The practice of gold leafing dates back thousands of years. It consists of genuine gold that has been pounded into extremely thin foil or flakes and applied to items made of wood or metal. It is then "burnished" in order to produce an authentic, aged effect.
Gold leaf can be applied using two different methods: water gilding and oil gilding. Only gold leaf applied through water gilding can be burnished.
Gold leafing measures 1/250,000th of an inch thick. A "burnisher" is a smooth stone shaped like a dog's tooth on a wooden handle.
The surface is thoroughly sanded and coated with a protein binder (rabbit skin glue) and "gesso," a white plaster-like material that acts as a filler. "Clay bole," a substance containing hydrous aluminum silicate, is mixed with equal parts water and glue and applied in several coats.
The gilder's "liquor" (water, alcohol and glue) is used to dampen the surface, the gold leaf is applied with the tip of a sable brush and polished with a burnisher to create a high luster. Gold leaf left unburnished provides a contrasting satin finish.
Long ago, gold-leafed items were fully burnished to maximize their reflective brilliance, but in more modern times tastes have changed, favoring an authentic antique appearance.