Kodak D-19bR

Every other replenisher in this reference adds more of what the developer already contains. This one removes an ingredient, leaves two others exactly where they were, and introduces a substance the working bath does not have.

Ingredient	D-19bR	D-19b	Change
Metol	4.0 g	2.2 g	1.8×
Sodium sulfite, anhydrous	72.0 g	72.0 g	unchanged
Hydroquinone	16.0 g	8.8 g	1.8×
Sodium carbonate, anhydrous	48.0 g	48.0 g	unchanged
Sodium hydroxide	7.5 g	—	added
Potassium bromide	—	4.0 g	removed
Water to make	1000 mL	1000 mL

The handbook prints its crystalline alternatives here as everywhere: 144.0 g of the sulfite heptahydrate, and 130.0 g of the carbonate decahydrate.

Purpose

To hold a tank of D-19b at constant volume and constant activity. Kodak’s instruction is one sentence: the D-19b developer should be maintained at a constant level in the tank by frequent addition of this replenisher.

Recommended uses

Tank development of X-ray, copy or record material in enough quantity for the level in the tank to fall — which, given D-19b’s published capacity of 72 sheets of 8 × 10 per 160 fluid ounces in a deep tank, means a great deal of film. This is a production replenisher and it was sold as a packed powder for that reason.

For a darkroom running a litre or two at a time, mix D-19b and discard it. A replenisher carrying 7.5 g/L of caustic soda is not something to keep on a shelf for occasional convenience.

When another formula is preferable

D-76R and DK-20R feed entirely different developers and are not interchangeable with this one; both take the opposite view on bromide, and DK-20R doubles it.

Fresh D-19b is the right answer wherever the tank is losing solution to carry-out rather than to chemistry — Kodak’s own instruction for the D-76 case, and the same reasoning applies.

Time compensation is the alternative where no replenisher exists, and it is what ILFORD recommends for its own withdrawn product. Kodak publishes no time-compensation schedule for D-19b, so that route would be your own measurement rather than a published one.

Mixing

Kodak’s printed order is Elon, sulfite, hydroquinone, carbonate, hydroxide, with the usual instruction to dissolve in the order given. The reasons are the handbook’s general rules — the Elon first because it is only slightly soluble in a sulfite solution without alkali, the sulfite next, the second agent under its protection, and the alkalis last so that no dissolved agent stands in a strongly alkaline solution before the preservative arrives.

⚠The caustic step is the hazardous part of this formula

Sodium hydroxide is corrosive as a solid and as a solution, and dissolving it releases heat. Seven and a half grams in a litre that already contains 48 g of carbonate is the most caustic mixing operation anywhere in this section of the formulary.

Add the hydroxide last, to the full volume of cool solution, in small portions, stirring, never the other way round. Splash goggles rather than glasses; gloves; the eyewash within reach that Level B assumes. Weigh it quickly — it takes up water and carbon dioxide from the air — and close the jar.

The 1949 handbook’s own remark about developer bottles is worth repeating for this one: glass stoppers are a poor choice, because the alkali makes them stick.

Behaviour

It is not a developer. No time, no temperature, and the keeping table has no dish or tank column for it — the row reads “used as Replenisher only”.

No rate is published, and no replacement limit either. For D-76R and DK-20R the handbook gives volumes and a 25 per cent limit; for this one it gives the instruction to maintain a constant level, frequently, and nothing more. That is a real gap in the record and the course does not fill it with a number. What is left is process control: a control strip, at a fixed interval, against a strip from freshly mixed developer.

Six months full and three months half-filled, which are D-19b’s own keeping figures and the best pair in the handbook’s table.

Image characteristics

None of its own. The criterion is that a replenished tank should give the negatives a fresh tank gives. For a high-contrast developer the quantity to watch is the gradient rather than a single density: the failure modes of this scheme both change the shape of the curve, and one of them — accumulating bromide — flattens it before it thins it.

The mechanism

Four decisions, and each one is a claim about the tank.

The agents go up by 1.8, together. Metol from 2.2 to 4.0 and hydroquinone from 8.8 to 16.0 g/L — the same factor, so the ratio between them is preserved and the superadditive pairing is not disturbed. Development is stoichiometric in the agent, and this is the replacement.

The sulfite does not move. At 0.571 mol/L the preservative is in enormous excess for the amount a tank consumes, and what is lost is lost by carry-out, which a solution at the same concentration restores exactly.

The carbonate does not move either — and this is the interesting one. Every other replenisher here multiplies the alkali by ten, because the bath it feeds has almost no alkali reserve. D-19b is the exception: 0.453 mol/L of carbonate is a very large reserve, and Part VIII’s buffer table puts the sulfite at only 1.3 times the alkali in this formula against 152 times in D-76.

So the base is restored as hydroxide instead.

7.5 g/L ÷ 40.00 g/mol = 0.1875 mol/L

Hydroxide

48 g/L ÷ 105.99 g/mol = 0.453 mol/L

Carbonate

Nearly two tenths of a mole of strong base per litre of replenisher, arriving in a tank whose carbonate concentration is already correct. The course reads that as Kodak replacing the alkalinity development consumed without changing the carbonate concentration, which would otherwise drift upward with every addition. That is a reading of the two published formulas together, not a statement Kodak makes; the handbook prints the quantities and no explanation.

And the bromide comes out entirely. D-19b carries 4.0 g/L, the second largest restrainer dose in this batch. The replenisher carries none. The reason is the one thing every replenisher scheme has to contend with: every silver ion reduced releases a bromide ion into the tank, so a working bath generates its own restrainer. A high-contrast developer that already carries a heavy dose is especially exposed to that accumulation, and adding more would compound it.

!Two Kodak replenishers, opposite answers

DK-20R carries twice the bromide of the bath it feeds. D-19bR carries none. Both are Kodak Limited, both in the same 1949 handbook, both on facing sections of the same table.

Neither choice is explained by any source this course holds. What the pair establishes is that a replenisher’s restrainer is a design decision rather than a rule — and that the decision runs one way in a fine-grain solvent developer carrying half a gram a litre, and the other way in a carbonate developer carrying eight times that. Anyone who tells you a replenisher “never contains bromide” or “always matches the bath” is generalising from one example.

Function of every ingredient

Metol, 4.0 g. Replacement for the primary agent. At 1.8 times the working bath, so a modest addition restores a larger volume. Its job in the tank is unchanged: start development in the shadows and make the pair superadditive. More would season the tank above its original activity; less would leave it topped up and slow.

Sodium sulfite, 72.0 g anhydrous. Preservative for the replenisher in its bottle and for the tank it enters, and a contributor to the buffer reserve. Held at working strength deliberately: it is not consumed appreciably, and changing it would change the tank. In a bottle carrying 16 g/L of hydroquinone with 7.5 g/L of caustic soda, its protective job is real work — that combination is the fastest-oxidising solution on any page of this section.

Hydroquinone, 16.0 g. Replacement for the working agent of D-19b, at the same 1.8 factor as the metol. This is the largest hydroquinone concentration in the film-developer section, and it is what makes this bottle the one to weigh most carefully. More would raise the contrast of a seasoned tank; less would let the gradient fall away as the bath ages.

Sodium carbonate, anhydrous, 48.0 g. Held at working strength for the reason given above: the concentration in the tank is already what the formula wants, and the deficit is in alkalinity rather than in carbonate. Its presence keeps each addition at the tank’s own carbonate level rather than diluting it. Raising it would push the carbonate concentration up with every addition, which is a drift; lowering it would dilute the tank’s buffer.

Sodium hydroxide, 7.5 g. The strong base, and the ingredient with no counterpart in the working bath. It neutralises the acid that development has produced and lifts the pH of a seasoned tank back towards where it began. More would push a replenished tank above its original energy, and in a formula this alkaline that means chemical fog, which is precisely the failure the bromide was there to prevent. Less and the tank goes flat. Note the classification rubric’s own example: sodium hydroxide is a Level A ingredient at 2 g in a litre of developer. At 7.5 g in a litre that also holds 48 g of carbonate, it is the reason the mixing step on this page carries the warning above.

Potassium bromide, absent. Worth listing as an ingredient by its absence, because the working bath has 4.0 g/L of it and the omission is deliberate. Adding bromide to a solution designed to top up a tank that is manufacturing its own would be self-defeating.

Water to 1000 mL. Cool for the hydroxide step, and enough of it in the vessel before the hydroxide goes in.

Interactions

Hydroxide against carbonate. Both are alkalis and they are not equivalent: the carbonate is a buffer pair with a reserve, the hydroxide is free base with none. Part VIII’s alkali lesson makes the distinction and uses Kodak’s own D-9 as the extreme case. Here the two are doing different jobs in one bottle — the carbonate maintaining a concentration, the hydroxide restoring a quantity.

Hydroxide against the agents. Both agents are more active at higher pH, and the hydroquinone disproportionately so, which is why over-replenishment shows up as rising contrast and fog rather than as a general speed-up.

Replenisher against accumulated bromide. No interaction, and here the absence is deliberate rather than merely unavoidable.

Carbonate against the acid fixer. Unchanged from the developer: carbonate and acid give carbon dioxide, which can blister a warm, swollen emulsion. Use a stop bath.

Variants

None published. Kodak prints one replenisher for D-19b and no modification of it, and unlike D-76R there is no manufacturer variant for a particular film.

A version at half the hydroxide, for a tank turning over slowly, is an obvious thing to want and nobody has published a result for it. That makes it a proposal, and a proposal with a written prediction belongs on a formula version record rather than in a formulary.

Safety

Level B, and this page carries the section’s heaviest combination. Hydroquinone at 16.0 g/L is the largest dose in the film-developer section and carries a Danger classification — serious eye damage, suspected genetic defects, suspected cancer, very high aquatic toxicity. Metol is a skin sensitiser. Sodium hydroxide is corrosive and dissolves exothermically. Sodium sulfite and sodium carbonate are Level A materials, but 0.45 mol/L of carbonate plus 0.19 mol/L of free hydroxide is a strongly caustic solution. See the classification rubric.

Splash goggles, gloves, eyewash within reach, and the hydroxide added last in small portions to a full volume of cool solution. Weigh the hydroquinone with extraction or inside an enclosure.

What is not a hazard here. The mixed solution evolves no gas — carbon dioxide comes off the carbonate only on contact with acid, which is a reason to keep this bottle away from the stop bath rather than a hazard of the bottle itself. Nothing is heated deliberately; the warmth you feel is the hydroxide dissolving, and it is a reason to add it slowly rather than a process step. There is no sensitising alkali and no cyanide chemistry here.

Storage

Small, tightly corked bottles, filled full: six months full, three months half-filled. Not a glass-stoppered bottle — the 1949 handbook’s own reason is that the alkali makes the stopper stick, and that is worse for a caustic solution than for a mild one.

Label it D-19bR — REPLENISHER — CAUSTIC. Three facts, each of which changes what someone does with the bottle. Store the dry hydroxide separately, closed, away from acids and away from anything it could be mistaken for. See the labelling SOP.

Incompatibilities

Acids of every kind. A strongly caustic solution meeting a concentrated acid is a violent neutralisation, and a carbonate meeting an acid also gives carbon dioxide. This bottle does not go near the stop bath, and the spent solution is not neutralised for disposal.

Fixer, in either direction, and here the alkalinity adds a second reason: an acid hardening fixer that receives enough alkaline carry-over throws out a sludge and stops working, which Kodak’s 1928 primer describes.

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

Aluminium and its alloys, which strong alkali attacks. Mix and store in glass or in a plastic rated for caustic solutions, never in a metal vessel of unknown alloy. See chemical incompatibilities.

Waste

The most caustic and the most hydroquinone-laden waste in this section, and it goes in its own labelled bottle, kept out of the fixer so the fixer can go for silver recovery. Do not neutralise it — that is a reaction you would be performing in a bottle for no benefit, and the disposal route does not require it.

Hydroquinone’s aquatic-toxicity classification is the constituent that matters most here. The disposal caveat governs, the general chemical waste SOP gives the procedure, and local regulation decides.

Troubleshooting

Gradient falling away in a replenished tank while density holds. The signature of accumulated bromide in a bath whose replenisher deliberately contains none. Count what has gone through, and expect this scheme to end rather than to run indefinitely.

Fog rising, base density climbing. Over-replenishment. You are adding free hydroxide faster than the film is consuming alkalinity, and in a formula this energetic the restrainer that would have covered you is not being replaced.

Everything slow, agents apparently fine. Under-replenishment of the hydroxide. Kodak publishes no rate; increase the addition, run a control strip, and record both.

Heat and spitting while mixing. The hydroxide going in too fast, or into too little water. Stop, let it cool, and add the rest in smaller portions.

A stuck stopper. The handbook predicted it. Use a cork or a plastic closure.

Experiments

Find the rate Kodak did not publish. Season a litre of D-19b with sheets or strips, replenishing at 20, 30 and 40 mL per 8 × 10 equivalent in three parallel litres, with a control strip after every second sheet. Plot gradient rather than density, because gradient is what this developer sells.

Separate the hydroxide from the agents. Season a litre, split it, add hydroxide alone to one half at the concentration this formula implies and agents alone to the other. If alkalinity is what the tank loses first, the hydroxide half recovers more.

Test the bromide decision against DK-20R’s. Replenish one seasoned litre with D-19bR as published and another with a version carrying 4.0 g/L of bromide, then compare gradient and base fog over several sheets. Kodak went one way here and the other way in DK-20R and explained neither, which makes this one of the few genuinely open questions in this batch of formulas.

Write the prediction down first, on a formula version record, and bring the plots into the developer laboratory report.