Different types of clay
Learning the properties of clay is really important for anybody who uses it regularly. Clay is an incredible material, and with it you can make anything from sculpture, functional pots, decorative pots and more.
How is clay made?
Clay can be found anywhere across the country. It’s difficult to work with if you’re a gardener, but if you’re a potter and you hit clay in your back garden, it’s a gold mine. The clay soil in our gardens is different from the clay that you might buy from a pottery supplier. It’s been processed to remove impurities so that it’s easier to work with. It is possible to process your own clay if you’d like to, but it’s a lot easier and less time consuming to simply buy a bale of clay and get going.
What are the 3 main types of clay?
The different varieties of clay have different properties, meaning some may be more suitable for your projects than others. Clay might be chosen for its colour, texture, plasticity or durability.
Earthenware is a commonly used clay, and one of the oldest types of clay it is possible to work with. Its high levels of plasticity means that it is extremely durable whilst being easy to work with – it’s a great type of clay for beginners.
Iron and other minerals in the clay mean that earthenware can reach its optimum hardness at temperatures between 950 degrees C and 1100 degrees C – which is lower than stoneware or porcelain clays. However this means that the clay is still porous and unvitrified, meaning that if earthenware pieces are unglazed, they are likely to absorb liquids. This means that unglazed earthenware is not food safe or suitable to hold liquids.
Terracotta is a type of earthenware clay. It has a beautiful red colour and is easy to work with. Ancient pots and amphoras that we can view today in museums are made from terracotta.
Stoneware is another popular type of clay, and is the clay that most functional potters would use to make their ceramics. It’s strong, durable and varies greatly in colour: from grey, brown and beige; often having a range of textures.
Fired at temperatues between 1150 degrees C and 1300 degrees C, it takes well with a range of glazes and slips. It is particularly good for both throwing or handbuilding, which makes it a popular choice with professional potters.
A lot of stoneware is non-porous and waterproof, so it’s perfect for use in functional pieces like mugs, dinnerware, vases and jugs.
Porcelain clay is suitable for a variety of household objects and even jewellery. Used commonly for decorative objects and fine art, it’s delicate when it’s fired but even more delicate to work with.
Porcelain fires at temperatures between 1200 degrees C and 1400 degrees C. Once fired it will be vitrified – ready to use in functional ceramics or chinaware.
The delicacy of porcelain means that it has a translucent finish that looks beautiful when glazed in bright colours, or even when decorated using underglaze pencils or paint.