POTTERY GLOSSARY
This is a compilation of terms and definitions commonly used in ceramics that is greatly helping me refine how I communicate with you.
I created this glossary to serve as a guide and to help us understand this unique world we love so much and that inspires us so deeply.
I hope this can be useful to you too. Enjoy!
A
Absorbency: The ability of a clay body to absorb water, impacting the drying and firing processes.
Alumina: A primary ceramic oxide that stiffens melted glazes, improves durability, and controls how a glaze flows during firing.
B
Ball Clay: A fine-grained, highly plastic sedimentary clay added to clay bodies to improve workability and flexibility.
Bat: A flat disk made of wood, plaster, or plastic that attaches to the potter's wheel head so you can throw and move delicate pieces easily.
Bat Pins: Pins used to secure a bat to the potter's wheel, ensuring stability during throwing.
Bentonite: A very plastic swelling clay used in tiny amounts to increase the plasticity of clay bodies or prevent glaze ingredients from settling.
Bisque (Bisque Ware): Pottery that has undergone its first firing in a kiln to harden it into a porous, chalky state ready for glazing.
Bisque Firing: The first firing of clay. It turns greenware into a stronger, porous ceramic piece that is ready to glaze.
Bone Ash: Processed and calcined animal bone used as a key ingredient to create translucent bone china.
Bone China: A type of porcelain that includes bone ash for added strength and whiteness.
Bone-Dry: Completely dry, unfired clay that is light in color, extremely fragile, and ready for its first firing (bisque firing).
Burnishing: Polishing the surface of leather-hard clay to compact it and produce a smooth, shiny surface.
D
Dipping: Immersing pottery in a fluid glaze or slip.
Dry Foot: The unglazed base of a piece. This prevents glaze from sticking the piece to the kiln shelf during firing.
Dunting: Cracking that occurs in ceramic pieces during cooling due to thermal stress.
C
Candling: A slow, low-temperature pre-firing that ensures even drying and prevent defects.
Calipers: An adjustable tool used to measure the inside and outside diameters of pots, ensuring accurate lid fits.
Casting Slip: A liquid clay used in slip casting, a technique for shaping pottery by pouring slip into molds.
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.
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 custom mixture of various clays, fluxes, and fillers blended for specific colors, textures, and firing temperatures.
Coiling: A hand-building technique of rolling out long, snake-like ropes of clay and stacking them layer by layer, then smoothing them together to form walls.
Cone / Pyrometric Cone: A small pyramid made of ceramic materials designed to melt at a specific heat and time combination, measuring the total heat work inside a kiln.
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.
Cut-off Wire: A wire or string with handles used to slice through blocks of clay or cut finished pots off the wheel head.
E
Earthenware: A low-fire clay body that remains more porous after firing. It is often used for terracotta, decorative ware and low-fire glazing.
Engobe: A liquid clay slip containing colorants, applied to leather-hard, bone dry or bisque (according to each manufacturer) pottery for surface decoration.
Extruding: Forcing clay through a mechanical die to produce uniform tubes, strips, or hollow shapes.
F
Feldspar: A rock-forming mineral used as a flux to melt glass and bond ceramic particles together at high temperatures.
Firing: The process of heating clay or glaze to specific temperatures in a kiln to achieve a permanent hard state, transforming them into ceramic material.
Flameware: A type of clay body that can withstand direct heat, used for making cooking pots.
Food Safe: A term used for finished ceramic surfaces considered suitable for contact with food when correctly fired and used as intended.
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.
G
Glaze: A liquid glass-forming coating applied to ceramic ware that melts into a smooth, protective surface during firing. It's 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.
Glazed / Vitrified Ware: Pottery that has been coated in liquid glass-formers and fired a final time, fusing the glaze and making the body dense and waterproof.
Greenware: A general term for any unfired pottery piece, from wet clay to bone-dry.
Grog: Pre-fired clay that has been ground into fine particles and added to a clay body to reduce its shrinkage, warping, cracking and improve its thermal shock resistance.
H
Hand-Building: The process of forming pottery using only your hands and simple tools rather than a wheel, creating pottery using techniques such as pinching, coiling, slab building and sculpting.
High-Temp Glaze / High Fire: Glaze that is formulated to mature at temperatures above 1.201ºC. These glazes are durable and popular in the making of stoneware and porcelain.
K
Kaolin: A pure, white primary clay (china clay) that forms the base of porcelain recipes and fires at high heat.
Kidney (Metal or Rubber): A kidney-shaped scraper made of flexible steel for smoothing thrown pots or rubber for shaping clay.
Kiln: An insulated furnace or oven built specifically for firing clay and glazes at controlled temperatures.
Kiln Wash: A protective refractory coating painted on kiln shelves to catch drips and stop runny glazes from gluing pots permanently to the shelf.
L
Leather-Hard: Partially dry clay that holds its shape, feels like hard cheese or leather, and is ideal for carving, trimming, or joining.
Low Fire: A lower firing temperature range often used for earthenware clay and bright decorative glazes and overglazes.
Lusters: Metallic glazes that give a shiny, iridescent finish to ceramics.
M
Maturing Temperature: The temperature range at which a clay body or glaze reaches its optimum level of strength and solidity.
Mid Fire: A popular firing range for many studio potters, often around Cone 5-6.
N
Needle Tool: A sharp pin set in a handle, used for cutting slabs, trimming rims, popping air bubbles, and measuring the depth of a pot.
O
Ovenware: Pottery formulated to withstand the thermal shocks of oven use.
Overglaze: Decoration applied over an already glazed and fired surface, often requiring an additional lower-temperature firing.
Oxidation: A firing atmosphere with ample oxygen, allowing for bright, vivid glaze colors.
P
Paper Clay: Clay mixed with reconstituted paper pulp or cellulose fibers to increase green strength, reduce shrinkage and make hand-building easier.
Pinch Potting: Pressing the thumb into a ball of clay and pinching the walls between the thumb and fingers to thin them out.
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.
Pottery: General term for pots and other articles made from fired clay.
Potter's Wheel: A motorized or manual rotating disk machine used to shape symmetrical round pots (throwing).
Pug Mill: A heavy machine with internal rotating blades used to mix, crush, and de-air raw clay into an usable, solid column.
Pyrometric Cone / Cones: A small pyramid made of ceramic materials designed to melt at a specific heat and time combination, measuring the total heat work inside a kiln.
R
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 Firing: A firing atmosphere with limited oxygen, often used in fuel-burning kilns to create distinctive clay and glaze effects.
Rib: A flat tool made of wood, metal, or rubber shaped like a kidney bean or the letter D, used to smooth, scrape, and shape clay.
S
Stain: A blend of ceramic oxides and water used to color raw clay, bisque ware or glazes.
Sgraffito: A technique of applying layers of color to leather-hard pottery and then scratching off parts to create contrasting patterns.
Shivering: A glaze fault where small pieces of glaze flake off the clay body, usually caused by poor glaze fit.
Shrinkage: The reduction in size of a clay body due to water loss during drying and firing. Different clay bodies shrink at different rates.
Sieve: A mesh tool used to strain clays and glazes to remove lumps.
Slab Building: A hand-building technique using flat sheets of clay to construct forms.
Slab Roller: A manually or mechanically operated rolling machine used to flatten uniform, wide sheets of clay.
Slip: A liquid suspension of clay and water mixed to a creamy consistency, used for joining, casting, decorating or surface treatment.
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.
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.
Sponge: A natural or synthetic absorbent tool used to apply or remove water from a pot during throwing.
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.
Strips: Flat wooden, plastic or acrylic bars used as a guide to roll out uniform, even clay slabs. They come in matching pairs of various thicknesses (usually ranging from 3mm to 12mm).
T
Tensile Strength: The resistance of a material to breaking under tension.
Throwing: The process of shaping pottery on a potter's wheel.
Trimming: Removing excess clay from a leather-hard piece, often to shape the foot ring or refine the form.
U
Underglaze: A coloured decoration product applied before the piece receives layers of a clear glaze. It is commonly used for painting, drawing and detailed ceramic design.
V
Vitrification: The process of firing pottery to the point where it becomes glass-like and impervious to liquid.
W
Ware: Finished pottery products.
Wax Resist: A wax coating used to prevent glaze from sticking to certain areas, such as the base of a pot or decorative sections.
Wedging: A method of kneading clay to remove air bubbles, even out moisture and prepare it for use.
Wet Clay: Fresh, pliable clay that bends and shapes easily without cracking.
Wheel Throwing: Shaping clay on a rotating potter’s wheel to create bowls, cups, vases and other forms.
REFERENCES
Google Gemini.
Decopot Pottery Supplies.
Nova Scotia Potters Guild.