An extremely thin sheet of gold about 4 millionths of an inch thick (about 0.1 micrometer), gold leaf has been applied to designs, letterings, and edgings of paper, wood, ceramics, textiles, metal, and other materials for decorative effect. Gilding (the term used for the application of gold leaf) has been around since the days of ancient Egypt, where it was used on royal mummy cases and furniture. It was also popular with medieval hand-copied books. In current times crafters often cover wooden picture frames with gold leaf.
Gold is one of the densest of all metals but is also soft and pliable. An ounce (28 grams) can be beaten out to 187 square feet (about 17 square meters) of gold leaf. The process of pounding fine gold into leaf is known as goldbeating and has undergone little change since antiquity. It begins with a small ingot, cast from gold alloyed with small amounts of silver and copper, which is rolled into a long ribbon having a thickness of only about 0.001 inch (0.025 millimeters). The ribbon is then cut up into squares, and these are placed between sheets of heavy paper and enclosed in a sheepskin. The squares are then hammered, re-cut, and hammered again until they reach the desired width and thickness. They are then trimmed into squares of about 3.4 inches (8.5 centimeters) per side and stored in books with layers of tissue paper between the leaves.
Current methods of gilding differ in their intricacies, but they all share the same common principles. First the object to be gilded is prepared by sanding out any imperfections. Then a sizing, either a glue or varnish, is applied to the surface. Once the sizing has reached the appropriate tackiness, a piece of gold leaf is picked up with a soft, natural bristle brush and laid atop the glue. The gold leaf is gently rubbed with the brush to make sure that it adheres. When the gilding is completed, the leaf-covered area may be burnished to a high luster with a wad of soft cotton. Loose bits of gold may be removed from the finished work and reused. Any spots in which the gold leaf detaches are redone following the same process.