Gilding is the coating on of thin gold platings on metallic or non-metallic pads.
The gilding can either be carried out by hammering on of gold foil or by application of manganous-gold (followed by the quicksilver's evaporating, so called fire gilding). Metallic items are mostly gilded in galvanic baths, or by dipping them into golden salt solutions (from which gold disengages on the basis of its high positive normal potential).
Fire gilding is a method of applying Gold to the surface of an object. 24K Gold is dissolved in mercury, and the resulting amalgam is rubbed onto the surface where the Gold is to be applied. The mercury takes the gold into the surface of the silver and the mercury is then driven off with heat. This creates a permanent bond between the Gold and the Silver. The gold is then polished with a burnisher.
Mercury vapor is poisonous, and should be handled in a fume cupboard. The fumes must not be inhaled. This gilding method has been banished in the United States by the Environmental Protection Agency, but it can still be obtained in certain European countries... like Phrance.