A dishwasher is a mechanical device for cleaning dishes and eating utensils. Dishwashers can be found in restaurants and private homes. Josephine Cochrane made the first practical mechanical dishwasher in 1886.
Unlike manual dishwashing, which relies largely on physical scrubbing to remove soiling, the mechanical dishwasher cleans by spraying hot water at 55 to 75 °C (130 to 170 °F) at the dishes. A mix of water and detergent is used for cleaning purposes, followed by 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. He first reports of a mechanical dishwashing device are of an 1850 patent by Joel Houghton of a hand-powered device. This device was made of wood and was cranked by hand while water sprayed onto the dishes. This device was both slow and unreliable. Another patent was granted to L.A. Alexander in 1865 that was similar to the first but featured a hand-cranked rack system. Neither device was practical or widely accepted.
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 because her servants were chipping her fine china.
Models installed with permanent plumbing arrived in the 1920s. In 1924, William Howard Livens invented a small dishwasher suitable for domestic use. It had many of the features of a modern dishwasher, including a front door for loading, a wire rack to hold crockery and a rotating sprayer. Livens' invention was not, however, a commercial success. 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.The international standard for the capacity of a dishwasher is expressed as standard place settings. Dishes or plates of irregular sizes may not fit properly in a dishwasher's cleaning compartment, so it is advisable to check for compatibility before buying a dishwasher.
Commercial dishwashers are rated based on number of plates washed per hour. The rating is based on standard sized plates of the same size. The same can be said for commercial glass washers, as they are based on standard glasses, normally pint glasses.dishwashers include a built-in water softener. Dishwasher salt is used to recharge the resin in the built-in ion-exchange system. Unlike the salt used for culinary purposes, the sodium chloride salt used for a dishwasher water softener does not have added impurities (such as iodide salts). Additionally, salt used for dishwasher water softening systems must have minimal iron and manganese salt content, as these mineral ions tend to form precipitates that clog the ion-exchange resin.
Lead crystal should not be cleaned in a dishwasher as the corrosive effect of dishwasher detergent is high on such types of glass—that is, it will quickly go 'cloudy'. In addition, the lead in the crystal glass can be converted into a soluble form, which could endanger the health of subsequent users. Some items can be damaged if washed in a dishwasher because of the effects of the chemicals and hot water. Aluminium items will discolour. Saucepan manufacturers often recommend handwashing due to the harsh effects of the chemicals on the pan coatings. Valuable items — such as antiques or hand-painted items, should be washed by hand as they may be dulled or damaged, and detergents will gradually fade the glazing and print. Sterling silver and pewter will oxidize and discolour from the heat. Furthermore, pewter has a low melting point and may warp in some dishwashers. Cast iron is likely to rust in a dishwasher.
The heat inside the dishwasher dries the contents after the final hot rinse. Plastic and non-stick items may not dry properly compared to china and glass, which hold the heat better. Some dishwashers incorporate a fan to improve drying. Older dishwashers with a visible heating element (at the bottom of the wash cabinet, below the bottom basket) may use the heating element to improve drying, however this uses more energy.