Clay Basics

Grog

A ceramic material formed by the high-temperature firing of a refractory clay, after which it is crushed and graded to size. Used as a non-plastic component of some clay bodies.

Glazeware

A ceramic piece that has had glaze applied and has gone through the second firing process.

Score and Slip

A method of joining two pieces of clay together. First, score the clay; this means that you make scratches in the surfaces that will be sticking together. Then you slip it; that is you wet the surface with some slip, using it like glue. Next, you press the two pieces together.

Clay

A natural earthy material that is plastic when wet, consisting essentially of a compound of alumina and silica chemically combined with water.

Stoneware

A relatively highly fired vitreous or semivitreous ceramic material. Traditionally made primarily from nonrefractory fire clay.

Porcelain

A vitreous ceramic material. Traditionally considered to be white and if, of thin section, translucent.

Fired

After your pottery has been Bisqued, it needs to be fired again. There are lots of different types of final firing.

Primary Clay

Clay found in close proximity to its parent rock source.

Earthenware

Clay most commonly found in nature, and is the raw material used to make tiles, bricks, and most pottery products found across the globe. Earthenware is generally porous, meaning it is not usually water tight. Fires at temperatures of 1300 to 2120° F. and is often brown or red in color.

Bisqueware

Clay that has gone through the first firing.

Raw Clay

Dirt that doesn't have anything growing on it.

Slip

Liquid mixture of clay and water applied over surface of vessel to affect color and texture.

Vitreous

Pertaining to the hard finish of a fired glaze, or the nonabsorbency of a fired body.

Ceramics

Pots and other articles made from clay hardened by heat.

Plasticity

Quality of clay that allows it to be manipulated and still maintain its shape without cracking.

Absorbance

The ability of a material to soak up water.

Leather Hard

The condition of a clay or clay body when it has been partially dried to the point where all shrinkage has been completed.

Bone Dry

The final stage of greenware dried to a completely dry state and ready to be fired. In this stage, the clay is very fragile, non-plastic and porous.

Firing

The process of heating pottery in a kiln to bring the glaze or clay body to maturity.

Plastic

This is the stage of clay that most of the work is done, like throwing it on the wheel. Plastic clay is soft and easily workable.

Porosity

Tiny pores in the clay to allow the escape of water during drying and firing

Terra Cotta

Type of earthenware where the fired body is porous which means it can be penetrated by water.

Greenware

Unfired clay articles.