Kodak D-32

This is the formula that made the formulary’s schema grow a combinations array. Kodak prints two ratios for D-32 and neither is a variant of the other: one part A to one part B gives warm black tones, one part A to two parts B gives still warmer ones. The tone is chosen by how much of the alkali stock goes in, which is a thing a flat list of ingredients cannot say at all.

Stock Solution A — the developing agent, its preservative, its restrainer and an acid

Ingredient	Quantity	Form the source specifies
Sodium sulfite (anhydrous)	6.3 g or 12.6 g (crystalline, which is the handbook's main column)	anhydrous
Hydroquinone	7 g
Potassium bromide	3.5 g or 35 mL of a 10% solution (as 35 c.c. of a 10 per cent solution, which is the handbook's own alternative)
Citric acid (anhydrous)	0.7 g
Water	to make 1000 mL	The 1949 handbook gives no temperature for this water. The 1928 printing starts with 500 c.c. at about 52 degrees C, dissolves the solids in it in the order given and makes up to a litre with cold water, which is the practical instruction and is recorded here rather than in the temperature field because it belongs to the other printing.
Preservative first, which is the handbook's general rule for every formula that does not contain Elon - and this one does not.

Stock Solution B — the alkali, in two forms

Ingredient	Quantity	Form the source specifies
Sodium carbonate (anhydrous)	30 g or 81 g (crystalline, which is the handbook's main column)	anhydrous
Sodium hydroxide	4.2 g	caustic soda
Water	to make 1000 mL	"Cold water to make 1000 c.c." in the 1949 printing; the 1928 printing prints the same litre as water added at the head of the stock instead. Cold is not a preference: the 1928 primer warns that dissolving caustic soda evolves considerable heat and that with hot water the solution will boil with explosive violence.

Mixed in the ratio — the working developer, warm black tones

1 part Stock Solution A + 1 part Stock Solution B

For use take 1 part A, 1 part B. Develop for about 6 minutes at 65 °F (18 °C).

The working bath holds 3.15 g/L of anhydrous sulfite, 3.5 g/L of hydroquinone, 1.75 g/L of potassium bromide, 0.35 g/L of citric acid, 15 g/L of anhydrous carbonate and 2.1 g/L of caustic soda.

Mixed in the ratio — still warmer tones

1 part Stock Solution A + 2 parts Stock Solution B

For still warmer tones 1 part A and 2 parts B.

Both printings give this ratio and neither gives a time for it. Two parts of B to one of A raises the alkali by a third - 20 g/L of carbonate and 2.8 g/L of caustic soda - and lowers the agent, the restrainer and the acid by a third at the same time. The tone is chosen by the ratio, which is why this formula needs two combinations rather than a variant.

Purpose

To develop lantern slide plates to a warm black image, and to let the worker choose how warm. Kodak Limited’s header is the fullest statement either printing makes: “Hydroquinone caustic-soda dish developer for warm black tones on lantern slides”. The 1928 primer simply heads it Warm Black Tones and prints it opposite D-34, Blue Black Tones.

A lantern slide is a positive on glass, projected and looked through. Its image colour is part of the picture rather than a detail, and Kodak’s answer was to publish two developers and let the operator pick — and then, inside one of them, a second knob.

What the source does not say is why it works. Neither printing offers any account of how a hydroquinone-caustic bath produces a warmer image than a metol-hydroquinone-carbonate one, and this page does not supply one.

Recommended uses

Lantern slides, for a warm image, which is what the header names.

Where the tone has to be adjusted rather than accepted. The 1+2 ratio is published, and it is the only published tone control in this formulary that works by moving one solution against another.

As the demonstration of what a two-stock ratio does that a dilution does not. D-34 on the facing page controls its result by diluting the mixed developer with water, which halves everything at once and changes no ratio. D-32 changes the alkali against the agent. Reading the two together is the clearest illustration in the corpus of the difference between diluting a developer and reformulating it.

As a mild introduction to caustic soda. Four point two grams per litre in stock B, against D-9’s 52.5, and with seven times its weight of carbonate beside it. The sodium hydroxide page already uses this formula as its example of the ion used as a trim rather than as the engine.

When another formula is preferable

• For a cold image on the same plate, D-34, which is the primer’s own answer on the facing page.
• For warm tones on paper, D-156 or D-166, which Kodak Limited describes in exactly those terms. A lantern slide developer is not a paper developer.
• For negatives, D-76 or D-72 as the job requires. A hydroquinone-only bath with 1.75 g/L of bromide is not a general negative developer.
• Where caustic soda should not be in the room at all, D-34 again: it is the same class of developer for the same material with a carbonate alkali and nothing else.
• Where the tank is the vessel. The handbook marks D-32’s tank cell “N.R.” — an abbreviation the course cannot expand from its own sources, but the dish figure of two hours beside it is the one that is published, and this is headed a dish developer in both printings.

Mixing

Two bottles, and the order within each of them is Kodak’s.

1. Stock Solution A. Dissolve, in this order, 6.3 g of anhydrous sodium sulfite (or 12.6 g of the crystals), 7.0 g of hydroquinone, 3.5 g of potassium bromide, and 0.7 g of citric acid; water to make 1,000 mL. Preservative first is the handbook’s rule wherever there is no Elon in the formula, and there is none here.
2. Stock Solution B. Dissolve 30 g of anhydrous sodium carbonate (or 81 g of the crystals), then 4.2 g of caustic soda, in cold water to make 1,000 mL. Add the caustic a little at a time to an open vessel; the 1928 primer’s warning about hot water and explosive boiling applies at any concentration.
3. The working developer. One part A to one part B for warm black tones. One part A to two parts B for still warmer ones.

On the bromide. Kodak Limited offers 35 mL of a 10 per cent solution as an alternative to weighing 3.5 g, and explains the practice in its own front matter: quantities under 10 grains or 0.7 gram are preferably expressed as a percentage solution, because expressing them as drops is very uncertain and can vary by 150 per cent. At 3.5 g the weighing is not marginal; at 0.7 g of citric acid on the line above it, it is — and the handbook does not offer a solution for the citric acid, which is worth noticing.

🧮What the two ratios actually change

Per litre of working bath:

	1 part A + 1 part B	1 part A + 2 parts B	change
Hydroquinone	3.50 g	2.33 g	−33 %
Sodium sulfite, anhydrous	3.15 g	2.10 g	−33 %
Potassium bromide	1.75 g	1.17 g	−33 %
Citric acid	0.35 g	0.23 g	−33 %
Sodium carbonate, anhydrous	15.0 g	20.0 g	+33 %
Sodium hydroxide	2.10 g	2.80 g	+33 %

The alkali goes up by a third and everything else goes down by a third. The ratio of alkali to agent therefore doubles — 4.3 grams of carbonate per gram of hydroquinone becomes 8.6. That is a different developer, not a dilution of the first one, and it is why the schema records two combinations rather than one formula and a note.

A second piece of arithmetic worth having. The citric acid is 0.35 g/L in the 1+1 bath, which is 0.0018 mol/L, or about 0.0055 mole-equivalents of acid if all three of its protons are available. Against it stand 0.053 mol/L of hydroxide and 0.14 mol/L of carbonate. So whatever the citric acid is doing in stock A, it is a small perturbation of the alkali once the two stocks meet — of the order of a tenth of the caustic soda and a few per cent of the total base. That is the course’s arithmetic; neither printing says what the citric acid is for, and this calculation does not tell us.

Behaviour

Two hours in a dish, two months in a full bottle, two weeks in a half-empty one. Those are Kodak Limited’s published keeping figures, and the last two are marked in 2 solutions — they belong to the stocks and not to the mixed developer. The fall from two months to two weeks for air space alone is steeper than most rows in the same table, which is a reason to follow the handbook’s advice and bottle stock A in small bottles rather than one large one.

Eighteen sheets of 8 by 10 per 160 fluid ounces in a narrow dish. That is the published useful life, and it is a modest figure — D-72 gives 24 at the same size and dilution.

About six minutes at 18 °C, or five to six at 21 °C, depending on which printing you are reading. The two are not reconcilable and both are recorded above. Neither printing publishes a time for the 1+2 ratio at all, which is a real gap in a formula whose second ratio is its selling point.

Its alkali is mostly a reservoir with a small free component. Fifteen grams per litre of carbonate hold the working concentration nearly constant as development proceeds — the primer’s own account of why carbonates are used — while 2.1 g/L of caustic soda sits on top as free hydroxide with nothing behind it. The two behave differently as the bath is used: the free hydroxide is spent and not replaced, the carbonate is buffered.

It is a hydroquinone-only developer, so it starts slowly and does not stop. There is no metol to bring the shadows up first. Six minutes is a long development time for a plate, and the shape of the curve over those six minutes is not something either source describes.

Image characteristics

Warm black, and warmer still on demand. That is Kodak’s claim, made in a header and a direction, and it is repeated in Kodak Limited’s own list of packed developers.

Nothing in either printing explains the mechanism, and the course will not invent one. What can be said honestly is where an image colour comes from in general: Part IV establishes that finely divided silver is coloured while filamentary silver is neutral black, so a warm tone is a particle-size reading — and Kodak’s own primer uses that mechanism elsewhere, for dichroic fog. Which feature of D-32 drives the silver into the finer form is not established anywhere in this corpus. The differences from the cold-tone formula on the facing page are all visible in the table — no metol, a caustic component in the alkali, a very low sulfite load, citric acid, and half again as much bromide relative to the agent — and any one of them, or all of them, could be the reason.

Wall’s independent version points the same way and explains no more. His Seed Hydroquinone Developer for Warm Tones is a stock of hydroquinone, sulfite, bromide and citric acid against a stock of carbonate and caustic soda, mixed in equal volumes, with the instruction that for still warmer tones use more B. A different plate maker, the same construction and the same control. That is strong evidence that the relationship between the ratio and the tone was real and well known, and it is not an explanation of it.

Contrast is not what the second ratio controls. More alkali and less agent is not the same move as more or less development, and neither source says which way the contrast goes.

The mechanism

Development is the reduction of exposed halide, with hydroquinone as the only reductant on this page.

AgBr + e⁻ → Ag + Br⁻

What the agent has to accomplish

⚗Two alkalis in one bottle, doing two different jobs

A carbonate is a partly dissociated base. Each carbonate ion that takes a proton leaves the rest untouched, so the solution holds a modest hydroxide concentration and holds it nearly constant as development consumes it:

CO₃²⁻ + H₂O ⇌ HCO₃⁻ + OH⁻

The reservoir, and why almost every developer uses one

Caustic soda has no such reserve. It is free hydroxide, present all at once and, in the 1928 primer’s words about a caustic alkali, soon exhausted.

D-32 carries both, at 15 g/L and 2.1 g/L in the 1+1 bath, and the hydroquinone is the reason it is worth carrying the second one. The IUPAC dataset gives benzene-1,4-diol a pKa₁ near 9.9 and a pKa₂ near 11.4; a carbonate developer works between the two and a caustic developer past both, so a few grams of hydroxide on top of a carbonate move the agent’s ionisation in a way that more carbonate could not economically do. That the more ionised species is the more active reducer is the obvious reading and the course has not sourced it - the hydroquinone page records the same caution.

C₆H₆O₂ → C₆H₅O₂⁻ + H⁺

The first ionisation, pKa about 9.9, which a carbonate developer reaches

And what the second ratio does to that. One part A to two parts B raises both alkalis by a third while lowering the agent by a third. Kodak says the result is a warmer image. It does not say why, and neither does this page.

Function of every ingredient

Hydroquinone, 7.0 g/L in Stock A, 3.5 g/L in the 1+1 bath. The whole of the developing power. There is no metol here to bring the shadows up first, so the image arrives slowly and builds density steadily — which is what a six-minute development time on a slide plate looks like. Kodak’s ranking puts hydroquinone at the low-potential end, needing the most alkali and tolerating the most bromide, and both of those facts are visible in this formula’s alkali and restrainer. More hydroquinone would raise contrast and maximum density and lengthen the time to first appearance; less would flatten it. Kodak’s own second ratio lowers it, by a third, at the same time as raising the alkali — so the two moves partly cancel in energy and evidently do not cancel in tone.

Sodium sulfite, 6.3 g/L anhydrous in Stock A, 3.15 g/L in the bath. The preservative, and a strikingly small dose — a fifth of what a normal paper developer such as D-72 carries in its stock, and a sixteenth of D-76’s. It takes up the quinone that hydroquinone’s oxidation produces. At this concentration it is doing nothing as a silver solvent; that begins an order of magnitude higher, as the solvent action and grain lesson sets out. More would keep the stock better and start to dissolve silver; less would give a stock that browns. The handbook prints the crystalline heptahydrate at exactly twice the weight as its own alternative.

Potassium bromide, 3.5 g/L in Stock A, 1.75 g/L in the bath. The restrainer. Half the agent’s weight is a heavy ratio by the standards of a general developer — compare D-34’s 2.1 g against 15 g of hydroquinone — and the reason is the caustic component of the alkali: the primer’s rule is that too much alkali produces chemical fog, and bromide is what compensates for it. Bromide also restrains hydroquinone far harder than it restrains metol, so a hydroquinone-only developer feels a given dose more than a mixed one does. More would clean the highlights further and slow the bath; less would fog the clear glass of a projected slide. It can be added at any stage of mixing, having no action on the agent, and the handbook offers it as 35 mL of a 10 per cent solution for anyone who would rather measure than weigh.

Citric acid, 0.7 g/L in Stock A, 0.35 g/L in the bath. Neither printing says what it is for. That is the honest statement and it is the one this page makes: Kodak prints the ingredient, prints its quantity, prints its position in the mixing order, and assigns it no function in 1928 or in 1949. What can be added without inventing: it is an acid, and stock A is therefore an acid solution of a developing agent with very little sulfite in it — and the 1928 primer’s own reasoning about two-solution developers is that oxidation progresses less readily in acid than in alkaline solution, which is why it puts bisulfite rather than sulfite in D-9’s agent stock. A stabiliser for stock A is therefore the obvious reading, and it is a reading. Against it: Wall’s independent warm-tone developer for Seed plates carries citric acid in the same position, and the citric acid page records no role for the substance in a developer at all. The course cannot establish whether the citric acid contributes to the warm tone the formula is named for, and does not assume it does not. This is the schema gap recorded as open item 10 in docs/FORMULARY-SCHEMA.md: function is a required string and cannot say that the source states none, so the sentence in the table is a description of what the ingredient is and this paragraph is where the absence is recorded.

Sodium carbonate, 30 g/L anhydrous in Stock B, 15 g/L in the bath. The bulk of the alkali, and the part of it with a reserve behind it. The primer’s account is that a carbonate is only partly dissociated at any moment, so it keeps a small hydroxide concentration nearly constant through a development, where a proportional quantity of caustic would be spent at once. More gives a faster bath and eventually chemical fog and a softened gelatin; less gives a slow one — and Kodak’s second ratio raises it by a third deliberately. The anhydrous salt is what the formula means; the handbook prints the decahydrate crystals at 81 g as its main column and recommends the anhydrous form in its own instructions, warning that crystals must be used at two and a half times the anhydrous weight. Using crystals weight for weight would give a bath a third as alkaline as intended.

Sodium hydroxide, 4.2 g/L in Stock B, 2.1 g/L in the bath. The trim. It is free hydroxide with no reservoir behind it, and at a seventh of the carbonate’s weight it is not the engine of this developer — it is what lifts the pH past what a carbonate alone will reach, which for hydroquinone is the difference between the first ionisation and something beyond it. More would push the bath towards D-9’s territory, with the fog and the softened gelatin that go with it; less would leave an ordinary carbonate developer. Two properties of the solid belong to its own page and matter here: it is deliquescent and takes up carbon dioxide from the air, so an old tub is weaker than its label, and dissolving it evolves enough heat to make hot water dangerous.

Water, and one temperature that is a safety instruction. A litre for each stock, both printed as make-up volumes in the 1949 handbook. The 1928 printing gives the useful practical detail the later one omits — 500 c.c. at about 52 °C to dissolve stock A’s four solids, made up cold — and prints stock B’s water as an addition rather than a make-up. Stock B’s water is specified cold, and that word is not about the chemistry of development at all.

Interactions

With the plate. Lantern plates clear in 30 seconds to a minute in a fixing bath and wash in 2 to 3 minutes, per the primer — a much shorter sequence than film habits suggest.

With an acid stop and an acid fixer. A developer carrying free hydroxide as well as carbonate puts more alkali into the next tray than a carbonate developer does. An acid rinse between is worth having, and F-1’s capacity figures show what it saves.

With air, in stock A. Six grams of sulfite per litre is not much protection. The handbook’s own storage advice — small bottles, minimum air space — is aimed at exactly this.

With carbon dioxide, in stock B, slowly: caustic soda converts itself to carbonate in a bottle that is often opened, which shifts the ratio of the two alkalis this formula is built on.

With the sulfite tub’s age. A small sulfite dose is more sensitive to a stale tub than a large one, since sulfite oxidises to sulfate on standing and sulfate is not a preservative.

Variants

D-34, Blue Black Tones, the other half of the pair, printed opposite this one in 1928. Metol and hydroquinone against a carbonate alkali, with a dilution as its control instead of a ratio. The two formulas are the corpus’s only published pair of tone alternatives for one material.

Kodak’s own second ratio, 1 part A to 2 parts B for still warmer tones. It is recorded above as a second combination rather than as a variant, because it is the maker’s own and because a variant would misdescribe it: nothing has been changed, the operator has chosen.

The 1928 printing, identical in every quantity and both ratios, differing only in the water statement for stock B and in the published time — about 5 to 6 minutes at 21 °C against about 6 minutes at 18 °C. Both are recorded; the course does not average them.

Wall’s Seed Hydroquinone Developer for Warm Tones, 1924. An independent maker’s version of the same construction: hydroquinone, sulfite, bromide and citric acid in A; carbonate and caustic soda in B; equal volumes; and for still warmer tones use more B. The course does not print Wall’s quantities, because the two columns of that table are not reliably aligned in the copy it has read and a number that might be off by a column is worse than no number. What is corroborated is the architecture and the control, which is what makes it worth citing at all.

No course variant is offered. The formula already carries its own tone control, and its caustic component — 4.2 g/L in a stock, 2.1 g/L in the tray — is already the mildest use of caustic soda in this formulary.

Safety

Level B, set by two ingredients: the caustic soda in stock B and the hydroquinone in stock A.

Sodium hydroxide is the hazardous solid here, even at 4.2 g/L. The hazard is in the weighing and the dissolving, not in the finished stock: the 1928 primer’s warning is that dissolving caustic soda evolves considerable heat, and with hot water the solution will boil with explosive violence and may cause serious burns if the hot alkali spatters on the hands or face. Cold water, the solid into the water and never the reverse, a little at a time, an open vessel, goggles, and the alkali spill procedure known before you start. Four grams is a small weight and the hazard of the tub is not proportional to it.

Hydroquinone is the most heavily classified substance in an ordinary developer. Gloves, no dust, no skin contact with the working solution.

Weigh the citric acid properly, or not at all. 0.7 g is exactly the threshold at which Kodak Limited says a quantity should be made up as a 10 per cent solution and measured by volume — and the handbook offers that alternative for the bromide on the line above and not for the citric acid. The weighing SOP and the balance check are the procedures; a scale that cannot resolve 0.05 g cannot weigh this ingredient honestly.

The working bath is a mild alkali and is handled as any developer is: gloves, tongs, no fingers.

Ventilation as for any darkroom. Nothing here evolves a gas.

Storage

Two months in a full stoppered bottle and two weeks half full, both as the two stocks — Kodak Limited’s own figures, and the four-fold penalty for air space is the sharpest argument in the handbook for its own advice: bottle stock in small bottles, because the air space in a large one grows every time it is opened.

Two hours standing in a dish. That is a working session, not a day.

The tank cell of the same row is marked “N.R.”, as is the deep-tank capacity. The course has not found that abbreviation expanded in its copy of the handbook and does not expand it here; what is published for this formula is a dish figure, and both printings head it a dish developer.

Stock B needs a bottle that caustic will not spoil. Plastic, or glass with a waxed cork rather than a ground stopper: the 1928 primer records that a glass stopper cements itself fast with the carbonate that forms, and that caustic frosts the inside of glass by dissolving it. Keep it closed against carbon dioxide.

The mixed developer is not stored. Mix the ratio the session wants and discard it.

Label both bottles with the formula, the letter, the strength and the date, per the labelling SOP, and record the batch on the formula version record — with the ratio used, because on this formula the ratio is part of what was made.

Incompatibilities

Acids, with stock B and with the working bath: neutralisation of a caustic solution is exothermic, and in any case an acid in the developer is a stop bath in the wrong tray.

Aluminium, zinc and tin, which caustic soda attacks with the evolution of hydrogen. No metal vessels or funnels for stock B.

Ground-glass stoppers, per the primer’s own note.

Fixer, in either direction. One pair of tongs per tray.

Oxidising agents, which destroy hydroquinone.

Anything the incompatibilities page lists against a strong alkali, which is the page to read rather than this paragraph.

Waste

Developer waste, and alkaline. Spent D-32 carries hydroquinone and its oxidation products, carbonate, caustic soda, sulfite, bromide, citrate and a little dissolved silver from the plate.

Keep it out of the acid stream. Developer and fixer wastes are collected separately; that separation is the basis of the general chemical waste SOP.

Hydroquinone is the constituent that makes this more than soapy water, and the caustic soda is what makes it corrosive rather than merely alkaline. Collect, label, and follow the disposal ruling. Local regulation decides, and this course cannot tell you what it says where you are.

Troubleshooting

Stock B got hot while mixing. The caustic went in too fast, or the water was not cold. Let it cool before handling and read the alkali spill SOP before the next attempt.

Stock A has gone brown. Oxidation; with 6.3 g/L of sulfite there is very little margin. Check the age of the sulfite tub, and bottle the stock in smaller bottles.

The slide is fogged. Too much alkali relative to the bromide. Check that stock B was made with the anhydrous carbonate figure if anhydrous carbonate was used — crystals weighed as though they were anhydrous give a weaker bath, but anhydrous weighed as though it were crystals gives one nearly three times as alkaline, and that is the direction that fogs.

The slide is thin, and six minutes did not fix it. Under-exposure, an exhausted bath — 18 sheets per 160 fl.oz. is the published life — or a stock B that has taken up carbon dioxide and lost its free hydroxide.

The tone is not warm. The honest answer is that neither Kodak nor this course can tell you which ingredient makes it warm, so there is no diagnostic chain to follow. What can be tried is Kodak’s own control: one part A to two parts B.

The 1+2 bath developed much faster than expected. No time is published for it in either printing. A third more alkali against a third less agent is not a neutral trade and the source leaves the outcome unstated; judge by eye, as a slide is meant to be judged.

The bottle of stock B will not open. The primer’s own observation: a glass stopper cements itself fast with the carbonate that forms. Warm the neck; expect alkali inside.

Experiments

Photograph the pair. D-32 and D-34, identical plates, developed to the same maximum density, then read and photographed by transmitted light against a neutral source. Kodak names two colours across two facing pages and shows nothing. This is the missing figure of the pair, and it is one afternoon’s work.

Walk the ratio. 1+1, 1+2, and beyond Kodak’s published pair — 1+3 and 2+1 — on identical plates, all developed to the same density by inspection, then read for colour. Kodak publishes two points on that line and Wall says simply for still warmer tones use more B. Nobody has plotted it.

Find out whether the citric acid does anything. Make stock A with it and without it, and develop identical plates at the same ratio, reading both density and colour. Then keep both stocks for a month and repeat. If the citric acid is a stabiliser, the difference will be in the second test and not the first; if it contributes to the tone, the reverse. Neither printing tells us, and this is how to find out.

Separate the two alkalis. Make stock B with the carbonate alone, and with the caustic alone at a strength giving the same initial pH, and compare tone, speed and how the bath behaves over eighteen sheets. The primer’s claim is that a carbonate holds its concentration and a caustic does not; this formula carries both, and no source says why.

Test the two published times against each other. Six minutes at 18 °C, from London, and five to six at 21 °C, from Rochester, on the same plate from the same box. The formulas are identical; the instructions are not.