The Process, Continued - Firing
Firing is the process of heating up the work. Almost all clay works are fired at least once, and most are fired two or more times.
The process of turning clay into a permanent pot always involves firing of the work. Over thousands of years of ceramic experimentation, a wide variety of methods have been developed to fire pottery. The most common mechanisms are firing in a kiln (essentially an oven, usually built of brick and/or metal), and firing in a pit.
Different energy sources are used in the firing, and the selection of firing method can affect the types of pots and the types of glazing that are fired.
The initial firing is called the "bisque" or "bisquit" firing. This firing transforms the dry clay on a molecular level into a permanent pot or sculpture. Before bisque firing, the pot would dissolve if placed in water. After bisque firing, the pot's shape is permanent. Usually the bisque firing is done in an electric kiln. The temperature is monitored using either cones or an electronic programmer. But, a gas kiln can also be used.
The cone system of controlling the temperature is both simple and ingenious. The cones are angled pieces of a material designed to melt at a particular temperature. Cones are used in one of two ways: 1) Electric kilns without electronic controllers have a small 3-prong pincer inside the kiln. The cone is placed between the pincers and when it melts, the topmost pincer (which has been held up by the rigid cone) falls. In falling, the pincer trips the switch to shut off electricity to the kiln. So, by using the proper cone, the kiln will shut itself off at just the right temperature.