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Metal clay: Firing metal clay in a kiln

Firing time and temperature determine the strength and rigidity of the finished product; insufficient firing will produce a weak or brittle piece. Different clays have different firing schedules; some pieces, depending on their size, can be torch-fired rather than requiring a kiln. See the metal clay firing chart and always check the manufacturer’s recommendations for your type of clay.
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Silver metal clay
Most fine silver clay can be fired directly on a fiber shelf, or supported by vermiculite or fiber blanket. Fine silver doesn’t oxidize, so pickling isn’t necessary. You can let your fired metal cool naturally, or you can quench it to cool it immediately. To quench, pick up the fiber shelf with a pair of tongs and place it on a heatproof surface, then use tweezers to transfer the hot piece to a bowl of water. Once the piece sizzles, it’s cool enough to touch. Dry it off and proceed to finishing.

Not all pieces or metals are suitable for quenching. Follow the project’s instructions carefully.

After firing, silver clay has a white surface. This isn’t a residue; it’s the irregular surface of the newly fired clay. The surface is quite porous; microscopically, it’s like a gravel road. This irregular surface reflects back all the colors of the light spectrum, so the human eye sees it as white. To see the silver, you must compress the surface so it becomes more reflective.
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Base metal clay
Most base metal clays must be fired in activated carbon to prevent the formation of oxides that would prevent the metal from sintering properly. The carbon consumes the oxygen in the kiln, creating a reducing atmosphere ideal for firing base metal clays. There are numerous factors in properly firing in carbon: as well as the time and temperature variables, there is the size of the piece, the position of the pan in the kiln, the type of kiln, the type of pan, the type of carbon, and the depth of carbon above and below the piece. Get to know your kiln by firing test strips, experimenting with different conditions before you fire an elaborate piece. Usually these clays will need to cool naturally in the carbon to prevent surface oxidation.

Safety notes:
Fire in a well-ventilated area or outside. If you’re kiln-firing, follow the kiln manufacturer’s specifications on creating a safe firing station. If you’re torch firing, wear cotton; synthetic materials can melt and stick to the skin if burned. Tie back your hair, wear closed-toed shoes, and don’t wear loose-fitting clothes.
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