Ball clay is a very fine-grained, highly plastic sedimentary clay added to clay bodies and glazes for workability and strength. It usually fires a light cream or off-white colour and rarely gets used on its own because it shrinks a lot.
What Is Ball Clay?
Ball clay gets its name from the old practice of cutting it into balls for transport. Its tiny particle size is what makes it so plastic, and that plasticity is why clay suppliers blend it into throwing bodies, especially porcelains and white stonewares that would otherwise be short and hard to work.
On its own, ball clay is too sticky and shrinks too much to make pots, and it can contain organic matter and fine carbon that need to burn out in the bisque. Mixed with kaolin, feldspar and silica, it gives a body the plasticity and dry strength that let thrown and hand-built work survive handling before the firing.
In glazes, a little ball clay helps keep the glaze suspended in the bucket and makes the dried coat stronger. Too much can make a glaze shrink and crack as it dries, which can lead to crawling. Most potters meet ball clay as an ingredient on a recipe or a clay data sheet rather than as something they use directly.
This pottery glossary entry from Le Studio Art Space is general educational content. Always follow the clay, glaze and kiln makers’ data for your own materials and equipment.