Kodak D-19b

This is the high-contrast formula the rest of the course cites. Kodak Limited printed it with everything the 1928 D-19 lacks — a keeping table, a capacity, a published replenisher, a second development time for two named films, and both salt forms for every ingredient that has two.

Ingredient	Quantity	The handbook’s alternative
Metol	2.2 g
Sodium sulfite, anhydrous	72.0 g	144.0 g crystalline
Hydroquinone	8.8 g
Sodium carbonate, anhydrous	48.0 g	130.0 g of the crystals
Potassium bromide	4.0 g	40 mL of a 10 per cent solution
Water to make	1000 mL

Kodak’s header: a “high-contrast dish or tank developer for X-ray film and paper, and general clinical, aerial, infra-red, industrial and scientific record photography”.

Purpose

A steep gradient in five minutes. Everything else about the formula — the bromide dose, the preservative load, the choice of carbonate — follows from that one requirement.

Recommended uses

Line and document work, copy negatives, and negatives made deliberately hard for a printing process that needs them. The list Kodak prints — clinical, aerial, infra-red, industrial, scientific record — is a list of subjects photographed for information rather than for tone.

Paper as well as film. Kodak’s header names paper, which none of the other headers in this batch do. Kodak’s paper developers of the same era — D-72 and its relatives, which belong to the paper section of this formulary rather than to this one — are built on the same carbonate chemistry at a lower agent load and a higher secondary-to-primary ratio still.

Tank work with replenishment, using D-19bR, which is the one replenisher in this batch that removes an ingredient rather than increasing it.

When another formula is preferable

• D-19 is the earlier Kodak printing of the same design and is more energetic in every line. Publish-and-compare rather than substitute: the two are not interchangeable at the same time.
• DK-50 for a normal-contrast negative that still develops briskly. Its own handbook note tells you how to raise its contrast, which covers the ground between the two.
• D-76 for any pictorial negative at all.
• A soft developer, D-23, is at the other end of the same axis and is worth mixing at the same time if you want to see the axis.

Mixing

Kodak’s printed order is Elon, sulfite, hydroquinone, carbonate, bromide, with the usual instruction to dissolve in the order given: the Elon first because it is only slightly soluble in a sulfite solution without alkali; the sulfite next; the second agent under its protection; the alkali last so that no dissolved agent waits unpreserved in an alkaline solution; and the bromide wherever suits you.

!Two salts, four ways to get this wrong

The handbook prints its main column in the crystalline salts and its parentheses in the anhydrous ones, and its own warning about the two systems of measure applies with equal force to the two systems of salt. Take one column or the other, all the way down.

• Sulfite. 144.0 g of the crystals or 72.0 g of the anhydrous salt. The heptahydrate is almost exactly half water by mass; the sodium sulfite entry covers the hydrate question.
• Carbonate. 130.0 g of the crystals or 48.0 g of the anhydrous salt, and these are two different encyclopaedia entries: the decahydrate and the anhydrous salt. The handbook’s general rule for anyone with the wrong jar is that crystals must be used at two and a half times the anhydrous quantity, and it recommends the anhydrous salt because the composition of the crystals is uncertain.
• Bromide. 4.0 g, or 40 mL of a 10 per cent solution. Kodak prefers the solution for small quantities, and its stated reason is worth borrowing for the whole darkroom: a “drop” is such an uncertain quantity that it varies by as much as 150 per cent depending on how it is measured.

Behaviour

Five minutes at 18 °C for X-ray films, seven for two named materials. That exception — Industrex Type D and Crystallex — is the only place in this batch where Kodak publishes a time for one product and a different time for another in the same sentence, and it is a useful reminder that a formula’s time belongs to a material and not to the formula.

Kodak publishes no dilution ratio. The instruction is “use without dilution or diluted as directed in the instructions issued with the material to be developed”, which points at documents the course does not hold. The gap is stated rather than filled.

The capacity is the highest in the handbook’s table: 36 sheets of 8 × 10 in a dish and 72 in a deep tank per 160 fluid ounces, half again the figures for D-76, DK-20 and DK-50, and the deep-tank figure is the largest for any developer on the page. The keeping is the best too — three months in a half-filled bottle where every other negative developer here manages two. Both facts sit oddly with the general expectation that a strongly alkaline hydroquinone bath oxidises fastest, and no source this course holds explains either, so they are reported and not accounted for.

Image characteristics

Contrast: high. That is the whole formula. Grain: coarse, and a non-issue for the work it was made for. Speed: unpublished, with 4.0 g/L of bromide as a strong reason to expect a raised threshold. Tonality: a short scale with the toe pushed well clear of base fog, which is what a record negative wants. Sharpness: not designed for, though a bath with a modest solvent load and a five-minute development is not the enemy of it either.

The mechanism

48 g/L ÷ 105.99 g/mol = 0.453 mol/L

Carbonate

72 g/L ÷ 126.05 g/mol = 0.571 mol/L

Sulfite

8.8 g/L ÷ 110.11 g/mol = 0.080 mol/L

Hydroquinone

4 g/L ÷ 119.00 g/mol = 0.034 mol/L

Bromide

The alkali is the design. Nearly half a mole of carbonate per litre, against 0.0052 mol/L of borax in D-76 — about ninety times the molar alkalinity. At that pH the hydroquinone is far more ionised than it is in a borax bath, so the agent that sits in reserve in a fine-grain developer is here the principal one, and there is nearly twice as much of it.

The proportions are the formula’s argument. The superadditivity lesson puts D-19b at 6.3 : 1 secondary to primary in moles, the steepest ratio of any Kodak MQ film developer in this reference, against DK-50’s 1.6 : 1 and D-76’s 3.9 : 1. A high-contrast developer is one that pairs a very small quantity of the fast agent with a large quantity of the contrast-giving one and then supplies the alkali to run it.

The sulfite is unusually balanced against the alkali here. Part VIII’s buffer table gives the sulfite as 1.3 times the alkali in this formula, against 3.3 in DK-50 and 152 in D-76. In D-76 the sulfite dwarfs the alkali and carries most of the acid-absorbing reserve; here the carbonate is a genuine co-equal, which is what a large reserve at a high pH looks like.

And the bromide does two jobs at once. Kodak’s own rule is that too much alkali tends to produce chemical fog, so a bath at 0.45 mol/L of carbonate needs a restrainer; four grams per litre is what Kodak used, eight times the dose in DK-50 and DK-20. Part VIII’s restrainer lesson works out what that does to the threshold. The second job follows from Kodak’s observation that bromide restrains hydroquinone strongly and metol far less: a heavy restrainer widens the gap between an exposed grain and an unexposed one, which is contrast.

Function of every ingredient

Metol, 2.2 g. The primary agent and the smallest dose in this batch. Its job is to start development in the shadows and to make the pair superadditive; the density is built by what follows. More metol would fill the shadows and flatten the curve — the opposite of the formula’s purpose; less would slow the whole bath, because the secondary agent works best on development the primary has begun. Together with the hydroquinone it puts this page at Level B.

Sodium sulfite, 72.0 g anhydrous. Preservative, sized for a large hydroquinone load in a strongly alkaline solution, which is the condition under which a developer oxidises fastest. It contributes buffer capacity too, though here it shares that duty with the carbonate rather than carrying it. Its silver-solvent action has five minutes to act and is not what the formula is for. More would improve keeping and slightly soften the image; less and the bath would brown in the bottle. Note it is 28 per cent less than the 1928 D-19 carries, which is the largest proportional change Kodak made in the revision.

Hydroquinone, 8.8 g. The working agent. It supplies the density and the gradient. More raises the gradient and the fog risk; less moves the formula towards a general-purpose developer. It carries the heaviest hazard classification of anything on this page.

Sodium carbonate, anhydrous, 48.0 g. The alkali, and the ingredient that makes the hydroquinone usable. Nearly half a mole per litre is both a high pH and a large reserve, so the bath holds its activity as it works instead of drifting the way a borax developer does — which is consistent with the capacity figure, though the course states the consistency and not a cause. Kodak’s 1928 rule applies in full: the quantity of alkali governs the energy, too much tends to produce chemical fog, too little makes it slow, and alkalis soften the gelatin. More carbonate means energy, fog and swelling; less moves the formula out of its purpose.

Potassium bromide, 4.0 g. The restrainer, doing both the jobs described above. More bromide raises the threshold further, cleans the base and costs shadow speed; less means fog in a bath that has no other defence against it. Because it acts unequally on the two agents, changing it changes the shape of the curve and not merely its position. It may be weighed as the solid or measured as 40 mL of a 10 per cent solution, and its position in the mixing order is free.

Water to 1000 mL. Nothing here needs hot water except the metol step, and 72 g of sulfite with 48 g of carbonate dissolves readily.

Interactions

Alkali and secondary agent, as in D-19: the carbonate is what makes the hydroquinone the working agent rather than a reserve.

Bromide against the two agents, unequally, which is what makes a heavy restrainer a contrast control and not only a fog control.

Carbonate against the acid fixer. Carbonate and acid give carbon dioxide, and a film carrying a carbonate developer into an acid fixing bath in warm conditions can blister as the gas forms inside the swollen gelatin. Kodak’s metaborate developers were designed to avoid exactly this, and the metaborate entry records the statement. Use a stop bath.

Carbonate against gelatin. Alkalis soften it, so the emulsion leaving this developer is more fragile than one leaving D-76.

Variants

D-19 is Kodak’s earlier printing of the same design, in the 1928 primer, and every quantity is larger: metol 2.5, sulfite 105, hydroquinone 9.8, carbonate 52.5 and bromide 6.3 grams per litre. The reductions are not uniform — the sulfite falls by nearly a third and the bromide by more than a third, while the two agents and the alkali fall by around a tenth — so this is a genuine reformulation rather than a rescaling. Kodak gives no reason for any of it, and the course does not supply one.

D-19bR is the published replenisher, and it is the most interesting one in this batch: half again the agents, the same sulfite and carbonate, no bromide at all, and 7.5 g/L of sodium hydroxide added.

Neither is recorded here as a variant, because Kodak published each as a formula in its own right. The formulary reserves that status for the course’s own modifications, which belong on a formula version record.

Safety

Level B, and this shares the film-developer section’s heaviest hazard set with D-19. Hydroquinone at 8.8 g/L carries a Danger classification — serious eye damage, suspected genetic defects, suspected cancer, very high aquatic toxicity — and metol is a skin sensitiser. Sodium carbonate, sodium sulfite and potassium bromide are Level A materials, but 0.45 mol/L of carbonate makes the mixed bath alkaline enough to be a real eye hazard on its own. See the classification rubric.

Splash goggles rather than glasses. Weigh the hydroquinone with extraction or inside an enclosure. Tongs, not fingers, in the dish, and remember that the same alkalinity that softens gelatin is unpleasant on skin.

What is not a hazard here. The developer evolves no gas in use; carbon dioxide is released only when the carbonate meets an acid, which is a carry-over question rather than a hazard of the tank. Nothing is heated. There is no sensitising alkali, no thiocyanate and no cyanide chemistry, and the ventilation control is for dust during weighing.

Storage

Tightly corked bottles, filled full, small rather than large: six months full and three months half-filled at 18 to 21 °C, which is the best half-full figure of any negative developer in the handbook’s table. Twenty-four hours in a dish and a month in a tank once it is working.

Keep the dry anhydrous carbonate closed and dry — it takes up water from the air, and a caked jar has changed in concentration as well as in handling. Label which carbonate you used, because 48 g and 130 g of the two salts make the same developer and 48 g of the wrong one does not. See the labelling SOP.

Incompatibilities

Acid, with the carbon-dioxide consequence described above: never straight from this developer into an acid fixer, and never acidified in a bottle.

Fixer, in either direction.

Oxidising agents — ferricyanide, dichromate, permanganate, persulfate — never with a developing agent. See chemical incompatibilities.

Waste

A strongly alkaline solution with a large hydroquinone load, which is the constituent that makes this developer’s waste the one to be most careful with; hydroquinone’s classification includes very high aquatic toxicity. Its own labelled bottle, kept out of the fixer so the fixer can go for silver recovery, and not neutralised. The disposal caveat governs, the general chemical waste SOP gives the procedure, and local regulation decides.

Troubleshooting

Fog, and a base that will not clear. The failure this formula is most prone to. Check the bromide first — 4.0 g/L is a large dose and a large error if it is missing — then check whether the carbonate was weighed as the anhydrous salt where the crystals were intended, which raises the alkalinity by a factor of about two and a half.

Contrast far lower than expected. The mirror-image error: crystals weighed gram for gram against the anhydrous figure, giving under 40 per cent of the alkali.

Shadows absent. Expected. A restrainer at this dose raises the threshold, and this developer is not trying to give you shadow detail.

Frilling, or an emulsion that marks easily. Alkalis soften gelatin. Keep the temperature down and use a stop bath.

Activity falling away in a replenished tank. D-19bR carries no bromide by design, so under-replenishment shows first as accumulated restrainer rather than as a shortage of agent — the negatives go flat before they go thin.

A bath that browns quickly. High pH plus a large hydroquinone load is the fastest-oxidising combination in this section, whatever the keeping table says about a well-filled bottle. Mix less at a time.

Experiments

Compare the two printings. D-19b as published here against D-19 as Kodak’s 1928 primer prints it, same film, same five minutes at 18 °C. Kodak revised five quantities and explained none of them; the two strips are evidence about what the revision did, with the standing caveat that a modern film is not the material either was written for.

Take the bromide down in steps. 4.0, 2.0, 1.0 and 0 g/L, everything else held. You will see the base fog rise and the gradient fall together, which is the double duty of the restrainer made visible in one series. It fits directly into the activity series.

Test the capacity claim. 36 sheets of 8 × 10 per 160 fluid ounces in a dish is 7.9 sheets per litre. Put eight sheets through a litre with a control strip after every second one, and find out whether the highest capacity figure in Kodak’s table survives contact with your materials.

Measure the pH the course cannot cite. Fresh D-19b against fresh D-76 and fresh DK-50, on a meter calibrated under the pH meter SOP. Three developers, three published alkalis, and three numbers no manufacturer in this corpus has printed.