Lithography
Lithography works on the principle that oil and water will not mix. The printing surface, which can be either a limestone block or a metal plate, is grained to prepare a fine surface. The artist then uses a greasy drawing material to make an image directly on this surface which is then treated chemically so that only the image will accept the printing ink. During printing the stone or plate is first sponged with water and then oily ink is rolled across the surface. The water, acting as a resist, prevents the ink from sticking to the bare areas of stone. Once inked the paper is laid on top of the inked stone and passed through the press under pressure.