Mercury gilding, also known as fire gilding, involves mixing pure gold together with liquid mercury to form a paste-like amalgam. This amalgam is then brushed onto the surface of a bronze object. Once the item has been covered with the amalgam, it is heated in a furnace until the mercury vaporizes, leaving the gold strongly bonded to the surface of the object, even in the finest details of the object. As a final step, the freshly mercury gilt object is burnished or polished using an agate tool. This gives a bright, high purity gold finish that is both beautiful and durable. Mercury gilding has been applied to most gilt bronze objects since the Renaissance. It is now almost abandoned, because its implementation releases mercury vapors that are very toxic and harmful to the health of the craftsman and the environment.