A lithograph is created using a printing technique based on the principle that oil and water do not mix. First an image is created or transferred photographically or digitally onto a thin printing plate made of metal or plastic. Oil-based ink is applied to the printing plate and only adheres to the image areas of the surface. Water is applied to the surface and is repelled by the areas where oil-based images have been drawn.

The application of each color is printed separately through careful alignment or registration. This process is typically done by computer analysis, and is most frequently used in the production of posters and open, or limited-edition prints. Lithography uses tiny dots of four colors--cyan, magenta, yellow and black--to fool the eye into seeing various hues and shades. Colors are "created" by printing different size dots of these four colors.

Certificates of Authenticity

Limited edition lithographic prints often include an artist's signature, typically written in pencil, though it can also be done in ink. Artists usually number their prints. A notation that says 7/50 indicates that the lithograph is the seventh in an edition of 50. The annotations "AP" indicate artist proof. The numbering of prints is a key issue amongst artists, galleries and collectors. Limited edition litho prints are usually produced in editions of 500-1000 or more, all at once, because the expense is in the setup of the printing process.