Print Faults: Weak Blacks, Mottle, Bronzing and the Rest

A print that will not go black is the commonest complaint in a darkroom and the one most often answered wrongly, because three different failures produce prints that all get described as “weak” and the correction for each ruins the other two.

This page separates them, gives the check order for a genuinely poor maximum black, and ends on the question that makes this a course rather than a manual: whether the black you did not reach was a fault at all.

What maximum black actually is

Maximum black is a reflection density limit set by the paper, its surface, the developer and the drying. It is not a number a printer can exceed by exposing longer.

Hurter and Driffield defined the useful version of this a century ago, when they defined the range of a bromide paper as the ratio between two exposures — one just short of producing any deposit, and the other just sufficient “to produce the deepest black the paper is capable of recording when viewed by reflected light”. The phrase the paper is capable of is the whole point: there is a ceiling, it belongs to the material, and the printer’s job is to reach it rather than to beat it.

The manufacturers publish the ceiling, and the numbers are worth knowing because they are far lower than most people guess:

Paper	Published maximum reflection density
ILFORD MULTIGRADE RC DELUXE	2.15
ILFORD MULTIGRADE IV RC DELUXE	2.05
Foma FOMABROM (glossy)	2.1
Foma FOMATONE MG Classic (glossy)	2.0
Foma FOMATONE MG Classic (matt)	1.6

Two things fall out of that table immediately.

Surface changes it more than anything else you control. Foma state that their published curves are valid for the glossy surface and that any other surface — the matt one — “causes a decrease in the maximum density value”, and for FOMATONE they give the figure: 2.0 glossy against 1.6 matt. That is not a small difference; it is most of a stop of print scale, and it is a decision made when you buy the box. A matt print is not a glossy print that failed.

The differences between makers and generations are real but modest. ILFORD’s own comparison sheet gives 2.15 for the current MULTIGRADE RC DELUXE against 2.05 for the paper it replaced, and describes the difference as “more depth and a slightly extended tonal range”. A tenth of a unit of density is visible side by side and invisible on its own.

Three failures that all get called a weak print

The three, and the test strip evidence that separates them

1. 1A. The print is simply too lightThe blacks are absent because you never gave them enough exposure. On a test strip, the darkest step is still climbing — each step is meaningfully darker than the one before it, right to the end. Fix: more exposure.
2. 2B. The deepest tone is greyOn a test strip the steps stop getting darker after some point, and where they stop is not black. The paper has reached a ceiling that is below its published maximum. Fix: find out why the ceiling moved — this is the check list below.
3. 3C. There is a black, but nothing separates above itThe darkest step is a real black and the two or three above it are almost the same tone. The print has a black point and no shadow separation. Fix: this is a contrast and placement problem — a softer grade, or a different base exposure — not a maximum black problem at all.

One test strip distinguishes all three, and the observation to make is not how dark the darkest step is but whether the steps are still changing. A, the steps are still climbing. B, they have stopped climbing below black. C, they have stopped climbing at black.

That single question — are the steps still getting darker? — is the print equivalent of the shadow witness on the negative page, and it settles the same proportion of cases.

The check order for a genuinely poor maximum black

You are in case B: the steps stop climbing before black. These are the causes in the order worth checking, which is roughly the order of how often they turn out to be the answer against how cheap they are to eliminate.

1. Underexposure that looks like case B because the strip was too short. Extend the strip by two more steps before anything else. It costs a fifth of a sheet and it eliminates the commonest confusion on this page.

2. A print developer that is exhausted, too cold or too dilute. All three lower the rate, and a paper developed at a lower rate for the same time is under-developed.

• Exhausted: ILFORD publish capacities per litre of working strength — 100 sheets of 8 × 10 inch RC or 50 of fibre for MULTIGRADE at 1+9, 70 RC or 45 FB for PQ UNIVERSAL at 1+9 and for BROMOPHEN at 1+3 — with the note that a cool-tone paper’s longer development times halve them.
• Too cold: the published times are for 20 °C.
• Too dilute: MULTIGRADE at 1+14 has its own longer time — 2 to 5 minutes against 1½ to 3 — and using the 1+9 time at 1+14 under-develops by construction.
• And too old in the dish: working strength paper developer left in an open dish “should not be kept for more than one working day”.

3. Development cut short. This is the fault the manufacturers warn about most directly, and the warning has a number attached at both ends. ILFORD’s RC sheet: the image begins to appear after approximately 10 seconds, and “prints developed for shorter times may be underdeveloped and lacking in contrast and density”. Their fibre sheet: the image begins to appear at approximately 20 seconds, the recommended time is 1½ to 3 minutes, and — the line that ends the argument — “development can be extended up to 6 minutes without any noticeable change in contrast or fog”.

✕Snatching, and why the sheet's six minutes is the answer to it

The habit is called snatching: pulling a print from the developer when it looks right under the safelight, which is usually well before the recommended time.

It cannot work, and the reason is in ILFORD’s two sentences above. The image appears in 10 to 20 seconds and continues to build for a minute or more after that, so a print pulled at 45 seconds has a part-built image everywhere. What it does not have is the last of its density in the deepest tones, which are the slowest to complete.

And the escape route that people reach for — “I will expose less and develop longer” — is closed from the other side by the same sheet: six minutes changes neither contrast nor fog noticeably. A paper developer is worked to completion by design, so there is no compensating trade to be made. Give the full time and control the print with the exposure and the grade.

The counterpart fault, muddy print from snatched development, has its own atlas entry.

4. Safelight or room fog raising the base. A raised base does not lower the maximum black directly, but it lowers the difference between white and black, which is what the eye reads as depth. ILFORD’s own warning is exactly this and is worth quoting because it describes the fault rather than the measurement: safelighting can “appear safe, but be causing low level fogging. This may not be seen as safelight fog, but only as a general loss of photographic quality, particularly reduced contrast and lack of clear highlights.”

5. Over-fixing dissolving the deepest deposits. Covered in full on the fixing page and worth repeating here as a number, because the error is so easy to make: ILFORD RAPID FIXER at 1+4 gives 1 minute for fibre paper and 30 seconds for RC, against 2 to 5 minutes for film. A printer using the film time on paper is over-fixing by two to five times, and the manufacturer’s name for the consequence is image etching.

6. An over-strong contrast filter losing the black point. A hard grade compresses the exposure range that the paper responds to, and if the base exposure is not re-established for the new grade, the tones that should have been black land on a part of the curve that is not black yet. The correction is a new test strip at the new grade, which is Part XIX’s method.

7. Paper that has aged. Old paper fogs before it slows, exactly as old film does, and a fogged base produces a print that reads flat regardless of grade. ILFORD give MULTIGRADE RC papers two years in excellent condition when stored cool and dry in the original packaging. The paper storage fog entry has the diagnosis.

Dry-down is a systematic error, not a fault

A print judged wet and a print judged dry are different objects, and the difference is consistent enough to be corrected for — which makes it an error in the measurement sense rather than a defect.

What changes as the print dries. Two things at once, and separating them is the whole of the subject. The material changes: the gelatin loses water, its refractive index and surface behaviour change, and the light returned by the print changes with it. The viewing conditions change: a wet print is inspected under a bright darkroom light at close range and a dry print is judged on a wall in room light.

How much it is. The course does not publish a figure, and the reason is not caution but evidence. Part XVIII’s maximum black experiment establishes that no manufacturer in this course’s corpus publishes a dry-down figure for a developing-out silver gelatin paper, and it takes the honest consequence: it teaches you to measure your own, on your paper, in your process, and it shows that a single number is a fiction because the difference is not the same at every density — it is smallest at paper white, largest through the upper mid-tones, and narrows again towards black.

How the printer compensates. By measurement rather than by feel. Part XVIII’s method is to read the same patches wet and dry, convert the density difference into an exposure correction using the local gradient, and state what the conversion assumes. The alternative that most printers actually use — “add a bit for dry-down” — is a guess that gets applied uniformly to a difference that is not uniform, which is why it costs the highlights.

Why judging a wet print under a bright inspection light misleads, specifically: the inspection light is far brighter than the light the print will hang in, and a bright light makes the deepest tones look deeper than they will. So the wet print flatters twice — once for being wet and once for the lamp — and both errors run the same way.

Dry-down error is an atlas entry of this page because it is diagnosable and preventable, even though it is not a defect of the material.

Mottle and uneven development on large sheets

The mechanism is identical to the film case and belongs to the flow-marks page: local exhaustion where the emulsion is dense, and whatever the solution does or fails to do about it.

What is specific to paper is scale and geometry. A big print in a dish is a large flat area lying still in a shallow layer of solution, and the solution under a large area of deep black is doing far more work than the average. The result is a soft patchiness in even tones — a sky, a wall, a background — and often a drift from the middle of a large print outwards.

The numbers that say when it matters. One 16 × 20 inch print is four 8 × 10s. ILFORD’s capacity for MULTIGRADE at 1+9 is 50 sheets of 8 × 10 on fibre per litre, so a litre holds about a dozen 16 × 20 prints — and the average is a poor guide, because a dark print consumes more than a light one.

The prevention is volume and agitation: a dish deep enough that the print is properly covered throughout, enough solution that the local reservoir is not the whole reservoir, and continuous rocking that changes direction rather than a steady rhythm that sets up a standing pattern. Uneven print development and print mottle are the entries.

Bronzing, and an honest limit on what the course can say about it

What is reported. A metallic sheen in the deepest tones of a print, seen by reflected light at an angle, on prints that have been heavily exposed and given extended development. Printers call it bronzing or silvering-out.

!The mechanism is not established in this course's corpus

The manifest for this page asked for the mechanism of bronzing or silvering-out from a technical or conservation source, and for a ruling on whether it is correctly related to silver mirroring or is a different phenomenon.

Neither is available. No source in this course’s corpus states a mechanism for a metallic sheen in the deep tones of a freshly made silver-gelatin print, and none relates it to mirroring. The course will not supply a plausible story in place of one.

What the corpus does establish is the other phenomenon, and stating it precisely is what keeps the two apart. The Image Permanence Institute defines silver mirroring as an oxidation of black-and-white images “in which the image silver migrates to the surface, creating a mirror-like appearance”, and the conservation catalogue for dry plates describes it as a bluish metallic sheen starting from the edges, visible under reflected light, on aged material.

Three observable differences let you tell them apart without knowing whether they share a mechanism, which is what a diagnosis actually needs:

	Bronzing as reported	Silver mirroring
When	On the print when it is made	After months or years of storage
Where	In the deepest tones, following image density	From the edges inwards, ignoring the image
What changes it	Exposure and development of that print	The enclosure, the mount and the atmosphere

So the page teaches the discrimination and declines the mechanism — and the atlas entry the register plans for bronzing is not published, for the same reason. The atlas’s rule is that an entry appears when its mechanism, its discriminating evidence and its corrective action are all supported; here the mechanism is not, so the row stays in src/data/defects-planned.json and is counted as outstanding rather than filled with a plausible story. When a Tier 1 or Tier 2 source establishing it is found, that is the entry to write.

What can be said practically follows from the reported conditions rather than from a mechanism: bronzing is associated with heavy exposure and extended development, so if you are seeing it, the diagnosis to test first is that you are exposing well past the black point and then developing long to compensate for something else. A shorter exposure at a harder grade puts the same tone on the print with less silver in it.

The handling faults

Tong marks. Two small crescents or a pair of parallel indentations where the tongs gripped. On a print they are usually lighter than their surroundings if the tong carried fixer, and a density change either way if the pressure was applied while the emulsion was soft. The prevention is a tong per tray, gripped at the very edge of the sheet, and never a tong that has been in the fixer touching a print in the developer.

Fingerprints from developer or fixer on dry paper. These are chemical rather than mechanical, and they are the most complete of all print faults: where fixer touched dry paper, the halide is dissolved before any exposure or development can happen, so the print has a white mark that no exposure will fill. Developer on dry paper does the opposite and gives a dark mark. Both are unrecoverable and both are prevented by the same thing — dry hands on the dry side, and a rinse and a towel between the wet side and the paper box. Kodak’s Z-133 makes it a facility requirement: separate the darkroom into a wet area and a dry area, keep a container of water for rinsing hands, and dry them on a clean towel before touching paper.

Squeegee damage. A wet emulsion is soft, and a squeegee with grit under its blade scores a line the length of the print. The blade is not the problem; what is on it is. Squeegee lines on prints is an existing entry.

RC blisters and drying heat. ILFORD’s RC sheet gives a hot-air drying limit of 85 °C for machine drying, and warns that RC papers “should not be glazed/ferrotyped or dried on a drum or flatbed glazer – as this can cause the polyethylene in the paper to stick to the glazing surface”. At room temperature they dry in 10 to 20 minutes without any equipment at all. The sheet does not name blisters, and the emulsion-stress page says plainly that the course has no source attributing an RC blister to drying heat; what the corpus does support is gas evolved when a carbonate developer meets an acid bath, in a layer sandwiched between two impermeable skins. Respect the published limit, avoid the glazer, and treat the blister attribution as unestablished.

Stains on prints, and reading their position

The chemistry of every stain on a print is on the fixing, washing and stains page and is not repeated here. What belongs here is the location reading, because on a print it is unusually informative:

• A stain at one edge or in a drip shape — solution that stayed on the sheet at a transfer between baths, usually dried developer before the stop.
• A stain in the highlights, appearing over months — residual chemistry, and Part XII’s two tests say whether it is a washing or a fixing failure.
• A general yellowing over the whole sheet including the borders — the whole sheet met the same thing: an oxidised developer, a contaminated bath, or a session-wide washing failure.
• A mark only where a tong touched — carried chemistry, not a bath fault.
• Only on the prints from the end of a session — capacity, and your running total names it.

Safelight and room fog on paper, as it appears in a print

The fog page owns safelight fog as a defect and Part XVI owns the test. What belongs here is what it looks like when you are holding the print rather than the test strip.

A base that will not stay white. The paper’s white is the lightest tone in the print, and if it has been fogged there is no exposure and no grade that will restore it, because the fog is added to everything.

A print that looks flat regardless of grade. Raise the base and you compress the print’s range from the bottom, so a grade harder gives a harder-looking print that still lacks separation in the light tones. Printers commonly respond by going harder still, which makes the highlights worse.

Variation across a session, tracking how long each sheet sat out. That variation is the identification, because a fault that is identical on every sheet met every sheet equally.

The packet test settles it in one sheet: an opaque object laid on a sheet on the bench, left for the working time a print actually takes, developed afterwards. The shape of the object appearing on a grey ground is the answer.

The question the page ends on

Everything above treats a black that was not reached as a fault. The last section asks whether it was.

Maximum black is a decision as well as a measurement. A high-key print — a portrait against white, a snow scene, a study in the top two zones — may be exactly right with nothing on it darker than a mid grey, and printing a black into it because a rule says every print needs one makes it a worse photograph. The same is true from the other end: a print may be deliberately made without a clean white.

What separates a decision from a fault is whether the printer can say why, and can say it in terms of the picture rather than in terms of the process. “I chose not to take the shadow under the chair to black because it pulls the eye out of the frame” is a decision. “It would not go black” is a fault wearing a decision’s clothes.

There is a practical test hidden in that, and it is the reason this section belongs in a diagnostic part rather than in an aesthetics one: make the version with the full black as well. If you have both prints on the table, the choice is real and you can defend it. If you have only the one you got, you do not know which you have.

✦What a print critique should ask about the blacks

Three questions, in this order, and they work on your own prints and on other people’s.

Is there a maximum black anywhere on the sheet? If yes, the printer reached the paper’s ceiling and everything after that is placement. If no, go on.

Was that a choice? Ask the printer, or ask yourself, before looking at the test strips.

Does the picture want one? This is the only one that is about the photograph. A print whose subject is light, air and the top of the scale does not want a black in it; a print of a doorway does.

Two of the three questions are answerable by measurement and the third is not, which is the honest shape of the problem.

Where the fixes live

This page identifies and explains. It does not own the remedies, and saying so is not modesty — it is how the course avoids two pages drifting apart.

• Part XVIII owns the developer and paper chemistry, the maximum-black and dry-down measurement, and the break/fix session for a print that will not go black.
• Part XIX owns the printing technique: test strips and the black point, contrast filtration, local control, and print development and session consistency.
• Part XVI owns the safelight and enlarger tests.

Atlas entries this page owns: poor maximum black, weak or grey blacks, print mottle, tong marks, fingerprints on paper, RC blisters and dry-down error.

And one this page owns and has not written: bronzing. It is unlinked above because there is no page to link to. The register plans the row, this page describes the appearance and the discrimination, and the entry stays unwritten until its mechanism is sourced — which is the atlas counting an obligation it has not discharged rather than quietly dropping it.

Weak blacks are a shared entry with a stated split: owned here as a defect, while Parts XVIII and XIX own the printing fix. Safelight fog on paper is owned as a defect by the fog page and cross-linked from here.

Alternative route

The diagnostic half of this page needs no darkroom. Three failures called a weak print, the check order, the location reading of stains, the difference between bronzing and mirroring, and the closing argument about decisions are all read with prints in front of you — your own, a friend’s, or any exhibition you can walk round. Reading other people’s prints for these faults is genuinely good practice, because you are diagnosing without knowing the answer, which is the condition the break/fix page puts you in deliberately.

The parts that need a darkroom are the tests: the extended test strip that separates the three failures, the packet test for safelight fog, and the wet-versus-dry readings that establish your own dry-down. Without one, two substitutions are honest and one is not.

• For the three-failure distinction, a set of machine-made or laboratory prints of the same negative at different exposures does the same teaching job, if you can get one. Failing that, work the distinction on described strips: the quiz below is exactly that exercise.
• For dry-down, there is no substitute at all, and the course says so rather than offering one. It is a measurement of a wet object becoming a dry one, and you need to make the wet object.
• For everything about capacity, fixing times and developer age, read the manufacturers’ sheets themselves. They are free, they are short, and most of the numbers on this page came from four of them.

Recap

Maximum black belongs to the paper, its surface, the developer and the drying, and the published figures run from about 2.0 to 2.15 on glossy and fall to 1.6 on a matt surface. Three different failures get called a weak print, and one test strip separates them by asking whether the steps are still getting darker. For a genuinely poor black the check order is a longer strip, then the developer’s capacity, temperature and dilution, then the development time — which the makers say can run to six minutes without penalty — then fog on the base, then over-fixing, then the grade, then the paper’s age. Dry-down is a systematic error that the course refuses to give a number for, because no maker publishes one and it is not the same at every density. Mottle on a large sheet is the film mechanism in a dish. Bronzing is reported and its mechanism is not established here, though three observations separate it from silver mirroring. And the last question is not diagnostic at all: a black that was not reached is a fault only if the printer cannot say why.

Check your understanding

Question 1. A print will not reach black at any exposure, in a freshly mixed developer. List the checks in order and say what each eliminates.

• Change the paper, then the developer, then the enlarger lamp
• Extend the test strip by two steps (eliminates plain underexposure disguised as a ceiling); check the developer temperature and dilution against the sheet, and how many sheets have gone through it (eliminates a slow bath even though it is fresh); check the development time against the recommended 1½ to 3 minutes, knowing that six minutes changes nothing (eliminates snatching); run the safelight packet test (eliminates a raised base); check the fixing time against the paper time rather than the film time (eliminates image etching); re-establish the base exposure for the grade in use; and check the paper's age and storage.
• Increase the exposure until it goes black; if it never does, the paper is faulty
• Test the fixer's clearing time first, since fixing is the last chemical step

Show the answer and why

Answer: Extend the test strip by two steps (eliminates plain underexposure disguised as a ceiling); check the developer temperature and dilution against the sheet, and how many sheets have gone through it (eliminates a slow bath even though it is fresh); check the development time against the recommended 1½ to 3 minutes, knowing that six minutes changes nothing (eliminates snatching); run the safelight packet test (eliminates a raised base); check the fixing time against the paper time rather than the film time (eliminates image etching); re-establish the base exposure for the grade in use; and check the paper's age and storage.

The order is by cost against likelihood, and note that "freshly mixed" in the question eliminates only one item on the list — a fresh developer can still be too cold, too dilute, or the wrong dilution's time. The most commonly skipped check is the first: a test strip whose darkest step is still climbing has not demonstrated a ceiling at all. And the least intuitive is the safelight, because a fogged base does not lower the maximum black; it lowers the difference between white and black, which is what the eye reads as depth.

Question 2. What happens to the deepest tone of a fibre print between the wet inspection and the dry print, and how would you compensate at the test-strip stage?

• It gets lighter by exactly a third of a stop; add a third of a stop
• It changes — the material dries and the viewing conditions change with it, both in the same direction, so the wet print flatters — but the course publishes no figure, because no manufacturer in its corpus publishes one and the difference is not the same at every density. Compensate by measuring your own: read the same patches wet and dry, convert the density difference into an exposure correction with the local gradient, and note the assumption.
• Nothing changes; dry-down is a myth
• It gets darker, so the print should be exposed less

Show the answer and why

Answer: It changes — the material dries and the viewing conditions change with it, both in the same direction, so the wet print flatters — but the course publishes no figure, because no manufacturer in its corpus publishes one and the difference is not the same at every density. Compensate by measuring your own: read the same patches wet and dry, convert the density difference into an exposure correction with the local gradient, and note the assumption.

The two components matter separately. The material component is a real change in the print and is what a densitometer reads. The viewing component is a change in how you are looking at it — a bright inspection lamp at close range against room light on a wall — and no chemistry will fix that one; only judging under the conditions the print will live in will. Part XVIII's measurement shows the difference is smallest at paper white, largest in the upper mid-tones and narrower again at black, which is why a single added fraction of a stop costs the highlights.

Question 3. Why does this page teach the difference between bronzing and silver mirroring without stating a mechanism for bronzing?

• Because bronzing is not a real phenomenon
• Because no source in the course's corpus states a mechanism for a metallic sheen in the deep tones of a freshly made silver-gelatin print, or relates it to mirroring — while the corpus does define mirroring as an oxidation in which image silver migrates to the surface of aged material. Three observations separate them anyway: when they appear, where they appear, and whether they follow image density, and those are what a diagnosis needs.
• Because mirroring and bronzing are the same thing under two names
• Because the mechanism is too complex for this level

Show the answer and why

Answer: Because no source in the course's corpus states a mechanism for a metallic sheen in the deep tones of a freshly made silver-gelatin print, or relates it to mirroring — while the corpus does define mirroring as an oxidation in which image silver migrates to the surface of aged material. Three observations separate them anyway: when they appear, where they appear, and whether they follow image density, and those are what a diagnosis needs.

This is Rule 1 doing something more useful than refusing to speak: the page reports what is established, states what is not, and then shows that the diagnosis does not actually depend on the missing piece. A reader can tell the two apart from a print in front of them — one arrives with the print and follows the blacks, the other arrives with age and comes in from the edges — and can act correctly on either without a mechanism. Where a mechanism would help is in prevention, and there the page falls back on the reported conditions rather than on a story.

Question 4. ILFORD state that fibre-paper development can be extended to six minutes without noticeable change in contrast or fog. What does that fact rule out as a printing strategy?

• It rules out using a hard grade
• It rules out the trade of exposing less and developing longer. On film that trade works, because film development is stopped part-way and the gradient depends on the time; a paper developer is worked to completion by design, so extra time past the recommended range adds essentially nothing and cannot compensate for a short exposure. The print is controlled by exposure and grade instead.
• It rules out using a stop bath
• It rules out fibre paper for beginners

Show the answer and why

Answer: It rules out the trade of exposing less and developing longer. On film that trade works, because film development is stopped part-way and the gradient depends on the time; a paper developer is worked to completion by design, so extra time past the recommended range adds essentially nothing and cannot compensate for a short exposure. The print is controlled by exposure and grade instead.

The sentence is usually read as reassurance — you cannot ruin a print by leaving it in too long — and that is true and useful. The deeper consequence is the one that changes practice: it closes the escape route from snatching. A printer who pulls prints early and then tries to recover them with a longer time in the next session is trying to move along a curve that is already flat. The corresponding fault at the other end is over-fixing, where the manufacturers give an equally blunt answer: there is no benefit in extending fixation, and image etching is the cost.

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