K₂O—Al₂O3—6SiO₂ common potash feldspar, HT alkaline flux close match to Custer. Toxic in inhalation.

In ancient Greek ceramics, early pre-Classical (Archaic) style featuring intricate geometric slip decoration.

CaO—3B₂O₃ traditional important LT alkaline flux, but is no longer being mined. Replace with Ferro 3134 for LT glazes, commercial Gerstley borate substitutes for HT glazes. Test all substitutes.

Super-cooled liquid, which softens and hardens over broad range of temperature and cools to form an amorphous, non crystalline solid. Level and rate of hardness (viscosity) controlled by temperature and by addition of fluxes and refractories, making possible the wide temperature range of ceramic clays/glazes.

The primary material that, in combination with fluxes, forms the glass essential to all fired ceramics. Primary glass-former at all temperatures is silica.

In heating ceramic materials, point where glass-formers and fluxes combine and soften to begin forming a glass. See sintering, dissolution.

Coating of powdered ceramic materials, usually prepared and applied in water suspension, which melts smooth and bonds to clay surface in glaze firing. See interface.

In high-fired wares, ideal state when clay body shrinks slightly more than glaze, putting glaze under slight compression, giving greater strength, resiliency. See crazing and shivering.

Kiln firing in which glazes are melted to form a smooth glassy surface.

The matching of glaze to clay body in terms of composition and coefficient of expansion so that it will adhere permanently. See glaze compression, interface.

The chemically active state of the melted glaze.

Decorating technique where resist materials are applied to prevent glaze from adhering to certain areas.

Calcined kaolin. See EPK, calcined.

An organic gum derived from fats and oils, sometimes used as brushing medium for engobes or for re glazing fired wares. Also used as a lubricant in burnishing. For applying glazes to glaze-fired or vitrified surfaces, add one teaspoon glycerin to 100 grams dry glaze.

An organic gum derived from fats and oils, sometimes used as brushing medium for engobes or for re glazing fired wares. Also used as a lubricant in burnishing. For applying glazes to glaze-fired or vitrified surfaces, add one teaspoon glycerin to 100 grams dry glaze.

Buff stoneware clay, produced by Cedar Heights Clay Company.

Ware with mottled slip or glaze treatment to create appearance of granite.

An early form of kiln originating in the Middle East, with a below-ground firebox, a grate supporting the wares within a cylindrical enclosure, and a piled shard roof.

Process of glaze-firing glazed green ware without a bisque-firing.

Glazing leather-hard or bone-dry wares for single-firing.

Any dry, unfired clay form.

Any dry, unfired clay form.

Crushed high-fired clay graded in sizes from 15-mesh (very coarse) to 150M (extra fine) added as a source of filler or tempering grit to clay bodies to reduce shrinkage and give structure for throwing or hand building. Does not shrink in firing, so in medium and coarse grades will show texture through thin to medium glaze. Toxic in inhalation.

Al₂O₃—2SiO₂—2H₂O English kaolin, more costly than other choices, but gives whiter porcelain. Less plastic than TILE-6. Best kaolin for translucent bone china.

A long, low horizontal sprung-arch or barrel-arch wood-fired kiln, often banked with earth, traditionally used by potters on the eastern slope of the Appalachian Mountains.

CMC Gum, Veegum Cer water soluble organic thickeners often added to glazes or slips as a suspension and/or brushing agent. Also used to allow glaze adhesion to vitrified or previously glaze-fired surfaces. Most commercial low-fire glazes and under glazes contain gum additives.