Kodak D-158

Most paper developers are published with a contrast in the header. This one is published with a colour: “normal developer for chloride paper giving blue-black tone on Velox, and high contrast on process materials”, and Kodak’s product list repeats it in five words — “giving blue-black image tone”. That makes it the useful counterpart to the two warm-tone formulas in this library, because the three of them together let you read image colour off a formula sheet.

Ingredient	Quantity	Form the source specifies
Metol	3.2 g	Kodak calls it Elon
Sodium sulfite	50.0 g	anhydrous — or 100.0 g crystalline
Hydroquinone	13.3 g
Sodium carbonate	69.0 g	anhydrous — or 186.0 g of the crystals
Potassium bromide	0.9 g	or 9 mL of a 10 per cent solution
Water to make	1000 mL

Purpose

To develop a chloride contact paper to a cold, blue-black image in half a minute. Kodak’s second purpose for it is high contrast on process materials — the line and copy films of the period — and the handbook publishes times for those as well.

Recommended uses

Velox and other chloride contact papers at 1:1, 30 to 40 seconds at 18 °C. Kodaline films at 1:1, three to four minutes. Kodaline papers at 1:1, two to three minutes. The handbook publishes one dilution and three times, which is the reverse of D-163’s five dilutions.

Thirty seconds is a short time to be watching a print, and the reason is the paper rather than the developer. Chloride papers are contact papers: slow enough to handle under a bright safelight and to print by a bare lamp, with a short tonal scale and a naturally cold image. The 1928 primer draws the line clearly — a slow bromide emulsion on paper is a bromide paper for enlarging, and “the less sensitive papers which are commonly used for contact printing by artificial light contain silver chloride in the place of silver bromide”. This formula was built for the second kind.

When another formula is preferable

• For bromide enlarging paper, D-72 at 1:4 or D-163 at 1:3 are the formulas published for it. This one is published for chloride paper, and the bromide dose reflects that.
• For warmth rather than a cold tone, D-156 and D-166 go the other way on the same two levers.
• For low contrast, D-165 has no hydroquinone at all.
• For a formula with a longer dish life, D-163 carries half again as much sulfite.
• If metol is a problem for your skin, D-173 is Kodak’s metol-free developer, and it too was published for Velox.

Mixing

Dissolve in the order printed. Kodak Limited’s rule, stated once for the whole handbook: 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. Bromide has no action on the agents and may go in at any stage.

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 9 mL of a 10 per cent stock.
6. Make up to 1000 mL, and dilute with an equal bulk of water for use.

!Where the two columns disagree

The handbook’s own two columns do not quite reconcile here. The avoirdupois column gives the hydroquinone as 1 oz 40 gr, which is 30.94 g in 80 imperial fluid ounces, or 13.6 g per litre; the metric column says 13.3. The sulfite, the carbonate and the bromide all convert to within a rounding step, and the Elon’s avoirdupois figure is illegible in the course’s scan and is not relied on here.

The handbook anticipated exactly this. Its weights and measures page carries a warning in capitals: the two systems “are not exact equivalents”, so one or the other must be used exclusively. The course prints the metric column here, as it does throughout the formulary, and records the discrepancy rather than quietly resolving it. Two per cent of the hydroquinone is inside anyone’s weighing error at this scale; the reason to write it down is that a reader who converts the avoirdupois column and gets a different answer should know that the handbook, not the reader, is the source of the difference.

Behaviour

Fast and short. Thirty to forty seconds at 1:1, which leaves very little room to judge a print by watching it. Chloride paper is developed to completion like any other developing-out paper; the short time is a consequence of a slow, thin, low-silver emulsion and a vigorous bath, not an invitation to pull the print early.

Capacity is published for prints as well as negatives, which puts it in a small group with D-163. Thirty-six sheets of 8 × 10 inches per 160 fluid ounces in a narrow dish, against 24 negatives in a dish and 48 in a deep tank. As with every formula in this library, the figures are for 65 to 70 °F and for the standard time.

Keeping is ordinary: a day in a dish, one to two weeks in a covered tank, three months in a full bottle and one in a half-filled one.

Image characteristics

Colour. Blue-black, and this is the rare case where the maker states the colour as the aim. The formula’s two extreme values are what produce it — the most carbonate and the least bromide in the paper library — and the mechanism section below explains why those two work in the same direction.

Contrast. Normal on chloride paper; high on the process materials the handbook also lists, which tells you that “contrast” here is largely a property of the material and only partly of the bath.

Tonality. Short-scaled, because a chloride contact paper is. A negative that prints well on bromide paper at grade 2 will often look hard on chloride paper, and that is not the developer’s doing.

Staining. None. Grain, acutance and speed are not meaningful properties of a paper developer.

The mechanism

69.0 g/L ÷ 105.99 g/mol = 0.651 mol/L

Sodium carbonate

13.3 g/L ÷ 110.11 g/mol = 0.121 mol/L

Hydroquinone

50.0 g/L ÷ 126.05 g/mol = 0.397 mol/L

Sodium sulfite

3.2 g/L ÷ 344.38 g/mol = 0.0093 mol/L

Metol, as the hemisulfate

0.9 g/L ÷ 119.00 g/mol = 0.0076 mol/L

Potassium bromide

The two numbers that make the colour are the largest and the smallest in the family. Carbonate at 0.651 mol/L is the highest of the Kodak paper formulas this course can publish; bromide at 0.0076 mol/L is the lowest, a third of D-163’s and an eighth of D-156’s. Both push the same way: fast reduction, with nothing much holding it back.

Why fast reduction reads as cold. The course has already established, in Part V’s chlorobromide project, that image colour is set by the rate of silver deposition rather than by the emulsion’s halide composition: Wall’s controlled series across the whole chloride-to-bromide range, developed in one metol-hydroquinone developer, gave the same coloured image every time, and warmer tones appeared only when he weakened the developer and raised its bromide — on every plate equally. Chapman Jones supplies the other half from the particle side, showing that image colour depends on the size of the silver particles, which slow deposition makes fine.

That is exactly the lever this formula pulls, in the cold direction. A great deal of alkali and almost no restrainer is a fast bath, and Kodak’s own three paper formulas make the series: the coldest has the most carbonate and the least bromide, and the warmest has the least carbonate and the most bromide. This page is where a reader can see a mechanism from the emulsion part turned into a purchasing decision about a developer.

The bromide is small but not absent, and it could not be. A bath at 0.65 mol/L of carbonate would fog a paper that had spent a minute under a safelight. Nine hundred milligrams per litre is Kodak buying just enough restraint to keep the whites clean without moving the colour — and, because bromide restrains hydroquinone far more than metol (the 1928 primer states it plainly), what little there is lands where the fog would appear.

The agents are in the usual print ratio. Four parts hydroquinone to one part metol by mass, thirteen to one by moles. The metol starts the image everywhere at once — it has the highest reduction potential of the agents Kodak ranked — and the hydroquinone builds density steadily and rapidly behind it. Part VIII works development through and this page does not repeat it.

Function of every ingredient

Metol, 3.2 g. The starter. Highest reduction potential of the agents Kodak ranked, so it begins in the thinly exposed regions and brings the whole image up together; on a paper that finishes in thirty seconds this is what gives you anything at all to look at. More metol speeds the appearance and softens the print; less leaves the low tones weak and hands the whole job to an agent that builds highlights first. It is a skin sensitiser and it sets this page’s safety level.

Sodium sulfite, 50.0 g anhydrous. The preservative. It scavenges dissolved oxygen and intercepts the oxidised forms of both agents before they become coloured products; at half a mole per litre it is also most of the bath’s acid-absorbing reserve, which is what the stop bath has to neutralise out of each print. More sulfite keeps better and eventually dissolves silver, which on paper only costs density; less and an open dish browns within the session.

Hydroquinone, 13.3 g. The contrast agent, awake because the alkali is carbonate. It gains density steadily and rapidly and decides how black the black is. It is strongly temperature dependent, which is why a cold dish gives a flat print. More raises contrast and maximum black; less gives a grey print that will not finish in thirty seconds. It carries the heaviest hazard classification here.

Sodium carbonate, anhydrous, 69.0 g (or 186.0 g of the crystals). The alkali, and the largest dose in this library. It sets the pH region where hydroquinone works, supplies a carbonate–bicarbonate buffer so the pH holds as the agents release acid, and — because it governs the energy of the bath, which the 1928 primer states directly — it is also the ingredient most responsible for the cold tone. More carbonate means chemical fog and a swollen, frilling gelatin; less means a slower bath and a warmer image. The crystalline form is the same substance with ten waters attached: weigh 186 g of it or 69 g of the anhydrous salt, never a number in between.

Potassium bromide, 0.9 g. The restrainer, at the smallest dose in the paper library. It suppresses development of grains carrying no latent image, which is what keeps a chloride paper’s whites white under a safelight. It is deliberately small: bromide is also the ingredient that warms an image, and this formula is published for a cold one. More bromide cleans the whites further, warms the tone and slows the bath; less fogs. Nine millilitres of a 10 per cent stock is the practical way to measure 0.9 g.

Water to 1000 mL. Not inert. Iron is the classic contaminant, and a stock that has crystallised in the cold has its most important constituents in the precipitate, to be redissolved by warming rather than decanted off.

Interactions

Alkali and colour. The interaction this page exists to teach. Carbonate and bromide both act on the rate of silver deposition and therefore on image colour, in opposite directions, and Kodak’s three paper formulas move them together: 69 g of carbonate with 0.9 g of bromide gives blue-black, 16 g with 6.3 g gives warm, and 25 g with 12.5 g gives warmer still.

Restrainer and agent. Unequal. Bromide restrains hydroquinone far more than metol, so the small dose here acts almost entirely on the agent building the highlight densities — which is where fog on a contact paper would show first.

Agent and agent. Metol and hydroquinone together develop faster than the sum of their separate contributions, which is superadditivity. The common explanation, that hydroquinone regenerates oxidised metol, is not stated by any source this course holds and is not asserted here.

Developer and material. The three published times — 30 to 40 seconds, two to three minutes, three to four minutes — are for one bath at one dilution on three materials. Nearly all of that range is the emulsion, not the developer, and it is a useful corrective to the habit of attributing everything on a print to the chemistry in the tray.

Variants

Kodak’s packaged alternatives. The handbook’s footnote to this formula says “alternatively use Velox Developer Powder, Velox Developer, or Kodaline Developer Powder”. It does not say that any of them is this formula, and no document in the course’s corpus states the composition of any of them, so under Rule 6 the course does not make the identification.

D-173 is Kodak’s own metol-free developer for the same paper, and has its own entry. It is not a variant of this formula — the agents are different — but it is the formula to reach for if this one is the problem.

The course’s own variants belong in the formula version record rather than here.

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. Sodium carbonate at 69 g/L is an eye hazard on its own account, and it is the highest concentration of it in this library.

Contact papers make the exposure problem worse, not better. A thirty-second development invites hands in the tray, because there is no time to fish for a print with tongs that are somewhere else. Set the tray out so that the tongs are in your hand before the print goes in — one pair per tray, never interchanged — and wear nitrile gloves if you will be handling prints at all. A sensitiser is a sensitiser at any dilution, and repeated small exposures are precisely the mechanism of sensitisation. The classification rubric sets what Level B assumes and the gloves page covers the choice.

Weighing is the other half. Four powders, two of them fine. Extraction running or an enclosure, never a draught, splash goggles on.

Storage

Stock in a tightly closed bottle filled as full as it will go: three months full, one month half filled. The handbook notes that glass stoppers stick in alkaline solutions and that several small bottles keep better than one large one repeatedly opened.

Working solution: 24 hours in a dish, one to two weeks in a covered tank. Label with the formula, the dilution and the date, per the labelling SOP.

A cold bottle that has thrown a deposit is warmed and redissolved rather than decanted; the handbook makes the point that the precipitate often contains the most important constituents of the solution.

Incompatibilities

Acid, in the next tray, deliberately. A splash of stop bath into this developer drops the pH out of the region where hydroquinone works, and this is a hydroquinone-dominated bath. Tongs never travel backwards along the tray sequence.

Fixer, in either direction. Thiosulfate carried back into a developer is an aggressive silver solvent that fogs and stains; 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

A dilute alkaline solution whose environmental load is the two developing agents, both of which carry aquatic-toxicity classifications. It carries essentially no silver, so it goes into its own labelled container and never into the fixer bottle. The disposal caveat governs and the general chemical waste SOP gives the procedure. Local regulation decides.

Troubleshooting

A warm or brownish image where you expected blue-black. Three candidates. The bath has aged and accumulated bromide from the paper, which warms the tone — that is the same lever D-156 pulls deliberately. The bath is cold, so deposition is slow. Or the paper is not a chloride paper, in which case the colour was never on offer.

Flat prints with weak blacks. Temperature first, because hydroquinone is the temperature-sensitive agent. Then exhaustion, counted against the published 36 sheets.

Grey whites. Fog, and with 0.9 g/L of bromide this bath has the least protection of any in the library. Check the safelight before the formula: a chloride paper is slow, which tempts printers into brighter safelights and longer exposure to them.

A print that is finished before you can look at it. The formula working correctly. If that is a problem, D-72 at 1:4 develops the same class of paper more slowly, at the cost of the published tone.

Experiments

The bromide series, from this formula to the warm ones. Mix three litres of working solution and add 10 per cent potassium bromide to bring two of them to about 3 g/L and 6 g/L in the working bath. Print the same negative in all three on the same chloride paper, developing each to completion. You are reproducing, as a one-variable series, the difference between this formula and D-156, and the prediction is a progressive warming with cleaner whites and slower development.

The alkali series. Mix the formula at 69, 45 and 25 g/L of carbonate, leaving everything else alone. The prediction from the mechanism above is that the print warms and slows as the alkali comes down. Record it against the developer laboratory report.

Chloride against bromide paper, one bath. Print the same negative on a contact paper and an enlarging paper in this developer at 1:1, matching density by exposure. Almost everything that differs between the two prints — scale, colour, time to completion — belongs to the emulsion, and seeing how much is a good corrective to developer-centred thinking.