Lithography

Lithography is one of the traditional printing methods in the early years of the nineteenth century. This method makes use of the principle of repulsion between be printed on a metal plate using a greasy substance. Then the plate is wetted. The grease on the plate repels the water and consequently only the non-printing areas become wet. When greasy printing ink is applied to the plate, it sticks to the greasy image but not to the non-printing areas. From this plate, the image can be printed on paper. In photolithography the printing stone is coated with a light-sensitive substance and then exposed to light through a paper negative of the matter to be printed. By washing with turpentine or with acid, an image, either flat or etched, can be produced on the plate for normal printing.