Ash: Wood ash, Coal ash or plan ash used as the fluxing agent in a glaze. Ash has a high silica content and when combined with clay forms a simple stoneware glaze.
Ball Clay: Clay used for high firing. Has high plasticity and is pale in color. Used as an ingredient in throwing clay as well as other clay bodies and glazes.
Banding Wheel: A round flat disk that spins freely on a base. Used to manually turn pieces while constructing them or decorating them.
Bat: A plaster or wooden disk used when throwing pots on the wheel and allows you to remove the disk from the wheel without moving the pot.
Bisque: First low-temperature firing. Usually between 1562 and 1832 degrees F (850 – 1000 C) Clay has porosity but is converted to a irreversible state called “pot”.
Bisque Ware: Term used for Ceramics that has been bisque fired.
Body: A term used to describe a particular mixture of clay – such as a stoneware body or a porcelain body.
Bone China: A clay body with bone ash in the recipe.
Coiling: A type of Ceramic Handbuilding Technique that uses coils or small ropes of clay attached together in a circular formation to create a desired shape.
Cones/Pyrometric Cones: Cone shapes about 1.5 inches tall made out of glazes that are designed to melt at a designated temperature. A set of cones of gradual melting temperatures leading up to and including the desired temperature are set in a place visible through a peak hole in the kiln to manually gauge the temperature reached inside the kiln.
Colorants: Oxides added to the base glaze recipe to give color. Includes oxides of copper, cobalt, chrome and others.
Earthenware: Pottery fired to low temperatures. Commonly seen in red terracotta ceramic pots used for plants or flowers. The body remains porous and requires glaze if it is to be used for water or food.
Elements: The metal heating coils in a electric kiln.
Firing: The process by which ceramic ware is heated in a kiln to bring glaze or clay to maturity.
Foot: The base of a piece of pottery on which it sits.
Glaze: A glass layer or coating that fuses to a clay piece during firing.
Glaze Base: The glaze recipe without any colorants, opacifiers, or suspenders.
Green ware: An unfired piece of clay. A Ceramic piece at this stage is very fragile and breaks or chips very easily.
Grog: A material added to clay to lessen warping and increase its resistance to thermal shock. Usually clay that has been heated to a high temperature and then ground up.
Leather-hard: A stage of clay during the drying process. Referring to the similarity to leather the clay is not hard but can be handled and still hold its shape. Stage when slabs of clay can be attached together, they are dry enough to hold the shape but still wet enough to fuse pieces together.
Non-Plastic: A drying stage of clay where it cannot be molded without breaking.
Plastic Clay: Clay that can be manipulated but is not too wet to hold its shape.
Porcelain: A white clay body with a high kaolin content. Low plasticity makes it difficult to work with but can be fired as high as 2552F (1400C) and when fired it has a highly desirable translucent body.
Rate of Firing: How fast a kiln is heating up.
Recipe: The list and quantities of ingredients used in a glaze or clay body.
Resist: Wax, latex, or paper is used to prevent slip or glaze from sticking to that surface of the pottery.
Ribs: Tools, that at one time were made out of ribs, that were used to lift the walls of thrown pots or to smooth and compact clay surfaces. Wooden and plastic ones of different shapes may be purchased but flat smooth rocks or shells or other things found in nature can also be used. Some are kidney shaped and referred to as kidneys.
Scrapers: Thin metal or plastic tools used to refine the clay surface. They come in many shapes and are sometimes referred to as ribs.
Scraffito: A decorative technique where by cutting or scratching through an outer layer of slip, glaze or engobe a different colored clay body is exposed. From the Italian word graffito, meaning to scratch.
Shrinkage: Reduction of size of a clay piece as it dries or is fired. In High Fire Stoneware
total shrinkage can be as much as 20%.
Silica: The primary glass-former in glazes; synonymous with flint, quartz, and silicon dioxide.
Single Fired: The making, glazing, and firing of pottery in a single operation.
Slab Building: Handbuilding technique where potter is constructed from flat slabs of clay.
Slip: A liquid mixture of clay and water. Slip is used to connect pieces of clay in hand building and can also have a colorant mixed with it to be used for surface decoration. Slip is also used in slip casting where a porous mold is used, (such as molds made with plaster). Slip is poured into the mold and the moisture is absorbed by the mold and the piece can removed when reaching the leather hard stage.
Stains: Coloring pigment used to decorate pottery or a pigment used to add color to glazes or clay bodies.
Stilts: Small shapes of bisque clay or sometimes metal or wire spurs used for supporting glazed pottery during firing. Used to keep glaze from fusing to the kiln shelf and allows for glaze to be applied to the bottom of bisque ware. Typically not used with High Fire pots as the glaze is more likely to run. Instead glaze is not applied on the bottom or near the bottom of high fire stoneware.
Stoneware: Vitrified clay usually fired above 2190F (1200C).
Terracotta: An iron-bearing earthenware clay that matures at a low temperature and fires an earth-red color.
Terra sigillata: A very fine slip used as a surface coating for burnishing or other surface decorations.
Throwing: Wedged and prepared clay is placed on a rotating potters wheel and formed into a symmetrical container shape by using hands and tools while the clay is turning in circles at various controlled speeds.
Trimming: After throwing a pot on a potters wheel it is inverted and placed back on the wheel when it is in its leather hard stage and it is centered and attached (with wetter clay) and excess clay is trimmed off and a foot is formed by using tools while the piece is turning.
Underglaze: A color usually applied to bisque-fired pottery and in most cases is covered with a glaze. A medium is used such as gum Arabic to adhere the color to bisque and then it needs to be fired before glazing.
Viscosity: The stiffness of a liquid or glaze, resistance to flowing or running.
Vitreous: A glassy, non-porous state.
Vitrification: Process by which clay materials bond to become dense, impervious and glassified during the hottest part of firing. The vitrification point is the temperature in which a clay can be fired to without melting or losing its shape. The resulting pots are hard and durable.
Wedging: Method of preparing clay by hand to evenly mix the clay and remove air. Compares to kneading bread dough except done as to not create air pockets or bubbles. There are different types of wedging but the spiral technique is advantageous for clay used for throwing. * See Wedging Techniques.
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