Gilding is an age-old art of applying gold leaf or gold dust to metal, porcelain, wood, paper, glass or other material. Gold is alloyed with copper or silver to make gold leaf. The Egyptians had been familiarized with gilding metals and wood. In the books of the Old Testament, this gold plate gilding is mentioned frequently and gilding has been an important part of art for several Asian countries. There are two main processes of gilding, mechanical and chemical. Chemical gilding is done in four ways: cold, wet, fire, and depletion gilding. Gilding metal is a copper alloy comprising 95 percent copper and 5 percent zinc.
The oldest and best method is to apply gold leaf to a surface that has first been treated with a preparation called sizing. When the sizing is partly dry, it acts like glue and holds the gold leaf firmly in place. Two or three applications are needed to make the gold leaf stick to cardboard or paper, because the material may absorb the first or second coating.
Mirrors and picture frames or moldings can be gilded with silver or gold leaf, however they must be given an application of yellow varnish to protect the gilding. To gild a book edge you must first give it a coat of glue, usually fish glue. Then apply the gold leaf to the book edges. A warm sizing is used to gild ivory pieces.
China, glass, and pottery are gilded by mixing gold dust to form paint, and applying it with a brush. The quantity of gold consumed for decoration of pottery and porcelain is very large. To make the gilding last, the article must be baked first in an oven at a low temperature and then in a kiln at a high temperature. If gilded dishes are washed too often and not rinsed well, the alkali in soap will eat the gold off them.
Apply gold leaf to iron and steel after it is heated until it turns bluish. Gilding metal is used for various purposes, including the jackets of bullets and driving bands on artillery shells.
Gild the decorations in a buildings; they are often decorated in gold leaf. Gilding is one of the chief decorations of the interior of Saint Peter's Church at Rome, and the Library of Congress at Washington, D.C. The dome of the State House in Boston is entirely covered in gold leaf.