In burners, when speed of air fuel exiting tip of burner is slower than combustion, and flame jumps back down burner tube to fuel orifice, resulting in smoky orange flame and overheated burner tube.

In a fuel kiln, the internal pressure resulting from proper balance of combustion pressure and damper setting, resulting in more economical and efficient heat work.

Refractory wall in some fuel-burning kilns to deflect heat and flames from direct contact with the wares.

 Al₂O₃—2SiO₂—2H₂O Secondary clays deposited in marshy areas. Very fine particle size, high plasticity, high in organic contaminates, and fires white or off-white. Used as the primary plasticizing clay in most clay bodies, but in large quantities promotes high shrinkage. 

A mechanically revolving vessel in which ceramic materials can be placed along with water and flint pebbles or high-fired porcelain slugs. Used to grind clay and glaze materials.

Hand-operated turntable for applying wax resist and banded decoration.

Early form of East Asian kiln, where tubular kiln chamber was excavated in an earthen bank. Predecessor to anagama and tube kiln.

BaCO₃ alkaline earth active HT flux, but also promotes matt glaze surface. Unsafe for low-fire functional glazes. Controversial in HT functional glazes, but toxicity problems from balanced HT glaze not proven. Often used as additive in clay bodies in very small percentages to render sulfates insoluble, reducing scrumming. Toxic in inhalation and ingestion.

Slip clay with very high iron content, often used as brown colorant for clay bodies.

Kiln arch that forms a perfect half circle, with the arch beginning and ending on a horizontal surface, using no skew bricks.

Clay body with enough content of dark clays and or metallic oxides to fire dark brown or black.

In glaze chemistry, the fluxes or melting agents that are combined with acids (glass-formers) and neutrals (refractory).

Safety valve used on most gas kilns, operates on minute electrical current generated by thermocouple. Natural-draft kilns equipped with Baso system often need no external electrical hookup at all. In operation, button on Baso valve is depressed and pilot flame is ignited, which heats up thermocouple, energizing small electromagnet in Baso valve, which holds valve open admitting gas to main burner. If pilot is extinguished, thermocouple cools, and Baso valve closes, shutting off gas.

Rigid flat disc of wood, plastic, or plaster placed on wheel head. When throwing is finished, bat is lifted off wheel head, avoiding damage or warpage.

A specialized controlled-crawl glaze designed to crack and crawl significantly during firing (due to extreme L.O.I. in glaze materials), and then melt into isolated beads on the surface.

A kiln with a stationary floor but where the kiln body can be raised upwards on vertical tracks, making it easy to load and unload large forms.

Al₂O₃—5SiO₂—7H₂O Montmorillonitic clay formed from decomposition of airborne volcanic ash. Finest particles of all clay, extremely plastic (3-times as powerful as ball clay), but shrinkage is too high to be used alone, add 2% to 3% to clay to increase plasticity. When added to glaze, will help keep in suspension and improve raw glaze adhesion.

Soluble metallic salt gives metallic luster under LT reducing conditions, especially in fuming and saggar applications. Toxic in inhalation and ingestion.

Initial kiln firing in which clay sinters without vitrifying, and though very porous, will no longer soften in water.

Slip clay with very high iron content, often used as brown colorant for clay bodies.

In ancient Greek ceramics, late Archaic and early Classical style in which figure first dominates, and where figures are in black against a red background.

Bonfire firing that is smothered with manure and/or sawdust at maximum temperature and then buried in sand, dirt, or ash, to trap smoke, causing wares to turn black.

Glaze defect where fired glaze surface contains bubbles, which often break open to leave sharp-edged craters in surface. Most often caused if volatization of materials in clay and glaze is still occurring when kiln is shut off, freezing bubbles in place. Best solution in high-firing is brief oxidation soak at end of firing to allow surface defects to heal. Same may be accomplished in low-firing by slowing down firing or by soaking kiln near maturation.

Firing defect where blisters form within clay body, raising large lumps on the surface. Caused by expansion of gases within clay, as a result of excessive early reduction (trapped carbon carbon coring), excessively fast bisque-firing (trapped carbon and sulfur), or over firing (volatization of fluxes).

In burners, when speed of air/fuel mixture exiting tip of burner is greater than combustion rate flame jumps off tip of burner and often blows out.

The process of mixing a glaze or slip with a motorized impeller-mixer.

A motorized impeller-mixer used in preparing casting slip. Unlike the handheld drill-mixer, a blunger is mounted on a heavy bracket or clamp, so that slip can be left blunging for extended time needed for proper casting slip.

Period of reduction atmosphere induced between cone 012 and 08 to bring out iron color and speckles in clay body, especially in high-fired stoneware.

Ca₃(PO₄)₂ HT flux opacifier in LT glazes translucence in HT glazes (from colloidal phosphorus globules) and especially in bone china (from supercharged glassy-phase). Toxic in inhalation. 

Translucent porcelain containing bone ash.

Completely dry (and very brittle) state clay must reach before firing.

Earliest and most basic firing process, where wares are fired in an open bonfire. See black ware firing.

Na₂O—2B₂O₃—10H₂O a major LT alkaline flux, available in granular or powdered form. Gives smooth finish, bright colors. Water soluble, so is often used in fritted form. In excessive amounts creates brittle glass and can cause blistering and pin holing. Available in granular and powdered form. Sometimes used with salt or soda in vapor glazing to lower firing temperature and/or achieve a smoother, shinier surface. Toxic in inhalation and ingestion. 

Type of wood-kiln firebox where primary air enters at top of firebox, passes down through wood, and combustion occurs at level of grates or hobs, and is supercharged by the heat of the coal bed. Heat and flames enter firing chamber below grate-level. In true Bourry-box, wood can be piled above grates and is gravity-fed down to combustion zone.

In glazes, phenomenon where a glaze gives different colors in thick and thin are the color breaks from thick to thin. Effect accentuated in reduction firing when glazes re oxidize to different color in thinner areas, as in Temmoku breaking from black to brown, or copper red from red to clear.

Method of achieving a shine by rubbing clay or slip with smooth hard object.

Iron-manganese are good color source for basalt bodies.