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. This pres was used by artist Albert de Belleroche. Shown open.