Lithography (from Greek λίθος - lithos, 'stone' + γράφειν - graphein, 'to write') is a method for printing using a stone (lithographic limestone) or a metal plate with a completely smooth surface. Invented in 1796 by German author and actor Alois Senefelder as a cheap method of publishing theatrical works, lithography can be used to print text or artwork onto paper or other suitable material.
Lithography originally used an image drawn (etched) into a coating of wax or an oily substance applied to a plate of lithographic stone as the medium to transfer ink to a blank paper sheet, and so produce a printed page. In modern lithography, the image is made of a polymer coating applied to a flexible aluminum plate. To print an image lithographically, the flat surface of the stone plate is roughened slightly—etched—and divided into hydrophilic regions that accept a film of water, and thereby repel the greasy ink; and hydrophobic regions that repel water and accept ink because the surface tension is greater on the greasy image area, which remains dry. The image can be printed directly from the plate (the orientation of the image is reversed), or it can be offset, by transferring the image onto a flexible sheet (rubber) for printing and publication.
As a printing technology, lithography is different from intaglio printing (gravure), wherein a plate is either engraved, etched, or stippled to score cavities to contain the printing ink; and woodblock printing, and letterpress printing, wherein ink is applied to the raised surfaces of letters or images. Most types of books of high-volume text are printed with offset lithography, the most common form of printing technology. The word lithography also denotes photolithography, a microfabrication technique used in the microelectronics industry to make integrated circuits and microelectromechanical systems.
Read more about Lithography: The Principle of Lithography, Microlithography and Nanolithography, Lithography As An Artistic Medium, Gallery