In the field of ceramics there are a number of terms or words used to describe what may be happening in your work. You may encounter a few of these in the process of troubleshooting glazes, making your pots, or purchasing new tools. Here, we’ll compile a list of the most common ceramic terminologies and their meanings to help in your future searches.
Absorbency
The ability of clay to soak up water, like a sponge.
Bone Dry
Dehydrated, unfired clay that is brittle and cool to the touch.
Bisque Firing
The initial firing after a piece of clay has completely dried, which turns greenware clay into ceramic. This firing usually occurs between cone 010 (approx.. 1657°F) to cone 04 (approx. 1945°F).
Bisqueware
Clay that has undergone a transformative chemical process in which it is heated to a point that it is no longer soluble in water. The piece is now considered ‘ceramic’ at this point.
Ceramic
Clay that has undergone a transformative chemical process in which it is heated to a point that it is no longer soluble in water. The piece is now considered ‘ceramic’ at this point.
Clay
Decomposed rock containing many fine particles of hydrous aluminum, silicates, and other minerals, which is used for brick, tile, and pottery; specifically.
Clay Body
A mixture of two or more clays and minerals combined to obtain a desired color, plasticity, strength, fired density, or other properties.
- Earthenware: Low-fire clay, still porous after firing. Cone range: 04-06.
- Stoneware: Mid-range to high fire clay that vitrifies after cone 5. Cone ranges: 5-10.
- Porcelain: High Fire Clay, vibrant white in color, translucent when thin. Cone range 8-12.
Crazing
A network of cracks on a glazed surface caused by tension during firing. Crazed pieces can harbor bacteria and should not be considered food-safe.
Firing
The process in which clay and glazes are heated to maturity (or at least beyond the point in which they are soluble in water).
Greenware
The process in which clay and glazes are heated to maturity (or at least beyond the point in which they are soluble in water).
Grog
Clay that has been fired and then ground into granules for ore or less fineness. Grog is considered a filler and added to clay bodies to promote even drying, reduce shrinkage, and give stability.
Hand Building
A broad term which describes a variety of methods in which a piece is built by hand, either by pinching, coiling, or slab building.
- Coiling: Creating forms by adding rope-like coils of clay to form the base and walls of the vessel.
- Pinch Pot: A method in which a ball of clay is pressed, pulled, and pinched into a desired shape by the thumb and fingers.
- Slab Method: A method in which the clay is rolled out into sheets of a desired thickness, cut, and joined together using the slip and score method..
Kaolin
A china clay in its purest form.
Leather Hard
The drying stage between wet and bone dry, in which clay has lost some of its water content but remains firm and pliable; the ideal stage for trimming, carving, and adding additions such as handles.
Mature
Clay that has been fired to a tight, hard, serviceable structure.
Plasticity
The quality that allows clay to be stretched, shaped and manipulated.
Shivering
Potentially sharp pieces of glaze that peel, chip, or flake off of the edges of fired pottery. Fired work that was effected by shivering are not considered food-safe and should never be used to hold food or drink.
Short
Non-plastic clay, poor working qualities.
Shrinkage
The decrease in size of a clay object due to drying and firing.
Slake
To moisten dry clay with water.
Slip
Clay that is diluted with water to a point where it can be applied with a brush, like a paint or glue. Slip can be made from the same clay body to join two or more pieces together or colorants can be added for decorative purposes.
Slip Casting
A process in which liquid clay is poured into a plaster mold to take the shape of an object.
Slip and Score
A joining technique where the two edges to be attached are scratched and adhered with a liquid clay (slip).
Thermal Shock
Breakage of a ceramic piece caused by a sudden change in temperature. Each distinct clay body has its own level or resistance to thermal shock.
Vitrification
A glass-like state of consistency, in which the clay has completely hardened and matured.
Wedging
Kneading the clay to make the clay homogenous, to align the particles, and to remove air pockets.
Wheel Throwing
A technique where clay is shaped into forms on a spinning potter’s wheel, allowing for the creation of symmetrical and rounded objects.
