The Variants of the Salt Print and How a Conservator Identifies One

Plain salted paper had a very short career as the state of the art. Talbot’s method reached the public in 1839; by the late 1840s photographers were adding organic material to the salting solution, and by 1855 hardly anybody was making prints with a plain salt solution alone. The reason is a single sentence in Reilly’s first chapter, and the whole of this page is downstream of it: where the light-sensitive layer penetrates deeply into the paper fibres, the maximum density obtainable is lowered and the print is matte, because the light reflected from the sheet is scattered and diffused by the fibres.

So the history of the salted paper is the history of people trying to stop the silver sinking in. And the identification of a salted paper is, in large part, the reverse question: how far did it sink, and what was holding it up?

Why the plain paper was modified almost at once

Three limits, all consequences of the image being in the sheet rather than on it.

The surface is matte and the paper texture is always visible, because there is no coating. The Getty Atlas’s description of an uncoated salt print is exactly this: a characteristic matte appearance, with a sunken-in appearance in the body of the paper substrate.

The maximum density is limited, for Reilly’s scattering reason. A deep black needs a lot of reduced silver on a matte surface — more than on a glossy one to reach the same apparent density — and there is not much silver in a salt print to begin with.

And the resolution is limited. Reilly reads the early history of printing papers as a steady evolution of techniques for producing papers capable of greater resolution and contrast, driven by the desire to reproduce the fine detail present in negatives on waxed paper and glass. Once the wet collodion negative arrived, a paper that threw that detail away was the bottleneck in the system.

There is also a fourth thing, and it is chemical rather than optical. Reilly is blunt: pure silver chloride paper is unsatisfactory, because it produces grey and flat images. Some organic material has to be present, and if the paper’s own sizing does not supply it, the salting solution must — which is why even Reilly’s “plain” formula carries 2 g of gelatin per litre.

🕰The accident that started it: English gelatin against French starch

Talbot used a plain salt solution and nothing else, and his prints were reddish brown. Reilly explains why: the sizing the English paper maker had already put in the sheet was gelatin, and gelatin is one of the “active” organic substances. French photographers found the same method gave different results on their own papers, because the French mills sized with starch, which is not active.

Two French scientists, Alphonse Davanne and Jules Girard, investigated and explained the difference. Until the late 1840s no organic binder was deliberately used in a salting solution at all — only chlorides, usually table salt or sea salt — so for a decade the binder in a salted paper was whatever the paper mill happened to have used, and nobody knew it was a variable.

The Getty Atlas confirms the split from the analytical side: the literature records English mills preferring gelatin as an internal size and French and other continental mills using starch, and a weak protein signal in an FTIR spectrum of a salt print may therefore come from the mill rather than from the photographer.

The binder ladder

Set the whole family out in one order — least binder to most — and every property moves monotonically with it.

The binder ladder: what more binder buys, and what it costs

more binder, more gloss, more density, shorter scale

1. Plain salted paper — no added binderOnly the mill's own sizing. Deep matte, lowest maximum density, longest tonal scale of the whole family. Reilly: "very soft-working papers" needing negatives of far greater density range than any modern develop-out paperthe reference case
2. Gelatin in the salting solution — 2 g per litreReilly's plain formula. Only enough to slightly inhibit the sinking of the image into the fibres. Gelatin is also chemically "active", so it raises density twice overthe course's starting formula
3. Starch: arrowroot, tapioca, rice — 2 to 4 per centVery matte to a dull gloss, according to how much starch and how smooth the stock. Considerably more brilliant than plain salted, a longer density range and more delicate detail. Not active, so it needs citric acid beside itfrom 1854
4. Whey — lactose as the active ingredientTried in the early 1850s and never important. Reilly names casein, agar-agar, carrageenin and Iceland moss in the same breath: real materials, each with a characteristic effect, none of which displaced the othersthe road not taken
5. Resin, usually as a resin soap with gelatin or starchThe resin is precipitated and made insoluble when the sheet meets the silver solution, as albumen is. Soft results like a platinum print — but thick resin is impermeable, so toning, fixing and washing become difficultimproved by Cooper in the 1880s
6. Matte albumen — albumen mixed with starchHübl's invention, first published February 1895: equal volumes of albumen and a 2 per cent arrowroot solution. Brownish red untoned, purplish black with gold, warm brown to black with gold and platinumthe commercial peak of the matte papers
7. Diluted albumen, 1+6 to 1+1Reilly: 1+6 gives a paper almost indistinguishable from other matte salted papers; 1+1 is half-matte. Even a 2 per cent albumen solution significantly improves depth and contrast over no binder at alla conscious choice, not a failure to make glossy paper
8. Pure albumen — the glossy albumen printA continuous transparent layer holding the silver entirely above the fibres. Highest maximum density, highest gloss, finest detail — and the shortest tonal scale, so it wants the least contrasty negative of the familyPart XXIII

One variable, eight positions. Reilly's own summary of the consequence is that albumen may be applied pure to produce a glossy paper or diluted to any strength with a corresponding loss of gloss, detail and brilliance of image - so the ladder is genuinely continuous rather than a set of discrete recipes.

Four properties move together as you go down the ladder, and one moves against them.

Going down the ladder	What happens	Reilly’s reason
Where the silver chloride forms	Deeper in the fibres → nearer the surface → in a discrete layer above them	The binder physically prevents penetration
Maximum density	Rises	Less light scattered and diffused by the fibres
Gloss and apparent brilliance	Rises	A smooth transparent binder minimises scattering in the whites too, so they look whiter
Sharpness and fine detail	Rises	An image confined to a thin surface layer is not spread by the fibres
Tonal scale	Falls	And this is the one that matters for printing. Hübl found glossy albumen equal to platinum paper in scale length, while salted papers exceeded platinum by a considerable margin

That last row is why this part comes before Part XXIII rather than after it. A plain salted paper wants the longest-scale negative of anything in this cluster; arrowroot and the other matte papers want slightly less; glossy albumen wants least. Reilly’s ordering is explicit, and the reason is the one above: to make a deep black on a matte surface you need relatively more reduced silver, which means longer exposures, which means the negative must carry enough density in the highlights to keep them from going dark meanwhile.

Arrowroot in detail, because it is the one you can actually make

Of everything on the ladder, arrowroot is the variant a reader can add to the course tonight from a supermarket ingredient, and its chemistry teaches the “active binder” distinction better than any other example.

What it is. Arrowroot is the starch of the rhizome of Maranta arundinacea. Reilly’s formula — 35 g of arrowroot, 35 g of salt and 3 g of citric acid, boiled — is in the formulary and is not restated here. The method matters: the starch is rubbed to a creamy paste with cold water, the salted water is brought to the boil, the cream is added in small amounts with constant stirring, the mixture is boiled gently for a few minutes, and the skin that forms on cooling is removed — Reilly identifies it as the residue of the hulls of the burst grains.

What it does to the print. Considerably more brilliant and richer-looking than a plain salted paper, with a longer density range and more delicate detail preserved. The surface runs from very matte to a dull gloss, depending on how much starch is applied and how smooth the paper underneath is.

And why it needs the citric acid, which is the point of teaching it. Starch is not an active organic substance. Reilly: it has no effect on the reduction of silver chloride, and if the citric acid were not present the prints would be grey and flat — the hallmarks of a pure chloride image. With both citric acid and starch present, the prints take on a warm purple after exposure and change to a yellowish-brown after fixation if they are not toned. The starch does the physics and the acid does the chemistry, and separating those two jobs is what a plain gelatin paper cannot show you, because gelatin does both at once.

Three handling consequences follow from the starch being inert and permeable.

A strong silver bath and a short float. Reilly: unlike albumen, starch is not coagulated or rendered insoluble by the silver solution, so a starch layer stays very permeable to water and too long a float lets fine silver chloride sink into the fibres, giving a loss of brilliance. Half a minute for a light coating; a minute and a half at most for a heavy one. Compare the two and a half to three minutes a plain gelatin-salted sheet takes.

Citric acid in the silver bath as well — 4 to 5 per cent, in his instruction for arrowroot papers, which also happens to give the maximum preservative effect for sensitised paper.

And a thick paste is brushed rather than floated. Solutions containing 2 per cent arrowroot or less are fluid enough to float; heavier coatings are obtained by immersing and drawing the sheet out over a glass rod, or by pinning it flat and brushing on a 3 to 4 per cent paste, letting it sink in for a minute or two, and evening it out with a dry round brush until the surface is uniformly matte.

!Is the arrowroot on a supermarket shelf the same material?

Probably close, and not guaranteed, and the difference is measurable. The arrowroot page sets this out in full. Two things a reader should know before buying a jar.

The botanical identity is not protected by the CAS number. CAS 9005-25-8 is a family number for starch of any botanical origin, so a label carrying it tells you nothing about the plant. What identifies arrowroot is the species, Maranta arundinacea, and the price — genuine arrowroot is dearer than the tapioca and corn starches sold beside it.

And even genuine arrowroot varies more than the procedure suggests. Malki and colleagues measured Sri Lankan arrowroot granules averaging about 45 μm long, while other published studies of the same species report widths of 20 to 40 μm and a Brazilian study an average of 56.6 μm; gelatinisation onset temperatures collected in the same paper run from 62.95 °C for a Brazilian sample to 75.02 °C for the Sri Lankan one — a spread of twelve degrees. The authors attribute the spread to botanical origin, plant physiology and stage of development at harvest, and the same paper found an A-type X-ray diffraction pattern where an earlier study found B-type.

Why it does not matter as much as it sounds. The historical instruction is to bring the salted water to the boil and add the cream, which is robust against a twelve-degree spread in gelatinisation onset — and that is probably why the method survived unchanged from Towler in 1864 to Reilly in 1980. Record the brand and the botanical name in your batch record anyway, because two jars labelled arrowroot are not guaranteed to be the same material.

Reilly’s own note that tapioca or rice starch may be used in the same manner is worth reading beside this: DeBrébisson’s first starch papers of 1854 used tapioca, and arrowroot only emerged later as the most suitable and widely used.

The albumenised salt print, which is the hinge to Part XXIII

There is no boundary between a salted paper and an albumen print. There is a dilution.

Reilly’s own numbers make the continuity explicit: pure albumen gives the familiar glossy paper; 1+1 with water gives a half-matte paper; 1+6 gives a paper almost indistinguishable from other matte salted papers; and even a 2 per cent albumen solution significantly improves depth and contrast over a paper with no organic binder at all. Many early prints were made with diluted albumen as a conscious choice — some photographers preferred it because it was easier to tone, and many chose matte for aesthetic reasons.

The albumenised salt print is the low end of that range: a thin albumen addition to a salting solution rather than a full albumen coat, so that the albumen arrives in the same operation as the chloride. Hardwich’s 1864 formula is in the formulary — three volumes of egg white to one of water, salted with ammonium chloride — and it is the formula in which the amount of water decides the surface.

!An empty page in the conservation literature, named

The AIC Photographic Materials Group wiki carries a page titled Albumenized Salt Print, and as read on 7 September 2026 every content section of it is an empty heading — Historical Facts, Identification Characteristics with its Image material, Color and Support sub-headings, Conservation, Housing and Storage, Exhibition, Emergency Recovery, References and Further Reading. The page carries no contributors and no date initiated.

That is worth naming rather than quietly omitting, because it is the conservation profession’s own acknowledgement that this variant has a place in the taxonomy and no published identification description. This course cannot give the AIC’s signatures for an albumenised salt print as it can for a plain salted paper print, because they have not been written. What it has instead is Reilly’s account of the material and the Getty Atlas’s remark that photographers diluting the albumen bath produced results that are semi-glossy or almost matte and difficult to distinguish from a salt print on a highly sized substrate — which is a statement that the distinction is hard, not a description of how to make it.

Contrast control, as the period actually practised it

There is no paper grade. Four levers were in real use and a fifth was available and disliked.

The chloride content of the salting solution. Reilly states it directly and gives the direction: the chloride content affects contrast, and lowering it tends to produce prints that lack brilliance and density. His working range for most salted papers is a chloride content around 2 to 2.5 per cent with the silver bath at 10 to 12 per cent.

Citrate. Reilly’s plain formula has a neutral-citrate variant and his statement of the effect is empirical and exact: it makes the prints more reddish in colour and slightly more brilliant. The Getty Atlas records that a salting solution is often sodium citrate and ammonium chloride at around 4 per cent by weight, so citrate was normal rather than exotic.

The binder, which is the whole of the ladder above.

And the light source, which is the one people forget because it is not in the tray. Reilly: a very intense source lowers print contrast while a weaker light raises it slightly — hence the old rule that dense vigorous negatives are printed in sunlight and thin ones in the shade, meaning facing open sky rather than in direct sun, and the practice of covering the printing frame with tissue paper or ground glass.

But the honest historical answer is that they controlled the negative. Reilly: for most of the nineteenth century photographers depended mainly on control of the negative density for contrast control in the print, which is why so many intensifier formulae are found in nineteenth-century photographic manuals. And his summing-up of the accumulated experience of many writers is that the best salted paper prints are always made in sunlight with optimum negatives, and without resorting to contrast-enhancing additions at all.

☠The fifth lever, which the course does not use and did not much like even then

Chromates. Reilly is straightforward: large increases in contrast are possible only with chromates, the technique does allow otherwise unprintable negatives to give good prints, and it has no place in regular practice. The discovery was Ferdinand Hrdliczka’s in the mid-1890s — by which time printing-out papers were already losing ground to develop-out — chromated papers reached the market in the late 1890s, and their sales amounted to only a small portion of the total.

His list of the drawbacks is worth having because none of them is the one this course refuses on: stability and predictability decline as the bichromate increases; the papers must be salted and stored in yellow or diffused light because the dichromate is itself light-sensitive; the salting solution must not touch metal; and the image colour goes browner.

The course’s own reason is the chromium ruling, which excludes chromium(VI) compounds at any level in any quantity on their carcinogenicity, mutagenicity and reproductive-toxicity classifications. Both bought salted paper kits ship a dichromate solution for this purpose. This course does not use it, does not print the quantities and does not have it in the room.

Additives whose function this course could not verify are simply not described. Reilly’s chapter five names whey, casein, agar-agar, carrageenin and Iceland moss as binders with characteristic effects; what those effects are, quantitatively, is not published in anything read for this course. The page names them and stops there rather than inventing a description.

How a conservator identifies a salted paper print

Start with the honest statement of what this is. Reilly, opening his own identification appendix: it is a very difficult task to set out guidelines for these materials because they are for the most part hand-crafted products; process identification of nineteenth-century print materials depends almost wholly on experience and judgement, and is a skill that slowly improves with practice. His guidelines are intended to narrow the range of possible choices, not to make a positive identification of an individual print.

The Getty Conservation Institute’s own founding meeting put a number on the same thing: the participating experts agreed that identification based solely on visual and microscopic inspection can successfully answer more than 75 per cent of identification questions — which is also a statement that nearly a quarter of them need something else.

What you look at, in order

The surface, in raking light. Salted paper prints are rough or matte-surfaced; albumen prints are smooth and display a greater or lesser gloss. Reilly’s caution is immediate: surface characteristics by themselves are little help, because many materials have similar surfaces and any surface can be altered by smoothing or by applied substances — corroborating indicators must also be present.

Whether the image sits in the sheet. This is the salted paper’s key signature. The Getty Atlas describes an uncoated salt print as having a sunken-in appearance in the body of the paper substrate, and under an optical microscope shows the deposit of photochemically reduced silver particles on top of and between the individual fibres. The AIC’s own identification line is the shortest version: the image is formed by silver deposited directly in the paper support.

Fibre visibility under magnification, which is the same observation at higher power — and with two warnings from the Atlas. At higher magnifications you can see sizing material coating the fibre surfaces and plugging between them; but the silver particles are too small to be resolved individually under an optical microscope, and the glossiness of a fibre is often difficult to distinguish from the glossiness of a surface sizing. Its conclusion is a rule for the whole subject: do not over-interpret an optical micrograph. FTIR gives much more reliable information about surface sizing.

Translucency and the watermark. Many unmounted salt prints are semitranslucent on a light table, which lets a paper watermark be detected. The Atlas treats this as important evidence rather than a curiosity: watermarks matter for both provenancing and authentication, and should be documented and added to the registrar’s database.

Image colour, with all the caveats. Reilly calls it one of the most important factors and immediately says that experience is vitally necessary and a list of colours is of very limited value. Prints in original condition are usually warm brown, purplish-brown, purple or purplish-black; they are seldom black and never green, although severely faded and yellowed albumen prints sometimes take a faint greenish tinge. The Getty Atlas adds that many salt prints of 1835 to 1850 were not gold toned at all and range from light brown to reddish brown. The AIC gives a wider range still — warm brown to cool grey.

The pattern of highlight staining. About 85 per cent of albumen prints show a readily noticeable yellow or yellowish-brown stain in the whites and highlights, and Reilly calls that, together with albumen’s surface texture, one of the two most reliable indicators that a print is an albumen print. Note what this is and is not: it is a strong positive indicator for albumen, not a negative one for salted paper, because other papers stain too.

And whether the print is too good to be a salt print. Reilly’s first guideline is counter-intuitive and useful: silver prints from this era generally show some deterioration or chemical blemish, and a perfectly intact, unblemished image usually indicates that a print is not an albumen or salted paper print — it is more likely photomechanical, or on a gelatin or collodion printing-out paper, which have generally survived in better condition.

The mount. Which is evidence about date and about risk at once, and the gold and permanence lesson carries the board and adhesive chemistry.

📷What the Graphics Atlas offers, and a warning about this course's copy

The Image Permanence Institute’s Graphics Atlas is the other standard identification resource, and its guided tour of a salted paper print names the six things it wants you to look at: Image Tones, Paper Fibers, Matte Surface, Retouching, Tears and Layer Structure, worked on four examples — Gore Hall at Harvard College, a photograph on silk, a tinted carte de visite and a yearbook portrait.

The warning is about the copy, not the resource. The site is built entirely from scripted image viewers, and the text mirrored into this course’s research corpus carries the navigation, those six view names and the four titles — and none of the descriptive prose the live site shows beside each view. So this page cites the Graphics Atlas for the questions it asks and takes its published descriptions of surface, fibre visibility and colour from the Getty Atlas and the AIC instead. If you have the live site in front of you, it is the best place to look at these features rather than read about them.

The distinctions that are actually hard

Four, and they fail in different ways.

Salted paper against albumen is easy at the extremes and genuinely hard in the middle. A glossy albumen print and a deep-matte plain salt print are not confusable. But the Getty Atlas states the awkward case directly: photographers who wanted to avoid gloss diluted the albumen bath, and the results are semi-glossy or almost matte and difficult to distinguish from a salt print printed on a highly sized substrate. Reilly’s version of the same problem is that with matte papers the materials are present in smaller quantities and tend to resemble one another, and differences in toning obscure whatever clues image colour might provide. The reliable discriminator is not visual: FTIR looks for the albumen protein.

Salted paper against matte collodion is a different question and it has a clean answer. Collodion papers are emulsion papers on a baryta substratum, so they have no visible paper fibres in the image and they contain barium. A salted paper has fibres and no barium.

Salted paper against platinum likewise: a platinotype has the fibres — the image is in the sheet, just as a salt print’s is — but the imaging metal is platinum and there is no silver. The Getty Atlas’s interpretation table makes exactly that separation.

And the calotype negative against the salted paper positive made from it. This is the one where the terminology is the problem rather than the object. Ware’s account is the sharp one: the term “calotype” has been used by some writers to denote all silver photographs on plain paper without discriminating between camera negatives and the positive prints made from them, which leads to a confusion of processes that are in principle different. The chemistry divides cleanly: photogenic drawings and salted paper prints are printed out from silver chloride, without development; calotypes are developed, from a latent image in silver iodide. The Getty Atlas records the practical consequence — many exhibited positive prints are labelled calotypes or Talbotypes when they are salt prints made from a salt paper or calotype negative.

What the analytical methods add

The Getty Conservation Institute’s own working strategy, from the Atlas’s introduction, is the order to follow.

The order the Getty Atlas prescribes, and what each step can and cannot settle

1. 11. Collect every visual and microscopic signature firstSurface in raking light, fibre visibility, where the image sits, colour, translucency and watermark, staining pattern, mount. The Atlas's founding meeting agreed this answers more than 75 per cent of identification questions on its own
2. 22. XRF for the imaging metal — and for the toning metal and the substrateNon-destructive. Silver identifies a silver print; gold or platinum says it was toned; barium says there is a baryta layer and therefore an emulsion paper; iron with silver says an iron-silver process. Traces of calcium and iron come from the paper itself
3. 33. FTIR for an organic binderAlbumen, collodion or gelatin. With one warning the Atlas gives twice: a surface coating can shield the binder's signal, and cellulose's own spectrum is a broad overlapping envelope that makes starch very hard to see against it
4. 44. Compare against the interpretation guide, working from the metal and the binder togetherNarrow to the processes sharing your imaging metal and your binder, then look for the best match across every signature
5. 55. Microsampling, rarely, and only with a conservator's and curator's approvalDestructive GC-MS can identify coating materials, per the AIC. The Atlas treats this step as the exception rather than the routine

The reason the order matters is cost and risk: each step is more expensive and more invasive than the one before, and most questions are answered before you reach step two.

What XRF actually says about a salted paper print, from the Atlas’s own analyses of three versions of Talbot’s The Open Door: silver as the imaging element, with traces of calcium and iron from the paper substrate. Its interpretation table marks paper fibres, silver and cellulose as the key signatures of a salted paper, and marks barium as absent — which is the single cleanest separation in the whole table, because barium present means a baryta layer and therefore a gelatin or collodion emulsion paper.

🔬Cobalt and arsenic, and what they are doing in a Talbot print

The Atlas’s most interesting finding is not about the photograph at all. XRF of Talbot’s prints, and of Hill and Adamson’s, showed cobalt and arsenic — first detected in the Scottish prints in 1997 — and the explanation is in the paper rather than in the process. The cobalt comes from smalt, a blue cobalt glass that paper makers added to the fibre mass to increase whiteness and combat yellowing during natural ageing; the arsenic was added during smalt manufacture to stop the molten glass foaming. Under low magnification the particles look like small specks of impurity; under higher magnification and good illumination they are bright blue.

Two things follow that a reader can use. Cobalt concentration varies greatly between papers, even from the same mill, so it is evidence about a batch of rawstock rather than about a photographer — and some of Talbot’s prints are on paper so heavily loaded with smalt that the sheet appears almost light blue. And it is a reminder of what the Atlas’s whole approach is for: an XRF spectrum of a salt print tells you about the paper mill as well as about the photographer, which is why the method is used for provenancing and authentication and not only for naming a process.

The modern equivalent is titanium: the interpretation table flags titanium as a marker of twentieth and twenty-first-century substrates containing titanium dioxide, so a “salt print” that shows titanium is a modern one.

And two limits, stated by the sources themselves. The Getty Atlas warns that a surface coating may shield the binder’s signal from FTIR, so the absence of an albumen band is weaker evidence than its presence. And its interpretation table carries a footnote that matters directly here: a small concentration of protein can be detected in some papers internally sized with gelatin, so a weak amide band in a salt print’s spectrum may be the mill’s size rather than a photographer’s binder.

Which is why an identification made by eye is always provisional. Reilly’s own conclusion is that his guidelines exist to narrow the range rather than to settle a case, and that the only real way to learn is to see and handle original prints — the tipped-in specimens in period journals being a particularly good source, because they are usually labelled with their process.

Dating a print from its process, and the limits of that

Reilly gives the chart, and it licenses much less than people assume.

Period	Most common printing paper
1840 – 1855	Salted papers
1855 – 1895	Albumen paper
1895 – 1905	Gelatin and collodion printing-out papers
from about 1905	Develop-out papers

What the chart does license, in Reilly’s own reading. 1840 to 1850 is nearly unambiguous: except for rare prints made by development, prints of that decade are plain salted paper prints. 1860 to 1885 is a time of reasonable certainty in the other direction: any given silver print of that period is very likely albumen, studio portraits and stereo views especially so, and a print of any kind from that period not on albumen is unusual.

What it does not license, and this is the more useful half. 1850 to 1860 is a transition and mid-decade is the worst case in the whole century: albumen coexisted with a number of different matte salted papers salted-and-sized with gelatin, whey or starch among other things, and Reilly says flatly that it is not possible to differentiate at a glance between these various types of matte salted paper. After 1885, an enormous number of photographs were still made on albumen but there can be little certainty from date alone, because the mid-1880s began a thirty-year period of great diversity that only the First World War ended.

And the direction of inference runs one way. A process identification constrains the date; a date constrains the process only where the chart is unambiguous. Reilly’s own framing is that a date is established first, from internal evidence in the image or on the mount, and the chart is then consulted — on the reasonable assumption that only rarely is there a significant lag between the making of a negative and the making of a print.

⁇Where the sources' dates for the same transition differ

Reilly’s chart gives salted papers 1840–1855 and albumen 1855–1895. The Getty Atlas says the salt print was the main positive process for salt paper and calotype negatives until about 1850, when Blanquart-Evrard introduced his albumen process, and that it was almost completely replaced by albumen by the middle of the 1850s, with albumen becoming the most important positive process after about 1855. The AIC dates Blanquart-Evrard’s simplified version of Talbot’s formula to 1847.

These are not really in conflict, and it is worth saying why rather than picking one: they are dating different events. The invention of albumen paper, its commercial availability, the point at which it outsold salted paper and the point at which salted paper effectively disappeared are four different dates spread over about eight years. The course uses “1840 to 1855” for the salted paper’s dominance, from Reilly’s preface, and says that the transition ran through the first half of the 1850s — which is what all three sources support.

Ware adds the caution that ends this section properly. A fully specified description of a photograph would need at least ten descriptors — substrate and sizing, binder, sensitiser chemistry, exposure, developer or print-out, wet process, finishing, optical process, generation, and positive or negative — and a nomenclature embodying all of them would be intolerably cumbersome. “Salted paper print” is a useful shorthand for a family, not a specification of an object.

Your own atlas entry

The process atlas entry for salted paper exists and was written from Part I, the chemical encyclopaedia and the conservation literature. Your job is to correct it from an object you made.

After the printing lab, fill these fields from your own print, with the conditions recorded beside each:

Field	What to record, and how you got it
Measured tonal scale	Steps distinguishable on a 21-step wedge printed to full maximum density, and the density range that implies, by Reilly’s method. Note that this is your paper’s scale, not the process’s
Maximum density	Reflection density, dry, on a patch printed past maximum. Say which instrument and whether it was checked
Image colour, before and after toning	Described in words against the untoned control, in daylight, dry — and, if you have a way to measure it, the reading and the method
Surface	In raking light, at a stated angle, described the way the Getty Atlas describes one: matte or semi-glossy, sunken-in or not, fibre visible or not
Fibre visibility	Under whatever magnification you have, with the magnification stated. Remember the Atlas’s warning not to over-interpret
Translucency and watermark	On a light table. Does your paper carry one, and can you read it through the print?
How it was made	Paper, salting solution, silver strength, exposure, toner and endpoint, fixer and time, wash regime — the whole record, because a print without its record is evidence about nothing

Why a print you made teaches identification better than a photograph of one. Three reasons, and the sources give all three. Reilly says it directly: for those so inclined, an excellent way to develop skills in print identification is actually to make albumen and salted paper prints, and a little direct experience makes the material much more familiar when it is encountered in historical form. His most emphatic instruction on the whole subject is not to rely on reproductions or descriptions of anything. And the third reason is the one this page has been circling: the properties that identify a salted paper — where the silver sits, how the surface reads in raking light, how the colour moves — are all continuous variables, and you cannot learn where a boundary is from one side of it.

Recap

One variable orders the whole family: how far the silver chloride is allowed to sink into the fibres. More binder means higher density, more gloss, finer detail — and a shorter tonal scale, so the negative that suits a plain salt print will not suit an albumen one.

Plain, gelatin, starch, whey, resin, matte albumen, diluted albumen, glossy albumen is a continuum, not a set of processes. Reilly’s dilution figures make it explicit: 1+6 albumen is almost indistinguishable from a matte salted paper.

Arrowroot separates the two jobs a binder does. Starch is inert, so it does the physics and the citric acid does the chemistry; without the acid the print is grey and flat.

Contrast was controlled by the negative, with the chloride, the citrate, the binder and the light as secondary levers — and by chromates, which this course excludes.

Identification is a narrowing, not a verdict. Paper fibres, silver and cellulose are the salted paper’s key signatures; the absence of barium separates it from every emulsion paper; the absence of albumen protein separates it from the albumen family, with the caveat that a gelatin-sized sheet gives a weak protein signal of its own. More than 75 per cent of questions are settled by looking, and nearly a quarter are not.

And the date chart cuts one way. 1840 to 1850 is nearly unambiguous, 1860 to 1885 is reasonably certain, and the 1850s are the worst case in the whole century.

Check your understanding

Question 1. Name three physical features that distinguish a salted paper print from an albumen print, and say which is most reliable.

• Colour, size and mount; colour is most reliable
• Surface (matte and sunken-in against smooth and glossy), where the image sits (in the fibres against in a layer above them), and highlight staining (about 85 per cent of albumen prints show it); of the three, the surface texture and the highlight yellowing are the two Reilly calls the most reliable indicators of albumen
• Translucency, watermark and paper weight; the watermark is most reliable
• Sharpness, tonal scale and image colour; sharpness is most reliable

Show the answer and why

Answer: Surface (matte and sunken-in against smooth and glossy), where the image sits (in the fibres against in a layer above them), and highlight staining (about 85 per cent of albumen prints show it); of the three, the surface texture and the highlight yellowing are the two Reilly calls the most reliable indicators of albumen

Reilly names highlight yellowing and albumen's characteristic surface texture - sometimes crackled or crazed - as the two most readily apparent and reliable indicators that a print is an albumen print, and puts the figure at about 85 per cent of extant albumen prints made after 1860 showing moderate to severe yellowing. He is equally clear that surface characteristics by themselves are little help without corroborating indicators, and that image colour requires experience and is confounded by fading, by photomechanical mimicry and by hand colouring. The hard case for all of these is a diluted-albumen print, which the Getty Atlas says is difficult to distinguish from a salt print on a highly sized substrate.

Question 2. Why does an arrowroot salting solution contain citric acid when a plain gelatin one does not?

• To stop the starch paste going mouldy
• Because starch is not an "active" organic substance and has no effect on the reduction of silver chloride, so without the acid the print would be grey and flat - while gelatin is active and does that job itself
• To lower the pH so the starch gelatinises properly
• To improve the keeping qualities of the sensitised sheet, which is its only function

Show the answer and why

Answer: Because starch is not an "active" organic substance and has no effect on the reduction of silver chloride, so without the acid the print would be grey and flat - while gelatin is active and does that job itself

Reilly divides the organic substances into two classes: the active ones - albumen, gelatin and the organic acids citric, tartaric and oxalic - which facilitate more complete reduction of silver chloride and themselves form light-sensitive compounds with silver nitrate, and the inactive ones, of which starch is the most useful, which only keep the sensitive material near the surface. He says explicitly that if the citric acid were not present in an arrowroot paper the prints would be grey and flat, the hallmarks of a pure chloride image. Improved keeping is a real secondary effect of citric acid but it is not why the formula has it.

Question 3. You are shown a nineteenth-century print with a slight sheen and yellowed highlights. What would you look at next, and what would each observation rule in or out?

• Whether paper fibres are visible in the image under magnification: if they are, it is not an emulsion paper on baryta
• The surface texture in raking light, for albumen's characteristic crackled or crazed appearance
• The image colour and whether it is purplish, which would be consistent with a gold-toned albumen or salted paper print and against a green cast that these papers never show in original condition
• The date from internal evidence and the mount, which narrows the field but cannot settle it in the 1850s

Show the answer and why

Answer: Whether paper fibres are visible in the image under magnification: if they are, it is not an emulsion paper on baryta, The surface texture in raking light, for albumen's characteristic crackled or crazed appearance, The image colour and whether it is purplish, which would be consistent with a gold-toned albumen or salted paper print and against a green cast that these papers never show in original condition, The date from internal evidence and the mount, which narrows the field but cannot settle it in the 1850s

All four, in roughly that order, and none of them alone is decisive - which is the point of the exercise. A slight sheen with yellowed highlights is the classic albumen presentation, and about 85 per cent of albumen prints show that staining, but a lightly albumenised or heavily sized salted paper can present the same way, which the Getty Atlas names as the specific hard case. Visible paper fibres rule out gelatin and collodion emulsion papers, which sit on baryta; the crazed texture is a positive albumen indicator; and the colour rules things out rather than in. The date narrows the field except in the 1850s, which Reilly identifies as the worst period in the century for this question.

Question 4. Which single analytical result most cleanly separates a salted paper print from a gelatin or collodion printing-out paper?

• The presence of silver, detected by XRF
• The presence of barium, which indicates a baryta layer and therefore an emulsion paper; a salted paper has none
• The presence of gold, which indicates toning
• The presence of cellulose, detected by FTIR

Show the answer and why

Answer: The presence of barium, which indicates a baryta layer and therefore an emulsion paper; a salted paper has none

The Getty Atlas's interpretation table marks barium as present for collodion and gelatin papers and absent for salted paper and albumen, and that is the cleanest single separation in it, because a baryta layer is a structural feature rather than a processing choice. Silver is present in all four and settles nothing on its own; gold says only that the print was toned; and cellulose is present wherever there is paper. The table marks paper fibres, silver and cellulose as the key signatures of a salted paper, which taken together say the image is in a plain sheet and made of silver.

Question 5. What does a process identification license you to conclude about a print's date?

• A precise year, from Reilly's chart
• A great deal for 1840 to 1850 and for 1860 to 1885, and very little for the 1850s or after 1885 - and the inference runs more reliably from date to process than the reverse only where the chart is unambiguous
• Nothing: process and date are independent
• The decade, always, because each process had a distinct period of use

Show the answer and why

Answer: A great deal for 1840 to 1850 and for 1860 to 1885, and very little for the 1850s or after 1885 - and the inference runs more reliably from date to process than the reverse only where the chart is unambiguous

Reilly's reading of his own chart is careful. Except for rare prints made by development, prints of 1840 to 1850 are plain salted paper prints; 1860 to 1885 is a period of reasonable certainty in which a silver print is very likely albumen and one that is not is unusual. But 1850 to 1860 is a transition in which albumen coexisted with several kinds of matte salted paper that cannot be differentiated at a glance, and the mid-1880s began a thirty-year period of great diversity in which date establishes very little. He also assumes, reasonably, that negative and print are close in date, which is what lets the chart be used at all.

Question 6. Predict what happens if the same negative is printed on a plain salted paper and on a glossy albumen paper made from the same salting chemistry.

• The two prints will be very similar, since the silver chemistry is identical
• The albumen print will have a higher maximum density, more gloss and finer detail, and a shorter tonal scale - so a negative matched to the plain salted paper will look flat and empty in the highlights on albumen
• The albumen print will have a longer tonal scale because the binder holds more silver
• The plain salted print will be sharper because there is no binder to scatter light

Show the answer and why

Answer: The albumen print will have a higher maximum density, more gloss and finer detail, and a shorter tonal scale - so a negative matched to the plain salted paper will look flat and empty in the highlights on albumen

Every property follows from where the silver sits. Reilly: a transparent binder minimises diffuse reflection and scattering by the paper fibres, which makes the whites whiter and the shadows denser, so a given amount of reduced silver produces a deep shadow on a glossy paper and a much paler one on a matte print. That raises maximum density, gloss and resolution and shortens the scale - Hubl measured glossy albumen as equal to platinum paper in scale length while salted papers exceeded platinum by a considerable margin. Which is why the negative is matched to the paper in this cluster and never the other way round.

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