Pottery Glossary

Definitions of common pottery terms

Bas-relief: a decorative method in pottery and sculpture in which figures or forms project only slightly from the surrounding surface. In bas relief or low relief, figures are not undercut to become three-dimensional.

Bat: a pottery bat is a flat disc that can be attached to the head of a potter's wheel, making it easier to throw and lift off larger pieces. Bats are made from wood, plaster of Paris, and plastic. Not all pottery bats are throwing bats. Square or rectangular bats are used for wedging and drying clay.

Band/banding wheel: a band is a lateral decorative area or glaze encircling a pottery vessel. Bands are applied using a hand-operated revolving banding wheel, which is a turntable on a pedestal base.

Bisque: Bisqueware is unglazed, air-dried (aka bone dry) greenware that has been bisque fired, or fired once, to a temperature preceding vitrification. Bisque is usually pink or flesh-tinted, and was historically used to make dolls and doll heads. Bisque can also be glazed and then fired again.

Burnishing: burnishing is polishing the surface of leather-hard, unfired clay with a hard, smooth object such as a stone or piece of metal. Burnished clay is shiny.

Celadon: celadon refers both to ceramics of a bluish/pale sea-green color and the Chinese and Korean porcelain and stoneware from which this type of ware originated. The term "celadon," however, originated in 17th century France.

Ceramics: the word ceramics derives from the Greek keramikos, meaning "of pottery." It can refer to the craft of making decorative and/or functional objects from fire-hardened clay, or to the objects themselves. Ceramics is a broader term than pottery, as it also refers to porcelain and other objects made from materials that permanently change when heated.

Chuck: chucks are hollow, open-ended cylinders of varying size that are used to support an upside-down pot on the potter's wheel so that the pot bottom can be easily trimmed - a task that's often overlooked by beginning or less skillful potters.

Clay/clay body: clay is a sedimentary byproduct of weathered rocks. Malleable when moist, it consists of small particles of alumina and silica. There are three primary clay groups - kaolinite, smectite, and illite - and about 30 different types of so-called "pure" clay. However, clay is usually a mix of different types of clay. The clay body that a potter works with, i.e. the clay mixture, will usually contain additives that alter color, plasticity, and/or firing temperature.

Coil/coiling: coiling is a method of making pottery without a potter's wheel. Clay is rolled by hand into a coil or serpentine shape, which is then joined to form a circle. Successive coils are added on top of one another in layers in order to form a vessel or cylinder, i.e. composite pots.

Cones or pyrometric cones: pyrometric cones are pyramidal objects designed to bend or melt at a precise temperature within a kiln as it's firing (or to cut power in electric kilns). A three-cone system or cone pack features a firing, guide, and guard cone. Pottery cones are numbered from 022 (coolest) to 42 (hottest), e.g. bisque firing is usually done between cones 08 and 06, equivalent to a temperature range of 1720 degrees Fahrenheit to 1835 degrees Fahrenheit.

Crazing/crackling: crackling or crazing refers to the forming of very fine cracks in the glaze of a fired pot. This occurs during the cooling process because, if not properly matched with the clay body, the glaze shrinks more than the clay as it changes from a liquid to a solid state. Crackling is done intentionally to create decorative rather than functional pottery. Crackling is especially common in Raku pottery.

Earthenware: earthenware is pottery that was fired at a low temperature - anywhere from 900 degrees Fahrenheit to 2150 degrees Fahrenheit, depending on the clay. Beginning potters often work with earthenware because its blend of materials - quartz, kaolin, ball clay, and feldspar - is inexpensive and easier to work with than finer clays. Earthenware is porous and colorful.

Electric kiln: electric kilns offer several advantages over fuel-burning kilns. They're easy and safe to operate, and they offer uniform firing results. On the down side, the oxygen-rich atmosphere makes reduction firing (firing with reduced oxygen) less practical.

Enameling kiln: enameling kilns are small tabletop kilns used for glaze testing or decorating jewelry, glass, metal, or pottery. Enameling is the application of a hard and glossy decorative or protective coating, usually translucent glass, that fuses with its substrate when fired in an enameling kiln.

Engobe: a colored clay slip applied to greenware or leather-hard clay bodies, usually before bisque firing, in order to add texture, color, and background or to prepare the surface for additional decorating.

Fire/firing: firing is the process of heating clay within a pottery kiln. Firing hardens the clay and gives it a permanent shape. Different types of clay mature at different temperature ranges and are thus known as low-fire or high-fire clays. Sometimes firing is done twice, once without glaze (bisque firing) and once with glaze (glaze firing).

Giffin grip: a Giffin grip is a device that attaches to a pottery wheel and uses three holders to keep a pot centered during bottom trimming.

Glass kiln: unlike most pottery kilns, glass kilns have heating elements in the lid. This combination of top firing and side firing provides more even heating for glass objects, which tend to be more horizontal than pottery. A glass kiln also provides slower cooling, which is necessary for the glass to anneal and become less brittle.

Glaze: a glaze is a functional or decorative coating applied to the surface of pottery that becomes glass during firing. Glazing can be done to waterproof pottery or to add color or texture. Different visual effects are achieved with gloss, matte, or opaque glazes, or by adding an overglaze or underglaze.

Glaze firing: glaze firing is when clay is fired in a pottery kiln after the application of a glaze. Glaze firing is usually the second firing and takes place after bisque firing.

Greenware: greenware is the term for pottery that has been shaped on a pottery wheel but not yet fired in a pottery kiln. Greenware must be air dried before firing. Bone dry greenware is ready for firing but extremely fragile. The stages of the greenware drying process are wet, damp, soft leather hard, leather hard, stiff leather hard, dry, and bone dry.

Kiln: a pottery kiln is an insulated furnace or oven in which clay, glass, and other materials are baked or "fired" in order to harden them or give them permanent shape. Most pottery kilns use electricity or natural gas as a fuel source. Specialty kilns are designed for applying enamel, creating glassware, or creating Raku ware.

Leather hard: leather hard is the stage in the clay drying process when pottery is dry enough to be handled but damp enough for trimming, sprigging, or adding other clay pieces, e.g. handles.

Pinch pots: pinch pots are the classic pottery projects for beginners. By pinching, or working clay with one's thumbs, fingers, and palms, one creates a pinch pot - a simple, hollowed-out piece of clay.

Plasticity: plasticity is the more commonly used pottery term for malleability or flexibility. It refers to the ease with which a particular type of clay or clay body can be formed into different shapes without breaking or cracking.

Porcelain: porcelain is a high-fire clay notable for its hard, white, smooth, and sometimes translucent finish. Of the three primary clay types (the other two are earthenware and stoneware), porcelain is the most difficult to work with on pottery wheels.

Potter's wheel: a potter's wheel, aka potter's lathe or pottery wheel, is a machine with a rotating wheel on which a potter shapes or "throws" clay. Pottery wheels can be driven by electricity or by hand power or foot power (the latter are known as kickwheels).

Pug/pug mill: pug is the act of mixing clay, and pug mills are machines that perform this task. Pugmills can be used to create clay recipes, recycle clay, mix it with water, or eliminate air bubbles from clay.

Raku kiln: Raku is a specialized type of pottery in which items are removed from a kiln while still very hot and then quickly subjected to some form of thermal shock, i.e. intense cooling. This process causes small but structurally sustainable cracks in the pottery surface, an effect known as crackling or crazing. Raku kilns are small and designed for easy accessibility to their contents.

Reduction firing: a reduction atmosphere within a pottery kiln is when there isn't enough oxygen to fully consume the fuel. This is done in gas kilns by reducing the draft, but isn't practical in the oxygen-rich atmosphere of electric kilns. Reduction firing results in pottery with unique color characteristics and subtler, earthier, richer colors.

Slip: a clay and water mix that has more clay than engobe but is thinner than slurry. A slip is applied to the surface of greenware. Slips are often used for decorative purposes, but they are also used for casting clay in molds.

Slurry: a slurry is a thick, viscous slip. It's most commonly used as a sort of glue that helps hold handles or other clay pieces in place when added during the leather-hard stage of the drying process. The term slurry is also applied to glaze mixes.

Sprigging: sprigging is the addition of embossed decorations or low-relief ornamentation to leather-hard or bisque-fired pottery. The sprig is created by pressing a slip or moist clay into a mold.

Stoneware: stoneware is a non-porous, high-fire clay that's harder and stronger than earthenware. Stoneware does not require glazing in order to be waterproof. Stoneware contains more clay than porcelain and is opaque rather than translucent.

Vitrification: vitrification is the transformation of a material into glass. In pottery, vitrification refers to the changes undergone by clays and glazes when they're fired in pottery kilns. At a given temperature, the pottery surface will become vitreous, i.e. glossy or glass-like.

Wedging: wedging is the process of kneading, cutting, and rolling clay by hand so that it's homogeneous, i.e. free of air bubbles and having a uniform texture and consistency.