Rank Xerox standard 1385 copying machine, c 1960.
© Science Museum / Science & Society Picture Library
This early Xerox Copier uses the attraction of opposite electric charges to reproduce words and images. Inside the copier, a metal plate coated with selenium facilitates this proces. A pattern of positive charges on the plate, representing the areas to be copied, attracts negatively charged particles - the toner - which is then heat-sealed on to a piece of paper. This proces was pioneered by Chester Carlson (1906-1968) in 1938, but the first commercial copiers were not produced until the 1950s.