Kodak D-163

Kodak Limited describes this one twice, four pages apart, and the two descriptions are worth reading together. The formula page calls it “a special developer for papers giving normal to high contrast; suitable also as a dish developer for negative materials; recommended for tropical use for papers”. The product list calls it “a universal developer for papers, giving normal or high contrast; suitable also as a dish developer for negative materials. Recommended for tropical use.” One stock solution, four published paper regimes, a negative regime, and a chart for developing in a hot room. It is the most instruction Kodak prints for any single formula in the handbook.

Ingredient	Quantity	Form the source specifies
Metol	2.3 g	Kodak calls it Elon
Sodium sulfite	75.0 g	anhydrous — or 150.0 g crystalline
Hydroquinone	17.0 g
Sodium carbonate	65.0 g	anhydrous — or 175.0 g of the crystals
Potassium bromide	2.8 g	or 28 mL of a 10 per cent solution
Water to make	1000 mL

Purpose

To develop any of Kodak Limited’s paper families to normal or high contrast from a single stock, and to keep working while it does it. Two properties set it apart from D-72: the hydroquinone is the highest in this library at 17 g/L against a metol dose of only 2.3 g/L, and the sulfite reserve is the largest at 75 g/L. The first is where “normal to high contrast” comes from. The second is why Kodak offers a stronger dilution purely for working life, and why this is the formula it recommends for the tropics.

Recommended uses

Bromide enlarging papers at 1:3, two minutes at 18 °C — the everyday case. Bromide papers at 1:1, also two minutes, when a long session will otherwise exhaust the dish. Bromesko papers at 1:3, one and a half minutes for the white glossy surface and one and a half to two for the others. Velox and gaslight contact papers at 1:1, 60 to 120 seconds. Negatives in a dish at 1:3, five to ten minutes.

That 1:1 bromide-paper instruction is worth pausing on, because it is not the usual reason a manufacturer offers a second dilution. Kodak does not claim it gives more contrast or a different tone; it says, in as many words, for longer working life, and it leaves the development time unchanged at two minutes. A bath twice as strong, working for the same time, has simply been given twice as much of everything to spend.

When another formula is preferable

• For a warm image tone, this is the wrong family entirely. D-156 and D-166 carry two and five times its bromide and much less carbonate, which is how Kodak buys warmth.
• For low contrast on lantern plates and bromide paper, D-165 removes the hydroquinone altogether.
• For chloride paper with a blue-black tone as the stated aim, D-158 is the developer built for Velox rather than one that also suits it.
• If metol is a problem for your skin, D-173 is Kodak’s own metol-free paper developer.
• For the simplest possible print developer to learn on, D-72 has fewer instructions attached and is documented in two independent printings.

Mixing

Dissolve in the order printed. Kodak Limited’s general rule, stated once in the handbook and applying to every formula in it: a developing agent dissolved before the preservative oxidises in air and forms coloured products, and where the formula contains Elon, the Elon goes first because it is readily soluble in warm water but only slightly soluble in a sulfite solution with no alkali in it. The handbook adds that potassium bromide has no action on the developing agents, so it is immaterial at what stage it goes in.

1. Dissolve the metol completely, in warm water.
2. Add the sodium sulfite.
3. Add the hydroquinone.
4. Add the sodium carbonate.
5. Add the potassium bromide, or 28 mL of a 10 per cent stock solution.
6. Make up to 1000 mL.

!One system of weights, all the way down

The handbook prints every sulfite and carbonate twice — 150.0 g of the crystals or 75.0 g anhydrous; 175.0 g of the crystals or 65.0 g anhydrous — and recommends the anhydrous forms for stability, ease of solution and bulk. The carbonate ratio here is 175 ÷ 65 = 2.69, which is the decahydrate’s molar ratio of 2.70 and not the two-and-a-half the handbook’s prose offers as a rule of thumb.

The same page carries the warning in capitals: the avoirdupois and metric columns “are not exact equivalents”, so one or the other must be used exclusively. Weigh in grams, or weigh in grains, and do not convert halfway down the list.

Behaviour

The stock is concentrated and the working baths are not. At 1:3 the working solution holds about 16 g/L of carbonate and 4.25 g/L of hydroquinone, which is a gentler bath than D-72 at 1:2. The vigour comes from the ratio of the agents rather than from brute alkalinity.

Capacity is published for prints, which is rare. The 1949 table gives 30 sheets of 8 × 10 inches per 160 fluid ounces at 1:3 and 36 at 1:1, both in a narrow dish, and a separate negative figure of 15 in a dish and 30 in a deep tank at 1:3. Two things follow. First, going from 1:3 to 1:1 — doubling the concentration — buys only a fifth more prints, which says that a dish’s working life is limited by aerial oxidation and carried-away volume as much as by chemical exhaustion. Second, prints exhaust a bath twice as fast as negatives do per sheet, which is what you would expect from a material that develops to completion.

⚗The maker's time–temperature chart, and what it is for

Printed immediately beneath this formula in the handbook, and applying to Kodak papers generally rather than to this developer alone, is a chart converting a development time at 65 °F to the equivalent at four higher temperatures. Reproduced as the handbook gives it:

18 °C (65 °F)	21 °C (70 °F)	24 °C (75 °F)	27 °C (80 °F)	30 °C (85 °F)
60 sec	45 sec	30 sec	25 sec	20 sec
90 sec	65 sec	45 sec	35 sec	25 sec
120 sec	90 sec	60 sec	45 sec	35 sec

The middle row is the useful one to read carefully: 90 seconds at 18 °C becomes 25 seconds at 30 °C, a factor of 3.6 across twelve degrees. That is a much steeper dependence than most darkroom rules of thumb allow, and it is the reason a formula gets recommended “for tropical use” at all. A print developer that finishes in 25 seconds is one where the difference between a print and a ruined print is a few seconds of inattention, and where a warm bath softens the gelatin as well — the 1928 primer notes that alkalis soften the emulsion and that an over-alkaline bath gives frilling and blisters in warm weather. This formula’s answer to both is its bromide and its sulfite, not a lower alkali.

The chart is Kodak’s, for Kodak papers of the period. It is not a general law and the course does not present it as one; the useful thing is its shape, which your own paper will have too and which you can measure in an afternoon.

Image characteristics

Contrast. Normal to high, and the highest of the Kodak paper formulas this course can publish. Tonality. Vigorous, with a strong maximum black. Colour. The handbook makes no colour claim for it, which in a family where D-156 and D-166 are sold on their tone is a statement in itself: this is the neutral member. Staining. None; 75 g/L of sulfite is a large interception reserve. Grain, acutance and speed are not meaningful properties of a print developer, and where this formula is used on negatives the handbook publishes no claim about any of them.

The mechanism

17.0 g/L ÷ 110.11 g/mol = 0.154 mol/L

Hydroquinone

2.3 g/L ÷ 344.38 g/mol = 0.0067 mol/L

Metol, as the hemisulfate

75.0 g/L ÷ 126.05 g/mol = 0.595 mol/L

Sodium sulfite

65.0 g/L ÷ 105.99 g/mol = 0.613 mol/L

Sodium carbonate

2.8 g/L ÷ 119.00 g/mol = 0.024 mol/L

Potassium bromide

Twenty-three hydroquinones to every metol, by moles. That ratio is the formula. The 1928 primer describes what each agent does in the tray: an Elon image “comes up very quickly and gains density slowly”, a hydroquinone image “comes up very slowly but gains density steadily and rapidly”. A bath with just enough metol to start the image and a great deal of hydroquinone to build it is a bath that separates the two behaviours as far as they will go — which is what a high-contrast developer is. It is also why the first appearance of the image tells you almost nothing here about how the print will finish.

The alkali is not the aggressive part. At 0.613 mol/L the carbonate is slightly below D-72’s 0.637 mol/L, and the working dilutions take it further down. Kodak did not reach for more alkali to get more contrast; it changed the ratio of the agents and left the pH region alone. That is a genuinely instructive design decision, because raising the alkali would have raised chemical fog and softened the gelatin — both of which the 1928 primer names — in a formula intended for hot darkrooms where both are already worse.

The sulfite is doing two things at 0.595 mol/L. It is the preservative, and it is the acid reserve that keeps the pH from falling as the agents are consumed and as the paper carries acid in. At this concentration it is approaching the region where sulfite becomes a silver solvent, and on film that would begin to matter; on paper it does not, because a print’s grain is far below anything visible and there is nothing to be gained by dissolving the image.

The bromide is set for the conditions rather than for the tone. At 0.024 mol/L it is half as much again as D-72’s, and it lands where it is needed: the 1928 primer records that bromide affects hydroquinone strongly and Elon much less, and this bath is overwhelmingly a hydroquinone bath. In a warm darkroom, where fog rises fastest, a restrainer aimed at the dominant agent is the efficient control. Part VIII covers restrainers in general.

Function of every ingredient

Metol, 2.3 g. The starter, and the smallest dose in the paper library. It has the highest reduction potential of the agents Kodak ranked, so it begins development in the thinly exposed regions and brings the whole image up at once; it is barely restrained by the bromide, so its contribution holds steady as the bath ages. At this dose it is present to get the reaction going and to make the hydroquinone superadditive, not to build density. More metol softens the print and speeds the first appearance; less and the bath becomes a slow hydroquinone developer that builds highlights before shadows. It is a skin sensitiser, and it is why this page is Level B.

Sodium sulfite, 75.0 g anhydrous. The preservative and the reserve. It scavenges dissolved oxygen and intercepts the oxidised forms of both agents before they become coloured products — which is what allows a dish of this developer to work through a long printing session without browning. It also supplies most of the acid-absorbing capacity, which is what a stop bath has to neutralise out of a carried-over print. More sulfite keeps better still and begins to dissolve silver, which costs print density for no gain; less and this formula loses the working life that is its whole selling point.

Hydroquinone, 17.0 g. The contrast agent and the bulk of the formula. It is the one that gains density steadily and rapidly, the one that decides how black the blacks are, and the one that is strongly temperature dependent — the 1928 primer notes that a small temperature change affects hydroquinone greatly and Elon very little, which is exactly why this formula needed a time–temperature chart. More hydroquinone raises contrast and maximum black and shortens the bath’s life; less and the vigour that distinguishes this formula from D-72 disappears. It carries the heaviest hazard classification on the page.

Sodium carbonate, anhydrous, 65.0 g (or 175.0 g of the crystals). The alkali. It puts the bath in the region where hydroquinone is an active agent rather than a reserve, and it supplies a carbonate–bicarbonate buffer pair so that the pH does not fall away as development proceeds. More carbonate means a faster bath, more chemical fog and a more swollen gelatin, which in a warm darkroom means frilling; less means a bath that will not reach maximum black in two minutes. That Kodak chose slightly less than D-72 for a more contrasty developer is the point worth carrying away.

Potassium bromide, 2.8 g. The restrainer. It suppresses development of grains carrying no latent image, which keeps the paper’s whites white and lets a safelight be survivable. Because it acts much more strongly on hydroquinone than on metol, its effect concentrates on the agent doing most of the work here. More bromide gives cleaner whites, a warmer tone and a slower bath, and eventually costs shadow separation; less gives a faster, colder, foggier print — and in a hot darkroom, a fogged one. The 10 per cent solution alternative is the practical form, since 2.8 g is an awkward weight.

Water to 1000 mL. Not inert. Iron is the classic contaminant, and a stock that has stood cold enough to crystallise has lost its most important constituents into the precipitate, which the handbook says must be redissolved by warming rather than discarded.

Interactions

Agent and agent. Metol and hydroquinone together develop faster than the sum of their separate contributions, which is superadditivity, and this formula leans on it harder than any other in the paper library because it has so little metol to spare. The usual explanation, that hydroquinone regenerates oxidised metol, is not stated by any source this course holds, and this page does not assert it.

Agent and alkali. The carbonate decides that hydroquinone is awake. Take the alkali away and the same 17 g/L becomes nearly inert, which is what Part VIII’s page on alkalis works through.

Agent and restrainer. Unequal by design. Bromide restrains hydroquinone far more than metol, so adding bromide to this bath does not slow it evenly — it slows the contrast-building half, warms the image and cleans the whites. That asymmetry is what the whole warm-tone family exploits.

Sulfite and dilution. Because Kodak’s two paper dilutions differ only in concentration, the 1:1 bath has twice the sulfite reserve of the 1:3 bath and the same development time. The published capacities say that this buys about twenty per cent more prints, not twice as many, which is the cleanest evidence in this library that a dish’s life is not purely a chemical quantity.

Variants

D-166 is described in the handbook as an alternative for bromide papers, and has its own entry; it is a quite different formula rather than a modification of this one, and it is an extra-warm-tone developer where this is a neutral one.

The packed powder and the liquid. The handbook marks D-163 as available as a Kodak packed developer powder and in solution form. The course publishes the formula, not the product: no document in the corpus states the composition of the packaged version, and under Rule 6 the two are not assumed to be the same thing. Where the handbook does state a relationship between a formula and its packaged liquid it says so explicitly — as it does for D-166, whose liquid form it states is double the strength of the mixed stock — and no such statement exists here.

The course’s own variants belong in the formula version record. “D-163” names a formula; a version number names a litre you mixed with one changed variable.

Safety

Level B. Metol is a skin sensitiser and sensitisation is permanent. Hydroquinone carries a Danger classification with suspected carcinogenicity and mutagenicity and causes serious eye damage — and at 17 g/L this stock holds more of it than any other formula in the paper library. Sodium carbonate at 65 g/L is an eye hazard in its own right, which is what makes the stock more dangerous than the working bath by a factor of four.

Weighing is the hazardous operation. Four of the five are powders and two are fine ones. Weigh with extraction running or inside an enclosure, never in a draught, with splash goggles on. Once the bath is diluted 1:3 the concentrations are modest, but a sensitiser is a sensitiser at any dilution: print tongs, one pair per tray, and gloves if your hands go in.

The tropical recommendation has a safety edge to it as well. Working a print developer at 30 °C means faster evaporation from an open dish, a bath that concentrates as the session goes on, and a warmer aerosol above it. The classification rubric sets what Level B assumes about ventilation, and a hot darkroom needs more of it rather than less.

Storage

Stock in a tightly closed bottle, filled as full as it will go: three months full, one month half-filled. The handbook is specific that glass stoppers stick when the solution is alkaline, and that stock keeps better in several small bottles than drawn repeatedly from one large one.

Working solution: 24 hours in a dish, one to two weeks in a covered tank. Label everything with the formula, the dilution and the date, per the labelling SOP — this is a formula with two working dilutions that look identical, and an unlabelled bottle of one of them is a bottle you will have to throw away.

Incompatibilities

Acid, deliberately, in the next tray. A splash of stop bath in the developer does not just consume a little carbonate — it drops the pH below the region where hydroquinone works, and in a bath that is seven parts hydroquinone to one part metol that is close to switching the developer off. Never move tongs from the stop tray back into the developer. Part X has the chemistry.

Fixer, in either direction. Thiosulfate carried back into developer is an aggressive silver solvent and will fog and stain; developer carried forward raises the fixer’s pH, and the 1928 primer records what follows — a white sludge, an alkaline bath and prints likely to stain brown.

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

Waste

Spent D-163 is a dilute alkaline solution carrying two developing agents with aquatic-toxicity classifications. It carries essentially no silver, because silver leaves a print in the fixer, so it goes into its own labelled container rather than into the fixer bottle, which would spoil a solution worth recovering. The stock solution is the concentrated form of the same problem and is never poured away as though it were the working bath.

The disposal caveat governs and the general chemical waste SOP gives the procedure. Local regulation decides.

Troubleshooting

Prints too contrasty, with blocked highlights and empty shadows. This formula’s normal state at the wrong dilution or on the wrong paper. Check that you are at 1:3 and not 1:1, and remember that Kodak’s 1:1 instruction is about working life rather than contrast — if you mixed it for contrast you have made a mistake the handbook did not invite.

A bath that dies faster than the published 30 prints. Almost always temperature and evaporation rather than chemistry. An open dish at 25 °C loses volume and concentrates while it oxidises; the capacity figures are for 65 to 70 °F.

Flat prints in a hot darkroom. Counter-intuitive, and usually a stale bath rather than a cold one. At 30 °C the published times fall to a third, so a bath that has been standing is being asked to work three times as fast as it can.

Whites turning grey through a long session. Bromide exhaustion is not the cause — bromide accumulates as the paper releases it. Look at safelight fog and at a bath that has warmed up, both of which get worse as a session goes on.

Slow, weak development after a splash of something. If the something was stop bath, the bath is finished; see Incompatibilities.

Experiments

Test the 1:1 working-life claim. Mix a litre at 1:3 and a litre at 1:1 and print the same negative repeatedly through each, at two minutes, keeping exposure constant and measuring the print density of the same patch. Kodak’s published capacities predict 30 prints against 36 — only a fifth more for twice the chemistry. If you get a much larger factor, the difference is telling you something about your dish, your session length and your air, which is exactly what the published figure cannot know.

Build your own time–temperature chart. Take one paper and one dilution, and find the development time that reaches maximum black at 18, 21, 24 and 27 °C. Compare the shape with Kodak’s chart above. This is the same discipline as Part IX’s activity series, applied to a variable most printers never control.

Change one agent at a time. Mix a litre at half the hydroquinone and a litre at double the metol, and print the same negative in each at 1:3. The prediction from the mechanism above is that the first loses contrast and maximum black while the second mainly speeds the first appearance. Record it against the developer laboratory report.

Put it on film. Kodak publishes 5 to 10 minutes at 1:3 at 18 °C for negative materials, which is an unusually wide bracket. Develop a step wedge at 5 and at 10 minutes and plot both curves. You are measuring how much of that bracket is contrast and how much is Kodak declining to be specific.