Ceramic Clays

Types of Ceramic Clays

There are few things more grounding that getting your hands dirty with clay. This basic art and craft has been in use for thousands of years. Read on to learn a bit more about ceramic clays.

Three main types of clay

There are three main types of clay that are used today, including:

  • Earthenware clay
  • Stoneware clay
  • Porcelain clay

The clays are defined by how much water can be absorbed by the material once fired and dried completely. This is determined by the firing temperature of the clays. In the above clays, earthenware clay is the least durable and is fired at the lowest temperature and cone. Stoneware clay is more durable than earthenware clay but less durable than porcelain clay. Porcelain clay is the most durable and is fired at the highest temperature and cone.

In addition to being defined by the amount of water that the clay can absorb, clays are also defined by the amount of impurities present. Earthenware clay has the most impurities, stoneware clay has less, and porcelain clay is considered the purest between the three families.

Temperature and cone

The temperature that clay is fired at is measured by the cone. The cone is quite literally a physical visual indicator that the temperature inside the kiln is uniformly reached. The cone physically starts to change shape as it passes through the range of temperatures that it is meant for.

Cones range from 022–10 and their temperatures are from 1112 degrees Fahrenheit to 2381 degrees Fahrenheit, respectively. Earthenware clay is a low-fire clay and is typically fired between cones 08-01 representing a temperature range form 1700 degrees Fahrenheit to 2100 degrees Fahrenheit. Stoneware clay is a medium-fire clay and is typically fired between cones 1–7 representing a temperature range from 2100 degrees Fahrenheit to 2300 degrees Fahrenheit. Porcelain clay is a high-fire clay and is typically fired between cones 9–10 representing a temperature range of 2335 degrees Fahrenheit to 2550 degrees Fahrenheit.

Other popular types of clay

Terracotta clay is a type of earthenware clay that is often used for bricks, tiles, and objects such as vases. This clay is the least durable of the three main families of clay, though it is used often. Terracotta clay will absorb water and is red due to the amount of iron found in the mineral content of the clay.

Casting clay is another type of clay that is popular. Casting clay is a clay material that is a fine powder that is mixed well with water. The clay is then casted into a mold in order to create complex and reproducible shapes. Casting slips are often used to make intricate sculptures reproducibly.