Do you know your clays?

Hi Everybody,

If you ask a potter, how many different clays there are, you would probably be told there are 3 different types, earthenware, porcelain, and stoneware.

There is, however, more to clay than that and over the next few months, I will do a series of blogs on different clays, including where they come from, their uses and firing temperatures. There are many specialist clays, used for a variety of ceramics, including sculpture, tile making, fine throwing clays, coloured clays, slip casting clays etc.

So, let’s start with the three main clays and one exotic one:

Earthenware: It fires at about 1060° Celsius. It can be taken to a slightly higher temperature when it will go darker in colour, stronger and less porous, as the clay molecules are compressed together by the heat. The red terracotta plant pots you can buy in garden centres are made from earthenware clay.

Stoneware fires to an even higher temperature, 1200-1300° Celsius, and once glazed is also frost proof, so suitable for outdoor ceramics, such as garden pots and architectural features. It also makes very hard-wearing domestic kitchen ceramics.

Porcelain fires to even higher temperature again, at about 1300 – 1340° Celsius, where you can produce fine, light strong ceramics.

Raku clay is historically a form of Japanese pottery, which first appeared in medieval Japanese ceramics during the 16th century, around 1550, and was traditionally used for making tea bowls for use during a Japanese tea ceremony. However, today, Raku has a grog added to the clay, which can make it rough and textured and is ideal for making large scale ceramic sculptures, as it has less shrinkage and can be made thicker. It can also withstand the shock in temperature change. Raku is fired at around 900° Celsius. More on Raku in my next blog.

We run a ceramic sculpture making course once a year, where we use raku clay and sculpt from a life model. If you are interested in this course, just drop us a line.