Xerography

Dry photocopying technique Schematic drawing of the xerographic photocopying process Xerography (from the Greek roots ξηρός xeros, meaning "dry" and -‍γραφία -‍graphia, meaning "writing") is a technique of printing and photocopying. Originally called electrophotography, it was renamed to emphasize that it uses no liquid chemicals, unlike reproduction techniques then in use such as cyanotype. History Xerography was invented by American physicist Chester Carlson, based significantly on contributions by Hungarian physicist Pál Selényi. Carlson applied for and was awarded U.S. patent 2,297,691 on October 6, 1942. Carlson's innovation combined electrostatic printing with photography, unlike the dry electrostatic printing process invented by Georg Christoph Lichtenberg in 1778. Carlson's original process was cumbersome, requiring several manual processing steps with flat plates. In 1946, Carlson signed an agreement with Haloid Photographic Company to develop it as a commercial product. Before that year, Carlson had proposed his idea to more than a dozen companies, but none was interested. Haloid's president, Joseph C. Wilson, saw the promise of Carlson's invention, and s