This is a partial list of duplicating processes used in business and government from the Industrial Revolution forward. Some are mechanical and some are chemical. There is naturally some overlap with printing processes and photographic processes, but the challenge of precisely duplicating business letters, forms, contracts, and other paperwork prompted some unique solutions as well. There were many short-lived inventions along the way.
Duplicating processes
Within each type, the methods are arranged in very rough chronological order.
The hectograph or gelatin duplicator is a printing process which involves transferring from an original sheet prepared with special inks to a gelatin pad.
The gelatin process is useful for print runs of somewhere between twenty and one hundred copies, depending upon the skill of the user and the quality of the original.
Before the popularization of spirit duplicators and the mimeograph, there were mechanized hectography machines which used a drum, rather than a simple flat pan of gelatin.
The prevalence of its use is one of the factors that prevented the development of the paperless office heralded early in the digital revolution.
In the early 1950s, RCA (Radio Corporation of America) introduced a variation on the process called Electrofax where images are formed directly on specially coated paper and rendered with a toner dispersed in a liquid.
Advances in technology developed the process of electrostatic copying technology where a high contrast electrostatic image copy is created on a drum and then a fusible plastic powder (called toner) is transferred to regular paper, heated and then fused into the paper similar to the technology used in laser printers.
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