CLAY MAKING
I will describe here the process that was initially used in the materials workshop, though it no longer applies to my more limited resources in my studio here in Wentworth Falls. It remains of interest however to illuminate the best method of constructing a stoneware body if the space and facilities are available.
The stoneware clay was made through what is commonly called a ‘wet method’ process. This involved weighing out particular amounts of the three different local clays. The clays have been chosen to give a balance of plasticity, fusibility and colour; one clay, for instance, known as Puggoon 184, is a red, high iron, dark-firing clay that is surprisingly refractory for a red clay. On it’s own, when used on the wheel, it’s throwing characteristics (plasticity) are not marvellous; it is stodgy and tends to ripple when drawn up to a height. However, when blended with another more plastic clay, and again with another more fusible clay, the workability is improved and more control is gained over the fired colour of the batch.
The three clays are weighed as dry material, and mixed together as a batch. To this is added feldspar, a crushed and powdered rock which is more fusible than clay and provides the degree of melt of the blend. Silica is also added at this stage; this contributes to the glass formation which develops in the clay body when it is fired. In this way the eventual melt (fusibility) of the fired clay can be more closely controlled. This is important in determining whether crazing can be avoided or encouraged in the glazes.
The blend of dry materials is placed in a 50 gallon ball mill with 80 litres of water, and mixed for one hour. This ensures a very thorough mix, and that all the materials are ground fine enough not to cause any speckling or iron-spotting in the fired clay. The wet mix is then run out through sluices into cloth covered brick drying beds. Water is absorbed through the bricks, and evaporated, until the clay assumes a plastic condition; then it is taken from the bed, wrapped in plastic (the manufactured sort) and stored in the pottery.