copying machine

A copier is a device that produces duplicates of text or graphics using light, heat, chemicals, or electrostatic charges. The most common method today is xerography, invented by Chester F. Carlson in 1937 and commercially available since 1950.12

Xerography utilizes photoconductivity, where certain materials conduct electricity better when exposed to light. In this process, an aluminum drum coated with selenium is used. Light from the original document creates an image on the drum, attracting charged ink particles (toner). These particles are then transferred to a sheet of paper and fused with heat. Modern copiers can also produce color copies, print on both sides, sort documents, and enlarge or reduce images.12

Another method, thermography, uses infrared light to transfer impressions to sensitized paper. The development of efficient copiers has greatly benefited businesses but also raised copyright concerns. Copiers are distinct from duplicating machines, which create copies from a prepared master.13