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Ceramic Clays
Home » Arts & Crafts » Ceramics » Ceramic ClaysAll pottery is made from clay. Natural clays can be dug up and cleaned for making pots or as a glaze ingredient. Clay can be found almost everywhere on the earth’s crust. When exposed to an extreme heat, clay becomes ceramic. Clay is usually fired to a temperature of 1290 degrees to become permanent. The heat fuses the clay particles together hardening it to a permanent state. Clay is soft and pliable making it easy to sculpt by hand.
Ready-prepared clays are blended mixtures ground and cleaned to remove impurities. Clay can be blended with additives such as sand or grog to add texture or increase their strength. Coloring stains can be mixed into clays to give coloring. The coloring stains can be purchased in powdered form and are available in both bold and subtle colors. Unless you desire clay that is dark in color, stains should be added to white or light colored base clay.
Clay types are as follows:
• Grog - A ground, high-fired clay found near coal seams. Some grog, such as crush red brick, will only withstand temperatures up to 2012 degrees. Grog enables you to hand build larger pieces by preventing shrinkage and adding strength to the pot.
• Red earthenware - Low-firing clay used mostly for handbuilding.
• White earthenware - Low-firing clay used as an off-white base. Not a good choice for handbuilding but is an excellent base for painting under-glaze colors onto a pot with a transparent glaze over the top.
• Stoneware clay - A mixture of ball clay and other minerals. High-firing clay that is generally gray in color but will fire to white or buff.
• China clay - High-firing clay commonly mixed with other clays or glazes. This type of clay cannot be formed by hand.
• Porcelain clay - High-firing clay that because of its very smooth body is excellent for handbuilding. This type of clay takes a little practice to use but can make beautiful pots as it can be made very thin and is good for fine details.
• Fire clay - High-firing clay usually found near coal seams. It fires to a buff color and can be used by itself or added to other clays.
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