Stoneware Glaze

The coating of glass over stoneware clay is a ‘glaze’. Glazes are composed of materials that melt to form a glass at the maturation temperature of the clay, approximately 2300F. A glaze for stoneware could be as simple as a local streambed clay. In most cases, glazes are composed of numerous finely powdered ingredients such as quartz, feldspar, limestone, clay, and oxides of metals (for color). These materials are readily available through distributors, but potters often use materials that are unique to their area. At our pottery we use cleaned wood ash, ground anorthosite (the bedrock of the Adirondack High Peaks), and local clays in our chemistry. It’s possible to find ingredients at the grocery. Borax and baking soda are of off-the-shelf examples. Glazes are rarely ‘painted’ on pottery. In studio practice pots are most often dipped. The pots are first fired to a low temperature that makes them stable, easier to handle, and absorbent. The glaze ingredients are mixed in a water suspension and the piece is dipped into the glaze. The water is drawn into the piece; the ingredients are left on the skin, touchable seconds after application. Decorations can then be applied using a brush to melt into the glaze when it reaches temperature