Unlike relief printing, planography is based on a chemical rather than mechanical process. The surface is inked with a roller and printing is done on a mechanical press.

Lithography

Lithography, which may appear somewhat mysterious at first, is based on the natural repulsion of oil and water. The technique may be summed up in five steps:
1. Using a crayon or a brush dipped in oily ink, the artist     draws a design on a limestone slab.
2. The stone is then bathed in a solution of nitric acid and     gum arabic. The solution allows the oil to thoroughly     penetrate the stone and makes the unoiled portion even     more sensitive to water and less sensitive to oil.
3. Before printing, water is generously applied to the stone.     The water saturates the unoiled portions.
4. The stone is inked with a roller. The ink will adhere only     to the oily areas; the water-soaked portions will repel     the ink.
5. Printing is done on a lithographic press (equipped with a     scraper).