Aluminium foil
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Aluminium foil (aluminum foil in North American English) is aluminium prepared in thin sheets (on the order of .03 millimeters 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 often called tinfoil, although it is not made from tin.
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.
Millions of tons of aluminium foil are used throughout the world in the protection and packaging of foods, cosmetics and chemical products. Usually, an extrememly thin layer (0.0065mm) is laminated to other materials, plastics and paper, 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 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. In the late 19th century and early 20th century, tin foil was in common use; aluminium foil largely supplanted it, but some people long continued to call aluminium foil by the name of its tin counterpart (perhaps due to its being shorter to say).
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. Aluminium foil is also used in tinfoil hats which purportedly reduces the effects of "mind control rays". Aluminium foil, like all metals, reacts when microwaved. This is due to the effect of electrons emitted by the microwave causing an arc to form between sharp points in the aluminum. Due to frequent use in food services, this commonly leads to kitchen fires.
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 which 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.
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 aluminum foil. Within a few hours all aluminum foil was sold out throughout the country.