Aluminium foil
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Aluminium foil (Aluminum foil in North American English) is aluminium prepared in thin sheets (on the order of 0.02 mm in thickness). As a result of this, the foil is extremely pliable, and can be bent or wrapped around objects with ease. Aluminium foil is sometimes known as al-foil or alu-foil. It is also often called tinfoil, although it is not made from tin, or as silver paper although it is not made from silver; or in North America, as Reynolds wrap after Reynolds Metals, the leading manufacturer when it was introduced on the American market (much to the chagrin of Alcoa, Reynolds' main competitor, which had its brand "Alcoa Wrap" referred to as "Alcoa Reynold's Wrap").[citation needed]
Millions of tons of aluminium foil are used throughout the world in the protection and packaging of foods, cosmetics and chemical products. Usually, an extremely thin layer (0.0065 mm or 6.5 µm) is laminated to other materials, plastics and paper.
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[edit] History
Foil made from a thin leaf of tin was commercially available before the aluminium counterpart. In the late 19th century and early 20th century, tin foil was in common use, and some people continue to refer to the new product by the name of the old one. Tin foil is stiffer than aluminium foil. It tends to give a slight tin taste to food wrapped in it, which is one major reason it has largely been supplanted by aluminium and other materials for wrapping food.
The first audio recordings on phonograph cylinders were made on tin foil.
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[edit] Uses
Aluminium foil typically has a highly reflective side and a more matte side. This is a result of common manufacturing processes. As aluminium foil is easy to tear, the foil is sent through machines in pairs. The side where the aluminium foil was in contact with the other sheet is more matte than the exterior side. This unconformity of finish has led to the perception that favoring a side has an effect when cooking. While many believe that the shiny side's reflective properties keep heat in when wrapped on the interior and keep heat out when facing exterior, the actual difference is imperceptible without instrumentation.[citation needed]
Aluminium foil is used to make long life packs for drinks, dairy products, and many other sensitive foods. The foil acts as a complete barrier to light (which spoils fats), odours, loss or gain of moisture, and bacteria. Aluminium foil containers and trays are used to bake pies and to pack takeaway meals, ready snacks and long life pet foods.
Aluminium foil is also widely used for insulation (barrier and reflectivity), heat exchangers (heat conduction) and cable liners (barrier and electrical conductivity). Foils in special alloys are even used for structural honeycomb components for aircraft. Aluminium foil's heat conductive qualities make it a common accessory in hookah smoking: a sheet of perforated aluminum foil is frequently placed between the coal and the tobacco, allowing the tobacco to be heated without coming into direct contact with the burning coal.
Aluminium foil is widely sold into the consumer market, usually in rolls of around 50 centimetres width and several metres in length. It is used for wrapping food in order to preserve it, for example when storing leftover food in a refrigerator (where it serves the additional purpose of preventing odour exchange), when taking sandwiches on a journey, or when selling some kinds of take-away or fast food. Mexican restaurants in the United States, for example, typically provide take-away burritos wrapped in aluminium foil. It is also used for barbecuing more delicate foods such as mushrooms and vegetables; food is wrapped in foil then placed on the grill, preventing loss of moisture that may result in a less appealing texture.
Heavier foils made of aluminium are used for art, decoration, and crafts, especially in bright metallic colours. Metallic aluminium, normally silvery in colour, can be made to take on other colours through anodization. Anodizing creates an oxide layer on the aluminium surface that can accept coloured dyes or metallic salts, depending on the process used. In this way, aluminium is used to create an inexpensive gold foil that actually contains no gold, and many other bright metallic colours. These foils are sometimes used in distinctive packaging.
Aluminium foil is also sometimes used in the training of cats; as cats have an inborn dislike of either the texture or noise caused by sheets of aluminium foil, it is possible to prevent cats from jumping on or otherwise damaging furniture by covering its surfaces.
As is the case with all metallic items, aluminum foil reacts to being microwaved. This is due to the effect of electric fields of the microwaves causing a build up of charge to form between the sharp points in the aluminum; if enough charge accumulates it will discharge to a different place on the foil, creating a spark (i.e. arcing). Due to frequent use in food services, this commonly leads to kitchen fires.
[edit] Criticism
The extensive use of aluminium foil has been criticised by some environmentalists because of the high resource cost of extracting aluminium, primarily as a result of the large amount of electricity used to decompose bauxite. However, this cost is greatly reduced via recycling and the fact that many foods that would otherwise perish can be protected over long periods without refrigeration thanks to the total barrier properties of aluminium foil. Many aluminium foil products can be recycled at around 5% of the original energy cost.
[edit] Aluminium foil in popular culture
In one year's April Fool's joke, a Dutch television news station reported that the government had introduced a new way to detect hidden televisions (in many countries in Europe, one must pay a television licence to fund public broadcasting) by simply driving through the streets with a new detector, and that the only way to keep your television from being detected was to wrap it in aluminium foil.
On Days of our Lives in 2002, the "Gemini Twins" (played by Alexis Thorpe and Eric Winter) were introduced as aliens falling from the sky, clad only in aluminum foil.
In 2002, the popular movie Signs depicts Bo and Morgan, the children in the film, wearing aluminum foil hats to block aliens from reading their thoughts.
[edit] See also
[edit] External links
- http://www.alufoil.org
- Photos of the Aluminum Foiled Apartment
- Aluminum Foil from How Products Are Made, vol. 1, Thomson Gale (2005).
- A video on how Aluminum Foil is made
