Kodak D-167

A staining developer with a deadline. Kodak Limited built D-167 for the press photographer who needed a negative in three minutes and would accept a stained one, and it wrote the design constraint into the directions rather than into a footnote: oxidation is very rapid and therefore solutions A and B should not be mixed until immediately before use.

Solution A — the two developing agents and their preservative

Ingredient	Quantity	Form the source specifies
Metol	5 g	Kodak calls it Elon and defines it as a specially purified monomethyl paraminophenol sulphate
Potassium metabisulfite	10 g
Pyrogallol	15 g	Kodak calls it pyro and defines it as 1:2:3 trihydroxybenzene
Water	to make 1000 mL	"Water to make 1000 c.c." The handbook gives no temperature for it here; its general instruction is that Elon is readily soluble in warm water, which is why it goes in first.
Kodak's printed order is also its stated general rule: the Elon first, because it is only slightly soluble in a sulphite solution without alkali; then the preservative; then the other developing agent.

Solution B — the alkali, and nothing else

Ingredient	Quantity	Form the source specifies
Sodium carbonate (anhydrous)	75 g or 200 g (crystalline, which is the handbook's main column)	anhydrous
Water	to make 1000 mL	"Water to make 1000 c.c." No temperature is given. A carbonate solution of this strength is easier to make warm and must be cool before it is used.

Mixed in the ratio — the working developer, mixed immediately before use

1 part Solution A + 1 part Solution B

Take 1 part of Solution A and 1 part of Solution B. Oxidation is very rapid and therefore solutions A and B should not be mixed until immediately before use. Develop for 2-3 minutes at 65 °F (18 °C).

The working bath holds 2.5 g/L of Elon, 5.0 g/L of potassium metabisulphite, 7.5 g/L of pyro and 37.5 g/L of anhydrous sodium carbonate. Kodak's sentence about oxidation is the only one of its kind in the handbook's developer section and it is part of the formula, not a caution attached to it.

Purpose

Kodak’s own header is the whole statement and it is unusually specific: “Pyro-‘Elon’ staining developer for rapid dish development of press and commercial negatives, giving high contrast and speed.” Five claims in one line — staining, rapid, dish, high contrast, speed — and no measurement behind any of them.

The word that matters most is staining, because Kodak has chosen it. A pyro developer’s oxidation product is yellow and is deposited in the film along with the silver, so the negative carries two densities: the silver and the colour. The staining and tanning developers lesson sets out what that is worth and what it costs, and the pyrogallol page carries what the course can and cannot establish about the product itself. This page does not restate either and does not go beyond them: the course cannot name the yellow compound, cannot give an equation for its formation and cannot describe the mechanism by which pyro tans gelatin, and nothing here quietly supplies any of the three.

Recommended uses

Press and commercial negatives, in a dish, in a hurry. That is what the header names.

Where a stain image is wanted with more energy than a classical pyro-soda gives. The working bath carries 37.5 g/L of anhydrous carbonate against the 7.5 g/L of Kodak’s A.B.C. pyro D-1, and it develops in two to three minutes against D-1’s seven to nine.

Where speed matters as much as the stain. This is the only pyro formula in the corpus that puts Elon beside the pyro rather than using pyro alone, and Kodak’s own header claims speed for it.

As the fast end of the pyro range, read against D-177. The two are printed a page apart in the same handbook, and between them they cover the class: D-167 fast, alkaline, unrestrained and Elon-assisted; D-177 slower, gentler, three solutions, with sulfite and bromide in it.

When another formula is preferable

• For general negatives with a stain image, D-177 or D-1, which are the pyro-soda developers of the same handbook and the same primer. D-167 is a specialist.
• Where no stain is wanted, D-76 or D-19. A hundred grams of sulfite per litre is the other end of the same dial.
• Where the negative must not be tanned, any non-pyro developer. Pyro hardens the gelatin it develops, which is a property and not a fault, and it is not always wanted.
• Where the darkroom cannot take a Level B agent, none of the pyro formulas. See Safety.
• Where a bath has to stand for a session. Kodak’s own instruction forbids mixing this one until it is needed, and the keeping table gives no figure for it in a dish that the course could read.

Mixing

Two bottles, in Kodak’s order, and mixed only when the tray is wanted.

1. Solution A. Dissolve the Elon first — Kodak’s general rule, because Elon is readily soluble in warm water and only slightly soluble in a sulphite solution without alkali, so a preservative dissolved first throws a white precipitate of the Elon base. Then 10 g of potassium metabisulphite. Then 15 g of pyro. Water to make 1,000 mL.
2. Solution B. Dissolve 75 g of anhydrous sodium carbonate — or 200 g of the crystals, which is the handbook’s main column — in water to make 1,000 mL.
3. The working developer. Equal parts, immediately before use.

That third step is an instruction and not a convenience. Kodak prints “oxidation is very rapid and therefore solutions A and B should not be mixed until immediately before use” inside the formula’s directions, in the place where other formulas print a development time. It is the only sentence of its kind in the handbook’s developer section.

🧮What equal parts put in the tray, and how it compares

Halving both stocks:

5.0 g/L ÷ 2 = 2.5 g per litre

Metol (Elon)

10.0 g/L ÷ 2 = 5.0 g per litre

Potassium metabisulphite

15.0 g/L ÷ 2 = 7.5 g per litre

Pyrogallol

75.0 g/L ÷ 2 = 37.5 g per litre

Sodium carbonate, anhydrous

Set that beside Kodak’s A.B.C. pyro D-1 at its tray dilution — 6 g/L of pyro, 10.5 g/L of sulfite and 7.5 g/L of carbonate — and the design is visible in one line. A quarter more pyro, half the preservative on a molar basis, five times the alkali, and an extra developing agent. D-1 develops in 7 to 9 minutes; D-167 in 2 to 3.

The preservative comparison needs a word of arithmetic, because the two formulas use different salts. Potassium metabisulphite is K₂S₂O₅ at 222.33 g/mol and gives two hydrogen sulfite ions on dissolving, so 5.0 g/L is about 0.045 mol/L of bisulfite. D-1’s 10.5 g/L of sodium sulfite at 126.05 g/mol is 0.083 mol/L. D-167 therefore carries a little over half D-1’s preservative, and D-1’s is already described in this course as a deliberately inadequate one. That is the course’s arithmetic on published weights, and it is the clearest single reason to expect this formula to stain hard.

Behaviour

It is fast, and Kodak says why it is dangerous to keep. Two to three minutes at 18 °C, from an alkali five times a classical pyro-soda’s. The same alkali is what makes the mixed bath oxidise as fast as it does; the primer’s general statement is that adding alkali to a developing agent increases its rate of oxidation enormously, and pyro is the agent it singles out as oxidising much more readily than Elon or para-aminophenol for a given amount of preservative.

The stocks keep and Kodak publishes the figures: three months in a full bottle, two months half full, both marked “in 2 solutions”. That is a good keeping record and it belongs entirely to the separation. The handbook’s storage advice applies with force here — bottle stock in small bottles, because the air space in a large one grows every time it is opened.

Twelve sheets of 8 by 10 per 160 fluid ounces in a narrow dish, twenty-four in a deep tank. The published useful life, and the lowest dish figure in the handbook’s developer table, shared with D-1, D-177 and D-82. A pyro developer is not an economical one.

Two cells of its keeping row could not be read, and this page says so rather than borrowing the neighbouring pyro rows’ 30 minutes in a dish and 3 hours in a tank. Those figures are D-1’s and D-177’s, not D-167’s.

There is no restrainer at all. No bromide anywhere in the formula, against D-177’s 1.7 g/L in its working stock and D-1’s 1.1 g/L in stock A. In a bath this alkaline that is a striking omission, and Kodak offers no comment on it. What the course can say is what the primer says generally — too much alkali produces chemical fog, and bromide is what compensates for it — and that D-167 is therefore relying on speed and on a short development time instead.

Image characteristics

A stained negative, on Kodak’s own word. The header calls it a staining developer, which settles that the colour is intended rather than tolerated.

High contrast and speed, on Kodak’s own word and no measurement. No characteristic curve, no development-time series and no comparison is printed for this formula anywhere the course has read. The claims are recorded as claims.

The stain is a second density and it does not photograph like the first. What that means for printing — that a stain image reads differently on graded and variable-contrast papers, and differently again through a densitometer’s blue and visual channels — is set out in the staining and tanning developers lesson and is not repeated here.

It will tan the gelatin as well as stain it. Pyro hardens the emulsion it develops. The pyrogallol page records that the tanning happens and that the course cannot describe the mechanism, and this page holds to that.

Everything after the tray has to respect the stain. The practices a modern pyro developer’s own maker publishes — a non-acid stop, a non-tanning fixer, a long wash, and no hypo eliminator, because the colouring intensifies during washing and an eliminator weakens it — are on the pyrogallol page. Kodak Limited prints none of them for D-167, and the difference between “Kodak did not say” and “it does not matter” is not one this course will collapse.

The mechanism

Two agents reduce exposed halide; one of them leaves its oxidation product behind.

AgBr + e⁻ → Ag + Br⁻

What both agents are doing

⚗Why this developer has to be two bottles, in Kodak's own words

The 1928 primer states the general case and then the particular one. The general case: a two-solution developer is a one-solution developer split into two parts, so that it oxidises less readily and therefore keeps well. The particular one: 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 says the same thing as a storage 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.

And it says it a third time, in the directions of this formula, as an instruction rather than a principle - oxidation is very rapid.

The acid preservative is the other half of the design. Potassium metabisulphite dissolves to give hydrogen sulfite, an acid salt, so Solution A is an acid solution of two developing agents:

S₂O₅²⁻ + H₂O → 2 HSO₃⁻

What the metabisulphite becomes in the bottle

The primer’s rule is that oxidation progresses less readily in acid than in alkaline solution, which is why an agent stock is preserved with an acid sulfite rather than a neutral one. It is the same reasoning that puts sodium bisulfite in D-9’s agent stock and in D-1’s.

What the course cannot say. It cannot name pyro’s yellow oxidation product, cannot give an equation for its formation and cannot describe how it hardens gelatin. The pyrogallol page records that gap explicitly, and this page does not fill it.

Function of every ingredient

Metol, 5.0 g/L in Solution A, 2.5 g/L in the tray. Kodak calls it Elon and its own front matter defines it as a specially purified form of monomethyl paraminophenol sulphate. It is the fast agent: high on Kodak’s reduction-potential ranking, needing the least alkali, working early and in the shadows. Its presence is what distinguishes D-167 from every other pyro formula in this corpus, all of which use pyro alone, and it is presumably where Kodak’s claim of speed in the header comes from — that last clause being a reading and not something the handbook says. More Elon would give a faster, flatter negative; less a slower and harder one. It carries the formula’s one mixing rule: dissolve it first, in warm water, because it is only slightly soluble in a sulphite solution without alkali and will otherwise precipitate as its insoluble base.

Potassium metabisulfite, 10.0 g/L in Solution A, 5.0 g/L in the tray. The preservative, and an acid one — it dissolves to hydrogen sulfite, so Solution A is an acid solution and the primer’s rule is that oxidation progresses less readily in acid than in alkali. But the important thing about this ingredient is how little of it there is. On a molar basis it is a little over half the preservative of Kodak’s A.B.C. pyro, and this course already describes that formula’s dose as deliberately inadequate: sulfite is the dial that decides whether a pyro developer stains, and a staining developer is that dial turned down. More of it would keep the stock longer and suppress the stain the header promises; less would give a stock that browns on the shelf. Kodak’s own chemical notes record that metabisulphite is a good preservative and an expensive one, costing two to three times sodium bisulfite for the same job, and that the two are customarily substituted weight for weight.

Pyrogallol, 15.0 g/L in Solution A, 7.5 g/L in the tray. Kodak calls it pyro and defines it as 1:2:3 trihydroxybenzene. It is the staining agent and the reason the formula exists: its oxidation product is yellow, is deposited in the film along with the silver, and adds a second density to the negative. It is also the agent Kodak names as oxidising much more readily than Elon or para-aminophenol for a given amount of preservative, which is why this developer is in two bottles. More pyro means more stain and more density; less means less of both. Three practical facts belong to its own page and matter here — it turns grey on exposure to light and air, Kodak supplied the crystal rather than the powder because the powder flies about the darkroom and settles on plates as spots, and it tans the gelatin it develops by a mechanism the course cannot describe.

Sodium carbonate, 75.0 g/L anhydrous in Solution B, 37.5 g/L in the tray. The alkali, alone in its bottle, and the largest carbonate dose in the developer half of this formulary — five times what D-1’s working solution carries and more than a paper developer such as D-72 holds at any of its published dilutions. It is what the two-to-three minutes are bought with. The primer’s rule is that the quantity of alkali governs the energy of a developer, that too much produces chemical fog, and that alkali softens gelatin and gives frilling or blisters in warm weather; with no bromide anywhere in this formula, the short development time is the only thing holding the first of those in check. The anhydrous salt is what the formula means and what the handbook recommends; its main column prints 200 g of the decahydrate crystals instead, and its own conversion rule is that crystals are used at two and a half times the anhydrous weight. Weighing crystals as though they were anhydrous would give a bath a third as alkaline as intended.

Water, a litre to each solution, both as make-up volumes. The handbook gives no temperature for either. Its general instruction supplies the practical half — Elon is readily soluble in warm water, which is why it goes in first — and the strength of Solution B is such that it is far easier to make warm than cold. The one thing the source does say about the meeting of the two waters is that it should happen as late as possible.

Interactions

With air, once mixed, and this is the formula’s defining interaction. Kodak’s instruction is categorical.

With the sulfite tub’s age. A small preservative dose is more sensitive to a stale tub than a large one, and metabisulphite loses sulfur dioxide on standing.

With everything after the tray. A stain image is affected by what follows it: the practices a modern pyro developer’s maker publishes — a non-acid stop, a non-tanning fixer, a long wash, no hypo eliminator — are recorded on the pyrogallol page. Kodak Limited publishes none of them for D-167, and this page will not put words in its mouth; a reader who wants the stain preserved has a manufacturer’s set of practices to draw on and the knowledge that they belong to a different formula.

With a non-hardening fixer, favourably, if the tanning is to be judged rather than added to. F-52 is the non-hardening bath in this formulary.

With warm weather, badly: an alkali this strong softens gelatin, and only pyro’s own tanning works the other way.

With iron. The primer’s chemical notes warn that bisulfite is difficult to prepare free from iron and that iron in the bisulfite produces a dark colour in a pyro solution. A stained developer is the one place where an accidental colour is hardest to diagnose.

Variants

D-177, the pyro-soda dish developer on the next page of the same handbook. Three solutions rather than two, sulfite as well as metabisulphite, bromide in the agent stock, no Elon, half the alkali and five to eight minutes rather than two to three. The two together are Kodak Limited’s whole pyro offering and they divide the class between them.

Kodak D-1, the standard A.B.C. pyro, printed in the 1928 primer and again in this handbook: three stocks, 6 g/L of pyro, 10.5 g/L of sulfite and 7.5 g/L of carbonate in the tray, 7 to 9 minutes at 18 °C. It is the classical formula this one is a press-room acceleration of. Its entry is planned and not yet written; the staining and tanning developers lesson prints its quantities.

The crystalline carbonate column, which is the handbook’s own main column and is recorded in the table above as the alternative form rather than as a variant, because it is the same formula stated in a different hydrate.

PMK, Pyrocat-HD and 510-Pyro are the modern pyro developers, and this course prints no composition for any of them: their makers do not publish one. Under the course’s ruling on proprietary formulations they are taught as behaviour and disclosed components only, and the staining lesson sets out exactly how much each datasheet does and does not give.

No course variant is offered. The obvious safening move — more preservative — is the move that destroys the stain, which is to say it produces a different developer rather than a safer version of this one.

Safety

Level B, and three of the four ingredients contribute.

Pyrogallol sets the level. Read its page before the jar is opened: the handling controls, the classification and the reason Kodak supplied a crystal rather than a powder are all there, and they are not summarised here. The short version is gloves, no dust, no skin contact, and weighing done deliberately.

Metol is the sensitiser. Metol dermatitis is the classic darkroom occupational complaint; gloves and no skin contact with the working bath.

Potassium metabisulfite gives sulfur dioxide in acid, and Solution A is acid. Weigh it in moving air, keep the tub closed, and keep every stronger acid away from the stock and its waste. Anyone with asthma should read that page first.

Sodium carbonate at 75 g/L is a strong alkali — not caustic, but not a mild solution either. Gloves and eye protection, and no dust while weighing.

Ventilation as for any darkroom, with the caveat that this formula’s agent stock is one of the few in the course that can smell of sulfur dioxide if it is old or if something acid has reached it.

Storage

Three months in a full stoppered bottle and two months half full, as the two solutions. Kodak’s own figures, and a good record — which belongs to the separation and not to the chemistry, because the mixed bath is not to be stored at all.

Small bottles. The handbook’s own advice, and it matters most for a stock with this little preservative in it: the air space in a large bottle increases every time it is opened.

Solution A dark as well as closed. Pyro turns grey on exposure to light and air, per its own page, and a browning agent stock is a stock that has already made some of the stain in the bottle instead of in the film.

The mixed developer is not stored, and Kodak says so inside the formula. Mix what the dish needs.

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. Label Solution A as containing pyro in words a person who has not read this page would understand.

Incompatibilities

Acids, with Solution A: metabisulphite plus a strong acid gives sulfur dioxide, and the stock is already acid.

Oxidising agents of every kind. Pyro is the most readily oxidised agent in the course.

Iron, from a tray, a clip or a contaminated tub: the primer records that iron in the bisulfite gives a dark colour in a pyro solution.

Fixer, in either direction. One pair of tongs per tray, and the more so with a bath that stains.

Light and air, for Solution A, which is a storage matter and an incompatibility in the practical sense.

Anything the incompatibilities page lists against a reducing agent or an alkali, which is the page to read rather than this paragraph.

Waste

Developer waste, alkaline, and carrying pyro and its oxidation products. It is not the silver stream; that is the fixer’s.

Keep it out of the acid stream, both because developer and fixer wastes are collected separately and because Solution A’s metabisulphite gives sulfur dioxide with acid.

Pyro is the constituent that makes this more than soapy water. Collect it, label it, and 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

A white precipitate while mixing Solution A. The metabisulphite went in before the Elon. Kodak’s own rule is Elon first; the precipitate is the insoluble Elon base, and in this formula there is no carbonate in the same bottle to redissolve it. Re-make the stock.

Solution A has gone brown or grey. Oxidation, and with this little preservative there is not much margin. Check the age of the metabisulphite tub, keep the bottle full and dark, and bottle it small.

The mixed bath went dark in the dish. Expected, and it is why Kodak forbids mixing it in advance. Mix for the sheet.

Fog, or a grey veil over the whole negative. An alkali this strong with no bromide in the formula has little defence. Check the carbonate arithmetic first — anhydrous weighed as though it were crystals gives a bath nearly three times as alkaline as intended — and take the shorter end of the two-to-three minutes.

The negative is thin. Two to three minutes is a short bracket. Check the temperature, and check whether Solution A is an old bottle: an oxidised agent stock develops less and stains more.

The stain is much stronger or weaker than expected. The preservative is the dial. A stale metabisulphite tub gives more stain; a generous weighing gives less. Neither is a fault of the formula.

Yellow-brown spots on the negative, not related to the image. Pyro dust. Kodak supplied the crystal rather than the powder for exactly this reason.

The negative is unusually hard to fix or dries oddly. Pyro tans the gelatin it develops. This is a property of the class and it is on the pyrogallol page.

Experiments

Measure the stain as a density in two channels. Develop a step wedge in D-167 and read it visually and through a blue filter. The difference between the two readings is the stain, and the staining lesson explains why it matters which one you print by. Kodak claims high contrast and publishes no curve at all.

Turn the preservative dial. Make Solution A at 10, 20 and 40 g/L of metabisulphite, everything else unchanged, and develop identical wedges. The claim in this course is that sulfite is the dial that decides whether a pyro developer stains; D-167’s dose is the low end of it and nobody has plotted the middle.

Test Kodak’s own instruction. Mix a working bath and use half of it at once; try the rest at fifteen minutes, an hour and a day on identical strips, recording the colour of the solution with the result. “Oxidation is very rapid” is not a number. Make it one.

Race it against D-1 and D-177. Same film, same exposure, each developed to the same visual density: 2 to 3 minutes here, 5 to 8 in D-177, 7 to 9 in D-1. Then read all three for stain, for grain and for the shape of the curve. Kodak prints all three formulas in one handbook and compares them nowhere.

Find the fog threshold. This formula has no restrainer. Add potassium bromide to the working bath at 0.5, 1 and 2 g/L and read the unexposed density each time. If the fog falls appreciably, Kodak’s omission is worth understanding; if it does not, the two-minute development is doing the work.