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Definition: lithography


(1) For the lithographic process in chip making, see photolithography and chip manufacturing.

(2) A printing technology that dates back to 1798 when Alois Senenfelder developed a method of imaging limestone from which a print was produced. Based on the principle that oil and water do not mix, an aluminum or plastic plate is coated with a photopolymer film that is exposed to light through a photographic mask. The exposed areas are chemically "hardened," and the unexposed areas are dissolved when the plate is put through a chemical process, which is the next stage. When printing a page, the plate is dampened, and the water adheres only to the unexposed, non-image areas, which repell the greasy ink that is applied to the plate immediately thereafter.

The most common lithographic printing uses the offset method, in which the ink is "offset" onto a rubber-coated cylinder that is pressed against the paper. See offset press.