Ceramic and Pottery Glossary of Terms

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Making ceramics can be a fun way to express yourself, and the results can take on many different forms and functions, from beautiful, delicate ceramics that make unique decor to durable and functional thrown pottery that can be used every day. To start learning about the art of ceramics, it's important to understand some common terms you might see as you research, learn, and practice this art form that can truly be enjoyed by anyone.

Absorbency: The ability of a clay body to absorb water, impacting the drying and firing processes

Alumina: A major component of clay used in ceramics that enhances stability and increases the firing temperature

Ball Clay: A highly plastic variety of clay that adds workability and increases strength, used in ceramic formulas

Bat: A flat disc made from wood, plastic, or plaster that attaches to a potter's wheel for throwing pottery

Bat Pins: Pins used to secure a bat to the potter's wheel, ensuring stability during throwing

Bentonite: A type of clay that increases plasticity and strength in a clay mixture

Bisque: Pottery that has been fired once but not yet glazed

Black Core: A defect in fired clay where the center remains black due to incomplete oxidation of carbon within the clay

Blackhard: A stage in drying clay where it has stiffened but is still slightly moist, prior to bisque firing

Bone China: A type of porcelain that includes bone ash for added strength and whiteness

Bone Dry: The condition of clay that is completely dry and ready for bisque firing

Burnishing: Polishing the surface of leatherhard clay to compact it and produce a smooth, shiny surface

Candling: A slow, low-temperature pre-firing that ensures even drying and prevent defects

Casting Slip: A liquid clay used in slip casting, a technique for shaping pottery by pouring slip into molds

Ceramic Change: Permanent chemical and physical changes that occur in clay and glazes when fired

Ceramics: Objects made from clay that are subject to a firing process

Chamois: A type of soft leather used to smooth and compress the rims of wheel-thrown pottery

Cheesehard: Clay that is firm and moist, ideal for carving or sculpting

China Clay: A pure form of clay favored for its whiteness and used in the production of porcelain; also known as kaolin

Chuck: A clay form used to hold pots upside down for trimming on a potter's wheel

Clay: A naturally occurring inorganic material made up of "plate-like" particles that is plastic when wet. It is used to make ceramics.

Clay Body: A mixture or formula of types of clay, minerals, and other additives that is used for pottery

Coiling: A hand-building technique favored for decorative ceramics in which clay is rolled into long strings or strands and coiled to construct pottery

Cones: Pieces of ceramic material used to visually indicate the temperature inside of a kiln. The cones melt at specific temperatures, showing when the ceramics in the kiln have been exposed to the right amount of heat.

Contraction: Non-reversible shrinkage of the clay during drying and firing

Crackle glaze: A decorative glaze that intentionally cracks during cooling to form a cracked pattern

Crawling: A defect caused by uneven glazing or over-glazing where the glaze retracts from the clay during firing, exposing bare clay

Crazing: Fine cracks that appear in the glaze of ceramic wares due to tension between the clay and glaze

Dipping: Immersing pottery in a fluid glaze or slip

Dunting: Cracking that occurs in ceramic pieces during cooling due to thermal stress

Earthenware: A type of clay pottery that has been fired at relatively low temperatures and is porous until glazed

Enamel/On-Glaze Decoration: A type of colorful decorative coating applied to ceramics, often glass-like in appearance

Firing: The process of heating clay or glaze to specific temperatures in a kiln to achieve a permanent hard state

Flameware: A type of clay body that can withstand direct heat, used for making cooking pots

Frit: A combination of glaze materials made by melting, cooling, and grinding glaze into a powder to then be used as part of a glaze formula

Glaze: A glassy coating made of a variety of materials and colorants that are ground and mixed with water, then applied to pottery to seal and decorate the surface

Glaze Fit: The compatibility of a glaze with a clay body

Greenware: Pottery that is going through the drying process and has not yet been fired

Grog: Fired clay that has been ground into particles that are then added to a clay body to reduce its shrinkage and improve its thermal shock resistance

Hand-Building: The process of forming pottery using only your hands and simple tools rather than a wheel

High-Temp Glaze: Glaze that is formulated to mature at temperatures above 2,200 degrees F. These glazes are durable and popular in the making of stoneware and porcelain.

Intermediate Glaze: Glaze that matures at mid-range temperatures, around 1,900 to 2,200 degrees F, and produces more vibrant colors than high-temp glazes

Iron Oxide: A common coloring agent used in clays and glazes to create red, yellow, or black hues

Kaolin/China Clay: A fine, pure white clay used in making high-quality porcelain

Kidney: A kidney-shaped rubber, wooden, or metal tool used to smooth and shape clay

Kiln: A furnace or oven built specifically for firing clay and glazes

Kilnwash: A protective coating applied to kiln shelves to prevent sticking from glazes

Kintsugi/Kintsukuroi: The Japanese art of repairing broken pottery with lacquer dusted or mixed with powdered gold, silver, or platinum

Leatherhard: A stage of drying during which clay is still damp enough to be joined or carved but holds its shape. Artists must work quickly during this very short drying stage.

Low Mid-Range: Ceramic processes that fire to temperatures between earthenware and stoneware

Low-Temp Glaze: Glaze designed to mature at lower temperatures, around 1,900 degrees F or lower

Lusters: Metallic glazes that give a shiny, iridescent finish to ceramics

Maiolica: A type of lead-glazed earthenware characterized by a white surface with brightly colored decoration

Maturing Temperature: The temperature at which a clay body or glaze reaches its optimum level of strength and solidity

Ovenware: Pottery formulated to withstand the thermal shocks of oven use

Oxidation: A firing atmosphere with ample oxygen, allowing for bright, vivid glaze colors

Paper Clay: Clay mixed with cellulose fibers to enhance strength and reduce shrinkage

Pinching: A hand-building technique involving squeezing the clay between the fingers and thumb

Pinholes: Small holes in the fired glaze surface caused by escaping gases during firing

Plasticity: The quality of clay that allows it to be shaped and to retain its shape

Porcelain: A high-fired, glass-like ceramic material known for its strength and translucence

Porosity: The measure of the empty spaces in a material, which affects the clay's absorbency

Potter's Wheel: A machine used in the shaping (throwing) of round ceramics

Pottery: General term for pots and other articles made from fired clay

Production Pottery: Pottery items produced in large quantities

Pug Mill: A machine used to mix and condition clay

Pyrometer: A device used to measure high temperatures in a kiln

Raku: A Japanese pottery firing process that involves removing the piece from the kiln while hot and allowing it to cool in the open air or in combustible materials

Reduction: A firing atmosphere with reduced oxygen, often producing rich, earthy glaze colors

Rib Tool: A flat, rigid tool used to shape, smooth, or scrape clay

Sagger: A ceramic container used to protect or support delicate pottery during firing

Salt Glaze: A glaze formed by introducing salt into a kiln at high temperatures, which vaporizes and forms a glassy coating

Sgraffito: A technique of applying layers of color to leatherhard pottery and then scratching off parts to create contrasting patterns

Shrinkage: The reduction in size of a clay body due to water loss during drying and firing

Sieve: A mesh tool used to strain clays and glazes to remove lumps

Slab: A flat piece of clay that is rolled out and used in hand-building techniques

Slab Roller: A mechanical device used to roll out uniform slabs of clay

Slip: Liquid clay used in decoration or as a bonding agent between pieces of clay

Slip Casting: A technique for forming pottery by pouring slip into a plaster mold

Slump Mold: A form used to support clay in a specific shape during slab construction

Slurry: A thick, creamy mixture of clay and water used in joining clay pieces and for surface decoration

Soaking: A period at the end of a kiln firing where the temperature is held to even out heat and complete the maturation of glazes

Stain: Colored oxides and other compounds used to color clay bodies and glazes

Stilt: A tripod or support used to hold pottery during firing to prevent it from sticking to the kiln shelves

Stoneware: A type of clay body fired to a high temperature that is very strong and dense

Tenmoku: A type of Japanese glaze that is thick, glossy, and dark, typically ranging from black to dark brown, often used in tea ware

Tensile Strength: The resistance of a material to breaking under tension

Thermal Shock: The stress a material undergoes when it experiences sudden changes in temperature

Throwing: The process of shaping pottery on a potter's wheel

Underglaze: Colored decoration applied on unfired clay that can be coated with a transparent glaze

Vitrification: The process of firing pottery to the point where it becomes glass-like and impervious to liquid

Ware: Finished pottery products

Wax Resist: A method of decorating pottery by applying wax to the surface that prevents glaze from adhering

Wedging: A method of kneading clay to remove air bubbles and prepare it for use

Whitehard: A stage of clay that is dried to a point where it is nearly as hard as bone dry but can still be carved

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