The process of overlaying or covering any metal, wood, etc., with a thin layer of gold alloy.The technique has been used since ancient times, and was practised by the pre-Columbian American Indians.The methods include: oil gilding or water gilding, by attaching gold leaf by means of an adhesive (called a 'mordant'); mercury gilding, by applying an amalgan of gold and mercury with a brush, thenheating the object to cause the mercury to vaporize and to leave a thin film of gold; friction gilding, by rubbing the surface with ashes of linen rags soaked in a solution of gold chloride,then burnishing and polishing; and electroplating, by depositing a layer of gold by an electric current, leaving a thin 'flash' of gold or a substantial covering, or leaving a more durable layerby 'hard gold plating'. After certain gilding processes, the effect was enhanced by 'tooling', i.e. by incising the gold surface to create a design or a textured surface.