Dishwasher
A dishwasher is a machine that is used to clean dishware, cookware, and cutlery automatically. Unlike manual dishwashing, which relies on physical scrubbing to remove soiling, the mechanical dishwasher cleans by spraying hot water, typically between, at the dishes, with lower temperatures of water used for delicate items.
A mix of water and dishwasher detergent is pumped to one or more rotating sprayers, cleaning the dishes with the cleaning mixture. The mixture is recirculated to save water and energy. Often there is a pre-rinse, which may or may not include detergent, and the water is then drained. This is followed by the main wash with fresh water and detergent. Once the wash is finished, the water is drained; more hot water enters the tub by means of an electromechanical solenoid valve, and the rinse cycle begin. After the rinse process finishes, the water is drained again and the dishes are dried using one of several drying methods. Typically a rinse-aid, a chemical to reduce the surface tension of the water, is used to reduce water spots from hard water or other reasons.
In addition to domestic units, industrial dishwashers are available for use in commercial establishments such as hotels and restaurants, where many dishes must be cleaned. Washing is conducted with temperatures of and sanitation is achieved by either the use of a booster heater that will provide an "final rinse" temperature or through the use of a chemical sanitizer.
History
The first mechanical dishwashing device was registered for a patent in 1850 in the United States by Joel Houghton. This device was made of wood and was cranked by hand while water sprayed onto the dishes. The 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. Some historians cite as an obstacle to adoption the historical attitude that valued women for the effort put into housework rather than the results—making household chores easier was perceived by some to reduce their value.The most successful of the hand-powered dishwashers was invented in 1886 by Josephine Cochrane together with mechanic George Butters in Cochrane's tool shed in Shelbyville, Illinois when Cochrane wanted to protect her china while it was being washed. Their invention was unveiled at the 1893 World's Fair in Chicago under the name of Lavadora but was changed to Lavaplatos as another machine invented in 1858 already held that name. Cochrane's inspiration was her frustration at the damage to her good china that occurred when her servants handled it during cleaning.
Europe's first domestic dishwasher with an electric motor was invented and manufactured by Miele in 1929.
In the United Kingdom, William Howard Livens invented a small, non-electric dishwasher suitable for domestic use in 1924. It was the first dishwasher that incorporated most of the design elements that are featured in the models of today; it included a door for loading, a wire rack to hold the dirty crockery and a rotating sprayer. Drying elements were added to his design in 1940. It was the first machine suitable for domestic use, and it came at a time when permanent plumbing and running water in the home were becoming increasingly common.
Despite this, Liven's design did not become a commercial success, and dishwashers were only successfully sold as domestic utilities in the postwar boom of the 1950s, albeit only to the wealthy. Initially, dishwashers were sold as standalone or portable devices, but with the development of the wall-to-wall countertop and standardized height cabinets, dishwashers began to be marketed with standardized sizes and shapes, integrated underneath the kitchen countertop as a modular unit with other kitchen appliances.
By the 1970s, dishwashers had become commonplace in domestic residences in North America and Western Europe. By 2012, over 75 percent of homes in the United States and Germany had dishwashers.
In the late 1990s, manufacturers began offering various new energy conservation features in dishwashers. One feature was use of "soil sensors", which was a computerized tool in the dishwasher which measured food particles coming from dishes. When the dishwasher had cleaned the dishes to the point of not releasing more food particles, the soil sensor would report the dishes as being clean. The sensor operated with another innovation of using variable washing time. If dishes were especially dirty, then the dishwasher would run for a longer time than if the sensor detected them to be clean. In this way, the dishwasher would save energy and water by only being in operation for as long as needed.
It is noteworthy that prices for dishwashers increased significantly around 2022-2025, in part influenced by United States government-imposed tariffs on importers.
Design
Wash chamber construction
Dishwashers might use either plastic or stainless steel for the construction of the wash chamber; stainless steel generally provides advantages over plastic construction. Also, though wash chambers can come in different dimensions, it appears the "24-inch" has become standard, at least in the United States.Size and capacity
Dishwashers that are installed into standard kitchen cabinets have a standard width and depth of 60 cm or , and most dishwashers must be installed into a hole a minimum of 86 cm or tall. Portable dishwashers exist in 45 and 60 cm or widths, with casters and attached countertops. There are also dishwashers available in sizes according to the European gastronorm standard. Dishwashers may come in standard or tall tub designs; standard tub dishwashers have a service kickplate beneath the dishwasher door that allows for simpler maintenance and installation, but tall tub dishwashers have approximately 20% more capacity and better sound dampening from having a continuous front door.The international standard for the capacity of a dishwasher is expressed as standard place settings. Commercial dishwashers are rated as plates 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.
Layout
Present-day machines feature a drop-down front panel door, allowing access to the interior, which usually contains two or sometimes three pull-out racks; racks can also be referred to as "baskets". In older U.S. models from the 1950s, the entire tub rolled out when the machine latch was opened, and loading as well as removing washable items was from the top, with the user reaching deep into the compartment for some items. Youngstown Kitchens, which manufactured entire kitchen cabinets and sinks, offered a tub-style dishwasher, which was coupled to a conventional kitchen sink as one unit. Most present-day machines allow for placement of dishes, silverware, tall items and cooking utensils in the lower rack, while glassware, cups and saucers are placed in the upper rack. One notable exception were dishwashers produced by the Maytag Corporation from the late sixties until the early nineties. These machines were designed for loading glassware, cups and saucers in the lower rack, while plates, silverware, and tall items were placed into the upper rack. This unique design allowed for a larger capacity and more flexibility in loading of dishes and pots and pans. Today, "dish drawer" models eliminate the inconvenience of the long reach that was necessary with older full-depth models. "Cutlery baskets" are also common. A drawer dishwasher, first introduced by Fisher & Paykel in 1997, is a variant of the dishwasher in which the baskets slide out with the door in the same manner as a drawer filing cabinet, with each drawer in a double-drawer model being able to operate independently of the other.The inside of a dishwasher in the North American market is either stainless steel or plastic. Most of them are stainless steel body and plastic made racks. Stainless steel tubs resist hard water, and preserve heat to dry dishes more quickly. They also come at a premium price. Dishwashers can be bought for as expensive as $1,500+, but countertop dishwashers are also available for under $300. Older models used baked enamel tubs, while some used a vinyl coating bonded to a steel tub, which provided protection of the tub from acidic foods and provided some sound attenuation. European-made dishwashers feature a stainless steel interior as standard, even on low-end models. The same is true for a built-in water softener.
Washing elements
European dishwashers almost universally use two or three sprayers which are fed from the bottom and back wall of the dishwasher, leaving both racks unimpeded. Such models also tend to use inline water heaters, removing the need for exposed elements in the base of the machine that can melt plastic items near to them. Many North American dishwashers tend to use exposed elements in the base of the dishwasher. Some North American machines, primarily those designed by General Electric, use a wash tube, often called a wash-tower, to direct water from the bottom of the dishwasher to the top dish rack. Some dishwashers, including many models from Whirlpool and KitchenAid, use a tube attached to the top rack that connects to a water source at the back of the dishwasher and directs water to a second wash spray beneath the upper rack, which allows full use of the bottom rack. Late-model Frigidaire dishwashers shoot a jet of water from the top of the washer down into the upper wash sprayer, again allowing full use of the bottom rack.Features
Mid-range to higher-end North American dishwashers often come with hard food disposal units, which behave like miniature garbage disposal units that eliminate large pieces of food waste from the wash water. One manufacturer that is known for omitting hard food disposals is Bosch, a German brand; however, Bosch does so in order to reduce noise. If the larger items of food waste are removed before placing in the dishwasher, pre-rinsing is not necessary even without integrated waste disposal units.Many new dishwashers feature microprocessor-controlled, sensor-assisted wash cycles that adjust the wash duration to the number of dirty dishes or the amount of dirt in the rinse water. A 'normal' cycle for models sold in the United States is typically 3 to 4 hours, though some models support selection of short cycles on the order of 30 minutes. Sensor-assisted cycle management can save water and energy if the user runs a partial load. In such dishwashers the electromechanical rotary switch often used to control the washing cycle is replaced by a microprocessor, but most sensors and valves are still required. However, pressure switches are not required in most microprocessor controlled dishwashers as they use the motor and sometimes a rotational position sensor to sense the resistance of water; when it senses there is no cavitation it knows it has the optimal amount of water. A bimetal switch or wax motor opens the detergent door during the wash cycle.
Some dishwashers include a child-lockout feature to prevent accidental starting or stopping of the wash cycle by children. A child lock can sometimes be included to prevent young children from opening the door during a wash cycle. This prevents accidents with hot water and strong detergents used during the wash cycle. Some dishwashers also offer WiFi connectivity, supporting remote monitoring of washing progress or start a cycle remotely.