Lithography

Lithography (from Ancient Greek: λίθος, lithos, meaning ‘stone’, and γράφειν, graphein, meaning ‘write’) is a method of printing originally based on the immiscibility of oil and water. The printer uses a stone or metal plate on which the image to be printed is ink-receptive (hydrophilic) and the non-printing areas are ink repellent (hydrophobic). A dampened paper sheet is placed on top and run through a printing press together with the plate. The pressure exerted by the press forces some of the dampening solution into the pores of the paper where it swells causing the paper to bulge slightly into contact with the image areas of the plate; these areas accept ink from rollers while non-image areas repel it. When dry, this type of print is known as a lithograph.