Top Dishwasher

Dishwasher

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This article is about the appliance. For manual dishwashing, see dishwashing. For the video game of the same name, see The Dishwasher: Dead Samurai.

A dishwasher containing clean dishes

An open dishwasher

A dishwasher is a mechanical device for cleaning dishes and eating-utensils. Dishwashers can be found in restaurants and private homes. Unlike manual dishwashing, which relies largely on physical scrubbing to remove soiling, the mechanical dishwasher cleans by spraying hot water, typically between 55 and 75 °C (130 and 170 °F) at the dishes, with lower temperatures used for delicate items. A mix of water and detergent is circulated by a pump. Water is pumped to one or more rotating spray arms, which blast the dishes with the cleaning mixture. Once the wash is finished, the water is drained, more hot water is pumped in and a rinse cycle begins. After the rinse cycle finishes and the water is drained, the dishes are dried using one of several drying methods (e.g. a heating element at the bottom of the tub, fans, Zeolites based drying, etc.). Typically a rinse aid is used to eliminate water spots for streak-free dishes and glassware.
Mechanical dishwashing devices were developed in the mid- to late-1800s. A domestic dishwasher was invented in the 1920s, but it did not see widespread use. Dishwashers became more common in wealthy homes in the 1950s. By the 1970s dishwashers had become common. Present-day machines feature a drop-down front panel door, allowing access to the interior. The inside of a dishwasher in the North American market are either stainless steel or plastic. Mid-to-higher end North American dishwashers often come with hard food disposal units, which behave like miniature garbage (waste) disposal units that eliminate large pieces of food waste from the wash water. Many new dishwashers feature microprocessor-controlled, sensor-assisted wash cycles that adjust the wash duration to the quantity of dirty dishes. Large heavy-duty dishwashers are available for use in commercial establishments (e.g. hotels, restaurants) where a large number of dishes must be cleaned. Washing is conducted with 65–71 °C / 150–160 °F temperatures and sanitation is achieved by either the use of a booster heater that will provide the machine 82 °C / 180 °F "final rinse" temperature or through the use of a chemical sanitizer.

Contents

• 1 History
• 2 Characterization
  • 2.1 Capacity
  • 2.2 Size
  • 2.3 Features
  • 2.4 Plumbing
  • 2.5 Sound damping
• 3 Detergent
  • 3.1 Biodegradable detergent
  • 3.2 Hand-washing detergent
• 4 Rinse aid
• 5 Dishwasher salt
• 6 Hazing of glassware
  • 6.1 Limescale deposit
  • 6.2 Silicate filming, etching, and accelerated crack corrosion
  • 6.3 Physical abrasion
  • 6.4 Devitrification
• 7 Items unsuitable for the dishwasher
• 8 Drying
• 9 Level of sanitizing
• 10 Commercial dishwashers
• 11 Robotics
• 12 Environmental impact
  • 12.1 Comparison with washing by hand
  • 12.2 Detergents and rinse aids
• 13 Alternative use as a cooking device
• 14 See also
• 15 References
• 16 External links

History

A hand-powered dishwasher and an early electric dishwasher both from about 1917.

The first reports of a mechanical dishwashing device are of an 1850 patent in the United States by Joel Houghton for a hand-powered wood 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.
The first reliable (hand-powered) dishwasher was invented in 1887 by Josephine Cochrane and unveiled at the 1893 Chicago World's Fair. Cochrane was quite wealthy and never washed dishes herself; she reportedly invented the dishwasher because her servants were chipping her fine china.

Advertisement in an 1896 issue of McClure's for The Faultless Quaker Dishwasher.

In England, William Howard Livens invented a small dishwasher suitable for domestic use in 1924. It was the first modern dishwasher, and incorporated most of the design elements that feature in the models of today;^[1] it included a front door for loading, a wire rack to hold the dirty crockery and a rotating sprayer. Drying elements were even 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 house was becoming increasingly common.^[2][3]
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 US and Germany had dishwashers.^[4]

Characterization

Capacity

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. Most Common residential dishwashers load between 15 and 22 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.

Size

North American counter-top dishwasher

Dishwashers that are installed into standard kitchen cabinets have a standard width and depth of 60 cm (Europe) or 24 inches (US), and most dishwashers must be installed into a hole a minimum of 86 cm (Europe) or 34 inches (US) tall. Portable dishwashers exist in 45 and 60 cm (Europe) or 18 and 24 inch (US) widths, with casters and attached countertops. 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.

Features

Play media

Clear model of a running dishwasher

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/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.
Today, "dish drawer" models mimic this style, while the half-depth design eliminates 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 are either stainless steel or plastic. Stainless steel tubs resist hard water, provide better sound damping, and preserve heat to dry dishes faster. They also come at a premium price. Older models used a baked enamel on steel and are prone to chipping and erosion; chips in the baked enamel finish must be cleaned of all dirt and corrosion then patched with a special compound or even a good quality two-part epoxy. All 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. The flutes (Or valve meters) of the dishwasher are prevalent in American models (With some appearing in European and Asian models influenced by US design) due to the higher pressure of the American water system (which averages at 90 torrs/min, as opposed to the 65 torrs/min pressure in other countries). The flutes help drain the excess water, preventing entropy within the system due to higher pressures at a lower volume. This is a removable fixture, as some areas require a higher or lower discharge based on their water system.
Mid-to-higher end North American dishwashers often come with hard food disposal units, which behave like miniature garbage (waste) 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 quantity of dirty dishes (sensed by changes in water temperature) or the amount of dirt in the rinse water (sensed chemically/optically). This 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 to be present. However, pressure switches (some dishwashers use a pressure switch and flow meter) 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.
European dishwashers almost universally use two or three spray arms which are fed from the bottom and back wall of the dishwasher leaving both racks unimpeded and also such models 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 more basic, and old fashioned water distribution and exposed elements in the base of the dishwasher. Some North American machines use a large cone or similar structure in the bottom dish rack to prevent placement of dishes in the center of the rack. The dishwasher directs water from the bottom of the dishwasher up through this structure to the upper wash arm to spray water on 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 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 arm, again allowing full use of the bottom rack (but requiring that a small funnel on the top rack be kept clear).
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 opening the door during a wash cycle. This prevents accidents with hot water and strong detergents used during the wash cycle.
A dishwasher should never be emptied before a complete process has been signified to be finished by the control system, as this will often leave the contents unwashed or still in a saturated state. It is a common misconception that to empty a dishwasher before the end of a cycle will save energy, as many of the contents may need to be re-run, hence almost doubling running costs.^{[citation needed]}