A
foil is a very thin sheet of
metal, usually made by
hammering or
rolling. Foils are most easily made with
malleable metals, such as
aluminium,
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,
aluminium foil is usually about 1/1000 inch (0.03 mm), whereas gold (more malleable than aluminium) 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.