Xerox Copier, 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. The new pattern of the toner is then heat-sealed on to a piece of paper. This proces was first pioneered by an American lawyer Chester Carlson (1906-1968), but copiers were not made commercially until the 1950s.