Lithography is a printmaking process based on the opposition of oil and water. The artist draws on a flat, ground limestone or metal plate with a greasy medium such as a lithographic crayon or an oily liquid wash called tusche. The etching of the stone does not create an engraved surface, but helps keep the drawing intact, and the white areas white. When printing, the stone is sponged with water, and ink is rolled on to the greasy sections, while the water repels the ink elsewhere. The stone is then covered with a sheet of paper and run through a press to create the print. The stone must be inked again for each additional print. For a color print, a different drawing is done for each color.