Kodak D-52

Every other paper developer in this library arrives with its restrainer already in it. This one does not. Kodak’s 1928 primer prints a four-chemical stock with no potassium bromide at all, and then gives four different bromide additions to be made at the tray — one for each of four named papers. That makes it the formula in this library that treats the restrainer as what it actually is: a setting, not an ingredient.

Ingredient	Quantity	Form the source specifies
Metol	1.5 g	Kodak calls it Elon
Sodium sulfite	22.5 g	Kodak’s own tested grade
Hydroquinone	6.3 g
Sodium carbonate	15.0 g	Kodak’s own tested grade
Water to make	1000 mL	500 mL of it at about 52 °C to start

Potassium bromide is added afterwards, to the diluted working solution, at one of four published rates.

Purpose

To develop any of a family of papers from one stock, with the restrainer set for each. The stock itself is the weakest in this library — half D-72’s metol, half its hydroquinone, and less than a quarter of its alkali — and the working baths derived from it are gentle.

Recommended uses

Four combinations, all developed for not less than one and a quarter minutes at 21 °C:

Paper	Dilution	Bromide added	Bromide in the working bath	Carbonate in the working bath
Vitava Alba	undiluted	4 mL of 10 % per litre	0.4 g/L	15.0 g/L
Vitava Rapid Black	undiluted	16 mL of 10 % per litre	1.6 g/L	15.0 g/L
Vitava Athena	1:1	8 mL of 10 % per litre	0.8 g/L	7.5 g/L
Vitava Zelta	1:1	16 mL of 10 % per litre	1.6 g/L	7.5 g/L

What the course can and cannot tell you about those four papers. The primer names them and nothing more — no emulsion type, no surface, no contrast grade, no image colour. So the course will not say what Alba or Zelta were. What it can say is what Kodak thought each of them needed, and that is readable straight off the table: a four-fold range of restrainer, and a two-fold range of alkali, arranged so that Alba gets the most vigorous bath in the set and Zelta the least.

When another formula is preferable

• For general printing from a stock that needs no additions, D-72, which is the neighbouring formula on the same page of the primer.
• For a softer print at normal strength, D-49.
• For a published warm tone rather than a printer-adjusted one, D-156 and D-166, which take the same two levers a great deal further and put a colour claim on the result.
• For low contrast without a restrainer decision, D-165, which drops the hydroquinone instead.

Mixing

Dissolve in the order given, starting with 500 mL of water at about 52 °C and making up to a litre cold. Kodak Limited’s later handbook states the rule the 1928 order follows: the Elon first, because it is readily soluble in warm water but only slightly soluble in a sulfite solution with no alkali in it; the preservative next; the second agent; the alkali last.

1. Metol, dissolved completely in the warm half-litre.
2. Sodium sulfite.
3. Hydroquinone.
4. Sodium carbonate.
5. Cold water to 1000 mL. The stock is finished; the bromide is not part of it.

Then, at the tray: dilute as the paper requires, and add the bromide to the diluted solution at the published rate. The distinction matters. Kodak’s instruction is per litre of developer as diluted for use, not per litre of stock, so adding 16 mL to a litre of stock and then diluting it 1:1 gives half the intended dose.

🧮Keeping a 10 per cent bromide stock, and why this formula needs one

A 10 per cent w/v solution contains 0.1 g of potassium bromide in every millilitre, so 4, 8 and 16 mL are 0.4, 0.8 and 1.6 g. Weighing those directly is possible; doing it four different ways in a printing session, in the dark, is not.

Make up 100 mL by dissolving 10.0 g of potassium bromide and making up to the mark, label it with its strength and the date per the labelling SOP, and dispense it with a syringe or a graduated pipette. The mixing SOP has the general procedure. This one bottle serves most of the formulas in this library, and it is the difference between a restrainer you can adjust and one you cannot.

Note also that the added solution is water: 16 mL in a litre is 1.6 per cent dilution of everything else, which is below anything that matters here but is exactly the kind of arithmetic that stops being negligible if you scale a formula up.

Behaviour

A weak stock, gently diluted, developing slowly. The published minimum is one and a quarter minutes for all four papers, which is longer than D-72 needs on a chloride paper and shorter than D-49 needs on a bromide one. Nothing here is in a hurry.

One time for four baths is the interesting instruction. Kodak varies the dilution and the bromide across the four papers and does not vary the time. That is the same discipline D-166 states explicitly a generation later: development time is not the control, because a print is developed to completion and lengthening the time adds density rather than changing the character of the result. Change the bath, hold the time, and compensate with exposure.

Nothing about its life is published. The 1928 primer gives no keeping table for developers and no sheet count for this formula, so this page carries no capacity and no shelf life. That is an absence in the source. Measure your own and record them in the lab notebook.

Image characteristics

Contrast. Gentle, and adjustable by the printer within a range Kodak defined. Tonality. Long, from a low-alkali bath. Colour. Not stated for any of the four papers. The chemistry points one way — the Zelta bath has the least alkali and the most bromide of the four, which is the direction Kodak’s warm-tone formulas move — but the primer makes no claim and neither does this page. Staining. None. Grain, acutance and speed are not meaningful properties of a paper developer.

The mechanism

15.0 g/L ÷ 105.99 g/mol = 0.142 mol/L

Sodium carbonate in the stock

6.3 g/L ÷ 110.11 g/mol = 0.057 mol/L

Hydroquinone in the stock

1.5 g/L ÷ 344.38 g/mol = 0.0044 mol/L

Metol in the stock, as the hemisulfate

0.4 to 1.6 g/L, or 0.0034 to 0.0134 mol/L

Bromide, across the four working baths

Why the bromide can be left out of the bottle. Kodak Limited’s handbook says it in one line: potassium bromide has no action on the developing agents, so it is immaterial at what stage it is added. Every other ingredient here has to be in the bottle because it interacts with the others while they dissolve — the metol needs to be in solution before the sulfite, the agents need the preservative before the alkali. The restrainer does not participate in any of that. It acts on the emulsion, not on the developer, so it can wait until the tray.

Why it is the right variable to hand to the printer. Bromide affects hydroquinone strongly and metol much less, which the 1928 primer states directly. So a bromide addition acts almost entirely on the agent that builds density steadily and rapidly, and leaves the agent that starts the image alone. The practical result is that adding bromide cleans up the whites and holds back the highlight densities without making the print slow to appear — which is precisely the adjustment a printer wants per paper, and precisely the one that a change in dilution or time could not give.

Where the four baths sit. Alba’s bath is the strongest and least restrained of the four; Zelta’s is the weakest and most restrained; Rapid Black gets full alkali with heavy restraint, and Athena a middling amount of both. Two variables, four settings, one time. Whatever those papers were, Kodak was compensating for differences in their speed and their fogging tendency, and it was doing it with the two levers this library uses everywhere else.

A caution about the stock’s own weakness. With only 0.142 mol/L of carbonate the stock is already close to the alkalinity of D-156’s stock, and halving it again for Athena and Zelta takes it below. A bath this gentle has very little reserve, and its behaviour will change noticeably as it works.

Function of every ingredient

Metol, 1.5 g. The starting agent, at half D-72’s dose. It has the highest reduction potential of the agents Kodak ranked, so it begins in the lightly exposed regions and brings the image up everywhere at once, and it is the agent the added bromide barely touches — which is what keeps all four working baths starting at about the same speed regardless of how much bromide went in. More metol would speed the appearance and reduce the effect of the printer’s adjustments; less and the bath would fail to start against 1.6 g/L of bromide. It is a skin sensitiser and sets this page’s safety level.

Sodium sulfite, 22.5 g. The preservative and the acid reserve, scaled to the agents. It scavenges dissolved oxygen and intercepts the oxidised agents before they form coloured products, and it carries most of what the stop bath has to neutralise out of a print. At half D-72’s dose in a stock that is then sometimes diluted again, the protection in the tray is thin, and an open dish of the Athena or Zelta bath should be regarded as a session’s worth and no more. More sulfite keeps longer; less and the tray browns.

Hydroquinone, 6.3 g. The contrast agent, at four times the metol by mass — the standard print ratio at half the usual quantity. It gains density steadily and rapidly, decides how black the blacks are, and is the agent everything else in this formula is arranged to modulate: the low alkali restrains it, and the printer’s bromide restrains it further. It is strongly temperature dependent. More hydroquinone raises contrast and would narrow the useful range of the bromide adjustment; less and one and a quarter minutes will not produce a black.

Sodium carbonate, anhydrous, 15.0 g. The alkali, at less than a quarter of D-72’s. It sets the pH region in which hydroquinone works and supplies a carbonate–bicarbonate buffer to hold it. Kodak uses it as the second of its two per-paper levers, at full strength for Alba and Rapid Black and halved for Athena and Zelta. More carbonate speeds the bath and reduces the printer’s control; less and the published time becomes a fiction. The primer’s own rule applies — too much alkali produces chemical fog, too little makes the developer slow, and alkalis soften the gelatin.

Potassium bromide, 0.4 to 1.6 g per litre of working bath. The restrainer, and the only ingredient in this formulary that the source deliberately leaves to the user. It suppresses development of grains carrying no latent image, which keeps the whites of a print white; because it acts far more strongly on hydroquinone than on metol, it holds back the highlight densities specifically. More bromide gives cleaner whites, a slower and warmer print and eventually a loss of shadow separation; less fogs. The four published doses are Kodak’s, for Kodak’s papers; for any other paper the dose is yours to find, and finding it is the experiment at the foot of this page.

Water to 1000 mL. Not inert. Iron is the classic contaminant; a stock that has crystallised in the cold is warmed and redissolved rather than decanted.

Interactions

Restrainer and agent. The asymmetry — bromide acts on hydroquinone far more than on metol — is what makes a per-paper bromide dose a sensible instrument rather than a blunt one. It changes the character of the development rather than merely its speed. Part VIII covers restrainers.

Restrainer and alkali. Kodak moves both across the four papers, and they are not independent: both act on the hydroquinone, from opposite directions. Alba’s bath has twice Zelta’s alkali and a quarter of its bromide, which is the widest separation of any pair here.

Agent and agent. The two develop faster together than separately — superadditivity — and at half the usual doses that cooperation is what keeps this weak stock working at all. No source this course holds explains the effect, so no explanation is offered for it here.

Bromide and the emulsion. Worth stating explicitly because it is the reason this formula’s design works: the restrainer acts at the surface of the silver halide grain, not on the developing agents in solution. That is why it can be added last, why the dose depends on the paper rather than on the developer, and why it is the ingredient a printer can reasonably be asked to set.

Variants

D-72 and D-49 are printed on the same pages of the same book, and the three together are a good short course in paper-developer design: one general formula, one softened by alkali, and one deliberately left open at the restrainer.

The formulas Kodak did not print here. The primer closes its paper section by saying that additional formulas are to be found in the Book of Formulas for Eastman Papers. That document is not in this course’s corpus, so whatever it contained is not published here. Under Rule 6 an unreadable source is not a source.

The course’s own variants belong in the formula version record — and this is the formula that most invites them, because Kodak has already shown you which two knobs to turn.

Safety

Level B, on metol, a skin sensitiser whose sensitisation is permanent, and hydroquinone, which carries a Danger classification with suspected carcinogenicity and mutagenicity and causes serious eye damage. Both are at the lowest doses in this library, which changes the splash hazard and not the sensitisation risk. Sodium carbonate at 15 g/L is the mildest alkali concentration here.

The bromide stock is the thing to handle carefully in this workflow. A 10 per cent solution is mild — potassium bromide is classified for skin and eye irritation with possible respiratory irritation — but making it means weighing 10 g of a fine hygroscopic powder, and it is a bottle that will live in the darkroom and be opened often. Weigh it with extraction running or inside an enclosure, label it clearly, and keep it away from the trays it is not going into.

Print tongs, one pair per tray, never interchanged. The classification rubric sets what Level B assumes and the gloves page covers the choice.

Storage

No keeping figures are published. The library’s general practice applies: stock in a tightly closed bottle filled as full as it will go, in several small bottles rather than one large one; working solution mixed for the session.

Label the working bath with its bromide dose as well as its dilution. This is the one formula here where two trays of the same dilution can be chemically different, and an unlabelled dish is one you will have to throw away. The labelling SOP has the fields.

Keep the 10 per cent bromide stock dated. It does not spoil in any way the course can source, but a bottle of unknown strength makes every one of the four doses meaningless.

Incompatibilities

Acid, deliberately, in the next tray. With only 15 g/L of carbonate in the stock and half that in two of the working baths, this is the formula in the library least able to absorb a splash of stop bath. Tongs never travel backwards along the sequence.

Fixer, in either direction. Thiosulfate carried back fogs and stains; developer carried forward raises the fixer’s pH, with the white sludge and brown-staining prints the 1928 primer describes.

Oxidising agents — ferricyanide, permanganate, persulfate — never meet a developing agent in a bottle or a drain. See chemical incompatibilities.

Waste

A dilute alkaline solution carrying two developing agents with aquatic-toxicity classifications, plus whatever bromide was added. Essentially no silver. Its own labelled container, never the fixer bottle. The disposal caveat governs and the general chemical waste SOP gives the procedure. Local regulation decides.

Troubleshooting

Grey, veiled whites. The first thing to check is whether the bromide went in at all. In a formula whose stock contains none, a forgotten addition is the easiest mistake in the library to make, and its symptom is exactly this.

Whites clean, blacks weak, development interminable. Too much bromide, most often because the addition was made to the stock and then not scaled for the dilution, or made twice.

A print that will not finish in a minute and a quarter. Expected on a cold bath; this is the gentlest formula here and it has the least in reserve. Bring the tray to 21 °C.

Different results from two trays that should match. Label the trays. See Storage.

Nothing like the results you expected from a named Vitava setting. Those settings were for those papers, and no paper sold today is one of them. Treat the four doses as a demonstrated range and find your own within it.

Experiments

Find your own bromide dose. Take one paper and one negative. Mix four working baths at the same dilution with 0, 0.4, 0.8 and 1.6 g/L of bromide, develop each print to completion for the same time, and match density by exposure. Compare maximum black, highlight cleanliness and image colour. This is Kodak’s four-paper table turned into a one-paper calibration, and it is the single most useful afternoon in this part of the formulary. Record it against the developer laboratory report.

Separate the two levers. Kodak varies dilution and bromide together across its four settings. Run the four combinations of 7.5 and 15 g/L of carbonate with 0.4 and 1.6 g/L of bromide, and see whether the effects add or interfere. The mechanism section above predicts interference, because both act on the same agent.

Test the “add it last” claim. Mix one litre with the bromide dissolved into the stock and one with it added to the diluted bath, at the same final concentration, and compare prints. Kodak Limited’s handbook says the stage does not matter. If it does for you, the difference is arithmetic — check the dilution — rather than chemistry.

Time against bromide. Develop the same paper for 75, 120 and 180 seconds in the 1.6 g/L bath. If the print gets darker but no cleaner, then time and bromide are doing genuinely different things, which is the claim this page rests on.