Stoneware Clay

What it is

Stoneware is the default body for most studio potters, and for good reason. It is plastic enough to centre quickly, strong enough to hold a tall wall without slumping, and it fires to a dense, vitrified matrix that resists chipping and water absorption. A typical stoneware contains ball clay for plasticity, kaolin for refractoriness, feldspar as a flux and silica as a filler.

The single most useful number to know about any stoneware is its total shrinkage, because it determines the size of everything you make. Most mid-fire stonewares shrink 10–13% from wet to fired; high-fire bodies sit at the lower end, heavily grogged sculptural bodies at the higher end. Always confirm the figure against the supplier datasheet rather than a general rule of thumb.

Stoneware comes in three broad temperaments. Smooth bodies are best for throwing and fine surface detail. Sanded or grogged bodies open up for hand-building and large forms because the grog gives the wall internal structure and reduces cracking. Speckled bodies contain iron-bearing granules that bloom through the glaze as dark freckles at cone 6 and above.

How to use it well

• Buy one body and use it exclusively for at least three months before switching — consistency teaches you faster than variety.
• Store opened bags in a sealed bin with a damp sponge to stop the outer layer from crusting.
• Test every new batch: throw three small cylinders, measure wet dimensions, then re-measure after bisque and glaze firing to confirm the actual shrinkage.
• Wedge by hand for small amounts; run anything over about 5 kg through a pug mill or wire it into slabs first.

Safety notes

• Dry clay and glaze dust contain respirable crystalline silica. Never sweep dry — wet-mop and sponge instead.
• Wear an N95 or P100 respirator when handling dry powder, mixing bodies or emptying the reclaim bin.
• Keep clay out of sinks and floor drains; it sets hard and blocks plumbing.

Compatible materials

Clay bodies

• This is a clay body — compare with porcelain, earthenware and raku bodies

Glazes & surface

• Cone 6 oxidation and reduction glazes
• Floating blue and tenmoku iron glazes
• Satin matte white and clear liner glazes

Where it sits in the process

Preparing and homogenising clay before forming.

Wedging  Clay & Preparation  Entry tier

Browse every tool in this stage from the Clay & Preparation category.