Metal clay

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Metal clay is a clay-like medium used to make jewelry, beads and small sculpture. It consists of very small particles of precious metals (such as silver, gold or platinum) mixed with an organic binder and water. Metalclay can be shaped just like any soft clay, by hand or using moulds. After drying, it is fired in a kiln, with a handheld gas torch, or on a gas stove. The binder burns away, leaving the pure, sintered metal. Shrinkage of between 8% and 30% occurs (depending on the product used), but this is exploited by artisans to produce very fine detail.

Silver precious metal clay results in objects containing .999 pure silver which is ideal for enamelling. Gold clay is much more expensive to use by itself, but can be used to make beautiful accents on silver objects.

Metal clay is sold in sealed packets to keep it moist and workable. It is also sold as a softer paste in a pre-filled syringe which can be used to produce extrude forms and as paper-like sheets, from which most of the moisture has been removed. Silver metal clay is also available in a dry powder form to which the user adds water to obtain any desired consistency.

There are two popular brands of this material, Precious Metal Clay (PMC) and Art Clay Silver (ACS). Precious Metal Clay or PMC was developed in the early 1990s in Japan by metallurgist Dr. A. Morikawa. The material consists of extremely fine precious metal powder and a water-soluble organic binder which burns off during firing. Success was first achieved with gold, and later duplicated with silver, PMC Original which had to be fired in a kiln and had a very high shrinkage rate. Mitsubishi Materials Corporation, a subsidiary of Mitsubishi, later developed two additional versions of silver called PMC+, which displays less shrinkage, and PMC3, which fires at lower temperatures in a kiln or by using a torch. A 22k gold coating material (Aura 22), and a 22k yellow gold alloy are also manufactured.^[1] PMC also manufacures an 18k gold clay and a platinum clay, but these latter two are only marketed in Japan.

Art Clay or ACS was developed by AIDA Chemical Industries. Art Clay followed PMC Original with their Art Clay Original clay, which allowed the user to use a handheld torch or gas hob for firing. The clay also shrank less, only 8-10%.

Further developments introduced the Art Clay Slow Dry, a clay with a longer working time. Art Clay 650 and Art Clay 650 Slow Dry soon followed - both clays that can be fired as low as 650C, allowing the user to combine the clay with glass and sterling silver which had previously been affected by the higher temperature needed to fire the previous clays. AIDA also manufacturers Oil Paste, a product only used on fired metal clay, and Overlay Paste, which is designed for drawing designs on glass and porcelain.

In 2006 AIDA also introduced the Art Clay Gold Paste, a more economical way to work with gold. The paste is painted onto the fired silver clay, then refired in a kiln, or with a torch or gas stove. When fired it bonds with the silver, giving a 22ct gold accent. The same year also saw Art Clay Slow Tarnish introduced, a clay which tarnishes less rapidly than the other metal clays.