Lithography is a type of printmaking based on the principle that oil and water don't mix. The artist draws on a special type of limestone that has been grained to a smooth flat surface. 

 

First the artist draws an image onto the stone, using greasy crayons and ink. The stone is then processed using gum arabic and different amounts of nitric acid. The composition of this special limestone allows a chemical process to take place resulting in two different surfaces forming on the stone. One surface is grease attractive- this

is were the drawing has been made and allows the image to be inked and printed. The other surface is grease repellent, this surface holds water and makes sure the non-image areas remain ink free.

 

During printing the artist sponges the stone, leaving a fine film of water on the non-images areas. While the stone is wet the artist rolls ink onto the stone, with the ink only transfering onto the image area. Paper is then put on top of the stone and put through a lithography press.The pressure transfers the ink onto the paper and you have a print!