Part XXII Overview: The First Silver Print

Take a sheet of good writing paper, soak it in salt water and dry it. Brush silver nitrate over the salted side and dry it again in the dark. There is now silver chloride in the paper — not on it, in it, among the fibres — and if you put a negative against that sheet and carry it into the sun, a picture appears while you watch. Nothing develops it. Nothing amplifies it. Every atom of silver in the finished print was put there by a photon that arrived and was used.

That is a salted paper print, and it is the oldest photographic printing process that has left us any surviving prints. It is also the first process in this course that puts silver nitrate in your hands in quantity, which changes the hazard, the waste and the cost of everything you do for the next three parts.

What this is, in one paragraph of chemistry

A salt goes into the paper first. Silver nitrate goes on top of it second. Where they meet, silver chloride precipitates in place, in the fibres, and a soluble nitrate is left behind to be washed out later.

NaCl + AgNO₃ → AgCl(s) + NaNO₃

The double-replacement that makes the light-sensitive substance, inside the sheet rather than in a beaker

You did that reaction in a beaker in Part IV and again in gelatin in Part V. Here it happens in cellulose, with nothing to control where the crystals form or how big they get, and with a large deliberate excess of silver nitrate left unreacted around them. That excess is not waste; it is the mechanism. Talbot established the ratio empirically in the 1830s — Reilly reports that he found papers with equal amounts of chloride and silver nitrate hardly light-sensitive at all, that about six times more nitrate was needed, and that the salting solution should be 2 to 4 per cent and the silver 12 per cent. Those numbers are still what the modern kits ship: Bostick & Sullivan’s salted paper kit contains a 100 mL bottle labelled 12 per cent silver nitrate.

Light then splits the silver chloride into silver and chlorine, and the chlorine has to go somewhere or the reaction runs backwards. What takes it up, and how much of the argument about that is settled, is the first lesson’s subject and the most interesting unresolved question in the part.

Three absences, and what each one costs you

Everything from Part VIII to Part XX rested on three things this process does not have.

No development, and therefore no amplification. In a silver gelatin material a developer finds an invisible speck of a few silver atoms and reduces a whole crystal around it; Part IV’s arithmetic puts the gain at of order 10⁷ to 10⁸ atoms of image silver per atom of latent image. Here there is no gain at all. Ware’s estimate for the exposure needed to build a visible photolytic particle rather than a latent-image speck is of the order of a million times; Reilly, writing from the practical side, says printing out needs in some cases 100,000 times more light energy than developing out. Take the two as bracketing the same fact from opposite directions. Its consequences are absolute: every salt print is a contact print, exposures are measured in minutes of sunlight rather than seconds under an enlarger, and there is no salted paper enlargement anywhere in the history of the process because the light bill is impossible.

No binder, and therefore no emulsion layer. There is no gelatin, no baryta, no supercoat. The image silver sits in the top fibres of a sheet of paper, in direct contact with the air, the mount and anything the mount is made of. That is why a salt print is matte and sunken in, why its maximum density is limited, why the paper’s texture is always visible in it, and why — as the permanence lesson argues — it is far more vulnerable than a modern print to a trace of sulfur in the air.

Where the image sits: three answers to the same question

Drawn to show the arrangement rather than the depth, and the three sections are stacked for comparison rather than being one object. The salt print's image zone is the only one of the three that is not a coating: the Getty Atlas describes an uncoated salt print as having a sunken-in appearance in the body of the paper substrate. Layer depths are drawn to be readable, not to scale: on real film the base is roughly a hundred times the emulsion, and drawn honestly the emulsion would vanish. Any thickness given in the labels is the real one.

No fixer that leaves the picture alone. This is the absence that surprises people, and it governs how you expose. The fixer of Part XI dissolves unexposed silver halide and leaves developed silver untouched, because developed silver is coarse. Printed-out silver is not coarse. Ware’s figures make the difference concrete: a whole-plate salt print carries about 3.3 mg of silver in total, roughly a tenth of a modern print, at a particle size perhaps a hundredth of a modern print’s, so the surface area available for attack is about a hundred times larger. A thiosulfate bath takes some of that image away along with the unexposed chloride, and the colour shifts as it goes. So the print must be exposed past the point where it looks right: Reilly’s starting figure is about two stops of overprinting for salted papers, Bostick & Sullivan tell you to stop when the print is one half to two thirds as dark as you want it to finish, and the size of that allowance is something you measure for your own fixer in the printing lab.

What it shares with the rest of the cluster

Four things, and all four were taught in Part XXI so that they would not have to be taught five times.

Contact printing, through the split-back frame, which exists precisely so that you can open half of it and look at a printing-out image without losing registration.

An ultraviolet-rich source. Reilly is exact about why: albumen and salted papers are primarily sensitive to ultraviolet and only much less so to visible blue, so the question about a light source is not how bright it looks but how much ultraviolet it emits. The Part XVI UV unit or the sun; nothing else.

A long-scale negative. Reilly puts it as bluntly as Ware does for cyanotype: even the densest and most contrasty negatives that will still print satisfactorily on develop-out papers do not have enough density range to make good prints on albumen or salted papers, plain salted paper wants the longest range of the family, and a compromise negative prints well on neither kind. The negatives and papers lesson owns this, and your standard negative from that part is what you print here.

Hand coating, with all of Part XXI’s discipline about even coatings, dedicated brushes and rods, and a paper chosen for what it is made of rather than for how it looks.

One thing is not shared, and it is the thing to unlearn from Part XXI. A cyanotype is handled in room light because its sensitiser responds to ultraviolet alone. A sensitised salted paper is not: silver chloride with excess silver nitrate is slow, but it is not insensitive, and it goes on printing out by itself in the dark. Reilly’s working light for these papers is a yellow 60 W incandescent bulb, and he adds that there is no need for the dim light of a modern safelight — but that is a nineteenth-century practice restated by a conservator, not a measured limit, and the salting lab says so and asks you to establish your own.

The historical weight, in one paragraph

This part does not re-tell the invention of photography; Part I owns Talbot, photogenic drawing and the negative-positive principle, and it should be read first. What matters here is scale. The salted paper print dominated photographic practice from 1840 to 1855 — Reilly’s sentence, in his preface, and the Getty Atlas agrees from the other direction, calling the salt print the process used almost exclusively for printing calotype negatives until about 1850 and noting its near-total replacement by albumen by the middle of the 1850s. For fifteen years this was photographic printing on paper. Then albumen took it, held the market until 1895, and ended up accounting for about 85 per cent of all surviving nineteenth-century photographic prints, which is Part XXIII’s story. The salt print’s decade and a half is the reason almost nothing from it survives in good condition and the reason conservators care so much about identifying what does.

Where this part sits in the history of the printing paper

Salted paper

Dominant 1840–1855Persisting, then a matte revival from the 1880s

Albumen

Dominant 1855–1895Losing to emulsion papers

Emulsion printing-out

Gelatin and collodion P.O.P., 1895–1905

Develop-out papers

From about 1905, and ever since

18401855187518951920

Periods of dominance rather than of existence, from Reilly's preface and his identification chart, and from the Getty Atlas salt-print chapter. Reilly's chart gives salted papers 1840–1855, albumen 1855–1895 and gelatin and collodion printing-out papers 1895–1905, and notes that only since about 1905 have most printing papers been of the develop-out variety. The bars are drawn on a linear scale from 1840 to 1920.

Safety framing: this is the silver nitrate part

The part’s level, 3, is difficulty. The safety letters are separate, assigned page by page from the classification rubric, and here the letter comes from one substance.

⚠What silver nitrate is, and the four rules that follow

The classification. PubChem’s aggregation of the harmonised European classification gives silver nitrate three pictograms — oxidiser, corrosive and environmental hazard — the signal word Danger, and the statements H272 (may intensify fire) and H314 (causes severe skin burns and eye damage), with acute and chronic aquatic toxicity beside them. Reilly, writing for photographers, adds the specific warning that matters most at this bench: silver nitrate can cause permanent, irreversible eye damage, and sheets dripping silver solution pose a special hazard to the eyes.

Splash goggles, not spectacles. The eye statement is the strongest thing the substance carries, and the highest-risk moment is a wet sheet being lifted over a tray at face height.

The stains are a marker, not the hazard, and they are permanent. Bostick & Sullivan put it in capitals on their own sheet: silver nitrate will stain all surfaces black including your skin. The stain appears over hours rather than at once, because it is silver bound to the protein of the skin being reduced. Reilly names the systemic condition that repeated absorption can eventually cause — argyria, an irreversible staining of the conjunctivae, blood vessel walls, gums and mucous membranes — and says all necessary precautions should be taken to avoid repeated absorption through the skin. Gloves, every time, and wash immediately after contact.

No metal, no ammonia, no organic mopping-up. Silver nitrate reacts with the metal of a brush ferrule and prints the reaction as a stain; Reilly specifies a Japanese brush bound with thread for exactly this reason and advises against a stainless steel tray. Ammonia added to a silver bath and then boiled down can form fulminating silver, which is explosive, and Reilly refuses to recommend that operation to anybody. The incompatibilities page and the silver nitrate handling SOP carry the full list.

Every drop containing silver is collected. Not because it is dilute or not, but because it is silver: the first wash of a salt print is the most concentrated silver-bearing solution this course ever produces, and it goes into the silver-bearing waste container along with the fixer and the toner. The disposal caveat governs the rest, and local regulation is the only document that can answer the question for your drain.

Reilly quantifies the reason the waste matters. Of the silver put onto a sensitised sheet, only about 6 to 8 per cent ends up in the image; the rest is washed or fixed away. Ware, working from chemical analyses of actual salt prints made in 1855, puts the retained fraction lower still, at about 2 per cent. The two figures are not measuring quite the same thing — Reilly is describing working practice with albumen and salted papers, Ware is reporting an analysis of finished nineteenth-century prints — and the course reports both rather than averaging them. Either way the conclusion for your bench is the same: more than nine tenths of the most expensive substance in the course leaves the sheet in the wash water and the fixer.

Two levels appear across the part. The two labs and the break/fix page are Level B, set by silver nitrate. The three lessons carry no safety level because they give no procedure. One substance the part discusses is deliberately never used: the potassium dichromate that both bought kits ship as a contrast agent. It is a chromium(VI) compound, the chromium ruling forbids chromium(VI) at any level, and the printing lab gives the alternative contrast controls that the period itself used.

The map

Six pages after this one, in the order the reasoning runs. Chemistry first, because nothing about the craft is intelligible without it; then the two sessions, split by the drying step that separates them; the gold and permanence lesson placed before the printing lab that tones, because you should know what gold does to a nanoparticle before you spend any; then identification, and then the fault clinic.

Page	What it settles	Level
Printing out: silver chloride made and darkened in the paper	The in-situ precipitation, why the excess silver is the mechanism, what accepts the chlorine, why the image is red, self-masking, and what the fixer takes back	—
Lab: salting and sensitising a sheet of paper	Two coatings, floating against brushing, silver nitrate handled properly, the bath’s exhaustion, and a silver mass balance you can actually close	B
Gold toning and the permanence of a printed-out silver image	Why colour and permanence are one subject here, what the four toner families differ in chemically, and what the evidence for permanence actually is	—
Lab: printing, toning, fixing and washing a salt print	Exposure by inspection, the first wash, the gold bath, a fixer unlike any other in the course, and the tests that check it	B
The variants of the salt print and how a conservator identifies one	The binder ladder from plain salted to glossy albumen, contrast control as the period practised it, and the signatures a conservator reads	—
Break/fix: the printed-out image that faded	Six failures common to this part, Part XXIII and Part XXIV, as symptoms with the evidence to collect	B

Behind the six sits a formulary that is already complete for this process, and no lesson page here restates a quantity that lives there. The two salting solutions (plain, arrowroot) and the albumenised one; the sensitiser; the three gold toners (borax, thiocyanate, acetate) and the platinum toner that the course publishes as chemistry only; the two fixers (the kit’s plain bath, Reilly’s alkaline one); and the sulfite washing aid. The process atlas entry is where the identification page’s conclusions land.

What you produce

Six things, and the last two are the reason the first four exist.

Salted sheets, which keep indefinitely in a cool dry place, so the salting is a batch operation you do once. Sensitised sheets, which keep one or two days and rather less in warm damp weather, which is why the two labs are two sessions. A gold-toned print with a recorded toning endpoint. A measured fix-down: the density your own fixer takes off your own print, which is the number that tells you how far to overprint and which no book can supply. Your own exposure record for a process whose speed depends on the sky. And the second row of the process comparison atlas, after Part XXI’s cyanotype row — the same standard negative, printed a different way, measured the same way — which is the argument the whole cluster is building towards and which Part XXV closes.

Cost

The band is ££, and one substance dominates it.

The planner carries a dated UK figure for silver nitrate: £59.95 for 25 g and £112.90 for 10 g, both checked on 5 September 2026, the cheaper of the two shown out of stock on the day. The price file’s own note says the difference cannot be explained from the listings alone and warns that silver moves with a commodity market rather than with a retailer. Take the low figure as what silver nitrate ought to cost and the high one as what you may have to pay today.

🧮What 25 g of silver nitrate is worth in sheets — the course's own arithmetic

From the sensitiser’s published strength on its formulary page — 120 g per litre, which is 12 per cent w/v — and nothing else:

25 g ÷ 120 g per litre = about 208 mL of 12 % sensitiser

Solution from one 25 g jar

Bostick & Sullivan state that 100 mL of their 12 per cent silver nitrate makes approximately fifty 8 × 10 inch prints when applied by drop count, so

208 mL × (50 prints ÷ 100 mL) = about 104 sheets of 8 × 10 in

Sheets, at the supplier's own coverage

which is £0.58 of silver per sheet at the low price and £2.71 at the high one, before paper.

What this arithmetic is and is not. It is the course’s own, from one published strength, one published coverage and one dated price. It assumes brush or rod coating at the supplier’s drop count and no waste. Floating uses far more, because the sheet only takes up part of what is in the tray and the tray has to be deep enough to float on — Reilly’s whole discussion of replenishing and decolorising a silver bath exists because floating is where the silver goes. Treat this as an order of magnitude for planning, which is all a per-print figure ever is, and read the salting lab’s mass balance for the real accounting.

Gold is the other expense and it is worse per gram, but it is used at a hundredth of the concentration: Reilly’s toning baths for matte salted papers carry 0.1 to 0.2 g of gold chloride per litre. The gold lesson does that arithmetic properly and says plainly where the price file cannot help.

!What the price file cannot yet tell you about this part

src/data/prices.json prices the silver nitrate, the gelatin, the borax, the sulfite, the carbonate and the gloves, and since the survey of 7 September 2026 it also prices the raw hypo and the solid citric acid. Gold chloride it still cannot price, and the gap it now records for that salt is written in the terms this part asked for. Hot-press cotton watercolour paper, kaolin and the thiocyanates are named gaps as well, and all three are consumed here. The consequence is stated on each practical page: its Estimated consumables cost table still leaves rows empty, and its subtotal is a floor rather than a total.

What you need first

Part II’s silver nitrate lesson and the SOP drawn from it. This part assumes both and does not re-teach them; where it repeats a control it says which page owns it. The waste containers lesson is the other half, because this part adds the largest silver stream in the course to them.

Part IV, for silver chloride and photolysis — the halides, precipitating them and the latent image, the last of which is the page this part spends its time contradicting in an instructive way.

Part XI’s fixing chemistry, because the fixer here does the same chemistry for a different purpose and with a different risk, and Part XII’s washing and permanence, whose residual silver and thiosulfate tests are applied to a salt print in the printing lab.

Part XXI’s materials lesson, for the negative, the paper and the ultraviolet source, none of which is re-argued here — with one correction the salting lab makes in detail: cyanotype needs an unbuffered paper because alkali destroys Prussian blue, and that particular reason does not carry over to a silver chloride image.

Part XX, which already established the gold redox arithmetic — one atom of gold for three of silver from gold(III), one for one from gold(I) — on a developed silver gelatin image. This part takes the same chemistry to a different substrate and cross-links rather than repeating it.

Alternative route

This part declares requiresUV, and the honest alternative is the sun. It is not a compromise here: every salt print made before the 1880s was made in daylight, Reilly says daylight has accounted for all but a tiny fraction of the albumen and salted paper prints ever made and remains the cheapest and most satisfactory source where mass production is not required, and both modern kit sheets list sunlight first. What you supply instead of a dose is a written record — date, time, sky, orientation, elapsed time and the print’s appearance at each inspection — through the daylight exposure SOP and the outdoor exposure session SOP.

Two of Reilly’s cautions belong with that offer, because they are specific to this process rather than general. Printing-out papers lose sensitivity below about 5 °C, so he calls printing outside in winter practically impossible. And a weak light cannot be compensated by a long exposure: Ware treats this as a case of low-intensity reciprocity failure and reports the nineteenth-century observation directly — inadequate light levels produced weak prints after wet processing regardless of how long the exposure ran. A dull sky is not a slow sun; it is a different and worse result.

No darkroom is needed and the part does not declare one. What is needed is a room whose windows can be covered and a working light that is not daylight and not fluorescent. Reilly’s own specification is a yellow incandescent bulb bright enough to work by comfortably.

Where there is no wet space at all, three of the seven pages need no facility of any kind: the chemistry lesson, the gold and permanence lesson and the identification lesson are reading and arithmetic from end to end, and the formulary entries behind them carry the composition and the mechanism at greater depth than the lessons do. The break/fix page is diagnosis from recorded evidence and can be worked with somebody else’s records. What has no substitute is the wash. A salt print is washed before toning, again before fixing, again after fixing and then for half an hour more; there is no version of this process that is not wet, and no version that skips it and lasts. If running water is the obstacle, this becomes a reading part, and saying so is better than pretending a dry route exists.

The pages of this part

Part22 of 28Level3 — AdvancedPages6Estimated time9.2 hoursHighest safety levelLevel B

✱3 of 6 pages in this part need a darkroom, a UV source or mains-powered equipment, marked below. Each says what can be improvised and, where one exists, gives an alternative route.

0 / 6 lessons in this part completed

• LessonPrinting Out: Silver Chloride Made and Darkened in the Paper60 min
• LabLab: Salting and Sensitising a Sheet of PaperB✱ Darkroom150 min
• LessonGold Toning and the Permanence of a Printed-Out Silver Image55 min
• LabLab: Printing, Toning, Fixing and Washing a Salt PrintB✱ UV180 min
• LessonThe Variants of the Salt Print and How a Conservator Identifies One45 min
• Break/fixBreak/Fix: The Printed-Out Image That FadedB✱ UV60 min