Why I Create My Own High Fire Clay Bodies, Part 1

David Terret Beumée


Mine is the journey of an artist, always seeking new beginnings. It is my desire at this time to share with students what I’ve learned in nearly five decades of potting and art-making.

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Working with Porcelain and White Stoneware at High Fire Temperatures

I’m a potter who works on the wheel, primarily making pots for the kitchen table. I have many expectations of the fired white stoneware and porcelain high fire clay bodies I create and use. A few of them are:

To achieve the clarity of glaze color I desire, I use porcelain bodies which fire to a white background. Then transparent or translucent glazes can gain maximum clearness as reflected against the white background of fired porcelain or white stoneware.

Creating a “Just Right” Feel

As a potter who works on the wheel, I need maximum workability from the clay I use, a kind of springy resilience and ability to stand up on the wheel. In the making of stoneware, iron-bearing fire clays and ball clays are used to excellent effect to create a kind of dense, “just right” feel.

In a porcelain body where only kaolin (china clays) are used, this excellent throwing quality is difficult or impossible to achieve, even with the addition of wet-mixed plasticizers. Kaolin (china) clays are also silica-poor, requiring up to 30% or more added (non-plastic) silica to achieve proper glaze fit, further reducing the workability of the porcelain.

This is why I enjoy creating white stoneware high fire clay bodies – to incorporate light-burning ball clays into the body to allow me increased ability to make larger forms while still attaining relatively white fired color.

high fire clay bodies into porcelain bowls

Eliminating a Potter’s Enemy

If a potter hopes to make sound, durable pots in high-fire ceramics, the formation of cristobalite (a primary phase of silica) is a deadly enemy. Cristobalite must be eliminated in the body by the use of a sufficient quantity of feldspar added to the blend of clays. This lowers both the absorption of the fired body (near 0% for porcelain) and the CTE (the coefficient of thermal expansion and contraction). Cristobalite is then absorbed into the melt at between 1280 – 1300C, high-fire temperatures.

Higher shrinkage rates are part of the deal with porcelain in comparison to stoneware clay bodies, especially stoneware bodies that contain percentages of grog or sand. A stoneware potter might expect 10 – 12% shrinkage in his fired wares, but a porcelain potter might encounter 17 – 20% shrinkage of their fired porcelain.

Thinking Bigger

Oversizing of thrown porcelain pots in the making phase must be anticipated. Imagine your amazement after packing a tight kiln and opening the door to a finished and cooled firing – and witness a whole lot of space where little existed previously.

Porcelain and white stoneware high fire clay bodies must also be engineered to keep warping at a bare minimum. Cracking of the body is eliminated in the process of combining feldspar, silica and plasticizer into the blend of chosen kaolin (china) clays.

Perhaps the most important reason I make my own porcelain and white stoneware is to ensure that my fired clay will fit a wide variety of glazes.

Much more on this in Why I Create My Own High Fire Clay Bodies, Part 2

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