Absorption- The capacity of a material to soak up liquid.
Adsorption- The collecting or liquid on a surface by condensation.
Armature- A framework around which clay can be modeled.
Banding- A method of applying a glaze or slip decoration by holding a brush tip against a rotating pot.
bas-relief- Raised or indented patterns which remain close to the surface plane.
Bat - A disk or slab of plaster or other material used for drying clay or supporting clay forms while being worked.
Bench Wheel - A portable turntable for rotating pottery being formed, decorated or otherwise worked.
Bisque - Clay which has been fired once, unglazed.
Bisque Fire - First firing of clay to drive out chemically combined water and carbonaceous materials prior to glazing.
Blow Hole - An opening at or near the top of a kiln, which facilitates steam escape or cooling.
Blowout - The explosion of clay in the kiln caused by the sudden escape of steam resulting from rapid heating or the presence of impurities.
Bone China - A creamy, transparent, English soft porcelain fluxed with ash from animal bone.
Bone Dry - The condition of unfired clay that has no absorbed moisture other than natural humidity.
Burnish - Using a smooth object to polish the surface of leather-hard clay.
Casting - A process of forming a clay object by pouring clay slip into a hollow plaster mold.
China - Whiteware clay bodies glazed at a lower temperature than that at which they are bisqued.
Clay - A compound of decomposed and altered feldspathic rock consisting of various hydrated silicates of aluminum along with non-plastics, such as quartz, and organic material.
Coil - Rope-like roll of clay used in hand building.
Collaring or Necking - A method or narrowing the neck of a pot by squeezing in with the fingers as the pot revolves on the potter's wheel.
Combing or Feathering- Decorating by gently drawing a coarse comb or feather tip through contrasting rows of wet clay slip or gaze.
Cone or Pyrometic Cone - A small triangular pyramid made of ceramic materials that are compounded to bend and melt at specific temperatures. The cone serves as a time-temperature indicator of heat work in a kiln.
Crackle Glaze - A glaze developing minute cracks which are considered decorative and are often accentuated by rubbed-in coloring material.
Crawling - Separating of those glaze coat during firing, exposing areas of unglazed clay.
Crazing - The undesirable formation of a network of cracks in the glaze caused by uneven clay or glaze contraction.
Dipping - Coating pottery by immersing it in slip or glaze.
Dry Foot - The bottom of a pot, which has been cleaned of all glaze before firing.
Dunting - Cracking of fired ware in a kiln which has cooled too rapidly.
Earthenware- Clay that matures at a low temperature but remains porous.
Elements - High resistance wire coils or bars used as the heat source in an electric kiln.
Emboss - To decorate a surface with raised ornamentation.
Fettle or Fettling - To finish or smooth the surface of leather-hard clay. Also to trim the excess clay from cast ware.
Filler - A material with little or no plasticity used to promote drying and reduce shrinkage of clay bodies or engobes.
Firebrick - A refractory insulation brick.
Fireclay - A clay used in clay bodies for its heat-resistant quality. Also used in the manufacture of kilns and other refractory equipment.
Firing - The heating of clay or glaze to a specific temperature.
Flaking - The peeling off of a glaze or slip from a clay structure.
Flux - A substance which promotes the melting of silica in a glaze.
Foot - The base of a ceramic piece.
Fusion Point - The temperature at which a clay or glaze material melts.
Glaze - A glass-like coating fusion bonded to a ceramic surface by heat.
Glaze Fire - A cycle during which glaze materials are heated sufficiently to melt and form a glassy surface coating when cooled.
Greenware - Unfired clay objects.
Grog - Fired clay that has been crushed into granules which may be added to a clay body to increase strength, control drying and reduce shrinkage.
High Relief - A strongly raised or deeply carved pattern.
Impressing - Method of decorating by stamping into a clay surface.
Incising - Engraving a decoration into unfired clay.
Kaolin - A white firing, highly refractory primary clay. Kaolin, meaning “high hill”, probably refers to Kaoling, the mountain in China where this white clay was first discovered.
Kiln - A furnace for firing ceramic products.
Kiln Furniture - Refractory shelves, posts and other equipment placed in a kiln to hold ware during firing.
Kiln Wash - A refractory mixture, usually of kaolin and flint, which is applied to the kiln shelves and floor to prevent fired glaze from adhering to them.
Kneading - Working clay on a surface with the palms of the hands in order to remove air from it and obtain a uniform consistency.
Leather Hard - The condition of raw clay ware when most of the moisture has evaporated leaving it still soft enough to be carved or joined to other pieces.
Mold - A plaster or bisqued clay shape from which a clay form can be reproduced.
Once Fire and Single Fire - A slow firing cycle which combines both bisque and glaze firings.
Overglaze - Glaze decoration applied on the surface of a fired glaze, which is then refired.
Peeling - Separation of the fired glaze or slip from a clay surface because the clay has contracted more than the glaze.
Pinholing - Tiny holes which appear in a fired glaze, often caused by poor clay preparation, improper glaze application or incorrect firing.
Pins - Refractory supports used to place ware in racks for firing.
Plaster of Paris - Calcined hydrated calcium sulfate, or gypsum, used in ceramics to make molds and bats.
Plasticity - The quality of clay that allows it to be easily manipulated and still maintain its shape.
Porcelain - A strong, vitreous, translucent, white clay body that matures at cone 12 or above.
Porosity - The capacity of a clay body to absorb moisture.
Pressing - The forming of clay objects by squeezing soft clay between two halves of a mold.
Pyrometer - A bi-metallic strip which translates heat energy into electrical energy used to indicate the temperature in a kiln.
Refractory - The quality of resistance to high temperatures. Also, high aluminasilica material used in the manufacture of kiln furniture and interiors.
Rib - A hand held tool made of hard material used to shape a pot when throwing.
Sagging - The slumping of a form while the plastic clay is still soft.
Sedimentary Clay - Clay that has been transported from its original site by water, air or ice and deposited in layers elsewhere.
Sgraffito - A decorative process by which a line is scratched through a layer of slip or glaze before firing to expose the clay body beneath. From the Italian, meaning “scratched out”.
Short - Clay that is nonplastic and breaks and crumbles easily.
Shrinkage - Contraction of the clay or glaze in either drying or firing.
Single Fire - See “once fire”.
Slake - To pour dry material into liquid and allow it to absorb the liquid to its fullest capacity.
Slip - A suspension of clay or glaze materials in water.
Slip Trailing - A decorating method which uses a syringe to apply slip to a clay surface.
Slurry - A creamy mixture of clay and water.
Spurs - Triangular refractory supports which keep glazed ware from touching kiln shelves during firing.
Spyhole - The opening in a kiln wall or door through which cones may be viewed during firing. Can also act as a steam vent during the early stages of firing.
Stilt - A ceramic tripod used to support glazed ware in a kiln during firing.
Stoneware - A grey to buff, nontranslucent clay body which matures between 6 and 10 cones.
Terra Cotta - A brownish-orange earthenware clay body, commonly used for ceramic sculpture or architectural ornament. From the Italian, meaning “baked earth”.
Throw or Throwing - Using the potter's wheel to make forms by hand from plastic clay.
Trimming - A method of paring away excess clay, usually from the bottom of pot to form a foot, while the clay is leather hard.
Underglaze - A colored decoration applied on raw or bisque ware before the glaze is applied.
Vitreous - The hard, glassy and nonabsorbent quality of a clay body or glaze. Vitrify or Vitrification - To fire to the temperature at which a clay or glaze attains its mature, hard, glass-like quality.
Wedge or Wedging - Mixing and de-airing clay by cutting it diagonally and slamming the pieces together.
Wheel Head - The turning disk or a potter's wheel on which the clay is thrown or worked.