What is clay?
Glaciers and rivers move the smaller rock particles, which pick up minerals and organic substances as they travel. At the same time, extremes of heat and freezing temperatures lead to the expansion and contraction of the earth's surface. Geological forces heave and tilt the earth, lakes dry out, and stream beds change, leaving deposits of clay. Dry clay is a crumbly material that becomes plastic when wet. The plasticity of the clay helps it to hold its form. When heated in a kiln, the clay becomes ceramic, and glass-like. A particle of clay, put under a microscope looks like a stop sign. The water held between the clay particles holds the clay together and gives clay a plastic quality. As the water evaporates form the clay the clay becomes less plastic and more fragile until it is fired in a kiln.