Stoneware

Ball Clay: A white or near-white firing clay that is highly plastic. Used as the clay ingredient in glazes and added to clay bodies to increase their plasticity, most often in porcelain.

Bisque: Once-fired but unglazed clay. Derives from the French "bisquet" meaning half-baked.

Bisque Fire: First firing of ware usually at a low temperature (012-04) to drive off water and harden ware so as to facilitate glazing.

Clay: A natural, fine-grained earthlike material, the product of the geological weathering or aging of the surface of the earth. The root of 1) Fine-grained earth materials formed by the decomposition of igneous rock; when combined with water, clay is plastic enough to be shaped; when dry, it is strong; when subjected to red heat or above, it will become progressively more dense and rock-like. 2) A compound of decomposed and altered feldspathic rock consisting of various hydrated silicates of aluminum along with non-plastics, such as quartz, and organic matter. It is also used as a source of alumina and silica in glazes.

Coiling: A method of hand-building pottery in which the clay is rolled out into long, narrow ropes of clay that are placed one on top of another and joined to build up the form. Either the coils are left visible or the joints are smoothed over.

Cones (Pyrometric): Made of ceramic materials, these cones are placed in a kiln where they can be viewed by the potter through spy or peepholes in the walls or door of the kiln. They are calculated to measure the heat work of the firing (temperature and duration) and are graded to soften and melt to indicate the potter that his or her clay and glazes have reached their maturity. Final temperature is designed by cone number, e.g., cone 4, cone 9.

Earthenware: Generally refers to a low-fired clay. More specifically, it is a non-vitreous clay with an absorbency from 5 to 20 percent.

Fired: 1)Heating the kiln to the required temperature for clay or glaze, at least 1300 Fahrenheit; most enamel-on copper melts from 1300 to 1600 Fahrenheit; most clay and glaze matures between 2000 and 2300 Fahrenheit. 2) Bonfiring in a pit or on the ground

Kiln: Furnace for firing clay, slumping glass, or melting enamels; studio kilns can achieve temperatures up to 2500 degrees Fahrenheit depending on their construction materials; they can be fueled carbonaceously, organically, or electronically.

Flux: The melting agent in a glaze.

Glaze: A liquid suspension of fine mineral particles that is applied to pottery and fired to its maturity to form a glassy surface that seals the clay and decorates the piece.

Greenware: Unfired pottery; also called raw-ware.

Hand-building: Assembled by hand. Finished object may include wheel-thrown, cast, coiled and/or slab elements.

Kiln: A furnace for firing pottery made of refractory and insulating materials.

Leather-Hard: Refers to the state in the drying of a raw pot with enough moisture has air-dried so that the piece can be lifted without distortion and yet is damp enough to be worked further.

Maturity: That point in a firing where the clay has reached it maximum non-porosity and hardness and hwen the glaze has flowed and formed a strong bond with the clay.

Plasticity: Refers to that quality in aclay that allows it to be worked and reshaped without cracking or crumbling.

Porcelain: A hard, totally vitreous clay, generally fired at high temperatures. It is usually whit or gray and free of impurities. In some cases when thin, the clay will be translucent.

Pottery: A loosely-used term meaning 'earthenware' or any clay piece that has been fired.

Raku Pottery: Raku is an ancient firing technique. First the pots are bisque fired. They are then placed in the raku kiln for approximately 15 minutes, where they are heated to 1800 deg F. They are red hot as they are removed with tongs and placed on a nest of pine needles in an airtight container. The trapped smoke enters the clay and turns the pots various shades of black. If glaze is applied, it crackles from the extreme heat change. and smoke enters the cracks.

Slab building: Ceramic ware formed from flat pieces of clay or 'slabs'.

Slip: A suspension of clay or glaze materials in water.

Sgraffito: A decorative process. A line is scratched through a layer of slip or glaze before firing to expose the clay underneath. From the Italian, meaning literally "scratched out".

Stoneware: High-fired clay with little or no rate of absorbency. Closer to porcelain than earthenware, it is more plastic and depends upon impurities for its color and texture. Grey to buff colored, non-translucent clay body which matures between cones 06 and 10.

Throwing: The act of forming clay on the potter's wheel.

Vitreous: Refers to the non-absorbency of a clay or a glaze.

Wedging: Freeing a clay of air and working a clay into a state of texture and moisture uniformity by an action of the heel of the hands and by cutting and pounding.