Metal clay

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Metal clay, is a clay-like medium used to make jewelry, beads and small sculpture, consists of very small particles of precious metals (such as silver, gold or platinum) mixed with an organic binder and water. Once the clay is worked, then dried, it is fired in a kiln or with a hand-held torch. The binder burns away, leaving just metal. The resulting object is smaller because the binder has been removed and the piece has shrunk during the process of "sintering".

Silver clay is the most-used of all metal clays, resulting in .999 pure silver. Gold clay is quite expensive, and not practical to use by itself, but the gold makes a beautiful accent on the silver. The clay comes in packets, which are small because the material is very expensive: $50 an ounce is an average for silver clay. It also comes in a pre-made paste, a pre-filled syringe and a paper or sheet type, which has nearly all the moisture removed. There are two popular brands of this material, Art Clay Silver (ACS) and Precious Metal Clay (PMC).

Precious Metal Clay or PMC is a plasticene-like precious metal compound developed in the early 1990s in Japan by metallurgist Dr. A. Morikawa. The material consists of extremely fine precious metal powder in a colloidal suspension, which burns off on firing. Success was first achieved with gold, and later duplicated with silver. The material is modelled into the desired shape, and then kiln-fired; which burns off the carrier, leaving only the pure metal. Shrinkage from 8 to 30% occurs (depending on the brand used), but this has been exploited by artisans as it allows very fine detail to be achieved.

Mitsubishi Materials Corporation, a subsidiary of Mitsubishi, has 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 was originally imported into North America by only one company, Rio Grande, which sponsored a number of workshops and symmposia, and started the PMC Guild^[2], which have lead to relatively fast acceptance of the material into the western market. Another brand, Art Clay Silver (ACS), made by Aida Corporation is also marketed throughout the world, and is sold in the US by Art Clay World, USA, Inc. Art Clay has additional varieties of metal clay, including a Slow Dry series, allowing the user to work with the clay 4 or 5 times longer before drying out; Silver Overlay Paste, which is used to bond to glass and porcelain as well as silver; Oil Paste, which is used after firing to join and repair fine silver to fine silver and Gold Paste, which can be painted on glass and porcelain as well as silver. Art Clay Silver also has a low-fire formula, 650 Lowfire Series, that allows users to use a kiln to fire the metal clay as low as 1200 degrees F. instead of 1472 degrees F. Silver clay also comes in a powder form to which water is added and kneaded to form a clay; ^[3] Its sold under the name Silver Smiths' metal clay; finishing is nearly identical to that of PMC or Art Clay products.