Dry clay materials are often used in conjunction with other materials to make up clay bodies for use in ceramics. The benefit of creating one’s own clay body with dry materials is that you can achieve the exact composition and qualities you are looking for. While it is more labor intensive to create your own clay, doing so allows you to alter qualities such as the water content, grog composition, and color to suit your needs.
One of our most commonly-used classes of dry clay material used in ceramics is ball clay, of which there are several different varieties. Ball clays are fine-particle, plastic clays that were formed millions of years ago from the deposition of clay and volcanic ash. Ball clays typically contain kaolinite, quartz, mica, iron and titanium, organic matter and other minerals. The organic matter and additional impurities tend to make the clay appear dark gray, black, brown or pink in its natural state. These materials burn out during firing, though, leaving the ball clay almost white. There are numerous types of ball clay available, and they differ in their mineral composition. Common ball clays include OM-4, Tennessee #1, and Kentucky Stone, to name a few. All ball clays, however, have in common high plasticity, fine particle size and high greenware strength. Because the trade-off for high plasticity is shrinkage, ball clays are often used in small amounts in a clay body (approximately 10%-25%).
Kaolin and Grolleg are also commonly used in ceramics. Kaolin, which is also sometimes called “China Clay”, is a high temperature, white clay material which contains high amounts of kaolinite. This type of clay material is found in porcelains. Grolleg refers to a specific type of China Clay mined England, which comes from an original, or primary, site of kaolin deposition. Other secondary deposits arise from movement through water over time and produce kaolins such as EPK, Pioneer and Georgia. These water-transported kaolins typically acquire more impurities and so tend to be less white. Like ball clay, kaolin is fine and very plastic.
Fire clays are another important class of clays. These highly refractory clays have a very high fusion point, which is a great feature when you are attempting to balance the temperature range of your claybody. Like ball clays, fire clays are also kaolinitic in nature, and they are commonly used for ceramic industry elements that require regular exposure to very high temperatures -- so you see them used in furnace linings and ceramic brick construction.
We carry all of these classes of dry clay materials, and more, including Cedar Heights Red Art and Gold Art and Albany Slip substitute. If you have any questions about our dry clay materials, please give us a call.