Dry clay forms are not ceramics until they are fired. Low-fire or earthenware ceramics are heated to 1700 or 1800 degrees Fahrenheit for several hours. Earthenware is porous and chips easily. This 19th Century pueblo pot is earthenware. It was decorated with slip and then fired just once.

Stoneware is more dense [particles are close together] and is fired to a higher temperature. Stoneware can hold liquids and rings when it is struck.
Richard Notkin made the remarkable little unglazed stoneware teapot below.

Alejandra Conte, a Brazilian potter from Sao Paulo, made this small, glazed stoneware double dish with handle.

Glazed stoneware or porcelain has been fired twice. Glazes are applied after the first (bisque) firing.

Porcelain requires the most refined white clay [kaolin clay with no iron] and is fired to 2300 degrees Fahrenheit. Its glass-like walls can be very thin. This extremely delicate piece by Geoffrey Swindell is porcelain.

Whatever method ceramists use to make their pieces, they must be practical when they think about proportions. The higher the firing temperature the more shrinkage. This shrinkage however is not proportional. Pieces shrink more in height than in width. So ceramists must make their pieces proportionally higher than they plan for them to be when finished. Also because of shrinkage, to make sure a lid will fit its pot, ceramists make both pieces at the same time using clay from the same batch and same dryness.

Imagine the planning Randall Schmidt had to do so that all the pieces of his sculpture called Katie’s Corner would fit together after they were fired.

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