Precious Metal Clay or PMC was developed in the early 1990s in Japan by metallurgist Dr. A. Morikawa. The material consists of microscopic particles of pure silver or fine gold powder and a water-soluble, non-toxic, organic binder which burns off during firing. Success was first achieved with gold, and later duplicated with silver. The original formula of PMC, now called "Standard" or "Original", must be fired in a kiln at 900 °C and has a shrinkage rate of 30%. Mitsubishi Materials Corporation, a subsidiary of Mitsubishi, later developed two additional versions of silver called "PMC+" which can be fired as low as 810 °C for 30 minutes, and "PMC3", which can be fired as low as 600 °C for 45 minutes. Both PMC+ and PMC3 have a shrinkage rate of 12-15% and may also be fired with a hand held butane gas torch.