Lithography

Lithography (from Ancient Greek λίθος (líthos) 'stone' and γράφω (gráphō) 'to write') is a planographic method of printing originally based on the immiscibility of oil and water. The printing is from a stone (lithographic limestone) or a metal plate with a smooth surface. It was invented in 1796 by the German author and actor Alois Senefelder and was initially used mostly for musical scores and maps. Lithography can be used to print text or images onto paper or other suitable material. A lithograph is something printed by lithography, but this term is only used for fine art prints and some other, mostly older, types of printed matter, not for those made by modern commercial lithography. Traditionally, the image to be printed was drawn with a greasy substance, such as oil, fat, or wax onto the surface of a smooth and flat limestone plate. The stone was then treated with a mixture of weak acid and gum arabic ("etch") that made the parts of the stone's surface that were not protected by the grease more hydrophilic (water attracting). For printing, the stone was first moistened. The water adhered only to the etched, hydrophilic areas, making them even more oil-repellant. An oil-based ink was then applied, and would stick only to the original drawing. The ink would finally be transferred to a blank sheet of paper, producing a printed page. This traditional technique is still used for fine art printmaking. In modern commercial lithography, the image is transferred or created as a patterned polymer coating applied to a flexible plastic or metal plate. The printing plates, made of stone or metal, can be created by a photographic process, a method that may be referred to as "photolithography" (although the term usually refers to a vaguely similar microelectronics manufacturing process). Offset printing or...