Jewellery Making Using Precious Metal Clay (PMC)

In the 1990's scientists in Japan developed a combination of binders and fine metal particles to create a material with the malleable properties of modelling clay, known as Precious Metal Clay (PMC). This product is now available to the jewellery making industry and to hobbyists as well.

PMC is also commonly known as 'Silver Clay' which, when heated, turns into pure silver. The binder in the material holds the silver particles together. When fired like normal modelling clay, the binder burns away, allowing the silver particles to bond and form a solid piece of pure silver. The beauty of Silver Clay is that it can be easily used at home with just a few specialist pieces of equipment, and can bring a whole new dimension to your jewellery making techniques.

Since its initial development, Silver Clay has undergone a transformation, making it easier than ever to use. Early examples of the clay needed to be fired at very high temperatures, requiring a kiln to complete the process. Modern metal clays are now capable of being fired in a common kitchen oven or even with a gas blowtorch. Although a kiln is not strictly necessary with modern materials, it is still a useful jewellery workshop item to have, as it enables the user to control the temperature of the firing accurately. Too high and the silver will melt into a blob. Two low and the binder will not burn off completely, leaving the final piece weak.

The early PMC suffered from one major drawback - shrinkage. Modern metal clays are now much more resistant to shrinking during the firing process, making them easier to manipulate into far more delicate and complex patterns. Acceptable levels of shrinkage for modern materials are between 10-15%, depending on the brand.

Metal clay can be thinned with water to make a paste that can be used to join elements, repair cracks and use as a surface texture. Because the clay is very dense, just stirring in additional water will not thin the mixture. The medium has to be mixed, rather like adding thinner to oil paint, with a palette knife. Once the required consistency has been reached, allow the mixture to 'rest' in an airtight container for a few hours before use.

Metal clay is perfect for developing texture in a piece, and this can be achieved by simply pressing the pattern into the surface of the clay. Patterned rollers, even leaves or lace can be used to achieve a delicate finish on the surface of the silver piece.

Firing temperatures for the clay are around 1500 degrees F, which is applicable for most types of metal clays. Firing time is around ten minutes, making the use of a small kiln the optimum choice for firing processes.

Once fired, the metal can be soldered, filed, sanded and polished like any other metal, but it is advisable to burnish the surface first to compact the surface structure. Once finished, the piece can be worn like any other piece of silver jewellery.

Silver clay is widely available from jewellery and craft suppliers, the two main brands being Precious Metal Clay (PMC) and Art Clay Silver. Gold clay is available, but its price is prohibitively expensive for novice users. The silver clay is a good starting point when exploring this versatile medium.