Glossary of Ceramic Terms

Bisque:    (bisk) first firing, generally to cone 04; as in bisqued (fired once) or bisqueware (a piece that has undergone its first firing), not yet food-safe

Cone:       originally referred to cones of claylike substances formulated to melt at a certain temperature so the potter could tell when the kiln had fired to the correct temperature, now more generally categorizing kiln temperature ratings: lowest around cone 020 up to 01 then to cone 1 up to cone 10 or 12

Glaze:      a thin coating of glass, applied before the final firing as a blend of powders mixed with water, either commercially bought or formulated in the studio and be either food-safe or not

Greenware: clay not yet fired, anything from a piece of wet clay through the leather-hard stage (hardened but still shapeable, like chocolate) to bone-dry

Grog:       finely ground fired ceramic material that is added to a clay to add strength and reduce its shrinkage

High-fire: cone 9 and up, clays like true porcelain become fully vitreous and attain a fine high glass-like ring

Low-fire: generally cone 06 to 03, most clays are not yet vitreous

Mid-fire:  cone 4 to 7, most clays become vitreous

Raku:       piece is taken from the kiln red-hot and placed in a closed can of burnables, like sawdust or newspaper, causing rainbow, crackle, or metallic finish glazes and turning the clay gray to black with the smoke; not food-safe

Sand:       sand is added to a clay to add strength and reduce its shrinkage

Slip:         liquid clay, either for attaching pieces or decoration, used only on greenware

Underglaze: colored, matte substance like glaze but with no melting agent, so it will neither seal the surface nor run, that is used to paint on designs

Vitreous:  clay becomes glass-like and non-porous, suitable for food or drink when glazed correctly

If you are looking for terminology relating to the SCA (Society for Creative Anachronisms), a medieval recreation group, please visit www.SCA.org.

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S. Schmidt of Reannag Teine.
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Revised: 02/25/08.

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