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Friday, September 3, 2010

Metal Clay in Jewelry Making !

For many jewelry makers who have dreamed of working with metal but have had nightmares about using the torch, Metal Clay, also called Precious Metal Clay (PMC) and Art Clay, may be their dream come true. However, keep in mind that while you don't need to use a torch to necessarily solder metals together, it can be helpful to know a little about metal work in order to clean and finish metal clay pieces.
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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. Metal clay can be shaped just like any soft clay, by hand or using moulds. After drying, it can be fired in a variety of ways including 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.
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Silver metal clay results in objects containing .999 pure silver - aka fine silver, which is ideal for enameling. Although gold metal clay is much more expensive to use, the color and richness is phenomenal. It can be used to make stunning solid gold objects or used sparingly to make beautiful accents on silver pieces. Lump metal clay is sold in sealed packets to keep it moist and workable. The silver versions are also available as a softer paste in a pre-filled syringe which can be used to produce extruded forms, in small jars of slip and as paper-like sheets, from which most of the moisture has been removed.
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There are two popular brands of this material, Precious Metal Clay (PMC) and Art Clay Silver (ACS).
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Precious Metal Clay or PMC was developed in the early 1990s in Japan by metallurgist Dr. 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", must be fired in a kiln at 900 °C (1,650 °F) and has a shrinkage rate of 30%. Mitsubishi Materials Corp later developed two additional versions of silver called "PMC+" which can be fired as low as 810 °C (1,490 °F) for 30 minutes, and "PMC3", which can be fired as low as 599 °C (1,110 °F) for 45 minutes. Both PMC+ and PMC3 have a shrinkage rate of 12-15% and may also be fired with a handheld torch for 4-7 minutes. A 22k gold gilding material called "Aura 22", and lump 22k yellow gold clay (an alloy of fine silver and gold) are also available. PMC also manufactures an 18k gold clay and a platinum clay, but these latter two are only marketed in Japan.
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Art Clay Silver or ACS was developed by AIDA Chemical Industries, another Japanese company. Art Clay followed PMC Standard with their Art Clay Original clay (more like PMC+ than PMC Standard), which allows the user to fire with a handheld torch or on a gas hob. Due to subtle differences in the binder and suggested firing times, this clay shrinks less than the PMC versions, approximately 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 650 °C (1,202 °F), allowing the user to combine the clay with glass and sterling silver which are affected negatively by the higher temperatures needed to fire the first generation clays. AIDA also manufacturers Oil Paste, a product only used on fired metal clay or milled fine silver, 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.
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A do-it-yourself version called Silver Smith's Metal Clay Powder is available in a dry powder form to which the user adds water to obtain any desired consistency.

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This book is a great guide for getting a start in Metal Clay Jewelry.
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