A very thin sheet of metal, usually gold, platinum, or tin. Cohesive gold foil is pure (24 carat) gold which, when condensed at room temperature against another piece of foil, will cohere or weld to form one piece. It can be condensed in small pieces into a retentive cavity using a gold foil mallet or condenser. A gold foil carrier is a pointed instrument which can be used to pick up small pieces of gold foil and pass them through an annealing flame to remove any protective coating prior to placing them in a tooth cavity. Platinum foil is pure platinum in thin sheet form which, because of its high melting point, is used as a former during the fabrication of a porcelain crown. Tin foil was used as an early 19th-century restorative material. See also gold.
Ferrier, W. I. Gold foil operations, University of Washington Press, 1959.
http://www.goldfoil.org/archives/Ferrier/FerrierWI%20Gold%20Foil%20Operations.pdf A historical paper describing the use of gold foil.