Assignment: The Toned Print

Two prints from one printing session, on paper from one box, at one exposure that was chosen for a toner you had already decided on. One of them never goes near the toner. The other does, for a reason you wrote down before you diluted anything, and everything after that — the measurement, the critique, the permanence statement, the mount — is an argument about the difference between them.

The untoned sheet is not a spare. It is the instrument. Nothing in this part can be judged in the absolute: the eye cannot say whether a print is a third of a stop light or whether a brown is warm, but it is very good at saying which of two sheets is darker and which way the difference runs. Every number and every sentence this assignment asks for is a comparison against that control, and a session run without one produces a toned print and no knowledge.

The brief

Produce, over about three hours plus a separate printing session:

1. One negative, already read and interpreted, printed to a printing map you can follow twice.
2. One paper, chosen because of how it answers the toner you intend to use, and not the other way round.
3. A matched set from one session at one exposure: the control, the print to be toned, and the spares the table below accounts for.
4. One written intention for the toning, in the form this page specifies, closed before the first bath is mixed.
5. One toned print, made to that intention, with the exposure compensated using the figures you measured earlier in this part.
6. Optionally, one third print given a partial, split or sequential treatment, with the sequence recorded whether or not it worked.
7. A measurement of what changed — matched-patch densities before and after, the hue described against the control under a named light, and the change in the tonal scale where the picture needs it.
8. A critique, by Part XIX’s three passes, with the control beside the toned print throughout.
9. A permanence statement whose four parts stay separate.
10. The chosen print finished and mounted to Part XIX’s standard, in materials chosen for compatibility with the toner you used.

Nothing here is a new technique. Every operation belongs to a page you have already worked through, and this page links rather than repeats. What is new is that the toner is chosen from an intention instead of from a catalogue, and that the print is made for it rather than subjected to it.

!The one sentence this assignment exists to make you write

Kodak state the negative version and the course adopts it without softening: toning cannot disguise poor print quality, and a good candidate is a properly exposed and processed print from a high-quality negative, with a full tonal scale and good detail in highlights and shadows.

The positive version is the sentence you have to produce, and “I want it warmer” is not it. An intention names what should happen to the shadows, what should happen to the highlights, and what you are willing to lose — because every route in this part costs something, and a maker who has not decided in advance what they are spending will spend it by accident.

Learning objectives

By the end of this assignment you should be able to:

• Write a toning intention as three testable clauses, and reject a toner that cannot deliver them even when it is the toner you own.
• Choose between conversion, replacement and deposition for a stated picture, and say what each choice costs in density, in hazard, in waste and in what the print may later be mounted on.
• Compensate a print exposure for a toner using your own measured density change and your own measured density-per-stop, and explain why a figure quoted from a data sheet is not transferable.
• State what an exposure compensation can and cannot restore, and recognise the case where the answer is to change the toner or the interpretation rather than the exposure.
• Run a toning session to a written procedure, with the ventilation, separation and waste arrangements the relevant practical page specifies, and stop a toner by eye against a reference rather than by the clock.
• Measure a toning result: matched patches, a stated noise floor, a ranked hue statement under a named light, and a claim no larger than the measurement supports.
• Critique a toned print against its untoned control by a fixed method, and answer honestly whether it is better or only different.
• Write a permanence statement in which what was done, what published procedure it follows, what was tested and what is inference remain four separate things.
• Choose mount, hinge and enclosure materials against a specification rather than an adjective, and identify the one toner in this part whose print is destroyed by the board a silver print wants.

Prerequisites

The three practical and evidential pages of this part, and their outputs. The sepia lab supplied your measured density loss on the indirect route and the arithmetic that turns it into stops; the selenium experiment supplied your measured density gain, the upper-scale slope change and your reading repeatability; the archival-evidence page supplied the four-part permanence statement and the reason its parts must not blur.

From Part XIX: the printing map and its notation, the three-pass critique this page extends rather than duplicates, the session consistency that makes a matched set matched, and the finishing and mounting that this page ends in. From Part XVIII, the dry-down figure and the density change per stop you measured for this paper in maximum black, base white and dry-down: that second number is the divisor in every compensation below, and without it the compensation cannot be calculated at all.

From Part XII, the archival processing sequence and the residual-hypo and silver tests. Those are the entry condition, not a refinement. A print that fails them cannot be toned; it can only be stained.

Safety classification

Level B, on the rubric’s own criteria, and the argument is worth making rather than asserting because two of the four Level A criteria fail and the others do not.

Level A’s waste criterion allows silver-bearing fixer, spent developer and dilute rinse water — “nothing that requires specialist neutralisation”. A selenium bath fails that before anyone has read a toxicology entry: HARMAN’s own sheet says do not empty into drains and dispose of the material and its container at a hazardous or special waste collection point, and Kodak’s guidance for amateurs, which is unusually permissive about sending developers, stop baths, silver-recovered fixers and wash waters to the sewer, lists selenium toners first among the things that must not go. A sulfide bath fails it for a different reason: it is half of an incompatible pair with every acid in the room. Level A’s ventilation control is “an openable window or an extractor”; HARMAN call their product a toxic chemical and strongly recommend working in a well-ventilated area, preferably with some form of air extraction. Those two together put the session at Level B, whose controls — local extraction or an open window with a fan, eyewash within reach, splash protection — are the ones the manufacturers’ sheets ask for.

Nothing on this page is above Level B, and that is a constraint on your choice rather than an observation. Any operation that would raise it is excluded from the assignment by the brief itself. Weighing anhydrous sodium sulfide to make a T-7a stock is a Level C operation and stays one; if you take the sulfide route, that weighing happens once, on another day, under the sepia lab’s conditions, or you buy the stock ready made. And the toners of the page we study and do not use are not available to this assignment at any dilution, under any supervision you can arrange at home: Level D is the level at which the course gives no procedure to anybody, and a chromium route is governed by its own course-wide policy.

What is not a hazard here, and why. Rather more than half of these three hours is dry work — the critique, the measurement, the writing, the trimming and the mounting — and it carries no chemical hazard at all, because the object in your hand is metallic silver, silver sulfide or silver selenide locked in hardened gelatin with the undeveloped halide dissolved out and washed away. Getty’s atlas is a useful check on the intuition here: a print given archival selenium toning shows no major colour change and yet XRF detects the selenium readily, which tells you the element is present, bound, and detectable — not that it is available to you. The control that applies to the dry print is a conservation control pointing at the print rather than at you: clean hands or gloves, no contact with the image surface, a support under a sheet that has to be turned. The one genuine hazard in the dry half is the mat cutter, and Part XIX introduced it with its controls.

Materials

Item	Quantity	Notes
The negative, read and interpreted	1	With the two sentences of intention from Part XIX
The printing map, versioned	1	The document the toned print is printed from
Paper, one box, one grade	about 8 sheets	Chosen for its response to the toner; record the box code
Print developer, stop, non-hardening fixer	1 L, 1 L, 2 × 500 mL	Working strength, as the finishing lab specifies
Washing aid	1 L	Fibre route only, and the diluent in ILFORD’s toned sequence
Your chosen toner	1 bath	Bought, with its own current safety data sheet read first
Trays that are not metal and are not your printing trays	3	Kodak: unchipped enamel, hard rubber or plastic only
Silver nitrate for the residual-thiosulfate test	about 1 g	HT-2, on the spare sheet
Mount board and backing board to a stated specification	1 sheet each	Buffered or unbuffered — the toner decides; see below
Hinging tissue and starch paste, or photo corners	2 hinges	The reversible attachment
A neutral mid-grey surround and a named lamp	1 each	The judging station recorded in Part XIX
Waste containers, labelled, for the streams the practical page names	2 or 3	Standing before the first tray is filled

Estimated cost

Band ££, and as in the rest of this part the chemistry is the cheap half. The capital — trays, tongs, enlarger, washer, cutter — exists by this page. What the session consumes is about eight sheets of paper, four litres of working solution, one bath of toner and one mount, and the paper and the mount are most of it. The dated figures live in the planner, and for this part the presentation materials are still gaps.

Estimated consumables cost

Every price with a number is the planner’s own dated UK figure and every quantity comes from the Materials table. This is costed on resin-coated 8 × 10 in, which is the route the price file can price; the fibre figures are in the prose beneath.

Consumed	This session	Sourced price	Cost this session
RC paper, 8 × 10 in	8 sheets	£33.50 for 25 to £96.18 for 100	£7.69 to £10.72
Paper developer concentrate	100 mL, for 1 L at 1+9	£10.52 per 500 mL to £20.03 per 1 L	£2.00 to £2.10
Stop bath concentrate	50 mL, for 1 L at 1+19	£10.66 to £12.18 per 500 mL	£1.07 to £1.22
Rapid fixer concentrate	200 mL, as two 500 mL baths at 1+4	£21.05 to £25.98 per 1 L	£4.21 to £5.20
Silver nitrate for the hypo test	1 g	£59.95 for 25 g to £112.90 for 10 g	£2.40 to £11.29
Toner concentrate	one bath	£11.87 to £32.99 a bottle across sepia, selenium and gold; no listing states a working dilution, so a bath has no derived cost	—
Washing aid concentrate	200 mL, fibre route	£17.99 per 1 L of concentrate	£3.60, on the fibre route only
Mount board and backing board	1 sheet each	None. Board bought against ISO 18902 is a gap	—
Hinging tissue and paste, or corners	2 hinges’ worth	None in the price file	—

The rows carrying numbers total about £17.40 to £30.50 on the resin-coated route, and that is a floor rather than a total: the board and the hinges have no sourced price at all, and the toner has a bottle price with no dilution behind it, so none of the three reaches the subtotal — and those three are exactly what makes this a toned, finished print rather than a work print. The silver nitrate row is wide because the price file holds two pack sizes at very different unit prices, and one gram is a small part of either jar.

Beneath the table, from one British retailer read on 6 September 2026, are the working figures the bottle prices imply. Three of these listings — the Kodak selenium, the Fotospeed sepia and the Moersch gold — are now records in the price file; the rest are magnitudes rather than planner data. Selenium: one litre of working bath at HARMAN’s protective dilution of 1+20 takes about 48 mL of concentrate, which is roughly £1.10 on Kodak Rapid Selenium Toner at £21.95 for 946 mL and £2.50 on Ilford Selenium Toner at £51.52 per litre; at their 1+3 dilution for a visible tone change the same litre takes 250 mL, so £5.80 or £12.90. Sepia: Fotospeed ST20 at £11.87 for 150 mL making 1.5 L puts a litre of working solution at about £7.90; Foma’s two-bottle Fomatoner Sepia was £23.99 for 2 × 250 mL, and its dilution is not on the retailer’s listing, so no per-litre figure is computed here. Blue was £23.99 for 150 mL and gold £32.99 for 250 mL of working solution, which is why the gold lesson carries a higher cost band than this page.

On fibre. The same retailer listed MULTIGRADE FB WARMTONE S-Matt 8 × 10 in at £58.50 for 25 sheets and £191.60 for 100, so eight sheets is £15.30 to £18.70 — between one and a half and two and a half times the RC row, and enough to change how many spares you are willing to print. That warmtone matt figure is not in src/data/prices.json. What the file does now hold is the glossy variable-contrast fibre paper, at £47.04 for 25 sheets to £150.28 for 100, which is £12.02 to £15.05 for the same eight sheets; add the £3.60 of washing aid the fibre route also needs. Warmtone, cooltone and matt are separate products at separate prices, and the file says so on its own face.

!What would settle the two gaps that matter most here

For the toner, the maker’s own dilution beside the price. The file now records three dated bottles and not one of the three listings states a working dilution or a capacity, so a cost per toned 8 × 10 print still has to be estimated from a bottle size rather than computed. For the board, a dated UK listing for four-ply board whose packet states that it meets ISO 18902 — and for the iron-blue case, for an unbuffered board of the same specification, which is a different product and not always stocked. The photographic retailer this course reads returned foam-centred board, slide mounts and copystands for “mount board” and nothing that mentions conservation quality, buffering or the standard, so the settling listing will come from a conservation supplier rather than a photographic one. Both are reported as unverified rather than filled with a plausible number.

Alternative route

This page needs a darkroom upstream and a ventilated wet area downstream, and those are two different requirements with two different answers.

The toning itself needs no darkness. Every bath here is worked in room light on a print that is already fixed, and the one exception is small: an indirect route’s bleach converts image silver back to a light-sensitive bromide, so you may prefer to bleach under safelight, though Kodak record the effect as extremely small and possibly not noticeable. What the session actually needs is air movement and a bench that is not where paper is stored.

The prints can be made by somebody else’s enlarger. The whole of this assignment survives prints brought in from a hired hour, a college darkroom, a workshop or a friend, and the part overview says so for every practical page here. What cannot be delegated is the matched-set discipline: the control and the print to be toned must come from one session, one box and one exposure, and the exposure must already carry the compensation. That is a constraint on whoever makes the prints, not on where they are toned, and it means the compensation arithmetic has to be done before you book the hour rather than after.

At contact size the assignment works unchanged. Using Part XVI’s frame, a print the size of the negative can be matched, toned, measured, critiqued and mounted by everything below. The measured patches will be small, so choose fewer and larger ones and say in the write-up that the patch size limited the reading.

Without the ventilation, there is no substitute control, and this page will not invent one. A sulfide or a selenium bath in a room with no air movement is not a smaller version of the same session. The one arrangement that supplies the control without altering a building is to work outdoors, on a bench, in daylight, with the waste containers there with you; that is the route the practical pages describe and it is the route here.

And if none of that is available, the assignment still has a form, and it is not a token one. Take a print you already own — one of yours, or an untoned print you can obtain two of — and do everything on this page except pour a bath: write the intention, choose the toner it implies and say why, calculate the compensation from the published figures with the calculation’s limits stated, build the judging station, run the three critique passes on the untoned sheet, and write the permanence statement for the print as it actually is, untoned. That last document is the most transferable thing in this part, and it is worth more than a toned print made without understanding. What genuinely cannot be done is the measurement, because there is no “after” to read, and that gap is reported rather than filled.

Choosing the toner from the intention

Most people choose a toner and then find a picture for it. This assignment reverses the order, and the reversal is the whole of its craft content.

Write the intention first, in three clauses, and close it before anything is diluted:

1. What should happen to the deep tones. Heavier and more separated; lighter and opened; unchanged.
2. What should happen to the highlights. Coloured; left as paper white; separated further from the tone above them.
3. What you are willing to lose. Maximum density; upper-scale contrast; the option of ever changing your mind; a protective claim; a particular mount.

Only then ask which mechanism can deliver it. The three routes of the mechanism lesson are not three flavours of one effect, and the intention usually eliminates two of them in a sentence.

If the intention says	The mechanism that can do it	Where it is taught	What it costs
Deeper blacks, more separation in the shadows, little colour change on a neutral paper	Direct conversion to silver selenide	Selenium	Density gain to compensate for; hazardous waste; extraction
A brown image with the whole scale re-coloured, and the shadows opened	Indirect: rehalogenating bleach, then sulfide conversion	Sulfide and sepia	Density loss to compensate for; the acid rule; fogging risk to stored paper
Warm highlights standing against untoned shadows	Partial bleach, then conversion — a genuine split	Partial, split and sequential	An unfinished print if the residual halide is not dealt with
A blue image	Deposition: ferricyanide oxidises the silver, an iron salt precipitates Prussian blue where it stood	Iron-blue	No protective claim, and a permanent incompatibility with buffered board
Red or orange	Sequential: sulfide first, then a gold blue toner	Gold and the others	Shadow density loss; gold’s price; two sessions
Cooler blacks on a warm paper, with protection	Replacement: gold plating the silver	Gold	Cost, and most of gold’s real use is in Parts XXI to XXV

Two things constrain the answer before your taste does.

The paper has already decided most of the colour. HARMAN say it plainly about their own selenium toner: the colour and degree of change vary with paper type, from cool chocolate-brown through purplish brown to little discernible change, and warm-tone papers usually produce the most visible effects. ILFORD recommend polysulphide and selenium toners for MULTIGRADE FB WARMTONE specifically, and note that on MULTIGRADE FB CLASSIC the glossy surface responds more favourably to toning than the matt. So “which paper” is part of “which toner”, and a cold-tone paper chosen for its blacks will answer a selenium bath with a density change and almost no colour — which may be exactly the intention, and is a failure if it was not.

A protective intention and a colour intention are different jobs with different dilutions. HARMAN publish two: 1+3 for normal toning, and 1+20 where the primary reason is protection of the image, with minimal tone change, complete in two to four minutes. If clause 1 of your intention is about appearance you are working at one dilution; if it is about permanence you are working at the other, and the print will look very nearly unchanged. Do not write an intention that quietly asks for both and then judge the result against whichever one it happened to deliver.

✕Four intentions that cannot fail, and what to write instead

1. “Warmer.” Warmer where? A sepia route re-colours the whole scale and lifts the shadows; a partial one colours the highlights and leaves the shadows neutral. Those are opposite pictures.
2. “More archival.” Name the threat and the treatment. ILFORD name the threat — oxidising gases — and recommend that prints made for display are toned against it. “More archival” names nothing and can therefore never be shown to have failed.
3. “Split toned.” Split between which two tones, at which point in the scale, and which of them keeps its detail? Moersch’s whole method is that the degree of bleaching sets the result, so an intention that does not say where the split falls has not specified the treatment.
4. “To see what happens.” Legitimate as an experiment and not as this assignment. If that is genuinely what you want, run it as a further experiment on the sepia lab or the selenium experiment, where the design supports it, and come back with an intention.

⚠The supply and safety-data check, which is part of choosing

Before a toner is chosen it has to be obtainable and documented, and those are two separate checks that the assignment asks you to record with dates.

On 6 September 2026 one British photographic retailer stocked, in stock and priced, a Kodak selenium concentrate, an Ilford selenium concentrate, two packaged sepia products, a gold working solution and a blue toner. So the supply route exists for every route this assignment permits.

The documents are less even, and the difference is worth knowing before you buy. HARMAN’s GB safety data sheet for its selenium toner is dated 18 July 2024, revision 1, written to UK REACH, classifying the mixture Acute Tox. 4, Skin Sens. 1 and Aquatic Chronic 3. Moersch’s sheet for the thiourea half of its MT3 toner is dated 6 January 2025. The most recent maker-published sheet the course could find for Kodak Rapid Selenium Toner — the cheapest bottle on the shelf — is version 4.2, revision date 31 July 2014, and Foma’s sheets for the packaged sepia kit are version 8.0 of 4 February 2016. An old sheet is not evidence of a safe product or a dangerous one; it is evidence that the classification you are working from may predate a revision, and it is a fact to record in the session log rather than to resolve by assumption.

One classification decides a choice for you. Moersch’s MT3 toner sheet classifies the mixture Carc. 2 (H351) and Repr. 2 (H361d) and states “For professional users only”. The course’s rubric puts carcinogens and reproductive toxins at Level C where a fume cupboard is the recognised control, and this assignment is Level B. Read the sheet for whatever you buy before you buy it, by the SOP, and let the classification eliminate a route rather than discovering the problem with the bottle open.

Printing for the toner

A toner does not lay colour over a finished print. It rebuilds the substance that produces the density, so the density changes, and Kodak’s instructions follow from that in two opposite directions: sepia, Sepia II Warm and Brown toners reduce print densities, so prints are developed fully and made slightly darker than normal; Rapid Selenium Toner tends to intensify, so print development may be shortened slightly, and a fully developed print toned in it yields an increased tonal scale. Kodak add the qualification that does most of the work: the modifications also depend on the paper emulsion type and grade.

That qualification is why this assignment will not accept a rule of thumb. Kodak’s direction is a manufacturer’s statement about their toners on unspecified papers; the number that goes on your printing map has to be yours.

Where the compensation figure comes from, and where it must not come from

1. 1Your measured density changeFrom this part’s own practical pages: the loss at a mid-tone patch in the sepia lab, or the gain and the upper-scale slope change in the selenium experiment. Signed, and larger than the noise floor that session established
2. 2Your measured density change per stopFrom Part XVIII, on this paper, in this developer, at the same part of the scale. It is the divisor, and without it the loss cannot be converted into anything you can set on a timer
3. 3The exposure correction, in stopsOne division. Applied at the base exposure on the printing map, in the same f-stop units the map’s local moves are already written in, so the local ratios travel unchanged
4. 4Recorded on the map as a new versionWith the paper, the developer, the toner, the dilution and the date, because the figure is valid for that combination and no other
5. 5What must not be used insteadA number read from a data sheet, a forum, or another photographer’s notebook. Kodak give a direction and explicitly decline to give a magnitude; a magnitude taken from a different paper in a different developer is a guess wearing a citation

The manifest for this assignment requires the compensation to come from the student's own measurements, and this is the reason: every published statement in the corpus gives a direction and refuses a number.

The arithmetic is the sepia lab’s, and it is one division:

ΔE = ΔD_toning / (ΔD / stop)

Exposure correction for the density a toner adds or removes

ΔD_toning is the density change the toner produced at a chosen patch, signed — negative for a sulfide route, positive for selenium. ΔD per stop is how much reflection density that paper gains per stop of extra exposure at the same part of the scale. ΔE is the exposure correction, in stops: add it for a toner that removes density, subtract it for one that adds. Divide at a mid-tone patch, because the assumption that ΔD per stop is constant fails near the toe and the shoulder, which is exactly where the interesting parts of most pictures live.

What the compensation restores, and what it cannot

• Untoned control
• Sepia toned, same exposure as the control
• Sepia toned, exposure compensated by a fifth of a stop

Show the numbers behind this plot

Three model print curves on one pair of axes, with relative log exposure increasing to the right so the darkest tones lie at the right-hand end. The untoned control, drawn solid, leaves a base density of 0.06, rises through 0.26 at log exposure 0.7 and 0.55 at 1.0, climbs steeply through 1.05 at 1.3 and 1.60 at 1.6, and shoulders to a maximum of 1.95. The sepia-toned print made at the same exposure, drawn dotted, sits below the control everywhere above the base: 0.21 at 0.7, 0.45 at 1.0, 0.86 at 1.3, 1.33 at 1.6, and a maximum of only 1.60. The third curve, dashed, is the same sepia toning on a print given a fifth of a stop more exposure: it reads 0.26 at log exposure 0.7 and 0.53 at 1.0, so through the toe and the mid-tones it lies on top of the control and the compensation has worked; but at 1.3 it reads 0.95 against the control's 1.05, at 1.6 it reads 1.39 against 1.60, and its maximum is 1.61 against 1.95. The gap therefore closes in the lower half of the scale and widens steadily towards the top, and the maximum density is short by about a third of a unit no matter how the exposure is adjusted. A vertical guide line marks the mid-tone patch at log exposure 1.0 where the division was made.

Series	Relative log exposure	Reflection density
Untoned control	0.10	0.06
Untoned control	0.40	0.10
Untoned control	0.70	0.26
Untoned control	1.00	0.55
Untoned control	1.30	1.05
Untoned control	1.60	1.60
Untoned control	1.80	1.86
Untoned control	2.00	1.95
Sepia toned, same exposure as the control	0.10	0.05
Sepia toned, same exposure as the control	0.40	0.08
Sepia toned, same exposure as the control	0.70	0.21
Sepia toned, same exposure as the control	1.00	0.45
Sepia toned, same exposure as the control	1.30	0.86
Sepia toned, same exposure as the control	1.60	1.33
Sepia toned, same exposure as the control	1.80	1.54
Sepia toned, same exposure as the control	2.00	1.60
Sepia toned, exposure compensated by a fifth of a stop	0.10	0.06
Sepia toned, exposure compensated by a fifth of a stop	0.40	0.11
Sepia toned, exposure compensated by a fifth of a stop	0.70	0.26
Sepia toned, exposure compensated by a fifth of a stop	1.00	0.53
Sepia toned, exposure compensated by a fifth of a stop	1.30	0.95
Sepia toned, exposure compensated by a fifth of a stop	1.60	1.39
Sepia toned, exposure compensated by a fifth of a stop	1.80	1.56
Sepia toned, exposure compensated by a fifth of a stop	2.00	1.61

Model curves, drawn to make one relationship visible and not measured from any paper. The directions are Kodak's; the shapes and every number are constructed. Read one thing from it: an exposure correction slides the whole curve along the exposure axis, and a toner changed the curve's shape, so the correction can land the mid-tones exactly and still leave the maximum density short. The curve is drawn to show the shape, not measured from a real material. Your own materials will differ, and measuring them is what the sensitometry part of the course is for.

🧮The arithmetic, worked on the constructed curves above

Every number in this box is invented to demonstrate the method. None is a measurement, and none belongs in your notebook.

At the mid-tone patch marked on the plot, the control reads 0.55 and the sepia-toned print made at the same exposure reads 0.45. The loss is 0.10, and suppose the session’s noise floor from the control sheet was 0.02, so it is a result.

From that paper’s own measurement in Part XVIII, the density change per stop at that part of the scale is 0.50. Then

ΔE = 0.10 / 0.50 = 0.20 stops

The correction, for these constructed figures

about a fifth of a stop darker for the next print. The dashed curve is that print, and it lands within 0.02 of the control at the patch the division was made at — which is not a coincidence, because that is what the division was for.

Now read the top of the plot, which is the part the arithmetic does not fix. The control’s maximum density is 1.95; the toned print’s is 1.60 before compensation and 1.61 after it. A fifth of a stop of extra exposure recovers almost nothing at the top, because those steps were already on the shoulder and more exposure has nowhere to put them. The shortfall of about 0.34 is a property of the substance the toner made, and no exposure decision reaches it.

So the compensation is a decision about where the print is right, not a repair. Compensate at the mid-tone and the picture’s mid-tones are where you intended, its shadows are lighter than the control and its blacks are not as black. If maximum black is what the picture is built on, that is the moment to change the toner or to change the interpretation — and saying so in the write-up is a better answer than printing three more sheets.

Two consequences for the map. Write the correction in stops, not in seconds, because the map’s local moves are already written as ratios and ratios survive a change of base while seconds do not. And re-anchor before you print: a short test strip through the negative’s clear rebate on the box you are about to use, as Part XIX requires, so that the correction is applied to this box’s speed rather than to the last one’s.

The matched set, and running the session

Eight sheets from one printing session, and what each one is for

1. 1A — the anchor test strip — through the clear rebate, on this box, before anything else
2. 2B — the untoned control — never toned; the reference for every number and every sentence
3. 3C — the print to be toned — identical to B: same exposure, development, fixing, washing
4. 4D — the second identical sheet — an endpoint judged by eye is judged once
5. 5E — the optional third treatment — partial, split or sequential; recorded whether or not it works
6. 6F — the sacrifice, trimmed into strips — one strip for HT-2, one to bleach and see how far conversion went
7. 7Two spares, unprinted — from the same box, for the repeat the critique may ask for
8. 8The holding dish of plain water — the control lives here during the run, wet, for comparison

The course's own layout for the session. HARMAN's instruction to make two identical prints and keep one in a holding dish of water is the origin of items 2 and 8; the rest follows from measuring a change rather than admiring one.

The preparation is the part that decides whether the session is worth running, and none of it happens on the day of toning.

Fix twice, in a non-hardening fixer, and do not extend it. Kodak’s position is unambiguous: improper fixing is probably the major cause of stains in toned prints, two-bath fixing gives the best results, and a hardening fixer is not recommended for prints intended for toning because it makes the emulsion less receptive. ILFORD reach the same instruction from the washing side — do not add a hardener, do not exceed the fixer’s capacity and do not extend the fixing time, because both make washing harder. Over-fixing is the fault that punishes you twice: it drives fixer into the base that no wash retrieves, and it turns a toned print yellow later.

Wash to a sequence you can name, and prove it. HT-2 on the trimmed strip from sheet F, by the residual-hypo and silver tests SOP. This is not belt and braces. Residual thiosulfate makes a rehalogenating bleach act as a reducer, and the highlights go irrecoverably; residual silver from an exhausted fixing bath returns as yellow stain in borders and highlights the moment a toner arrives, and will be blamed on the toner.

Write the session out on one sheet before you fill a tray, and put it on the wall. The relevant practical page — the sepia lab or the selenium experiment — owns the bath sequence, the temperatures, the volumes and the waste arrangements, and this page does not repeat them. What the written plan adds for this session is: every bath and its volume; every time, marked as a clock time or an endpoint; the ventilation arrangement actually running, checked by the SOP before the session and not during it; where each labelled waste container stands and which tongs belong to which tray; and where the session stops, which is the end of the wash and not the moment the print looks right.

Set up for separation before the bottle is opened. Paper boxes and negatives leave the room. The acid stop bath leaves with them if you are toning in sulfide — a sulfide bath and an acid are an incompatible pair whose product fogs unexposed paper as well as being a gas with a workplace exposure limit. Trays are dedicated, and Kodak are explicit that toning solutions do not go into metal trays or tanks: unchipped enamel, hard rubber or plastic only.

📓Stop by eye against the control, never by the clock

HARMAN build the method into their own instructions for a first attempt, and it is the single most useful habit in this part. Keep the control in a holding dish of plain water beside the toner, about 4 °C warmer than the bath. Do not watch the print continuously in the toner, because continuous watching makes a gradual change invisible; lift it and compare it against the wet control at intervals. Toning continues into the wash, so the print comes out before it looks right, and there is no way to learn where “before” is except by having the untoned sheet in your other hand.

Record the lift times, not just the total. If the print goes back for more — which HARMAN allow for explicitly — that is two immersions with a stop between them, and it is a different treatment from one continuous immersion of the same total length.

The optional third print

Sheet E is where the assignment stops being a comparison and becomes an experiment, and it is optional because it is the part most likely to fail on a first attempt. Fail it in writing rather than quietly.

Three treatments are available, and they are mechanically different.

Partial. Stop the bleach short on an indirect route. Moersch’s account is that the degree of bleaching sets the image tone: the same toner behind a three-minute bleach and a two-minute bleach gives two different colours, and a brief bleach at high dilution converts only the highlights, leaving warm highlights against untoned shadows — with smoother transitions the more dilute the bleach is, because a slow bleach makes a gradient across the scale rather than an edge.

Split. The same operation seen as a result rather than as a method: two substances in one sheet, distributed by how far the bath reached. It is not a blend of two colours and it does not behave like one.

Sequential. Two toners in order, where each changes what the next one finds. Kodak’s published example is sepia or brown first, a thorough wash, then Blue Toner T-26, with red or orange appearing after roughly 15 to 30 minutes at 32 °C — a truer red on cold-tone papers, an orange on warm-tone ones. They add the warning that decides whether it is worth attempting: multiple toning usually produces a density loss in the shadow areas, so the technique starts from a print of higher-than-normal contrast. That is “print for the toner”, applied twice over, and it means sheet E should have been printed harder than B and C if you intended a sequential treatment. Decide that before the printing session, not after it.

!A partly toned print can be an unfinished one, and the difference is chemical

After a partial bleach and a sulfide bath there are three substances in the sheet: silver sulfide from the toning, metallic silver the bleach never reached, and a residual silver halide that was bleached and never converted. The first two are stable. The third is not — it is light-sensitive, it is the component that will fog or discolour later, and it has to be either converted by a second pass through the toner or fixed out.

So a split-toned print that has been dried with unconverted halide still in it is not a split-toned print but an unfinished one, and the write-up has to say which of the two you have. The mechanism lesson owns this chemistry; what this assignment adds is the requirement to state, for sheet E, what you did about the residue.

Whatever you attempt, record it as a sequence with times, not as a name. “Bleached 40 seconds at 1+20, rinsed, toned 2 minutes, rinsed, second bleach 20 seconds, toned 1 minute” can be repeated by somebody else and by you. “Split toned” cannot.

Measuring what changed

You have three things to measure and one of them is not a number. Take all three against the control, and read the control’s own before-and-after first, because that is what tells you how small a change you are entitled to call a change.

The noise floor, from the control. Sheet B was printed, washed, dried and read like everything else, and if it was carried through a plain water soak and a wash alongside the toned print it will have moved slightly. The largest of its patch-to-patch differences is the smallest change this session can detect, and it goes at the top of the analysis rather than the bottom, because it constrains everything below it rather than commenting on it.

Matched-patch densities, before and after. Mark five patch centres on the back of every sheet with a soft pencil, through a template laid corner-to-corner, spanning the scale: a highlight with detail, an upper mid-tone, a mid-tone, a lower mid-tone, and the deepest shadow that still holds separation. Read all five on all sheets dry, before anything is wetted — there is no second chance at the “before” half. Then read them again dry after the sequence, and record the signed change. If you have no densitometer, the comparison is still available: match each patch against your Part XIX ring-around and record the cell number, which converts “darker” into a count of thirds of a stop.

Read the change patch by patch, not as an average. A loss concentrated in the shadows and a loss spread flat across the scale are different results with different causes and different consequences for the picture, and averaging them destroys precisely the information the measurement was for.

The hue, ranked and referenced. Three dry prints, one named light source, no instrument. What you may write is a ranked statement with the control as the reference: which sheet moved furthest, in which direction, under which lamp, at what illuminance, on the grey surround, at the recorded distance — the judging station Part XIX made you fix once and record. What you may not write is a magnitude, an invented colour name, or a comparison with anybody else’s print. Getty’s own conservation description of a well-toned selenium print is a model of the register to use: no major colour change, and a slight increase in image contrast and brilliance.

The tonal scale where the picture needs it. This is the measurement that is easy to skip and is the one the critique will use. Pick the two or three areas that carry the picture, name them, and say what happened to the separation within each. Two adjacent tones that the control distinguishes and the toned print does not is a loss whether or not the maximum density improved, and the reverse — two tones the control merges and the toned print separates — is the strongest thing a selenium bath can do for a picture.

=What each route is expected to show, so a surprise is recognisable

These are directions from the manufacturers and from this part’s own pages, not predictions of your numbers.

• Selenium should show its change in the upper scale and the maximum density, with the toe and the highlights nearly unmoved, and least colour change on a cold-tone paper.
• A full sulfide route should show density lower everywhere above the toe, with the whole scale re-coloured, and the change in image colour depending more on the paper’s emulsion than on the bath.
• A partial route should show almost no change at one end of the scale and a large one at the other, with the crossover where you stopped the bleach.
• A change at base white on any route is not a toning result. It is a stain, and it belongs to the printing session’s fixer.

A result that contradicts one of these is worth reporting, and the first question to ask is whether it exceeds the noise floor.

Judging it as a picture

Use Part XIX’s three passes — technical, structural, intention, in that order — and do not restate them here. This page adds three things to that method and nothing else.

The control stays on the bench for all three passes. Every claim in the technical pass is made as a comparison: not “the shadows are heavy” but “the shadows are heavier than the control, by about one ring-around cell, in the two areas the picture is built on”. The critique gets sharper the moment the reference is physically present, which is the same reason the ring-around exists.

The intention pass has a second document to read. Part XIX’s intention pass reads back the two sentences written before the first exposure. Here you read those and the three-clause toning intention, and you answer each clause separately, yes or no, before any qualification. That is why the intention had to be written in clauses: a single sentence can be argued into having been fulfilled, and three clauses about the shadows, the highlights and what you were willing to lose cannot.

And the honest question, which is this assignment’s own and is not in Part XIX. Laid beside its control, is the toned print better, or only different — and what evidence are you offering?

That question is harder than it looks because toning always produces a difference and difference reads as improvement. The discipline is the same one the technical pass uses: an answer counts only if it names something on the paper. “The separation in the wet roof tiles, which the control merges, is now two distinguishable tones, and the roof is what the picture is about” is an argument. “It has more presence” is not, and it could be attached to almost any toned print without becoming false — which is what makes it useless.

Three honest answers exist and all three are acceptable if argued.

• Better, and the evidence is a named improvement in an area that carries the picture, against a named cost you accepted.
• Only different, and the interesting question becomes why you expected otherwise — usually because the intention was written about the process rather than about the picture.
• Worse, which is the most useful outcome and the least often written. A sepia route that lifted the shadows out of a picture whose subject was in the shadows is a good result for the assignment and a bad print, and saying so is worth more than a fourth attempt.

✦Show somebody the pair without saying which is which

The one experiment this page can offer that costs nothing. Lay the two prints side by side in the judging station, do not say which is toned, and ask a viewer only which they prefer and what on the paper makes them say so. Their answer is data precisely because they have neither your intention nor your investment, and the second half of the question is what turns an opinion into a critique.

Write down what they said before you tell them anything, including the remarks you disagree with, which are the ones you will otherwise lose.

The permanence statement

The archival-evidence page sets out the four parts and why they must stay separate: what was done, what published procedure it follows, what was tested and against what criterion, and what is inference. This assignment is marked on whether they stay separate, and it asks for one addition — name the toner’s document and its date, because the currency of the sheet you worked from is part of what you did.

Here is a statement for a sepia print, which is the harder case and is not the worked example on the evidence page. Every claim in it either names a source or labels itself an inference.

Printed on a warm-tone fibre-base paper, box code recorded in the session log, developed to a fixed time, fixed in two baths of a non-hardening rapid fixer at the maker’s time for each, and washed by ILFORD’s optimum permanence sequence. A trimmed strip from an identical sheet in the same session was tested with HT-2 for residual thiosulfate and passed by the course’s stated criterion. The print was then toned by the indirect route: rehalogenating ferricyanide-bromide bleach to completion, rinse, sulfide redevelopment to completion, rinse and full wash, at the times and temperatures in the session log. The exposure was increased by a fifth of a stop over the untoned control, from this paper’s own measured density loss of 0.10 at a mid-tone patch divided by its measured 0.50 density per stop. Measured against the untoned control from the same session: maximum density fell by 0.34, the mid-tone matched to within 0.02, and the hue moved from neutral to a warm brown, ranked against the control under a 4000 K lamp at the recorded station. Toning to a silver sulfide image is recommended by two manufacturers as protection against oxidising gases: ILFORD name sulphide toning among the toners that give a protective effect, and Kodak state that toning converts the silver image to an inert compound and that all their toners protect the image. The degree of conversion achieved here was not measured, the international standard that measures it prescribes no treatment and no criterion a print can meet, and no claim is made about how long this print will last. Mounted with two Japanese tissue hinges and starch paste on board whose packet states that it meets ISO 18902. Recommended display: below 100 lux, ultraviolet-blocking glazing, no permanent display.

Four things in that paragraph are doing work worth naming.

The test is a measurement and is reported as one. HT-2 on a strip from an identical sheet, by a stated criterion, with a pass or a fail. It is the only sentence in the statement a stranger could repeat.

The manufacturers are quoted as manufacturers. Kodak’s claim that toning converts the image to an inert compound and that all their toners protect it, and ILFORD’s more discriminating note that sulphide, polysulphide and some metal replacement toners give a protective effect while blue and red toners may not and the image might fade, are two Tier 1 makers who do not agree. The statement reports what each says and does not adjudicate between them, because this page cannot.

The degree of conversion is the gap and it is named. ISO 18915:2000 is the standard written for exactly this question and its published scope says it describes methods for evaluating the effectiveness of chemical conversion treatments, does not recommend general or specific treatments, and puts treatment times and temperatures outside its scope. It is a measuring instrument, not a specification a print can be certified against, and this course has read its scope and none of its normative text.

And the identification problem belongs in the record. Getty’s atlas is blunt about the sepia case: even when sulfur shows clearly in an XRF spectrum, the main source of the signal is not the silver sulfide of the image but the barium sulfate of the baryta layer beneath it, which makes the source of the sulfur signal extremely difficult to separate. So a future conservator may not be able to establish from the object that your print was sulfide toned. You are the only source for that, which makes the session log part of the object rather than an accessory to it — the opposite of the selenium case, where Getty report that XRF detects selenium even in a print toned very briefly as part of archival processing.

✕Four sentences that will fail this assignment

“Archival.” Name the sequence. “Museum quality.” IPI say plainly that acid-free, archival, museum-quality and conservation board are marketing terms, not standardised or legal ones. “Will last N years.” Nothing in this course’s corpus attaches a figure in years to a toned silver-gelatin print on the strength of its toning. “Fully toned.” Only if you bleached a test strip and looked — and sheet F exists so that you can. If you did, say so, because it is the most informative sentence in the statement.

Finishing and mounting

Finish the chosen print exactly as Part XIX specifies — dried, flattened, trimmed, spotted, hinged and labelled — with two decisions that Part XIX did not have to make because it had not toned anything.

The mount material now depends on the toner, and for one toner the usual answer is wrong. IPI’s requirement for a board meeting ISO 18902 is a pH between 7.0 and 9.5, buffering with at least 2 per cent calcium carbonate, and freedom from lignin. The Library of Congress agree for the ordinary case: buffered paper may be used with silver prints, along with platinum and chromogenic prints and acetate and nitrate films. For a sulfide- or selenium-toned print, therefore, the answer is Part XIX’s answer unchanged — buy against ISO 18902, buffered.

An iron-blue toned print inverts it. The same Library of Congress passage recommends unbuffered paper, at pH 6 to 7, for cyanotypes, and a blue-toned silver gelatin print carries the same pigment. Prussian blue is destroyed by alkali, and the gold and iron lesson holds the chemistry, the pH at which it happens and how quickly. The alkaline reserve that protects the paper attacks the image, and it is the image you cannot replace. Nothing in this course’s sources addresses that specific object — a silver-gelatin support carrying a cyanotype’s pigment — so the reading is the course’s own and it is stated as such: treat a blue-toned print as a Prussian blue object for every material it will touch, which means unbuffered board, unbuffered interleaving, unbuffered enclosure, and an adhesive you have checked rather than assumed.

The attachment stays reversible whatever the toner. IPI’s position is that heat mounting, spray adhesive and pressure-sensitive tape are not recommended for preservation framing because they are not easily removable, and that it is best to choose a method that can be undone. Two hinges of Japanese tissue and starch paste, or corners of an inert plastic or good paper, and the print can be taken off a board that turns out to have been the wrong one. That option is worth more on a toned print than on an untoned one, because you have added a second chemistry to the object and the storage question is now genuinely open.

And the display advice is not the toner’s to change. The Library of Congress put exhibit light levels in the range of 30 to 100 lux and ultraviolet below 75 microwatts per lumen, and they say that permanent display is not recommended at all. A toned print is still a photograph. Toning, on the best reading of the evidence, addresses oxidising gases; it does not address light, and nothing in the corpus suggests otherwise.

What to submit

• The matched pair: the untoned control and the toned print, both finished to the same standard, and the toned one mounted.
• Sheet E and its record, if you attempted the third treatment, with the sequence as run and an explicit statement of what you did about any unconverted halide.
• The printing map, versioned, showing the compensation in stops, the anchor test strip it was applied to, and the box code.
• The three-clause toning intention, in the version written before the first bath was mixed, not a version reconciled with the result.
• The toning procedure as run: the written plan from the wall, annotated with what actually happened — bath temperatures, immersion and lift times, stop and wash times, the ventilation arrangement, which waste went into which container.
• The measurement: the noise floor from the control, the matched-patch table before and after with signed changes, the ranked hue statement with its lamp and station, and the tonal-scale finding in the areas that carry the picture.
• The critique, in three passes with the control present throughout, ending in the assignment’s own question answered with evidence: better, only different, or worse.
• The permanence statement, four parts kept separate, naming the toner’s document and its date.
• The materials record: what the mount board’s packet actually claims, and the buffered or unbuffered decision with its reason.
• The two supply and safety records with dates: where the toner was bought and at what price, and the version and revision date of the safety data sheet you read.

Where this goes next

The toned print is one of the required works of the capstone. The brief’s capstone specification lists toning among the eleven things the Pure Silver Portfolio requires — build or modify, calculate, expose, formulate, process, document, measure, print, tone one, cross-print in an alternative process, evaluate permanence — and the capstone manifest carries it through as Stage 5, which asks for a toned print with a stated intention and a measured compensation, printed against a matched untoned control from the same session. That is this page, at portfolio scale, and the capstone’s own readiness test names “a toning session record” among the documents you must already have. Keep this one; it is the record it means.

And the alternative processes have their own toning chemistry, which is not this chemistry. Parts XXI to XXV tone their own materials, and the difference is mechanical rather than cosmetic. A cyanotype carries a pigment rather than a metal image, so its toner works by bleaching the Prussian blue away with an alkali and putting something else in its place — a fourth route, not one of the three here. Gold on a salted-paper or albumen print is doing something a gold bath on a silver gelatin enlargement is not, which is why the three alternative-process gold baths in the formulary are written for those parts. What transfers from this page is not the chemistry but the method: intention first, control alongside, compensation from your own measurement, and a permanence claim no larger than the evidence.

Recap

• The control is the instrument. Two prints from one session at one exposure, one of them never toned, and every number and every sentence measured against it. HARMAN build the same habit into their own first-time instructions for a reason.
• Choose the toner from the intention, in three clauses: what happens to the deep tones, what happens to the highlights, and what you are willing to lose. “Warmer” and “more archival” are intentions that cannot fail, and an intention that cannot fail is not one. And check the supply and the safety data sheet before the taste: one toner in the shops is classified Carc. 2 and Repr. 2 and is outside this Level B assignment on the rubric’s own terms.
• Print for the toner, with your own number. ΔE = ΔD_toning ÷ (ΔD per stop), divided at a mid-tone, with both figures measured by you in this part and in Part XVIII. Every manufacturer statement in this corpus gives a direction and explicitly declines to give a magnitude.
• Compensation is a choice of where the print is right, not a repair. An exposure change slides the curve; the toner changed its shape. Land the mid-tones and a sulfide route’s maximum density is still short, and if maximum black is what the picture is built on, that is the moment to change the toner rather than to print a fourth sheet.
• Measure the change, and state the noise floor first. Matched patches read dry before and after, a hue statement that is ranked and referenced rather than named, and the separation in the two or three areas that carry the picture. A change at base white is a stain, not a result.
• Answer the honest question with evidence. Better, only different, or worse — and any of the three is acceptable if it names something on the paper. Difference reads as improvement, which is exactly why the question is asked.
• The permanence statement keeps its four parts apart, names the toner’s document and its date, and reports the degree of conversion as unmeasured. ISO 18915 exists, measures precisely that, and prescribes no treatment and no criterion a print can be certified against.
• The mount is chemistry. Buffered board meeting ISO 18902 for a sulfide- or selenium-toned print; unbuffered for an iron-blue one, because the alkaline reserve that protects the paper destroys the pigment. Reversible hinges either way, and display below 100 lux regardless of what you toned it with.

Check your understanding

Question 1. You measure your sepia-toned print against its control and find the mid-tone 0.10 lower and the maximum density 0.34 lower. Your paper gains 0.50 in reflection density per stop at the mid-tone. What correction does the method give, and what does it fix?

• About two thirds of a stop, which restores both the mid-tone and the maximum density
• About a fifth of a stop, which lands the mid-tone on the control and leaves the maximum density short, because an exposure change slides the curve while the toner changed its shape
• No correction: the density loss should be recovered by developing longer instead
• About a fifth of a stop, applied as a change to the local dodging and burning rather than to the base exposure

Show the answer and why

Answer: About a fifth of a stop, which lands the mid-tone on the control and leaves the maximum density short, because an exposure change slides the curve while the toner changed its shape

The division is 0.10 divided by 0.50, which is 0.20 stops, and it is made at a mid-tone patch precisely because the assumption that density per stop is constant fails near the toe and the shoulder. What the correction does is move the whole characteristic curve along the exposure axis; what the toner did was change the curve’s shape, lowering the ceiling by rebuilding the substance that produces density. Steps already on the shoulder have nowhere to go, so a fifth of a stop recovers almost nothing at the top and the maximum density stays about a third of a unit short. That is not a failure of the arithmetic but its correct result, and the decision it forces is where the print should be right — and if maximum black is what the picture is built on, the answer is a different toner or a different interpretation rather than a fourth sheet. The correction goes on the base exposure and not on the local moves, because the local moves are written as ratios and ratios survive a change of base.

Question 2. A student writes as their toning intention: "I want this portrait to feel warmer and more archival." What is wrong with it, and what would make it usable?

• Nothing — it names a colour direction and a permanence goal, which is what an intention is for
• It is two claims neither of which can fail, and it hides a decision: "warmer" does not say whether the shadows or the highlights should carry the colour, and "more archival" names no threat, no treatment and no dilution — and the protective and colour dilutions of the same toner are different treatments
• It is too long and should be reduced to a single word naming the toner
• It should have been written after the print was toned, when the result could be described accurately

Show the answer and why

Answer: It is two claims neither of which can fail, and it hides a decision: "warmer" does not say whether the shadows or the highlights should carry the colour, and "more archival" names no threat, no treatment and no dilution — and the protective and colour dilutions of the same toner are different treatments

A full sulfide route re-colours the whole scale and lifts the shadows; a partial bleach colours the highlights and leaves the shadows neutral. Both could be called "warmer" and they are opposite pictures, so the word decides nothing and cannot be shown to have failed. "More archival" is worse: ILFORD name the specific threat toning addresses, oxidising gases, and recommend toning prints made for display against it, while HARMAN publish two different dilutions for two different jobs — 1+3 for a visible tone change and 1+20 where the primary reason is protection with minimal tone change, complete in two to four minutes. An intention that quietly asks for both will be judged against whichever the bath happened to deliver. The usable form is three clauses: what should happen to the deep tones, what should happen to the highlights, and what you are willing to lose — and the third clause is the one that makes the first two honest.

Question 3. You are mounting two toned prints: one selenium-toned on fibre paper, one blue-toned. The shop offers four-ply board whose packet states that it meets ISO 18902. What do you buy?

• That board for both, since meeting the standard is the strongest quality claim available
• That board for the selenium print, and an unbuffered board of the same standard for the blue-toned one, because ISO 18902 requires at least 2 per cent calcium carbonate and alkali destroys Prussian blue
• Neither: buy board marked acid-free and museum-quality instead, which is the stricter specification
• That board for the blue print and unbuffered board for the selenium print, since selenium is the more reactive of the two

Show the answer and why

Answer: That board for the selenium print, and an unbuffered board of the same standard for the blue-toned one, because ISO 18902 requires at least 2 per cent calcium carbonate and alkali destroys Prussian blue

ISO 18902 asks for a pH between 7.0 and 9.5, buffering with at least 2 per cent calcium carbonate, and freedom from lignin, and the Library of Congress list silver prints among the materials buffered paper may be used with — so for a selenium- or sulfide-toned silver gelatin print the ordinary answer holds. The same Library of Congress passage recommends unbuffered paper at pH 6 to 7 for cyanotypes, and a blue-toned silver gelatin print carries exactly that pigment: the alkaline reserve that protects the paper hydrolyses the Prussian blue, and it is the image you cannot replace. Note what the third option gets wrong in the other direction: IPI state that acid-free, archival, museum-quality and conservation board are marketing terms that are neither standardised nor legal, which is why the printed claim to meet the standard is what to look for. No source in this course addresses a silver-gelatin support carrying a cyanotype’s pigment, so treating it as a Prussian blue object for every material it touches is the course’s own reading, and it is labelled as one.

Question 4. Your toned print and its control are dry. The toned print reads 0.06 higher than the control at base white, and your control sheet’s own before-and-after differences were at most 0.02. What have you measured?

• A genuine toning effect in the highlights, since 0.06 is three times the noise floor
• A stain from the printing session’s fixer, which the toner revealed rather than caused, because there is no image silver at base white for a toner to convert
• A densitometer calibration drift, which should be corrected by subtracting 0.06 from every reading
• Normal dry-down, which affects the toned sheet more than the control

Show the answer and why

Answer: A stain from the printing session’s fixer, which the toner revealed rather than caused, because there is no image silver at base white for a toner to convert

Base white is where the emulsion holds no developed silver, so a toner has nothing there to convert, plate or replace — which is why a change at base white cannot be a toning result whatever its size relative to the noise floor. What it is, on Kodak’s own account of toning faults, is residual silver left by an exhausted or overloaded fixing bath, forming a yellow stain that only appears when the toner arrives; and improper fixing is, they say, probably the major cause of stains in toned prints. The fault belongs to the printing session, and the remedies are upstream: fresh two-bath non-hardening fixing, the running total watched against capacity, and the residual-silver and residual-thiosulfate tests run on a strip before any print is committed to a bath. Subtracting the offset would be the worst response, because it would hide a processing defect inside a correction and carry it into every figure in the table.

Question 5. The assignment asks whether the toned print is better or only different. Which answer would be accepted, and why is the question asked at all?

• "It has more presence and feels more finished" — accepted, because a judgement about a print is ultimately subjective
• "The wet roof tiles, which the control merges into one tone, are now two distinguishable tones, and the roof is what the picture is about; the cost was a lighter black in the doorway, which I accepted" — accepted, because it names things on the paper and states the cost
• "Better, because selenium toning is known to improve any print" — accepted, because it cites the mechanism
• Any answer is accepted provided the print was toned to the written intention

Show the answer and why

Answer: "The wet roof tiles, which the control merges into one tone, are now two distinguishable tones, and the roof is what the picture is about; the cost was a lighter black in the doorway, which I accepted" — accepted, because it names things on the paper and states the cost

The question exists because toning always produces a difference and difference is habitually read as improvement, so a maker who does not test the claim will make it by default. An answer counts on the same terms as the technical pass of the critique: it names something on the paper that another person could check on the same sheet, and it names what the improvement cost, since every route in this part costs something. "More presence" fails the test Part XIX gives for a sentence in a critique — it could be attached unchanged to almost any toned print without becoming false, which is precisely what makes it carry no information. "Selenium improves any print" is a claim about a class rather than about this object, and it is not what the manufacturers say either: their statements are about density and protection, and both depend on the paper. Note that "worse" is also an acceptable answer, and is the most useful one, because a sepia route that lifted the shadows out of a picture whose subject was in the shadows is a good result for the assignment and a bad print.

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