Gold leaf is a very thin sheet of gold used for decorative purposes. Gold leaf can be as thin as 3 millionths of an inch (0.0000076 cm), and in this form it is almost transparent; no other metal can be made this fine. Gold leaf is used for gilding many materials, including glass, bronze, plaster, paper, wood, ceramics, and textiles.
The basic process for producing gold leaf has changed very little since ancient times. Various colors are obtained by alloying pure gold with silver and copper. The highest purity gold used for gold leaf is usually about 23 karat. The gold alloy is melted, cast into an ingot, and rolled to a thickness of about 0.0015 inch (0.00375 cm). This sheet is cut into 2-inch (5-cm) squares, which are interleaved with larger square sheets of parchment and hammered by hand or machine down to a thickness of about 0.0004 inch (0.001 cm). Cutting, repacking with parchment, and beating are continued until the desired thickness of leaf is obtained. The finished leaf is cut into 3 ½-inch (8.5-cm) squares, which is the standard size of a sheet of gold leaf. Gold leaf for decorative purposes can also be produced by electrolysis, cathode sputtering, and vacuum vaporization.