Lithography

Draw a bold mark on a sheet of glass or glazed tile with a wax crayon, then flood the whole surface with water and tip it off.

Expect a clean film of water everywhere except on the crayon, which stays dry and repels the water into beads at its edge.

Now dab an oily ink across the whole tile with a roller or cloth.

Expect the ink to take on the crayon and to be pushed off the wet areas.

That is the entire principle, on a tile, in five minutes. Everything after this is about making it reliable and repeatable.

Grind a fine-grained limestone slab flat with abrasive and a levigator or a second stone, working through progressively finer grits, then rinse and dry it completely.

Test it: breathe on the surface, or drop water on it, and watch how readily it takes water in.

The stone must be porous and scrupulously clean. Any grease — a fingerprint — will print, and it will print permanently.

Note that the grain you leave decides the drawing's texture: a coarse grain holds crayon in a rough tooth, a fine grain suits washes and delicate line.

Draw your image with a greasy lithographic crayon. Then apply the etch — a weak acid solution in gum arabic — over the whole stone, and leave it before washing off.

The name is misleading and worth correcting: it does not bite anything away. It does two things chemically. The gum makes the bare stone strongly water-attracting and grease-rejecting, and the acid helps fix the greasy image into the stone's surface.

Test the result by damping the stone and rolling up. Expect a crisper separation than in step 1, and one that survives repeated inking.

Print three impressions: one with the stone too wet, one too dry, one correct.

Expect the too-wet stone to print pale and patchy as water invades the image, and the too-dry stone to scum — ink creeping across the blank areas until the whole thing greys over.

Record how narrow the good band is.

Lithography is a continuous balancing act between water and ink, held by the operator on every single impression. That is its great weakness by hand — and step 6 explains how the offset press automated exactly this judgement.

On a fresh area, apply a diluted greasy wash with a brush rather than a crayon line, and process it as before.

Expect a genuine continuous-looking tone, breaking into a grain where it thins.

Then attempt the same soft gradient with a burin on metal, or picture doing so.

Engraving builds tone from thousands of deliberate marks. Lithography lets a brushstroke be a brushstroke. That is why artists took to it immediately — it is the first printing process that records a gesture instead of translating it.

Invented by a playwright who could not afford a printer. Alois Senefelder was trying to publish his own plays cheaply and was experimenting with etching stone as a substitute for copper. The usual account has him writing a laundry list on a limestone slab with a greasy crayon and realising the stone had recorded it. Whether or not the laundry list is true, the discovery's shape is: he was looking for a cheaper intaglio and found a completely different principle.

It is the first genuinely new printing principle in three and a half centuries. Relief and intaglio are both about depth; planographic printing is about surface chemistry. Once the image no longer had to be a shape, it could be made by anything that changed the wettability of a surface — which is exactly how a photographic image is put onto a plate today, and why nearly all commercial printing is now lithographic.

It gave artists a press they could use themselves. Goya, Daumier, Toulouse-Lautrec and Munch worked directly on stone. Daumier's political cartoons could be drawn and printed fast enough to be topical, which made lithography the engine of the illustrated satirical press — and, because posters could now be large, colourful and quick, of the poster as an art form.

Colour, by repetition. Chromolithography prints from a separate stone per colour, each registered to the last, sometimes a dozen or more. It put full-colour images into ordinary homes for the first time, and it is the direct ancestor of the four-colour separation used in every printer today.

Honest limits. Stone is heavy, fragile and finite in size, and preparing it is laborious — metal plates replaced it commercially for exactly those reasons. The water-ink balance of step 4 needs constant attention. The stone must be kept immaculately free of grease, which in practice means a fingerprint can ruin an afternoon. And the chemistry is not permanent: an image left inked and undamped will scum, and a stone can be ground down and reused, which is why so few original stones survive.