FIRECLAY is, technically, any clay from which a standard grade of
firebrick can be made; impure kaolin, ball clay and refactory stoneware
clay are commonly used, but these are generally not what the potter has
in mind. In this paper fireclay refers to a hard, kaolinitic shale that
does not slake down readily in water, hence is not particularly plastic,

has a low drying shrinkage and few drying problems. Fireclays by
themselves reach usable maturities somewhere between cone 14 and

cone 24 so they must be mixed with fluxing materials or left as very
immature bodies. Clays of this sort are useful in the following
applications:

J) When one is working at very high temperatures.

2) In bodies that need not have low absorption and high fired strength
but must have good drying characteristics and low fired shrinkage, as
for sculpture.

3) Where the colour and texture of reduced fireclay body is more
important than workability and final durability.

4) When more normal pottery clays are not available.

The latter has been very important in STARTING fireclay pottery
traditions but these traditions continue because fireclay technologies
are quite different from those of stoneware and porcelain, creating a
period of difficulty for potters undertaking to make the change.

To make a pottery body from fireclay it will be necessary to add the
following:

1) Taaspar or-nenieline avenite to act as a flux in developing a
glass p , about 20% depending upon the other materials.

2) Silica to assist in the glass phase. 10% to 20%.

3) Ball clay to provide plasticity, about 25% depending upon the
es coor rare th of non-plastic materials that
you have added.

4) You will also probably want to add 2% to 4% iron oxide to
improve the final colour although many fireclays contain enough iron

originally.

Such a body will have very good drying and firing characteristics and
colour and texture that are particularly suitable to large decorative

applications, but it will not have the workability of traditional