The gilded surface on the bronze is produced by applying a pasty mixture (amalgam) of gold and mercury. The bronze is then heated by charcoal fire to evaporate the mercury, leaving the gold bonded to the surface. This gold surface layer is then burnished with a hard, smooth metal or stone tool to make it more compact and shiny. Today, mercury amalgams are more commonly known for their use in repairing dental cavities. In the 8th century in China and in the 19th century in Europe, dentists began making mercury amalgams — following techniques similar to those used for decorating metalwork — to create dental fillings.