Foil (metal)
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, called gold leaf. Extremely thin foil is called metal leaf. Leaf tears very easily and must be picked up with special brushes.
Material criticality
Metals are among the most important materials to the industrialized world, everything from infrastructure to personal electronic devices heavily relies on metals for production. As a result, global supply is being increasingly monitored and examined. For example, a recent study analyzed the varying levels of risk to the copper metals around the world. Another study found that increasing metal scarcity could alter typical industrial behavior. It also noted that metals heavily concentrated in certain geographic areas, such as strontium in China or the platinum group in South Africa and Russia; pose greater risk for supply disruptions.