Derived from the Greek word keramos, ceramics means “burned clay.” Originally, the term was referred to china; nowadays, the term is also used for non-metallic, inorganic substances such as refractories, glass and cements as ceramics. For this reason, ceramics are now regarded as no-metallic, inorganic substances that are manufactured through a process of moulding and exposure to high temperatures.
Ceramics are divided into secondary categories: pottery, stoneware, earthenware and porcelain.
Conventional ceramics are made from natural materials such as clay and silica rock. Typical examples include china, fibrebricks, cements and glass. Ceramics are made by mixing, shaping and firing natural minerals including pottery stones, feldspar and clay.
What is pottery?
Commonly known as the art of making pots, ceramic ware or a potter’s studio, pottery is generally considered to be containers made from clay. Pottery includes glazed ceramics fired at higher temperatures than earthenware – between 1,000 – 1,250°C and has water absorption properties.
Pottery is clay that is modelled, dried and fired usually with a glaze or finish into a vessel or decorative object. A natural product dug from the earth, clay is decomposed from rock but a clay body is not the same as clay. Clay bodies are clay mixed with additives that give the clay different properties when fired. Therefore, pottery is made from a mixture of clay and other materials.
Most of our ceramic pots are made from stoneware and dolomite. Dolomite powder can be used in the manufacture of ceramic glazes and is often used as a raw material for ceramic pots.
Earthenware is a type of pottery that has been kneaded, shaped and fired at low temperatures at approximately 800°C. Usually glazed, earthenware is porous and has impurities, but they’re small and invisible to the naked eye. Unglazed areas are easy to scratch - they give off a powder when scoured. Earthenware has a natural colour like grey, red, brown, yellow, cream or off-white and is sometimes dyed before it’s shaped. Modern uses include terracotta flower pots, red bricks and stoves.
Made from clay, earthenware is not fired to the point of vitrification. Earthenware is made waterproof by the application of a liquid clay mixture applied before firing. For both practical and decorative reasons, earthenware is usually glazed. There are two main types of glazed earthenware. One is covered with a transparent lead glaze, which is cream in colour and thus called creamware. The second type is covered with an opaque white tin glaze and is known as tin-enamelled, tin-glazed, majolica, faience or delft.
Composed of purer clay, stoneware is hardened by fire and lacks water absorption properties. Stoneware often isn’t glazed and does not require a glaze like earthenware for it to be usable. Stoneware is however, often glazed for decorative purposes such as kitchenware and tableware. Sometimes the clay is dyed before it’s shaped. Bowl-shaped stoneware articles give a clear sound when they are tapped. Difficult to scratch, stoneware is commonly used for artisan pots, tea sets, pavement brikcs and common colours include off-white, grey/blue-grey and beige.
Stoneware is primarily made from stoneware clay or non-refractory fire clay. Often accompanied by impurities such as iron or carbon, stoneware often has a ‘dirty’ or distressed look.
Porcelain is a white and translucent ceramic. Also known as china, it is delicate, non-porous and usually difficult to scratch. Available in both glazed and unglazed varieties with bisque, porcelain is a hard, fine-grained ceramic ware that consists essentially of kaolin, quartz and a feldspathic rock.
Porcelain is baked at high temperatures to achieve vitreous, or glassy qualities such as translucence and low porosity. Porcelain is made from mixtures of high-purity clays or pottery stones, silicas and feldspars.
There are two basic techniques for creating pottery: hand-built and wheel thrown. Within these two techniques are also different ways of forming the clay.
1. Hand-built – This is the earliest forming method and you only need to have clay and a workspace to make hand-built pottery. There are three hand-built techniques: pinch pot, coil pot and slab pot.
2. Wheel-Thrown – This is a more difficult technique than the hand-built technique and requires the use of a potter’s wheel. The potter needs to be knowledgeable in using the wheel and make sure to centre the clay before working it. The correct amount of water must also be used as well as making sure the wheel turns at a steady rate.
A glaze allows potters to seal their pottery and is applied after the pot has gone through the firing process in the kiln for the first time. The first firing hardens the clay and only after the glaze is applied does the pottery gets placed in the kiln again. The glaze then melts and sticks to the pottery, providing protection and waterproof properties to the outside of the vessel.