The Pure Silver Formulary

A formulary is usually an appendix of recipes. This one is meant to be read. Every formula page gives the quantities exactly as its cited source states them, and then explains what each ingredient is, why it is there, what it does chemically, what changes on the negative or print if you use more or less of it, and how it interacts with the others. A formula you understand at that level is one you can adapt, diagnose and, eventually, design.

How to read a formula page

Identity and provenance. The name, its other names, who devised it and when, and the source the quantities were taken from. A formula whose provenance could not be established does not appear here.

Status. Verified formulas are reproduced from a Tier 1 source. Variants are the course’s own modifications, always shown as separate entries with a link to what they modify, an explanation of why they differ and what the consequence is. Historical study entries record formulas the course does not ask you to mix, because their ingredients or their era’s practice belong at safety level C or D.

The formula. Ingredient, quantity, the form the source specifies (anhydrous, crystalline, a stated solution strength), and a one-line function. Water to a stated final volume, at a stated temperature where the source gives one.

Mixing order. Where order matters, and it usually does, the page says why: which ingredient must be in solution before which, and what happens if you get it wrong.

Behaviour. Dilutions, capacity and shelf life appear only where a source states them. Image characteristics (grain, acutance, effective speed, contrast, tonality, colour, staining, compensating behaviour) are described in words that can be checked against your own negatives.

The mechanism. How and why the formula works, from the chemistry of each ingredient to the appearance of the result. This is the section that distinguishes the formulary from a recipe book, and it is mandatory on every page.

Safety, storage, incompatibilities, waste, troubleshooting, experiments, references. The practical sections, in that order.

Bought products, and why they read differently

Some of what a darkroom actually uses is not a formula at all. Nobody outside Harman knows what is in MULTIGRADE developer, and no amount of care will make a page that pretends otherwise honest. So those entries are a different kind of page, listed here beside the formulas in their own category and marked bought product — composition not published.

A product page gives what the maker publishes, which is often a great deal: dilutions, capacity, development times, and for several of the ILFORD developers the pH and specific gravity at each dilution. It gives the components the maker discloses on its own safety data sheet, each with the concentration band that sheet prints — a hazard document read as a hazard document, never reassembled into a recipe. It states plainly what is not disclosed, so the boundary is on the page rather than left for you to infer. And it names the nearest open formula this course does teach, with the comparison, because the useful question is rarely “what is in it” and almost always “should I buy this or mix that”.

⚠Safety

Every formula carries a safety level. The level is assigned from the specific substances and quantities on the page, and it assumes the controls listed in the classification rubric. Read the chemical encyclopaedia entry for each ingredient before you weigh it for the first time.

The formulas

Alternative-process chemistry

• Albumen sensitising solutionBStatus verifiedFor paper, alt-processReuse reusableHardwich's 90 grains of silver nitrate to the ounce of distilled water — the nitrate bath for albumenised paper, which has to make the silver chloride, leave a large excess of free silver behind, and coagulate the binder into silver albumenate, all in one three-minute float.
• Albumen solution with its chlorideAStatus verifiedFor paper, alt-processReuse reusableReilly's litre of egg white salted with 15 g of ammonium chloride and acidified with 2 mL of glacial acetic acid — the undiluted coating solution of glossy albumen paper, in which the halide is dissolved in the binder and the binder is spoiled on purpose.
• Albumenised salting solutionAStatus verifiedFor paper, alt-processReuse reusableHardwich's 1864 salting bath of three volumes of egg white to one of water, salted with ammonium chloride — the formula in which the binder and the chloride arrive in the same operation, and in which the amount of water decides the surface.
• Ammonium citrate developerAStatus verifiedFor paper, alt-processReuse eitherThe citrate bath modern palladium printing actually uses — a neutral grey where oxalate gives brown, sold premeasured with no mass on the label, and published at a strength by exactly one printer. What the two ammonium citrates have to do with it, and why this bath needs no separate acid.
• Arrowroot salting solutionAStatus verifiedFor paper, alt-processReuse reusableReilly's boiled starch cream — thirty-five grams of arrowroot, thirty-five of salt and three of citric acid — the salting solution for a matte paper whose binder does nothing chemically, which is exactly why the acid has to be there.
• Borax kallitype developerBStatus verifiedFor paper, alt-processReuse reusableSeventy-five grams of borax in four hundred millilitres of hot water — the alkaline half of the traditional kallitype kit, why an alkali with no reducing power in it turns the print from brown to black, and what the high pH costs the paper in iron.
• Bostick and Sullivan cyanotype and toning kitsBStatus bought product — composition not publishedFor paper, alt-processReuse one-shotFour bottles from one supplier, whose strengths are published on a store page and nowhere else — a classic sensitiser a quarter richer in iron than the open formula, a bleach-and-tone pair that replaces ammonia with potassium carbonate, and a company that publishes ninety safety data sheets and not one for anything it actually sells premixed.
• Bostick and Sullivan platinum and palladium kitsDStatus bought product — composition not publishedFor paper, alt-processReuse replenishedFive kits from Santa Fe built out of three bottles and two powders — a ferric oxalate a quarter stronger than the competing supplier's, a contrast bottle whose chlorate is published once and contradicted twice, and two noble-metal solutions whose listings carry a stock number and nothing else, from a company with eighty-nine safety data sheets and not one for anything it sells premixed.
• Bostick and Sullivan Ziatype kitBStatus bought product — composition not publishedFor paper, alt-processReuse one-shotA print-out palladium kit from Santa Fe whose instruction sheet names every chemical in the box and gives a strength for only three of them — a lithium chloropalladite the maker will not quantify, a ferric ammonium oxalate it will not quantify either, a colour chart with three starting points that cannot be made from the box, and a bottle of dichromate this course will not use.
• Classic cyanotype sensitiserBStatus verifiedFor paper, alt-processReuse one-shotThe traditional two-bottle blueprint sensitiser — Herschel's two chemicals with Valenta's green salt of 1897 — set out at Mike Ware's weights, with the arithmetic of why every published version of it is a different formula and why none of them is wrong.
• Cyanide fixing and toningDStatus historical studyFor paper, plateReuse reusableThe wet-plate era's second fixer, faster than hypo and leaving a whiter plate, tried once on albumen prints and rejected — recorded here at Level D as chemistry, evidence and image colour, with no procedure, and with the nineteenth century's "cyanide toning bath" shown to be a thiocyanate.
• Daguerre's 1839 process outlineDStatus historical studyFor plateReuse reusableThe five operations of Daguerre's own manual, the two aqueous solutions it publishes with quantities, the fixing chemistry that made silver iodide the hardest salt in photography to remove, and why the course describes this process and will never perform it.
• Double-coated albumen procedureBStatus verifiedFor paper, alt-processReuse reusableFloat a sheet twice on albumen and it is no thicker than after once, because the second float dissolves the first coat. The bath that stops it — 70 per cent isopropyl alcohol carrying the same chloride as the albumen — is the whole of what double coating adds, and it is the step that made the glossy paper of 1880.
• Fizeau's gilding solutionDStatus historical studyFor plateOne gram of gold chloride and three of hypo, published in 1840 as a way of fixing the daguerreotype rather than of colouring it, and the first gold toner in photography — with the tetrathionate nobody knew was in it.
• Gallo-nitrate of silver (1841)BStatus historical studyFor paper, alt-processReuse one-shotThe one liquid that both sensitised and developed the calotype — an acidified silver nitrate stock mixed with saturated gallic acid at the moment of use, spoiling within minutes, and the first developer in the history of photography.
• Herschel's 1842 cyanotypeBStatus verifiedFor paper, alt-processReuse one-shotThe first cyanotype formula, from Herschel's own notebook rather than from the manuals that claim to quote him — a very dilute iron salt, a saturated ferricyanide, mixed one to one, and the reason his own proportions are the slowest and bluest of them all.
• Herschel's argentotypeBStatus historical studyFor paper, alt-processThe first iron-silver process, from the postscript of 29 August 1842 — a latent picture in an iron paper brought out by a wash of silver nitrate whose strength Herschel never published anywhere, on a paper whose strength he published exactly once, in a letter to a literary weekly.
• Herschel's hydrargyro-cyanotypeDStatus historical studyFor paper, alt-processReuse one-shotHerschel washed a finished cyanotype with a mercury(I) salt, watched the blue vanish, then brought the picture back in brown with a flat-iron — a documented transformation whose chemistry is still conjecture and whose mercury bath nobody has ever published a strength for.
• Kallitype sensitiserBStatus verifiedFor paper, alt-processReuse one-shotTwo bottles — ten per cent silver nitrate and twenty per cent ferric oxalate — mixed in equal parts in the coating dish at the moment of use, why swapping citrate for oxalate turns a printing-out process into a developing-out one, and what the excess iron costs you afterwards.
• Lead additions to platinum sensitisersDStatus historical studyFor paper, alt-processFor nineteen years there was lead in commercial platinum paper, and an X-ray spectrum of a Willis sheet still shows it. It was never a contrast control - it was a chloride scavenger that made the platinum reduce, and it stayed in the paper rather than in the picture.
• Mercuric sepia platinotypeDStatus historical studyFor paper, alt-processThe brown platinum print was neither a hot developer nor a toner. It was a platinum print with mercury in it, at strengths William Willis printed in a patent in 1878 — and most of the literature said otherwise until X-ray fluorescence was pointed at the prints.
• Mike's CyanotypeBStatus verifiedFor paper, alt-processReuse one-shotMike Ware's ammonia-free route to the Simple Cyanotype sensitiser, which buys the neutralisation ready-made as triammonium citrate instead of titrating it in — the same solution, odourlessly, at the cost of the one contrast control cyanotype has ever had.
• Nicol's kallitypeBStatus verifiedFor paper, alt-processReuse one-shotThe kallitype as its inventor's own published instructions gave it — one bottle carrying the iron and the silver together, a quarter more iron per unit of silver than the modern sensitiser, no clearing bath at all, and the reason almost none of the prints survive.
• Niépce's bitumen heliograph coating (1829)DStatus historical studyFor plateThe varnish of the first photograph, published in 1829 with its composition fixed by the vessel it is made in — half a glass of powdered bitumen, oil of lavender dropped on to saturation, three lines of oil standing over it — with no water in it anywhere, and no quantity for it in any of the twelve printings read.
• Pellet's positive-working processBStatus verifiedFor paper, alt-processThe blueprint run backwards — a gum-and-iron film in which light destroys the image instead of making it, developed in yellow prussiate so that the blue forms where the light never reached, with the patent that hid its own numbers and the 1881 formula that made it work.
• Photographers' Formulary cyanotype and toning kitsBStatus bought product — composition not publishedFor paper, alt-processReuse one-shotThe one bought product in this formulary whose maker publishes the whole composition — four named solids with weights, two stock strengths and a mixing ratio that lands twenty per cent short of the open formula's ferricyanide — and why the boundary of what is not disclosed turns out to lie in the grade of the iron salt, the botany of the starch, and a gram of dichromate the course will not use.
• Photographers' Formulary platinum and palladium printing kitsDStatus bought product — composition not publishedFor paper, alt-processReuse one-shotA bought product whose instruction sheet prints the whole composition — seven items with weights, a 20 per cent iron, a 20 per cent platinum and a 15 per cent palladium — and whose maker publishes 105 kit safety data sheets, none of them for this kit, and 124 substance sheets, none of them for ferric oxalate, potassium chlorate or either noble metal salt.
• Pizzighelli and Hübl's 1886 formulationsDStatus historical studyFor paper, alt-processReuse one-shotThree stock bottles and four mixtures — the first published platinum sensitiser anyone outside Willis's factory could actually make, in which the platinum and the iron never move and only the potassium chlorate does. Recorded at Level D as chemistry and history, with no procedure.
• Plain salted paper salting solutionAStatus verifiedFor paper, alt-processReuse reusableReilly's twenty grams of common salt and two grams of gelatin in a litre — the first of the two coatings that make a salt print, and the one that decides the colour, the contrast and how much free silver the sheet will carry.
• Rochelle salt kallitype developerAStatus verifiedFor paper, alt-processReuse reusableOne tartrate salt and hot water — the kallitype developer that gives sepia because of what it does not contain, why a bath with nothing in it that can reduce silver develops a silver image anyway, and the arithmetic that shows borax, not tartrate, choosing the colour.
• Salted paper sensitising solutionBStatus verifiedFor paper, alt-processReuse replenishedOne hundred and twenty grams of silver nitrate in a litre of distilled water — the second of the two coatings that make a salt print, the bath that turns the chloride in the paper into silver chloride, and the source of the free silver that lets a print-out image build at all.
• Schulze's scotophorus mixture (1727)CStatus historical studyReuse reusableThe oldest preparation in this course, published in 1727 with its composition stated entirely by operation — silver dissolved in parting acid, the acid tempered with water, chalk imbued with it until saturated — and the reason no source has ever supplied a number for any of it.
• Sodium citrate developerAStatus verifiedFor paper, alt-processWillis's palladiotype developer — one citrate salt, a tenth as much citric acid, and no oxalate anywhere. Why the man who invented the oxalate developer replaced it for palladium, what the swap does to the highlights, and the one thing about it the chemistry of the sources will not settle.
• Sodium citrate kallitype developerAStatus verifiedFor paper, alt-processReuse replenishedTwo hundred grams of one salt in a litre of water, and nothing in it that can reduce silver — how a bath made of nothing but a ligand develops a kallitype, why the tray time is twenty times longer than the image takes, and what the iron left behind costs.
• Talbot's calotype iodised paper (1841)BStatus historical studyFor paper, alt-processThe first photographic material designed to be insensitive — silver iodide precipitated inside a sheet of writing paper with the halide deliberately in excess, so that the paper keeps indefinitely in a drawer and becomes sensitive only when a second solution is brushed on at the moment of use.
• Talbot's photogenic drawing paper (1839)BStatus historical studyFor paper, alt-processThe first silver formula in photography, and the first counter-intuitive one — a weak salt bath and a strong silver bath, deliberately mismatched, so that every crystal of silver chloride sits in a pool of unreacted silver nitrate and the darkening does not stop.
• The New Cyanotype (1995)BStatus verifiedFor paper, alt-processReuse one-shotMike Ware's redesign of the blueprint sensitiser — crystalline ammonium iron(III) oxalate in place of the ill-behaved citrate, most of the potassium crystallised out and thrown away, and a single bottle that keeps for years, prints in minutes and holds an exposure scale of about 2.2.
• The Simple Cyanotype (2019)BStatus verifiedFor paper, alt-processReuse one-shotMike Ware's third cyanotype sensitiser, which never buys ferric ammonium citrate at all but builds a dicitratoferrate in the beaker from iron(III) nitrate, citric acid and ammonia — and where the volume of ammonia, and nothing else, sets the contrast.
• Three-solution drop system for platinum and palladiumDStatus historical studyFor paper, alt-processReuse one-shotThree bottles and a shot glass — ferric oxalate, ferric oxalate with potassium chlorate, and the noble metal — in which the number of drops from each bottle is the contrast grade. Recorded at Level D as chemistry and history, with no procedure.
• Van Dyke Brown sensitiserBStatus verifiedFor paper, alt-processReuse one-shotNine grams of ferric ammonium citrate, one and a half of tartaric acid and 3.8 of silver nitrate, made up as three solutions and combined in that order — the cheapest way to put a silver image on plain paper, why the silver in it is not the light-sensitive part, and what the acid is doing.
• Ware's argyrotypeBStatus verifiedFor paper, alt-processMike Ware's 1991 redesign of the iron-silver print — silver sulfamate made in the beaker instead of silver nitrate, so that the whole process can work acid, clear properly, and put a purplish-brown nanoparticle silver image on plain paper from one bottle.
• Ware's improved Classic cyanotypeDStatus historical studyFor paper, alt-processReuse one-shotThe widely circulated cyanotype sensitiser that adds oxalic acid and 0.2 g of ammonium dichromate to the classic two-bottle formula. Recorded at Level D as chemistry and provenance, with no procedure, because chromium(VI) is not used at any level in this course.
• Ware's print-out platino-palladiotypeBStatus verifiedFor paper, alt-processReuse one-shotThe Malde-Ware ammonium system — a well-characterised iron salt whose photoproduct is soluble, an ammonium salt of the noble metal, and water held in the paper as vapour, so that the palladium or platinum is reduced during the exposure and there is nothing left for a developer to do.
• Wedgwood and Davy's silver nitrate on leather (1802)BStatus historical studyFor paper, alt-processThe first photographic formula ever published — one part of silver nitrate to about ten of water, brushed on white tawed leather — and the reason the leather worked better than the paper, which neither of its authors knew.
• Willis's potassium oxalate developerBStatus verifiedFor paper, alt-processReuse reusableOne salt in water, and it reduces nothing — the platinotype developer dissolves the immobile iron(II) that light has made, so the iron can travel to the platinum. Willis's own patent strength, the hot bath and the cold, and why temperature was the tone control.

Bleaches

• Rehalogenating ferricyanide-bromide bleachBStatus verifiedFor film, plate, paperReuse one-shotThe bleach that begins every sepia toner and every redevelopment intensifier — ferricyanide to oxidise the image and bromide to catch the silver as a halide, so that nothing leaves the print and the picture can be built a second time.

Cleaning solutions

• EDTA and sodium sulfite clearing sequenceAStatus verifiedFor paper, alt-processReuse eitherThree trays and two rinses that take the iron out of an iron-silver print before it can stain it — an acid chelating bath, a sulfite reduction and an alkaline chelating bath, in that order, because chelation alone gets only half the iron off the paper.
• EDTA, citric acid and hydrochloric acid clearing sequenceBStatus verifiedFor paper, alt-processReuse reusableThree trays of dilute acid between the developer and the wash — the baths that take the unreduced iron out of a platinum or palladium print, at the six published strengths, and why the one that is right for platinum will eat a palladium image.

Emulsion-making solutions

• Chrome alum subbing dipBStatus verifiedFor plateThe two per cent chrome alum dip a 1941 plate manual gives for substratuming glass, printed as the source prints it — one salt, no gelatin, and no formula anywhere in this corpus for the compound sub the course's own manifest asked for.
• Davey and Knott's double-jet iodobromide emulsionBStatus verifiedFor film, plateKodak's 1952 conversion emulsion — two jets run into a salted gelatin for ninety seconds, a silver chloride skeleton turned into a twenty-one per cent iodobromide, and a formula built so that it cannot be sulfur-and-gold sensitised.
• KCl gaslight paper emulsionBStatus verifiedFor paperReuse one-shotFive grams of silver nitrate whisked into a salted gelatin in three portions over five minutes, unwashed, briefly ripened and coated wet on watercolour paper — the one emulsion in this formulary that somebody has demonstrably made, photographed and had a reader repeat.
• Trumm's bromide paper emulsionBStatus verifiedFor paperReuse one-shotThe most completely published emulsion formula in this corpus — three solutions, two timed hours at temperature, twelve changes of wash water and a made-up sixteen kilograms — printed here with one ingredient removed and the removal stated.
• Wall's soft-working gaslight paperBStatus verifiedFor paperReuse one-shotA commercial chlorobromide paper emulsion of 1929 — five hundred grams of silver into a chloride-rich salted gelatine, seventy-five minutes at fifty degrees, never washed, and finished with three grams of chrome alum in eleven kilograms.

Film developers

• 510-PyroBStatus verifiedFor filmReuse one-shotJay DeFehr's single-bottle staining developer, printed from his own publication of it — ten grams of pyrogallol, five of ascorbic acid and a quarter-gram of phenidone dissolved in triethanolamine to make a hundred millilitres, with no water and no sulfite anywhere in the formula.
• Beutler two-solution developerBStatus verifiedFor filmReuse one-shotMetol and a little sulfite in one bottle, sodium carbonate in the other, diluted twelvefold at the tank and thrown away. The formula that gets its sharpness by leaving out the ingredient every fine-grain developer is built on.
• ILFORD MICROPHEN developerBStatus bought product — composition not publishedFor filmReuse eitherA bought film developer sold as two bags of powder, and the one ILFORD developer whose central claim its maker's own tables let you check. What HARMAN publishes, what its two safety data sheets disclose, which of the two bags actually carries the Danger label, and the open formula to mix instead.
• ILFORD PERCEPTOL developerBStatus bought product — composition not publishedFor filmReuse reusableA bought film developer sold as two bags of powder whose two safety data sheets name two substances between them — a metol salt and sodium sulphite. What HARMAN publishes, why the shortest disclosed-component table in this library is not a formula, and the open developer with exactly those two ingredients that you can mix instead.
• Kodak D-1BStatus verifiedFor film, plateReuse reusableThe standard A.B.C. pyro — three stock bottles that meet only in the tray, a preservative dose a tenth of D-76's, and a yellow oxidation product that Kodak deliberately left in the negative.
• Kodak D-167BStatus verifiedFor film, plateReuse one-shotKodak Limited's pyro-Elon staining developer for press work — fifteen grams of pyro and a deliberately small preservative in one bottle, a strong carbonate in the other, and Kodak's own warning that the two must not meet until the tray is wanted.
• Kodak D-177BStatus verifiedFor film, plateReuse one-shotKodak Limited's pyro-soda dish developer — a concentrated pyro stock made 150 millilitres at a time, diluted to a litre as the second solution, and met by a sulfite-and-carbonate third, with a published ratio for average negatives and another for portraits.
• Kodak D-19BStatus verifiedFor film, plateReuse reusableKodak's high-contrast developer as its own 1928 primer prints it - four times D-76's hydroquinone, a hundred times its alkalinity, and five minutes. Published alongside the revised D-19b so the reader can see what Kodak changed.
• Kodak D-19bBStatus verifiedFor film, plate, paperReuse replenishedKodak Limited's revision of the high-contrast X-ray developer, printed with a keeping table, a capacity, a replenisher and a note about two films it does not suit. The formula the rest of this course cites when it needs a carbonate developer.
• Kodak D-19bRBStatus verifiedFor film, plate, paperReuse replenishedThe replenisher that takes an ingredient away. Kodak drops the restrainer entirely, leaves the carbonate alone and adds caustic soda - three decisions that say what a high-contrast tank actually loses and what it gains on its own.
• Kodak D-23BStatus verifiedFor film, plateReuse eitherTwo chemicals, no alkali, no restrainer and eighteen minutes. The simplest developer the course can print in full, and the one that shows most clearly what each of D-76's other ingredients was actually for.
• Kodak D-25BStatus verifiedFor film, plateReuse eitherD-23 with fifteen grams of an acid salt added, and Kodak printing both ends of the trade - minimum grain, at the cost of one to two stops of exposure and a bath run seven degrees warmer to keep the time the same.
• Kodak D-25RBStatus verifiedFor film, plateReuse replenishedOne replenisher for two different developers, and it contains an alkali neither of them has. What that says about what a tank of metol-sulfite developer actually loses as it works.
• Kodak D-32BStatus verifiedFor plateReuse one-shotKodak's warm-black lantern slide developer — hydroquinone with citric acid in one bottle, carbonate and a little caustic soda in the other, and the ratio between them printed as the tone control.
• Kodak D-34BStatus verifiedFor plateReuse one-shotKodak's blue-black lantern slide developer — metol and hydroquinone with very little sulfite in one bottle, carbonate and bromide in the other, equal parts, and a second dilution printed as the control for softer tones.
• Kodak D-76BStatus verifiedFor film, plateReuse eitherFour chemicals in a litre, unchanged since 1928, and still the developer every other film developer is described against. What each of the four is doing, what the sulfite costs you, and what Kodak actually publishes about it.
• Kodak D-76dBStatus verifiedFor filmD-76 with the same two agents, the same sulfite and a completely different alkali - four times the borax, and boric acid beside it. Kodak Limited's buffered borax negative developer, and the formulary's clearest demonstration that where a buffer sits and how much it holds are two separate settings.
• Kodak D-76RBStatus verifiedFor film, plateReuse replenishedThe replenisher for D-76, and the clearest evidence in the formulary of what a tank of developer actually runs out of - the same sulfite, half again the agents, and ten times the borax.
• Kodak D-9BStatus verifiedFor film, plateReuse one-shotThe process tray developer at the far end of the range — hydroquinone, bisulfite and an equal weight of bromide in one bottle, caustic soda in another, and half a mole of free hydroxide per litre the moment they meet.
• Kodak DK-20BStatus verifiedFor film, plateReuse replenishedExtra-fine grain reached by a completely different route from D-25 - one gram of a silver-complexing salt, a real alkali and a restrainer, in fifteen minutes at eighteen degrees, with no published exposure penalty.
• Kodak DK-20RBStatus verifiedFor film, plateReuse replenishedFive ingredients, five different multipliers, and a published replenishment rate that works out at almost exactly the rate Kodak gives for a completely different developer. What a replenisher's proportions reveal about what a tank consumes.
• Kodak DK-50BStatus verifiedFor film, plateReuse reusableThe general-purpose sheet-film developer of the Kodak catalogue, and the one formula in this reference whose own handbook tells you what happens when you change an ingredient - and what you get to hold constant while you do it.
• KODAK PROFESSIONAL XTOL DeveloperBStatus bought product — composition not publishedFor filmReuse eitherSixteen pages in which Kodak publishes a specific gravity to three decimals, a pH to two, a replenishment rate adjustable in ten-millilitre steps and eight tables of development times - and, of what is in the packets, two words. What J-109 states, what no document states, why this page carries no safety data sheet, and the open formula to mix instead.
• PMK pyroBStatus verifiedFor filmReuse one-shotGordon Hutchings's staining developer, printed in full from its maker's own kit sheet — a hundred grams of pyrogallol to the litre in one bottle, three hundred grams of metaborate in the other, and a working bath so dilute that its entire preservative is a fifth of a gram.
• Pyrocat-HDCStatus verifiedFor film, plateReuse one-shotSandy King's catechol-and-phenidone staining developer, printed from his own publication of it — fifty grams of catechol and two of phenidone in one bottle, seven hundred and fifty grams of potassium carbonate in the other, and a working bath of half a gram of developing agent to the litre.
• Rodinal-type p-aminophenol developerBStatus verifiedFor plate, paperThe liquid concentrate class that Agfa patented in 1891 and has never described, published here as Wall printed it in 1924 - one developing agent, a great deal of caustic soda, and a working bath with almost no sulfite in it at all.

Fixers

• Alkaline plain-hypo fixing bathAStatus verifiedFor paper, alt-processReuse one-shotReilly's fixer for albumen, salted paper and every other printing-out process — a fifteen per cent hypo bath made slightly alkaline with two grams of carbonate, used two baths deep, four minutes each, and thrown away the same day.
• Dilute alkaline thiosulfate fixer for iron-silver printsAStatus verifiedFor paper, alt-processReuse one-shotFifty grams of hypo, ten of carbonate and two of sulfite in a litre — Sandy King's fixer for kallitype and its relatives, weak on purpose, because the only bath that can remove the residual silver from an iron-silver print is also the one thing in the darkroom that can dissolve the image.
• FOMAFIX rapid fixerAStatus bought product — composition not publishedFor film, paperReuse reusableThe rapid fixer Foma puts in the fixing row of every one of its own paper and film sheets — what its two datasheets publish about dilution, times and capacity, the four substances its Czech safety data sheet names, the fixing agent that is not one of them, and the open non-hardening bath to mix instead.
• ILFORD HYPAMBStatus bought product — composition not publishedFor film, paperReuse reusableRAPID FIXER's twin — the same fixing agent, the same dilutions, almost the same published numbers — and the one ILFORD lets you harden. Its safety data sheet, issued the same day as its twin's, carries one extra line of boric acid, and that line carries the whole bottle into a reproductive-toxicity classification its twin does not have.
• ILFORD RAPID FIXERAStatus bought product — composition not publishedFor film, paperReuse reusableThe ammonium thiosulphate fixer most darkrooms actually use — what HARMAN publishes across four of its own sheets, the three components its safety data sheet discloses, the fourteen years between those two documents, and the open non-hardening bath to mix instead.
• Kodak bisulphite fixing bath (1928)AStatus verifiedReuse reusableThe acid fixing bath for a darkroom with no acetic acid — hypo, a little sulfite and less bisulfite, printed by Kodak in 1928 without a formula number and with an honest account of what it gives up.
• Kodak F-1BStatus verifiedFor film, plate, paperReuse reusableKodak's American acid hardening fixing bath — two pounds of hypo made to two litres, and a hardener of sulfite, acetic acid and potash alum stirred into it cold, with the capacity figures every other fixing page in the 1928 primer is measured against.
• Kodak F-14BStatus verifiedFor filmReuse reusableKodak's deep tank fixing bath for roll films — F-1's hypo and F-1's alum with half the sulfite and rather more acid, which is the primer's own recipe for a bath that lasts a long time and hardens a little less.
• Kodak F-2BStatus verifiedFor filmReuse reusableKodak's motion picture fixing bath — the same two pounds of hypo as its deep-tank cousins carrying a fifth of F-1's sulfite and two-fifths of its alum, published without a word of explanation for either.
• Kodak F-24AStatus verifiedFor film, plate, paperReuse reusableKodak's non-hardening fixing bath — F-5's hypo with the alum and the boric acid gone and the acid rebuilt out of bisulfite, and the one fixing formula whose instructions govern the developer, the rinse and the wash as well as the fixer.
• Kodak F-5BStatus verifiedFor film, plateReuse reusableKodak's acid hardening fixing bath — hypo, sulfite, acetic acid, boric acid and potash alum in one litre, with the handbook's own mixing order, its ten-minute fixing time, its keeping table and the narrow pH window the whole design exists to hold.
• Kodak F-52AStatus verifiedFor paper, film, plateReuse reusableKodak's non-hardening acid fixing bath — two ingredients, no alum and no boric acid, for every occasion when hardening the emulsion would spoil what comes next.
• Kodak F-54BStatus verifiedFor paperReuse reusableKodak's acid hardening fixing bath for paper — hypo dissolved in warm water, then a measured dose of the F-53 hardener stock added cold, and its films-and-plates twin F-54a printed alongside it.
• Kodak F-6BStatus verifiedFor film, plate, paperReuse reusableKodak's odourless acid hardening fixing bath — F-5 with the boric acid replaced by twice its weight of Kodalk, which is not a subtraction but a neutralisation, and the one fixing formula whose published capacity halves if you skip the stop bath.
• Plain hypo fixing bathAStatus verifiedFor paper, alt-processReuse eitherFour hundred grams of hypo in a litre of hot water — the whole of fixing with nothing else in the tray, published by Wall in 1924, and the bath every other fixer in this formulary is a defended version of.
• Plain sodium thiosulfate fixer for printed-out papersAStatus verifiedFor paper, alt-processReuse reusableFifty grams of hypo in a litre of water — the weakest bath in this formulary by a factor of three, published by Bostick & Sullivan for salted paper, and weak because the image it has to leave behind is a tenth the silver of a modern print at a hundredth the particle size.
• TF-2 alkaline fixerBStatus verifiedFor film, paper, alt-processReuse reusableBill Troop's sodium thiosulfate fixer held on the alkaline side by one per cent of Kodalk — no stop bath, no hardener, no hypo clearing agent — published by its own authors with a warning attached about the films it is not for.

Hardeners

• Kodak F-1a hardener stockBStatus verifiedFor film, plate, paperReuse reusableThe American acid hardener stock — sulfite, 28 per cent acetic acid and powdered potash alum in four litres, dissolved in an order Kodak spells out twice, and added one part to eight of plain hypo whenever a hardening fixer is wanted.
• Kodak F-53BStatus verifiedFor film, plate, paperReuse reusableThe acid hardener stock — sulfite, glacial acetic acid and potash alum in a litre, mixed in four separate steps for reasons the handbook spells out, and the bottle that turns plain hypo into a hardening fixer.
• Kodak Hardener F-5aBStatus verifiedFor film, plate, paperReuse reusableKodak's American hardener stock — the hardener half of Fixing Bath F-5 at five times the strength, one part into four of thirty per cent hypo to make the bath, or two parts in eighteen as the hardening bath a sulfide-toned print goes through at the end.
• Kodak SB-4BStatus verifiedFor film, plateReuse reusableKodak Limited's chrome alum hardening bath for hot weather — thirty grams of the violet salt and a neutral sulphate to the litre, three minutes between the developer and the fixer, and a bath that announces its own death by turning from violet-blue to yellow-green.

Intensifiers

• Kodak IN-1DStatus historical studyFor film, plateThe mercury intensifier, printed unchanged by Kodak in 1928 and 1949 — a mercuric chloride and bromide bleach, and a silver-cyanide blackener. Recorded here as chemistry and history at Level D, with no procedure, because no control a reader can assemble makes it reasonable.
• Kodak IN-21DStatus historical studyFor film, plateThe uranium intensifier — a uranyl nitrate and acetic acid stock, a ferricyanide stock, one to one to six, and a reddish-brown image that an alkaline wash takes straight off again. Recorded at Level D as chemistry and history, with no procedure.
• Kodak IN-4DStatus historical studyFor film, plateThe chromium intensifier — 90 grams of potassium bichromate and 64 millilitres of hydrochloric acid to the litre, diluted one to ten, bleached and redeveloped. Recorded at Level D as chemistry and history, because chromium(VI) is not used at any level in this course.
• Kodak IN-5BStatus verifiedFor film, plateReuse one-shotThe silver intensifier — four stock solutions combined in a fixed order to make a bath that carries silver and a developing agent at once, adds density to a transparency in proportion to the silver already there, and dies in half an hour.

Other

• Iodide hypo checkBStatus verifiedFor paperReuse reusableKodak's fixer test — a nineteen per cent solution of potassium iodide, five drops of it against five drops of the bath, and a yellow-white cloud of silver iodide that says the fixing bath is carrying more silver than it can hold in solution.
• Kodak HT-2BStatus verifiedFor paper, filmReuse reusableKodak's residual-hypo test — silver nitrate in dilute acetic acid, one drop on a sacrificial sheet for two minutes, running the reaction that fades a badly washed print deliberately and in miniature so that you find out now rather than in thirty years.
• Kodak ST-1CStatus verifiedFor paper, filmReuse reusableKodak's residual-silver test — two grams of sodium sulfide in 125 millilitres, diluted one to nine, one drop on a margin for two or three minutes. It answers the question a longer wash cannot, and it is the sepia toner run deliberately, on the silver that should not be there.

Paper developers

• FOMATOL LQN developerBStatus bought product — composition not publishedFor paperReuse reusableA bought paper developer sold as a liquid concentrate — what Foma publishes about it, the four components its Czech safety data sheet names and the two the sheet leaves out, the disagreement between two of the maker's own sheets, and the open formula to mix instead.
• ILFORD BROMOPHEN developerBStatus bought product — composition not publishedFor paperReuse reusableA bought paper developer sold as two bags of powder — what ILFORD publishes about it, what its two safety data sheets disclose, the arithmetic in its own literature that does not add up, and the open formula to mix instead.
• ILFORD MULTIGRADE developerBStatus bought product — composition not publishedFor paperReuse reusableA bought paper developer whose composition its maker does not publish — what ILFORD does publish, what its own safety data sheet discloses, what the two documents together still leave unknown, and the open formula to mix instead.
• Kodak D-156BStatus verifiedFor paperReuse reusableKodak's warm-tone paper developer — the same five chemicals as D-72 with a quarter of the alkali and three and a half times the bromide, and a published capacity that is a judgement about colour rather than a number.
• Kodak D-158BStatus verifiedFor paper, filmReuse reusableKodak's developer for chloride contact paper, published with a colour as its stated aim — the most alkali and the least bromide in the paper library, which is what a blue-black tone is made of.
• Kodak D-166BStatus verifiedFor paperReuse reusableThe warmest developer in the Kodak paper library — twelve and a half grams of bromide to a litre, tone adjusted by dilution rather than by time, and a published emergence time that turns exposure judgement into a stopwatch reading.
• Kodak D-170BStatus verifiedFor paperReuse one-shotA paper developer with no alkali in it at all — Kodak's Dolmi developer for bromide papers, which is amidol, sulfite, bromide and water, and which lasts thirty minutes in a dish.
• Kodak D-173BStatus verifiedFor paperReuse reusableKodak's metol-free paper developer, published in 1949 for the express purpose of letting people with metol dermatitis keep printing — p-aminophenol hydrochloride at 0.375 g with hydroquinone, and a mixing order that argues with the handbook's own rule.
• Kodak D-49BStatus verifiedFor paperReuse reusableKodak's portrait bromide paper developer of 1928 — D-72 with a third of the alkali taken out and a little more bromide put in, and a development time given as a minimum rather than a target.
• Kodak D-51BStatus verifiedFor paperReuse one-shotKodak's 1928 amidol developer for bromide papers — an alkali-free stock of sulfite and Acrol, published with no development time, and with a keeping claim that Kodak itself abandoned twenty-one years later.
• Kodak D-52BStatus verifiedFor paperReuse reusableThe paper developer that leaves the restrainer out of the bottle — a weak metol–hydroquinone stock with no bromide in it at all, and four published bromide doses to be added at the tray, one for each paper.
• Kodak D-72BStatus verifiedFor paper, film, plateReuse reusableThe archetype paper developer — metol, hydroquinone and a great deal of carbonate — printed by Kodak twice, twenty-one years apart, with the same quantities and two different accounts of what it is for.

Reducers

• Kodak R-4BStatus verifiedFor film, plateReuse one-shotFarmer's reducer as Eastman Kodak printed it in 1928 — one gram of ferricyanide in thirty-two millilitres, tipped into a litre of thirty-grams-per-litre hypo and poured over the negative at once. The same two chemicals as R-4a at less than half the oxidiser.
• Kodak R-4aBStatus verifiedFor film, plate, paperReuse one-shotFarmer's reducer as Kodak Limited printed it — a ferricyanide stock and a hypo stock, each made to its own litre, kept apart because together they will not keep, and mixed one to four to twenty-seven only as the negative goes under them.
• Kodak R-4bBStatus verifiedFor film, plateReuse one-shotThe two-bath Farmer's reducer — a 7.5 g/L ferricyanide bath, then a 200 g/L hypo bath, one after the other rather than mixed, which Kodak Limited classes as almost proportional rather than cutting and offers a step at a time.

Sensitisers

• Erythrosin sensitising stock, two per centBStatus verifiedFor emulsion, plate, paperOne gram of a red dye in fifty millilitres of half water and half drinking-grade ethanol — the two per cent stock that makes a silver bromide emulsion see green, dosed thereafter in drops, and printed at the same strength in the same solvent by a 1941 manual and a modern practitioner seventy-two years apart.
• Steigmann aurous ammonium thiocyanate solutionBStatus verifiedFor emulsion, plateSix millilitres of one per cent gold chloride run into fifty of one per cent ammonium thiocyanate and left until it clears — the aurous stock a gold digestion is dosed from, published with a dose the course can cite and cannot perform.

Stop baths

• Citric Acid Stop BathAStatus variantFor paper, film, plateReuse reusableThe course's own citric substitution for Kodak's SB-1, matched proton for proton rather than gram for gram — a solid acid with no vapour, published as a variant with its arithmetic shown and nothing about it attributed to a manufacturer.
• ILFORD ILFOSTOPAStatus bought product — composition not publishedFor film, paperReuse reusableThe citric stop bath that reports its own exhaustion by colour — what HARMAN publishes for it across five of its own sheets, the two components its safety data sheet discloses, the dye that appears on neither document, and the open citric bath to mix instead.
• Kodak SB-1BStatus verifiedFor paper, film, plateReuse reusableThe acid stop bath — seventeen millilitres of glacial acetic acid in a litre of water, published by Kodak twice at two different strengths, with a capacity, a rinse time and a measured effect on the fixer that follows it.
• Kodak SB-1aBStatus verifiedFor plate, filmReuse reusableThree times SB-1's acid and less than half its capacity — Kodak's stop bath for plates leaving a caustic developer, and the clearest published demonstration that a stop bath's life is set by what comes into it.
• Kodak SB-5BStatus verifiedFor film, plateReuse reusableKodak's nonswelling acid rinse for photofinishing — an acid stop bath carrying forty-five grams of sodium sulfate per litre, so that the film can be stopped without being swollen, published in 1946 and printed again, with different times and half the capacity, in 1977.

Toners

• Gold-acetate tonerBStatus verifiedFor paper, alt-processReuse replenishedThe alkaline gold bath the nineteenth century used most and the twentieth abandoned — twenty grams of fused sodium acetate and forty to fifty millilitres of a one per cent gold stock, which will not tone anything for the first twenty-four hours.
• Gold-borax tonerBStatus verifiedFor paper, alt-processReuse reusableThe alkaline gold toner for printing-out and salted papers — four grams of borax and eight millilitres of a one per cent gold stock in warm water, six to twelve minutes at 21 °C, and gold(I) reached without a sulfur ligand at all.
• Gold-thiocyanate tonerBStatus verifiedFor paper, alt-processReuse replenishedThe gold toner the printing-out processes actually use — a two per cent ammonium thiocyanate stock and a 0.2 per cent gold stock, fifty millilitres of each in a litre of water, mixed cold and replenished by the print.
• HARMAN SELENIUM TONERBStatus bought product — composition not publishedFor paperReuse reusableThe selenium toner HARMAN sells for its own papers — what its technical sheet publishes across two dilutions with two different purposes, the three components its safety data sheet discloses, including the first selenium species any manufacturer in this corpus names by CAS number, and why the nearest open formula is the one page in this library the course asks nobody to make.
• Kodak GP-1BStatus verifiedFor paperReuse one-shotKodak's gold protective solution — ten millilitres of a one per cent gold stock, a thiocyanate, and a litre of water, for ten minutes at 20 °C. The simplest gold formula published, and the one whose second quantity its maker never converted to a weight.
• KODAK Rapid Selenium TonerBStatus bought product — composition not publishedFor paper, filmReuse reusableKodak's packaged selenium toner — the maker whose toning publication would name its active ingredient only as "a sulfite salt", and whose own safety data sheet names sodium selenite by CAS number. A product opaque about capacity and keeping, unusually open about pH, density and composition, and the only selenium toner in this library whose nearest open formula was published by Kodak itself.
• Kodak T-1aBStatus verifiedFor paperReuse reusableThe hypo alum sepia toner — the sepia route that reaches a silver sulfide image without a sulfide reagent ever being handled, by acidifying hot hypo until it precipitates its own sulfur, and the reasons that is not the same as being safe.
• Kodak T-21CStatus historical studyFor paperReuse replenishedKodak's gold toner for warm-tone papers — a hot thiosulfate-persulfate stock ripened with silver chloride, a gold stock added to the whole of it, eight hours' standing, and a bath worked at 43 °C that tones highlights and shadows at the same rate.
• Kodak T-26CStatus historical studyFor paperReuse one-shotKodak's blue toner — gold and thiourea in warm water with tartaric acid and sodium sulfate, toning the highlights first and the shadows last, and the reason the odourless alternative to a sulfide bath is not a way around the sulfide question.
• Kodak T-52CStatus verifiedFor paper, plateReuse one-shotKodak Limited's two-solution sepia toner, printed in 1949 — a plain ferricyanide-bromide bleach with no acid in it, a 200 g/L sodium sulfide stock made once outside the session, and a working bath at a fortieth of that stock.
• Kodak T-55DStatus historical studyFor paper, plateReuse reusableKodak Limited's direct selenium toner, 1949 — six grams of selenium powder boiled into a sulfite solution, diluted one to five, ten to fifteen minutes at 18 °C. Published as chemistry at Level D, because the course does not ask anyone to boil elemental selenium.
• Kodak T-56DStatus historical studyFor paperReuse one-shotKodak Limited's sulfide-selenium toner, 1949 — T-52's bleach, and a sulfide stock with 5.7 g of selenium powder dissolved into it, giving warmer and redder browns than sulfide alone. Level D, because the selenium is dissolved in the sulfide.
• Kodak T-7aCStatus verifiedFor paper, film, plateReuse one-shotKodak's American sulfide sepia toner — a bleach carrying oxalate against blue spots and acetic acid against blisters, a sodium sulfide stock, and two working baths whose published strength Kodak more than doubled between 1928 and 2006 without saying why.
• Lead, thallium and nickel cyanotype tonersDStatus historical studyFor paper, alt-processThree baths that change a cyanotype by walking a heavy-metal cation into the Prussian blue lattice rather than by converting or bleaching the pigment — lead for violet, thallium for a bluer blue, nickel for ten times the resistance to alkali. Recorded at Level D as chemistry, with no procedure.
• Moersch MT1 SelentonerBStatus bought product — composition not publishedFor paperThe selenium toner Wolfgang Moersch sells, whose instructions open by arguing that selenium is not the best route to permanence — a concentrate worked anywhere from 1+5 to 1+400, a safety data sheet that names a selenate rather than a selenite and prints a pH where every other maker prints nothing, and a maker who states in his own words that every selenium toner he knows of contains thiosulfate.
• Moersch MT3 VariotonerCStatus bought product — composition not publishedFor paperReuse reusableThe odourless brown toner Wolfgang Moersch sells — a three-part kit whose hue is set by how much alkali you add rather than by the toner itself, three safety data sheets that between them name four substances and give the pH and density of every bottle, and a maker who publishes an adjustment table running from brown-black to bright yellow while his own text says the alkali works the other way.
• Platinum toner for printing-out papersCStatus historical studyFor paper, alt-processReuse one-shotThe acid platinum bath that gave the matte papers of 1895 to 1925 their brown and olive-black tones — fifty millilitres of a one per cent chloroplatinite stock and four grams of citric acid, published here as chemistry only, because this course never handles platinum.
• Tannic acid toner for cyanotypeBStatus verifiedFor paper, alt-processReuse reusableThe two-bath brown-to-black toner for cyanotypes — an ammonia bleach that destroys Prussian blue and a tannic acid bath that puts something else in its place, published with weights by a supplier and with only half its chemistry established.
• Uranium tonerDStatus historical studyFor paper, film, plateReuse one-shotThe uranyl-and-ferricyanide bath that laid a red-brown uranium ferrocyanide where the silver was, intensifying the image as it coloured it, and left a picture whose colour an alkaline wash takes off again. Recorded at Level D as chemistry and history, with no procedure.

Universal developers

• ILFORD PQ UNIVERSAL developerBStatus bought product — composition not publishedFor paper, filmReuse reusableThe one ILFORD bath that develops both a print and a sheet of film — what HARMAN publishes for each job, what its safety data sheet discloses, what its regulatory section discloses that its composition table does not, and the open universal developer to mix instead.
• Kodak D-163BStatus verifiedFor paper, film, plateReuse reusableKodak Limited's universal paper developer — one stock, two dilutions and four published paper regimes, with the highest hydroquinone and the largest sulfite reserve in the paper library, and a maker's time–temperature chart for hot darkrooms.
• Kodak D-165BStatus verifiedFor paper, plateReuse reusableA metol-only low-contrast developer for lantern plates, photogravure transparencies and bromide paper — no hydroquinone at all, which is what makes it the clearest demonstration in the formulary of what the second agent was for.

Washing aids

• ILFORD WASHAIDAStatus bought product — composition not publishedFor film, paperReuse reusableThe hypo clearing agent HARMAN calls a hypo-eliminator — what its own literature publishes for it across six sheets, the three components its safety data sheet discloses, the fourth substance that appears only in the regulatory section, and the patented sulfite bath the course teaches instead.
• Kodak HE-1BStatus verifiedFor paper, film, plateReuse reusableThe hypo eliminator — peroxide and ammonia to convert residual thiosulfate to sulfate, published by Kodak with a capacity, a test and three warnings, and printed here as evidence rather than as advice.
• Kodak Hypo Clearing Agent (the washing accelerator of US 2,860,978)AStatus verifiedFor film, paperReuse reusableKodak has never printed what is in the packet, but in 1954 it patented the bath - Henn and Crabtree's sulfite washing accelerator, with quantities, a pH window, measured residual-hypo figures and a mechanism, published here with the line between the patent and the packet drawn.
• One per cent sodium sulfite washing aidAStatus verifiedFor paper, alt-processReuse one-shotTen grams of sulfite in a litre — the published hypo clearing agent, what ion exchange actually means here, why water alone will not do it, and why one manufacturer prints a bath ten times stronger.