Arrowroot and albumenised salted paper

Between a bare salted paper print, where the silver is in the fibres, and a glossy albumen print, where it sits in a protein film, there is a whole middle ground the nineteenth-century trade filled with thin binders. This entry covers the two the register names together: arrowroot, a starch cream, and lightly albumenised salted paper, egg white used thinly rather than as a coating in its own right.

The chemistry

The silver chemistry is the salt print’s, unchanged: a chloride goes into the sheet, silver nitrate meets it, silver chloride forms, and light darkens it while an excess of silver takes the liberated chlorine out of circulation. What the binder changes is where the silver sits and what else is in the layer with it.

Reilly’s organising idea is the useful one, and it is the reason arrowroot has a formula of its own. He classes the organic substances that go into these papers into those that are chemically active and those that are not. Citric acid is active: it facilitates the more complete reduction of silver chloride and itself forms light-sensitive compounds with silver nitrate — silver citrate among them. Starch is not active.

⚗So arrowroot paper carries citric acid instead

Reilly’s arrowroot preparation is one of the most explicit published in this family, and the course records it as history rather than as an instruction: 35 g of sodium chloride and 3 g of citric acid boiled with the arrowroot cream into a litre of salting solution, the sheet then sensitised by floating on 12 per cent w/v silver nitrate containing 4 to 5 per cent w/v citric acid.

The reason for the acid is stated as an outcome rather than a mechanism. Without it, Reilly writes, the prints would be grey and flat; with it they take on a warm purple.

The acid does a second job in the silver bath. Citric acid keeps sensitised paper usable for several weeks, and Reilly records 5 per cent w/v — 50 g in the litre, by his own replenishment arithmetic — as the concentration giving the maximum preservative effect, with as little as 1 per cent extending the life noticeably. A print-out paper that keeps is a different working proposition from one that must be coated the same day.

The albumenised salted paper is the other half of the row, and the useful way to state it is that there is no boundary between a salted paper and an albumen print — there is a dilution. A thin albumen layer raises the apparent sharpness and cleans the highlights without producing the gloss the 1850s objected to; the protein is chemically active in Reilly’s sense, so no citric acid has to be added to do the job the starch cannot.

⚗How thin is thin: Reilly's dilutions, and where this row sits on them

Reilly puts numbers on the continuity, and they are the reason this row is a position on a scale rather than a recipe.

Albumen, diluted with water	What you get
Pure	The familiar glossy albumen paper
1 + 1	Half-matte
1 + 6	Almost indistinguishable from other matte salted papers
2 per cent solution	Still a significant improvement in depth and contrast over no binder at all

Albumenised salted paper is the low end of that range: the albumen goes into the salting solution rather than onto the sheet as a coat of its own, so it arrives in the same operation as the chloride. Hardwich’s 1864 formula — three volumes of egg white to one of water, salted with ammonium chloride — is in the formulary, and the variable that decides the surface in it is the water.

That last row of the table is the one worth carrying away: even a very small amount of an active binder buys something measurable, which is why so many photographers diluted deliberately rather than failing to make a glossy paper. Some preferred it because it toned more easily; many simply wanted a matte print. Part XXII’s variants lesson sets the whole family out as a ladder from plain paper to pure albumen and shows that four properties rise together as you descend it — the silver sits nearer the surface, maximum density rises, gloss rises, sharpness rises — while the tonal scale falls, which is why a matte sheet wants a longer-scale negative than a glossy one.

Three handling consequences follow from starch being inert and permeable, and they are what separate an arrowroot sheet from an albumen one at the bench. Silver does not coagulate starch as it coagulates albumen, so the layer stays permeable to water and a long float lets fine silver chloride sink into the fibres, costing exactly the brilliance the binder was added to buy: Reilly floats a light coating for half a minute and a heavy one for no more than a minute and a half, against the two and a half to three minutes a plain gelatin-salted sheet takes. The silver bath carries citric acid at 4 to 5 per cent, which does double duty as the preservative. And a thick paste is not floated at all — 2 per cent arrowroot or less is fluid enough for a tray, while a 3 to 4 per cent paste is brushed onto a pinned sheet, left to sink in, and evened out with a dry brush until the surface is uniformly matte.

Historical workflow

Salt, coat, dry, sensitise, print out, rinse, tone, fix, wash — the salt print’s sequence with a coating step inserted. What distinguishes the two variants is what goes into that step and what has to be added to compensate for it.

Where they sit in the trade’s chronology is with the other matte materials. Reilly groups the arrowroot and matte albumen papers with the matte collodion and matte gelatin printing-out papers popular between 1895 and 1925, and records that platinum toning was preferred for all of them, because its effects harmonise especially well with a matte surface. That grouping is the most useful single fact about this row: these papers were sold to the same buyers, for the same reason, and were meant to look alike.

The image

Matte or semi-matte, with the paper still showing. That is what the binder is being kept thin to achieve, and it is why these papers are grouped with matte albumen rather than with glossy albumen.

Colour. Reilly’s own comparison is the clearest statement the course holds: without citric acid an arrowroot print is grey and flat, and with it warm purple. On plain salted paper the same author reports that adding a neutral citrate makes the prints more reddish and slightly more brilliant, and the sodium citrate page records that why absorbing the halogen should shift the colour towards red is not explained by any source the course has read, and does not supply a reason.

The paper is still the biggest variable. Reilly’s caveat belongs with every observation in this family: the porosity of the paper stock remains the largest single factor in the result. A binder reduces that dependence; it does not remove it.

Permanence

The salt print’s, with two refinements.

The binder holds silver, and held silver is what yellows. The albumen print’s characteristic failure is retained silver in every area of the sheet converted to silver sulfide, and the stain is more stable than the image. A lightly albumenised sheet carries less protein than a fully coated one and should on that reasoning retain less silver — but the course has read no measurement of it and does not claim the improvement.

Citric acid is a preservative for the paper, not for the print. Its documented effect is on the shelf life of the sensitised sheet before exposure. Nothing read here says it changes what happens to the finished print in a drawer.

Everything the salt print’s own entry says about fixing and washing applies unchanged: dilute thiosulfate, thorough washing, and the evidence that the difference between a print that survives and one that fades is procedural.

Hazards

Silver nitrate at 12 per cent w/v for floating, named explicitly in the rubric under Level B, and the sensitiser is a standing bath rather than a brushed-on film, which means a larger volume in the room.

Citric acid is a Level A material and appears at up to 5 per cent in the silver bath and 3 g per litre in the salting solution.

Boiling is part of the arrowroot preparation — the cream is boiled into the salting solution — so there is a hot-liquid step in a process that otherwise has none.

Platinum toning, if the period look is wanted, is Level C on the platinum toner’s own page and is published there as chemistry rather than offered for use.

Waste is silver-bearing throughout and belongs to recovery.

Where the course teaches it

Part XXII, in The Variants of the Salt Print and How a Conservator Identifies One, which is where this row belongs and which is now written. Part XXIII owns albumen proper.

The lesson does three things this entry depends on. It sets the binder ladder out in full, from plain salted paper through gelatin, starch, whey, resin, matte albumen and diluted albumen to the pure protein coat, and shows that the family is genuinely continuous rather than a set of discrete recipes. It treats arrowroot in detail, on the grounds that it is the one a reader can actually make, with the boiled-cream method, the skin of burst grain hulls that is removed on cooling, and the float times above. And it treats the albumenised salt print as the hinge to Part XXIII, which is the same argument this row exists to make, arrived at from the other end.

Two further pages carry the practice. Lab: Salting and Sensitising a Sheet of Paper is where a salting solution is made and a sheet floated, and Reilly’s arrowroot salting solution holds the weights.

!What the course still cannot give you, and it is the profession's gap rather than this atlas's

The AIC Photographic Materials Group’s wiki carries a page for the albumenised salt print, and as read on 7 September 2026 it has no content at all: Historical Facts, Identification Characteristics, Conservation, Housing and Storage, Exhibition, Emergency Recovery and References are all empty headings, with no contributors listed and no date initiated. It is cited here for that absence.

It is worth naming rather than passing over, because it is the conservation profession’s own record that this variant has a place in the taxonomy and no published identification description. So this entry cannot give the AIC’s signatures for an albumenised salt print as it can for a plain salted paper print, because nobody has written them. What stands in their place is Reilly’s account of the material and the Getty Atlas’s observation that diluting the albumen bath gives results that are semi-glossy to almost matte and hard to tell from a salt print on a heavily sized sheet — which states that the distinction is difficult, not how to draw it.

The register counts arrowroot and albumenised salted paper as one row, because the design names the two variants together, and notes that splitting them would raise the total by one. This entry follows the register and keeps them together, which is the right call for a different reason as well: they are two answers to the same question — how to get the benefit of a binder without the gloss — and the interesting thing about them is the comparison. A starch needs an added active substance to make a good print; a protein does not. That is Reilly’s distinction between active and inactive organic substances, and it is visible on the finished sheet as the difference between grey and flat, and warm purple.