Lithographic printing pres, c 1860.
© Science Museum / Science & Society Picture Library
Lithography, discovered in 1796 by Alois Senefelder (1771-1834), relies on the repulsion of oil and water to print from a flat surface, originally Bavarian limestone. A greasy crayon is used to sketch on the stone, which is then sponged with gum solution. The gum is repelled by the grease, making the undrawn areas ink-repellent. The stone is placed on the pres, inked, paper laid on it, and the wheel turned to draw it under a bar which preses down to make the print. This pres was used in Paris by the artist Albert de Belleroche.