Peter's Pottery
Firings and Kilns
The clay needs to be heated to a high temperature to make it hard and strong. The earliest kilns were just fire pits or holes in the side of hills. These have evolved to built structures for holding the pottery and controlling the heat.
All scources of energy have been used, such as wood, gas and electricity. Wood produces an ash and this gives a natural glaze to the clay. But a wood firing needs inputs of a lot of time and effort.
Wood and gas produce a flame and so consume oxygen. This allows a process called reduction to take place. This can add to the beauty of the clay and the glaze. There is no reduction when using an electric kiln and this process is called oxidation.
Each clay matures at differing temperatures. This is when the clay reaches its greatest hardness, and when it could no longer be heated without beginning to melt. Earthenware is fired to approximately 1100 oC (2012 oF). Stoneware is fired to around 1250 oC to 1280 oC. (2282 to 2336 oF)Porcelain is fired to a maximum of about 1350 oC (2462oF).
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