The use of clay also extends to pottery. In its minimal form, pot-making is as simple as flattening a ball of clay and patiently pinching it until the smooth, even, curving walls of a bowl emerge. With the use of a potter’s wheel, the symmetry of a pot emerges from the constant spin of the clay sitting on the wheel head, coaxed up into shape by the pressure of wet fingers. When throwing a pot on the wheel, an important characteristic of the clay is its plasticity. A short clay is not so malleable and may crack when shaped into a curve or a bulge, and the addition of stuffs like soda or potassium salts can improve the texture to make it more optimal for handling. The recipe for a clay, whether in sculpture or pottery, depends in part on from where it was sourced, and in part on the materials added and mixed to match personal preference for the final color and texture.
A clay bowl, of course, is wet and malleable, and cannot hold its form if held or handled. A low temperature kiln firing completely dries out the piece, and in the absence of water, it becomes a lighter, paler object. A second firing, achieved at temperatures higher than 1000 degrees centigrade, causes the particles to melt and fuse into the recognizable heft of stoneware. The sequential firing is crucial, because if the temperature rises too high before all of the water has evaporated from the walls of the vessel, the water vapor becomes trapped in pockets of the fusing stone that can lead to cracks, and at worse, an explosion.
Traditional decoration of pots relies on glazes, which get their color not from bright pigments but from the addition of finely ground metals like copper, cobalt, and iron. Before firing, a glaze is usually a dull white, or gray, or light pink. The transformation into the rich greens, resonant blues, and rusty reds we see rely on the chemical reactions that take place during firing, influenced by both temperature and oxygen level in the kiln. Glazes can be imagined as coming to life in the presence of these licking flames: glazes are fluid, crawling and creeping and shivering depending on the surface of the clay to which they try to adhere. Sometimes, the presence of different materials in the glaze of a neighboring vessel causes a pot to blush magenta instead of blue, or turn black instead of white, as if they had been conspiring while huddled inside the kiln. These incidental events, although unintended by the potter, often lend a dash of unique personality to the finished product.