A heavy earthy mineral that is plastic when wet, sets upon drying and can be changed
into a hard material with the application of heat. A hydrated silicate of aluminum and
other minerals.
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Clay bodies are a mixture of certain clays, minerals, fluxes and/or colorants in specific proportions to produce a desired physical characteristic after firing.
Clays and clay bodies are used in an amazingly wide range of industries and products including dinnerware, brick, tiles, sanitary ware, electrical insulators, heat insulation, cosmetics, paper, rubber, farming, fireworks, forensics, space exploration and medicine to name just a few.
Prepared bodies can be customized by wedging (vigorously kneading) colorants, texturizers and fluxes in by hand, allowing the users to fine-tune the clay body toward their ultimate goal.
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| Generally speaking, clays are grouped into two main categories; Earthenware and Stoneware. |
| Earthenware clays are the most common naturally occurring clays on the planet and have been used by some of the earliest of cultures. These clay bodies are characterized by low temperature ranges, usually cone 020 (1159oF) to cone 02 (2016oF), and are very porous in nature even when fired to their maturing temperatures making them less desirable than stoneware for the production of tableware. |
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| Stoneware clays are high firing with maturing temperatures ranging from cone 2 (2088oF) to cone 12 (2383oF). The body itself vitrifies (fusing of the clay particles and the loss of porosity) creating a dense material that has very low absorbency (usually 0 to 5%) and can hold water. Stoneware bodies are similar to porcelains but contain color impurities and do not turn translucent. |
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It is a basic rule that you may fire stoneware clays to earthenware temperatures, but glaze fit and body strength issues may be a problem. Earthenware clays however, should NEVER be fired to stoneware temperatures as they will melt, destroying anything around them and in extreme cases the inside of the kiln.
All clays are composed of materials dug directly from deposits found all over the globe. These clay beds can vary chemically over a wide area and may have 'impurities' that fluctuate as the beds are mined. While clay mining companies do blend sedimentary clays (clays deposited by water or ice), it is still a good practice to periodically test clay bodies to insure that glaze/clay fit problems do not arise.
HAVE FUN, BE CREATIVE, MAKE A MESS!!! |
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