Unlike manual dishwashing, which relies largely on physical scrubbing to remove soiling, the mechanical dishwasher cleans by spraying hot (55-65 degrees Celsius or 130-150 degrees Fahrenheit) water on the dishes. First detergent-added water is used for cleaning purposes, then clean water to remove the detergent residue. Some dishwashers have multiple wash and rinse periods within the complete cycle. In some dishwashers, a rinsing aid can be added to the rinse cycle. As there is no human contact during the process, strong detergents may be used which would be too alkaline for habitual exposure to the skin. Many dishwashers have a heating element to achieve fast drying and sanitation of the dishes. In some models, this element can also be used to heat cold water to the desired wash temperature.

Human dishwashers

The word dishwasher may also refer to a person who washes dishes in a commercial setting. These employees rinse dishes, load them into a stainless steel dishwasher, unload them, and stack them into their respective dish holders. Pots and pans are also washed by hand by scrubbing them in a soap and water mix, immersing them in a rinse of plain water, and then immersing them in a water/sanitizer solution for a period. Silverware is washed by placing loose silverware in a tray, washing them several times like this, then sorting them into circular holders, and washing them again in the dishwasher.

History

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 1893 Chicago World's Fair. Cochrane was quite wealthy and was the granddaughter of John Fitch, the inventor of the steamboat. 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 the 1920s. In 1937, William Howard Livens invented a small dishwasher suitable for home. It had all the features of a modern dishwasher, including a front door for loading, a wire rack to hold crockery and a rotating sprayer. 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 residences in the US.