Glossary of Ceramic Terms for Pottery and Ceramics

This glossary is a practical reference for beginners, hobby potters, and ceramic artists who want clear explanations without digging through forum threads or overly technical definitions. Use it to quickly look up pottery vocabulary, understand studio jargon, and jump to deeper Bay of Clay guides where a topic deserves more than a short definition.

How to use this page: linked terms open a fuller guide when Bay of Clay has a strong standalone explanation. Unlinked terms stay here as quick-reference definitions so the glossary remains useful without sending you in circles.

Start with these pottery basics

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A • B • C • D • E • F • G • H • I • K • L • M • O • P • R • S • T • V • W

A

Absorbency — Absorbency is how readily a ceramic material takes in water through its pores. In pottery, it matters most when ware is still porous—especially at the bisque stage—because that helps glaze coat the piece evenly before the final firing. A material may have high porosity in structure, but its actual absorbency depends on how open those pores still are after firing.

B

Bisque — Bisque is pottery that has been fired once without glaze. In the usual sequence, a piece moves from greenware to bisque and only then to glaze firing. That first firing hardens the clay for safer handling while still leaving enough absorbency for glaze to stick evenly before the final firing.

Black core — Black core is a firing defect in which the inside of a clay body stays dark because carbon and other materials did not fully burn out. It is usually a sign that the piece was fired too fast, too thick, or without enough oxygen for complete burnout.

Blackhard — Blackhard is a late drying stage between leatherhard and fully dry whitehard. At this point the piece feels rigid and can no longer be meaningfully reshaped, but it still holds enough moisture to look darker than bone-dry clay. Potters usually treat blackhard ware as a stage for careful handling rather than further forming.

Bone china — Bone china is a type of ceramic body developed in 18th-century Britain to replicate the translucency of Chinese porcelain. It is made using bone ash as a key ingredient, which gives it strength, whiteness, and translucency, making it especially popular for fine tableware.

Burnishing — Burnishing is a surface-finishing technique in which leatherhard or nearly dry clay is rubbed with a smooth hard tool such as a stone, spoon, or polished rib. This compresses the surface and creates a soft sheen without glaze, which is why it is often used on low-fired or decorative work.

C

Casting slip — Casting slip is a carefully formulated liquid clay body used in slip casting. It is poured into a porous mold, which absorbs water from the outer layer and leaves a clay wall behind. Once the desired thickness forms, the extra slip is poured out and the piece is removed after it stiffens.

Ceramic — The term ceramic comes from the Greek word keramos , meaning clay. In pottery and ceramics, it refers to objects made from clay that are permanently hardened through the use of heat during firing.

Ceramic change — Ceramic change is the permanent transformation that happens when clay is fired and stops being ordinary unfired earth. As heat rises in the kiln, the clay loses chemical water and undergoes irreversible changes that turn it into ceramic, which is why fired pottery cannot simply be turned back into workable clay again.

Cheesehard — Cheesehard is an early drying stage when clay is firmer than freshly made work but still soft enough to bend, stretch, and adjust easily. In the usual sequence, it comes before leatherhard, when the piece still has enough softness for gentle shaping but is starting to hold itself more reliably.

China — China is a common tableware term for fine white ceramic dishes and serving pieces. In everyday use it often overlaps with porcelain or bone china, though the exact meaning can vary by region, product line, or how strictly someone is using ceramic terminology.

Clay — Clay is the basic raw material of pottery. Its fine particles give it plasticity when wet, which makes shaping possible. In studio practice, potters usually work not with raw clay alone but with a formulated clay body designed for a certain kind of forming, firing, and glaze use.

Clay body — A clay body is a prepared blend of clays and other materials chosen to work a certain way in making and firing. It builds on raw clay by adding or balancing qualities such as strength, texture, shrinkage, firing range, and glaze fit. Materials like grog may be added to change how the body handles and dries.

Coiling — Coiling is a hand-building method in which long rolled ropes of clay are stacked and joined to build a form upward. Compared with slab building, it is often better for rounded forms, and compared with pinching, it allows larger or taller pieces to be built more gradually. The joined coils may be smoothed away or left visible as part of the design.

Cones — Ceramic cones are small indicators that bend when a kiln has received a certain amount of heatwork. Potters use them because firing results depend on both heat and time, not just a temperature number, which is why cones help verify what really happened inside the kiln.

Contraction — Contraction is the temporary decrease in size that happens as clay, glaze, or kiln furniture cools after heating. Unlike shrinkage, which is a permanent change, contraction is part of normal heating-and-cooling movement and matters because different materials may contract at different rates.

Crazing — Crazing is a network of fine cracks that appears in a glaze after firing because the glaze fit is off and the surface ends up under tension. It is one of the most common glaze-fit problems. Sometimes potters use it intentionally as a crackle effect, but on functional ware it is usually treated as a defect because it can affect durability and cleanability.

D

Decorative — In ceramics, decorative describes work made mainly for visual impact rather than everyday use. That can include sculptural pieces, display vessels, wall work, or pottery forms whose main purpose is ornament rather than food or household use. Surface choices such as majolica decoration or metallic lusters often fall into this decorative side of ceramics.

Dunting — Dunting is cracking caused by thermal stress during heating or cooling, often when a piece changes temperature too quickly. It commonly shows up as clean cracks in bisque or glazed ware and is often linked to uneven thickness, rapid cooling, or stress around quartz inversion points in the firing cycle.

E

Earthenware — Earthenware is a low-fired clay body that remains more porous than stoneware or porcelain. It is often used for decorative work and for glazed functional pieces when properly made and sealed. Compared with higher-fired clay bodies, it usually matures at lower temperatures and stays more open in structure.

F

Firing — Firing is the kiln process that turns dried clay into ceramic and matures glaze. In a basic pottery sequence, the first firing creates bisque and a later firing finishes the glazed piece. Temperature, timing, cooling, and atmosphere all shape how the clay body and glaze behave together.

Flameware — Flameware is ceramic ware made to handle direct flame or stovetop heat, which requires special clay bodies and careful design. It is more thermally shock resistant than ordinary ovenware, but it still depends on proper materials and use to avoid cracking.

Frit — A frit is a pre-melted and ground mixture of glaze materials used in ceramic glaze formulation. The fritting process reduces the solubility and potential toxicity of raw glaze ingredients by binding them together, making glazes safer and more stable to use.

G

Glaze — Glaze is a glass-like coating that melts onto a ceramic surface during firing. Potters use glaze for color, surface character, and function: it can decorate a piece, help seal the surface, and change how porous or absorbent the finished ware remains.

Glaze fit — Glaze fit describes how well a glaze and clay body move together after firing and cooling. If they expand or contract at mismatched rates, defects can appear. Crazing happens when the glaze is under tension and develops fine cracks, while shivering happens when the glaze is under too much compression and flakes or peels away. Good glaze fit matters for both durability and food-safe performance.

Greenware — Greenware is any unfired pottery after forming and drying but before its first trip through the kiln. In practical terms, it sits between making and bisque firing. It is stronger than wet clay, but still fragile enough that careless drying or handling can ruin a piece before firing ever begins.

Grog — Grog is crushed pre-fired clay added to a clay body to change how that body handles. It adds tooth, reduces shrinkage, improves drying strength, and helps larger or thicker work resist cracking. That is why grogged clay bodies are often chosen for hand building, sculpture, and other forms where strength matters more than silky smooth texture.

H

Hand building — Hand building is pottery made without using a potter’s wheel. Instead of throwing, the form is built directly by hand using methods such as coiling, slab building, and pinching. These techniques connect closely because they are all different ways of controlling shape and thickness without wheel rotation.

High-temperature glaze — A high-temperature glaze is formulated to mature in hotter firings, often in the upper stoneware or porcelain range. These glazes are usually valued for durability and depth of surface, but they need a compatible clay body and firing schedule to work well.

I

Intermediate glaze — An intermediate glaze matures in the mid-range between low-fire and high-fire temperatures. Many studio potters like this range because it can produce strong functional ware while still offering a wide mix of colors and surfaces without the extremes of very low or very high firing.

K

Kiln — A kiln is the high-heat chamber used to fire pottery. By controlling temperature, atmosphere, and timing, the kiln transforms fragile greenware into bisque and then into finished ceramic. It is the tool that makes both clay maturity and glaze results possible.

L

Lead — Lead is a glaze ingredient that was historically used as a flux to help glazes melt at lower temperatures. Because lead can leach from unstable surfaces and create serious food-safety risks, it is treated with great caution and is generally avoided in modern functional pottery.

Leatherhard — Leatherhard is the working stage between softer drying states such as cheesehard and later rigid stages such as blackhard and whitehard. The clay is firm enough to hold its shape but still soft enough to trim, carve, join, or refine, which is why handles, attachments, and surface details are often added at this point.

Low-temperature glaze — A low-temperature glaze matures in low-fire ranges, often below cone 1 and commonly around cone 06–01. These glazes can produce bright color and smooth surfaces, but they are often less durable than mid-range or high-fire glazes, which matters when choosing them for functional ware.

Lusters — Lusters are decorative metallic finishes applied over an already glazed and fired ceramic surface, usually in a later low-temperature firing. They are used for visual effect rather than strength or durability, which is why they belong more to decorative surface treatment than to everyday functional ware.

M

Majolica — Majolica usually refers to brightly colored tin-glazed earthenware decorated over a white opaque glaze surface. It sits in a decorative tradition where color, painted surface, and white glaze ground matter as much as the clay body itself, which is why the term is often discussed alongside decorative glaze finishes and surface treatments.

O

Ovenware — Ovenware refers to ceramic pieces meant to be used in an oven, such as baking dishes or casserole forms. These pieces are made from clay bodies and designs that can handle gradual heating, but unlike flameware, they are not intended for direct contact with a burner or open flame.

Oxidation — Oxidation is a kiln atmosphere with enough oxygen present for materials in the clay and glaze to burn and react fully. Potters often contrast oxidation with reduction, where oxygen is limited and materials react differently. That difference can noticeably change glaze color, clay appearance, and defect behavior even at similar firing temperatures.

P

Pinching — Pinching is the most direct hand-building method: a form is made by pressing and thinning a ball of clay with the fingers. Compared with coiling or slab work, it is simpler and usually better suited to smaller forms, which is why many beginners first learn shape, wall thickness, and moisture control through pinch pots.

Porcelain — Porcelain is a high-fired ceramic material known for its whiteness, smoothness, strength, and translucency when thin. Compared with stoneware and earthenware, it is usually finer and less forgiving to work with, but it can produce especially refined finished surfaces.

Porosity — Porosity refers to how many tiny open spaces exist inside a ceramic body. Those pores affect strength, durability, and how much water a piece can potentially hold. In simple terms, porosity describes the structure of the body, while absorbency describes how much water that porous structure actually takes in.

Pottery — Pottery usually refers to clay-made ceramic objects such as bowls, mugs, plates, vases, and planters. The word is often used broadly in everyday speech, but in a narrower sense it usually points to formed vessels and functional wares rather than every kind of ceramic object.

Potter’s wheel — A potter’s wheel is a rotating device used to shape clay into symmetrical ceramic forms such as bowls, cups, and vessels. Clay is centered on the wheel and formed as it spins, a process known as throwing.

R

Raku — Raku refers to a low-fire ceramic process in which pottery is removed from the kiln while still hot and placed into combustible materials. This rapid cooling and reduction create unpredictable surface effects, making each raku piece visually unique.

S

Salt glaze — Salt glaze is a ceramic firing technique in which salt is introduced into a hot kiln, causing sodium vapor to react with the silica and alumina in the clay body. This process produces a distinctive, durable, orange-peel textured surface on the pottery.

Shrinkage — Shrinkage refers to the permanent reduction in size that occurs as clay dries and is fired. Unlike expansion and contraction, which are caused by temperature changes and are reversible, shrinkage happens only during drying and firing and cannot be reversed.

Slab — A slab is a flat sheet of clay used in slab building. Compared with coiling or pinching, slab work is especially useful for straight lines, flat planes, and angular forms such as boxes, trays, and constructed mugs. Potters roll or press the clay into even sheets, then cut and join those pieces into the final form.

Slip — Slip is liquid clay mixed with water, sometimes with added colorants. Potters use it to join clay pieces together, decorate surfaces, alter texture, or pour into molds during casting. Because it is made from clay rather than glue, slip helps attachments bond more naturally when used at the right moisture stage.

Stoneware — Stoneware is a high-fired pottery material known for strength, durability, and relatively low porosity. Compared with earthenware it usually fires denser and harder, while compared with porcelain it is often easier to manage in everyday studio use. That balance is why it is so common for functional ware.

T

Temperature — Temperature in ceramics refers to the level of heat reached during firing, but potters usually think about it together with time and heatwork. Temperature affects clay maturity, glaze behavior, color response, strength, and porosity, which is why even small changes can noticeably alter the result.

Throwing (wheel-thrown) — Throwing is the process of shaping clay on a rotating potter’s wheel. After centering the clay, the potter opens it, pulls the walls, and forms the shape as the wheel spins. Wheel-thrown work is especially associated with round, symmetrical forms such as bowls, cups, and vases.

V

Vitrification — Vitrification is the stage in firing where a clay body becomes denser and less porous as its materials begin to fuse together. As vitrification increases, the ceramic usually becomes stronger and less absorbent, though too much heat can also lead to warping or slumping if the clay body is pushed past its safe range.

W

Ware — Ware is a general pottery term for ceramic objects or product types. Potters and ceramic suppliers often use it to group pieces by use or style, as in dinnerware, ovenware, stoneware, or decorative ware.

Wedging — Wedging is a clay preparation method similar to kneading dough. Potters wedge clay to even out moisture, align texture, and reduce trapped air before forming. Good wedging makes clay more consistent and easier to work with, especially before wheel throwing or when joining several pieces together.

Whitehard — Whitehard is the fully dry stage just before a piece is ready for the kiln. At this point the clay has lost its free moisture, usually looks lighter in color, and feels chalky or room-temperature cool rather than damp. Because it is completely dry, it is also very fragile and must be handled carefully before firing.