The physicochemical process of the lithograph print is based on the antagonism between water and fats. The surface that has traditionally been used is limestone although currently it is used a flexible sheet of zinc or aluminum that must be treated to get a granular surface as the stones.
These plates are prepared by introducing them in acid and scraping with sand or pumice stone to acquire the porousity of the limestone. Following, the inverted image is drawn using oil and the surface is covered with an aqueous preparation of nitric acid and arabic gum to set the lithographic image and the virgin areas are cleaned. Next, the plate is soaked with water, that will penetrate only the clean areas and will be repelled by the grease in the lithographic image. The printing ink is applied with a roller on the wet plate so that only the grease design will accept the ink.
Before printing, the stone is dried and errors are corrected with a blade or a pumice stone, the plate re-washed and more ink is re-applied. Finally the plate is placed in the press and the image is transmitted to paper.