Literally meaning "stone drawing," this type of print is made by drawing or painting onto the surface of a limestone using a greasy crayon or liquid wash and is best known for its flat painterly surface. Because lithography is planographic, the resultant design lies on the surface of the paper, rather than pressed in or raised up from the page, as in other techniques. Colors appear smooth and uniform in tone. It is possible to use multiple colors in a lithograph, each color, as in the other techniques described here, requiring its own stone and several subsequent runs through the press. This process can also be sued with metal plates, most commonly aluminum which allows the artist to easily incorporate photographic techniques in the composition. In the 19th century it was popular to use zinc, thus called a zincograph.