Standard low-pressure measure of gas pressure, based on pressure required to lift a column of water. Household natural gas pressure is usually 7" or 7 W.C.I. Industrial natural gas pressure may be 12" to 15" or more. Propane household systems usually carry 11" of pressure, but propane kiln systems may be equipped with adjustable regulators delivering up to 20 P.S.I. (pounds per square inch). See manometer.

Small balls or rolls of refractory clay mixture (40 alumina, 10 ball clay, 50 kaolin) placed under wares and posts, and between pots, lids, etc., in vapor-glazing and wood firing processes, to keep surfaces from sticking together.

Small balls or rolls of refractory clay mixture (40 alumina, 10 ball clay, 50 kaolin) placed under wares and posts, and between pots, lids, etc., in vapor-glazing and wood firing processes, to keep surfaces from sticking together.

Distortion of clay forms caused by uneven stresses within clay due to forming method, uneven drying, uneven support in firing, or uneven or excessive heat in firing.

European term referring to a fired piece discarded due to damage in firing.

Standard low-pressure measure of gas pressure, based on pressure required to lift a column of water. Household natural gas pressure is usually 7" or 7 W.C.I. Industrial natural gas pressure may be 12" to 15" or more. Propane household systems usually carry 11" of pressure, but propane kiln systems may be equipped with adjustable regulators delivering up to 20 P.S.I. (pounds per square inch). See manometer.

Amount of water required to bring a dry clay to its state of ideal plasticity. Common clay test used to determine this amount. The more water needed, the finer the particle size, the more plastic the clay, and the greater the drying shrinkage.

Na₂SiO₃ comes as a liquid used as a deflocculant in slips, as an air-setting binder for LT refractories. Lana Wilson (and many clay artists/artisans) promotes its use in magic water for use in place of slurry for joining wet or soft leather-hard ceramic forms. Add 1.5% sodium silicate and 1.5% soda ash by weight to a measure of water. Toxic in ingestion. Skin irritant.

The stage during bisque-firing or single-firing, below 1200°F, when carbonates, nitrates, sulfates, organic contaminants, and chemically combined water volatize and outgas. See carbon coring, out gassing.

Melted wax or wax emulsion used to prevent slip or glaze from adhering to a clay surface, either in decorating, or in preparing work for glazing.

Bricks with angled side faces, tapering along the length of the brick, which when laid together form a curved arch. Standard wedge bricks give 9" thick arch.

Process of kneading the clay with the hands to remove air bubbles and ensure homogenous mass.

Working the clay up and down in a cone shape on the wheel to align the platelates in a spiral formation and thus increase control in centering and throwing.

2(PbCO₃)—Pb(OH)₂former source of lead for glazes. Highly toxic in absorption, inhalation, and ingestion. Remove from studio and dispose of in a responsible fashion.

Low-temperature white clay body.

CaCO₃ alkaline earth, contributing calcium oxide to glaze powerful AT flux major HT flux for glazes gives strong durable glass. Sometimes used in low-fire clay bodies to extend firing range and give greater fired strength.

CaSiO₃used in partial replacement of silica and whiting in HT bodies, improves thermal shock resistance. In some cases, it is used in place of whiting to eliminate L.O.I. Toxic in inhalation.