Clay is a highly malleable substance. It retains a given shape when molded, leaving a smooth and unbroken surface. The earth's minerals contained within the clay bodies are like magic chemicals that fuse and melt during the firing process – when the clay is baked in a kiln at high temperatures. This chemical change allows the vessel or clay body to become hard and tough when cool. There are a rich variety of clays that impart different colors, textures and consistencies – such as red and white earthenware clays, or smooth and course stoneware clays
The artist-craftsperson goes through a process called wedging before a piece is worked either on the wheel or hand-built. The clay is first cut, smacked and slapped to expel any air bubbles and create an even consistency throughout.
The clay is then shaped with the artist's main tools, the hands. The obliging nature of clay allows almost any shape. When the shaping is complete, the piece is set aside and allowed to dry. Drying is done slowly to avoid cracking as the evaporation of water changes the size and shape of the piece.
Once the pieces are leather-hard, they become known as greenware. At this point, decorations or carvings, handles or modeled pieces can be added. When this greenware is thoroughly dry it is ready for firing in a pottery kiln which can reach temperatures many times higher than the conventional oven. This first firing is known as the bisque, or biscuit. Bisque ware is usually porous with the natural color of the clay used and somewhat rough – like the familiar terra-cotta pot.
Most pottery pieces are more useful and made more pleasing in appearance when coated with a glaze. The glaze coating, made up mainly of silica, serves to seal surfaces and make them smooth, hygienic and colorful. In most cases the glaze mixture is applied to the bisque area with a small brush, hand dipped or sprayed on. Color and surface textures of the glaze develop during the second or what is known as a "glost" firing.
Within this basic process there many variables of clay bodies and techniques such as wood firing, crystal firing, raku and even adding horsehair to create used and useful pieces of art.