Types of Clay to Make Pottery
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All pottery is made using clay through a process of manipulating and molding its composition by hand or on a ceramic wheel. The outcome of a ceramic piece depends on the type of clay used, so it is important to understand various clays and their composition. Generally, pottery clay is classified as earthenware, stoneware, porcelain, ball clay and fire clay.
Often referred to as the "common clay," earthenware contains numerous minerals and iron oxides. It is red, rough, opaque and very porous. Earthenware is fired at a low temperature and used to make vases, terra cotta pots, urns, roofing tiles and decorative ceramics.
Stoneware is the most widely used clay in pottery, whose composition of iron, calcium and feldspar make it is easy to manipulate and mold into different shapes. This gray to dark brown clay is fired at a high temperature and is seen in various pieces of dinnerware.
Composed of kaolin, ball clay, feldspar and flint, porcelain clay is considered the richest form of clay used in ceramics, but does not have a high degree of plasticity and flexibility. Porcelain clay requires a very high heat, and produces an esthetically beautiful result seen in dinner plates, fine porcelain china and decorative ceramics.
With a varying degree of plasticity, fire clay generally has a very rough texture. This is a high-firing clay that contains high amounts of aluminum and silicates, and a small amount of iron. Fire clay is generally used for insulating bricks, hard firebrick and kiln furniture.
As a finer-grained clay, ball clay is composed of kaolinite, mica and quartz. Its is believed to date back to the time when clay was mined by hand. The composition of the clay shrinks during the firing process, and it is generally seen in wall tiles and construction ceramics such as bricks and roof tiles.
Many professional potters use a variation of several types of clay so that their pottery can retain a certain look and texture. It is best to try them all out and see which works best for your own pieces through trial and error. With any type of clay, the more water it holds, the more it will shrink when it dries. You can add feldspar or flint, which prevents water absorption.
About this Author
Serena Norr is a New York-based writer and editor since 2001. Her articles have appeared in "City Living," "Tea & Coffee Trade Journal," "Time Out New York," "Film Monthly," "Shecky's," "Princeton Review," and "Beyond Race." Additionally, she specializes in health and wellness, motherhood, and beauty-related topics. She attained her Bachelors of Arts degree in English at Hunter College.