Clay comes in many varieties with different propertes. Different clays are suitable for different uses and situations. Some clay is particularly strong and durable, making it ideal for large-scale or outdoor use. Other types are chosen for their colour, texture or flexibility.
Popular types of clay include earthenware, stoneware and porcelain:
Earthenware is the oldest and most commonly-used clay. It is highly plastic. This means it is very durable and easy to work with.
Earthenware clay contains iron and other minerals that enable it to reach its optimum hardness at lower temperatures - between 950°C and 1100°C (1745°F and 2012°F). This results in a softer, unvitrified and porous ceramic with rich clay colours and a low shrink factor after firing.
Unglazed earthenware, such as terracotta, is porous. It is used for bricks, tiles and plant pots. Unless it is glazed, earthenware is not suitable for creating vessels that hold liquids, like vases or mugs.
Stoneware clay is malleable and often grey in its raw state. The type of firing that the clay undergoes will affect the clay's colour - it ranges from light grey to medium grey and brown.
Stoneware clay is usually fired at temperatures ranging from 1150°C – 1300°C (2100°F to 2372°F). Once fired, it becomes stone-like, forming a hard, dense and variegated clay. It is a tough and forgiving material to use during throwing, hand-building and firing stages. This makes it a popular choice for both student and professional potters.
Stoneware is excellent for functional pieces such as dinnerware. It is non-porous and therefore waterproof. This makes it well-suited for sculptural pieces and work intended for outdoor use.
Stoneware clay is tough and waterproof, making it well-suited for sculptural work.
Porcelain clay is a versatile material suitable for the creation of functional household objects, decorative items and fine art. Its name comes from the Italian word ‘porcellana’, which translates as ‘cowrie shell.’ This is due to its resemblance to the surface of a shell.
Porcelain fires to temperatures between 1,200°C and 1,400°C (2,200°F and 2,600°F). It has a white,translucent finish. This plain, uncoloured surface makes porcelain ideal for vibrant glaze work.
Paper clay is a half-solid, half-fluid mix of clay, paper pulp and water. When fired, the paper pulp burns away giving a thin and light, yet strong finish.
Paper clay in the greenware state is very strong and versatile. At this stage, the dry clay can have more wet clay attached to it, creating multiple layers. This enables more sculptural freedom than is possible with other clays.