Keum-Boo is an ancient Asian metalworking technique, meaning literally, "attached gold". It is a simple, reliable process through which thin, hand cut sheets of pure 24k gold foil are applied to the surface of fine silver as a decorative embellishment. The surfaces are heated to 750-850F and the gold sheet is burnished on to the silver, making a permanent bond. The beauty of using Keum-boo with PMC is that silver metal clay, unlike conventional fine silver sheet, needs no preparation. It's never cleaner than when it comes out of the kiln.