Engineering:Dishwashing

Short description: Process of cleaning cooking utensils and other items to prevent foodborne illness

Washing dishes in Germany, 1951

Dishwashing, washing the dishes, doing the dishes, or washing up in Great Britain, is the process of cleaning cooking utensils, dishes, cutlery and other items to prevent foodborne illness. This is either achieved by hand in a sink using dishwashing detergent or by using a dishwasher and may take place in a kitchen, utility room, scullery or elsewhere.

Implements

A dish wand, a modern-day implement for washing dishes by hand, consisting of a hollow handle filled with a mixture of water and dish soap that is absorbed out through the sponge at the end when pressed and scrubbed against dishes

Dish washing is usually done using an implement for the washer to wield, unless done using an automated dishwasher. Commonly used implements include cloths, sponges, brushes or even steel wool. As fingernails are often more effective than soft implements like cloths at dislodging hard particles, washing simply with the hands is also done and can be effective as well. Dishwashing detergent is also generally used, but bar soap can be used acceptably, as well. Rubber gloves are often worn when washing dishes by people who are sensitive to hot water or dish-washing liquids, those who do not want to touch the old food particles, or those who do not wish to get as wet. According to dermatologists, the use of protective gloves is highly recommended whenever working with water and cleaning products, since some chemicals may damage the skin, or allergies may develop in some individuals. Many people also wear aprons.

There is also variation in the temperature and state of water. Some people prefer cold water or hot water, and some people prefer running water or standing water.

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Sanitization

Where dishes are to be shared among many, such as in restaurants, sanitization is necessary and desirable in order to prevent spread of microorganisms. Most restaurants have three-compartment sinks (depending on country or state regulations) and use the three-sink system (washing, rinsing and sanitizing of dirty dishes) with the first compartment containing a combination of warm water and soap or detergent. Water within the first compartment often needs to be between 95 and 120 degrees Fahrenheit (35 and 49 °C) (according to applicable health codes).

Most institutions have a dish-washing machine which sanitizes dishes by a final rinse in either very hot water or a chemical sanitizing solution such as dilute bleach solution (50-100 parts per million chlorine; about 2 ml of 5% bleach per litre of water, approximately one capful of bleach per gallon water). Dishes are placed on large trays and fed onto rollers through the machine. Dishwashers typically exceed 145 °F (63 °C) and kill all germs, while hand-washing reaches temperatures of at most 104 °F (40 °C).

While not environmentally friendly, the use of bleach is critical to sanitation when large groups are involved: it evaporates completely, it is cheap, and it kills most germs. Cabinets, refrigerators, countertops, and anything else touched by people in a large group setting should be periodically wiped or sprayed with a dilute bleach solution after being washed with soapy water and rinsed in clean water.

However, bleach is less effective in the presence of organic debris, so a small amount of food residue can be enough to permit survival of, e.g., Salmonella bacteria. Scrubbing followed by soaking in bleach is effective at reducing Salmonella contamination, but even this method does not eliminate Salmonella bacteria.

In hand-washing, plastic brushes with nylon bristles are preferred to washcloths or sponges, which can spread microorganisms. Use of soap or sanitizer is mandatory in washing by hand in public food facilities.

In the UK, hand-washing often excludes rinsing after washing and sometimes prefers air-drying to using a towel; in the US rinsing is typical, as is drying with a towel. The UK method of drying apparently reduces smudges and bacteria, while the US method is faster.

Traditional dishwashing practice

Developing countries

Nuns washing dishes. Key Monastery, Spiti, India. 2004

Traditionally, dishwashing is done by scrubbing the utensils with wet fabric dipped in scrub ash to scrub away the dirt. The utensils are then rinsed in clean water and hung to drip dry. Scrub ash (kharani) is specially made by burning wood for dishwashing. This is a common practice in villages of Asian developing countries like Nepal, Indonesia, and India .

Dishwasher

A dishwasher containing clean dishes

An open dishwasher

A dishwasher is a machine for cleaning dishware and cutlery automatically. Unlike manual dishwashing, which relies largely on physical scrubbing to remove soiling, the mechanical dishwasher cleans by spraying hot water, typically between 45 and 75 °C (110 and 170 °F), at the dishes, with lower temperatures used for delicate items.

A mix of water and dishwasher detergent is pumped to one or more rotating spray arms, blasting 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 electro-mechanical solenoid valve, and the rinse cycle(s) begin. After rinsing finishes the water is drained again, the dishes are dried using one of several drying methods. Typically a rinse-aid, a chemical to reduce 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 65–71 °C (149–160 °F) and sanitation is achieved by either the use of a booster heater that will provide an 82 °C (180 °F) "final rinse" temperature or through the use of a chemical sanitizer.

In popular culture

• Dishwasher Pete, or Pete Jordan, is a fanzine author whose goal was to wash dishes in every state in the United States.
• The Dishwasher is an Xbox Live Arcade game in which the protagonist is an undead dishwasher.
• Dishdogz is a 2005 film about a boy working as a dishwasher during his summer break.
• In his book Down and Out in Paris and London by George Orwell, he describes his experience working as a dishwasher or plongeur in a French hotel in 1929. He describes the job, the interactions with other employees, and his thoughts on the place of a plongeur in society.
• There is a Western cultural cliché that restaurant patrons who can't pay the tab would instead work off their debt by washing dishes.