A foil is a very thin sheet of metal, usually made by hammering or rolling a piece of metal. Foils are most easily made with malleable metals, such as aluminum, copper, tin, and gold. Foils usually bend under their own weight and can be torn easily. The more malleable a metal, the thinner foil can be made with it. For example, aluminum foil is usually about 1/1000 inch (0.03 mm), whereas gold (more malleable than aluminum) can be made into foil only a few atoms thick. Such extremely thin foil is called leaf. Leaf tears very easily and must be picked up with special brushes.
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