Fixers compared

These five are not five ways of doing one job. Two are acid hardening baths, one is an acid bath that deliberately does not harden, one is plain hypo with nothing in it at all, and one is held above neutral so that it will not attack a printed-out image. Which of those a bath is decides nearly everything else about it, which is why the first column of this matrix is the kind of bath and not a score.

!The cost column is empty, and the price file says why

Every bath here is mostly sodium thiosulfate, and this matrix was written when the course’s price file could not price the raw salt. It named the gap rather than guessing: the retailers it read sold ready-made rapid fixer rather than hypo by the kilogram. That gap has since been closed, at £14.70 for a kilogram of the pentahydrate read on 7 September 2026, so the column is unscored only until its cells are computed against that figure — which is what makes it a shopping question rather than a chemistry one, and a better outcome than a plausible band nobody could check.

Fixers

Five fixing baths from plain hypo to an alkaline bath for printing-out papers, compared on what kind of bath each is, what it does to the gelatin, and what the makers publish about capacity and keeping.

5 subjects on 11 axes. 45 of the 55 cells carry a score with its reasoning and its source; 10 are not established, of which 3 say why for that subject in particular and 7 are answered by their column's own note. 2 scored cells are marked inferred, meaning the course reasoned them out of something a source states rather than reading them off it.

What is in this matrix, and what is not

The five fixing baths this course has written from primary sources. They are not five ways of doing one job: two are acid hardening baths for negatives and prints, one is an acid bath that deliberately does not harden, one is plain hypo with nothing in it at all, and one is held alkaline for printing-out papers. Setting them in one matrix is only defensible because the first axis says which kind each one is, and because several of the columns are unscored for the printing-out baths where the question a developed-out print asks does not arise. The rapid ammonium-thiosulfate fixer the brief also names is not here: no formula for one has been written, and the modern packaged fixers the price file carries are products rather than formulas.

Fixers: every axis against every subject. Each score links to the section that argues it.

Axis	F-5acid hardening	F-52non-hardening	F-54for papers	Plain hypoWall, 1924	Alkaline plain hypoReilly, 1980
Kind of bath	Acid, hardening	Acid, non-hardening	Acid, hardening	Plain	Alkaline
Thiosulfate strength	Standard2/3	Standard2/3	Standard2/3	At the published optimum3/3	Deliberately weak1/3
Hardens the gelatin	Yes	No	Yes	No	No
Leaves the print able to take a toner	No*, an inference by this course	Yes	No*, an inference by this course	—not established	—not established
Published capacity	High3/3	Moderate2/3	High3/3	—not established	—not established
Keeping	Months4/5	Months4/5	Months4/5	—not established	Hours1/5
Materials it is published for	Film and plates	Film, plates and paper	Paper	Paper and hand-coated processes	Paper and hand-coated processes
Complexity	Moderate2/4	Simple1/4	Involved3/4	Simple1/4	Simple1/4
Safety classification	Level B2/4	Level A1/4	Level B2/4	Level A1/4	Level A1/4
Waste stream	Fixer and silver stream	Fixer and silver stream	Fixer and silver stream	Fixer and silver stream	Fixer and silver stream
Cost	—not established	—not established	—not established	—not established	—not established

— not established: the column's own note, or the cell's, says what is missing. * an inference by this course from something a source states, rather than a statement a source makes. Every score in the grid is a link to the paragraph that argues it. 1 of the 11 axes are empty for every subject (Cost), and each of them says why in its own section.

Kind of bath

The question What kind of fixing bath is this: plain, acid non-hardening, acid hardening, or deliberately alkaline?

Read this column first. Everything else in the matrix follows from it, and two baths that differ here are not alternatives to each other.

The scale: Character of the bath, a set of alternatives with no ordering

What kind of fixing bath it is, which decides nearly everything else about it: what it does to gelatin, what it does to a toner, and how it fails.

1. PlainThiosulfate and water. Nothing to buffer it, preserve it or harden the emulsion.
2. Acid, non-hardeningAcid and preservative, no alum. Stops development and keeps its own sulfite, and leaves the gelatin able to take a toner.
3. Acid, hardeningAcid, preservative and an alum. Toughens the emulsion, and the same alum works against even toning afterwards.
4. AlkalineDeliberately held above neutral so the bath neither sulfurises nor bleaches a printed-out image.

Where a cell is empty The source does not describe the bath's character, which for a published fixing formula would be unusual.

F-5acid hardening

Acid, hardeningstated by the source

Kodak Limited's own header is a tropical acid hardening fixing bath for films and plates. It is the 1928 primer's general description of an acid hardening bath - a preservative, an acid to neutralise carried-over developer, and potash or chrome alum - with one addition, the boric acid, which is there to hold the pH inside the window where the alum still hardens.

Sources:Kodak Limited, 1949§ Kodak formula F-5, tropical acid hardening fixing bath for films and plates, metric column · Eastman Kodak Company, 1928§ Acid fixing baths, on why an acid bath is used and what the standard hardener contains

Argued in:F-5, purpose

F-52non-hardening

Acid, non-hardeningstated by the source

Kodak Limited states the case negatively in the header itself: a non-hardening acid fixing bath for use when hardening is not desired, or must be avoided. The acid is potassium metabisulfite, which acidifies and preserves in one salt, and there is no alum in the formula at all.

Sources:Kodak Limited, 1949§ Kodak formula F-52, non-hardening acid fixing bath, metric column and header

Argued in:F-52, purpose

F-54for papers

Acid, hardeningstated by the source

Hypo at 25 per cent with 125 mL of the F-53 acid hardener stock per litre, which delivers 6.25 g of sulfite, 9.4 mL of glacial acetic acid and 12.5 g of potassium alum into the bath. The hardener is a published formula of its own with its own page, and the source's line is a volume of that stock rather than a list of solids.

Sources:Kodak Limited, 1949§ Kodak formula F-54 and Kodak formula F-53, metric columns

Argued in:F-54, purpose · F-53, the hardener stock

Plain hypoWall, 1924

Plainstated by the source

Hypo and water and nothing else, which is a design and not an omission. No acid, so development does not stop when the print enters; no sulfite, so nothing protects the thiosulfate or the carried-over developer; no alum, so the emulsion leaves as soft as it arrived. Wall assigns it, with the alkaline bath, to printing-out papers.

Sources:E. J. Wall, F.C.S., F.R.P.S., 1924§ Fixing and Clearing, Plain bath · Eastman Kodak Company, 1928§ Acid fixing baths, on a plain solution of hypo being seldom used as a fixing bath

Argued in:Plain hypo, purpose

Alkaline plain hypoReilly, 1980

Alkalinestated by the source

Two grams of anhydrous sodium carbonate a litre, whose only job is to hold the bath on the alkaline side of neutral so that it neither sulfurises nor bleaches a printed-out image. It is the only bath in this matrix designed around what the fixer must not do to the image rather than around what it must do to the halide.

Sources:James M. Reilly, 1980§ Chapter 9, Fixation and Washing, The Practice of Fixation

Argued in:Alkaline plain hypo, purpose

Thiosulfate strength

The question What concentration of the fixing agent does the formula publish, against the 30 to 40 per cent the 1928 primer gives as the optimum for fixing speed?

The scale: Thiosulfate strength, ordered

The published concentration of the fixing agent, as w/v of the crystalline salt, read against the 30 to 40 per cent that Kodak's 1928 primer gives as the optimum for fixing speed. Strength is not the same thing as speed, and a bath below the optimum may be there for a reason the cell states.

1. 1Deliberately weakUnder 20 per cent, well below the published optimum, and dilute for a stated reason rather than by economy.
2. 2StandardRoughly 20 to 30 per cent, which is where the makers' own published negative and print baths sit, just under the primer's optimum.
3. 3At the published optimumInside the 30 to 40 per cent range the 1928 primer gives as the optimum for fixing speed.

Where a cell is empty The formula does not state a thiosulfate quantity, which would make it not a fixing formula.

F-5acid hardening

Standardposition 2 of 3stated by the source

240 g of crystalline hypo a litre, which the handbook also prints as 150 g of the anhydrous salt: about 24 per cent as the crystals, under the 30 to 40 per cent the 1928 primer gives as the optimum for fixing speed. Kodak buys the ten-minute fixing time with the acid and the sulfite rather than with more hypo.

Sources:Kodak Limited, 1949§ Kodak formula F-5, metric column · Eastman Kodak Company, 1928§ The Properties of Fixing Baths, the 30 to 40 per cent hypo optimum

Argued in:F-5, behaviour

F-52non-hardening

Standardposition 2 of 3stated by the source

250 g of crystalline hypo a litre, a 25 per cent bath, near the bottom of the range Kodak elsewhere calls optimum for speed. It is the same hypo strength as F-54 on the facing page, so the difference between the two baths is entirely the hardener and not the fixing agent.

Sources:Kodak Limited, 1949§ Kodak formula F-52, metric column · Eastman Kodak Company, 1928§ The Properties of Fixing Baths, the 30 to 40 per cent hypo optimum

Argued in:F-52, behaviour

F-54for papers

Standardposition 2 of 3stated by the source

250 g of crystalline hypo a litre, dissolved in 500 mL of warm water before the hardener goes in: the same 25 per cent as the non-hardening F-52, which is what makes the pair a controlled comparison of hardening rather than of strength.

Sources:Kodak Limited, 1949§ Kodak formula F-54, metric column

Argued in:F-54, behaviour

Plain hypoWall, 1924

At the published optimumposition 3 of 3stated by the source

400 g of hypo crystals a litre, dissolved in hot water: a 40 per cent bath, at the top of the 30 to 40 per cent range the 1928 primer names as the optimum for fixing speed and the strongest bath in this matrix. With nothing else in the solution, strength is the only variable the formula has.

Sources:E. J. Wall, F.C.S., F.R.P.S., 1924§ Fixing and Clearing, Plain bath · Eastman Kodak Company, 1928§ The Properties of Fixing Baths, the 30 to 40 per cent hypo optimum

Argued in:Plain hypo, behaviour

Alkaline plain hypoReilly, 1980

Deliberately weakposition 1 of 3stated by the source

150 g of the pentahydrate a litre, a 15 per cent bath, deliberately weaker than a negative fixer. Reilly's reason is not economy: the bath is discarded long before strength becomes the limit, because the number of prints through it is capped for permanence rather than for exhaustion.

Sources:James M. Reilly, 1980§ Chapter 9, Fixation and Washing, The Practice of Fixation

Argued in:Alkaline plain hypo, behaviour

Hardens the gelatin

The question Does the bath contain a hardening agent, and does the source say so?

The scale: Does the source say so, a set of alternatives with no ordering

For an axis that asks a plain question of the evidence. Yes and no are both statements a source makes; a source that says nothing produces an unscored cell instead.

1. YesA source states it.
2. Yes, with a conditionA source states it and attaches a condition, which the cell gives.
3. NoA source states the opposite.

Where a cell is empty The source neither states nor implies whether the emulsion leaves the bath harder than it entered.

F-5acid hardening

Yesstated by the source

Potash alum, with boric acid holding the bath in the narrow pH window where alum still hardens. The 1928 primer gives the test and the range: a properly hardened emulsion resists a water bath between 54 and 77 degrees C, and the primer prefers potash alum over chrome alum for a bath in long use.

Sources:Kodak Limited, 1949§ Kodak formula F-5, metric column · Eastman Kodak Company, 1928§ The Properties of Fixing Baths, the 54 to 77 degree C hardening range and its melting-point test; the preference for potash alum over chrome alum for long usage

Argued in:F-5, behaviour

F-52non-hardening

Nostated by the source

The header says so: for use when hardening is not desired, or must be avoided. Kodak's own period examples are Transferotype and Bromoil papers, both of which depend on the gelatin remaining able to swell, absorb and release, and there is no alum in the formula to interfere.

Sources:Kodak Limited, 1949§ Kodak formula F-52, header and metric column

Argued in:F-52, purpose

F-54for papers

Yesstated by the source

The 125 mL of F-53 stock delivers 12.5 g of potassium alum to the litre. The hardening is the whole reason the formula is a two-bottle job rather than a single weighing, and the handbook's rule for adding a separately made hardener applies: slowly, into cold hypo, with vigorous stirring.

Sources:Kodak Limited, 1949§ Kodak formula F-54 and Kodak formula F-53; Making up solutions, on adding a separately made hardener slowly to cold hypo with vigorous stirring

Argued in:F-54, mixing

Plain hypoWall, 1924

Nostated by the source

No alum, so the emulsion leaves as soft as it arrived. That is the point of the bath rather than a shortcoming of it: the printing-out papers it is assigned to are handled wet with care, and a hardener would work against the after-treatment.

Sources:E. J. Wall, F.C.S., F.R.P.S., 1924§ Fixing and Clearing, Plain bath

Argued in:Plain hypo, purpose

Alkaline plain hypoReilly, 1980

Nostated by the source

Two ingredients, hypo and carbonate, and no hardening agent among them. An albumen or salted paper print carries its image in or on the paper rather than in a gelatin layer, so there is nothing a hardener would be hardening.

Sources:James M. Reilly, 1980§ Chapter 9, Fixation and Washing, The Practice of Fixation

Argued in:Alkaline plain hypo, purpose

Leaves the print able to take a toner

The question Does a source state that a print fixed in this bath will take a toner evenly, or warn that it will not?

This question is asked of a developed-out print, which is toned after fixing. In printing-out practice the gold or platinum bath comes before the fixer, so the question changes shape and the cells for those two baths say so instead of answering it.

The scale: Does the source say so, a set of alternatives with no ordering

For an axis that asks a plain question of the evidence. Yes and no are both statements a source makes; a source that says nothing produces an unscored cell instead.

1. YesA source states it.
2. Yes, with a conditionA source states it and attaches a condition, which the cell gives.
3. NoA source states the opposite.

Where a cell is empty The source says nothing about after-treatment, and the course will not deduce a toning result from an ingredient list.

F-5acid hardening

Noan inference by this course

Kodak does not warn against toning after F-5 in so many words. What it does is publish F-52 for the cases where hardening must be avoided, which is the same statement made from the other side, and a hardened gelatin layer is exactly what a toner has to get into. The course scores the complement and marks it as an inference rather than a Kodak sentence.

Sources:Kodak Limited, 1949§ Kodak formula F-52, header; Kodak formula F-5, metric column

Argued in:F-52, purpose - the case stated negatively

F-52non-hardening

Yesstated by the source

This is what the bath is for. A hardened emulsion resists everything that follows it - toner, selenium, dye, bleach, redevelopment and the wash - and Kodak publishes F-52 for the cases where that resistance costs more than the mechanical toughness buys. Where a print is going to be toned, the fixer is chosen here.

Sources:Kodak Limited, 1949§ Kodak formula F-52, header - for use when hardening is not desired, or must be avoided

Argued in:F-52, recommended uses

F-54for papers

Noan inference by this course

The same inference as F-5 and on the same evidence: F-54 delivers 12.5 g of potassium alum a litre, and Kodak's non-hardening bath exists for the work this one would obstruct. It is worth stating for F-54 in particular, because it is the paper bath of the pair and prints are what get toned.

Sources:Kodak Limited, 1949§ Kodak formula F-54 and F-53; Kodak formula F-52, header

Argued in:F-54, recommended uses

Plain hypoWall, 1924

Not established

The question does not arise in this form. Wall assigns the plain bath to printing-out papers, and in printing-out practice the gold bath comes before the fixer rather than after it, so there is no toner waiting on the other side of this bath to be obstructed. What the source does establish is the opposite worry: an untoned printed-out image loses density and shifts colour in the fixer, which is the image changing and not the bath staining it.

Sources:E. J. Wall, F.C.S., F.R.P.S., 1924§ Fixing and Clearing, Plain bath

Argued in:Plain hypo, behaviour

Alkaline plain hypoReilly, 1980

Not established

As for the plain bath: the gold or platinum toning of an albumen or salted paper print happens before fixation, so this column's question belongs to a developed-out print and not to this one. Reilly's own observation about the bath is about colour rather than toning - the print changes markedly during fixing, from brilliant purple or brown to a duller yellower brown with a loss of density, and that is the image layer changing physically.

Sources:James M. Reilly, 1980§ Chapter 9, Fixation and Washing; Chapter Eight, Toning

Argued in:Alkaline plain hypo, behaviour

Published capacity

The question How much material does the source publish for a made-up volume of this bath, and under what rinse conditions?

The scale: Published capacity, ordered

How much material the maker publishes for a made-up volume. The bases differ between sources, so every cell gives the figure and the volume it is per.

1. 1LowA small published figure, or one deliberately held down for a reason the cell states.
2. 2ModerateThe ordinary published figure for its class.
3. 3HighAt or near the top of the maker's own table for baths of its kind.

Where a cell is empty The source publishes no capacity for the bath. A fixing bath with no published capacity is worked by the clearing-time test instead, and the 1928 primer's rule is the one the course uses: fixing time is twice the clearing time, and a bath that takes 12 to 15 minutes to clear is finished.

F-5acid hardening

Highposition 3 of 3stated by the source

120 sheets of 8 by 10 inches per 160 imperial fluid ounces, in a narrow dish and a deep tank alike, with a water rinse between development and fixing. It is the top figure on the 1949 fixing table and it is stated for negatives, which fix in a fresher bath than prints do.

Sources:Kodak Limited, 1949§ Table of keeping properties and useful life of solutions, F-5 row

Argued in:F-5, behaviour

F-52non-hardening

Moderateposition 2 of 3stated by the source

60 sheets of 8 by 10 inches per 160 imperial fluid ounces with a water rinse, and 90 with the chrome alum hardening bath SB-3 in between - half the figure for the hardening baths, and the price of leaving the alum out. The pair of figures is unusually informative, because it prices the hardening question in sheets.

Sources:Kodak Limited, 1949§ Table of keeping properties and useful life of solutions, F-52 row

Argued in:F-52, behaviour

F-54for papers

Highposition 3 of 3stated by the source

120 sheets of 8 by 10 inches per 160 imperial fluid ounces, and the same figure whether a water rinse or the SB-3 hardening bath precedes it - unlike F-52, where the two conditions give different numbers. The bath already carries its own alum, so an extra hardening bath in front of it changes nothing it measures.

Sources:Kodak Limited, 1949§ Table of keeping properties and useful life of solutions, F-54 row

Argued in:F-54, behaviour

Plain hypoWall, 1924

Not established

Nothing specific to this subject to add: the column’s own note above is the whole answer.

Alkaline plain hypoReilly, 1980

Not established

Reilly publishes two numbers and neither of them is a capacity. The first is a permanence limit - no more than 10 to 15 prints of about 8 by 10 inches to the litre, for maximum print permanence - and the second is what estimates in the literature suggest a 15 per cent bath could take, up to 150 prints of the same size. A limit set to keep residual silver out of a print and an estimate of exhaustion are answers to different questions, and averaging them or picking one would misrepresent both.

Sources:James M. Reilly, 1980§ Chapter 9, Fixation and Washing, The Practice of Fixation

Argued in:Alkaline plain hypo, behaviour

Keeping

The question What keeping figures does the source publish for the made-up bath, standing, in a tank and bottled?

The scale: Keeping, ordered

The longest keeping figure the maker publishes for the solution in a full, closed bottle. The cell gives the shorter working figures with it.

1. 1HoursPublished in hours: a bath made for the session it is used in.
2. 2DaysPublished in days.
3. 3WeeksPublished in weeks.
4. 4MonthsPublished in months in a full stoppered bottle; the half-filled figure is always shorter and is given in the cell.
5. 5IndefiniteThe maker's own word. It keeps until something contaminates it.

Where a cell is empty The source publishes no keeping table for the bath.

F-5acid hardening

Monthsposition 4 of 5stated by the source

Three months in a full stoppered bottle, two weeks half full, one month in a tank and one week standing in a dish. The gap between the full and half-full bottle is far wider than for any developer on the same table, which is the sulfite in an acid bath being consumed by the air in the headspace.

Sources:Kodak Limited, 1949§ Table of keeping properties and useful life of solutions, F-5 row

Argued in:F-5, storage

F-52non-hardening

Monthsposition 4 of 5stated by the source

Three months bottled, and the row is the interesting one on the whole table: Kodak gives the same three months whether the bottle is full or half full, where every other bath in this matrix is penalised for the air space. A metabisulfite bath with no alum in it has less to lose.

Sources:Kodak Limited, 1949§ Table of keeping properties and useful life of solutions, F-52 row

Argued in:F-52, storage

F-54for papers

Monthsposition 4 of 5stated by the source

Three months full, two weeks half full, one month in a tank, one week in a dish - the same row as F-5, which is what you would expect of two baths that carry the same hardener chemistry at the same acidity.

Sources:Kodak Limited, 1949§ Table of keeping properties and useful life of solutions, F-54 row

Argued in:F-54, storage

Plain hypoWall, 1924

Not established

Nothing specific to this subject to add: the column’s own note above is the whole answer.

Alkaline plain hypoReilly, 1980

Hoursposition 1 of 5stated by the source

Both baths are made up fresh on the day they will be used, because unused fixer solutions break down very rapidly. It is the only bath in this matrix whose keeping is measured in the length of a printing session, and it follows from having no preservative and a pH above neutral.

Sources:James M. Reilly, 1980§ Chapter 9, Fixation and Washing, The Practice of Fixation

Argued in:Alkaline plain hypo, storage

Materials it is published for

The question Which materials does the source publish this bath for?

The scale: Materials it is published for, a set of alternatives with no ordering

Which materials the maker publishes the formula for. It is a statement about the document, not a judgement about what would happen if you used it elsewhere.

1. Film and platesPublished for negative materials only.
2. Film, plates and paperPublished for negative materials and for prints.
3. PaperPublished for prints only.
4. Paper and hand-coated processesPublished for prints, including hand-coated and printing-out papers.

Where a cell is empty The source does not say what the bath is for.

F-5acid hardening

Film and platesstated by the source

Kodak's header names films and plates, and the fixing instruction is given for them: they fix properly in ten minutes in a freshly prepared bath, and prolonged immersion at high temperatures is harmful. The handbook prints F-54 for papers on a nearby page rather than extending this one.

Sources:Kodak Limited, 1949§ Kodak formula F-5, header and fixing note

Argued in:F-5, recommended uses

F-52non-hardening

Film, plates and paperstated by the source

Published for papers, films and plates wherever hardening is unwanted, which makes it the widest-scope bath in this matrix. The scope follows from the negative definition: the bath is specified by what it does not do, and that is wanted on every material.

Sources:Kodak Limited, 1949§ Kodak formula F-52, header and metric column

Argued in:F-52, recommended uses

F-54for papers

Paperstated by the source

Published for papers, straight from the formula. That is the division of labour in the 1949 handbook: F-5 for negatives, F-54 for prints, and F-52 for anything on either side of that line where the alum has to come out.

Sources:Kodak Limited, 1949§ Kodak formula F-54, header and metric column

Argued in:F-54, recommended uses

Plain hypoWall, 1924

Paper and hand-coated processesstated by the source

Wall assigns the plain bath, with the alkaline one, to printing-out papers, and the acid and acid-alum baths to plates, film and developed papers. The course adds one modern use of its own kind: a laboratory bath whose fixing you want to watch with no hardener in the way.

Sources:E. J. Wall, F.C.S., F.R.P.S., 1924§ Fixing and Clearing, Plain bath and the division between plain, alkaline and acid baths

Argued in:Plain hypo, recommended uses

Alkaline plain hypoReilly, 1980

Paper and hand-coated processesstated by the source

Albumen, salted paper and all silver printing-out papers, which is the class Reilly wrote the bath for. It is not offered for negatives at any strength, and the 15 per cent concentration would be an odd choice for one.

Sources:James M. Reilly, 1980§ Chapter 9, Fixation and Washing, The Practice of Fixation

Argued in:Alkaline plain hypo, recommended uses

Complexity

The question What does mixing this bath demand: how many solids, in what order, at what temperature, and is a second solution needed?

The scale: Complexity to make and work, ordered

What mixing and using the formula actually demands: how many things are weighed, whether order and temperature matter, and whether the bath has to be made in parts or ripened before use.

1. 1SimpleA handful of solids into water in a stated order, at room temperature, used straight away.
2. 2ModerateSeveral solids, an order that matters and a stated dissolving temperature, or a stock that is diluted before use.
3. 3InvolvedTwo or more solutions to mix separately and combine correctly, a hot bath, or a ripening period before the formula works.
4. 4SpecialistNeeds equipment, control or handling beyond a domestic laboratory, and the course says so on the page.

Where a cell is empty The source publishes no mixing instruction.

F-5acid hardening

Moderateposition 2 of 4stated by the source

Five components in the handbook's own order - hypo, sulfite, acid, alum - and the order is the whole difficulty. Get it wrong and the bath throws an aluminium sulfite sludge, which the 1928 primer describes as one of the standard fixing-bath troubles. Nothing needs heating beyond dissolving the hypo.

Sources:Kodak Limited, 1949§ Kodak formula F-5, with the instruction to dissolve the chemicals in the order given; Making up solutions, on the order hypo, sulphite, acid, alum · Eastman Kodak Company, 1928§ Fixing Bath Troubles, on sulphur and aluminium sulphite sludges

Argued in:F-5, mixing

F-52non-hardening

Simpleposition 1 of 4stated by the source

Two solids: the hypo, then the potassium metabisulfite. There is no alum to precipitate, no separately made hardener to add slowly, and no pH window to hold, which is what a bath defined by an omission looks like on the bench.

Sources:Kodak Limited, 1949§ Kodak formula F-52, metric column and mixing instruction

Argued in:F-52, mixing

F-54for papers

Involvedposition 3 of 4stated by the source

Two solutions rather than one. F-53 is mixed as a formula in its own right and then 125 mL of it goes into the litre, and the handbook's rule for a separately made hardener governs the join: slowly, into cold hypo, with vigorous stirring. A hardener poured fast into warm hypo is the sludge failure again.

Sources:Kodak Limited, 1949§ Kodak formula F-54 and Kodak formula F-53; Making up solutions, on adding a separately made hardener slowly to cold hypo with vigorous stirring

Argued in:F-54, mixing · F-53, the hardener stock

Plain hypoWall, 1924

Simpleposition 1 of 4stated by the source

One solid in hot water. Dissolving 400 g of hypo crystals in a litre cools the solution sharply, which is why the source says hot water, and that is the entire mixing instruction.

Sources:E. J. Wall, F.C.S., F.R.P.S., 1924§ Fixing and Clearing, Plain bath

Argued in:Plain hypo, mixing

Alkaline plain hypoReilly, 1980

Simpleposition 1 of 4stated by the source

Two solids, mixed fresh on the day of use. The simplicity is load-bearing rather than incidental: a bath that has to be made new for every session is only practical if making it is a two-minute job.

Sources:James M. Reilly, 1980§ Chapter 9, Fixation and Washing, The Practice of Fixation

Argued in:Alkaline plain hypo, mixing

Safety classification

The question What is the course's hazard-assessed level for this bath, and which substance sets it?

The scale: Safety classification, ordered

The course's own hazard-assessed classification for the formula or process, from the safety library. The cell names the substance that sets it.

1. 1Level ADomestic-scale care. No specialist control is required by the substances themselves.
2. 2Level BGloves, eye protection and ventilation as stated; a sensitiser, an irritant or a dust that must not be breathed.
3. 3Level CA serious hazard with a named control; restricted procedures, and never a first session.
4. 4Level DStudied and never performed at home. The course gives the chemistry, the history and the hazards, and no procedure.

Where a cell is empty The bath has not been classified. Every formula in this course carries a level, so an empty cell here would be a fault rather than a finding about the evidence.

F-5acid hardening

Level Bposition 2 of 4stated by the source

Glacial acetic acid at about 99.5 per cent is what sets the level: it is corrosive, it is measured by volume into a made-up solution, and the bottle is the hazard rather than the bath. Boric acid is classified for reproductive toxicity, and the potash alum is the mildest thing in the formula.

Sources:Prepared by an international group of experts on behalf of the International Labour Organization and the World Health Organization, with the financial assistance of the European Commission, 2010§ Physical dangers, chemical dangers and routes of exposure for the glacial acid · Prepared by an international group of experts on behalf of the International Labour Organization and the World Health Organization, with the financial assistance of the European Commission, 2014§ Effects of long-term or repeated exposure; classification

Argued in:F-5, safety

F-52non-hardening

Level Aposition 1 of 4stated by the source

Nothing here is handled concentrated. The acidity comes from potassium metabisulfite as a solid rather than from a bottle of glacial acid, and there is no alum. The one rule that travels with the bath is the standing one for every sulfite and metabisulfite in the darkroom: keep it away from stronger acids, which liberate sulfur dioxide from it.

Sources:Kodak Limited, 1949§ Kodak formula F-52, metric column

Argued in:F-52, safety · Chemical incompatibilities

F-54for papers

Level Bposition 2 of 4stated by the source

The level comes from the hardener stock rather than from this formula's own line: F-53 carries the glacial acetic acid and the potassium alum, and mixing F-54 means mixing F-53 first. A formula whose ingredient is another formula inherits that formula's handling.

Sources:Prepared by an international group of experts on behalf of the International Labour Organization and the World Health Organization, with the financial assistance of the European Commission, 2010§ Physical dangers, chemical dangers and routes of exposure for the glacial acid · Kodak Limited, 1949§ Kodak formula F-53, metric column

Argued in:F-54, safety · F-53, the hardener stock

Plain hypoWall, 1924

Level Aposition 1 of 4stated by the source

One salt and hot water. Sodium thiosulfate is the least hazardous substance in this matrix to handle, and what makes the bath a Level A procedure rather than a trivial one is what comes out of it: a used bath carries dissolved silver, and that is a waste question rather than a handling one.

Sources:E. J. Wall, F.C.S., F.R.P.S., 1924§ Fixing and Clearing, Plain bath

Argued in:Plain hypo, safety

Alkaline plain hypoReilly, 1980

Level Aposition 1 of 4stated by the source

Hypo and two grams of sodium carbonate. The carbonate is a dust irritant on the balance and nothing at 2 g in a litre, and the bath is the mildest thing in this matrix. Its spent volume still carries silver from a printing-out paper, which carries more of it than a developed-out print does.

Sources:James M. Reilly, 1980§ Chapter 9, Fixation and Washing, The Practice of Fixation · Prepared by an international group of experts on behalf of the International Labour Organization and the World Health Organization, with the financial assistance of the European Commission, 2024§ Routes of exposure; eye and respiratory tract irritation

Argued in:Alkaline plain hypo, safety

Waste stream

The question Which stream does the spent bath belong to, and what is in it?

The scale: Waste route, a set of alternatives with no ordering

Which of the five streams that leave a silver darkroom this bath belongs to. They are kept apart because they are chemically incompatible and have different destinations, and that much is a consequence of reactions rather than of statutes. What may lawfully be done with any of them depends on where you are.

1. Developer streamAlkaline, organic and oxygen-demanding. Its own labelled container, and never mixed with the fixer bottle, which would ruin a recoverable solution.
2. Stop bath streamAcid. Its own container: acid meeting a sulfite or a thiosulfate liberates sulfur dioxide at once.
3. Fixer and silver streamThiosulfate carrying dissolved silver, at thousands of milligrams per litre. It never goes to a drain and it is the stream silver recovery exists for.
4. Hazardous collection onlyA heavy metal, a sulfide or a cyanide bath. The whole volume is a collected waste and no part of it is a drain question.

Where a cell is empty The waste chemistry of the bath has not been established.

F-5acid hardening

Fixer and silver streamstated by the source

A used fixing bath is the silver stream by definition: it holds the halide that development did not reduce, as a soluble complex. Kodak's own figures put fixer and bleach-fix at 3,000 to 5,000 mg of silver per litre against a mean regulated sewer limit its disposal publication gives as 1.2 mg/L, and silver compounds carry the very-toxic-to-aquatic-life classifications. It never goes to a drain, and it is the one stream silver recovery exists for.

Sources:Eastman Kodak Company, 1998§ Silver concentrations in photographic processing solutions · Eastman Kodak Company, 1999§ Properly dispose of photographic processing chemicals

Argued in:F-5, waste · The disposal caveat

F-52non-hardening

Fixer and silver streamstated by the source

The same stream, with one thing less in it: no aluminium. That matters only for how the recovered solution behaves and not for whether it is collected, and the bath is collected for the same reason as every other fixer here - the dissolved silver.

Sources:Eastman Kodak Company, 1998§ Silver concentrations in photographic processing solutions

Argued in:F-52, waste · The disposal caveat

F-54for papers

Fixer and silver streamstated by the source

A print fixer carries less silver per litre than a film fixer, because a print holds less silver than a negative of the same area, but the stream is the same one and the acid in it is the reason it is never combined with a developer bottle. Acid meeting a sulfite liberates sulfur dioxide at once.

Sources:Eastman Kodak Company, 1998§ Silver concentrations in photographic processing solutions · Eastman Kodak Company, 1999§ Properly dispose of photographic processing chemicals

Argued in:F-54, waste · The disposal caveat

Plain hypoWall, 1924

Fixer and silver streamstated by the source

A printing-out paper carries far more silver into the fixer than a developed-out print does, because most of the coated silver is still there when the print goes in. The bath is therefore the richest silver stream in this matrix and the strongest case in it for recovery rather than disposal.

Sources:Eastman Kodak Company, 1998§ Silver concentrations in photographic processing solutions · James M. Reilly, 1980§ Chapter 9, Fixation and Washing

Argued in:Plain hypo, waste · The disposal caveat

Alkaline plain hypoReilly, 1980

Fixer and silver streamstated by the source

As the plain bath, and made worse by the practice: the bath is discarded after ten to fifteen prints for permanence, so a session produces several litres of silver-bearing solution rather than one. The course's own open question about the silver-bearing first wash from the printing-out processes sits directly behind this cell.

Sources:James M. Reilly, 1980§ Chapter 9, Fixation and Washing, The Practice of Fixation · Eastman Kodak Company, 1998§ Silver concentrations in photographic processing solutions

Argued in:Alkaline plain hypo, waste · The disposal caveat

Cost

The question What does a litre of this bath cost to mix from raw chemicals, on the dated UK prices behind the laboratory planner?

An entire column, empty for one documented reason. The gap is in the price file's own list, which is the difference between a hole somebody noticed and a hole nobody did.

The scale: Cost, ordered

The course's relative cost band for mixing a litre from raw chemicals, on the dated UK prices in the price file behind the laboratory planner. The bands are relative and the course defines no money threshold for them, so every cell gives the priced subtotal it rests on and names the ingredients the price file could not price.

1. 1£The cheapest band: bulk photographic chemicals, in doses of a few grams to a hundred grams a litre.
2. 2££The ordinary band. Several bulk chemicals, or one bought in a small jar at a laboratory price.
3. 3£££One ingredient dominates the cost, and it is usually a silver salt.
4. 4££££A noble metal at working strength. The chemistry is a significant purchase in itself.

Where a cell is empty Every bath in this matrix is mostly sodium thiosulfate, and the price file holds no price for the raw salt. It says so itself: sodium thiosulfate pentahydrate is one of the 21 gaps the file names, because the retailers it read sell ready-made rapid fixer rather than the salt. No cell in this column can be filled until that gap is, and filling it is a shopping question rather than a chemistry one.

F-5acid hardening

Not established

Nothing specific to this subject to add: the column’s own note above is the whole answer.

F-52non-hardening

Not established

Nothing specific to this subject to add: the column’s own note above is the whole answer.

F-54for papers

Not established

Nothing specific to this subject to add: the column’s own note above is the whole answer.

Plain hypoWall, 1924

Not established

Nothing specific to this subject to add: the column’s own note above is the whole answer.

Alkaline plain hypoReilly, 1980

Not established

Nothing specific to this subject to add: the column’s own note above is the whole answer.