Unlike manual dishwashing, which relies largely on mechanical action to remove soiling, mechanical dishwashers use the circulation of quite hot (55-65 degrees Celsius) water and very strong detergents (most far too basic to be exposed to skin) to achieve its cleaning effect. The dishwasher therefore is mainly a device for spraying water on the dishes - first detergent-added water for cleaning purposes, then pure water (though sometimes with a rinsing aid added) to remove the detergent residue. Some dishwashers also contain a heating element to achieve fast drying of the dishes.
The first reports of a mechanical dishwashing device are of an 1850 patent by Joel Houghton of a hand-powered device.
Modern dishwashers are descended from the 1886 invention of Josephine Cochrane, also hand-powered, which she unveiled at the World's Fair. Josephine was quite wealthy and was the granddaughter of John Fitch, the inventor of the steam boat. She never washed dishes herself and only invented the dishwasher as her servants were chipping her fine china.
Models installed with permanent plumbing arrived in 1920s, and electric drying elements were added in 1940.
Adoption was greatest at first in commercial environments, but by the 1970s dishwashers had become commonplace in domestic situations.