5 Types of Clays used in the Ceramic Industry

Also known as porcelain clay or China clay, Kaolin is widely used for manufacturing porcelain. It is naturally occurring and considered the purest clay on Earth. There are two color variations found in Kaolin – White Kaolin and Red Kaolin. The former is widely used for applications, while the second one is because of the clay’s higher presence of iron oxide.

Kaolin is less plastic than other clays and is mixed with ball clay and other components to enhance its plasticity. However, this type of clay has the highest temperature maturity levels dealing with heat as high as 1800°C. Due to these properties, Kaolin is widely used in crockery production, papermaking, plastics, and even morphine.

Unlike Kaolin, Ball Clays are highly plastic and have many applications. The color of ball clay depends on the state of the material and ranges from white to dark grey. They can be used in applications handling temperatures up to 1200°C. However, they exhibit the property of excessive shrinkage and hence are not used on a standalone basis. Instead, they are mixed with various components which accentuate their chemical and physical properties.

The most common use of ball clay is in producing sanitaryware and wall and floor tiles. It also exhibits excellent rheological stability and becomes pure white upon curing. They are mixed with stoneware clays to give the products a good finish. They are also used in non-ceramic applications like refractories and insulators.

Stoneware clays are highly plastic but rarely found in their pure state. They undergo a lot of processing before they become ready to use. They get their name because they become stone-like hard when fired. Their temperature maturity range is about 1200°C. It exhibits a variety of colors when fired, ranging from tan or light grey to chocolate brown.

Because of its rugged and durable qualities, stoneware clays are used to produce highly functional products like dinnerware. When fired to maturity, they become leak-proof and are one of the most dependent clay materials. At the same time, their composition varies from source to source, and this needs to be checked before using the clay.

Earthenware clays are one of the earliest discovered clay types commonly found across the world. This clay has high plastic properties and is very easy to work with. This is why they are widely used in various industrial applications and by artists. However, unlike other clay forms, earthenware contains various other mineral contaminants, which have pros and cons. In addition, its temperature maturity range is near 1000°C.

Natural earthenware clays like terracotta are unglazed and have limited functional use. At the same time, modern earthenware clays are compound clays with varied compositions that make the clay more useful. The natural colors of earthware clays are red, yellow or grey; when fired, they can become brown, orange or even white. In addition, because of their lower temperature maturity, they are softer and have a low shrink factor.

Fire clay gets its name because it has a very high temperature operating range. This type of clay reaches the maturity stage when fired to around 1500°C. For this reason, they are also called refractory clays and contain a high amount of alumina. In addition, they are often mixed with stoneware clays, enhancing their temperature resistance and giving the clay a bit of extra roughness.

The most common application of fire bricks is refractories, which are used in furnace linings for glass and metal smelting. They can maintain their physical and chemical properties even at very high temperatures. Refractory cement is also made from this clay by mixing additives.