Photogenic drawing

Photogenic drawing is the first silver process on paper, and its chemistry is a deliberate inefficiency. Talbot’s own summary of the 1834 discovery is the whole of it — “a lesser quantity of salt produced a greater effect” — and understanding why that is true rather than absurd is what the rest of this entry is for. The Part I lesson establishes the history; readers regularly merge this process with the calotype that replaced it, which loses the single distinction the whole of Part IV depends on.

The chemistry

Salt goes into the paper first and silver nitrate is brushed on afterwards, so silver chloride precipitates inside the fibres where the two solutions meet. Orthodox stoichiometry wants about one third of the silver nitrate’s own weight in salt — Ware computes 34.4 per cent — and Ware records what happens if you supply it: the attempt fails dismally, the surface going lilac and then stopping.

Talbot supplied about a twentieth. Ware reads his Notebook P as implying roughly 1 per cent w/v salt against about 20 per cent w/v silver nitrate, which converts something like one part in seven of the silver and leaves the other six sitting unreacted around every crystal.

⚗Why the leftover is the mechanism and not the waste

Photolysis in a silver halide frees a halogen atom. If nothing takes that halogen up it attacks the fresh silver and the reaction reaches a standstill at a barely visible grey — which is the whole reason a plain silver chloride paper stalls. Excess silver ions in a damp sheet let water carry the chlorine away, so the darkening keeps going. Ware identifies the combination — the crystal plus the free silver around it — as the chemical secret of photogenic drawing paper, and it is the reason the stoichiometrically correct ratio fails completely.

The general principle has a name: a halogen acceptor. The later printing-out papers supply one deliberately, as sodium citrate in a salting solution or as the albumen itself, and sodium citrate’s page works through the consequences.

This is printing out in its purest form: light does the entire job, you watch the picture arrive, and you stop when it looks right. James Reilly’s standard account puts the cost of that at up to 100,000 times more light energy than developing out, and names the consequence — you cannot enlarge onto such a paper, so every print is a contact print.

Historical workflow

By the spring of 1834 Talbot was laying leaves, lace and other flat objects on the dried sheet under a sheet of glass pressed down tight, putting it in the sun until the open ground went dark, and carrying it into the shade. Ware notes that he first called these images sciagraphs, shadow drawings, before settling on photogenic drawings.

The camera was the hard case, and Talbot says why in one sentence: an hour or two in the camera obscura gave a marked outline of roof and chimneys against the sky and left the shaded parts blank or nearly so. In the brilliant summer of 1835 he attacked it with repeated alternate washes of salt and silver, used the paper moist, and cut a bright-day exposure to ten minutes — the pictures “very pretty” but “quite miniatures”. Ware lists six conditions that had to be met at once: excess silver, a small format, a wide aperture, patience, a bright subject rich in blue and ultraviolet, and some way of stopping the image changing. Neglect any one and the attempt fails.

The negative-positive idea is here from the beginning, as a nuisance turned into a method. Ware quotes Talbot’s Notebook M of 28 February 1835: if the paper is transparent the first drawing may serve as an object to produce a second, in which the lights and shadows would be reversed.

The image

Colour, and it depends on the fixer. A chloride-fixed sheet has lilac highlights and deep maroon shadows; a thiosulfate-fixed one has clear white highlights and a reddish-brown image. Talbot preferred the first, and Ware records that he went on using halide fixation for years after a better answer existed partly for that reason and partly because hypo was costly and scarce at first.

Surface. There is no binder and no baryta. The light-sensitive material is inside the paper, which is why the fibres show in the finished image, why the sheet stays translucent enough to print through, and why the Getty atlas describes the family’s look as matte and sunken in.

Detail. Soft, and the atlas gives the reason: a print made from a paper negative is less sharp because the individual fibres of the negative scatter the light passing through them, and waxing reduces the effect without abolishing it.

Permanence

Talbot’s two fixers were the same insight as his sensitiser run backwards — if a deficiency of salt makes paper sensitive, an excess should make it dull — and both leave the silver salt in the sheet. Ware records that Talbot and Herschel, who were precise about language, called the halide treatments fixing and Herschel’s thiosulfate something else entirely, washing out, and that the modern habit of calling the second “fixing” and the first “stabilisation” has blurred a distinction they intended.

The failure is published by the man who invented it. Of iodide fixation, in The Pencil of Nature: “after the lapse of some days the dark parts of the picture begin to fade, and gradually the whole picture becomes obliterated, and is reduced to the appearance of a uniform pale yellow sheet of paper.” His verdict is that the process “must be considered as not sufficiently certain to be retained in use.”

Read the direction of that failure, because it is diagnostic. In the presence of excess iodide the nanoparticle image silver is oxidised back to pale primrose-yellow silver iodide, so the picture fades towards the ground rather than the ground darkening towards the picture. A salt-fixed sheet fails the other way.

Hazards

Silver nitrate, handled wet and at strength — Ware’s reading puts Talbot’s sensitiser at about 20 per cent w/v against a saturated solution of around 150 per cent. Silver nitrate is named explicitly in the course’s rubric under Level B, and it stains skin, clothing and every surface it reaches. Potassium iodide and sodium chloride, as fixers, are the mild part of the page.

The waste stream is silver-bearing and belongs to silver recovery, not to a drain.

Where the course teaches it

As history in Part I, as chemistry in Part XXII — and as a procedure nowhere, on purpose. That last clause is now a decision rather than a gap, and it is worth stating in the present tense.

Part I reads the process as history and makes no sheet.

Part XXII, Salted Paper: The First Silver Print, owns the practice this process is the ancestor of, and it is written. Printing Out: Silver Chloride Made and Darkened in the Paper is the chemistry — photolysis without development, what the excess silver nitrate is for, and the arithmetic of a process that amplifies nothing — and it takes up Talbot’s own stabilising practice directly: his treatment for a photogenic drawing was a strong salt solution, which the lesson explains through the surface charge on the crystal rather than as a period habit. Lab: Salting and Sensitising a Sheet of Paper is where a reader makes the sensitised sheet, and the printing lab exposes one by inspection. Both name this process among the ones they bear on.

Why there is still no procedure under Talbot’s own name. Talbot’s photogenic drawing paper is published at status: historical-study and carries no steps, and the reason is documentary rather than practical. The figures in it are Ware’s readings of Talbot’s unpublished Notebook P and of Malone’s account of Reading practice, expressed as per cent w/v — one of them explicitly an assumption of Ware’s own. They are the best evidence there is and they are not Talbot’s numbers, so printing them as a recipe would publish a modern reconstruction under a nineteenth-century name. Talbot himself said the whole art lies in finding the proportion that answers best, which is a statement that no single number is the formula.

The distinction the course teaches remains the one this process exists to establish. Photogenic drawing spends the whole of the light; the calotype spends a little of it to make a trigger and lets chemistry do the rest. Ware puts the gain at about a hundredfold, and Part IV takes the latent image apart properly. Every silver process this course teaches after Part I is a developed one, which is precisely why the print-out ancestor has to be understood first.