Kodak D-1

Three bottles that never meet until the tray is filled, and a preservative dose one tenth of D-76’s. Kodak’s Rochester primer heads this formula Standard A. B. C. Pyro and numbers it D-1; Kodak Limited in London calls it a normal-contrast pyro-soda developer for general use. Everything strange about it comes from one deliberate shortage: there is not enough sulfite in it to hide what the developing agent turns into, and that was the intention.

Stock Solution A — the developing agent, kept acid and kept away from the alkali

Ingredient	Quantity	Form the source specifies
Sodium bisulfite	9.8 g
Pyrogallol	60 g	Kodak calls it pyro and defines it as 1:2:3 trihydroxybenzene
Potassium bromide	1.1 g or 11 mL of a 10% solution (11 c.c. of a 10 per cent solution, which is the handbook's own alternative for a quantity too small to weigh reliably)
Water	to make 1000 mL	"Water to make 1000 c.c." No temperature is given. The 1928 primer's general mixing rule is that a developer is mixed at a temperature not usually above 52 degrees C, and that each chemical is completely dissolved before the next goes in.
Preservative first, which is the handbook's rule for every formula that has no Elon in it: the agent must never be alone in water with air. The bromide is last and its position is immaterial, because bromide has no action on the developing agents.

Stock Solution B — the preservative, on its own and at the concentration that keeps best

Ingredient	Quantity	Form the source specifies
Sodium sulfite (anhydrous)	105 g or 210 g (crystalline heptahydrate, which is the handbook's main column and is exactly twice the weight)	anhydrous
Water	to make 1000 mL	"Water to make 1000 c.c.", which puts this stock at 10.5 per cent sulphite. The 1928 primer states that a plain sulphite solution oxidises readily below 10 per cent and very slowly above it, and that sulphite stocks should therefore be made at around 10 per cent for maximum keeping. B sits just over that line.

Stock Solution C — the alkali, on its own

Ingredient	Quantity	Form the source specifies
Sodium carbonate (anhydrous)	75 g or 200 g (crystalline decahydrate, which is the handbook's main column)	anhydrous
Water	to make 1000 mL	"Water to make 1000 c.c." A solution carrying 200 g of carbonate crystals to the litre is far easier to make warm than cold, and must be cool before it meets the agent stock.

Mixed in the ratio — dish (tray) development

1 part Stock Solution A + 1 part Stock Solution B + 1 part Stock Solution C + 7 parts water

For Dish Development - Take 1 part A, 1 part B, 1 part C and 7 parts of water.

Ten parts in all, so every stock strength divides by ten: 6.0 g/L of pyro, 0.98 g/L of sodium bisulphite, 0.11 g/L of potassium bromide, 10.5 g/L of anhydrous sodium sulphite and 7.5 g/L of anhydrous sodium carbonate. The same ratio is printed in 1924, 1928 and 1944.

Mixed in the ratio — tank development

1 part Stock Solution A + 1 part Stock Solution B + 1 part Stock Solution C + 11 parts water

For Tank Development - Take 1 part A, 1 part B, 1 part C and 11 parts of water.

Fourteen parts in all: 4.29 g/L of pyro, 0.70 g/L of sodium bisulphite, 0.079 g/L of potassium bromide, 7.5 g/L of anhydrous sodium sulphite and 5.36 g/L of anhydrous sodium carbonate. The 1928 primer and the 1944 formulary print eleven parts of water too; the 1924 primer prints twenty-five, which is recorded in the provenance and discussed in the body.

Purpose

To develop a plate or a negative to normal contrast using pyrogallol as the sole developing agent, from stocks that are mixed only at the moment of use because the agent will not keep any other way.

Kodak Limited’s 1949 header is “Normal-contrast pyro-soda dish or tank developer for plates and films”, and the 1944 formulary puts the same thing in more words: a normal-contrast pyro-soda developer for use in dish or tank for the development of films and plates — general use. Kodak’s Rochester primers of 1924 and 1928 print the identical composition under a different name, Standard A. B. C. Pyro, and that name is what the formula is usually called. The A, B and C are the three bottles.

The second purpose is not in any header and is the reason the formula still matters. A pyro developer leaves two images. Pyrogallol’s oxidation product is yellow, and the 1928 primer states that it is deposited in the film along with the silver, so the negative carries a silver density and a colour density on top of it. Every modern staining developer — PMK, Pyrocat-HD — is a descendant of this arrangement. The staining and tanning developers lesson sets out what a stain image is worth and what the course can and cannot establish about it, and the pyrogallol page carries the chemistry of the agent itself. What this course cannot do it does not do here: it cannot name the yellow compound, cannot give an equation for its formation, and cannot describe the mechanism by which pyro tans the gelatin it develops.

Recommended uses

Plates and sheet film in a dish, at one part of each stock and seven of water, 5 to 7 minutes at 18 °C in the London printing and 7 to 9 in the Rochester one.

Roll and sheet film in a tank, at one part of each stock and eleven of water, about 12 minutes at 18 °C in London and 13 to 15 in Rochester. The tank bath is about 70 per cent of the dish strength.

Where the stain is the point, at the classical setting. Ten and a half grams of sulfite per litre in the dish bath is enough preservative to keep the bath usable for half an hour and nowhere near enough to suppress the colour. Among Kodak Limited’s three pyro developers it sits in the middle: more preservative than D-167, which carries no sulfite at all and which Kodak alone of the three actually calls a staining developer, and less than half of D-177’s. On the sulfite reading that puts D-1 second of the three for stain, which is a reading of published numbers and not a measurement.

As the reference formula for the whole staining tradition. Read against D-76 the design becomes visible in a single number, and the sulfite and preservation lesson uses the pair to make the point. If you want to understand why PMK and Pyrocat-HD are sold as two concentrates that meet in the tank, mix this and watch Solution A darken.

As a historical negative developer for a historical process. This is what a general-purpose developer looked like before the borax and metol-hydroquinone formulas displaced it, and it was still in a Kodak handbook in 1949.

When another formula is preferable

• For a pyro negative with less stain and more latitude, D-177: the same agent with two and a half times the alkali and more than twice the sulfite, in a concentrated 150 mL storage stock.
• For a hard, fast, heavily stained press negative, D-167: Elon beside the pyro, five times this formula’s alkali, a fifth of its preservative and two to three minutes.
• Where no stain at all is wanted, D-76 or D-23. A hundred grams of sulfite per litre is what a developer looks like when it is designed to hide its oxidation product; a hundred grams against ten is the difference.
• For high contrast, D-19, which is what that formula exists for.
• Where the bath must last a session. Thirty minutes in a dish is the published life and it is the shortest figure in Kodak Limited’s entire developer table. Mix for the sheet, not for the evening.
• Where the agent is the objection. Pyrogallol sets this page at Level B and there is no way to keep the formula and lose the agent; see Safety.
• Where a modern staining developer with published times for modern films is wanted, PMK or Pyrocat-HD — with the warning that both of those pages are behaviour-only, because neither maker publishes a composition.

Mixing

Three bottles, mixed separately, combined only in the tray or tank.

1. Solution A. Dissolve, in this order, 9.8 g of sodium bisulfite, then 60 g of pyro, then 1.1 g of potassium bromide — or 11 mL of a 10 per cent bromide solution; water to make 1,000 mL. Preservative first is the handbook’s rule wherever there is no Elon in the formula, and here it is not a nicety: pyro alone in water with air is already oxidising.
2. Solution B. Dissolve 105 g of anhydrous sodium sulfite — or 210 g of the crystals, which is the handbook’s main column; water to make 1,000 mL.
3. Solution C. Dissolve 75 g of anhydrous sodium carbonate — or 200 g of the crystals; water to make 1,000 mL. Add the powder to the water and not the water to the powder: the 1928 primer is explicit that a desiccated carbonate or sulfite poured into a little water cakes and then dissolves only with difficulty.
4. The working developer, mixed when the tray is wanted and not before: one part A, one part B, one part C and seven of water for a dish; eleven of water for a tank.

Why the bromide is offered twice. A gram and a tenth is at the edge of what a darkroom balance resolves, so Kodak prints the same dose as 11 mL of a 10 per cent stock. Below about 0.7 g a weighing varies far more than the formula tolerates, and the volume of a made-up solution does not.

!Anhydrous or crystalline, and never a mixture of the two systems

Kodak Limited prints the sulfite and the carbonate twice each. The sulfite is 105 g anhydrous or 210 g crystalline — exactly twice, because the heptahydrate is half water by mass, which the 1928 primer states as “crystals containing seven parts of water to one of sulphite … which contain, when pure, 50 per cent of dry sulphite”. The carbonate is 75 g anhydrous or 200 g crystalline, a factor of 2.67. Notice that the handbook’s own general rule a few pages earlier says to multiply carbonate by two and a half when using crystals, and the formula’s own columns use 2.67; the molar ratio of the decahydrate to the anhydrous salt is 286.14 ÷ 105.988 = 2.70, so the formula’s columns are nearer right than the rule of thumb. Follow the columns.

The same page carries Kodak’s warning in capitals: the avoirdupois and metric columns “are not exact equivalents”, so one or the other must be used exclusively. Nothing on this page converts between them, and neither should you halfway down an ingredient list.

🧮What the three bottles become in the tray

Each stock is one tenth of the dish bath (1 + 1 + 1 + 7 = ten parts) and one fourteenth of the tank bath (1 + 1 + 1 + 11 = fourteen parts):

60 g/L ÷ 10 = 6.0 g per litre

Pyrogallol, dish

105 g/L ÷ 10 = 10.5 g per litre

Sodium sulfite, dish

75 g/L ÷ 10 = 7.5 g per litre

Sodium carbonate, dish

9.8 g/L ÷ 10 = 0.98 g per litre

Sodium bisulfite, dish

1.1 g/L ÷ 10 = 0.11 g per litre

Potassium bromide, dish

In the tank the same five divide by fourteen instead: 4.29, 7.5, 5.36, 0.70 and 0.079 g per litre.

Set the three pyro developers of Kodak Limited’s handbook beside each other at their working strengths, and beside the developer everything else is compared with:

Working bath	Agent	Preservative	Carbonate, anhydrous	Bromide	Time at 18 °C
D-1, dish	6.0 g/L pyro	10.5 g/L sulfite	7.5 g/L	0.11 g/L	5–7 min
D-1, tank	4.29 g/L pyro	7.5 g/L sulfite	5.36 g/L	0.079 g/L	about 12 min
D-177	6.25 g/L pyro	25 g/L sulfite	18.75 g/L	0.85 g/L	5–8 min
D-167	7.5 g/L pyro + 2.5 g/L metol	5 g/L metabisulfite only	37.5 g/L	none	2–3 min
D-76	2 g/L metol + 5 g/L hydroquinone	100 g/L sulfite	none (2 g/L borax)	none	8 min, but at 20 °C

The pyro barely moves across the three and everything else does. D-1 carries the least alkali of the three and about an eighth of D-177’s bromide, and it is the one Kodak calls normal-contrast rather than staining or press. The D-76 row is on a different clock — Kodak publishes its eight minutes at 20 °C for Tri-X, not at 18 °C — and it is there for the preservative column, which is the whole argument: 10.5 grams per litre against a hundred, a tenth as much, in a developer whose agent oxidises far more readily than D-76’s.

Behaviour

Thirty minutes in a dish. That is Kodak Limited’s published working life for the mixed bath, and it is the shortest figure in the handbook’s whole developer table. Three hours in a covered tank — a factor of six, bought with a lid. The mixed developer is not a solution you keep; it is a solution you use and pour away.

One month in a full stoppered gallon bottle, two weeks half full, and the table says “in 3 solutions”. That qualification is the formula’s whole design written into a keeping table: the month belongs to A, B and C sitting separately, and nothing on the page offers a keeping figure for the mixture. The difference between the full and half-full bottle is the air space, which the handbook’s storage note explains directly — every time stock is drawn from a large bottle the air space grows, which is why stock is better kept in several small bottles.

Twelve sheets of 8 × 10 inches per 160 fluid ounces in a narrow dish, twenty-four in a deep tank. That is a published capacity, and a capacity is a statement that the bath is reused: Kodak’s own column heading is the number of sheets “processed for standard time … without loss of quality”. It is also the lowest pair of figures in the table, level with D-167, D-177 and D-82 and exactly half of what the same table allows D-16. The thirty-minute dish life bounds how long that reuse can go on, and in practice the two numbers together describe a session rather than a week.

Two dilutions, and they are not simply strong and weak. The tank bath at 1 + 1 + 1 + 11 is about 70 per cent of the dish strength in every constituent, and Kodak roughly doubles the time for it. That is the ordinary trade of a tank developer: less agent per litre, more litres, more time, and less oxidation per sheet because the surface area of a covered tank is small.

⁇Four printings, two tank dilutions, and two sets of times

The composition of D-1 is not in dispute anywhere in the corpus: 9.8, 60.0 and 1.1 g in A, 105.0 g of sulfite in B and 75.0 g of carbonate in C, in Rochester in 1928 and in London in 1944 and 1949. The 1924 printing gives avoirdupois only, on a 32-ounce basis, and its Solution A agrees within the rounding that basis carries; its sulfite and carbonate lines are not legible in the copy the course holds, so the 1924 agreement rests on Solution A and on the three-solution arrangement rather than on all five quantities. Two things around the composition do disagree outright.

The tank dilution. Kodak’s 1924 primer prints 1 part A, 1 part B, 1 part C and 25 parts of water for tank development. Every later printing in the corpus — 1928, 1944 and 1949 — prints eleven. The course publishes eleven, on the strength of three printings against one and of the 1924 edition giving no times to go with its figure, and records the 1924 reading here rather than silently dropping it. Whether it is a change of policy or a misprint the course cannot say; no source in the corpus comments on it.

The times. For the same two dilutions at the same 18 °C, Rochester in 1928 gives about 7 to 9 minutes in a tray and 13 to 15 in a tank, and London in 1944 and 1949 gives 5 to 7 and about 12. Both are printed in development above with their own sources. The course does not choose, and the obvious explanation — that the plates and films sold in America in 1928 and in Britain in 1949 were not the same materials — is an interpretation, not something either handbook states.

What follows for you. Neither set of times is a time for a modern film, and no Kodak publication in the corpus gives one. Treat both as a starting bracket for a test strip and use the developer laboratory report to find your own.

Image characteristics

A stained negative, and second of Kodak Limited’s three pyro developers for how much stain survives. That ranking is the course’s reading of the preservative column — no sulfite at all in D-167, 10.5 g/L here, 25 g/L in D-177 — set against Kodak’s own graded statement that more sulfite means less yellow, and against the fact that Kodak reserves the word staining in its headers for D-167. It is a reading of published numbers and not a measurement anybody has published.

A second density that behaves differently from the silver. What a stain image does on graded and variable-contrast paper, and how it reads through the different channels of a densitometer, is set out in the staining and tanning developers lesson rather than repeated here.

Highlights before shadows. Kodak’s 1928 ranking of developing agents by reduction potential puts hydroquinone lowest, then Athenon, then pyro, then Kodelon, then Elon highest, and states what the ranking means at the tray: a high-potential agent makes the image flash up all over at once because it starts even in the lightly exposed parts, while a low-potential agent like pyro brings up the highlights first and leaves the shadows until the highlights are somewhat developed. That is a statement about the agent, made by Kodak, and it is what a pyro tray looks like.

Normal contrast, and that is all Kodak claims. No gamma, no curve, no development series, no grain description and no speed figure is published for this formula in any printing the course holds. The header word is “normal-contrast” and the course does not improve on it.

Tanning, by a mechanism the course cannot describe. Pyro hardens the gelatin it develops. The pyrogallol page establishes that this happens and records honestly that the chemistry joining the observation to the rest is not in this corpus.

The mechanism

Development is reduction: the agent gives up electrons, silver ion at a latent-image centre becomes metallic silver, and the halide leaves the crystal. Part VIII works that through and this page does not repeat it.

AgBr + e⁻ → Ag + Br⁻

What the pyro is doing, grain by grain

What is worth understanding here is why the same five substances are in three bottles rather than one, because each separation buys something specific.

⚗Three bottles, three different reasons

Agent from alkali is the first and oldest separation. The 1928 primer’s reason is specific to this agent: a two-solution developer is a one-solution developer split so that it oxidises less readily, and the reason why it is customary to keep a developer like pyro in two solutions is because pyro oxidises much more readily than Elon or para-aminophenol with a given amount of preservative. Kodak Limited states the same as a general rule — developers particularly susceptible to aerial oxidation are divided into two or three solutions in which the developing agent is kept separate from the alkali.

Acid preservative from neutral preservative is the second, and it is why A contains bisulfite while B contains sulfite. The primer is explicit: a solution of an agent such as pyro, stored for a considerable time, keeps best with an acid sulfite such as sodium bisulfite rather than sodium sulfite, which is slightly alkaline; and sodium bisulfite “keeps satisfactorily in more dilute solutions and is a better preservative than sulphite in the absence of carbonate”. So the agent bottle gets 9.8 g of the acid salt and none of the neutral one.

Preservative from alkali is the third, and it is the one most people miss. Solution B could have been folded into Solution C — Kodak’s own D-21 does exactly that — and there is a keeping reason not to. The primer states that a plain sulfite solution oxidises readily in contact with air below about 10 per cent and very slowly above it, so sulfite stocks should be made at around 10 per cent for maximum keeping. Solution B is 10.5 per cent. It is not an arbitrary strength; it is the strength at which a bottle of sulfite looks after itself.

And the three become one at a cost that Kodak names. When the bisulfite of A meets the carbonate of C, it is neutralised:

NaHSO₃ + Na₂CO₃ → Na₂SO₃ + NaHCO₃

What happens the moment A meets C

The primer states the consequence in terms — in compounding a two-solution formula from a one-solution one, it is necessary to allow for this neutralisation of the carbonate by using an extra quantity. Put numbers on it for the dish bath:

0.98 g/L ÷ 104.06 g/mol = 0.0094 mol/L

Bisulfite in the dish bath

7.5 g/L ÷ 105.988 g/mol = 0.0708 mol/L

Carbonate in the dish bath

About 13 per cent of the carbonate is converted to bicarbonate the instant the solutions meet, and the same reaction hands the bath a further 0.0094 mol/L of sulfite — about 1.2 g/L on top of B’s 10.5. The alkali you weighed is not quite the alkali you get, and the arithmetic above is the course’s, from Kodak’s stated reaction.

What the course cannot say. The identity of pyro’s yellow oxidation product, the equation for its formation, and the mechanism of its tanning action are all outside what this corpus establishes. No pH is published for this formula and none is offered here.

Function of every ingredient

Sodium bisulfite, 9.8 g in Solution A — 0.98 g/L in the dish bath. The preservative of the agent bottle, and an acid one. Sodium sulfite is slightly alkaline, and an alkaline preservative around pyro is a slow developer running in the bottle; the bisulfite gives an acid solution instead, in which the 1928 primer states that a readily oxidisable agent keeps best. It is a keeping decision and not a stain decision: at not quite a gram per litre in the working bath it is far too little to suppress the colour, and the sulfite that governs the stain arrives separately in Solution B. More of it would keep Solution A longer and neutralise more of Solution C’s carbonate; less would give a bottle that browns within weeks. Two practical facts come from its own page and the primer’s chemical notes: bisulfite is difficult to prepare free from iron, and iron in a pyro solution forms an inky substance that colours the bath, and potassium metabisulfite may be substituted for it weight for weight — which is what the 1924 printing of this very formula offers as an alternative, and what D-177 and D-167 use instead.

Pyrogallol, 60 g in Solution A — 6.0 g/L in the dish bath and 4.29 g/L in the tank. Kodak calls it pyro and defines it as 1:2:3 trihydroxybenzene. The only developing agent in the formula and the reason for every other decision on the page. It reduces exposed silver halide, and its own oxidation product is yellow and is deposited in the film with the silver, so the negative gets a second, coloured density on top of the silver one. It also tans the gelatin it develops, by a mechanism the course cannot describe. More pyro gives more density and more stain; less gives less of both and a bath that exhausts sooner. At 60 g/L Solution A is a 6 per cent solution, nowhere near pyro’s solubility of roughly 500 to 600 g/L, so there is no excuse for undissolved powder. Two facts from its own page matter at the bench: it turns grey on exposure to light and air, so Solution A lives full, closed and dark; and Kodak supplied the crystal rather than the powder form precisely because the powder flies about a darkroom and settles on plates and paper as spots.

Potassium bromide, 1.1 g in Solution A — 0.11 g/L in the dish bath and 0.079 g/L in the tank. The restrainer, and a very small dose of one. Its job is to suppress the chemical fog that any carbonate-alkali developer will otherwise produce, by occupying the surface of the halide crystal where development would otherwise start without an exposure to justify it; the restrainers and antifoggants lesson sets out the mechanism. It sits in the agent bottle rather than with the alkali, which is possible because bromide has no action on the developing agents, so the handbook says its position in the mixing order is immaterial. More would clean the highlights, cost shadow speed and slow the bath; less would fog. It is about an eighth of what D-177 carries in its working bath, and D-167 carries none at all — three formulas from one handbook, spanning the whole range from a restrainer to no restrainer, and the dose tracks the alkali in every case.

Sodium sulfite, 105 g anhydrous in Solution B — 10.5 g/L in the dish bath, and the single number that decides what kind of developer this is. It does three things and they are not independent. It scavenges dissolved oxygen so the bath does not oxidise while you use it; it intercepts the agent’s oxidation product, which is exactly what suppresses the stain, because the stain is that oxidation product deposited in the film; and at high concentrations it is a solvent for silver bromide, which is where D-76’s fine grain comes from — but 10.5 g/L is nowhere near that region, so this formula gets none of that effect. Kodak’s 1928 primer states the whole dial in one sentence: a pyrogallol developer without sulfite gives a very yellow negative whose image is partly silver and partly oxidised pyrogallol; with sulfite the image is much less yellow; with a great deal of sulfite you get almost as blue an image as with Elon. D-1 sits low on that scale on purpose. More sulfite moves the negative towards a conventional one and makes the bath keep longer; less stains harder and gives a bath that browns in the tray. The handbook prints the crystalline heptahydrate at exactly twice the weight as its alternative, and weighing crystals as though they were anhydrous would halve the preservative.

Sodium carbonate, 75 g anhydrous in Solution C — 7.5 g/L in the dish bath and 5.36 g/L in the tank. The alkali, and without it nothing happens at all: a developing agent must be in alkaline solution to work, and the 1928 primer’s rule is that the quantity of alkali governs the energy of the developer, that too much tends to produce chemical fog, that too little makes it slow, and that alkalis soften the gelatin and can cause frilling. A carbonate is a reservoir rather than a dose — only partly dissociated at any moment, so it holds the hydroxide concentration roughly steady through a development where a caustic alkali would present everything at once and then collapse. At 7.5 g/L this is the mildest of the three pyro developers in the handbook, two and a half times less than D-177 and five times less than D-167, and the 5-to-7-minute time is where that lands. More carbonate means a faster, harder, foggier bath; less means times that become impractical. Remember that about 13 per cent of it is consumed by Solution A’s bisulfite the moment they meet. The anhydrous salt is what the formula means and what the handbook recommends; the main column prints 200 g of the decahydrate crystals instead, and weighing crystals as though they were anhydrous would give a bath under two-fifths as alkaline as intended.

Water, three times to make 1,000 mL, plus the seven or eleven parts that make the working bath. Not an inert ingredient. No temperature is published for any of the three stocks; the 1928 primer’s general rule is that a developer is mixed at a temperature not usually above 52 °C and that each chemical is completely dissolved before the next goes in, and its specific warning for desiccated carbonate and sulfite is that the chemical goes into the water and never the water onto the chemical, or it cakes. Kodak Limited’s storage note adds the reason not to throw away a stock that has crystallised in the cold: the precipitate often contains the most important constituents of the solution, and it should be redissolved by warming.

Interactions

Agent and alkali. The carbonate decides how hard and how fast the pyro works, and Kodak Limited’s own three pyro formulas are a ready-made series on exactly this variable: 7.5, 18.75 and 37.5 g/L of anhydrous carbonate in the tray, developing in 5 to 7, 5 to 8 and 2 to 3 minutes. One agent, one handbook, three settings.

Agent and sulfite, which is the interaction this formula is famous for. The preservative and the stain are competing for the same species — the oxidised agent — so protecting the bath and printing the colour are the same dial turned in opposite directions. There is no setting that gives both, and D-1 chooses the stain. This is why a staining developer cannot be made to keep the way D-76 keeps, and why every developer of this class is sold or published as separate solutions.

Bisulfite and carbonate, at the moment of mixing: the acid preservative from Solution A neutralises about 13 per cent of Solution C’s carbonate and turns into sulfite as it does so. Kodak states the reaction and states that a formula split into solutions must allow extra carbonate for it. It is also why you cannot re-derive a one-bottle version of this formula by simply pouring the three together and making up to volume — the arithmetic of the alkali changes.

Restrainer and alkali. The bromide dose tracks the carbonate dose across the handbook’s pyro formulas: least alkali and least bromide here, most alkali and no bromide at all in D-167, where the two-to-three-minute development is too short for fog to matter.

With air, and it governs everything. Thirty minutes in a dish against three hours in a covered tank; one month in a full bottle against two weeks in a half-empty one. Every keeping figure Kodak publishes for this formula is a statement about oxygen.

With iron. Iron in the bisulfite forms an inky substance with the pyro, colouring the solution a dirty bluish-red, which the primer records as having no effect on the image but which is the hardest possible fault to diagnose in a developer whose whole purpose is to leave a colour in the film. The same chapter records that the B solution of a two-solution pyro developer browns if it is mixed in dirty vessels.

With everything after the tray. Kodak Limited prints nothing about stop baths, fixers or washing for this formula. The practices that modern staining-developer makers publish are recorded on the pyrogallol page and belong to those products. If the tanning is to be judged on its own rather than added to, a non-hardening fixer such as F-52 is the one to use.

Variants

Kodak’s own two-solution version, published on the same page. The 1928 primer prints a Two Solution Pyro Tray Developer immediately beneath D-1 — numbered D-21 in the 1924 edition — whose Stock Solution A is identical, and whose Stock Solution B carries the sulfite and the carbonate together at 105 g and 75 g per litre. It is used one part A, one part B and eight parts of water. That is ten parts, so the working bath is the same working bath as D-1’s tray dilution, ingredient for ingredient, and yet the primer gives it about 6 minutes where D-1 gets 7 to 9. The arithmetic is the course’s and it is worth stating plainly: two formulas on one page, the same five substances at the same five concentrations, two different published times. Nothing in the corpus explains it, D-21 has no entry in this formulary, and the honest reading is that Kodak’s times of this period are approximate. The chemistry of the difference between them is only in the keeping: folding B into C puts the sulfite next to the alkali, which is the arrangement the primer’s own 10-per-cent rule and its acid-preservative rule both argue against.

D-177, Kodak Limited’s other general-purpose pyro developer: potassium metabisulfite instead of sodium bisulfite, a concentrated 150 mL storage stock instead of a litre, more than twice the sulfite and two and a half times the alkali.

D-167, the pyro-Elon staining developer for press work: a second agent, five times this formula’s alkali, a fifth of its preservative, no bromide, and two to three minutes.

The 1924 printing, which offers potassium metabisulfite as an alternative to the sodium bisulfite in Solution A, and prints twenty-five parts of water for tank development rather than eleven. Recorded in the provenance and discussed under Behaviour; the course publishes the later reading.

The crystalline sulfite and carbonate columns, which are the handbook’s own main columns and are recorded in the table above as alternative forms, not as a different formula.

PMK and Pyrocat-HD are the living descendants of this arrangement — a pyro or catechol concentrate and an alkali concentrate that meet in the tank — but neither is a variant of D-1 in any sense the course can document, because neither maker publishes a composition to compare. Both pages are behaviour-only for that reason.

No course variant is offered. The one thing a reader would want to change is the preservative, and raising it produces D-177, which Kodak already published. Lowering it produces a developer that will not survive the tray.

Safety

Level B, and the agent sets it. The classification rubric sets what Level B assumes: splash goggles, better ventilation than a closed room, an eyewash within reach, and experience with concentrated reagents.

Pyrogallol is the reason, and its own page carries the detail. The aggregated ECHA notifications on PubChem give it a Warning signal word with harmful by ingestion, skin contact and inhalation, skin and eye irritation, suspected of causing genetic defects, and harm to aquatic life with long-lasting effects. Three of those — harmful in contact with skin, harmful if inhaled, and suspected of causing genetic defects — are notified unanimously. Read that page before opening the jar. There is no occupational exposure limit to measure a darkroom against, so the control is to keep the dust out of the air and the solution off the skin rather than to work to a number.

Sixty grams per litre is a concentrated agent solution. A splash of Solution A is not a splash of working developer, and it will stain skin brown. Nitrile gloves, eye protection, an apron, and tongs rather than fingers.

Weigh the pyro without making dust. Kodak’s own reason for supplying the crystal rather than the powder was that the powder flies about and settles on materials; the health reason is the same fact with a different consequence. Weigh with extraction running or inside an enclosure, never in a draught.

Sodium bisulfite gives sulfur dioxide when it meets a stronger acid, and Solution A is already acid. Keep every acid — including a stop bath — away from the stock bottle and its waste, and weigh it in moving air. Anyone with asthma should read its page first.

Sodium sulfite and sodium carbonate are the ordinary darkroom solids, and 200 grams of carbonate crystals is still an alkaline dust: gloves, eye protection and no clouds while weighing.

What is not a hazard here. Nothing in this formula evolves a gas in normal use — the sulfur dioxide risk is a mixing and waste-handling risk, not a tray risk — nothing is strongly alkaline at 7.5 g/L of carbonate, and nothing is heated beyond the warm water used to dissolve the solids. There is no solvent, no oxidiser and no heavy metal anywhere on the page. The ventilation requirement is for dust while weighing and for the acid stock bottle, not for vapour while developing.

Storage

Three bottles, never one. The month and the fortnight in Kodak’s keeping table are printed “in 3 solutions”, and the arrangement is not a convenience. Mixed, the developer has thirty minutes in a dish.

Solution A full, closed, dark — and divided into small bottles. It is the bottle that decides whether the formula works: 6 per cent pyro with less than a gram of bisulfite for every six grams of agent. Pyro turns grey on exposure to light and air, so a stock that has darkened has already made some of its stain in the bottle instead of in the film. Kodak Limited’s storage note argues for several small bottles rather than one large one, because the air space in a large bottle grows every time it is opened, and it warns against glass stoppers because the alkali makes them stick — the second point applies to C rather than to A, but a corked or plastic closure is the right choice for all three.

A curiosity worth knowing about, from Kodak’s own 1928 practice. Where a pyro stock had to be kept a long time and drawn off at intervals, the primer describes fitting an absorption bottle of alkaline pyro to the air intake of the storage vessel, so that the air drawn in as liquid is withdrawn has its oxygen stripped out before it reaches the stock. It is a neat demonstration of how avidly alkaline pyro takes up oxygen — which is the same fact that makes this developer hard to keep.

Solutions B and C are the durable ones. B is at the 10.5 per cent that the primer names as the region where a sulfite solution stops oxidising quickly; C has nothing in it that oxidises usefully at all. Both will still crystallise if stored cold, and the handbook’s instruction then is to warm and redissolve rather than decant, because the precipitate often contains the most important constituents.

Label all three with the formula number, the letter, the strength and the date, per the labelling SOP, and record the batch on the formula version record. Label Solution A as containing pyro in words that someone who has not read this page would understand.

Incompatibilities

Acids of any kind, and Solution A in particular. An acid bisulfite stock plus a stronger acid gives sulfur dioxide. This is also why the same tongs must never go from a stop-bath tray back into the developer: a splash of acetic acid does not merely neutralise 7.5 g/L of carbonate, it takes the bath out of the region where the pyro works at all. SB-1 is a stop bath, not a rinse, and the boundary between the two trays is absolute.

Oxidising agents — ferricyanide, dichromate, permanganate, persulfate. Pyro is the most readily oxidised agent in this course, and permanganate is used deliberately on pyro negatives to attack the stain image in preference to the silver.

Iron, from a tray, a clip, a rusty balance pan or a contaminated tub of bisulfite. It darkens a pyro solution and is the hardest fault to see in a developer that is meant to leave a colour.

Fixer, in either direction. Thiosulfate carried back into the developer is a far more aggressive silver solvent than anything in this formula and will fog and stain; developer carried into the fixer shortens its life and contaminates a stream that would otherwise go for silver recovery.

Light and air, for Solution A, which is a storage matter and a practical incompatibility at once.

The chemical incompatibilities page is the reference rather than this paragraph.

Waste

Spent D-1 is a dilute alkaline solution carrying pyrogallol and its oxidation products, sulfite, bisulfite, carbonate and a little bromide. It is not the silver stream: developer carries negligible silver, so pouring it into the fixer bottle recovers nothing and ruins a solution that would otherwise go for recovery.

Pyrogallol is the constituent that makes this more than soapy water. Its aggregated classification carries harm to aquatic life with long-lasting effects, notified by the large majority of reports, with the precautionary statement to avoid release to the environment. Collect it in its own labelled bottle.

Keep it out of the acid stream for a second reason as well: bisulfite and a strong acid give sulfur dioxide, and a waste container is the last place you want that.

Follow the general chemical waste SOP and the disposal ruling. Local regulation decides, and this course cannot tell you what it says where you are.

Troubleshooting

Solution A has gone grey, brown or inky. Grey or brown is pyro oxidising: check that the bottle is full, closed and dark, and check the age of the bisulfite. A dirty bluish-red or inky colour is a different fault — iron in the bisulfite combining with the pyro, which the 1928 primer records as having no effect on the image, but which tells you the tub of bisulfite is contaminated.

The mixed bath went dark in the tray. Expected past about half an hour, which is Kodak’s own dish figure. Mix the volume you are about to use.

Thin negatives with no stain worth looking at. An oxidised Solution A has spent its agent in the bottle. Alternatively the carbonate was weighed as crystals against the anhydrous column, which would leave the bath under two-fifths as alkaline as intended and slow it drastically.

Fog, or a veil across the whole frame. Check the carbonate arithmetic in the other direction — anhydrous weighed against the crystalline column would nearly triple the alkali — and then check that the bromide actually went into Solution A. At 1.1 g per litre it is easy to leave out and easy to get wrong on a coarse balance, which is why Kodak offers it as 11 mL of a 10 per cent solution instead.

Negatives too soft. Kodak publishes no contrast control for this formula beyond the two dilutions and the time. The dish dilution is the stronger of the two.

Undissolved powder in Solution C, or a hard cake at the bottom of the jug. Desiccated carbonate and sulfite were added to too little water, or the water was poured onto the powder. The primer’s rule is the chemical into the water, never the reverse.

Crystals in a stock bottle after a cold night. Warm the bottle and redissolve them. Do not pour the clear liquid off the top: the precipitate often contains the most important constituent of that stock.

Yellow-brown spots on plates or paper unrelated to the image. Pyro dust, which is exactly why Kodak sold the crystal form rather than the powder.

The negative is unusually hard to fix, or dries with an odd surface. Pyro tans the gelatin it develops. That is a property of the class rather than a fault of the batch, and it is one reason a non-hardening fixer is the sensible partner.

Experiments

Turn the sulfite dial and watch the stain move. Mix Solution B three times — at 105 g/L as published, at 210 g/L and at 25 g/L — and develop matched strips from one exposure batch at the dish dilution. Read each visually and through a blue filter; the difference between the two readings is the stain. Kodak’s 1928 primer predicts the direction in words and this course has never measured it. Run it as a controlled series with the developer laboratory report.

Take the alkali series across one handbook. D-1, D-177 and D-167 carry 7.5, 18.75 and 37.5 g/L of anhydrous carbonate in the tray and develop in 5 to 7, 5 to 8 and 2 to 3 minutes. Plot time against alkali for one film. Three points, one handbook, and the handbook draws no graph.

Test the two printings against each other. Develop identical strips for 5 to 7 minutes and for 7 to 9 at 18 °C in the same dish bath. If the densities separate clearly, the difference between London and Rochester is a real difference in the materials each was written for; if they do not, both are brackets around the same target and the course was right not to choose.

Find out what the three bottles are worth. Keep one set as A, B and C, and mix a second set into a single bottle at the same total concentrations, and develop matched strips from each at a day, a week and a month. Kodak’s table gives one month for the three solutions and no figure at all for a mixed bath. This is the experiment that makes the whole architecture of a staining developer visible.

Ask what the bisulfite actually costs the alkali. Mix the dish bath as published and mix a second with Solution C raised by 13 per cent, and compare development times. Kodak states that a split formula needs extra carbonate to allow for the neutralisation; nobody in this corpus says how much D-1 was given.

Run D-1 against D-76 on the same negative. Ten grams of sulfite per litre against a hundred, one agent against two, a stain against no stain. It is the clearest single demonstration in the formulary of what a preservative is for and what it costs.