How does lithography create an image on a flat surface?

Lithography is a planographic printing process that relies on the fundamental principle that water and grease are immiscible.12

To create an image on a flat surface, such as a porous limestone block or a metal plate, an artist draws or paints directly onto the surface using greasy materials like litho crayons or tusche (a greasy black ink). Once the drawing is complete, the surface is treated with an etch—a mixture of gum arabic and nitric acid—which desensitizes the non-image areas and fixes the grease into the stone's pores.12

During the printing process, the surface is dampened with water. Because the greasy image repels water while the blank, porous areas absorb it, the surface remains wet in non-image areas. When an ink-charged roller is passed over the stone, the oily ink adheres only to the greasy drawing and is repelled by the wet, blank areas. The final image is then transferred to paper using a lithographic press that applies sliding or scraping pressure.12