Precious Metal Clay is metal clay that is made of pure silver or gold powder and a water-soluble (non-toxic) binding agent that burns off during the firing process. PMC Standard is the first version of silver clay introduced to the jewelry making market in 1996. PMC Standard contains 70% fine silver and 30% binder, and shrinks about 28% during the sintering process.
PMC Standard must be fired at 1650ºF for 2 hours. PMC+ was the next innovation of silver clay, introduced in 1999. PMC+ is 85% fine silver and 15% binder by weight. PMC+ shrinks much less during sintering than Standard, from 12 to 15%, because the silver particles are smaller than those in Standard. PMC Plus can be fired as low as 1470F for 30 minutes, but is much stronger and more fully sintered when fired at 1650ºF for 2 hours. PMC3 silver clay is made of 85% fine silver and 15% binder by weight, the same as PMC Plus, but the silver particles are smaller so the firing time can be as little as 10 minutes at 1110ºF. PMC3 shrinks 12-15% during firing. Since PMC3 contains smaller particles of silver, the firing can be as short of 10 minutes at 1110ºF, but maximum strength is obtained when fired at 1650ºF for 2 hours.