What is lithography?
Lithography means "stone writing" (Greek: lithos = stone, graphein = write). It was invented around 1796 by Alois Senefelder. It is a planographic method: the printing surface is flat. In woodblock printing the picture is raised. In etching the picture is in grooves. In lithography there is no height at all. The picture is only a chemical difference on a flat surface: some parts like grease, other parts like water.
The plate: stone or aluminium
Artists use a smooth, flat slab of limestone. The stone is ground very smooth with sand. Today a thin aluminium plate is also used, because it is light and easy to store. The surface must be flat and clean, because even a fingerprint is greasy and will print.
Drawing, fixing and wetting
- Drawing: use a greasy crayon or liquid greasy ink called tusche. Soft crayon makes grey tones; hard crayon makes fine lines.
- Fixing (etching the stone): a coat of gum arabic with a drop of weak acid is spread on the stone. This does not cut grooves. It fixes the grease in the drawing and makes the blank parts love water.
- Washing out: the artist washes away the crayon with a solvent. A faint ghost of grease stays in the stone.
- Wetting: a damp sponge wets the stone. Water spreads on the blank parts but not on the greasy drawing.
Inking and the press
While the stone is still damp, the artist rolls oily ink with a roller. The ink sticks to the drawing and slides off the wet blank stone. For each print the artist sponges the stone again and re-inks it. Then a sheet of paper is laid on the stone, covered, and pulled through a scraper press. A wooden bar rubs hard across the back and pushes the paper on the stone. The print is mirrored.
Common problems: too little water makes ink stick to the whole stone (scumming, a dirty background). Too much water washes the ink off the drawing and the print turns pale.
Colour lithography and today
For colour, the artist makes one stone or plate for each colour and prints them one by one, with registration marks to line them up. Posters, music covers and famous artworks were printed this way. Modern offset printing of books, newspapers and packaging follows the same oil-and-water idea, using aluminium plates and rubber rollers.
Key formulas and definitions
- Lithography = planographic = printing from a flat surface
- Grease holds ink; water on blank parts repels ink
- Gum arabic + weak acid = fixes the drawing
- Too little water = scumming; too much water = pale print
- Print = mirror image
- Colour = one stone or plate for each colour
Worked examples
1. Why does lithography need no cutting at all?
The picture is made by grease on a flat stone. Grease holds ink and wet blank stone repels it, so no raised parts or grooves are needed.
2. A fingerprint on the stone shows up on the print. Why?
The fingerprint left grease. Grease holds ink, so it printed.
3. An artist wants a print with 3 colours. How many stones or plates?
3, one for each colour.
Common mistakes
- Thinking the acid cuts deep lines like in etching. In lithography the acid only fixes the image.
- Touching the stone with bare fingers. The grease prints.
- Letting the stone dry out while inking. This causes scumming.
- Using too much water, which washes away the drawing.