ILFORD BROMOPHEN developer

This is a product page, not a formula page, and the difference is the point of it. Everything else in this library is a list of quantities with a source attached and an account of what each quantity is doing. Nobody outside Harman knows the quantities in these two bags. What follows is what its maker publishes, which for dilution, time, capacity, keeping and even the pH of the stock is a great deal; what its maker’s own two safety data sheets disclose, which is more than most; what the two kinds of document together still leave unknown; and the open formula to mix if you would rather know than buy.

HARMAN technology Limited (ILFORD Photo) — sold as two part powder

Components the maker discloses — from the safety data sheet, which classifies hazards and does not state a formula

Component	Concentration as the sheet gives it	Hazard codes
Hydroquinonenamed on the sheet as 1,4-dihydroxybenzenehydroquinonequinolCAS 123-31-9One of the two developing agents ILFORD names, in part A, the smaller bag	60-100%	H302, H317, H318, H341, H351, H400, H410
Sodium metabisulfitenamed on the sheet as sodium metabisulphiteCAS 7681-57-4	10-30%	H302, H318
Phenidonenamed on the sheet as 1-phenyl-3-pyrazolidoneCAS 92-43-3The other developing agent ILFORD names; the product description calls BROMOPHEN a phenidone/hydroquinone developer	1-5%	H302, H317, H400, H410
Sodium carbonate (anhydrous)named on the sheet as sodium carbonateCAS 497-19-8	30-60%	H319
Sodium sulfite (anhydrous)named on the sheet as Sodium sulphiteCAS 7757-83-7	30-50%
Potassium bromideCAS 7758-02-3	1-5%	H319
BenzotriazoleCAS 95-14-7	<1%	H302, H319, H411

Not disclosed. HARMAN publishes no composition for BROMOPHEN. Two safety data sheets name seven components between them and give each a concentration band for the purpose of classifying a hazard, which is not an assay: the bands are wide, their upper limits sum to more than each bag, and the sheets are for the two bags separately. Nothing published anywhere says what mass of part A meets what mass of part B, so even the two tables cannot be combined; and no quantity, no ratio between the two developing agents, no alkali loading, no restrainer loading, no working-solution pH and no formulation date appears in ILFORD's literature. A reader who needs to change one term at a time, and see what it does, has to mix an open formula instead of buying this one.

Nearest open formula. Kodak D-72 — Both are alkaline superadditive paper developers mixed from powder into a stock that is then diluted for the dish, and they do the same job on the same papers at the same temperature. D-72 is published in full and made from five weighed chemicals whose functions can each be named; BROMOPHEN arrives as two sealed bags whose maker names two developing agents and nothing else. D-72 pairs metol with a large excess of hydroquinone in sodium carbonate and dilutes one in four for bromide enlarging papers; BROMOPHEN pairs phenidone with hydroquinone, dilutes one in three, develops a resin-coated print in two minutes against Kodak's minute and a half, publishes a stock pH and a print capacity where Kodak's two printings give neither, and keeps as a stock for six months where D-72's stock keeps three. The exchange is a longer-lived, better-documented bath against the ability to change one ingredient and see what happens.

Purpose

To develop a black and white print on any ILFORD paper to full black in about two minutes at ordinary room temperature, from a carton of powder that keeps indefinitely on the shelf until you open it. ILFORD describes BROMOPHEN as “a phenidone/hydroquinone developer supplied in powder form”, suitable for the dish or tray developing of all resin-coated and fibre-based black and white papers, made into a stock solution that is diluted 1+3 for use, “economical, clean working” and with good keeping properties, giving “a slightly warm of neutral image tone with most papers”.

Four of those words are the whole product. Powder: it posts cheaply, it survives a warehouse, and an unopened packet has no clock running on it at all. Phenidone: this is the one ILFORD developer in the corpus that still uses the original pyrazolidone rather than Dimezone S, which is what the liquid concentrates get. Economical: ILFORD’s own word, and the reason a printer who goes through developer by the gallon buys cartons rather than bottles. Slightly warm of neutral: the sheet gives PQ UNIVERSAL exactly the same description and MULTIGRADE a plainly neutral one, so BROMOPHEN is not alone in being warm — but it is the only one of the three ILFORD sends you to, by name, when you are printing on Warmtone paper and want the warmest tone that paper will give.

Recommended uses

Dish or tray printing at 20 °C, at 1+3, made up from the stock for the session and thrown away at the end of it. That is the use ILFORD documents and the one every published figure on this page belongs to. The sheet asks for the working solution to be prepared directly before it is needed, for enough of it to fill the dish about half full, and for all the process solutions to be within one degree of the working temperature.

On MULTIGRADE Warmtone papers, for the warmest image tone. This is ILFORD’s own recommendation and it is unusually specific: the developer sheet names those papers, and the MULTIGRADE FB WARMTONE sheet says from its own side that the warmest results in the ILFORD range come from HARMAN’s warm-tone developer and from BROMOPHEN. A maker that tells you which of its developers to buy for a colour is telling you the others will not give it.

Where the whole carton can be used. ILFORD’s instruction is emphatic: always make the stock up to the volume stated on the carton, and do not try to make a smaller quantity by using fractional parts of each powder. Larger quantities are made with whole multiples of packs. That is the single biggest practical constraint on the product, and it is not a constraint a formula has.

With the interleaving method when you are printing a batch. The sheet’s instruction for multiple sheets is to slide them into the dish one at a time emulsion side down, then repeatedly pull the bottom sheet to the top of the pile until the time is up, and to lift the print out ten seconds before the end so it can drain. Fibre paper goes limp when wet, absorbs far more solution and is harder to interleave than the resin-coated base, which stays rigid.

Not for film. ILFORD states flatly that BROMOPHEN is not suitable for developing films, and that it is not designed for high-temperature or machine processing. Its stablemate PQ UNIVERSAL is the one that doubles as a dish film developer; this one does not.

When another formula is preferable

• When you want to understand a print developer rather than use one, mix D-72. It is the same job done by five chemicals you can name, weigh and change, and it is the comparison this page is built around.
• When you cannot use a whole carton. This is the reason to mix rather than buy that applies most often to a home printer. ILFORD forbids splitting the packets, so the smallest quantity of BROMOPHEN that exists is a litre of stock — four litres of working solution. Every open formula in this library scales to whatever volume you want, because you weigh it.
• For a deliberately warm image tone from a formula you control, D-156 cuts D-72’s alkali to a quarter and raises the bromide, and D-166 goes further still with twelve and a half grams of bromide to the litre and the tone adjusted by dilution.
• For the coldest blue-blacks, D-158 is Kodak’s chloride-paper developer with the most alkali and the least bromide in the paper library, and D-170 is an amidol developer with no alkali in it at all.
• For soft, open highlights with no restrainer in the stock, D-52 leaves the bromide out of the bottle and puts it in the reader’s hands as an optional addition.
• When you want a liquid you measure rather than a powder you dissolve, ILFORD’s own answer is MULTIGRADE developer, which is half the development time on resin-coated paper and a neutral tone instead of a warm one.
• When the darkroom is not at 20 °C and cannot be brought there. ILFORD is explicit that these developers are designed for ambient room temperature and that high temperatures reduce the solution life considerably and shorten development to the point where uneven processing appears.

What the maker publishes

A powder gives its maker less to say than a bottle does — there is no concentrate strength to quote — and ILFORD says a great deal anyway. It is worth setting out at length, because the sheer quantity of it is what makes a page about an undisclosed product useful rather than merely careful.

The mixing procedure, step by step. The carton holds two bags. Part A is the smaller bag and part B the larger one. Dissolve part A in about three-quarters of the total solution volume of warm water at about 40 °C; stir until most of it has dissolved; keep stirring while gradually adding part B; keep stirring until no more powder dissolves. ILFORD then adds a sentence worth its weight in avoided panic: “it is normal for a few grains of powder to remain un-dissolved.” Add cold water to the final volume, stir, let it cool to 20 °C, and store it in a tightly capped bottle. To use it, treat the stock as though it were a liquid concentrate and dilute it 1+3 directly before the session.

The pH — but of the stock, not of the tray. ILFORD prints a table of pH and specific gravity for fresh solutions, and BROMOPHEN’s row reads 10.30 to 10.50 with a specific gravity of 1.106 for the stock. At the 1+3 working dilution the sheet gives a specific gravity of 1.025 and no pH at all. That is the opposite way round from MULTIGRADE, whose published pH is for the working solution. ILFORD adds that the figures were obtained under controlled laboratory conditions, that a user’s own measurements may differ slightly, and that the right use of the table is to make your own control measurement on your own fresh solution and compare later ones against it.

The times, for two paper bases, with a recommended figure and a range around it on fibre: two minutes for resin-coated at 1+3, and two minutes recommended for fibre within a range of one and a half to three. Four ILFORD paper sheets repeat those numbers for their own papers and none of them disagrees.

The plateau and the emergence time. On correctly exposed fibre prints ILFORD says the image will begin to appear after 35 seconds with these developers, and that development “may be extended to 6 minutes without any noticeable change in contrast or fog”. That second sentence is worth more than the recommended time, because it says the recommended time sits inside a wide flat region and not on a slope — Part XVIII draws the two curves that make it true.

The batch-printing advice, which is a real technique and easy to miss: to hold print-to-print consistency through a long run of either base, ILFORD suggests reducing exposure slightly and extending development, which moves the working point further into the plateau.

The capacity, per litre of working solution: 70 resin-coated or 45 fibre 8 × 10 prints. Those two numbers are the ones you can check in your own tray, and they are the ones this page uses.

The keeping, in six figures. Unopened packets keep indefinitely at 5–20 °C. Once opened, make the stock immediately. The stock keeps six months in a full capped container and three months in a half-full one. Working solution lasts one working day in an open dish and 24 hours in a capped bottle.

The water advice, which reads as housekeeping and is chemistry. Water from a pressure main comes out full of dissolved air, so ILFORD asks the printer to draw off what is needed and leave it standing for a few minutes first. On this product the instruction bites twice over: once for the litre of stock you mix from the packets, and again for every litre of working solution diluted out of it.

🧮The one place ILFORD's own arithmetic does not close

The sheet’s availability section says a 1 litre carton of BROMOPHEN “makes enough working strength solution at 1+3 to process 700 8 × 10 inch sheets of RC paper or 450 of FB paper”.

Take ILFORD’s own three published figures and follow them through. A 1 litre carton makes 1 litre of stock; the sheet says so, twice, and tells you to make it up to the volume printed on the carton. Diluted 1+3 that is 4 litres of working solution. At the sheet’s own capacity of 70 resin-coated prints per litre, that is 280 prints, and at 45 fibre prints per litre it is 180. The availability section says 700 and 450.

The same section gives PQ UNIVERSAL, a 1+9 liquid concentrate with a capacity of 70 and 45 per litre, figures of 700 and 450 from a 1 litre bottle — where the arithmetic closes exactly, because a litre of concentrate at 1+9 is ten litres of working solution. The BROMOPHEN row is that row’s numbers under a different dilution.

Both totals above are the course’s arithmetic on ILFORD’s printed figures, and the course does not know which of the maker’s two statements is wrong. Use the per-litre capacity, because it is the one you can verify by counting prints into a measured tray, and count sheets rather than believing either figure. Then run the experiment at the foot of this page and find out.

What is not disclosed

The formula. Not the quantity of any ingredient, not the ratio between the two developing agents, not the alkali loading, not the restrainer level, and not the date the current formulation was fixed. ILFORD names two developing agents in a product description and stops.

The mass of each bag, which is the boundary peculiar to this product. The composition tables below are for part A and part B separately, as percentages of each bag. Nothing HARMAN publishes says how much part A meets how much part B in the bottle. The sheet tells you which bag is larger and no more. So even a reader who was willing to treat two hazard tables as assays — and the next callout is about why nobody should — would still have two unconnected lists and no way to join them.

The working-solution pH. ILFORD publishes 10.30 to 10.50 for the stock and a specific gravity for the 1+3 dilution with the pH column left empty. The number you would actually measure in the tray is not published for this developer, though it is for the other two on the same sheet.

Anything measurable in the hazard sheets that would let you infer a formula. Section 9 of both safety data sheets is a column of the words Not known: appearance “Solid”, colour not known, odour not known, pH not known, density not known, solubility not known.

!Why the bands in the table cannot be added up

Two composition tables in one carton look even more like an assay than one does, and the urge to solve them for whatever is left over is correspondingly stronger. Doing the arithmetic once is the cure.

For part A, add the upper limits — 100, 30 and 5 — and you get 135 per cent, which is more than a bag. Add the lower limits and you get 71 per cent, leaving nearly a third of the bag unaccounted for by any named substance. For part B, the upper limits give about 116 per cent and the lower limits about 61. All four totals are the course’s arithmetic on HARMAN’s own printed figures, and none of them is a composition.

That is not sloppiness on HARMAN’s part. A concentration band on a safety data sheet exists to support a classification: it is chosen so that the mixture’s hazard can be calculated conservatively, and a band wide enough to do that is far too wide to mix from. Part A’s hydroquinone band runs from 60 to 100 per cent — a range that includes “the bag is nothing else at all”. A safety data sheet read as a hazard document is evidence. Reassembled into a recipe it is a fabrication with citations attached, and this page does not attempt it.

Nothing about why. No source in the corpus says why ILFORD kept phenidone in this powder while moving its liquid concentrates to Dimezone S, why the stock sits at 10.4 rather than 10.2 or 10.8, or what makes it warmer in tone than the company’s other two dish developers. Those are the interesting questions and the literature does not touch them.

Disclosed components

Every component in the table above, part A first and then part B, in the order each safety data sheet prints them. The concentration against each is the band that sheet states, as a percentage of its own bag, and the function line is given only where the maker says so.

1,4-dihydroxybenzenehydroquinonequinol, CAS 123-31-9, 60–100 % of part A. This is hydroquinone, and the mangled name is the sheet’s own: it runs three synonyms together with no separator between them. It is the first entry on the part A sheet, it carries much the widest band on either sheet, and it is the component that gives part A almost all of its hazard classification — H302, H317, H318, H341, H351, H400 and H410. It is also the reason part A is labelled a suspected mutagen and a suspected carcinogen and carries the signal word Danger where part B carries Warning. It is one of the two developing agents ILFORD names.

Sodium metabisulphite, CAS 7681-57-4, 10–30 % of part A. Sodium metabisulfite is the second entry on the part A sheet and the one that is doing something ILFORD never mentions. In water it gives bisulphite, and a bisulphite solution is mildly acidic; the two developing agents therefore go into a reducing, mildly acidic solution before any alkali reaches them, which is exactly the condition in which a developing agent does not oxidise. That reading is the course’s, from where the substance sits in developer formulation generally, and ILFORD says nothing about it. The sheet classifies it H302 and H318 and gives it no function.

1-phenyl-3-pyrazolidone, CAS 92-43-3, 1–5 % of part A. This is Phenidone, and here the maker does tell you what it is for: the product description calls BROMOPHEN a phenidone/hydroquinone developer. It sits at the bottom of part A’s table in the narrowest band on it, and it is the substance that makes the developer work — which is the signature of a superadditive pair rather than a sign that it hardly matters. The chemical page has the full account of the molecule, including the quantitative claim in Kendall’s 1942 Ilford patent about substituting it for metol; that claim is about metol substitution in general and not about this product, and nothing on this page transfers it.

Sodium carbonate, CAS 497-19-8, 30–60 % of part B. The first entry in the larger bag, at the top of the sheet’s descending order — though its band and the sulphite’s overlap, so which of the two actually weighs more is not something the table settles. Sodium carbonate is the alkali, and the CAS the sheet prints is the anhydrous salt’s rather than either hydrate’s. Carbonate against bicarbonate is a genuine buffer pair, and a buffer is what a paper developer needs: a print developer is a tray open to the air that must hold its pH through seventy prints, each of which puts acid into the bath as it develops. The identification of carbonate as the buffering alkali here is the course’s reading of a component list; ILFORD does not say it. The sheet’s only classification for it is H319.

Sodium sulphite, CAS 7757-83-7, 30–50 % of part B. Sodium sulfite is the second entry in part B and the sheet records it as not classified — the only component on either sheet with no hazard statement at all. In a print developer its established work is preservation: it consumes dissolved oxygen and intercepts the quinone that hydroquinone becomes, which is what Part VIII’s lesson on sulfite and preservation sets out. Meeting the metabisulphite from part A, some of it is the same ion by a different route. The course does not turn a band spanning 30 to 50 per cent of one bag into a concentration.

Potassium bromide, CAS 7758-02-3, 1–5 % of part B. Potassium bromide is the classical inorganic restrainer, and the first half of the trade name reads as an acknowledgement of it — BROMophen — which is the course’s reading of a name and not a statement by ILFORD. It suppresses fog by raising the bromide-ion concentration in solution, at a cost in shadow speed that Part VIII’s lesson on restrainers works through. ILFORD states no function for it and the sheet classifies it only H319; that it is a restrainer here is the course’s reading, not a maker’s statement.

Benzotriazole, CAS 95-14-7, less than 1 % of part B. The smallest entry on either sheet and the most heavily flagged. Benzotriazole is named three times on the part B sheet: in the composition table with H302, H319 and H411; in section 2.3, which states that “this product contains: 95-14-7 (Endocrine disrupting properties)”; and in section 12.6, which records it as listed for evaluation for endocrine disruption under EU legislation. It is the organic antifoggant that holds fog down without the shadow-speed penalty a bromide exacts — again the course’s reading of its class and not an ILFORD statement. Its presence alongside a bromide is what a bath built to hold its whites through a long session looks like.

⚗Two sheets, one product, and what the split tells you

Both safety data sheets carry the same product code, 1960549, and the same date of issue. They are one product documented twice, and the split between them is not arbitrary: almost every hazard in this carton is in the small bag.

Part A is Acute Tox. 4, Skin Sens. 1B, Eye Dam. 1, Muta. 2, Carc. 2, Aquatic Acute 1 and Aquatic Chronic 1, signal word Danger, and its section 7 says to store it locked up. Part B is Eye Irrit. 2 and nothing else, signal word Warning, with no locked-up instruction and no occupational exposure limit assigned to anything in it.

That is a useful map of the job. The bag you must not breathe, splash or leave within a child’s reach is the little one, and it is the first one you open. The big one is soda ash, sulphite and two restrainers.

Behaviour

It is not the fast one, and that is deliberate. Two minutes for a resin-coated print at 1+3 is double what ILFORD asks for its own MULTIGRADE developer and the same as PQ UNIVERSAL, and it is a third longer than the minute and a half Kodak publishes for D-72 on a bromide enlarging paper at 1:4 and 21 °C. A slower bath is easier to agitate evenly and easier to lift a print from at a consistent moment; the slowness is only a cost when you are making a great many work prints in an evening.

It develops to completion, not to a density you choose. This is the largest single difference between printing and film processing, and it is where beginners lose prints. Two minutes is a point inside a plateau rather than a target: ILFORD’s six-minute claim says the black has finished rising while the base has not started to lift. So a sheet left an extra minute comes out the same, and a sheet lifted at ninety seconds does not read as lighter — it reads as thin, weak in the blacks, and blotchy wherever the solution first reached the paper.

It exhausts by counting, not by looking. Seventy 8 × 10 resin-coated prints to a litre, forty-five on fibre, and the useful discipline is to count sheets rather than to judge the colour of the tray. The figure falls on fibre because that base soaks up far more solution and carries more of it away.

It has three clocks, not one. The unopened packet has no clock at all. The stock has a six-month clock that halves to three when the bottle is half empty. The working solution has a one-day clock. Almost every disappointment with this product is one of those three clocks being read as another.

It is formulated for one temperature. Twenty degrees, plus or minus one, is the whole tolerance ILFORD allows. A cooler dish can be worked with a longer time; a warmer one shortens development until covering the sheet evenly becomes difficult and, the sheet warns, cuts the solution life considerably. Note too that the stock is made at about 40 °C and must be back down to 20 °C before it is diluted.

⚗What the published pH is actually telling you

10.30 to 10.50 for the stock sits nearly two pH units above the 8.60 to 8.70 ILFORD publishes for its own ID-11 film developer, and every pH unit is a factor of ten in hydroxide-ion concentration. That gap is what makes a print develop in two minutes and a film take ten, and Part VIII’s lesson on alkalis and buffers works through why: a developing agent works as its anion, and the fraction ionised is set by the pH against the agent’s pK_a.

The catch specific to this product is that the figure is for the stock and the tray gets the 1+3 dilution, for which ILFORD publishes no pH. Diluting a carbonate-buffered solution fourfold does not divide its pH by anything — a buffer is what resists that — but the course will not print a number the maker does not give, and neither should you. Use the band as a control measurement on your own fresh stock, with a meter calibrated that day, and measure your own working solution to find out what yours actually is.

Image characteristics

Image tone: slightly warm of neutral, on most papers. This is ILFORD’s own phrase and it is a claim about the product rather than a measurement, and it is not a claim to being the warmest thing ILFORD sells: the same sheet describes PQ UNIVERSAL in identical words. What separates BROMOPHEN is what comes next in the paragraph — the recommendation of it for MULTIGRADE Warmtone papers “to get the warmest image tone”, which is the most specific statement any of ILFORD’s literature makes about a developer and a colour.

Contrast: not something the tray decides. If six minutes changes neither contrast nor fog, then on a variable-contrast paper the contrast is set by the filter and the exposure and by nothing else. That is a property worth having rather than a shortcoming: it is what makes split-grade printing reproducible from one sheet to the next.

Maximum black: reached at the recommended time — but the published curves are somebody else’s. Here is a small trap worth naming. ILFORD recommends BROMOPHEN for MULTIGRADE FB WARMTONE, and then publishes that paper’s characteristic curves developed in MULTIGRADE at 1+9 for two minutes. A paper’s published curve is always a curve of a paper-and-developer pair, and for this pairing the maker’s own curve is not the pairing the maker recommends. Your Warmtone prints in BROMOPHEN are off the published curve, in the direction the maker says you want.

Fog: low, and the whites are the thing to watch. “Clean working” is ILFORD’s phrase for it, and the disclosed presence of both a bromide and an organic antifoggant is consistent with a bath built to hold its whites through a long session — though how much of either is present is not published.

Grain, acutance and film speed do not apply. This is a paper developer and ILFORD says plainly it is not for film.

The mechanism

Everything in this section that goes beyond the two agent names is marked as what it is.

What the maker states. BROMOPHEN is a phenidone/hydroquinone developer supplied as a powder in two parts, made into a stock at pH 10.30 to 10.50, diluted 1+3, developing a print in one and a half to three minutes at 20 °C, showing the image at about 35 seconds on a correctly exposed fibre print, and holding contrast and fog steady out to six minutes.

What follows from that without needing anything else: it is a PQ developer. A pyrazolidone with hydroquinone is the classical form of the superadditive pair, and the pair is the central mechanism of Part VIII’s superadditivity lesson. The fast agent — here Phenidone — reduces silver at the latent-image site and is itself oxidised; the hydroquinone, present in much the larger quantity, regenerates it from solution. The consequence a printer can see is that a very small amount of one substance transforms the behaviour of a much larger amount of another, which is consistent with the pyrazolidone sitting in the narrowest band on part A’s sheet and the hydroquinone in the widest. Two hazard bands are not a ratio and this page does not treat them as one, and here the point is sharper than usual: the two bands are percentages of one bag, and the bag’s share of the finished bottle is not published either.

Why the powder is two bags, and why that order. Part A holds the agents and an acid preservative; part B holds the alkali, the sulphite and the restrainers; and ILFORD’s instruction is to dissolve A first, in warm water, and add B to it. The developing agents therefore never sit in an alkaline solution without a preservative already dissolved around them, which is the same reasoning that puts metol before carbonate in every hand-mixed formula in this library — see Part VIII on reading a developer formula. That is the course’s reading of the procedure and of where those substances sit in developer chemistry. ILFORD prints the order and gives no reason for it.

Inference, labelled as inference. The regeneration account of superadditivity is the standard one and no source in this course’s corpus states it for this product. The identification of sodium carbonate as the buffering alkali, of sodium metabisulphite as the acid preservative, and of potassium bromide and benzotriazole as the antifogging pair all follow from what those substances do in developers generally and are not ILFORD statements.

What is unknown and stays unknown. The ratio of phenidone to hydroquinone. The mass of part A against part B. The carbonate loading in the finished stock. The bromide and benzotriazole loadings. The working pH at 1+3. Why ILFORD kept Phenidone here and moved MULTIGRADE and PQ UNIVERSAL to Dimezone S — Part XVIII reads that split as a solution-stability decision, and marks it as the course’s inference, because ILFORD names the substances and explains nothing.

!Reading a safety data sheet, and what its defects teach

These two sheets have the same visible faults as their MULTIGRADE stablemate, and noticing them is part of the skill the course is trying to build.

They run synonyms together. Hydroquinone is printed as “1,4-dihydroxybenzenehydroquinonequinol”: three synonyms concatenated with no separator. A reader who did not already know the substance would struggle to look it up. The CAS number is the field to trust, every time, and it is why every line in the table above carries one.

Their dates do not agree. Both sheets give a date of issue of 18 July 2024 and a date of revision of 17 July 2027, three years in the future. That is almost certainly a review date printed in the wrong field, and it is exactly the kind of thing to record when you file a sheet rather than to correct silently. The course’s procedure for that is recording a safety data sheet.

The nearest open formula

Kodak D-72, and the comparison is the reason this page exists.

D-72 is the archetype alkaline paper developer: metol and a large excess of hydroquinone in sodium carbonate, with potassium bromide as the restrainer, mixed from five weighed chemicals into a stock and diluted one in four for bromide enlarging papers. BROMOPHEN is the same class of bath, mixed the same way — powder into water, stock into a bottle, stock diluted for the dish — with a pyrazolidone in place of the metol and an organic antifoggant alongside the bromide. Four of BROMOPHEN’s seven disclosed components — hydroquinone, sodium sulphite, sodium carbonate and potassium bromide — are, by name, four of D-72’s five ingredients.

	Kodak D-72	ILFORD BROMOPHEN
Composition	Published in full, twice, twenty-one years apart	Not published
Developing pair	Metol and hydroquinone	Phenidone and hydroquinone, both named by the maker
Alkali	Sodium carbonate, quantity published	Sodium carbonate named; no quantity, and that it is the buffer is inferred
Restrainer	Potassium bromide, quantity published	Potassium bromide and benzotriazole named; no quantities, and the role is inferred
Sold as	Five chemicals you weigh	Two sealed bags you may not split
Smallest batch	Whatever you choose to weigh	One carton, one litre of stock
Working dilution	1:4 for bromide enlarging papers	1+3, the only one published
Published pH	None, in either printing	10.30 to 10.50, for the stock only
Published paper time	1½ minutes at 1:4 on bromide enlarging paper, at 21 °C	2 minutes at 1+3, resin-coated or fibre, at 20 °C
Capacity in prints	None published in either Kodak printing	70 resin-coated or 45 fibre 8 × 10 per litre
Stock keeping	3 months full, 1 month half-full	6 months full, 3 months half-full
What you can change	Any of five quantities, one at a time	The dilution, the time and the temperature

The last two rows are the whole argument. Buying the carton gets you a stock that keeps twice as long as D-72’s, a published capacity, a published stock pH, and exactly three variables. Mixing D-72 gets you a bath with no published capacity and no published pH, and eight variables, five of which are quantities you chose — in any volume you like. Part XVIII’s comparison session puts the two in adjacent trays with the same negative, which is the only way to find out what the difference is worth to you.

Safety

Level B, and the reasoning belongs on the page rather than in a database.

Part A is where the hazard lives. HARMAN classifies it Acute Tox. 4, Skin Sens. 1B, Eye Dam. 1, Muta. 2, Carc. 2, Aquatic Acute 1 and Aquatic Chronic 1, signal word Danger, with H302, H317, H318, H341, H351 and H410. Skin sensitisation is what pushes it past Level A on the classification rubric: sensitisation is not reversible, and a Level A page assumes substances that are at most irritant at the concentrations handled. Eye Dam. 1 — serious eye damage, not irritation — is what makes splash goggles rather than spectacles the right answer, and splash goggles are a Level B assumption. The suspected-mutagen and suspected-carcinogen classifications are read against the Level C criterion and do not meet it, because that criterion turns on a fume cupboard or specialist disposal being the recognised control, and HARMAN’s own control is ventilation, gloves, eye protection and, for the dust, a dust mask. Level B.

Part B is comparatively benign, classified Eye Irrit. 2 and nothing else, signal word Warning, with no occupational exposure limit assigned to any of its components. Handling it carelessly is still handling a dust.

The dust is the difference from a liquid. This is the one thing a powder developer asks for that a bottled concentrate does not. Part A’s sheet asks you to avoid breathing dust, and its section 8 says a dust mask or dust respirator with filter type P to EN143 or EN405 may be appropriate; its section 6 goes further and asks for full personal protection including respiratory protection when clearing a spillage. Open the bags low in the mixing vessel, over water, not at head height over a dry bench; never blow a bag out; and treat a spilt powder as a solid spill, swept or vacuumed and not brushed into the air.

Personal protection, as the sheets specify it. Eye protection with side protection to EN ISO 16321-1. Impervious gloves to EN 374, with the breakthrough time taken from the glove maker rather than assumed — the course’s glove selection page is where that goes. Protective clothing. Hands and exposed skin washed thoroughly after handling, and contaminated clothing taken off and washed before it is worn again. Do not eat, drink or smoke while mixing.

Ventilation and eyewash. Both sheets ask for ventilation or local exhaust ventilation and for a washing facility for eye and skin cleaning to be present. A darkroom with an extractor running and an eyewash within reach meets that; a sealed bathroom does not.

Tongs, on every print. Sensitisation is built out of many small contacts rather than one memorable splash, and an evening spent lifting sheets out by hand is far more skin exposure than a spilt tray would ever give. Part A’s own sheet classifies two of its three components as sensitisers.

Published exposure limits, quoted by part A’s sheet from EH40/2005: hydroquinone at 0.5 mg/m³ and disodium disulphite at 5 mg/m³, both as long-term eight-hour limits. They are workplace air limits for the pure substances and neither is a limit for a tray of diluted paper developer; they are here because the sheet prints them.

⚠The one line on the technical sheet to disagree with

ILFORD’s technical sheet opens its mixing instructions with the sentence “Photographic chemicals are not hazardous when used correctly.” The same company’s safety data sheet for part A of this same product classifies it as harmful if swallowed, a skin sensitiser, a cause of serious eye damage, a suspected mutagen and a suspected carcinogen, gives it the signal word Danger, and instructs the user to store it locked up.

Both documents come from HARMAN. The technical sheet’s very next sentence asks for gloves, eye protection and an apron and sends the reader to the safety data sheets, so nobody is being misled on purpose — but a sentence of that shape gets quoted around a darkroom until somebody decides gloves are optional. The classification is the fact. Every load in that sentence is carried by “used correctly”, and it is the safety data sheet, not the technical sheet, that defines it.

Storage

The unopened packets, cool and dry at 5–20 °C, keep indefinitely — the one keeping figure in this whole library with no number on it, and the strongest practical argument for a powder over a concentrate. Part A’s safety data sheet adds an instruction the technical sheet does not: store locked up, which in a domestic darkroom means a cupboard a child cannot open.

Once a packet is open, the clock starts and ILFORD gives you no grace at all: prepare the stock solution immediately. A part-used bag of hygroscopic alkali and oxidisable developing agent is not something the maker is willing to put a figure on, and neither is this course.

The stock, in a tightly capped bottle: six months full, three months half-full. The halving is the instruction hidden inside the two numbers — the enemy is the air above the liquid, not the calendar. Decanting a dwindling stock into smaller bottles as it goes down is the standard answer to that; ILFORD does not suggest it, and it is the course’s inference from the maker’s own two figures.

The working solution is not stored at all. Dilute what the session needs, and pour it away when the session ends. The 24-hour figure for a capped bottle is a concession the sheet makes rather than a plan it recommends, and it is a tiny fraction of what the stock in the next bottle along will keep for.

Label everything, with the product, the dilution and the date mixed, using the labelling SOP — and for this product label the stock bottle with the date the packets were opened, because that is the date the six months runs from. A tray of clear liquid in a darkroom is indistinguishable from three other trays of clear liquid, and an unlabelled or undated container is the failure that costs a whole printing session.

Incompatibilities

Acid, and the stop bath above all. ILFORD’s own instruction is to keep both stop bath and fixer out of the developer and to wash every vessel after use. Acetic or citric acid carried back on a pair of tongs does not simply weaken this bath — it drops it out of the pH region in which a phenidone–hydroquinone pair works at all.

Fixer, travelling in either direction. Thiosulfate reaching the developer dish dissolves silver and stains; developer carried forward into the fixer shortens the fixer’s life and stains prints at the other end instead. It is a waste problem as much as a print problem, since a paper developer holds almost no silver and tipping it into the fixer spoils a solution a refiner would otherwise pay for.

Strong oxidisers. Ferricyanide, dichromate, permanganate and persulfate must not meet a developing agent on a shelf, in a dish or in a drain. The chemical incompatibilities page lists the pairs and gives the reaction behind each of them.

Damp, for the powders. Neither sheet says it and it is not a chemical incompatibility in the sheet’s sense, but a carbonate-and-sulphite powder left open in a humid darkroom cakes, and the stock that crystallised in cold storage is the same family of problem at the other end of the process. ILFORD’s “cool and dry” is doing work.

✕What section 10 of the sheets says, and why it is not the last word

Section 10.5 of both safety data sheets gives incompatible materials as “Not known”, and section 7.2 of both gives them as “None known”. Read literally, that says a photographic developer has no chemical incompatibilities, which is false in a darkroom where the next tray is an acid and the one after it is a thiosulfate.

A safety data sheet answers one narrow question: what makes this product, sitting in its own container, unstable or dangerous. It was never meant to be a compatibility chart for a darkroom sequence. What governs here is the course’s incompatibilities page, together with HARMAN’s technical sheet, which does say in plain words that stop bath and fixer must be kept out of the developer.

Waste

Bottled separately, and not poured into the fixer. Spent paper developer is alkaline, carries negligible silver, and contains both developing agents in their oxidised forms. HARMAN classifies part A Aquatic Acute 1 and Aquatic Chronic 1, very toxic to aquatic life with long lasting effects, and its section 6 asks that spillages or uncontrolled discharges into watercourses be alerted to the appropriate regulatory body — which is a strong hint about the drain. Part B is much milder, with low toxicity to fish, invertebrates and algae recorded, but its benzotriazole carries H411 and is listed for endocrine-disruption evaluation.

What the sheets say to do with it: dispose of contents in accordance with local, state or national legislation, and send it to a licensed recycler, reclaimer or incinerator, or to a hazardous or special waste collection point.

ILFORD’s own advice to domestic users in the United Kingdom is to bottle each waste chemical on its own, label the bottle, and leave it in the chemical cupboard at a Household Waste and Recycling Centre.

Empty packets are not clean. A bag that held 60 to 100 per cent hydroquinone has a dusting of it left inside. Rinse the bags into the mixing vessel while you are making the stock, which is where that material belongs, rather than putting a dusty bag in a kitchen bin.

The disposal caveat governs, and the rule where you live decides. The general chemical waste SOP is the procedure this course follows. Under any jurisdiction the two bottles stay apart, because the fixer is worth something at a refiner and this bath is not.

Troubleshooting

A few grains of powder will not dissolve. ILFORD says this is normal, in those words. Do not keep stirring, do not add hot water, and do not decide the packet was faulty. Make up to volume, cool, and use it.

Prints thin in the blacks, a little warm, and patchy. Nine times in ten this is development cut short rather than a fault in the bath; muddy print from snatched development sets out the whole diagnosis. Give it the full two minutes and change the exposure instead.

The image takes far longer than 35 seconds to appear on fibre paper. Either the print is underexposed or the developer is going. Count the prints that have been through the litre against the published capacity of 45 before you blame the bath, then check the temperature, then mix fresh from the stock.

Grey where the paper should be white. Two candidates, told apart by putting a strip of unexposed paper straight into the developer. Developer fog on paper is the developer’s fault; safelight fog and paper storage fog are not.

Highlights going grey and flat towards the end of a session. That is developer exhaustion. Seventy prints to the litre is HARMAN’s figure for HARMAN’s papers; the number that matters is the one you measure, and it falls on fibre and falls further in a dish that has been standing open.

Prints from one session do not match prints from the next. Check the dilution first: 1+3 is 250 mL of stock into 750 mL of water, not 250 into a litre, and a misread dilution ratio changes both the time and the capacity. Then check the temperature. Then check the date on the stock bottle. If the drift is gradual through one evening rather than between sessions, it is session exposure drift and the bath is not the cause.

The stock has gone dark in the bottle. Oxidation of the developing agents, which is what oxidised developer covers. A half-empty bottle past its three-month life should be treated as suspect and tested against a control strip before a print you care about goes in it.

Crystals in the bottom of the stock bottle after a cold night. See stock crystallised in cold storage — the carbonate and sulphite loading in this stock is high enough for that to be a real possibility in an unheated darkroom, and the answer is warmth and patience, not a fresh carton.

Streaks running one way across a fibre print. Agitation, not chemistry — and usually too many sheets interleaved at once, which ILFORD warns will give uneven processing when the agitation cannot keep up with the pile. See mottled development.

Experiments

Measure the pH of the fresh stock, then measure the working solution ILFORD does not publish. This is the cheapest possible calibration of your own meter and your own water, and it is the one ILFORD explicitly asks for. Do it with a meter calibrated that day — the calibration procedure is the whole experiment’s validity — and record both figures. The stock goes against ILFORD’s 10.30 to 10.50; the 1+3 figure goes in your notebook as a number this page could not give you.

Settle the 700-against-280 question. Make one litre of stock, dilute the whole of it 1+3 to four litres, and print your way through it in batches of twenty resin-coated sheets with one identical control sheet at the start of each batch. Plot the maximum black of the controls against the number of prints. If the tray is still working at 700 sheets, the availability figure is right and the capacity table is conservative. If it dies somewhere near 280, ILFORD’s availability row has been copied from the PQ UNIVERSAL line above it. Either result is worth writing down.

Test the six-minute plateau. Print five identical sheets from one negative at one exposure and develop them for 1 minute, 1½ minutes, 2 minutes, 4 minutes and 6 minutes at 1+3. The prediction from the maker’s claim is that the last four are indistinguishable in maximum black and that only the first is weak. If the six-minute print has a grey base, you have found the far end of the plateau on your paper and your safelight, which is worth knowing.

Test ILFORD’s own tone recommendation. One Warmtone paper, one negative, two trays: BROMOPHEN at 1+3 for two minutes against MULTIGRADE developer at 1+9 for its own time. The maker says the first is warmer. Dry both fully before you judge, because image colour on a fibre paper changes as it dries, and remember that the paper’s published curves were made in the other developer.

The comparison that matters most: this against D-72. Same negative, same paper, same session, the bought powder at 1+3 and the mixed developer at 1:4, both at their published times, and note that Kodak’s is published for 21 °C and ILFORD’s for 20. Part XVIII’s session sets it up properly with a third arm and a control. Record it in the formula version record — a bought product gets a line in that record too, with its dilution, the date its packets were opened and how many prints had already been through the tray, because those are the only variables you have.

Weigh the two bags, and then see how far it gets you. This one is a lesson in the limits of reverse-engineering rather than a route around them. A kitchen scale will give you the mass of part A against part B — one number ILFORD does not publish. Now try to reach a formula from there. Part A is somewhere between 60 and 100 per cent hydroquinone; part B is somewhere between 30 and 60 per cent carbonate; the two ranges multiply, and what comes out the other end is a hydroquinone quantity uncertain by a factor of several and a carbonate quantity no better. You will have measured something true and still not have a formula, which is exactly why this page is a product page and D-72 is not.

Keep a column for the emergence time. Write down the second at which the image appears, beside the print number and the age of the stock, and compare it with ILFORD’s 35 seconds on fibre. It costs nothing to record, and after a month of printing it will tell you a bath is failing before a ruined print does.