparation as a suspension of chalk in an aqueous solution of silver nitrate, for the reading that the intended product was Baldewein's phosphor and the necessary salt calcium nitrate, for the statement that the silver carbonate so formed decomposed photochemically, and for the reading of the title as a rueful, almost self-mocking description; and section 1.2 for the eighteenth century interest in the luminous minerals that Schulze was pursuing; 7.5.4 Thiosulphate fixation, for the oxidation of colloidal image silver by air in the presence of thiosulphate; 9.3 Coating Weight and Particle Size, for the particle radius and the small fraction of applied silver that survives in a plain-paper print; 7.8 Calotype Paper, and in particular 7.8.1 Iodizing, for the John Whatman Turkey Mill substrate, the 3.8 per cent w/v (0.224 M) silver nitrate and 5.7 per cent w/v (0.343 M) potassium iodide readings of Talbot's grains and ounces, the statement that the two to three minute immersion ensured the iodide was in chemical excess and precipitated silver iodide within the paper fibres, the criticality of the timing of both stages — too long in the iodide re-dissolving the silver iodide and prolonged rinsing causing it to fall off — and the stability and long storage of the iodized paper; 7.8.2 to 7.8.5 for the exciting, exposing, developing and fixing that follow; 6.2 Development of the Calotype, for the latent image, the hundredfold gain over photogenic drawing paper and the larger, more neutral silver particles of a developed image; 6.7 Patents, for patent No. 8,842 of 8 February 1841 and No. 9,753 of 1 June 1843; 10.4, for Furlong's single-solution iodising through the tri-iodoargentate complex and its re-precipitation on dilution; 10.5, for Cundell's and Lady Eastlake's judgement that Talbot's directions were too vague to follow; 11.2, for Guillot-Saguez's 4.1 per cent potassium iodide iodising with no silver at all and the free-iodine indicator it produced; 15 Summary of Calotype Variations and Table 1, for the three distinguishable methods of iodizing; 7.5.1 Iodide fixation, for the equations of iodide conversion and of the complexation that dissolves silver iodide, and for the fading of iodide-fixed images in the presence of excess iodide; 23.3 Significance of Halogen Acceptors; 23.4 Impurity Adsorption onto Silver Halide Crystals; 23.5 Sensitized Silver Halide; and 23.6 Fixed Silver Halide, for the finding that fixed silver iodide is completely insensitive even to direct sunlight while fixed silver chloride goes dull violet and fixed silver bromide pale grey; 6.1, on the 34.4 per cent of its own weight of salt that silver nitrate needs for chemical equivalence, on the failure of a paper made to those proportions, on Talbot's chosen proportion reading like chemical heresy, on saturated silver nitrate being around 150 per cent w/v so that "six or eight times diluted" implies about 20 per cent, on the silver meeting about one twentieth of its weight of salt, and on the six conditions that had all to be met at once; 7.3 Photogenic Drawing Paper, on the invariant procedure of dilute halide first and strong silver second, on the 1834 discovery that a strong response to light depends on the halide being substantially less than chemical equivalence, on J. Whatman's Turkey Mill as a gelatin-sized rag paper, on the salting strengths implied by Notebook P (0.6 to 2.3 per cent w/v) with a customary trough at 1.1 per cent, on Malone's 0.7 to 1.4 per cent at the Reading Establishment and his two-minute immersion, on the silver solutions of 23 to 18 per cent w/v with Notebook P values of 20 and 11 per cent, on drying by radiant heat from a fire, on the ten-minute photogram in direct sunlight and the camera exposures in the order of hours, and on the multiple alternate coatings and moist use that cut camera exposures to about thirty minutes; 7.4 Ammonio-Nitrate of Silver Paper, on Alfred Swaine Taylor's 1839 formulation, the 2 per cent salting used with it, the colder image colour and greater resistance to fading, and the cautionary note on silver nitride; 7.5 and 7.5.1 to 7.5.4, on the two meanings of fixation, on Talbot's 1 to 2 per cent w/v potassium iodide deduced from Notebook P, on the equations of iodide fixation and of the fading it causes, on the strong salt solution read as saturated at 31.7 per cent w/v with the excess wiped off and no final rinse, on the complexation that dissolves a little of the residual halide, on bromide fixation, and on thiosulphate fixation with its three pitfalls and its clear highlights and reddish-brown image; 7.6 Waterloo Paper; 16.5 Implications for Conservation, on the lilac veil a chloride-fixed photogenic drawing acquires and the Becquerel effect that puts it at risk even under ultraviolet-free light; 17 Case Histories, on the threshold exposure of the order of 200 lux hours for chloride-stabilised photogenic drawings against 30 kilolux hours or more for thiosulphate-fixed ones; 23.1 to 23.6, on silver nitrate not being photosensitive by itself, on the limiting density of about 0.02 reached by photolysis in a pure silver halide crystal and the 10 nm limit on the particle, on water and silver(I) ions as the major halogen acceptor, on gelatin not being an effective scavenger of halogen at print-out levels of exposure, on the disproportionation equations and their equilibrium constants, on the acid generated during exposure, and on the difference between "sensitized" silver halide carrying adsorbed silver ions and "fixed" silver halide carrying adsorbed halide ions; 5.10 Siderotype processes, for the argentotype's descendants and their reputation; 7.5.4 Thiosulphate fixation, for the three pitfalls — washing out the excess silver before the thiosulfate, the ease with which colloidal silver is oxidised in the presence of thiosulfate, and the consequences of insufficient washing afterwards; 9.3 Coating weight and particle size, for the 2 per cent survival of applied silver in a salt print, the coating weight of about 0.1 g per square metre, the 30-fold density loss on complete conversion to silver sulphide and the yellow-orange colour of 10 nm silver; 9.2 Reciprocity law and its failure, for high- and low-intensity reciprocity failure in print-out silver, the use of bright sun against north sky as a contrast control by Burton, Towler, Crawford and Reilly, and Schaaf's explanation that slower printing gives smaller and more fixer-vulnerable silver particles; 7.5.4 Thiosulphate fixation, for the three pitfalls of fixing a print-out silver image and the requirement that excess silver be washed out before the thiosulphate; 9.3 Coating Weight and Particle Size, for the image coating weight of about 0.1 g per square metre, the 3.3 mg of silver in a whole-plate print, the thirtyfold fall in optical density on complete conversion to silver sulphide, the yellow-orange colour of 10 nm silver and the apple-skin account of surface sulphiding; 22.1 and 22.2, for surface plasma resonance and Wiegel's table of the colours of nanoparticle silver against particle diameter; 22.5 Effect of Aggregation, for the shift of a yellow 10 to 20 nm sol to red-brown; 22.6 Effects of Surface Adsorption, including Henglein on colloidal silver as an electron pool; 22.9 Effect of Sulphiding on the Colour of Silver, for the extinction coefficients of 16,000 against 560 dm3 per mol per cm and Henglein's sulphide monolayer; 23.7 Back-reactions Destroying Print-out Silver, for the oxidation of silver by nitrate in acid conditions; 23.8 Significance of Redox Potentials, for the table of standard potentials including the silver, nitrate and thiosulfate couples; 2.1 Silver Compounds, on silver nitrate not being light-sensitive per se but becoming so in the presence of organic matter, on Wedgwood recording contact images around 1797 with white kidskin leather as his preferred substrate, on Michael Gray's explanation that such leather was tawed rather than tanned and that its residual chloride would form silver chloride with the silver nitrate, and on Chaussier's 1799 synthesis of thiosulphate not being an essential prerequisite for a lasting silver image; 22 Colours of silver images, for the plasmon colours of finely divided photolytic silver; 3.5 Contact Prints and Photograms, which quotes the two or three minutes in direct sun and the failure in the camera obscura; 23.2 and 23.3, on the limiting density of the order of 0.02 reached by photolysis inside a pure silver halide crystal, on the 10 nm limit to the silver particles, on the necessity of a halogen acceptor for a print-out image, and on water and silver(I) ions together constituting the major halogen acceptor; 23.5, on "sensitized" silver halide carrying adsorbed silver ions, the excess positive charge that attracts photoelectrons to the crystal surface, and the net photolysis Light + 2AgX to 2Ag + X2; 1.6 Ambivalent Daguerreotypes; 1.7 direct processes and chirality; 5.3 Herschel's versions of photography; 5.9 Herschel's photo-etymology; 5.10 Siderotype processes; 7.5 Fixation: chemistry and etymology; 7.5.4 Thiosulphate fixation; 1.7 The negative image; 1.8 Negative-positive processes; 3.1 The 'Gernsheim question'; 3.2 Proto-photography; 5.10 Siderotype processes; 6.2 Development of the calotype; 2.6 Bitumen; 2.7 Resins; 3.8 exposure of the heliographic process; 3.9 Niepce in England 1827; 22 Colours of silver images; 23 Chemical models for silver photography; 6.1 Invention of photogenic drawing; 6.2 Development of the calotype; 6.6 Publications; 6.7 Patents; 7.5 Fixation: chemistry and etymology; 7.8 Calotype paper; 8 chronology; 10.1 Innovations at Saint Andrews; 17.3 Deterioration by environment; 2.1 Silver compounds and the tawed-leather explanation; 7.5 Fixation: chemistry and etymology; 7.5.1 iodide fixation; 7.5.2 chloride fixation; 22 Colours of silver images; 23.5 to 23.7 halogen acceptors, fixed silver halide, back-reactions; 7.4 Ammonio-nitrate of silver: cautionary note on diammine silver solutions; 23.4 and 23.5: impurity adsorption onto silver halide crystals, with the alternating silver-ion and chloride-ion array drawn for sensitized silver chloride; 9.6 Sparling's Iron Toner: oxidation of thiosulphate to tetrathionate by removing two electrons, and tetrathionate as a sulphiding toner of silver metal; 23.4 Impurity adsorption onto silver halide crystals; 23.5 sensitized silver halide with adsorbed excess silver ion; 23.2 Photolytic silver; 23.3 Significance of halogen acceptors; 23.11 Gurney-Mott model of the latent image; 21.1 Coating Weight, Covering Power and Photometric Equivalent; 21.2 Nutting density equation; 21.3 Extinction coefficients of photolytic silver, including the coating weights of modern silver-gelatin enlarging papers; 21.1 Coating Weight, Covering Power and Photometric Equivalent; 21.2 the Nutting density equation; 21.3 Extinction Coefficients of Photolytic Silver; 9.2 Reciprocity Law and its Failure; note 34 on the Herschel Effect as the quenching of the latent image by long-wavelength light; 7.4 Ammonio-nitrate of silver: the cautionary note on diammine silver solutions; 23.2 Photolytic silver; 23.3 Significance of halogen acceptors; 22 Colours of silver images, in particular 22.1 surface plasma resonance absorption, 22.2 size and colour of nanoparticle silver, 22.3 refractive index of the environment, 22.5 effect of aggregation and 22.9 effect of sulphiding; 23.1 explanation of the phenomena; 23.2 photolytic silver; 23.10 sulphiding of silver images; 16.4 Becquerel Effect: photolytic silver inside the crystal sensitising the host lattice to longer wavelengths; 16.5 Implications for Conservation, including the risk from yellow and red safelights; 21.6 Quantum yields from silver halide photolysis; 23.2 Photolytic silver; 23.3 Significance of halogen acceptors; 23.11 Gurney-Mott model of the latent image; 9.1 Exposure Considerations: a 100 W tungsten bulb at one metre gives about 100 lux and midday summer sun about 100,000 lux; 21.6 Quantum Yields, the order-of-a-million exposure ratio between a latent and a visible photolytic image; 22.3 Refractive index of the environment; 23.2 Photolytic silver; 23.3 Significance of halogen acceptors; 23.4 to 23.6 impurity adsorption on silver halide crystals; 23.11 Gurney-Mott model; 23.3 Significance of Halogen Acceptors: gelatin as the halogen acceptor in development emulsions, and note 503 on Sheppard, Photographic Gelatin, Photographic Journal 65 (1925); 9.1 Exposure Considerations: midday summer sun about 100,000 lux and a 100 W tungsten bulb at one metre about 100 lux; 9.1 Exposure Considerations: midday summer sun about 100,000 lux at English latitudes; 9.1 Exposure Considerations: midday summer sun about 100,000 lux at English latitudes; 22 Colours of silver images; 23.5 to 23.7 halogen acceptors and back-reactions; Section 7.2 and the discussion of sulphiding - that complete conversion of nanoparticle silver to silver sulphide causes a drop in optical density by a factor of about 30, and that in modern silver-gelatin papers the higher concentration of silver and its larger particle size make the loss of density on sulphiding far less apparent; Section 22, Colours of Silver Images - photolytic silver has a particle size in the 10 to 100 nanometre region, in contrast to the micron-sized bundles of filamentary metallic silver formed in most chemically developed silver-gelatin emulsions; 22.1, Surface Plasma Resonance Absorption, that for most metals the resonances give absorption maxima in the ultraviolet but that for copper, silver and gold the variation of the dielectric function with frequency gives sharp absorption bands in the visible, first investigated by Faraday in 1857, that Mie treated spherical particles in 1908 and Gans extended the treatment to ellipsoids, that a dipolar approximation is valid and absorption predominates when particles are much smaller than the wavelength while multipolar terms and scattering matter at larger radii, and that Creighton and Eadon's calculations show colour to be a rare characteristic among nanoparticle metals, copper, silver and gold being likely to remain the only ones with distinctive colours; 22.2, Size and Colour of Nanoparticle Silver, the table of transmitted and scattered colour against particle diameter calculated by Wiegel and confirmed by experiment, and the statement that elongation to a prolate spheroid shifts the main absorption band to shorter wavelengths while introducing a new longer-wavelength band, an effect Skillman and Berry investigated experimentally in silver emulsions in agreement with the theory of Gans; 22.3, Refractive Index of the Environment, that raising the refractive index of the host matrix moves the maximum of the silver absorption band to longer wavelengths, the silver chloride matrix at n equals 2.071 shifting the 390 to 400 nm band of silver hydrosols to about 550 nm; 22.5, Effect of Aggregation, that linear aggregation of spherical particles introduces a long-wavelength band so that a yellow 10 to 20 nm hydrosol becomes red-brown, and that as the axial ratio of a prolate spheroid goes from 1 to 2 to 3 the colour shifts from yellow to red to blue; 22.6, Effects of Surface Adsorption, that adsorbed ligands can profoundly affect the plasmon absorption band, with cited cases of a 390 nm band shifting to 510 to 550 nm on adsorption of thiolic ligands, and the quoted admission that a quantitative theoretical model for these effects has not yet been developed; 22.7, that Berry and Skillman showed neutral density can arise in nanoparticle silver from a wide range of particle size and shape distributions, the absorption across the visible being the envelope of a family of peaks, their polydisperse colloid having been obtained by the development of a fine grain emulsion; section 7.2, that the distinctive colours of printed-out silver images are due to very small silver particles with sizes less than the wavelength of visible light while a developed paper image appears neutral-toned owing to the much larger silver filaments produced by development, and that the small particle size of a print-out image implies a very high surface area relative to mass; and section 22 on sulfiding, that the optical extinction coefficient of nanoparticle silver is about 16,000 dm3 per mol per cm at the absorption maximum against about 560 for nanoparticle silver sulfide, so complete sulfiding of nanoparticle silver drops the maximum optical density by a factor of nearly thirty, with the qualification that the visual effect is smaller because the eye is insensitive near 400 nm, and the statement that silver sulfide in sufficient concentration is a good stable pigment, as the sulfide toning of modern silver-gelatin papers attests, but that the quantities of silver in early salt prints are so small that conversion greatly weakens the density; Section 7.2, that the distinctive colours of printed-out silver images are due to very small silver particles with sizes less than the wavelength of visible light while a developed paper image appears neutral-toned owing to the much larger silver filaments produced by development, and that the small particle size of a print-out image implies a very high surface area relative to mass and therefore exposed to attack; and section 22 on sulfiding, that the optical extinction coefficient of nanoparticle silver is about 16,000 dm3 per mol per cm at the absorption maximum against about 560 for nanoparticle silver sulfide; Section 7.2, that photolytic silver has a particle size in the 10 to 100 nanometre region in contrast to the micron-sized bundles of filamentary metallic silver formed in most chemically developed silver-gelatin emulsions, and that modern silver-gelatin prints contain about ten times the silver of a salt print; and the discussion of sulphiding, that of the chemicals avid to attack silver the most destructive are those containing sulphur, which form the highly insoluble stable substance silver sulphide, that darkroom workers have long used sulphide as an effective brown-toner for modern silver-gelatin prints, and that the answer to why the same substance causes drastic fading in salted paper prints lies in the covering power of the respective pigments, which can be quantified photometrically - complete conversion of nanoparticle silver to silver sulphide causing a drop in optical density by a factor of about 30, while in modern papers the higher concentration of silver and its larger particle size make their loss of density on sulphiding far less apparent; Section 9.3, Coating Weight and Particle Size, for the 1855 analyses finding only about 2 per cent of the silver taken up by the sheet remaining in the finished image, a coating weight of about 0.1 g/m2, about 3.3 mg of silver in a whole-plate print against roughly ten times that in a modern silver-gelatin print, and the hundredfold surface area that follows from a hundredfold smaller particle; Section 22.2, for the table of transmitted and scattered colour against particle diameter for nanoparticle silver; Section 23.3, Significance of Halogen Acceptors, for the proposal that water and silver(I) ions together are the major halogen acceptor in a Talbot sensitiser and that gelatin is not an effective halogen scavenger at print-out exposures; Section 23.2, for photolytic silver needing an exposure of the order of a million times that which forms a latent image; Section 9.3, Coating Weight and Particle Size, for about 3.3 mg of silver in a whole-plate salt print at a coating weight of about 0.1 g/m2, roughly a tenth of a modern print, for the hundredfold surface area that follows from a hundredfold smaller particle, and for complete conversion of nanoparticle silver to silver sulphide dropping the optical density by a factor of about thirty; Section 17.4, Salted Paper Prints, for thiosulphate-fixed salt prints having been exhibited under Class 1 Gallery Illumination with no significant change measured by densitometry, for McElhone's quantitative study of a salted paper print by Benjamin Turner and a lightly albumenised print by Baldus of 1855 in which densities fell by about 0.02 after 30 kilolux hours under UF-1 filtration below 100 lux, for that change being within the precision of the densitometer, and for the implied threshold exposure lifetime of nearly 300 hours; Section 16.2, for the threshold exposure of chloride-stabilised photogenic drawings and salt prints being of the order of 200 lux hours, and for the recommendation that 100 kilolux hours is an acceptable risk for thiosulphate-fixed material; Section 17.5, Albumen Prints, for the restricted access of oxygen to image silver protected by a binder, for Pretzel and Martin's study of Lady Hawarden's albumen prints finding average threshold exposure lifetimes of the order of one or two years or about 10,000 hours with nearly as much change in dark storage as on exhibition, for the sulfur-containing molecules of egg protein binding silver ions strongly and retaining silver in the highlights, for Reilly and co-workers' incubation studies showing the Maillard protein-sugar reaction as a further contributor to highlight yellowing and demonstrating that the instability of albumen prints is inherent rather than due to inadequate processing and is greatly accelerated at high relative humidity, for gold toning as recommended by the Fading Committee usually greatly improving the permanence of albumen prints and shifting the colour to a rich purplish brown, for there being no evidence that Talbot ever used gold toning, and for Ware's closing hope that an equally thoroughgoing study will soon be made of salted paper prints also; Section 22.9, for the extinction coefficients of nanoparticle silver at about 16,000 and of nanoparticle silver sulphide at about 560 dm3 mol-1 cm-1 and the near-thirtyfold drop in maximum optical density on complete sulphiding, and for silver sulphide appearing yellow rather than black at nanoparticle thickness; Section 23.8, for the table of standard redox potentials including Ag+/Ag at +0.7991 V and Ag2S/Ag at -0.71 V; Section 9.3, Coating Weight and Particle Size, for the 1855 analyses finding about 2 per cent of the silver taken up remaining in the final image, for a coating weight of about 0.1 g/m2, for about 3.3 mg of silver in a whole-plate print against roughly ten times that in a modern silver-gelatin print, for nanoparticle radii of about 10 nm and the hundredfold surface area that follows, and for complete conversion of nanoparticle silver to silver sulphide dropping the optical density by a factor of about thirty; Section 9.2, for low-intensity reciprocity failure in salted paper printing and the observation that printing under dull light cannot be compensated by extending the exposure, with Schaaf's explanation and Ware's objection to it; Section 9.5, Old Hypo Colouring Baths, for Blanquart-Evrard's observation about old hypo and for Malone's addition of nitric acid at the Reading Establishment; Section 22.1 and 22.2, for surface plasma resonance absorption, for Mie's 1908 theory, for colour being a rare property among nanoparticle metals with copper, silver and gold the exceptions, and for Wiegel's table of transmitted and scattered colour against particle diameter; Section 22.3, for the refractive index of the host matrix shifting the absorption maximum, with the worked case of silver chloride at n = 2.071 moving the 390 to 400 nm band of a silver hydrosol to 550 nm and giving sunned silver chloride its violet colour; Section 22.5, for linear aggregation moving a yellow 10 to 20 nm sol to red-brown; Section 22.6, for adsorbed ligands changing the plasmon band and Henglein's statement that no quantitative theoretical model for the effect yet exists; Section 22.7, Problem of Photolytic Silver, for the rich purplish or brownish black of an unprocessed print, for the shift to yellowish brown on wet processing that disappoints everyone, for Berry and Skillman's polydisperse-colloid account of neutral density, for Ware's own statement that the reason for the initial black remains conjectural, and for the enrichment towards brown on drying attributed to coalescence ripening; Section 22.9, for the extinction coefficients of nanoparticle silver at about 16,000 and nanoparticle silver sulphide at about 560 dm3 mol-1 cm-1 and the resulting near-thirtyfold drop in density on complete sulphiding, and for Henglein's observation that dilute sulphide first enriches and then destroys a silver sol; Section 23.1, for silver nitrate alone not being photosensitive because there is no available oxidation half-reaction, and for papers sensitised with silver nitrate alone depending on the cellulose or the sizing; Section 23.2, Photolytic Silver, for the exposure of the order of a million times that needed for a latent image, for the limit imposed by the crystal lattice, and for the measured limiting yield of 1.2 x 10^19 atoms per square metre corresponding to an optical density of order 0.02; Section 23.3, Significance of Halogen Acceptors, for the proposal that water and silver(I) ions together are the major halogen acceptor in a Talbot sensitiser, for the statement that gelatin is known not to be an effective scavenger of halogen at print-out levels of exposure, and for the paper sizing therefore not being essential to the photochemistry although it retains the image in the surface fibres; Section 23.5, Sensitized Silver Halide, for adsorbed excess silver ions attracting photoelectrons to the crystal surface so that silver specks grow free of the lattice constraint, for the net photolysis, for the four possible fates of the liberated halogen, for the disproportionation equilibria and their constants, and for the acid generated by disproportionation; Section 23.6, Fixed Silver Halide, for the opposite behaviour when halide is in excess; Section 23.7, Back-reactions Destroying Print-out Silver, for the oxidation of silver by nitrate in acid conditions and by hypochlorous acid, and for the observation that the three equations sum to zero so that the outcome depends on relative rates; Section 23.8, for the table of standard redox potentials; Section 9.2, for low-intensity reciprocity failure in salted paper printing and the observation that printing under a dull light cannot be compensated by extending the exposure, and for the general advice of about 1855 that such prints should be much overexposed to compensate for the inevitable loss in the thiosulphate fixer; Section 9.3, for about 3.3 mg of silver in a whole-plate salt print at a coating weight of about 0.1 g/m2 and for the hundredfold surface area of nanoparticle silver; Section 22.7, for the shift from a rich purplish or brownish black to yellowish brown on wet processing, and for the enrichment towards brown on drying attributed to coalescence ripening with the note that the colour change is promoted by heat and was used to tone some early salt prints; Section 9.5, for Blanquart-Evrard's old hypo colouring bath and the practice of artificially ageing a fixing bath with acid, silver nitrate and oxidising agents, and for Malone's nitric acid at Reading being probably one of the causes of the fading of those prints; Section 7.1, Classification and Nomenclature, for the ten descriptors that would fully define the optical-chemical history of a photograph and the argument that a nomenclature embodying all of them would be intolerably cumbersome, for the primary division of Talbot's work into printed-out photogenic drawings and salted paper prints on one side and developed calotypes on the other, for the term salted paper print denoting a tonally positive image printed by contact on Talbot's photogenic drawing paper from a negative of whatever type, for Talbot not using the term himself, for the loose use of "calotype" to denote all silver photographs on plain paper leading to a confusion of processes that are in principle different, and for the argument that what matters for conservation is the present chemical composition rather than how it was achieved optically; Section 17.1, Identification of Processes, for the claim by some curators and conservators to identify Talbot's processes by visual inspection alone, for the distinctive colour differences between modern replicas fixed by chloride, iodide and thiosulfate, for bromide fixation being said to give distinguishable results with the differences subtle rather than distinctive and no precise descriptions yet published, and for calotypes being distinguished from photogenic drawing negatives by colour and by chronological or circumstantial evidence; Section 22.2 and 22.3, for the table of transmitted and scattered colour against nanoparticle diameter and for the refractive index of the host matrix shifting the absorption maximum; Section 9.3, Coating Weight and Particle Size, for the 1855 analyses finding about 2 per cent of the silver taken up remaining in the image and for the coating weight of about 0.1 g/m2 with about 3.3 mg of silver in a whole-plate print; Section 23.1, for silver nitrate alone not being photosensitive without an oxidisable substance present, which is why the reagent bottle is not the same hazard as the coated sheet; Section 9.3, Coating Weight and Particle Size, for about 3.3 mg of silver in a whole-plate salt print at a coating weight of about 0.1 g/m2, roughly a tenth of a modern print, for the hundredfold surface area of nanoparticle silver, for the remark that it takes very little hostile impurity to react with this tiny amount of silver and cause the print to fade, and for the near-thirtyfold drop in optical density on complete conversion of nanoparticle silver to silver sulphide; Section 22.9, for the extinction coefficients of about 16,000 for nanoparticle silver and about 560 for nanoparticle silver sulphide, for silver sulphide appearing yellow rather than black at nanoparticle thickness because its absorption band is centred in the ultraviolet and only tails into the blue, and for Henglein's finding that dilute sulphide first shifts a silver sol from yellow to brown by surface adsorption while exposure to air then replaces the band with the feeble spectrum of colloidal silver sulphide - so that a little sulphiding enriches and an excess destroys; Section 9.2, for low-intensity reciprocity failure and the observation that printing under a dull light cannot be compensated by extending the exposure; Section 9.5, for the old hypo colouring bath, the artificial ageing of fixing baths with acid, silver nitrate and oxidising agents, and Malone's nitric acid at Reading being probably one of the causes of the fading of those prints; Section 17.4, for McElhone's measurement of a salted paper print by Benjamin Turner and a lightly albumenised Baldus print showing density changes of about 0.02 after 30 kilolux hours, within the precision of the densitometer, and for thiosulphate-fixed prints tending to fade in light rather than fog, possibly by photoinduced oxidation of image silver, with the caution that Talbot did not always wash his prints after fixation so residual silver levels in some may still be high; Section 7.9, Albumenised and Waxed Papers — the attribution to Blanquart-Evrard, Talbot's 1842 notebook experiments with albumen as a binder, and the statement that there is no evidence Talbot ever albumenised his positive prints; the printing-out chapter's statement that in the albumen print "the albumen itself acts as a scavenger for the chlorine"; section 17.5, Albumen Prints — the sulphur-containing molecules in the egg protein binding silver ions very strongly, and footnote 639, that "egg albumen contains a much higher concentration of the thio-aminoacid, cysteine, than does gelatin"; Section 17.5, Albumen Prints — the restricted access of oxygen to image silver protected by a vehicle, Pretzel and Martin's study of Lady Hawarden's albumen prints giving average threshold exposure lives of the order of one or two years or about 10,000 hours with nearly as much change in dark-stored as in exhibited material, the sulphur-containing molecules in egg protein binding silver ions very strongly and retaining silver in the highlights despite the fixer, Reilly's incubation studies showing the Maillard reaction to be an important factor in highlight yellowing, the facilitated oxidation of colloidal silver in the shadows, the statement that Reilly's studies demonstrate the instability of albumen prints to be inherent rather than due to inadequate processing and greatly accelerated at high relative humidity, and the improvement in permanence from gold toning as recommended by the Fading Committee; footnote 639, that egg albumen contains a much higher concentration of cysteine than gelatin; Table 20.3 and its commentary — threshold exposures in kilolux seconds for photogenic drawing, cyanotype, salted paper, albumen and silver-gelatin, the four sensitivity categories, the "highly variable" range of 80,000 to 2,880,000 for albumen prints and the warning that less stable mavericks can lurk in any population because of uncertainties about processing quality, and the caution about the reciprocity assumption; section 20.9, The Collection Environment — Reilly's recommended storage of 30 to 40 per cent relative humidity and a temperature not exceeding 18 °C; section 20.10, Wrapping Materials and Enclosures — the consensus against buffered enclosures, its origin in a 1980 statement citing no experimental evidence, Reilly's demonstration that Maillard degradation is accelerated by alkali and the tentative 1982 recommendation that followed, Reilly's subsequent incubation of albumen prints in contact with calcium carbonate buffered paper yielding no detectable deterioration and his conclusion that carbonate buffering "is not by itself a major threat to albumen prints", the introduction of Atlantis Silversafe Photostore in 1982, and the contrasting cases of cyanotypes, platinotypes and salted paper prints; 5.8 Invention of siderotype, for Smee's gift of potassium ferricyanide in April 1842, his letter of 10 May 1842 suggesting the ammonio-citrate and ammonio-tartrate of iron, and Herschel's reply of 15 June 1842 that the citrate had furnished him with an infinity of beautiful photographic processes; 5.9 Herschel's photo-etymology and Table 5.3, for the coining of argentotype, argyrotype, chrysotype, cyanotype, kelainotype and the collective siderotype; 5.10 Siderotype processes, for the statement that towards the end of the nineteenth century Herschel's argentotype suddenly fathered a whole family of derivative iron-silver processes — Van Dyke Brown, Kallitype, Sepiaprint and Brownprint — and that they did not enjoy a high reputation for permanence unless toned with gold or platinum; 2.6 Bitumen — the 1822 contact prints, photohardening and the washing away of the soluble asphalt with lavender oil and petroleum, and the three to four hour contact exposure in sunlight; 3.8 — the estimated speed of the bitumen process at less than 10^-6 ISO and the resulting practical camera exposure of about five days; 3.9 — the Getty Conservation Institute and National Media Museum examination of four surviving Niepce plates, the pewter substrate, the identification of the Le Gras image as hardened bitumen and of the Cardinal d'Amboise plate as bitumen used as a photoresist over a deeply etched surface, and Ware's statement that the molecular structure of bitumen is so complex and variable as to constitute a chemist's worst nightmare; Sections 22 and 23, for the net photolysis of a silver halide, the fate of the liberated halogen and the role of halogen acceptors in preventing recombination; and 1.6 Ambivalent Daguerreotypes and 1.7, for the statement that virtually none of the light falling on a daguerreotype is absorbed by it, that the highlights are microscopic globules of silver amalgam which scatter light diffusely while the shadows are polished silver which reflects it specularly, and that a direct photographic image is a mirror of reality whose chirality can only be restored by re-photographing it; 5.10 Siderotype processes; 5.3 Herschel's versions of photography; 1.7 The negative image; 1.8 Negative-positive processes; 3.2 Proto-photography; 6.2 Development of the calotype; 6.7 Patents; 7.5.4 Thiosulphate fixation; 7.8 Calotype paper; 10.1 Innovations at Saint Andrews; 2.6 Bitumen; 2.7 Resins; 3.8 exposure of the heliographic process; 3.9 Niépce in England 1827; 6.1 Invention of photogenic drawing; 7.5 Fixation: chemistry and etymology; 8 chronology; 17.3 Deterioration by environment; 6.1 Invention of photogenic drawing; 6.6 Publications; 7.5 Fixation: chemistry and etymology; 10.1 Innovations at Saint Andrews; 17.3 Deterioration by environment; 23.2 Photolytic Silver, for the exposure of the order of a million times that needed for a latent image; 5.10 Siderotype processes; 7.5 Fixation: chemistry and etymology; 7.8.6 and the calotype's fixing: a wash in water to remove the excess silver nitrate; 7.4 Ammonio-nitrate of silver: the cautionary note on diammine silver solutions and silver nitride; 7.4 Ammonio-nitrate of silver: the cautionary note that solutions of diammine silver can, with time, deposit a black solid precipitate of silver nitride — 'fulminating silver' — a highly sensitive contact explosive detonating at a touch and sometimes even when wet, and that storing such solutions is not recommended; Silver nitrate in isolation is not photosensitive, becoming so only in the presence of a readily oxidisable substance; the retained fraction of silver found by analysis of nineteenth-century salt prints

Used by:P29 The Capstone Chemistry Report: From Photon Capture to Finished Print · Albumen · Ammonia solution (ammonium hydroxide) · Arrowroot · Bitumen of Judea · Borax (sodium tetraborate decahydrate) · Boric acid · Bromine · Calcium nitrate tetrahydrate · Ethanol · Gelatin · Gum arabic · Oil of lavender · Potassium alum · Potassium citrate · Silver · Silver bromide · Silver chloride · Silver iodide · Silver nitrate · Silver(I) oxide · Trisodium citrate dihydrate · Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Tartaric acid · Thiourea · Borax kallitype developer · Daguerre's 1839 process outline · Fizeau's gilding solution · Talbot's gallo-nitrate of silver · Herschel's argentotype · Dilute alkaline thiosulfate fixer for iron-silver prints · EDTA and sodium sulfite clearing sequence · Kallitype sensitiser · Kodak HT-2 · Kodak ST-1 · Nicol's kallitype · Niépce's bitumen heliograph coating · EDTA, citric acid and hydrochloric acid clearing sequence · Plain sodium thiosulfate fixer for printed-out papers · Arrowroot salting solution · Plain salted paper salting solution · Rochelle salt kallitype developer · Salted paper sensitising solution · Schulze's scotophorus mixture · Sodium citrate kallitype developer · Talbot's calotype iodised paper · Talbot's photogenic drawing paper · Van Dyke Brown sensitiser · Ware's argyrotype · Wedgwood and Davy's silver nitrate on leather · P1 Daguerre and the Daguerreotype: A Mirror With a Memory · P1 Herschel: Hypo, Prussian Blue and the Words of Photography · P1 1839 and the Many Inventors of Photography · P1 Niepce and Heliography: Light That Hardens · P1 Silver Salts and Light: Schulze to Ritter · P1 Talbot: Photogenic Drawing, the Calotype and the Negative-Positive Principle · P1 Wedgwood, Davy and the Problem of Permanence · P1 Experiment: The Image That Would Not Stay · P2 Storage, Incompatibilities and Secondary Containment · P2 Silver Nitrate: The Reagent That Sets the Rules · P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P3 Oxidation, Reduction and the Electron That Makes the Picture · P3 Solutions, Solubility and Precipitation · P4 Part IV Overview: Silver and Light · P4 Development as Amplification · P4 Grain, Speed and Resolution · P4 Reciprocity Failure and the Life of the Latent Image · P4 Experiment: Precipitating the Silver Halides · P4 Silver and the Silver Ion · P4 Spectral Sensitivity and Colour Response · P4 The Latent Image · P4 Darkroom Session: The Latent Image Made Visible · P4 The Silver Halides · P5 Gelatin, the Photographic Binder · P6 Pinhole Exposure and Reciprocity Correction · P7 Assignment: Architecture, Low Viewpoint and the Flat Plane · P7 Assignment: Landscape, Sky, Foreground and Filters · P7 Assignment: Night, the Very Long Exposure and Solargraphy · P7 Assignment: Panorama, Curved Plane and Multiple Pinholes · P7 Pinhole Portfolio Review and the Exposure Record as Data · P7 Assignment: Portrait, Environmental Portrait and Self-Portrait · P7 Assignment: Still Life and Controlled Light · P7 Assignment: Time in the Frame, Moving Water, Clouds, People and Traffic · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 What a Toner Actually Does to a Silver Image · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P22 Part XXII Overview: The First Silver Print · P22 Gold Toning and the Permanence of a Printed-Out Silver Image · P22 Printing Out: Silver Chloride Made and Darkened in the Paper · P22 Lab: Printing, Toning, Fixing and Washing a Salt Print · P22 The Variants of the Salt Print and How a Conservator Identifies One · P22 Lab: Salting and Sensitising a Sheet of Paper · P22 Break/Fix: The Printed-Out Image That Faded · P23 Egg Albumen: A Protein Binder and What It Does to Silver · P23 The Albumen Print as an Object, and How It Decays · P24 Part XXIV Overview: When Iron Reduces Silver · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory · Argentotype · Bayard direct positive · Calotype negative · Daguerreotype · Heliography on bitumen of Judea · Photogenic drawing · Salted paper print · Van Dyke Brown · The disposal caveat · Chemical incompatibilities · Ammoniacal silver quench and prohibition · Silver nitrate at the coating bench · Handling silver nitrate

Can the First Photographs Last?retrieved 2026-09-06

Sections: The whole article, read for this page and found to concern the light sensitivity, handling and display of Talbot's and Herschel's earliest printed-out images at the National Museum of Photography, Film and Television in Bradford, and to contain no measurement of the protection given to a silver image by any toner

Used by:P20 Toning, Permanence and What the Evidence Actually Supports

Chemistry of the Iron-based Processes: An Outline for Non-Chemistsretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: There are several other iron-based processes; A modernized version of platinum-palladium printing; The traditional clearing agent of dilute hydrochloric acid and why disodium EDTA replaced it; The key compound is ferric oxalate; the best example — platinum printing; the development reaction; The best example — platinum printing; the development reaction; The definition of iron(II) and iron(III) and of oxidation and reduction as electron transfer, and the note that the chemistry of the citrate is similar in principle to that of the oxalate but more complicated; The definition of iron(II) and iron(III) and of oxidation and reduction as electron transfer; the note that other salts of organic acids such as the citrate are also used and that the chemistry is similar in principle but more complicated for the citrate ion; The definition of iron(III) and iron(II) photochemistry, and the note that the citrate case is similar in principle to the oxalate but more complicated; The account of clearing for non-chemists, that the traditional clearing agent of dilute hydrochloric acid tends to dissolve palladium and weaken the cellulose structure of the paper, and that "a better modern reagent is disodium Edta, short for ethylenediaminetetraacetate, which is effective in binding iron(III) strongly under mildly acid conditions, and removing it from the paper"; and the statement that kallitype and argentotype are members of the same iron-based family as platinotype and palladiotype, with appropriate changes in the chemistry, although the principles are the same; The account for non-chemists, that "all the excess unreacted sensitizer chemicals and soluble reaction products are removed from the paper by baths of dilute (2%) hydrochloric acid, thus 'fixing' or, more accurately, 'clearing' the platinum image", and that "the traditional clearing agent of dilute hydrochloric acid tends to dissolve palladium and weaken the cellulose structure of the paper. A better modern reagent is disodium Edta ... which is effective in binding iron(III) strongly under mildly acid conditions, and removing it from the paper"; The definition of iron(II) and iron(III) and of oxidation and reduction as electron transfer; the dissected and solid-state photochemical equations; the statement that the iron(II) is re-oxidised by atmospheric oxygen so that the exposure alone leaves nothing permanent; the two-electron platinum stoichiometry and the remark that these ratios matter in formulating a sensitiser correctly; the explanation that the reduction cannot occur in a dry sensitiser because the ions are immobile; the modernised print-out route at about 70 per cent relative humidity where paper carries about 8 per cent water by weight; and the note that the citrate and tartrate are used in the Van Dyke, Brownprint and Argyrotype processes with a chemistry similar in principle but more complicated than the oxalate's; The definition of iron(II) and iron(III) and of oxidation and reduction as electron transfer; the closing note that salts of organic acids such as the citrate or tartrate are also employed, in the Van Dyke, Brownprint and Argyrotype processes, with a chemistry similar in principle but rather more complicated with the citrate ion; The best example — platinum printing, for the plain-language account of why an insoluble photoproduct needs a solvent before it can reduce anything; The definition of iron(II) and iron(III) and of oxidation and reduction as electron transfer, and the statement that the chemistry of the citrate is similar in principle to that of the oxalate but more complicated; The whole article — the definitions of iron(II) and iron(III) and of oxidation and reduction as electron transfer; the statement that all the iron imaging systems have the same basis; the photochemical equation for iron(III) and oxalate under ultraviolet light; the observation that iron(II) is a reducing agent because it readily gives up an electron, and can therefore reduce the compounds of a noble metal to the metallic state; and the closing paragraph naming gold, silver and mercury as the other metals used historically, with the note that other salts of organic acids such as the citrate or tartrate are also employed, as in the Van Dyke, Brownprint and Argyrotype processes, with a chemistry similar in principle but rather more complicated than the oxalate's; The whole article — oxidation and reduction as electron transfer, the dissected and solid-state photochemical equations, the observation that the colour change on exposure is slight and that atmospheric oxygen re-oxidises the iron(II) so the result is not permanent, the two-electron platinum stoichiometry, the statement that the second reaction cannot occur in the dry sensitizer because the ions are immobile and cannot encounter one another, the role of potassium oxalate developer in dissolving the insoluble ferrous oxalate, and the closing note that the citrate and tartrate are used in the Van Dyke, Brownprint and Argyrotype processes with a chemistry similar in principle but rather more complicated; The summary of gum bichromate — the gum as viscous binder for artists' pigments, the photochemical reduction of chromium(VI), the cross-linking of the gum and the washing away of the excess pigmented gum

Used by:Ammonium iron(III) citrate · Ammonium iron(III) oxalate · EDTA disodium salt dihydrate · Ferric oxalate · Potassium oxalate, anhydrous · Potassium oxalate monohydrate · Potassium tetrachloropalladate(II) · Potassium tetrachloroplatinate(II) · Sodium tetrachloropalladate(II) · Classic cyanotype sensitiser · Herschel's 1842 cyanotype · Herschel's argentotype · EDTA and sodium sulfite clearing sequence · EDTA, citric acid and hydrochloric acid clearing sequence · Van Dyke Brown sensitiser · Ware's argyrotype · Willis's potassium oxalate developer · P21 Iron, Light and Prussian Blue · P24 Part XXIV Overview: When Iron Reduces Silver · P24 The Siderotype Principle: Iron Reduces Silver · Argentotype · Gum bichromate · Kallitype · Van Dyke Brown

Chrysotype Manual: Science and Practice of Photographic Printing in Nanoparticle Gold (Chrysonomicon Part II), revised digital editionretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Section 2.11, Regulating the humidity, and 2.11.1 the Equilibrium method — the humidity chamber containing a saturated solution of a salt in continuous contact with excess solid at a specified temperature, usually 20 degrees C; Table 2.3, Substances for making constant RH enclosures at 20 degrees C, for the eight salts with their relative humidities and their solubilities in grams per litre, calcium nitrate being H6 at 56 per cent and 1290 g/L; the statement that the salts were selected for their convenience, relative cheapness and low toxicity; the statement that the relative humidity in such a system varies very little with temperature provided a saturated solution is maintained by contact with excess solid, because the tendency of the vapour pressure of water to increase with temperature is offset by an increase in the solubility of the salt in most cases, while the absolute humidity does increase; and 2.11.2, the Timed method over pure water at 100 per cent relative humidity, which must be timed and kept under 30 to 40 minutes; 3.6 The Choice of Gold Salt; 3.7 Opening Sealed Glass Vials; Appendix — Hydrogen tetrachloroaurate(III) trihydrate; 2.3.3 Surface-sizing paper with gelatin — the formaldehyde hardening bath and the reason for replacing it, with note 25 on the strength of commercial formalin; 2.3.1 Tub, surface or external sizing; 2.3.3 Surface-sizing paper with gelatin — ossein, acid and lime cure, Bloom number, the swelling and dissolution procedure, the storage life of the solution, and hardening the size; 2.3.3 Surface-sizing paper with gelatin — hardening the size, and note 26 on glyoxal and glutaraldehyde as alternatives to formaldehyde; 2.3.3 Surface-sizing paper with gelatin — the formaldehyde bath it replaces, the 2 per cent glyoxal bath and its wash, the brush-on sizing alternative, and note 26 on glyoxal's formula and the 40 per cent solution; 3.6 The Choice of Gold Salt; Table II.1, Gold content of commonly available gold compounds; II.2.3 Gold assay; Table 2.3, substances for making constant relative-humidity enclosures at 20 °C; Appendix IV.1, chemistry of siderotype printing; alternative developers, oxalic acid; 2.3.1 Tub, surface or external sizing — alum in the papermakers' sizing bath; 4.1.4 Preparing stock solutions for Version S sensitizer — the ligand solution; 4.1.4 Preparing stock solutions for Version S sensitizer - the four interchangeable alkali weights; Appendix IV.1, chemistry of siderotype printing; 4.1.2 chemicals required for processing; alternative developers, tartaric acid; appendix of chemicals, L-(+) tartaric acid; The complexes of gold(I), especially cyanide, used in the commercial wet extraction of gold from ores and residues, and Ware's judgement that cyanide is far too toxic for photographic use; The routes from gold(III) to gold(I): the sulfur ligands against the plain mild alkaline buffers such as acetate, borate, carbonate or chalk, in which gold(III) slowly oxidises water instead over as much as twenty-four hours, as summarised on the course's chloroauric acid page; The routes from gold(III) to gold(I): the sulfur ligands against the plain mild alkaline buffers such as acetate, borate, carbonate or chalk, in which gold(III) slowly oxidises water instead over as much as twenty-four hours; and the assay of the gold compounds, as summarised on the course's chloroauric acid page; The routes from gold(III) to gold(I): the sulfur ligands thiosulfate, thiocyanate and thiourea, which both assist the reduction and stabilise the product, against the mild alkaline buffers; and the assay of the gold compounds, as summarised on the course's chloroauric acid page; The routes from gold(III) to gold(I): the sulfur ligands thiosulfate, thiocyanate and thiourea, which assist the reduction and stabilise the product, against the mild alkaline buffers; and the assay of the gold compounds, as summarised on the course's chloroauric acid page; The gold compounds and their assay; the sulfur-ligand and alkaline-buffer routes to gold(I), as summarised on the course's chloroauric acid page; The gold compounds and their assay, and the distinction between gold(III) and gold(I) toning, as summarised on the course's chloroauric acid and gold(III) chloride pages; The sulfur-ligand and alkaline-buffer routes from gold(III) to gold(I), and the gold compounds and their assay, as summarised on the course's chloroauric acid page; 2.3.2 and 2.3.3, Surface-sizing paper with gelatin — the Bloom number wanted, the procedure of swelling 30 g of gelatin in 600 cm3 of water for about 30 minutes at room temperature, making up to 1 litre and warming to 40 to 45 °C with the warning that gelatin is denatured above it, the re-use of the sizing solution, and the statement that its storage life even refrigerated is limited to a few days and that it decomposes unless preservatives are added; 2.3.3 Surface-sizing paper with gelatin: ossein and hide gelatin, acid and lime cure, the Bloom number as the specification, the swelling and dissolution procedure, and the storage life of the made-up solution; IV.3 Problems of Chrysotype Chemistry — the redox potential E°([AuCl4]−/Au,4Cl−) = +1.00 V and the statement that gold(III) is a vigorous oxidising agent; the 1:3 stoicheiometry of the reduction of gold(III), written as Au(III) + 3Fe(II) → Au(0) + 3Fe(III), which lowers the yield of gold metal by a factor of three; IV.4 Chemistry of New Chrysotype, that most simple binary compounds of gold(I) in water are unstable with respect to disproportionation, 3Au(I) → 2Au(0) + Au(III), so the answer must be sought among the complexes of gold(I); the named water-soluble stable gold(I) complexes, the sulphito, cyano, thiocyanato and thiosulphato species [Au(SO3)2]3−, [Au(CN)2]−, [Au(SCN)2]− and [Au(S2O3)2]3−; and the statement that these complexes have such large formation constants that the redox potential is depressed below even that of the iron photoproduct, with E°([Au(CN)2]−/Au,2CN−) = −0.6 V as the example; IV.4 Chemistry of New Chrysotype - the named water-soluble stable gold(I) complexes, the sulphito, cyano, thiocyanato and thiosulphato species, and the statement that their formation constants are so large that the redox potential is depressed below even that of the iron photoproduct, with E-standard for the dicyanoaurate couple given as -0.6 V; The table of saturated salt solutions for constant relative-humidity enclosures at 20 degrees; The three-solution sensitiser; the alternative first baths and the colours they give; humidity control; The table of saturated salt solutions for constant relative-humidity enclosures at 20 °C

Used by:Calcium nitrate tetrahydrate · Chloroauric acid · Formaldehyde · Gelatin · Glutaraldehyde · Glyoxal · Gold(III) chloride · Lithium chloride · Oxalic acid · Potassium alum · Sodium bicarbonate · Sodium carbonate (anhydrous) · Sodium carbonate decahydrate · Sodium carbonate monohydrate · Tartaric acid · Cyanide fixing and toning · Gold-acetate toner · Gold-borax toner · Steigmann gold sensitiser stock · Gold-thiocyanate toner · Kodak GP-1 · Kodak T-21 · Kodak T-26 · Plain salted paper salting solution · P5 Gelatin, the Photographic Binder · P20 Gold, Iron-Blue and the Other Metal Toners · P20 The Toners We Study and Do Not Use · P25 Experiment: Tonal Scale, Contrast and Image Colour in Palladium · Chrysotype · Print-out platino-palladiotype

Cyanomicon: History, Science and Art of Cyanotype - Photographic Printing in Prussian Blueretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Sections 6.5, 7.2.3, 7.3.8 and 7.3.9 — the traditional cyanotype exposure scale of about 0.9 and a UVA negative density range of 0.9 to 1.2, the New Cyanotype scale of about 1.6 to 2.4, the statement that the UVA density range required in the negative should equal the logarithmic exposure scale of the sensitiser because there is no Callier effect in contact printing, and the instruction to develop a camera negative 75 to 100 per cent longer than normal aiming at a contrast index of 0.7 to 1.3, with the note that those contrast indices are more or less incompatible with normal silver printing so one negative cannot serve both; Table II.1, which lists soluble Prussian blue as KFe[Fe(CN)6], insoluble Prussian blue as Fe4[Fe(CN)6]3 and Turnbull's blue as Fe3[Fe(CN)6]2 with variable water, establishing that the composition is a family rather than a single formula; 7.5 Mike's cyanotype, with 7.5.1 Sensitizer chemicals needed and 7.5.2 Preparation of Mike's cyanotype sensitizer, for the quantity, the naming, the dissolution and the reason the variant exists; 7.4.2 Preparation of Simple cyanotype sensitizers, the section Ware states this variant reproduces, for the citric acid and ammonia quantities of the three contrast grades this salt replaces; 7.4.12 Typical results, for the exposure scales and sensitiser pH values of those grades; 6.7.5 Ammonium dicitratoferrate(III) characterised 1998 and 6.7.6 Simple cyanotype 2019, for why a two-fold citrate excess is the design; 7.7 List of chemicals and hazards, the entry headed Ammonium citrate, tribasic; 7.8 Environmental issues and disposal; Appendix III.5 and Table III.1, for the ligand-to-metal charge transfer, the oxidative decarboxylation and the role of the alpha-hydroxy group; 4.3 Survey of negative-working formulae and Valenta's green salt of 1897, Table 4.2; 6.7.2 Ferric ammonium citrate failings; 7.1 Classic cyanotype sensitizer, preparation, exposure and wet processing; 7.2 An improved Classic cyanotype sensitizer; 7.2.3 Shortcomings of the Classic cyanotype process; 9.3 peptization of Prussian blue, with Holtzman on the destruction of Prussian blue by a pH 9.4 buffer; Appendix III.5 Composition of ammonium iron(III) citrate, Table III.2; Appendix III.6 Photochemistry of citratoferrate(III); Appendix III.4 Photochemistry of trisoxalatoferrate(III); 7.2.3 Shortcomings of the Classic cyanotype process; 7.2.4 Remedies for shortcomings of the Classic process; 4.7 Kwech's commercial blueprint sensitizers, Table 4.3; 9.2 Bleaching of cyanotypes by alkali, including Holtzman's pH 9.4 result and the comparison with saturated calcium carbonate; 9.4.5 Buffered substrates and the ISO 9706 and ISO 11108 alkaline reserve; paper requirements and the sulphamic acid pre-treatment; footnote on the solubility of calcium carbonate; 4.4.1 Robert Hunt's chromo-cyanotype — the chromatype and the dichromate-plus-ferrocyanide sensitiser; 7.2 and 7.4.10 — the 0.3 per cent hydrogen peroxide bath, its preparation from the 6 per cent "20 volume" solution, and the statement that it makes no ultimate difference to the print densities; 9.1.9 regain of colour by faded Prussian blue; the re-oxidation equations and the warning against dichromate; Chapter 4, commercial blueprint papers — the dichromate development bath and urea peroxide as the preferred oxidant; 2.10 Herschel's Memoranda and the proto-cyanotype developed in perchloride of iron; 4.6 Pellet's positive process and the Pizzighelli-Itterheim and Waterhouse-Fisch formulae; 4.7 Kwech's commercial blueprint sensitizers, Table 4.3; 9.3 peptization of Prussian blue; Appendix II, composition of soluble and insoluble Prussian blue; Appendix III.7 Photochemistry of hexacyanoferrate(III); 2.2 John Mercer's 1828 observation of light-formed Prussian blue on cloth, with the quotation from his notebooks and note 113; 3.4 Herschel's proto-cyanotype developed in ferric chloride or nitrate; 3.7 Chemistry of blueprinting; 4.9 Cyanotypes on fabrics and textiles, on the nineteenth-century two-bath dyeing of Prussian blue; 6.7.5 Ammonium dicitratoferrate(III) characterised 1998; 6.7.6 Simple cyanotype 2019, the reasoning, the four claimed benefits of the nitrate by-product and the US patent 2,113,423 of 1938; 7.2.1 Choice of paper, on alkaline buffering hydrolysing the iron salt; 7.4 The Simple cyanotype process 2019; 7.7 List of chemicals and hazards, the entry for Iron(III) nitrate (nonahydrate); 7.8 Environmental issues and disposal; Appendix II, Table of the iron blues; 3.2 and 3.3, the defect Prussian blue lattice with systematic vacancies, its microporosity and its use as an antidote to thallium and caesium; 8.6 Heavy metal incorporation, and 8.6.1 Lead, for the procedure attributed to Oscar Bolle about 1900 through George E. Brown's Ferric & Heliographic Processes, the violet shift, the pH dependence, the EM-EDX evidence, the fourfold light-fading factor, the undiminished alkali vulnerability, the reversal by dilute nitric acid and the warning about the sweet taste; 8.6.2 and 8.6.3 for the thallium and nickel toners; 8.6 Heavy metal incorporation and 8.6.3 Nickel, for the 5 to 10 per cent bath of a nickel(II) salt, the slight shift towards a greenish-blue, the order-of-magnitude gain in alkali resistance, the possible loss of highlight density and the sentence "Nickel(II) salts are listed carcinogens. Consult the MSDS."; Figure 8.2, the plate showing an untoned print beside lead(II), nickel(II) and thallium(I) toned prints; 8.7 Insoluble metal ferricyanides, for Murray's 1933 and 1935 patents and the bright yellow highlight from nickel(II); 9.2, for Holtzman's work on the alkali resistance of the iron blues, the pH 9.4 buffer, the 10 per cent w/v nickel(II) sulphate soak, the hue shifts measured in Methuen notation, the mid-tone density losses attributed to peptisation, and the table of losses after 10 minutes at pH 9.4, captioned Table 9.5 and called Table 14 in the text; 9.3, on peptisation of Prussian blue; Appendix II.2, for cation exchange in the cubic voids of the lattice and for the statement that soluble Prussian blue may be rendered less liable to peptize by treatment with multiply-charged cations, most notably Fe(III) and Ni(II), which are believed to be partially exchanged for the potassium ions, and Appendix II.3 for the defect lattice of the "insoluble" form; and 1.10, for the colour notation adopted from The Methuen Handbook of Colour, in which the first number is the hue page, the letter A to F the tone and the last digit the intensity; Appendix III.4 Photochemistry of trisoxalatoferrate(III); 2.1 A brief history of Prussian blue; Appendix II, Chemistry of Prussian Blue — II.2 soluble, II.3 insoluble, II.4 Turnbull's blue and Table II.1, II.5 the electronic spectrum, II.8 hydrolysis, II.9 Prussian white; 9.2 Bleaching of cyanotypes by alkali, including Holtzman's pH 9.4 result; 9.3 peptization; 7.4.10 the hydrogen peroxide bath; 9.4.5 buffered substrates; Paper requirements and 9.4.5 — the 5 to 10 per cent w/v sulphamic acid pre-treatment of chalk-buffered papers and why oxalic acid is unsuitable; 7.3 New Cyanotype processing — mineral-acid development at 1 to 5 per cent w/v and the ranking of the acids; the footnote crediting the sulfamic recommendation; 3.3 Prussian blue for ion exchange, for the microporous lattice as a sponge for cations resembling potassium, the Chernobyl and reindeer caesium work, Heydlauf's proposal of Prussian blue as the preferred antidote for thallium poisoning, and the description of thallium(I) sulphate as colourless, odourless, tasteless and readily soluble with delayed symptoms; footnote 234 on Cs+ and Tl+ being singly charged and of a size similar to K+; 4.1.3, for mercury(I) being conjectured to enter the lattice "in the same way as thallium(I) is known to be"; 8.6 Heavy metal incorporation and 8.6.2 Thallium, for the cornflower-blue shift and the refusal to recommend the practice; Figure 8.2, the plate showing an untoned print beside lead(II), nickel(II) and thallium(I) toned prints; Appendix II.2, for cation exchange in the cubic voids and the Prussian-blue reactrode for determining thallium(I) ions; 7.1 The Classic cyanotype process 1842/1897, for the open formula this kit is a printing of and for the iron content of the green salt at 14 to 18 per cent by weight across present-day commercial material; 7.2 An improved Classic cyanotype sensitizer with endnote 614, which attributes the widely circulated improved formula to bostick-sullivan.com; 7.2.3 Shortcomings of the Classic cyanotype process and its exposure scale of about 0.9; 9.2 Bleaching of cyanotypes by alkali, including Holtzman's result that a buffer at pH 9.4 completely decolourises Prussian blue by irreversible hydrolysis in one to ten minutes; 3.7 Chemistry of blueprinting, for the solarisation and reoxidation equations; 7.1 The Classic cyanotype process 1842/1897, with 7.1.1 Sensitizer chemicals needed, 7.1.2 Preparation of Classic cyanotype sensitizer and the quotation of Christina Z. Anderson's 2020 posting on the 10/10 mixture, 7.1.3 Mixing and coating, 7.1.4 Printing exposure and 7.1.5 Wet processing and reoxidation; 7.2 An improved Classic cyanotype sensitizer and 7.2.3 Shortcomings of the Classic cyanotype process, its seven numbered drawbacks and the exposure scale of about 0.9; 7.2.4 Remedies for shortcomings of the Classic process; 4.3 Survey of negative-working formulae, Valenta's green salt of 1897, Table 4.2 comparing the green and brown salts, Whitaker's 1883 range and optimum, and the recommended stock strengths for both salts; 3.7 Chemistry of blueprinting, with the solarisation and reoxidation equations; 3.6 the proto-photographic exposure estimate; 6.7.1 to 6.7.3 the classic process, ferric ammonium citrate failings and paper problems; 6.8 A caveat on incompatible cyanotype processes; 7.7 List of chemicals and hazards, the entries for ammonium iron(III) citrate and the warning against a dichromate reoxidation bath; 7.8 Environmental issues and disposal; 9.1 the fading experiments with Table 9.3, and Tables 9.5 and 9.6 for alkaline hydrolysis and aqueous washing; Appendix III.5 Composition of ammonium iron(III) citrate with Table III.2; Appendix III.6 Photochemistry of citratoferrate(III); Appendix III.7 Photochemistry of hexacyanoferrate(III); 4.1.1 Proto-cyanotype and the saturation of potassium ferricyanide at about 33 per cent w/v; 4.1.2 Negative-working cyanotype, which quotes Herschel's Memoranda entry of 13 August 1842 and his solarisation notes, records the change of mixing proportions on 16 August 1842, and gives Table 4.1 Early cyanotype formulations (final concentrations); 4.3 Survey of negative-working formulae, Whitaker's 1883 range, Valenta's green salt of 1897 and Table 4.2; 3.6 the proto-photographic exposure estimate; 3.7 Chemistry of blueprinting and solarisation; 6.7.1 to 6.7.4 the shortcomings of the classic process and the variability of ferric ammonium citrate; 7.1 The Classic cyanotype process 1842/1897, its preparation, coating volumes, exposure and wet processing; 9.1.1 to 9.1.4 the fading experiments, Table 9.2 and Table 9.3; Appendix III.6 Photochemistry of citratoferrate(III); Appendix III.7 Photochemistry of hexacyanoferrate(III); 4.1.3 Hydrargyro-cyanotype, pages 86 to 87, which names the process, states that the name appears only in Herschel's Memoranda, describes the sequence, identifies the salt as mercury(I) nitrate in endnote 271, offers the lattice-trapping conjecture, records that Ware repeated and confirmed the process, and declines to recommend it; 4.1.2 Negative-working cyanotype, for Herschel's standard 'Method (a)' and the Memoranda entry of 13 August 1842 that is the only source of its concentrations, with Table 4.1 Early cyanotype formulations; 4.1.4 Positive-working cyanotype, for Herschel's separate use of mercury(II) chloride and the affinity of mercury(II) for cyanide; 3.1 and Table 3.1 Varieties of complex iron cyanides; 3.2 and 3.3, the defect lattice of Prussian blue and its use as an ion-exchange host for caesium and thallium(I); Appendix II.9 Prussian white and its formula, oxidation and reversible electrochemical reduction; Appendix II.11 Prussian brown or yellow; endnote 172, on the kelainotype and the volatility of a mercury image; endnote 270, on Hunt's list of seven cyanotype processes; endnote 182, on Sutton and Dawson's 1867 dictionary; 4.1.5, on the 2007 'Herschelotype' claim; 2.9 Misapprehension of Herschel's processes, on the misdirected practical instruction in the manuals that followed 1842; 4.3, the survey of about sixty published recipes and its averages, and Table 4.2; 2.6 Discovery of cyanotype, on Alfred Smee's 1840 electrolytic preparation of potassium ferricyanide and the specimen he sent to Herschel; 2.7 and 2.8, on siderotype and the kelainotype; 5.3 Herschel's cyanotype tests, on the Herschel specimens at Austin, of which those derived from mercury are now blank; 7.1.1, for the statement that the classic sensitiser's chemicals are not dangerous and can be safely handled by children under supervision, and 7.1.5 Wet processing and reoxidation, for the 0.3 per cent hydrogen peroxide bath of about half a minute that brings the solarised shadows back at once without changing the final densities; 9.2, for Holtzman's finding that a buffer at pH 9.4 destroys Prussian blue by irreversible hydrolysis in one to ten minutes; 8.6 Heavy metal incorporation, page 265, for the statement that treating a Prussian blue image with a solution of a heavy metal salt may cause the incorporation of the metal cation into the lattice and so modify its colour, that not all cations cause a perceptible effect, and for the conjecture that the metal may need two accessible oxidation states to intervene in the electronic charge-transfer transition, with lead, thallium, nickel and copper listed as effective and alkali and alkaline-earth cations of similar size and charge as ineffective; 8.6.1 Lead, pages 265 to 266, for the procedure attributed about 1900 to Oscar Bolle, the warm bath of lead(II) acetate solution of specific gravity 1.24, the violet shift sometimes inaccurately called lilac or lavender, the pH dependence, the working strength of about 5 per cent w/v, the acidity of a freshly made solution, the adjustment to pH 7.5 to 8 with about 20 cc of ammonia of specific gravity about 0.9 per litre, the filterable lead hydroxide precipitate, the dependence of the result on the cyanotype formula, the X-ray spectrometric detection of lead correlating with the iron signal, the light-fading exposure factor of about four, the undiminished vulnerability to alkali, the reversal by dilute nitric acid and the warning about the sweet taste of a cumulative poison; 8.6.2 Thallium, page 267, for the bath of thallium(I) sulphate solution of about 5 per cent w/v, the slight but agreeable shift to a cornflower blue, and the refusal to recommend it to the general public owing to the severe toxic hazard; 8.6.3 Nickel, page 267, for the 5 to 10 per cent solution of a nickel(II) salt, the sulphate, chloride or nitrate being named, the slight shift towards a more greenish-blue, the order-of-magnitude gain in resistance to alkaline hydrolysis, the possible slight loss of highlight density and the sentence "Nickel(II) salts are listed carcinogens. Consult the MSDS."; 8.6.4 Copper, page 268, for the tetraamminecopper(II) nitrate toner of Whiting's 1889 United States patent and its Bartolozzi red; 8.7 Insoluble metal ferricyanides, for Murray's 1933 and 1935 patents and the 10 to 20 per cent metal salts used in the first wet bath; Figure 8.2, the plate showing an untoned cyanotype beside lead(II), nickel(II) and thallium(I) toned prints; 3.3 Prussian blue for ion exchange, for the microporous lattice, its use as an antidote for thallium(I) and radiocaesium, and the description of thallium(I) sulphate as colourless, odourless, tasteless and readily soluble with delayed symptoms; 9.2 Bleaching of cyanotypes by alkali, pages 290 to 292, for Holtzman's finding that a buffer at pH 9.4 destroys Prussian blue by irreversible hydrolysis in one to ten minutes and that 0.25 molar sodium carbonate at about pH 10.7 does it in under half a minute, for Holtzman's recommendation of nickel incorporation and his "stable indefinitely" result, for Ware's own test on Herschel and Ware cyanotypes, the hue shifts in Methuen notation, the mid-tone density losses attributed to peptisation, and the table of shadow-tone losses after ten minutes at pH 9.4, captioned Table 9.5 and called Table 14 in the text; 9.3 Peptization of Prussian blue; Appendix II.2, for the structure of "soluble" Prussian blue, the interior radius of 182 pm calculated for the cubic cavity, the Shannon and Prewitt cation radii, the statement that treatment with multiply-charged cations, most notably iron(III) and nickel(II), renders the blue less liable to peptization and that this confers greater resistance to decomposition by alkalies, the statement that toning by lead(II) or thallium(I) is very probably due to cation exchange in the cubic voids, the suggestion that lead enters as the singly charged PbOH+ species, and the Prussian-blue electrode for determining thallium(I); Appendix II.3 for the defect lattice of the "insoluble" form; 1.10, for the Methuen colour notation and Figure 1.14 with its named blues; and endnotes 656 to 662, 693, 694 and 695, for the bibliographic standing of each of these findings; 7.5 Mike's cyanotype, with 7.5.1 Sensitizer chemicals needed and 7.5.2 Preparation of Mike's cyanotype sensitizer, its five numbered steps, its recorded solution colours and its two-bottle arrangement; 7 the opening list of five cyanotype formulations and its one-line summary of this one; 7.1 The Classic cyanotype process 1842/1897; 7.2.3 Shortcomings of the Classic cyanotype process; 7.3 The New cyanotype process 1995 and 7.3.3 Use of dichromate; 7.4 The Simple cyanotype process 2019 in full, with 7.4.1 Sensitizer chemicals needed, 7.4.2 Preparation of Simple cyanotype sensitizers and its three contrast grades, 7.4.4 Choice of paper, 7.4.6 Addition of surfactant, 7.4.7 Coating, 7.4.8 Drying, 7.4.9 Printing exposure, 7.4.10 Wet processing, 7.4.11 the workflow summary, 7.4.12 Typical results with the three sensitiser pH values and 7.4.13 Sensitizers separated for longer storage; 6.7.2 Ferric ammonium citrate failings; 6.7.3 Paper problems; 6.7.4 New cyanotype 1995; 6.7.5 Ammonium dicitratoferrate(III) characterised 1998, with the Matzapetakis formula and the 1998 authors' own preparation; 6.7.6 Simple cyanotype 2019, its reasoning, its four claimed benefits of the nitrate by-product, the speeds against New and Classic, the exposure scale of about 2.7 and the maximum density of about 1.4; 6.8 A caveat on incompatible cyanotype processes; 3.6 Photochemical principles; 3.7 Chemistry of blueprinting, for the two-step blueprint reaction, solarisation and aerial reoxidation; 7.6 Diagnosis of fogged highlights with Table 7.1; 7.7 List of chemicals and hazards, the entries for ammonium citrate tribasic, iron(III) nitrate nonahydrate, potassium ferricyanide, citric acid, aqueous ammonia and Tween 20 with their HMIS ratings; 7.8 Environmental issues and disposal; Appendix III.2 Quantitative aspects of the photochemistry, for the internal-filter fractions absorbed by the photoactive component at 365 and 420 nm; Appendix III.6 Photochemistry of citratoferrate(III), for the speciation against pH, the quantum yields of 0.45 at 365 nm and 0.28 at 436 nm and the slow equilibria above pH 3; Appendix III.7 Photochemistry of hexacyanoferrate(III), for its quantum yields of the order of 0.01; 7.3 The New cyanotype process 1995, with 7.3.1 Sensitizer chemicals and apparatus needed, 7.3.2 Preparation of New cyanotype sensitizer and its six numbered steps and parenthetical notes, 7.3.3 Use of dichromate, 7.3.4 Use of Tween 20 surfactant, 7.3.5 Choice of papers, 7.3.6 Drying, 7.3.7 Citric acid to prevent fogging, 7.3.8 Negatives and exposure, 7.3.9 Wet processing and contrast control, 7.3.10 Washing and reoxidation with Figs 7.1 and 7.2, 7.3.11 New cyanotype workflow summary and 7.3.12 Effects of heat-drying and darktime with Fig 7.3; 7.2.3 Shortcomings of the Classic cyanotype process, its seven numbered drawbacks and the exposure scale of about 0.9; 7.2.4 Remedies for the shortcomings, its seven numbered answers, the factor of 4 to 8 in sensitivity and the exposure scale of about 2.2; 7.2.5 Modified chemistry for the New cyanotype process, the 7:3 molar ratio, the 3.034:1 weight ratio and the statement that the filtrate is 0.4 molar ammonium ferric oxalate and 0.3 molar ammonium ferricyanide; 7 the opening list of five cyanotype formulations; 6.7.4 New cyanotype 1995 and its account of the reasoning and of the disadvantages; 6.8 A caveat on incompatible cyanotype processes; 7.7 List of chemicals and hazards, the entries for ammonium iron(III) oxalate, potassium ferricyanide, ammonium dichromate, citric acid, nitric acid, hydrochloric acid, oxalic acid and Tween 20, with the HMIS ratings; 7.8 Environmental issues and disposal, including the statement that dichromate is recommended in very small amount in the New Cyanotype as a preservative but can be entirely omitted; Appendix III.1 Light-sensitive iron(III) carboxylates with Table III.1; Appendix III.2 Quantitative aspects of the photochemistry and the internal-filter fractions at 365 and 420 nm; Appendix III.4 Photochemistry of trisoxalatoferrate(III) with the Hatchard and Parker mechanism, the quantum yields and the redox potentials; Appendix III.7 Photochemistry of hexacyanoferrate(III); Appendix III.8 Photochemistry of the blueprint process 1, with the dissociation constants, the acid-promoted release of iron(II) and the Prussian white route to solarisation; 4.2 Pellet's process, with the patent dates and names, Poitevin's 1863 observation on the hardening of gum by iron(III), the account of Prussian white in the exposed regions, the Pizzighelli and von Itterheim stock solutions and the 20 : 8 : 5 mixing ratio, the ferrocyanide developer, the disagreement between published accounts on when to coat, the Waterhouse and Fisch alternative, and footnote 286 on diluting the hydrochloric acid; 4.1.4 Positive-working cyanotype, on why Herschel could never perfect it; Table 2.1 Early Siderotype processes; 3.1 and Table 3.1 Varieties of complex iron cyanides; 3.7 Chemistry of blueprinting, for solarisation and reoxidation; 9.4.1 on the binder layer in relief that identifies a Pellet print; Appendix III.1 Light-sensitive iron(III) carboxylates and Table III.1; 7.1 The Classic cyanotype process 1842/1897, for the open sensitiser this kit is a printing of and for the iron content of the green salt at 14 to 18 per cent by weight in present-day commercial material; 9.2 Bleaching of cyanotypes by alkali, for what the toning kit's first bath does; 7.4 The Simple cyanotype process 2019, with 7.4.1 Sensitizer chemicals needed, 7.4.2 Preparation of Simple cyanotype sensitizers and its five numbered steps and three contrast grades, 7.4.3 Equipment and materials, 7.4.4 Choice of paper, 7.4.5 Negatives and control of contrast, 7.4.6 Addition of surfactant, 7.4.7 Coating, 7.4.8 Drying, 7.4.9 Printing exposure, 7.4.10 Wet processing, 7.4.11 Simple cyanotype workflow summary, 7.4.12 Typical results with the three sensitiser pH values, and 7.4.13 Sensitizers separated for longer storage; 6.7.5 Ammonium dicitratoferrate(III) characterised 1998 and the Matzapetakis structure; 6.7.6 Simple cyanotype 2019, its account of the reasoning, the four benefits claimed for the nitrate ion, the speed against New and Classic, the exposure scale of about 2.7 and the maximum density of about 1.4; 6.8 A caveat on incompatible cyanotype processes, with the statement that Simple and Classic sensitisers tolerate only a very weak acid developer; 7 the opening list of five formulations; 7.1 the Classic process this one replaces; 7.2.3 Shortcomings of the Classic cyanotype process, its seventh drawback and the exposure scale of about 0.9; 7.3 the New cyanotype process; 7.5 Mike's cyanotype; 7.6 Diagnosis of fogged highlights with Table 7.1; 7.7 List of chemicals and hazards, the entries for ammonia, citric acid, iron(III) nitrate nonahydrate, potassium ferricyanide and Tween 20 with their HMIS ratings; 7.8 Environmental issues and disposal; 5.4 on negative density ranges and the exposure scales of the iron-based sensitisers; 7.1.4 Printing exposure, for the classic process's own exposure time; Appendix III.2 Quantitative aspects of the photochemistry, for the internal-filter fractions absorbed by the photoactive component at 365 and 420 nm; Appendix III.4 Photochemistry of trisoxalatoferrate(III), for the quantum yield of about 1.2 between 250 and 420 nm and its independence of pH; Appendix III.5 Composition of ammonium iron(III) citrate with Table III.2; Appendix III.6 Photochemistry of citratoferrate(III), with the speciation against pH and the quantum yields; Appendix III.7 Photochemistry of hexacyanoferrate(III); Appendix III.8 Photochemistry of the blueprint process 1; 9.2 Bleaching of cyanotypes by alkali, including Holtzman's result that a buffer at pH 9.4 completely decolourises Prussian blue by irreversible hydrolysis in one to ten minutes, as summarised on the course's Prussian blue page; 4.3 Survey of negative-working formulae — the preparation of the green form of ammonium ferric citrate by Eduard Valenta in 1897, called the only significant chemical advance in the entire history of the cyanotype process, and Table 4.2, which compares the green and brown salts by first preparation, iron content (19 to 28 per cent brown against 14 to 18 per cent green), basic against acidic nature, speed, reversal, edge etch, image colour and light fastness; Appendix III.6 Photochemistry of citratoferrate(III), for the photo-inactive monomer below pH 1.5 and the photo-active dimer above pH 2, the quantum yield of 0.45 at 365 nm and pH 4 falling to 0.28 at 436 nm, the identification of the initial photoproduct as acetone dicarboxylic acid, and the statement that the nature of the iron(II) photoproduct remains unknown; 6.7.2 and 7.2.3, for the ferric ammonium citrate solution being an excellent nutrient medium for moulds that will usually cover its surface within a week or two, the thymol remedy, and the deliquescence that leaves a coating tacky enough to damage negatives; Appendix III.6 Photochemistry of citratoferrate(III), for the photo-inactive monomer between pH 0.5 and 1.5, the photo-active dimer above pH 2, the quantum yield maximum of 0.45 at 365 nm at pH 4 falling to 0.28 at 436 nm, the identification of the initial photoproduct as acetone dicarboxylic acid, its further decarboxylation to acetone, and the statement that the nature of the iron(II) photoproduct remains unknown; 6.7.5 Ammonium dicitratoferrate(III) characterised 1998; 4.3 and Table 4.2, for the green salt of Eduard Valenta of 1897 at 14 to 18 per cent iron against the brown salt at 19 to 28 per cent; 7.2 An improved Classic cyanotype sensitizer, with 7.2.1 Sensitizer chemicals needed and 7.2.2 Preparation of improved Classic cyanotype sensitizer, and the paragraph heading the section that the formula is widely circulated, that it is not known where it originated, that the highlights are claimed to remain whiter, that the New cyanotype would probably be more worthwhile, and that the sensitiser should not be placed in the hands of children; endnote 614, which gives the origin as bostick-sullivan.com/techart.php; 7.2.3 Shortcomings of the Classic cyanotype process, its seven numbered drawbacks and the exposure scale of about 0.9; 7.2.4 Remedies for the shortcomings, in particular point 6 on chemically equivalent amounts and image bleeding; 7 the opening list of five formulations, in which the improved Classic is "more toxic; better range and density"; 4.4.4 Other iron(III) sensitizers, on Hnatek's 1955 investigation of carboxylic acid additions, on low pH preventing hydrolysis of iron(III), on the sensitivity maximum at pH 3 to 4, and on a small amount of dichromate assisting stability and shelf-life; 4.10 to 4.12 on commercial blueprint sensitizers, with Kwech's Table 4.3 and the 7 per cent dichromate development bath; 4.9 on dichromate baths for cyanotype on fabric and the documented case of ill-health; 4.13 Type AB blueprint paper and Knierim's dichromate-free formulation; 6.7.4 and 6.7.5 on the dichromate preservative and on nitrate replacing it; 6.8 A caveat on incompatible cyanotype processes, with the statement that Simple and Classic sensitisers tolerate only a very weak acid developer; 7.1.2 to 7.1.5 the classic sensitiser it modifies; 7.3.1 and 7.3.3 Use of dichromate in the New cyanotype, its role as preservative, its effect on contrast and shelf-life; 7.4 and 7.5 the Simple and Mike's cyanotypes, which contain neither dichromate nor oxalate; 7.6 Diagnosis of fogged highlights with Table 7.1; 7.7 List of chemicals and hazards, the entries for ammonium dichromate, oxalic acid, ammonium iron(III) citrate and potassium ferricyanide; 7.8 Environmental issues and disposal, with the reduction of chromium(VI) by ascorbic acid; Appendix III.5 Composition of ammonium iron(III) citrate with Table III.2; Appendix III.6 Photochemistry of citratoferrate(III); Appendix III.7 Photochemistry of hexacyanoferrate(III); 3.1 Chemistry of Prussian blue; 7.1 Classic cyanotype sensitizer; 7.2.3 Shortcomings of the Classic cyanotype process; 9.2 Bleaching of cyanotypes by alkali; 3.6 Photochemical principles; 3.7 Chemistry of blueprinting; 5.4 Cyanotypes of British algae by Anna Atkins; 7.1.4 Printing exposure; 7.1.5 Wet processing and reoxidation; 7.7 List of chemicals and hazards; 7.8 Environmental issues and disposal; 9.2 Bleaching of cyanotypes by alkali; 2.4 Herschel's research records; 2.5 Anthotype and phytotype; 2.6 Discovery of cyanotype; 2.7 Invention of siderotype; 2.8 Publication of siderotype; 3.1 Chemistry of Prussian blue; 3.7 Chemistry of blueprinting; 5.4 Cyanotypes of British algae by Anna Atkins; 9.2 Bleaching of cyanotypes by alkali; 2.6 Discovery of cyanotype; 2.8 Publication of siderotype; 3.1 Chemistry of Prussian blue: ferric ferrocyanide containing iron in two states of oxidation, the colour attributed to electrons hopping between them; and the insoluble form Fe4[Fe(CN)6]3 with its 4 to 3 ratio of iron(III) to iron(II); 3.1 Chemistry of Prussian blue: ferric ferrocyanide, iron present in two states of oxidation, and the colour attributed to electrons hopping between them; 6.4.4 Ultra-violet light sources - the penumbra relation given as blur = gap x aspect value, where the aspect value is the largest linear dimension of the source divided by its distance from the print, derived from similar triangles; the table of aspect values and resulting blur for a gap of 0.1 to 0.5 mm, giving 0.01 for the sun, 0.1 for a NuArc 2125 and 4 for a light bed or open sky; and the criterion that the eye resolves about 0.1 mm at its near point of 250 mm while 0.25 mm is taken as acceptably sharp, so that 0.3 mm of blur is taken as the onset of a fuzzy or soft image; 6.4.3 Contact-printing frames - the simplest option is a sheet of plate glass 4 mm thick, not 2 mm picture glass which may bend or crack under pressure, on a flat baseboard covered with a felt blanket or porous plastic to absorb outgassing and take up surface unevenness, held with strong clips; 3.6 Photochemical principles - an average UVA irradiance in sunlight of about 30 to 40 W/m2 and 2 to 4 minutes to full density there, from a 34 J/m2 just-perceptible threshold and a 7 to 8 stop exposure scale; 6.4.4 Ultra-violet light sources - the light integrator on a commercial unit that accumulates dose rather than time because arc emission varies with time, and the aspect-value treatment of source geometry and image blur; 6.4.3 Contact-printing frames - the felt blanket or porous plastic behind the print to absorb outgassing; Appendix III.2 - two minutes predicted and observed for a full-scale platinum-palladium image at 50 W/m2 at 365 nm, and an absorbed fraction of 0.65 at 365 nm falling to 0.03 at 420 nm; 3.6 Photochemical principles - the limiting sensitivity of any proto-photographic material lying in the near ultraviolet and blue over about 300 to 400 nm and requiring about 34 J/m2 for a just-perceptible image; the tropical sun delivering about 900 W/m2 of which only about 7 per cent is actinic, giving an average UVA irradiance of about 30 to 40 W/m2, and an exposure scale of 7 to 8 stops implying 2 to 4 minutes to full density in average sunlight; 6.4.4 Ultra-violet light sources - the eight sources in ascending order of cost, the sun subtending 0.5 degrees and moving through 0.5 degrees in 2 minutes, the north summer sky about 3 stops weaker than direct sun, the statement that lamps peaking around 410 nm are not effective for cyanotype because that wavelength is an absorption maximum of ferricyanide acting as an internal filter, the rejection of short-wave mercury lamps as more dangerous with no advantage, and the light integrator on a commercial unit that accumulates dose rather than time because arc emission varies; 6.4.2 - the prevailing relative humidity having very little effect on cyanotype printing but profoundly affecting some other iron-based processes, and the drying and resting instructions; Appendix III.2 - the fraction of incident light absorbed by the photoactive trisoxalatoferrate at 365 nm being 0.65 for a typical cyanotype coating and falling to 0.03 at 420 nm, the quantum yield of 0.45 at 365 nm at pH 4 falling to 0.28 at 436 nm, and the two minutes predicted and observed for a full-scale platinum-palladium image at 50 W/m2 at 365 nm; 6.4.4 Ultra-violet light sources - the penumbra relation given as blur = gap times aspect value, the aspect value being the largest linear dimension of the source divided by its distance from the print, derived from similar triangles; and the criterion that the eye resolves about 0.1 mm at its near point of 250 mm while 0.25 mm is taken as acceptably sharp, so that 0.3 mm of blur is taken as the onset of a fuzzy or soft image, most conspicuous where local contrast is high; Table 3.1, the four products of ferric and ferrous salts with ferricyanides and ferrocyanides, in which ferric ferricyanide, Prussian yellow or Berlin brown, is soluble and a powerful oxidant which easily oxidises water and paper, being reduced via green intermediates to Prussian blue, while ferric ferrocyanide, Prussian blue, is highly insoluble and the most stable of the four, to which the others revert; Appendix II.10 Berlin green, that a mixture of iron(III) chloride and hexacyanoferrate(III) is powerfully oxidising and that any inclusion of ferric ions in the developer for a cyanotype leads to blue fogging of the background; Appendix II.11 Prussian brown or yellow, that the brown mixture of iron(III) and hexacyanoferrate(III) rapidly turns blue when spotted onto cellulose filter paper or any other oxidisable substrate, that ferric ion in the presence of hexacyanoferrate(III) has a very high oxidising power much stronger than either ion separately because the insolubility of Prussian blue drives the reaction and makes the redox potential about +1.5 V, so that it forms in the presence of almost any oxidisable substance; Appendix II.12, the standard potentials E°(Fe3+/Fe2+) = +0.771 V and E°([Fe(CN)6]3−/[Fe(CN)6]4−) = +0.356 V and the note that the iron(III)/iron(II) potentials are considerably raised from their standard values by the formation of insoluble products; 9 Vulnerability and Conservation of Cyanotypes — the three pathways of destruction, photochemical reduction, alkaline hydrolysis and aqueous peptization, referred to as fading, bleaching and dispersing, and Table 9.1 giving for alkaline hydrolysis the cause as any substance of alkaline pH above 7, the products as hydrated ferric oxide and ferrocyanide ions, and the reversibility as decreasing to irreversible as the ferric oxide ages; 9.2 Bleaching of cyanotypes by alkali, that painters soon realised any alkali rapidly destroyed Prussian blue so the pigment could not be used for frescoes, that alkaline sensitivity is the most serious drawback with this pigment, that Holtzman found a buffer at pH 9.4 completely decolourises Prussian blue in 1 to 10 minutes depending on the method of preparation, that this is not a highly alkaline pH and is the same as that of a saturated solution of calcium carbonate, the buffer commonly incorporated in archival papers and boards, and that a 0.25 molar solution of sodium carbonate at pH about 10.7 is high enough to destroy the Prussian blue of a cyanotype in less than half a minute; the note that a freshly bleached cyanotype can be partially restored by dilute acid and added ferrocyanide but that over time the ferric oxide-hydroxide hydrolysis product becomes insoluble in dilute acid and cannot regenerate Prussian blue, and that hydrolysed Prussian blue leaves behind a yellow-brown stain of iron(III) oxide-hydroxide which may bind strongly to cellulose; and 9.4.5 Buffered substrates, that buffered papers and mount boards contain calcium carbonate included as a reservoir to neutralise acid, that ISO 9706:1994 for permanent paper requires a pH between 7.5 and 10.0 and an alkali reserve of at least 0.4 moles of acid per kilogram corresponding to at least 2 per cent w/w calcium carbonate, and the note that such papers boast of being acid free while probably containing a chalk filler; 3.5 Chemical history of siderotype — the whole class of processes sharing the ferric salts of organic acids, the equation "UV light + 2Fe3+ + C2O42- → 2Fe2+ + 2CO2", and the statement that iron(II) can reduce the compounds of a noble metal such as platinum, palladium, silver or gold to the metallic state, which is the basis of the platinotype, palladiotype, argyrotype and chrysotype; 3.6 Photochemical principles — the Grotthuss-Draper and Stark-Einstein laws, one absorbed photon per molecule transformed, the maximum sensitivity of any proto-photographic material lying over about 300 to 400 nm and requiring about 34 J/m2 for a just-perceptible image, a speed of about 10^-5 ISO or one ten-millionth of a 100 ISO camera film, the sun's 900 W/m2 of which about 7 per cent is actinic, an average UVA irradiance of 30 to 40 W/m2, an exposure scale of 7 to 8 stops from just-perceptible to maximum density and therefore full density in 2 to 4 minutes of average sunlight; the opening of chapter 7 with the five formulations summarised as Classic, Classic improved, New, Simple and Mike's, the statement that the Classic recipes' narrow exposure scale suits only the short density range of normal negatives made for grade 2 or 3 gelatin-silver paper, and that the contrast of the negative should always be adapted to the process and not the reverse; 6.7.1 and 6.7.2, the classic process's poor absorption, loss of Prussian blue in wet processing and mould in the citrate bottle; 7.1.3 Mixing and coating — about 1.5 cc of mixed sensitiser for a 10 by 8 inch print coated by rod, possibly twice that by brush; 7.1.4 and 7.1.5, a lamp exposure around 20 to 30 minutes, the print-out and reversal that make a correct exposure look blocked up, the considerable leaching of blue pigment during washing, the 1 per cent citric acid first bath, the slow aerial reoxidation of Prussian white over several hours and the 0.3 per cent hydrogen peroxide alternative, and the instruction never to use a dichromate bath for reoxidation; 7.2 and its preamble, that the improved Classic sensitiser should not be placed in the hands of children; 7.2.3 item 7, the Classic process's exposure scale of only about 0.9, three stops, comparable with a grade 3 silver-gelatin paper and quite unable to render the density range of 2 or 2.4 that the other siderotypes need; 7.3.1 and 7.3.5, the equipment list specifying 100 per cent cotton or linen paper, sized but unbuffered, and tungsten lighting to work under rather than fluorescent or daylight, and the named unbuffered papers including Hahnemuhle Platinum Rag; 7.3 item 7, the New process's exposure scale of around 2.2 matching negatives also intended for salted paper, platino-palladiotype, argyrotype or chrysotype so that one negative can serve all of them; 7.4, the Simple cyanotype's exposure scale of about 2.7 with a maximum density of about 1.4, being less than half the speed of New cyanotype but about four times a typical Classic formula, and 100 cc of sensitiser sufficing for about 65 prints 10 by 8 inches; 7.8 Environmental issues and disposal — the qualification of the frequently quoted hydrogen cyanide warning, that the heating has to be very strong and the acid very concentrated and neither is done in cyanotype, that the traditional process will not emit any significant, perceptible or harmful amount of hydrogen cyanide during normal exposure and processing, that from all points of view there is no safer photographic process, and that the only chemical in the work recognised as hazardous is potassium or ammonium dichromate, a listed human carcinogen, which the traditional process does not need; 9.4.5 — ISO 9706:1994 and ISO 11108:1996 requiring 0.4 moles of alkali per kilogram of paper, the worked calculation that a 250 g/m2 sheet coated with 25 cm3/m2 of a 0.5 molar iron(III) sensitiser therefore carries an eightfold molar excess of alkaline reserve available to hydrolyse the iron(III), and the recommendation of a 10 per cent sulphamic acid soak where a buffered paper is unavoidable; Appendix III.4 and III.6 — quantum yields of about 1.2 for trisoxalatoferrate(III) between 250 and 420 nm against an ideal maximum of 2, and a maximum of 0.45 at 365 nm for the citrate system falling to 0.28 at 436 nm; Appendix III.7, quantum yields of the order of 0.01 for the photolysis reactions of hexacyanoferrate(III) alone; 7.1 The Classic cyanotype process 1842/1897, read in full for this session — 7.1.1 Sensitizer chemicals needed, with 20 g of the green ammonium iron(III) citrate, 10 g of potassium ferricyanide, 1 cc of a 20 per cent v/v Tween 20 solution and 200 cc of purified water, the statement that the only innovation suggested is the surfactant, that the green form at about 14 per cent iron is preferable to the brown at 19 per cent or more, and that General Purpose Reagent grade at 98 to 99 per cent purity is adequate for the ferricyanide; 7.1.2 Preparation of Classic cyanotype sensitizer, the two stock solutions whose "concentrations are not critical so they do not need to be made up with great precision", 20 g dissolved in about 70 cc of purified water at room temperature and made up to 100 cc "or more, up to 200 cc", 10 g dissolved in about 80 cc and made up to 100 cc of a 10 per cent w/v solution, the furry mould that covers the citrate solution within a week or two, the thymol crystals floated on the surface with the parenthesis that thymol is harmful, the instruction to keep both in brown bottles in a cupboard or box, and the quotation of Christina Z. Anderson's 2020 posting on preferring a 10/10 mixture to the 20/8 recommended by the books; 7.1.3 Mixing and coating, the equal volumes mixed immediately before use, the "relatively short life" of the mixture, the separate labelled syringe or pipette for each solution and a third for the mixture, the guide of about 1.5 cc for a 10 by 8 inch print by rod against possibly twice that by brush, and the 2 to 5 drops of 20 per cent Tween 20 per 10 cc introduced with the words "although it is not part of the traditional formula"; 7.1.4 Printing exposure, the print-out and reversal to a pale blue-grey, the somewhat reversed shadows, the distinctly green highlights, the "blocked up" appearance at the correct exposure and the lamp exposure of around 20 to 30 minutes; 7.1.5 Wet processing and reoxidation, the face-down immersion in gently running water until the yellow sensitizer has entirely disappeared from the highlights with 20 minutes stated to suffice, the considerable leaching-out of blue pigment and the truncation of the tonal scale in the high values, the note that the tonal scale may be strengthened by development first in a bath of very dilute weak acid such as 1 per cent w/v citric acid rather than plain water together with the warning that too strong an acid bath may cause blue fogging of the highlights and degrade the paper white, the several hours of aerial oxidation of Prussian white to Prussian blue during drying, the half minute in dilute 0.3 per cent hydrogen peroxide before the final wash with the statement that it "does not make any difference to the final densities", and the instruction that under no circumstances should a bath of potassium or ammonium dichromate be used for reoxidation. 7.2.3 Shortcomings of the Classic cyanotype process, the seven numbered drawbacks — the ill-characterised citrate, the two separate stocks and the mould, the poor absorption by cellulose fibres and the deliquescent tackiness that can damage negatives, the 20 to 30 minute exposures against 2 to 4 minutes for palladiotype, the peptization of the image substance with its serious loss of gradation in the high values and artificially high contrast, the bleeding of excess iron(II) into adjacent highlights, and the exposure scale of only about 0.9 or three stops. 7.2.4 Remedies for shortcomings of the Classic process, for what the oxalate fixes and this formula cannot. 7.3.9 Wet processing and contrast control, for the mineral-acid development bath that belongs to the New cyanotype and not to this one, and the instruction that a spoonful of citric acid may be added to the wash water to keep it below pH 7. 7.4.10 Wet processing, for the Simple cyanotype's half to one minute in 1 per cent citric acid, the instruction to use citric acid more dilute than 1 per cent if the highlights appear unduly blued, and the 50 cc of 6 per cent hydrogen peroxide per litre of wash bath. 7.6 Diagnosis of fogged highlights, the six numbered causes and Table 7.1's yes/no algorithm, with the note that fog is unwanted image substance and stain is unwanted residual chemistry and that the two are told apart by colour, grey against yellow. 7.7 List of chemicals and hazards, the HMIS ratings for ammonium iron(III) citrate at health 1 and potassium ferricyanide at health 1, the statement that the ferricyanide is classified as a low toxic hazard but may act as a skin, eye and lung irritant and is incompatible with concentrated acids which may release hydrogen cyanide gas, and the standing instruction to wear safety glasses, a lab coat and gloves when handling any chemical. 7.8 Environmental issues and disposal, the argument that the processing solutions are very dilute, the qualification that the heating has to be very strong and the acid very concentrated to get much hydrogen cyanide and that neither is done in cyanotype, and the separate warning about the proto-cyanotype's 20 to 50 times longer exposure. 6.4.2 Using glass rods to coat paper, the rod of 6 to 12 mm external diameter, the requirement that the paper be level, the five passes with the first two rapid and the last three as slow as possible, the blotting of residual liquid because crystals formed there can damage the negative, the immediate rinsing of the rod, and the drying instruction of about an hour hanging in the dark or a uniform warm air stream at 40 degrees C for 10 minutes with the note that a hairdrier is uneven and that relative humidity has very little effect on cyanotype. 3.6 Photochemical principles, for the theoretical estimate of 2 to 4 minutes to full density in average sunlight for a proto-photographic process and the average UVA irradiance of 30 to 40 W/m2 behind it; 4.9 Cyanotypes on fabrics and textiles - the nineteenth-century two-bath industrial practice in which a ferric salt, usually the nitrate or chloride, was mordanted to the fibres of cotton, linen, silk and wool and followed after rinsing by an acidic bath of potassium ferrocyanide; the argument that the iron-based processes are the best suited of all photographic processes to delicate textiles because they employ no sizing agent or binder such as gelatin or gum that would stiffen the flexibility and spoil the drape; Wendy Wilson's finding that the mordanting of sensitizer to cotton and silk fibres appears to be better with ferrioxalate than with ferricitrate sensitizers; the former recommendation of a potassium dichromate bath for development and reputedly for light-fastness, the toxic, allergenic and carcinogenic hazards that make it particularly inadvisable on fabrics which may come into contact with human skin, and the well-documented case history of an artist working with cyanotype on textiles who suffered considerable ill-health as a direct consequence of using dichromate baths; the Nashua Pillow Company of New Hampshire, the popularity of fabric cyanotype for quilt covers and cushions in North America in 1880 to 1920, the catalogue's claim of superiority over prints on paper which Ware says is hard to understand the basis of, and the sale of sensitized blueprint cloth in 1900 under the trade mark Silkdown at 75 cents per square yard. 4.4.2 John Mercer's chromatic photographs - Mercer's 1847 method quoted from his own words, his preference for a ferric oxalate sensitizer because of his interest in printing on textiles rather than paper, and the statement that he had already shown ferric oxalate to be a good mordant for dyeing wool and cotton whereas the citrate is ineffective in not being absorbed by the cellulose fibres. 5.4 Cyanotypes of British algae by Anna Atkins - Anna Atkins 1799 to 1871, the absence of any evidence of the method or formula she used, the likelihood that she used Herschel's rapid standard negative-working method, Whatman's Turkey Mill paper, processing that needed nothing more than pure water, negative cyanotypes printed directly from diaphanes of the seaweeds themselves dried and pressed and usually unsupported, each labelled with its Linnaean binomial in her hand on a translucent slip, the part-book issued privately over 1843 to 1853 in twelve parts making an approximate total of 420 plates or more which varies between the known copies, the hand-printing of over 5000 cyanotypes that the edition demanded, the distribution of more than a dozen copies of the first fascicle in October 1843 against the June 1844 publication of the first part of Talbot's Pencil of Nature, and Talbot's 1864 comment that the whole of these prints remain unaltered after the lapse of several years. 6.4.2 Using glass rods to coat paper - the glass rod or thick-walled capillary tube of 6 to 12 mm external diameter whose straight central section is equal in length to the width of the coating area, the coated area 1 to 2 cm larger than the negative, the sheet taped to a very flat surface checked with a spirit level, about 1.5 cc for a 10 by 8 inch print with other sizes in proportion to their area, the five passes with the first two rapid at 3 or 4 seconds and the last three as slow as 10 to 15 seconds, the blotting of residual liquid because crystals formed there can damage the negative, and the remedy of two strips of sensitizer for a paper on which the coating beads. 9.2 Bleaching of cyanotypes by alkali - Holtzman's finding that a buffer at pH 9.4 completely decolourises Prussian blue by irreversible hydrolysis in 1 to 10 minutes depending on the method of preparation, that this is the pH of a saturated solution of calcium carbonate, and that a 0.25 molar solution of sodium carbonate at about pH 10.7 destroys the Prussian blue of a cyanotype in less than half a minute; the yellow-brown stain of iron(III) oxide-hydroxide left behind and its strong binding to cellulose substrates, paper or fabric; and the partial restoration of freshly bleached cyanotypes by dilute acid and added ferrocyanide, lost over time as the hydrolysis product becomes insoluble. 9.3 Peptization of Prussian blue - the considerable loss of image substance during wet processing that obliges as much as two or three stops of over-exposure depending on the paper and its sizing; Ian and Angela Moor's 1989 densitometered washing experiments at 15 minutes giving an average loss in image density of 18 per cent in tapwater at pH 7.5 to 8.5, 4 per cent in distilled water at pH 6 to 6.5 and a reported 0.00 per cent in deionised water at pH 6.3 to 6.6; Sarah Wagner's 1991 Library of Congress work reporting dramatic lightening by immersion in tap water and slight lightening in deionised water over 1.5 hours; and Table 9.6, the losses as 100 delta D after 5 minutes, 20 minutes, 1 hour and 4 hours in flowing tap water at pH 7.2 plus or minus 0.1 and in a static bath of purified water at pH 6.5 plus or minus 0.1, both at 20 C, for the Smee, Herschel, Lietze, Valenta and Ware sensitizers. 9.4.4 Avoidance of alkali - the statement that cyanotypes are destroyed by mild alkali at pH 8 to 10 much more rapidly than cellulose paper is destroyed by correspondingly mild acid at pH 6 to 4, and that the conservator should be prepared to subordinate the interests of the paper to the interests of the image; the exclusion of any de-acidification treatment; the caution about ammonia-containing glass cleaners when framing, and the note that the violet intensification caused by ammonia gas is reversible while aqueous ammonia causes hydrolysis; and the advice that thorough washing so that no trace of residual sensitizer remains improves resistance to light-fading and alkaline hydrolysis. 9.4.5 Buffered substrates - buffered papers and mount boards containing chalk, the ISO 9706 and ISO 11108 requirements including an alkali reserve of at least 0.4 moles of acid per kilogram corresponding to at least 2 per cent w/w calcium carbonate, the calculation that a permanent or archival paper carries an eightfold molar excess of alkaline reserve over the iron(III) a siderotype coating puts on it at 25 cubic centimetres per square metre of a 0.5 molar solution, and the caveat against applying any adhesive to the verso within the picture area because many adhesives are alkaline and hydroxide can migrate through plain paper. 9.4.6 Storage enclosures - the test in which processed cyanotypes of all five sensitizers were partially coated with a paste of calcium carbonate and distilled water and held above 95 per cent relative humidity, showing a serious density loss of 100 delta D about 40 to 60 within 48 hours against the adjacent control areas; the Image Permanence Institute experiments by Held, Burge and Nishimura in which papers at pH 3.1 and 10.3 and commercial buffered paper at pH 9.3 and non-buffered paper at pH 6.4 were contacted with Herschel, Lietze and Valenta test prints and aged at 70 C and 86 per cent relative humidity for 15 days, the finding that all specimens in contact with alkaline and even neutral papers were seriously faded and that only acidic paper almost fully protected the images, the order of stability with Herschel least stable and Lietze most stable, and the authors' quoted conclusion that alkaline enclosures should not be used, that the data also precludes recommending neutral pH enclosures, and that acidic enclosures cannot be recommended either because they may deteriorate the paper substrate; the note that ISO 18902:2007 recommends buffered papers for the storage of all photographic materials without discussing or excluding cyanotypes; the argument against archival polyester sleeves because they admit light but not air, and the preference for a non-buffered archival wrapping paper such as Atlantis Silversafe Photostore in a four-flap folder, being fairly opaque but relatively porous; the calculation that less than one cubic centimetre of air suffices to reoxidise a typical 10 by 8 inch cyanotype; the demonstration that cyanotypes in anoxic housings are very susceptible to light-fading; and the recommendation of a deep window mat providing a reservoir of air in an unsealed package; 3.6 Photochemical principles, for the estimate that a proto-photographic process spans 7 to 8 stops between a just-perceptible image and maximum density and therefore reaches full density in 2 to 4 minutes of average sunlight at 30 to 40 W/m2 of ultraviolet. 4.2 and Table 4.2, the comparison of brown and green ammonium ferric citrate, giving the brown as first prepared about 1840 at 19 to 28 per cent iron, basic, slow, with relatively slight solarisation, a distinctive edge etch, a dull blue image and fair resistance to light fading, against the green of Valenta 1897 at 14 to 18 per cent iron, acidic, about one stop faster in the midtones, with a stronger solarisation effect and therefore a higher Dmax, no edge etch, a brighter blue and greater susceptibility to fading. 4.3 Survey of negative-working formulae, for the comparison of about sixty published recipes expressed as per cent w/v in the final mixed sensitiser, the scatter chart Fig 4.1, the clustering of the brown-salt recipes about 10 per cent citrate and 8 per cent ferricyanide and of the green-salt recipes about 13 and 6, the statement that the process appears to work satisfactorily almost regardless of the proportions chosen and that there is presumably little difference to the visible outcome, and Channing Whitaker's 1883 tests over the range 2 per cent to 20 per cent against 20 per cent to 2 per cent, his settling on 15 per cent to 10 per cent, his remark that "the same blue results with any good proportions of the chemicals named", and his findings that excess citrate speeds printing but shortens the storage life of the coated paper while excess ferricyanide gives a finer quality but greatly lengthens the exposure through the internal filter effect. 6.4.2, for the statement that the prevailing relative humidity has very little effect on the results of printing in cyanotype although it can profoundly affect some of the other iron-based processes, and for the note that heat-dried paper should rest half an hour to an hour before exposure. 6.5, for the equality of the negative's ultraviolet density range with the sensitiser's logarithmic exposure scale in contact printing because there is no Callier effect, for the traditional cyanotype's exposure scale of about 0.9 to 1.2 matching a negative developed for a grade 3 silver-gelatin paper, and for the New Cyanotype's range of about 1.6 to 2.4. 6.7.1, for the classic process's poor absorption, loss of Prussian blue in wet processing, restricted exposure scale, poor tonal gradation and low density. 7.1.4 and 7.1.5, for the lamp exposure of around 20 to 30 minutes, the print-out sequence and the blocked-up appearance of a correct exposure, the 20-minute wash face down in gently running water, the considerable leaching-out of blue pigment and the truncation of the tonal scale in the high values, the note that the tonal scale may be strengthened by a first bath of very dilute weak acid such as 1 per cent w/v citric acid but that too strong an acid bath may cause blue fogging of the highlights and degrade the paper white, the slow aerial reoxidation over several hours, the 0.3 per cent hydrogen peroxide alternative with the statement that it makes no difference to the final densities, and the instruction that under no circumstances should a dichromate bath be used for reoxidation. 7.2 and 7.2.1, for the improved Classic sensitiser containing oxalic acid and 0.2 g of ammonium dichromate in 200 cc, and for Ware's own comment that these are poisonous and that the sensitiser should not be placed in the hands of children. 7.2.3, the seven numbered shortcomings of the Classic process, and item 5 in particular, that a significant proportion of the image substance is peptised and washes out during wet processing because of poor absorption and retention by the paper fibres, resulting in a serious loss of gradation in the high values, truncating the tonal scale and conferring an artificially high contrast, with gross overexposure and double coating named as the only remedies offered; and item 7, that the classic process has an exposure scale of only about 0.9, three stops, comparable with a grade 3 silver-gelatin printing paper, and is quite unable to render the long density range of 2 or even 2.4 that the other siderotypes need. 7.2.4 items 5 and 7, that the oxalate route yields an ammonium Prussian blue more resistant to peptisation with little loss of image substance on wet processing, delicate gradation in the high values and a high Dmax verging on black, and that because there is little or no image loss the exposure scale of the New process is around 2.2. 7.3.3 Use of dichromate, for the statement that the dichromate is optional, that it introduces a toxic substance into the working environment in very small amount, that it is a strong oxidising agent intended as a preservative that prevents impurities forming Prussian blue in the sensitizer over time and usually gives a shelf-life of several years, that its presence will also tend to increase the contrast of the sensitizer significantly with reference to the D/logH curves of Figs 7.1 and 7.2, and that omitting it may shorten the shelf-life to a few months. 7.3.9, for the New Cyanotype's printing exposure range of about 2.1 to 2.4 after mineral-acid development against about 2.6 developed in water alone with a somewhat reduced maximum density, and for the statement that Fig 7.1 shows the characteristic curves for a sensitiser without dichromate developed in water and in 1 per cent nitric acid. 7.3.12, for the measured effects of heat-drying and darktime on the New Cyanotype on Buxton paper with Stouffer 3110 step tablets: heat-drying at 42 degrees C for 5 minutes shortens the tonal scale by about one stop from 2.3 to 2.0 and may coarsen the texture, 19 hours of darktime at 58 per cent RH and about 20 degrees C lengthens it from 2.3 to 2.6 but weakens the Dmax perceptibly, flattens the shadows and causes edge fog with a rim at the tideline, and doing both returns the scale to about 2.3 with a loss of Dmax, so it is best to do neither. 6.8, for the incompatibility of developing agents between the formulations, New being best with a mineral acid developer for optimum Dmax while Simple and Classic can only tolerate a very weak acid below 1 per cent citric because stronger acids cause blue chemical fog in the highlights. 9.1.1 and 9.1.2, the experimental method of the fading study: five formulations named Smee, Herschel, Lietze, Valenta and Ware with their final sensitiser concentrations in Table 9.2; Atlantis Silversafe Photostore at 120 g/m2, a pure cotton conservation paper sized with Aquapel alkyl ketene dimer and containing no buffer or filler, used for the comparative tests, with gelatin-sized Fabriano 5 HP and historic Whatman papers compared against it; rod coating with closely controlled volumes; drying at room temperature in the dark; sun exposure in a glazed hinged-back frame for all but the Ware formulation, which used four Philips TLADK30/05 tubes peaking at 360 nm at 8 cm; a calibrated Kodak No. 3 step tablet giving a maximum of 21 steps in half-stop intervals, described as large enough to be accurately densitometered; exposures sufficient to make the first two steps indistinguishable so that maximum density was reached; the purple veiling of the highlights after prolonged sun exposure, which usually disappeared in wet processing; Stouffer Graphic Arts T2115 control specimens kept in a light-proof box with baffled access to the same atmosphere; and the measurement conditions, an X-Rite model 310 densitometer in diffuse reflectance mode reading to a precision of 0.002, checked against a standard density plaque and recalibrated when necessary to absolute density readings with an accuracy of plus or minus 0.01 over the range 0.06 to 1.74 before and after each set of experiments, with all densities referred to the red channel of the reflectance colour head because that corresponds to the waveband where the absorption by Prussian blue has its maximum value. 9.1.3, for the characteristic curves of Figs 9.1a to 9.1f plotted as diffuse reflectance density against the logarithm of relative exposure on axes running to 1.6 in density. Appendix II.5, for the strong broad absorption band of Prussian blue centred around 700 nm, 690 nm for the "soluble" variety and 730 nm for the "insoluble", and for the weaker band at 400 nm. 9.1.9, for the long-standing practice of re-oxidising solarised or faded cyanotypes in a dilute dichromate bath and Ware's note that the strong yellow colour of dichromate would tend to make the hue greenish if any were incorporated. 9.1.10 and the fading discussion generally, for the finding that a Prussian blue layer of optical density 1.55 over one square metre contains about 5 x 10^-4 moles. 7.8 Environmental issues and disposal, for the argument that the processing solutions are very dilute and that apart from dichromates there is nothing in the sensitizer or the processing baths that can be described as hazardous when dilute, so that treating the effluent as chemical waste is quite unnecessary from an environmental viewpoint; for ferric ammonium citrate as permitted food additive E381, ferricyanide reducing in the environment to the more stable ferrocyanide as permitted additive E536 used as an anticaking agent in table salt, and Prussian blue as very insoluble and a valuable antidote to poisoning by thallium and caesium; for the qualification that the heating has to be very strong and the acid very concentrated to get much hydrogen cyanide and that neither of these things is done in cyanotype; and for the statement that the only chemical in the work recognised as hazardous is potassium or ammonium dichromate, a listed human carcinogen, followed immediately by the sentence that it does not need to be used in traditional cyanotype at all.; 6.4.1 Paper characteristics — the seven numbered requirements, the quotation of paper chemist John C. Roberts on the shift from acidic papermaking at pH 4 to 5 up to the early 1970s towards neutral and slightly alkaline systems, the greater than 98 per cent alpha-cellulose requirement and the statement that mixed furnish absorbs sensitiser unevenly and causes granularity or blotchiness, alkyl ketene dimer internal sizing with alum-rosin acceptable and gelatin sizing now less commonly available, the requirement that the paper be free of calcium carbonate with the note that it precipitates insoluble calcium oxalate and hydrolyses the iron salt and that the quoted pH should preferably be below 7, hot-pressed surfaces preferred with the note that Not and Rough may be difficult to coat and lose resolution and that some heavily calendered commercial papers roughen on wet processing, 160 to 200 g/m2 to A4 and 240 to 300 g/m2 for larger prints with the note that very heavy papers wash slowly, the prohibition on clay fillers, retention aids, wet-strengthening agents, optical brightening agents, bleaches, alkaline buffers, dyes and titanium dioxide which is stated to be photoreactive, and wove preferred to laid; the ISO 9706:1994 and ISO 11108:1996 requirement of 0.4 moles of alkali per kilogram and the calculation of the eightfold molar excess for a 250 g/m2 sheet; the statement that oxalic acid is unsuitable for decalcification because calcium oxalate is as insoluble as calcium carbonate, that hydrochloric acid can be used and that a 10 per cent solution of sulphamic acid has been found convenient and effective, and that the procedure is tedious and undesirable and degrades paper surface and strength; the Ruscombe Mill description of Buxton paper; the naming of Arches Platine, Weston Diploma Parchment and Hahnemuehle Platinum Rag as machine-made papers in which calcium carbonate is entirely omitted; and the wire and felt sides and the instruction to handle paper only by the edges. 6.4.2 Using glass rods to coat paper — the bicycle-handlebar rod of 6 to 12 mm external diameter, the requirement that the paper be level, about 1.5 cc of sensitiser for a 10 by 8 inch print with other sizes in proportion to area, five passes with the first two rapid at 3 or 4 seconds and the last three as slow as possible at 10 to 15 seconds, blotting the residual liquid, rinsing the rod immediately, the remedy of two strips of sensitiser for a paper that beads, and the statement that brush coating is wasteful, of little consequence for cyanotype and a serious disadvantage for platinotype, that brushes with metal ferrules should be avoided and that a broad Japanese hake brush is suitable; the drying instruction to leave the sheet horizontal until the reflective sheen goes, hang it in the dark for about an hour, or use a uniform warm air stream at 40 degrees C for 10 minutes followed by half an hour to an hour of resting, with the note that direct heating with a hairdrier is uneven and that prevailing relative humidity has very little effect on cyanotype but can profoundly affect some of the other iron-based processes. 6.4.3 Contact-printing frames — the 4 mm plate glass rather than 2 mm picture glass, the felt blanket or porous plastic sheet to absorb the carbon dioxide evolved by the photochemical reaction, the statement that an impervious backing can produce bubbles that blur the image under a bank of fluorescent tubes although not under a near point source, the hinged-back frame for inspecting a print-out process, the 20 micrometre limit on a protective polyester interleaf under a close diffuse source against 50 to 100 micrometres under a small distant one, and the three technical benefits of masking the borders with rubylith including the tell-tale check on clearing. 6.4.4 Ultra-violet light sources — UVA of 320 to 400 nm with maximum output near 365 nm, the statement that lamps peaking near 410 nm are not effective for cyanotype because ferricyanide absorbs there and acts as an internal filter, the aspect value w over d with blur equal to gap times aspect value and the table giving 0.01 for the sun, 0.1 for a NuArc 2125 and 4 for a light bed or open sky with the corresponding blur for gaps of 0.1 and 0.5 mm, the 0.3 mm figure taken as the onset of a soft image, the eight sources in ascending order of cost with the sun about four times faster than a small UV source and the north summer sky about three stops weaker than direct sun and about half the speed of that small source, the sun subtending 0.5 degrees and moving through 0.5 degrees in two minutes, the light integrator that accumulates dose rather than time because small high-intensity mercury arcs vary, and the instruction to warm mercury-vapour lamps for about five minutes because they do not reach full output from cold. 6.5 Making suitable silver-gelatin negatives — the statement that iron-based papers are about a million times less sensitive than silver-gelatin enlarging papers so they cannot be projection-printed, the four options of small prints, large format, enlarged internegatives or inkjet negatives, the statement that the UVA density range required in the negative should equal the logarithmic exposure scale of the sensitiser because there is no Callier effect in contact printing, the traditional cyanotype exposure scale of about 0.9 to 1.2 matching a negative developed for a grade 3 enlarging paper, the new cyanotype scale from about 1.6 to about 2.4 which is longer than any silver-gelatin paper, the instruction to develop 75 to 100 per cent longer than normal and to aim at a contrast index of 0.7 to 1.3, the statement that those contrast indices are more or less incompatible with normal silver printing so one negative cannot serve both, and the five internegative routes with the author's note that much of what he wrote has become obsolete as silver-gelatin materials ceased to be manufactured. 6.6.1 to 6.6.6 Inkjet-printed digital negatives — the four things the ink density depends on and the instruction to recalibrate if any of them changes, the 100-step tablet at 1 per cent intervals of relative opacity printed with identical parameters and materials to the negatives themselves, the definition of the Standard Printing Exposure and the formula SPE equals E times P over 100, the criterion that overexposure is judged by shadow tones blocking up and not by highlights blowing out, the instruction to adjust the printer driver's maximum ink density until the 99 per cent opacity step prints as just white with 2 or 3 per cent regarded as satisfactory, the note that placing the effective maximum density higher spends more of the 256 levels on the shadows and compresses the rest, the warning that inks may lack the UVA blocking opacity to give paper-base white at an excessive SPE, the layer-opacity fine adjustment where the driver cannot reach 99 per cent, the gamma slider set to about 1.8 to 2.4 as a generic tone-correction curve which is stated to agree with individually derived personal curves for platinum-palladium, the instruction to let the negative cure overnight or at least 12 hours because inks change density with time, and the naming of Pictorico OHP and PermaJet Digital Transfer Film as the ceramic coated transparency materials used. 7.3.5 Choice of papers — the instruction to use only papers not buffered with chalk, the statement that any paper claiming conformance to ISO 9706 will contain alkali and that alkalies are hostile to cyanotype chemistry, the list of unbuffered papers naming Arches Platine, Bergger COT 320 and 160, Hahnemuhle Platinum Rag, Legion Revere, Buxton and Herschel from Ruscombe Mill, Wyndstone Vellum, Awagami Masa and Atlantis Silversafe Photostore, the remedy of 5 per cent v/v hydrochloric acid or 5 to 10 per cent w/v sulphamic acid for about 10 minutes followed by washing where a buffered paper such as Fabriano Artistico or Whatman Watercolour is unavoidable, and the paper weights of 160 g/m2 to A4 and 240 g/m2 or more at A3 to minimise cockling and bellying from hydroexpansion. 7.3.6 Drying — an hour at room temperature in the dark, the alternative of 5 to 10 minutes of soaking followed by 40 degrees C air for about 5 minutes, the note that heat drying does not appear to influence image colour but may increase contrast slightly, that rapid drying can reduce chemical fogging from paper impurity but over-rapid drying may worsen loss of image substance in wet processing, and the statement that the coated side should remain light yellow and that a green or blue shift after some hours in the dark at normal relative humidity signals impurities or additives hostile to this process and possibly to other siderotypes. 7.3.8 Negatives and exposure — the requirement of a long density range in the UV of at least 1.8 and as much as 2.4. 7.3.9 Wet processing and contrast control — the printing exposure range of about 2.1 to 2.4 density units or 7 to 8 stops with dilute acid development and the softest gradation of about 2.6 with plain water. 7.3.12 Effects of heat-drying and darktime — heat drying shortening the tonal scale by about one stop from 2.3 to 2.0 and possibly coarsening the texture, 19 hours of darktime at 58 per cent relative humidity and about 20 degrees C lengthening the scale from 2.3 to 2.6 while weakening Dmax and causing edge fog, and the conclusion that it is best to do neither. 9.2 Bleaching of cyanotypes by alkali — Holtzman's finding that a buffer at pH 9.4 completely decolourises Prussian blue by irreversible hydrolysis in 1 to 10 minutes and that this is the pH of a saturated solution of calcium carbonate. 9.4.4 Avoidance of alkali — the statement that cyanotypes are destroyed by mild alkali at pH 8 to 10 much more rapidly than cellulose is destroyed by correspondingly mild acid at pH 6 to 4, and the recommendation that the conservator subordinate the paper to the image. 9.4.5 Buffered substrates — the summarised text of ISO 9706:1994 requiring a pH between 7.5 and 10.0 and an alkali reserve of at least 0.4 moles of acid per kilogram corresponding to at least 2 per cent w/w calcium carbonate, and of ISO 11108:1996 requiring cotton, cotton linters, hemp or flax; and the worked calculation that a 250 g/m2 sheet contains 0.1 moles of hydroxide equivalent per square metre while a typical coating weight of 25 cm3/m2 of a 0.5 molar iron(III) sensitiser deposits 0.0125 moles of iron(III), giving an eightfold molar excess of alkaline reserve. 9.4.6 Storage enclosures — the test in which processed cyanotypes of all five sensitisers were partly coated with a calcium carbonate paste and held above 95 per cent relative humidity, with serious density loss within 48 hours.; 3.6 Photochemical principles — the Grotthuss-Draper law of 1818, the Stark-Einstein law of about 1912 requiring one absorbed photon per molecule transformed, the limiting sensitivity of any proto-photographic material at about 34 J/m2 for a just-perceptible image over 300 to 400 nm, a speed of about 10^-5 ISO, the sun's 900 W/m2 of which about 7 per cent is actinic, an average ultraviolet irradiance of 30 to 40 W/m2, an exposure scale of 7 to 8 stops and therefore full density in 2 to 4 minutes of average sunlight; 3.7 Chemistry of blueprinting — the switch of oxidation states, the instability of the intermediate ferrous ferricyanide, the solarisation and reoxidation schemes, and the account of why pure Prussian blue is not photoreduced but Prussian blue with an oxidisable impurity trapped in its lattice is; 6.7.2 Ferric ammonium citrate failings — the preparation from polymeric ferric hydroxide, the iron content of 14 to 28 per cent w/w, the colour range, the phrase "ill-characterised substance", the deliquescence, and the Mallinckrodt Chemical Works investigation of 1949; 6.7.5 Ammonium dicitratoferrate(III) characterised 1998 — the formula (NH4)5Fe(C6H4O7)2.2H2O, the tetrabasic terdentate citrate with one carboxylate uncoordinated, and the authors' precipitation of the salt with ethanol; 6.7.6 Simple cyanotype 2019; 7.1.4 Printing exposure and 7.1.5 Wet processing and reoxidation — the print-out and reversal, the distinctly green highlights, the "blocked up" appearance at correct exposure, the 20 to 30 minute lamp exposure, the 20 minute face-down wash, the considerable leaching of blue pigment, the 1 per cent w/v citric acid first bath and the blue fogging it causes if too strong, the several hours of aerial reoxidation during drying, the half minute in 0.3 per cent hydrogen peroxide and the statement that it makes no difference to the final densities, and the instruction never to use a dichromate bath for reoxidation; 7.2.3 Shortcomings of the Classic cyanotype process, its seven numbered drawbacks including peptisation of the image, bleeding from excess iron(II) and an exposure scale of only about 0.9; 7.2.4 Remedies for shortcomings of the Classic process — the oxalate's factor of 4 to 8 in sensitivity, the ammonium Prussian blue more resistant to peptisation and alkalies, the chemically equivalent mixing that suppresses bleeding, and the New process's exposure scale of about 2.2; 7.7 List of chemicals and hazards, the entries for ammonium iron(III) citrate and potassium ferricyanide with the statement that the latter is incompatible with concentrated acids, which may release hydrogen cyanide gas; 7.8 Environmental issues and disposal — the qualification of the frequently quoted hydrogen cyanide warning, that the heating has to be very strong and the acid very concentrated and that neither is done in cyanotype, the note that Prussian blue is a valuable antidote to poisoning by thallium and caesium, and the account of the proto-cyanotype's 20 to 50 times longer exposure and the perceptible odour of hydrogen cyanide or cyanogen when the frame is opened; 9.2 Bleaching of cyanotypes by alkali — Holtzman's finding that a buffer at pH 9.4 destroys Prussian blue by irreversible hydrolysis in 1 to 10 minutes, that 0.25 molar sodium carbonate at about pH 10.7 does it in less than half a minute, the yellow-brown iron(III) oxide-hydroxide stain left behind, and the nickel(II) treatment with Table 9.5; 9.3 Peptization of Prussian blue; Appendix II.1 Methods of preparation — the three routes, the names Prussian white, Berlin white, Williamson's salt and Everitt's salt, the solubility product of about 10^-41, and the naming of the "soluble" and "insoluble" forms; II.2 "Soluble" Prussian blue — KFe[Fe(CN)6] with variable water, the Keggin and Miles face-centred cubic lattice, the cation radii table and the effect of replacing potassium by ammonium on peptisation, and Samain's reformulation; II.3 "Insoluble" Prussian blue — Fe4[Fe(CN)6]3.14H2O, one quarter of the hexacyanoferrate(II) sites vacant; II.4 Turnbull's blue with Table II.1 — the irreversible electron transfer, the retention of the historical name, and Reguera's Mossbauer finding of a 3:2 iron ratio; II.5 Electronic spectrum of Prussian blue — the band near 700 nm, 690 nm for the "soluble" and 730 nm for the "insoluble" form, the extinction coefficient of 1.55 x 10^4 dm3/mol/cm, and the assignment of the transition as low-spin iron(II) to high-spin iron(III); II.8 Hydrolysis of Prussian blue — stability to acids down to pH 1 or 2, decomposition by alkalies at pH 10 and above, the hydrolysis equation, the transformation of the hydrous oxide to goethite over days, and the destruction of the lattice by concentrated oxalate; II.9 Prussian white — the composition M2Fe[Fe(CN)6], the air and peroxide oxidation equations, the hydroxide those oxidations generate and the recommendation to reoxidise under acidic conditions, and the absence of colour for want of an intervalence transition; Appendix III.2 Quantitative aspects of the photochemistry — the exposure equation, the internal-filter calculation giving an absorbed fraction of 0.65 at 365 nm and 0.03 at 420 nm, the 32.8 J/m2 threshold and about 3000 J/m2 for maximum density under ideal assumptions, the practical 6000 J/m2 in about two minutes at 50 W/m2, the coating weights, and the finding that only about 6 per cent of the sensitiser is converted into image substance; III.3 The Jones-Condit Equation and the approximation t = 4A^2 minutes for a mid-density image; III.4 Photochemistry of trisoxalatoferrate(III); III.6 Photochemistry of citratoferrate(III) — the photo-inactive monomer between pH 0.5 and 1.5, the photo-active dimer above pH 2, the quantum yield of 0.45 at 365 nm at pH 4 falling to 0.28 at 436 nm, the two crystalline dinuclear citratoferrate(III) anions characterised by X-ray diffraction, the identification of acetone dicarboxylic acid as the organic photoproduct and the statement that the nature of the iron(II) photoproduct remains unknown; III.7 Photochemistry of hexacyanoferrate(III) — the photoaquation releasing hydrogen cyanide, the rise in pH during irradiation, and quantum yields of the order of 0.01; III.8 Photochemistry of the blueprint process, the ligand-stripping argument with the irradiate-then-mix experiment, the redox potentials of +0.356 V and +0.02 V, the competition between hexacyanoferrate(III) and hexacyanoferrate(II) for free iron(II), and the Suzuki and Murray explanations of solarisation with the +0.46 V couple; and the Notes and References for those sections, entries 721, 722, 723, 747, 749, 751 and 756; 7.6 Diagnosis of fogged highlights and Table 7.1, the published statement of the same algorithm with the note that a margin of clear uncoated paper and a coated but masked border are needed for reference and comparison; 6.3 The processing environment - no darkroom or special safelighting needed, ordinary curtains or blinds for a dim room, a preference for a 40 watt tungsten bulb at two metres or more, the warning that some fluorescent tubes have a significant ultraviolet output that may fog sensitized paper, and the statement that the sensitizers and processing chemistry are odourless with no fumes normally evolved so no special ventilation is needed, coupled with the requirement for clean working and the immediate removal of spills because the sensitizer stains most surfaces strongly; 6.4.3 the masking of the printing frame with a window of Rubylith, the three technical benefits including less carbon dioxide evolved and less redundant non-image pigment to bleed into the picture area, and the statement that a printer who exposes the whole coated area will never know for certain whether the print is properly cleared; 6.7.3 Paper problems; 6.8 A caveat on incompatible cyanotype processes - the elimination of potassium from New cyanotype, the sparingly soluble potassium iron(III) oxalate that can form on the paper and wreck the print, the suggestion that brush marks and other defects may be due to friction promoting microcrystal formation, and the developer incompatibility, New cyanotype wanting 1 per cent nitric or hydrochloric or 5 per cent sulphamic acid while Simple and Classic tolerate only under 1 per cent citric because stronger acids cause blue chemical fog in the highlights; 7.1.4 Printing exposure - the print-out to blue and the reversal to a pale blue-grey, the somewhat reversed shadows giving a solarized look, the distinctly green highlights and the blocked-up appearance at correct exposure; 7.1.5 Wet processing and reoxidation - the face-down wash until the yellow sensitizer has entirely disappeared from the highlights, the considerable leaching of blue pigment, the 1 per cent w/v citric acid first bath and the statement that if it is too strong it may cause blue fogging of the highlights and degrade the paper white, the several hours of aerial reoxidation during drying, the half minute in 0.3 per cent hydrogen peroxide with the statement that it makes no difference to the final densities, and the instruction that under no circumstances should a dichromate bath be used for reoxidation; 7.7 List of chemicals and hazards - the potassium hexacyanoferrate(III) entry with the statement that it is incompatible with concentrated acids, and the ammonium dichromate entry with its health hazard rating of 4 as a known human carcinogen, the statement that the very small quantity used in the sensitizers described does not represent a serious risk if the chemical is handled sensibly, the strong advice against the use of a dichromate bath to fix or re-oxidise cyanotypes, and the reference to the medical literature describing in some detail the unpleasant consequences to an artist who used a dichromate bath for quilting fabrics; 7.2.3 Shortcomings of the Classic cyanotype process, the seven numbered drawbacks - the ill-characterised citrate, the brief shelf-life of the mixed sensitizer and the mould that covers the citrate solution within a week or two unless a fungicide such as thymol is added, the poor absorption and the deliquescent tackiness that can damage negatives at high humidity, the 20 to 30 minute exposures, the peptisation that truncates the tonal scale in the high values, the bleeding of excess iron(II) into adjacent highlights, and the exposure scale of only about 0.9 or three stops; 7.3.6 Drying - about an hour at room temperature in the dark, the alternative of 5 to 10 minutes of soaking until the surface loses its reflective sheen followed by heat-drying at about 40 degrees Celsius, the statement that rapid drying can reduce chemical fogging from paper impurity but that over-rapid drying may worsen the loss of image substance in wet processing, and the instruction that the coated side should remain light yellow and that a green or blue coating means chemically fogged highlights; 7.3.7 Citric acid to prevent fogging - to about 2 per cent final concentration, one drop of 0.05 cc of a 40 per cent w/v solution per cc of sensitizer, with the instruction not to add it to the stock because it shortens the shelf-life; 7.3.12 Effects of heat-drying and darktime - the shortening of the tonal scale by about one stop from 2.3 to 2.0 by heat-drying, the lengthening from 2.3 to 2.6 by 19 hours of darktime with a perceptibly weakened maximum density and some edge fog with a rim at the tideline, and the conclusion that it is best to do neither; 9.2 Bleaching of cyanotypes by alkali - Holtzman's finding that a buffer at pH 9.4 completely decolourises Prussian blue by irreversible hydrolysis in 1 to 10 minutes, that this is the pH of a saturated solution of calcium carbonate, and that 0.25 molar sodium carbonate at about pH 10.7 destroys it in less than half a minute; 9.3 Peptization of Prussian blue - the loss of image substance during wet processing and the two or three stops of over-exposure it forces, the Moor densitometered washing experiments of 1989 giving an average loss of image density of 18 per cent in tap water at pH 7.5 to 8.5, 4 per cent in distilled water at pH 6 to 6.5 and 0.00 per cent in deionised water at pH 6.3 to 6.6, all at 15 minutes, Sarah Wagner's 1991 Library of Congress washing work, Table 9.6 giving losses as 100 times the density change for five sensitizers in tap water at pH 7.2 plus or minus 0.1 and purified water at pH 6.5 plus or minus 0.1 after 5 minutes, 20 minutes, 1 hour and 4 hours, the edge etch effect with the experiments that establish what it is and is not, the statement that solutions of high ionic strength promote peptization, and the use of 5 to 10 per cent sodium hexametaphosphate to remove blue from the highlights of a fogged cyanotype and of 20 per cent potassium oxalate to decompose and dissolve Prussian blue for stain removal; 9.4.5 Buffered substrates - the ISO 9706 and ISO 11108 specifications, the calculation that a permanent or archival paper carries an eight-fold molar excess of alkaline reserve over the iron(III) a coating puts on it, and the simulation in which a calcium carbonate paste at 95 per cent relative humidity cost 40 to 60 units of density within 48 hours on all five sensitizers; 4.11 Commercial blueprint papers - the five criteria for an ideal copying paper, the ferricyanide acting as an internal filter, and the consequence that with the light-sensitive component in great excess over the ferricyanide even slight over-exposure generates excess ferrous iron which washes over into unexposed portions as bleeding and in the exposed regions gives the colour a greyish cast, called burning out; Appendix II.11 Prussian brown or yellow - the statement that the brown mixture of iron(III) and hexacyanoferrate(III) rapidly turns blue when spotted onto cellulose filter paper or any other oxidisable substrate, that the redox potential of the pair is about plus 1.5 volts because the insolubility of Prussian blue drives the reaction, that this is the basis of a qualitative analytical spot test cited to Feigl's Spot Tests in Inorganic Analysis, and the consequence that any inclusion of ferric ions in the developer for a cyanotype leads to blue fogging of the background; Appendix III.8 Photochemistry of the blueprint process 1 - the account of solarisation, Suzuki's mechanism and why the low quantum yield of hexacyanoferrate(III) photoreduction disallows it, Murray's mechanism in which excess iron(II) reduces the Prussian blue already formed to Prussian white, the redox potentials that support it, the experimental confirmation with irradiated and unirradiated trisoxalatoferrate(III) and citrate solutions, the further experiment showing the reduction is much faster and more complete when the print is irradiated in situ and the inference that Prussian blue itself becomes photochemically activated, the aerial and peroxide reoxidation equations, and the statement that each of these oxidations consumes protons and generates hydroxyl ions which may build up sufficiently to cause some hydrolysis of the Prussian blue, so that the oxidations should for preference be carried out under acidic conditions; 6.7.2 Ferric ammonium citrate failings — the pharmacy origin, the preparation from polymeric ferric hydroxide, the iron content of 14 to 28 per cent w/w with the colour running from light green to dark brown, the phrase "ill-characterised substance", the deliquescence and compaction on storage, the Mallinckrodt Chemical Works investigation of 1949 and its failure to draw any structural inference, and the statement that no two people working apart can be sure they are using the same chemical; 6.7.3 Paper problems — the dependence on absorption into the interfibrillar space of the surface cellulose fibres, the nanoparticle photoproduct washing out of the coarse pores, and the surfactant as the remedy; 6.7.4 New cyanotype 1995 — the reasoning for abandoning the citrate for a pure, monomeric, small-molecule oxalate, the single-bottle sensitiser with dichromate as preservative, the non-deliquescent coatings, the three stops of speed, the maximum density verging on black, the reduced tendency of the ammonium Prussian blue to peptize, and the four stated disadvantages: a more complicated preparation, a moderate toxicity no worse than kallitype or palladiotype, greater expense, and a crystallisation under ill-defined conditions that gives a variable yield and disturbs PiezoDN calibration by as much as a third of a stop; 6.7.6 Simple cyanotype 2019 — the reasoning, the four benefits claimed for the nitrate by-product, the speed of less than half New and about four times a typical Classic, the exposure scale of about 2.7 falling to 1.8 by ammonia and to about 1.2 by water development, the maximum density of about 1.4, the shelf life of about a month, the absence of mould, and John Isner's PiezoDN figures of a third of a stop against a tenth; 6.8 A caveat on incompatible cyanotype processes — the whole of it, including "a chemical nonsense", the potassium iron(III) oxalate crystals that wreck the print, brush marks from friction promoting microcrystals, the developer incompatibility between the mineral-acid New process and the very weak acid the Simple and Classic sensitisers tolerate, and the remark about naming an arbitrary mixture after the mixer without step-tablet evidence; 6.9 Cyanotype composites with other processes — the matched exposure scales of New cyanotype and platino-palladiotype and the immediate deposition of Prussian blue on a finished platinum print; 6.10 Recent novel photochemistry for cyanotype — the thionine Blythtype of Blyth and Richardson with its three claimed advantages, and the Russian workers' benzene(cyclopentadienyl)iron(II) ferricyanide sensitive to visible light; 7 the opening list of five formulations with Ware's one-line summary of each; 7.2.3 Shortcomings of the Classic cyanotype process, all seven numbered drawbacks with the Tennant quotation of 1906, the mould in the citrate stock, the deliquescent tacky coating, the 20 to 30 minute exposure, the peptization passage with "a serious loss of gradation in the high values, truncating the tonal scale, and conferring an artificially high contrast", the bleeding, and the exposure scale of about 0.9 compared with a Grade 3 silver-gelatin paper; 7.2.4 Remedies for shortcomings of the Classic process, all seven numbered answers, the factor of 4 to 8 in sensitivity, the ammonium Prussian blue more resistant to peptization and alkalies, the chemically equivalent mixing that suppresses bleeding, and the exposure scale of about 2.2 that matches salt printing, platino-palladiotype, argyrotype and chrysotype; 7.2.5 Modified chemistry for the New cyanotype process — the crystallisation of potassium iron(III) oxalate from a concentrated pictorial sensitiser, the "rare chemical" status of ammonium ferricyanide, the 1994 procedure, and the commercial blueprint papers kept below 5 per cent ferricyanide and therefore too low in maximum density for pictorial purposes, with note 618 giving the solubility of potassium ferric oxalate as 6.6 g per 100 cc; 7.3.3 Use of dichromate — potassium substitutable for ammonium, the 20 per cent w/v solution route for a balance that cannot weigh 0.1 g, the acknowledgement that it introduces a toxic substance, its role as a preservative giving a shelf life of several years, the statement that it "will also tend to increase the contrast of the sensitizer significantly", and that omitting it may shorten the shelf life to a few months; 7.3.4 Use of Tween 20 surfactant — that the oxalate sensitiser is much more readily absorbed than the citrate so a wetting agent is usually quite unnecessary, the hard-sized papers such as Buxton where it helps the coating and the retention of Prussian blue, the final concentration of about 0.1 to 0.25 per cent, the instruction not to add it to the bulk stock, and the warnings about gelatin-sized papers and about a Tween solution that shows a deposit; 7.3.6 Drying and 7.3.12 Effects of heat-drying and darktime — heat-drying the coating shortening the exposure scale by about a stop from 2.3 to 2.0 and slightly coarsening the texture, heat-drying the paper before coating giving no benefit at all, the 19 hours of darktime at 58 per cent relative humidity and about 20 degrees C after a 2 minute exposure lengthening the scale from 2.3 to 2.6 while weakening the maximum density, flattening the shadows and causing edge fog with a rim at the tideline, the Stouffer 3110 step tablets in duplicate of Fig 7.3, and the conclusion "so it is best to do neither"; 7.3.7 Citric acid to prevent fogging; 7.3.9 Wet processing and contrast control — the nitric acid bath at 0.1 to 1 per cent v/v, hydrochloric at the same strengths, sulphamic at 1 to 5 per cent w/v, citric as a last resort, the rejection of acetic acid because it forms insoluble strongly coloured basic iron(III) acetate, and the exposure range running from about 2.6 in water to about 2.1 at 1 per cent nitric; 7.3.10 Washing and reoxidation; 7.4.5 Negatives and control of contrast; 7.4.6 Addition of surfactant, with the statement that success depends on the sensitizer penetrating the interfibrillar space where the pigment will be trapped and not remaining in the coarse pores from which it washes out, the 0.25 to 0.5 per cent final concentration, the instruction not to use Tween 80 because it causes foam, and the note that the appropriate amount is found by trial and depends on the paper; 7.4.8 Drying, that heat drying appears to increase contrast slightly by about a stop and that over-rapid drying may diminish penetration and worsen the loss of image substance; 7.4.12 Typical results, the three grades at exposure scales of about 2.7, 2.4 and 1.8 at sensitiser pH about 4, 6 and 8 on Buxton 160 gsm with 0.3 per cent Tween and an 8 and a half minute exposure developed half a minute in 1 per cent citric acid, and the fourth strip at about 1.3 developed in water only; 7.4.13 Sensitizers separated for longer storage; 7.5 Mike's cyanotype, the statement that it is for workers who cannot obtain or cannot tolerate handling strong ammonia and that it produces odourlessly a sensitiser that should be identical with the first Simple sensitiser, and its one-bottle and two-bottle preparations; 7.7 List of chemicals and hazards; 7.8 Environmental issues and disposal, including the statement that dichromate can be entirely omitted; 4.1.3 Hydrargyro-cyanotype; 4.2 Pellet's process — the British patent of 1877, the French patent of the same year and the US patent of 1881, the names Cyanofer and Papier Gommoferrique, Poitevin's 1863 observation that ferric salts harden gum and ferrous salts do not, the ferric chloride and gum arabic in the sensitiser layer, the re-solubilised gum and the wiped-off Prussian white in the exposed regions, the 1878 Paris exhibition and Eder's admiration, the "catch-all" patent language, Lietze's quoted failure to produce good prints, and the process being deemed defunct by 1943; 4.4.6 Cyanotype using uranium and vanadium salts — the uranium(VI) addition claimed to catalyse the photoreduction, Ware's own test showing uranyl nitrate at 1 to 2 per cent giving about one stop in both ferrioxalate and ferricitrate sensitisers with little further advantage above that, his conclusion that its use is not worth the toxic risk, the vanadium pentoxide additive with a claimed fourfold speed increase from a 1924 US patent, and the uranotype in which the sensitiser is entirely a uranium(VI) salt developed in ferricyanide to uranyl ferrocyanide, originated by Burnett; 4.5 Cyanotype diapositives on glass and film — the gelatin-coated plate and the fixed-out fogged lantern plate, George Brown's collodion route, Ware's own diapositives on Pictorico OHP film, the zeolyte coating that holds the image nanoparticles without bleeding, the glass rod suffering intolerable friction on the ceramic-treated surface, the squeegee, foam brush and PTFE rod alternatives, and the absence of any alkaline buffer meaning the film is used out of the box; 4.6 Cyanotype negatives made in camera — the Jones-Condit derivation, the in-camera to contact ratio of about 5 times the square of the f-number with its table and the factor of 4 at 1:1, the hour minimum at f/4 in sun for New cyanotype against a day for the traditional formula, the pinhole calculation giving 2500 hours and the conclusion "it won't work!", the low optical density of a blue negative in the operative part of the spectrum, the unbalanced tonal rendering in which green foliage does not register, and John Beaver's 2002 scan-and-invert answer; 4.7 Printing cyanotypes by projection; 4.8 Cyanotypes on ceramics — the thermal decomposition of Prussian blue around 200 degrees C with evolution of cyanogen and hydrogen cyanide leaving only weak brown iron-oxide images, the bisque-fired tile body whose porosity must be restricted with a sizing agent such as gelatin, Studio Glithero's blueware, and the warning that gesso containing chalk destroys the image; 4.9 Cyanotypes on fabrics and textiles — the nineteenth-century two-bath industrial dyeing practice with a ferric salt mordant followed by an acidic ferrocyanide bath, the argument that the iron processes suit delicate textiles because they use no binder to stiffen the drape, Wendy Wilson's finding that mordanting to cotton and silk is better with ferrioxalate than with ferricitrate, the former recommendation of a potassium dichromate bath for fabric cyanotypes and the statement that its toxic, allergenic and carcinogenic hazards make the practice particularly inadvisable on fabrics that touch skin with a well-documented case history behind it, and the Nashua Pillow Company cushion covers of 1880 to 1920; and Notes and References, entry 589, which gives the first publication of the New cyanotype as Ware, M J, "A New Blueprint for Cyanotypes", Ag+ Photographic, 7 (1995), pp74-80, together with Barnier, J, "The New Cyanotype", Photo Techniques, 18, 1 (1997), pp12-15, and entry 618 for the solubility of potassium ferric oxalate; 8 Methods for Toning Cyanotypes, pages 260 to 269, read in full for this session. The chapter opening, for W. Russell Young III's advice that a photographer who wants a colour other than Prussian blue should use another printing method, for the judgement that most toning procedures are "more curious than valuable" with little reproducibility and less permanence, for Megan Gent's 1992 survey of major collections in which no curator interviewed could report having definitely identified a toned cyanotype, for the purplish-brown single-layer prints of about 1906 that Gent found in Royal Family snapshot albums in the Royal Archives at Windsor sharing album pages with conventional blue cyanotypes and indicative of tannic acid toning, and for the statement that the most reliable procedures fall into five categories most of which begin with hydrolysis of the Prussian blue. 8.1 Hydrolysis of Prussian blue, page 261, for the dilute 1 to 5 per cent alkali, the named alternatives aqueous ammonia, sodium carbonate, sodium or potassium hydroxide, calcium hydroxide and sodium tetraborate, the breaking up of the lattice by hydroxide ion, the conversion of the iron(III) to insoluble yellow-brown ferric hydroxide while the soluble and stable ferrocyanide ion is washed away, the statement that prompt treatment with acid can partially restore the breakdown but that it soon becomes irreversible, the trisodium phosphate route to a golden yellow believed to be ferric phosphate with the Iron Pillar of Delhi as its analogy and its popularity for yellow images on fabric, and the ammonia vapour treatment that does not fully hydrolyse the pigment but imparts an impermanent violet reversible within a few hours in air. 8.2 Ferro-gallate and tannate, pages 261 to 262, for the conversion of the image to ferric hydroxide and its reaction with gallic or tannic acid to form ferric gallate or ferric tannate "ink", for gallic acid as 3,4,5-trihydroxybenzoic acid, a polyphenolic acid, for tannic acid as properly gallotannic acid because there are other tannic acids in the family of tannins and as a much larger molecule comprising ten gallate groups in pairs bound to a central glucose molecule, for tannins as a wide family of plant-produced astringent polyphenolic substances found in gallnuts, sumac, witch hazel, tea leaves, oak bark and leaves, seeds and fruit skins especially grapes, for the credit of the toning process to John Mercer as its originator, for the seven numbered steps with the 1 minute presoak, the ca. 5 minutes in 1 per cent v/v ammonia until the image is bleached to pale yellow, the named substitutes of 1 per cent w/v caustic soda or caustic potash and ca. 5 per cent w/v domestic washing soda, the half-minute rinse, the 1 minute in 1 per cent v/v acetic acid to neutralise residual alkali, the second half-minute rinse, the 5 to 10 minutes in 1 per cent tannic acid and the 20 minute wash, for the note that curtailing the time in the alkali bath can yield interesting split-tone effects, for the statement that the treatment generally intensifies the image and imparts a rich purplish-brown colour, that staining of the paper base is a problem and that the colour is very sensitive to alkali, and for the reported best purplish-browns from immersing first in gallic or tannic acid for a few minutes, rinsing, then treating with alkali and optionally returning briefly to the gallic acid bath. 8.3 Assorted beverages, pages 262 to 263, for the fashion for natural products containing tannins and similar phenolic substances that react chromogenically with iron salts, for black and green teas, several varieties of black coffee and red wine used both with and without preliminary bleaching to yield rather muddy brown and black images, for the stained paper base as a common by-product, for the statement that the source of the tannin affects the colour more from staining than from the specific reaction with iron(III), for grape tannins tending toward purple/brown and green tea toward green/brown, for oak-derived tannin being gallic and usually sold as a white powder that gives no stain in itself but does react chemically with iron(III), for the life expectancy of such images not yet having been established, for Mrhar's admission that some of the procedures are "unreliable and capricious" and for Lukasz Brzezinski's note of significant colour shifts within a year or two. 8.4 Iron-mordanted dyes, page 263, for the ferric hydroxide acting as a mordant for vegetable dyes, Mercer's invention of the method, its suitability for textiles, and his finding that madder on unhydrolysed Prussian blue gave a very rich purple. 8.5 Black toners, page 264, for the silver nitrate and ferrous oxalate conversion to a black silver image, for Planchon's copper(II) sulphide process, and for Reginald Heron's 1970s chromogenic method in which the products of bleaching Prussian blue in a sulphite bath catalyse the oxidative reaction of hydrogen peroxide with polyphenols such as catechol, resorcinol and quinol to form near-black dyestuffs, said to give a fair imitation of a platinum print, with Heron's own report that samples have survived 25 years but that the original black has faded to a passable brown. 8.6 Heavy metal incorporation and 8.6.1 to 8.6.4, pages 265 to 268, for the incorporation of a heavy metal cation into the lattice, the conjecture that the metal needs two accessible oxidation states, and lead, thallium, nickel and copper as the four that work. 8.7 Insoluble metal ferricyanides, page 268, for Murray's 1933 UK and 1935 US patents and the 10 to 20 per cent manganese(II), cobalt(II), nickel(II), zinc(II) and cadmium(II) salts used in the first wet bath to colour the high values. 9.1.6 Results, reversibility of repeated fade and regain, page 281, for the regain of density in the dark being usually greater than 95 per cent within one day and 99 per cent within five days or more, for the diminishing oscillation of the fade over repeated cycles, for the permanent loss over repetition being at most of the order of 3 or 4 in units of 100 delta D, and for McElhone's monitoring showing no detectable fading at 50 lux over 2000 hours. 9.1.7 Results, effect of conditions on fading, pages 283 to 285, for the sentence that of the many toning procedures suggested for cyanotypes most de-stabilise the image and cannot be recommended, for the lead(II) acetate exception improving resistance to light fading by a factor of about four while its colour shift and toxicity debar it as a conservation treatment, for the perfunctory 4 minute wash giving a maximum fade of 42 against 16 for a 20 minute wash under the same 2 kilolux-hour exposure, and for the dichromate re-oxidation bath showing no significant benefit. 9.2 Bleaching of cyanotypes by alkali, pages 290 to 292, for Holtzman's finding that a buffer at pH 9.4 completely decolourises Prussian blue by irreversible hydrolysis in one to ten minutes and that 0.25 molar sodium carbonate at about pH 10.7 destroys it in less than half a minute, for the question whether an alkali bleached cyanotype can be restored and the dependence of that on whether it has been washed, and for the reductive chelation stain removal of one hour at room temperature in a solution 5 per cent w/v in each of sodium dithionite and tetrasodium EDTA at pH about 9 with sodium sulphite as a less effective substitute. 9.3 Peptization of Prussian blue, pages 293 to 294, for Ian and Angela Moor's 1989 densitometered washing experiments at 15 minutes, an average loss in image density of 18 per cent in tapwater at pH 7.5 to 8.5, 4 per cent in distilled water at pH 6 to 6.5 and 0.00 per cent in deionised water at pH 6.3 to 6.6, and for Sarah Wagner's 1991 Library of Congress work. Appendix II.8 Hydrolysis of Prussian blue, pages 320 to 321, for the stability of the pigment to acids of moderate strength down to pH 1 or 2 below which there is some risk of release of hydrogen cyanide, for the equation of hydrolysis by hydroxide to a hydrous iron(III) oxide gel and hexacyanoferrate(II) in solution, and for the transformation of that gel over a few days to more highly polymerized crystalline forms such as goethite which dilute acids cannot readily dissolve.; Appendix II.11, Prussian brown or yellow — the statement that a brown mixture of iron(III) and hexacyanoferrate(III) rapidly turns blue when spotted onto cellulose filter paper or any other oxidisable substrate, that the redox potential of the pair is about plus 1.5 volts because the insolubility of Prussian blue drives the reaction, and that this is the basis of a qualitative analytical spot test cited to Feigl's Spot Tests in Inorganic Analysis; 7.8 Environmental issues and disposal, for the qualification of the frequently quoted hydrogen cyanide warning, that the heating has to be very strong and the acid very concentrated and neither is done in cyanotype; 7.2.3, for the classic cyanotype's exposure scale of only about 0.9 or three stops; 7.3 item 7, for the New cyanotype's exposure scale of around 2.2 matching negatives intended for salted paper, platino-palladiotype, argyrotype or chrysotype; the statement that the contrast of the negative should always be adapted to the process and not the reverse; Appendix II.11, Prussian brown or yellow — the statement that a mixture of iron(III) and hexacyanoferrate(III) rapidly turns blue when spotted onto cellulose filter paper or any other oxidisable substrate, the redox potential of about plus 1.5 volts driven by the insolubility of the product, and the identification of this as the basis of a qualitative analytical spot test cited to Feigl; 7.6 Diagnosis of fogged highlights and Table 7.1, the published form of the fogging algorithm; 6.7.2, for solid ammonium iron(III) citrate being highly deliquescent, becoming sticky in humid environments and compacting into an intractable mass on storage; Appendix III.6, photochemistry of citratoferrate(III) — the photo-inactive monomer below pH 1.5 and the photo-active dimer above pH 2, the quantum yield of 0.45 at 365 nm and pH 4 falling to 0.28 at 436 nm, the identification of the initial organic photoproduct as acetone dicarboxylic acid, and the statement that the nature of the iron(II) photoproduct remains unknown; 4.3 Survey of negative-working formulae and Table 4.2, for the green and brown forms of ammonium iron(III) citrate and their iron contents of 14 to 18 and 19 to 28 per cent; 3.6 Photochemical principles, for the Stark-Einstein law, the maximum sensitivity of any proto-photographic material of about 34 J/m2 for a just-perceptible image and a speed of about 10^-5 ISO; 9.4.5, for the ISO 9706 and ISO 11108 alkaline reserve of 0.4 moles per kilogram of paper and the calculation of the molar excess over a siderotype coating; 8.6.1, for the alkali vulnerability of Prussian blue being undiminished by lead toning; 4.4.6 Cyanotype using uranium and vanadium salts, for the statement that uranyl ferrocyanide has been used as a toner of platinotypes, where the action is catalytic and an uncleared print gives Prussian blue and uranyl ferrocyanide simultaneously; 4.1.3 Hydrargyro-cyanotype, for Herschel's coating of a finished cyanotype with mercurous nitrate, the disappearance of the blue within hours, the brown image raised by a flat-iron, its slow fading and regeneration, Ware's conjecture that mercury(I) is trapped in the Prussian blue lattice as thallium(I) is known to be and then reduces the substance to Prussian white, and his statement that he has repeated and confirmed the process but cannot recommend it owing to the high toxic hazard of mercury salts especially when heated; 4.4.6 Cyanotype using uranium and vanadium salts, for the uranyl addition claimed to enhance sensitivity by catalysing the photoreduction of iron(III), Ware's own finding that 1 to 2 per cent uranyl nitrate increases printing speed by about one stop with little further gain and is not worth the toxic risk, the vanadium pentoxide patent of 1924 claiming a fourfold speed increase, the true uranotype in which the sensitiser is a uranium(VI) salt alone, and the use of uranyl ferrocyanide as a toner of platinotypes where the action is catalytic and an uncleared print yields uranyl ferrocyanide and Prussian blue simultaneously; 8.6 Heavy metal incorporation, for the conjecture that a metal needs two accessible oxidation states to affect the colour and for the list of lead, thallium, nickel and copper as effective against alkali and alkaline earth cations as ineffective; 8.6.1 Lead, for Bolle's bath of about 1900, the violet shift, the pH dependence, the X-ray evidence that the lead signal correlates with the iron signal, the approximately fourfold light-fading protection with the alkali vulnerability undiminished, and the sweet taste of a cumulative poison; 8.6.2 Thallium, for the cornflower-blue shift and the refusal to recommend it owing to the severe toxic hazard; 8.6.3 Nickel, for the slight greenish-blue shift; 7.2.3 item 7, for the classic cyanotype's exposure scale of about 0.9, three stops, comparable with a grade 3 silver-gelatin paper and unable to render the density range of 2 or 2.4 the other siderotypes need; 7.3 item 7, for the New Cyanotype's exposure scale of about 2.2 matching negatives also intended for salted paper, platino-palladiotype, argyrotype or chrysotype; 7.4, for the Simple cyanotype's exposure scale of about 2.7 with a maximum density of about 1.4; 3.6 Photochemical principles, for the maximum sensitivity of any proto-photographic material at about 34 J/m2 and a speed of about 10 to the minus five ISO; 7.8, Environmental issues and disposal — the qualification of the frequently quoted hydrogen cyanide warning, that the heating has to be very strong and the acid very concentrated to liberate much hydrogen cyanide from ferricyanide and that neither is done in cyanotype, and the statement that the traditional process will not emit any significant, perceptible or harmful amount of hydrogen cyanide during normal exposure and processing; 8.6 Heavy metal incorporation, page 265, for the statement that treating a Prussian blue image with a solution of a heavy metal salt may cause the incorporation of the metal cation into the lattice and so modify its colour, with lead, thallium, nickel and copper listed as effective; 8.6.1 Lead, pages 265 to 266, for the violet shift and the warning about the sweet taste of a cumulative poison; 8.6.2 Thallium, page 267, for the bath of thallium(I) sulphate, the slight but agreeable shift to a cornflower blue, and the refusal to recommend it to the general public owing to the severe toxic hazard; 8.6.3 Nickel, page 267, for the order-of-magnitude gain in resistance to alkaline hydrolysis and the sentence that nickel(II) salts are listed carcinogens; 3.7 Chemistry of blueprinting; 7.1 Classic cyanotype sensitizer; 7.2.3 Shortcomings of the Classic cyanotype process; 2.5 Anthotype and phytotype; 2.4 Herschel's research records; 2.6 Discovery of cyanotype; 3.1 Chemistry of Prussian blue; 3.7 Chemistry of blueprinting; 7.1 Classic cyanotype sensitizer, preparation, exposure and wet processing; 7.2.3 Shortcomings of the Classic cyanotype process; 9.2 Bleaching of cyanotypes by alkali; 9.3 peptization of Prussian blue; 3.1 Chemistry of Prussian blue; 9.2 Bleaching of cyanotypes by alkali; 9.3 peptization of Prussian blue; 7.2 An improved Classic cyanotype sensitizer; 7.2.3 Shortcomings of the Classic cyanotype process; 9.3 peptization of Prussian blue; 9.2 Bleaching of cyanotypes by alkali, including Holtzman's result that a buffer at pH 9.4 completely decolourises Prussian blue by irreversible hydrolysis in one to ten minutes; 9.3 peptization; The cyanide question: the qualification that the heating has to be very strong and the acid very concentrated to get much hydrogen cyanide, and that neither is done in cyanotype; Coating by glass rod: the paper level, the pool poured along one edge, the rod rocked to load by capillary action, five passes of which the first two are quick and the last three slow; the specific coating volume for a 10 by 8 inch sheet; blotting the residual liquid because crystals formed there can damage the negative; drying flat until the sheen has gone, then an hour in the dark, and the objection to a hairdryer as uneven rather than hot; Coating implements: the glass rod against the hake brush, the rod rinsed under the tap immediately after each coating, and the instruction to blot the residual liquid because crystals formed there can damage the negative; 6.4.4 Ultra-violet light sources - the light integrator on a commercial unit that accumulates dose rather than time, because the source's emission varies with time; 6.4.3 Contact-printing frames - the felt blanket or porous plastic behind the print to absorb the carbon dioxide the iron processes outgas during exposure; Section 6.7.3, Paper problems - a correct choice of paper and sizing is vital because the iron-based processes depend on absorption of the sensitizer into the interfibrillar space within the surface cellulose fibres, and absorption can be improved by a surfactant such as Tween 20; section 7.2.3, the traditional sensitizer being poorly absorbed by cellulose fibres and tending to remain on the surface or in the pores, deliquescence causing tackiness that can damage negatives at high humidity; section 7.2.4, the crystallization of sparingly soluble potassium ferric oxalate rendering a mixture useless, with a gritty sensitizer producing small white spots on the print typical of surface crystals; section 6.8, brush marks and other defects possibly due to friction promoting formation of microcrystals of potassium ferric oxalate in the coating; section 7.1.3, mixing and coating, with two to five drops of 20 per cent Tween 20 per 10 cc; Section 6.7.3, Paper problems - the dependence of the iron-based processes on absorption of the sensitizer into the interfibrillar space within the surface cellulose fibres, and the consequence when the sensitizer remains in the coarse pores between fibres; Section 7.6, Diagnosis of fogged highlights, and Table 7.1, an algorithm for the six most probable causes of fogging - the sensitizer already decomposed, a hostile chemical in the paper, inadequate safelighting, a mask or negative not dense enough in its maximum value, faulty wet chemistry reducing the sensitizer, and an inadequate clearing procedure; the procedure of comparing a coated but masked border with an uncoated margin; the note that fog is unwanted residual image substance and stain is unwanted other residual chemicals, usually distinguishable as grey against yellow; the detection of the mask fault by including an area of high UV blocking such as Rubylith; section 7.3.7, chemical fogging or greening of the coating due to paper impurities prevented by adding citric acid to the sensitizer to about 2 per cent before coating; section 9.3, the use of sodium hexametaphosphate at 5 to 10 per cent to remove the blue in the highlights of a fogged cyanotype; section 6.8, stronger acids causing blue chemical fog in the highlights of Classic and Simple cyanotype; the appendix on Prussian brown, for the statement that iron(III) with hexacyanoferrate(III) is a powerfully oxidising pair whose insoluble product drives the reaction, and the consequence that any inclusion of ferric ions in the developer for a cyanotype leads to blue fogging of the background; Section 6.8, A caveat on incompatible cyanotype processes - mixing New cyanotype sensitizer with Simple or Classic sensitizer being a chemical nonsense because the whole point of the New preparation is to eliminate potassium ions, and crystals of the sparingly soluble potassium ferric oxalate can form on the paper and wreck the print; the suggestion that brush marks and other defects may be due to friction promoting formation of microcrystals of potassium ferric oxalate in the coating; the separate incompatibility of developing agents, in which New is best with a 1 per cent nitric or hydrochloric or 5 per cent sulphamic mineral acid developer while Simple and Classic can only tolerate a very weak acid under 1 per cent citric, stronger acids causing blue chemical fog in the highlights; section 6.9, Cyanotype composites - coating a processed platinum-palladium print with new cyanotype sensitizer reported to cause immediate deposition of Prussian blue on the graduated tones without any light exposure, suggesting the Pt/Pd image acts catalytically; and the reverse order not being possible with platinotype because traditional platinotype developer will rapidly bleach and dissolve any Prussian blue, the effect of oxalate on the pigment; Section 9.2, Bleaching of cyanotypes by alkali - Holtzman's finding that a buffer at pH 9.4 completely decolourises Prussian blue by irreversible hydrolysis in 1 to 10 minutes depending on the method of preparation, and that this is the pH of a saturated solution of calcium carbonate, the buffer commonly incorporated in archival papers and boards; a 0.25 molar solution of sodium carbonate at about pH 10.7 destroying the Prussian blue of a cyanotype in less than half a minute; Table 9.5, the losses at pH 9.4 for 10 minutes for Smee, Herschel, Lietze, Valenta and Ware sensitizers, and the order-of-magnitude protection given by nickel(II) treatment, which itself costs density by peptisation; the yellow-brown stain of iron(III) oxide-hydroxide left behind and its strong binding to cellulose; the partial restoration of freshly bleached cyanotypes by dilute acid and added ferrocyanide, and the loss of that possibility over time; sections 9.4.4 and 9.4.5, avoidance of alkali and buffered substrates; The formation of Prussian white, ferrous ferrocyanide, as the product of the fading of Prussian blue by light, accounting for the tonal reversal a cyanotype undergoes on extended exposure, which photographers call solarisation; the statement that this fading transformation is not brought about solely by light and that the chemical reduction of Prussian blue to Prussian white must be accompanied by an oxidisable substance; the note that reversal is desirable in a print-out image because the self-masking action of Prussian blue in the shadows is diminished, allowing more light in and forming more white product, with the Prussian white afterwards oxidised back to blue slowly by air or rapidly by a bath of an oxidising agent such as hydrogen peroxide; Herschel's own 1842 observation of the darkening and then the reversal, for which he coined the term solarising; the green-against-brown comparison table, in which the brown salt shows relatively slight reversal and the green a stronger effect with a higher Dmax; section 7.3.8, exposure continued until the high values appear green, the mid-tones blue and the shadow tones substantially reversed to a pale grey-blue, giving the image a solarized appearance; Section 7.2.3, third shortcoming - the traditional sensitizer being poorly absorbed and, being deliquescent, causing a tackiness which can damage negatives if the humidity is high; section 6.7.2, solid ferric ammonium citrate being highly deliquescent, becoming sticky in humid environments and on storage compacting into an intractable mass; 6.4.3 Contact-printing frames - the simplest option given as a sheet of plate glass 4 mm thick, not 2 mm picture glass which may bend or crack under pressure, on a flat baseboard covered with a felt blanket or porous plastic to take up surface unevenness, held with strong clips; 6.4.4 Ultra-violet light sources - the penumbra relation given as blur = gap times aspect value, the aspect value being the largest linear dimension of the source divided by its distance from the print, with 0.3 mm of blur taken as the onset of a fuzzy image; Section 7.2.3, sixth shortcoming - in heavily exposed print areas the classic sensitizer tends to produce excess ferrous iron which diffuses into and stains adjacent highlight areas with Prussian blue, the defect referred to as bleeding; section 7.2.4, ammonium ferric oxalate mixed in chemically equivalent amounts with ferricyanide to avoid excess iron(II) and so suppress image bleeding; section 9.3, Peptization of Prussian blue - the tendency to peptize causing a considerable loss of image substance which washes out during wet processing and necessitates heavy over-exposure, and the observation that solutions of high ionic strength promote peptization; the edge etch effect, its demonstration by printing a step tablet against the boundary of the sensitized area, its disappearance if the print rests in the dark at normal humidity for a few hours before wet processing, its being much worse with the brown variety of ammonium ferric citrate than the green, and its being greatly reduced or absent in papers sized with gelatin; the use of sodium hexametaphosphate at 5 to 10 per cent to remove blue from the highlights of a fogged cyanotype; the note that a masked border gives a tell-tale check on the effectiveness of clearing, and that wet processing removes large quantities of redundant non-image pigment that may bleed into and stain the picture area; Section 7.2.3, second shortcoming - the two ingredients have to be stored as separate stock solutions because the mixed sensitizer has an inconveniently brief shelf-life, and the solution of ferric ammonium citrate proves to be an excellent nutrient medium for the growth of moulds which will usually cover the surface within a week or two, with a preservative fungicide such as thymol added to prevent it; section 7.2.4, ammonium ferric oxalate mixed with potassium ferricyanide at pictorial concentrations causing sparingly soluble potassium ferric oxalate to crystallize out and render the mixture useless, with a gritty sensitizer producing small white spots on the print typical of surface crystals; section 6.7.2, solid ferric ammonium citrate being highly deliquescent, becoming sticky in humid environments and on storage compacting into an intractable mass; section 7.3, the dichromate preservative giving a shelf-life of several years, without which it may be reduced to a few months; section 7.6, the first branch of the fogging algorithm, in which fog apparent on coating indicates a decomposed sensitizer; 6.4.4 Ultra-violet light sources - the penumbra relation given as blur = gap x aspect value, where the aspect value is the largest linear dimension of the source divided by its distance from the print, derived from similar triangles; the table of aspect values and resulting blur for a gap of 0.1 to 0.5 mm, giving 0.01 for the sun, 0.1 for a NuArc 2125 and 4 for a light bed or open sky; and the criterion that the eye resolves about 0.1 mm at its near point of 250 mm while 0.25 mm is taken as acceptably sharp, so that 0.3 mm of blur is taken as the onset of a fuzzy or soft image, most conspicuous where local contrast is high; 6.4.3 Contact-printing frames - the simplest option is a sheet of plate glass 4 mm thick, not 2 mm picture glass which may bend or crack under pressure, on a flat baseboard covered with a felt blanket or porous plastic to take up surface unevenness, held with strong clips; Section 7.2.3, Shortcomings of the Classic cyanotype process - a significant proportion of the image substance, soluble potassium Prussian blue, tends to be peptized and wash out during wet processing due to poor absorption and lack of retention by the paper fibres, resulting in a serious loss of gradation in the high values, a truncated tonal scale and an artificially high contrast, with gross over-exposure or double coating as the only remedies offered; the exposure scale of the classic process of about 0.9, three stops; section 6.7.3, Paper problems - the photoproduct in nanoparticle form must be securely trapped within the fibres or it will be easily washed out, leaving blown-out highlights and murky unresolved shadows, and absorption improved by a surfactant such as Tween 20; section 7.2.4, ammonium ferric oxalate yielding a Prussian blue more resistant to peptization with a Dmax verging on black; the crystallization of potassium ferric oxalate that forced commercial blueprint papers to stay at 5 per cent or less ferricyanide and so to yield a maximum density too low for pictorial purposes; section 9.3, Table 9.6, densitometered washing losses in tap water against purified water for five sensitizer types, and the Moor and Wagner washing experiments; Section 7.6 and Table 7.1 - the distinction between fog, unwanted residual image substance, and stain, unwanted other residual chemicals especially ferric salts, usually distinguishable as grey against yellow; the algorithm branch in which a stain of sensitizer after the wash indicates an inadequate clearing process, and a stain in uncoated areas of the paper indicates contaminated wet chemistry; the note that most acids assist clearing because a low pH prevents hydrolysis of the iron(III) to its insoluble yellow hydrated oxide; section 9.2, hydrolysed Prussian blue leaving a yellow-brown stain of iron(III) oxide-hydroxide which may bind strongly to cellulose, and the reductive chelation treatment of 5 per cent w/v each of sodium dithionite and tetrasodium EDTA at about pH 9 recommended for removing iron stains from platinotypes, with sodium sulphite substitutable at some loss of effectiveness; section 6.7.3, sensitizer remaining in the coarse pores between fibres being easily washed out

Used by:P29 Capstone Stage 5: The Toned Print and the Alternative-Process Print · P29 The Capstone Chemistry Report: From Photon Capture to Finished Print · Ammonium citrate (tribasic) · Ammonium iron(III) citrate · Ammonium iron(III) oxalate · Calcium carbonate · Copper(II) sulfate · Hydrogen peroxide · Iron(III) chloride hexahydrate · Iron(III) nitrate nonahydrate · Lead(II) acetate · Nickel(II) sulfate · Potassium oxalate, anhydrous · Prussian blue · Sulfamic acid · Thallium(I) sulfate · Bostick and Sullivan cyanotype and toning kits · Classic cyanotype sensitiser · Herschel's 1842 cyanotype · Herschel's hydrargyro-cyanotype · Lead, thallium and nickel cyanotype toners · Mike's Cyanotype · The New Cyanotype (1995) · Pellet's positive-working process · Photographers' Formulary cyanotype and toning kits · The Simple Cyanotype (2019) · Tannic acid toner for cyanotype · Van Dyke Brown sensitiser · Ware's argyrotype · Ware's improved Classic cyanotype · Printing processes compared · P1 Assignment 1: A Botanical Cyanotype Photogram, After Atkins · P1 Herschel: Hypo, Prussian Blue and the Words of Photography · P1 1839 and the Many Inventors of Photography · P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve · P3 Oxidation, Reduction and the Electron That Makes the Picture · P16 Build: The Contact Printing Frame and Its Light Source · P16 Build: The UVA Exposure Unit · P16 Ultraviolet for the Alternative Processes: Sources, Dose, Uniformity and Hazard · P19 Lab: Dodging, Burning, Edge Work and Local Contrast · P20 Gold, Iron-Blue and the Other Metal Toners · P21 Part XXI Overview: Photography in Prussian Blue · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Assignment: Cyanotype at Scale, on Fabric, and the Botanical Sequence · P21 Experiment: The Exposure Scale, Maximum Density and Contrast of a Cyanotype · P21 What These Processes Need: The Negative, the Paper and the Light · P21 Iron, Light and Prussian Blue · P21 Break/Fix: The Cyanotype That Went Wrong · P21 The New Cyanotype and the Other Ways to Make a Blue Print · P21 Lab: Toning the Prussian Blue Image · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Contrast Control in Iron-Based Printing · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · P24 The Siderotype Principle: Iron Reduces Silver · P25 Cost, Permanence and When a Platinum Print Earns Its Price · P25 Noble Metal Chemistry and the Platinotype · P25 The Additives We Study and Do Not Reproduce · P25 Assignment: The Process Comparison Atlas · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 Uranium, Mercury and the Heavy-Metal Treatments · Process atlas · Anthotype · Cyanotype (classic) · Iron-blue toned silver gelatin print · Cyanotype (New Cyanotype) · Toned cyanotype · The acid exclusion rule at a hexacyanoferrate or thiocyanate bench · Hand-coating a sheet with a rod and with a brush · Dedicating tools to one process · Operating the UVA exposure unit · Blotchy and streaked hand coating · Blotchy kallitype development · Blue fog in cyanotype highlights · Cross-contamination between alternative processes sharing a bench · Cyanotype bleached by alkaline wash water or buffered paper · Bronzing and reversal from cyanotype over-exposure · Mottled coating from uncontrolled humidity · Newton's rings · Prussian blue bleeding into the highlights by peptisation · Sensitiser gone cloudy in the bottle · Uneven contact print from pressure, glass or source geometry · Weak cyanotype maximum density · Yellow iron stain in cyanotype highlights

Gold in Photography: History and Art of Chrysotype (Chrysonomicon Part I), revised digital editionretrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: 5.1 Chemical background; 5.2 Daguerreotypes 1840-65; 5.1 Chemical background; Jarman's gold printing trials — the cold 12 per cent Rochelle salt developer and the hard, contrasty image it gave; 5.5 Later printing-out papers — silver chloride in gelatine or collodion with excess silver nitrate and a halogen absorber such as sodium citrate; 1.2 the vegetable acids and the discovery of light-sensitive iron(III) salts; 2.9 Herschel and ferrotartaric acid, with note 201; 5.5 gold-thiocyanate toners and the Namias formulation; 5.6 Kodak GP-2 and blue toner T-26; Gold toning with gold(I) stabilised by thiourea — Hélain 1902, Ruzicka and the blue toner formulations; The chapter on gilding and electro-gilding — the electrolyte generally used for electro-gilding being a solution of gold(I) in potassium cyanide, the complex salt gold potassium cyanide, which produces a smooth coherent film of metal where plain gold chloride gives a deposit that is too crystalline; and the account of Hunt's 1844 gold printing in Researches on Light, where the compound employed was the "protocyanide of potassium and gold", which Ware identifies as potassium dicyanoaurate(I), prepared at the time by Karl Himly's method from fulminating gold and potassium cyanide, with Ware's judgement that the preparation offers a challenging combination of hazards not recommended for the amateur chemist today, and his caution that the relative proportions of gold and silver in the resulting image were never reported so it cannot be considered a true gold print; 5.2 Daguerreotypes 1840-65, for Fizeau usually credited with the first use of gold salts for gilding daguerreotypes, for the announcement to the Académie des Sciences by Arago on 23 March 1840 and Fizeau's own publication in August 1840, for the evidence that August Friedrich Karl Himly had already put the idea into use by 19 October 1839, for Fizeau's method reported verbatim in Gaudin's 1844 manual as a 0.2 per cent solution of gold chloride added slowly with stirring to an equal volume of a 0.6 per cent solution of hypo, the slightly yellowish liquid rapidly becoming colourless, then poured onto the carefully washed plate held horizontally and heated from beneath by a spirit burner; for the note that the method is still used to good effect by latterday daguerreotypists; for the identification of the product as the gold(I) complex known as Fordos and Gélis' salt, sel d'or, trisodium bisthiosulfatoaurate(I) dihydrate; for Hardwich's 1855 observation that the preparation also yields sodium tetrathionate, a sulphiding agent towards silver, so that an image toned in the mixed bath may be partially sulphide-toned; for the pure crystalline salt isolated by precipitation with ethyl alcohol and sold by apothecaries; for Gaudin's note that the pure salt gives less warm colours than Fizeau's mixed bath; and for the footnote that "gold chloride" named both the acid hydrogen tetrachloroaurate and the neutral salt sodium tetrachloroaurate, with much better results usually obtained from the neutral salt. Also, in the same section, the two golden daguerreotypes of 1845 by Philipp Graff found in the Netherlands in 1996, exceptional for a specular golden appearance quite unlike gold-toned daguerreotypes and suspected of having been galvanised, and Barger's remark that the reports that gilded daguerreotypes appear gold coloured are part of the myth of the process. Also 5.3, for gold toning of salted paper first published by P. F. Mathieu in 1847; 3.9, Smee's letter offering the ammonio-citrate and ammonio-tartrate, Herschel's reply of 15 June 1842, the misreport in The Athenaeum of 6 August and the corrective letter of 20 August that carries the only published make-up of the paper; 3.10, the 1842 Royal Society paper; Table 3.1, the 771 prepared papers of 1839 to 1843 and the 314 silver experiments among them, with the note that a single coated sheet was cut up and treated variously to make a cyanotype, a chrysotype or an argentotype; 4.16, the modern reconstructions and the notoriously ill-defined properties of ammonium ferric citrate; 3.13 A Mysterious Absence, for Hunt's 1844 anticipation of the process announced as kallitype in 1889, for the attribution to Dr W. W. J. Nicol and footnote 204 giving British Patents nos. 5374 and 7312, and for the quotation of Hunt on ferric oxalate washed with silver nitrate; 2.4 Elizabeth Fulhame; Closing section on painters and optical aids, with its references to Kemp, Steadman, Nickel and Hockney; 5.1 Chemical background — that when toned with gold the image silver is partially replaced by elemental gold which tends to coat the silver nanoparticles, protecting them and modifying their colour; that in reducing the gold salt to deposited gold metal a chemically equivalent amount of metallic silver is dissolved out of the image, so that a gold(III) salt costs three silver atoms per gold atom deposited while gold(I) costs one, and that all useful gold toners therefore employ gold(I); the two broad categories of gold(I) toner, the first using sulphur-containing molecules — thiosulphate, thiocyanate or thiourea — to assist the reduction of gold(III) and stabilise the gold(I), the second dissolving sodium tetrachloroaurate(III) in a mild alkaline buffer such as sodium acetate, borate, carbonate, phosphate or chalk, under which conditions gold(III) reduces to gold(I) over as much as 24 hours by oxidising water, with the note that too alkaline a solution becomes ineffective; 5.5, that the printing-out papers were usually gold toned before the fixing bath and that ammonium thiocyanate was the most-used reagent to complex and reduce gold(III) to gold(I); 5.6, the thiourea blue toners of Hélain 1902 and Ruzicka in the 1930s for slow chlorobromide papers, and that the blue result depended critically on the particle size of the original silver image so that slow chlorobromide papers gave much finer results than faster bromide papers and should not be hardened in the fixing bath; 5.7 Gold Toning of Sulphided Images, that a sulphide-toned original treated in a gold bath gives a crimson colour supposed to be due to the formation of a double sulphide of gold and silver, that Nelson patented the hypo-alum gold bath in 1932 which became Kodak Gold Toner T-21, in which persulphate oxidises the thiosulphate to generate colloidal sulphur and assist the sulphiding of the silver, and that there is no record of prints toned by this means having been analysed to determine the relative proportions of gold and silver sulphide in the final image; the remark that when mixed toning baths become this complicated and the composition of the resulting image correspondingly uncertain, the value of the whole enterprise is called into question; 5.8 Bromide Enlarging Papers, that in modern bromide papers the colour change brought about by gold toning is very slight or even imperceptible because the silver formed in developed bromide papers has a filamentary structure much larger than nanoparticle silver and appears neutral black, and that gold protection rather than toning is what is recommended today when archival stability is paramount, GP-1 being the popular example whose 10-minute treatment shifts the colour slightly towards a bluish-black and is reputed to increase the permanence of the image; Table 5.1, the chronological summary of gold toning methods grouped as sel d'or, alkaline gold toners, silver solvent toners, sulphiding gold toners and gold protective solutions; 5.9, that Mortensen's Metalchrome process uses gold toning of a sulphide-toned print to achieve red colours which are then modified by aniline dyes; and 5.10, that chrysotype is not gold toning but a straight printing medium in which no silver is involved; Chapter 5, Gold Toning, 5.1 Chemical background, for gold being used as a toner from the first days of photography although never a satisfactory imaging medium of its own, for the two claimed benefits of greater permanence and a satisfying colour, for the word toning not entering use until about 1855 with colouring and gilding used before it, for the printed-out image always being nanoparticulate photolytic silver whatever the vehicle, for its yellowish brown colour when fixed, for the enormous surface area making it a highly vulnerable target for sulfur-containing attackers including hydrogen sulfide and sulfur dioxide from the air and the thio-aminoacids methionine and cysteine present in albumen and gelatin, for complete conversion to silver sulphide greatly weakening density and colour and accounting for the putty-coloured faded look of many early photographs, for gold partially replacing the image silver and tending to coat the nanoparticles so protecting them and modifying their colour usually to a rich purplish brown on albumen, for a chemically equivalent amount of silver being dissolved out of the image, for three silver atoms lost per gold atom deposited from gold(III) against one for one from gold(I), for the conclusion that all useful gold toners employ gold(I), for gold(I) not being a commonly stable oxidation state so that making up a toner involves reducing the available gold(III), for the two broad categories of gold(I) toner - reduction and stabilisation by sulfur-containing molecules, thiosulfate, thiocyanate or thiourea, and simple dissolution in a mild alkaline buffer such as acetate, borate, carbonate, phosphate or chalk in which gold(III) reduces to gold(I) over as much as 24 hours by oxidising water - and for a solution made too alkaline becoming ineffective, and for about nine variations of gold toning being distinguishable; 5.2 Daguerreotypes, for Fizeau's 1840 gilding bath of 0.2 per cent gold chloride added to an equal volume of 0.6 per cent hypo, for the product being the gold(I) complex Fordos and Gelis' salt or sel d'or, and for Hardwich's 1855 observation that the preparation also yields sodium tetrathionate which is a sulphiding agent; 5.3 Salted Paper Prints 1839-58, for there being no evidence that Talbot ever gold-toned his prints, for Malone's preference for the old-hypo colouring bath at Reading, for the 3,000 or more Hill and Adamson salt prints of 1844 to 1847 having survived much better than the 10,000 Reading prints with no evidence that the Scottish photographers used gold either and their stability probably attributable to careful fixing and very thorough washing, for Mathieu's Autophotographie of 1847 being the first published account of gold-toning salt prints, for Le Gray's 1850 sel d'or at 4 g per litre and his switch in the second edition to a 0.1 per cent acidic gold(III) chloride further acidified with hydrochloric acid which required heavy overexposure because much image silver was dissolved, for Sutton's 1855 criticism of it, for Humbert de Molard's 1851 gold chloride neutralised with excess chalk and the argument that it anticipated the alkaline bath, for gold toning of salt prints not being widely entertained in Britain until 1855, for Sutton's February 1855 Gold versus Old Hypo announcement that his old-hypo prints had totally perished or grievously faded, for Hardwich's continued reservation that some sulphiding occurs even with pure sel d'or, for the Fading Committee appointed on 21 May 1855 and its first report of 21 November 1855 identifying residual thiosulfate from imperfect washing as the most common cause with sulphurous London air also implicated and recommending, though not unanimously, that gold in some form should be used, for Sidebotham's 1861 account of his own 1852 gold-toned prints being as beautiful as the day they were printed while few old-hypo prints survived at all, for Hardwich's alkaline baths of about 0.1 per cent gold chloride in a mild alkali at 5 to 10 per cent, for Waterhouse of Halifax introducing a sodium carbonate bath in 1858 and Maxwell Lyte trisodium phosphate in 1859, and for gold chloride often being made by dissolving a sovereign in aqua regia; 5.4 Albumen Prints, for the significant sulfur content of egg white making sulphiding a particular risk so that gold toning became essential standard practice, for albumen toning slowly by sel d'or, and for Hardwich's 1858 recommendation of the more energetic alkaline toners before fixing which many albumen prints owe their survival to; 5.5 Later Printing-out Papers, for the excess silver nitrate and halogen absorber such as sodium citrate in gelatin and collodion printing-out papers, for the orangey brown as-printed colour usually transformed by gold toning before fixing, for ammonium thiocyanate as the reagent that complexes and reduces gold(III) to gold(I), for its first use on print-out papers by Meynier in 1863 and Liesegang in 1868, for typical formulae of 1 to 2 per cent ammonium thiocyanate with 0.2 per cent gold chloride mixed only when needed by adding the gold slowly to the thiocyanate, and for Namias's stabilised variant; 5.6, for thiourea gold toners, Ruzicka's 0.03 per cent gold with 0.11 per cent thiourea, and the three-stock citric acid version; 5.7, for gold toning of sulphided images and the absence of any analysis of the proportions of gold and silver sulphide in prints toned in the mixed baths; 5.8, for the colour change on modern bromide papers being slight or imperceptible because developed filamentary silver is much larger than nanoparticle silver, for gold protection rather than toning being what is recommended today, and for GP-1 containing 0.01 per cent gold chloride and 1 per cent sodium thiocyanate; Herschel's chrysotype of 1842 and its commercial failure; the taming of the gold salts; Fizeau's gilding of daguerreotypes; the introduction of alkaline gold toning and the thiocyanate toners of 1867; the two routes to gold(I)

Used by:Chloroauric acid · Gold(III) chloride · Potassium sodium tartrate tetrahydrate · Trisodium citrate dihydrate · Tartaric acid · Thiourea · Cyanide fixing and toning · Fizeau's gilding solution · Herschel's argentotype · Nicol's kallitype · P1 Silver Salts and Light: Schulze to Ritter · P1 The Camera Obscura: An Image Without Chemistry · P20 Gold, Iron-Blue and the Other Metal Toners · P22 Gold Toning and the Permanence of a Printed-Out Silver Image · Chrysotype · Gold toned silver gelatin print

John Herschel's Cyanotype: Invention or Discovery?retrieved 2026-09-04, 2026-09-05

Sections: The positive-working cyanotype — Herschel's addition of gum arabic to his potassium ferrocyanide developer to inhibit the spreading of the image substance, and Ware's remark that adding it to the sensitizer might have succeeded; Doebereiner's 1831 photolysis of ferric oxalate; John Mercer's notebook observation of 1828; Smee's letter offering the ammonio-citrate and ammonio-tartrate of iron; the Memoranda and the prepared-paper numbering; the 1864 priority defence; the note that the whole negative-working process was accomplished with three test papers; Doebereiner 1831 and John Mercer 1828; January 1839; Herschel's photographic programme and the vegetable colours

Used by:Gum arabic · Herschel's 1842 cyanotype · P1 Herschel: Hypo, Prussian Blue and the Words of Photography · Anthotype

Outgassing during Siderotype Exposures: Image Resolution Degraded by Outgassing in Contact-printing Siderotypesretrieved 2026-09-06

Sections: Chemical Theory and Light Source Geometry and Image Acutance in Contact Printing - the statement that all the siderotype processes evolve carbon dioxide as a product of their primary photochemical reactions, applying to ferric oxalate, ammonium ferric oxalate and ammonium ferric citrate sensitizers alike; the worked calculation from a specific coating volume of about 25 cubic centimetres per square metre of a solution about 0.7 molar in iron(III), giving 0.0175 moles and 392 cubic centimetres of carbon dioxide per square metre at standard temperature and pressure, a maximum of about 25 cubic centimetres for an A4 print, an equivalent layer thickness of about 0.4 mm at full conversion and about 0.05 mm for an average picture three stops down on Dmax, and the expectation that the gas localises into bubbles giving possible local gaps of about 0.1 to 0.5 mm; the penumbra relation blur equals gap times aspect value, the aspect value being the largest linear dimension of the source divided by its distance from the print, derived from similar triangles; the table of aspect values giving 0.01 for the sun, 0.1 for a NuArc 2125 and 4 for a light bed or open sky, with the resulting blur for a gap of 0.1 to 0.5 mm; the criterion that the eye resolves about 0.1 mm at its near point of 250 mm while 0.25 mm is taken as acceptably sharp, so that 0.3 mm of blur is taken as the onset of a fuzzy or soft image, most conspicuous where local contrast is high; the observation that blurring became glaringly apparent only when step-test papers were backed with impervious plastic film, and was cured by backing the paper with a conservation-grade felt blanket; and the note that gelatine sizing may block the pores, that parchmentised paper has lower porosity, and that plastic substrates and papers adhered to aluminium are impermeable; Chemical Theory — the statement that the outgassing argument applies to the Chibatype process for hardening pigmented colloids, which uses an ammonium ferric citrate sensitiser, and to the use of diazidostilbenes to photoharden pigmented colloids, where the photolysis evolves nitrogen gas; and the statement that it will not apply to dichromated colloids, where there is no gas evolution

Used by:P21 Assignment: Cyanotype at Scale, on Fabric, and the Botanical Sequence · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes

Papermaking: Additives Cause Degradationretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Surface sizing, on the practice of immersing or floating the formed sheet in a bath of a hydrophilic film-forming colloid, most commonly gelatin or starch; the explanation that a papermill's surface sizing starch is not the familiar substance of that name but oxidised starch, made by treating starch with hydrogen peroxide or sodium hypochlorite, whose carboxylate groups bind iron(III) and so diminish the efficiency of a siderotype sensitiser, shorten the exposure scale and may sequester iron(III) and eventually cause staining; the conclusion that in general no good purpose is served by starch-sizing a paper intended for siderotype processes; and the summary specification for siderotype paper, which excludes cationic starch as a retention aid and surface sizing with gelatin or oxidised starch; The paper specification — the additives a siderotype paper must not carry, including optical brightening agents and white pigments such as titanium dioxide; Damage by Alkaline Buffers; The whole article. Symptoms — the blotching phenomenon reported on certain papers with siderotype processes using ammonium ferric oxalate, described as fibrous, woolly or cloudy lighter patches correlating with fibre flocculation in the formation of the web and most conspicuous with printing-out processes capable of fine tonal separation in the upper values. Diagnosis — the absence of blotching from historical texts, its appearance since the universal change in commercial papermaking in the mid-1980s from acidic to alkaline chemistry, the addition of retention aids at the wet end of the mill for lower running cost and easier drainage, and the hypothesis that these high molecular weight cationic polyelectrolytes such as cationic polyacrylamide or cationic starch bear quaternary alkylammonium cations that attract and trap the small mobile anions of the sensitiser chemistry, named as the trisoxalato and dioxalato ferrate ions, hexacyanoferrate(III), and the tetrachloro complexes of palladium(II) and platinum(II), rendering them less reactive; with the parenthetical explanation that retention aids interact much less strongly with the oligomeric, weakly charged sensitisers of the traditional development processes, which is why classic cyanotype and development platinotype do not generally suffer from blotching. Rationale — the author's statement that the crucial test would be to determine whether retention aids are always present in the afflicted papers, that papermakers tend not to be explicit about the chemical content of their products, the quoted review stating that there is hardly a single paper mill in Central, Western or Southern Europe that does not use retention aids, and the counter-example of the Ruscombe Mill Buxton and Herschel papers whose maker gives a personal assurance that retention aids were always absent and which have never suffered blotching. Possible Cures — the addition of a high concentration of an ionic salt to swamp the cationic retention aids with mobile anions, with ammonium nitrate named for its solubility, compatibility and humectant action at a final concentration of about 15 to 20 per cent w/v, the note that United States patent 2,113,423 of 1938 covered the addition of ammonium nitrate to blueprint sensitiser, and the observation that the Malde-Ware print-out platinum-palladium sensitisers for Methods 2 and 3 are deliberately formulated with 17 per cent w/v ammonium nitrate and are much less susceptible to blotching than the Method 1 sensitiser which does not contain it. Damage by Alkaline Buffers — that papers for archival or fine art use are required to be buffered to an alkaline pH usually with added chalk, that chalk is hostile to iron(III) chemistry because its alkalinity causes hydrolysis of the iron(III) complex, that with cyanotypes it is directly destructive of the Prussian blue image substance which is rapidly bleached at pH 9, and the suggestion that decalcification with dilute hydrochloric or sulphamic acid may also proof the sheet against blotching because the small chloride or sulphamate anions neutralise the cationic polyelectrolytes. Effects of Surface Sizing — that blotching can also be caused by surface sizing applied after the sheet is formed, usually by immersion or flotation in gelatin or starch with hardening agents that are often chemical reductants; that gelatin-sized papers must be avoided if the sensitiser contains a significant proportion of platinum because gelatin binds strongly to platinum(II) and the resulting amino-acid complex is less readily reduced by the iron(II) photoproduct, this problem not arising with the more reactive palladium; and that papermill surface sizing with starch uses oxidised starch, the product of treating starch with hydrogen peroxide or sodium hypochlorite, whose carboxylate groups bind iron(III) as carboxylates do in ferrioxalates and ferricitrates, diminishing the efficiency of the sensitiser, shortening the exposure scale and possibly sequestering iron(III) so as eventually to cause staining, with the conclusion that no good purpose is served by starch-sizing a paper intended for siderotype and that papers internally sized with alum-rosin or alkyl ketene dimer seem perfectly compatible. Paper for Siderotypes, Summary Specification — nearly 100 per cent alpha-cellulose furnish of long-fibre cotton or linen but not mixed, weight about 160 to 240 gsm, wove mould not laid and no watermarks in the picture area, absolutely no alkaline buffer, clay filler or aluminosilicate, retention aid such as cationic polyacrylamide or cationic starch, wet strength aid such as Kymene polyamidoamine-epichlorohydrin resin, optical brightening agent, dye or white pigment such as titanium dioxide, and no residual bleach; internal body sizing with alkyl ketene dimer such as Aquapel with alum-rosin also acceptable; no surface sizing such as gelatin or oxidised starch; no aldehyde hardening agents; and a heavily cold-pressed or calendered surface. Dated Buxton, November 2020.

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Platinomicon: A Technical Account of Photographic Printing in Platinum and Palladiumretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: 10.2 — the acetato-oxo-triiron(III) cation, and why acetic acid is not a good clearing agent for siderotype processes; 6.16 Palladiotype processing and 8.11 Japanese handmade papers — Willis's citrate developer and clearing baths, and the preference for mildly acidic diammonium citrate as developer and clearing agent on lightweight washi; 8.10, a practitioner's step-wedge comparison of ammonium citrate against potassium oxalate; 8.11 Japanese handmade papers "washi", for the statement that alkaline tetrasodium EDTA damages the fibres of the lightest weights and that mildly acidic diammonium citrate is therefore preferred as developer and clearing agent, a finding Ware credits to Gilles Lorin; 1.4 why ferrous citrate cannot reduce platinum; 11.3 Siderotype by reduction of noble metals, redox potentials; 7.6 stability of the sensitizer solution; 10.5 the print-out sensitizer; 11.2 Ferric oxalate versus ammonium ferric oxalate; 11.3 Siderotype by reduction of noble metals; Clearing baths and reducing agents: the redox potential of ascorbic acid between pH 2 and 7, citing Borsook and Keighley (1933); Table 11.1, Redox potentials of "noble" metals; 2.7 Willis on Palladiotype: citrate developer and clearing baths; 9.2 the recommended palladiotype procedure; 10.2 why citric acid is preferable to acetic acid for clearing; the disodium EDTA clearing bath and its citric acid conversion; 10.9 Chelation of iron — the four pKa values of H4EDTA and the pH of its sodium salts, the hexadentate ligand and its donor atoms, the Fe(II)EDTA formation constant; 9.6 iron staining — chelating agents from the 1930s, the 50 per cent limit on removing Fe(III) from cellulose, and the dithionite plus tetrasodium EDTA treatment; 1.4 Willis's choice of ferric oxalate and Döbereiner 1831; 6.2 Ferric oxalate, formula weights and the instructions for preparing standard 25% w/v ferric oxalate solution; 10.5 excess oxalate and print-out; 11.2 Ferric oxalate versus ammonium ferric oxalate; 11.3 siderotype by reduction of noble metals and the redox potentials; The photochemistry of ferric oxalate — the insolubility of the ferrous oxalate photoproduct and why development is dissolution; "Section 3.3, Glycerine development of Platinotypes, for the attribution question and for glycerine inhibiting rather than developing; section 11.13, Choice of cation, for humectants among the ways of controlling water in the sheet; the list of parameters promoting neutral colour in palladium prints, item 7, Concentration of humectants in the sensitizer; the account of Pizzighelli's variants containing glycerol as a humectant for use in very dry environments; the section on increasing the viscosity of the developer to diminish rates of diffusion, which is the basis of the glycerine method; the gold toning of platinotypes due to A. W. Dollond, with the equation for the platinum-catalysed oxidation of glycerol by gold(III); the chronology entry for 1893; and the glossary entries Humectant and Humidify"; The explanation of gum bichromate — gum arabic as a viscous binder for artists' pigments mixed with a soluble dichromate, the photochemical reduction of chromium(VI) to chromium(III), the cross-linking that insolubilises the gum and traps pigment, and the water development; Pizzighelli's variations and Jarman's 1907 water-development paper, both of which add gum arabic, and Ware's judgement of formulations with eight ingredients; 2.4 the traditional three clearing baths of dilute hydrochloric acid; 4.1 Irving Penn's clearing and its effect on palladium; 11.2 pre-treating chalk-buffered papers with dilute acid; Appendix IV on paper additives; 1.7, for the verso annotation "2° 10 gr Acetate of Lead" on Willis's first silver-free platinum print of 17 March 1878; Appendix VII.5, the transcribed text of British Patent No 16,003 of 21 November 1887, for the developer to which "a solution of a salt of lead, preferably the acetate" is added "until a permanent precipitate begins to form" and for the two-solution modification applying plumbic acetate first; the chemicals appendix entry for lead(II) acetate trihydrate, Pb(CH3COO)2.3H2O, RMM 379.33, CAS 6080-56-4; The thermodynamics of hydration — the exothermic dissolution of lithium chloride, its enthalpy, and the contrast with ammonium chloride; The section on catalytic and electroless image amplification, for the treatment of a palladium nanoparticle latent image in a bath of nickel(II), cobalt(II) or copper(II) chloride at about 4 per cent with sodium hypophosphite at 2 per cent, the quoted claim that nickel, cobalt or a mixture has produced outstanding images with excellent black rendition, the resulting high contrast, and the citation of Calligaris, Callaby and Rossello, United States Patent 3,650,747 of 21 March 1972; and the suggestion of electroless deposition of a non-noble metal such as nickel onto a catalytic potential image in palladium; 2.4 the Platinotype Company Special D Salts and the traditional clearing baths; 4.1 Irving Penn's stock solutions and developer; 5.2 instructions for preparing standard 25% ferric oxalate solution; 6.4 excess oxalate and print-out; 9.3 the oxalate developer and its pH; 11.2 decalcifying paper; 1.1 Discoveries of platinum and palladium; 2.7 Palladium supplements platinum; 6.6 Sodium tetrachloropalladate; Chronology of Platinotype & Palladiotype; Alphabetical List of Relevant Chemicals — Palladium(II) chloride; Table 11.5 — substances for making constant relative-humidity enclosures; 6.5 Agents for increasing contrast — the Pizzighelli and Hübl drop-counting system, the mechanism by which chlorate truncates the exposure scale, the reported deterioration in image quality and graininess, the hexachloroplatinate(IV) alternative, and the conclusion that contrast agents become unnecessary with a correctly calibrated negative; §5.3 and the account of Anderson's American practice; 6.15 Platinotype processing; Appendix VI chemical data, Potassium oxalate (monohydrate); 1.4 Willis and the potassium oxalate developer; 6.15 Platinotype processing and the Special D Salts; 6.16 and 6.17 Palladiotype processing and processing variations; Appendix VI chemical data, Potassium oxalate (monohydrate); 2.8 Palladiotype launched by Willis; 2.9 Processing of Platinotype and Palladiotype; 6.6 Sodium tetrachloropalladate; 11.7 Aquation of platinum(II) and palladium(II); Table 11.1, Redox potentials of "noble" metals; Alphabetical List of Relevant Chemicals; 1.6 William Willis's invention; 6.3 Potassium tetrachloroplatinate and the instructions for the standard platinum solution; 6.4 Health warning: platinum allergy; 6.5 Agents for increasing contrast; 11.7 Aquation of platinum(II) and palladium(II); 11.8 The iron(II)-platinum(II) redox reaction; Table 11.1, Redox potentials of "noble" metals; Alphabetical List of Relevant Chemicals — Potassium tetrachloroplatinate(II); 3.8 — Steichen's treatment of Stieglitz's yellowed Palladiotypes with a solution of sodium acetate, the XRF and re-creation evidence, and the suggestion that the name was mistaken for sodium citrate; 2.7 and 6.16 — Willis's Palladiotype developer and clearing baths, given twice with slightly different figures; 2.8, the launch of Palladiotype in 1917 and the Camera Club demonstration with a 5 per cent potassium citrate bath; 6.6 Sodium tetrachloropalladate and the instructions for preparing the standard palladium solution; 11.7 Aquation of platinum(II) and palladium(II); Table 11.1, Redox potentials of "noble" metals; Alphabetical List of Relevant Chemicals — Sodium tetrachloropalladate(II); Section 8.11, Japanese handmade papers, for the finding that on the lightest washi alkaline tetrasodium EDTA damages the fibres so that "the use of mildly acidic diammonium citrate as developer and clearing agent is preferred", credited to Gilles Lorin in a private communication; section 8.10, for Stan Klimek's step-wedge test on Hahnemuhle Platinum Rag in which ammonium citrate "yielded equal response with the potassium oxalate and a very neutral black which is so hard to get from all other papers I have used"; section 6.5, Agents for increasing contrast, for the statement that hexachloroplatinate(IV) "cannot be employed with any chemistry involving ammonium cations, in sensitizer or developer, because ammonium hexachloroplatinate(IV), (NH4)2PtCl6, has a very low solubility and will crystallise out", and for Ware's own refusal of contrast-enhancing agents as "undesirable image-degrading agents"; section 6.16, Palladiotype processing, for Willis's trisodium citrate 20 per cent w/v with citric acid 2.2 per cent and the four to five minutes of development; section 6.17, for the comparison of oxalate against citrate on palladium, the brownish grey fogging of the high values by the oxalate bath and the clear highlights left by the citrate one; section 11.3, for the redox potential of the citrato-iron couple at +0.372 V against +0.02 V for the oxalato couple; section 10.3, for the hydrolysis of iron(III) above pH 4 and its irreversible transformation to goethite; section 9.11, for the photosensitivity of a re-used developer; Appendix V, the alphabetical list of relevant chemicals, which runs from ammonium chloride to ammonium iron(III) oxalate with no ammonium citrate entry between them; Appendix VI, Chemical Preparations, which prepares ammonium ferric oxalate and ferric oxalate and no citrate; Appendix VII.3 and VII.4, for Willis's British patents No 1117 of 1880 and No 1681 of 1887, the first listing "the tartrate or citrate of soda, of potash, or of ammonia" among the salts claimed for the developing solution and the second dissolving "thirty five (35) grains of ammonic citrate" with 100 grains of diammonic orthophosphate and 10 grains of ammonic chloroplatinite in one fluid ounce of water; section 4.3, for Ware's description of Jean-Claude Mougin as the leading contemporary French exponent of platinum-palladium printing; 2.4 Alternatives to Platinotype — Nicol's kallitype, for the 1889 invention at Mason College, the naming, Dick Stevens's survey and the dearth of surviving specimens; 10.1 Summary for non-chemists and 10.3 Hydrolysis and precipitation, for the four stages of iron(III) hydrolysis and the eventual goethite; 10.4 Free radicals, for the air re-oxidation of iron(II) being slow in acid and rapid in base and for the Fenton chemistry that follows; 10.10 Chemistry of clearing siderotypes, for iron(III) hydrolysing above pH 4, for the irreversible transformation to goethite, for the warning against a first bath at pH 10 in which iron(III) is hydrolysed rather than complexed, and for the sulphite reduction step; 11.1 Photochemistry of iron(III) oxalates, for the Döbereiner reaction and the 0.022 g per 100 cc solubility of iron(II) oxalate; 11.3 Siderotype by reduction of noble metals, for the redox potentials of the complexed iron couples against the noble metals; 6.1 Expression of solution concentrations, for the definition of per cent w/v; 6.2 Ferric oxalate, for the polymorphism, the formula weights in circulation from 375.76 to 483.84, the 25 per cent standard solution and the excess oxalic acid; 6.3 Potassium tetrachloroplatinate, for the disputed solubility and the 2.4 hour aquation half-time; 6.4 Health warning: platinum allergy; 6.5 Agents for increasing contrast, for the truncation of the high values rather than compression of the scale, the graininess, the false sparkle, the hexachloroplatinate(IV) alternative and the judgement that contrast agents become unnecessary when a correctly calibrated negative is made; 6.6 Sodium tetrachloropalladate; 6.10 Coating procedure, for specific coating volumes of 24 to 36 cm³/m² and the 1.4 cm³ guide figure for an 8 × 10; 6.11 Drying and humidity control; 9.6 and 10.10 Chemistry of clearing siderotypes, for the chemisorbed iron(III), the hydrolysis above pH 4, the calcium oxalate equation and the irreversible transformation to goethite; 11.1 Photochemistry of iron(III) oxalates; 11.3 Siderotype by reduction of noble metals, for the redox potentials of +0.02 V for the iron oxalato couple, +0.73 V for tetrachloroplatinate and +0.62 V for tetrachloropalladate; 11.4 Printing in palladium and platinum compared, for the aquation constants of 0.17 for palladium and 0.015 for platinum at 20 °C; 5.4 for the exposure scale of about 2.0 for the unmodified platinotype sensitiser; and 5.10 Electron microscopy, for the ellipsoidal platinum nanoparticles of 15 to 25 nm; Section 4.2, for the independent account of this kit's origin and of its central chemical choice — that in 1997 Bostick & Sullivan launched a palladium printing-out process in kit form which "strongly resembled the printing-out platinum-palladium method that had been published twelve years earlier in the UK", with "the difference that some of the ammonium cation was replaced by lithium or caesium cations, based on the erroneous supposition that these cations would serve to control the humidity of the sensitizer", and that the substitution "imposes the limitation that Ziatype cannot make a platinum print - only palladium"; section 11.13, Choice of cation, for the thermodynamic argument behind that judgement — lithium as "one of the worst cations in this respect", the structure-making and structure-breaking distinction, the two enthalpies of solution, the finding that lithium "will totally inhibit the print-out process" in a pure platinotype sensitizer and that with palladium and gold "high degrees of hydration may be called for, with increased risk to the negative", and the caesium problem of salts of low solubility; section 11.12, Effects of gold(III), for the redox potentials that make a gold-palladium sensitiser stable where a gold-platinum one is not, and for the caution that gold(III) "will quite rapidly oxidise any free oxalate ions arising from the partial dissociation of trisoxalatoferrate(III)"; section 11.15, Factors influencing image colour, for the twenty parameters and for the account of nanoparticle size against fibre water; section 11.16 with Tables 11.4 and 11.5, for the control of humidity by saturated salt solutions and for the conversion between relative humidity and absolute water content at different temperatures; section 5.5, for the observation that with hydration before exposure "there is no need to impose a strict method of contrast control on the composition of the sensitizer" and that "the addition of potassium chlorate or dichromate to the platino-palladiotype can cause 'graining' and truncation of the tonal scale"; and section 6.5, for the judgement that contrast-enhancing agents "become unnecessary when a correctly calibrated negative is made".; 1.3, Herschel's use of ammonium ferric citrate to reduce gold, silver and mercury but not platinum, the naming of the four processes and the Philosophical Magazine footnote proposing "siderotype"; 2.4, the kallitype and its subspecies as variations on Herschel's original argentotype of 1842; 11.3 and Table 11.1, the citrato-iron couple at +0.372 V against silver at +0.80 V, gold at +1.00 V, platinum at +0.73 V and palladium at +0.62 V; Table 11.2, the siderotype processes with their iron salts and image substances; the glossary entry Argentotype; Section 7.3, Processing chemicals, for the three reagents and their quantities — disodium EDTA 5 per cent w/v, 2 litres, written with the formula of the dihydrate and made by dissolving 100 g of the solid in 2 litres of water; tetrasodium EDTA 5 per cent w/v, 2 litres, also written as a dihydrate and made the same way; and sodium metabisulphite 2.5 per cent w/v, 1 litre, 25 g or a level tablespoonful in a litre, with the statement that "alternatively, sodium sulphite or sodium hydrogen sulphite (sodium bisulphite) or Kodak Hypoclear powder may be used" and that this solution "should be made up fresh for a day's printing, and not stored and re-used"; and the heading statement that these quantities suffice for about sixty 10 by 8 inch prints. Section 7.9, Processing solutions, for the make-up instructions read as written — about 50 g of disodium EDTA in about 1 litre of tap water with stirring at room temperature, capacity about fifty 10 by 8 prints per litre; about 25 g of sodium disulphite in about 1000 cc of tap water, used for one printing session only and not stored; about 50 g of tetrasodium EDTA in about 1000 cc of tap water, capacity about a hundred 10 by 8 prints per litre — together with the three published conversions between the EDTA salts: 31 g of citric acid to each 100 g of tetrasodium EDTA to make the disodium salt, with the remark that the citrate ion can only assist the clearing; the alkali table for making either salt from about 35 g of the free acid H4EDTA in a litre, giving sodium hydroxide 9.6 g or 19.2 g, sodium carbonate anhydrous 12.7 g or 25.4 g, sodium carbonate decahydrate 34.3 g or 68.6 g and sodium bicarbonate 20.2 g or 40.3 g; and the instruction to convert the disodium salt into the tetrasodium salt by adding about 45 g of it to 9.6 g of sodium hydroxide, or the equivalent alkali from that table, dissolved in 1 litre of water. Section 7.22, Wet processing procedure, for the sequence and the times — 10 minutes in disodium EDTA with the warning that this first bath must be acidic at pH 3 to 4 and that tetrasodium EDTA at pH about 9 must not be used for it, half a minute's rinse, 10 minutes in the disulphite bath which does not keep and is made fresh for each session, half a minute's rinse, 10 minutes in tetrasodium EDTA, and a wash of at least 30 minutes with at least three fresh static baths where water is short — together with the capacities stated there, about sixty 10 by 8 prints for the first bath and at least sixty for the two-litre final bath, the instruction to save the spent first bath for recovery of precious metals, the safety warning not to let the processing solutions reach the skin and to use print tongs or gloves, and the inspection instruction to look for a yellow stain of residual iron in the borders of unexposed sensitiser under a bluish light and to prolong the final bath if it is there. Section 10.9, Chelation of iron, for the four pKa values of the free acid — 2.0, 2.7, 6.2 and 10.3 — for the consequence that the mono- and disodium salts are mildly acidic at pH 3 to 4, the trisodium salt about neutral and the tetrasodium salt alkaline at pH 9 to 10, for the hexadentate wrap of the ligand around an octahedral metal centre, and for the iron(III) formation constant of 10 to the twenty-fifth. Section 10.10, Chemistry of clearing siderotypes, for the whole of the mechanism this page teaches: the ions left in an exposed sensitiser layer, the chemisorption of iron(III) to the hydroxylic functions of cellulose, the hydrolysis of iron(III) above pH 4 to colloidal iron(III) hydroxide and its irreversible ageing to the insoluble oxyhydroxide goethite, the consequent rule that all the iron(III) must be removed at the wet processing stage before the print dries, the calcium equation by which hardness or a chalk buffer precipitates calcium oxalate and drives the iron complex apart, the three bath equations, the warning that tetrasodium EDTA as the first bath hydrolyses rather than complexes the iron with eventual yellow or brown staining "in spite of the fact that it has been recommended by Bostick and Sullivan", the reason the final bath is long-lived, the statement that the final bath leaves the paper alkaline which is desirable for its preservation, and Ware's report of Matthew Clarke and Dana Hemmenway's X-ray fluorescence comparison, in which this procedure left less residual iron than any other combination they tested — comparable with or less than the iron already in the uncoated paper — and accelerated ageing of the cleared papers produced no perceptible yellow stain. Section 9.6, Conservation treatments for iron stains, for the finding that chelating agents alone remove only about 50 per cent of the iron(III) from suspensions of cellulose pulp even with ligands more powerful than EDTA, for the peak formation constant of the iron(II) EDTA complex of 2 times 10 to the fourteenth at about pH 10, for the standard potentials quoted on this page, for the reduction of iron(III) by hydrogen sulphite, and for the statement that sulphite reduction "is also now routinely incorporated in the modern procedure for clearing other siderotypes recommended by the author"; also for the conservators' dithionite treatment, which this page names and does not give. Sections 4.2 and 4.3, for the Malde-Ware collaboration beginning in 1982 and for the sequenced treatment with disodium EDTA, then sodium sulphite in Kodak Hypoclear, then tetrasodium EDTA being listed among the innovations that method introduced; and the note in the historical chapter that Irving Penn had already introduced a 5 per cent sodium bisulphite bath after the hydrochloric acid clearing, observing that "the paper seems to whiten and generally clear", which Ware identifies as now a key step in the Malde-Ware sequence; 2.4 Alternatives to Platinotype — Nicol's kallitype, for the invention, the naming, the commercial failure, the scarcity of surviving specimens and Anderson's and Child Bayley's condemnations; 10.10 Chemistry of clearing siderotypes, for iron(III) chemisorbed to the hydroxylic functions of cellulose, hydrolysis above pH 4, the irreversible transformation to goethite on drying, the calcium oxalate equation and the three-bath clearing sequence; 11.1 Photochemistry of iron(III) oxalates, for Döbereiner 1831, the solid-state equation, the solubility of iron(II) oxalate at 0.022 g per 100 cc, the solubilisation by oxalate and the Hatchard and Parker mechanism; 11.3 Siderotype by reduction of noble metals, for the redox potentials of the oxalato- and citrato-iron couples and of the noble metals; 11.12 Effects of gold(III), for the oxidation of free oxalate by gold(III); VI.2 Ferric oxalate, for the four preparation routes and Stevens's review of them; Appendix VII.1, the transcribed text of William Willis's British Patent No 2011 of 5 June 1873, for the First Method — paper coated with chloro-platinate of potassium at 10 grains to 1 ounce of water, then with nitrate of lead at 40 grains to 1 ounce of water, then with ferric oxalate at 60 grains to 1 ounce of water and as little oxalic acid as will dissolve it, exposed until a faint brown image appears, floated on a hot solution of potassic oxalate, washed in weak oxalic acid, in water, in hyposulphite of soda and in water again; and for the Second Method, in which an 8 grain silver nitrate solution stands in place of the lead; Appendix VII.2, British Patent No 2800 of 12 July 1878, for the coating solution carrying "preferably two grains of plumbic chloride" per fluid ounce and the substitution of four grains of mercuric chloride for it; Appendix VII.3, British Patent No 1117 of 15 March 1880, for the statement that "it was found necessary to use a salt of lead or of silver" and that "I can dispense with the lead and silver salts, and by avoiding their use can obtain greatly superior results", and for the 1.7 and 4 grains of platinous salt per square foot that replaced them; Appendix VII.4, British Patent No 1681 of 2 February 1887, for the ferric oxalate coating of about 60 grains per fluid ounce with a salt of lead or of mercury or a mixture of them dissolved in it, the one to three grains of mercuric chloride the patent actually numbers, and the remark that "I find the mercuric salt very useful where a warm tone or effect somewhat resembling sepia is desired"; Appendix VII.5, British Patent No 16,003 of 21 November 1887, for "by ensuring the presence or contact of a salt of mercury or of lead with the image at the time of its development, I obtain a better reducing action", for the coating of 60 grains of ferric oxalate with one grain each of plumbic chloride and mercuric chloride per fluid ounce, for the developer of 90 grains of potassic oxalate and 9 grains of potassic chloro-platinite per fluid ounce to which a solution of a lead salt, "preferably the acetate", is added "until a permanent precipitate begins to form", for the warning that with a lead salt "there must be no salt used in the developer which would entirely prevent the solution of the lead salt", for the two-solution application of plumbic acetate followed at once by the rest of the developer, and for the claim that lead or mercury "one or the other of which is in all cases essential"; Appendix VIII.1 and VIII.2, the conversion of obsolete units, for 1 grain = 0.0648 g and 1 imperial fluid ounce = 28.413 cm3; 1.7 Willis's Platinotype Company of London, for the verso annotation of the first silver-free platinum print of 17 March 1878 reading "2° 10 gr Acetate of Lead", for Willis's 1880 address to the Edinburgh Photographic Society explaining that he had omitted the lead salt altogether and increased the platinum, and for John Spiller's February 1880 permanence tests; 1.8, for the 1880s criticism that platinotypes yellowed with sulphides and for the statement that analysis shows lead was still present in some of Willis's papers post-1892; 2.9 Processing of Platinotype and Palladiotype, for the 25 to 33 per cent oxalate developer and the pre-1892 use of it hot at 140 to 170 F; 3.12 Platinum printers contemporary with Stieglitz, for Imogen Cunningham's interest in adding lead oxalate to the sensitizer, cited to her undated typescript of about 1910 in the Imogen Cunningham Archive; 3.10 Paul Strand's platinum prints, for Alisha Chipman's five categories of Strand's prints by the additional metals lead, mercury, palladium and gold; 5.5 X-ray spectrometry, for Jacqueline Rees's 1993 XRF of Willis's "KK" Platinotype paper of about 1906 at the Victoria and Albert Museum, in which zinc and lead were found at very low levels, and for Matthew Clarke's 2011 re-examination of the same paper; 6 Traditional Platinotype and Palladiotype, introduction, for the statement that additives such as mercury and lead salts "would not be generally recommended today for reasons of health and safety, and image permanence"; 6.5 Agents for increasing contrast, pages 136 to 137, for the statement that "Willis makes no mention of contrast control in his patents or sensitizer formulae", for the Pizzighelli and Hübl chlorate drop system, for sodium hexachloroplatinate(IV) and for the dichromate added to the developer by Willis and Clements; 6.7 Salts of mercury(II) and lead(II), pages 138 to 139, for the weak, fibrous or grainy image that plain platinum gives, for the conversions of the patent lead quantities to 9.12 per cent w/v and 0.275 M for the 1873 lead nitrate and 0.456 per cent w/v and 0.0164 M for the 1878 plumbic chloride, for the statement that lead and mercury salts "hasten the response of the platinum chemistry, thus improving the image quality by smoothing out and intensifying the tones", and for the statement that mercury and lead need not be introduced into a palladium sensitizer; 6.8 Choice of papers, for the avoidance of gelatin sizing and of a chalk buffer; 9.1 Staining of Platinotypes by sulphides, and 9.2 Slow development of iron stains, pages 189 to 191, for van Monckhoven's and Spiller's 1880 tests, for the attribution of the yellow discoloration to the lead and silver salts of the early sensitizers, for the particle-size explanation of why a black sulphide looks yellow, for George Dawson's clean result on the 1880 papers, for Andrew Pringle's 1887 observation and the acrimonious correspondence that followed, and for Henry Chapman Jones's rival attribution of the stain to residual iron; 10.5, for the collapse of the iron redox potential on oxalate complexation to +0.02 V; 11.1, for the photolysis and development equations; 11.7 Aquation of platinum(II) and palladium(II), for the aquation equilibrium and the constants 0.015 for platinum and 0.17 for palladium at 20 C with a half-time of 2.4 hours; 11.9 Effects of mercury(II), lead(II) and silver(I), pages 238 to 240, for the chloride-scavenging hypothesis, for the lead chloro-complexes PbCl+, PbCl2, PbCl3- and PbCl4 2-, for the two lead reduction potentials -0.126 V and -0.266 V and the conclusion that lead should remain as lead(II) and not contribute to the image substance, for Clarke's XRF finding that the lead signal does not correlate with image density but is a more or less uniform background suggesting an insoluble colourless salt such as the oxalate or chloride, for the solubility products of lead chloride and lead oxalate and the formation constant of the bisoxalatoplumbate(II) complex, for the silver chloride analogy, for the experimental observation that added chloride inhibits image formation, for the self-inhibition of platinum development and the list of other metals that bind chloride well; Appendix VII.2, the transcribed text of William Willis's British Patent No 2800 of 12 July 1878, for the coating solution of 15 grains of potassic chloro-platinite, 70 grains of ferric oxalate and preferably two grains of plumbic chloride per fluid ounce, the substitution of four grains of mercuric chloride for the two of plumbic chloride, the developing solution of 120 grains of potassic oxalate and 7 grains of potassic chloro-platinite per fluid ounce, the float or immersion "preferably hot", the weak acid wash and the statement that mercuric chloride may also be used in the developing solution; Appendix VII.4 and VII.5, the texts of patents No 1681 of 2 February 1887 and No 16,003 of 21 November 1887, for the 60 grains of ferric oxalate with one grain each of plumbic and mercuric chloride per fluid ounce, the lead-free option of two or more grains of mercuric chloride, the developer of 90 grains of potassic oxalate with 9 grains of potassic chloro-platinite, the five grains of mercuric chloride per fluid ounce of developer, and Willis's statement that a salt of lead or of mercury is "in all cases essential"; Appendix VIII.1 and VIII.2, the conversion of obsolete units, for 1 grain = 0.0648 g, 1 imperial fluid ounce = 28.413 cm3 and 1 grain per fluid ounce = 0.228 per cent w/v; 1.6 and 1.7, for the 1873 lead nitrate patent, the five-shilling licence, the 1888 launch of the "platinum-in-the-bath" method, Willis's own warning that its developer undergoes slow mutual decomposition, and its withdrawal in 1892; 1.8, for cold development; 1.9 Sepia Platinotype with mercuric salts, pages 33 to 35, for the whole history of the sepia paper — the mistaken belief that a hot bath alone made it, the "very slight" warming a hot bath actually gives, the 1878 developer route at 140 to 160 F, the "double tones" and Willis's explanation of them, the sepia paper first marketed circa 1885, the Company's "Special Sepia Solution" and "Sepia Crystals", the 1892 admission that cold development would not work for sepia, the 1893 "heart-breaking problem" and the glycerine experiments, grades S and RS in the 1894 and 1906 lists, development at 160 to 170 F in 1911, W. H. Smith's 1911 warning and 1915 demonstration of faded specimens, F. C. Lambert's remark that mercury-developed images dissolve in Farmer's reducer, Paul Anderson's 1917 recommendation and his claim that the image is pure platinum, and Hübl's mercuric citrate of 1902; 5.9 Identification of toned platinotypes, for Stulik and Vo's XRF survey of Gertrude Käsebier's prints; 5.10, for the electron microscopy of platinum nanoparticles of 15 to 25 nm; 6.7 Salts of mercury(II) and lead(II), pages 138 to 139, for the weak fibrous image pure platinum gives, the conversions of the patent quantities, the 0.02 to 0.1 molar mercuric citrate of later formulations, the glycerine method, and the statement that mercury need not go into a palladium sensitizer and brings problems of toxicity and disposal; 6.8, for the avoidance of gelatin sizing and of a chalk buffer; 6.10, for coating volumes of 24 to 36 cm3/m2; 9.12 Fading of Platinotypes and kelainotypes, for the argument that a pure platinotype cannot fade, the faded Watson-Schütze and Sears prints in the Library of Congress, the volatility explanation and the instruction not to over-use mercury(II) additives; 9.13 Methods for toning Platinotypes; 10.5, for the stepwise formation constants of the oxalato-iron(III) complexes and the collapse of the iron redox potential on complexation to +0.02 V; 11.1, for the photolysis and development equations; 11.7 Aquation of platinum(II) and palladium(II), for the aquation equilibrium, the constants 0.015 for platinum and 0.17 for palladium and the 2.4-hour half-time; 11.8, for the iron(II)-platinum(II) redox reaction; 11.9 Effects of mercury(II), lead(II) and silver(I), pages 238 to 240, for the chloride-scavenging hypothesis, the mercury chloro-complex formation constants, the palladium-like result, the self-inhibition of platinum development, Borlinetto's copper chloride and Jacoby's zinc oxalate; 11.10 Mercury in platinotypes and palladiotypes, pages 240 to 242, for Ware's own quantitative XRF experiment at Pt:Hg 1:1, the Hg:Pt ratios of about 4 and 2 in the finished image, Lewis and Koseki's 2015 measurements of 0.2 to 0.3 for sensitized and 0.8 to 1.1 for developed prints, the bisoxalatomercurate(II) complex and its potentials, the photosensitivity of the stored developer, the possibility of platinum-mercury bonded complexes, and the admission that no clear explanation of the colour has been put forward; 2.4 Alternatives to Platinotype — Nicol's kallitype, for W. W. J. Nicol of Mason College Birmingham, the 1889 invention, the Greek naming, Nicol's own 1891 statement of his motives, the commercial failure of the Birmingham Photographic Company paper through faulty stock, the dearth of surviving specimens, Anderson's 1913 condemnation and Child Bayley's, Stevens's reply, and the pronounced fading and yellowed highlights of the few identified survivors; footnote 300, for British Patent No. 5,374 of 29 March 1889 and the British Journal of Photography of 14 March 1890, and footnote 301 for Nicol's "The Kallitype" of 24 July 1891; 10.10 Chemistry of clearing siderotypes, for chemisorbed iron(III), hydrolysis above pH 4, the calcium oxalate equation, the irreversible transformation to goethite on drying, and the three-bath clearing sequence; 11.1 Photochemistry of iron(III) oxalates, for Döbereiner 1831, the solid-state photolysis equation and the 0.022 g per 100 cc solubility of iron(II) oxalate; 11.3 Siderotype by reduction of noble metals, for the redox potentials of the oxalato and citrato iron couples and Table 11.1 of noble-metal potentials; 6.1 Expression of solution concentrations, for the definition of per cent w/v; 6.2 Ferric oxalate, for the polymorphism, the disputed formula weights from 375.76 to 483.84 and the excess oxalic acid; 6.3 Potassium tetrachloroplatinate, for the disputed solubility, the 18.5 per cent standard solution and the 2.4 hour aquation half-time; 6.4 Health warning: platinum allergy; 6.5 Agents for increasing contrast, for the truncation of the high values rather than compression of the scale, the graininess, the false sparkle, and the judgement that contrast agents become unnecessary when a correctly calibrated negative is made; 6.6 Sodium tetrachloropalladate; 6.10 Coating procedure, for specific coating volumes of 24 to 36 cm³/m² and the guide figure of 1.4 cm³ for an 8 × 10 on Cranes cotton paper; 6.11 Drying and humidity control; 9.6 and 10.10 Chemistry of clearing siderotypes, for the chemisorbed iron(III), the hydrolysis above pH 4 and the irreversible transformation to goethite; 11.1 Photochemistry of iron(III) oxalates; 11.3 Siderotype by reduction of noble metals, for the redox potentials of +0.02 V for the iron oxalato couple, +0.73 V for tetrachloroplatinate and +0.62 V for tetrachloropalladate; 11.4 Printing in palladium and platinum compared, for the aquation constants of 0.17 for palladium and 0.015 for platinum at 20 °C; 5.10 Electron microscopy, for the ellipsoidal platinum nanoparticles of 15 to 25 nm; and 5.4 for the exposure scale of about 2.0 for the unmodified platinotype sensitiser; 1.16 Researches of Pizzighelli and Hübl, for the two Austrian army captains, the 1882 German publication, the Voigtländer Prize, the French and English translations of 1883 and the commercial consequence; 5.1 Willis's formulae, for the 60 grains per fluid ounce of both constituents in patent 1117 of 1880, the 0.33 molar platinum, the 1.7 to 4 grains per square foot and the 20.4 cm³/m² specific coating volume derived from them; 5.3 Pizzighelli's formulations and Table 5.1, for the 1887 print-out stocks A B C D, for the conversion of "1 part in 6 water" to about 15.6 per cent w/v and 0.376 molar, for the same 0.4 parts of potassium chlorate in 100 parts of the iron solution and for the 5 : 6 : 2 and 5 : 4 : 4 ratios; 6.2 Ferric oxalate, for the polymorphism, the formula weights from 375.76 to 483.84, the 25 per cent w/v standard, the 2 g per 100 cc of oxalic acid and the attribution of that standard to the analysis of Pizzighelli and Hübl; 6.3 Potassium tetrachloroplatinate, for the disputed solubility, Cassell's 1 in 6 and Anderson's 1 in 5, and the 0.225 molar development sensitizer; 6.4 Health warning: platinum allergy, for the 1911 identification of the occupational disease among platinotype paper workers and for the handling rules; 6.5 Agents for increasing contrast, for the attribution of the drop-counting chlorate system to Pizzighelli and Hübl, for the reoxidation mechanism, for the graininess and the false sparkle, and for the hexachloroplatinate(IV) and dichromate alternatives; 11.1 Photochemistry of iron(III) oxalates, for Döbereiner, the photolysis equations, the 0.022 g per 100 cc solubility of iron(II) oxalate and the solubilising role of the oxalate developer; 11.2 Ferric oxalate versus ammonium ferric oxalate, for the polymeric structure and the contrast with the monomeric trisoxalatoferrate(III); 11.3 Siderotype by reduction of noble metals, for the redox potentials; Section 2.9, Processing of Platinotype and Palladiotype, for the whole of the traditional procedure — black platinotypes cleared "for about 10 minutes in each of three successive baths of hydrochloric acid, in which the concentrated acid (36 % w/w) was diluted 1:60 (0.2 M, pH below 1)", a more dilute acid of half that strength for sepia platinotypes, the statement that these procedures "were intended to remove the residual iron salts from the print, but were not always successful" and that some workers used much longer times, the final wash of about 20 to 30 minutes, and Willis's quite different recommendation for his Palladiotype papers — development in trisodium citrate at 20 per cent w/v with 2 per cent citric acid and clearing in the same, eight times diluted to 2.5 per cent w/v with 1.2 per cent added citric acid, in three baths of 10, 15 and 20 minutes followed by a water wash; also the Abel's Weekly statement that "the Palladiotype developer and clearing baths have no tendency to injure the beautiful surface of the paper employed for coating" where undue immersion of matt Platinotypes in the oxalate and acid baths does destroy their bloom, and Ware's reading that Willis, a shrewd and observant chemist, would not have recommended a different clearing agent had the old one served. Section 6.15, Platinotype processing, for the same three baths at 1:60 for about ten minutes each with the concentrated acid identified as 36 % w/w and ca. 12 M, the half-strength sepia bath, and the final wash of about 30 minutes. Section 6.16, Palladiotype processing, for Willis and Clements's unambiguous published figures converted to per cent w/v — developer trisodium citrate dihydrate (FW 294.10) 20 per cent w/v with citric acid (FW 192.12) 2.2 per cent w/v for 4 to 5 minutes; clearing bath trisodium citrate dihydrate 20 per cent w/v with citric acid 9 per cent w/v as a stock, "diluted 8x for use, to 2.5 % citrate + 1.1% citric acid", with three sequential baths of at least 10 minutes each and a final wash in running water for 30 minutes, and more dilute solutions (ca. 4x) for the Sepia Vellum paper — together with Paul L. Anderson's evidence that American workers did not adopt it, and his rule that Palladiotypes "must be cleared in 1:200 hydrochloric acid, not the 1:60 acid used for platinum, which otherwise dissolves palladium and bleaches the image partially", confirmed by McCabe and by Gottlieb in 1993. Section 6.17, Processing variations, for clearing "in 1:200 hydrochloric acid or dilute acidified citrate, according to the two 'traditions' of Palladiotype processing – US and UK", for the finding that the acid bath "will tend to etch away the 'fog' of palladium in the high values, especially if 1:60 dilution is used, so the two procedural faults in US processing tend to be self-cancelling", and for the deliberate short-clearing experiments simulating Stieglitz's impatience. Section 2.7, for the same self-cancelling pair of errors stated from the other side and for the expectation of "some loss of image densities compared with citrate clearing" when hydrochloric acid is used on a palladiotype. Section 1.9, for Paul Anderson's 1917 clearing bath for mercury-developed sepia platinotypes — "Water 300 ounces, Hydrochloric acid C. P. 1 ounce" for not more than two minutes in a single bath — and for Ware's judgement that "he was right in pointing out that such a dilute acid clearing bath would leave much residual iron in the paper", with the unanswered question of why a normal-strength acid bath should damage an image supposed to be pure platinum. Section 4.1, for Irving Penn's practice — the customary 30 per cent potassium oxalate developer with 0.5 per cent oxalic acid, clearing "in the traditional three baths of 1:64x diluted hydrochloric acid (37% w/v)", his own statement that a heavy coating "then requires a long time in the HCL to remove the residual iron. (6-10 hours seem to be what I require.)", the density loss in his palladium-containing images and the disintegration of many fine-art papers that followed those prolonged treatments, and his novel 5 per cent sodium bisulphite bath after the acid, of which he wrote "the paper seems to whiten and generally clear". Section 7.21, for the masked border as "a direct visual check, by comparison with the adjacent uncoated margins of the paper sheet, as to the completeness of clearing". Section 7.22, Wet processing procedure, for the modern EDTA sequence this page is measured against and for the instruction to examine the print for yellow stain in the borders of unexposed sensitizer under a bluish light. Section 7.23, for the statement that there is no convenient reagent for dissolving platinum images while "palladium is slightly attacked by dilute hydrochloric acid in air". Sections 8.5 and 8.6, for chalk-buffered papers, the precipitation of calcium oxalate, the hydroxide liberated by it, the pre-treatment of a buffered paper with 1 to 2 per cent v/v hydrochloric acid or 5 to 10 per cent w/v sulphamic acid, and the reason oxalic acid is the wrong choice for that job. Section 9.1, for Henry Chapman Jones's 1895 demonstration that unexposed Platinotype paper still held detectable iron after four hours in dilute hydrochloric acid, and for his observation of more iron in the darker parts of an image than the lighter. Section 9.2, Slow development of iron stains, for the recommendation of five to ten minutes in each of three successive baths at 1:60 followed by washing "for as much as two hours", for the statement that Palladiotypes "cannot be treated so brutally without incurring intolerable image loss" and that the necessity of the weaker 1:200 acid is one reason they are less well cleared and more susceptible to yellowing than Platinotypes, and for the point that commercial papers were coated to their very edges so that no clear margin existed against which to judge the clearing. Section 9.5, for the conservators' reductive treatments — 4 per cent sodium disulphite followed by dilute hydrofluoric acid, and the modern sodium dithionite and tetrasodium EDTA treatment at pH about 9 — with the redox potentials quoted on this page and the statement that chelating agents alone remove only about 50 per cent of the iron(III) from cellulose pulp. Section 9.6, for Matthew Clarke and Dana Hemmenway's XRF comparison at the National Gallery of Art and for the conclusion that "the iron-stain can be avoided entirely by printmakers today, even in palladium printing, by using - instead of hydrochloric acid – for the clearing baths, a reducing agent in concert with a modern chelating agent such as EDTA". Section 10.3, for the four stages of iron(III) hydrolysis and the timescales attached to each. Section 10.4, for the re-oxidation of iron(II) by air, slow in acid and rapid in base, and for the Fenton chemistry that scissions cellulose. Section 10.8, for the chemisorption of iron(III) to the vicinal hydroxyls of cellulose, the calico-printers' use of the same binding as a mordant, and the mu-oxo-bridged binuclear species proposed as the chromophore of the slow yellow stain. Section 10.9, for EDTA's four pKa values and the pH of each of its sodium salts. Section 10.10, Chemistry of clearing siderotypes, for the inventory of ions left in an exposed sensitiser layer, the rule that iron(III) hydrolyses above pH 4, the calcium equation, and the three-bath EDTA logic. Section 11.3, Table 11.1, for the redox potentials of the noble metals as their tetrachloro complexes — platinum +0.73 V, palladium +0.62 V — for the citrato-iron couple at +0.372 V, and for the statement that kinetic factors may make such reduction reactions too slow to be useful unless the noble-metal complex is sufficiently labile. The opening of Chapter 11 and section 11.4, Printing in palladium and platinum compared, for the statement that the characteristics and some of the difficulties of platinum printing "arise from the relative slowness of the chemical reactions of platinum complexes" where palladium "affords much speedier reactions; the greater vigour of its chemistry largely accounts for the differences between the two noble metals when used for photographic printing". Appendix VIII.1 and VIII.2, for the conversions used on this page: 1 grain = 0.0648 g, 1 ounce avoirdupois = 437.5 grains = 28.3495 g, 1 imperial fluid ounce = 28.413 cm3, 20 fluid ounces = 568.261 cm3, and 1 grain per fluid ounce = 0.228 per cent w/v; 6.1 Expression of solution concentrations, for the definition of % w/v and the objection to parts-by-weight-in-parts-by-volume recipes; 6.2 Ferric oxalate, for the polymorphism, the disputed formula weights, the 25 per cent standard solution and the 2 g per 100 cc of oxalic acid; 6.3 Potassium tetrachloroplatinate, for the disputed solubility, the 18.5 per cent standard solution and the 0.9 : 1 mixing ratio; 6.4 Health warning: platinum allergy; 6.5 Agents for increasing contrast, for the Pizzighelli and Hübl drop-counting system, the chlorate mechanism, the graininess and false sparkle, the hexachloroplatinate(IV) alternative and the dichromate-in-the-developer alternative; 6.6 Sodium tetrachloropalladate, for the two preparations of the 0.5 M solution and the equal-volume mixing; 6.10 Coating procedure, for specific coating volumes and weights; 6.11 Drying and humidity control; 6.15 Platinotype processing; 6.16 Palladiotype processing; 6.18 Partial reversal of tonality; 5.3 Pizzighelli's formulations, for the four stock solutions A B C D and the 5 : 6 : 2 and 5 : 4 : 4 ratios; 4.1 Irving Penn's initiative and Table 4.1, for Penn's four stock solutions; 1.16 Researches of Pizzighelli and Hübl; 2.11 Rôle of Paul Anderson in the USA; 11.1 Photochemistry of iron(III) oxalates; 11.3 Siderotype by reduction of noble metals, for the redox potentials; 11.4 Printing in palladium and platinum compared; 5.10 Electron microscopy, for the ellipsoidal platinum nanoparticles of 15 to 25 nm within the surface cellulose fibres; 10.10 Chemistry of clearing siderotypes, for the chemisorbed iron(III), the hydrolysis above pH 4, the calcium oxalate equation and the irreversible transformation to goethite; 2.4 Alternatives to Platinotype — Nicol's kallitype, for the 1889 invention, the naming, the dearth of surviving specimens and Anderson's and Child Bayley's condemnations; 10.10 Chemistry of clearing siderotypes, for iron(III) hydrolysis above pH 4, chemisorption to cellulose, the irreversible transformation to goethite and the calcium oxalate equation; 11.1 Photochemistry of iron(III) oxalates, for the Döbereiner reaction and the 0.022 g per 100 cc solubility of iron(II) oxalate; 11.3 Siderotype by reduction of noble metals, for the redox potentials of the oxalato and citrato iron couples and the table of noble-metal potentials; Appendix VII.3, the specification of Willis's British patent No 1117 of 15 March 1880, for tartrate of soda or of potash named among the developing salts; 2.8, for the launch of Palladiotype in 1917 under the platinum embargo and for W. H. Smith's Camera Club demonstration with baths of 5 per cent potassium citrate acidified with 0.26 per cent citric acid; 2.9, for Willis's recommendation of trisodium citrate at 20 per cent w/v with 2 per cent citric acid, for the clearing baths, for the comparative test of oxalate against citrate on palladium and its finding of higher density, warmer colour and perceptible chemical fog under oxalate, and for the Abel's Weekly statement that the Palladiotype baths do not injure the surface of the paper; 3.5 and 3.6, for the question of what Stieglitz actually developed his palladium prints in and for the platinum and mercury found in them; 3.8, for the suggestion that "sodium acetate" in the Steichen story may be a mishearing of sodium citrate; 6.5, for the contrast agents, for Willis and Clements recommending dichromate in the oxalate bath and for Ware's own refusal to use any of them; 6.8, for the black specks that appear less markedly under citrate than under oxalate; 6.16, for the converted figures — trisodium citrate dihydrate, FW 294.10, at 20 per cent w/v with citric acid, FW 192.12, at 2.2 per cent w/v, developed 4 to 5 minutes; for the clearing stock at 20 per cent citrate and 9 per cent citric acid diluted eightfold; for the fourfold dilution recommended for Sepia Vellum Palladiotype paper; and for Paul Anderson's evidence that American workers ignored all of it; 6.17, for the finding that oxalate reduces palladium(II) to some extent and fogs the high values, that it also gives a warmer colour and higher speed, and that the citrate bath leaves clear highlights; 6.18, for oxalate being slightly more effective than citrate at promoting tonal reversal; 9.11, for the plague of black spots increasing with the vigour of the developer and for a re-used developer remaining photosensitive; 10.3 and 10.10, for iron(III) hydrolysis above pH 4, chemisorption to cellulose and the irreversible transformation to goethite; 10.5, for the oxalato formation constants and the collapse of the iron redox potential on complexation; 11.1, for Doebereiner's photolysis, the 0.022 g per 100 cc solubility of iron(II) oxalate and the development equations; 11.3, for the citrato-iron potential of +0.372 V, the statement that it does not reduce platinum(II) or palladium(II) under the printing conditions, and Table 11.1 of noble-metal potentials; 11.4, for the kinetic contrast between platinum and palladium; Appendix VII.3, for the transcribed text of Willis's British patent No 1117 of 15 March 1880; Appendix VIII.2, for 1 grain per fluid ounce being 0.228 per cent w/v; Appendix V, for the formula weights; 1.4 Willis's three components, for the developer defined as the bath that dissolves the photochemically formed ferrous oxalate, and for ferrous citrate being too weak a reductant for platinum; 2.8 and 2.9 Processing of Platinotype and Palladiotype, for Willis's trisodium citrate developer at 20 per cent w/v with citric acid, the 5 per cent potassium citrate demonstration of 1917, the potassium oxalate developer it replaced and the reason Willis gave for the change; 6.5 Agents for increasing contrast, for the oxidant mechanism, the graininess it causes and Ware's own refusal to use such agents; 10.3 Hydrolysis and precipitation; 10.5 Coordination by oxalate, for the oxalate formation constants and the redox potential of the oxalato couple; 10.9 Chelation of iron; 10.10 Chemistry of clearing siderotypes, for iron(III) hydrolysis above pH 4, chemisorption to cellulose, the irreversible transformation to goethite and the calcium oxalate equation; 11.1 Photochemistry of iron(III) oxalates, for the Döbereiner reaction and the 0.022 g per 100 cc solubility of iron(II) oxalate; 11.3 Siderotype by reduction of noble metals, for the citrato couple at +0.372 V and the table of noble-metal potentials; Appendix VII.3, the specification of Willis's British patent No 1117 of 15 March 1880, for the citrate of soda developer; 10.10 Chemistry of clearing siderotypes — iron(III) chemisorbed to the hydroxylic functions of cellulose, its hydrolysis above pH 4 to a polymeric colloidal hydroxide, the irreversible transformation to insoluble iron(III) oxyhydroxide if it is not removed before the print dries, calcium from hard water or a chalk buffer promoting hydrolysis, and the disodium EDTA, sulphite and tetrasodium EDTA clearing sequence; 11.1 Photochemistry of iron(III) oxalates, for the photosensitivity of the citrate, malonate, tartrate and glycollate complexes and the Balzani and Carassiti mechanism for alpha-hydroxycarboxylato-iron(III) salts; 11.3 Siderotype by reduction of noble metals, for the redox potentials of the citrate couple and of the four noble metals; 11.1 Photochemistry of iron(III) oxalates, for the Balzani and Carassiti mechanism for alpha-hydroxycarboxylato-iron(III) salts and the statement that no clear criterion has emerged for what makes such a complex photosensitive; 10.10 Chemistry of clearing siderotypes, for iron(III) chemisorbed to cellulose, its hydrolysis above pH 4 to a polymeric colloidal hydroxide and the irreversible change to insoluble oxyhydroxide if it is not removed before the print dries; 4.2 and the timeline entry for 1985, for the Malde-Ware collaboration begun in 1982, the workshop manual The Ammonium System, the six innovations of the method and the introduction of the glass coating rod in 1986; 7.2 Sensitizer chemicals; 7.6 Iron solution preparation, for the formula weight 428.07, the molarity 1.40 M and the pH of about 5; 7.7 Platinum solution preparation, for the formula weight 372.98, 0.67 M and pH about 3; 7.8 Palladium solution preparation, for both methods, the formula weights 284.29, 53.49 and 177.31, 0.67 M and pH about 2; 7.9 Processing solutions, for the per-litre capacities, the citric acid conversion of tetrasodium to disodium EDTA and the alkali table for making either salt from H4EDTA; 7.11 and 7.12 with Table 7.1, Characteristics of print-out platinum-palladium sensitizers; 8.4 Development versus print-out processes; 10.5 Coordination by oxalate, for the stepwise formation constants, the free oxalate in equilibrium and the redox potentials; 10.6 Solubility of potassium ferrioxalate, for why potassium is excluded and for the statement that the Malde-Ware method uses 0.7 molar ferrioxalate; 10.10 Chemistry of clearing siderotypes, for the three baths and their equations and for Clarke and Hemmenway's XRF comparison; 11.1 Photochemistry of iron(III) oxalates, for the Hatchard and Parker mechanism, the quantum yield and the ligand-to-metal charge transfer band; 11.3 Siderotype by reduction of noble metals, for the table of redox potentials; 11.4 Printing in palladium and palladium compared, for the lanthanide contraction, Table 11.3 and the XRF measurements of image composition; 11.5 Effects of gelatin sizing on platinum printout; 11.7 Aquation of platinum(II) and palladium(II), for the equilibrium constants and the 2.4 hour half-time; 11.8 The iron(II)-platinum(II) redox reaction; 11.11 The 'inhibited edge' effect; 11.13 Choice of cation, for the structure-breaking argument and the two enthalpies of solution; 11.14 Optical properties of metal nanoparticles and the eighteen factors governing image colour; Appendix VII.1, VII.2, VII.3, VII.4 and VII.6, for the transcribed texts of William Willis's British patents No 2011 of 5 June 1873, No 2800 of 12 July 1878, No 1117 of 15 March 1880, No 1681 of 2 February 1887 and No 20,022 of 4 September 1913, and in particular for the 1880 sentence "The developing solution of potassic oxalate is made by dissolving one hundred and twenty (120) grains or more of the salt in one fluid ounce of water"; Appendix VIII.1 and VIII.2, for the grain, the imperial fluid ounce, the avoirdupois pound and the statement that 1 grain per fluid ounce is 0.228 per cent w/v; Appendix VIII.3, for 1 grain per square foot being 0.6975 g/m2; Appendix V, for the formula weights of potassium oxalate monohydrate and potassium tetrachloroplatinate(II) and their hazard summaries; 1.6 and 1.7, for Willis's three chemical obstacles, the unidentified French chemist's note, his having to prepare the salt himself, and the collapse of the 1888 platinum-in-the-bath developer; 1.8, for Willis's own 1892 statement of what cold development achieved and for the fact that he never published it; 1.9, for sepia platinotype, the hot developer at 140 to 160 F, the double tones, the 1893 glycerine experiments and W. H. Smith's 1911 refusal to advocate mercury in developers; 2.8 and 2.9, for the processing of platinotype and palladiotype, the 25 per cent and near-saturated 33 per cent strengths, the hot bath at 140 to 170 F, the shift to cold development after 1892, the Special D Salts analysis and working strengths, and the hydrochloric acid clearing sequence; 2.11, for Paul Anderson's near-saturated oxalate developer for palladium; 3.5 and 3.6, for the platinum and mercury found in Stieglitz's palladium prints and the used-developer explanation; 4.2, for Irving Penn's 30 per cent oxalate with 0.5 per cent oxalic acid; 5.7, for Satista; 6.5, for contrast agents and the dichromate added to the developer bath; 6.15, 6.16 and 6.17, for Willis's 120 to 130 grains per fluid ounce, the saturated later practice, Ware's own 28 per cent standard, the rule that the bath be neutral or barely acid, the 0.1 per cent and 2 per cent oxalic acid additions, and the comparison of oxalate against citrate development for palladium; 7.22 and 7.25, for the substitution of a 30 per cent oxalate bath for the first EDTA bath in pure platinum printing; 9.11, for the plague of black spots and the photosensitivity of a re-used developer; 9.13, for the direct reduction of tetrachloroplatinate by oxalate; 10.3, for the four stages of iron(III) hydrolysis; 10.5, for the stepwise formation constants of the oxalato-iron(III) complexes and for the collapse of the iron redox potential on complexation; 10.10, for the clearing sequence and the rule that iron(III) hydrolyses above pH 4; 11.1, for Doebereiner's photolysis, the 0.022 g per 100 cc solubility of iron(II) oxalate and the development equations; 11.3, for Table 11.1 of noble-metal redox potentials and the citrato-iron potential; 11.4, for the kinetic contrast between third-row platinum and second-row palladium and for the fibrous image that results when the salts wash out before they react; 11.9 and 11.10, for chloride scavenging, Borlinetto's copper chloride, Jacoby's zinc oxalate and the bisoxalatomercurate(II) complex; Appendix III, the chronology, for the patent dates, the 1892 cold development paper and the 1893 glycerine development; 11.7 aquation of the tetrachlorometallate anions; 11.8 stoichiometry; Willis's palladiotype developer and clearing baths; 9.6 Clearing agents: the redox potential of ascorbic acid quoted as varying from -0.283 to -0.066 V as the pH varies from 2 to 7, citing Borsook and Keighley 1933; Section 6.12, where a step tablet's exposure scale is read directly from the printed steps because there is no Callier effect in contact printing; Section 6.12, where the exposure scale of a step tablet is read directly because there is no Callier effect in contact printing; and section 7.19, ultraviolet light sources - long-wave ultraviolet or UVA covering 320 to 400 nm with a maximum output around 365 nm, calculated in section 12.5 to be the optimum wavelength for the siderotype processes, and the warning against short-wave mercury lamps; Table 11.1, Redox potentials of noble metals — platinum E(PtCl4^2−/Pt,4Cl−) +0.73 V and E(PtBr4^2−/Pt,4Br−) +0.68 V, palladium E(PdCl4^2−/Pd,4Cl−) +0.62 V and E(PdBr4^2−/Pd,4Br−) +0.60 V, silver E°(Ag+/Ag) +0.80 V, gold E(AuCl4−/Au,4Cl−) +1.00 V and E(AuBr4−/Au,4Br−) +0.87 V, mercury E°(Hg2+/Hg) +0.85 V; and the accompanying statement that the ferrous complex is a weaker reducing agent than the oxalato-complex and does not reduce platinum(II) or palladium(II) although it will reduce gold(III) and silver(I) under the printing conditions, the ease of reduction being reflected in the relative values of the redox potentials; Table 7.1, Characteristics of print-out platinum-palladium sensitizers, cited here for its stated measurement condition rather than for its figures - the exposure range given as delta log H from fog plus 0.04 to 0.9 Dmax, read in reflectance on an X-Rite 312 - which is the pair of endpoints this course adopts for every exposure-scale figure it measures itself, and for the exposure ranges tabulated against 32, 55 and 80 per cent relative humidity that make humidity a contrast control in the noble-metal processes and not in cyanotype.; 6.5 Agents for increasing contrast — the statement that the unmodified platinotype sensitiser has a very long exposure scale of about 2.0, that the drop-counting chlorate system of Pizzighelli and Hübl became standard practice with users whose negatives presumably have insufficient density range, that potassium chlorate reoxidises some of the iron(II) photoproduct and so truncates the exposure scale, that its use can cause image deterioration and graininess, and that with modern negative-making these contrast agents become unnecessary when a correctly calibrated negative is made. 6.10 Coating procedure — specific sensitiser coating volumes per unit area for typical papers falling in the region of 24 to 36 cm3/m2, the guide of 1.4 cm3 for each 21 by 26 cm area on Cranes 100 per cent cotton paper, four or five passes of the coating rod taking about half a minute in total, and the note that papers differ in absorptivity. 4.1 Irving Penn's initiative — the reconstruction of Penn's brush-coating practice giving a specific coating volume of 46 cm3/m2 from his own observation that 28.5 cc barely sufficed to coat two 20 by 24 inch sheets, or 61 cm3/m2 on the three-plate reading, against the parenthetical statement that economical rod coating requires about 30 cm3/m2, and the estimate of about 0.05 cm3 for the volume of one drop. 6.11 Drying and humidity control — ambient relative humidity of about 55 plus or minus 5 per cent in the author's studio, at least one hour allowed for the paper to equilibrate, the commercial imperative of complete desiccation for shelf life with Willis's tins of anhydrous calcium chloride, and the simulation by heat drying at 45 degrees C for 10 minutes followed by storage in a calcium chloride desiccant chamber at about 9 to 27 per cent relative humidity. 6.12 Test target images — the author's target of eight Stouffer T3110 step tablets of 31 steps in increments of 0.1, the rubylith-masked regions that report on residual substances in coated but unexposed areas, and the rule that because there is no Callier effect in contact printing the exposure scale equals the density range between the last step printing maximum black and the first step printing paper white, given for the T3110 tablet as the difference of the two step numbers divided by ten. 6.13 Ultraviolet light source — the rejection of sunlight as too variable for controlled investigation especially in the United Kingdom, the Philips facial tanning unit of six 20 watt UVA actinic tubes peaking near 365 nm which is calculated to be the optimum wavelength for the siderotype processes, and the five minute run-up before each test exposure with the note that the tubes take about three minutes to reach steady output. 7.12 Sensitizer characteristics and Table 7.1 — the exposure range defined as delta log H from fog plus 0.04 to 0.9 Dmax with development quoted in log H units where zero is total print-out, the note that the parameters vary with the paper, and the tabulated values: platinum 1.5 at 32 and 55 per cent relative humidity and 1.8 at 80 per cent; palladium 2.0, 2.2 and 2.4 at 32, 55 and 80 per cent; platinum-palladium 3 to 1 giving 1.6, 2.0 and 2.2; and platinum-palladium 1 to 1 giving 1.6, 1.8 and 2.0; with the observation that platinum loses speed as humidity rises while palladium gains it, so that mixtures vary little with humidity. 7.13 Choice of print contrast — contrast fine-tuned by the platinum to palladium ratio or by regulating the humidity of the sensitised paper before exposure. 7.17 Drying and storage — about an hour at room temperature and humidity in the dark, or 40 degrees C air for about 10 minutes, with sensitised paper used within a few hours or stored light-tight and air-tight over silica gel or anhydrous calcium chloride below 10 per cent relative humidity, which is stated to keep for six months without loss of quality. 7.18 Humidifying — the statement that the key to the print-out process lies in controlling the humidity of the sensitised paper just before exposure, optimum results between 50 and 80 per cent ambient relative humidity, only partial print-out and considerable development below 50 per cent, weakening of maximum density above 80 per cent because the sensitiser diffuses too deeply into the paper, the humidifying tank over a saturated salt solution with ammonium chloride at 80 per cent, sodium chloride at 76 per cent and calcium nitrate tetrahydrate at 56 per cent, the requirement of excess solid salt in contact with its saturated solution, a minimum of half an hour in the tank for evenness, and the alternative of pure water at 100 per cent relative humidity where 5 to 20 minutes gives a warm-toned result and 30 to 40 minutes a fuller print-out and colder tone while more than an hour weakens the image and causes clearing problems. 7.19 and 7.20 — the same aspect-value blur table as the Cyanomicon and the statement that negatives should have a long density range at UVA wavelengths of at least 1.8 for platinum and as much as 2.4 for palladium, that with the widespread use of inkjet internegatives optical densitometry is of little value so the correct density range is arrived at empirically, and that the print-out process is self-masking in regions of high print density so the shadows do not block up as they do in a development paper. 8.5 Criteria for siderotype papers — the greater than 98 per cent alpha-cellulose furnish of cotton or linen alone with the warning that mixed furnish causes fibrous granularity or blotchiness, wove rather than laid, hot-pressed or cold-pressed surfaces with the note that some heavily calendered papers swell and roughen on wet processing, internal sizing with alkyl ketene dimer given with its reaction with the glycosidic hydroxyl groups of cellulose to form a cellulose alkyl beta-keto ester where the alkyl group is hexadecyl, weights of about 160 g/m2 to 360 g/m2 with the pounds-per-ream conversion, the prohibition on alkaline reserve with the calcium oxalate precipitation and the hydroxide-driven hydrolysis of ammonium ferric oxalate and the pretreatment of 1 to 2 per cent v/v hydrochloric acid or 5 to 10 per cent w/v sulphamic acid for 10 to 20 minutes with the note that oxalic acid is chemically inappropriate, the requirement that the quoted pH be below 7 and the observation that this runs contrary to usual paper conservation thinking, the prohibition on optical brightening agents, wet strength agents, retention aids, bleaches, dyes and pigments with the statement that the greatest imponderable in plain paper printing is the effect of papermakers' additives which they are usually reluctant to disclose and that each commercial paper has its own idiosyncrasies which may vary from batch to batch or be changed without notice, the requirement of porosity to allow the photochemically evolved carbon dioxide to diffuse to the verso with the note that china clay fillers and gelatin surface sizing block the pores, and the unproven suggestion that biocides and microbial colonies may cause blotchiness. 8.6 Conflicting standards of archival papers — the same Roberts quotation and the same summaries of ISO 9706:1994 and ISO 11108:1996. 9.10 and 9.11 — the hypothesis that randomly distributed black spots arise from microcrystals of iron(II) oxalate precipitated in the coated layer by reducing-agent impurities or additives in the paper such as aldehydes used to harden gelatin size or sulphites used in pulp treatment, that they are paper-dependent, that they worsen with the vigour of the developer and are more common with palladium than platinum, and that they have never been observed with the print-out ammonium iron(III) oxalate version. 5.4 Sizing agents in Willis's papers — the iodine spot test using 5 per cent w/v iodine and 10 per cent w/v potassium iodide in water, known as Lugol's solution, performed by Sarah Wagner at the National Gallery of Art, which showed the presence of starch in the KK, AA and Japine Platinotype papers, and the gas chromatography and mass spectrometry that identified rosin in the sensitised side of KK. 5.5 X-ray spectrometry — the elements detected in Willis's KK Platinotype paper and their suggested origins, with copper listed as a queried paper impurity possibly from the brass blades of a Hollander beater. 11.6 Characteristic curves by densitometry — step tests of the Malde-Ware print-out version read on an X-Rite 312 densitometer in reflectance mode, giving palladium the longest exposure scale at delta log H about 2.4 with a mid-tone slope of about 0.78 against platinum at about 1.9 and 0.96, mixtures giving intermediate values, and a maximum density of about 1.45 for most of the tests. 3.11 Composites with cyanotype and gum printing — the statement that the new cyanotype process has about the same exposure scale as the platino-palladiotype so a single negative serves both, whereas the classical cyanotype process cannot render the density range of a negative made for platinum-palladium.; 2.4 Alternatives to Platinotype, Nicol's kallitype — the invention in 1889 by Dr W. W. J. Nicol, an academic chemist at Mason College, Birmingham, the name from the Greek for beautiful, Nicol's 1891 letter to the British Journal of Photography stating his motive, the commercial failure of the Birmingham Photographic Company's paper through a faulty paper stock that caused rapid fading, the dearth of surviving historical specimens, Anderson's 1913 condemnation and Child Bayley's account of a batch that bore no sign to distinguish the front of the paper from the back, Stevens's objection to both, and the observation that the few identified century-old specimens show pronounced fading and seriously yellowed highlights; 10.10 Chemistry of clearing siderotypes, for iron(III) chemisorbed to cellulose, its hydrolysis above pH 4 and the irreversible transformation to insoluble iron(III) oxyhydroxide if it is not removed before the print dries; 11.3 Siderotype by reduction of noble metals, for the redox potentials of the oxalato- and citrato-iron(III) couples and of silver, platinum, palladium and gold; 10.10 Chemistry of clearing siderotypes — the inventory of what remains in the sheet after printing, the statement that the chief problem for effective clearing is iron(III), some of it chemisorbed to the hydroxylic functions of cellulose, that above pH 4 iron(III) hydrolyses to a polymeric colloidal hydroxide which lodges in the fibres and imparts a yellow stain, that calcium from hard water or a chalk buffer precipitates calcium oxalate and promotes hydrolysis, and that freshly formed iron(III) hydroxide can be redissolved in dilute acid initially but if not soon removed transforms irreversibly into iron(III) oxyhydroxide, the mineral goethite, which is quite insoluble in dilute acids — hence the instruction to remove all the iron before the print dries; the three-bath sequence with its reasons, disodium EDTA at about 5 per cent and pH 3 to 4 which suppresses hydrolysis and chelates iron(III), the explicit warning not to use tetrasodium EDTA for the first bath despite its being recommended by a supplier because at pH about 10 the iron(III) is hydrolysed rather than complexed with eventual yellow or brown staining, a sodium sulphite or disulphite bath at about 2.5 per cent made fresh each session because it oxidises in air to sulphate and intended to reduce residual iron(III) still bound to the cellulose to iron(II) which is less strongly bound and less extensively hydrolysed, and a tetrasodium EDTA bath at about 5 per cent and pH 9 to 10 which is the optimum for chelating iron(II) and leaves the sheet alkaline; and the report that Matthew Clarke and Dana Hemmenway found this procedure the most effective of all they tested by X-ray fluorescence, leaving residual iron comparable with or less than the original iron content of the uncoated paper, with accelerated ageing producing no perceptible yellow stain. 10.9 Chelation of iron, for the four acid dissociation constants of H4EDTA at pK 2.0, 2.7, 6.2 and 10.3, for the consequence that mono- and disodium salts are mildly acidic at pH 3 to 4 while the tetrasodium salt is alkaline at pH 9 to 10, for EDTA's four carboxylato and two tertiary amino donor groups occupying up to six coordination positions, and for the peak formation constant of the iron(II) EDTA complex of 2 x 10^14 at about pH 10. 9.6, for the finding that even powerful chelating ligands such as CDTA and DTPA remove only about 50 per cent of the iron(III) from suspensions of cellulose pulp, and for the reductive route using sodium dithionite with tetrasodium EDTA. 10.8 Staining of cellulose by iron(III), for the strong binding of iron(III) to cellulose and for the proposed oxo-bridged binuclear species whose metal-to-metal charge transfer absorbs strongly in the visible and produces a brown colour. 2.4 Alternatives to Platinotype, for the survival record of historical kallitypes, Stevens's finding of a single specimen in a survey of many major American collections, the handful reported to the author by curators and conservators, and the statement that the few identified century-old specimens show pronounced image fading and seriously yellowed highlights suggesting the presence of residual iron(III), together with the observation that current practitioners hedge their bets by toning with platinum, palladium or gold and that Sandy King claims toning totally replaces the silver rather than coating it. 4.7, for the identification characteristics of a platinotype and for the note that pale yellow or straw-coloured staining probably due to residual iron(III) may also occur in other siderotype processes such as kallitype, and for the slightly invasive hydrogen peroxide test in which platinum in an image catalyses the evolution of oxygen while pure palladium prints do not respond; 6.5 Agents for increasing contrast — Pizzighelli and Hübl's 1882 drop-counting system of three sensitiser solutions with controlled amounts of potassium chlorate, its reiteration by Anderson and its adoption as standard practice today; the statement that potassium chlorate is a strong oxidising agent whose effect is to re-oxidise some of the iron(II) photoproduct, thereby making it unavailable for reducing platinum(II) and so truncating the exposure scale of the process and giving a more distinct tonal separation; the note that chlorate can cause a deterioration in image quality and an increase in graininess and that the 'false sparkle' of lost gradation in empty highlights is aesthetically unacceptable for the platinotype ethos; sodium hexachloroplatinate(IV) as an alternative mild oxidising agent, sold at a very high price and said to cause less image deterioration, with the conflicting opinions about whether it works with palladium and the incompatibility with ammonium cations; Willis & Clements' recommendation of a very small amount of potassium dichromate in the potassium oxalate developer bath to achieve "brilliant prints", its use by Paul Strand and Ned Scott on flat negatives, and the note that dichromate reacts readily with oxalic acid and is reduced to oxalato-chromium(III) complexes so the additive will not be stable in an oxalate developer indefinitely and will lose effectiveness especially at low pH; and Ware's own conclusion that with modern negative-making these contrast-enhancing agents become unnecessary when a correctly calibrated negative is made, that he avoids "these undesirable image-degrading agents", and that the negatives should be made correctly in the first place. 6.11 Drying and humidity control, for ambient relative humidity around 55 per cent and at least an hour to equilibrate, and for the desiccated storage of sensitised platinotype paper. 11.16 Control of humidity and Table 11.4, for the effect of relative humidity on the colour of a platinum-palladium print-out. 11.15 Factors influencing image colour, for gelatin sizing protecting nanoparticle metals and favouring smaller particles and warmer colours, and for residual iron(III) from imperfect clearing. 11.6 Characteristic curves by densitometry, for the unmodified platinotype sensitiser's very long exposure scale of about 2.0 and for step tablets with a density range of about 3 always exceeding the process's exposure scale of no more than about 2.4. Footnote 595, for the redox potential E(ClO3-, 6H+/Cl-) = +1.45 V; 6.2 Ferric oxalate — the substance as a chemists' nightmare, ill-characterised, evidently polymorphic, apparently uncrystallisable, with a structure unknown until one polymeric form was solved in 2015, notoriously variable in composition and properties according to the method of preparation and therefore the supplier, listed by very few fine chemical houses and usually about a hundred times the price of ferrous oxalate, with formula weights quoted from 375.76 anhydrous through 447.81, 465.83 and 483.84 for the hexahydrate, slow and difficult to dissolve although finally very soluble, and solutions said by some to decompose in six to nine months in the dark, with the note that at least one well-respected platinum printer makes up fresh ferric oxalate the night before every printing session; VI.2 Ferric oxalate, for the statement that the properties of the solutions and solids resulting from the preparation methods vary considerably, and for the four chemically distinct routes — precipitation of iron(III) hydroxide and dissolution in oxalic acid, precipitation and peroxide oxidation of iron(II) oxalate, the reaction of solid iron(III) nitrate with solid oxalic acid, and double decomposition of barium oxalate with iron(III) sulphate; 11.1 Photochemistry of iron(III) oxalates, for the insolubility of iron(II) oxalate at 0.022 g per 100 cc, the statement that it cannot reduce a noble metal salt in aqueous solution unless solubilised by complexation with oxalate, and the quantum yield of about 1.2 between 250 and 420 nm; 10.5 Coordination by oxalate, for the redox potential of the oxalato couple at +0.02 V and for the free oxalate present in a concentrated ferrioxalate solution; 10.10 Chemistry of clearing siderotypes, for iron(III) chemisorbed to cellulose, hydrolysis above pH 4, the irreversible transformation to goethite on drying and the calcium oxalate equation; 11.15 Factors influencing image colour, for the four properties that set the colour of a nanoparticle image and for the effect of gelatin sizing in favouring smaller particles and warmer colours; 2.4 Alternatives to Platinotype — the survival record of historical kallitypes, Stevens's single specimen from a survey of many major American collections, the handful reported by curators and conservators, the statement that the few identified century-old specimens show pronounced image fading and seriously yellowed highlights suggesting residual iron(III), and the author's own identification in early twentieth-century amateur archives of probable kallitypes mostly very deteriorated and showing severe iron stains, fogging and fading; 4.7, for the identification characteristics of a platinum print and for the note that pale yellow or straw-coloured staining probably due to residual iron(III) may also occur in other siderotype processes such as kallitype; 6.2 Ferric oxalate, for the variability of the substance with the method of preparation, for solutions said by some to decompose in six to nine months in the dark, and for the practice of one respected printer who makes a fresh solution the night before every session; 10.10 Chemistry of clearing siderotypes, for iron(III) chemisorbed to cellulose, hydrolysis above pH 4, the irreversible conversion to goethite if the print dries with the hydroxide still in it, and the promotion of hydrolysis by calcium from hard water or a chalk buffer; 10.5 Coordination by oxalate — the trisoxalatoferrate(III) anion and its stepwise formation constants K1 about 10^9, K2 about 10^7 and K3 about 10^4 for an overall Kf of about 10^20; the statement that complexation by oxalate diminishes the redox potential from the standard value Eo(Fe3+/Fe2+) = +0.771 V to E(FeIII(C2O4)3^3-/FeII(C2O4)2^2-) = +0.02 V; and the explanation that the difference follows from oxalate binding iron(III) with Kf about 10^20 against about 10^5 for iron(II). 11.1 Photochemistry of iron(III) oxalates — Doebereiner 1831, the solid-state equation, the solubility of iron(II) oxalate at 0.022 g per 100 cc, the statement that it cannot reduce platinum(II) or palladium(II) in aqueous solution unless solubilised by complexation with oxalate ions, the Hatchard and Parker radical mechanism, the ligand-to-metal charge transfer band at lambda max 260 nm, the measured quantum yield of about 1.2 between 250 and 420 nm falling slightly to 0.9 at 500 nm and very sharply thereafter, the independence of quantum yield from pH, and the photosensitivity of the citrate, malonate, tartrate and glycollate complexes with the Balzani and Carassiti mechanism for alpha-hydroxycarboxylato-iron(III) salts. 11.3 Siderotype by reduction of noble metals — the oxalato-iron(II) complex as a moderate reducing agent, the EDTA couple at -0.12 V, the citrato couple at +0.372 V with the statement that it is a weaker reducing agent than the oxalato-complex and does not reduce platinum(II) or palladium(II) although it will reduce gold(III) and silver(I) under the printing conditions, and Table 11.1 giving E(PtCl4^2-/Pt) +0.73 V, E(PdCl4^2-/Pd) +0.62 V, Eo(Ag+/Ag) +0.80 V, E(AuCl4^-/Au) +1.00 V and Eo(Hg2+/Hg) +0.85 V. 11.15 Factors influencing image colour — the four physico-chemical properties that set the colour of a nanoparticle image, and the governing effect of the water in the fibres on particle size, with a large reservoir permitting larger and more neutral particles and a restricted pool constraining the chemistry to small particles that show marked colours, brown or sepia for silver and palladium; the effect of surfactants and of gelatin sizing in protecting smaller particles and warming the colour. 12.3 Absorbance of the photoactive species — the internal filter effect, the statement that it is substantially absent in iron-silver sensitizers, and the stoichiometric ratios Fe:Ag = 1:1 against Fe:Pt(II) and Fe:Pd(II) = 2:1. 6.2 Ferric oxalate — the substance as a chemists' nightmare, ill-characterised, polymorphic, apparently uncrystallisable, notoriously variable with the method of preparation, listed by very few fine chemical houses and usually about a hundred times the price of ferrous oxalate, with formula weights from 375.76 anhydrous to 483.84 for the hexahydrate, slow and difficult to dissolve, and a solution said by some to decompose in six to nine months in the dark; 1.6 to 1.9, for Willis's invention, the patents of 1873 and 1878, the founding of the Platinotype Company in 1878, the cold-development paper of 1892 and the sepia papers made with mercury; 2.3 Price history of platinum; 2.6 to 2.8, for the 1916 embargo and the launch of Palladiotype in 1917; 6.4 Health warning, platinum allergy; 6.10 Coating procedure, for the specific coating volumes of 24 to 36 cm3/m2 and the guide of about 1.4 cm3 for an 8 by 10 area; 6.11 Drying and humidity control; 6.15 and 6.16 for the two processing traditions; 6.18 Partial reversal of tonality; 7.12 Table 7.1, for the relative speeds, exposure ranges and colours against relative humidity; 9.5, for the Clarke and Hemmenway accelerated ageing study; 9.7 Acidity catalysed by platinum; 11.3 Table 11.1 of redox potentials and Table 11.2 of siderotype processes; 11.4, for the comparison of the two metals; 11.6, for the exposure scales of about 2.4 and 1.9 and the maximum density of about 1.45; 1.7 Willis's Platinotype Company of London, for the first commercial papers of 1879 at one shilling for a demy sheet and about fourpence a square foot; 2.2 Platinum catalysis, for Ostwald's 1902 discovery and the strategic premium that followed; 2.3 Price history of platinum, for the German ban of 1901, the 1920 peak at 800 shillings per troy ounce and the 1931 minimum of 93 shillings; 2.6 Platinotype embargoed in Britain, for the 1916 embargo and the statement that by 1920 the price had risen to five times that of 1900; 2.7 Palladium supplements platinum, for palladium at 6 pence a grain or 12 pounds an ounce against about 2 pounds an ounce for platinum in the 1890s; 3.7 Tonal reversal; 3.8 Steichen's treatment of Stieglitz's Palladiotypes; 3.9 Problems of conserving Palladiotypes, for the suspicion that the treated prints re-yellowed and for Severson's 1984 finding that optical densities of a Stieglitz palladium print had increased by 30 per cent in the mid-tones and 15 per cent in the shadows after travel; 3.10 Paul Strand's platinum prints and the Warm Black Japine paper; 4.1 Irving Penn's initiative, for his clearing times of six to ten hours, his density loss in palladium-containing images and the disintegration of many fine-art papers he tested; 6.10 Coating procedure, for the specific coating volumes of 24 to 36 cm3/m2 and the coating weights of 6 to 9 millimol/m2; 6.6 Sodium tetrachloropalladate, for the 0.5 M standard solution; 9.5, for the Clarke and Hemmenway accelerated ageing at 70 degrees and 75 per cent relative humidity for four weeks, and its finding that stain correlated with residual iron, was worse for palladium than for platinum, occurred without any platinum salt present and was greater on gelatin-sized papers; 9.7 Acidity catalysed by platinum, for the 1989 sulfur dioxide experiment, its pH figures and Ware's own arithmetic on how far the exposure exceeds anything a print has met; 9.8 Offset imaging, autoplatinography, for the NARA results of 2013 to 2014 and the finding that untoned silver prints on specialist papers also cause offsetting; 11.4 Printing in palladium and platinum compared, for the statement that very few practitioners attempt pure platinum, the XRF ratios from a 1:1 sensitiser, the recommendation of a 2:1 sensitiser and the note that palladium is not as resistant to chemical attack as platinum and may be less permanent archivally, especially if chemical treatments are later applied; 2.9 Processing of Platinotype and Palladiotype, for the hot bath of 60 to 77 degrees and the three hydrochloric acid baths of about ten minutes each followed by a 20 to 30 minute wash; 6.13 Ultraviolet light source, for the 120 W UVA unit and its five-minute run-up; 6.14 Exposure determination, for the third-of-a-stop test-strip method and the standard 5 or 10 minute exposures; 6.15 Platinotype processing, for Willis's 120 to 130 grains per fluid ounce, the later saturated practice at about 32 per cent, the 28 per cent standard used in Ware's own work, the neutral-or-just- acid rule and the Special D Salts composition; 6.16 Palladiotype processing, for Willis and Clements' trisodium citrate developer at 20 per cent with 2.2 per cent citric acid for 4 to 5 minutes, the citrate clearing stock diluted eightfold in three baths of at least ten minutes, the 30-minute wash, and Anderson's evidence about American practice and the 1:200 acid; 6.17 Processing variations, for the oxalate developer fogging palladium highlights brownish-grey and the self-cancelling pair of errors; 6.18 Partial reversal of tonality; 7.22 Wet processing procedure; 9.2 Slow development of iron stains, for the masked-margin argument and the five-to-ten minute clearing times; 9.5, for the Clarke and Hemmenway accelerated-ageing study at 70 degrees and 75 per cent relative humidity for four weeks and its finding that stain correlated with residual iron and was worse for palladium than for platinum; 9.6 Conservation treatments for iron stains, for the disulphite reduction chemistry and its redox potentials; 9.7 Acidity catalysed by platinum, for the recommendation of a reducing agent with a modern chelating agent in place of hydrochloric acid and the statement that accelerated ageing of Malde-Ware prints produced no stain; 9.11 Black spots in platinum-palladium prints, for the photosensitivity of a re-used developer; 10.10 Chemistry of clearing siderotypes, for the chemisorbed iron(III), the hydrolysis above pH 4 and the irreversible transformation to goethite; 11.3 for the EDTA iron couple at -0.12 V; 1.6 William Willis's invention, for the 1872 start, the platinic chloride failures, the turn to the platinous salts in 1873 and the patent of 5 June 1873; 1.7 Willis's Platinotype Company of London, for the silver-free print of 17 March 1878, the 1878 patent, the founding of the company in 1878 rather than 1879, the first commercial papers of 1879 and the removal of the lead salt after Spiller's 1880 tests; 1.8 Perfection of Platinotype, for the 1892 cold-development paper, the secrecy, the loss of the Company's records in the Blitz and the acidic embrittlement of the substrate; 1.9 Sepia Platinotype with mercuric salts, for the mercury sensitiser, the "double tones" problem, the 1885 marketing, the 1911 warning by W. H. Smith and the 1915 demonstration of faded specimens; 1.16 Researches of Pizzighelli and Hubl, for the 1882 publication, the Voigtlander Prize, the English translation of 1883 and Pizzighelli's 1887 print-out discovery using sodium ferric oxalate; 2.2 Platinum catalysis and 2.3 Price history of platinum, for Ostwald's 1902 ammonia oxidation, the German ban of 1901, the 1920 peak of 800 shillings per troy ounce and the 1931 minimum of 93 shillings; 2.6 Platinotype embargoed in Britain, for the 1916 embargo and the 1918 resumption; 2.7 Palladium supplements platinum, for Wollaston's 1803 discovery, Burnett's 1856 suggestion, von Hubl's 1895 recommendation of a palladium admixture and the humidity dependence he records; 2.8 Palladiotype launched by Willis, for the 1917 date; 2.9 Processing of Platinotype and Palladiotype; 5.10 Electron microscopy, for the ellipsoidal platinum nanoparticles of 15 to 25 nm within the surface cellulose fibres; 6.1 Expression of solution concentrations; 6.2 Ferric oxalate, for the polymorphism, the disputed formula weights and the 25 per cent standard solution; 6.3 Potassium tetrachloroplatinate, for the disputed solubility and the 24-hour maturation; 6.4 Health warning, platinum allergy, for the 1911 identification and the statement that palladium remains available to an allergic printer; 6.5 Agents for increasing contrast, for the chlorate mechanism, the exposure scale of about 2.0 for the unmodified sensitiser, and the judgement that a calibrated negative makes contrast agents unnecessary; 6.6 Sodium tetrachloropalladate, for the two preparations of the 0.5 M solution; 6.7 Salts of mercury(II) and lead(II), for the patent strengths and the glycerine method; 6.15 Platinotype processing and 6.16 Palladiotype processing; 6.18 Partial reversal of tonality; 7.11 Sensitizer composition and image colour; 7.12 Sensitizer characteristics and Table 7.1; 7.13 Choice of print contrast; 8.2 Water content of cellulose, for the 8 per cent by weight at 70 per cent relative humidity and the ten water molecules per sensitiser ion; 9.7 Acidity catalysed by platinum, for the 1989 sulfur dioxide experiment and its figures; 9.8 Offset imaging, autoplatinography, for the five hypotheses and the NARA results of 2013 to 2014; 11.3 Siderotype by reduction of noble metals, for Table 11.1 of redox potentials and Table 11.2 of siderotype processes; 11.4 Printing in palladium and platinum compared, for the lanthanide contraction, the XRF ratios from a 1:1 sensitiser and the recommendation of a 2:1 sensitiser; 11.6 Characteristic curves by densitometry, for the exposure scales and the maximum density of about 1.45; 11.7 Aquation, for the equilibrium constants and the 2.4-hour half-time; 11.8 The iron(II)-platinum(II) redox reaction, for the outer-sphere pathway and the overall stoicheiometry; 11.9 Effects of mercury(II), lead(II) and silver(I), for the chloride-scavenging hypothesis; 3.4 Multiple coating of platinum papers, for Kosel's double-coating of about 1913, Struss's "multiple printing" of 1913 and his observation that repeated printings add to the blacks while the print seems to lighten; 6.3 Potassium tetrachloroplatinate, for the near-saturation that made double-coating necessary; 6.11 Drying and humidity control, for the ambient 55 per cent plus or minus 5, the hour's equilibration and the calcium chloride desiccant chamber at 9 to 27 per cent; 6.12 Test target images, for the eight identical Stouffer T3110 step tablets on one sheet allowing subsequent division and differential processing; 6.13 and 6.14, for the 120 W UVA unit, the five-minute run-up and the third-of-a-stop test-strip method; 6.15 and 6.16 for the developers; 6.17 Processing variations, for the oxalate developer fogging palladium highlights brownish-grey and the citrate bath leaving them clear; 6.18 Partial reversal of tonality, for the six factors and the note that with pure ferric oxalate under dry conditions there is very little print-out at all while 2 per cent oxalic acid converts about a tenth of the sensitiser to the ferrioxalate anion; 7.11 Sensitizer composition and image colour; 7.12 Sensitizer characteristics and Table 7.1, for the relative speeds, exposure ranges, development in log H units and colours of platinum, palladium and two mixtures at 32, 55 and 80 per cent relative humidity; 7.13 Choice of print contrast, for humidity and metal ratio as the two published fine controls; 7.18 Humidifying, for the saturated salt solutions; 11.6 Characteristic curves by densitometry, for the exposure scales of about 2.4 for palladium and 1.9 for platinum, the mid-tone gammas of 0.78 and 0.96, the substantial non-linear toe and the maximum density of about 1.45; 11.11 The inhibited edge effect; 11.15 Factors influencing image colour; 6.1 Expression of solution concentrations, for the definition of per cent w/v and the objection to parts-by-weight-in-parts-by-volume recipes; 6.2 Ferric oxalate, for the polymorphism, the disputed formula weights, the 25 per cent standard solution with 2 g of oxalic acid per 100 cc, the six to nine month keeping figure and the printer who mixes it fresh the night before; 6.3 Potassium tetrachloroplatinate, for the disputed solubility and the 24-hour maturation; 6.4 Health warning, platinum allergy; 6.6 Sodium tetrachloropalladate, for the two preparations of the 0.5 M solution and the instruction that iron and metal solutions are mixed in equal volumes shortly before coating; 6.8 Choice of papers and 6.9 Silica and aluminosilicates in papers; 6.10 Coating procedure, for the specific coating volumes of 24 to 36 cm3/m2, the coating weights of 6 to 9 millimol/m2, the guide of 1.4 cm3 for an 8 by 10 inch area on Crane's, and the preference for a glass rod over a brush; 6.11 Drying and humidity control, for the ambient 55 per cent plus or minus 5, the hour's equilibration, the 45 degree heat-drying and the calcium chloride desiccant chamber at 9 to 27 per cent; 6.18 Partial reversal of tonality, for the reversal conditions including a coating dried below about 30 per cent relative humidity; 7.10 Suitable modern papers, for the named unbuffered papers, the gelatin warning, the sulphamic acid and hydrochloric acid decalcifying baths and the paper weights; 7.14 Mixing the sensitizer solutions, for the syringes, the shot glass and the three-draw mixing; 7.15 Use of surfactant; 7.16 Coating by glass rod; 1.9 Sepia Platinotype with mercuric salts, for the mercury in the developer of the 1878 patent, the "double tones" problem, the shift to mercury in the coating, the "Special Sepia Solution" and "Sepia Crystals" trade secrets, W. H. Smith's 1911 warning that the Platinotype Company never advocated mercury in their developers because it was not stable, F. C. Lambert's note that mercury-developed sepia images are soluble in Farmer's reducer, and Smith's 1915 demonstration of severely faded specimens; 6.5 Agents for increasing contrast, for the chlorate mechanism, the graininess and false sparkle, the hexachloroplatinate(IV) alternative and its incompatibility with ammonium ions, the Willis and Clements dichromate recommendation for palladiotype used by Paul Strand and Ned Scott, the instability of dichromate in an oxalate bath, and the conclusion that with modern negative-making these agents become unnecessary; 6.7 Salts of mercury(II) and lead(II), for the patent concentrations — lead(II) nitrate at 9.12 per cent w/v in 1873, lead chloride at 0.456 per cent and mercuric chloride at 0.912 per cent in 1878, the 1880 patent dispensing with the lead, and the 1887 patents returning to both — for the mercuric citrate preference of later formulations, for the glycerine method, and for the statement that mercury and lead need not be introduced into a palladium sensitiser; 11.9 Effects of mercury(II), lead(II) and silver(I), for the chloride scavenging hypothesis, the mercury(II) chloride formation constants, the lead solubility products, the statement that lead is too electropositive to be reduced by the iron(II) photoproduct, Clarke's X-ray fluorescence finding that the lead signal does not correlate with image density, the inhibiting effect of added chloride and the list of other chloride-binding cations; 11.10 Mercury in platinotypes and palladiotypes, for Ware's own controlled preparation of a mercury-containing platinum sensitiser at 0.34 mol/dm3 and its quantitative X-ray fluorescence analysis, for the Hg:Pt ratios of about 4 at low exposures and 2 at high, for Lewis and Koseki's 2015 comparison of mercury-sensitised prints at Hg:Pt of 0.2 to 0.3 against mercury-developed prints at 0.8 to 1.1, for the possibility of platinum-mercury bonded species, for the bisoxalatomercurate(II) complex and its redox potentials, and for the light sensitivity of a stored mercury-containing oxalate developer; 11.4, for the statement that mercury(II) makes a palladium image more neutral rather than warmer, so there is little reason to employ it; 6.12 Test target images, for the multiple identical step tablets on one sheet allowing subsequent division and comparison; 11.6 Characteristic curves by densitometry, for the palladium exposure scale of about 2.4 with a mid-tone slope of about 0.78, platinum's 1.9 and 0.96, and the maximum density of about 1.45; 6.5, for the unmodified traditional platinotype sensitiser's exposure scale of about 2.0; 1.4 Charles Burnett's experiments — that Burnett (1820-1907) of Edinburgh worked not from iron but from a uranium(VI) salt being reduced to uranium(IV) under the action of light in the presence of organic matter such as the paper or its sizing agent, the uranium(IV) in turn reducing a noble metal salt to the metal; that his uranium printing processes were capable of yielding images in stable substances just like the siderotypes; that he made the first palladium prints in 1856 and obtained fine images in gold and silver; that none of his prints is known to have survived; that his priority was challenged by Abel Niepce de Saint Victor (1805-1870), who published and sought patent rights in 1858 for uranium printing processes essentially identical to those Burnett described a year earlier, prompting Burnett's accusation of monstrous and systematic plagiarism; and that a similar uranium sensitizer was later employed by Jacob Wothly in 1866 to make feeble blue-black prints in platinum and palladium which had to be intensified by toning in a bath of gold chloride, so that the process went no further and died the same death as the egregious and unsuccessful Wothlytype of patent 1864. 6.5 Agents for increasing contrast, pages 136 to 137, for the statement that Willis makes no mention of contrast control in his patents or sensitizer formulae. 6 Traditional Platinotype and Palladiotype, introduction, for the statement that additives such as mercury and lead salts would not be generally recommended today for reasons of health and safety, and image permanence; 11.3 Siderotype by reduction of noble metals, redox potentials; 11.7 aquation of the tetrachlorometallate anions; 11.3 Siderotype by reduction of noble metals, redox potentials; 11.7 aquation of the tetrachlorometallate anions; 11.8 stoichiometry; Willis's palladiotype developer and clearing baths; Anderson on American practice; the 1917 dating; 7.12 Sensitizer characteristics and Table 7.1, for relative speed, exposure range and image colour against relative humidity; 1.4 why ferrous citrate cannot reduce platinum; 11.3 redox potentials; 11.7 aquation of the tetrachlorometallate anions; 11.8 the overall stoichiometry; Willis's three requirements; Pizzighelli's 1887 print-out observation; the soluble iron(II) photoproduct and in-situ reduction; self-masking and the absence of black spots; 7.12 Sensitizer characteristics and Table 7.1, for relative speed, exposure range, development in log exposure units and image colour against relative humidity; 11.3 Siderotype by reduction of noble metals, redox potentials; the palladium toner and its acidity; 1.4 Charles Burnett's experiments — the uranium(VI) to uranium(IV) photoreduction in the presence of organic matter, the uranium(IV) reducing a noble metal salt to the metal, the first palladium prints of 1856, the survival of none of his prints, the 1858 priority challenge by Abel Niepce de Saint-Victor, and Wothly's 1866 platinum and palladium attempt beside the Wothlytype of 1864; The instruction to save a spent bath for recovery of precious metal; the clearing baths and their capacities; Specific coating volume of 24 to 36 cm3 per square metre; the coated area about 1 cm larger than the negative; the instruction that the plate be horizontal, checked with a spirit level; brush coating consuming more and being expensively wasteful; ambient relative humidity of about 55 per cent plus or minus 5 with at least an hour for the paper to equilibrate, and coating below about 30 per cent named among the factors promoting tonal reversal; Clearing: the chemisorbed iron(III) that water will not touch and the hydrolysis above pH 4; the three-bath sequence of disodium EDTA at pH 3 to 4, sodium sulfite and tetrasodium EDTA at pH 9 to 10, with its quantities and bath capacities; the instruction not to use tetrasodium EDTA for the first bath; the sulfite bath made fresh because it oxidises in air to sulfate; the X-ray fluorescence comparison finding the sequence the most effective tested; the masked margin as the only visual test of complete clearing; the Prussian brown appendix on the ferricyanide spot test; Coating: the specific coating volume of 24 to 36 cm3 per square metre and the guide volume for an 8 by 10 area; the coated area about 1 cm larger than the negative; the equal-volume rule for iron and metal solution; a working relative humidity of about 55 per cent plus or minus 5 with an hour to equilibrate, and coating below about 30 per cent named among the factors promoting tonal reversal; the potassium oxalate developer at 28 per cent and the instruction that the bath be neutral or only just acid; the three clearing baths, their strengths, pH windows, times and capacities, and the instruction not to use tetrasodium EDTA first; the masked margin as the only visual test of complete clearing; a gas-permeable backing because carbon dioxide is a photolysis by-product; the final wash of 30 to 60 minutes or at least three fresh static baths; Section 6.10, coating procedure, and section 6.11, drying and humidity control - ambient relative humidity of about 55 per cent plus or minus 5 in the author's studio, with at least one hour allowed for the paper to come to equilibrium with the atmosphere before printing; Section 10.10, Chemistry of clearing siderotypes - iron(III) chemisorbed to the hydroxylic functions of cellulose as the chief problem for effective clearing, its hydrolysis above pH 4 to a polymeric colloidal hydroxide lodging in the fibres, the irreversible transformation of that hydroxide into insoluble iron(III) oxyhydroxide if it is not removed before the print dries, calcium from hard water or a chalk buffer promoting hydrolysis, and the disodium EDTA, sulphite and tetrasodium EDTA sequence with the reasons for each; section 10.8, the strong binding of iron(III) to cellulose accounting for persistent yellow staining; Section 6.11, Drying and humidity control - an ambient relative humidity of about 55 per cent plus or minus 5 used for many tests, with at least one hour allowed for the paper to come to equilibrium with the atmosphere, which is typical of hand-coated practice where the sensitized paper is printed the same day; sensitized platinotype paper not lasting longer unless well dried to inhibit the decomposition reactions; the commercial imperative of complete desiccation, and Willis marketing the product sealed in tins with anhydrous calcium chloride; the simulation of those conditions by resting the freshly coated paper about 10 minutes to allow absorption by the cellulose fibres, heat drying in an air stream at 45 degrees Celsius for 10 minutes, and storage in an anhydrous calcium chloride desiccant chamber at about 9 to 27 per cent RH; the reversibility of drying and rehumidification, with hysteresis in the response to water; section 11.16, Control of humidity - the influence of the relative humidity of the sensitizer before exposure on the image colour of a 1:1 platinum-palladium print-out, tested with the same sensitizer on 160 gsm paper at 80, 56 and 15 per cent RH, with Table 11.4 giving the absolute water content of the atmosphere at each relative humidity and temperature and Table 11.5 the saturated salt solutions that hold a constant humidity; section 3.16, print-out occurring more easily with palladium salts, with preliminary experiments indicating the effect may only be seen with dry sensitizers below about 30 per cent RH, and Stieglitz deliberately printing at Lake George in conditions of low relative humidity; Section 10.10, Chemistry of clearing siderotypes - the ions present after exposure and which are easily washed out; the chief problem being iron(III), some of which is chemisorbed to the hydroxylic functions of cellulose, and which above pH 4 hydrolyses to polymeric colloidal iron(III) hydroxide that lodges in the fibres and imparts a yellow stain; calcium from hard water or a chalk buffer precipitating insoluble calcium oxalate and promoting aquation and hydrolysis of the iron(III) complex; freshly formed iron(III) hydroxide being redissolvable in dilute acid at first but transforming irreversibly into iron(III) oxyhydroxide, the mineral goethite, which is quite insoluble in dilute acids, so that all the iron(III) must be removed at the wet stage before the print dries; the three-bath sequence of about 5 per cent disodium EDTA at pH 3 to 4, about 2.5 per cent sodium sulphite or disulphite made up fresh each session because it oxidises to sulphate in air, and about 5 per cent tetrasodium EDTA at pH 9 to 10; the warning not to use tetrasodium EDTA for the first bath in spite of its recommendation by Bostick and Sullivan, because at pH about 10 the iron(III) is hydrolysed rather than complexed, with yellow or brown staining as the eventual result; Clarke and Hemmenway's XRF finding that this procedure left less residual iron than any other combination tested, comparable with or less than the uncoated paper; section 10.8, Staining of cellulose by iron(III), the strong binding of iron(III) to cellulose and the slow appearance of yellow staining through formation of a mu-oxo bridged binuclear iron(III) species absorbing strongly in the visible by metal-to-metal charge transfer, the bleaching of that colour by acetate without removing the iron as shown by XRF, and the re-yellowing of Steichen's treated Stieglitz palladiotypes; the observation that alum-rosin sized papers show less tendency to iron staining than modern ones; Section 6.12 - test targets that include regions masked from irradiation with rubylith to provide information on residual substances in unexposed but coated areas, where the stain will be most evident; the preparation of a test target specifically for printing stained images to test treatments for the removal of the yellow stain

Used by:Acetic acid (glacial) · Ammonium citrate (dibasic) · Ammonium citrate (tribasic) · Ammonium iron(III) citrate · Ammonium iron(III) oxalate · Ascorbic acid · Chloroauric acid · Citric acid (anhydrous) · EDTA disodium salt dihydrate · Ferric oxalate · Iron(II) oxalate · Glycerol · Gum arabic · Hydrochloric acid · Lead(II) acetate · Lithium chloride · Nickel(II) sulfate · Oxalic acid · Palladium(II) chloride · Potassium carbonate (anhydrous) · Potassium chlorate · Potassium oxalate, anhydrous · Potassium oxalate monohydrate · Potassium tetrachloropalladate(II) · Potassium tetrachloroplatinate(II) · Sodium acetate (anhydrous) · Trisodium citrate dihydrate · Sodium tetrachloropalladate(II) · Ammonium citrate developer · Borax kallitype developer · Bostick and Sullivan platinum and palladium kits · Bostick and Sullivan Ziatype kit · Herschel's argentotype · EDTA and sodium sulfite clearing sequence · Kallitype sensitiser · KODAK PROFESSIONAL XTOL Developer · Lead additions to platinum sensitisers · Mercuric sepia platinotype · Nicol's kallitype · Photographers' Formulary platinum and palladium printing kits · Pizzighelli and Hübl's 1886 formulations · EDTA, citric acid and hydrochloric acid clearing sequence · Three-solution drop system for platinum and palladium · Rochelle salt kallitype developer · Sodium citrate developer · Sodium citrate kallitype developer · Van Dyke Brown sensitiser · Ware's argyrotype · Ware's print-out platino-palladiotype · Willis's potassium oxalate developer · Printing processes compared · P8 How Development Works · P15 Build: The Densitometer Optical Head (Transmission and Reflection) · P15 Density Depends on How You Look: Geometry and Spectral Response · P20 Gold, Iron-Blue and the Other Metal Toners · P21 Experiment: The Exposure Scale, Maximum Density and Contrast of a Cyanotype · P21 What These Processes Need: The Negative, the Paper and the Light · P24 Part XXIV Overview: When Iron Reduces Silver · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Contrast Control in Iron-Based Printing · P24 Lab: Printing a Kallitype · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · P24 The Siderotype Principle: Iron Reduces Silver · P25 Part XXV Overview: Platinum and Palladium · P25 Cost, Permanence and When a Platinum Print Earns Its Price · P25 Lab: Exposing, Developing and Clearing a Palladium Print · P25 Noble Metal Chemistry and the Platinotype · P25 Experiment: Tonal Scale, Contrast and Image Colour in Palladium · P25 Lab: Preparing the Sensitiser and Coating for Palladium · P25 The Additives We Study and Do Not Reproduce · P25 Assignment: The Process Comparison Atlas · P26 Uranium, Mercury and the Heavy-Metal Treatments · Process atlas · Chrysotype · Kallitype · Palladiotype · Platinotype · Print-out platino-palladiotype · Gold-toned and palladium-toned kallitype · Uranotype and Wothlytype · Segregating alternative-process waste · Hand-coating a sheet with a rod and with a brush · Clearing an iron-silver print and testing it for residual iron · Running a platinum or palladium session · Blotchy and streaked hand coating · Iron-silver highlights that will not clear · Mottled coating from uncontrolled humidity · Platinum print stain from incomplete clearing · Yellow iron stain in cyanotype highlights

Preparations for Alternative Printingretrieved 2026-09-05

Sections: Digital Negatives - the instruction to find the exposure time with your standard alternative printing setup that produces a near maximum density through the clear film base, with the 2 per cent step of a 50-step tablet then just visually distinguishable from it, and to inspect a print of that tablet made at the standard exposure to find the step that prints just white. Cited as the nearest description in this corpus of anchoring an exposure on clear film base, and as evidence that the technique belongs to alternative-process printing under ultraviolet rather than to silver gelatin enlarging

Used by:P19 Lab: Test Strips, Base Exposure and the Print's Black Point

Prints of Gold: the Chrysotype Process Re-inventedretrieved 2026-09-04, 2026-09-06

Sections: The Fading Committee of 1850 and gold toning; why finely divided gold shows so many colours; The account of the Photographic Society's Fading Committee of 1850, whose recommendations included the toning of prints with gold salts to coat the silver particles with a protective layer of gold which is quite impervious to attack, and the note that albumen prints treated in this way usually have a rich purplish-brown colour with little evidence of fading; and the statement that the chrysotype is not gold toning in the sense of a retrospective manipulation of an existing silver image but a straight printing medium; The account of the recognition of impermanence in the earliest days of photography, the Photographic Society's Fading Committee, whose year Ware gives as 1850, and its recommendation that prints be toned with gold salts to coat the silver particles with a protective layer of gold which is quite impervious to attack, with the observation that albumen prints treated in this way usually have a rich purplish-brown colour with little evidence of fading; The colours of colloidal gold and the particle-size argument

Used by:Chloroauric acid · P20 Gold, Iron-Blue and the Other Metal Toners · P20 Toning, Permanence and What the Evidence Actually Supports · Chrysotype

Siderotype Data Sheetretrieved 2026-09-07

Sections: The whole one-page record form — the fields for sensitiser concentration and volume, coating temperature and relative humidity, coating volume per sheet and number of passes, three drying rows headed Initial, Store and Humidify each with agent, temperature, relative humidity and times in and out, exposure in units with the ultraviolet source named, and a processing row with columns for Steam, Dev, Clear #1, Clear #2, Clear 3 and Wash

Used by:P24 Contrast Control in Iron-Based Printing

Siderotype Workshop Notes: New Chrysotyperetrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: Table 3, Salts for the control of Relative Humidity atmospheres — anhydrous calcium chloride at 9 per cent, saturated calcium chloride at 45, saturated calcium nitrate at 56, saturated sodium chloride at 76 and saturated ammonium chloride at 80, and the note that the 9 per cent box can also be used for storing coated paper; Overview of Chrysotype; Chemicals for Preparing New Chrysotype Sensitizer; Clearing agents, for tetrasodium EDTA 5 per cent w/v, 2 litres, 100 g of the solid in 2 litres of water, with the statement that two such clearing baths are required and a capacity of about fifty 10 by 8 prints per litre; and for sodium metabisulphite 2.5 per cent w/v, 25 g or a level tablespoonful in a litre, with sodium sulphite, sodium bisulphite or Kodak Hypoclear powder as alternatives and the instruction to make it fresh for a day's printing and not to store or re-use it. The wet processing steps 4 to 9, for the variant sequence in which both the first and the third clearing baths are tetrasodium EDTA at 5 per cent for 10 minutes with a half-minute rinse each side of a 10-minute sodium metabisulphite bath — printed there as 2 per cent where the solutions list gives 2.5 per cent — for the economy of rotating the exhausted first bath out and the third bath into its place after about fifty prints, and for the final wash of 30 to 60 minutes

Used by:Calcium nitrate tetrahydrate · Chloroauric acid · EDTA and sodium sulfite clearing sequence

Siderotype Workshop Notes: New Cyanotyperetrieved 2026-09-05, 2026-09-06, 2026-09-07

Sections: The table of processing solutions, for the entry "Nickel sulphate NiSO4.6H2O 5% w/v — Dissolve 50 g in 1 litre of water", and the toning section heading "Greenish-blue – Nickel(II) sulphate", with its immersion instruction, its note on alkaline hydrolysis and its warning that nickel(II) salts are listed carcinogens; The table of processing solutions, for the entries "Lead(II) acetate Pb(OCOCH3)2.3H2O 5% w/v — Dissolve 50 g in 1 litre of water" and "Nickel sulphate NiSO4.6H2O 5% w/v — Dissolve 50 g in 1 litre of water", and for the note on strengths defining per cent w/v as grams of solute in 100 cc of solution; the Toning Cyanotypes section, for the headings "Violet – Lead(II) acetate" and "Greenish-blue – Nickel(II) sulphate", the 5 per cent lead acetate solution adjusted to pH 7.5 to 8 with a little ammonia checked on pH paper, the filterable precipitate, the statement that the colour is permanent and stabilises the Prussian blue against light fading, the warning that lead(II) acetate is a seriously toxic heavy metal salt, and the nickel paragraph reprinting the Cyanomicon text; and the neighbouring tannic acid and trisodium phosphate toners on the same page; Overview of Cyanotype; Chemicals for Preparing and Processing New Cyanotype Sensitizer, in which the ammonium dichromate, the Tween 20 and the citric acid are each marked OPTIONAL; Preparation of New Cyanotype Sensitizer, its five numbered steps and the parenthesis that the dichromate may be omitted; Notes on the New Cyanotype Process - Choice of Paper, Addition of Citric Acid to the Sensitizer, Addition of Surfactant to the Sensitizer, Coating, Drying, Printing Exposure and Negatives, Wet Processing and Contrast Control, Permanence and Stability; Summary of New Cyanotype Procedure; Toning Cyanotypes; The Drying section, for the 2009 statement that dryness does not appear to influence image colour or contrast, recorded here as the earlier and weaker form of the claim that the 2020 Cyanomicon replaces with a measurement.; The processing table and its capacities - the acid development bath of 5 to 10 minutes with contrast rising with acid strength, a capacity of six to ten 10 by 8 inch prints per litre and the instruction not to re-use the bath; the wash of about 30 minutes in non-alkaline, non-hard water; the 0.3 per cent hydrogen peroxide bath of no more than half a minute; and the permanence note that Prussian blue is destroyed by alkali and that buffered wrappings and mounts above pH 9 should be avoided; Chemicals for Preparing and Processing New Cyanotype Sensitizer, in which the ammonium dichromate, the Tween 20 and the citric acid are each marked OPTIONAL; Notes on the New Cyanotype Process — Addition of Surfactant to the Sensitizer, Drying, Wet Processing and Contrast Control, Permanence and Stability; "Chemicals for toning Cyanotypes", page 4, for the four solutions this session uses and the two it names but does not use - ammonium hydroxide 1 per cent v/v made by diluting 10 cc of concentrated about 27 per cent ammonia to 1 litre, sodium carbonate which may be the hydrated form at 5 per cent w/v made by dissolving 50 g in 1 litre, tannic acid C76H52O46 at 1 per cent w/v made by dissolving 10 g in 1 litre, acetic acid at 1 per cent v/v made by diluting 10 cc of concentrated about 90 per cent acid to 1 litre, and lead(II) acetate and nickel(II) sulphate each at 5 per cent w/v - together with the note on strengths defining per cent w/v as grams of solute in 100 cc of solution and per cent v/v as cc of liquid in 100 cc of solution. "Toning Cyanotypes", page 11, for the four headed procedures - "Purplish-brown - Tannic acid" with the same seven numbered steps as Cyanomicon 8.2 and the sentence that shortening the time in step 2 can yield interesting split-tone effects, "Yellow - Trisodium phosphate" for a heavily printed cyanotype bleached to a golden yellow probably iron(III) phosphate, "Violet - Lead(II) acetate" and "Greenish-blue - Nickel(II) sulphate", and for the statement that the tannic acid treatment generally intensifies the image and imparts a rich purplish-brown colour, that staining of the paper base is a problem and that the colour is very sensitive to alkali.; Preparation of sensitizer, step 2 — 0.1 g of ammonium dichromate added to the ammonium iron(III) oxalate solution, with the parenthesis that the small amount of ammonium dichromate may be omitted but that the contrast and shelf-life of the sensitizer will be diminished; The processing table and its capacities - the acid development bath of 5 to 10 minutes with contrast rising with acid strength, a capacity of six to ten 10 by 8 inch prints per litre, and the instruction not to re-use the bath

Used by:Nickel(II) sulfate · Lead, thallium and nickel cyanotype toners · The New Cyanotype (1995) · P21 Experiment: The Exposure Scale, Maximum Density and Contrast of a Cyanotype · P21 Break/Fix: The Cyanotype That Went Wrong · P21 The New Cyanotype and the Other Ways to Make a Blue Print · P21 Lab: Toning the Prussian Blue Image · P24 Contrast Control in Iron-Based Printing · Blue fog in cyanotype highlights

Siderotype Workshop Notes: Platino-palladiotyperetrieved 2026-09-06, 2026-09-07

Sections: Humidifying — the humidifying tank as a tray with a close-fitting lid in which the paper is placed face down over, but not in contact with, a saturated aqueous solution providing an atmosphere of constant known relative humidity; the three most useful saturated solutions, ammonium chloride at 80 per cent, common salt at 76 per cent and calcium nitrate tetrahydrate at 55 per cent; the requirement that there be excess solid salt in contact with its saturated solution and that the paper be evenly exposed to the vapour; the minimum of half an hour for evenness and the upper limit being not critical and able to be a few hours; and the alternative of pure water at 100 per cent relative humidity, where the timing becomes critical instead; Chemicals for Preparing Platino-palladiotype Sensitizer, and Preparation of Platino-palladiotype Sensitizer Solutions, for the open formula this kit is compared against — the 60 per cent w/v ammonium iron(III) oxalate iron solution and the 19 per cent w/v ammonium tetrachloropalladate(II) made from 1.8 g of ammonium chloride and 3 g of palladium(II) chloride; Mixing the Sensitizer Solutions, for equal volumes and for the rule that the iron volume equals the combined metal volume; Humidifying, for the constant-humidity enclosure and the three saturated salt solutions; and Clearing, for the three-bath sequence and the reason its order cannot be reversed.; Overview of Platinotype and Palladiotype; Platinum Allergy: Health & Safety; Chemicals for Preparing Platino-palladiotype Sensitizer; Chemicals for Processing Platino-palladiotypes, with the definition of per cent w/v; Preparation of Platino-palladiotype Sensitizer Solutions — Iron solution steps 1 to 5, Platinum solution steps 1 to 4, Palladium solution Method 1 steps 1 to 4 and Method 2 steps 1 to 5; Notes on the Platino-palladiotype Process — Choice of Paper, Choice of Sensitizer Composition and Image Colour, Sensitizer Characteristics and its table, Choice of Print Contrast, Mixing the Sensitizer Solutions, Addition of Surfactant to Sensitizer, Coating, Drying & Storage, Humidifying, Printing Exposure and Negative Masking with the carbon dioxide footnote; Wet Processing Procedure steps 1 to 9; Finishing; Permanence & Stability; Summary of Platino-palladiotype Procedure, steps 1 to 15; Printing in 100% Platinum; The humidifying tank, for the saturated solutions used to hold a constant relative humidity at room temperature - ammonium chloride at 80 per cent, common salt at 76 per cent and calcium nitrate tetrahydrate at 55 per cent - and for the half-hour minimum equilibration.

Used by:Calcium nitrate tetrahydrate · Bostick and Sullivan Ziatype kit · Ware's print-out platino-palladiotype · P21 Experiment: The Exposure Scale, Maximum Density and Contrast of a Cyanotype

Siderotype Workshop Notes: Print-out Palladiotyperetrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: Humidifying — cat litter trays as ideal for the purpose because photographic dishes are too shallow and their lip makes sealing difficult, the sheet held on the underside of the lid by two strips of self-adhesive magnetic tape, and the same three saturated solutions with calcium nitrate tetrahydrate at 55 per cent; Regulation of Image Colour, for drier conditions at about 55 per cent relative humidity yielding Van Dyke brown or sepia tones and a softer image with a longer exposure range and great delicacy in the high values, against near-neutral tones when well humidified at 70 to 80 per cent; Choice of Print Contrast, for the contrast being fine-tuned by regulating the humidity of the sensitized paper before exposure; Making up the processing solutions — disodium EDTA at about 5 per cent w/v, its capacity, and the conversion of the tetrasodium salt with citric acid; Making up the processing solutions: disodium EDTA at about 5% w/v and its capacity; tetrasodium EDTA at about 5% w/v; the citric acid conversion of the tetrasodium to the disodium salt; the alkali table for making either salt from H4EDTA; Chemicals for Palladiotype Sensitizer; Palladium solution 19% w/v ammonium tetrachloropalladate(II), Method 2; Chemicals for Palladiotype Sensitizer; Palladium solution 19% w/v ammonium tetrachloropalladate(II); Chemicals and solutions — sodium metabisulphite 2.5% w/v; Wet processing sequence, step 4; Outline procedure, step 11; Chemicals for Palladiotype Sensitizer, and the outline procedure, for the palladium-only printing-out notes of 2014 and their 2.5 per cent w/v sodium metabisulphite bath between the two EDTA baths; Overview of Palladiotype and Platinotype; Making up the Processing Solutions, for the bath capacities; Coating Paper with Sensitizer using a Glass Rod, for the 1.5 cc per 10 by 8 inch print; Humidifying; Wet Processing Procedure; Permanence and Stability; Chemicals for Palladiotype Sensitizer, for the statement that the published batch makes at least thirty 10 by 8 inch prints; Chemicals for Processing Palladiotypes, for the statement that the processing quantities suffice for about sixty prints; Coating Paper with Sensitizer using a Glass Rod, for the 1.5 cc per 10 by 8 inch print and the average specific coating volume of 25 cc per square metre; Wet Processing Procedure step 2, for the instruction that the spent first bath should be saved for recovery of precious metal; Permanence and Stability; Making up the Processing Solutions, for the three baths at 5, 2.5 and 5 per cent w/v, the capacities of about 50 to 60 and about 100 prints per litre, the tetrasodium-from-disodium conversion and the alkali table; Printing Exposure and Negative Masking, for the negative density range of about 2.4, the exposure of a few minutes under an average UVA source, the 40 seconds under an 800 W lamp, the carbon dioxide pathway and the felt blanket, and the three reasons for masking the borders; Wet Processing Procedure steps 1 to 9; Finishing; Permanence and Stability; Overview of Palladiotype and Platinotype; Regulation of Image Colour; Choice of Print Contrast; Humidifying; Printing Exposure and Negative Masking; Permanence and Stability; Regulation of Image Colour, for the drier-sepia and well-humidified-neutral statement; Choice of Print Contrast, for the negative density range of about 2.4 and humidity as the fine control; Humidifying, for the 50 to 80 per cent optimum, the partial print-out below 50 per cent, the weakened maximum density above 80 per cent, the saturated salt table and the timing at 100 per cent; Printing Exposure and Negative Masking; Wet Processing Procedure; Chemicals for Palladiotype Sensitizer, for the batch that makes at least thirty 10 by 8 inch prints; Preparation of Palladiotype Sensitizer Solutions, Methods 1 and 2; Notes on the Palladiotype Process — Choice of Paper, Mixing the Sensitizer Solutions, Addition of Surfactant, Coating Paper with Sensitizer using a Glass Rod, steps 1 to 11; Drying and Storage; Humidifying, for the saturated salt table and the six-month desiccated keeping; Summary of Palladiotype Workflow

Used by:Calcium nitrate tetrahydrate · EDTA disodium salt (anhydrous) · EDTA disodium salt dihydrate · Palladium(II) chloride · Potassium tetrachloropalladate(II) · Sodium metabisulfite · Ware's print-out platino-palladiotype · P25 Part XXV Overview: Platinum and Palladium · P25 Cost, Permanence and When a Platinum Print Earns Its Price · P25 Lab: Exposing, Developing and Clearing a Palladium Print · P25 Noble Metal Chemistry and the Platinotype · P25 Experiment: Tonal Scale, Contrast and Image Colour in Palladium · P25 Lab: Preparing the Sensitiser and Coating for Palladium · Palladiotype

Simple Cyanotype: preparation of sensitizers and instructions for their use, one-bottle and two-bottle versions with contrast controlretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Substance and Formula, the chemicals list for 100 cc, which names citric acid, iron(III) nitrate nonahydrate, ammonia solution with its specific gravities, potassium ferricyanide and Tween 20 and does not name this salt; Safety; Preparation of One-bottle Sensitizer A. Cited for a negative finding; Chemicals required — ammonia solution and its concentrations; preparation of the sensitisers; safety in preparation; Introducing three varieties of cyanotype; Paper — unbuffered papers, and the pre-treatment of buffered papers in dilute hydrochloric or sulphamic acid; Chemicals required and quantities for 100 cc; preparation of the one-bottle sensitiser; wet processing in 1% citric acid; Chemicals needed for preparing and processing Simple Cyanotype sensitizers; Chemicals needed for Preparing and Processing Simple Cyanotype Sensitizers, with the warning printed against iron(III) nitrate nonahydrate; Safety in Preparation; Preparation of One-bottle Sensitizer A, steps 1 and 2; Processing — the destruction of Prussian blue by alkali; Permanence and stability; paper requirements — the destruction of Prussian blue by alkali and the treatment of chalk-buffered papers; Paper — pre-treatment of buffered papers in 5 to 10 per cent w/v sulphamic acid; Safety in Preparation, for the instruction to protect the eyes and to avoid inhaling ammonia vapour; Apparatus for Preparing the Sensitizers; Preparation of One-bottle Sensitizer A; Preparation of Two-bottle Sensitizers, Solution I ammonium dicitratoferrate and Solution II potassium ferricyanide, each made up to 50 cc, and To use Two-bottle Sensitizers; Choice of Paper; Addition of Surfactant to the Sensitizer; Coating; Drying; Printing Exposure; Wet Processing; Permanence and Stability; Summary of Simple Cyanotype Procedure; Introducing Three Varieties of Cyanotype; Chemicals needed for Preparing and Processing Simple Cyanotype Sensitizers; Safety in Preparation; Apparatus for Preparing the Sensitizers; Preparation of One-bottle Sensitizer A, and of Sensitizers B and C; Preparation of Two-bottle Sensitizers, Solution I ammonium dicitratoferrate and Solution II potassium ferricyanide, and To use Two-bottle Sensitizers; Equipment and Materials for Coating and Printing Cyanotypes; Choice of Paper; Negatives and Control of Contrast; Addition of Surfactant to the Sensitizer; Coating; Drying; Printing Exposure; Wet Processing; Permanence and Stability; Summary of Simple Cyanotype Procedure; Typical results for Simple Cyanotype, one-bottle version, with the three sensitiser pH values and the water-developed fourth strip; Printing Exposure - since this is substantially a print-out process, a traditional hinged-back contact printing frame will enable inspection of the desired result, the exposure being continued until the high values appear light green, the mid-tones firm blue and the deepest shadows reversed to a pale blue-grey; Printing Exposure - about 5 to 10 minutes under an average 365 nm UVA light source; and the hinged-back frame that permits inspection because the process prints out, with the exposure continued until the high values are light green and the deepest shadows reversed; Printing Exposure - about 5 to 10 minutes under an average 365 nm UVA light source for the simple cyanotype; and the hinged-back contact printing frame that allows inspection because the process prints out; Page 2, for the Simple Cyanotype's high Dmax of about 1.5 and its exposure scale varying from 2.7 to 1.4 depending on the sensitizer formula, and for the New Cyanotype's maximum density verging on black given numerically as 1.7 with an exposure about one eighth of the Classic. Pages 5 and 6, for the three one-bottle contrast grades set by the volume of ammonia alone: A low contrast with exposure scale about 2.7, B medium at about 2.3, C high at about 1.8, with intermediate scales obtainable by mixing A and C proportionally. Page 12, Wet Processing, for development in 1 per cent citric acid for half a minute to a minute until Prussian blue starts to run off, the instruction to use more dilute acid if the highlights appear unduly blued, the statement that omitting the acidic bath and processing in water alone produces a much shorter exposure scale of about 1.3 with higher contrast and no fogging but a somewhat weakened Dmax, the 10-minute wash face down in gently running water with the prohibition on alkaline water above pH 7 and on hard water containing calcium salts, the statement that the reversed shadow tones regain density fairly rapidly by air reoxidation during wet processing and drying, and the instruction that if completion of the regain is required immediately, for example for densitometry, 50 cc of 6 per cent hydrogen peroxide may be added per litre of the first wash bath. Page 13, Typical results, for the four test strips A, B, C and D on Buxton paper at 160 gsm with Tween at 0.3 per cent and an 8 and a half minute exposure under a facial unit, A, B and C developed in 1 per cent citric acid for half a minute and D in water only, with the sensitizer pH given as about 4, 6 and 8 for the three grades.; The summary statement that the one-bottle sensitiser is faster than an average Classic two-bottle formula but slower than New, has excellent tonal separation with a Dmax of about 1.5 and an exposure scale varying from 2.7 to 1.8 depending on the sensitiser formula so that contrast can be fine-tuned to match widely differing negatives; Choice of Paper — 160 g/m2 adequate to A4 and 240 g/m2 or more at A3 to minimise bellying of the wetted area so that the sheet contacts the negative better; Negatives and Control of Contrast — negatives may have a density range in the ultraviolet of as much as 2.7 for the low-contrast sensitiser, and the statement that sensitisers may be formulated to match their exposure scale to the density range of silver-gelatin negatives prepared for other processes such as platinotype or palladiotype; Addition of Surfactant — the statement that the success of cyanotype depends on the sensitiser penetrating the interfibrillar space of the surface cellulose fibres where the pigment will be trapped, and not simply remaining in the coarse pores of the paper from which it washes out; Wet Processing — the note that omitting the acid bath and processing in water alone gives a much shorter exposure scale of about 1.3 with higher contrast and a slightly weakened Dmax; and the workflow summary giving rod coating at about 1.5 cc per 10 by 8 inch area with 5 to 8 passes, drying 1 to 2 hours at room temperature or 40 degrees C air for 10 minutes, and a negative density range from 1.8 to a maximum 2.8 in the UVA.; Introducing three varieties of cyanotype — the New cyanotype's maximum density verging on black at 1.7, and the Simple cyanotype's high maximum density of about 1.5 with an exposure scale varying from 2.7 to 1.4 depending on the sensitizer formula; and the preparation of Solution I, ammonium dicitratoferrate, in situ from iron(III) nitrate, citric acid and ammonia, with the three contrast grades A, B and C set by the volume of ammonia; The processing solution - about 1 per cent w/v citric acid made by dissolving 10 g in a litre, with the instruction to use one litre for two or three prints only; the development of half a minute to a minute until Prussian blue starts to run off; the statement that omitting the acid bath and processing in water alone shortens the exposure scale from about 2.7 to about 1.3 with higher contrast, no fogging and a somewhat weakened maximum density; and the instruction that more dilute acid should be used if the highlights are unduly blued; Introducing three varieties of cyanotype — the New cyanotype's maximum density verging on black at 1.7 and the Simple cyanotype's maximum density of about 1.5 with an exposure scale varying from 2.7 to 1.4 depending on the sensitizer formula; Preparation of Sensitizers A, B and C, in which the three contrast grades differ only in the volume of ammonia; Negatives and Control of Contrast; Wet Processing; Printing Exposure - about 5 to 10 minutes under an average 365 nm UVA light source, and the hinged-back contact printing frame that permits inspection because the process prints out, the exposure continued until the high values are light green, the mid-tones firm blue and the deepest shadows reversed to a pale blue-grey; Paper requirements and the treatment of alkaline-buffered papers before coating; the capacity of the first bath, a litre of 1 per cent citric acid limited to two or three prints; Permanence and stability, and paper requirements - the destruction of Prussian blue by alkali and the treatment of chalk-buffered papers; Introducing three varieties of cyanotype and their behaviour on exposure; Wet processing and the behaviour of the image during washing; Introducing three varieties of cyanotype, and the maximum densities each reaches

Used by:Ammonium citrate (tribasic) · Ammonia solution (ammonium hydroxide) · Ammonium iron(III) citrate · Calcium carbonate · Citric acid (anhydrous) · Iron(III) chloride, anhydrous · Iron(III) nitrate nonahydrate · Potassium ferrocyanide (anhydrous) · Prussian blue · Sulfamic acid · Mike's Cyanotype · The Simple Cyanotype (2019) · P16 Build: The Contact Printing Frame and Its Light Source · P16 Build: The UVA Exposure Unit · P16 Ultraviolet for the Alternative Processes: Sources, Dose, Uniformity and Hazard · P21 Experiment: The Exposure Scale, Maximum Density and Contrast of a Cyanotype · P21 What These Processes Need: The Negative, the Paper and the Light · P21 Iron, Light and Prussian Blue · P21 Break/Fix: The Cyanotype That Went Wrong · P21 The New Cyanotype and the Other Ways to Make a Blue Print · Cyanotype (classic) · Cyanotype (New Cyanotype) · Operating the UVA exposure unit · Blue fog in cyanotype highlights · Cyanotype bleached by alkaline wash water or buffered paper · Bronzing and reversal from cyanotype over-exposure · Prussian blue bleeding into the highlights by peptisation · Uneven contact print from pressure, glass or source geometry · Weak cyanotype maximum density

The Argyrotype Processretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: An alternative silver salt; Chemicals needed for the sensitizer; Structure and Stability of Silver Images — colloidal dimensions of brown silver images and their vulnerability; The diagnosis of residual iron(III) and of nitrate as an oxidising anion, the argument for replacing silver nitrate with a soluble silver salt having a non-oxidising anion, and the chemicals list for the sensitizer; An Alternative Silver Salt — nitrate as an oxidising anion that tends to dissolve the colloidal image silver during wet processing especially under acidic conditions, the kallitype's alkaline-buffered developers and the hydrolysis of excess iron(III) they cause, the principle of replacing silver nitrate with a soluble salt of silver having a non-oxidising anion, silver fluoride and the other candidates debarred by their properties or toxicity, and silver sulphamate NH2SO3Ag as the little-known and relatively innocuous salt that fits, made in situ and used in an acidic sensitizer of pH 2 to 3; Chemicals needed for the Sensitizer; Making up the Sensitizer; Some Alternatives in the Chemistry, for silver carbonate and for precipitating the oxide from silver nitrate; Wet Processing; Image Permanence; Precautions and Disclaimer, for the statement that the sensitizer solution is irritant and toxic and will stain skin and fabrics; An Alternative Silver Salt — silver sulphamate in place of silver nitrate, and the mildly acidic working conditions it permits; Structure and Stability of Silver Images, for the colloidal dimensions of a brown silver image, for colour depending on shape, size, aggregation and chemical environment, and for residual iron(III) oxidising image silver; An Alternative Silver Salt, for nitrate as an oxidising anion that dissolves colloidal image silver under acidic conditions, for the kallitype's answer of alkaline-buffered developers of high pH such as borax, and for the hydrolysis of the excess iron(III) and the deposition of insoluble ferric hydroxide in the image that those developers cause; History, for Herschel as the first to devise an iron-silver process; Structure and Stability of Silver Images, for the colloidal dimensions of brown silver and the danger of residual iron(III) oxidising the image; An Alternative Silver Salt, for nitrate as an oxidising anion that dissolves colloidal image silver; Wet Processing, for the 2 per cent sodium thiosulphate bath prepared by dissolving about 20 g of the crystals in a litre, its capacity of about ten 10 by 8 inch prints, the five-minute water wash before it and the warning against highly chlorinated water; Fix the print, for the three minutes, for the statement that the bath removes traces of insoluble silver salts and intensifies the image so that the shadow gradation strengthens and the colour shifts rapidly from red to brown, that overlong treatment and exposure to air can cause loss of image density especially in the highlights and may be used deliberately to reduce an overexposed print, that a standard non-acid fixer may be used instead, and that "if very delicate highlight detail is desired, a little ammonia may be added to the clearing bath to make it distinctly alkaline (pH 9 to 10); this inhibits the dissolution of silver, but may raise the level of residual iron in the image"; and the Overview, on the difficulty of the iron-silver processes being to clear the print of iron salts without dissolving the image silver in the presence of the oxidising nitrate ion, for which alkaline developers were necessarily recommended but are not very effective at removing excess iron(III), which is better done in acid; and the explanation that brown silver images consist of colloidal particles of about 20 nm, far smaller than the wavelength of visible light, which are correspondingly vulnerable to reagents that oxidise silver; The Overview, for the statement that the difficulty of the iron-based silver processes is to clear the print of iron salts without dissolving the image silver in the presence of the oxidising nitrate ion, that alkaline developers were necessarily recommended for that reason but are not very effective at removing excess iron(III), which is better done in acid, and that the brown silver image consists of colloidal particles of about 20 nm, far smaller than the wavelength of visible light and correspondingly vulnerable to reagents that oxidise silver; and Wet Processing, for the clearing bath of de-chlorinated water and the note that a little ammonia added to the clearing bath to make it distinctly alkaline at pH 9 to 10 "inhibits the dissolution of silver, but may raise the level of residual iron in the image"; Structure and Stability of Silver Images; An Alternative Silver Salt, for the statement that nitrate is an oxidising anion which dissolves colloidal image silver, that the kallitype answers it with alkaline-buffered developers of high pH such as borax, and that those in turn hydrolyse the excess iron(III) to ferric hydroxide in the image; Structure and Stability of Silver Images, for the colloidal dimensions of a brown silver image; An Alternative Silver Salt, for nitrate as an oxidising anion which dissolves colloidal image silver during wet processing especially under acidic conditions, for the kallitype's answer of alkaline-buffered developers of high pH such as borax, and for the hydrolysis of the excess iron(III) those developers cause and the ferric hydroxide they deposit in the image; Structure and Stability of Silver Images, for the colloidal dimensions of a brown silver image and for colour depending on shape, size, aggregation and chemical environment; An Alternative Silver Salt, for nitrate as an oxidising anion that dissolves colloidal image silver under acidic conditions, for the kallitype's answer of alkaline-buffered developers of high pH such as borax, and for the ferric hydroxide those developers deposit in the image; Structure and Stability of Silver Images; An Alternative Silver Salt, for nitrate as an oxidising anion that dissolves colloidal image silver, for the kallitype's answer of alkaline-buffered developers of high pH such as borax, and for the ferric hydroxide those developers deposit in the image; Structure and stability of silver images; An alternative silver salt; Chemicals needed for the sensitizer; Making up the sensitizer; Choice of paper; Coating; Printing; Adjustment of colour; Wet processing; Image permanence; Introduction; History; Structure and Stability of Silver Images; An Alternative Silver Salt; Chemicals needed for the Sensitizer; Making up the Sensitizer; Some Alternatives in the Chemistry; Choice of Paper; Coating; Printing; Adjustment of Colour; Wet Processing; Image Permanence; Precautions and Disclaimer; References, which give the first publication as the British Journal of Photography 139 (6824), 17-19, of 13 June 1991; The statement that like any colloidal silver image, especially one on plain paper unprotected by a colloid binder layer, the print is inevitably rather susceptible to attack by oxidising acids and sulphur-containing substances, and that the image is receptive to the usual toning treatments if improved permanence is desired; Introduction, placing the iron-silver processes between cyanotype and the noble metals; History, for Herschel devising the first iron-silver process and dubbing it Argentotype in 1842, for Van Dyke, Kallitype, Sepiaprint and Brownprint as its derivatives, for the Byzantine complexity some of the recipes acquired and their poor reputation for stability, and for Child Bayley's 1932 account; Structure and Stability of Silver Images, for the colloidal particle size of about 20 nm and the vulnerability that follows from it; An Alternative Silver Salt, for the diagnosis that residual iron(III) will oxidise the image silver and for the substitution of silver sulphamate for silver nitrate; Image Permanence; An Alternative Silver Salt, for the diagnosis that residual iron(III) will oxidise the image silver; Wet Processing, for the clearing bath and the option of a little ammonia to make it distinctly alkaline at pH 9 to 10, which inhibits the dissolution of silver but may raise the level of residual iron in the image; Image Permanence, for the statement that a colloidal silver image on plain paper unprotected by a colloid binder layer is inevitably rather susceptible to attack by oxidising acids and sulphur-containing substances, that with residual iron and silver very low the image stability and lightfastness are good, and that the image is receptive to the usual toning agents though these may have to be used at lower concentration than usual; An Alternative Silver Salt — the statement that nitrate is an oxidising anion which tends to dissolve the colloidal image silver during wet processing especially under acidic conditions, that to minimise this loss the kallitype process employs alkaline-buffered developers of high pH such as borax, and that these create a new problem because they cause hydrolysis of the excess iron(III) in the sensitizer and the deposition of insoluble ferric hydroxide in the image, which ultimately causes it to fade; An Alternative Silver Salt, for nitrate as an oxidising anion that tends to dissolve the colloidal image silver during wet processing especially under acidic conditions, and for the alkaline-buffered developers the kallitype uses to avoid it; Printing, for the print-out image obtained at normal humidity, the half to one stop of development that occurs in the high values during wet processing, the considerable dry-down, and the instruction that it is better to overexpose than underexpose because a dense image can always be reduced; Wet Processing, for the 5-minute wash in water at room temperature with the warning against highly chlorinated water, for the yellow unexposed sensitizer of excess iron and silver salts washing out within that time, for bleeding of colloidal silver indicated by a red-brown stain running off dense areas and its remedy, for the 2 per cent sodium thiosulphate fix of 3 minutes that intensifies the image and shifts the colour from red to brown, for the warning that overlong treatment loses density especially in the highlights, and for the option of a little ammonia in the clearing bath to pH 9 or 10, which inhibits the dissolution of silver but may raise the level of residual iron; Image Permanence; An Alternative Silver Salt, for residual iron(III) oxidising the image silver and for nitrate as an oxidising anion dissolving colloidal silver during wet processing especially under acidic conditions; Choice of Paper, for the statement that papers not meeting the specification will stain or lose image substance, and for the surfactant's role in minimising bleeding of the colloidal metal image; Wet Processing, for bleeding indicated by a red-brown stain running off dense areas of the image with its remedies, for the warning against highly chlorinated water while the silver nanoparticles are still vulnerable, and for the warning that overlong treatment in the thiosulphate bath loses image density especially in the highlights; History, for Herschel's argentotype of 1842 and its derivatives; Structure and Stability of Silver Images, for the colloidal particle size of about 20 nm, far smaller than the wavelength of visible light, whose colour depends on shape, size, aggregation and chemical environment, and which are rapidly dissolved by reagents that oxidise silver; An Alternative Silver Salt, for the objection that nitrate is an oxidising anion which tends to dissolve the colloidal image silver during wet processing especially under acidic conditions, for the kallitype's alkaline-buffered developers as the answer to that and for the hydrolysis of the excess iron(III) they cause, and for silver sulphamate, NH2SO3Ag, as a soluble silver salt with a non-oxidising anion that permits an acidic sensitizer at pH 2 to 3; Printing, for the print-out image and the half to one stop of development that occurs in wet processing; Wet Processing; Image Permanence; An alternative silver salt - the objection to silver nitrate as an oxidising anion which tends to dissolve the colloidal image silver during wet processing; the clearing bath and the note that adding ammonia to make it distinctly alkaline at pH 9 to 10 inhibits the dissolution of silver but may raise the level of residual iron in the image; the statement that residual iron and silver in the unexposed areas should be very low for good image stability; An alternative silver salt - the objection that alkaline-buffered developers of high pH such as borax cause hydrolysis of the excess iron(III) in the sensitizer and the deposition of insoluble ferric hydroxide in the image, which ultimately causes it to fade; the objection to silver nitrate as an oxidising anion tending to dissolve the colloidal image silver during wet processing; the clearing bath and the trade-off in which added ammonia at pH 9 to 10 inhibits the dissolution of silver but may raise the level of residual iron; the statement that like any colloidal silver image, especially on plain paper unprotected by a colloid binder layer, an argyrotype is inevitably rather susceptible to attack by oxidising acids and sulphur-containing substances, but that with residual iron and silver very low the image stability and lightfastness are good; the receptiveness of the image to the usual toning treatments if improved permanence is desired; The statement that like any colloidal silver image, especially those on plain paper unprotected by a colloid binder layer, the print is inevitably rather susceptible to attack by oxidising acids and sulphur-containing substances, and that the image is receptive to the usual toning treatments if improved permanence is desired

Used by:Ammonium iron(III) citrate · Silver · Silver(I) oxide · Silver sulfamate · Sulfamic acid · Borax kallitype developer · Herschel's argentotype · Dilute alkaline thiosulfate fixer for iron-silver prints · EDTA and sodium sulfite clearing sequence · Kallitype sensitiser · Nicol's kallitype · Rochelle salt kallitype developer · Sodium citrate kallitype developer · Van Dyke Brown sensitiser · Ware's argyrotype · P22 Break/Fix: The Printed-Out Image That Faded · P24 Part XXIV Overview: When Iron Reduces Silver · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Lab: Printing a Kallitype · P24 Lab: Printing a Van Dyke Brown · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · P24 The Siderotype Principle: Iron Reduces Silver · Argentotype · Van Dyke Brown · Iron-silver highlights that will not clear · The iron-silver print that faded within weeks · Silver mirroring and sulfiding in an untoned printed-out print

The New Chrysotype Processretrieved 2026-09-04, 2026-09-06

Sections: Making up the processing solutions — the 1 per cent w/v disodium EDTA first bath and the instruction not to use tetrasodium EDTA; Making up the processing solutions: the 1% w/v disodium EDTA developer, the instruction not to use tetrasodium EDTA, and the criteria for a first bath; Making up the Processing Solutions, for the recommended developer of disodium EDTA at about 1 per cent w/v, about 10 g in a litre, used for a few prints only in one session and not stored, with the instruction "Do not use tetrasodium Edta, which is alkaline, and will cause iron stains"; and Clearing Baths number I and III, for tetrasodium EDTA at about 5 per cent w/v, 50 g in a litre of tap water at room temperature, two such baths being required, the statement that they may be stored and will have a capacity of around fifty 10 by 8 prints per litre, and the two-bath rotation by which the first bath is replaced by the third when it is exhausted

Used by:EDTA disodium salt (anhydrous) · EDTA disodium salt dihydrate · EDTA and sodium sulfite clearing sequence · Chrysotype

The New Cyanotype Processretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: A chemical solution; Sensitizer chemicals needed; Preparation of sensitizer; Processing — the 0.3 per cent peroxide bath and the note that the treatment makes no difference to the final result; The Nature of Prussian Blue; Processing — dilute nitric, hydrochloric or sulphamic acid as the development bath and the effect of acid strength on contrast; The Nature of Prussian Blue; Disadvantages of the Traditional Process, its five numbered points; A Chemical Solution; Sensitizer Chemicals needed; Preparation of Sensitizer, its seven numbered steps, the filtrate volume of about 62 cc, the option of making the sensitiser up to 200 cc and the shelf life of at least four to five years; Use of Wetting Agent; Choice of Papers; Coating Techniques; Drying; Negatives; Exposure; Wet Processing; Disadvantages of the Traditional Process, its five numbered points; A Chemical Solution; Preparation of Sensitizer, for the filtrate volume and the option of making up to 200 cc; Use of Wetting Agent; Choice of Papers; Drying; Exposure; Wet Processing; Sensitizer chemicals needed and Preparation of sensitizer — 0.1 g of ammonium dichromate per 100 cc of finished sensitiser, or 0.5 cc of a 20 per cent w/v solution, with the alternative given for a reader who cannot weigh so small an amount; the statement that with added dichromate the single-bottle sensitiser can last five years at least; Exposure and negatives, for a required negative density range of at least 1.8 obtained by overdeveloping 70 to 80 per cent, for the contrast being lessened by adding citric acid so that a density range of 2.6 or so can be accommodated, and for the contrast being increased by the addition of more ammonium dichromate solution; The sensitiser, its preparation by crystallising out potassium iron(III) oxalate, and the wet-processing acids

Used by:Ammonium iron(III) oxalate · Hydrogen peroxide · Potassium ferrocyanide (anhydrous) · Potassium ferrocyanide trihydrate · Sulfamic acid · The New Cyanotype (1995) · P21 The New Cyanotype and the Other Ways to Make a Blue Print · P24 Contrast Control in Iron-Based Printing · Cyanotype (New Cyanotype)

The Platino-Palladiotype Processretrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: Making up the processing solutions — the EDTA and sulphite clearing sequence; Making up the Processing Solutions, for both EDTA baths at about 5 per cent w/v made by dissolving 50 g of the solid in each litre of water, for the first bath being disodium EDTA at pH around 3 to 4 which "is optimum for complexing iron(III) and is acid enough to avoid hydrolysis leading to yellow iron stains" with a capacity of about fifty 10 by 8 prints per litre, and for the middle bath — Kodak Hypoclearing Agent, or alternatively a solution of sodium sulphite — whose "inorganic sulphite in this tends to reduce any residual iron(III) to iron(II) which is then removed in the final tetrasodium Edta bath", with the advantage that "these last two baths have a high pH (ca. 9) which is optimum for complexation of iron(II) and leaves the paper in a beneficial alkaline condition". Wet Processing Procedure for Platinum-Palladium Prints, for the tabulated sequence at room temperature with intermittent agitation: disodium EDTA 5 per cent 10 minutes, rinse half a minute, Kodak Hypo Clearing Agent working solution 10 minutes, rinse half a minute, tetrasodium EDTA 5 per cent 10 minutes, wash in running water minimum 30 minutes. Hazards and Safety Precautions, for the general instruction that all chemicals be clearly labelled and stored in a safe child-proof place, that spillages be mopped up promptly and skin contact washed off immediately with plenty of cold running water, and that "dry powdery solids present a greater risk than solutions, because the dust can be inadvertently inhaled, so it should be well-contained and a mask worn"; Making up the Processing Solutions and Wet Processing Procedure for Platinum-Palladium Prints, for the modern three-bath sequence this page names as the alternative — disodium EDTA 5 per cent for 10 minutes, a half-minute rinse, Kodak Hypo Clearing Agent working solution for 10 minutes, a half-minute rinse, tetrasodium EDTA 5 per cent for 10 minutes and a wash of at least 30 minutes — with the statement that the first bath at pH around 3 to 4 "is optimum for complexing iron(III) and is acid enough to avoid hydrolysis leading to yellow iron stains"; and Hazards and Safety Precautions, for the instruction that spillages be mopped up promptly, that skin contact be washed off immediately with plenty of cold running water, and that dry powdery solids present a greater risk than solutions because the dust can be inhaled; Disadvantages of the Traditional Platinotype, for the six objections including the chlorate one; Improved Method for Platinum-Palladium Printing; and the statement under print contrast that oxidising agents are not recommended because their effect is not to contract the tonal scale uniformly but simply to truncate the high values; Introduction; Disadvantages of the Traditional Platinotype; Improved Method for Platinum-Palladium Printing; Chemicals required for the Sensitizers; Making up the Sensitizer Solutions; Chemicals required for the Processing Solutions; Making up the Processing Solutions; Hazards and Safety Precautions; Choosing the Sensitizer and its table; Mixing the Sensitizer; Coating the Paper; Drying; Storage; Humidifying; Making the Exposure; Wet Processing Procedure for Platinum-Palladium Prints; Printing in Pure 100% Platinum; Control of Print Contrast; Control of Print Colour; Platinum Printout and Gelatin; Disadvantages of the Traditional Platinotype, for the objections to the development process; the statement under print contrast that oxidising agents truncate the high values rather than contracting the scale uniformly; Making up the Processing Solutions and Wet Processing Procedure for Platinum-Palladium Prints, for the sulphite bath interposed between the two EDTA baths, the pH of about 9 that is optimum for complexation of iron(II), and the instruction to judge the wet processing by examining the print under a bluish light for yellow stain in the masked, unexposed margin; The statement that the modern clearing sequence leaves the paper at a high pH with no residual iron; the maximum-density argument for the more soluble platinum salt; and the note that clearing is judged by examining the masked margin under a bluish light; The print-out route, the ammonium salt, and the humidity requirement

Used by:Sodium sulfite · EDTA and sodium sulfite clearing sequence · EDTA, citric acid and hydrochloric acid clearing sequence · Three-solution drop system for platinum and palladium · Ware's print-out platino-palladiotype · Willis's potassium oxalate developer · P25 Lab: Exposing, Developing and Clearing a Palladium Print · P25 Noble Metal Chemistry and the Platinotype · Print-out platino-palladiotype

Towards an Unproblematic Cyanotype Chemistryretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Ammonium dicitratoferrate(III) characterised 1998; the reasoning behind the formulation; the nitrate by-product as preservative; Simple Cyanotype 2019 — the reasoning and the four benefits claimed for the nitrate by-product; Herschel's Classic Cyanotype 1842; Ferric Ammonium Citrate Failings; Paper Problems; New Cyanotype 1995 — the web statement of the same argument as Cyanomicon 6.7, read for the author's own summary of what goes wrong with the classic sensitiser; Herschel's Classic Cyanotype 1842; Ferric Ammonium Citrate Failings; Paper Problems; New Cyanotype 1995; Ammonium Dicitratoferrate(III) Characterised 1998, with the Matzapetakis reference and the preparation the 1998 authors used; Simple Cyanotype 2019, the reasoning, the four benefits of the nitrate by-product, the reference to US patent 2,113,423 of 1938, the speed against New and Classic, the exposure scale, the maximum density and the shelf life; Ferric Ammonium Citrate Failings; New Cyanotype 1995; Ammonium Dicitratoferrate(III) Characterised 1998; Simple Cyanotype 2019, the reasoning, the four benefits of the nitrate by-product, the reference to US patent 2,113,423 of 1938, the speed against New and Classic, the exposure scale, the maximum density and the shelf life

Used by:Citric acid (anhydrous) · Iron(III) nitrate nonahydrate · Classic cyanotype sensitiser · The Simple Cyanotype (2019) · P21 The New Cyanotype and the Other Ways to Make a Blue Print

moersch-photochemie.de

Brown Toning Part 1: Thiourea and Sulphurretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-08

Sections: Toner — that sodium sulphide solutions of 0.5 to 2 per cent tone quickly within 30 to 60 seconds after bleaching, that solutions of sodium sulphide and liver of sulphur smell unpleasantly like rotten eggs and the smell gets worse in the first rinse water, that the hydrogen sulphide released is a health hazard and can cause fogging on unexposed photographic material, that sulphur solutions should not be used in a darkroom with no ventilation and little supply of fresh air, and that the risk can be ruled out by toning outdoors and watering the print twice before returning indoors; the bleach bath, that the print must be thoroughly rinsed before bleaching because remains of fixer thiosulphate would make the bleach act as a reducer; and the statement that odourless toners in shops are thiourea toners, which are highly alkaline with a pH up to 13.4 and whose toning times should not exceed one minute; Split toning and two-bath development — the SE20c catechol developer and two-tray development with SE1 sepia; captions for Kentmere Fine Print VC and MGW; Selenium pre-toning and bleaching — the incompleteness of the conversion after six minutes and the treatment of the remainder; Alkaline thiourea and potassium bromide toners, Agfa 520 and 525; The odourless thiourea toners as the alternative to the sulfide bath; The bleach bath; Toner — Agfa 520 and 525; MT3 Vario matching table; The observation that after six minutes in a selenium bath not all the silver has been transformed to silver selenide, and that toning reaches the higher densities first; Indirect toning: the observation that toning in sodium sulphide goes beyond the bleached areas and will affect the shadows with increasing time, while a thiourea toner cannot tone the remaining metallic silver but only the areas where it finds a silver salt; the remark that where sodium- or polysulphide toner is no advantage over odourless thiourea when toning indirectly the choice is easy; and the note that with warmtone papers the colour turns yellowish owing to the pH value of the toner; Brown Toning Part 1, Thiourea and Sulphur, the maker's own English guide dated internally to 2007 — the MT3 Vario matching table, which holds the toner part at 50 mL and runs the alkaline activator from 5 to 30 mL for brown-black, through 50 to 60 mL for medium brown, 90 mL for yellowish brown and 130 mL for dark yellow, to 180 mL for bright yellow, with water to a litre in every column, and the statement beneath it that the colour saturation becomes higher the more alkali solution is added to the toner; the statement that the bleach concentrate of the MT3 is diluted between 1+10 and 1+200, that a dilution of 1+75 works sufficiently slowly to be able to assess the progress of the bleaching, and that bleach diluted to 1+50 or higher requires only two to five minutes of washing before toning to remove the yellow coloration of the gelatin; the caution that bromide silver papers require a longer bleaching time or a stronger bleach than chloride silver papers; the instruction that before bleaching the print has to be thoroughly rinsed because remains of the thiosulphate of fixing would make the bleach act as a reducer so that redevelopment would be impossible and at least the highlights would vanish irretrievably; the advice that with a highly alkaline toner it can be worth hardening the gelatine on some papers to preserve the brilliance of the paper surface; the account of the bleach, that for transferring the image silver into a silver salt it makes little difference which formulation is used, that most bleaches contain potassium ferricyanide and potassium bromide, that the ratio between them has little effect on the result while a higher bromide content and a higher pH make the bleach work faster, and that too short a rinse can yellow the whites whichever bleach was used; the free formulas Agfa 500, 501 and 502 and the alkaline thiourea baths Agfa 520 and 525 with the rule that the higher the pH the darker the brown tone, that all thiourea toners are highly alkaline, that it is an early sign of exhaustion if the print is not fully toned after 30 seconds, that the answer is to regenerate with alkali rather than to extend the time, and that prints left too long in a highly alkaline bath soften the gelatine and dry to a dull surface so toning times should not exceed one minute; the statement that the resulting brown tone depends on the form of the silver that was removed, that is on the ratio of silver chloride to silver bromide in the emulsion, and that a high content of bromide silver promotes deep brown hues while chloride-rich and mixed emulsions tone yellow irrespective of the toner; the 2007 list of papers that could still be toned to deep brown; the statement that thiourea toner cannot tone the remaining metallic silver but only the areas where it finds silver salt, in that case silver bromide, where sodium sulphide toning goes beyond the bleached areas; the statement that a bleached but untoned image is silver bromide which must either be dissolved by fixation or converted into silver sulphide by toning again, in MT5 sodium sulphide or in MT3 thiourea; the instruction that a complete bleach loses contrast and density while bleaching only to the mid-tones preserves the shadow density and the original tonal impression; the account of the edge between toned and untoned areas after a partial bleach and of how longer toning smooths the transition; the pre-toning sequences in selenium or sodium sulphide before the bleach, with the plate captions giving bleach 1+30 for 40 seconds then setting B, bleach 1+20 for 30 seconds then setting A, bleach 1+10 for 30 seconds then setting E, bleach 1+40 for 90 seconds then setting C, selenium 1+10 for 2.5 minutes then bleach 1+20 for 1 minute then setting C, selenium 1+10 for 6 minutes then setting E, and MG Warmtone bleached in 1+40 for 30 seconds then setting D; the note that Adox Nuance can be taken to bright yellow, red brown or warm black in MT3 because of its high silver content; the observation that after pre-toning in selenium and bleaching, toning in setting C increases colour saturation slightly while maximum black remains as it is; the statement that whether the second toning is in sodium sulphide or in thiourea makes no difference to the result, so the odourless option was chosen; and the remark that odourless toners in shops are thiourea toners, that they all contain bleach and toner concentrates, and that some of them allow fine tuning of the colours by adjusting the pH value; Pre-toning — the instruction to pre-tone with selenium or sodium sulphide to protect the shadows from being bleached away, that with selenium toner the duration decides whether only the shadows or also the mid tones are protected because selenium toner always starts in the shadows, and that solutions of sodium sulphide by contrast affect the complete range of tone values; the statement that the selenium toners of all manufacturers the author knows of contain thiosulphate, so that the print must be rinsed thoroughly before bleaching, that no rinse is needed between an alkaline fixer and a selenium toner, and that after a sour fixer the print should be rinsed for around 10 minutes; the worked examples of MT1 Selenium 1+10 for 2 minutes and MT1 Selenium Toner 1+10 for 6 minutes, with the observation that after about 3 minutes in a strong dilution a split tone appears, that the highlights change from initially blue to the red of the neighbouring densities before they will survive a bleach, and that after 6 minutes not all the silver has been transformed to silver selenide, the small rest amount being tonable in thiourea after re-halogenation; the plate MGIV neutral tone developer against MT1 Selenium toner 1+50 for 5 minutes and MT5 sulphur toner 1+10 for 3 minutes, with the statement that on that paper the sulphur toner's increase in shadow density is higher and its protective effect considerably higher than selenium toner at a similar dilution for the same duration, and that selenium would not have reached the upper mid tones; the note that Ilford MG IV reacts slowly to all kinds of toning and that selenium toning is hardly visible on it with a neutral tone developer; the pre-toned example at selenium 1+10 for 2 and a half minutes before a bleach at 1+20 for 1 minute; and Over-toning with Selenium, in which selenium follows a sulphur toner at 1+10 for 5 minutes and the highlights as well as the shadows receive a reddish hue; The bleach used at 5 and 20 g per litre of ferricyanide and bromide, bleaching to the deep shades in 30 seconds and lightly in 8 seconds; indirect toning, and the observation that a thiourea toner cannot tone remaining metallic silver but only the areas where it finds silver salt; Working instructions — the statement that with an alkaline fixer no rinse is needed between fixer and selenium toner, whereas an acid fixer must be rinsed out thoroughly; The bleach bath, that the print must be thoroughly rinsed before bleaching because remains of fixer thiosulphate would make the bleach act as a reducer and redevelopment would be impossible, at least the highlights vanishing irretrievably, and that a higher bromide content and a higher pH make a bleach work faster while the ratio of the two salts has little effect on the result of toning; Toner, that sodium sulphide solutions of 0.5 to 2 per cent strength tone quickly within 30 to 60 seconds after bleaching, that with longer toning times the toner also reaches unbleached areas, that solutions of sodium sulphide smell unpleasantly like rotten eggs and that the smell gets worse in the first rinse water, that the hydrogen sulphide released is a health hazard and can cause fogging on unexposed photographic material, that sulphur solutions should not be used in a darkroom with no ventilation and little supply of fresh air, and that the risk can be ruled out by toning outdoors and watering the print twice before returning indoors; that a high bromide silver content promotes deep brown hues while silver chloride and mixed emulsions with a high chloride content tone yellow irrespective of the toner; that it is by no means irrelevant which developer is used before toning; and the warning that a print in which not-yet-toned metallic silver has been bleached to silver bromide is no longer archival, because silver bromide would tone uncontrolled over time by gas action, so it must either be dissolved by fixation or converted to silver sulphide by toning again; The bleach bath - that for the purpose of transferring image silver into a silver salt it makes little difference which formulation is used, that most bleaches contain potassium ferricyanide and potassium bromide and the ratio between them has little effect on the result of toning while a higher bromide content and a higher pH make the bleach work faster, and the instruction that the print must be thoroughly rinsed before bleaching because remains of fixer thiosulfate would make the bleach act as a reducer and redevelopment would be impossible, at least the highlights vanishing irretrievably; the statement that with the same toner setting the degree of bleaching determines the image tone, that bleaching briefly at high dilution warms only the highlights and the higher the dilution the smoother the transitions, and that it is often an advantage for image contrast to stop the bleach before it wipes out the deepest shadows; the account of pre-toning, that if the toner is to reach the shadows fully the bleach would have to go as far in the shadows, costing contrast and density, and that pre-toning in selenium or sodium sulfide instead protects the shadows from being bleached away, selenium protecting the shadows and then the mid-tones according to time while sodium sulfide affects the complete range; the note that after a partial bleach and tone there is silver sulfide from toning beside a small amount of silver salt which can be converted by toning again; and the warning that a print in which not-yet-toned metallic silver has been bleached to silver bromide is no longer archival, because silver bromide would tone uncontrolled over time by gas action, so it must either be dissolved by fixation or converted to silver sulfide by toning again; Page 11, the pre-toning instruction that selenium toner always starts in the shadows so that the toning time decides whether the mid tones are protected as well, whereas solutions of sodium sulphide affect the complete range of tone values; page 12, that ILFORD Multigrade IV reacts rather slowly to all kinds of toning and that selenium toning in particular is hardly visible on this paper if a neutral tone developer was used; page 26, that the selenium toners of all manufacturers known to the author contain thiosulphate, that no rinse is needed between an alkaline fixer and a selenium toner and that after a sour fixer the print should be rinsed for around 10 minutes; and page 28, the example of MT1 at 1+10 for 6 minutes after which not all the silver has been transformed to silver selenide; Page 26, the statement that the selenium toners of all manufacturers the author knows of contain thiosulphate so that the print must be rinsed thoroughly before bleaching, that no rinse is needed between an alkaline fixer and a selenium toner, and that after a sour fixer the print should be rinsed for around 10 minutes; page 28, the example of MT1 Selenium toner at 1+10 for 6 minutes, that after about 3 minutes in a strong dilution a split tone appears with the shadows red and the not yet fully toned densities separating in a cooler colour, that the progress of toning is easy to judge, that only when the highlights change from initially blue to the red of the neighbouring densities will they remain after bleaching, and that after 6 minutes not all the silver has been transformed to silver selenide while the small remaining amount can be toned in thiourea after re-halogenation; page 11, the pre-toning instruction that selenium toner always starts in the shadows so that the toning time decides whether the mid tones are protected as well, whereas solutions of sodium sulphide affect the complete range of tone values; page 12, that ILFORD Multigrade IV reacts rather slowly to all kinds of toning and that selenium toning in particular is hardly visible on this paper if a neutral tone developer was used; and page 14, the warning that a print in which not yet toned metallic silver has been bleached to silver bromide is no longer archival because the silver bromide would tone uncontrolled over time by gas action, so it must either be dissolved by fixation or converted by toning again; The bleach bath, that for transferring image silver into a silver salt it makes little difference which formulation is used, that most bleaches contain potassium ferricyanide and potassium bromide, that the ratio between them has little effect on the result of toning while a higher bromide content and a higher pH make the bleach work faster, and the instruction that the print must be thoroughly rinsed before bleaching because remains of fixer thiosulphate would make the bleach act as a reducer and redevelopment would be impossible, at least the highlights vanishing irretrievably; Toner, that sodium sulphide solutions of 0.5 to 2 per cent strength tone quickly within 30 to 60 seconds after bleaching, that with longer toning times the toner also reaches unbleached areas, that solutions of sodium sulphide and liver of sulphur smell unpleasantly like rotten eggs, that the smell gets worse in the first rinse water, that the hydrogen sulphide released is a health hazard and can cause fogging on unexposed photographic material, that sulphur solutions should not be used in a darkroom with no ventilation and little supply of fresh air, and that the risk can be ruled out by toning outdoors and watering the print twice before returning indoors; the alkaline thiourea and potassium bromide baths Agfa 520, thiourea 5 g, potassium bromide 40 g and sodium hydroxide 3 g per litre, and Agfa 525, the same with 15 g of sodium hydroxide, with the statements that odourless toners in shops are thiourea toners, that the higher the pH value the darker the brown tone, that 520 produces a delicate yellowish hue and 525 a stronger darker nuance, that both baths are long-lived and are regenerated with sodium hydroxide, that all thiourea toners are highly alkaline with a pH up to 13.4, and that prints left too long in them soften the gelatin and dry to a dull surface so toning times should not exceed one minute; the MT3 Vario matching table running from brown-black at 5 to 30 mL of alkaline activator per litre through medium brown, yellowish brown and dark yellow to bright yellow at 180 mL; the statements that a high bromide silver content promotes deep brown hues while silver chloride and mixed emulsions with a high chloride content tone yellow irrespective of the toner, that it is by no means irrelevant which developer is used before toning, that the usual characteristic of polysulphide toners is to go on toning further in the final wash, that toning in a polysulphide toner is stopped in a sulphite solution to prevent this, that short polysulphide toning times of 30 to 90 seconds give cold brown hues while longer times give more reddish colours, that direct sulphur toning does not necessarily give a brown tone with any paper but that the protecting effect on the silver is there even when little colour change is visible, that with suitable neutral- and cold-tone emulsions sulphur toner can be applied exclusively for archival purposes, that maximum black can increase enormously and that even with short toning times the highlight densities receive a stabilising effect; the account of pre-toning, that pre-toning in sodium sulphide affects the complete range of tone values while selenium protects the shadows and then the mid-tones according to time; and the warning that a print in which not-yet-toned metallic silver has been bleached to silver bromide is no longer archival, because silver bromide would tone uncontrolled over time by gas action, so it must either be dissolved by fixation or converted to silver sulphide by toning again; Page 11, that selenium toner always starts in the shadows so that the toning time decides whether the mid tones are protected as well, whereas solutions of sodium sulphide affect the complete range of tone values; page 12, that direct sulphur toning does not necessarily give a brown tone with any given paper, that the protecting effect on the silver is there even when only a small colour change is visible, that with suitable neutral- and coldtone emulsions sulphur toner can be applied exclusively for archival purposes, and that in contrast to selenium even short sulphur toning times give the highlight densities a stabilising effect; page 13, that after bleaching a print toned in MT5 sulphur toner at 1+10 for 3 minutes the print is not yet fully toned but the protective effect is considerably higher than with selenium toner in a similar dilution for the same duration, since with selenium the upper mid tones would not have been reached; page 28, the example of MT1 Selenium toner at 1+10 for 6 minutes, after which not all the silver has been transformed to silver selenide while the small remaining amount can be toned in thiourea after re-halogenation; and page 14, that a print in which not-yet-toned metallic silver has been bleached to silver bromide is no longer archival because the silver bromide would tone uncontrolled over time by gas action, and must either be dissolved by fixation or converted by toning again; The observation that after six minutes in a selenium bath not all the silver has been transformed to silver selenide; toning reaching the higher densities first; The recommendation that a darkroom with no ventilation and little fresh air is not used for sulphur solutions, and that the risk can be ruled out by toning outdoors and watering the print twice before returning indoors; the note that the smell is worst in the first rinse after the toner

Used by:P29 Capstone Stage 5: The Toned Print and the Alternative-Process Print · Catechol · Silver selenide · Sodium hydroxide (caustic soda) · Sodium sulfide · Thiourea · HARMAN SELENIUM TONER · Kodak T-26 · Moersch MT3 Variotoner · Moersch MT1 Selentoner · Rehalogenating ferricyanide-bromide bleach · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 What a Toner Actually Does to a Silver Image · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P20 Toning, Permanence and What the Evidence Actually Supports · Selenium toned silver gelatin print · Handling a sulphide toner and its waste

MT1 Selentoner (MT1 Selenium toner): product page, Moersch Photochemie online shopretrieved 2026-09-06

Sections: The Description tab, for the dilution range of 1+10 to 1+400 and for the maker's regulatory statement that selenium toner based on sodium selenite may now only be marketed below 1 vol per cent, that this product does not contain sodium selenite but sodium selenate, and that the preparation therefore did not have to be changed; Description — selenium toner concentrate, dilution 1+10 to 1+400, and the maker's regulatory statement that selenium toner based on sodium selenite may now only be marketed in vol % below 1, that this product does not contain sodium selenite but sodium selenate, that the preparation did not have to be changed and that all information on dilution to working solution in the instructions and under the picture examples is up to date as before; Product safety — the consumer labelling giving the signal word Caution, the single hazard statement harmful if swallowed, and the precautionary text; Additional information and the shop's variation data — the two pack sizes of 250 ml and 1 litre and their prices; and the links naming the maker's own guide and safety data sheet for this product; Description - selenium toner concentrate, dilution 1+10 to 1+400; and the maker's regulatory statement that the legal regulations have changed so that selenium toner based on sodium selenite may now only be marketed in vol per cent below 1, that this product does not contain sodium selenite but sodium selenate, that the preparation therefore did not have to be changed, and that all information on dilution to working solution in the instructions and under the picture examples is up to date as before

Used by:Sodium selenate · Moersch MT1 Selentoner · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim

MT3 Variotoner: product page, Moersch Photochemie online shopretrieved 2026-09-06

Sections: Description, Additional information and Product safety tabs — the description of the product as an odourless thiourea toner for indirect sulphur toning; the statement that, due to the variable mixability of toner and activator and varying degrees of bleaching, shades from light yellow to golden ochre to reddish brown can be achieved; the instruction that the prints must be completely washed before bleaching; the statement that bleaching times depend on the paper, the desired image tone and the dilution of the bleaching agent; the instruction that if bleaching is not to be carried out completely, in order to maintain the depth of the shadows, the bleach is diluted at least 1+20 so that the progress can be judged, the bleaching time then being between 20 seconds and three to four minutes; the statement that diluted bleaching agents at 1+30 or more must be washed out of the carrier and gelatine much faster than strong bleaching agents at 1+10, and that before toning, water must be added until the yellow colour disappears completely; the statement that the bleach solutions have an almost unlimited shelf life, that the toner can be refreshed with concentrate when the effect wears off, that the toning of the bleached areas is complete after 20 to 30 seconds, and that partial applications are possible and the concentrates can be kept for years even after opening; the two kits, Kit 1 with a bleach concentrate of 100 mL making 1 to 4 litres of working solution and a toner concentrate of 100 mL with 250 mL of activator making 2 litres, and Kit 2 with 250 mL of bleach making 2.5 to 16 litres and 250 mL of toner with 1000 mL of activator making 5 litres; the maker's explanation that different amounts of activator are required depending on the desired image tone and that for this reason all concentrates are also available as single products; the GPSR consumer labelling for each of the three parts with its UFI code and hazard and precautionary statements; and the shop's variation data giving the four purchasable items and their prices including VAT at the retrieval date

Used by:Moersch MT3 Variotoner

Safety data sheet according to 1907/2006/EC Article 31: MT3 VARIO TONER part 3 (Activator)retrieved 2026-09-06

Sections: Section 1, product identifier, application and UFI; section 2, classification, pictogram, signal word, hazard and precautionary statements; section 3, composition, naming potassium carbonate alone with its CAS and EC numbers, its classification and its concentration; section 7, handling and storage; section 8, glove specification and the statement that the product as supplied contains no substance with an occupational exposure limit; section 9, physical and chemical properties including the pH and the solvent content; section 12, ecological information; section 13, disposal; section 14, transport

Used by:Moersch MT3 Variotoner

Safety data sheet according to Regulation (EC) No 1907/2006 (REACH): BLEACH (MT3 Vario, Part 1)retrieved 2026-09-06

Sections: Section 1, product identifier and UFI; section 2, classification, pictograms, signal word, hazard and precautionary statements and the supplemental statement EUH032; section 3, composition, naming potassium hexacyanoferrate(III) and sodium bromide with their CAS and EC numbers, classifications and concentration figures; section 5.2, products of combustion; section 7.2, storage; section 8, exposure controls, glove specification and the absence of an occupational exposure limit; section 9, physical and chemical properties; section 10.3 and 10.4, hazardous reactions and conditions to avoid; section 12, ecological information; section 13, disposal and the hazardous-waste properties; section 14, transport; section 15, regulatory information

Used by:Moersch MT3 Variotoner

Safety data sheet according to Regulation (EC) No 1907/2006 (REACH): MT1 SELENTONERretrieved 2026-09-04, 2026-09-06

Sections: Section 3, the composition table naming Ammonium sulfite, CAS 10196-04-0, EC 233-484-9, at 10 per cent w/w and classified Eye Irrit. 2 and STOT SE 3, H319 and H335, alongside ammonium thiosulfate at 20 per cent and sodium selenate at 2 to 3 per cent; sections 2.1 and 2.2, the classification of the mixture, its signal word and pictograms; section 8.2, the glove specification and the instruction not to let the product enter drains; section 9, form, colour, the ammonia-like odour, density 1.20 g/cm3 at 20 degrees C and pH 9.53 at 20 degrees C; sections 10.3 and 10.5, violent reaction with strong acids and release of toxic materials with acids; section 13, disposal as hazardous waste. Printing date and revision 16 February 2025, version 3; Section 3: composition; Section 2: classification of the mixture; Section 13: disposal considerations; Sections 1.1 and 1.2, trade name, UFI and the application as a toner for silver gelatine prints; section 2.1, the classification of the mixture; section 2.2, signal word and pictograms; section 3, the composition table naming Sodium selenate CAS 13410-01-0, EC 236-501-8, REACH registration number 01-2120772103-63-xxxx, at 2 to 3 per cent w/w and classified Acute Tox. 2, STOT RE 2, Aquatic Acute 1 and Aquatic Chronic 1; section 7.2, storage conditions; section 8.1, control parameters recorded as not available; section 8.2, the glove specification and the instruction not to let the product enter drains; section 9, form, colour, odour, density, miscibility and pH; sections 10.3 and 10.5, violent reaction with strong acids and release of toxic materials with acids; section 11, the oral LD50 of 7 mg/kg in rat attributed to ECHA, the symptom list including the entry "risk of absorption via the skin", and the statements that the mixture shall not be classified as germ cell mutagenic or as a reproductive toxicant; section 12.1, the aquatic endpoints; section 13, disposal as hazardous waste and the hazardous properties HP5, HP6 and HP14. Printing date and revision 16 February 2025, version 3; Section 3: composition/information on ingredients; Section 9: physical and chemical properties; Section 10: stability and reactivity; Section 8: exposure controls and glove data; Section 3, composition and information on ingredients — 2 to 3 per cent w/w sodium selenate, CAS 13410-01-0, with 10 per cent w/w ammonium sulfite and 20 per cent w/w ammonium thiosulfate; section 8, glove data; Section 3, composition and information on ingredients — 2 to 3 per cent w/w sodium selenate, CAS 13410-01-0, with 10 per cent w/w ammonium sulfite and 20 per cent w/w ammonium thiosulfate; Section 3, composition and information on ingredients, as the comparison for what this maker discloses on a sheet for a product he sells in the same range; Section 1.1, trade name MT1 SELENTONER and the UFI; section 1.2, application of the mixture; section 1.3, manufacturer and address; sections 2.1 and 2.2, classification of the mixture, signal word, pictograms, hazard statements and precautionary statements; section 2.3, PBT and vPvB; section 3, composition and information on ingredients; section 4, first aid; sections 5.2 and 5.3, non-combustible and advice for firefighters; section 6, accidental release; section 7, handling and storage including the recommended storage temperature; section 8.1, control parameters recorded as not available, and section 8.2, eye, skin and body protection with the nitrile glove data; section 9, physical and chemical properties; section 10, stability and reactivity including the violent reaction with strong acids and the release of toxic materials with acids; section 11, toxicological information including the oral LD50 and the symptom list; section 12, ecological information; section 13, disposal considerations and the hazardous properties HP5, HP6 and HP14; section 14, transport; section 15, Seveso III and the GB REACH lines; and section 16, the relevant H-phrases and the disclaimer; Version 3, revision 16 February 2025 — Section 2.1 classification of the mixture, Acute Tox. 2 H300, STOT RE 2 H373, Eye Dam. 1 H318, Skin Sens. 1 H317, Aquatic Acute 1, with pictograms GHS07, GHS08 and GHS09; Section 10.3, violent reaction with strong acids, and 10.5, release of toxic materials with acids; Section 12.1, toxic to aquatic organisms with long lasting effects; Section 13.1, this material and its container must be disposed of as hazardous waste, do not empty into drains; Sections 2.1 and 2.2, the mixture classified Acute Tox. 2 H300, STOT RE 2 H373, Eye Dam. 1 H318 and Skin Sens. 1 H317, signal word Danger, pictograms GHS07, GHS08 and GHS09; section 3, the composition naming ammonium sulfite at 10 per cent w/w, ammonium thiosulfate at 20 per cent w/w and sodium selenate CAS 13410-01-0 at 2 to 3 per cent w/w; section 9, pH 9.53 at 20 degrees C and an ammonia-like odour; section 10.3 and 10.5, violent reaction with strong acids and release of toxic materials with acids; and section 13, that the material and its container must be disposed of as hazardous waste and must not be emptied into drains; Sections 2.1 and 2.2, the mixture classified Acute Tox. 2 H300, STOT RE 2 H373, Eye Dam. 1 H318 and Skin Sens. 1 H317, signal word Danger, pictograms GHS07, GHS08 and GHS09; section 3, the composition naming Ammonium sulfite CAS 10196-04-0 at 10 per cent w/w, Ammonium thiosulfate CAS 7783-18-8 at 20 per cent w/w and Sodium selenate CAS 13410-01-0 at 2 to 3 per cent w/w, the last classified Acute Tox. 2, STOT RE 2, Aquatic Acute 1 and Aquatic Chronic 1; section 8.1, control parameters recorded as not available; section 9, form fluid, colour colourless, odour ammonia like, density 1.20 g/cm3 at 20 degrees C, fully miscible with water and pH 9.53 at 20 degrees C; section 10.3 and 10.5, violent reaction with strong acids and release of toxic materials with acids; section 11, the oral LD50 of 7 mg/kg in rat from ECHA and the symptom list including risk of absorption via the skin; section 12.1, toxic to aquatic organisms with long lasting effects; and section 13, that the material and its container must be disposed of as hazardous waste, must not be emptied into drains, and carry the hazardous properties HP5, HP6 and HP14. Printing date and revision 16 February 2025, version 3; Composition — 2 to 3 per cent w/w sodium selenate with 10 per cent w/w ammonium sulfite and 20 per cent w/w ammonium thiosulfate

Used by:Ammonium sulfite · Selenium · Sodium selenate · Sodium selenite · HARMAN SELENIUM TONER · KODAK Rapid Selenium Toner · Moersch MT3 Variotoner · Moersch MT1 Selentoner · P20 Part XX Overview: Toning Chemistry · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · Selenium toned silver gelatin print

Safety data sheet according to Regulation (EC) No 1907/2006 (REACH): MT3 Part 2 TONERretrieved 2026-09-06

Sections: Section 1, product identifier and application; section 2, classification, pictograms, signal word, hazard and precautionary statements, the statement that the product is for professional users only and the record that packages not exceeding 250 mL require no pictogram, signal word or hazard statement; section 3, composition, naming thiourea alone with its CAS and EC numbers, its classification and its concentration figure; section 5.2, products of combustion; section 7, handling and storage; section 8, the thiourea DNEL and PNEC values and the glove specification; section 9, physical and chemical properties; section 10.3 and 10.4, hazardous reactions and conditions to avoid; section 11, the ECHA acute toxicity values; section 12, ecological information; section 13, disposal and the hazardous-waste properties; section 14, transport; The document header, printing date 6 January 2025, version 3, UFI 8H30-X02A-400V-XUHW; and section 2, the classification Acute Tox. 4 (H302), Carc. 2 (H351), Repr. 2 (H361d) and Aquatic Chronic 2 (H411) with pictograms GHS07, GHS08 and GHS09, and the statement 'For professional users only'. Cited here for the date and for the two hazard classes that decide whether this toner may be chosen for the assignment

Used by:Moersch MT3 Variotoner · P20 Assignment: The Toned Print

Selenium Toningretrieved 2026-09-06

Sections: The rule that irrespective of the dilution or temperature the toner always reaches the higher densities first; the account of the increase in dmax and the more differentiated deep shadows; and the observation that after six minutes in a selenium bath not all the silver has been transformed to silver selenide; The rule that a selenium toner always reaches the higher densities first, so that toning time decides how far up the scale a pre-tone protects the print from a subsequent bleach; Selenium toning, the maker's own guide in English — the opening judgement that discussions of image silver stabilisation by selenium appear pointless to him, that gold, sulphur and Sistan are more effective routes to archival permanence, and that even weak selenium toning is better than none; the statement that a fine printer has other reasons, and that selenium toner allows the densities of the shadows to be increased exclusively; the rule that irrespective of the dilution or temperature the toner always reaches the higher densities first; the account of the distinctive increase in dmax, the more differentiated deep shadows, the higher contrast range and the shift of image tone towards cooler and less green tints, with the shift dependent on the composition of the paper emulsion and on the developer; the statement that the greenish cast can be shifted to more pleasant hues in highly diluted working solutions; the two dilution regimes, 1+100 to 1+400 to reach the highlights before a decrease in shadow density occurs and 1+5 to 1+20 for 20 to 60 seconds to intensify the shadows alone; the warning that toning short and strong must be stopped abruptly, that clearing agents are no stop baths for selenium toners, and that the practical stop is quick dilution in running water with both surfaces gently wiped with cotton wool; the statement that all papers are accessible to selenium toning, that warmtone paper tones quickly with a clear change in image colour while with coldtone paper the alteration is often barely visible even in a strong solution for a longer duration; the diagnostic that how far toning really progressed is only visible if you bleach, that a red brown image with tonality in the highlights means the goal is reached, and that worn-out highlights mean toning was too short for maximum protection; the term hidden selenium toning for the small membrane created around the silver grain in the highlights; the note that after bleaching and fixing the untoned silver is removed and the print becomes lighter, and that reverse development with any developer can be used instead of fixing to restore the original condition; the instruction that on warmtone paper the progress of toning is easier to judge and that shifting the image tone calls for higher dilutions or the shadows lose density before the highlights are reached; the rule that the warmer the print was developed, the higher the toner should be diluted to prevent excessive cooling of the image tone; and the plate captions giving selenium toning at 1+100 for 2 minutes, 1+10 for 2 minutes then bleached, 1+10 for 40 seconds, 1+10 for 1 minute 30 seconds, 1+10 for 5 minutes, 1+50 for 3 minutes, 1+20 for 2 minutes and 1+6 for 4 minutes; The statement that, irrespective of dilution or temperature, a selenium toner always reaches the higher densities first, so that strong short baths at 1+5 to 1+20 for 20 to 60 seconds intensify the shadows alone while dilutions of 1+100 to 1+400 are needed to reach the highlights before the shadows begin to lose density; the account of the accompanying increase in Dmax, better differentiation in the deep shadows and a shift of image tone towards cooler and less green tints; the observation that all papers respond but that on cold-tone papers the change is often barely visible even in a strong solution for a long time; and the diagnostic that how far selenium toning has really progressed is only visible if the print is bleached, a red-brown image with tonality in the highlights showing that the goal was reached and worn-out highlights showing that toning was too short; The rule that irrespective of the dilution or temperature the toner always reaches the higher densities first; the account of a distinctive increase in dmax, more differentiated deep shadows, a higher contrast range and a more or less strong shift of the image tone towards cooler and less green tints, with the shift dependent on the composition of the paper emulsion and on the developer; the statement that all papers are accessible to selenium toning, that some tone quickly while with others the effect is only visible in direct comparison to an untoned print, that in any case the print gains in brilliance and an increase of the shadow densities is visible and measurable, and that warmtone paper tones quickly with a clear change in image colour whereas with coldtone paper the alteration is often barely visible even in a strong solution for a longer duration; the two dilution regimes, 1+100 to 1+400 if the toner is to reach the highlights before a decrease in shadow density occurs and 1+5 to 1+20 for only 20 to 60 seconds if only the shadows are to intensify; the warning that clearing agents are no stop baths for selenium toners and that a short strong toning is stopped by a quick dilution in running water with both surfaces gently wiped with cotton wool; the term hidden selenium toning for the small membrane created around the silver grain in the highlights; and the instruction that the warmer the print was developed the higher the toner should be diluted to prevent excessive cooling of the image tone; The whole of the maker's own English guide - the opening judgement that recent discussions about image silver stabilisation by means of selenium toning appear pointless to him, that there are more effective ways to achieve archival permanence like toning in gold, sulphur or Sistan, and that even weak selenium toning is better in terms of archival permanence than no toning at all; the statement that a fine printer has other reasons and that selenium toner allows the densities of the shadows to be increased exclusively; the rule that irrespective of the dilution or temperature the toner always reaches the higher densities first; the account of a distinctive increase in dmax, more differentiated deep shadows, a higher contrast range and a more or less strong shift of the image tone towards cooler and less green tints, with the shift dependent on the composition of the paper emulsion and on the developer; the statement that the greenish cast of the image silver can be shifted to more pleasant hues in highly diluted working solutions; the two dilution regimes, 1+100 to 1+400 if the toner is to reach the highlights before a decrease in shadow density occurs, and 1+5 to 1+20 for only 20 to 60 seconds if only the shadows are to intensify; the warning that toning short and strong must be stopped abruptly, that clearing agents are no stop baths for selenium toners, and that the process is sufficiently stopped by a quick dilution in running water with both surfaces gently wiped with a piece of cotton wool; the statement that all papers are accessible to selenium toning, that some tone quickly while with others the effect is only visible in direct comparison to an untoned print, that in any case the print gains in brilliance and an increase of the shadow densities is visible and measurable, and that warmtone paper tones quickly with a clear change in image colour whereas with coldtone paper the alteration is often barely visible even in a strong solution for a longer duration; the diagnostic that how far toning really progressed is only visible if you bleach, that a remaining red brown image in which even the highlights show enough tonality means the goal is reached, and that highlights or mid tones appearing worn out mean toning was too short to give the print maximum protection from the environment; the term hidden selenium toning for the small membrane created around the silver grain in the highlights; the note that after bleaching, subsequent fixing removes the still untoned silver and the print becomes lighter, while reverse development with any developer can be used instead of fixing to restore the original condition; and the instruction that on warmtone paper the progress of toning is easier to judge, that shifting the image tone calls for higher dilutions or the shadows start losing density before the highlights have been reached, and that the warmer the print was developed the higher the toner should be diluted to prevent excessive cooling of the image tone; The opening judgement that recent discussions about image silver stabilisation by means of selenium toning appear pointless to the author, that there are more effective ways to achieve archival permanence such as toning in gold, sulphur or Sistan, and that even weak selenium toning is better in terms of archival permanence than no toning at all; and the bleach diagnostic, that how far toning really progressed is only visible if you bleach, that a remaining red-brown image in which even the highlights show enough tonality means the goal is reached, that highlights or mid tones appearing worn out mean toning was too short to give the print maximum protection from the environment, and that in the highlights a small membrane will nonetheless have been created around the silver grain, which the author calls hidden selenium toning

Used by:KODAK Rapid Selenium Toner · Moersch MT3 Variotoner · Moersch MT1 Selentoner · P20 What a Toner Actually Does to a Silver Image · P20 Experiment: Selenium Toning and the Print Curve · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Toning, Permanence and What the Evidence Actually Supports

mubychem.com

Calcium Nitrate Tetrahydrate: safety data sheet, Muby Chemicals / Mubychem Group, sheet dated 1 December 2020retrieved 2026-09-08

Sections: Section 1, Product Identification, for the CAS number, the molecular weight of 236.15 and the EC number the sheet prints; Section 2, Hazards Identification, for the classification according to Regulation (EC) No 1272/2008, the signal word and the hazard and precautionary statements; Section 9, Physical and Chemical Properties, for the appearance, the pH of a 10 per cent solution, the relative density and the melting point of 43 degrees C; Section 10, Stability and Reactivity, for the decomposition products and the incompatibilities; Section 11, Toxicological Information, for the oral LD50 in the rat; Section 12, Ecological Information, for the fish LC50 and the statement that the material is not considered an environmental hazard; Section 14, Transport Information, for UN 1454 and hazard class 5.1 packing group III

Used by:Calcium nitrate tetrahydrate

nhs.uk

Burns and scalds: Treatmentretrieved 2026-09-04, 2026-09-05

Sections: What to do if you have a burn or scald; What to do if you have a burn or scald; when to call 999; Treatment - cool running water for 20 minutes as soon as possible, remove clothing and jewellery near the burn but nothing stuck to it, cover with cling film laid over rather than wrapped, and the routes to 111 and to accident and emergency; Treatment - hold the burn under cool running water for 20 minutes as soon as possible, remove clothing and jewellery near the area but not anything stuck to it, and cover by laying cling film over the cooled injury; Treatment - cool running water for 20 minutes as soon as possible, remove clothing and jewellery near the burn but nothing stuck to it, and cover with cling film laid over rather than wrapped; What to do if you have a burn or scald; when to call 999 or attend accident and emergency; things you can do to help while burns and scalds heal

Used by:P2 Lab: Commissioning Your Laboratory · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P5 Build an Emulsion Coating Station · P14 Build: The LED Light Source and Exposure Timer · P14 Low-Voltage Electronics for the Darkroom Builder · P15 Build: The Densitometer Electronics and Firmware · P15 Build: The Densitometer Optical Head (Transmission and Reflection) · First aid quick reference

Cuts and grazesretrieved 2026-09-04, 2026-09-05

Sections: Treatment: stop the bleeding with pressure, clean by rinsing, cover with a sterile dressing; do not remove an embedded object yourself; when to contact 111 or a GP; Treatment - pressure to stop the bleeding, rinse the wound clean, cover with a sterile dressing, and do not try to remove an embedded object yourself; Treating cuts and grazes; when to get medical help; What to do if the wound is bleeding a lot; How to clean and dress a cut or graze; and the immediate-action list — call 999 or go to A&E if you cannot stop the bleeding, if you lose feeling near the wound or have trouble moving it, if you have a bad cut on the palm of your hand, or if there is something stuck in the cut, such as a shard of glass, which you do not try to take out yourself

Used by:P6 Build the Modular Pinhole Camera · P6 Making and Measuring Pinholes · P14 Build: The Enclosure and Exposure Stage · First aid quick reference · Glass handling, cutting and breakage response

nssdc.gsfc.nasa.gov

Moon Fact Sheet, NASA Space Science Data Coordinated Archiveretrieved 2026-09-04

Sections: Mean values at opposition from Earth: apparent visual magnitude -12.74 and apparent diameter 1896 seconds of arc

Used by:P7 Assignment: Night, the Very Long Exposure and Solargraphy

Sun Fact Sheet, NASA Space Science Data Coordinated Archiveretrieved 2026-09-04, 2026-09-05

Sections: Visual magnitude V(1,0) of -26.74; Sun Observational Parameters, apparent diameter from Earth at 1 A.U. of 1919 seconds of arc; Rotational and orbital parameters, obliquity of the ecliptic 23.44 degrees; Obliquity to ecliptic, 23.44 degrees for the Earth, which is the extreme value of the solar declination; Sun Observational Parameters, apparent diameter from Earth at 1 A.U. of 1919 seconds of arc

Used by:P7 Assignment: Night, the Very Long Exposure and Solargraphy · Solargraph camera placement and retrieval

omronfs.omron.com

Solid State Relay G3MB, PCB-mounting SSR, data sheetretrieved 2026-09-05

Sections: Ratings by load type - 2 A at 240 VAC general purpose against 1 A at 240 VAC for a tungsten load on the G3MB-202P; operate and release time of one half of the load power source cycle plus 1 ms maximum for the zero-cross models against 1 ms maximum without; leakage current 1.50 mA at 200 VAC; Precautions - the leakage flows through the snubber circuit even with no power at the input; Load ratings by load type for the G3MB-202P - 2 A at 240 VAC general purpose against 1 A at 240 VAC tungsten; operate and release times of one half of the load power source cycle plus 1 ms maximum for the zero-cross models against 1 ms maximum for the non-zero-cross model; leakage current 1.50 mA at 200 VAC; output ON voltage drop 1.60 V RMS maximum; insulation resistance 1000 megohms minimum at 500 VDC and dielectric strength 2500 VAC for one minute; and the precaution that a model without a zero-cross function must be chosen for phase control; Leakage current 1.50 mA at 200 VAC; Precautions - the leakage flows through the device's snubber circuit even when there is no power at the input, so the load side is treated as live until the supply is proved off; Leakage current 1.50 mA at 200 VAC; output ON voltage drop 1.60 V RMS maximum

Used by:P17 Build: The Switched Output · P17 Switching Lamps Safely: Isolation, Certified Modules and the Mains Boundary · P17 Break/Fix: The Timer That Lies · Lamp glowing faintly between exposures

Solid State Relay G3NA, panel-mounting SSR, data sheetretrieved 2026-09-05

Sections: Load ratings by load type - the G3NA-210B rated 4 A for general use and tungsten against a 10 A device rating, the G3NA-220B and G3NA-225B likewise at 4 A, and the 40 A G3NA-240B at 6 A; leakage current 5 mA maximum at 100 VAC and 10 mA maximum at 200 VAC; and the precaution that leakage current flows through the snubber circuit even when there is no power input, so the supply must be proved off before wiring; Leakage current 5 mA maximum at 100 VAC and 10 mA maximum at 200 VAC, and the precaution that leakage current flows through the snubber circuit even when there is no power input

Used by:P17 Switching Lamps Safely: Isolation, Certified Modules and the Mains Boundary · Lamp glowing faintly between exposures

openstax.org

Chemistry 2e, Appendix H: Ionization Constants of Weak Acidsretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Appendix H: ionisation constant of boric acid; Appendix H: ionisation constants of boric, acetic and carbonic acids; Appendix H, for the ionisation constant of boric acid; Appendix H: the ionisation constant of boric acid, 5.4 x 10 to the minus 10; Appendix H: ionisation constants at 25 degrees C for acetic acid, boric acid, carbonic acid and sulfurous acid; Appendix H: ionisation constants for acetic acid and carbonic acid at 25 degrees C; Appendix H: ionisation constants of boric, carbonic, phosphoric and sulfurous acids; Appendix H: ionisation constants of weak acids — sulfurous acid, Ka1 1.6 x 10^-2 and Ka2 6.4 x 10^-8; Appendix H, ionisation constants of weak acids — sulfurous acid Ka2 giving pKa2 7.19, boric acid giving pKa 9.27 and carbonic acid Ka2 giving pKa2 10.33; Appendix H, ionisation constants of weak acids — carbonic acid Ka1 and Ka2 giving pKa1 6.35 and pKa2 10.33, sulfurous acid Ka2 giving pKa2 7.19, and boric acid giving pKa 9.27; Appendix H, ionisation constants of weak acids — sulfurous acid Ka2 giving pKa2 7.19 and boric acid giving pKa 9.27; Appendix H, ionisation constants of weak acids — sulfurous acid Ka1 1.6 x 10-2 and Ka2 6.4 x 10-8, giving pKa1 1.80 and pKa2 7.19; boric acid giving pKa 9.27; Appendix H, ionisation constants of weak acids — acetic acid, sulfurous acid Ka2 giving pKa2 7.19, boric acid giving pKa 9.27 and carbonic acid giving pKa1 6.37; Appendix H, ionisation constants of weak acids - sulfurous acid, Ka2 6.4 x 10^-8

Used by:Borax (sodium tetraborate decahydrate) · Boric acid · Borax kallitype developer · Kodak D-76d · P3 Acids, Bases and pH · P3 Buffers and Buffer Capacity · P3 Lab: Measuring pH and Trusting the Number · P8 Alkalis, Buffers and pH · P8 Sulfite: Preservative, Buffer, Silver Solvent · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Break/Fix: The Developer That Went Wrong · P9 Experiment: Comparing Developing Agents · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P10 Experiment: Measuring Stop Bath Capacity · P10 Why Stopping Works · P27 Designing an Experiment That Yields a Number

Chemistry 2e, Appendix J: Solubility Productsretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Appendix J — calcium salts: CaCO3 and CaC2O4·H2O; Appendix J, the nickel block — Ni(OH)2 1.6 x 10-16, NiCO3 1.4 x 10-7, NiS(alpha) 4 x 10-20 and NiS(beta) 1.3 x 10-25 at 25 degrees C, with no entry for the sulfate; Appendix J, searched for a silver selenide entry and none found; Appendix J, silver salts — Ag2S, AgCl, AgBr and AgI; Appendix J, the thallium block — TlCl 1.7 x 10-4, TlSCN 1.6 x 10-4, Tl2S 6 x 10-22 and Tl(OH)3 6.3 x 10-46 at 25 degrees C, with no entry for the sulfate; Appendix J, Solubility Products, the silver block — AgCl 1.6 × 10⁻¹⁰, AgBr 5.0 × 10⁻¹³ and AgI 1.5 × 10⁻¹⁶ at 25 degrees C; Appendix J, the silver halides: silver chloride 1.6 x 10-10, silver bromide 5.0 x 10-13, silver iodide 1.5 x 10-16 at 25 C; Appendix J — the solubility products at 25 degrees C for silver sulfide, 1.6 by 10 to the minus 49, against silver bromide at 5.0 by 10 to the minus 13 and silver chloride at 1.6 by 10 to the minus 10; Appendix J: solubility products at 25 degrees C for silver chloride, silver bromide and silver iodide; Appendix J: solubility products of silver chloride, silver bromide and silver iodide at 25 degrees C; Appendix J: solubility products at 25 degrees C for silver chloride, silver bromide, silver iodide, silver thiocyanate, silver cyanide and silver sulfide; Appendix J: solubility products at 25 °C for silver chloride and silver bromide; Appendix J — solubility products at 25 degrees C for silver chloride, silver bromide and silver iodide; Appendix J — silver bromide 5.0 x 10^-13 and silver iodide 1.5 x 10^-16; Appendix J — silver sulfide at 1.6 x 10^-49 and silver bromide at 5.0 x 10^-13; Appendix J, solubility products at 25 degrees C — silver chloride 1.6 x 10^-10, silver bromide 5.0 x 10^-13, silver iodide 1.5 x 10^-16; Appendix J, Solubility Products at 25 C - silver bromide 5.0 x 10 to the minus 13 and silver sulfide 1.6 x 10 to the minus 49, the pair that drives the halide-to-sulfide exchange; Appendix J, Solubility Products at 25 degrees C - silver bromide 5.0 x 10 to the minus 13 and silver sulfide 1.6 x 10 to the minus 49, the pair the sulfide route is argued on and for which this page has no selenide counterpart; Appendix J, Solubility Products at 25 degrees Celsius - silver bromide 5.0 x 10 to the minus 13 and silver sulfide 1.6 x 10 to the minus 49; Saturation as equal rates of dissolution and crystallisation, supersaturation, and the temperature trend for solids

Used by:Calcium carbonate · Nickel(II) sulfate · Silver selenide · Silver sulfide · Thallium(I) sulfate · Daguerre's 1839 process outline · Iodide hypo check · Davey and Knott's double-jet iodobromide emulsion · Kodak ST-1 · P3 Solutions, Solubility and Precipitation · P4 Experiment: Precipitating the Silver Halides · P4 Silver and the Silver Ion · P4 The Silver Halides · P5 Project 1: A Silver Chloride Contact Printing Emulsion · P5 Project 2: A Chlorobromide Paper Emulsion · P8 How Development Works · P11 Overview: Making the Image Permanent · P11 Experiment: Clearing Time and Fixer Capacity · P11 Fixer Capacity, Exhaustion and Residual Silver · P11 How Fixer Works · P20 What a Toner Actually Does to a Silver Image · P20 Selenium Toning: Selenosulfate, Silver Selenide and the Protection Claim · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · Stock solution crystallised in cold storage

Chemistry 2e, Appendix K: Formation Constants for Complex Ionsretrieved 2026-09-04, 2026-09-06

Sections: Appendix K — Formation constants for complex ions: the silver diammine complex; Appendix K — the formation constant of the tetrathiocyanatoargentate ion; Appendix K — the formation constant of the tetrathiocyanatoargentate ion, and those of the diamminesilver and dichloroargentate ions for comparison; Appendix K — the formation constant of the tetrathiocyanatoargentate ion, with the diamminesilver and dichloroargentate ions for comparison; Appendix K: formation constants for [AgCl2]- and [Ag(NH3)2]+; Appendix K: formation constants for the silver complexes with chloride (1.8 x 10^5), ammonia (1.7 x 10^7), thiocyanate (1.2 x 10^10) and cyanide (1 x 10^21), and for the hexafluoroaluminate and hexacyanoferrate ions; Appendix K: formation constant of the diammine silver ion; Appendix K: formation constants for the silver complexes with chloride, ammonia, thiocyanate and cyanide; Appendix K, formation constants for complex ions — the silver-chloride and silver-thiocyanate entries; Appendix K, formation constants for complex ions — silver with two cyanide ions giving the dicyanoargentate ion, 1 x 10^21; iron(III) with six cyanide ions giving hexacyanoferrate(III), 2 x 10^43; iron(II) with six cyanide ions giving hexacyanoferrate(II), 1.5 x 10^35; and silver with two chloride ions, 1.8 x 10^5, for the contrast

Used by:Ammonia solution (ammonium hydroxide) · Ammonium thiocyanate · Potassium thiocyanate · Sodium thiocyanate · P1 Wedgwood, Davy and the Problem of Permanence · P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve · P4 Experiment: Precipitating the Silver Halides · P4 Silver and the Silver Ion · P8 Solvent Action, Physical Development and Grain · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide

Chemistry 2e, Appendix L: Standard Electrode (Half-Cell) Potentialsretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Appendix L, for the standard reduction potentials of the nickel(2+)/nickel couple at -0.257 V and of the hexaamminenickel(2+)/nickel couple at -0.49 V; Appendix L — the chromium half-reactions; Appendix L: the two oxygen couples, O2 + 4H+ + 4e- to water at +1.229 V and O2 + 2H2O + 4e- to hydroxide at +0.401 V; Fe3+/Fe2+ at +0.771 V; Appendix L: Ag+ / Ag at +0.7996 V against AgCl / Ag at +0.22233 V, the diammine complex at +0.373 V and the bis(thiosulfato) complex at +0.017 V; Appendix L: standard reduction potentials for the silver, silver-complex, iron, halogen, oxygen, dichromate and gold couples; Standard reduction potentials: the silver ion to silver couple, and what a cell potential does and does not predict; Appendix L: the silver half-cells — Ag+ + e- gives Ag at +0.7996 V, AgCl + e- gives Ag + Cl- at +0.22233 V, the diammine at +0.373 V, the bis(thiosulfato) complex at +0.017 V and the dicyanide at -0.31 V; Appendix L: the silver ion to silver couple at +0.7996 V and the silver chloride to silver couple at +0.22233 V; the absence of any silver bromide entry; Appendix L — the bis(thiosulfato)argentate couple at +0.017 V and the silver ion couple at +0.7996 V against the standard hydrogen electrode at 0 V; Appendix L, standard reduction potentials — the dichromate half-reaction in acid, Cr2O7^2- with fourteen hydronium ions and six electrons giving two chromium(III) ions and water, at +1.232 V, and the chromate half-reaction in base at -0.13 V

Used by:Nickel(II) sulfate · Potassium dichromate · P3 Aerial Oxidation: Why Chemistry Dies in a Half-Empty Bottle · P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve · P3 Oxidation, Reduction and the Electron That Makes the Picture · P4 Development as Amplification · P4 Silver and the Silver Ion · P8 How Development Works · P12 Experiment: Small-Scale Metallic Replacement · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes

Chemistry 2e, section 1.4: Measurementsretrieved 2026-09-04, 2026-09-05

Sections: 1.4 Measurements: the kilogram and the litre; density; the freezing and boiling points of water; 1.4 Measurements: SI base units, the litre as the cubic decimetre, density, temperature; 1.4 Measurements: the freezing point of water; the kilogram and the litre; 1.4 Measurements: the litre as the cubic decimetre, and density

Used by:P2 Lab: Commissioning Your Laboratory · P2 Measuring Mass, Volume, Temperature and Density, and Knowing How Wrong You Are · Checking the balance and verifying the thermometer · Verifying volumetric glassware by weighing water

Chemistry 2e, section 1.5: Measurement Uncertainty, Accuracy, and Precisionretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: 1.5 Measurement Uncertainty, Accuracy, and Precision: significant figures, reading a meniscus, accuracy against precision; 1.5 Measurement Uncertainty, Accuracy, and Precision: significant figures in measurement, reading a meniscus, rounding rules, accuracy and precision; 1.5 Measurement Uncertainty, Accuracy, and Precision: significant figures, accuracy against precision; Measurement uncertainty, accuracy and precision — significant figures, the distinction between a precise and an accurate measurement, and the rule that a computed result carries the uncertainty of its worst input; Precision and accuracy, and the rule that a numerical scale generally permits measurement to one-tenth of its smallest division; Measurement Uncertainty, Accuracy, and Precision - the rules for significant figures in addition and in multiplication, and the statement that a result calculated from a measurement is at least as uncertain as the measurement; Measurement Uncertainty, Accuracy, and Precision - the distinction between a precise and an accurate measurement, and the rule that a result computed from a measurement is at least as uncertain as the measurement it came from; Measurement Uncertainty, Accuracy, and Precision - the rule that a result calculated from a measurement is at least as uncertain as the measurement, and the distinction between precision and accuracy; Measurement Uncertainty, Accuracy, and Precision — the distinction between precision, results that agree with each other, and accuracy, a result close to the true value; Measurement Uncertainty, Accuracy, and Precision - the distinction between precision, results that agree with one another, and accuracy, a result close to the true value; Measurement Uncertainty, Accuracy, and Precision - the distinction between precision, results that agree closely with one another, and accuracy, a result close to the true value; 1.5 Measurement Uncertainty, Accuracy, and Precision: accuracy against precision, significant figures; 1.5 Measurement Uncertainty, Accuracy, and Precision: reading a meniscus, and reading a scale to a tenth of its smallest division; 1.5 Measurement Uncertainty, Accuracy, and Precision: the convention that the last displayed digit of a balance reading is uncertain, and significant figures in a calculated result; 1.5 Measurement Uncertainty, Accuracy, and Precision - the convention that the last displayed digit is uncertain, and accuracy against precision

Used by:P2 Lab: Commissioning Your Laboratory · P2 Measuring Mass, Volume, Temperature and Density, and Knowing How Wrong You Are · P3 Lab: Measuring pH and Trusting the Number · P9 Assignment: The Developer Laboratory Report · P9 Experimental Design for the Darkroom · P14 Experiment: Calibrating the Sensitometer · P15 Experiment: Calibrating the Densitometer in Both Modes · P15 Assignment: Characterising a Film and Developer with Your Own Instruments · P27 Part XXVII Overview: From Observation to Measurement · P27 Designing an Experiment That Yields a Number · P27 Experiment: Four Curve Families, Measured · Checking the balance and verifying the thermometer · Verifying volumetric glassware by weighing water · Weighing a solid · Balance drifting, or reading below its minimum weighable mass

Chemistry 2e, section 11.1: The Dissolution Processretrieved 2026-09-04

Sections: 11.1 The Dissolution Process: the three energy steps; calcium carbonate as the strongly endothermic case; sodium hydroxide as the exothermic one; ammonium nitrate and the cold pack

Used by:P3 Solutions, Solubility and Precipitation

Chemistry 2e, section 11.2: Electrolytesretrieved 2026-09-04

Sections: 11.2 Electrolytes: ion-dipole attraction; dissociation and hydration; sparingly soluble ionic compounds as strong electrolytes; 11.2 Electrolytes: ion-dipole attraction, hydration, and sparingly soluble salts as strong electrolytes

Used by:P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P3 Solutions, Solubility and Precipitation

Chemistry 2e, section 11.3: Solubilityretrieved 2026-09-04

Sections: 11.3 Solubility: saturation as equal rates of dissolution and crystallisation; supersaturation; the temperature trend for solids and its stated exception

Used by:P3 Solutions, Solubility and Precipitation

Chemistry 2e, section 11.4: Colligative Propertiesretrieved 2026-09-06

Sections: Vapor pressure lowering and Raoult's law, including the definition of a nonvolatile substance and the worked example whose nonvolatile solute is glycerin itself; freezing point depression, and the phase diagram showing vapour pressure lowering and freezing point depression as the same displacement

Used by:Glycerol

Chemistry 2e, section 12.1: Chemical Reaction Ratesretrieved 2026-09-04

Sections: 12.1 Chemical Reaction Rates: average rate over an interval against instantaneous rate at a moment

Used by:P3 Rates, Temperature and Catalysts

Chemistry 2e, section 12.2: Factors Affecting Reaction Ratesretrieved 2026-09-04

Sections: 12.2 Factors Affecting Reaction Rates: physical state and degree of subdivision, so that a heterogeneous reaction proceeds only at the interface between the phases and faster where that interface is larger; temperature; concentration; 12.2 Factors Affecting Reaction Rates: the chemical nature of the reactants, physical state and subdivision, temperature, concentration and catalysis; and the statement that for many chemical processes reaction rates are approximately doubled when the temperature is raised by 10 degrees C; 12.2 Factors Affecting Reaction Rates, including the rule of thumb that reaction rates approximately double for a 10 degree C rise

Used by:P3 Aerial Oxidation: Why Chemistry Dies in a Half-Empty Bottle · P3 Rates, Temperature and Catalysts · P8 Development Kinetics: Time, Temperature, Agitation and Exhaustion

Chemistry 2e, section 12.5: Collision Theoryretrieved 2026-09-04, 2026-09-06

Sections: 12.5 Collision Theory: the three postulates; activation energy and the transition state; the Arrhenius equation with R = 8.314 J per mol per K; and the linear form whose slope against 1/T is -Ea/R; Collision theory and activation energy: why a thermodynamically favourable reaction may be immeasurably slow; 12.5 Collision Theory: the Arrhenius equation, R = 8.314 J per mol per K, and the linear form whose slope against 1/T is minus Ea over R; Collision theory and the Arrhenius equation: the exponential dependence of rate on activation energy; 12.5 Collision Theory - the Arrhenius equation, the gas constant R as 8.314 J per mol per K, and the linear form whose slope against the reciprocal of absolute temperature is minus the activation energy over R

Used by:P3 Rates, Temperature and Catalysts · P4 Development as Amplification · P8 Development Kinetics: Time, Temperature, Agitation and Exhaustion · P8 How Development Works · P27 Experiment: The Development Time and Temperature Series

Chemistry 2e, section 12.7: Catalysisretrieved 2026-09-04

Sections: 12.7 Catalysis: a catalyst increases the rate without being consumed, by offering a path of lower activation energy; 12.7 Catalysis: a catalyst raises the rate without being consumed by providing an alternative mechanism whose rate-determining step has a lower activation energy, leaving reactant and product energies unchanged

Used by:P3 Aerial Oxidation: Why Chemistry Dies in a Half-Empty Bottle · P3 Rates, Temperature and Catalysts

Chemistry 2e, section 13.1: Chemical Equilibriaretrieved 2026-09-04

Sections: 13.1 Chemical Equilibria: equilibrium as dynamic, proceeding in both directions at equal rates

Used by:P3 Solutions, Solubility and Precipitation

Chemistry 2e, section 13.2: Equilibrium Constantsretrieved 2026-09-04

Sections: 13.2 Equilibrium Constants: the reaction quotient and the equilibrium constant; pure solids omitted from the expression

Used by:P3 Solutions, Solubility and Precipitation

Chemistry 2e, section 13.3: Shifting Equilibria, Le Chatelier's Principleretrieved 2026-09-04

Sections: 13.3 Shifting Equilibria: the statement of Le Chatelier's principle and its explanation in terms of unequal forward and reverse rates

Used by:P3 Solutions, Solubility and Precipitation

Chemistry 2e, section 14.1: Bronsted-Lowry Acids and Basesretrieved 2026-09-04

Sections: 14.1 Bronsted-Lowry Acids and Bases: proton donor and acceptor; conjugate pairs; amphiprotic species; autoionisation of water; Kw = 1.0 x 10^-14 at 25 degrees C, endothermic, about 5.6 x 10^-13 at 100 degrees C

Used by:P3 Acids, Bases and pH

Chemistry 2e, section 14.2: pH and pOHretrieved 2026-09-04

Sections: 14.2 pH and pOH: pH as a logarithm; neutrality at 25 degrees C; 14.2 pH and pOH: definitions; pH + pOH = 14.00 at 25 degrees C; neutrality defined by equal ion concentrations, and pure water neutral at pH 6.31 at 80 degrees C; 14.2 pH and pOH: the definitions and the temperature dependence of neutrality

Used by:P3 Part III Overview: Chemistry Foundations for Photographers · P3 Acids, Bases and pH · P3 Lab: Measuring pH and Trusting the Number

Chemistry 2e, section 14.3: Relative Strengths of Acids and Basesretrieved 2026-09-04

Sections: Strong acids and the levelling effect of water; 14.3 Relative Strengths of Acids and Bases: strong against weak; the acid ionisation constant; per cent ionisation and its dependence on concentration; the levelling effect; 14.3 Relative Strengths of Acids and Bases: the acid ionisation constant and per cent ionisation

Used by:Hydrochloric acid · P3 Acids, Bases and pH · P3 Buffers and Buffer Capacity

Chemistry 2e, section 14.4: Hydrolysis of Saltsretrieved 2026-09-04, 2026-09-06

Sections: The ammonium ion as the conjugate acid of ammonia and its acid ionisation constant; Section 14.4, its third learning objective and the treatment of salts whose cation is an acid — "Describe the acid ionization of hydrated metal ions"; Worked example — the pH of a sodium bicarbonate solution; Salts of a weak acid and a strong base; 14.4 Hydrolysis of Salts: why the salt of a weak acid gives an alkaline solution; sodium hydrogencarbonate worked; 14.4 Hydrolysis of Salts: the hydrogencarbonate ion as an amphiprotic species, with an acid constant of 4.7 x 10^-11 and a base constant of 2.3 x 10^-8; 14.4 Hydrolysis of Salts: sodium hydrogencarbonate as an amphiprotic salt giving a basic solution; The amphiprotic hydrogencarbonate ion and the worked pH of a sodium bicarbonate solution

Used by:Ammonium bromide · Nickel(II) sulfate · Sodium bicarbonate · Sodium metaborate (anhydrous) · P3 Acids, Bases and pH · P3 Buffers and Buffer Capacity · P3 Lab: Measuring pH and Trusting the Number · P8 Alkalis, Buffers and pH

Chemistry 2e, section 14.5: Polyprotic Acidsretrieved 2026-09-04, 2026-09-05

Sections: Carbonic acid, second ionisation constant; Carbonic acid, first and second ionisation constants; Diprotic acids — the two ionisations of sulfuric acid; 14.5 Polyprotic Acids: carbonic acid as a diprotic acid with well-separated constants; 14.5 Polyprotic Acids: carbonic acid, whose two constants are separated by about ten thousand so the two ionisations can be treated separately; Stepwise ionisation of a polyprotic acid and the separation of its successive constants

Used by:Potassium carbonate (anhydrous) · Sodium bicarbonate · Sodium carbonate (anhydrous) · Sodium carbonate decahydrate · Sodium carbonate monohydrate · Sulfuric acid · P3 Acids, Bases and pH · P3 Buffers and Buffer Capacity · P10 Experiment: Measuring Stop Bath Capacity

Chemistry 2e, section 14.6: Buffersretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: How buffers work; buffer capacity; selection of suitable buffer mixtures; A solution of acetic acid and sodium acetate as the type example of a buffer, and how it resists a change in pH; 14.6 Buffers: how a conjugate pair absorbs added strong acid or base; buffer capacity and its dependence on total concentration; the loss of usefulness when one member falls below about 10 per cent of the other; the Henderson-Hasselbalch equation and the assumption under which it holds; 14.6 Buffers: the Henderson and Hasselbalch equation and the assumption under which it holds; How buffers work; buffer capacity; the loss of usefulness when one member of the pair falls below about a tenth of the other; The Henderson-Hasselbalch equation and the conditions under which a conjugate pair buffers; The Henderson-Hasselbalch relation and the buffer region either side of a pKa; The Henderson-Hasselbalch relation, and the buffer region within about one pH unit either side of a pKa

Used by:Borax (sodium tetraborate decahydrate) · Sodium acetate (anhydrous) · Sodium carbonate (anhydrous) · Borax kallitype developer · P3 Buffers and Buffer Capacity · P3 Lab: Measuring pH and Trusting the Number · P8 Alkalis, Buffers and pH · P8 Sulfite: Preservative, Buffer, Silver Solvent · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Break/Fix: The Developer That Went Wrong · P9 Experiment: Comparing Developing Agents · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P10 Experiment: Measuring Stop Bath Capacity

Chemistry 2e, section 15.1: Precipitation and Dissolutionretrieved 2026-09-04

Sections: The common-ion effect on the solubility of a slightly soluble salt; 15.1 Precipitation and Dissolution: the solubility product; the reaction quotient rule for precipitation; the common ion effect worked on silver iodide

Used by:Potassium chloride · P3 Solutions, Solubility and Precipitation

Chemistry 2e, section 15.3: Coupled Equilibriaretrieved 2026-09-04, 2026-09-05

Sections: 15.3 Coupled Equilibria, Example 15.16: dissolution of silver bromide in thiosulfate, Ksp 5.0 x 10^-13, Kf 4.7 x 10^13, net K = 24, and the calculation of the sodium thiosulfate needed to dissolve 1.00 g of silver bromide in 1.00 L; 15.3 Coupled Equilibria, Example 15.16: silver bromide dissolved by thiosulfate, and the arithmetic of how much thiosulfate a given mass needs; Example 15.16 — the combined equilibrium for silver bromide in thiosulfate and its net constant of 24; Example 15.16 — silver bromide dissolving in thiosulfate, with a formation constant of 4.7 x 10^13 for the bis(thiosulfato)argentate ion and a net constant of 24 for the combined equilibrium

Used by:P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve · P4 Experiment: Precipitating the Silver Halides · P11 Experiment: Clearing Time and Fixer Capacity · P11 How Fixer Works

Chemistry 2e, section 17.1: Review of Redox Chemistryretrieved 2026-09-04

Sections: 17.1 Review of Redox Chemistry: redox defined as a change in oxidation number; the oxidation-number formalism; the half-reaction method for balancing, step by step, in acid and in base

Used by:P3 Oxidation, Reduction and the Electron That Makes the Picture

Chemistry 2e, section 17.3: Electrode and Cell Potentialsretrieved 2026-09-04

Sections: 17.3 Electrode and Cell Potentials: a half-cell potential is measurable only as a difference; the standard hydrogen electrode at exactly 0 V; standard state as 1 M, 1 bar, 298 K; the stronger oxidant is the couple with the greater standard potential

Used by:P3 Oxidation, Reduction and the Electron That Makes the Picture

Chemistry 2e, section 17.4: Potential, Free Energy, and Equilibriumretrieved 2026-09-04

Sections: Potentials at nonstandard conditions: the Nernst equation and its convenient form with the constants folded in at 298 K

Used by:P8 How Development Works

Chemistry 2e, section 19.2: Coordination Chemistry of Transition Metalsretrieved 2026-09-04, 2026-09-06

Sections: The colour of transition-metal complexes — ions with a partly filled d subshell usually form coloured complex ions while d0 and d10 ions usually form colourless ones, illustrated with the series of hexaaqua ions in which Ni(2+) is the d8 member; Coordination compounds — ligands, coordination number and the colour of transition-metal complexes; 19.2 Coordination Chemistry of Transition Metals: the coordinate covalent bond as a Lewis acid-base interaction; ligand, coordination sphere and coordination number; the diammine silver ion as coordination number two; monodentate, polydentate and chelate; 19.2 Coordination Chemistry of Transition Metals: ligands as Lewis bases, donor atoms, coordination number and the naming of complex ions; Coordination compounds — ligands, coordination number, the spectrochemical series and the origin of colour in transition-metal complexes

Used by:Nickel(II) sulfate · Prussian blue · P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve · P4 Silver and the Silver Ion · P21 Iron, Light and Prussian Blue

Chemistry 2e, section 2.3: Atomic Structure and Symbolismretrieved 2026-09-04

Sections: 2.3 Atomic Structure and Symbolism: protons, neutrons and electrons; atomic number; isotopes; the atomic mass unit

Used by:P3 Atoms, Ions and Bonds: Reading a Photographic Formula

Chemistry 2e, section 2.6: Molecular and Ionic Compoundsretrieved 2026-09-04

Sections: 2.6 Molecular and Ionic Compounds: predictable ionic charges from the periodic table; Table 2.5, the common polyatomic ions; the -ate and -ite convention

Used by:P3 Atoms, Ions and Bonds: Reading a Photographic Formula

Chemistry 2e, section 3.1: Formula Mass and the Mole Conceptretrieved 2026-09-04

Sections: 3.1 Formula Mass and the Mole Concept: formula mass for an ionic compound; molar mass

Used by:P3 Atoms, Ions and Bonds: Reading a Photographic Formula

Chemistry 2e, section 3.3: Molarityretrieved 2026-09-04

Sections: 3.3 Molarity: definition of molarity; dilution of solutions and the derivation of the dilution equation; 3.3 Molarity: dilution of solutions and the derivation of the dilution equation

Used by:P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · Mixing a working solution from a stock

Chemistry 2e, section 3.4: Other Units for Solution Concentrationsretrieved 2026-09-04, 2026-09-05

Sections: 3.4 Other Units for Solution Concentrations: mass percentage, volume percentage, mass-volume percentage, parts per million; 3.4 Other Units for Solution Concentrations: mass-volume percentage as grams of solute per 100 millilitres of solution; 3.4 Other Units for Solution Concentrations - mass-volume percentage

Used by:P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · Mixing a solution to a final volume · Solid added to a litre rather than made up to a litre

Chemistry 2e, section 4.2: Classifying Chemical Reactionsretrieved 2026-09-04

Sections: 4.2 Classifying Chemical Reactions: molecular, complete ionic and net ionic equations; spectator ions; the silver nitrate and sodium chloride precipitation; 4.2 Classifying Chemical Reactions: oxidation-reduction as one of the three reaction classes, and the spectator ion; 4.2 Classifying Chemical Reactions: solubility guidelines; net ionic equations

Used by:P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P3 Oxidation, Reduction and the Electron That Makes the Picture · P3 Solutions, Solubility and Precipitation

Chemistry 2e, section 6.4: Electronic Structure of Atoms (Electron Configurations)retrieved 2026-09-04

Sections: 6.4 Electronic Structure of Atoms: the yttrium-to-silver series filling the 4d subshell, and the note that copper, silver and gold have completely filled d orbitals

Used by:P4 Silver and the Silver Ion

Chemistry 2e, section 7.1: Ionic Bondingretrieved 2026-09-04

Sections: 7.1 Ionic Bonding: electrostatic attraction; properties of ionic solids; why there is no sodium chloride molecule; the three-dimensional lattice; 769 kJ/mol to separate solid NaCl into gaseous ions; 7.1 Ionic Bonding: ionic solids as poor conductors because the ions cannot move; 7.1 Ionic Bonding: the three-dimensional lattice of sodium chloride with each ion surrounded by six of opposite charge, and the statement that ionic solids are poor conductors because the ions cannot move

Used by:P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P4 The Latent Image · P4 The Silver Halides

Chemistry 2e, section 7.2: Covalent Bondingretrieved 2026-09-04

Sections: 7.2 Covalent Bonding: pure and polar covalent bonds; electronegativity difference as a rough guide to bond type, with its stated exceptions; polyatomic ions held together covalently

Used by:P3 Atoms, Ions and Bonds: Reading a Photographic Formula

Chemistry 2e, section 9.4: Effusion and Diffusion of Gasesretrieved 2026-09-04

Sections: 9.4 Effusion and Diffusion of Gases: diffusion as dispersal in response to a concentration difference, with the particles unaware of any gradient and simply moving randomly; the factors on which the rate depends - temperature, the mass of the particles, the concentration gradient, the surface area available and the distance travelled

Used by:P3 Diffusion, Swelling and the Journey Into the Emulsion

University Physics Volume 3, section 3.4: Interference in Thin Filmsretrieved 2026-09-05, 2026-09-06

Sections: Interference in Thin Films: the half-wavelength phase shift on reflection at an interface beyond which is a medium of higher refractive index, the absence of a shift at an interface with a medium of lower index, the resulting conditions on 2t at perpendicular incidence, and the statement that where a film is very thin and the path difference negligible the two rays are exactly out of phase so that destructive interference occurs at all wavelengths; 3.4 Interference in Thin Films - the rule that light 'undergoes a 180 degree or pi radians phase change upon reflection at an interface beyond which is a medium of higher index of refraction' while 'no phase change takes place when reflecting from a medium of lower refractive index', a shift equivalent to a path difference of half a wavelength; the resulting conditions on twice the film thickness at perpendicular incidence; the statement that where the film is very thin and the path difference negligible the two rays are exactly out of phase so that destructive interference occurs at all wavelengths and the film is dark there; the wedge of air between two glass slides, which shows a dark band where the slides touch; and Newton's rings used to test a lens against a blank, where 'each successive ring of a given color indicates an increase of only half a wavelength in the distance between the lens and the blank'

Used by:P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory · Newton's rings

University Physics Volume 3, section 4.1: Single-Slit Diffractionretrieved 2026-09-04

Sections: 4.1 Single-slit diffraction: Huygens wavelets across an aperture and the path-difference construction that puts them out of phase

Used by:P6 Diffraction and the Optimum Pinhole

University Physics Volume 3, section 4.5: Circular Apertures and Resolutionretrieved 2026-09-04, 2026-09-05

Sections: 4.5 Circular apertures and resolution; 4.5 Circular apertures and resolution: the first minimum of a circular aperture at theta = 1.22 lambda / D, and the Rayleigh criterion; 4.5 Circular apertures and resolution: the first minimum of a circular aperture at 1.22 lambda / D; 4.5 Circular apertures and resolution: diffraction spreading at a small circular aperture; 4.5 Circular Apertures and Resolution - the first minimum of the diffraction pattern of a circular aperture of diameter D occurs at theta = 1.22 lambda / D, provided the aperture is large compared with the wavelength; 4.5 Circular apertures and resolution - the first minimum of a circular aperture and the Rayleigh criterion; 4.5 Circular apertures and resolution - the first minimum of a circular aperture at theta = 1.22 lambda / D

Used by:P1 The Camera Obscura: An Image Without Chemistry · P6 Diffraction and the Optimum Pinhole · P6 Making and Measuring Pinholes · P6 Pinhole Geometry: Blur, Focal Distance, Field of View and Falloff · Measuring a pinhole with a Class 2 laser pointer · Burr smear · Diffraction glow from an undersized hole

opg.optica.org

Pinhole Opticsretrieved 2026-09-04

Sections: Abstract only: the statements that the pinhole camera offers freedom from distortion and virtually infinite depth of field, that its astigmatism can be corrected by proper choice of aperture, and that its angular field can be made to exceed 90 degrees; the course has not obtained the full text; Abstract only; the full text was not available to this course; Abstract only: freedom from distortion, virtually infinite depth of field, and an angular field that can be made to exceed 90 degrees; Abstract only: the statement that a pinhole camera offers freedom from distortion and virtually infinite depth of field, and that its astigmatism can be corrected by proper choice of aperture; the course has not obtained the full text; Abstract: freedom from distortion, virtually infinite depth of field, and an angular field that can exceed 90 degrees

Used by:P6 Curved Film Plane and Multiple-Pinhole Experiments · P6 Diffraction and the Optimum Pinhole · P6 Pinhole Geometry: Blur, Focal Distance, Field of View and Falloff · P6 Break/Fix: Unexpectedly Soft Images and Wrong Reciprocity Corrections · P7 Seeing Like a Pinhole: The Image, Its Makers and Previsualisation

osha.gov

Eye and face protection, 29 CFR 1910.133retrieved 2026-09-04, 2026-09-05

Sections: General requirements; criteria for protective eye and face protection; 1910.133(a)(1) and (a)(2): eye or face protection where there is a hazard from flying particles, and side protection where there is a hazard from flying objects; Paragraph (a)(1) and (a)(2) - eye or face protection where there is a hazard from flying particles, with side protection where there is a hazard from flying objects; General requirements, including prescription lenses and protection worn over them

Used by:P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P6 Build the Modular Pinhole Camera · P14 Build: The Enclosure and Exposure Stage · Putting protective equipment on, changing gloves and taking it off

Hazard Communication, 29 CFR 1910.1200retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Paragraph (g)(2): the sixteen section numbers and headings; (g)(3); (g)(5); (g)(6); Paragraph (g)(2): the sixteen section numbers and headings a safety data sheet carries, in that order; Paragraph (g)(2), the sixteen safety data sheet sections — Section 4, First-aid measures; Section 16, other information including the date of preparation or last revision; Paragraph (g)(2), the sixteen safety data sheet sections in order; (g)(3), sub-headings with no relevant information; (g)(5), new hazard information within three months; Paragraph (g)(2): the sixteen section numbers and headings; Paragraph (g)(2), the sixteen section numbers and headings, including section 10 on stability and reactivity

Used by:P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P26 Assignment: Assessing a Historical Process for Hazard · First aid quick reference · Reading GHS and CLP · Opening the laboratory · Labelling a container · Recording a safety data sheet · A container found unlabelled, or a solution of unknown age

p2infohouse.org

Disposal of Small Volumes of Photographic-Processing Solutions, publication J-52retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Effluent regulations — frequently regulated parameters and their mean limits; Characteristics of photographic-processing effluents; Septic-tank systems — solutions containing dichromate; chlorine demand and ammonium in effluent; Effluent regulations: most frequently regulated parameters and their mean limits; Septic-tank systems — solutions containing sodium or potassium dichromate; Further reading — ferricyanide in photographic effluents; Effluent regulations — the frequently regulated parameters and their mean limits; Characteristics of photographic-processing effluents, for the pH window sewer codes most frequently set; Characteristics of photographic-processing effluents, for the sewer pH window; Effluent regulations — the most frequently regulated parameters and their mean limits; The frequently regulated parameters for effluent entering a sewer system and their mean limits - biochemical oxygen demand 350 mg/L, chemical oxygen demand 650 mg/L, total suspended solids 200 mg/L, chlorine demand 25 mg/L, pH 5.6 to 9.4 and silver 1.2 mg/L - and the statement that the five-day biochemical oxygen demand of photographic effluent depends on the amount of processing solution and wash water present and typically ranges from 100 to 1000 mg/L; Effluent regulations — frequently regulated parameters and their mean limits, giving pH 5.6 to 9.4 as the window sewer codes most frequently set; Effluent regulations: the most frequently regulated parameters and their mean limits; biochemical and chemical oxygen demand; Effluent regulations — the most frequently regulated parameters for effluents entering a sewer system and their mean limits, biochemical oxygen demand 350 mg/L, chemical oxygen demand 650 mg/L, total suspended solids 200 mg/L, chlorine demand 25 mg/L, pH 5.6 to 9.4, silver 1.2 mg/L and iron 17 mg/L; Silver recovery — the acidity of the fixer as an important factor, a bath above pH 6.5 slowing the reaction and one below pH 4 dissolving the steel wool so that it is unavailable for silver replacement, with most fixers falling in the usable range of 4 to 6.5; the statement that typical photographic effluent has a five-day biochemical oxygen demand of 100 to 1,000 mg/L; Silver recovery — metallic replacement described as the most convenient way to recover silver from fixers in small-scale operations, with the acidity of the fixer an important factor, a bath at pH 6.5 or higher slowing the reaction and one at pH 4 or lower dissolving the steel wool so that it is unavailable for silver replacement, and most fixers falling within the usable range of 4 to 6.5; Effluent regulations — the mean regulated sewer limits, silver 1.2 mg/L and iron 17 mg/L; The effluent parameters municipalities most often regulate and their mean limits, including silver at 1.2 mg/L; typical photographic effluent biochemical oxygen demand; Effluent regulations: the most frequently regulated parameters and their mean limits; Effluent regulations: the most frequently regulated parameters and their mean limits, including silver and pH; Effluent regulations: the most frequently regulated parameters and their mean limits, including silver

Used by:Acetic acid (glacial) · Ammonium citrate (dibasic) · Ammonium citrate (tribasic) · Ammonium dichromate · Ammonium iron(III) citrate · Ammonium iron(III) oxalate · Ammonium persulfate · Ammonium thiocyanate · Borax (sodium tetraborate decahydrate) · Boric acid · Citric acid (anhydrous) · Copper(II) sulfate · Ferric oxalate · Hydrochloric acid · Iron(III) chloride, anhydrous · Iron(III) chloride hexahydrate · Iron(III) nitrate nonahydrate · Nitric acid · Oxalic acid · Potassium carbonate (anhydrous) · Potassium citrate · Potassium dichromate · Potassium ferricyanide · Potassium hydroxide (caustic potash) · Potassium metabisulfite · Potassium oxalate, anhydrous · Potassium oxalate monohydrate · Potassium permanganate · Potassium persulfate · Potassium sodium tartrate tetrahydrate · Silver · Silver nitrate · Silver(I) oxalate · Silver(I) oxide · Silver sulfamate · Sodium acetate (anhydrous) · Sodium bicarbonate · Sodium bisulfite · Sodium carbonate (anhydrous) · Sodium carbonate decahydrate · Sodium carbonate monohydrate · Trisodium citrate dihydrate · Sodium hexametaphosphate (Calgon) · Sodium hydroxide (caustic soda) · Sodium metabisulfite · Sodium metaborate (anhydrous) · Sodium metaborate tetrahydrate (Kodalk) · Sodium sulfate · Sodium sulfite · Sodium thiocyanate · Sodium thiosulfate (anhydrous) · Sulfuric acid · Tartaric acid · Ammonium citrate developer · Borax kallitype developer · Iodide hypo check · Kodak HT-2 · Kodak Hypo Clearing Agent and the washing accelerator Kodak patented · Kodak ST-1 · Nicol's kallitype · EDTA, citric acid and hydrochloric acid clearing sequence · Rochelle salt kallitype developer · Sodium citrate developer · Sodium citrate kallitype developer · Wedgwood and Davy's silver nitrate on leather · Willis's potassium oxalate developer · P2 Waste: Streams, Silver, and the Drain You Must Not Use · P2 Silver Nitrate: The Reagent That Sets the Rules · P12 Silver Recovery and the Responsible Darkroom · P12 Experiment: Small-Scale Metallic Replacement · The disposal caveat · Routing general chemical waste · Collecting and segregating waste across a multi-run session · Routing silver-bearing waste

parallaxphotographic.coop

Parallax Photographic Coop — product search for "ferricyanide", "ferric ammonium citrate", and the alternative-processes rangeretrieved 2026-09-05, 2026-09-06

Sections: Potassium Ferricyanide for Cyanotype Process, 20 g at 5.95 pounds inclusive of VAT and 100 g at 15.95 pounds; Ferric Ammonium Citrate for Cyanotype Process, 50 g at 9.95 pounds and 250 g at 24.95 pounds; and, on the alternative-processes range page, Hahnemuhle Platinum Rag 300 gsm 8 by 10 inch, 25 sheets, at 23.95 pounds and shown out of stock on the day; The four cyanotype chemicals listed as their own products on the day: Potassium Ferricyanide 20 g at 5.95 pounds and 100 g at 15.95 pounds, Ferric Ammonium Citrate 50 g at 9.95 pounds and 250 g at 24.95 pounds. Those four are the whole of what the search for "ferric" returned: no standalone ammonium ferric oxalate and no ferric nitrate, ammonium ferric oxalate appearing only inside the description of a bought cyanotype kit; Black and white film chemicals; alternative processes

Used by:P21 Part XXI Overview: Photography in Prussian Blue · P21 The New Cyanotype and the Other Ways to Make a Blue Print · The Pure Silver laboratory planner

patents.google.com

Photographic developer, United States patent 2,289,367retrieved 2026-09-04, 2026-09-05

Sections: Objects of the invention; the substitution ratio for metol; Object of the invention; substitution ratio for metol; Objects of the invention; the substitution ratio for metol; Examples I and II; Objects of the invention; the substitution ratio against metol; Objects of the invention; the substitution ratio for metol; Example I, the agent used alone; Example II, the agent as a metol substitute; Objects of the invention, including the provision of a substitute for metol; the statement that replacing the metol of a metol-hydroquinone developer with about one fifth to one sixth of its weight of the pyrazolidone gives similar development characteristics; Example I, the agent used alone; Example II, the agent as a metol substitute; The claim that replacing the metol of a metol-hydroquinone developer with about one fifth to one sixth of its weight of 1-phenyl-3-pyrazolidone gives similar development characteristics; Objects of the invention, including the provision of a substitute for metol; the statement that replacing the metol of a metol-hydroquinone developer with about one fifth to one sixth of its weight of 1-phenyl-3-pyrazolidone gives similar development characteristics; Example I, the agent used alone at 3 g in 500 cubic centimetres; Example II, the agent as a metol substitute at 0.15 g in 500 cubic centimetres against 4 g of hydroquinone

Used by:Dimezone S · Metol · Phenidone · 510-Pyro · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 Superadditivity: Why Two Agents Beat One · P9 Assignment: The Developer Laboratory Report · P9 Experiment: Comparing Developing Agents

Photographic light-sensitive material and process of making the same, United States Patent 1,574,944retrieved 2026-09-04, 2026-09-06

Sections: The description: that sensitiveness corresponds to nuclei in the grains, which Sheppard attributes to his compounds forming small, mostly ultramicroscopic nuclei of silver combined with sulphur, selenium or tellurium, such as silver sulfid; that too high a concentration causes fog and sometimes reversal; that 2 to 3 grains of a sensitizing compound such as thiosinamine to 100 pounds of dry gelatin, equivalently 1 part of thiosinamine to 300,000 parts of emulsion computed as the weight of its non-aqueous ingredients, is within the useful limits; that the solution added should be kept under about 2 per cent of the volume of the melted emulsion; and that a gelatin whose natural sulphur compound has been oxidised out gives emulsions of impractically low light-sensitiveness which his compounds restore, in one case by a factor of ten or over twenty; The sensitising compounds and their proportions; the preparation of an inert gelatin by oxidising its natural sulfur compound; melting and setting points as gelatin properties to be adjusted for; The sensitising compounds and the nuclei of silver sulfid; the proportions of 2 to 3 grains per 100 pounds of dry gelatin and 1 part in 300,000 of dry emulsion; the upper limit set by fog; and the preparation of an inert gelatin by oxidation; The identification of the sensitising impurity in gelatin and the mechanism of sulfur sensitisation

Used by:Davey and Knott's double-jet iodobromide emulsion · P4 The Latent Image · P5 Gelatin, the Photographic Binder · P5 Washing, Digestion and Sensitisation · Hand-coated bromide paper

Photographic silver bromide emulsion containing some silver iodide, United States Patent 2,592,250retrieved 2026-09-04, 2026-09-06

Sections: Soluble halide content of the finished emulsion; Silver iodide content of the emulsion; Example I, and the description that governs it. Solution No. 1, inert gelatin 102.6 gms, KCl 102.6 gms, water 2873 ccs, at 40 C; Solution No. 2, KCl 513 gms, water 2668 ccs, at 45 C; Solution No. 3, AgNO3 1000 gms, water 2668 ccs, at 45 C; Solution No. 4, KBr 820.8 gms, KI 205.2 gms, water 2565 ccs, at 45 C. Run Solutions Nos. 2 and 3 simultaneously into Solution No. 1 in a vessel, taking 90 seconds to do this. Then ripen for 1 minute at 45 C. Next add Solution No. 4 then ripen for 20 minutes at 45 C. Next add 1206 gms. of inert gelatin (dry). Then ripen at 45 C. for 15 minutes during which time the gelatin dissolves. Set and shred the emulsion and then wash until free from all soluble bromide and then add about 770 ccs. of 10% solution of KCl (by weight), and then add water to make 18 litres. The description adds that the invention relates to emulsions capable of forming an internal latent image; that the first step is to form, in the presence of a small amount of inert gelatin, a silver salt more soluble in water than silver bromide, that is silver chloride or silver thiocyanate, by adding separate solutions of potassium chloride and of silver nitrate to a gelatin solution; that the silver iodide content should preferably be at least 6 per cent of the total silver halide and is preferably brought to 10 to 20 per cent; that it is desirable to avoid digestion, that is, treatments after washing which increase sensitivity such as heat treatment; that during all of the emulsion-making procedure the temperature of the solutions and emulsions should not be above about 50 C; that the soluble halide content of the finished emulsion should be above 0.03 gram of potassium bromide per litre, preferably between 0.03 and 0.3 gram per litre, or the equivalent of any other bromide or chloride, equivalent meaning the same suppressing action on the silver ion; and that ammonia is ordinarily used during emulsification but that a neutral emulsion uses none and is precipitated in the neighbourhood of 70 to 90 C. The patent's own reference list names Mees, The Theory of the Photographic Process (1942), page 166; Berg, Marriage and Stevens, Journal of the Optical Society of America 31 (1941), page 385; Huse and Muelendyke on the spectral sensitivity of mixtures of silver iodide and silver bromide, The Photographic Journal, June 1926; and Wall, Photographic Emulsions (1929), pages 52 and 53, footnote 3; Internal latent image emulsions and the iodide content range

Used by:Potassium bromide · Potassium iodide · Davey and Knott's double-jet iodobromide emulsion · P4 Grain, Speed and Resolution · P4 The Latent Image · P4 The Silver Halides

Photographic washing accelerators, United States Patent 2,860,978retrieved 2026-09-06

Sections: Example 6, in which the inventors state that repeating Examples 1 to 5 with lithium, potassium and ammonium sulfites in place of the sodium sulfite found all of them fully as effective as the sodium sulfite for hypo elimination from fixed photographic materials, and that amine sulfites such as triethanolamine sulfite and the sulfite salts of ethylene diamine would also be entirely suitable; and the three-part mechanism the specification proposes for a sulfite washing bath; Example 8, where the hypo and silver concentrations of the test prints were estimated with what the Google Patents optical character recognition renders as "the Kodak HT-Z solution", stated there to contain acetic acid 125.0 cc. and silver nitrate 7.5 grams; The whole specification, application Serial No. 420,454 of 1 April 1954, granted 18 November 1958 - the statement of the invention as an aqueous solution containing one or more soluble sulfites used as a washing medium for fixed photographic images, with the preferable pH range of 4 to 10 and the substantially neutral solution at pH 7 called particularly useful; the objections to the earlier oxidising and alkaline eliminators, that they are inconvenient, unstable, soften the emulsion and remove the soluble sodium thiosulfates but not the less soluble silver thiosulfates; Example 1, the Velox F-3 prints bathed 5 minutes in water, in 2 per cent sodium bisulfite and in 2 per cent sodium sulfite, with residual silver falling from 0.017 to 0.002 mg per square inch and residual hypo of 0.22, 0.12 and 0.03 mg per square inch; Example 2 on Microcard paper; Example 3, the comparison against sodium metaborate, sodium sulfate and the peroxide-ammonia eliminator; Example 4, sulfite with bisulfite; Example 6, the other soluble sulfites; Example 7, the preferred washing solution of sodium sulfite 20.0 g, sodium bisulfite 5.0 g and Sequestrene Na-4 0.5 g per litre, its use on films, papers and microfilms and the statement that it can be greatly diluted for long immersion; the three-part mechanism, (a) thiosulfate ions absorbed to the gelatin displaced by sulfite ions until equilibrium is reached, (b) an alkaline solution also displacing the alum, which has a marked mordanting action for thiosulfate ions, and (c) sulfite left in the print stabilising residual hypo; Example 8, the prints fixed in Kodak F-5 loaded with silver, immersed 5 minutes, washed 20 minutes and incubated for two weeks; Example 10, the washing accelerator containing per litre of working strength bath 20 grams of sodium sulfite and 5 grams of sodium bisulfite, and the selenium additions of 1.0 to 0.02 gram per litre; and the single claim

Used by:Ammonium sulfite · Kodak HT-2 · Kodak Hypo Clearing Agent and the washing accelerator Kodak patented

Preparation of silver halide grains of cubic-regular shape, United States Patent 3,655,394retrieved 2026-09-04, 2026-09-06

Sections: Example 6 — the infrared-sensitised, sulfur- and gold-sensitised cubic-grain emulsion, and the tetraazaindene addition made with it; The abstract and the description: a double-run precipitation running an aqueous silver nitrate solution and an aqueous halide solution simultaneously into an agitated aqueous solution of a peptizer while holding the pH at no more than 4.0 and the pAg between 8.6 and 9.2, preferably at 30 to 70 C, with quantities of halide ion greatly in excess of silver ion avoided; the citation of Berry and Skillman, Precipitation of Twinned AgBr Crystals, Photographic Science and Engineering 6(3), May to June 1962, for the finding that a change in pAg alone decides whether a double run gives regular cubes or octahedra; Example 1, a potassium bromide and potassium iodide solution and a silver nitrate solution in equal molar amounts added simultaneously to rapidly agitated aqueous gelatin at 70 C over 35 minutes, the pH held at 2.0 with sulphuric acid and the pAg at 9.0 by adjusting the relative rates of addition, giving cubic-regular silver bromoiodide of about 0.2 micrometre average grain size, one portion of which is sulfur- and gold-sensitized as described in Waller, United States Patent 2,399,083; Example 5, in which spectrally sensitised, sulfur- and gold-sensitized cubic emulsions made at pH 5.6 give fog of 0.79 to 0.97 against 0.04 for the same emulsion made at pH 2.0; and Example 6, which adds 4 g of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene and 2.5 ml of 6-methoxyquinoline per silver mole with an infrared sensitiser at 400 mg per silver mole; Example 1: cubic-regular silver bromoiodide of about 0.2 micron average grain size, and the statement that particularly good results come from grains below 0.5 micron; Example 1: cubic-regular grains of about 0.2 micron; the statement that particularly good results are obtained below 0.5 micron; the pAg range that selects the habit; Spectral sensitisation with a cyanine dye specified by its anodic and cathodic half-wave potentials, and the note that a sensitising dye is prone to desensitise the grains in the blue; Preparation of silver halide grains of cubic-regular shape: the statement, citing Berry and Skillman on the precipitation of twinned silver bromide crystals, that a change in pAg alone lets a double-run precipitation give regular cubes or octahedra; the running of the solutions into a rapidly agitated aqueous solution of a peptiser, preferably gelatin; the avoidance of a large excess of halide ion where regular grains are wanted; and Example 1, run at 70 °C with the pH held at 2.0 and the pAg at 9.0 for 35 minutes, giving cubic-regular silver bromoiodide of about 0.2 micrometre average grain size; Double-run precipitation at controlled pAg; the pAg 8.6 to 9.2 and pH 4.0 conditions for cubic-regular grains; the citation of Berry and Skillman 1962; the peptiser; and the rule that a large excess of halide is avoided if the grains are to be regular

Used by:Tetraazaindene · Davey and Knott's double-jet iodobromide emulsion · P4 Development as Amplification · P4 Grain, Speed and Resolution · P4 Experiment: Precipitating the Silver Halides · P4 Spectral Sensitivity and Colour Response · P4 The Silver Halides · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P5 Precipitation, Nucleation and Crystal Growth

Production of photographic silver halide emulsions of increased light sensitivity, United States Patent 2,399,083retrieved 2026-09-04, 2026-09-06

Sections: The soluble gold salts named for sensitisation; quantity of gold salt and pH during digestion; The description and claims 2 and 4: that adding a small quantity of a soluble gold salt before or during digestion, at a pH not greater than about 8, gives a very considerable increase in sensitivity; that the gelatin's own sulphur compounds, such as thiosinamine or allyl isothiocyanate, are believed essential to the effect, so that inert gelatins benefit from a positive addition of one; that including a small quantity of an alkali or ammonium thiocyanate with the gold salt improves the result further; that the quantity of gold is much smaller than would make any appreciable difference to the tone of the image and that too much loses the speed increase; and the claimed quantity, for an emulsion of normal silver halide content of about 2 to 3 per cent calculated as metallic silver, of an amount of gold salt per litre equal to that in 1 to 100 cc of a 1 to 10,000 solution; The statement that all normal gelatin contains small proportions of sulfur compounds such as thiosinamine or allyl isothiocyanate, and that inert gelatins benefit from a positive addition of one; Gold salts added before or during digestion at a pH not greater than about 8; the sulfur compounds naturally present in gelatin as a requirement for the gold effect; the improvement from adding an alkali or ammonium thiocyanate with the gold salt; and the loss of speed from too much gold; Ilford's 1946 patent — small quantities of a soluble gold salt added before or during digestion at a pH not greater than about 8

Used by:Gold(III) chloride · Davey and Knott's double-jet iodobromide emulsion · P4 The Latent Image · P5 Gelatin, the Photographic Binder · P5 Washing, Digestion and Sensitisation · Gold toned silver gelatin print

Silver halide emulsions, United States Patent 4,469,784retrieved 2026-09-06

Sections: The general description of grain formation — the statement that precipitation or physical ripening of the silver halide grains may be performed in the presence of a cadmium salt, a zinc salt, a lead salt, a thallium salt, an iridium salt or a complex salt thereof, a rhodium salt or a complex salt thereof, or an iron salt, and that the amount of metal ions used is usually at least 10^-6 mol per mol of silver halide; the same list repeated for metal ion doping of the central core of a core-shell grain; and Example 1, whose Emulsion A is a monodispersed 0.2 micron silver bromide emulsion precipitated by simultaneous addition at 60 degrees C with the pH held at 6.5 and the pAg at 9.3 and then sulfur- and gold-sensitised, with no dopant named; Example 1, in which emulsions precipitated by simultaneous addition at 60 C with the pH held at 6.5 and the pAg at 9.3 were sulfur- and gold-sensitized as described in U.S. Pat. No. 2,399,083; Example 3, whose post-ripening is carried out at 60 C and pAg 8.0 with 5 x 10-6 mol of sodium thiosulfate, 3 x 10-6 mol of chloroauric acid and 4 x 10-4 mol of potassium thiocyanate per mol of silver bromide; the description's statement that the controlled double jet method is the form of simultaneous mixing in which the pAg of the liquid phase is kept constant; and its statement of what a manufacturer of that period wanted from the halide, that preferred silver halide emulsions are composed of at least 50 mol per cent of silver bromide and that among these, silver bromoiodide emulsions particularly containing about 10 mol per cent or less of silver iodide are most preferred

Used by:Thallium(I) sulfate · Davey and Knott's double-jet iodobromide emulsion

Silver halide grains and photographic emulsions, United States Patent 3,772,031retrieved 2026-09-06

Sections: Example 7: a silver bromide emulsion prepared by the double-jet method by running a solution of silver nitrate and a solution of potassium bromide into a kettle containing bone gelatin maintained at pH 6.0 and pAg 9.0, kettle temperature 70 C, run time 42 minutes, giving grains of 0.15 to 0.20 micrometre edge length, portions of which are sensitized with 10 mg of sodium thiosulfate per silver mole for 90 minutes at 55 C, and with 10 mg of sodium thiosulfate and 5 mg of potassium chloroaurate per silver mole for 60 minutes at 55 C; and Example 9, whose Emulsion 1 carries 900 g of gelatin in a batch made up to 4,000 grams per mole of silver

Used by:Davey and Knott's double-jet iodobromide emulsion

photocornucopia.com

Rodenstock Enlarging Lenses: technical manual and performance dataretrieved 2026-09-04, 2026-09-05

Sections: Performance data pages: the fall-off-in-illumination diagrams, whose plotted quantity is labelled 1 - cos4; Performance data pages, the fall-off-in-illumination diagrams labelled 1 - cos4; Rodagon - recommended working aperture reached by stopping down two stops, with the 50 mm f/2.8 rated for 2x to 15x on 24x36 mm; the statement under Apo-Rodagon-D that the effective aperture of a lens focused at a scale of about 1:1 is approximately two f-stops smaller than the nominal aperture; Rogonar - a recommended scale range of 2x to 8x at a working aperture of f/11; Rogonar-S - stopping down by two to three stops recommended for optimal contrast and sharpness up to the image corners; Rodagon - recommended working aperture reached by stopping down two stops; Apo-Rodagon-N - one to two stops; Apo-Rodagon-D - optimum working aperture between f/5.6 and f/8 because the effective aperture at a scale of about 1:1 is approximately two f-stops smaller than the nominal aperture, so that stopping down further gives visible blur from diffraction; the published performance charts, whose fall-off in illumination is plotted in f-stops against relative image height with the 1 minus cosine-to-the-fourth reference curve drawn on the same axes; and the statement that enlarging lenses have no helical focusing facility because focusing is performed with the enlarger's bellows extension; Rogonar - three single elements, a recommended scale range of 2x to 8x and a working aperture of f/11; Rogonar-S - four elements in three groups, stopping down by two to three stops recommended for optimal contrast and sharpness up to the image corners, with the model table giving 50 mm for 24x36 mm, 75 mm for 6x6 cm, 90 mm for 6x7 cm and 105 mm for 6x9 cm; Rodagon - six elements, recommended working aperture reached by stopping down two stops, with 50 mm f/2.8 rated 2x to 15x for 24x36 mm and 135 to 150 mm for 4x5 inch; Apo-Rodagon-N - optimal working aperture reached by stopping down only one to two stops; Apo-Rodagon-D - optimum working aperture between f/5.6 and f/8, with the statement that the effective aperture of a lens focused for a scale of about 1:1 is approximately two f-stops smaller than the nominal aperture, so that stopping down beyond nominal f/8 gives visible blur from diffraction; Rodagon-WA - a shorter focal length giving a 70 per cent larger projection area at a shorter projection distance, and shorter exposures with less loss of contrast from stray light; the published performance charts, whose fall-off in illumination is plotted in f-stops against relative image height with a 1 minus cosine-to-the-fourth reference curve drawn on the same axes; and Modular-Focus - the statement that enlarging lenses have no helical focusing facility because focusing is performed with the enlarger's bellows extension; The published performance charts, whose fall-off in illumination is plotted in f-stops against relative image height with the 1 minus cosine-to-the-fourth reference curve drawn on the same axes; and the recommended working apertures, two stops down from maximum for a six-element lens; Apo-Rodagon-D - the statement that the effective aperture of a lens focused for a scale of about 1 to 1 is approximately two f-stops smaller than the nominal aperture; Rogonar-S and Rodagon - the recommendation to stop down two to three stops from maximum for optimal contrast and sharpness to the corners; and the published performance charts, whose fall-off in illumination is plotted in f-stops against relative image height with a 1 minus cosine-to-the-fourth reference curve drawn on the same axes; Recommended working apertures - stopping down two stops for a six-element Rodagon and two to three for a Rogonar-S, and the rated scale range of 2x to 8x for a simple three-element lens; the published performance charts, whose illumination fall-off is plotted in f-stops against relative image height against the 1 minus cosine-to-the-fourth reference curve; Published performance charts for enlarging lenses, including the plotted fall-off in illumination against relative image height with the 1 minus cos to the fourth reference curve; Apo-Rodagon-D - the optimum working aperture given as between f/5.6 and f/8, 'because the effective aperture of a lens focused for a scale of about 1:1 is approximately two f-stops smaller than the nominal aperture and therefore stopping down to smaller apertures than nominal f/8 would result in visible blur because of diffraction'; Rogonar-S - stopping down by 2 to 3 stops recommended for optimal contrast and sharpness up to the image corners; Accessories, Modular-Focus - the statement that enlarging lenses have no helical focusing facility because focusing is performed with the enlarger's bellows extension; Rogonar-S - stopping down by 2 to 3 stops recommended for optimal contrast and sharpness up to the image corners; Rogonar - a recommended scale range of about 2x to 8x at a working aperture of f/11; Rodagon - the recommended working aperture reached by stopping down by only 2 stops from open aperture, the 6-element design holding a uniformly high contrast from the picture centre to the edges; Apo-Rodagon-N - 1 to 2 stops; Apo-Rodagon-D - an optimum working aperture between f/5.6 and f/8, because the effective aperture at a scale of about 1:1 is approximately two f-stops smaller than the nominal aperture and stopping down further gives visible blur from diffraction; the Recommended scale range and Maximum film format columns tabulated for every focal length of every family; the published performance charts, which plot modulation transfer as separate sagittal and meridional curves at 40, 20, 10 and 5 line pairs per millimetre, together with distortion, longitudinal chromatic aberration and fall-off in illumination against the 1 minus cosine-to-the-fourth reference, all of them as functions of relative image height at 0.3, 0.5, 0.7, 0.85 and 1; and the statement that enlarging lenses have no helical focusing facility because focusing is performed with the enlarger's bellows extension; Published performance charts for each enlarging lens - fall-off in illumination in f-stops plotted against relative image height, drawn against the 1 minus cosine to the fourth reference curve, alongside distortion, longitudinal chromatic aberration and modulation transfer function at stated apertures and magnifications

Used by:P6 Pinhole Geometry: Blur, Focal Distance, Field of View and Falloff · P7 Assignment: Architecture, Low Viewpoint and the Flat Plane · P16 Build: An LED Enlarger Head · P16 Experiment: Commissioning the Enlarger · P16 Enlarger Optics: Condenser, Diffusion, Lens, Alignment and Falloff · P16 Break/Fix: The Room That Fogs and the Light That Is Not Even · P19 Lab: Dodging, Burning, Edge Work and Local Contrast · Enlarger alignment and uniformity check · Enlarger lamphouse or bellows leak · Negative popping · One soft corner from misalignment · Uneven enlargement from mixing chamber, alignment, lens falloff or mechanical vignette

photoformulary.homestead.com

Arrowroot starch: safety data sheet published in Photographers' Formulary's bulk chemical SDS libraryretrieved 2026-09-06

Sections: The sheet the supplier publishes under the heading Arrowroot Starch, which is Sigma-Aldrich S4251 for "Starch, from potato", version 5.4 of 27 February 2015, CAS 9005-25-8, EC 232-679-6 — classified only as a combustible dust with signal word Warning and no precautionary statements; section 3.1 component "High-polymeric carbohydrate material" at "<= 100 %"; section 8, ACGIH TWA 10 mg/m³ with the remarks "Dermatitis" and "Not classifiable as a human carcinogen", OSHA Table Z-1 limits of 15 and 5 mg/m³ and a NIOSH recommendation of 5 mg/m³; section 10.5, incompatible with strong oxidizing agents

Used by:Photographers' Formulary platinum and palladium printing kits

Bulk Chemical SDS Sheets: the index of Photographers' Formulary's substance safety data sheetsretrieved 2026-09-06

Sections: The whole index, enumerated: 124 substance sheets for the chemicals the supplier sells loose, including arrowroot starch, citric acid, oxalic acid and potassium oxalate, and six iron sheets — ferric ammonium citrate, ferric ammonium oxalate, ferric ammonium sulfate, ferric chloride, ferric nitrate and ferric sulfate. Cited for what is not in it: no sheet for ferric oxalate, none for potassium chlorate, none for potassium chloroplatinite and none for sodium tetrachloropalladate

Used by:Photographers' Formulary platinum and palladium printing kits

Citric acid, anhydrous: safety data sheet published in Photographers' Formulary's bulk chemical SDS libraryretrieved 2026-09-06

Sections: Sigma-Aldrich 791725, Citric acid, anhydrous, Redi-Dri, ACS reagent, version 5.2 of 28 May 2015 — CAS 77-92-9, EC 201-069-1; Eye irritation 2A, signal word Warning, H319 and nothing else; section 9, pH 1.8 at about 50 g/L, melting point 155 to 157 °C; section 10.5, incompatible with oxidizing agents, bases, reducing agents and nitrates; section 11, LD50 oral rat 5,400 mg/kg

Used by:Photographers' Formulary platinum and palladium printing kits

Cyanotype Kit 07-0090: instructions and safety data sheetsretrieved 2026-09-06

Sections: The 35-page safety-data bundle for the dry kit: the instruction sheet followed by four Sigma-Aldrich substance sheets, each a section 3.1 Substances sheet — Starch, from potato S4251, sections 1 to 3, 8, 10 and 13; Ammonium iron(III) citrate 09714, sections 1 to 3, 7, 8, 10, 12 and 13; Potassium hexacyanoferrate(III) 455946, sections 1 to 3, 7, 8, 9, 10, 12 and 13; and Potassium dichromate 483044, sections 1 to 3, 6, 7, 8, 9, 10, 12 and 13

Used by:Photographers' Formulary cyanotype and toning kits

Kit SDS Sheets: the index of Photographers' Formulary's kit safety data sheetsretrieved 2026-09-06

Sections: The whole index, enumerated: 105 kit safety data sheets keyed by catalogue number, including 07-0010, 07-0022 and 07-0023 together, 07-0024, 07-0028, 07-0070, 07-0075, 07-0080, 07-0090, 07-0091, 07-0095, 07-0100, 07-0106 and 07-0110 — and none for 07-0001, 07-0003, 07-0005, 07-0007 or 07-0009. Cited for that negative fact, which is why the disclosed components on this page are read off an instruction sheet rather than off a hazard document

Used by:Photographers' Formulary platinum and palladium printing kits

Liquid Cyanotype Kit 07-0091: instructions and safety data sheetsretrieved 2026-09-06

Sections: The 35-page safety-data bundle for the liquid kit — the same four Sigma-Aldrich substance sheets at the same four version numbers, bound behind the liquid kit's own instruction sheet

Used by:Photographers' Formulary cyanotype and toning kits

Liquid Cyanotype Kit, catalogue number 07-0092: instructionsretrieved 2026-09-05, 2026-09-06

Sections: Liquid Cyanotype Kit 07-0092 — the statement that the kit contains solutions to make approximately twenty 4 by 5 prints; the contents table giving arrowroot starch 4 g, potassium ferricyanide solution (Sol B) 8 g in 100 mL water, ferric ammonium citrate (green) (Sol A) 20 g in 100 mL water and potassium dichromate 0.2 g; the sizing solution scaled to 4 g of arrowroot starch in 250 mL; and the 1 per cent dichromate solution, whose table gives 20 mL of water and 0.2 g of dichromate while the sentence beneath it directs the reader to add 100 mL; Toner Solutions, Brown to Black Tones: 'Ammonium 28% 10 ml, Water 1000 ml' and 'Tannic Acid 20 grams, Water 1000 ml', with the same two-step immersion direction; a second Photographers' Formulary printing of the same toner, carrying the same tannic acid strength and a tenfold weaker ammonia bath

Used by:Photographers' Formulary cyanotype and toning kits · Tannic acid toner for cyanotype

Oxalic acid dihydrate: safety data sheet published in Photographers' Formulary's bulk chemical SDS libraryretrieved 2026-09-06

Sections: Sigma-Aldrich 247537, Oxalic acid dihydrate, version 4.9 of 6 May 2015 — CAS 6153-56-6, Index-No. 607-006-00-8, formula C2H2O4 · 2H2O, molecular weight 126.07; Acute toxicity Oral 4, Acute toxicity Dermal 4 and Serious eye damage 1, signal word Danger, H302 + H312 and H318; section 9, pH 1 at 126.1 g/L, melting range 104 to 106 °C; section 10, avoid moisture, incompatible with bases, metals, acid chlorides and alkali metals; section 11, LD50 oral rat 1,080 mg/kg

Used by:Photographers' Formulary platinum and palladium printing kits

Photographers' Formulary New Kallitype Printing Kit, catalogue number 07-0075: instructionsretrieved 2026-09-04, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Development - the 20 per cent sodium citrate developer and how it is made up and replenished; Chemicals contained in this kit, for the later kit that carries no borax at all; Mixing the solutions — Developer Solution; Development, for the residual black substance and the agitation that keeps it off the highlights; Clearing, for the instruction that the rinse water must be neutral or slightly acidic and that water with a basic pH will make the print difficult to clear; Fixing Bath, reading distilled water at 52 degrees C / 125 degrees F 1000 ml and sodium thiosulfate pentahydrate 50 g, with the instruction to stir until all solids have dissolved, the statement that sodium thiosulfate does not have an extended shelf life once mixed with water so that the kit ships two packets each adequate to fix four or five 8 by 10 kallitype prints, and the requirement that "the use of distilled water or water with a neutral or slightly base ph is important. Acidic water accelerates the tendency of thiosulfate to bleach highlights formed by the silver nitrate in your print"; the Fixing section, that the fix removes residual silver nitrate, that the print is fixed in a 5 per cent solution for two to five minutes, that the fix bath tends to bleach the print so that a print should be printed darker than wanted, that the plain solution is not stable for long periods, and that a pH-neutral commercial fixer diluted from 1:9 to 1:19 is suitable if a sodium thiosulfate fix is unavailable; the 3 per cent citric acid clearing bath before it; and the final wash, running water then a five-minute hypo clear soak and a 15 to 20 minute wash; Mixing the Solutions, Clearing Bath, reading distilled water at 20 degrees C 5000 ml and citric acid 150 g to make a 3 per cent solution, 30 g per litre; and the Processing section, Clearing, for the statement that once development is complete the residual iron compounds must be cleared from the paper, that most of them have dissolved into the developer but some remain in the paper's fibres, that this is done in a series of 3 per cent citric acid baths of which two are recommended and a third may be used, that the baths are moved up in rotation so the freshest is always the last, that a bath should easily allow for two or three 8 by 10 prints, that rinsing after development in water of neutral or slightly acidic pH extends the life of the baths while water with a base pH will make the print difficult to clear, that clearing runs until the whites are free of a yellow or grey fog, and that a print taking longer than 10 minutes to clear indicates a paper too absorbent to use without sizing; Chemicals contained in this kit; Ferric Oxalate; Mixing the solutions — The Sensitizer; Sensitizing the Paper; Exposure; Development; Clearing; Toning; Fixing; Final Wash; Final Notes and Suggestions; Processing, Clearing — for the statement that rinsing after development in water of neutral or slightly acidic pH extends the life of the clearing baths while water with a base pH will make the print difficult to clear, for the series of citric acid baths moved up in rotation so that the freshest is always the last, and for clearing run until the whites are free of a yellow or grey fog; Chemicals contained in this kit, for the later kit that carries no Rochelle salt at all; Mixing the solutions — Developer Solution; Development, for the residual black substance and the agitation that keeps it off the highlights; Chemicals contained in this kit; Mixing the solutions — Developer Solution, for the 300 g in 1500 mL make-up, the 52 °C water and the 500 mL replenisher; Development, for the two to three minutes, the tilted-tray pour, the black residue and the dichromate note; Clearing; Fixing; Final Notes and Suggestions; Clearing — the statement that once development is complete residual iron compounds must be cleared from the paper, that most have dissolved into the developer but some remain in the fibres, that this is accomplished in a series of baths of 3 per cent citric acid of which two are recommended and a third may be used, that the baths are moved up in rotation so the freshest is always last, that the print should be drained before entering, that the useful life easily allows two or three 8 by 10 prints per bath, that rinsing after development in water of neutral or slightly acidic pH extends the life of the baths while water with a base pH makes the print difficult to clear, that the end point is whites free of a yellow or grey fog, and that a print taking longer than ten minutes is on paper too absorbent to use without sizing; Toning, for the suggestion that the photographer skip toning until the print has been judged and re-soak and tone it later, against the available literature's suggestion that a kallitype should be toned to improve its archival stability and that toning should precede fixing to avoid bleaching the highlights; Fixing and Final Wash; Development, for the statement that contrast may be increased by adding small amounts of potassium dichromate to the developer solution and that this substance is not provided with the kit but can be obtained as part of the traditional kallitype kit or on request; The Negative, for the recommendation of a more contrasty negative than a silver gelatin print needs, reached by selecting high-contrast lighting, developing film about 50 per cent longer, or boosting contrast by 10, 20 or 30 per cent in software; Sensitizing the paper, for the note that some studies show slightly better densities with slightly more silver nitrate solution, with no proportion named; Chemicals contained in this kit — arrowroot starch 20 g, ferric oxalate 30 mL, silver nitrate 2 g, sodium citrate 300 g, citric acid 150 g and two 50 g packets of sodium thiosulfate pentahydrate, with no dichromate supplied and the note that it can be obtained from the traditional kit or on request; Chemical safety and Ferric Oxalate, repeating the traditional kit's account word for word; Mixing the solutions — the silver nitrate dissolved as 2 g in 20 mL of distilled water warmed to about 49 degrees C, kept in a separate bottle and combined with the ferric oxalate only just before coating; Developer solution, 300 g of sodium citrate made up to 1.5 litres, described in the same paragraph both as a 10 per cent and as a 20 per cent solution; the replenishment schedule of 100 mL after about four 8 by 10 prints and 100 mL after each further two; Clearing bath, 150 g of citric acid in 5 litres for a 3 per cent solution, used as two or three successive baths rotated so the freshest is last, with the instruction to clear until the whites are free of yellow or grey fog and the warning that a print taking more than ten minutes to clear is on paper too absorbent to use unsized; Fixing bath, 50 g of sodium thiosulfate per litre, with the statement that the use of distilled water or water with a neutral or slightly base pH is important because acidic water accelerates the tendency of thiosulfate to bleach highlights; Paper, for Arches Watercolor 140 lb hot press; The negative, for a more contrasty negative than a silver gelatin print needs; Sensitizing the paper, for equal volumes mixed in a shot glass, about half a millilitre of each for a 4 by 5 and 1 to 2 mL of each for an 8 by 10, the statement that most research shows the best print density results from equal proportions while some studies show slightly better densities with slightly more silver nitrate solution, and the drop table of 6 to 8, 8 to 12 and 12 to 20 drops of each solution; Exposure, for 10 to 20 minutes under a sunlamp and 4 to 6 minutes in a UV light box; Development, for two to three minutes with constant agitation, the image appearing almost immediately, the instruction to develop the full time so the developer reacts with all available iron and silver, and the residual black substance that forms next to dark tones and accumulates in the developer; Clearing; Toning, for the suggestion to skip toning until the print has been judged and to re-soak and tone later; Fixing, for a weak 5 per cent solution for two to five minutes and the note that the fix bath tends to bleach highlights so the print should be over-exposed to compensate; Final Notes and Suggestions, for coated paper being used within an hour or two after drying and for the ferric oxalate and silver nitrate solutions being stored in dark brown bottles; Clearing, for the end point of whites free of a yellow or grey fog, for the rotation of two or three baths of 3 per cent citric acid, for the statement that a print taking longer than ten minutes to clear is on paper too absorbent to use unsized, and for the warning that water with a base pH will make the print difficult to clear; Development, for the residual black substance that forms next to dark tones, accumulates in the developer and may be filtered out; Fixing, for the statement that the fix bath tends to bleach highlights and that the print should be over-exposed to compensate; Final Notes and Suggestions, for coated paper being used within an hour or two of drying, for the storage of the two solutions in dark brown bottles and the instruction not to leave them uncapped, and for coated papers fogging if left exposed to too bright a light; The 20 per cent sodium citrate developer, its preparation and its replenishment; The clearing agent of 3 per cent citric acid; draining the print before the first clearing bath; clearing until the whites appear free of a yellow or grey fog; a print taking over ten minutes being on paper too absorbent to use without sizing

Used by:Trisodium citrate dihydrate · Borax kallitype developer · Dilute alkaline thiosulfate fixer for iron-silver prints · EDTA and sodium sulfite clearing sequence · Kallitype sensitiser · EDTA, citric acid and hydrochloric acid clearing sequence · Rochelle salt kallitype developer · Sodium citrate kallitype developer · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Contrast Control in Iron-Based Printing · P24 Lab: Printing a Kallitype · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · Kallitype · Clearing an iron-silver print and testing it for residual iron

Potassium oxalate monohydrate: safety data sheet published in Photographers' Formulary's bulk chemical SDS libraryretrieved 2026-09-06

Sections: Sigma-Aldrich 379727, version 4.11 of 16 June 2016, as republished in the supplier's own bulk library — section 1, Potassium oxalate monohydrate, CAS 6487-48-5, EC 209-506-8, formula C2K2O4 · H2O, molecular weight 184.23; section 2, Acute toxicity Oral 4 and Dermal 4, signal word Warning, H302 + H312; section 3.1, one component at "<= 100 %"; section 9, beige powder, pH 7.0 to 8.5 at 50 g/L and 25 °C, relative density 2.127; section 10, avoid moisture, incompatible with halogens, ammonia, cyanides and heavy metals, decomposition to carbon oxides and potassium oxides; and section 11, in which every line reads "No data available"

Used by:Photographers' Formulary platinum and palladium printing kits

Sensitizer B Platinum/Palladium 07-0022 and 07-0023: safety data sheetsretrieved 2026-09-06

Sections: The whole fourteen-page document, which is the only sheet in the supplier's library filed under the platinum and palladium sensitiser — Sigma-Aldrich 12302 for Ammonium iron(III) oxalate trihydrate, CAS 13268-42-3, formula C6H12FeN3O12 · 3H2O, molecular weight 428.06, version 5.2 of 22 December 2014, Acute toxicity Oral 4 and Dermal 4 with signal word Warning and H302 + H312, its section 3.1 component "Triammonium iron(3+) trioxalate trihydrate" at "<= 100 %", section 11 carrying no toxicological data at all, and DOT UN3077 class 9 packing group III; followed by Columbus Chemical Industries 4730 for Silver Nitrate, Crystal, ACS of 31 August 2012, Oxidizing solids 2, Acute toxicity Oral 4, Skin corrosion 1B, Serious eye damage 1 and the two aquatic categories, UN1493 class 5.1 packing group II. Cited because neither substance is what the same company's own product page and instruction sheets say is in the bottle

Used by:Photographers' Formulary platinum and palladium printing kits

physics.nist.gov

Uncertainty of Measurement Results (NIST Reference on Constants, Units, and Uncertainty)retrieved 2026-09-06, 2026-09-07

Sections: Basic definitions - Type A evaluation of uncertainty as the statistical analysis of series of observations and Type B as evaluation by other means; and Combining uncertainty components; Basic definitions - Type A evaluation of uncertainty as the statistical analysis of series of observations and Type B as evaluation by other means; Basic definitions - Type A evaluation given as the method of evaluation of uncertainty by the statistical analysis of series of observations and Type B as the method of evaluation by means other than the statistical analysis of series of observations; Evaluating uncertainty components: Type B, whose stated sources are previous measurement data, experience with or general knowledge of the behaviour and property of relevant materials and instruments, manufacturer's specifications, data provided in calibration and other reports, and uncertainties assigned to reference data taken from handbooks; and Combining uncertainty components, where the combined standard uncertainty is the positive square root of the estimated variance obtained from the law of propagation of uncertainty; Basic definitions - Type A evaluation of uncertainty as the statistical analysis of series of observations and Type B as evaluation by other means, whose stated sources include manufacturer's specifications and data provided in calibration reports; and Combining uncertainty components

Used by:P27 Experiment: Agitation, Stand and Semi-Stand Development · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Experiment: Four Curve Families, Measured · P27 Experiment: The Development Time and Temperature Series

pictorialplanet.com

510-Pyroretrieved 2026-09-05

Sections: The section headed "Formula", with its five lines and the footnote on the phenidone change; "Some benefits"; "Longevity"; "Developing Agents"; "Darkroom Printing"

Used by:510-Pyro

pinholeday.org

Worldwide Pinhole Photography Dayretrieved 2026-09-04

Used by:P7 Seeing Like a Pinhole: The Image, Its Makers and Previsualisation

pinholeresource.com

Pinhole Resourceretrieved 2026-09-04

Used by:P7 Seeing Like a Pinhole: The Image, Its Makers and Previsualisation

plato.stanford.edu

The Mohist Canons, in the Stanford Encyclopedia of Philosophyretrieved 2026-09-04

Sections: Opening section on the dating and scope of the Canons

Used by:P1 The Camera Obscura: An Image Without Chemistry

pmc.ncbi.nlm.nih.gov

Characterization of arrowroot (Maranta arundinacea) starch as a potential starch source for the food industryretrieved 2026-09-05, 2026-09-07

Sections: Introduction, on amylose and amylopectin, the anhydroglucose units and their alpha(1,4) and alpha(1,6) linkages, the molecular weights, the semi-crystalline and amorphous lamellae of the granule and the A, B and C crystalline types, and on Maranta arundinacea and the starch content of its rhizome; Results and Discussion, for the granule shapes and dimensions, the amylose content and its literature range, the swelling power and solubility, the least gelation concentration, the differential scanning calorimetry onset, peak and conclusion temperatures with the values reported from Indonesia, Venezuela and Brazil, the A-type X-ray diffraction pattern and the earlier study that found B-type, and the account of what heating does to the hydrogen bonding of the amorphous regions; Results and Discussion, for the granule dimensions of Sri Lankan arrowroot and the spread of published widths and gelatinisation onset temperatures between samples from Sri Lanka, Indonesia, Venezuela and Brazil, and for the A-type X-ray diffraction pattern against an earlier study finding B-type, attributed to extraction process, growing conditions and genotype

Used by:Arrowroot · P22 The Variants of the Salt Print and How a Conservator Identifies One

Functional Properties and Extraction Techniques of Chicken Egg White Proteinsretrieved 2026-09-07

Sections: Section 1, Introduction — "Egg white (EW) consists of about 88% water, 11% protein, 0.2% fat and 0.8% ash"; sections 2.1 to 2.7, the major proteins as a proportion of total egg white protein with molecular weight and isoelectric point — ovalbumin 54 per cent, 45 kDa, pI 4.5, "a major contributor to the foaming, gelling and emulsifying properties of EW"; ovotransferrin 12 to 13 per cent, 77 kDa, pI 6.0, with two ligand centres that "can bind to metal ions such as Fe, Cu or Zn"; ovomucoid 11 per cent, 28 kDa, pI 4.1, nine disulfide bonds and no free sulfhydryl groups; lysozyme 3.4 to 3.5 per cent, 14.3 kDa, pI 10.7; ovomucin 1.5 to 3.5 per cent, pI 4.5 to 5.0, whose association with lysozyme and globulin gives it excellent foaming ability; ovomacroglobulin 0.5 per cent; avidin 0.05 per cent, 68.3 kDa, pI 10.0, irreversibly denatured at 70 °C; Section 1 — egg white as about 88 per cent water and 11 per cent protein; section 2.1 — ovalbumin at 54 per cent of total egg white protein and its contribution to foaming and gelling

Used by:P23 Egg Albumen: A Protein Binder and What It Does to Silver · P23 Lab: Preparing and Coating Albumen Paper

pubchem.ncbi.nlm.nih.gov

PubChem compound summary: 1H-Benzotriazole (CID 7220)retrieved 2026-09-04, 2026-09-05

Sections: Physical description; solubility; CAS; GHS classification; Uses (HSDB, Hawley's Condensed Chemical Dictionary, Kirk-Othmer and Patty's Toxicology entries); GHS Classification: GHS09 with H411, toxic to aquatic life with long lasting effects; Uses and the gravimetric determination of silver by precipitation with benzotriazole; GHS classification from the aggregated ECHA notifications; GHS classification aggregated from the ECHA C&L Inventory notifications; GHS classification aggregated from the ECHA C&L Inventory notifications; the gravimetric determination of silver by precipitation with benzotriazole; GHS Classification, the ECHA C&L aggregated entry giving signal word Warning with the exclamation mark and environmental hazard pictograms, and H302 and H319 as the dominant statements

Used by:Benzotriazole · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P8 Restrainers and Antifoggants · P9 Overview: Experiments on Development · P9 Experiment: The Activity Series - Alkali and Restrainer · P18 Print Developer Chemistry and the Developer-Paper Pair

PubChem compound summary: 2,4-Diaminophenol hydrochloride (CID 8715)retrieved 2026-09-04, 2026-09-05

Sections: CAS; molecular formula and weight; physical description (HSDB, CAMEO, MSDSonline); solubility (HSDB, CAMEO); GHS classification — the aggregated ECHA C&L notifications, the NITE-CMC entry and Safe Work Australia's HCIS entry; GHS Classification, the ECHA C&L aggregated entry with signal word Danger and the GHS06, GHS07 and GHS08 pictograms, used here for the hazard classification of 2,4-diaminophenol dihydrochloride

Used by:Amidol · P18 Print Developer Chemistry and the Developer-Paper Pair

PubChem compound summary: 4-(Hydroxymethyl)-4-methyl-1-phenylpyrazolidin-3-one (CID 92238)retrieved 2026-09-04

Sections: CAS; molecular formula and weight; IUPAC name; connectivity SMILES; physical description (Sigma-Aldrich safety data sheet); GHS classification — the aggregated ECHA C&L notifications; Solubility heading, which returns no values

Used by:Dimezone S

PubChem compound summary: 4-Aminophenol (CID 403)retrieved 2026-09-04

Sections: CAS; molecular formula and weight; IUPAC name; physical description (CAMEO, Haz-Map, EPA CDR); solubility (CAMEO, HSDB, HMDB); GHS classification — the aggregated ECHA notifications; ChEBI description; GHS classification — the harmonised CLP entry and the aggregated ECHA notifications; solubility

Used by:p-Aminophenol · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol

PubChem compound summary: 5-Methyl-1H-[1,2,4]triazolo[1,5-a]pyrimidin-7-one (CID 75629)retrieved 2026-09-04

Sections: CAS registry numbers; molecular formula and weight; IUPAC name; GHS classification — the aggregated ECHA C&L notifications for EC 219-706-7; Solubility and Physical Description headings, which return no values

Used by:Tetraazaindene

PubChem compound summary: 5-Nitrobenzimidazole (CID 7195)retrieved 2026-09-04

Sections: Physical description; solubility; CAS; GHS classification; Uses (HSDB and Haz-Map entries)

Used by:6-Nitrobenzimidazole

PubChem compound summary: Acetic Acid (CID 176)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Physical description; solubility; CAS; GHS classification; GHS classification — signal word, pictograms and hazard statements for the concentrated acid; GHS classification, aggregated from the ECHA C&L Inventory; physical description; solubility; Experimental properties, density 1.049 at 20 degrees C; GHS classification aggregated from 5076 ECHA C&L reports, H226 flammable liquid and vapour at 99.7 per cent and H314 causes severe skin burns and eye damage at above 99.9 per cent; Experimental properties, density 1.049 at 20 degrees C; GHS classification aggregated from 5076 ECHA C&L reports, H226 at 99.7 per cent and H314 at above 99.9 per cent; Computed properties; physical description (CAMEO); GHS classification; Computed properties; GHS classification (ECHA C&L Inventory aggregation); Computed properties - molecular weight; GHS classification of the concentrate; GHS classification aggregated from 5076 ECHA C&L reports — H226 flammable liquid and vapour at 99.7 per cent and H314 causes severe skin burns and eye damage at above 99.9 per cent; experimental density 1.049 at 20 degrees C; Experimental properties — density 1.049 at 20 degrees C; GHS classification aggregated from 5076 ECHA C&L reports, H226 at 99.7 per cent and H314 at above 99.9 per cent; Experimental properties — density 1.049 at 20 degrees C; GHS classification aggregated from 5076 ECHA C&L reports across 68 notifications, H226 at 99.7 per cent, H314 at above 99.9 per cent and H318 at 14.7 per cent; Experimental properties — density 1.049 at 20 degrees C; GHS classification aggregated from 5076 ECHA C&L reports; Experimental properties — density 1.049 g/mL at 20 degrees C; GHS classification aggregated from 5,076 ECHA C&L reports, H314 in more than 99.9 per cent of the reports carrying hazard codes and H226 in 99.7 per cent, describing the concentrated acid; GHS classification aggregated from 5076 ECHA C&L reports, H226 flammable liquid and vapour at 99.7 per cent and H314 causes severe skin burns and eye damage at above 99.9 per cent

Used by:Acetic acid (glacial) · Albumen solution with its chloride · Talbot's gallo-nitrate of silver · Kodak SB-1 · Kodak SB-1a · Kodak SB-5 · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P2 Measuring Mass, Volume, Temperature and Density, and Knowing How Wrong You Are · P3 Acids, Bases and pH · P3 Lab: Measuring pH and Trusting the Number · P10 Overview: Stopping Development · P10 Experiment: Measuring Stop Bath Capacity · P10 Stop Bath Formulations and the Fixer Interaction · P10 Why Stopping Works · P11 Lab: Mixing Fixers from Scratch · Stop bath preparation

PubChem compound summary: Aluminum potassium sulfate dodecahydrate (CID 62667)retrieved 2026-09-04, 2026-09-05

Sections: CAS; computed molecular formula and weight; IUPAC name; physical description (Haz-Map, citing the Merck Index and Hawley); GHS classification — the aggregated ECHA notifications; ChEBI description; GHS Classification, ECHA C&L Inventory EC 616-521-7: reported as not meeting GHS hazard criteria by 43 of 43 companies; GHS Classification, ECHA C&L Inventory EC 616-521-7; GHS classification aggregated from 43 reports across 2 ECHA C&L notifications, all of which state that the substance does not meet GHS hazard criteria and none of which carries a hazard statement code; GHS classification aggregated from 43 reports across 2 ECHA C&L notifications, all of which state that the substance does not meet GHS hazard criteria

Used by:Potassium alum · Kodak SB-4 · P5 Coating, Drying and Hardening · P5 Project 4: Coating Glass Dry Plates and a Lantern Slide · P5 Lab: Coating Your First Emulsion · P5 Gelatin, the Photographic Binder · P11 Overview: Making the Image Permanent · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline · P11 Lab: Mixing Fixers from Scratch

PubChem compound summary: Ammonia (CID 222)retrieved 2026-09-04, 2026-09-07

Sections: Physical description; GHS classification; GHS classification and physical description; the aggregated classification of ammonia solution

Used by:P1 Wedgwood, Davy and the Problem of Permanence · P23 Lab: Sensitising, Printing and Toning an Albumen Print

PubChem compound summary: Ammonium Bromide (CID 25514)retrieved 2026-09-04

Sections: Identity, computed properties and CAS; the harmonised classification under Regulation (EC) No 1272/2008; the aggregated ECHA C&L notifications; the NITE-CMC entry; solubility from HSDB; physical description from CAMEO and Haz-Map

Used by:Ammonium bromide

PubChem compound summary: Ammonium Chloride (CID 25517)retrieved 2026-09-04, 2026-09-05, 2026-09-07, 2026-09-08

Sections: Physical description; solubility; pH; chemical dangers; reactivity profile; hazards summary; fire hazards; storage conditions; CAS; GHS classification; GHS classification; solubility; Solubility (HSDB): strongly endothermic dissolution; hydrochloric acid and sodium chloride decrease solubility in water; GHS classification aggregated from ECHA C&L notifications — signal word Warning, H302 and H319; Physical description; pH of aqueous solutions; GHS classification; GHS aggregation: signal word Warning with H302 and H319

Used by:Ammonium chloride · Albumen solution with its chloride · Double-coated albumen procedure · P3 Solutions, Solubility and Precipitation · P23 Lab: Preparing and Coating Albumen Paper · Albumen print · Preparing and coating albumen paper

PubChem compound summary: Ammonium dichromate (CID 24600)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Physical description — CAMEO, Haz-Map and the ILO-WHO safety card; Solubility — HSDB and the ILO-WHO card; CAS; GHS classification — the aggregated ECHA C&L notifications and the harmonised CLP entry; GHS classification, aggregated from the ECHA C&L Inventory as Ammonium dichromate, EC 232-143-1, 194 reports across 10 notifications; physical description from CAMEO Chemicals; solubility in water from the Hazardous Substances Data Bank; GHS classification — the harmonised CLP entry and the aggregation of 194 reports across 10 notifications to the ECHA C&L Inventory, with H340, H350 and H372 each in 100 per cent of reports and no notifier declining to classify; GHS classification aggregated from 194 reports across 10 ECHA notifications for ammonium dichromate, EC 232-143-1 — signal word Danger, six pictograms, with H301, H312, H314, H317, H330, H334, H340, H350 and H372 each at 100 per cent of reports and H360 at 45.9 per cent; GHS classification aggregated from 194 reports across 10 ECHA notifications, including H340 and H350 at 100 per cent of reports; GHS classification aggregated from the ECHA C&L Inventory, the same shape as the potassium salt's, and the CAMEO reactivity profile, as summarised on the course's ammonium dichromate page; GHS classification, aggregated from the ECHA C&L Inventory; GHS classification, aggregated from the ECHA C&L Inventory; CAMEO reactivity profile

Used by:Ammonium dichromate · Ware's improved Classic cyanotype · P21 The New Cyanotype and the Other Ways to Make a Blue Print · P24 Contrast Control in Iron-Based Printing · P24 Lab: Printing a Kallitype · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · Gum bichromate · The chromium policy

PubChem compound summary: Ammonium Hydroxide (CID 14923)retrieved 2026-09-04, 2026-09-05

Sections: Physical description; solubility; CAS; GHS classification; ChEBI description; GHS classification aggregated from the ECHA C&L Inventory for ammonia, aqueous solution, 6,275 reports across 116 notifications; physical description and vapour pressure; GHS classification; Physical description: the irritant vapour of ammonia solution; GHS classification; vapour hazard; GHS classification: the harmonised entry under Regulation (EC) No 1272/2008 for ammonia solution — Danger, GHS05, GHS09, with H314 and H400; physical description, the irritant vapour

Used by:Ammonia solution (ammonium hydroxide) · The Simple Cyanotype (2019) · P4 Experiment: Precipitating the Silver Halides · Toned cyanotype · Ammoniacal silver quench and prohibition

PubChem compound summary: Ammonium Persulfate (CID 62648)retrieved 2026-09-05

Sections: Identity, computed properties and CAS; the harmonised classification under Regulation (EC) No 1272/2008; the NITE-CMC entries of FY2006, FY2008 and FY2024; the Safe Work Australia HCIS entry; solubility from HSDB and from the ILO-WHO card; physical description from CAMEO, the EPA Chemical Data Reporting programme and Haz-Map

Used by:Ammonium persulfate

PubChem compound summary: Ammonium Sulfite (CID 25041)retrieved 2026-09-06

Sections: Names and Identifiers — Molecular Formula, Computed Properties, CAS, Related CAS, European Community (EC) Number, MeSH Entry Terms and Depositor-Supplied Synonyms; Chemical and Physical Properties — Physical Description, Color/Form, Odor, Solubility, Density, Stability/Shelf Life, pH and Other Experimental Properties; Safety and Hazards — GHS Classification and Hazard Classes and Categories in both blocks, Health Hazards, Fire Hazards, First Aid, Storage Conditions, Personal Protective Equipment, Protective Action Criteria, Stability and Reactivity, and the Clean Water Act and CERCLA entries under Regulatory Information; Toxicity — Human and Non-Human Toxicity Excerpts, Populations at Special Risk, Antidote and Emergency Treatment, and Ecotoxicity Values; Use and Manufacturing — Uses, Industry Uses, Methods of Manufacturing and U.S. Production; Food Additives and Ingredients. Read through the PUG and PUG-View APIs

Used by:Ammonium sulfite

PubChem compound summary: Ammonium thiocyanate (CID 15666)retrieved 2026-09-04, 2026-09-05

Sections: Identity, computed properties and CAS; GHS classification aggregated from the ECHA C&L Inventory, with the NITE-CMC and Safe Work Australia entries; solubility from HSDB; the two CAMEO datasheets, for the solid and for the liquor; Identity and the GHS Classification section, as summarised on the course's ammonium thiocyanate page; Physical description; GHS classification

Used by:Ammonium thiocyanate · Steigmann gold sensitiser stock · Gold-toned and palladium-toned kallitype

PubChem compound summary: Ammonium thiosulfate (CID 6096946)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Physical description; solubility; CAS; GHS classification; computed molecular weight; Names and identifiers — CAS 7783-18-8 and EC 231-982-0; solubility; Names and identifiers — CAS 7783-18-8 and EC 231-982-0; GHS classification and the aggregated ECHA notifications; CAS; computed properties; GHS classification; The CAMEO datasheet reproduced on the entry, which describes an ammonium thiosulfate solution of 60 per cent or less as an odourless colourless liquid, and the solid as hygroscopic with an odour of ammonia

Used by:Ammonium thiosulfate · ILFORD HYPAM · ILFORD RAPID FIXER · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P11 Overview: Making the Image Permanent

PubChem compound summary: Barium sulfate (CID 24414)retrieved 2026-09-04

Sections: CAS registry numbers; molecular formula and weight; ChEBI description; physical description (CAMEO, ILO-WHO ICSC, NIOSH, HSDB); solubility (CAMEO, HSDB, NIOSH, DrugBank); GHS classification — the aggregated ECHA C&L notifications for barium sulfate and for barite, and the NITE-CMC entry

Used by:Barium sulfate

PubChem compound summary: Borax (B4Na2O7.10H2O) (CID 16211214)retrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: GHS classification aggregated from 2,865 reports across 31 ECHA C&L notifications for disodium tetraborate decahydrate: Danger, GHS07 and GHS08, with H360 in 93.2 per cent of classifying reports and H319 in 12.6 per cent; GHS classification aggregated from 2,865 reports across 31 ECHA C&L notifications for disodium tetraborate decahydrate: Danger, GHS07 and GHS08, with H360 in 93.2 per cent of classifying reports and H319 in 12.6 per cent; ILO-WHO Chemical Safety Card 0567 carries the same two statements; Physical description; solubility; CAS; GHS classification; other experimental properties; methods of manufacturing; Physical description; solubility; Solubility, for the HSDB records of 5.93 g per 100 mL at 25 °C, 3.17 g per 100 g at 25 °C and 1 g in 16 mL of cold or 0.6 mL of boiling water, and for the aqueous solution being alkaline to litmus and to phenolphthalein at about pH 9.5; GHS classification, aggregated from the ECHA C&L Inventory; other experimental properties, for efflorescence in warm dry air; uses, for the registered herbicide use; Solubility — the HSDB record that an aqueous borax solution is alkaline to litmus and to phenolphthalein, at about pH 9.5; Solubility and properties (HSDB): the aqueous solution is alkaline, pH about 9.5; Properties (HSDB): the aqueous solution is alkaline to litmus and phenolphthalein, pH about 9.5; GHS classification (ECHA C&L Inventory aggregation): Danger, H360 in 93.2 per cent of reports; Solubility (HSDB): 3.17 g per 100 g at 25 degrees C, and 1 g in 16 mL of water against 1 g in 0.6 mL of boiling water; ILO-WHO card, 5.1 g per 100 mL at 20 degrees C; GHS classification for disodium tetraborate decahydrate; GHS classification for disodium tetraborate decahydrate; other experimental properties; Solubility, and the spread between sources; GHS classification for disodium tetraborate decahydrate; GHS classification for disodium tetraborate decahydrate, and the reproductive-toxicity statement carried by 93.2 per cent of reports; GHS classification for disodium tetraborate decahydrate aggregated from 2,865 reports across 31 ECHA notifications — signal word Danger, with H360 for reproductive toxicity at 93.2 per cent of reports and H319 at 12.6 per cent

Used by:P29 Capstone Stage 2: Formulating and Documenting Your Chemistry · P29 Planning the Capstone: The Project Plan and Its Hazard Assessment · Borax (sodium tetraborate decahydrate) · Sodium metaborate (anhydrous) · Borax kallitype developer · Rochelle salt kallitype developer · P3 Acids, Bases and pH · P3 Buffers and Buffer Capacity · P3 Lab: Measuring pH and Trusting the Number · P3 Solutions, Solubility and Precipitation · P8 Overview: What a Developer Is · P8 Alkalis, Buffers and pH · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P8 Assignment: Reading a Developer Formula · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P24 Lab: Printing a Kallitype

PubChem compound summary: Boric Acid (CID 7628)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Physical description; solubility; CAS; GHS classification; other experimental properties; uses; Names and identifiers — CAS 10043-35-3 and EC 233-139-2; GHS classification, the aggregated ECHA notifications and the reproductive-toxicity statements; Solubility: the ILO-WHO figure of 5.6 g per 100 mL at 20 degrees C and the HSDB temperature curve, 4.72 per cent w/w at 20 degrees C, 10.27 at 50 degrees C and 27.53 at 100 degrees C; GHS classification aggregated from the ECHA C&L Inventory notifications; molecular formula and weight; GHS classification aggregated from 2,123 ECHA C&L reports — H360 in 88.7 per cent of the reports that classify it and H360FD in 11.2 per cent, with reproductive toxicity the only hazard class in the aggregated classification; GHS classification aggregated from 2,123 ECHA C&L reports — Danger, GHS08, H360 may damage fertility or the unborn child in 88.7 per cent of the classifying reports and H360FD in 11.2 per cent, with reproductive toxicity the only hazard class present; GHS classification aggregated from 2,123 ECHA C and L reports: Danger, GHS08, H360 may damage fertility or the unborn child in 88.7 per cent of them

Used by:Boric acid · ILFORD HYPAM · Kodak F-5a · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P11 Fixer Formulations: Plain, Acid, Hardening, Rapid, Neutral, Alkaline · P11 Lab: Mixing Fixers from Scratch · Mixing a fixer

PubChem compound summary: Bromine (CID 24408)retrieved 2026-09-04

Sections: Physical description — CAMEO, Haz-Map, OSHA, the ILO-WHO safety card and NIOSH; Solubility — CAMEO, HSDB, the ILO-WHO card and NIOSH, including the hydrolysis figure; CAS; GHS classification — the harmonised CLP entry under Regulation (EC) No 1272/2008, the aggregated ECHA C&L notifications, the two NITE-CMC blocks, the HSDB block and the Australian HCIS block

Used by:Bromine

PubChem compound summary: Bromocresol Purple (CID 8273)retrieved 2026-09-05

Sections: Uses — used as a pH indicator for the pH range of 5.2 to 6.8 and 10.2 to 11.8, and as indicator pH 5.2 yellow, pH 6.8 purple; dissociation constants, pKa 6.3; Uses — a pH indicator over the range 5.2 to 6.8, yellow at 5.2 and purple at 6.8; Dissociation Constants, pKa 6.3; Uses — a sulfonphthalein dye used as a pH indicator over the range 5.2 to 6.8, yellow at 5.2 and purple at 6.8; Dissociation Constants, pKa 6.3; GHS classification aggregated from 101 ECHA C&L reports, H315 and H319 at 93.1 per cent and H335 at 92.1 per cent; Uses — used as a pH indicator for the pH range of 5.2 to 6.8, and as indicator pH 5.2 yellow, pH 6.8 purple; Dissociation Constants, pKa 6.3

Used by:P10 Overview: Stopping Development · P10 Experiment: Measuring Stop Bath Capacity · P10 Stop Bath Formulations and the Fixer Interaction · P10 Why Stopping Works

PubChem compound summary: Cadmium bromide (CID 9816930)retrieved 2026-09-04, 2026-09-06

Sections: Physical description — CAMEO and Haz-Map; Solubility — HSDB; CAS; molecular formula and weight; GHS classification — the aggregated ECHA C&L notifications and the NITE-CMC blocks; GHS classification — the ECHA C&L aggregate giving signal word Warning with GHS07 and GHS09, H302, H312, H332 and the two aquatic statements, read against the NITE-CMC blocks in the same record carrying H340 and H350; GHS classification: the ECHA C&L aggregate giving signal word Warning with GHS07 and GHS09, H302, H312, H332, H400 and H410, read against the NITE-CMC blocks in the same record carrying H340 for genetic defects and H350 for cancer; GHS classification, aggregated from the ECHA C&L Inventory, and the NITE-CMC blocks carrying H340 and H350

Used by:Cadmium bromide · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · The Level D policy

PubChem compound summary: Calcium carbonate (CID 10112)retrieved 2026-09-04

Sections: Computed properties and molecular formula; CAS registry numbers; GHS classification — the two ECHA C&L aggregations, both reporting that the substance does not meet GHS criteria; Solubility (HSDB, CAMEO, EU Food Improvement Agents); Physical description (CAMEO, ICSC, OSHA, EU Food Improvement Agents)

Used by:Calcium carbonate

PubChem compound summary: Catechol (CID 289)retrieved 2026-09-04, 2026-09-05, 2026-09-07

Sections: CAS; molecular formula and weight; IUPAC name; physical description (CAMEO, NIOSH, OSHA, ICSC, Haz-Map); solubility (CAMEO, HSDB, ICSC, NIOSH); GHS classification — the aggregated ECHA notifications; OEHHA and ChEBI descriptions; GHS classification, the aggregated ECHA notifications; solubility; physical description; GHS classification — the aggregated ECHA notifications and the proportions behind each statement; the California OEHHA statement citing IARC; GHS classification from the aggregated ECHA notifications, and the physical description and solubility

Used by:Catechol · Pyrocat-HD · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P8 Staining and Tanning Developers · P27 Assignment: The Developer Comparison, Measured and Printed

PubChem compound summary: Chlorine (CID 24526)retrieved 2026-09-04

Sections: Physical description — CAMEO, Haz-Map, OSHA, the ILO-WHO safety card and NIOSH; Solubility — CAMEO, HSDB with the hydrolysis speciation, the ILO-WHO card and NIOSH; CAS; GHS classification — the harmonised CLP entry under Regulation (EC) No 1272/2008, the aggregated ECHA C&L notifications, the two NITE-CMC blocks, the HSDB block and the Australian HCIS block; ChEBI description

Used by:Chlorine

PubChem compound summary: Chlorohydroquinone (CID 301)retrieved 2026-09-04

Sections: CAS; molecular formula and weight; IUPAC name; ChEBI description; physical description (Hawley, MSDSonline); solubility (HSDB); GHS classification — the aggregated ECHA C&L notifications

Used by:Chlorohydroquinone

PubChem compound summary: Chromic potassium sulfate dodecahydrate (CID 24596)retrieved 2026-09-04

Sections: CAS; computed molecular formula and weight; IUPAC name; physical description (Haz-Map, citing CHEMINFO and Alfa Aesar). The record carries no GHS Classification section; Physical description; CAS; GHS classification; CAS, computed formula and molecular weight, physical description; the record carries no GHS classification section

Used by:Chrome alum · Dry plate and lantern slide · The chromium policy

PubChem compound summary: Citric Acid (CID 311)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: GHS classification from the aggregated ECHA notifications for EC 201-069-1 and the Safe Work Australia HCIS entry for CAS 77-92-9: Warning, GHS07, with H315, H319 and H335; Physical description; solubility; CAS; GHS classification; ChEBI description; GHS classification aggregated from 4373 ECHA C&L reports across 57 notifications, H319 at 84.7 per cent and H335 at 23 per cent, with 359 of 4373 reports stating that the substance meets no GHS hazard criterion; solubility in water 59.2 per cent w/w at 20 degrees C; GHS classification aggregated from 4373 ECHA C&L reports across 57 notifications, H319 at 84.7 per cent and H335 at 23 per cent, with 359 of 4373 reports stating that the substance meets no GHS hazard criterion; GHS classification aggregated from ECHA C&L notifications — H319 causes serious eye irritation in 84.7 per cent of 4,373 company reports and H335 may cause respiratory irritation in 23 per cent, signal word Warning, with 8.2 per cent of reports recording that the substance does not meet GHS hazard criteria; the harmonised entry under Regulation (EC) No 1272/2008 giving the same two statements; and the ChEBI description naming citrate a chelator; GHS classification — the aggregated ECHA C&L notifications, H319, H335 and H315; GHS classification; physical description; the monohydrate and its efflorescence in dry air; Molecular weight and CAS; solubility; the aggregated ECHA notifications behind the hazard block; GHS classification aggregated from 4373 ECHA C&L reports — H319 causes serious eye irritation at 84.7 per cent and H335 may cause respiratory irritation at 23 per cent, with 359 of 4373 reports stating that the substance meets no GHS hazard criterion; Experimental properties — solubility 59.2 per cent w/w at 20 degrees C; GHS classification aggregated from 4373 ECHA C&L reports, H319 at 84.7 per cent and H335 at 23 per cent, with 359 of 4373 reports stating that it meets no GHS hazard criterion; Experimental properties — solubility in water 59.2 per cent w/w at 20 degrees C; GHS classification aggregated from 4373 ECHA C&L reports across 57 notifications, H319 at 84.7 per cent and H335 at 23 per cent, with 359 of 4373 reports stating that the substance meets no GHS hazard criterion; GHS classification aggregated from 4,373 reports across 57 ECHA notifications — signal word Warning, pictogram GHS07, with H319 at 84.7 per cent of reports and H335 at 23 per cent, and 359 of 4,373 reports stating that it does not meet GHS hazard criteria; GHS classification aggregated from the ECHA C&L Inventory; Physical description; GHS classification

Used by:P29 Planning the Capstone: The Project Plan and Its Hazard Assessment · Citric acid (anhydrous) · Citric Acid Stop Bath · ILFORD ILFOSTOP · EDTA, citric acid and hydrochloric acid clearing sequence · Arrowroot salting solution · The Simple Cyanotype (2019) · Sodium citrate developer · P10 Overview: Stopping Development · P10 Experiment: Measuring Stop Bath Capacity · P10 Stop Bath Formulations and the Fixer Interaction · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P25 Lab: Exposing, Developing and Clearing a Palladium Print · Arrowroot and albumenised salted paper

PubChem compound summary: Copper sulfate (anhydrous) (CID 24462)retrieved 2026-09-04

Sections: Computed properties and molecular formula; CAS; GHS classification — the entry under Regulation (EC) No 1272/2008, the aggregated ECHA C&L notifications, NITE-CMC and HCIS; Solubility (HSDB, ILO-WHO ICSC, Haz-Map); Physical description (CAMEO, ICSC, Haz-Map)

Used by:Copper(II) sulfate

PubChem compound summary: Copper sulfate pentahydrate (CID 24463)retrieved 2026-09-04, 2026-09-06

Sections: Computed properties; CAS; the entry under Regulation (EC) No 1272/2008 for the pentahydrate; Solubility (ILO-WHO ICSC, HSDB); Physical description (CAMEO); GHS classification and identity — the harmonised entry giving Danger and H318, causes serious eye damage, alongside H302, H315 and H410, very toxic to aquatic life with long lasting effects, as summarised with its sources on the course's copper sulfate page

Used by:Copper(II) sulfate · P20 Gold, Iron-Blue and the Other Metal Toners

PubChem compound summary: Diammonium Citrate (CID 18171)retrieved 2026-09-04, 2026-09-06

Sections: Identity, computed properties and CAS; GHS classification aggregated from the ECHA C&L Inventory; solubility from HSDB; physical description from CAMEO and Haz-Map; the ChEBI description; Identity, CAS and computed properties; the GHS classification aggregated from the ECHA C&L Inventory across 390 reports in 12 notifications; solubility from HSDB, soluble in about one part of water

Used by:Ammonium citrate (dibasic) · Ammonium citrate developer

PubChem compound summary: Diethyl Ether (CID 3283)retrieved 2026-09-04, 2026-09-06

Sections: Physical description — CAMEO, Haz-Map, OSHA, the ILO-WHO safety card and NIOSH; Solubility — CAMEO, HSDB, the ILO-WHO card and NIOSH; CAS; GHS classification — the harmonised CLP entry under Regulation (EC) No 1272/2008, the aggregated ECHA C&L notifications, the two NITE-CMC blocks and the Australian HCIS block; ChEBI description; Physical description, for CAMEO's statement that the liquid is less dense than water and that its vapours are heavier than air; GHS classification, for the harmonised CLP entry under Regulation (EC) No 1272/2008 giving signal word Danger with H224, H302 and H336; and the ChEBI description recording its use as an inhalation anaesthetic; Physical description; boiling point; GHS classification

Used by:Diethyl ether · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · Wet-plate collodion negative

PubChem compound summary: Diethylenetriaminepentaacetic acid (CID 3053)retrieved 2026-09-06

Sections: Names and identifiers — the record title Diethylenetriaminepentaacetic acid for CAS 67-43-6, CID 3053, with the synonyms pentetic acid and DTPA, the molecular formula C14H23N3O10, the molecular weight 393.35 and the IUPAC name 2-[bis[2-[bis(carboxymethyl)amino]ethyl]amino]acetic acid; GHS classification aggregated from 530 reports across 37 notifications to the ECHA C&L Inventory, signal word Danger, with H319 in 98.7 per cent of reports, H332 in 71.7, H373 in 51.5, H360D in 46.2 and H361 in 34.3, and 7 of 530 reports finding that the substance meets no GHS hazard criterion

Used by:ILFORD WASHAID

PubChem compound summary: Dipotassium Oxalate (CID 11413)retrieved 2026-09-04

Sections: Computed properties and molecular formula; physical description; CAS; GHS classification

Used by:Potassium oxalate, anhydrous

PubChem compound summary: Dipotassium tetrachloroplatinate (CID 61440)retrieved 2026-09-04, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Computed properties and molecular formula; CAS; GHS classification — the aggregated ECHA C&L notifications; Physical description — Haz-Map (Merck Index; Sigma-Aldrich); GHS classification; molecular weight; GHS Classification, aggregated from the ECHA C&L Inventory under Dipotassium tetrachloroplatinate, EC 233-050-9; GHS classification aggregated from the ECHA C&L Inventory; Molecular weight; GHS classification; GHS classification, aggregated from the ECHA C&L Inventory; GHS classification, aggregated from the ECHA C&L Inventory under Dipotassium tetrachloroplatinate, EC 233-050-9; GHS aggregation: H334, may cause allergy or asthma symptoms or breathing difficulties if inhaled

Used by:Potassium tetrachloroplatinate(II) · Three-solution drop system for platinum and palladium · Ware's print-out platino-palladiotype · P25 Part XXV Overview: Platinum and Palladium · P25 Cost, Permanence and When a Platinum Print Earns Its Price · P25 Noble Metal Chemistry and the Platinotype · P25 Lab: Preparing the Sensitiser and Coating for Palladium · Matte albumen print · Platinotype · The Level D policy · Running a platinum or palladium session

PubChem compound summary: Disodium tetrachloropalladate (CID 11000870)retrieved 2026-09-04, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Computed properties and molecular formula; CAS; ChEBI description; GHS classification — the aggregated ECHA C&L notifications; GHS classification; molecular weight; GHS classification aggregated from the ECHA C&L Inventory; molecular weight; Molecular weight; GHS classification; GHS classification aggregated from the ECHA C&L Inventory; Physical description; CAS; GHS classification; GHS aggregation: signal word Danger with H317 and H318 in about three-quarters of reports, and the aquatic statements H400 and H410

Used by:Sodium tetrachloropalladate(II) · Three-solution drop system for platinum and palladium · P25 Part XXV Overview: Platinum and Palladium · P25 Cost, Permanence and When a Platinum Print Earns Its Price · P25 Noble Metal Chemistry and the Platinotype · P25 Lab: Preparing the Sensitiser and Coating for Palladium · Palladiotype · Running a platinum or palladium session

PubChem compound summary: Edetate Disodium (CID 636371)retrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: Computed properties and molecular formula; CAS registry number; Physical description (Haz-Map, quoting JECFA and a Mallinckrodt Baker sheet); the absence of any GHS classification block; Computed properties and CAS, for comparison with the anhydrous salt; the ECHA C&L aggregation for the dihydrate; Physical description; CAS; GHS classification; Uses (HSDB, Merck Index via Haz-Map, JECFA functional classes); CAS registry numbers and computed properties for the dihydrate; the ECHA C&L aggregation, in which all six reporting companies record the substance as not meeting GHS hazard criteria; GHS classification for ethylenediaminetetraacetic acid disodium salt dihydrate, EC 680-249-5 — reported as not meeting GHS hazard criteria in all 6 reports from 2 ECHA notifications; GHS classification aggregated from the ECHA C&L Inventory

Used by:EDTA disodium salt (anhydrous) · EDTA disodium salt (anhydrous) · EDTA disodium salt dihydrate · EDTA and sodium sulfite clearing sequence · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P25 Lab: Exposing, Developing and Clearing a Palladium Print

PubChem compound summary: Erythrosine (CID 3259)retrieved 2026-09-04, 2026-09-05

Sections: CAS registry numbers; molecular formula and weight; IUPAC name; physical description (EU Food Improvement Agents, EPA CDR, HMDB); solubility (HMDB); GHS classification — the aggregated ECHA C&L notifications for EC 240-046-0; Identity, the two CAS registry numbers, molecular formula and weight, solubility, and the GHS Classification section aggregating the ECHA C&L notifications for EC 240-046-0; GHS Classification, ECHA C&L Inventory EC 240-046-0: reported as not meeting GHS hazard criteria by 37 of 39 companies, with PubChem's own note that only 5.1 per cent of companies provided GHS information; Names and Identifiers for the two CAS registry numbers 15905-32-5 for the free acid and 16423-68-0 for the disodium salt; GHS Classification: the ECHA C&L result under EC 240-046-0 and PubChem's caveat on the proportion of companies providing information; the two CAS numbers; GHS classification, and the notifications reporting that the substance does not meet GHS criteria

Used by:Erythrosin · Erythrosin sensitising stock · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P5 Washing, Digestion and Sensitisation · Reading GHS and CLP

PubChem compound summary: Ethanol (CID 702)retrieved 2026-09-04

Sections: Physical description; solubility; CAS; GHS classification; ChEBI description

Used by:Ethanol

PubChem compound summary: Ethyl 2-cyanoacrylate (CID 8419)retrieved 2026-09-04, 2026-09-05

Sections: GHS classification, ECHA C&L aggregation: H302 harmful if swallowed, reported in 100 per cent of notifications, and H315 causes skin irritation, both with the signal word Warning; GHS classification aggregated from ECHA notifications - H302 harmful if swallowed and H315 causes skin irritation, signal word Warning

Used by:P6 Build the Modular Pinhole Camera · P14 Build: The Enclosure and Exposure Stage

PubChem compound summary: Ferric Ammonium Citrate (CID 118984355)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Physical description; CAS; GHS classification; GHS classification; physical description; CAS; GHS classification aggregated from 1,576 reports across 11 ECHA notifications for ferric ammonium citrate, EC 214-686-6, of which 89.8 per cent of the reports carrying hazard codes give H315 and H319 and 10.2 per cent of all reports state that the substance does not meet GHS hazard criteria; GHS classification — the aggregated ECHA C&L notifications under EC 214-686-6, 1,576 reports across 11 notifications, and the 161 reports declining to classify; GHS classification aggregated from 1,576 reports across 11 ECHA notifications — signal word Warning, pictogram GHS07, H315 and H319 each at 89.8 per cent of the reports carrying hazard codes, with 161 of 1,576 reports stating that the substance does not meet GHS hazard criteria

Used by:Ammonium iron(III) citrate · Van Dyke Brown sensitiser · P1 Assignment 1: A Botanical Cyanotype Photogram, After Atkins · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Iron, Light and Prussian Blue · P24 Lab: Printing a Van Dyke Brown · Van Dyke Brown

PubChem compound summary: Ferric ammonium oxalate (CID 26580)retrieved 2026-09-04, 2026-09-06

Sections: Computed properties and molecular formula; physical description; CAS; GHS classification; GHS Classification, aggregated from the ECHA C&L Inventory; physical description; GHS classification — signal word Warning with H302 and H312, harmful if swallowed and in contact with skin; Physical description; CAS; GHS classification

Used by:Ammonium iron(III) oxalate · Ware's print-out platino-palladiotype · P21 The New Cyanotype and the Other Ways to Make a Blue Print · Cyanotype (New Cyanotype) · Print-out platino-palladiotype

PubChem compound summary: Ferric chloride hexahydrate (CID 6093258)retrieved 2026-09-04

Sections: Physical description; CAS; GHS classification

Used by:Iron(III) chloride hexahydrate

PubChem compound summary: Ferric ferrocyanide (Prussian blue) (CID 2724251)retrieved 2026-09-04, 2026-09-06

Sections: Computed properties and molecular formula; CAS; GHS classification — the ECHA C&L aggregation under EC 237-875-5; Solubility (HSDB, DrugBank); Physical description (Haz-Map, quoting the Merck Index and MSDSonline); Compound summary — the identity of Prussian blue as ferric ferrocyanide, as summarised with its sources on the course's Prussian blue page; GHS classification — the ECHA C&L aggregation under EC 237-875-5 and its majority of reports declining to classify; Solubility, the HSDB and DrugBank figure of 6 mg/mL at 25 degrees C

Used by:Prussian blue · P20 Gold, Iron-Blue and the Other Metal Toners · P21 Iron, Light and Prussian Blue

PubChem compound summary: Ferric nitrate (CID 25251)retrieved 2026-09-05

Sections: Experimental Properties — Solubility, Melting Point and Physical Description, for the Merck Index entry on the nonahydrate and the CRC Handbook entry on the hexahydrate; GHS Classification, for the anhydrous parent's own aggregation; Hazards Summary, for Hawley

Used by:Iron(III) nitrate nonahydrate

PubChem compound summary: Ferrous oxalate (CID 10589)retrieved 2026-09-04, 2026-09-06

Sections: Computed properties and molecular formula; CAS registry numbers; GHS classification — the two ECHA C&L aggregations and the NITE-CMC entry; Physical description (CAMEO, Haz-Map quoting the Merck Index); Computed properties — molecular formula and molecular weight of the anhydrous salt

Used by:Iron(II) oxalate · Willis's potassium oxalate developer

PubChem compound summary: Ferrous Sulfate (CID 24393)retrieved 2026-09-04

Sections: ChEBI description; physical description; solubility; CAS; GHS classification; ChEBI description — hydrate relations and dehydration temperatures

Used by:Iron(II) sulfate, anhydrous · Iron(II) sulfate heptahydrate

PubChem compound summary: Ferrous sulfate heptahydrate (CID 62662)retrieved 2026-09-04

Sections: ChEBI description; physical description; CAS; GHS classification; Physical description; CAS; GHS classification

Used by:Iron(II) sulfate heptahydrate · Tintype (ferrotype)

PubChem compound summary: Formaldehyde (CID 712)retrieved 2026-09-04

Sections: CAS; computed molecular formula and weight; IUPAC name; physical description (NIOSH, OSHA, ICSC, CAMEO, Haz-Map); solubility (NIOSH, CAMEO, HSDB, ICSC, HMDB); GHS classification — the aggregated ECHA notifications; the California Office of Environmental Health Hazard Assessment and ChEBI descriptions; GHS Classification, ECHA C&L Inventory EC 200-001-8 and the harmonised classification; GHS classification, aggregated from 6,451 reports across 102 ECHA C&L notifications

Used by:Formaldehyde · P5 Gelatin, the Photographic Binder · Reading GHS and CLP

PubChem compound summary: Gallic acid (CID 370)retrieved 2026-09-04, 2026-09-06

Sections: CAS; molecular formula and weight; IUPAC name; ChEBI description; physical description (USCG, Hawley, ILO-WHO ICSC, MSDSonline); solubility (HSDB, HMDB, ILO-WHO ICSC, CAMEO); GHS classification — the aggregated ECHA C&L notifications; GHS classification, aggregated from the ECHA C&L Inventory; solubility; physical description; GHS classification - the aggregated ECHA C&L notifications, H315, H318, H319 and H335 with their reporting percentages

Used by:Gallic acid · Talbot's gallo-nitrate of silver · P21 Lab: Toning the Prussian Blue Image

PubChem compound summary: Glutaraldehyde (CID 3485)retrieved 2026-09-04

Sections: CAS; computed molecular formula and weight; IUPAC name; physical description (NIOSH, OSHA, ICSC, CAMEO, Haz-Map); solubility (NIOSH, CAMEO, HSDB, ICSC); GHS classification — the aggregated ECHA notifications; ChEBI description; GHS Classification: H334 respiratory sensitisation and H317 skin sensitisation in more than 99.9 per cent of reports; GHS Classification, ECHA C&L Inventory EC 203-856-5

Used by:Glutaraldehyde · P5 Coating, Drying and Hardening · P5 Gelatin, the Photographic Binder

PubChem compound summary: Glycerol (CID 753)retrieved 2026-09-06

Sections: Computed Properties, for the molecular formula, molecular weight, hydrogen-bond donor and acceptor counts, topological polar surface area and XLogP3; Physical Description, Color/Form, Odor and Taste; Solubility; Density; Melting Point; Boiling Point; Vapor Pressure; Flash Point; Autoignition Temperature; Viscosity; pH; Dissociation Constants; LogP; Stability/Shelf Life; Decomposition; Other Experimental Properties, for the freezing points of aqueous solutions; Uses; Reactivity Profile; Air and Water Reactions; Explosive Limits and Potential; Skin, Eye and Respiratory Irritations; GHS Classification and Hazard Classes and Categories, aggregated from 5,617 reports across 16 notifications to the ECHA C&L Inventory; GHS Classification — the aggregated ECHA C and L entry, Not Classified

Used by:Glycerol · Ware's argyrotype

PubChem compound summary: Glyoxal (CID 7860)retrieved 2026-09-04

Sections: CAS; molecular formula and weight; IUPAC name; ChEBI description; physical description (CAMEO, OSHA, Haz-Map, ILO-WHO ICSC); solubility (HSDB, CAMEO); GHS classification — the harmonised entry under Regulation (EC) No 1272/2008, the aggregated ECHA C&L notifications, the NITE-CMC entries and Safe Work Australia's HCIS; The harmonised classification under Regulation (EC) No 1272/2008: H315, H317, H319, H332 and H341; GHS Classification: the harmonised classification under Regulation (EC) No 1272/2008, and the notified data under EC 203-474-9

Used by:Glyoxal · P5 Coating, Drying and Hardening · P5 Gelatin, the Photographic Binder

PubChem compound summary: Gold trichloride (CID 26030)retrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: Computed properties and molecular formula; CAS; ChEBI description; GHS classification — the aggregated ECHA C&L notifications and the NITE-CMC entry; Physical description — Haz-Map (Hawley and MSDSonline); Physical description; GHS classification; GHS classification and physical description — the aggregated ECHA C&L notifications and the NITE-CMC entry, and the compilation's description of the substance as a yellow to red solid soluble in water, as summarised with its sources on the course's gold(III) chloride page; Identity as gold trichloride, CID 26030, molecular formula AuCl3, molecular weight 303.32, CAS 13453-07-1, with the ECHA C&L aggregation giving GHS05 and GHS07 under the signal word Danger with H314 in 11.8 per cent of reports and H315 in 88.2 per cent; GHS classification aggregated from 51 reports across 7 ECHA notifications for gold trichloride, EC 236-623-1 — signal word Danger, pictograms GHS05 and GHS07, with H315, H319 and H335 each at 88.2 per cent of reports and H314 at 11.8

Used by:Gold(III) chloride · P1 Daguerre and the Daguerreotype: A Mirror With a Memory · P20 Gold, Iron-Blue and the Other Metal Toners · P22 Gold Toning and the Permanence of a Printed-Out Silver Image · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last

PubChem compound summary: Hexasodium hexametaphosphate (CID 24968)retrieved 2026-09-04

Sections: Physical description; solubility; CAS; GHS classification; Uses (HSDB, Kirk-Othmer, Hawley's Condensed Chemical Dictionary, JECFA functional classes, EU Cosmetics Inventory)

Used by:Sodium hexametaphosphate (Calgon)

PubChem compound summary: Hydrochloric Acid (CID 313)retrieved 2026-09-04, 2026-09-06

Sections: Physical description; solubility; CAS; GHS classification; GHS classification aggregated from ECHA C&L notifications — H314 causes severe skin burns and eye damage in 99.9 per cent of the 5,109 company reports carrying hazard codes, H335 in 59 per cent, H331 toxic if inhaled in 49.4 per cent, H290 may be corrosive to metals in 22.8 per cent and H318 in 20 per cent, signal word Danger, with one report in 5,109 recording no GHS hazard; and the physical description and solubility; Computed properties - molecular weight; GHS classification for hydrogen chloride, EC 231-595-7, aggregated from 5,109 reports across 116 notifications to the ECHA C&L Inventory - H314 in 99.9 per cent of the reports that carry hazard codes, H335 in 59 per cent and H331 in 49.4 per cent, as summarised with its sources on the course's hydrochloric acid page

Used by:Hydrochloric acid · EDTA, citric acid and hydrochloric acid clearing sequence · P3 Acids, Bases and pH · P26 Assignment: Assessing a Historical Process for Hazard

PubChem compound summary: Hydrogen peroxide (CID 784)retrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: Computed properties and molecular formula; CAS; GHS classification — the concentration-banded entry under Regulation (EC) No 1272/2008, the aggregated ECHA C&L notifications, NITE-CMC, HCIS and HSDB; Solubility (CAMEO, HSDB); Physical description (CAMEO's concentration-banded datasheets, Haz-Map quoting NIOSH); GHS classification and the concentration-dependent entries, read to establish that the hazard statements carried by the reagent belong to concentrated solutions and that the 3 per cent pharmacy product diluted further is a different material from the one the pictograms describe; GHS classification and the concentration-dependent entries, read to establish what the pictograms belong to and that a 3 per cent pharmacy product is a different material from the concentrate; GHS classification aggregated from the ECHA C&L Inventory

Used by:Hydrogen peroxide · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P24 Contrast Control in Iron-Based Printing · P25 Experiment: Tonal Scale, Contrast and Image Colour in Palladium

PubChem compound summary: Hydroquinone (CID 785)retrieved 2026-09-04, 2026-09-05, 2026-09-08

Sections: GHS classification aggregated from 2,485 reports across 36 ECHA C&L notifications: Danger, GHS05, GHS07, GHS08 and GHS09, with H302, H317, H318, H341, H351 and H400; GHS classification aggregated from 2,485 reports across 36 ECHA C&L notifications: Danger, GHS05, GHS07, GHS08 and GHS09, with H302, H317, H318, H341, H351 and H400 near-unanimous, and H312 and H410 as minority views; CAS; molecular formula and weight; physical description (CAMEO, NIOSH, OSHA, ICSC); solubility (HSDB temperature series, ICSC, NIOSH); GHS classification — the aggregated ECHA notifications; ChEBI description; GHS classification (harmonised entry and ECHA notifications); CAS; computed properties; GHS classification; Computed properties - molecular formula and molecular weight; GHS classification; GHS classification: skin sensitisation, serious eye damage, and the aquatic hazard statements; GHS classification — the harmonised CLP entry and the aggregated ECHA notifications; GHS classification — the harmonised CLP entry and the aggregated ECHA notifications; solubility; Molecular formula and weight; solubility; GHS classification — the harmonised CLP entry and the aggregated ECHA notifications; Solubility; GHS classification — the harmonised CLP entry and the aggregated ECHA notifications; Molecular formula and weight, 110.11; GHS classification — the harmonised CLP entry and the aggregated ECHA notifications; GHS Classification - the harmonised CLP entry with signal word Danger and the GHS05, GHS07, GHS08 and GHS09 pictograms, carrying H302, H312, H317, H318, H341, H351 and H410; GHS aggregation: signal word Danger with H302, H317, H318, H341, H351 and H400

Used by:P29 Capstone Stage 2: Formulating and Documenting Your Chemistry · P29 Planning the Capstone: The Project Plan and Its Hazard Assessment · Hydroquinone · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P3 Oxidation, Reduction and the Electron That Makes the Picture · P4 Darkroom Session: The Latent Image Made Visible · P8 Overview: What a Developer Is · P8 Experiment: Watching a Developer Oxidise · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P9 Experiment: Comparing Developing Agents · P18 Lab: Mixing and Comparing Print Developers · Weighing and handling developing agents

PubChem compound summary: Iodine (CID 807)retrieved 2026-09-04, 2026-09-06

Sections: Physical description — CAMEO, Haz-Map, OSHA, the ILO-WHO safety card and NIOSH; Solubility — CAMEO, HSDB, HMDB, the ILO-WHO card and NIOSH; CAS; GHS classification — the harmonised CLP entry under Regulation (EC) No 1272/2008, the aggregated ECHA C&L notifications, the two NITE-CMC blocks and the Australian HCIS block; The harmonised classification, with H312, H332 and H400, set against the aggregated ECHA notifications and the Japanese NITE-CMC block that gives H330; and the physical description, for the vapour pressure of the solid at room temperature

Used by:Iodine · Daguerre's 1839 process outline

PubChem compound summary: Iron chloride (FeCl3) (CID 24380)retrieved 2026-09-04

Sections: Physical description; solubility; CAS; GHS classification; ChEBI description; Solubility; physical description; reactivity; Physical description; solubility; GHS classification

Used by:Iron(III) chloride, anhydrous · Iron(III) chloride hexahydrate · Photogravure

PubChem compound summary: Iron(III) nitrate nonahydrate (CID 16211566)retrieved 2026-09-05

Sections: Names and Identifiers, for the CAS and EC numbers, molecular formula and IUPAC name; Molecular Weight; Experimental Properties, for the physical description, melting point and density; GHS Classification and Hazard Classes and Categories, aggregated from the ECHA C&L Inventory across 97 reports and 13 notifications; Hazards Summary; Threshold Limit Values; Toxicological Information, Adverse Effects; Names and Identifiers, for the CAS number, EC number, molecular formula and IUPAC name; Molecular Weight; Experimental Properties, for the physical description, melting point and density; GHS Classification and Hazard Classes and Categories, aggregated from 97 reports across 13 notifications to the ECHA C&L Inventory; Hazards Summary; Names and Identifiers, for the CAS number, EC number, molecular formula and IUPAC name; Molecular Weight; Experimental Properties, for the physical description, melting point and density; GHS Classification, aggregated from the ECHA C&L Inventory across 97 reports and 13 notifications; Hazard Classes and Categories; Hazards Summary; Threshold Limit Values

Used by:Iron(III) nitrate nonahydrate · Mike's Cyanotype · The Simple Cyanotype (2019)

PubChem compound summary: Isopropanol (CID 3776)retrieved 2026-09-04, 2026-09-05, 2026-09-07, 2026-09-08

Sections: Physical description; solubility; CAS; GHS classification; ChEBI description; GHS classification — signal word, pictograms and hazard statements; solubility; GHS classification — signal word Danger, H225, H319 and H336; Physical description; GHS classification; GHS aggregation: signal word Danger with H225, H319 and H336

Used by:Isopropyl alcohol · Double-coated albumen procedure · P23 Lab: Preparing and Coating Albumen Paper · Albumen print · Preparing and coating albumen paper

PubChem compound summary: L-Ascorbic Acid (CID 54670067)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: CAS; molecular formula and weight; IUPAC name; physical description (CAMEO, EU Food Improvement Agents, ICSC, Haz-Map); solubility (HSDB, ICSC, DrugBank, HMDB); ChEBI description; GHS classification — the aggregated ECHA notifications and the "not classified" majority; Solubility; physical description; GHS classification — cited here for the comparison with the free acid; GHS classification — the aggregated ECHA notifications and the "not classified" majority; solubility; CAS and molecular formula; ChEBI description; GHS classification - the aggregated ECHA notifications and the "not classified" majority; ChEBI description: L-ascorbic acid has a role as a food antioxidant; GHS classification — the aggregated ECHA notifications, of which 97.3 per cent report that the substance does not meet GHS criteria

Used by:Ascorbic acid · Sodium ascorbate · 510-Pyro · KODAK PROFESSIONAL XTOL Developer · P3 Aerial Oxidation: Why Chemistry Dies in a Half-Empty Bottle · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol

PubChem compound summary: L-Tartaric acid (CID 444305)retrieved 2026-09-04, 2026-09-05, 2026-09-07

Sections: Physical description; solubility; CAS; GHS classification; ChEBI description; GHS classification; molecular weight; GHS classification aggregated from 4,731 reports across 33 ECHA notifications for (+)-tartaric acid, EC 201-766-0 — signal word Danger, pictograms GHS05 and GHS07, with H319 at 57.8 per cent of reports, H335 at 55.4, H315 at 54.3, H302 at 42.5, H317 at 42.5 and H318 at 41.2, and 44 of 4,731 reports stating that it does not meet GHS hazard criteria; Physical description; GHS classification

Used by:Tartaric acid · Van Dyke Brown sensitiser · P24 Lab: Printing a Van Dyke Brown · Van Dyke Brown

PubChem compound summary: Lead nitrate (CID 24924)retrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: Physical description — CAMEO, Haz-Map and the ILO-WHO safety card; Solubility — HSDB and the ILO-WHO card; CAS; GHS classification — the aggregated ECHA C&L notifications and the NITE-CMC blocks; GHS classification, for the aggregated ECHA C&L entry with signal word Danger and hazard statements H272, H302, H317, H318, H332, H351, H360Df, H372 and H410, and for the spread of agreement between notifiers; Solubility, for 56.5 g per 100 cm3 in water at 20 C; CAS and computed properties; GHS classification aggregated from the ECHA C&L Inventory; GHS classification — signal word Danger with H272, H302, H317, H318, H332, H351, H360Df, H372 and H410, aggregated from 318 reports across 21 notifications with unusually weak agreement, as summarised with its sources on the course's lead nitrate page; Physical description; GHS classification for lead compounds

Used by:Lead(II) nitrate · Lead additions to platinum sensitisers · P25 The Additives We Study and Do Not Reproduce · P26 Uranium, Mercury and the Heavy-Metal Treatments · Woodburytype

PubChem compound summary: Lead(II) acetate (CID 9317)retrieved 2026-09-06

Sections: Names and Identifiers — Molecular Formula, Computed Descriptors, CAS, Related CAS, European Community (EC) Number, UN Number and ICSC Number; Chemical and Physical Properties — Experimental Properties (Physical Description, Color/Form, Odor, Melting Point, Solubility, Density, pH, Other Experimental Properties) from HSDB 1404 and the ILO-WHO safety card; Safety and Hazards — GHS Classification, all four aggregated blocks, and Hazard Classes and Categories; Safety and Hazard Properties — Physical Dangers, Chemical Dangers, NIOSH Recommendations; Exposure Control — Permissible Exposure Limit, Threshold Limit Values, Immediately Dangerous to Life or Health; Stability and Reactivity — Hazardous Reactivities and Incompatibilities; Handling and Storage — Safe Storage and Storage Conditions; Hazards Identification — EPA Hazardous Waste Number; Toxicology — Toxicity Summary, Evidence for Carcinogenicity, Signs and Symptoms; Use and Manufacturing — Uses, Methods of Manufacturing and General Manufacturing Information; GHS classification, the harmonised block for lead di(acetate) under Regulation (EC) No 1272/2008 and the notified aggregate over it; physical description, including the sweet taste and the efflorescence and carbon-dioxide uptake of the trihydrate on standing; density of the anhydrous salt and of the trihydrate; solubility, including the trihydrate's 1 g in 1.6 mL of cold water; the incompatibility list, including bromates, carbonates, phosphates, sulfates, chlorides, citrates, tartrates and tannin, and the explosive lead acetate-lead bromate double salt; the dust-explosion note; and the NIOSH and ACGIH exposure limits with their tie to a blood lead concentration, all as summarised on the course's lead(II) acetate page

Used by:Lead(II) acetate · Lead, thallium and nickel cyanotype toners

PubChem compound summary: Lithium chloride (CID 433294)retrieved 2026-09-04

Sections: Computed properties and molecular formula; CAS; GHS classification — the two ECHA C&L aggregations, the NITE-CMC revisions of FY2010, FY2022 and FY2025, and HCIS; Solubility (HSDB, CAMEO, ILO-WHO ICSC); Physical description (CAMEO, ICSC, Haz-Map); Physical description; CAS; GHS classification

Used by:Lithium chloride · Collodion print-out paper · Print-out platino-palladiotype

PubChem compound summary: Mercuric Chloride (CID 24085)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Physical description — CAMEO, Haz-Map and the ILO-WHO safety card; Solubility — CAMEO, HSDB and the ILO-WHO card; CAS; GHS classification — the aggregated ECHA C&L notifications and the harmonised CLP entry; ChEBI description; GHS classification, aggregated from the ECHA C&L Inventory, as summarised on the course's mercury(II) chloride page; Computed properties, for the molecular formula and the molecular weight of 271.50; CAS; ChEBI description, which names photographic intensification among its former uses; GHS classification, for the harmonised entry under Regulation (EC) No 1272/2008 with signal word Danger, pictograms GHS05, GHS06, GHS08 and GHS09, and hazard statements H300, H314, H341, H361f, H372, H400 and H410; Solubility, for 6.9 g per 100 cm3 in water at 20 C and 33 g per 100 cm3 in alcohol at 25 C; GHS classification, aggregated from the ECHA C&L Inventory; GHS classification, aggregated from the ECHA C&L Inventory - signal word Danger with H300, fatal if swallowed, and H310, fatal in contact with skin, both in 100 per cent of 218 reports, alongside H314, H372 and H410, as summarised with its sources on the course's mercury(II) chloride page; GHS classification aggregated from the ECHA C&L Inventory; GHS classification, aggregated from the ECHA C&L Inventory - signal word Danger with H300 in 100 per cent of 218 reports and H310, fatal in contact with skin, in 26.6 per cent, alongside H314, H317, H318, H341, H361, H372 and H410, as summarised with its sources on the course's mercury(II) chloride page; GHS classification aggregated from the ECHA C&L Inventory — signal word Danger with H300, fatal if swallowed, and H310, fatal in contact with skin, alongside H314, H341, H361, H372 and H410, as summarised with its sources and its notification counts on the course's mercury(II) chloride page

Used by:Mercury(II) chloride · Kodak IN-1 · Mercuric sepia platinotype · Willis's potassium oxalate developer · P20 The Toners We Study and Do Not Use · P25 The Additives We Study and Do Not Reproduce · P26 Assignment: Assessing a Historical Process for Hazard · P26 Uranium, Mercury and the Heavy-Metal Treatments · The Level D policy

PubChem compound summary: Mercurous nitrate (CID 25247)retrieved 2026-09-06

Sections: Identity, CAS numbers and molecular formula; GHS classification aggregated from 27 reports across 5 notifications to the ECHA C&L Inventory; the fire-hazard block on accelerated burning and on smoke containing mercury vapour and oxides of nitrogen; the reactivity profile from Bretherick on nitrates with reducing agents

Used by:Herschel's hydrargyro-cyanotype

PubChem compound summary: Mercury (CID 23931)retrieved 2026-09-04, 2026-09-06

Sections: Solubility — CAMEO, HSDB, the ILO-WHO safety card and NIOSH; CAS; GHS classification — the harmonised CLP entry under Regulation (EC) No 1272/2008, the aggregated ECHA C&L notifications, the two Japanese NITE-CMC blocks and the Australian HCIS block; ChEBI and OEHHA descriptions; The harmonised classification under Regulation (EC) No 1272/2008, with H330, H360D, H372, H400 and H410; and the physical description, for the vapour pressure of a liquid metal at ordinary room temperature; The harmonised classification under Regulation (EC) No 1272/2008, with H330, H360D, H372, H400 and H410, and the physical description for a liquid metal with a vapour pressure at ordinary room temperature; Chemical and physical properties, Vapor Pressure: the NIOSH value of 0.0012 mmHg, the Merck Index value of 2 x 10^-3 mmHg at 25 C, and the ILO-WHO International Chemical Safety Card value of 0.26 Pa at 20 C; and the harmonised classification under Regulation (EC) No 1272/2008, signal word Danger with H330, H360D, H372, H400 and H410, as summarised with its sources on the course's mercury page

Used by:Mercury · Daguerre's 1839 process outline · Fizeau's gilding solution · P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory

PubChem compound summary: Metol (CID 5930)retrieved 2026-09-04, 2026-09-05, 2026-09-08

Sections: GHS classification — the harmonised CLP entry and the aggregated ECHA C&L notifications: Warning, GHS07, GHS08 and GHS09, with H302, H317, H373, H400 and H410; GHS classification — the harmonised CLP entry and the aggregated ECHA C&L notifications: Warning, GHS07, GHS08 and GHS09, with H302, H317, H373, H400 and H410, and H319 as a minority view among suppliers; CAS; molecular formula and weight; physical description (CAMEO, ILO-WHO ICSC, Haz-Map); solubility (CAMEO, ICSC); GHS classification — the harmonised CLP entry, the aggregated ECHA notifications and Safe Work Australia's HCIS; GHS classification and the skin-sensitisation statement, as summarised on the course's metol page; GHS classification (harmonised entry under Regulation (EC) No 1272/2008 and ECHA notifications); CAS; computed properties; GHS classification (harmonised entry and ECHA notifications); GHS classification — the harmonised CLP entry and the aggregated ECHA notifications; GHS classification — the harmonised CLP entry and the aggregated ECHA notifications; solubility; Molecular formula and weight; solubility; GHS classification — the harmonised CLP entry and the aggregated ECHA notifications; Solubility; GHS classification — the harmonised CLP entry and the aggregated ECHA notifications; Molecular formula and weight; GHS classification — the harmonised CLP entry and the aggregated ECHA notifications; Molecular formula and weight, 344.39 for the hemisulfate; GHS classification — the harmonised CLP skin-sensitisation entry; GHS Classification - the aggregated ECHA C&L entry with signal word Warning, the GHS07, GHS08 and GHS09 pictograms, and H302, H317, H319, H373 and H410 among its statements; GHS aggregation: signal word Warning with H302, H317, H373 and the aquatic statements

Used by:P29 Capstone Stage 2: Formulating and Documenting Your Chemistry · P29 Planning the Capstone: The Project Plan and Its Hazard Assessment · Metol · Kodak IN-5 · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P8 Overview: What a Developer Is · P8 Experiment: Watching a Developer Oxidise · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P8 Assignment: Reading a Developer Formula · P8 Superadditivity: Why Two Agents Beat One · P9 Experiment: Comparing Developing Agents · P18 Lab: Mixing and Comparing Print Developers · Weighing and handling developing agents

PubChem compound summary: N-(4-Hydroxyphenyl)glycine (CID 67149)retrieved 2026-09-04

Sections: CAS; molecular formula and weight; IUPAC name; physical description (Haz-Map from the Merck Index and an Alfa Aesar safety data sheet); ChEBI description; GHS classification — the aggregated ECHA notifications; GHS classification — the aggregated ECHA notifications; ChEBI description and its allergen role

Used by:Glycin · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol

PubChem compound summary: Nickel sulfate (CID 24586)retrieved 2026-09-06, 2026-09-07

Sections: Names and Identifiers — Record Description, Molecular Formula, Computed Descriptors, CAS, Related CAS, Deprecated CAS, European Community (EC) Number, UN Number and ICSC Number; Chemical and Physical Properties — Experimental Properties (Physical Description, Color/Form, Odor, Boiling Point, Melting Point, Solubility, Density, Stability/Shelf Life, Decomposition and Other Experimental Properties) from CAMEO, CRC, CHRIS, the Merck Index, Weast and the ILO-WHO safety card; Safety and Hazards — GHS Classification, all eight blocks, and Hazard Classes and Categories; Chemical Dangers, OSHA Standards, NIOSH Recommendations, Spillage Disposal, Cleanup Methods, Disposal Methods, Preventive Measures, Safe Storage and Storage Conditions; Exposure Control — Permissible Exposure Limit, Threshold Limit Values, Immediately Dangerous to Life or Health, Occupational Exposure Limits, Inhalation Risk, Effects of Short Term Exposure, Effects of Long Term Exposure and Personal Protective Equipment; Stability and Reactivity — Air and Water Reactions, Reactive Group and Reactivity Profile; Regulatory Information — Federal Drinking Water Guidelines and CERCLA Reportable Quantities; Toxicity — Toxicity Summary, Evidence for Carcinogenicity, Carcinogen Classification, Health Effects, Exposure Routes, Signs and Symptoms, Human Toxicity Excerpts, Absorption Distribution and Excretion, Biological Half-Life, Interactions and Ecotoxicity Values; Use and Manufacturing — Uses, Industry Uses, Methods of Manufacturing and U.S. Production; GHS classification, the harmonised block for nickel sulphate and the notified aggregate over it; the minimum eliciting level for a patch-test reaction in nickel-sensitive subjects, of the order of 112 ppm nickel or 0.05 per cent nickel sulfate; and the relative molecular masses of the anhydrous salt and the hexahydrate, as summarised on the course's nickel(II) sulfate page; GHS classification aggregated from the ECHA C&L Inventory

Used by:Nickel(II) sulfate · Lead, thallium and nickel cyanotype toners · P25 The Additives We Study and Do Not Reproduce

PubChem compound summary: Nitric Acid (CID 944)retrieved 2026-09-04, 2026-09-06

Sections: Physical description; solubility; CAS; GHS classification; GHS classification and hazard statements; solubility; physical description; GHS classification, for the harmonised CLP entry reported there — signal word Danger, H272, H314 and H330 — cited here only for the acid etch, which is not part of this formula; Physical description; GHS classification; GHS classification — harmonised entry (H272, H314, H330); Physical description (CAMEO): reddish-brown vapours, very toxic by inhalation

Used by:Nitric acid · Daguerre's 1839 process outline · Niépce's bitumen heliograph coating · P1 Niepce and Heliography: Light That Hardens · P1 Wedgwood, Davy and the Problem of Permanence · P4 Silver and the Silver Ion · Heliography on bitumen of Judea

PubChem compound summary: Oxalic Acid (CID 971)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Physical description; solubility; CAS; GHS classification; ChEBI description; GHS classification; solubility; GHS classification, aggregated from the ECHA C&L Inventory as Oxalic acid, EC 205-634-3, 1,282 reports across 20 notifications; molecular formula and weight for the anhydrous acid; GHS classification aggregated from 1,282 reports across 20 ECHA notifications — signal word Danger, H302 at 99.8 per cent of reports, H312 at 99.7 per cent and H318 at 31.1 per cent; GHS classification aggregated from 1,282 reports across 20 ECHA notifications — signal word Danger, pictograms GHS05 and GHS07, H302 at 99.8 per cent of reports, H312 at 99.7 per cent and H318 at 31.1 per cent

Used by:Oxalic acid · Nicol's kallitype · Ware's improved Classic cyanotype · P24 Part XXIV Overview: When Iron Reduces Silver · P24 Lab: Printing a Kallitype

PubChem compound summary: Palladium Chloride (CID 24290)retrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: Computed properties and molecular formula; CAS; ChEBI description; GHS classification — the aggregated ECHA C&L notifications; Solubility — CAMEO and HSDB; Physical description — CAMEO and Haz-Map; GHS Classification, aggregated from the ECHA C&L Inventory, and the physical description; GHS classification aggregated from 299 reports across 19 ECHA notifications for palladium dichloride, EC 231-596-2 — signal word Danger, pictograms GHS05, GHS06, GHS07 and GHS09, with H317 for allergic skin reaction at 77.6 per cent of reports, H318 at 63.2, H290 at 64.5, H302 at 60.2, H400 and H410 each at 58.5, H319 at 22.7, H315 at 22.4, H335 at 19.4 and H301 at 12.7

Used by:Palladium(II) chloride · Ware's print-out platino-palladiotype · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last

PubChem compound summary: Phenidone (CID 7090)retrieved 2026-09-04, 2026-09-05

Sections: Molecular formula and weight; IUPAC name — for the structural comparison with 1-phenylpyrazolidin-3-one; CAS; molecular formula and weight; IUPAC name; physical description (Haz-Map); GHS classification — the aggregated ECHA notifications; solubility heading, which returns no values; GHS classification — the two notifications, H302 and H411; CAS; computed properties; Molecular formula and weight; GHS classification and the two notifications it rests on; absence of a solubility record; Molecular formula and weight; GHS classification and the notifications it rests on; Molecular formula and weight, 162.19; GHS classification and the notifications it rests on, H302 and H411; the solubility heading, which returns no values

Used by:Dimezone S · Phenidone · 510-Pyro · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P8 The Classical Developing Agents: Metol, Hydroquinone, Phenidone · P8 Superadditivity: Why Two Agents Beat One · P9 Experiment: Comparing Developing Agents

PubChem compound summary: Phenoxyethanol (CID 31236)retrieved 2026-09-06

Sections: Names and identifiers — CAS 122-99-6 and EC 204-589-7; experimental properties, an oily colourless liquid with a characteristic odour, relative density about 1.11 at 20 degrees C and a water solubility of about 2.6 g per 100 mL at 20 degrees C; use and manufacturing, the EPA Safer Chemical functional use classes preservatives and antioxidants and solvents, the cosmetics preservative classification, and the HSDB record of use as a solvent for inks, dyes and cleaners; GHS classification aggregated from 4299 ECHA C&L reports, signal word Danger with H302, H318 and H335, Acute Tox. 4 in 99.8 per cent of reports and Eye Irrit. 2 in 87 per cent

Used by:ILFORD ILFOSTOP

PubChem compound summary: Potassium Bromide (CID 253877)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Molar mass and solubility, quoted only where potassium bromide is the subject of the comparison; Physical description; solubility; pH; reactivity profile; storage conditions; density and melting point; CAS; GHS classification; GHS Classification, the aggregated ECHA C and L notifications; CAS; GHS classification (ECHA notifications); Computed properties - molecular weight; solubility (HSDB); Solubility (HSDB): 67.8 g per 100 g at 25 degrees C; 1 g in 1.5 mL of water and 1 mL of boiling water; Solubility; physical description; GHS classification; GHS classification aggregated from the ECHA C&L Inventory notifications; GHS Classification - the aggregated ECHA C&L entry giving signal word Warning with H315, H319 and H335

Used by:Ammonium bromide · Potassium bromide · Davey and Knott's double-jet iodobromide emulsion · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P3 Solutions, Solubility and Precipitation · P8 Restrainers and Antifoggants · P9 Overview: Experiments on Development · P9 Experiment: The Activity Series - Alkali and Restrainer · P18 Lab: Mixing and Comparing Print Developers

PubChem compound summary: Potassium Carbonate (CID 11430)retrieved 2026-09-04, 2026-09-05

Sections: Physical description; solubility; CAS; GHS classification; Solubility; GHS classification; Physical description (EU Food Improvement Agents; ICSC); GHS classification; Computed properties - molecular weight

Used by:Potassium carbonate (anhydrous) · Pyrocat-HD · P2 Storage, Incompatibilities and Secondary Containment · P3 Atoms, Ions and Bonds: Reading a Photographic Formula

PubChem compound summary: Potassium Chlorate (CID 6426889)retrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: Physical description — CAMEO, Haz-Map and the ILO-WHO safety card; Solubility — HSDB and the ILO-WHO card; CAS; GHS classification — the harmonised CLP entry under Regulation (EC) No 1272/2008, the aggregated ECHA C&L notifications and the three NITE-CMC blocks; GHS classification; GHS classification aggregated from 262 reports across 8 ECHA notifications — signal word Danger, pictograms GHS03, GHS06, GHS07 and GHS09, with H271 at 99.2 per cent of reports, H332 at 93.9, H302 at 84, H301 at 16 and H411 at 93.9; GHS classification; the harmonised CLP entry

Used by:Potassium chlorate · Three-solution drop system for platinum and palladium · P24 Contrast Control in Iron-Based Printing · P25 The Additives We Study and Do Not Reproduce

PubChem compound summary: Potassium Chloride (CID 4873)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Identity, computed properties and CAS; the aggregated ECHA C&L notifications; solubility from HSDB, CAMEO and the EU food-additive specification; physical description; GHS Classification, ECHA C and L Inventory: the large majority of notifications state that the substance does not meet GHS hazard criteria; GHS Classification, ECHA C&L Inventory: 825 of 875 reports stating that the substance does not meet GHS hazard criteria, with the note that only 5.7 per cent of companies supplied information and that ten notifications do carry hazard statement codes

Used by:Potassium chloride · Davey and Knott's double-jet iodobromide emulsion · KCl gaslight paper emulsion

PubChem compound summary: Potassium Citrate (monohydrate, CID 2735208)retrieved 2026-09-05

Sections: Identity, computed properties and CAS for the monohydrate; the two ECHA C&L records and their notification counts; the physical description from Haz-Map; the ChEBI description

Used by:Potassium citrate

PubChem compound summary: Potassium Cyanide (CID 9032)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Physical description — CAMEO, NIOSH, Haz-Map and the ILO-WHO safety card; Solubility — CAMEO, HSDB, NIOSH and the ILO-WHO card; CAS; GHS classification — the aggregated ECHA C&L notifications; ChEBI description; GHS classification, aggregated from the ECHA C&L Inventory; the physical description, on the release of hydrogen cyanide by contact with acids and on the ILO-WHO safety card's record of the dry salt as hygroscopic and odourless; and the solubility of 716 g per litre at 25 °C from the same card — all as summarised on the course's potassium cyanide page; GHS classification — H300, H310 and H330, fatal if swallowed, in contact with skin or if inhaled; and the reactivity with acids. Cited only for the period stain-removal instruction this page refuses; GHS classification, aggregated from the ECHA C&L Inventory, and the release of hydrogen cyanide on contact with acids, as summarised on the course's potassium cyanide page; GHS classification; GHS classification, aggregated from the ECHA C&L Inventory — signal word Danger with H300 fatal if swallowed, H310 fatal in contact with skin and H330 fatal if inhaled, each in 99.8 per cent of 575 reports across 30 notifications; and the physical description, on the release of hydrogen cyanide by contact with acids; GHS classification, aggregated from the ECHA C&L Inventory - signal word Danger with H300, H310 and H330 each in 99.8 per cent of 575 reports, as summarised with its sources on the course's potassium cyanide page; GHS classification, aggregated from 575 reports across 30 notifications to the ECHA C&L Inventory — signal word Danger, with H300 fatal if swallowed, H310 fatal in contact with skin and H330 fatal if inhaled each in 99.8 per cent of reports; and the ChEBI description, which records the substance as an inhibitor of EC 1.9.3.1, cytochrome c oxidase; GHS classification, aggregated from the ECHA C&L Inventory; physical description, on the release of hydrogen cyanide by contact with acids

Used by:Potassium cyanide · Cyanide fixing and toning · Talbot's gallo-nitrate of silver · Kodak IN-1 · P1 Daguerre and the Daguerreotype: A Mirror With a Memory · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Assignment: Assessing a Historical Process for Hazard · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · Ambrotype · Daguerreotype · Tintype (ferrotype) · The Level D policy

PubChem compound summary: Potassium Dichromate (CID 24502)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Solubility — the ILO-WHO safety card figure, for comparison with the ammonium salt; Physical description — CAMEO, Haz-Map and the ILO-WHO safety card; Solubility — CAMEO, HSDB and the ILO-WHO card; CAS; GHS classification — the aggregated ECHA C&L notifications and the harmonised CLP entry; ChEBI description; GHS classification, aggregated from the ECHA C&L Inventory; GHS classification, aggregated from the ECHA C&L Inventory, as summarised on the course's potassium dichromate page; GHS classification — carcinogenicity, mutagenicity and respiratory sensitisation; GHS classification aggregated from ECHA notifications: H272, H300, H310, H330, H314, H317, H334, H340, H350, H360, H372, H410; The aggregated GHS classification, for the carcinogenicity, germ cell mutagenicity and reproductive toxicity statements that place chromium(VI) outside every level of this course.; GHS classification — the twelve hazard statements aggregated from 491 reports across 19 notifications, including H340 for genetic defects and H350 for cancer; GHS classification, for the carcinogenicity, mutagenicity and reproductive toxicity statements that put chromium(VI) outside this course at any concentration; GHS classification, for the carcinogenicity, mutagenicity and reproductive toxicity statements that place chromium(VI) outside this course at any concentration; GHS classification aggregated from 491 reports across 19 ECHA notifications, including H340, H350, H360, H334 and H317; GHS classification aggregated from 491 reports across 19 ECHA notifications for potassium dichromate, EC 231-906-6 — signal word Danger, six pictograms, with H272 at 92.3 per cent of reports, H301 at 98.6, H312 at 91, H314 at 99.8, H317 at 98.6, H330 at 99.8, H334 at 99.8, H340 at 99.8, H350 at 99.8, H360 at 78.4, H372 at 91 and H410 at 99.8; GHS classification aggregated from 491 reports across 19 ECHA notifications, including H340, H350, H360, H334, H317 and H372; GHS classification aggregated from the ECHA C&L Inventory; GHS classification, aggregated from 491 reports across 19 notifications to the ECHA C&L Inventory — twelve hazard statements including H272, H314, H317, H334, H340 for genetic defects, H350 for cancer, H360 for reproductive toxicity, H372 and H410; GHS classification, aggregated from 491 reports across 19 notifications to the ECHA C&L Inventory - twelve hazard statements including H340 and H350 each in 99.8 per cent of reports and H360 in 78.4 per cent, as summarised with its sources on the course's potassium dichromate page; GHS classification aggregated from the ECHA C&L Inventory — twelve hazard statements including H317, H334, H340, H350 and H360, with H340, H350 and H334 each in 99.8 per cent of 491 reports across 19 notifications and H317 in 98.6 per cent, as summarised with its sources and its notification counts on the course's potassium dichromate page; GHS classification, aggregated from the ECHA C&L Inventory; physical description

Used by:Ammonium dichromate · Potassium dichromate · Borax kallitype developer · Kodak IN-4 · Nicol's kallitype · Rochelle salt kallitype developer · Van Dyke Brown sensitiser · Willis's potassium oxalate developer · P3 Oxidation, Reduction and the Electron That Makes the Picture · P21 Experiment: The Exposure Scale, Maximum Density and Contrast of a Cyanotype · P21 The New Cyanotype and the Other Ways to Make a Blue Print · P22 Lab: Printing, Toning, Fixing and Washing a Salt Print · P22 The Variants of the Salt Print and How a Conservator Identifies One · P24 Part XXIV Overview: When Iron Reduces Silver · P24 Contrast Control in Iron-Based Printing · P24 Lab: Printing a Kallitype · P25 The Additives We Study and Do Not Reproduce · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Assignment: Assessing a Historical Process for Hazard · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · Carbon print · Collotype · Gum bichromate · Photoglyphic engraving · Photogravure · Woodburytype · The chromium policy · The Level D policy

PubChem compound summary: Potassium ferricyanide (CID 26250)retrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: Physical description; Solubility; CAS; GHS classification — the aggregated ECHA C&L notifications; ChEBI description; GHS classification; solubility; physical description; CAS; GHS classification; solubility; physical description; GHS classification aggregated from the ECHA Classification and Labelling Inventory notifications for potassium hexacyanoferrate(III), CAS 13746-66-2, in which 14 of 285 reports say the substance meets no GHS hazard criteria and H319, H411, H302, H361, H315 and H335 appear among the reports that do classify it; GHS classification aggregated from the ECHA Classification and Labelling Inventory for potassium hexacyanoferrate(III), in which 14 of 285 reports say the substance meets no GHS hazard criteria and H319, H411, H302, H361, H315 and H335 appear among the reports that do classify it; GHS classification — the aggregated ECHA C&L notifications, 285 reports across 12 notifications with the statement frequencies, and the 14 reports declining to classify; GHS classification aggregated from the ECHA inventory for potassium hexacyanoferrate(III), in which 14 of 285 reports state that the substance meets no GHS hazard criteria and H319, H411, H302, H361, H315 and H335 appear among those that do classify it; GHS classification aggregated from the ECHA inventory for potassium hexacyanoferrate(III), in which 14 of 285 reports state the substance meets no GHS hazard criteria and H319, H411, H302, H361, H315 and H335 appear among those that do classify it; GHS classification; physical description; GHS classification; the release of hydrogen cyanide on contact with concentrated acid

Used by:Potassium ferricyanide · P1 Assignment 1: A Botanical Cyanotype Photogram, After Atkins · P1 Herschel: Hypo, Prussian Blue and the Words of Photography · P20 Lab: Bleaching and Redeveloping a Sepia Print · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Iron, Light and Prussian Blue · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · Cyanotype (classic) · Iron-blue toned silver gelatin print · Cyanotype (New Cyanotype)

PubChem compound summary: Potassium Ferrocyanide (CID 9605257)retrieved 2026-09-04

Sections: Physical description — EU Food Improvement Agents and Haz-Map; CAS; GHS classification — the aggregated ECHA C&L notifications; ChEBI description; GHS classification — the aggregated ECHA C&L notifications for tetrapotassium hexacyanoferrate, EC 237-722-2; Physical description; CAS; GHS classification

Used by:Potassium ferrocyanide (anhydrous) · Potassium ferrocyanide trihydrate · Iron-blue toned silver gelatin print

PubChem compound summary: Potassium ferrocyanide trihydrate (CID 161067)retrieved 2026-09-04

Sections: Physical description — Merck Index and Alfa Aesar via Haz-Map; CAS; computed molecular formula and weight; GHS Classification (no record held)

Used by:Potassium ferrocyanide trihydrate

PubChem compound summary: Potassium Hydroxide (CID 14797)retrieved 2026-09-04

Sections: Physical description; solubility; CAS; GHS classification; other experimental properties; uses; Physical description; GHS classification

Used by:Potassium hydroxide (caustic potash) · Collotype

PubChem compound summary: Potassium Iodide (CID 4875)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Physical description; solubility; pH; reactivity profile; stability and shelf life; storage conditions; CAS; GHS classification; Solubility — 148 g per 100 g of water at 25 degrees C (HSDB); GHS classification aggregated from 721 reports across 53 notifications to the ECHA C and L Inventory, giving Danger with H302, H315, H317, H319, H334, H372, H373 and H411; storage conditions, a tight container below 40 degrees C and preferably between 15 and 30 degrees C; GHS Classification, the aggregated ECHA C and L notifications; GHS classification, aggregated from the ECHA C&L Inventory; solubility; stability; Solubility; GHS classification; GHS classification aggregated from the ECHA C&L Inventory — H302, H315, H317, H319, H334, H372 and H373, with the sensitisation and organ-damage statements that put it outside the course's Level A ceiling; Physical description; GHS classification

Used by:Potassium iodide · Iodide hypo check · Davey and Knott's double-jet iodobromide emulsion · Talbot's calotype iodised paper · P8 Restrainers and Antifoggants · P11 Experiment: Clearing Time and Fixer Capacity · Bayard direct positive

PubChem compound summary: Potassium Metabisulfite (CID 28019)retrieved 2026-09-04

Sections: Physical description; solubility; CAS; GHS classification; depositor-supplied synonyms

Used by:Potassium metabisulfite

PubChem compound summary: Potassium oxalate monohydrate (CID 2724193)retrieved 2026-09-04, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Computed properties and molecular formula; physical description; Computed properties and molecular formula; physical description; CAS; GHS classification; GHS classification; Computed properties, for the molecular formula and weight; GHS classification, aggregated from the ECHA C&L Inventory; GHS classification aggregated from 165 reports across 6 ECHA notifications — signal word Warning, with H302 and H312 at 100 per cent of the reports carrying those codes, H319 at 36.4 per cent and H315 at 23 per cent; GHS classification aggregated from 165 reports across 6 ECHA notifications — signal word Warning, pictogram GHS07, with H302 and H312 at 100 per cent of the reports carrying those codes, H319 at 36.4 per cent and H315 at 23 per cent; GHS classification aggregated from the ECHA C&L Inventory, and the CAMEO health hazard entry; GHS aggregation: signal word Warning with H302, H312, H315 and H319

Used by:Potassium oxalate, anhydrous · Potassium oxalate monohydrate · Three-solution drop system for platinum and palladium · Willis's potassium oxalate developer · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Lab: Printing a Kallitype · P25 Lab: Exposing, Developing and Clearing a Palladium Print · P25 Experiment: Tonal Scale, Contrast and Image Colour in Palladium · Running a platinum or palladium session

PubChem compound summary: Potassium palladium chloride (CID 61438)retrieved 2026-09-04

Sections: Computed properties and molecular formula; CAS; GHS classification — the aggregated ECHA C&L notifications; Physical description — Haz-Map (Alfa Aesar); Physical description; GHS classification

Used by:Potassium tetrachloropalladate(II) · Gold-toned and palladium-toned kallitype

PubChem compound summary: Potassium Permanganate (CID 516875)retrieved 2026-09-05

Sections: Identity, computed properties and CAS; the harmonised classification under Regulation (EC) No 1272/2008; the aggregated ECHA C&L notifications with their reporting percentages; the NITE-CMC entries of FY2006 and FY2014; the Safe Work Australia HCIS entry; solubility from HSDB and from the ILO-WHO card; physical description from CAMEO and Haz-Map; the ChEBI description

Used by:Potassium permanganate

PubChem compound summary: Potassium Persulfate (CID 24412)retrieved 2026-09-04

Sections: Identity, computed properties and CAS; the harmonised classification under Regulation (EC) No 1272/2008; the aggregated ECHA C&L notifications; the NITE-CMC and Safe Work Australia entries; solubility from HSDB; physical description from CAMEO, Haz-Map and OSHA

Used by:Potassium persulfate

PubChem compound summary: Potassium sodium tartrate (CID 9357)retrieved 2026-09-04, 2026-09-06

Sections: The three ECHA C&L entries, all reporting that the substance does not meet GHS hazard criteria; solubility from HSDB and the EU food-additive specification; physical description; The three ECHA C&L entries, all reporting that the substance does not meet GHS hazard criteria; solubility from HSDB and the EU food-additive specification; molecular weight of the anhydrous salt

Used by:Potassium sodium tartrate tetrahydrate · Rochelle salt kallitype developer

PubChem compound summary: Potassium sodium tartrate tetrahydrate (CID 165453)retrieved 2026-09-04, 2026-09-06

Sections: Identity, computed properties and CAS for the tetrahydrate; physical description from Haz-Map. The record carries no GHS classification and no solubility section; Identity, computed molecular formula and weight, CAS, and the Haz-Map physical description; the record carries no GHS classification section and no solubility section; Identity, computed properties and CAS for the tetrahydrate; physical description

Used by:Potassium sodium tartrate tetrahydrate · Rochelle salt kallitype developer · Kallitype

PubChem compound summary: Potassium thiocyanate (CID 516872)retrieved 2026-09-04

Sections: Identity, computed properties and CAS; GHS classification aggregated from the ECHA C&L Inventory, with the NITE-CMC and Safe Work Australia entries; physical description

Used by:Potassium thiocyanate

PubChem compound summary: Pyrogallol (CID 1057)retrieved 2026-09-04, 2026-09-05, 2026-09-07, 2026-09-08

Sections: CAS; molecular formula and weight; IUPAC name; physical description (CAMEO, ICSC, EPA CDR, Haz-Map); solubility (CAMEO, HSDB, ICSC); ChEBI description; GHS classification — the aggregated ECHA notifications; GHS classification; solubility; physical description; GHS classification — the aggregated ECHA notifications; solubility; GHS classification; solubility; GHS classification — the aggregated ECHA notifications and the proportions behind each statement; GHS classification from the aggregated ECHA notifications - harmful in contact with skin, harmful if inhaled and suspected of causing genetic defects at 100 per cent of notifiers, together with harmful if swallowed and harmful to aquatic life with long-lasting effects; GHS aggregation: H412, harmful to aquatic life with long-lasting effects, alongside H312, H332 and H341; GHS aggregation: H312 harmful in contact with skin, H332 harmful if inhaled and H341 suspected of causing genetic defects, each at 100 per cent of reporting notifiers, with H302 and H412

Used by:Pyrogallol · 510-Pyro · Kodak D-1 · PMK pyro · P8 Alternative Developing Agents: p-Aminophenol, Ascorbate, Glycin, Catechol, Pyrogallol · P8 Staining and Tanning Developers · P27 Assignment: The Developer Comparison, Measured and Printed · Collecting and segregating waste across a multi-run session · Weighing and handling developing agents

PubChem compound summary: Selenious Acid (CID 1091)retrieved 2026-09-04

Sections: GHS classification, ECHA C&L aggregation: H301 toxic if swallowed in 100 per cent of reports, H331 toxic if inhaled in 99.1 per cent, H410 very toxic to aquatic life with long lasting effects

Used by:P6 Making and Measuring Pinholes

PubChem compound summary: Selenium (CID 6326970)retrieved 2026-09-04, 2026-09-05

Sections: Physical description — CAMEO, NIOSH, OSHA and the ILO-WHO safety card; Solubility — HSDB, NIOSH and CAMEO; CAS; GHS classification — the aggregated ECHA C&L notifications; ChEBI description; Solubility — HSDB, the dissolution of elemental selenium in potassium sulfite solution; GHS classification and identity, as summarised on the course's selenium page; Physical description; solubility; GHS classification

Used by:Selenium · Sodium selenosulfate · Kodak T-55 · Selenium toned silver gelatin print

PubChem compound summary: Sensodyne (CID 168963)retrieved 2026-09-04, 2026-09-06, 2026-09-07

Sections: Computed properties and molecular formula; CAS; GHS classification; Computed properties and molecular formula; GHS classification; GHS classification; molecular formula; GHS classification, aggregated from a single ECHA notification under the entry Diiron trioxalate, EC 220-951-7 — signal word Warning, pictogram GHS07, and the statements H302 and H312 at 100 per cent of reports; The record's title, which resolves to a proprietary toothpaste rather than the substance, and the ECHA aggregation beneath it under Diiron trioxalate, EC 220-951-7, giving signal word Warning, pictogram GHS07 and the statements H302 and H312 at 100 per cent of the reports in a single notification; The record's own title and computed properties, which resolve the query to a proprietary toothpaste rather than to the substance, and the ECHA aggregation beneath it under Diiron trioxalate, EC 220-951-7; GHS classification aggregated from the ECHA C&L Inventory; Physical description; CAS; GHS classification

Used by:Ferric oxalate · Kallitype sensitiser · Nicol's kallitype · Three-solution drop system for platinum and palladium · P24 Part XXIV Overview: When Iron Reduces Silver · P24 Lab: Printing a Kallitype · P24 The Siderotype Principle: Iron Reduces Silver · P25 Lab: Preparing the Sensitiser and Coating for Palladium · Kallitype

PubChem compound summary: Silver (CID 23954)retrieved 2026-09-04, 2026-09-05

Sections: Computed properties; CAS; Solubility (HSDB, NIOSH, CAMEO, ICSC 0810); Physical description (CAMEO, NIOSH, OSHA, Haz-Map, ICSC); GHS classification — the three particle-size records under Regulation (EC) No 1272/2008 and the aggregated ECHA C&L notifications; GHS classification aggregated from the ECHA C&L Inventory — the silver entries carrying H400, very toxic to aquatic life, and H410, very toxic to aquatic life with long lasting effects, with the environmental hazard pictogram

Used by:Silver · P12 Silver Recovery and the Responsible Darkroom

PubChem compound summary: Silver bromide (CID 66199)retrieved 2026-09-04, 2026-09-05

Sections: Computed properties; CAS; Physical description (Haz-Map, citing the Merck Index and an Alfa Aesar sheet) — yellowish odourless solid, darkened by light, water solubility 0.135 mg/L at 25 °C; GHS classification (ECHA C&L Inventory aggregation); Physical description; solubility; Physical description, CAS; Physical description; GHS classification; Computed properties - molecular formula and molecular weight; Computed properties - molecular weight; Physical description: yellowish solid darkened by light; water solubility 0.135 mg/L at 25 degrees C; GHS classification and the thinness of its notification base; Physical description (Haz-Map, citing the Merck Index): yellowish odourless solid darkened by light, water solubility 0.135 mg/L at 25 degrees C; Computed molecular weight 187.77; Physical description; solubility; solubility product; GHS Classification, the ECHA C&L Inventory aggregation: signal word Danger with GHS08 and GHS09, and H360D, H400 and H410 among the reports carrying codes — read with the minority-report caveat the chemical page sets out

Used by:Silver bromide · P1 Daguerre and the Daguerreotype: A Mirror With a Memory · P1 Silver Salts and Light: Schulze to Ritter · P1 Experiment: The Image That Would Not Stay · P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P3 Solutions, Solubility and Precipitation · P4 Experiment: Precipitating the Silver Halides · P4 The Silver Halides · P11 How Fixer Works · Hand-coated bromide paper · Hand-coated chlorobromide paper · Refrigerated emulsion labelling and food separation

PubChem compound summary: Silver Chloride (CID 24561)retrieved 2026-09-04, 2026-09-05, 2026-09-07

Sections: Computed properties; CAS; Physical description (Haz-Map, citing the Merck Index) — white solid, darkened by light, water solubility 1.93 mg/L at 25 °C; GHS classification (ECHA C&L Inventory aggregation); Physical description; solubility; Physical description, CAS, GHS classification; Molecular weight; CAS; Physical description; GHS classification; Physical description (Haz-Map, quoting the Merck Index): water solubility 1.93 mg/L at 25 degrees C; computed properties; Computed properties - molecular weight; Physical description: white solid darkened by light; water solubility 1.93 mg/L at 25 degrees C; Physical description (Haz-Map, quoting the Merck Index): white solid darkened by light, water solubility 1.93 mg/L at 25 degrees C; Identity, molecular formula and solubility; Molecular weight; solubility; CAS; Molecular weight; solubility; solubility product; Physical description (Haz-Map, from the Merck Index): white solid darkened by light, water solubility 1.93 mg/L at 25 °C

Used by:Silver chloride · P1 Daguerre and the Daguerreotype: A Mirror With a Memory · P1 Silver Salts and Light: Schulze to Ritter · P1 Talbot: Photogenic Drawing, the Calotype and the Negative-Positive Principle · P1 Wedgwood, Davy and the Problem of Permanence · P1 Experiment: The Image That Would Not Stay · P2 Silver Nitrate: The Reagent That Sets the Rules · P3 Solutions, Solubility and Precipitation · P4 Experiment: Precipitating the Silver Halides · P4 The Silver Halides · P22 Printing Out: Silver Chloride Made and Darkened in the Paper · Bayard direct positive · Hand-coated silver chloride contact paper · Ammoniacal silver quench and prohibition

PubChem compound summary: Silver iodide (CID 24563)retrieved 2026-09-04, 2026-09-06

Sections: Computed properties; CAS; Solubility (HSDB) — 28 × 10⁻⁷ g/L in water at 25 °C, and the list of solvents; Physical description (Haz-Map, citing the Merck Index) — light yellow odourless solid, gradually darkened by light; GHS classification (ECHA C&L Inventory aggregation); Solubility: 28 × 10⁻⁷ g/L at 25 °C, and the HSDB list of solvents, which records silver iodide as soluble in aqueous solutions of sodium chloride and of sodium thiosulfate among others, with no concentration given for any of them; Solubility (HSDB) — 28 × 10⁻⁷ g/L in water at 25 degrees C, and solubility in aqueous solutions of potassium iodide, sodium thiosulfate and the alkali thiocyanates; Physical description (Haz-Map, citing the Merck Index) — light yellow odourless solid, gradually darkened by light; GHS classification (ECHA C and L Inventory aggregation) — Warning, with H400 and H410; GHS classification, aggregated from the ECHA C&L Inventory; Physical description, solubility, CAS; Computed properties - molecular weight; solubility (HSDB): soluble in solutions of potassium iodide, sodium chloride, potassium cyanide, ammonium hydroxide and sodium thiosulfate; Physical description: light yellow solid gradually darkened by light; Physical description: light yellow solid gradually darkened by light; water solubility; Physical description and solubility: a light yellow, odourless solid gradually darkened by light, with a water solubility of 2.8 x 10^-6 g per litre at 25 C; Physical description; solubility

Used by:Silver iodide · Daguerre's 1839 process outline · Iodide hypo check · Talbot's calotype iodised paper · P1 Daguerre and the Daguerreotype: A Mirror With a Memory · P3 Solutions, Solubility and Precipitation · P4 Experiment: Precipitating the Silver Halides · P4 The Silver Halides · P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory · Hand-coated bromide paper

PubChem compound summary: Silver Nitrate (CID 24470)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: GHS classification aggregated from 803 reports across 35 ECHA C&L notifications: Danger, GHS03, GHS05, GHS08 and GHS09, with H272, H290, H314, H318, H360D, H400 and H410; GHS classification aggregated from 803 reports across 35 ECHA C&L notifications: Danger, GHS03, GHS05, GHS08 and GHS09, with H272, H290, H314, H318, H360D, H400 and H410; and the narrower harmonised entry under Regulation (EC) No 1272/2008; Computed properties; CAS; Solubility (HSDB, CAMEO, ICSC); Physical description (CAMEO, ICSC, Haz-Map); GHS classification — the harmonised entry under Regulation (EC) No 1272/2008 and the ECHA C&L Inventory aggregation; GHS classification — signal word, pictograms and hazard statements; GHS Classification: the ECHA C&L headline giving GHS03, GHS05, GHS08 and GHS09 with signal word Danger; GHS classification — the harmonised entry under Regulation (EC) No 1272/2008, and the notified additions; GHS classification; GHS Classification: the ECHA C and L headline giving GHS03, GHS05, GHS08 and GHS09 with signal word Danger; GHS classification; molecular weight; GHS classification aggregated from the ECHA C and L notifications and the harmonised CLP entry — Danger, with H272, H314, H318, H400 and H410; GHS classification and incompatibilities, as summarised on the course's silver nitrate page; GHS classification; molecular weight; solubility; GHS classification — the harmonised entry under Regulation (EC) No 1272/2008 and the ECHA C&L Inventory aggregation; Solubility; GHS Classification: the ECHA C&L headline giving GHS03 oxidiser, GHS05 corrosive, GHS08 health hazard and GHS09 environmental, signal word Danger; GHS classification — the harmonised entry under Regulation (EC) No 1272/2008; GHS classification; solubility; molecular weight; GHS classification, hazard statements and solubility; Physical description, solubility, CAS, GHS classification; Molecular weight; CAS; Physical description (CAMEO; ICSC); GHS classification; CAS; computed properties; GHS classification; Computed properties; CAS; GHS classification (harmonised entry under Regulation (EC) No 1272/2008 and the ECHA C&L Inventory aggregation); solubility (HSDB); physical description (CAMEO, ICSC); Computed properties - molecular formula and molecular weight; CAS; Solubility (HSDB): 122 g per 100 cc of water at 0 degrees C and 245 g per 100 g of water; Computed properties (molecular weight 169.87); Solubility (HSDB); GHS classification — harmonised entry under Regulation (EC) No 1272/2008 (H272, H314, H400, H410) and the ECHA C&L Inventory aggregation; Solubility (HSDB, CAMEO); Physical description (CAMEO, ICSC); GHS classification — harmonised entry under Regulation (EC) No 1272/2008 and the ECHA C&L Inventory aggregation; GHS Classification: the harmonised entry under Regulation (EC) No 1272/2008 — Danger, GHS03, GHS05, GHS09, with H272, H314, H400 and H410; GHS Classification: the harmonised entry under Regulation (EC) No 1272/2008 — Danger, GHS03, GHS05 and GHS09, with H272, H314, H400 and H410 — and the wider ECHA C&L aggregation; GHS classification aggregated from 803 reports across 35 ECHA C&L notifications — Danger, with H314 in 99.9 per cent of the classifying reports, H410 in 99.8 per cent, H400 in 99.6 per cent, H272 in 97.4 per cent and H318 in 33 per cent; the harmonised entry under Regulation (EC) No 1272/2008 carrying H272, H314, H400 and H410; GHS classification aggregated from Regulation (EC) No 1272/2008 - pictograms GHS03 oxidiser, GHS05 corrosive and GHS09 environmental hazard, signal word Danger, with H272, H314 and the aquatic statements; GHS classification aggregated from Regulation (EC) No 1272/2008 - GHS03, GHS05 and GHS09 with signal word Danger, H272 and H314 and the aquatic hazard statements; GHS classification aggregated from Regulation (EC) No 1272/2008 - GHS03 oxidiser, GHS05 corrosive and GHS09 environmental hazard with signal word Danger, H272 may intensify fire, H314 causes severe skin burns and eye damage, and the aquatic hazard statements; identity, CAS and molecular weight 169.87; GHS classification aggregated from ECHA C&L notifications — signal word Danger, H272, H290, H314, H318, H360D, H400 and H410; GHS classification aggregated from 803 reports across 35 ECHA notifications — H272, H314, H318, H400 and H410, signal word Danger; GHS classification aggregated from 803 reports across 35 ECHA notifications — signal word Danger, with H272, H314, H318, H400 and H410; GHS classification aggregated from 803 reports across 35 ECHA notifications — signal word Danger, pictograms GHS03, GHS05, GHS08 and GHS09, with H272 at 97.4 per cent of reports, H314 at 99.9 per cent, H318 at 33 per cent, H400 at 99.6 per cent and H410 at 99.8 per cent; GHS classification, aggregated from 803 reports across 35 notifications to the ECHA C&L Inventory, and the narrower harmonised entry under Regulation (EC) No 1272/2008, as summarised with its sources on the course's silver nitrate page; Molecular weight; CAS; GHS classification; GHS classification: the harmonised entry under Regulation (EC) No 1272/2008 — Danger, GHS03, GHS05, GHS09, with H272, H314, H400 and H410; GHS Classification: the harmonised entry under Regulation (EC) No 1272/2008, Danger, GHS03, GHS05, GHS09, with H272, H314, H400 and H410; GHS classification aggregated from the ECHA C and L notifications and the harmonised CLP entry: Danger, with H272, H314, H318, H400 and H410; The aggregated harmonised classification: signal word Danger with H272 and H314, the oxidiser, corrosive and environmental pictograms, and the acute and chronic aquatic statements; GHS classification (harmonised entry under Regulation (EC) No 1272/2008); physical description (CAMEO, ICSC); solubility (HSDB); GHS classification, harmonised entry, H272, H314, H400 and H410; physical description from CAMEO on blackening in contact with organic material; The aggregated harmonised classification: Danger with H272 and H314 and the aquatic statements

Used by:P29 Capstone Stage 3: Exposing, Processing and Measuring · P29 Planning the Capstone: The Project Plan and Its Hazard Assessment · Silver nitrate · Albumen sensitising solution · Trumm's bromide paper emulsion · Wall's soft-working gaslight paper · Talbot's gallo-nitrate of silver · Herschel's argentotype · Davey and Knott's double-jet iodobromide emulsion · Kallitype sensitiser · Kodak HT-2 · Kodak IN-5 · Nicol's kallitype · Salted paper sensitising solution · KCl gaslight paper emulsion · Talbot's calotype iodised paper · Talbot's photogenic drawing paper · Van Dyke Brown sensitiser · Wedgwood and Davy's silver nitrate on leather · P1 Silver Salts and Light: Schulze to Ritter · P1 Talbot: Photogenic Drawing, the Calotype and the Negative-Positive Principle · P2 Storage, Incompatibilities and Secondary Containment · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P2 Silver Nitrate: The Reagent That Sets the Rules · P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P3 Solutions, Solubility and Precipitation · P4 Experiment: Precipitating the Silver Halides · P4 Silver and the Silver Ion · P5 Project 3: A Bromide Enlarging Emulsion · P5 Project 1: A Silver Chloride Contact Printing Emulsion · P5 Project 2: A Chlorobromide Paper Emulsion · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P12 Lab: Testing for Residual Thiosulfate and Residual Silver · P22 Part XXII Overview: The First Silver Print · P22 Lab: Printing, Toning, Fixing and Washing a Salt Print · P22 Lab: Salting and Sensitising a Sheet of Paper · P23 Lab: Sensitising, Printing and Toning an Albumen Print · P24 Part XXIV Overview: When Iron Reduces Silver · P24 Lab: Printing a Kallitype · P24 Lab: Printing a Van Dyke Brown · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · P24 The Siderotype Principle: Iron Reduces Silver · P26 Assignment: Assessing a Historical Process for Hazard · Albumen print · Argentotype · Arrowroot and albumenised salted paper · Hand-coated bromide paper · Hand-coated chlorobromide paper · Hand-coated silver chloride contact paper · Kallitype · Photogenic drawing · Salted paper print · Van Dyke Brown · Ammoniacal silver quench and prohibition · An emulsion preparation session · Residual hypo and residual silver tests · Silver nitrate at the coating bench · Handling silver nitrate · Responding to a silver nitrate spill · The student's project SOP

PubChem compound summary: Silver oxalate (CID 62364)retrieved 2026-09-06, 2026-09-07

Sections: Safety and Hazards, Hazards Identification, GHS Classification — the notification group aggregated from the ECHA C&L Inventory against EC 208-568-3, its pictograms, signal word, hazard statements with their percentages of reports, precautionary statement codes and notification summary; Chemical and Physical Properties, Computed Properties — molecular formula C2Ag2O4 and molecular weight 303.76. Read through the PUG and PUG-View APIs and mirrored at .research/sources/altprocess-emulsion/pubchem-silver-oxalate-ghs.txt; GHS classification

Used by:Silver(I) oxalate · Kallitype sensitiser · Nicol's kallitype

PubChem compound summary: Silver selenide (CID 6914520)retrieved 2026-09-04

Sections: Computed properties and molecular formula; CAS registry number; the absence of any GHS classification, solubility or physical description

Used by:Silver selenide

PubChem compound summary: Silver sulfamate (CID 23304053)retrieved 2026-09-07

Sections: Names and Identifiers — Computed Descriptors, Molecular Formula and Synonyms; Chemical and Physical Properties — Computed Properties. Read through the PUG REST property and synonym endpoints; the record returns two synonyms, no depositor-supplied CAS number and no EC number

Used by:Silver sulfamate

PubChem compound summary: Silver sulfide (CID 166738)retrieved 2026-09-04

Sections: Computed properties and molecular formula; CAS registry numbers; the absence of any GHS classification block

Used by:Silver sulfide

PubChem compound summary: Silver(I) oxide (CID 9794626)retrieved 2026-09-06

Sections: Names and Identifiers — Molecular Formula, Computed Descriptors, CAS, European Community (EC) Number and Depositor-Supplied Synonyms; Chemical and Physical Properties — Computed Properties, Molecular Weight; Safety and Hazards — GHS Classification and Hazard Classes and Categories, both notification groups aggregated from the ECHA C&L Inventory; Stability and Reactivity — Reactivity Alerts, CSL Reaction Information; Regulatory Information. Read through the PUG-View API; the record carries no Experimental Properties section of any kind; Molecular formula, molecular weight and CAS number; GHS Classification, both aggregated ECHA C and L notification groups

Used by:Silver(I) oxide · Ware's argyrotype

PubChem compound summary: Sodium Acetate (CID 517045)retrieved 2026-09-04

Sections: Identity, computed properties and CAS; the aggregated ECHA C&L notifications; solubility from HSDB and the ILO-WHO card; physical description from the EU food-additive specification and Haz-Map

Used by:Sodium acetate (anhydrous)

PubChem compound summary: Sodium Acetate Trihydrate (CID 23665404)retrieved 2026-09-04

Sections: Identity, CAS, molecular weight and the ECHA C&L entry, cited only where the trihydrate is the subject

Used by:Sodium acetate (anhydrous)

PubChem compound summary: Sodium Ascorbate (CID 23667548)retrieved 2026-09-04

Sections: CAS; molecular formula and weight; IUPAC name; ChEBI description; physical description (CAMEO from NTP, EU Food Improvement Agents, Haz-Map); solubility (CAMEO, HSDB); GHS classification — the aggregated ECHA notifications and the "not classified" majority; Molecular formula and weight, 198.11; GHS classification — 98.9 per cent of 361 reports state that the substance meets no GHS criterion

Used by:Sodium ascorbate · P9 Experiment: Comparing Developing Agents

PubChem compound summary: Sodium Bicarbonate (CID 516892)retrieved 2026-09-04

Sections: Physical description; solubility; CAS; GHS classification; Computed properties - molecular weight; GHS classification; Molecular formula and weight, 84.01; GHS classification aggregated from the ECHA C&L Inventory notifications

Used by:Sodium bicarbonate · P3 Lab: Measuring pH and Trusting the Number · P9 Break/Fix: The Developer That Went Wrong

PubChem compound summary: Sodium Bisulfite (CID 23665763)retrieved 2026-09-04, 2026-09-06

Sections: Physical description; solubility; CAS; GHS classification; depositor-supplied synonyms; Names and identifiers — CAS 7631-90-5 and EC 231-548-0; GHS classification aggregated from the ECHA C&L notifications; Molecular formula and weight; the note that the dry salt sold under this name is usually largely sodium metabisulfite

Used by:Sodium bisulfite · ILFORD HYPAM · ILFORD RAPID FIXER · P8 Sulfite: Preservative, Buffer, Silver Solvent

PubChem compound summary: Sodium Carbonate (CID 10340)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Physical description; solubility; CAS; GHS classification; Solubility and physical description, cited only where the anhydrous salt is the subject; Solubility; physical description; GHS classification, cited only where the anhydrous salt is the subject; GHS classification; Physical description (EU Food Improvement Agents; ICSC); Computed properties; CAS; Computed properties - molecular weight; solubility (HSDB); Computed properties - molecular weight; Computed properties - molecular weight; GHS classification; Solubility (HSDB): 30.7 g per 100 g at 25 degrees C, and 6, 8.5, 17 and 28 weight per cent at 0, 10, 20 and 30 degrees C; ILO-WHO card, 30 g per 100 mL at 20 degrees C; GHS classification aggregated from the ECHA C&L Inventory notifications; GHS classification aggregated from the ECHA C&L Inventory notifications, and the divergent NITE-CMC and Safe Work Australia classifications; GHS Classification - the aggregated ECHA C&L entry giving signal word Warning and H319 as its dominant statement; GHS classification - the ECHA C&L aggregation and the NITE-CMC and Safe Work Australia entries that classify it Danger with H318; Computed properties - relative molecular mass 105.99; CAS 497-19-8

Used by:Sodium carbonate (anhydrous) · Sodium carbonate decahydrate · Sodium carbonate monohydrate · Dilute alkaline thiosulfate fixer for iron-silver prints · P2 Storage, Incompatibilities and Secondary Containment · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P3 Buffers and Buffer Capacity · P3 Lab: Measuring pH and Trusting the Number · P3 Solutions, Solubility and Precipitation · P9 Overview: Experiments on Development · P9 Experiment: The Activity Series - Alkali and Restrainer · P18 Lab: Mixing and Comparing Print Developers · P21 Lab: Toning the Prussian Blue Image · Hydrate substituted for an anhydrous salt at the same mass

PubChem compound summary: Sodium Carbonate Decahydrate (CID 151402)retrieved 2026-09-04

Sections: Identity, computed molecular weight and CAS; GHS classification aggregated from two ECHA C&L entries and the Safe Work Australia entry; physical description from Haz-Map; Physical description (Merck Index, via Haz-Map); Computed properties; CAS; Computed properties - molecular weight; Computed properties - relative molecular mass 286.14; CAS 6132-02-1

Used by:Sodium carbonate decahydrate · P2 Storage, Incompatibilities and Secondary Containment · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P3 Atoms, Ions and Bonds: Reading a Photographic Formula · Hydrate substituted for an anhydrous salt at the same mass

PubChem compound summary: Sodium Carbonate Monohydrate (CID 2735133)retrieved 2026-09-04

Sections: Physical description; CAS; GHS classification; computed molecular weight; Computed properties - molecular weight

Used by:Sodium carbonate monohydrate · P3 Atoms, Ions and Bonds: Reading a Photographic Formula

PubChem compound summary: Sodium Chloride (CID 5234)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Solubility, quoted only for the comparison between the two chlorides; Physical description; colour and form; solubility; pH; other experimental properties; hazards summary; CAS; GHS classification; Solubility; Other Experimental Properties — 36.0 g per 100 g of water at 25 °C; Solubility: 36.0 g per 100 g of water at 25 °C, and 1 g in 2.8 mL of water against 2.6 mL of boiling water; Molecular weight; CAS; GHS classification and the proportion of reports stating no hazard; Molecular weight; CAS; Computed properties; CAS; solubility (HSDB); GHS classification (ECHA C&L Inventory aggregation); Solubility (HSDB): 36.0 g per 100 g of water at 25 degrees C; Molecular formula and weight; solubility; Solubility (HSDB): 36.0 g per 100 g of water at 25 °C, one gram dissolving in 2.8 mL

Used by:Potassium chloride · Sodium chloride · Albumen solution with its chloride · Daguerre's 1839 process outline · Arrowroot salting solution · P1 Talbot: Photogenic Drawing, the Calotype and the Negative-Positive Principle · P2 Lab: Commissioning Your Laboratory · P3 Solutions, Solubility and Precipitation · P8 Solvent Action, Physical Development and Grain · Arrowroot and albumenised salted paper · Ammoniacal silver quench and prohibition

PubChem compound summary: Sodium Citrate Dihydrate (CID 71474)retrieved 2026-09-04, 2026-09-06

Sections: Identity, computed properties and CAS; the aggregated ECHA C&L notifications; solubility from the ILO-WHO card; physical description; The ECHA C&L aggregation for the dihydrate, in which the substance is not classified; Identity, computed properties and CAS; the aggregated ECHA C and L notifications; Identity, computed properties, CAS and the aggregated ECHA C&L notifications

Used by:Trisodium citrate dihydrate · EDTA, citric acid and hydrochloric acid clearing sequence · Sodium citrate developer · Sodium citrate kallitype developer

PubChem compound summary: Sodium Cyanide (CID 8929)retrieved 2026-09-04, 2026-09-06

Sections: Physical description — CAMEO, Haz-Map, the ILO-WHO safety card and NIOSH; Solubility — CAMEO, HSDB, the ILO-WHO card and NIOSH; CAS; GHS classification — the aggregated ECHA C&L notifications, the NITE-CMC block and the Australian HCIS block; ChEBI description; GHS classification, aggregated from the ECHA C&L Inventory, as summarised on the course's sodium cyanide page

Used by:Sodium cyanide · Cyanide fixing and toning

PubChem compound summary: Sodium Hydroxide (CID 14798)retrieved 2026-09-04, 2026-09-06

Sections: Physical description; solubility; CAS; GHS classification; other experimental properties; uses; GHS classification aggregated from ECHA C&L notifications, corrosive, with only four of nearly seven thousand reports recording no hazard; and the physical description, corrosive to metals and tissue and toxic by ingestion; Physical description (EU Food Improvement Agents; CAMEO); GHS classification; GHS classification; CAMEO reactivity: dissolution in water is strongly exothermic

Used by:Sodium hydroxide (caustic soda) · EDTA and sodium sulfite clearing sequence · P2 Storage, Incompatibilities and Secondary Containment · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P3 Solutions, Solubility and Precipitation

PubChem compound summary: Sodium metaborate (CID 145326)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Physical description; solubility; CAS; GHS classification; methods of manufacturing; other experimental properties; uses; depositor-supplied synonyms; Other experimental properties (tetrahydrate and dihydrate data); methods of manufacturing; uses; depositor-supplied synonyms; Other experimental properties — the aqueous pH of the tetrahydrate against concentration, and its solubility; Other experimental properties, the entry marked /Sodium metaborate tetrahydrate/, giving the pH of aqueous solution at 20 degrees C as a function of weight per cent — 10.52 at 0.1%, 10.8 at 0.5%, 11.0 at 1.0%, 11.4 at 4.0%, 11.8 at 10.0% and 12.0 at 15.0% — and the entry for the tetrahydrate giving its solubility in water as 41.9% at 20 degrees C and its melting point as 53.5 degrees C; Other experimental properties: aqueous pH of the tetrahydrate against concentration at 20 degrees C; Other experimental properties: the aqueous pH of the tetrahydrate against concentration at 20 degrees C, from 10.52 at 0.1 per cent to 12.0 at 15 per cent

Used by:Sodium metaborate (anhydrous) · Sodium metaborate tetrahydrate (Kodalk) · PMK pyro · TF-2 alkaline fixer · P3 Acids, Bases and pH · P3 Buffers and Buffer Capacity

PubChem compound summary: Sodium metaborate tetrahydrate (CID 23694267)retrieved 2026-09-04, 2026-09-06

Sections: Computed properties; CAS; GHS classification; Computed properties; physical description; CAS; GHS classification; Computed properties; GHS classification; GHS classification; Other experimental properties — aqueous pH of the tetrahydrate against concentration at 20 degrees C

Used by:Sodium metaborate (anhydrous) · Sodium metaborate tetrahydrate (Kodalk) · Kodak F-6 · TF-2 alkaline fixer · P8 Alkalis, Buffers and pH

PubChem compound summary: Sodium Pyrosulfite (CID 656671)retrieved 2026-09-04, 2026-09-06

Sections: Physical description; solubility; CAS; GHS classification; depositor-supplied synonyms; GHS classification aggregated from ECHA C&L notifications — H302 harmful if swallowed at 98.9 per cent of reports and H318 causes serious eye damage at 99.5 per cent; and the physical description, a white crystalline solid with a slight sulphur odour, toxic by inhalation, which may decompose to emit oxides of sulphur on strong heating and is a corrosive acid when moist; Physical description (CAMEO; NIOSH); Molecular formula and weight; solubility

Used by:Sodium metabisulfite · EDTA and sodium sulfite clearing sequence · P2 Storage, Incompatibilities and Secondary Containment · P8 Sulfite: Preservative, Buffer, Silver Solvent

PubChem compound summary: Sodium Selenate (CID 25960)retrieved 2026-09-06

Sections: Names and Identifiers — Molecular Formula, Computed Properties, CAS and European Community (EC) Number, Depositor-Supplied Synonyms; Chemical and Physical Properties — Physical Description, Density, Melting Point, Solubility, Decomposition; Safety and Hazards — GHS Classification and Hazard Classes and Categories, aggregated from 133 reports across 21 notifications to the ECHA C&L Inventory, and separately the NITE-CMC classification of FY2016; Stability and Reactivity — Air and Water Reactions, Reactive Group, Reactivity Profile, Hazardous Reactivities and Incompatibilities; Fire Hazards; Uses and Use and Manufacturing; the ChEBI description. Read through the PUG and PUG-View APIs

Used by:Sodium selenate

PubChem compound summary: Sodium Selenite (CID 24934)retrieved 2026-09-04, 2026-09-06

Sections: Physical description — CAMEO, Haz-Map and the ILO-WHO safety card; Solubility — CAMEO, HSDB and the safety card; CAS; GHS classification — the aggregated ECHA C&L notifications; ChEBI description; Uses and Use and Manufacturing; CAS and identity; GHS classification aggregated from the ECHA C&L notifications; Uses and Use and Manufacturing; CAS and identity; GHS classification aggregated from the ECHA C&L notifications

Used by:Sodium selenite · HARMAN SELENIUM TONER · KODAK Rapid Selenium Toner

PubChem compound summary: Sodium selenosulfate (CID 11424269)retrieved 2026-09-04

Sections: Computed properties and molecular formula; CAS registry number; GHS classification — the single ECHA C&L notification under list number EC 803-438-8; the absence of any solubility or physical-description entry

Used by:Sodium selenosulfate

PubChem compound summary: Sodium Sulfate (CID 24436)retrieved 2026-09-04, 2026-09-05

Sections: Identity, computed properties and CAS; the aggregated ECHA C&L notifications and the NITE-CMC entry; solubility from HSDB and the ILO-WHO card; physical description; Identity, CAS 7757-82-6 and molecular weight 142.04; the aggregated ECHA C&L notifications, in which 4127 of 4277 company reports state that the substance meets no GHS hazard criterion; solubility, HSDB's soluble in about 3.6 parts of water with a maximum of 1 part in 2 at 33 degrees C; Computed properties; CAS; CAS; computed properties; GHS classification (ECHA notifications)

Used by:Sodium sulfate · Kodak SB-5 · P2 Storage, Incompatibilities and Secondary Containment · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels

PubChem compound summary: Sodium sulfide, hydrated, with not less than 30% water (CID 237873)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-08

Sections: Physical description — CAMEO Chemicals and EPA Chemical Data Reporting; CAS; GHS classification — the aggregated ECHA C&L notifications; computed molecular formula and weight; GHS classification aggregated from 24 notifications to the ECHA C and L Inventory — Danger, with H290, H301, H302, H311, H314, H318 and H400, H314 and H400 appearing in every report and H311 in 96.2 per cent; the record being for the hydrated material of commerce carrying not less than 30 per cent water; GHS classification aggregated from 1,100 reports across 24 ECHA C&L notifications — Danger, with H314 and H400 in every report, H311 in 96.2 per cent, H301 in 65.3 per cent and H318 in 62.9 per cent, and no notifier reporting that it meets no criteria; the CAMEO reactivity profile, which records that it is a deliquescent solid, that contact with acids liberates hydrogen sulfide, and that it may explode on rapid heating or shock; GHS classification aggregated from the ECHA Classification and Labelling Inventory notifications for disodium sulphide, EC 215-211-5 - signal word Danger with the corrosive, acute-toxicity, irritant and environmental pictograms, H314 causes severe skin burns and eye damage and H400 very toxic to aquatic life in 100 per cent of reports, H311 toxic in contact with skin in 96.2 per cent, H301 toxic if swallowed in 65.3 per cent and H290 may be corrosive to metals in 14.7 per cent; GHS classification; the release of hydrogen sulfide on contact with acid; GHS aggregation: H314 in every ECHA notification on record, with H311 and H301

Used by:Sodium sulfide · Kodak ST-1 · P12 Lab: Testing for Residual Thiosulfate and Residual Silver · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · Sulphide (sepia) toned silver gelatin print · Handling a sulphide toner and its waste

PubChem compound summary: Sodium Sulfite (CID 24437)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: GHS classification aggregated from 2,482 reports across 19 ECHA C&L notifications: Danger, GHS05 and GHS07, with H302, H314, H315 and H319; GHS classification aggregated from 2,482 reports across 19 ECHA C&L notifications: Danger, GHS05 and GHS07, with H302, H314, H315 and H319, and the note that 24.9 per cent of reports state the substance does not meet GHS hazard criteria at all; CAS and molecular weight, quoted only for the comparison between the two salts; Physical description; solubility; CAS; GHS classification; depositor-supplied synonyms; GHS classification; solubility; GHS classification aggregated from ECHA C&L notifications — H302 harmful if swallowed at 18.3 per cent of reports, H314 causes severe skin burns and eye damage at 51.8 per cent, H315 causes skin irritation at 19.3 per cent and H319 causes serious eye irritation at 21 per cent, with about a quarter of reports recording no GHS hazard at all; the physical description, a white odourless powder that sinks in water and dissolves slowly; and the solubility figures; Solubility: 22 g per 100 mL at 20 degrees C; GHS classification; Physical description; GHS classification; Computed properties; GHS classification; Computed properties; CAS; CAS; computed properties; GHS classification (ECHA notifications); Computed properties - molecular weight 126.05; HSDB properties of the heptahydrate; Computed properties - molecular formula and molecular weight; Computed properties - molecular weight; Solubility (HSDB): 30.7 g per 100 g of water at 25 degrees C, and the unstable heptahydrate; ILO-WHO card, 22 g per 100 mL at 20 degrees C; GHS classification aggregated from the ECHA C&L notifications; solubility; Solubility; GHS classification aggregated from the ECHA C&L notifications; Molecular formula and weight; solubility; Solubility; GHS classification aggregated from the ECHA C&L notifications and the proportions behind each statement; Molecular formula and weight; solubility; GHS classification aggregated from the ECHA C&L Inventory notifications; Computed molecular weight 126.04; GHS classification aggregated from the ECHA C&L Inventory notifications; GHS Classification - the aggregated ECHA C&L notifications giving signal word Danger with H302, H314, H315 and H319; GHS classification aggregated from 2,482 reports across 19 ECHA notifications — signal word Danger, pictograms GHS05 and GHS07, with H314 at 51.8 per cent of reports, H319 at 21, H315 at 19.3 and H302 at 18.3, and 618 of 2,482 reports stating that it does not meet GHS hazard criteria; GHS classification aggregated from the ECHA C&L Inventory; GHS aggregation: signal word Danger with H314 in about half of the reports; GHS aggregation: Danger with H314, and the incompatibility with acids

Used by:P29 Capstone Stage 2: Formulating and Documenting Your Chemistry · P29 Planning the Capstone: The Project Plan and Its Hazard Assessment · Sodium sulfate · Sodium sulfite · Dilute alkaline thiosulfate fixer for iron-silver prints · EDTA and sodium sulfite clearing sequence · Kodak F-5a · TF-2 alkaline fixer · P2 Storage, Incompatibilities and Secondary Containment · P2 Lab: Commissioning Your Laboratory · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P3 Aerial Oxidation: Why Chemistry Dies in a Half-Empty Bottle · P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P3 Buffers and Buffer Capacity · P3 Oxidation, Reduction and the Electron That Makes the Picture · P3 Solutions, Solubility and Precipitation · P8 Experiment: Watching a Developer Oxidise · P8 Lab: Mixing D-23 and D-76 from Raw Chemicals · P8 Solvent Action, Physical Development and Grain · P8 Sulfite: Preservative, Buffer, Silver Solvent · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P11 Lab: Mixing Fixers from Scratch · P18 Lab: Mixing and Comparing Print Developers · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P25 Lab: Exposing, Developing and Clearing a Palladium Print · Clearing an iron-silver print and testing it for residual iron · The student's project SOP · Weighing and handling developing agents

PubChem compound summary: Sodium tetraborate (CID 10219853)retrieved 2026-09-04, 2026-09-06

Sections: Computed properties — molecular formula and molecular weight; Computed properties — molecular formula and molecular weight of the anhydrous salt

Used by:Borax (sodium tetraborate decahydrate) · Borax kallitype developer

PubChem compound summary: Sodium thiocyanate (CID 516871)retrieved 2026-09-04

Sections: Identity, computed properties and CAS; GHS classification aggregated from two ECHA C&L entries, with the NITE-CMC and Safe Work Australia entries; physical description from CAMEO and Haz-Map

Used by:Sodium thiocyanate

PubChem compound summary: Sodium Thiosulfate (CID 24477)retrieved 2026-09-04, 2026-09-05

Sections: Physical description; solubility; CAS; GHS classification; computed molecular weight; Computed molecular weight, used only for the crystals-to-anhydrous conversion; Computed properties; CAS; CAS; computed properties; Computed properties - molecular formula and molecular weight; Computed properties - molecular weight of the anhydrous salt; Computed molecular weight 158.11; Computed properties - relative molecular mass 158.11; CAS 7772-98-7

Used by:Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve · P11 Lab: Mixing Fixers from Scratch · Hydrate substituted for an anhydrous salt at the same mass

PubChem compound summary: Sodium Thiosulfate Pentahydrate (CID 61475)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Computed molecular weight, used only for the anhydrous-to-crystals conversion; Physical description; CAS; GHS classification; computed molecular weight; GHS classification; physical description; solubility; GHS classification; Identity; CAS; Computed properties; CAS; CAS; computed properties; GHS classification (ECHA notifications); Computed properties - molecular formula and molecular weight; Computed properties - molecular weight 248.19 for the pentahydrate; Computed properties - connectivity SMILES showing a central sulfur bonded to a terminal sulfur; molecular weight; GHS Classification and Names and Identifiers: the ECHA C&L result reported as not meeting GHS hazard criteria, and the molecular weight of the pentahydrate; Computed molecular weight 248.19; Computed properties - relative molecular mass 248.19; CAS 10102-17-7

Used by:Sodium thiosulfate (anhydrous) · Sodium thiosulfate pentahydrate · Dilute alkaline thiosulfate fixer for iron-silver prints · TF-2 alkaline fixer · P1 Herschel: Hypo, Prussian Blue and the Words of Photography · P2 Concentration and Dilution: The Arithmetic Every Formula Assumes · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · P3 Atoms, Ions and Bonds: Reading a Photographic Formula · P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve · P3 Oxidation, Reduction and the Electron That Makes the Picture · P5 Project 3: A Bromide Enlarging Emulsion · P11 How Fixer Works · P11 Lab: Mixing Fixers from Scratch · Hydrate substituted for an anhydrous salt at the same mass

PubChem compound summary: Sulfamic acid (CID 5987)retrieved 2026-09-04, 2026-09-07

Sections: Names and Identifiers, and Safety and Hazards — GHS Classification, for the acid whose anion this salt carries; Computed properties and molecular formula; CAS; GHS classification — the entry under Regulation (EC) No 1272/2008, the aggregated ECHA C&L notifications, NITE-CMC and HCIS; Solubility (HSDB, ILO-WHO ICSC); Physical description (CAMEO, ICSC, Haz-Map); Physical description; GHS classification

Used by:Silver sulfamate · Sulfamic acid · Argentotype

PubChem compound summary: Sulfuric Acid (CID 1118)retrieved 2026-09-04

Sections: Physical description; solubility; CAS; GHS classification

Used by:Sulfuric acid

PubChem compound summary: Sulfuric acid, chromium(3+) potassium salt (2:1:1) (CID 61489)retrieved 2026-09-04, 2026-09-05

Sections: GHS classification — the aggregated ECHA notifications under Chromium potassium bis(sulphate), EC 233-401-6, and under Sulphuric acid, chromium potassium salt, EC 233-627-5; computed molecular weight of the anhydrous salt; GHS Classification, ECHA C&L Inventory EC 233-401-6: Warning, GHS07, H315, H319 and H335, with no sensitisation and no carcinogenicity statement notified; GHS Classification, ECHA C&L Inventory EC 233-401-6: signal word Warning, GHS07, H315, H319 and H335, with no sensitisation and no carcinogenicity statement notified; GHS Classification, ECHA C&L Inventory EC 233-401-6; GHS Classification, ECHA C&L Inventory EC 233-401-6: signal word Warning, GHS07, H315, H319 and H335, with no sensitisation or carcinogenicity statement notified; GHS classification — the ECHA C&L notifications under Chromium potassium bis(sulphate), EC 233-401-6, and under Sulphuric acid, chromium potassium salt, EC 233-627-5; GHS classification under two ECHA entries — Chromium potassium bis(sulphate), EC 233-401-6, and Sulphuric acid, chromium potassium salt, EC 233-627-5; GHS classification, ECHA notifications: signal word Warning, GHS07, H315, H319 and H335, with no sensitisation, carcinogenicity or mutagenicity statement notified

Used by:Chrome alum · Trumm's bromide paper emulsion · Wall's soft-working gaslight paper · Kodak SB-4 · Chrome alum subbing dip · P5 Project 3: A Bromide Enlarging Emulsion · P5 Project 2: A Chlorobromide Paper Emulsion · P5 Coating, Drying and Hardening · P5 Project 4: Coating Glass Dry Plates and a Lantern Slide · P5 Gelatin, the Photographic Binder · The chromium policy · Reading GHS and CLP · Routing chromium(III) from the coating station

PubChem compound summary: Tannic acid (CID 16129778)retrieved 2026-09-04, 2026-09-06

Sections: CAS; molecular formula and weight; IUPAC name; ChEBI description; physical description (USCG, HSDB); solubility (HSDB); GHS classification — the aggregated ECHA C&L notifications under EC 226-562-9; GHS classification - the aggregated ECHA C&L notifications under EC 226-562-9; physical description; solubility; Physical description; GHS classification

Used by:Tannic acid · P21 Lab: Toning the Prussian Blue Image · Toned cyanotype

PubChem compound summary: Tetrachloroauric acid (CID 122706823)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Computed properties and molecular formula; CAS; GHS classification — the aggregated ECHA C&L notifications and the NITE-CMC entry; Physical description — Haz-Map; The aggregated ECHA classification behind the encyclopaedia's Level B entry, with H314 in every report, and the compound record for tetrachloroauric acid, CID 122706823; Identity, deliquescence, and the GHS Classification section: signal word Danger with GHS05, GHS07, GHS08 and GHS09; GHS Classification, ECHA C&L Inventory: signal word Danger with GHS05, GHS07, GHS08 and GHS09; Identity as tetrachloroauric acid, CID 122706823, molecular formula AuCl4H and molecular weight 339.8, with the ECHA C&L aggregation giving GHS05, GHS07, GHS08 and GHS09 under the signal word Danger and including H290 and H314; Physical description; GHS classification

Used by:Chloroauric acid · Fizeau's gilding solution · Steigmann gold sensitiser stock · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P5 Washing, Digestion and Sensitisation · P22 Gold Toning and the Permanence of a Printed-Out Silver Image · Chrysotype · Gold toned silver gelatin print · Gold-toned and palladium-toned kallitype

PubChem compound summary: Thallium(I) sulfate (CID 24833)retrieved 2026-09-06, 2026-09-07

Sections: Names and Identifiers — Molecular Formula, Computed Descriptors, CAS, Related CAS, Deprecated CAS, European Community (EC) Number, UN Number, ICSC Number and Depositor-Supplied Synonyms; Chemical and Physical Properties — Computed Properties and Experimental Properties (Physical Description, Color/Form, Odor, Boiling Point, Melting Point, Solubility, Density, Vapor Pressure, Stability/Shelf Life, Corrosivity, Other Experimental Properties) from CAMEO, HSDB and the ILO-WHO safety card; Safety and Hazards — GHS Classification, all six blocks, and Hazard Classes and Categories; Health Hazards, Fire Hazards, Chemical Dangers, OSHA Standards, Disposal Methods, EPA Hazardous Waste Number, RCRA Requirements, CERCLA Reportable Quantities and Federal Drinking Water Standards; Exposure Control — Permissible Exposure Limit, Threshold Limit Values, Immediately Dangerous to Life or Health, Inhalation Risk and Personal Protective Equipment; Stability and Reactivity — Reactive Group and Reactivity Profile; Toxicity — Evidence for Carcinogenicity, Exposure Routes, Signs and Symptoms, Non-Human Toxicity Values, Human Toxicity Excerpts, Ecotoxicity Values and Environmental Fate; Use and Manufacturing — Uses, Methods of Manufacturing and General Manufacturing Information; GHS classification, the harmonised block for dithallium sulphate and the notified aggregate over it; the stability of the salt; solubility, and the anions that precipitate thallium(I) from solution; the record of the rodenticide's withdrawal and the restrictions that followed; and the exposure limits and target organs, as summarised on the course's thallium(I) sulfate page; The harmonised CLP classification for dithallium sulphate under Regulation (EC) No 1272/2008; The harmonised CLP classification for dithallium sulphate under Regulation (EC) No 1272/2008 — Danger with H300, H315, H372 and H411, Acute Tox. 2 carrying an asterisk that marks it a minimum classification, as summarised with its sources on the course's thallium(I) sulfate page

Used by:Thallium(I) sulfate · Lead, thallium and nickel cyanotype toners · P25 The Additives We Study and Do Not Reproduce · P26 Uranium, Mercury and the Heavy-Metal Treatments

PubChem compound summary: Thiourea (CID 2723790)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: GHS classification under Regulation (EC) No 1272/2008 for thiourea, EC 200-543-5 — signal word Warning with H302, H351 suspected of causing cancer, H361d suspected of damaging the unborn child, and H411; Physical description; solubility; CAS; GHS classification — the harmonised CLP entry, the aggregated ECHA notifications, NITE-CMC and HSDB; ChEBI description; GHS classification and identity, as summarised on the course's thiourea page; CAS and identity; the harmonised CLP classification under Regulation (EC) No 1272/2008 and the aggregated ECHA notifications; GHS classification under Regulation (EC) No 1272/2008 for thiourea, thiocarbamide, CAS 62-56-6, EC 200-543-5 - signal word Warning with the irritant, health-hazard and environmental pictograms, H302 harmful if swallowed, H351 suspected of causing cancer, H361d suspected of damaging the unborn child and H411 toxic to aquatic life with long lasting effects; GHS classification under Regulation (EC) No 1272/2008 for thiourea, thiocarbamide, EC 200-543-5 - signal word Warning with the irritant, health-hazard and environmental pictograms, H302 harmful if swallowed, H351 suspected of causing cancer, H361d suspected of damaging the unborn child and H411 toxic to aquatic life with long lasting effects; and the California OEHHA description that thiourea can cause cancer according to an independent committee of scientific and health experts; GHS classification - the harmonised entry under Regulation (EC) No 1272/2008 giving Warning with GHS07, GHS08 and GHS09 and the statements H302, H351 suspected of causing cancer, H361d suspected of damaging the unborn child, and H411, as summarised with its sources on the course's thiourea page; GHS classification from Regulation (EC) No 1272/2008 and the ECHA C&L aggregation - GHS07, GHS08 and GHS09 with H302, H351 suspected of causing cancer, H361 or H361d for reproductive toxicity, and H411 toxic to aquatic life with long lasting effects; GHS classification

Used by:P29 Capstone Stage 5: The Toned Print and the Alternative-Process Print · Thiourea · Kodak T-26 · Moersch MT3 Variotoner · P20 Lab: Bleaching and Redeveloping a Sepia Print · P20 Sulfide and Sepia Toning: Bleach, Redevelop, Convert · P20 The Toners We Study and Do Not Use · P22 Gold Toning and the Permanence of a Printed-Out Silver Image · Gold toned silver gelatin print

PubChem compound summary: Thymol (CID 6989)retrieved 2026-09-04, 2026-09-06

Sections: CAS; molecular formula and weight; IUPAC name; ChEBI description; physical description (HSDB, MSDSonline, JECFA); solubility (HSDB, HMDB, JECFA); GHS classification — the harmonised entry under Regulation (EC) No 1272/2008, the aggregated ECHA C&L notifications, the NITE-CMC entries, Safe Work Australia's HCIS and HSDB; GHS classification — signal word Danger, with H302 harmful if swallowed, H314 causes severe skin burns and eye damage and H411 toxic to aquatic life with long lasting effects among the aggregated statements

Used by:Thymol · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype

PubChem compound summary: Titanium dioxide (CID 26042)retrieved 2026-09-04

Sections: CAS registry numbers; molecular formula and weight; physical description (NTP via CAMEO, ILO-WHO ICSC, NIOSH, Merck Index); solubility (HSDB, EU Food Improvement Agents, ICSC, NIOSH); GHS classification — the harmonised entry under Regulation (EC) No 1272/2008 and the separate aggregated ECHA C&L notifications for titanium dioxide, rutile, anatase and titanium oxide, with the NITE-CMC entries; Physical description; solubility; harmonised classification for the powder form

Used by:Titanium dioxide · Silver gelatin developing-out print on resin-coated base

PubChem compound summary: Triammonium citrate (CID 18954)retrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Identity, CAS, molecular weight and GHS classification, cited only where the tribasic salt is the subject; Names and Identifiers, for the CAS registry number, the EC number, the ChEBI description and the deprecated CAS numbers; Depositor-Supplied Synonyms, for the trade spellings and the E and INS numbers; Computed Properties, for the molecular formula and molecular weight; Experimental Properties, for the physical description and the water solubility; Chemical Classes; Food Additive Classes and Use and Manufacturing, for the JECFA functional class; GHS Classification and Hazard Classes and Categories, aggregated from 278 reports across 16 notifications to the ECHA C&L Inventory; Identity, CAS 3458-72-8, molar mass 243.22 and EC 222-394-5, cited only to separate the two salts; Names and Identifiers, for the CAS and EC numbers, the molecular formula and the ChEBI description; Computed Properties, for the molecular weight; Experimental Properties, for the physical description and the water solubility; GHS Classification and Hazard Classes and Categories, aggregated from 278 reports across 16 notifications to the ECHA C&L Inventory

Used by:Ammonium citrate (dibasic) · Ammonium citrate (tribasic) · Ammonium citrate developer · Mike's Cyanotype

PubChem compound summary: Triethanolamine (CID 7618)retrieved 2026-09-05

Sections: CAS, molecular formula and weight, IUPAC name; Experimental Properties — physical description, melting point, boiling point, density, vapour pressure, solubility, pH and dissociation constants; GHS Classification and Hazard Classes and Categories; Skin, Eye, and Respiratory Irritations; IARC Classification; the Cosmetic Ingredient Review conclusion and the N-nitrosodiethanolamine literature

Used by:510-Pyro

PubChem compound summary: Tripotassium citrate (anhydrous, CID 13344)retrieved 2026-09-05

Sections: Identity, CAS and molecular weight for the anhydrous grade; the two ECHA C&L records with their notification counts and the proportion of companies that provided information; solubility from HSDB; the physical description from the EU food-additive specification

Used by:Potassium citrate

PubChem compound summary: Trisodium citrate (CID 6224)retrieved 2026-09-04, 2026-09-06

Sections: Identity, CAS and molecular weight for the anhydrous grade; the second ECHA entry filed as "Citric acid, sodium salt", which does carry a hazard statement; the HSDB entry giving the pH of the dihydrate solution; Molecular weight and CAS of the anhydrous grade; the second ECHA entry filed as "Citric acid, sodium salt", which does carry a hazard statement; the HSDB entry giving the pH of a solution of the dihydrate as about 8; Molecular weight and CAS of the anhydrous grade; the second ECHA entry filed as "Citric acid, sodium salt", which does carry a hazard statement; the HSDB entry giving the pH of the dihydrate solution

Used by:Trisodium citrate dihydrate · Sodium citrate developer · Sodium citrate kallitype developer

PubChem compound summary: Uranyl nitrate hexahydrate (CID 61640)retrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Physical description — Haz-Map quoting CAMEO; CAS; molecular formula and weight; GHS classification — the aggregated ECHA C&L notifications; GHS classification, aggregated from the ECHA C&L Inventory, and the second classification block from the Japanese NITE-CMC scheme, as summarised on the course's uranyl nitrate page; GHS classification, aggregated from the ECHA C&L Inventory across 39 reports and 2 notifications, and the second classification block from the Japanese NITE-CMC scheme, as summarised on the course's uranyl nitrate page; GHS classification aggregated from the ECHA C&L Inventory and the NITE-CMC block; GHS classification, aggregated from the ECHA C&L Inventory — H300 and H330 in 100 per cent of 39 reports across 2 notifications, with H272 as an oxidiser; and the second classification block from the Japanese NITE-CMC scheme, adding suspected genetic defects and possible carcinogenicity; GHS classification — signal word Danger with H272, H300, H330, H373 and H411, aggregated from 39 reports across 2 notifications, with a separate NITE-CMC block adding suspected genetic defects and possible carcinogenicity, as summarised with its sources on the course's uranyl nitrate hexahydrate page; Physical description; CAS; GHS classification; GHS classification, aggregated from 39 reports across 2 ECHA C&L notifications; GHS classification, aggregated from the ECHA C&L Inventory, and the second classification block from the Japanese NITE-CMC scheme

Used by:Uranyl nitrate hexahydrate · Kodak IN-21 · Uranium toner · P25 The Additives We Study and Do Not Reproduce · P26 Part XXVI Overview: What Level D Means and Why These Pages Have No Procedure · P26 Uranium, Mercury and the Heavy-Metal Treatments · Uranium toned print · Uranotype and Wothlytype · Reading GHS and CLP · The Level D policy

PubChem GHS Classification: pictograms, signal words, hazard and precautionary statementsretrieved 2026-09-04, 2026-09-05

Sections: Precautionary statements P305+P351+P338, P305+P354+P338, P302+P352, P264; Hazard class pictograms; GHS hazard statements; precautionary statements (GHS Rev. 11, 2025); Precautionary statements — P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P354+P338, P305+P351+P338, P316, P317, P321, P342+P316, P362+P364, and the codes marked obsolete in Rev. 11; GHS Classification (Rev. 11, 2025) Summary — Hazard Class Pictograms; GHS Hazard Statements, with their hazard class, category, signal word and assigned precautionary statements; Precautionary Statements, including the codes marked obsolete in Rev. 11; Precautionary statements P305+P351+P338 and P305+P354+P338, and P337+P317

Used by:P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P2 Reading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels · First aid quick reference · Reading GHS and CLP · Checking and using the eyewash · Recording a safety data sheet

puresilver.runbook.academy

Pure Silver — Chemistry selector method and evidence

Used by:Chemistry selector · Formula designer

Pure Silver — Dilution and concentration method and evidence

Used by:Dilution and concentration

Pure Silver — Exposure log method and evidence

Used by:Exposure log

Pure Silver — Laboratory notebook and formula versions method and evidence

Used by:Laboratory notebook and formula versions

Pure Silver — Pinhole and exposure method and evidence

Used by:Pinhole and exposure

Pure Silver — Sensitometry workbench method and evidence

Used by:Sensitometry workbench

Pure Silver — Student inventory method and evidence

Used by:Student inventory

Pure Silver — Tone-reproduction laboratory method and evidence

Used by:Tone-reproduction laboratory

src/data/prices.json, entry silver-nitrateretrieved 2026-09-07

Sections: Two UK listings checked on 5 September 2026 - Parallax Photographic Coop, Silver Nitrate 25 g at 59.95 pounds and shown out of stock, and Firstcall Photographic, Bellini Silver Nitrate 10 g at 112.90 pounds and shown in stock - together with the file's own note that the two work out at 2.40 and 11.29 pounds per gram and that the difference cannot be explained from the listings alone; Sodium sulfite anhydrous at 13.68 to 19.98 pounds per kilogram, sodium carbonate anhydrous at 7.20 pounds per 500 g, borax decahydrate at 9.98 pounds per 200 g, nitrile gloves at 6.64 to 14.99 pounds a box and silver nitrate at 59.95 pounds per 25 g to 112.90 per 10 g, all checked 5 September 2026; sodium thiosulfate pentahydrate as a raw salt at 14.70 pounds per kilogram, checked 7 September 2026; and the file's own named gaps for gold chloride and for hot-press cotton watercolour paper; Silver nitrate at 59.95 pounds for 25 g and 112.90 pounds for 10 g, photographic gelatin at 17.45 pounds for 100 g and nitrile gloves at 6.64 to 14.99 pounds a box of 50 to 100, all checked 5 September 2026; citric acid monohydrate at 10.00 pounds for 250 g, checked 7 September 2026; and the file's own named gaps for hot-press cotton watercolour paper and for kaolin

Used by:P22 Part XXII Overview: The First Silver Print · P22 Lab: Printing, Toning, Fixing and Washing a Salt Print · P22 Lab: Salting and Sensitising a Sheet of Paper · Consumables calculator

pyrostains.blogspot.com

510-Pyro (the formulator's own weblog)retrieved 2026-09-05

Sections: The sidebar headed "510-Pyro Formula", carried on every page of the blog; the December 2006 archive — "Pyromaniacs unite!", "Developing Kodak Technical Pan film" with its concentrate arithmetic and its two agitation regimes, "Printing stained negatives with VC papers", and the development data posted for Frederic Harster; the October 2007 essay "Staining and tanning"; the 2010 posts "Pyro for Pushers!", "Jim Byers on Stand Development", "Love on the Rocks...." and "Arctic Pyro"

Used by:510-Pyro

reading.ac.uk

Safety Code of Practice 22: Control of exposure to ultraviolet radiation, 2nd editionretrieved 2026-09-04

Sections: Section 15: Personal protective equipment

Used by:P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong

research.usu.edu

Chemical Resistance Guide: Permeation and Degradation Data, 8th editionretrieved 2026-09-04, 2026-09-05

Sections: Permeation and degradation table, entry 66, Formaldehyde 37% in 1/3 Methanol/Water; Specific Gloves Used for Testing; Permeation and degradation table, entry 71, Glutaraldehyde 25%; Specific Gloves Used for Testing; Definition of key terms; permeation testing methodology; permeation and degradation tables; Nitrile (Sol-Vex 37-165) column; the guide's own statement that its figures are advisory and that suitability must be determined by the purchaser; Introduction to the 8th edition, and the statement that the recommendations are advisory and that suitability must be determined by testing by the purchaser; Definition of Key Terms — permeation, penetration, degradation, breakthrough time and permeation rate; Specific Gloves Used for Testing, for the model and thickness of each column; Key to Degradation Ratings; the permeation and degradation tables; Permeation and degradation table, sodium hydroxide 50 per cent and potassium hydroxide 50 per cent against unsupported nitrile, neoprene and natural rubber

Used by:Formaldehyde · Glutaraldehyde · P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P4 Experiment: Precipitating the Silver Halides · Glove selection · Responding to an alkali spill

rest.uniprot.org

UniProtKB entry P01012 (OVAL_CHICK): Ovalbumin, Gallus gallusretrieved 2026-09-07

Sections: The reviewed entry OVAL_CHICK, version 210 of 2 September 2026 — sequence length 386 amino acids, molecular mass 42,881 Da, gene SERPINB14, family "Belongs to the serpin family. Ov-serpin subfamily"; the single annotated FT DISULFID feature 74..121; the SQ block, from which the course counted six cysteine and seventeen methionine residues. Also the neighbouring reviewed entry TRFE_CHICK (P02789), whose RecName is Ovotransferrin and whose AltName list carries Conalbumin, which is the authority for the synonym used in the older literature

Used by:P23 Egg Albumen: A Protein Binder and What It Does to Silver

rhdesigns.co.uk

RH Designs Timer 3 instructionsretrieved 2026-09-05

Sections: Package contents - the Timer 3, a mains lead fitted with a plug and one IEC connector; and the description of the foot switch as having precisely the same effect as pressing the Control Dial, except setting exposure

Used by:P17 Switching Lamps Safely: Isolation, Certified Modules and the Mains Boundary

StopClock Professional and StopClock Vario instructions, issue 7retrieved 2026-09-05

Sections: Package contents and installation - the timer, a mains lead fitted with a plug and two IEC connectors; StopClock functions as a mains switch and can control loads of up to 750 W; the optional foot switch exactly replicates the operation of the Start/Stop key; Package contents - the timer, a mains lead fitted with a plug and two IEC connectors; StopClock functions as a mains switch and can control loads of up to 750 W; this appliance must be earthed; do not attempt to open the unit or to remove any covers; the optional foot switch exactly replicates the operation of the Start/Stop key; Package contents; the statements that StopClock functions as a mains switch and can control loads of up to 750 W, with most enlargers at 100 to 250 W; the warning that the appliance must be earthed, the 5 A plug fuse and internal T4A; the instruction not to open the unit or remove any covers; and the description of the optional foot switch as exactly replicating the operation of the Start/Stop key

Used by:P17 Part XVII Overview: Build the Pure Silver Timer · P17 Build: The Switched Output · P17 Switching Lamps Safely: Isolation, Certified Modules and the Mains Boundary

rightsstatements.org

Rights Statementsretrieved 2026-09-06

Sections: The twelve standardised rights statements in their three groups - In Copyright, No Copyright and the undetermined statements - published as linked data at stable URIs for cultural heritage institutions to communicate a reuse position to people and to machines

Used by:P26 Assignment: Assessing a Historical Process for Hazard

rit.edu

A Consumer Guide to Framing Photographsretrieved 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: How to Select the Right Mat Board, Window Mats, and Backing Paper, which states that one of the best indicators of quality is that the board meets ISO 18902, and that none of the standard's requirements on its own implies sufficient preservation quality; How to Select the Right Mat Board, Window Mats, and Backing Paper — that one of the best indicators of quality is that the board meets ISO 18902, that in addition to passing the Photographic Activity Test the standard requires all paper and paperboard materials to have a pH between 7.0 and 9.5, to be buffered with at least 2 per cent calcium carbonate and to be lignin-free, and that none of those requirements on its own implies sufficient preservation quality; How to Select the Right Mounting Method, that heat mounting, spray-adhesive mounting and pressure-sensitive tapes are not recommended for preservation framing because they are not easily removable and that it is best to select a method that can be undone; and the account of oxidation reactions from poor framing materials in which faded silver migrates to the surface and is converted back into metallic silver, forming a mirror-like sheen; The account of oxidation reactions from poor framing materials, in which faded silver migrates to the surface of the print and is converted back into metallic silver by other pollutants, forming a mirror-like sheen; How to Select the Right Mat Board, which states that a board meeting ISO 18902 must have a pH between 7.0 and 9.5, be buffered with at least 2 per cent calcium carbonate and be lignin-free, and that none of those requirements on its own implies sufficient preservation quality; and How to Select the Right Mounting Method, which states that heat mounting, spray adhesive and pressure-sensitive tapes are not recommended for preservation framing because they are not easily removable; The mechanism given for silver mirroring inside a frame — the reactions caused by poor framing materials, like those from air pollution, are often oxidation reactions that result in image fading, and the faded silver can migrate to the surface of the print and be converted back into metallic silver by other pollutants, forming a mirror-like sheen; the worked example of a print whose edges mirrored under a poor-quality mat while the uncovered oval stayed clear; lignin as a cause of fading, mirroring and severe yellowing; How to Select the Right Materials — the advice to look for the printed claim that a material meets ISO 18902 rather than buying the standard, ISO 18902's recommendation of glazing that blocks at least 97 per cent of ultraviolet energy, and the warning that acid-free, archival, museum-quality and conservation board are marketing terms that are neither standardised nor legal; How to Select the Right Mat Board, Window Mats, and Backing Paper - ISO 18902 requires paper and paperboard to have a pH between 7.0 and 9.5, to be buffered with at least 2 per cent calcium carbonate and to be lignin-free; and How to Select the Right Mounting Method for Your Photograph, which states that heat mounting, spray-adhesive mounting and pressure-sensitive tapes are not recommended for preservation framing because they are not easily removable, and names photo corners of inert polyester and hinges of Japanese tissue with starch adhesive as the reversible methods; How to Select the Right Mat Board, Window Mats, and Backing Paper, for the statement that acid-free, archival, museum-quality and conservation board are marketing terms that are neither standardised nor legal, and that the printed claim to meet ISO 18902 is what to look for instead; ANATOMY OF A FRAME PACKAGE - the frame, the glazing, the window mat or spacer whose main purpose is to hold the glazing away from the surface of the photo, the mat board to which the photograph is attached, the filler board behind it which must also be nonreactive because a poor-quality board might give off harmful pollutant gases, and the back paper which keeps dust and insects out, reduces humidity fluctuations and limits infiltration of airborne pollutants; Labeling - useful data for a label on the back and the instruction to use a pencil or a waterproof, fade-resistant pigment ink pen when labelling by hand and a laser printer when printing labels, because many inkjet inks are sensitive to fading or abrasion; Damage by moisture - blocking, the adhesion of the glazing to the surface of a photo when the top layer softens at high humidity, which is often impossible to reverse without destroying the print, and which is why a window mat or spacers are used; How to Select the Right Materials - the warning that acid-free, archival, museum-quality and conservation board are marketing terms that are neither standardised nor legal, and the advice to look for the printed claim that a material meets ISO 18902; How to Select the Right Mounting Method for Your Photograph - the statement that heat mounting, spray-adhesive mounting and pressure-sensitive tapes are not recommended for preservation framing because they are not easily removable, that it is best to select a method that can be undone, that photo corners work well with photos that are sturdy and should be made from an inert plastic such as polyester or a high-quality paper with acid- and rubber-free adhesives, and that hinges made from Japanese tissue and starch adhesive work best for fragile photos; How to Select the Right Mat Board - pH between 7.0 and 9.5, buffering with at least 2 per cent calcium carbonate, and lignin-free; How to Select the Right Glazing - ISO 18902's recommendation of glazing that blocks at least 97 per cent of UV energy; and RECOMMENDATIONS FOR DISPLAY, including the rotation of prints on and off display; How to Select the Right Mat Board, Window Mats, and Backing Paper, which states that one of the best indicators of quality is that the board meets ISO 18902, that in addition to passing the Photographic Activity Test the standard requires all paper and paperboard materials to have a pH between 7.0 and 9.5, to be buffered with at least 2 per cent calcium carbonate and to be lignin-free, and that none of those requirements on its own implies sufficient preservation quality since some acid-free products may still fade or yellow a photo; and How to Select the Right Mounting Method for Your Photograph, which states that heat mounting, spray-adhesive mounting and pressure-sensitive tapes are not recommended for preservation framing because they are not easily removable and that it is best to select a method that can be undone; How to Select the Right Materials - the advice to look on the package for the statement that a material meets ISO 18902 rather than buying the standard; that some materials say only that they pass ISO 18916 or pass PAT, which is an excellent test and usually a good indicator but less than meeting ISO 18902; the statement that there are many other terms used to suggest that a product is of a certain quality which are not standardized or legal terms but simply marketing terms, such as acid-free, archival, museum-quality or conservation board; and the mat board requirements of ISO 18902, a pH between 7.0 and 9.5, buffering with at least 2 per cent calcium carbonate and lignin-free, with the warning that none of these requirements on its own implies sufficient preservation quality and that some acid-free products may still fade or yellow a photo; and How to Select the Right Glazing, that ISO 18902 recommends glazing that blocks at least 97 per cent of ultraviolet energy and also requires the glazing to pass the photographic activity test; Silver image deterioration in a frame - that the reactions caused by poor framing materials, like those from air pollution, are often oxidation reactions resulting in image fading, and that the faded silver can migrate to the surface and be converted back into metallic silver by other pollutants, forming a mirror-like sheen; The frame package: glazing, air gap, window mat, hinges, mat board, filler board and back paper; heat mounting, spray adhesives and pressure-sensitive tapes not recommended for preservation framing; Framing materials and image deterioration - the reactions caused by poor framing materials, like those from air pollution, often being oxidation reactions resulting in image fading, with the faded silver able to migrate to the surface and be converted back into metallic silver by other pollutants, forming a mirror-like sheen; the worked example of a print whose edges mirrored under a poor-quality mat while the uncovered oval stayed clear; The mechanism of silver image deterioration inside a frame - oxidation reactions from poor framing materials and air pollution causing image fading, with faded silver able to migrate to the surface and be converted back to metallic silver by other pollutants; Silver image deterioration in a frame - the reactions caused by poor framing materials, like those from air pollution, often being oxidation reactions that result in image fading, with the faded silver able to migrate to the surface and be converted back into metallic silver by other pollutants, forming a mirror-like sheen; The mechanism given for silver mirroring inside a frame - the reactions caused by poor framing materials, like those from air pollution, are often oxidation reactions that result in image fading, and the faded silver can migrate to the surface of the print and be converted back into metallic silver by other pollutants, forming a mirror-like sheen; the worked example of a print whose edges mirrored under a poor-quality mat while the uncovered oval stayed clear

Used by:P29 Capstone Overview: What the Pure Silver Portfolio Asks · P29 Capstone Stage 6: Permanence, Presentation and the Finished Portfolio · P29 The Capstone Chemistry Report: From Photon Capture to Finished Print · P29 The Pure Silver Portfolio: The Specification · P12 Permanence and Image Deterioration · P19 Part XIX Overview: Fine Printing · P19 Assignment: The Exhibition Print and Its Critique · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Assignment: The Toned Print · P20 Toning, Permanence and What the Evidence Actually Supports · P22 Break/Fix: The Printed-Out Image That Faded · Mounting a print and putting it in an enclosure · Edge fading from mount and adhesive · The iron-silver print that faded within weeks · Silver mirroring and sulfiding in an untoned printed-out print · Silver mirroring

IPI Media Storage Quick Reference, 2nd editionretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: The storage recommendations for photographic prints and negatives and the glossary definition of silver mirroring as oxidation of black-and-white images in which the image silver migrates to the surface, creating a mirror-like appearance; and the statement that enclosures cannot overcome deficiencies in the storage climate and that improving the climate is more effective overall; Glossary — silver mirroring defined as oxidation of black-and-white images in which the image silver migrates to the surface, creating a mirror-like appearance; microspots as small coloured spots, usually red or orange, caused by localised oxidation of black-and-white images; silver image decay as the defect that may be manifested as microspots, silver mirroring or overall image discoloration; life expectancy (LE) as a rating for the expected longevity of recording materials; PAT as the photographic activity test, which evaluates chemical or photographic interactions between enclosure materials and photographic images, there attributed to ISO 14523; Enclosures — enclosures cannot overcome deficiencies in the storage climate and improving the climate is more effective overall; the reference list, which gives ISO 18916 (2007), ISO 18902 (2001), ISO 18911 (2000), ISO 18918 (2000) and ISO 18920 (2000) with their full titles; Enclosures - the statement that enclosures cannot overcome deficiencies in the storage climate and that improving the climate is more effective overall, since environmental improvements simultaneously reduce the risks associated with harmful enclosures, airborne pollutants and the inherent instability of the collection materials themselves; Key Points from the ISO Standards - all product components should pass the photographic activity test, plastics should be polyester, polypropylene or polyethylene and not PVC or acetate, and papers and paperboards should be neutral-sized, lignin-free and buffered; and the numbered reference list from which the course takes the full titles and years of ISO 18916 (2007) and ISO 18902 (2001); Enclosures - the statement that enclosures cannot overcome deficiencies in the storage climate, that some products advertise additional protection from airborne pollutants and/or excessive humidity although standards to evaluate their effectiveness are lacking, and that while providing more inert enclosures is desirable, improving the climate is more effective overall; and the Glossary definitions of silver mirroring as oxidation of black-and-white images in which the image silver migrates to the surface creating a mirror-like appearance, of microspots as small coloured spots usually red or orange caused by localised oxidation, and of silver image decay as the defect that may be manifested as microspots, silver mirroring or overall image discoloration; Glossary, for silver mirroring defined as an oxidation of black-and-white images in which the image silver migrates to the surface creating a mirror-like appearance, and for silver image decay manifesting as microspots, silver mirroring or overall image discoloration; The four temperature categories and the statement that "for all four environments, RH should be kept between 30% and 50%"; the guide's own account of decay rate as depending primarily on temperature and relative humidity. The document was searched for an albumen-specific recommendation and carries none: its media list does not separate nineteenth-century printing-out papers from photographic paper prints in general; Polyester Base Photographic Film, black-and-white - silver image decay named as the decay related to temperature and humidity, with harmful enclosures and poor air quality as the other concerns, an ISO recommendation of 21 degrees C and 50 per cent relative humidity as maxima, and a simplified recommendation of cool storage at 50 per cent maximum to minimise the possibility of silver image decay; Acetate-Base Photographic Film, black-and-white, whose ISO recommendation instead depends on humidity and gives 2 degrees C at 50 per cent, 5 degrees C at 40 per cent and 7 degrees C at 30 per cent, with acetate decay added to the preservation issues; and the glossary definition of silver image decay as a defect manifested as microspots, silver mirroring or overall image discoloration; Glossary — silver mirroring defined as oxidation of black-and-white images in which the image silver migrates to the surface, creating a mirror-like appearance; and silver image decay as the defect that may be manifested as microspots, silver mirroring or overall image discoloration; Glossary — silver mirroring defined as oxidation of black-and-white images in which the image silver migrates to the surface, creating a mirror-like appearance, and silver image decay as the defect that may be manifested as microspots, silver mirroring or overall image discoloration; Glossary — silver mirroring, microspots and silver image decay; Enclosures — enclosures cannot overcome deficiencies in the storage climate; The role of temperature, relative humidity and air quality in the physical survival of photographs, and the identification of mechanical damage as a distinct decay pathway from chemical decay; Glossary - silver mirroring defined as an oxidation of black-and-white images in which the image silver migrates to the surface, creating a mirror-like appearance; silver image decay manifested as microspots, silver mirroring or overall image discoloration; Storage recommendations for photographic materials - the effect of temperature and relative humidity on the rate of deterioration; Glossary - silver mirroring defined as oxidation of black-and-white images in which the image silver migrates to the surface, creating a mirror-like appearance; silver image decay as the defect that may be manifested as microspots, silver mirroring or overall image discoloration

Used by:P29 Capstone Stage 6: Permanence, Presentation and the Finished Portfolio · P12 Permanence and Image Deterioration · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Toning, Permanence and What the Evidence Actually Supports · P22 Break/Fix: The Printed-Out Image That Faded · P23 The Albumen Print as an Object, and How It Decays · P27 Experiment: Four Curve Families, Measured · P28 Fixer Faults, Washing Faults and the Stains They Leave · P28 Print Faults: Weak Blacks, Mottle, Bronzing and the Rest · Silver gelatin developing-out print on fibre base · Cracked emulsion from flattening a bone-dry fibre print · Silver mirroring and sulfiding in an untoned printed-out print · Paper storage fog · Silver mirroring

IPI Storage Guide for Acetate Filmretrieved 2026-09-05, 2026-09-06

Sections: Storage Enclosures for Film Collections — the requirement that an enclosure meet ANSI Standard IT9.2-1991 and pass the ANSI Photographic Activity Test, ANSI Standard IT9.16-1993, which guarantees that the enclosure will not chemically interact with the film to cause staining or fading; the reference list, which names the 1991 Journal of Imaging Technology paper on a hydrogen peroxide test to evaluate redox blemish formation on processed microfilm; What Do the Predictions Predict - that the Guide does not predict the life span of individual pieces of film or specific collections, that the predictions are based on extrapolations from accelerated aging and should be seen as a convenient way to quantify and express how good or bad a storage environment is rather than as literal predictions of how long a collection will last, that for the numbers to be taken as literal predictions the collection would have to reproduce exactly the circumstances under which the aging experiments were done, and that each individual film has a unique history; and the analogy that the data describe major trends but do not predict the specific behaviour of individual samples, in the way an actuarial table does not say when any given person will die

Used by:P12 Permanence and Image Deterioration · P20 Toning, Permanence and What the Evidence Actually Supports

Photo Storage, Display, & Labeling Materials: A Guide to ISO 18902 'Photo-Safe' Testingretrieved 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: The account of ISO 18916, the Photographic Activity Test, and of the additional requirements of ISO 18902 — the alkali reserve of at least 2 per cent calcium carbonate, the lignin limit expressed as a Kappa number of 7 or below, and the colorant-bleed test; the statement that a material passing only the pH requirements or only the PAT is not necessarily photo-safe; and the statement that photo-safe refers only to the chemical reactivity of a material and says nothing about abrasion, creases or tears; The reactant and damage table, which pairs oxidising agents, reducing agents, acids, high alkali, lignin, chromophores and unstable colorants with image fade, silver mirroring, gold or red spots, yellowing, weakening and colorant stain; the Photographic Activity Test as ISO 18916; The reactant and damage table pairing oxidising agents, reducing agents, acids, high alkali, lignin, chromophores and unstable colorants with image fade, silver mirroring, gold or red spots, yellowing, weakening and colorant stain; the Photographic Activity Test as ISO 18916 and the additional requirements of ISO 18902; The reactants and damage table, pairing unstable colorants, oxidising agents, reducing agents, chromophores, high alkali, acids and lignin with image fade, silver mirroring, gold or red spots, yellowing, weakening, colorant stain and brittleness; Testing Requirements — the Photographic Activity Test as ISO 18916, using one detector that screens for oxidation and reduction reactions which can cause image fade, silver mirroring and red or gold spots and a second that screens for chromophores; the requirement that all materials pass the PAT to be considered photo-safe; the acid-free, alkali reserve of at least 2 per cent calcium carbonate, lignin-free at a Kappa number of 7 or below and colorant bleed requirements of ISO 18902; the statement that materials passing only the pH requirements or only the PAT are not necessarily photo-safe, and that photo-safe refers only to chemical reactivity and does not imply the material will not damage a photograph physically; TESTING REQUIREMENTS - the Photographic Activity Test as ISO 18916, using one detector that screens for oxidation and reduction reactions which can cause image fade, silver mirroring and red or gold spots and a second that screens for chromophores, with the statement that all materials must pass the PAT to be considered photo-safe; the acid-free requirement of a pH equal to or greater than the reference water and less than 10 by cold extraction; the alkali reserve of at least 2 per cent calcium carbonate for paper-based materials, with the note that its useful life is limited because it is consumed as it reacts with acid; the lignin-free requirement of a Kappa number of 7 or below, equivalent to a lignin concentration of 1 per cent or less; the colorant bleed test for coloured paper and labelling materials; ISO 18902 REQUIREMENTS BY MATERIAL TYPE - no post-consumer recycled paper and neutral or alkaline sizing for paper, no plasticizers and no chlorinated, nitrate or acetate plastic, no rubber-based adhesive, glazing of optical density at least 1.5 in the 300 to 380 nanometre range with photographs not framed in direct contact with the glazing, and the requirement that a wood frame's framing package be sealed along the edges with aluminized polyester tape or another impermeable barrier meeting the standard; and the statements that materials passing only the pH requirements or only the PAT are not necessarily photo-safe and that photo-safe refers only to chemical reactivity and does not imply that the material will not interact physically with a photograph; Introduction and Testing Requirements - that photo-safe is the term used by ISO 18902 to define materials that will not induce chemical damage in photographs over time; that the Photographic Activity Test is an International Standard in itself, ISO 18916, which explores the possibility of chemical interactions between photographs and a given material after prolonged contact using two detectors, one screening for oxidation and reduction reactions which can cause image fade, silver mirroring and red or gold spots and the other for chromophores that yellow the support; that all materials must pass the PAT to be considered photo-safe; that materials passing only the pH requirements or only the PAT are not necessarily photo-safe; and that the standard's definition of photo-safe refers only to chemical reactivity and does not imply that the material will not damage a photograph physically by abrasion, creases or tears; Testing requirements - the Photographic Activity Test as ISO 18916, and the statement that acid-free, archival, museum-quality and conservation board are marketing terms that are neither standardised nor legal, so that the printed claim to meet the standard is what to look for; Introduction and Testing Requirements — the account of ISO 18902 and the term photo-safe; the Photographic Activity Test of ISO 18916 with its two detectors, one screening for oxidation and reduction reactions causing image fade, silver mirroring and red or gold spots and the other for chromophores causing yellowing of the support; Acid-Free, the statement that acidic environments accelerate degradation of paper and plastic supports while highly alkaline environments can also cause decay such as weakening of a gelatin binder, so that an upper pH limit of 10 is incorporated and paper-based materials and adhesives must be measured by a cold extraction pH method; Alkali Reserve (Buffering), the requirement that paper-based materials include an alkali reserve of at least 2 per cent calcium carbonate with the note that its useful life is limited because it is consumed as it reacts with acid; and Lignin-Free, the Kappa number as the measure of lignin content.; The reactant damage table pairing each layer of a photograph with the reactants that attack it and the damage each produces, including image fade, silver mirroring and yellowing; and the account of the Photographic Activity Test as ISO 18916; The reactant damage test table pairing each layer of a photograph with the reactants that attack it - unstable colorants, oxidising agents, reducing agents, chromophores, high alkali, acids and lignin - and the damage each produces, including image fade, silver mirroring, gold or red spots, yellowing, weakening, colorant stain and brittleness; and the statement that the Photographic Activity Test is an International Standard in itself, ISO 18916; Testing Requirements — the Photographic Activity Test as ISO 18916, using one detector that screens for oxidation and reduction reactions which can cause image fade, silver mirroring and red or gold spots; and the warning that acid-free, archival, museum-quality and conservation board are marketing terms that are neither standardised nor legal; Testing Requirements — the Photographic Activity Test as ISO 18916; and the warning that acid-free, archival, museum-quality and conservation board are marketing terms that are neither standardised nor legal; The marketing terms acid-free, archival, museum-quality and conservation board; the requirements ISO 18902 adds beyond the Photographic Activity Test; the alkaline reserve as a consumable; Introduction and Testing requirements - photo-safe as defined by ISO 18902 for silver gelatin among other processes, the Photographic Activity Test ISO 18916 required of all materials, the statement that materials passing only the pH requirement or only the PAT are not necessarily photo-safe, the lignin-free and colorant-bleed requirements, the prohibition on rubber-based adhesives, and the note that photo-safe refers only to chemical reactivity and not to abrasion, creases or tears; Testing requirements - the Photographic Activity Test as ISO 18916, and the warning that acid-free, archival, museum-quality and conservation board are marketing terms that are neither standardised nor legal; Testing requirements - the Photographic Activity Test as ISO 18916, using a detector that screens for oxidation and reduction reactions which can cause image fade, silver mirroring and red or gold spots; the warning that acid-free, archival, museum-quality and conservation board are marketing terms that are neither standardised nor legal; Testing Requirements - the Photographic Activity Test as ISO 18916, using one detector that screens for oxidation and reduction reactions which can cause image fade, silver mirroring and red or gold spots; the warning that acid-free, archival, museum-quality and conservation board are marketing terms that are neither standardised nor legal

Used by:P29 Capstone Stage 6: Permanence, Presentation and the Finished Portfolio · P12 Overview: Permanence and Responsibility · P12 Assignment: Your Archival Processing Sequence · P12 Permanence and Image Deterioration · P19 Lab: Washing, Drying, Flattening and Mounting the Print · P20 Toning, Permanence and What the Evidence Actually Supports · P21 Assignment: Cyanotype at Scale, on Fabric, and the Botanical Sequence · P21 What These Processes Need: The Negative, the Paper and the Light · P22 Gold Toning and the Permanence of a Printed-Out Silver Image · P22 Break/Fix: The Printed-Out Image That Faded · P25 Cost, Permanence and When a Platinum Print Earns Its Price · P25 Assignment: The Process Comparison Atlas · Mounting a print and putting it in an enclosure · Storing unfixed prints for later fixing · Cyanotype bleached by alkaline wash water or buffered paper · Edge fading from mount and adhesive · Silver mirroring

Photographic Negatives: Nature and Evolution of Processes, 2nd editionretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: The account of negative supports and their deterioration, cited here for the storage and enclosure practice a negative collection needs rather than for a process identification; Cellulose Acetate Film Negatives — process; Gelatin Dry Plate Negatives — Subbing; Step 4, Fix; Gelatin Dry Plate Negatives — Background, Early gelatin glass plates, Subbing, Binder, Binder stability, Structural stability and Storage; Cellulose Nitrate Film Negatives — Background, Celluloid, Roll film, Process, Subbing, Stability/Deterioration with the six-stage table, Storage and Identification; Collodion on glass: Step 7 Fix, Step 8 Wash, and the table of process variations; Gelatin Dry Plate Negatives — Subbing: the glass support coated with a substratum, described as a thin layer of gelatin hardened with a chrome alum solution, to receive the binder and prevent emulsion blisters; Collodion on glass, Step 7 Fix — sodium thiosulfate as the primary fixer for collodion negatives in the 1850s, the introduction of potassium cyanide as a fixer for ambrotypes giving the wet plate photographer a second fixing agent, cyanide being a faster fixer than hypo but also very poisonous, and both continuing in use for negatives throughout the collodion era; Step 8 Wash, on washing out the silver thiosulfate or silver cyanide compounds formed during fixing; and the table "The effect of processing on wet plate images", giving hypo a darker, brownish grey image colour and cyanide a lighter, milky-tan one; Calotype Negative — Process, steps 2 to 4: the sensitising of the iodised sheet, the exposure of one to ten minutes made while the paper was still moist, and the development with the same solution used to sensitise it; Calotype Negative — Process, step 1 Iodize: that the two separate coats of silver nitrate and potassium iodide create the desired precipitate of silver iodide together with a byproduct of potassium nitrate that is then rinsed off the paper, and that the iodized paper could be kept until needed for exposure; and steps 2 to 4, for the sensitising, the exposure of one to ten minutes made while the sheet was still moist, and the development with the same solution; Collodion and gelatin dry plate process descriptions, the wash step: the plates needed to be washed thoroughly to eliminate the silver thiosulfate complexes formed during the fixing of the image; Gelatin dry plate and collodion process descriptions, the wash step: plates needed to be washed thoroughly to eliminate the silver thiosulfate complexes formed during the fixing of the image; Glossary: latent image, chemical development, physical development; Gelatin dry plate: ribbon-like filamentary silver particles; Cellulose acetate film negatives: the processing sequence, and the recommendation to tone the image silver to a more stable compound for chemical stability; Gelatin Dry Plate Negatives: mould growth on gelatin at high relative humidity and shrinkage at low humidity; Gelatin Dry Plate Negatives: binder stability, mould growth at high relative humidity, shrinkage at low humidity, and the storage recommendation of below 18 °C at 30 to 40 per cent relative humidity; Gelatin Dry Plate Negatives: binder, binder stability, mould growth at high relative humidity, and the storage recommendation; Bibliography and glossary: the citation of ISO 14523:1999, Photography, Processed Photographic Materials, Photographic Activity Test for Enclosure Materials, and of ISO 18902 for filing enclosures; Cellulose Acetate Film Negatives — the processing sequence, whose optional sixth step is toning, described as changing the structure of the silver particles by the addition of a more noble metal such as gold or the formation of a more stable silver compound such as silver sulfide, recommended to increase the chemical stability of the silver image and in practice rarely performed; Gelatin Glass Plate Negatives — silver image deterioration by oxidation causes fading, discoloration and mirroring, a bluish-silver sheen on the surface of the binder, and plates protected by a varnish overcoat rarely show signs of image oxidation; the storage recommendation of below 18 degrees C and 30 to 40 per cent relative humidity; Glossary — silver mirroring as chemical deterioration of the silver image leading to bluish silver deposits on the surface of the binder; Cellulose acetate, image processing - that an additional step referred to as toning was recommended to increase the chemical stability of the silver image but that in practice this step was and is rarely performed, and that toning involves changing the structure of the silver particles by the addition of a more noble metal, that is, oxidation-resistant, such as gold, or the formation of a more stable silver compound such as silver sulfide; and Polyester, Stability/Deterioration, that black and white films on polyester base together with toning, a stabilizing treatment of the silver image, can provide an extraordinarily long-lived pictorial record, a statement whose footnote refers back to the same author's acetate storage guide rather than to a study of toning; Collodion on glass, Step 7 Fix — that sodium thiosulfate was the primary fixer for collodion negatives in the 1850s, that the introduction of potassium cyanide as a fixer for ambrotypes gave the wet-plate photographer a second fixing agent, that cyanide was a faster fixer than hypo but also very poisonous, and that both continued in use for negatives throughout the collodion era; Step 8 Wash, on removing the silver thiosulfate or silver cyanide compounds formed during fixing; and the table of process variations, giving hypo a darker brownish-grey image colour and cyanide a lighter milky-tan one; The gelatin dry plate sequence, Step 6, Intensify (optional) — that a mistakenly underexposed plate made intensification necessary on occasion and that mercuric-ammonium chloride, mercuric iodide or cuprous bromide were used to make the silver image more dense or more opaque, with silver or chromium ions among the other intensifiers used. The collodion sequence, Step 9, Intensify (optional) — that after washing, if the negative was too thin or weak to be printed, the image was usually intensified with gallic acid and silver nitrate to increase its opacity; and the statement under Image that intensification or redevelopment can affect wet plate images by making them darker and more neutral in colour; Collodion Glass Plate Negatives, 1851 to about 1885. Background, for the wet plate term deriving from the necessity of exposing and processing the plate while still damp with the sensitising chemistry to achieve optimum exposure speed, and for the mobile darkroom that followed. Process, for the ten steps named in outline; for iodizing the collodion with cadmium or potassium iodide and bromide depending on the formula; for the fine deposit of silver iodide and silver bromide formed on and just under the surface of the thin collodion layer in the silver bath; for camera exposures of twenty seconds to three minutes; for development, while the binder is still moist, being physical development with a solution containing a reducing agent and free silver ions, pyrogallic acid in acid solution in the early years and ferrous sulfate the most common developer by 1860; for sodium thiosulfate as the primary fixer of the 1850s and potassium cyanide introduced for ambrotypes as a faster but very poisonous second agent, both continuing in use for negatives throughout the era; for optional intensification with gallic acid and silver nitrate; and for varnishing with gum sandarac or shellac once dry, protecting the layer and preventing the silver image from oxidising. Process Variations, for preserved and dry collodion formulas using hygroscopic overcoats such as honey or beer, and for the removal of free silver nitrate before the coat with a large proportion of bromide as restrainer to prevent fogging. Binder and Image, for the silver particles deposited on the surface and suspended immediately below it, for the extreme sharpness of the result, for the dull milky-tan or brownish-grey appearance by reflected light, and for the table of the effect of processing which gives pyrogallic acid a darker more burnt-umber image and ferrous sulfate a lighter one, hypo a darker brownish grey and cyanide a lighter milky tan. Stability and Deterioration, for glass composition as the most important factor, for alkali leaching or weeping glass softening the binder and varnish, for unvarnished negatives being extremely fragile and easily abraded and oxidised, for silver mirroring as a blue-purplish metallic deposit, and for emulsion frilling from improper cleaning of the glass. Storage, for cool to moderate temperature below 18 C and 30 to 40 per cent relative humidity, with below 40 per cent critical against alkali leaching and below 30 per cent not recommended. Identification, for viewing against a dark background and for the manufacturing irregularities that mark a handmade plate, including rough-cut edges, glass thicker than machine-made, plates not perfectly square, uneven varnish and binder edges, and an uncoated corner where the plate was held; Fixing in hypo giving a darker, brownish grey image colour and fixing in cyanide a lighter, milky tan; Gelatin Glass Plate Negatives — silver image deterioration by oxidation, mirroring, the protection given by a varnish overcoat, and the storage recommendation below 18 °C and 30 to 40 per cent relative humidity; Gelatin Dry Plate Negatives, Preservation and Storage: high relative humidity promotes mould growth in the gelatin layer and softens the binder so that it adheres to whatever touches it, low relative humidity exacerbates lifting and flaking through shrinkage of the gelatin, drastic changes in relative humidity do both, and glass plates should be stored below 18 degrees C at 30 to 40 per cent relative humidity; Cellulose Nitrate Film Negatives, Anti-curl layer - that after 1903 a layer of gelatin began to be applied to the back of the plastic support 'to compensate for the tension exerted by the binder layer and provide dimensional stability to the negative', and that it carried the anti-halation dyes, removed in processing; Cellulose Acetate Film Negatives, Binder - the four layers named in order as gelatin emulsion, cellulose nitrate subbing, cellulose acetate support and bottom gelatin anti-curl layer, with the statement that the anti-curl layer 'is always present on the base side of the film to counteract the tension exerted by the gelatin emulsion and provide dimensional stability'; Polyester Film Negatives, Background, Process and Support - that polyester was first employed for negatives requiring high dimensional stability, that PET is cast from a melt and biaxially oriented by stretching in both directions and then, while still mechanically restrained, 'heated considerably above the stretching temperature', which grows crystallites and locks the polymer chains together 'so that the sheet is dimensionally stable up to much higher temperatures', and that PET has the highest strength, toughness, stiffness and tear resistance of any commercial film base at normal temperatures

Used by:P29 Capstone Stage 3: Exposing, Processing and Measuring · Ammonium thiosulfate · Chrome alum · Gelatin · Nitrocellulose · Potassium cyanide · Chrome alum subbing dip · Cyanide fixing and toning · Talbot's gallo-nitrate of silver · Talbot's calotype iodised paper · P3 Complexes: How an Insoluble Salt Is Persuaded to Dissolve · P3 Diffusion, Swelling and the Journey Into the Emulsion · P4 Development as Amplification · P4 Silver and the Silver Ion · P5 Build an Emulsion Coating Station · P5 Coating, Drying and Hardening · P5 Gelatin, the Photographic Binder · P7 Pinhole Portfolio Review and the Exposure Record as Data · P12 Permanence and Image Deterioration · P20 Toning, Permanence and What the Evidence Actually Supports · P26 Cyanide in the Historical Darkroom, and the Ferricyanide That Is Not Cyanide · P26 Uranium, Mercury and the Heavy-Metal Treatments · P26 Wet-Plate Collodion: The Process That Made the Nineteenth Century Look Like That · Ambrotype · Dry plate and lantern slide · Plate coating and drying · Negative popping

Understanding Preservation Metricsretrieved 2026-09-07

Sections: Preservation Index and Time-Weighted Preservation Index, for PI expressed in years and calibrated so that 20 degrees C at 45 per cent relative humidity gives 50 years for a preservation problem object, for a PI of 100 years meaning twice as long to reach the same state, and for the opening argument that the effects of the environment follow a continuum with no clean line dividing good conditions from bad; The opening argument that the effects of the environment follow a continuum with no clean line of temperature or relative humidity dividing storage conditions into bad and good, and the Preservation Index calibrated so that 20 degrees C at 45 per cent relative humidity gives 50 years for a typical preservation problem object

Used by:P22 Gold Toning and the Permanence of a Printed-Out Silver Image · P22 Break/Fix: The Printed-Out Image That Faded

safetyequipment.org

Emergency Eyewash and Shower Equipment: a guide to ANSI/ISEA Z358.1-2014 (R2020)retrieved 2026-09-04, 2026-09-05

Sections: Why an eyewash is needed; definitions (tepid); eyewash equipment; Personal eyewash equipment and its role as a supplement to, not a substitute for, plumbed or portable eyewash; What ANSI/ISEA Z358.1-2014 (R2020) requires — fifteen minutes of flushing fluid to both eyes, a valve that opens in one second or less and stays open, a unit reachable within ten seconds, and tepid fluid at 16 to 38 degrees Celsius; Why an eyewash is needed; definitions, including tepid; eyewash equipment, its fifteen-minute delivery, its one-second valve and its ten-second reach; Why an eyewash is needed; eyewash equipment

Used by:P2 Protecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong · P4 Experiment: Precipitating the Silver Halides · First aid quick reference · Checking and using the eyewash · Opening the laboratory

science.nasa.gov

Solar Eclipse Safetyretrieved 2026-09-04, 2026-09-05

Sections: Eclipse eye safety; eye safety for partial and annular solar eclipses; indirect viewing; Eclipse Eye Safety - the statement that except during the brief total phase it is not safe to look directly at the Sun without specialised eye protection, that viewing any part of the bright Sun through a camera lens, binoculars or a telescope without a special-purpose solar filter will instantly cause severe eye injury, and that ordinary sunglasses, however dark, are not safe for viewing the Sun

Used by:P1 The Camera Obscura: An Image Without Chemistry · Outdoor exposure session

screwfix.com

Screwfixretrieved 2026-09-05

Sections: Nitrile gloves, safety spectacles and goggles, eyewash, PVA adhesive

Used by:The Pure Silver laboratory planner

search.worldcat.org

Modern Photographic Processing (2 vols)retrieved 2026-09-05, 2026-09-07

Sections: High-definition developers - the Beutler Formula printed as two solutions of a litre each, the sentence that typical high-definition one-use developers are those of Beutler and Crawley, Beutler's own finding on silver halide solvents and unsharp negatives, the low sulfite and low metol concentration of the Neofin series, and the modification of the Beutler formula suggested by Arthur Kramer; Cited for an absence. The two volumes are the standard reference on developer chemistry and would very probably settle whether a bromide addition reproduces a used bath; this course does not hold them and quotes nothing from them

Used by:Beutler two-solution developer · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does

The Film Developing Cookbookretrieved 2026-09-05, 2026-09-06

Sections: The acutance chapter - Beutler as the formulator of two high-acutance developers of the 1950s still manufactured by Tetenal as Neofin Blue and Neofin Red, Neofin Blue being optimised for medium and slow films, and the caution that Beutler-type developers tend to compress tones excessively, especially with a cold light head; Read in Google Books snippet view. The fixers chapter, for the passage stating that developers or stop baths high in potassium salts can partly convert ammonium or sodium thiosulfate into potassium thiosulfate, which is inactive compared with the ammonium or sodium salts, and for the first of the precautions that follow it, never to use a stop bath based on potassium metabisulfite or another potassium salt; and the alkaline sodium thiosulfate fixers heading, for the judgement that an alkaline sodium thiosulfate fixer washes out of negative and print materials more rapidly than any acid fixer and would be appropriate for materials containing little or no silver iodide, such as some hand-coated materials used in alternative processes; Pyro-metol formulas — the three formulas printed side by side, BJ Pyro-metol, Wimberly WD2D and PMK, with the note on substituting sodium metabisulfite for sodium bisulfite; Using PMK — the standard dilution, the working-solution composition per litre in the tanning-developer table, and the statements about shelf life and about Hutchings having waited eleven years to publish; Read in Google Books snippet view, which returns the publisher's own text around a searched term and never a whole page. The fixers chapter, under the heading "Alkaline sodium thiosulfate fixers", printing TF-2 ALKALINE FIXER as water 750 ml, sodium thiosulfate 250 g, sodium sulfite anhydrous 15 g, sodium metaborate 10 g, water to make 1 liter; the paragraph beneath it, that it is simple to construct an alkaline sodium thiosulfate fixer, that one formula is TF-2, that although this fixer will wash out of negative and print materials more rapidly than any acid fixer the authors only give the formula for users who are determined to use sodium rather than ammonium thiosulfate and who would like a formula superior to the traditional acid hypo fixers, that it would however be appropriate for negative or print materials containing little or no silver iodide such as some hand-coated materials used in alternative processes, and that if sodium thiosulfate is used to fix contemporary print or negative materials one should fix for three times the clearing time rather than the traditional recommendation of twice, which will alleviate though it may not eliminate concerns about the ability of sodium thiosulfate to fix iodide-containing materials; the passage immediately before the heading SODIUM THIOSULFATE FIXER FORMULAS, that an alkali buffering system may be used to keep pH within the desired range, which will probably be between 8.5 and 10, and that a combination of sodium metaborate and sodium bisulfite would be suitable for trial; the passage stating that developers or stop baths high in potassium salts can partly convert ammonium or sodium thiosulfate into potassium thiosulfate, which is inactive compared with the ammonium or sodium salts, and the precautions that follow it, the first being never to use a stop bath based on potassium metabisulfite or another potassium salt and the second concerning a water stop; the report that preliminary findings were that sodium thiosulfate fixers were not adequate for modern films and papers, that some Kodak researchers went so far as to suggest thiosulfate be replaced by more stable chemicals, and that layoffs ended further investigation; the pyro instructions, that sulfite inhibits stain, that for maximum stain an alkaline fixer low in sulfite should be used, and that after such a fixer the negatives are ready to be washed unless the wash water is acid, with Hutchings's advice of a full 20 to 30 minute wash to intensify the pyro stain further; and the index entry "TF-2 Alkaline Fixer, 120"

Used by:Beutler two-solution developer · Dilute alkaline thiosulfate fixer for iron-silver prints · PMK pyro · TF-2 alkaline fixer

The Theory of the Photographic Processretrieved 2026-09-04

Sections: 21.6 Quantum yields from silver halide photolysis; 23.2 Photolytic silver; 23.3 Significance of halogen acceptors; 23.11 the Gurney-Mott model of the latent image

Used by:P29 The Capstone Chemistry Report: From Photon Capture to Finished Print

sis.se

ISO 5-3:2009, Photography and graphic technology - Density measurements - Part 3: Spectral conditions, third edition, 2009retrieved 2026-09-05, 2026-09-06, 2026-09-07

Sections: Cited by number only, for the structural fact taken from the publisher's free preview that the ISO 5 series has four parts and that transmittance density and reflection density are standardised by different parts of it, Part 2 and Part 4 respectively; no geometry, spectral condition or value from any part of ISO 5 is printed anywhere in this course; Cited by number only, as the standard that specifies the spectral conditions a density value is quoted under, so that a geometry alone does not define one; Cited by number only, as the standard that specifies the spectral conditions under which a density is quoted; consulted in the publisher's free preview for the existence of named spectral conditions and of spectral products, and for nothing else; Cited by number only, as the standard specifying spectral conditions; consulted in the publisher's free preview, whose introduction records that a density value is fully defined only by giving both geometric and spectral conditions, that the term status density identifies many of those conditions, that spectral response is the product of the detector's spectral sensitivity and the spectral modification by every optical component and filter in the path, that the combination of those components multiplied wavelength by wavelength and tabulated is called the spectral products, that this revision supplements the older 10 nm spectral products with spectral weighting factors interpolated to 1 nm, that the traditional illumination for both transmittance and reflection density is based on Planckian radiation at approximately 2856 K known as CIE standard illuminant A, and that process-control instruments using an LED source have been introduced; Cited by number only, and consulted in the publisher's free preview: the foreword's list of the four parts of ISO 5, from which the existence and title of Part 4, geometric conditions for reflection density, is taken. Part 4 itself has not been obtained by this course and nothing is reproduced from it; Cited by number only, consulted in the publisher's free preview: the introduction's statement that a density value is fully defined only by giving both geometric and spectral conditions, that the term status density identifies many of those conditions, and that spectral response is the product of the detector's spectral sensitivity and the spectral modification by every optical component and filter in the path; Cited by number for what a spectral condition is - that a density is defined by its geometric and its spectral conditions together, the spectral response being the product of the detector's sensitivity and every filter in the path. No value, tolerance or geometry is quoted from it.; Cited by number only, for what a spectral condition is - a density is defined by its geometric and its spectral conditions together, the spectral response being the product of the detector's sensitivity and every filter in the path. No value, tolerance or geometry is quoted from it.; Cited by number only, as what a spectral condition is; the Part XV instrument's narrow green band is not a spectral product and no conformance is claimed; Cited by number only, as the standard specifying the spectral conditions a density measurement is made under, and for the point that a density value is fully defined only by giving both its geometric and its spectral conditions; no table, weighting factor or spectral product from it appears in this course

Used by:P13 Paper Sensitometry: Reflection Density, Grades and ISO(R) · P15 Part XV Overview: Build a Densitometer · P15 Experiment: Calibrating the Densitometer in Both Modes · P15 Density Depends on How You Look: Geometry and Spectral Response · P18 Experiment: Maximum Black, Base White and Dry-Down · P20 Experiment: Selenium Toning and the Print Curve · P21 Experiment: The Exposure Scale, Maximum Density and Contrast of a Cyanotype · P21 Lab: Toning the Prussian Blue Image · P27 Experiment: Four Curve Families, Measured · P27 Assignment: The Developer Comparison, Measured and Printed

store.waveformlighting.com

realUV LED Strip Lights, product pageretrieved 2026-09-05

Sections: Specifications - 365 nm or 395 nm at FWHM 10 nm, radiant output 0.7 W per foot at 365 nm and 0.9 W per foot at 395 nm, DC 12 V, supplied on 1 m and 5 m reels, with a plug-in supply able to power up to 5 m of strip; Specifications - 365 nm or 395 nm, FWHM 10 nm, radiant output 0.7 W per foot at 365 nm and 0.9 W per foot at 395 nm, DC 12 V; and the description's claim that products marketed as ultraviolet are often near-UV at 405 nm, violet at 420 nm or a red-plus-blue mixture

Used by:P16 Build: The UVA Exposure Unit · P16 Ultraviolet for the Alternative Processes: Sources, Dose, Uniformity and Hazard

stores.photoformulary.com

Cyanotype Kit, catalogue number 07-0090: instructions, current printing on the supplier's own siteretrieved 2026-09-06

Sections: Cyanotype Kit 07-0090 — the competing kit's own instruction sheet, cited here only for the strengths it publishes, 20 per cent w/v ferric ammonium citrate and 8 per cent w/v potassium ferricyanide mixed in equal parts, and for its ammonia-and-tannic-acid toning route, against which this supplier's carbonate bleach is compared; Cyanotype Kit 07-0090, the printing served from the supplier's own store — the statement that the kit contains the chemicals to prepare 1000 mL of sensitizer solution to do approximately twenty-four 8 by 10 prints; the account of the blue as Prussian blue formed from ferrous ions, themselves from the photo reduction of the ferric ammonium citrate, and potassium ferricyanide, with the warnings that Prussian blue fades in alkali, that perspiration is alkaline and a touched print can be permanently damaged, that prints fade in strong light and recover in the dark and damp, and that a faded print can be treated with a hydrogen peroxide oxidation bath; the CHEMICALS CONTAINED IN THIS KIT table giving arrowroot starch 20 g, potassium ferricyanide 40 g, ferric ammonium citrate (green scale) 100 g and potassium dichromate 1 g; the Chemical Safety section naming potassium ferricyanide and potassium dichromate as the two needing special attention, its account of why bound cyanide is not free cyanide, its statement that dichromates are both toxic and an oxidizer, that spillage on skin gives a chemical burn appearing as ulceration and that all chromium salts are potential carcinogens, and its instruction to wash excess solid dichromate down a drain with copious amounts of water and never to put it in a wastepaper basket; MIXING THE STOCK SOLUTION, three dark brown containers, two of 500 mL and one of 100 mL, distilled water throughout, Stock Solution A as 400 mL of water at 20 °C/68 °F plus 100 g of ferric ammonium citrate and water to make 500 mL, Stock Solution B as the same with 40 g of potassium ferricyanide, and the optional 1 per cent dichromate solution as 1 g in 100 mL; Mixing the Sensitizer Solution, the direction to mix in subdued light and use as soon as feasible, the statement that the sensitizer solution is stable for about 2 to 4 hours after mixing, the standard sensitizer as equal parts of the two stocks, the lower contrast sensitizer as the mixed standard diluted with water, and the higher contrast sensitizer as six drops of the 1 per cent dichromate solution per 2 mL of standard sensitizer at a stated cost of about two steps on a Kodak No. 2 step tablet; SENSITIZING THE PAPER, the three-minute float sized side down or brush coating top to bottom and side to side, drying in the dark, the statement that correctly dried sensitised paper is greenish-yellow and that blue means ferrous salts are already present by exposure or contamination, and the instruction not to touch the surface; Exposure, sunlight or a General Electric 275 or 300 watt sunlamp at 12 to 18 inches, contact printing without glass where possible because glass absorbs ultraviolet, 10 to 20 minutes, the olive-green appearance before washing, printing out and judging by inspection, and the direction to expose until the high values carry considerably more tone than wanted and the shadows have begun to reverse because the highlights lighten in the wash; Washing, five minutes in softly running soft water, the warnings that iron salts in hard water alter the print, that a short wash leaves ferric salts that cause fading and that prolonged washing lightens the image particularly in slightly alkaline water; Contrast Increase, an initial wash bath of a 0.2 per cent potassium ferricyanide solution made as 2 g in 1000 mL; Peroxide After-Bath and After Treatment, the 5 per cent oxalic acid spot application to clear blue whites and the Prussian blue watercolour for spotting; OTHER SURFACES, cloth of at least 50 per cent cotton soaked in the standard sensitiser; the sizing procedure from 20 g of arrowroot starch boiled five minutes in a litre of water; Toner Solutions, brown to black from ammonia 28 per cent 10 mL in 1000 mL of water followed by tannic acid 20 g in 1000 mL, green from a 1 per cent sulphuric acid solution made from the supplier's 48 per cent acid, and violet from a mild borax solution or a warm 5 per cent lead acetate solution; and the five-row TROUBLESHOOTING table

Used by:Bostick and Sullivan cyanotype and toning kits · Photographers' Formulary cyanotype and toning kits

New Cyanotype Kit, catalogue number 07-0095: instructionsretrieved 2026-09-06

Sections: New Cyanotype Kit 07-0095 — the contents of ferric ammonium oxalate 30 g, potassium ferricyanide 10 g, ammonium dichromate as 10 mL of a 1.25 per cent solution, citric acid 10 g and distilled water to make 100 mL; the claims made for it against the classic formula; the ripening effect over a couple of days; the coating figures of about 1.5 mL per 8 by 10 by rod and about twice that by brush; and the chemical safety section on ammonium dichromate; The kit contents and yield — chemicals for 100 mL of sensitiser, approximately fifty 8 by 10 sheets by coating rod, ammonium dichromate supplied as 10 mL of a 1.25 per cent solution; the claims over the classic formula of a smoother texture, a maximum density near black, a longer tonal scale and printing time cut by approximately two thirds; and the chemical safety section naming ammonium dichromate as needing special attention

Used by:Photographers' Formulary cyanotype and toning kits · P21 The New Cyanotype and the Other Ways to Make a Blue Print

Photographers' Formulary Palladium Printing Kit, catalogue numbers 07-0007 and 07-0009: instructions, current printing on the maker's own storeretrieved 2026-09-06

Sections: The eight printed pages of the palladium sheet served from the same store — the catalogue line that 07-0007 and 07-0009 contain 15 and 30 mL of 15 per cent palladium solution prepared from sodium tetrachloropalladate; the opening comparison, that palladium prints have almost the same scale, richness and delicacy as platinum but are warmer and smoother, that palladium is warm-black to sepia against platinum's neutral-grey, and that palladium prints, unlike platinum prints, will solarize; the statement that "palladium is less sensitive to contrast control with potassium chlorate than is platinum" and that twice as much chlorate is therefore used; the warning that "palladium metal can be etched from the print if the clearing solution contains too much Citric Acid"; the contents table with potassium chlorate at 0.26 g and the palladium solution at 15 per cent; the negative specification of a density range between 1.3 and 1.5; the dilute citric acid at 30 g made to 2000 mL, described as much weaker than the platinum bath; the developer at 227 g in 700 mL with an indefinite life, replenishable to maintain volume; the coverage paragraph, which calls the bottle "the 15-ml 20% palladium solution"; the five drop tables, identical in parts to the platinum sheet's; and the worked example printing 0.304 × 55 drops = 1.67 drops before rounding to 17; The Negative — the statement that the negative should have good separation of detail in the shadows and a long density range, and that best results are obtained if the density range of the negative is between 1.3 and 1.5.

Used by:Photographers' Formulary platinum and palladium printing kits · P21 What These Processes Need: The Negative, the Paper and the Light

Photographers' Formulary Platinum Printing Kit, catalogue numbers 07-0001, 07-0003 and 07-0005: instructions, current printing on the maker's own storeretrieved 2026-09-06

Sections: CHEMICALS CONTAINED IN THIS KIT and FERRIC OXALATE. Cited only as the competing supplier's version of the same three-bottle system, for its 20 per cent ferric oxalate against this supplier's 27, for its weighed chlorate sachet of 0.18 g against a chlorate published here only as a percentage, and for the paragraphs on the two forms of ferric oxalate that this supplier never writes; The seven printed pages served from the maker's own store, read in full for this entry — the catalogue line that 07-0001, 07-0003 and 07-0005 contain 5, 15 and 30 mL of 20 per cent platinum solution; the opening statement that platinum salts are not light sensitive and that the paper is coated with a mixture of potassium chloroplatinite and light-sensitive ferric oxalate, exposed by contact printing, developed in potassium oxalate and cleared with citric acid; the table headed CHEMICALS CONTAINED IN THIS KIT — arrowroot starch 20 g, ferric oxalate Sensitizer A 30 ml, ferric oxalate Sensitizer B 30 ml, citric acid 30 g, potassium chlorate 0.18 g, platinum salt solution 20% at 5, 15 or 30 ml, potassium oxalate 227 g; THE NEGATIVE TO BE PRINTED, for the density range of 1 to 1.5 and the grade-1 rule of thumb; PAPER, for pure linen and 100 per cent rag, the rejection of Bristol because the platinum falls off during development, and single-ply only; SIZING OF THE PAPER, for the 50-drop porosity test and the arrowroot sizing boiled five minutes in a litre; FOR YOUR CHEMICAL SAFETY, for potassium oxalate as an anticoagulant and a poison, ferric oxalate as a poison, and potassium chlorate as "a dangerous and explosive chemical" whose quantity "is so minuscule that no special precautions need be taken", with the drain-flushing disposal instruction and the refund clause; FERRIC OXALATE, for the misnomer, the two forms, the refusal to recommend the green tripotassium salt, the 20 per cent trihydrogen solution made by the iron alum and oxalic acid procedure with a slight excess of oxalic acid, the 460 nm sensitivity, the red safelight and the 50 °C/122 °F ceiling, and the potassium ferricyanide spot test for photoactivity and excess ferrous ions; PLATINUM SALTS, for potassium chloroplatinite, the varying content of the much less soluble potassium hexachloroplatinate, the near-saturation of the 20 per cent solution and the fine red precipitate that must not be carried into the sensitiser; MIXING THE SOLUTIONS, for Sensitizer B from the whole 0.18 g sachet, the dilute citric acid at 30 g in 1000 mL of water at 120 °F made to 1500 mL, and the developer at 227 g in 500 mL of which not all dissolves; AREA COVERED, for the 20-drops-per-millilitre assumption, the 4 sheets, 12 sheets and "about ten 8X10's"; MIXING THE SENSITIZER, for the five drop tables and the 55-to-56-drop worked example; SENSITIZING and DRYING THE PAPER; EXPOSURE, for the 10 to 20 minutes and the General Electric 275 or 300 watt bulb; PROCESSING THE EXPOSED PRINT, for development in saturated potassium oxalate at room temperature or 90 to 100 °F for at least two minutes and the statement that a platinum print cannot be overdeveloped; ETCHING, for the three citric acid trays at five minutes each with tray rotation and the warning that an unetched print will darken with age and be destroyed; and WASHING, for the complete water change every five minutes for an hour; The Negative — the statement that the negative should have good separation of detail in the shadows and a long density range, that best results are obtained if the density range of the negative is between 1 and 1.5, and the rule of thumb relating it to a good silver print; and the contrast-control system of drop-counted potassium chlorate solution.

Used by:Bostick and Sullivan platinum and palladium kits · Photographers' Formulary platinum and palladium printing kits · P21 What These Processes Need: The Negative, the Paper and the Light

Sensitizer B Platinum/Palladium, catalogue numbers 07-0022 and 07-0023: product pageretrieved 2026-09-06

Sections: Sensitizer B Platinum/Palladium, catalogue numbers 07-0022 and 07-0023 — the product description, "30 ml of Ferric Oxalate 20% solution plus a packet containing 0.26 g potassium chlorate for palladium printing or 0.18 g potassium chlorate for platinum printing", and the type selector repeating both weights. Cited as a second, independent printing of the iron strength and the two chlorate weights, and as the listing that gives the sensitiser's safety data sheet its catalogue numbers

Used by:Photographers' Formulary platinum and palladium printing kits

The Liquid PMK Pyro Developer, catalogue number 01-5060, to make 50 litres of working solution: technical informationretrieved 2026-09-05, 2026-09-07

Sections: DEVELOPMENT TIMES, the Ilford, Kodak, Agfa and Other Films tables with their exposure indices at 70 °F and 80 °F; LIFE OF THE STOCK SOLUTIONS; CONTENTS OF YOUR KIT; DEVELOPMENT TIMES - the Ilford table giving FP4 Plus at EI 80 for 10 minutes and HP5 Plus at EI 200 for 13 minutes at 70 degrees F, and the Kodak table giving Tri-X 400 at EI 250 for 15 minutes; and LIFE OF THE STOCK SOLUTIONS

Used by:PMK pyro · P27 Assignment: The Developer Comparison, Measured and Printed

The PMK Pyro Film Developer, catalogue number 01-5045, to make 25 litres of working solution: technical informationretrieved 2026-09-05, 2026-09-07

Sections: PMK STOCK SOLUTIONS; WORKING SOLUTION OF PMK; FOR YOUR CHEMICAL SAFETY; PMK STOCK SOLUTIONS, the A and B tables; MIXING THE STOCK SOLUTIONS; WORKING SOLUTION OF PMK; CAPACITY OF PMK; FILM DEVELOPMENT TEMPERATURE; AGITATION PROCEDURE; STOP AND FIXING BATHS; PYRO AFTER BATH; FINAL WASH; FOR YOUR CHEMICAL SAFETY; the opening paragraph on what the formula is constituted to achieve; PMK STOCK SOLUTIONS and MIXING THE STOCK SOLUTIONS - the two stocks and the statement that partially filled and stoppered bottles will last for years; WORKING SOLUTION OF PMK, at 1+2+100; CAPACITY OF PMK - a minimum of 300 mL of working solution per 80 square inches of film, used one-shot; FILM DEVELOPMENT TEMPERATURE and AGITATION PROCEDURE; PYRO AFTER BATH; and FOR YOUR CHEMICAL SAFETY, which asks for gloves and a dust mask and instructs that the pyro be weighed and added outside or under a ventilating hood

Used by:510-Pyro · PMK pyro · P27 Assignment: The Developer Comparison, Measured and Printed

The Pyrocat-HD Developer, catalogue numbers 01-5080 and 01-5082 (dry) and 01-5081 and 01-5083 (liquid), to make 10 or 50 litres of working solution: technical informationretrieved 2026-09-05, 2026-09-06

Sections: Stock Solution A and Stock Solution B, in the 100 mL and 500 mL columns; FOR YOUR CHEMICAL SAFETY, the catechol paragraph; the development recommendations for trays, semi-stand and rotary processing; the post-development sequence; the note on how this printing differs from the Post-Factory Photography version and from the earlier metol version, and the keeping time of solution A; Ed Buffaloe's Test Results with 120 Roll Film and his time chart; King's development recommendations - sheet film in trays with normal agitation at 10 seconds every minute; with minimal agitation at 10 seconds every three minutes and times about 50 per cent longer; and with semi-stand agitation at a special working solution of 1 part A to 1 part B to 200 or 400 parts water, agitation for one minute at the start of development followed by 30 seconds at the halfway point, times of 40 to 50 minutes for slow and medium-speed films and 50 to 60 for fast films, and a warning that dichroic fog may result from extended development of high-speed films; the rotary instruction to use a minimum of 75 mL of standard working solution per sheet of 4x5 film; and Ed Buffaloe's semi-stand account of two 35 mm rolls of Delta 3200 at 1:1:200 for 30 minutes with agitation for one minute at the start and 30 seconds in the middle, of which the first printed with extremely high acutance and the second, of a very high-contrast scene, was ruined because the bromides released by the intense development in the heavily exposed areas diffused out and caused uneven development in surrounding areas

Used by:Pyrocat-HD · P27 Experiment: Agitation, Stand and Semi-Stand Development

stouffer.net

Frequently asked questions, and How to use the T2115 21 stepretrieved 2026-09-05, 2026-09-06

Sections: Frequently asked questions, What is the difference between Calibrated and Uncalibrated guides - the same quality and the same production batches, with calibration adding a densitometer reading of each step recorded for reference, giving the exact optical density value usable for densitometry and sensitometry; Frequently asked questions, What is the difference between Calibrated and Uncalibrated guides - the same quality from both, produced with the same detail and control and coming from the same batches in a production run, calibration consisting of each step being read with a densitometer and those readings recorded for reference, which provides the exact optical density value usable for densitometry and sensitometry; The maker's statement that calibrated and uncalibrated guides come from the same batches in a production run and are made with the same control, and that what calibration adds is that each step is read on a densitometer and the readings recorded, giving an exact optical density value usable for densitometry and sensitometry.; Frequently asked questions, calibrated against uncalibrated guides - the maker's statement that the same quality may be expected from an uncalibrated product as from a calibrated one and that both come from the same production batches, and that what calibration adds is a densitometer reading of each step recorded for reference, giving the exact optical density value usable for densitometry and sensitometry; Frequently asked questions, calibrated against uncalibrated guides - calibration adds a densitometer reading of each step recorded for reference, giving the optical density value usable for densitometry; Frequently asked questions, calibrated against uncalibrated guides: calibration adds a densitometer reading of each step recorded for reference; Using a 21-step transmission wedge - the 0.15 density increment as half a stop per step, and reading the first step that shows a density rise above base plus fog; Using a 21-step wedge - the 0.15 increment as half a stop per step and the nominal starting density

Used by:P14 Experiment: Calibrating the Sensitometer · P14 Sensitometer Design Principles · P15 Experiment: Calibrating the Densitometer in Both Modes · P21 Experiment: The Exposure Scale, Maximum Density and Contrast of a Cyanotype · P27 Experiment: Four Curve Families, Measured · Densitometer daily five-minute check · Sensitometer exposure session · Cut-off toe · Densitometer: scale error

Transmission Step Wedgesretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: Transmission step wedge specification table: the T2115 with 21 steps at a density increment of 0.15, which the maker gives as half a stop per step; The T2115 21-step transmission guide: 21 steps, density increment 0.15, maximum density 3.05; Transmission step wedges: the T2115 21-step guide, density increment 0.15 and maximum density 3.05; the printable step table; and the FAQ on what calibration means; Transmission step wedges: the T2115 21-step guide, density increment 0.15 (half a stop per step), maximum density 3.05, on a 0.5 by 5 inch strip; and the T2115 step specification table of target densities and percentage transmissions; Transmission step wedges: the T2115 21-step guide at a density increment of 0.15, half a stop per step, to a maximum density of 3.05; Transmission step wedges: the T2115 21-step guide, 21 steps at a density increment of 0.15, which is half a stop per step, to a maximum density of 3.05; and the T2115 specification table of target densities against percentage transmission; Product table — T2115, 21 steps at a 0.15 density increment to a maximum density of 3.05, 1/2 x 5 inches; and the note that only the T2120CC and T1530CC are calibrated against NIST Standard Reference Material 38120C; Product table — T2115, 21 steps at a 0.15 density increment, half a stop per step, maximum density 3.05; the note that the calibrated parts are the T2120CC and T1530CC, measured against NIST Standard Reference Material 38120C; Product table — T2115, 21 steps at a 0.15 density increment, f-stop equivalent and maximum density 3.05; and the statement that the T2120CC and T1530CC are the parts calibrated against NIST Standard Reference Material 38120C by a densitometer conforming to ANSI PH2.19-1986; Product table — T2115, 21 steps at a 0.15 density increment, half a stop per step, maximum density 3.05, size 1/2 x 5 inches; and the note that the calibrated parts are the T2120CC and T1530CC, measured against NIST Standard Reference Material 38120C; Product table — T2115, 21 steps at a 0.15 density increment, half a stop per step, maximum density 3.05; Product table - the T2115, 21 steps at a 0.15 density increment to a maximum density of 3.05, and the note that only the CC parts are calibrated against a NIST standard reference material; Product table - the T2115 with 21 steps at a 0.15 density increment, described as half a stop, to a maximum density of 3.05; and the statement that the T2120CC and T1530CC are the parts calibrated against NIST Standard Reference Material 38120C; Product table - the T2115, 21 steps at a 0.15 density increment, half a stop per step, to a maximum density of 3.05, on a piece 1/2 by 5 inches; and the note that the calibrated parts are the T2120CC and T1530CC, measured against NIST Standard Reference Material 38120C on a densitometer conforming to ANSI PH2.19-1986; Product table - the T2115, 21 steps at a 0.15 increment to a maximum density of 3.05, half an inch by five inches, and the note that only the CC parts are calibrated against a NIST standard reference material; Product table - the T2115, 21 steps at a nominal 0.15 increment to a maximum density of 3.05, half an inch by five inches; and the note that the T2120CC and T1530CC are calibrated against NIST Standard Reference Material 38120C on a densitometer conforming to ANSI PH2.19-1986; Product table - the T2115, 21 steps at a nominal 0.15 increment to a maximum density of 3.05, on a piece half an inch by five inches; Product table - the T2115, 21 steps at a nominal 0.15 increment to a maximum density of 3.05, half an inch by five inches; and the note that only the CC parts are calibrated against a NIST standard reference material; Product table - the T2115, 21 steps at a nominal 0.15 increment from about 0.05 to a maximum density of 3.05; the note that the T2120CC and T1530CC compare with NIST Standard Reference Material 38120C by means of a densitometer conforming to the conditions specified in ANSI PH2.19-1986; and the statement that the T5100C is designed specifically for densitometer calibration and can be used with many different densitometers; Product table - the T2115, 21 steps at a nominal 0.15 increment from about 0.05 to a maximum density of 3.05; and the note that only the T2120CC and T1530CC are calibrated, against NIST Standard Reference Material 38120C; Product table - the T2115, 21 steps at a nominal 0.15 increment to a maximum density of 3.05, on a piece half an inch by five inches, from which the 6.0 by 12.7 mm size of one step is computed; and the note that only the T2120CC and T1530CC are calibrated, against NIST Standard Reference Material 38120C; Product table - the T2115, 21 steps at a nominal 0.15 increment to a maximum density of 3.05, on a piece half an inch by five inches; and the note that only the T2120CC and T1530CC are calibrated, against NIST Standard Reference Material 38120C; Product table - the T2115, 21 steps at a nominal 0.15 increment from about 0.05 to a maximum density of 3.05, which is the exposure scale each strip carries; and the note that only the T2120CC and T1530CC are calibrated; The product specification table - the T2115 at 21 steps of a 0.15 density increment, half a stop per step, to a maximum density of 3.05 on a piece 1/2 by 5 inches, and the note that the calibrated parts are read on a densitometer against NIST Standard Reference Material 38120C; The specification table, for the T2115 at 21 steps of a nominal 0.15 to a maximum density of 3.05 on a piece 12.7 by 127 mm, the T3110 at 31 steps of a nominal 0.10 to a maximum density of 3.05, and the T4105 at 41 steps of 0.05 to 2.05; and for the statement that the T2120CC and T1530CC are the calibrated parts, compared against NIST Standard Reference Material 38120C on a densitometer conforming to ANSI PH2.19-1986, with the T5100C sold for densitometer calibration.; Product table — the T2115, 21 steps at a nominal 0.15 density increment to a maximum density of 3.05; and the note that only the T2120CC and T1530CC are supplied calibrated, against NIST Standard Reference Material 38120C; Product table - the T2115, 21 steps at a nominal 0.15 density increment to a maximum density of 3.05; and the note that only the T2120CC and T1530CC are supplied calibrated; Product table - the T2115, 21 steps at a nominal 0.15 density increment to a maximum density of 3.05; and the note that only the T2120CC and T1530CC are supplied calibrated, against NIST Standard Reference Material 38120C; Product table - the T2115, 21 steps at a nominal 0.15 density increment to a maximum density of 3.05 on a half by five inch part; and the note that the calibrated parts are the T2120CC and T1530CC, whose steps compare with a NIST Standard Reference Material 38120C step tablet by means of a densitometer conforming to ANSI PH2.19-1986; Specification table - the T2115 at 21 steps of 0.15 to a maximum density of 3.05, and the T4110 at 41 steps of 0.10 to 4.05, which sets how much of a curve one wedge can reach; Specification table - the T2115 at 21 steps of 0.15 to a maximum density of 3.05, which is the scale a stray-light ceiling truncates; Specification table - the nominal density increments of each wedge type, and the separate note that the T2120CC and T1530CC are calibrated against NIST Standard Reference Material 38120C by a densitometer conforming to ANSI PH2.19-1986, which the uncalibrated types are not; Specification table - the T2115 with 21 steps at 0.15 density increment to a maximum density of 3.05, and the note that the calibrated wedges are checked against NIST Standard Reference Material 38120C; Transmission step wedge specifications - the physical sizes of the wedges, the 21-step T2115 at half an inch by five inches, and the density increments of each type; Specification table for transmission step wedges, including the 21-step T2115 at a 0.15 increment, usable as the reference against which an easel illumination map is read

Used by:P5 Project 3: A Bromide Enlarging Emulsion · P5 Project 1: A Silver Chloride Contact Printing Emulsion · P5 Lab: Coating Your First Emulsion · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P5 Assignment: The Hand-Coated Print · P6 Commissioning the Camera: Light-Tightness, Flare and the First Negatives · P6 Curved Film Plane and Multiple-Pinhole Experiments · P6 Lab: Processing Your First Film · P9 Overview: Experiments on Development · P9 Assignment: The Developer Laboratory Report · P9 Experimental Design for the Darkroom · P9 Lab: Preparing Standard Test Negatives · P9 Experiment: The Solvent Series - Sulfite, Dilution and Agitation · P13 Part XIII Overview: Measuring the Response of Silver to Light · P13 Exposure, Density and the Logarithm · P13 Lab: A Step-Wedge Exposure Series · P14 Part XIV Overview: Build a Sensitometer · P14 Experiment: Calibrating the Sensitometer · P14 Sensitometer Design Principles · P14 Build: The Enclosure and Exposure Stage · P15 Part XV Overview: Build a Densitometer · P15 Experiment: Calibrating the Densitometer in Both Modes · P15 Build: The Densitometer Electronics and Firmware · P15 Build: The Densitometer Optical Head (Transmission and Reflection) · P15 Density Depends on How You Look: Geometry and Spectral Response · P15 Break-Fix: Diagnosing a Misbehaving Densitometer · P15 Assignment: Characterising a Film and Developer with Your Own Instruments · P19 Reading the Negative and Making the Work Print · P20 Experiment: Selenium Toning and the Print Curve · P21 Experiment: The Exposure Scale, Maximum Density and Contrast of a Cyanotype · P27 Part XXVII Overview: From Observation to Measurement · P27 Experiment: Agitation, Stand and Semi-Stand Development · P27 Designing an Experiment That Yields a Number · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Experiment: Four Curve Families, Measured · P27 Experiment: The Development Time and Temperature Series · Blocked shoulder · Densitometer: high-density compression · Densitometer: scale error · Low contrast index · Uneven density across a strip · Uneven enlargement from mixing chamber, alignment, lens falloff or mechanical vignette

talbot.bodleian.ox.ac.uk

An Account of the Processes employed in Photogenic Drawing — guest post on the William Henry Fox Talbot Catalogue Raisonne blogretrieved 2026-09-06

Sections: The whole of the post: the 34.4 per cent of its own weight of salt that silver nitrate needs for chemical equivalence, the failure of a paper made to those proportions, the silver meeting only about one twentieth of its weight of salt, and the observation that the mechanism was not understood until the middle of the twentieth century, "which accounts for the historiographic observation that silver photography, for the first century of its life, was led by empirical practice rather than chemical theory"

Used by:Talbot's photogenic drawing paper

thameswater.co.uk

Hard water: water quality help and adviceretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Hardness of water — the classification bands in mg/L as CaCO3; Hardness of water — the classification bands in mg/L as calcium carbonate; Hardness of water - the classification bands in mg/L as calcium carbonate; Hard water - the classification bands in milligrams per litre as calcium carbonate, soft up to 100, slightly hard 100 to 150, moderately hard 150 to 200, hard 200 to 300 and very hard above 300; and the statement that all the water in the company's region is hard because it passes through chalky limestone; Reported water hardness by supply area, expressed in milligrams of calcium carbonate per litre, as the basis for expecting a deposit from tap water

Used by:Calcium carbonate · Sodium hexametaphosphate (Calgon) · P3 Acids, Bases and pH · P3 Lab: Measuring pH and Trusting the Number · P21 Break/Fix: The Cyanotype That Went Wrong · Drying marks and squeegee lines on prints

thelightfarm.com

Photographic Emulsion Chemistry (The Focal Library)retrieved 2026-09-04, 2026-09-05

Sections: Chapter VIII, Hardening, pages 158 to 162 — the two classes of hardener, glyoxal as the simplest dialdehyde, and the kinetic result of one glyoxal molecule per two gelatin units; Page 74, the iodide range of 1.0 to 8.0 per cent in a bromide emulsion; page 80, the Bacteriocides section; page 94, Quantities of Sensitizer, for the active sulphur content of gelatins running from 1 to 2 parts per million for the inert types to 100 parts per million for active gelatins, and for Bekunov's 25 to 150 parts per million of thiosulphate in the gelatin at an assumed 200 g of gelatin per gram mole of silver; page 158, the chrome alum dose of 0.5 to 2 per cent of the gelatin weight, its point of addition immediately before coating, its pH dependence near 6.0 and its coagulation failure mode; page 161, that excessive hardening of the layers will interfere with developer penetration; Page 74: chlorobromide emulsions being of greater speed and softer in contrast as the bromide content increases, and chloride and chlorobromide emulsions being produced by either the single-jet or the double-jet technique but frequently by reversed precipitation. Page 158, the chrome alum dose of 0.5 to 2 per cent of the gelatin weight, its introduction into the molten emulsion immediately before coating, its dependence on pH and its effectiveness at the usual coating pH of about 6.0, the rapidity of the reaction, and the coagulation that follows too rapid an addition; Chapter VIII, Coating, the Hardening section, pages 158 to 162: chrome alum as the most commonly used inorganic hardener; the dependence of its action on pH, effective at the usual coating pH values of about 6.0 and far less effective at higher pH; the rapidity of the reaction; the coagulation that follows too rapid an addition through a temporary excessive local concentration; and the observation that excessive hardening of the layers will interfere with developer penetration; Chapter VI, Spectral Sensitization: dye adsorption on page 114, dye aggregation on page 116, the mechanism of dye sensitization on page 129 with electron transfer on page 130 and energy transfer on page 131, and desensitization on page 134; page 125, Optimum Quantity of Sensitizer, for sensitivity rising with the quantity of dye adsorbed to a maximum at a point reached before total coverage of the crystals, for the rapid loss of useful speed if too much dye is added, for smaller quantities than that giving maximum speed often being preferred commercially, and for the exact position of the maximum being a function of the particular dye and the nature of the emulsion; Chapter V, Chemical Sensitization, page 95: 'It appears from published data that the quantities of gold used are of much the same order as that of the sulphur sensitizer, e.g. from 1 to 30 mg. of gold, either as chloroauric acid or a more complex gold salt, being used per gram mole of silver. If a gold sensitizer is added at the completion of digestion, then larger quantities are needed.'; Figure 5.9, Quantity of gold, for a sodium aurothiocyanate iodobromide emulsion, plotting relative log speed against quantity of gold in moles times ten to the sixth, with an optimum near 3 by 10^-6 moles and a maximum increase over sulphur sensitization alone of about 0.33 log exposure units; page 94, Quantities of Sensitizer, for the active sulphur content of gelatins and for Bekunov's 25 to 150 parts per million of thiosulphate in the gelatin at an assumed 200 g of gelatin per gram mole of silver; page 95 for the statement that only a fraction, usually around 10 per cent, of the sulphur sensitizer has broken down by the time the speed has reached its maximum; Chapter IV, the five stages of emulsion preparation and the neutral against ammonia distinction; Chapter V, quantities of sensitizer; Chapter VIII, hardening; Page 94, Quantities of Sensitizer: the 1 to 2 parts per million of active sulphur in inert gelatins against 100 in active ones, Bekunov's 25 to 150 parts per million of thiosulphate in the gelatin for an iodobromide emulsion of 3.1 molar per cent iodide, and the assumption of 200 g of gelatin per gram mole of silver; page 95, the speed-against-digestion-time curves at four doses, the finding that larger quantities give a lower maximum speed, the statement that only about 10 per cent of the sensitizer has broken down at the speed maximum, and the warning that very small quantities probably bring on fog before useful sensitivity; page 74 for the 1.0 to 8.0 per cent iodide range in a bromide emulsion; pages 75 to 81 for noodle washing, its dilution of the emulsion and the pAg endpoint; page 158 for chrome alum at 0.5 to 2 per cent of the gelatin weight; Chapter VIII, Coating: trough coating at a closely controlled 36 to 40 °C and the reason for that range; setting as hydrogen bonding; drying from about 85 per cent water to about 5 per cent and the finding that slower drying gives a more orderly array of gelatin molecules; Chapter IV: physical ripening by excess halide, the neutral against ammonia distinction and the higher temperatures a neutral make needs; the effect of excess halide on grain growth; Page 74: chlorobromide emulsions of greater speed and softer in contrast as the bromide content increases, and the iodide range for bromide emulsions; page 66, ammonia emulsions ripening at 40 to 45 °C where neutral emulsions need much higher temperatures; page 158, the chrome alum dose of 0.5 to 2 per cent of the gelatin weight, its point of addition immediately before coating, its pH dependence near 6.0, and coagulation from too rapid an addition; Chapter VIII, Coating, pages 153 to 162: emulsion concentration and the silver-to-gelatin ratio; wet and dry layer thicknesses; trough coating at 36 to 40 °C and why that range; chilling by cooled rollers or cold air; setting as hydrogen bonding and the role of the guanidino groups of arginine; drying from about 85 per cent water to about 5 per cent, with gelatin retaining 10 to 12 per cent of its weight of water, and the finding that slower drying gives a more orderly array; the Hardening section, with the chrome alum dose of 0.5 to 2 per cent of the gelatin weight, its pH dependence, its coagulation failure mode and its speed, the formaldehyde dose and its fog on storage, glyoxal's kinetics, the aldehydes as reducing agents needing a stabiliser, and the hardening accelerators; and Plasticizers, on glycerol and tackiness. Page 81, storage below 5 °C and the keeping of digested against undigested emulsion; Chapter VIII, Coating: layers 30 to 600 micrometres thick at coating drying to 2 to 40 micrometres, water falling from about 85 per cent to about 5 per cent because the gelatin retains 10 to 12 per cent of its own weight; page 158 for chrome alum at 0.5 to 2 per cent of the gelatin weight, its addition immediately before coating, its pH dependence near 6.0 and coagulation from too rapid an addition; page 161 for excessive hardening interfering with developer penetration; Chapter VIII, Coating: the closely-controlled 36 to 40 °C trough-coating range and the reason for choosing it; setting as hydrogen bonding rather than chemical reaction; drying from about 85 per cent water to about 5 per cent; page 161 on excessive hardening interfering with developer penetration; Page 74: chloride and chlorobromide emulsions produced by single-jet or double-jet technique, and reversed precipitation in which the silver is added to insufficient halide with the remaining halide added afterwards; pages 94 and 95, Quantities of Sensitizer, for Bekunov's 25 to 150 parts per million of thiosulphate in the gelatin at 200 g of gelatin per gram mole of silver, for larger quantities producing a lower maximum speed, for only about 10 per cent of the sensitizer having broken down at the speed maximum, and for the warning that very small quantities probably bring on fog before useful sensitivity; page 95 for gold at 1 to 30 mg per gram mole of silver as chloroauric acid or a more complex gold salt, with larger quantities needed if the gold is added at the completion of digestion, and Figure 5.9 showing an optimum near 3 × 10^-6 moles of gold and a maximum gain of about 0.33 log units over sulphur sensitisation alone; page 96, Restrainers, for the adenine naturally present in hide gelatins at 30 to 50 parts per million against 4 to 6 in ossein gelatins; page 125 for the optimum quantity of spectral sensitiser, the rapid loss of useful speed if too much dye is added, and the statement that the position of the maximum is a function of the particular dye and the nature of the emulsion; Chapter VIII, Coating: setting as the formation of hydrogen bonds between gelatin chains, and drying from about 85 per cent water to about 5 per cent because the gelatin retains 10 to 12 per cent of its own weight; page 158, chrome alum introduced carefully into the molten emulsion immediately before coating, its action dependent on pH and effective near 6.0, and coagulation of the emulsion from too rapid an addition giving a temporary excessive local concentration; page 161, excessive hardening of the layer interfering with developer penetration, and all the aldehyde hardeners being reducing agents and prone to give fog; Chapter VIII, Hardening, pages 158 to 162: the two classes of hardener, the chrome alum dose and its pH dependence, the formaldehyde mechanism, dose and fog on storage, glyoxal kinetics, and the hardening accelerators; page 96, restrainers naturally present in gelatin; Chapter IV, Emulsion Preparation, pages 57 to 74: the five stages of a make; emulsification by single jet and double jet (Figure 4.1); the complex-ion equations for silver bromide in excess bromide and the ammine complex; the cause of ripening; the ten emulsion variables; Table 4.1, effect of emulsification time on grain size and speed; multiple emulsification; the effect of iodide and Figure 4.2; gelatin and slower grain growth; the octahedral emulsion of pages 66 to 67; and the ammonia against neutral distinction on page 66; Page 161: excessive hardening of the layers interfering with developer penetration; chapter VIII, Coating, for the water content of a layer falling from about 85 per cent to about 5 per cent on drying; Chapter IV, pages 75 to 81: emulsion separation and washing, noodle washing and its two endpoint measurements, coagulation washing, solvent, salt and sulphonic-acid precipitation, acylated gelatin, redispersion and bacteriocides. Chapter V, Chemical Sensitization, pages 83 to 96: digestion and Figure 5.1; sulphur sensitization; the nature of the sensitizing substance and of digestion fog; gold sensitization; sensitization by metals other than gold; quantities of sensitizer including Bekunov's 25 to 150 ppm and Figure 5.8; the gold range and Figure 5.9; and restrainers naturally present in gelatin. Page 125, the optimum quantity of spectral sensitiser; Page 74, chlorobromide emulsions being of greater speed and softer in contrast as the bromide content increases; The five stages of a make; washing and the retardation of chemical sensitisation by excess halide; sulfur digestion and what it does to speed; the coating water figures; Page 74 — chlorobromide emulsions of greater speed and softer contrast as the bromide content increases; ammonia and the temperature of digestion; The pH dependence of chromium(III) cross-linking of gelatin; the water content of a coating wet and dry; The five stages of a make; Ostwald ripening; the retardation of chemical sensitisation by excess halide; Page 158, the chrome alum dose of 0.5 to 2 per cent of the gelatin weight, its point of addition immediately before coating, and its pH dependence near 6.0; The swelling of noodles during washing and the fall in emulsion concentration; the requirement that a coatable emulsion not drop appreciably below 5 per cent gelatin; the preference for direct determination of pAg as a wash endpoint; page 94, Quantities of Sensitizer, 1 to 2 parts per million of active sulphur in inert gelatins against 100 in active ones; Chapter VIII, Coating, the closely-controlled 36 to 40 degrees C trough-coating range, setting as hydrogen bonding, and drying from about 85 per cent water to about 5 per cent; Page 81: storage below 5 °C, a stable finished emulsion kept for several months, and undigested material usually only a few days; Chapter VIII, Coating - setting as the formation of hydrogen bonds between gelatin chains as the temperature falls; Chapter VIII, Coating - drying from about 85 per cent water to about 5 per cent because the gelatin retains 10 to 12 per cent of its own weight; Page 161 - excessive hardening of the layer interfering with developer penetration; Chapter VIII, Coating - setting as the formation of hydrogen bonds between gelatin chains, and the behaviour of the layer as it is laid; Chapter VIII, Coating - drying from about 85 per cent water to about 5 per cent, and the gelatin retaining 10 to 12 per cent of its own weight; Chapter VIII, Coating - setting as the formation of hydrogen bonds between gelatin chains, and drying from about 85 per cent water to about 5 per cent

Used by:Glyoxal · Trumm's bromide paper emulsion · Wall's soft-working gaslight paper · Kodak SB-4 · Erythrosin sensitising stock · Steigmann gold sensitiser stock · P5 Part V Overview: Photographic Emulsions · P5 Project 3: A Bromide Enlarging Emulsion · P5 Build an Emulsion Coating Station · P5 Project 1: A Silver Chloride Contact Printing Emulsion · P5 Project 2: A Chlorobromide Paper Emulsion · P5 Coating, Drying and Hardening · P5 Project 4: Coating Glass Dry Plates and a Lantern Slide · P5 Lab: Coating Your First Emulsion · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P5 Break/Fix: Emulsion Coating Defects · P5 Gelatin, the Photographic Binder · P5 Precipitation, Nucleation and Crystal Growth · P5 Assignment: The Hand-Coated Print · P5 Washing, Digestion and Sensitisation · P18 Paper Emulsions: Halide, Grain, Image Tone and Speed · Hand-coated bromide paper · Hand-coated chlorobromide paper · Dry plate and lantern slide · Hand-coated silver chloride contact paper · The chromium policy · An emulsion preparation session · Refrigerated emulsion labelling and food separation · Bubbles and pinholes in a coating · Coating mottle and drying marks · Frilling · Repellency spots · Thin coat · Uneven coating thickness

The Light Farm: silver gelatin emulsion making for the artistretrieved 2026-09-04, 2026-09-05

Sections: Tutorial 17, Ammonium Bromide Plain Silver Negative Emulsion, part 1 — the substitution of 4.1 g of ammonium bromide for 5 g of potassium bromide in her modification of Kodak AJ-12, the reason given for it, and the side-by-side comparison of the two emulsions; Paper coating tutorial — hardening the emulsion by adding glyoxal immediately before coating, and the penetration consequence in thick patches; Tutorial 9, KCl Gaslight Paper — The Recipe: the salted gelatin of 150 g water, 3 g potassium chloride and 25 g gelatin, the 5 g silver solution, and the precipitation temperature; Dry Plate Recipes: The Light Farm Glass Negative Emulsion #1; Tutorial Workshops, Plain Silver BrI Dry Plate Emulsion — The Recipe, headed as an adaptation of Kodak Publication No. AJ-12, 1969 Revision: the domestic-scale plain-silver iodobromide make that Part V performs in place of this formula, with its noodle wash of six changes of three minutes in ice water through a potato ricer, its coating rate of one tablespoon per 4 by 5 plate, and the finding on her dry plate recipes page that the pH lowering curves during washing were identical from 10 to 7.8 over two separate trials, with the endpoint given as a pH between 7 and 8 and overwashing to be avoided; Tutorial Workshops, Dry Plate — Glass: the statement that no subbing coat is used at all, with clean 1/16 inch glass coated directly on a moistened plastic-wrap bed over levelled glass, the water-puddle levelling test and the fixing test that confirms it; Tutorial Workshops, AmBr with Variations — The Recipe, stated as developed by the author rather than adapted from anyone: the two per cent erythrosin stock made as 1 g of the dye in 50 mL of solvent, the solvent being half distilled water and half drinking-grade ethanol, with the reason given for drinking grade being that laboratory and shop grades carry added ingredients whose effect she does not know; the dye dosed as 3 to 4 drops into the salted gelatin of a make carrying 5 g of silver nitrate, added after the 10 per cent potassium iodide and before the silver; the handling practice of buying the exact amount to be mixed rather than weighing the powder, staging the solvent, an amber dropper bottle, a beaker about twice the final volume and a plastic spoon, wearing latex or nitrile gloves, never getting the face near the materials, treating a dust mask as prudent, rinsing the dye bottle into the beaker in stages, and labelling the dropper bottle with concentration, solvent and date; and the statement that up to now, colourblind or ortho, the work could be done under a red safelight, while panchromatic sensitisation requires darkness or a very dim headlamp; The Light Farm Glass Negative Emulsion #1, dry plate recipes, the digestion step and its footnote. The step reads '6-7 drops Steigmann standard aurous ammonium thiocyanate solution', stirred one minute at 40 °C, after which the temperature is brought up so that the emulsion itself reaches 52 °C and is pulled. The footnote reads 'Steigmann standard aurous ammonium thiocyanate solution: From SPSE Handbook of Photographic Science and Engineering, Edited by Woodlief Thomas, Jr., 1973, pp 518-519. Add 6.0 ml of a 1% gold chloride solution to 50 ml of a 1% ammonium thiocyanate solution, allowing it to clear before using. (Store in dark dropper bottle.)' She adds that a 1 per cent gold chloride solution is available ready made from Photographers' Formulary, and that a 1 per cent ammonium thiocyanate solution is 1 g in 99 to 100 ml of distilled water at about 52 °C, cooled before use. The emulsion the dose sits in is ammoniacal: its Part B is 5.2 g of silver nitrate in 5 ml of water with 5 ml or more of 28 per cent ammonia added drop by drop until the silver hydroxide precipitate just redissolves, with her own note that excellent ventilation is a very good thing there; the make carries 10.8 g of silver nitrate in all and yields about 200 ml; Tutorial Workshops, KCl Gaslight Paper — The Recipe, headed 'A homemade CHLORIDE EMULSION, by T. Thorne Baker for American Photography, March 1943. KCl Gaslight Paper Version, adapted by Denise Ross for The Light Farm, 2012', with the background and the annotated original on the preceding page. The salted gelatin is distilled water 150 g (150 ml), or 135 ml if vodka is used instead of Everclear, potassium chloride 3 g, and photographic gelatin 25 g stirred in slowly after the chloride has dissolved; the silver solution is silver nitrate 5 g in distilled water 25 g (25 ml). Cover and bloom 30 minutes to several hours; set the covered cup in a water bath preheated to 49 to 52 °C and hold until the salted gelatin itself reads 49 to 51 °C. Under safelight, start a 5 minute timer and whisk the salted gelatin continuously in one direction; pour in about one third of the silver solution while whisking, whisk 1 minute, add the second third, whisk 1 minute, add the remainder and whisk to the end of the 5 minutes. Cover with plastic wrap, stand the stacked cups in a pot, pour in near-boiling water to half the height of the outer cup and lid the pot, for approximately 30 minutes. Cool to about 40 °C and coat 50 to 55 ml per 11 by 15 inch sheet of 90 lb hot-press watercolour paper, wet-coated with a 9 inch puddle pusher; dry the sheets in the dark and store lightproof. Develop 2.5 to 3 minutes, dilute stop 1 minute, two-bath fix 3 minutes in each, then wash; her step wedge was developed in Photographers' Formulary BW65 at 1 to 1 to 4. The batch may be halved after ripening and the second half refrigerated up to one week in a lightproof container and remelted at 50 to 51 °C without stirring, or the whole batch refrigerated before ripening and remelted at 50 °C then cooled to 40 °C to coat. The tools page states that the first recipe calls for 15 ml of Everclear and names a wetting agent, neither of which is placed in the recipe itself. The safelight is a string of red LED mini-lights or a 25 W yellow bug light, and the background page adds that a pure chloride emulsion is sensitive only to ultraviolet and the edge of the violet. Her 30 January 2013 addendum assesses an independent reader's first batch and gives the tested direction for thickening a thin coat by adding gelatin 2 to 3 g at a time; Tutorial Workshops: the KCl gaslight paper recipe adapted from Baker 1943; the Plain Silver BrI dry plate emulsion adapted from Kodak AJ-12; AmBr with Variations; and the dry-plate glass and coating tutorials; Tutorial Workshops, Plain Silver BrI Dry Plate Emulsion — The Recipe, headed as an adaptation of Kodak Publication No. AJ-12, 1969 Revision: the 55 °C bath, the salted gelatin of 45 mL water, 5 g potassium bromide and 2 g gelatin, the 1 mL of 10 per cent potassium iodide, the second gelatin of 5 g in 25 mL, the silver solution of 5 g in 45 mL warmed immediately before use to cut down pepper, the addition at 5 mL per minute over ten minutes, the ten-minute unstirred hold, the refrigerated set, the potato-ricer wash in six three-minute changes of ice water, the 45-minute ripening at 55 °C with 5 mL of ethanol, the coating window in the low-to-mid 30s to lower 40s °C, and the 15 mL per 4 × 5 inch plate at ten to twelve plates per batch. Dry Plate recipes page for the pH endpoint measured from 10 down to 7.8 on two trials, and for the several-days refrigerated keeping of washed noodles with the instruction never to freeze. Odds and Ends for the transmitted-colour ladder of undyed emulsions; Tutorial Workshops: Dry Plate, Glass, for the water-puddle levelling method, the fixer test for level, the plastic-wrap coating bed with dam bars, and the drying room at about 24 °C with fabric taped over the air vent; Getting Started (Tools and Materials) for the puddle pusher made from taped and puttied glass rod, the plate glass, the whisk and the corrosion warning, and the red LED string or 25 W yellow bug light; Getting Started (Heat) for the water-bath arrangements from a nested Pyrex stack in a pot up to an immersion circulator; Tutorial Workshops: KCl Gaslight Paper — Background, and KCl Gaslight Paper — The Recipe, headed "A homemade CHLORIDE EMULSION, by T. Thorne Baker for American Photography, March 1943. KCl Gaslight Paper Version, adapted by Denise Ross for The Light Farm, 2012": the quantities, the 49 to 51 °C melt, the five-minute three-portion addition with continuous whisking, the thirty-minute ripening in a hot-water stack, the 40 to 42 °C coating window, 50 to 55 mL per 11 × 15 inch sheet of wet 90 lb hot-press watercolour paper, the processing sequence, the hold-and-split instruction, the 30 January 2013 addendum on thin coats and gelatin additions, and the safelight. Also Getting Started (Tools and Materials) for the ethanol, the puddle pusher and the whisk-corrosion warning; Tutorial Workshops: KCl Gaslight Paper — The Recipe, for the three-portion five-minute addition schedule and the 40 to 42 °C coating window carried over from Project 1; Odds and Ends, for the transmitted-colour ladder of undyed emulsions and the safelight consequence; Tutorial Workshops: Getting Started (Heat) for the two working temperatures and the viscosity argument; Getting Started (Paper Coating, Wet Paper Method) for the wet-paper method, the puddle pusher, the troubleshooting of too-warm and too-cool emulsion, bubbles, the case against hardening and the Selectol lift-off; KCl Gaslight Paper, The Recipe, for the 40 to 42 °C coating window and the volume per sheet; Getting Started (Tools and Materials) for the sheet count per batch; Dry Plate, Glass, for levelling, the plastic-wrap bed, dam bars, the spoon-spread coating and the drying room; Tutorial Workshops, Dry Plate — Glass: 1/16 inch glass thin enough for holders that will not take 2 mm picture-framing glass, four 4 × 5 plates from an 8.5 × 11 inch sheet, edges smoothed with a 220 mesh diamond hand pad, holders taking glass an eighth of an inch under the named format, the water-puddle levelling test and the fixing test that confirms it, the moistened plastic-wrap bed over levelled glass with six plates and four dam bars at a 1/16 to 1/8 inch gap, the tablespoon of emulsion per 4 × 5 plate spread with the bottom of a round-bowled spoon, the instruction not to rework a plate, cutting the emulsion between plates and bars when dry, and the warm drying room with fabric over the air vent; the statement that no subbing coat is used at all; Tutorial Workshops: Getting Started (Paper Coating, Wet Paper Method) for the wet-paper method, the puddle-pusher stroke, the appearance of too-warm and too-cool emulsion, bubbles, the case against hardening and the Selectol lift-off and its remedy; Dry Plate, Glass, for the levelled plastic-wrap bed, dam bars, the spoon-spread plate coating, not reworking a plate, and cutting the emulsion between plates when dry; Tutorial Workshops, AmBr with Variations — The Recipe, stated as developed by the author rather than adapted: salted gelatin of 45 mL distilled water, 4.1 g ammonium bromide and 2 g gelatin, bloomed fifteen minutes and held thirty minutes in a 55 °C bath, then 1 mL of 10 per cent potassium iodide, then 3 to 4 drops of a 2 per cent erythrosin solution for an ortho or panchromatic emulsion; the 2 per cent stock made as 1 g in 50 mL of half distilled water and half drinking-grade ethanol, with the dye-handling practice of buying the exact amount, never weighing the powder, gloves, keeping the face away and a dust mask; the six five-minute wash changes totalling thirty minutes, the sixty-minute ripening at 55 °C, the finals of 5 mL of ethanol optionally with 2 drops of 10 per cent potassium bromide as insurance against excessive base fog and a further 5 mL of ethanol at 34 to 35 °C, and coating in the low-to-mid 30s °C; the single-jet addition at 5 mL per minute and the note allowing a syringe or stopcock burette for a sequential second addition; the statement that up to now, colourblind or ortho, you could work under a red safelight and that panchromatic sensitisation requires darkness or a very dim headlamp; the Steigmann aurous ammonium thiocyanate preparation quoted from the 1973 SPSE handbook and the 6 to 7 drop dose in her ammoniacal glass negative emulsion; the note that orange and red filters are useless with orthochromatic material for the same reason a red safelight is usable; Tutorial Workshops and Dry Plate pages: the Selectol Soft lift-off, in which an emulsion bubbled, frilled at the edges and lifted clean off the paper, with a hardening fixer preventing it completely and the advice to switch developers or use a hardening protocol if an emulsion lifts, and the same remedy given for frilling plates as a hardening fixer in the second fixing tray; the reasoned case for not hardening, that unhardened emulsion tones and spots more readily and that random thicker patches will not necessarily ruin a print because processing chemistry penetrates them, against the observation that hardened emulsion resists penetration especially by the fixer so that thick areas darken later in room light; the addendum treating a thin, streaky coat as a gelatin problem corrected by adding 2 to 3 g of gelatin at a time; undissolved potassium bromide pellets giving black slugs or sunspots; warming the silver solution before precipitation to cut down pepper; the drying room held near 24 °C with fabric taped over the air vent to exclude dust without blocking airflow; a paper whose sizing recipe had been changed by its maker causing blistering during processing, and a later lot of a different paper producing mottled fading late in the wash; the instruction not to rework a plate because the emulsion sets fast; Tutorial Workshops, Getting Started (Tools and Materials): photographic gelatin, hard 250 Bloom; Getting Started (Heat): the two working temperatures of emulsion making; KCl Gaslight Paper, The Recipe: bloom, melt and hold temperatures; Tutorial Workshops: Plain Silver BrI Dry Plate Emulsion, the recipe, for the single-jet addition at 5 ml per minute and the ripening hold; Dry Plate, Odds and Ends, for the transmitted-light colour ladder, the percentage-solution method for iodide, and the AJ-12 iodide proportion; AmBr with Variations, for the sequential double addition; Deep Dive into AmBr, for the practitioner's case against ammonia; The reasoned case for an unhardened emulsion: that it tones more readily and spots more readily, that random thicker patches will not necessarily ruin a finished print because processing chemistry penetrates even the thickest areas, and that the trade-off is a tender wet layer handled gently and at the corners all the time it is wet, never squeegeed but pulled from the last wash and hung by a corner, and no longer tender once dry; against the observation that a hardened emulsion resists penetration especially by the fixer so that thick areas darken later in room light; the note that a change of paper lot can cause blistering or mottled fading, which is why brand and lot belong in the record; Tutorial Workshops: Plain Silver BrI Dry Plate Emulsion, the recipe, for the potato-ricer wash of six three-minute changes and the 45 minutes at 55 °C; Dry Plate, Odds and Ends, for why an emulsion is washed and the noodle surface-area rule; the dry-plate recipes pages for the pH endpoint and the Steigmann gold preparation; AmBr with Variations for the erythrosin dose, the solvent and the handling advice; The chlorobromide adaptation and its digestion; the safelight caution for a mixed-halide emulsion; Coating glass without a sub, on a moistened plastic-wrap bed; The KCl gaslight-paper adaptation of T. Thorne Baker's 1943 chloride emulsion, its quantities, ripening and coating; Tutorial Workshops, Plain Silver BrI Dry Plate Emulsion, The Recipe: the salted gelatin held at 55 degrees C, the warmed silver solution and its stated purpose of cutting down pepper, the addition rate of one teaspoon per minute, the ten-minute hold without stirring, the second gelatin added before the set, the refrigerated set, the six three-minute changes of ice water through a ricer and straining bag, the forty-five-minute ripen at 55 degrees C, the five millilitres of ethanol as the finals with two drops of ten per cent potassium bromide as the variant, and the coating temperature and rate; Tutorial 14, Dry Plate — Glass: a 3M diamond hand pad, 220 mesh, for smoothing plate edges; glass bought with all four sides already smoothed, so that only two cut edges of each plate need dressing by hand; the local merchant's 1/16 inch stock arriving in sheets too large to handle easily without breakage; plates reusable if they are not scratched; the instruction never to touch the plates without cotton or clean nitrile gloves; and each prepared blank stored in the individual negative sleeve that will later hold the finished plate; Tutorial Workshops, Dry Plate - Glass: the puddle-of-water levelling test, with the fixing tray named as the confirmation that finds a slope the puddle missed; the moistened plastic-wrap bed vacuum-sealed onto moistened levelled glass; six plates and four dam bars, a 1/16 to 1/8 inch gap between every plate and its neighbours with the bars butted tight against each other, and four or six plates as the working maximum; the instruction never to touch the plates without cotton or clean nitrile gloves; one tablespoon, 15 mL, per 4 x 5 inch plate, poured and spread with the bottom of a round-bowled spoon; chasing bubbles to the edges, leaving a bubble caught between plates, and the instruction to resist reworking a plate because the emulsion sets up fast; cutting the emulsion between plates and dam bars with a sharp blade when dry rather than pulling the plates apart, and propping the plates to dry the smear on the underside; the small room radiator set to about 75 F for a cool damp climate; the fabric taped over the air vent to stop dust without stopping airflow; and storing finished plates in individual negative sleeves or a paper safe; Tutorial Workshops, Dry Plate recipes: the several-days refrigerated keeping of washed noodles in a lightproof container, with the instruction never to freeze them, and the warning that an emulsion held too long will fog. KCl Gaslight Paper, The Recipe: the hold-and-split instruction, with the second half refrigerated up to a week in a lightproof container and remelted at 50 to 51 °C without stirring; Tutorial Workshops and Dry Plate pages - undissolved potassium bromide pellets giving black slugs or sunspots, and warming the silver solution before precipitation to cut down pepper; Tutorial Workshops and Dry Plate pages - handling the melt before coating and the instruction not to rework a plate because the emulsion sets fast; Tutorial Workshops and Dry Plate pages - the drying room held near 24 degrees Celsius with fabric taped over the air vent to exclude dust without blocking airflow, and the paper lots whose sizing change produced blistering and mottled fading; Tutorial Workshops and Dry Plate pages - undissolved potassium bromide pellets giving black slugs or sunspots, and the instruction to strain the melt; Tutorial Workshops and Dry Plate pages - the Selectol Soft lift-off in which an emulsion bubbled, frilled at the edges and lifted clean off the paper, with a hardening fixer preventing it completely, and the same remedy given for frilling plates as a hardening fixer in the second fixing tray; Tutorial Workshops and Dry Plate pages - the coating practice, the wetting agent named in the tools list with no dose given anywhere, and the cleaning of supports; Tutorial Workshops and Dry Plate pages - the addendum treating a thin, streaky coat as a gelatin problem corrected by adding 2 to 3 g of gelatin at a time

Used by:Ammonium bromide · Glyoxal · Potassium chloride · Potassium iodide · Trumm's bromide paper emulsion · Chrome alum subbing dip · Erythrosin sensitising stock · Steigmann gold sensitiser stock · KCl gaslight paper emulsion · P5 Part V Overview: Photographic Emulsions · P5 Project 3: A Bromide Enlarging Emulsion · P5 Build an Emulsion Coating Station · P5 Project 1: A Silver Chloride Contact Printing Emulsion · P5 Project 2: A Chlorobromide Paper Emulsion · P5 Coating, Drying and Hardening · P5 Project 4: Coating Glass Dry Plates and a Lantern Slide · P5 Lab: Coating Your First Emulsion · P5 Project 5: Designing an Emulsion, and Making the One We Can Source · P5 Break/Fix: Emulsion Coating Defects · P5 Gelatin, the Photographic Binder · P5 Precipitation, Nucleation and Crystal Growth · P5 Assignment: The Hand-Coated Print · P5 Washing, Digestion and Sensitisation · Hand-coated chlorobromide paper · Dry plate and lantern slide · Hand-coated silver chloride contact paper · An emulsion preparation session · Glass handling, cutting and breakage response · Plate coating and drying · Refrigerated emulsion labelling and food separation · Black spots · Bubbles and pinholes in a coating · Coating mottle and drying marks · Comets · Frilling · Repellency spots · Thin coat · Uneven coating thickness

The Photographic Emulsionretrieved 2026-09-04

Sections: RP525, The Photographic Emulsion: The Mechanism of Hypersensitization — the organic preservatives; the synthesis, melting point and silver compound of nitrobenzimidazol; its effect on after-ripening and on dye sensitization; RP525, The Photographic Emulsion: The Mechanism of Hypersensitization — abstract and section I; The mechanism of hypersensitization — the contrast between ammonia's positively charged silver complex and the negatively charged complexes formed in cyanide, thiosulphate, sulphite or thiocyanate solutions; RP525, The Photographic Emulsion: The Mechanism of Hypersensitization — the organic preservatives, nitrobenzimidazol, the insolubility of its silver compound and its effect on after-ripening; RP525 — the organic preservatives, nitrobenzimidazol, the insolubility of its silver compound and its effect on after-ripening; Silver Ion and Gelatin, Bureau of Standards Journal of Research: the break in the silver-ion combination curves at about pH 4.7, and the finding that gelatin lowers silver ion activity; The ripening study in which samples drawn at about 30, 60 and 120 minutes give four stages from one batch, and the observation that the texture of the silver bromide on the centrifuge bowl wall roughens with each successive sample; The silver-ion and gelatin equilibrium, and the sensitisation study using sodium sulphite; RP525: the silver compound of nitrobenzimidazol, its preparation and the silver-electrode measurement showing it more insoluble than silver bromide at pH 7.1 and readily displaced by hydrogen at pH 3.5; the finding that mol for mol it produces about ten times the effect of soluble bromide in delaying after-ripening, with the authors&apos; own caution that something more than the decrease in silver ion concentration must be involved; and the selective depression of dye sensitisation

Used by:6-Nitrobenzimidazole · Ammonia solution (ammonium hydroxide) · Ammonium thiocyanate · Benzotriazole · Tetraazaindene · P5 Gelatin, the Photographic Binder · P5 Precipitation, Nucleation and Crystal Growth · P5 Washing, Digestion and Sensitisation · P8 Restrainers and Antifoggants

ti.com

ADS111x ultra-small, low-power, I2C-compatible, 860-SPS, 16-bit ADCs with internal reference, oscillator and programmable comparator, data sheet SBAS444retrieved 2026-09-05, 2026-09-08

Sections: Section 5.5, electrical characteristics - gain match between any two gain settings of 0.02 per cent typical and 0.1 per cent maximum, integral nonlinearity 1 LSB, single-ended offset error plus or minus 3 LSB and offset drift 0.005 LSB per degree C. Section 6.1, noise performance - input-referred noise of one least-significant bit on every range, 62.5 microvolts RMS on plus or minus 2.048 V and 7.81 microvolts on plus or minus 0.256 V; Section 7.5.1.1 and Table 7-2, I2C address selection - the ADDR pin tied to GND gives the target address 1001000b. Section 8.1, register map - four registers reached through an address pointer whose low two bits select them, 00b the conversion register and 01b the config register. Section 8.1.2 - the conversion result in 16-bit two's complement. Section 8.1.3 and Table 8-3, the config register - bit 15 OS, which starts a single conversion when written as 1 and reads back as 1 when the device is not converting; MUX[2:0], of which 100b is AIN0 against ground and 101b is AIN1 against ground; PGA[2:0] setting the full-scale range, 010b for plus or minus 2.048 V and 101b for plus or minus 0.256 V; MODE, 1b for single-shot; DR[2:0], 100b for the default 128 samples per second; and COMP_QUE[1:0] set to 11b to disable the comparator. Section 5.3, recommended operating conditions - supply 2.0 to 5.5 V and no analogue input above the supply plus 0.3 V. Section 5.5 - 16 bits with no missing codes, integral nonlinearity 1 LSB, single-ended offset error plus or minus 3 LSB, offset drift 0.005 LSB per degree C, and gain match between any two gain settings of 0.02 per cent typical and 0.1 per cent maximum. Section 6.1, noise performance - input-referred noise of one least-significant bit on every range, 62.5 microvolts RMS on plus or minus 2.048 V and 7.81 microvolts on plus or minus 0.256 V, with effective and noise-free resolution both a full 16 bits at every data rate up to 128 SPS; Section 6.1, noise performance - input-referred noise of one least-significant bit on every range, 62.5 microvolts RMS on plus or minus 2.048 V and 7.81 microvolts on plus or minus 0.256 V, with effective and noise-free resolution both a full 16 bits at every data rate up to 128 samples per second; section 5.5 - gain match between any two gain settings of 0.02 per cent typical and 0.1 per cent maximum; Section 5.3, recommended operating conditions - supply 2.0 to 5.5 V, full-scale input range programmable from plus or minus 0.256 V to plus or minus 6.144 V, and no analogue input above the supply plus 0.3 V. Section 5.5, electrical characteristics at a 3.3 V supply - 16 bits with no missing codes, data rates 8 to 860 samples per second, integral nonlinearity 1 LSB at 8 SPS on the plus or minus 2.048 V range, single-ended offset error plus or minus 3 LSB, offset drift 0.005 LSB per degree C, gain error 0.01 per cent typical and 0.15 per cent maximum, gain match between any two gains 0.02 per cent typical and 0.1 per cent maximum. Section 6.1, noise performance - input-referred noise of 62.5 microvolts RMS on the plus or minus 2.048 V range and 7.81 microvolts RMS on the plus or minus 0.256 V range, one least-significant bit in each case, with effective and noise-free resolution both a full 16 bits at every data rate up to 128 SPS; Section 5.5, electrical characteristics at a 3.3 V supply - 16 bits with no missing codes and data rates of 8, 16, 32, 64, 128, 250, 475 and 860 samples per second; section 6.1, noise performance - effective and noise-free resolution both a full 16 bits at every data rate up to 128 SPS; Section 5.5, electrical characteristics: the eight selectable data rates from 8 to 860 samples per second

Used by:P15 Experiment: Calibrating the Densitometer in Both Modes · P15 Build: The Densitometer Electronics and Firmware · P15 Break-Fix: Diagnosing a Misbehaving Densitometer · P15 Photodiodes, ADCs and Measuring Light Over Three Decades · P17 Experiment: Calibrating the Timer · Calibrating the darkroom timer

OPT101 monolithic photodiode and single-supply transimpedance amplifier, data sheet SBBS002retrieved 2026-09-05, 2026-09-08

Sections: Features and Electrical Characteristics - responsivity 0.45 A/W at 650 nm, quoted equivalently as 0.45 V per microwatt at the internal feedback resistor; Features and Electrical Characteristics - responsivity 0.45 A/W at 650 nm and 0.45 V per microwatt at the internal feedback resistor, with the photodiode and its transimpedance amplifier on one die; Section 6.5, electrical characteristics - output offset voltage 5 to 10 mV with 7.5 mV typical and a temperature coefficient of plus or minus 10 microvolts per degree C; responsivity 0.45 V per microwatt at 650 nm with a temperature coefficient of 100 ppm per degree C and a unit-to-unit variation of plus or minus 5 per cent; nonlinearity plus or minus 0.01 per cent of full scale, specified at a full-scale output of 24 V. Section 6.6, photodiode characteristics - photodiode dark current 2.5 pA doubling every 7 degrees C, and op-amp input bias current 165 pA doubling every 10 degrees C. Section 8.1 - the output is the photocurrent times the feedback resistor plus a pedestal of approximately 7.5 mV introduced for single-supply operation; Section 5, pin functions - VS on pin 1, the op-amp inverting input on pin 2 left unconnected for the internal feedback path, the most negative supply on pin 3 tied to common for single-supply working, the 1 megohm feedback network on pin 4 joined to the output on pin 5, and the photodiode anode on pin 8 tied to ground. Section 6.1, features - a single supply from 2.7 to 36 V. Section 6.5, electrical characteristics at 25 C, taken at RL = 10 kilohms - responsivity 0.45 A/W and 0.45 V per microwatt at 650 nm with a temperature coefficient of 100 ppm/C and a unit-to-unit variation of plus or minus 5 per cent; output offset voltage 5 to 10 mV with 7.5 mV typical, drifting plus or minus 10 microvolts per degree C; nonlinearity plus or minus 0.01 per cent of full scale, specified at a full-scale output of 24 V; internal feedback resistor 1 megohm trimmed to plus or minus 0.5 per cent; bandwidth 14 kHz; output voltage high limited to the supply minus 1.3 to 1.15 V. Section 6.6, photodiode characteristics - active area 2.29 by 2.29 mm. Section 8.1, overview - the output is the photocurrent times the feedback resistor plus a pedestal of approximately 7.5 mV introduced for single-supply operation, so the output is 7.5 mV with no light. Section 8.3.3, noise performance - the output stage powers down when the output is within about 50 mV of the negative supply, reducing the bandwidth and with it the noise, from a nominal 300 microvolts RMS to about 100. Section 9.1 - decoupling capacitors close to the device pins where the supply is not of low impedance; Section 6.6, photodiode characteristics - an active area of 2.29 by 2.29 mm, or 5.2 square millimetres; and section 6.5, responsivity 0.45 V per microwatt at 650 nm through the internal 1 megohm feedback resistor, with the output voltage high limited to the supply minus 1.15 to 1.3 V, from which the optical power needed at the detector is computed; Section 6.5, electrical characteristics - output offset voltage 5 to 10 mV with 7.5 mV typical and a temperature coefficient of plus or minus 10 microvolts per degree C; responsivity temperature coefficient 100 ppm per degree C. Section 6.6, photodiode characteristics - photodiode dark current 2.5 pA doubling every 7 degrees C, and op-amp input bias current 165 pA doubling every 10 degrees C. Section 8.1 - the pedestal of approximately 7.5 mV introduced for single-supply operation, so the output is 7.5 mV with no light; Section 6.5, electrical characteristics at 25 C - photodiode current responsivity 0.45 A/W and voltage output 0.45 V per microwatt at 650 nm through the internal 1 megohm feedback resistor trimmed to plus or minus 0.5 per cent, unit-to-unit variation plus or minus 5 per cent, responsivity temperature coefficient 100 ppm per degree C, nonlinearity plus or minus 0.01 per cent of full scale specified at a full-scale output of 24 V, output offset voltage 5 to 10 mV with 7.5 mV typical and a temperature coefficient of plus or minus 10 microvolts per degree C, dark voltage noise 300 microvolts RMS from 0.1 Hz to 20 kHz at plus and minus 15 V, bandwidth 14 kHz, and output voltage high limited to the supply minus 1.3 to 1.15 V. Section 6.6, photodiode characteristics - active area 2.29 by 2.29 mm or 5.2 square millimetres, dark current 2.5 pA doubling every 7 degrees C, capacitance 1200 pF; and the op-amp input bias current of 165 pA doubling every 10 degrees C. Section 6.1 features - single supply from 2.7 to 36 V; Section 6.5, electrical characteristics at 25 C - photodiode current responsivity 0.45 A/W and voltage output 0.45 V per microwatt at 650 nm through the internal 1 megohm feedback resistor, bandwidth 14 kHz, output offset voltage 5 to 10 mV with 7.5 mV typical, dark voltage noise 300 microvolts RMS from 0.1 Hz to 20 kHz; section 6.6 - active area 2.29 by 2.29 mm; Section 6.5, electrical characteristics: bandwidth 14 kHz; Responsivity of 0.45 A/W at 650 nm and the note that responsivity is a curve rather than a single conversion factor; Output offset voltage of 5 to 10 mV, typically 7.5 mV, with a temperature coefficient of plus or minus 10 microvolts per degree Celsius; photodiode dark current of 2.5 pA at effectively short-circuit, doubling every 7 degrees Celsius; op-amp input bias current 165 pA doubling every 10 degrees; Responsivity of 0.45 A/W at 650 nm, quoted at one wavelength; nonlinearity of plus or minus 0.01 per cent of full scale specified at a full-scale output of 24 V, with the output high limited to the supply minus 1.15 to 1.3 V; Nonlinearity of plus or minus 0.01 per cent of full scale, specified at a full-scale output of 24 V, against an output high limited to the supply minus 1.15 to 1.3 V

Used by:P14 Experiment: Calibrating the Sensitometer · P14 Build: The LED Light Source and Exposure Timer · P15 Experiment: Calibrating the Densitometer in Both Modes · P15 Build: The Densitometer Electronics and Firmware · P15 Build: The Densitometer Optical Head (Transmission and Reflection) · P15 Break-Fix: Diagnosing a Misbehaving Densitometer · P15 Photodiodes, ADCs and Measuring Light Over Three Decades · P17 Experiment: Calibrating the Timer · Calibrating the darkroom timer · Densitometer: ambient leak · Densitometer: drifting zero · Densitometer: high-density compression · Densitometer: scale error

OPT3001 ambient light sensor, data sheet SBOS681retrieved 2026-09-05

Sections: Features and electrical characteristics - precision optical filtering to match the photopic response of the human eye with significant infrared rejection, measurements from 0.01 lux to 83 klux with a full-scale illuminance of 83865.6 lux, a 23-bit effective dynamic range obtained by automatic range selection, lowest-range resolution 0.01 lux, matching between ranges better than 0.2 per cent typical, infrared response at 850 nm of 0.2 per cent, and measurement drift across temperature of 0.01 per cent per degree C

Used by:P15 Photodiodes, ADCs and Measuring Light Over Three Decades

unblinkingeye.com

An Introduction to Pyro Staining Developers, With Special Attention to the Pyrocat-HD Formularetrieved 2026-09-05, 2026-09-06

Sections: INTRODUCTION TO PYRO STAINING DEVELOPERS and HISTORICAL USE OF PYRO; MUCH MORE ABOUT STAIN, and its account of image stain against general stain and of the stain's behaviour on graded, variable-contrast and ultraviolet-sensitive printing materials; PYROCAT-HD FORMULA, the Stock Solution A and Stock Solution B tables; MIXING THE STOCK SOLUTIONS; WORKING SOLUTIONS OF PYROCAT-HD; VARIATIONS ON THE FORMULA; GENERAL DEVELOPMENT PROCEDURES; DEVELOPMENT OF SHEET FILM IN TRAYS; ROTARY DEVELOPMENT OF SHEET AND ROLL FILM; DEVELOPMENT OF FILM IN TANKS; PYROCAT-HD and IS PYROCAT-HD BETTER THAN OTHER PYRO DEVELOPERS; INTRODUCTION TO PYRO STAINING DEVELOPERS and HISTORICAL USE OF PYRO; Toxicity; MUCH MORE ABOUT STAIN with its four printing-process sections and the curve comparisons; RECOMMENDED DEVELOPMENT TIMES and the table of optimum contrast index by process; Development of film in tanks, on the second page - Normal Agitation given as continuous agitation for the first 60 seconds then 5 to 10 seconds every 30 to 60 seconds; Minimal Agitation given as continuous agitation for the first 60 seconds then 10 seconds every third minute, with a five-minute pre-soak strongly recommended, three claimed results of great apparent sharpness through maximum adjacency effects, a compensating effect and increased emulsion speed, and development times about 50 per cent longer; and Stand Development, described as a highly specialised method using extremely dilute developers and very long times whose purpose is extreme adjacency effects and maximum apparent sharpness, said to be fraught with dangers, with high-speed films named as poor candidates, with the warning that even when it works one or more frames are often ruined by an air bubble or bromide drag, with the instruction to make two or more back-up shots of important scenes, a working dilution of about 2 parts A plus 2 parts B plus 400 to 500 parts water, 60 seconds of continuous vigorous agitation and then no further agitation, and times for most films in the 45 to 60 minute range. Fourth page - the statement that the contrast-index charts are based on rotary processing in BTZS type tubes with a five-minute pre-soak, and the table of optimum contrast index by printing process

Used by:510-Pyro · Pyrocat-HD · P27 Experiment: Agitation, Stand and Semi-Stand Development

Making Kallitype Prints: A Fresh Look at a Beautiful Printing Processretrieved 2026-09-06, 2026-09-07, 2026-09-08

Sections: About My Method, for the one-developer principle and the objection to the dozens of developers in the older texts; Necessary Materials — 2) Developer; Notes on Image Permanence, for residual ferrous iron oxidising image silver; Refinements to the Process, for the recommendation to use no other developer unless an unusual colour is wanted that toning cannot reach; and, on page two, Working Procedures step 5 First Rinse, for the neutral-or-acid rule and the ferrous hydroxide compounds an alkaline rinse forms; Necessary Materials, item 5) Fixer, giving the formula in full — "Add 50g sodium thiosulfate, 10g sodium carbonate and 2g sodium sulfite to 750ml water. Stir. When dissolved, add water to 1000ml. You can also prepare the fixer as a concentrated solution at 4X the strength above and dilute 1:3 for a working solution" — and The Basic Chemicals, whose list names sodium thiosulfate crystals, sodium carbonate and sodium sulfite among the seven substances the method needs; item 6) Hypo Clear, the 1 per cent sodium sulfite solution mixed just before use and discarded after about an hour; Working Procedures step 10) Fix, "Fix for four minutes. For maximum archival quality, use two separate fixing baths and fix for two minutes in each, with a 30-second rinse in running water between. The second bath should always be fresh fixer", with step 11) the one-minute rinse after it, step 12) the two minutes in 1 per cent sulfite and step 13) the final rinse of 20 to 30 minutes, or an hour if the hypo clear is omitted; step 5) First Rinse, that the rinse after development must be neutral or slightly acidic because an alkaline rinse forms ferrous hydroxide compounds in the paper that make complete clearing difficult or impossible; step 6) Clearing, that the density lost in clearing returns during toning and fixing; step 8) Toning, and the article's repeated instruction that gold, platinum and palladium toning is done before fixing while selenium is done after, because selenium reacts with residual silver nitrate and stains; the reasons given for toning before fixing — shadow depth increased, bleaching during fixing minimised and a more dramatic change of tone — and the statement that the major reason for fading or image recession during fixing is bleaching of the silver, which a print toned with a more noble metal does not suffer; the permanence argument that residual iron(II) will eventually oxidise the image silver so that all untoned kallitypes will eventually fade; and the sensitiser, equal parts of 10 per cent silver nitrate and 20 per cent ferric oxalate, about 2 mL of the combined solution for an 8 by 10 print, from which this page computes the silver an 8 by 10 carries; The opening comparison with platinum printing, for the statement that kallitype and platinotype share ferric oxalate as the light-sensitive element and almost identical processing, so that the developers and clearing agents used for platinum can be used for kallitype — which is the bridge this page rests on; Necessary Materials item 3, Clearing Agent, for King's own recommendation of a 3 per cent citric acid solution, 30 g in 750 mL of water then water to make 1000 mL; item 6, Hypo Clear, for the 1 per cent sodium sulfite solution mixed just before use; and Working Procedures steps 5 to 7 and 12, for the first rinse of 1 to 2 minutes in water that must be neutral or slightly acidic because an alkaline rinse forms iron(II) hydroxide compounds in the paper that make complete clearing difficult or impossible, for the clearing step run until there is absolutely no stain left in the sensitised but unexposed areas with the judgement that a paper taking more than about four minutes to clear is unsuitable, for the instruction to renew the clearing bath frequently because proper clearing is absolutely vital to print stability, for the observation that "the image will lighten considerably during clearing, but don't worry because all the lost density will return during toning and fixing", for the 30 to 60 second second rinse before toning, and for the 1 per cent sodium sulfite hypo-clear bath placed after fixing rather than before it; the masking of the negative with red lithographer's tape or a frame cut in construction paper, and the description of the test area as "those areas that were masked during exposure"; together with the permanence argument that it is impossible to remove all residual iron(II) from the paper and that any that remains will eventually oxidise the silver, and the warning that unreplenished developer accumulates iron(II) and makes clearing progressively harder; Necessary Materials — 1) Sensitizer, Solution A and Solution B; What is a Kallitype? And a Little History; Notes on Image Permanence; About My Method; Paper; The Negative; and, on page two, Working Procedures steps 1 to 14, Refinements to the Process, Metal Additives and Toning; What is a Kallitype? And a Little History, for the statement that in Nicol's original patent the print was developed in a silver nitrate bath and that a revision of the early 1890s moved the silver into the sensitiser, and for ferric oxalate giving more maximum density and better contrast control than the citrate processes; the comparison of a toned kallitype with a platinum print; Notes on Image Permanence, for residual *ferrous* iron eventually oxidising the image silver and for direct toning as the answer; Necessary Materials 1) Sensitizer, for the 20 per cent ferric oxalate stock, the 24 hours to dissolve, and the two-to-three-month limit before print fog; 2) Developer, for the 20 per cent sodium citrate bath; 3) Clearing Agent, for the 3 per cent citric acid; and, on page two, Working Procedures step 5 First Rinse, for the one to two minutes in water that must be neutral or slightly acidic and the ferrous hydroxide that an alkaline rinse forms, and step 6 Clearing; About My Method, for the one-developer principle; Necessary Materials — 2) Developer; and, on page two, Working Procedures step 4 Development, step 5 First Rinse for the neutral-or-acid rule, step 6 Clearing; Notes on Image Permanence, for residual iron oxidising image silver; Refinements to the Process, for the recommendation to use no other developer unless an unusual colour is wanted that toning cannot reach; Necessary Materials — 2) Developer, for the 200 g make-up; About My Method, for the one-developer principle; Notes on Image Permanence, for residual iron and the oxidation of image silver; and, on page two, Working Procedures step 4 Development, for the pour, the 5 to 10 minutes against 15 to 30 seconds, the replenishment rate, the dichromate contrast range and the "rather unpleasant brown color"; step 5 First Rinse, for the neutral-or-acid rule; step 6 Clearing; Refinements to the Process, for the recommendation to use no other developer; The statement that the advantage of kallitype is greater control of contrast, making it possible to print negatives with a wider range of densities than the other two iron-silver processes; and the negative section, which gives the best negative for kallitype as having a density range of about log 1.8, describes it as a very contrasty negative that will not print well even on a grade 0 or 1 paper, states that for in-camera sheet film this range is reached by developing about 50 per cent longer than normal for a grade 2 silver-gelatin paper, and notes that the great advantage of digital negatives is that they all have close to the same density and contrast range so that exposure time and contrast are consistent.; What is a Kallitype? And a Little History — the family placing of kallitype beside Van Dyke and argyrotype, the statement that in kallitype the light-sensitive element is ferric oxalate while in Van Dyke and argyrotype it is ferric ammonium citrate, and the three advantages claimed for the oxalate; the attribution of the basic theory to Herschel's paper of 1842 and of the patent to W. W. J. Nicol in 1889; Notes on Image Permanence, for residual iron(II) oxidising the image silver and for the claim that all untoned kallitypes will eventually fade; Notes on Image Permanence — the statement that the major danger to long-term permanence is residual iron(II), that even very small quantities will eventually oxidise the silver and the image will fade, that the key to maximum archival quality is direct toning in which the image silver is replaced with another noble metal resistant to oxidation by residual iron, and that maximum permanence also requires removing all residual iron, fixing to remove unused silver and removing all residual hypo by an adequate wash; the comparison of kallitype with platinum-palladium, that both are based on ferric oxalate, that platinum developers and clearing agents work for kallitype, that a well-made kallitype toned with platinum or palladium is for all practical purposes identical in tonal range and colour to a true platinum or palladium print and that it would be impossible for even an expert to distinguish them, that full toning of a kallitype requires only about a quarter as much chemistry as a Pt/Pd print, and that toning is done after development and clearing when it is obvious whether the print is a keeper whereas the metal in a Pt/Pd sensitiser cannot be recovered from a failed print; Necessary Materials item 3, the clearing agent of 3 per cent citric acid; item 6, hypo clear of 1 per cent sodium sulfite mixed just before use and discarded after about an hour; page two Working Procedures steps 5 to 13 — the first rinse in neutral or slightly acidic water because an alkaline rinse forms iron(II) hydroxide compounds making complete clearing difficult or impossible, clearing until there is absolutely no stain in the sensitised but unexposed areas with a paper needing more than about four minutes judged unsuitable, the instruction to renew the citric acid bath frequently because proper clearing is absolutely vital to print stability, the warning that the image lightens considerably during clearing and that the density returns during toning and fixing, toning for 5 to 20 minutes before fixing with the print fully toned when the shadows have taken the colour of the toning metal, and fixing, hypo clear and a final wash of 20 to 30 minutes or an hour without the hypo clear; Toning, for the three reasons to tone before fixing — increased shadow depth, minimised bleaching during fixing and a more dramatic change of tone — for the argument that all untoned kallitypes will eventually fade, for the elimination of solarisation in heavily exposed shadows, and for the rule that double toning must begin with the more noble metal because the more noble metal always replaces the less noble; the toner formulas — Gold Toner 1 of 5 g citric acid and 5 mL of 5 per cent gold chloride in a litre, Gold Toner 2 of 50 mL of 1 per cent gold chloride, 50 mL of 1 per cent thiourea and 0.5 g tartaric acid in a litre, the platinum and palladium toner of 5 g citric acid and 5 mL of a 20 per cent solution of potassium chloroplatinite or sodium chloropalladite in a litre, and two selenium toners — with the observations that the gold toners increase contrast by about a step through loss of density in the high values while changing Dmax little if at all, that Gold Toner 2 works on all areas at about the same time while Gold Toner 1 works first on the highlights, that platinum gives a very neutral black and palladium a brownish black, that with the noble-metal toners the final density is somewhat greater than untoned while contrast is identical, that about 20 mL of solution fully tones a 5 by 7 image, and that selenium should be used after fixing because before fixing it reacts with residual silver nitrate and stains; Page two, Working Procedures step 4, Development — contrast controlled by the addition to the developer of a few millilitres of a 5 per cent potassium dichromate solution, with a practical limit ranging from as little as 1 mL per litre of developer up to about 16 mL per litre, which allows the use of negatives from a density range as low as about 1.2 to a maximum of about 2.2, and the warning that if too much dichromate is added printing times will increase considerably and the image will take on a granular look; the developer replenishment rate and the consequence of not replenishing; The Negative, for a density range of about log 1.8 as the starting point; Metal Additives, for gold, platinum, palladium and mercury(II) chloride added to the sensitiser to modify colour and tonal range, and for the observation that the image is then more likely to stain and much more difficult to clear; Necessary Materials — the basic chemicals list, 1) Sensitizer with Solution A of 10 g silver nitrate in 70 mL of distilled water made up to 100 mL and Solution B of 20 g ferric oxalate powder in 75 mL made up to 100 mL, with the statements that ferric oxalate takes a long time to dissolve and should be mixed about 24 hours before use, that in powder form it lasts indefinitely but once in water degrades slowly with a resulting increase in print fog, and that no more should be mixed than will be used in two to three months; 2) Developer, a 20 per cent solution of sodium citrate; 3) Clearing agent, 3 per cent citric acid; 5) Fixer, 50 g sodium thiosulfate, 10 g sodium carbonate and 2 g sodium sulfite made up to a litre; 6) Hypo clear, 1 per cent sodium sulfite mixed just before use; Paper, for the four-to-five-minute clearing criterion; The Negative, for a density range of about log 1.8 reached by developing film about 50 per cent longer than normal; page two Working Procedures steps 1 to 14 — about 2 mL of combined solution for an 8 by 10, five minutes taped down then 15 to 30 minutes hanging to dry with a fan permitted but no forced heat because it may fog, development for 5 to 10 minutes although visually complete in 15 to 30 seconds because much of the residual iron leaves at that stage, contrast controlled by 1 to 16 mL of 5 per cent potassium dichromate per litre allowing density ranges from about 1.2 to 2.2, developer replenishment at about 200 mL per 500 square inches with the warning that unreplenished developer accumulates iron(II) and makes clearing progressively harder, a first rinse of 1 to 2 minutes in neutral or slightly acidic water because an alkaline rinse forms iron(II) hydroxide compounds that make clearing difficult or impossible, clearing until no stain remains in the masked areas, toning for 5 to 20 minutes before fixing, fixing four minutes or two plus two, hypo clear for two minutes and a final rinse of 20 to 30 minutes or an hour without it; Refinements to the Process and Metal Additives; Toning, for the argument that all untoned kallitypes will eventually fade and for the observation that untoned kallitypes frequently show tone reversal in heavily exposed shadows; What is a Kallitype? And a Little History, for the statement that ferric oxalate permits more Dmax than either Van Dyke or argyrotype with the qualification that the difference is not huge but that well-made comparison prints side by side show more richness in the shadows, and that shadows in printing-out processes often appear murky because they are fully exposed before the highlights have printed in; Necessary Materials item 5, the fixer of 50 g sodium thiosulfate, 10 g sodium carbonate and 2 g sodium sulfite made up to a litre; item 6, the hypo clear of 1 per cent sodium sulfite; Necessary Materials item 1, for ferric oxalate lasting indefinitely as a powder but degrading slowly once in solution with a resulting increase in print fog, and for the instruction to mix no more than will be used in two to three months; Paper, for the statement that papers which will not clear completely in about four to five minutes should not be used; page two Working Procedures step 3, for drying with a fan permitted but never with forced heat because it may cause fogging; step 4, for development that is visually complete in 15 to 30 seconds but continued for five to ten minutes because much of the residual iron leaves at that stage, for the developer replenishment rate of about 200 mL per 500 square inches and the warning that unreplenished developer accumulates iron(II) and makes clearing progressively harder with an unpleasant stain in the masked areas and a possible loss of permanence, and for the instruction to pour the developer over the print as quickly as possible; step 5, for the first rinse in neutral or slightly acidic water because an alkaline rinse forms iron(II) hydroxide compounds that make complete clearing difficult or impossible; step 6, for clearing until there is absolutely no stain in the sensitised but unexposed areas and for renewing the citric acid bath frequently; Notes on Image Permanence, for residual iron(II) oxidising the image silver and for the argument that all untoned kallitypes will eventually fade; Toning, for the elimination of tone reversal in heavily exposed shadows; What is a Kallitype? And a Little History, for the ferric oxalate against ferric ammonium citrate comparison and the three advantages claimed for the oxalate — more Dmax with the note that the difference is not huge, greater contrast control, and greater shadow depth from a developing-out rather than a printing-out process because in a POP process the shadows are fully exposed before the highlights have printed in; the attribution to Herschel 1842 and Nicol 1889, and Nicol's original patent developing the print in a silver nitrate bath with a revision of the early 1890s moving the silver into the sensitiser; Notes on Image Permanence; Necessary Materials, for the two solutions and the statement that ferric oxalate lasts indefinitely as a powder but degrades in solution with a resulting increase in print fog; page two, Working Procedures step 4, for development visually complete in 15 to 30 seconds but continued for 5 to 10 minutes because much of the residual iron leaves at that stage; Clearing until there is absolutely no stain left in the sensitised but unexposed areas; renewing the citric acid bath frequently; the four-to-five-minute limit before a paper is judged unsuitable; the warning that the image lightens considerably during clearing and that the density returns during toning and fixing; the requirement that the rinse before clearing be neutral or slightly acidic

Used by:Borax kallitype developer · Dilute alkaline thiosulfate fixer for iron-silver prints · EDTA and sodium sulfite clearing sequence · Kallitype sensitiser · Nicol's kallitype · Rochelle salt kallitype developer · Sodium citrate kallitype developer · P21 What These Processes Need: The Negative, the Paper and the Light · P24 Part XXIV Overview: When Iron Reduces Silver · P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Contrast Control in Iron-Based Printing · P24 Lab: Printing a Kallitype · P24 Lab: Printing a Van Dyke Brown · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · P24 The Siderotype Principle: Iron Reduces Silver · Clearing an iron-silver print and testing it for residual iron

The Carbon Transfer Processretrieved 2026-09-06

Sections: Sensitizing Carbon Tissue — the description of the dark effect as a slow insolubilization of the gelatin of sensitized, unexposed tissue whose practical consequence is a gradual gain in speed accompanied by a loss of contrast, and the working response of timing the exposure closely after sensitizing; and the introductory account of the collapse of commercial tissue manufacture, with Hanfstaengl continuing small-scale production until about 1990 and a single United States supplier of monochrome tissue as of early 2007

Used by:P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes

Vandyke Notesretrieved 2026-09-07

Sections: Processing — the account of reading Ware on the problems iron-based silver processes have, the conclusion that with tap water at about pH 8 there is a danger of insoluble iron being left in the print after a conventional wash, and the change of practice to a series of trays of water with a pinch of citric acid added so that the pH falls just below 7, eight changes of one minute each with the trays rotated afterwards, which he calls probably overkill; the 5 per cent plain hypo for two minutes at which point image reduction becomes apparent, the three minutes in a hypo clearing agent of 20 g of sodium sulfite per litre, and the initial wash of 30 minutes in an archival print washer; Gold Toner, for Clerc's thiourea gold toner taken from Dick Stevens's Making Kallitypes, for the statement that gold toner moves the image colour toward purple and finally to a neutral grey when toned to completion and does not reduce the image, for split tones of purple-brown and grey, and for washing an hour after toning; and the selenium notes, that Kodak rapid selenium toner contains ammonium thiocyanate which reduces the silver image so it must be used very weak, 2 mL in 500 mL, that reduction takes place mainly in the darkest part of the image, and that selenium moves the colour from reddish-brown towards chocolate brown and finally to a yellow-brown the author does not find appealing; Vandyke Formula, for the report that adding more tartaric acid seemed to increase contrast slightly and move the image colour towards a more neutral grey but made graininess a problem, that more silver nitrate and more ferric ammonium citrate had little effect, and that doubling all three gave excellent contrast and rich blacks but grain again; Contrasting Agent, for premixed potassium dichromate solutions from 1 to 5 per cent, one drop added according to the contrast wanted, and the statement that with one drop of 3 per cent dichromate added to 12 drops of sensitiser the exposure must be nearly doubled; Coating, for double coating because single-coated dark areas are very weak; The Vandyke Brown Print, for the process being based on the argentotype of 1842 and for the name coming from the resemblance to Van Dyck's pigment; Vandyke Formula, for the three solutions taken from Bob Schramm's article in Post-Factory Photography, the instruction to combine A and B and add C slowly while stirring, the brown bottle and the ageing of a few days before use, the year-old sensitiser that was still fine, and the results of varying each ingredient — more tartaric acid raising contrast slightly and moving the colour towards neutral grey at the cost of graininess, more silver nitrate and more ferric ammonium citrate having little effect, and doubling everything giving excellent contrast and rich blacks but grain again; Coating, for the five-pass rod method, the paper box between sheets, and double coating because single-coated dark areas are very weak; the note that slight fogging appeared until he began working under a 7 watt red bulb about a metre above the coating area; Exposure, for the red construction-paper mask slightly larger than the negative that makes it possible to see whether the print has cleared or fogged, and exposures of four to twelve minutes under his own bank of BL fluorescent tubes at about 8 cm; Processing, for the print showing about half its final density out of the frame, the great darkening in the fixer and further darkening on drying, the decision to abandon tap water at about pH 8 in favour of eight trays acidified with citric acid to just below pH 7 after reading Ware on residual iron, the 5 per cent plain hypo for two minutes at which point image reduction becomes apparent, the three minutes in a clearing agent of 20 g of sodium sulfite per litre, and the initial wash of 30 minutes; Vandyke Reducer and the selenium and gold toning notes; Coating, for the report of slight fogging that stopped when the author began working under a 7 watt red bulb about a metre above the coating area, and for the red construction-paper mask that makes it possible to see whether the print has cleared and whether it has fogged; Vandyke Formula, for the sensitiser aged a few days in a brown bottle and for a bottle a year old that was still fine; Processing, for the change from an alkaline tap-water wash to trays acidified with citric acid after reading Ware on residual iron, and for the 5 per cent plain hypo of two minutes at which point image reduction becomes apparent; Paper, for the observation that with some papers the chemistry of the sensitiser does not match the chemistry of the paper, resulting in blotchy or grainy images; Processing — the statement that Vandyke is a print-out process, that after exposure a faint image is visible showing approximately half of its final density, that the image darkens greatly in the fixer and more again on drying, and that it is better to print a bit dark and reduce back; The Vandyke Brown Print, for the process being based on the argentotype invented in 1842 by Herschel and for the name coming from the resemblance to the pigment used by Van Dyck; Vandyke Formula, for the effects of varying each of the three ingredients and for the drop of 1 per cent gold chloride that shifts the image colour towards purplish-brown; Coating, for double coating because single-coated dark areas are very weak

Used by:P24 Lab: Clearing, Toning and Making an Iron-Silver Print Last · P24 Contrast Control in Iron-Based Printing · P24 Lab: Printing a Van Dyke Brown · P24 Break/Fix: The Iron-Silver Print That Would Not Clear · P24 The Siderotype Principle: Iron Reduces Silver

vernier.com

pH Sensor (PH-BTA) user manualretrieved 2026-09-04

Sections: Specifications - range, accuracy, temperature range, isopotential point; Care and maintenance - short and long term storage and the prohibition on distilled water; Troubleshooting - why distilled water reads erratically; solutions the sensor must not be used in; Specification — range pH 0 to 14 and accuracy plus or minus 0.2 pH units, with readings not temperature-compensated; Care and maintenance: short- and long-term storage and the prohibition on distilled water; Troubleshooting: erratic readings in distilled water; Care and maintenance - short and long term storage and the prohibition on distilled water; Troubleshooting - the shock treatment for a sensor stored dry or responding sluggishly

Used by:P3 Lab: Measuring pH and Trusting the Number · P9 Experiment: The Activity Series - Alkali and Restrainer · P9 Break/Fix: The Developer That Went Wrong · P9 Assignment: The Developer Laboratory Report · Calibrating a pH meter · pH meter reading a constant value

vishay.com

VEML7700 high accuracy ambient light sensor with I2C interface, document 84286retrieved 2026-09-05

Sections: Features and basic characteristics - 16-bit resolution, a range from 0 lx to about 140 000 lx, a digital resolution down to 0.0042 lx per step at a gain of 2 with an 800 ms integration time, the maximum illuminance quoted instead at a gain of one eighth with a 25 ms integration time, gain settings of one eighth, one quarter, 1 and 2, and a dark offset of 3 steps at the most sensitive setting

Used by:P15 Photodiodes, ADCs and Measuring Light Over Three Decades

waveformlighting.com

realUV 365 nm LED Strip Light Irradiance Pattern, document BP_7021retrieved 2026-09-05

Sections: Measurement orientation and illustration - irradiance in microwatts per square centimetre as a function of distance, measured from a single 1 m strip section perpendicular to the strip axis, calibrated to 365 nm, with the maker's notes that multiple strip rows will in theory linearly increase the irradiance and that the values are not guaranteed and are for reference only

Used by:P16 Build: The UVA Exposure Unit

web.archive.org

Classical Cyanotype: the B&S formula and instructions, other formulas, toning and bleachingretrieved 2026-09-05, 2026-09-06

Sections: Classical Cyanotype, the section headed "The B&S Formula and Instructions" and signed by Dick Sullivan — solution A of ferric ammonium citrate 27.2 g with oxalic acid 0.5 and water to make 100 mL, solution B of potassium ferricyanide 9.2 g with oxalic acid 0.5 g and ammonium dichromate 0.2 g and water to make 100 mL, mixed in equal parts, about one dropper of each per 8 by 10, exposed until "the high values are a little too dark and the shadows have begun to reverse", washed five minutes, with an optional bath of 20 mL of household 3 per cent hydrogen peroxide in 200 mL of water. Cited here for one purpose only: it is the company's own published house formula, and it is not the formula the company publishes for the kit.; Classical Cyanotype, the B&S formula and instructions signed by Dick Sullivan, giving solution A of ferric ammonium citrate 27.2 g with oxalic acid 0.5 g to 100 mL and solution B of potassium ferricyanide 9.2 g with oxalic acid 0.5 g and ammonium dichromate 0.2 g to 100 mL; and, under Other variations on the cyanotype formula, Bob Schramm's contribution at 250 cc scale with the claim of whiter whites and no bleeding

Used by:Bostick and Sullivan cyanotype and toning kits · Ware's improved Classic cyanotype

Daguerre (1787-1851) and the Invention of Photography, in the Heilbrunn Timeline of Art Historyretrieved 2026-09-04, 2026-09-06

Sections: Daguerre (1787-1851) and the Invention of Photography, whole essay; Daguerre and the Invention of Photography, whole essay; Daguerre and the invention of photography

Used by:Daguerre's 1839 process outline · P1 Daguerre and the Daguerreotype: A Mirror With a Memory · P1 1839 and the Many Inventors of Photography · Daguerreotype

The Atlas of Analytical Signatures of Photographic Processes: Albumenretrieved 2026-09-04, 2026-09-05, 2026-09-07, 2026-09-08

Sections: History — Blanquart-Evrard's presentation to the French Academy of Sciences on 27 May 1850 and the period of the process's dominance; Process — the separation of egg white from yolk and the addition of sodium or ammonium chloride; Visual characteristics — gloss, the criticism of glossiness in the 1850s photographic literature, double coating and burnishing; Process Description and the timeline of figure 2 — the appearance of the first commercially produced albumen photographic paper in 1854, which was still only a paper substrate coated with salted albumen that needed to be sensitized with a solution of silver nitrate, and the appearance of presensitized albumen paper with a longer shelf life only after 1872, with the note that some photographers did not trust commercially sensitized paper and for reasons of economy chose to prepare their own; the statement that almost all photographers who published their techniques proposed highly personalized procedures using different substrates, different chemical substances and different ratios, but that most published recipes and procedures are essentially similar; and the schematic cross section of an albumen photograph showing toned silver particles held in albumen above the paper substrate; Process Description — the requirements on the rawstock of wet strength, light weight and freedom from metallic and chemical impurities, the Rives and Steinbach mills and their machine-made stock internally sized with starch and resin soaps, the use of fresh eggs in most published recipes, the separation of egg white leaving no trace of yolk or blood, the addition of a solution of sodium or ammonium chloride, the beating to a stiff froth, the overnight liquefaction of the froth into a much more homogenised and uniform solution of salted albumen, the filtering and the mixing with water, the coating by floating, the statement that the major difference between many of the published recipes lay in whether the albumen salt solution was used as prepared or diluted with various amounts of water and that more diluted coating solutions gave less glossy prints, and the criticism of glossiness in the photographic literature of the 1850s and the later change of taste; Process Description — the two steps of handmade albumen paper, the requirements on the rawstock of wet strength, light weight and freedom from metallic and chemical impurities, the Rives and Steinbach mills and their machine-made stock internally sized with starch and resin soaps, the separation of egg white from yolk, the addition of a solution of sodium chloride or ammonium chloride, the beating to a stiff froth, the overnight liquefaction of the froth to a more homogenised solution, the filtering and the mixing with water, the coating by floating, and the statement that the major difference between many of the different published recipes lay in whether the albumen salt solution was used as prepared or diluted with various amounts of water, more diluted coating solutions giving less glossy prints; the criticism of glossiness in the photographic literature of the 1850s and the later change of taste; the timeline of the process, naming 1835 to about 1855 the experimental albumen period and the main era of albumenized prints, about 1855 to about 1890 the main albumen period, and about 1890 to the late 1920s the post-albumen period of albumen variants; the ATR-FTIR criteria for naming and categorising albumen-based photographs, in which similar intensities of the Amide I peak at 1640 per cm and the cellulose shoulder at 1100 per cm indicate a single-coated albumen photograph, a cellulose shoulder of lower intensity than the Amide I peak indicates an albumen-rich or double-coated photograph, and a much lower concentration of albumen, probably produced using diluted albumen, is to be called an albumenized photograph; and the Matte-Albumen Process section, on diluted or highly diluted albumen, on the most important variant being introduced in 1895 by the German photochemist A. F. Hübl, on matte-albumen paper being prepared by mixing albumen stock with a salted solution of starch and coating it on a usually rough substrate, on its use by several manufacturers to compete with platinum papers, and on the end of its commercial production in the late 1920s; The process timeline, which dates double-albumen coating and burnishing to 1870; Process Description — the statement that earlier albumen prints, created before about 1870, were usually less glossy than double-coated albumen photographs and those made glossy by surface burnishing and varnishing, and that preparing the paper with aged or partially putrefied albumen also produced higher-gloss prints; the ATR-FTIR section — the account of how a thicker albumen layer attenuates the cellulose signal of the paper substrate, the statement that after about 1870 public preference turned toward glossy prints and that photographers and the photographic materials industry responded by introducing double-coated albumen photographic paper known to yield high-gloss photographs, and the objective spectroscopic criterion that followed from analysing a large number of salted, albumenised and albumen photographs — a single-coated albumen print of 1855 to 1870 gives similar intensities for the Amide I peak at about 1640 cm⁻¹ and the shoulder of the cellulose envelope at about 1100 cm⁻¹, while a print made after about 1870 with more binder than a single coating can deposit gives a cellulose shoulder at 1109 cm⁻¹ of lower or much lower intensity than the Amide I peak at 1646 cm⁻¹ and may be described as albumen-rich or double-coated; and the microscopic section — the fine network of surface microcracks found in most albumen prints produced before 1870 and its absence, or reduced visibility, in prints made after 1870 that were burnished and heat treated; Historical background — the attribution to Blanquart-Evrard, the presentation of 27 May 1850, the process dominating photographic printing between 1855 and 1890 and surviving in variants into the late 1920s, the first commercial albumen paper of 1854 and the first presensitised paper of 1872; Figure 2, the timeline of the process; Process description — the two paper mills, the separation of the whites, the chloride, the beating to a stiff froth and the standing overnight, and the dilution that decides gloss; Figure 3, the schematic cross-section; Identification — the microcrack network, the two-layer structure and the visibility of paper fibres under the albumen layer; Historical background and Process description — the attribution to Blanquart-Evrard, the presentation of 27 May 1850, the two paper mills and their starch and resin soap sizing, the separation of the whites, the sodium or ammonium chloride, the beating to a stiff froth and the standing overnight, the filtering, and the dilution with water that decides gloss; Visual characteristics — earlier prints less glossy than double-coated, burnished and varnished ones, aged or partially putrefied albumen producing higher-gloss prints, the thickness measurement of 0.204 mm and the yellowing visible in Dmin areas; Microscopic characteristics — the network of surface microcracks and its absence on burnished prints after 1870; the two-layer structure and paper fibres visible under the albumen layer at 80×; Figure 2, the timeline; Process description — the requirement for a lightweight paper of great wet strength free of metallic impurities, the two mills and their starch and resin soap sizing, the separation of the whites leaving no yolk or blood, the sodium or ammonium chloride, the beating to a stiff froth, the standing overnight, the filtering, and the dilution with water that decides gloss; Visual characteristics — aged or partially putrefied albumen giving higher-gloss prints; Visual characteristics — the tendency of unmounted albumen photographs to curl inside into tight rolls that are fragile and difficult to handle, the mounting on card stock, and the bleaching or tonality change some adhesives produced; Visual characteristics — the dark border of untrimmed prints, the range of colour tonalities, the strong tendency of thin albumen prints to curl into tight rolls, the thickness measurement of 0.204 mm on an unmounted print stored flat, earlier prints less glossy than double-coated, burnished and varnished ones, aged or putrefied albumen giving higher gloss, the yellowing visible in Dmin areas, and the aniline tints added to counteract yellowing; Microscopic characteristics — the fine network of surface microcracks as the most typical microscopic signature, its presence in most prints made before 1870 and its absence on burnished and heat-treated prints after 1870, the two-layer structure with paper fibres visible under the albumen at 80×, and retouching marks now visible over a faded image; Identification Problems — the beeswax, paraffin, collodion and shellac varnishes identified by ATR-FTIR on surviving prints; Important Variants — the protalbin and matte-albumen processes; Figure 2, the timeline; Process description and identification characteristics; Historical background; Process description; Visual characteristics; the gloss and its reception; Process description; Visual characteristics; the reception of gloss in the 1850s; Albumen print: the coating, the gloss, and the identification of single and double coating; Microscopic characteristics - the most typical microscopic signature of albumen photographs being a fine network of surface microcracks rather uniform across the surface layer; such a network found in most albumen prints produced before 1870, while prints produced after 1870 that were sometimes burnished and heat treated may not fully exhibit the microcrack pattern or may show no surface cracks at all; Microscopic characteristics - the fine network of surface microcracks rather uniform across the surface layer, typical of unburnished period albumen prints and found in most produced before 1870; Microscopic characteristics and the identification of albumen prints, including the network of surface microcracks typical of unburnished period prints

Used by:Albumen · Albumen sensitising solution · Albumen solution with its chloride · Albumenised salting solution · Double-coated albumen procedure · P23 Part XXIII Overview: Albumen Printing · P23 Egg Albumen: A Protein Binder and What It Does to Silver · P23 Lab: Preparing and Coating Albumen Paper · P23 Lab: Sensitising, Printing and Toning an Albumen Print · P23 The Albumen Print as an Object, and How It Decays · P25 Assignment: The Process Comparison Atlas · Albumen print · Matte albumen print · Preparing and coating albumen paper · Albumen crazing and yellowing · Albumen layer dissolving during sensitising · Yellow-brown highlight stain from residual silver

The Atlas of Analytical Signatures of Photographic Processes: Carbonretrieved 2026-09-04, 2026-09-06

Sections: Historical Background; The preparation of canvas, silk or linen for the transfer of carbon prints, coated three or four times with a solution of gelatin, glycerin, sugar and chrome alum; Historical Background; Process Description; Historical Background — Poitevin's invention of the carbon process in 1855 and Swan's development of it for general application in 1864; Mungo Ponton's 1839 discovery of the light sensitivity of paper coated with potassium dichromate, with the note that Ponton did not mix the dichromate with gelatin so that the cellulose substrate and the small concentration of gelatin present as internal size were the only organic materials available for the photochemical reduction; Becquerel's 1840 repetition and his explanation that the internal size played an important part; Talbot's 1852 discovery that a mixture of organic colloids such as glue, gelatin or starch with potassium dichromate is rendered insoluble by exposure to light, patented as part of his photomechanical printing process; the independent 1858 discovery by Sutton and Pouncy; the account of why early carbon prints lacked halftones, with Abbe Laborde's 1858 diagnosis, Burnett's 1858 proposal to expose through the paper substrate and its cost in exposure time and resolution, Fargier's 1860 patented collodion-varnish and strip solution, and Swan's 1864 modifications including the addition of sugar to make a less brittle image layer and the face-down attachment to a temporary or final support; the single- and double-transfer descriptions and the reason the single-transfer image is reversed; the Autotype Company from 1868, Johnson's 1869 waterproof temporary support and 1870 substitution of soap for sugar, Sawyer's 1874 Flexible Temporary Support, the addition of the Woodburytype to the company's photomechanical department in 1880, the Keramic and Artistic Finish departments, the printing of compass dials on mica during the Second World War, and the 2005 acquisition by MacDermid. Identification: Carbon Process Prints — the noticeable relief effect observed at nearly 180 degrees to the print surface with dark areas standing higher than the highlights, the greater gloss of dark areas due to the higher concentration of gelatin, surface cracks concentrated in the dark thicker areas, the absence of light fading where only carbon-based pigments were used and its presence where organic dyes were, the absence of the silver mirroring typical of older silver gelatin and albumen photographs, and the printed or embossed permanence designations on card mounts; the microscopic characteristics above 25x of larger pigment particles and clusters irregularly distributed in the lighter areas, the smaller brighter red-lake particles added to imitate gold-toned albumen, and the delamination visible at the edges of a loose print; the XRF signature of a total absence of silver together with small amounts of photochemically produced chromium embedded in the image layer that washing and clearing cannot remove, at a concentration roughly proportional to the tonality of the photograph and absent in the Dmin area; the FTIR identification of gelatin by the Amide I peak at 1626 and Amide II at 1533 reciprocal centimetres, the differentiation of gelatin from albumen by the peaks between 1450 and 1300, the appearance of cellulose peaks near 1100 in Dmin where the layer is thin, the collodion varnish peaks at 1637, 1274 and 838, and the danger of misidentifying a collodion-varnished carbon print as a collodion photograph; and Identification Problems — that carbon prints and Woodburytypes have almost identical visual and analytical signatures and that a shellac layer detected in the Dmin of a Woodburytype is one of the separations; Historical background; process description; the photochemical reduction of the dichromate salt and the binding of the colloid; The photochemical reduction of the dichromate salt and the binding of the colloid; The photochemical reduction of the dichromate salt and the binding of the colloid; the relief image in continuous tone

Used by:Ammonium dichromate · Glycerol · Potassium dichromate · P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes · Carbon print · Gum bichromate · Woodburytype

The Atlas of Analytical Signatures of Photographic Processes: Collodionretrieved 2026-09-04, 2026-09-05, 2026-09-06

Sections: Process description — the alcohol-ether soluble halides used in a collodion emulsion; Nineteenth-century toning recipes for collodion printing-out papers, most of which called for a borax-gold chloride solution; The comparative table of analytical signatures for collodion and neighbouring print processes, in which the Wothlytype row carries silver, gold and uranium as inorganic constituents with a collodion binder and a brown tonality, uranium being the entry that distinguishes it from the glossy and matte collodion rows beside it; Process description; the collodion positive; The collodio-chloride emulsion — one portion of collodion with silver nitrate and citric or tartaric acid, another with alcohol-ether soluble halides, combined under non-actinic light; Process description; the collodion positive and its supports; The analytical table for the collodion processes — the Wothlytype row carrying silver, gold and uranium in a collodion binder with a brown tonality; Historical background; process description; the salting of collodion with soluble halides

Used by:Lithium chloride · Gold-borax toner · P26 Uranium, Mercury and the Heavy-Metal Treatments · Ambrotype · Collodion print-out paper · Tintype (ferrotype) · Uranotype and Wothlytype · Wet-plate collodion negative

The Atlas of Analytical Signatures of Photographic Processes: Cyanotyperetrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: The identification and material description of the cyanotype process, cited for the image-forming species and for the behaviour of Prussian blue as a pigment held in the paper fibres; The identification and material description of the cyanotype process, cited here for the image-forming species of an iron-blue print and for its behaviour as a pigment held in the paper fibres rather than in a binder; The identification and material description of the cyanotype process, cited here for the claim that the alternative-process milestone changes the material the image is made of rather than the way a silver image is treated; The identification and material description of the cyanotype process, cited for the image-forming species being an iron(III) hexacyanoferrate(II) held in the paper fibres with no binder; The steps of the cyanotype process; the first commercial cyanotype paper; Pellet's Process (Positive Cyanotype) — the coating mixture of gum arabic, ammonium ferric citrate and ferric chloride, the process description, its dates of use, and the FTIR note that the analytical signal of gum arabic is very weak; Cyanotype: process description; Formula-based variants; Pellet's Process (Positive Cyanotype); Cyanotype: process description; Pellet's Process (Positive Cyanotype); Process description and image characteristics; Process Description, for the workflow the kit sheet describes without naming any chemical — coating with a mixture of an iron(III) salt and potassium ferricyanide, drying in the dark, contact exposure to ultraviolet, a water bath that both completes the blue and dissolves the unexposed sensitiser, and hydrogen peroxide as an optional aid; Process Description, the five steps of coating, drying, exposure, sensitometric control and the water bath with an optional hydrogen peroxide addition; Formula-Based Variants, on the number of published formulas and on Valenta's introduction of the green salt after 1897, with the statement that the final chemical composition of the image is identical whichever form is used; Historical background, including the presentation of the paper on 16 June 1842 and the preparation of Prussian blue by Diesbach between 1704 and 1710; Process description, the five steps and the role of the water bath and of hydrogen peroxide; Pellet's Process (Positive Cyanotype), page 16 — process description, visual characteristics, microscopic characteristics, analytical signatures and identification problems; Figure 3 Timeline of the cyanotype process; Process Description, for the workflow the kit sheet describes — coating with a mixture of an iron(III) salt and potassium ferricyanide, drying in the dark, contact exposure to ultraviolet, a water bath that both completes the blue and dissolves the unexposed sensitiser, and hydrogen peroxide as an optional aid; Process description; Historical background; Historical background; Process description; Main application of the cyanotype process; Historical background; Main application of the cyanotype process; Process Description, the five steps of coating, drying in the dark, contact exposure to ultraviolet, sensitometric control by inspection and the water bath that both completes the blue and dissolves the unexposed sensitiser, with the optional hydrogen peroxide addition; Process Description, the five numbered steps and the statement of the general principle as the photochemical reduction of iron(III) salts to an iron(II) salt that reacts with potassium ferricyanide to form an intensely blue complex, the yellow-greenish sensitised layer, the water bath that both completes the blue and dissolves the unexposed sensitiser, the optional hydrogen peroxide addition, and the note that the blue image can otherwise be assessed only after the material is fully dried and oxidised by exposure to air; Important Variants of the Cyanotype Process, on the low sensitivity of potassium ferricyanide alone and on Valenta's green salt increasing light sensitivity while the final chemical composition of the image remains identical; Process Description - the five steps of coating, drying, exposure, sensitometric control and the water bath that both completes the blue and dissolves the unexposed sensitiser, with hydrogen peroxide as an optional aid; Important Variants of the Cyanotype Process — Valenta's green salt increasing light sensitivity while the final chemical composition of the image remains identical, and the account of Pellet's positive-working process, its difficulty and delicacy compared with the basic cyanotype, and the statement that Pellet prints are indistinguishable from cyanotypes by microscopy and by X-ray fluorescence because the image substance is the same; Process description and image characteristics, for the identification of a cyanotype as an object; Process description and identification characteristics; Process description - the steps of the cyanotype process and the appearance of the finished print

Used by:P29 Capstone Stage 6: Permanence, Presentation and the Finished Portfolio · P29 Capstone Stage 5: The Toned Print and the Alternative-Process Print · P29 The Assignment Path: Fourteen Pictures That Build One Photographer · P29 The Capstone Chemistry Report: From Photon Capture to Finished Print · Ammonium iron(III) citrate · Gum arabic · Potassium ferricyanide · Potassium ferrocyanide (anhydrous) · Potassium ferrocyanide trihydrate · Prussian blue · Bostick and Sullivan cyanotype and toning kits · Classic cyanotype sensitiser · Herschel's 1842 cyanotype · Pellet's positive-working process · Photographers' Formulary cyanotype and toning kits · P1 Assignment 1: A Botanical Cyanotype Photogram, After Atkins · P1 Herschel: Hypo, Prussian Blue and the Words of Photography · P1 1839 and the Many Inventors of Photography · P21 Lab: Mixing, Coating and Printing a Classic Cyanotype · P21 Iron, Light and Prussian Blue · P21 Break/Fix: The Cyanotype That Went Wrong · P21 The New Cyanotype and the Other Ways to Make a Blue Print · P21 Lab: Toning the Prussian Blue Image · P25 Assignment: The Process Comparison Atlas · Cyanotype (classic) · Blue fog in cyanotype highlights

The Atlas of Analytical Signatures of Photographic Processes: Platinotyperetrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07

Sections: The note that a paper selected for platinum printing is usually surface sized with starch or gelatin, and the list of sizing and coating materials described in the photographic literature — starch, agar-agar, gum arabic or gelatin — with the remark on the FTIR analysis of complex polymer carbohydrates; Process description: the Ware-Malde process, fixing, clearing and washing with EDTA; The steps of the platinotype process; XRF detection of residual iron after clearing; "Glycerin-Developed Platinotypes - process description and Identification; the list of important variants of the platinotype process; and the account of A. W. Dolland's gold-toning and image-intensifying process of about 1894"; Process History: Willis's first patent of 1873 and its suggestion of iridium and gold salts; Sizing and coating materials described in the photographic literature — starch, agar-agar, gum arabic or gelatin — and the FTIR analysis of complex polymer carbohydrates; The introduction of lead by Willis in 1873 and its elimination in the 1880 patent; the later formulas that added lead oxalate to facilitate a more uniform reduction of platinum salts during development; the recommendation of lead oxalate by Pizzighelli and Hübl; and the caution that mounting boards and paper substrates may themselves contain lead; Lead oxalate in the platinotype process; the caution on lead in mounting boards; Sepia platinotype papers and mercury chloride; XRF detection of mercury; Process History: the palladiotype and the Ziatype; Contrast adjustment with dichromate salts; XRF detection of chromium; The steps of the platinotype process; Process History; Identification: XRF detection of palladium in platinotypes; Process History; Process Description; Identification: XRF of platinotype prints; Process History: the palladiotype and the Ziatype; Identification: XRF detection of palladium; Uranium Toning; XRF and FTIR detection of uranium toning; The steps of the platinotype process, for the developer's role and for contrast adjusted with potassium chlorate or dichromate; XRF detection of residual iron after the best clearing procedures; Process Description and Identification, for the faint brownish print-out image of photochemically generated ferrous oxalate, for the account of hotter development giving smaller particles and warmer tones, and for the observation that potassium chlorate leaves no analysable residue but is responsible for a visually detectable patchiness in the platinum image; Ziatype, Important Variants of the Ziatype Process, and Identification: Ziatypes — the invention dated to 1996 and attributed to Richard Sullivan in Santa Fe; the process description, that it "uses a lithium palladium complex salt in combination with ferric ammonium oxalate to facilitate photochemical reduction of palladium and provide enough hygroscopic water to allow for POP image development" and that "Tonality and contrast of Ziatype photographs are controlled chemically, unlike other Pizzighelli processes in which both tonality and contrast are controlled by humidity"; the statement that Ziatypes "do not exhibit any unique visual, microscopic, or analytical signatures that would allow differentiating them from old or new palladium-based photographs", that XRF detects palladium and residual iron, that "Only when potassium dichromate is used to adjust the contrast of the final print can a very small amount of chromium be detected", and that tungsten, gold and caesium may likewise be found; and the note that a Ziatype looks like a palladiotype, a kallitype or a toned cyanotype and that an instrument is usually needed to tell them apart.; The steps of the platinotype process, for the faint brownish print-out image of photochemically generated ferrous oxalate and for contrast adjusted with potassium chlorate or dichromate; XRF detection of residual iron after the best clearing procedures; Historical Background, for the statement that the chemistry of Willis's first platinotype process "also included the addition of silver or lead nitrates into the sensitizing solution", that silver nitrate was omitted from the 1878 patent, and that the 1880 patent "excluded the use of both silver and lead while increasing the amount of platinum compounds in the sensitizing solution"; the paragraph beneath figure 13, for the detail of the XRF spectrum of an early platinotype showing lead, for "Early platinotype formulas used the addition of lead oxalate to facilitate good uniform development of the platinotype image", for the lead oxalate recommended by Pizzighelli and Hübl for their print-out variant, and for "Several later platinotype formulas used the addition of lead oxalate to facilitate a more uniform reduction of platinum salts during development"; the following paragraphs, for potassium dichromate and potassium chlorate as the agents actually used to increase contrast and for the patchiness the chlorate causes; the CAUTION box, for the warning that some mounting boards and paper substrates contain small amounts of lead and that the board must be measured and subtracted; Packham's Process, for the warm-red tone obtainable by development in a solution modified by copper chloride, mercury chloride or lead acetate; The steps of the platinotype process and the paragraph beneath it, for tonality controlled by a hot or cold developer, by the concentration of the developing solution or by adding a mercury salt to it, and for Hübl's use of mercury citrate; Image Color and Tonality, for the browner image given by smaller platinum particles, the sepia platinotype papers made by adding mercury chloride to the sensitizing solution, the statement that mercury chloride acts as a retardant for the development of platinum particles and that the effect is physical rather than a toning, the warning that "mercury-toned" is not an accurate description, the XRF detection of mercury and figures 15a and 15b, the observation that mercury is usually at a much lower concentration than platinum but that some prints carry a high concentration, and figure 16, the Willis and Clements advertisement of 1899 for sepia platinum paper; Toned Platinotypes, for Hinton's 1897 verdict, for uranium toning and for Packham's 1894 catechu process as a safer alternative to the mercury-based process; the palladiotype process description, for the statement that adding mercury(II) chloride to a palladium sensitizer does not greatly affect the final tonality; the glycerin-developed platinotype, for local development with a mercury-containing developer on the hands or face; The steps of the platinotype process, for the starch or gelatin sizing, for the faint brownish print-out image of photochemically generated ferrous oxalate, and for contrast adjusted with potassium chlorate or dichromate; XRF detection of residual iron after the best clearing procedures; Historical background, for Willis's three patents, the silver and lead of the first, the founding of the Platinotype Company in 1879, the hot-developed papers of 1880 and cold-developed papers of 1892, and the 1887 print-out variant; The platinotype process consists of several distinct steps, for the seven steps and for contrast adjusted with potassium chlorate or dichromate and tonality controlled by the developer or by a mercury salt; Visual Characteristics, for the deeply matte surface, the brown to rich black tonality and the yellowing of highlights in prints that were not completely cleared of ferric salts; The XRF section for platinotype, for the finding that the platinum peaks of most platinotype images are accompanied by spectral peaks for iron and that "many fixing/clearing procedures were developed and carried out in the past to dissolve unexposed ferric oxalate. However, our investigation shows that even after applying the best fixing and clearing procedures, enough iron is left in the platinotype photograph to allow for its detection using XRF"; and the corresponding palladiotype section, for iron peaks "from traces of iron still left in the photograph after clearing using complexing agents" and for the calcium almost always present in the paper substrate; The seven steps of the platinotype process; the statement that contrast could be adjusted by adding potassium chlorate or dichromate salts; the note that the chlorate treatment cannot be detected analytically because of its solubility but is responsible for a visually detectable patchiness in the platinum image; the lead oxalate additions; the sepia papers made with mercury(II) chloride; the commercial arc from 1880 to 1941; The steps of the platinotype process, for the developer's place in the sequence, for the image appearing almost immediately, and for tonality controlled by hot or cold developer and by the concentration of the developing solution; Uranium Toning: Hinton's procedure of toning a fully processed black platinotype in a toner made by mixing a solution of uranium nitrate and acetic acid together with solutions of potassium ferricyanide and ammonium sulfocyanide, to a deep-brown or red-brown tonality; that the process can be reversed by washing the print in a dilute solution of ammonia; the uranium L-alpha peak at 13.61 keV and L-beta at 17.22 keV in X-ray fluorescence; and the identification of the deposit as the uranium complex of the hexacyanoferric anion by its C-N stretch at 2062 per centimetre in the infrared; Historical background, for Willis's three patents of 1873, 1878 and 1880, for the hot-developed papers of 1880 and the cold-developed papers of 1892; The steps of the platinotype process, for the developer's place in the sequence and the statement that the image appears almost immediately; the paragraph beneath it, for tonality controlled by hot or cold developer, by the concentration of the developing solution, or by adding a mercury salt to it, and for contrast adjusted with potassium chlorate or dichromate; Uranium Toning - Hinton's procedure of toning a fully processed black platinotype in a bath made from uranium nitrate and acetic acid with potassium ferricyanide and ammonium sulfocyanide, to a deep-brown or red-brown tonality; that the process can be reversed by washing the print in a dilute solution of ammonia; the uranium L-alpha peak at 13.61 keV and L-beta at 17.22 keV in X-ray fluorescence; and the identification of the deposit as the uranium complex of the hexacyanoferric anion by its C-N stretch at 2062 per centimetre in the infrared; Historical background, for the commercial arc from 1880 to 1941; Process description, for the seven steps and the faint brownish image of photochemically generated ferrous oxalate; Historical background, for the commercial arc from 1880 to 1941, the fifteen kinds listed in 1911 and the statement that only after 1917 did photographers begin to use palladium and then platinum-palladium mixtures on paper they coated themselves; the analytical finding that iron remains detectable by X-ray fluorescence after the best clearing; Process description, for the faint brownish image of photochemically generated ferrous oxalate, the instantaneous appearance of the image in the developer, and the analytical finding that enough iron remains after the best fixing and clearing to be detected by X-ray fluorescence at the iron K-alpha line at 6.40 keV, with different concentrations in the maximum and minimum density regions; Historical background, for the commercial arc from the first papers of 1880 to the end of British manufacture in 1941 and the fifteen kinds listed in 1911; Process description, for the seven steps and the faint brownish image of photochemically generated ferrous oxalate; the statement that contrast was adjusted with potassium chlorate or dichromate; the sepia papers made with mercury(II) chloride; the uranium toning procedure attributed to Hinton; and the analytical finding that iron remains detectable by X-ray fluorescence after the best clearing; Process description, for the statement that contrast could be adjusted by adding potassium chlorate or dichromate salts and tonality by the developer's temperature and concentration, and the note that the chlorate treatment cannot be detected analytically but is responsible for a visually detectable patchiness in the platinum image; Process description, for the statement that contrast could be adjusted by adding potassium chlorate or dichromate salts and that the chlorate cannot be detected analytically because of its solubility but is responsible for a visually detectable patchiness; the lead oxalate additions; the sepia papers made with mercury(II) chloride; and the uranium-toning procedure attributed to Hinton, its deep-brown to red-brown tonality, its reversal by washing in dilute ammonia, the uranium L-alpha and L-beta peaks at 13.61 and 17.22 keV and the identification of the deposit as the uranium complex of the hexacyanoferric anion by its C-N stretch at 2062 per centimetre; Process description and Historical background, for the conservation account of the platinotype against which a student's own palladium print is compared; Uranium Toning — Hinton's procedure of toning a fully processed black platinotype in a bath made from uranium nitrate and acetic acid with potassium ferricyanide and ammonium sulfocyanide, to a deep-brown or red-brown tonality; that the process can be reversed by washing the print in a dilute solution of ammonia; the uranium L-alpha peak at 13.61 keV and L-beta at 17.22 keV in X-ray fluorescence; and the identification of the deposit as the uranium complex of the hexacyanoferric anion by its C-N stretch at 2062 per centimetre in the infrared; Process description; the commercial arc from 1880 to 1941; Historical background, including the 1878 patent, the strategic-metal ban and the introduction of the palladiotype; the presence of palladium in early platinotypes; Historical background; Process description; the commercial arc from 1880 to 1941; sizing materials; A. Horsley Hinton's uranium toning of platinum prints, 1897; the identification of uranium by its L-alpha line at 13.61 keV under X-ray fluorescence; The identification of uranium by its L-alpha line at 13.61 keV under X-ray fluorescence; Process description and image characteristics of the platinotype, and the identification of the process

Used by:Arrowroot · EDTA disodium salt dihydrate · Ferric oxalate · Glycerol · Gold(III) chloride · Gum arabic · Lead(II) acetate · Lead(II) nitrate · Mercury(II) chloride · Palladium(II) chloride · Potassium dichromate · Potassium oxalate monohydrate · Potassium tetrachloropalladate(II) · Potassium tetrachloroplatinate(II) · Sodium tetrachloropalladate(II) · Uranyl nitrate hexahydrate · Borax kallitype developer · Bostick and Sullivan platinum and palladium kits · Bostick and Sullivan Ziatype kit · Kallitype sensitiser · Lead additions to platinum sensitisers · Mercuric sepia platinotype · Nicol's kallitype · Photographers' Formulary platinum and palladium printing kits · Pizzighelli and Hübl's 1886 formulations · EDTA, citric acid and hydrochloric acid clearing sequence · Three-solution drop system for platinum and palladium · Rochelle salt kallitype developer · Sodium citrate developer · Sodium citrate kallitype developer · Uranium toner · Willis's potassium oxalate developer · P20 The Toners We Study and Do Not Use · P25 Part XXV Overview: Platinum and Palladium · P25 Cost, Permanence and When a Platinum Print Earns Its Price · P25 Lab: Exposing, Developing and Clearing a Palladium Print · P25 Noble Metal Chemistry and the Platinotype · P25 Experiment: Tonal Scale, Contrast and Image Colour in Palladium · P25 The Additives We Study and Do Not Reproduce · P25 Assignment: The Process Comparison Atlas · P26 Uranium, Mercury and the Heavy-Metal Treatments · Process atlas · Palladiotype · Platinotype · Uranium toned print · Uranotype and Wothlytype · Platinum print stain from incomplete clearing

The Atlas of Analytical Signatures of Photographic Processes: Salt Printretrieved 2026-09-04, 2026-09-05, 2026-09-06, 2026-09-07, 2026-09-08

Sections: Process description; The section on internal sizing, on the preference of English paper mills for gelatin and of French and other continental mills for starch, and on the difficulty of detecting starch sizing by ATR-FTIR because both the starch and the cellulose fibres are complex carbohydrates, so that microanalytical tests requiring physical sampling would be needed; Identification: tonality of untoned salt prints, 1835 to 1850; The salting solution, which is often sodium citrate and ammonium chloride rather than sodium chloride alone; Process Description, on soaking paper in a salt solution of around 4 per cent often of sodium citrate with ammonium chloride, on brushing with a silver nitrate solution of around 12 per cent sometimes containing citric acid, and on the wash, tone, fix and final wash; the section on internal sizing, on the preference of English paper mills for gelatin and of French and other continental mills for starch, and on the difficulty of detecting starch sizing by ATR-FTIR because both the starch and the cellulose fibres are complex carbohydrates, so that microanalytical tests requiring physical sampling would be needed; Process Description, on soaking good quality paper in a salt solution of around 4 per cent that is often sodium citrate with ammonium chloride, brushing with a silver nitrate solution of around 12 per cent sometimes containing citric acid, and the wash, tone, fix and final wash that follow; the section on internal sizing, on the preference of English paper mills for gelatin and of French and other continental mills for starch, and on detecting sizing by ATR-FTIR; Process Description, on a salting solution of around 4 per cent that is often sodium citrate with ammonium chloride, on brushing a generous coating of a silver nitrate solution of around 12 per cent by weight sometimes containing a small amount of citric acid, on drying in darkness or very subdued light, on perhaps ten minutes of bright sunlight through the negative, and on the several rinses that remove the excess silver nitrate before toning and fixing; The historical introduction, for the description of geometric images formed on a glass bottle containing a sediment of calcium carbonate mixed with diluted nitric acid contaminated with a small concentration of silver, for the demonstration that the darkening was photochemical and not thermal, and for the timeline placing Schulze's shadowgraphs before Niepce, Talbot and Herschel; Sizing, on the preference of English paper mills for gelatin as the internal size and the use of starch-based internal sizing by French and other continental mills; Process Description; Historical background, Hercules Florence and Talbot; Historical background; Process description; Visual characteristics; Historical Background, for Talbot's 1834-35 development of photography on paper, the salt print as the main positive process for salt paper and calotype negatives until about 1850, Blanquart-Evrard's albumen positive of 1850 and albumen's dominance after about 1855, and for Mathieu's 1847 proposal of gold toning taken up after 1850 by Le Gray; Process Description, for the salting solution around 4 per cent by weight, the silver nitrate around 12 per cent, the exposure until the image is darker than required, the 5 per cent sodium thiosulfate fix and the wash of an hour; Identification, Visual Characteristics, for the matte, sunken-in appearance and the light to reddish brown tonality of untoned prints; Historical Background, for Mathieu's 1847 proposal of gold toning to modify tonality and stabilise the silver image, for its wider use after 1850 when Le Gray recommended it and its further acceleration after the Fading Committee of 1855, and for chemically reduced silver particles being much larger than photochemically reduced ones so that Blanquart-Evrard's developed prints were more stable against both light and pollutant fading; Historical Background, for Talbot's 1834-35 work, for the adoption of Herschel's thiosulfate, for the salt print being the main positive process until about 1850 and its near-complete replacement by albumen by the mid-1850s, for Blanquart-Evrard's developed positive of 1851-55 producing up to several hundred prints a day from one negative, and for the statement that chemically reduced silver particles are usually much larger than photochemically developed ones so that those images were dark brown or black and more stable against light and pollutant fading; Process Description, for the salting solution around 4 per cent by weight, the silver nitrate around 12 per cent sometimes with a little citric acid, the exposure until darker than required, the several rinses to remove excess silver nitrate, the 5 per cent thiosulfate fix and the hour of washing; Identification, Visual Characteristics, for the matte sunken-in appearance and the light to reddish brown tonality of untoned prints; Process Description, for exposure under a negative with a UV source for perhaps 10 minutes in bright sunlight until the image is darker than required, for washing in several rinses of water to remove excess silver nitrate, for toning if desired usually in a gold toner, for fixing in 5 per cent sodium thiosulphate or dilute print fixer, and for washing for an hour; Historical Background and Process Description, for the salting solution often being sodium citrate and ammonium chloride at usually around 4 per cent by weight, for a number of articles and manuals publishing improvements focused on sizing and on sensitising or fixing formulas, for paper companies producing special photographic paper with good wet strength and free of the metal particles that cause black spots, and for only two modifications greatly affecting appearance and light-fading stability - Mathieu's 1847 gold toning and Blanquart-Evrard's chemical development of positives, whose chemically reduced silver particles are usually much larger than photochemically produced ones so that the prints were dark brown or black and more stable against light and pollutant fading; Identification: Salt Prints, Visual Signatures, for identification being challenging because a number of processes look similar, for photographers diluting the albumen bath to avoid gloss so that the results are semi-glossy or almost matte and difficult to distinguish from a salt print on a highly sized substrate; Visual Characteristics, for the characteristic matte appearance, for an uncoated salt print having a sunken-in appearance in the body of the paper substrate, for most salt prints being made on quality writing paper with noticeable differences between papers when handling unmounted images, for many unmounted salt prints being semitranslucent on a light table so that a watermark can be detected, for watermarks being important for provenancing and authentication and needing to be documented in the registrar database, for many salt prints of 1835 to 1850 not being gold toned with tonality from light brown to reddish brown, and for the claim that a print from a paper negative is less sharp because of light scattering by the negative's fibres with the qualification that well-waxed or varnish-saturated negatives do not provide such clues; Microscopic Characteristics, for the deposit of photochemically reduced silver particles on top of and between individual fibres of the paper substrate, for higher magnifications showing sizing material coating the fibre surfaces and plugging between them, for silver particles being too small to be detected individually under an optical microscope, for the difficulty of distinguishing fibre glossiness from surface sizing, for the warning against over-interpreting optical micrographs, and for FTIR providing much more reliable information on the presence or absence of surface sizing; Analytical Signatures, XRF, for silver as the imaging element with traces of calcium and iron from the substrate, for the detection of cobalt and arsenic in Talbot's and in Hill and Adamson's prints, for these being due to smalt - blue cobalt glass - added to the paper fibre mass to increase whiteness and combat yellowing during ageing, with arsenic from smalt manufacture, for smalt particles appearing as small specks under low magnification and bright blue under higher magnification and good illumination, and for cobalt concentration varying greatly between papers even from the same mill, with some Talbot prints on paper so heavily loaded that the sheet appears almost light blue; FTIR, for the analysis being complicated because the main organic component is cellulose whose functional groups overlap into a broad spectral envelope, for gelatin size being detectable by a small Amide I peak at about 1640 per cm and possibly Amide II at about 1530, for starch sizing being much harder because both starch and cellulose are complex carbohydrates with strong spectral overlap, and for the literature recording English mills preferring gelatin as internal size while French and other continental mills used starch; Interpretation Guide, Table 1, for the full comparison of salted paper, albumen, collodion, gelatin, platinotype, palladiotype, kallitype and tannin-toned cyanotype against surface coating, paper fibres, Ag, Au, Pt, Fe, Hg, Ba, other inorganics, cellulose, albumen, collodion, gelatin, other organics and tonality, with paper fibres, silver and cellulose marked as key signatures for salted paper, barium absent from salted paper and albumen but present in collodion and gelatin, titanium dioxide as a marker of modern substrates, and the footnote that a small concentration of gelatin protein can be detected in some papers internally sized with gelatin; Process Description, for good quality handmade or mould-made watercolour paper soaked in a salt solution often of sodium citrate and ammonium chloride at usually around 4 per cent by weight and dried, and for brushing a generous coating of about 12 per cent silver nitrate sometimes containing a little citric acid in subdued light and drying in darkness or very subdued light; Identification, Visual Characteristics, for the matte sunken-in appearance and for the light to reddish brown tonality of untoned prints; Process Description, for exposure until the image is darker than required; Process description and identification characteristics; Process description; Visual characteristics; the variants of the salt print; Processing: the several rinses before toning, and the identification characteristics of a finished salted paper print

Used by:Ammonium chloride · Arrowroot · Silver chloride · Sodium chloride · Trisodium citrate dihydrate · Arrowroot salting solution · Plain salted paper salting solution · Salted paper sensitising solution · Schulze's scotophorus mixture · Talbot's photogenic drawing paper · P1 1839 and the Many Inventors of Photography · P1 Talbot: Photogenic Drawing, the Calotype and the Negative-Positive Principle · P22 Part XXII Overview: The First Silver Print · P22 Gold Toning and the Permanence of a Printed-Out Silver Image · P22 Printing Out: Silver Chloride Made and Darkened in the Paper · P22 Lab: Printing, Toning, Fixing and Washing a Salt Print · P22 The Variants of the Salt Print and How a Conservator Identifies One · P22 Lab: Salting and Sensitising a Sheet of Paper · P22 Break/Fix: The Printed-Out Image That Faded · P25 Assignment: The Process Comparison Atlas · Arrowroot and albumenised salted paper · Photogenic drawing · Salted paper print · The printing-out processing line

The Atlas of Analytical Signatures of Photographic Processes: Woodburytyperetrieved 2026-09-06

Sections: Historical Background — the invention by Walter Bentley Woodbury and Joseph Wilson Swan, patented 1864 with working details published 1865; the statement that the process was one of the first successful photomechanical processes fully able to reproduce the delicate halftones of photographs and the only practical fully continuous-tone photomechanical process ever invented; its dependence on Ponton's 1839 photosensitivity of dichromate-containing organic colloids, on Poitevin's 1855 carbon patent for the photochemical formation of the gelatin relief, on Fargier's 1861 and Swan's 1864 idea of washing unhardened gelatin from the lower part of the layer, and on Auer's 1852 nature printing for the metal mould; the contested priority between Woodbury and Swan and the note that many historical findings speak to Swan's priority under the name photo-mezzotint while Woodbury made it a workable method; the displacement of the process by collotype and halftone by the end of the nineteenth century when it could not be adapted to rotary printing; the eleven-step process description, including the gelatin, albumen, sugar and ammonium dichromate layer poured on polished glass about one-eighth of an inch thick, the reported exposure of up to sixty minutes, the hot-water washout forming a positive gelatin relief thickest under the lightest areas of the negative, the pressing of the dried relief into a smooth lead plate at 35 MPa, the filling of the lead matrix with hot pigmented gelatin ink, and the shellac-varnished calendered receiving paper; and the note that Woodburytype prints made with carbon black or other stable inorganic pigments are superbly stable from light fading while the gelatin binder may be compromised at higher temperature and humidity. Identification: Woodburytypes — the size rule that any image larger than 11 by 14 inches would be a carbon print or a Stannotype and that Woodburytypes above 8 by 10 were seldom made; the flush trimming on all four sides to remove the margin smeared by excess gelatin ink; the absence of fading and of silver mirroring in both processes; the slight surface relief most pronounced at the boundary between light and dark under raking light; the pigment microparticles and larger clusters visible above 25x that could not be eliminated; the red, pink and sometimes blue particles in brown-purple prints made to resemble toned albumen; the partial lift and cracking of the pigmented gelatin at edges and within the image; the white spots from air bubbles formed during development; and the edge deformation and ink smearing from the shearing cut. Analytical Signatures — the absence of any imaging metals; the 3 to 5 per cent alum or chromium alum hardening bath applied after printing and the small chromium peak it can leave; the finding that all the inorganic elements detected are also present in the mounting board so that most of the signal originates there rather than in the printed image; the statement that both carbon and Woodburytype prints contain chromium but that the concentration in carbon prints is typically about five times higher, which makes the relative rather than absolute amount the most important analytical signature separating them; the difficulty of attributing lead between paper substrate and ink; and the note that the technical literature recommends small amounts of mercury chloride to increase shelf life but that after analysing several dozen prints the authors have not been able to identify such a treatment

Used by:P26 Light-Hardened Colloids: Bitumen, Dichromate and the Pigment Processes

The Daguerreotype Mediumretrieved 2026-09-04, 2026-09-06

Sections: The daguerreotype medium — the silvered copper plate polished to a mirror and sensitised over iodine; The daguerreotype medium; the polished silver surface; exposure times and the camera; The daguerreotype medium; exposure times; the camera; The Process: exposure times for the earliest daguerreotypes of three to fifteen minutes, and the reduction to less than a minute after changes to sensitisation and lenses; The daguerreotype medium: the silver-plated copper plate cleaned and polished until it looks like a mirror, then sensitised over iodine until it takes a yellow-rose colour; the historical exposure times, three to fifteen minutes for the earliest daguerreotypes and reduced to under a minute by changes to the sensitising and better lenses; and the statement that the image is laterally reversed unless the camera carried a mirror or prism

Used by:Mercury · Daguerre's 1839 process outline · P1 Daguerre and the Daguerreotype: A Mirror With a Memory · P7 Assignment: Portrait, Environmental Portrait and Self-Portrait · P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory · Daguerreotype

The history of photography in picturesretrieved 2026-09-04

Sections: Anna Atkins, British Algae; Latticed Window at Lacock Abbey, 1835

Used by:P1 Herschel: Hypo, Prussian Blue and the Words of Photography · P1 Talbot: Photogenic Drawing, the Calotype and the Negative-Positive Principle

webbook.nist.gov

Mercury: phase change data, in the NIST Chemistry WebBook, NIST Standard Reference Database Number 69retrieved 2026-09-06

Sections: Phase change data, Antoine Equation Parameters: log10(P) = A - B/(T + C) with P in bar and T in kelvin, A 4.85767, B 3007.129, C -10.001, over 298.14 to 749.99 K, calculated by NIST from Hicks, 1963

Used by:P26 The Mercury Daguerreotype: Iodine, Amalgam and a Mirror With a Memory

webvision.pitt.edu

Light and Dark Adaptation, in Webvision — The Organization of the Retina and Visual Systemretrieved 2026-09-05

Sections: Dark adaptation - an initial rapid fall in threshold, a second mechanism entering after 5 to 8 minutes with a further rapid fall, and a minimum threshold of about 10 to the minus 5 candela per square metre reached after about forty minutes in the dark

Used by:P16 Build: Making a Room Dark and Proving It

wickes.co.uk

Wickesretrieved 2026-09-05

Sections: Hardwood plywood sheet

Used by:The Pure Silver laboratory planner

ww1.microchip.com

ATmega328P 8-bit AVR microcontroller with 32K bytes in-system programmable flash, data sheetretrieved 2026-09-05

Sections: Features - six-channel 10-bit ADC in the SPDIP package, eight in TQFP and VQFN; Operating Voltage 1.8 to 5.5 V, with 20 MHz requiring 4.5 to 5.5 V

Used by:P14 Low-Voltage Electronics for the Darkroom Builder

xrite.com

X-Rite 361T Desktop Transmission Densitometer, product brochure L11-010retrieved 2026-09-05, 2026-09-06, 2026-09-07

Sections: Specification table — repeatability plus or minus 0.01 D from 0.0 to 5.0 D, linearity plus or minus 0.02 D over the same range, and zero stability plus or minus 0.02 D per eight hours; cited only as the commercial benchmark a home-built instrument's certificate is read against; Specification table - measuring range 0 to greater than 6.0 D, apertures of 1, 2 and 3 mm, repeatability plus or minus 0.01 D and linearity plus or minus 0.02 D from 0.0 to 5.0 D on the Ortho and Visual responses, zero stability plus or minus 0.02 D per eight hours, and a two-minute warm-up; Specification table - repeatability plus or minus 0.01 D and linearity plus or minus 0.02 D from 0.0 to 5.0 D on the Ortho and Visual responses, zero stability plus or minus 0.02 D per eight hours, measuring range 0 to greater than 6.0 D and apertures of 1, 2 and 3 mm; taken here as the benchmark a home-built instrument's own certificate is read against; Specification table - repeatability plus or minus 0.01 D and linearity plus or minus 0.02 D from 0.0 to 5.0 D on the Ortho and Visual responses, zero stability plus or minus 0.02 D per eight hours, and a two-minute warm-up; taken here as the benchmark the finished chain is measured against; Specification table - measuring areas of 1, 2 and 3 mm with 0.5 mm optional, taken here as the reference for choosing an aperture; and repeatability of plus or minus 0.01 D with linearity of plus or minus 0.02 D from 0.0 to 5.0 D, taken as the benchmark a home-built head is measured against; Specification table - measuring range 0 to greater than 6.0 D; measuring areas 1, 2 and 3 mm with 0.5 mm optional; repeatability plus or minus 0.01 D from 0.0 to 5.0 D on Ortho and Visual at the 2 and 3 mm apertures and only to 3.5 D on UV; linearity plus or minus 0.02 D over the same ranges; warm-up two minutes, five for UV; zero stability plus or minus 0.02 D per eight hours; X-Rite Ortho and X-Rite UV responses; conformance claimed to ANSI PH2.19 and ISO 5/2; and the statement that the UV response measures film-base fog an ordinary densitometer cannot see; Specification table — repeatability plus or minus 0.01 D from 0.0 to 5.0 D on the Ortho and Visual responses at the 2 and 3 mm apertures, linearity plus or minus 0.02 D over the same ranges, zero stability plus or minus 0.02 D per eight hours, warm-up two minutes, and a measuring range of 0 to greater than 6.0 D; cited here only as what a commercial instrument publishes about itself; Specification table - measuring areas of 1, 2 and 3 mm with 0.5 mm optional; repeatability plus or minus 0.01 D and linearity plus or minus 0.02 D from 0.0 to 5.0 D; cited only as what a commercial metal-cased instrument publishes about itself; Specification table - repeatability plus or minus 0.01 D and linearity plus or minus 0.02 D from 0.0 to 5.0 D, and zero stability plus or minus 0.02 D per eight hours; cited only as what a commercial metal-cased instrument publishes about itself; Specification table - repeatability plus or minus 0.01 D and linearity plus or minus 0.02 D from 0.0 to 5.0 D; cited only as what a commercial metal-cased instrument publishes about itself; Specification table - repeatability plus or minus 0.01 D and linearity plus or minus 0.02 D over 0.0 to 5.0 D, and zero stability plus or minus 0.02 D per eight hours; cited only as what a commercial metal-cased instrument publishes about itself, never as a figure a home-built instrument may claim; Specification table - repeatability plus or minus 0.01 D, zero stability plus or minus 0.02 D per eight hours, and a two-minute warm-up; taken here as the benchmark a home-built instrument's own certificate is read against, never as a figure it may claim

Used by:P29 Capstone Stage 1: The Instrument, Its Calculation and Its Commissioning · P15 Part XV Overview: Build a Densitometer · P15 Experiment: Calibrating the Densitometer in Both Modes · P15 Build: The Densitometer Electronics and Firmware · P15 Build: The Densitometer Optical Head (Transmission and Reflection) · P15 Density Depends on How You Look: Geometry and Spectral Response · P27 Part XXVII Overview: From Observation to Measurement · P27 Experiment: Agitation, Stand and Semi-Stand Development · P27 Designing an Experiment That Yields a Number · P27 Experiment: Exhaustion, Capacity and What a Used Developer Actually Does · P27 Experiment: Four Curve Families, Measured · P27 Assignment: The Developer Comparison, Measured and Printed · P27 Experiment: The Development Time and Temperature Series · Densitometer daily five-minute check

X-Rite 361T Transmission Densitometer, operation manual, part number 361T-500retrieved 2026-09-05, 2026-09-06

Sections: Chapter four, calibration - a calibrated transmission reference of five steps from approximately 0.06 D at step 1 to 4.0 D at step 5, of which step 4 is the cal step and steps 1, 2, 3 and 5 are used for checking linearity; the check procedure, which is to zero the unit and then measure the cal step, the unit being properly calibrated if the measurement is within 0.02 D of the density specified and needing recalibration if it is not; the calibration procedure itself, in which Cal LO is taken with all film removed and Cal HI on the cal step; the frequency of calibration, once a week under normal operating conditions or when the instrument asks; the handling instruction that the reference is held at the edges only, that fingerprints or other foreign substances on the measurement area cause errors, that anything other than a soft camel-hair brush may change densities, and that change is minimised by storing in a dark, cool, dry place; and the statement introducing the Quick CAL procedure that the zero, called Calibration Low, is the major factor of drift over a period of time. Chapter eight, specifications - zero stability plus or minus 0.02 D per eight hours, ambient interference expressed as a decrease in D of less than 0.25 per cent, warm-up two minutes and five for the ultraviolet response, and an operating temperature range of 10 to 40 degrees C; Chapter four, calibration - the two-point procedure in which the zero, called Calibration Low, is taken with all film removed and the scale, called Calibration High, is taken on the marked cal step of a five-step transmission reference; the check tolerance of 0.02 D on that step; and the statement introducing the Quick CAL procedure that the zero is the major factor of drift over a period of time; Chapter eight, specifications - illumination at 0 degrees with light collection by a diffusing surface, an incident-light aperture angle of approximately plus or minus 5 degrees, ambient interference stated as a decrease in D of less than 0.25 per cent, a two-minute warm-up, and the appendix listing the 361 reflection heads as separate purchased units with their own apertures of 3.4 and 1.7 mm rather than as a mode of the transmission instrument; Chapter eight, specifications - measuring geometry per ANSI PH2.19 and ISO 5/2, illumination at 0 degrees, light collection by a diffusing surface, incident-light aperture angle approximately plus or minus 5 degrees; source colour temperature approximately 2850 K; interinstrument agreement plus or minus 0.02 D; slope stability plus or minus 1 per cent per year; ambient interference stated as a decrease in D of less than 0.25 per cent; operating temperature 10 to 40 degrees C; and the calibration procedure, which enters a calibration high value read from a supplied step tablet and stores a separate N-factor for the Ortho and UV responses; Chapter four - the statement introducing the Quick CAL procedure that the zero, called Calibration Low, is the major factor of drift over a period of time, and the check tolerance of 0.02 D on the cal step; chapter eight, specifications - ambient interference stated as a decrease in D of less than 0.25 per cent, zero stability plus or minus 0.02 D per eight hours, and a two-minute warm-up; Chapter four - the check procedure in which the unit is zeroed and the cal step measured, the unit being properly calibrated if that measurement is within 0.02 D of the density specified; and the frequency of calibration, once a week under normal operating conditions; Chapter eight, specifications - ambient interference stated as a decrease in D of less than 0.25 per cent, warm-up time two minutes and five for the UV response, zero stability plus or minus 0.02 D per eight hours, and an operating temperature range of 10 to 40 degrees C; Chapter four, Density Calibration Check - the procedure of zeroing the unit and then measuring the cal step on the transmission reference, the unit being properly calibrated if the measurement is within 0.02 D of the density specified and needing recalibration if it is not; the frequency of calibration, once a week under normal operating conditions; and the handling instruction that the reference is held at the edges only because fingerprints or other foreign substances on the measurement area cause errors; Chapter four, calibration - the check procedure, which is to zero the unit and then measure the cal step, the unit being properly calibrated if the measurement is within 0.02 D of the density specified and needing recalibration if it is not; the recommended interval of once a week under normal operating conditions; Cal LO taken with all film removed and Cal HI on the cal step; the statement that the zero, Calibration Low, is the major factor of drift over a period of time; and the handling instructions for the reference - held at the edges only, fingerprints and foreign substances on the measurement area cause errors, nothing but a soft camel-hair brush is used on it, and change is minimised by storing it in a dark, cool, dry place; Specification - ambient interference given as a decrease in D of less than 0.25 per cent, for a bench instrument in a sealed metal case; Specification - zero stability of plus or minus 0.02 D per eight hours, and a two-minute warm-up before any specification applies; Specification - ambient interference given as a decrease in D of less than 0.25 per cent, for an instrument in a sealed metal case; Specification - a two-minute warm-up before any specification applies, and zero stability of plus or minus 0.02 D per eight hours

Used by:P15 Experiment: Calibrating the Densitometer in Both Modes · P15 Build: The Densitometer Electronics and Firmware · P15 Build: The Densitometer Optical Head (Transmission and Reflection) · P15 Density Depends on How You Look: Geometry and Spectral Response · P15 Break-Fix: Diagnosing a Misbehaving Densitometer · P15 Assignment: Characterising a Film and Developer with Your Own Instruments · P15 Photodiodes, ADCs and Measuring Light Over Three Decades · P27 Experiment: Four Curve Families, Measured · Densitometer daily five-minute check · Densitometer: ambient leak · Densitometer: drifting zero · Densitometer: high-density compression · Session exposure drift