ceramic

The majolica figure of a turkey, designed as a piece of ceramic artwork by Sandro Vacchetti in 1932. The colourful nature of majolica-ware has kept it popular with collectors, and this has ensured that the technique has never been fully abandoned by artisans in ceramics.

Object made from clay, hardened into a permanent form by baking (firing) at very high temperatures in a kiln. Once clay has been turned into ceramic, it can no longer be recycled in water. Ceramics are very versatile. They are used not only for dishes, vessels, and other decorative or functional household objects, but also for building construction and decoration (bricks, tiles), for specialist industrial uses (linings for furnaces used to manufacture steel, fuel elements in nuclear reactors, and so on). Different types of clay and different methods and temperatures of firing create a variety of results. Ceramics may be cast in a mould or hand-built, using the pinch, coil, or slab methods. Alternatively shapes and vessels can be formed by ‘throwing’ on a potter's, or pottery, wheel. Technically, the main categories are earthenware (including terracotta), stoneware, and hard- and softpaste porcelain (see pottery and porcelain).

Western history

Roman Potter's wheel; lead glazing; decorative use of slip (watered-down clay).

medieval Sgraffito (scratched) tiles and other products (earthenware decorated with slip of a contrasting colour, which is then scratched through) such as those made in Bologna, Italy. Lead-glazed jugs made in England and France, coloured bright green or yellow-brown with copper or iron oxides. Tin-glazed ware in southern Italy and Spain by the 13th century, influenced by established Islamic techniques.

14th-century Germany Stoneware developed from hard earthenwares; tin glazes developed; colour added by thin slips mixed with high-temperature colours. Later, mottled brown glaze recognized as characteristic of Cologne, referred to as ‘tigerware’ in Britain.

15th century Hispano-Moresque painted ware imitated by Italians, developing into majolica by mid-century, using the full range of high-temperature colours; centres of the craft included Tuscany, Faenza, Urbino, and Venice. Some potteries, such as that at Gubbio, additionally used lustre glazes. Typical products are dishes and apothecary jars.

16th century Potters from Faenza spread tin-glazed earthenware (majolica) skills to France, Spain, and the Netherlands, where it became known as faience; from Antwerp the technique spread to England. The English in the 17th century named Dutch faience ‘Delftware’, after the main centre of production.

17th century Faience centres developed at Rouen and Moustiers in France, Alcora in Spain, and in Switzerland, Austria, and Germany. Blue underglaze was increasingly used, in imitation of Chinese blue and white designs, reflecting the growth of orientalism.

18th century European developments in porcelain, also in using a rich palette of low-temperature enamel colours. The vitreous enamel process, first developed at Strasbourg in about 1750, spread around northern Europe.

19th–20th century The Industrial Revolution changed the course of ceramic history. Large pottery factories opened in the UK, Europe, and the USA, and handcrafted pottery declined for a time. However, by the end of the 19th century and in the 20th century, manufacturers became aware of the market for individual work, and began to use independent ceramicists. The trend of ‘pottery painting’ (painting on fired clay) continued into the 21st century. Ceramics were also increasingly used in the creation of fine art.

Making ceramics There are a number of ways to create ceramic objects. Hand-building, throwing on a potter's wheel, and either slip casting or using a press mould are the most common methods. Ceramicists may use only one method or a combination of techniques to create the finished product.

Hand-building can be broken down into three techniques: pinch, coil, and slab.

Pinch is the earliest method of hand-building. Pinch pots of all sizes, dating back thousands of years, can be found all over the world. A simple pinch pot is made by first rolling the clay into a ball; it should feel comfortable in the palm of the hand. The ball is then held in one hand and a hole pressed into the clay with the thumb of the other hand, leaving a thickness of about 1 cm/0.5 in at the bottom for a base. The clay is shaped into a pot by turning it slowly, and pinching the sides with the thumb on the inside and fingers on the outside.

Coil has also been used to create ceramic vessels for thousands of years. The coil method is used all over the world to create very large pots (up to 2 m/6 ft tall) for storage, planting, and decorative purposes. Coil pots are made by first creating a flat base out of clay and then rolling out large coils or round bands of clay and placing them, initially on top of the base, and then on top of each other, to create a vessel or container. The placing of the coils dictate the form of the pot – coils placed towards the outer rim will cause the pot to curve out while coils placed towards the inner rim will give the vessel an inward curve.

Slab or sheet is a very versatile hand-building method, which was used in prehistoric times to create sarcophagi (coffins) and is employed today in the creation of both functional objects (tiles, roofing, flooring) and artistic endeavours (vessels, boxes, sculpture). Slab-building simply means building with sheets of clay. The sheets can be made in a number of ways. Clay may be simply rolled out with a rolling pin; repeatedly pounded, lifted, and thrown onto a table or floor until it is flat and has an even surface; or a slab roller can be used. A slab roller is a bench with heavy rollers that can be adjusted to roll out large amounts of clay into slabs of the required thickness. Once a slab is created, the ceramicist can cut it into tiles, wrap it around a cylinder to create a vessel, or place it into a press mould.

The potter's wheel creates more uniform shapes than those made by hand-building. However, although the use of a potter's wheel is often believed to be the most dominant method of making ceramics, in some areas of the world the local clay is too rough or rocky to be used on a wheel, and traditional hand-building methods continue to be used. Vessels created on the wheel are described as ‘thrown’ – the rotating wheel throws the clay outwards while the potter's hands control and form it against the spinning force. The two main types of potter's wheels are the kick wheel and the electric wheel. The kick wheel is manual and fully operated by the potter, while the electric wheel spins when switched on.

Slip casting and press moulds are used when multiples of the same shape are needed. These methods are used by manufacturers, who need to make thousands of the same pot, dish, or object, as well as by independent ceramicists. In slip casting, slip or liquid clay (clay mixed with water) is poured into a sealed plaster mould; the mould usually has two or more parts. The plaster absorbs the water from the slip, so that a thin layer of clay forms inside the walls of the mould. When the clay layer is thick enough, the extra slip is poured out and the thin layer of clay is left inside the mould to dry out. The mould is then opened and the clay form removed. Press moulds are usually one-piece, open, plaster forms such as a bowl. When press-moulding, clay (not slip) is pressed directly into the mould. The plaster again absorbs any water left in the clay, and when the clay is hard enough to maintain its shape it is taken from the mould.

Decorating and glazing ceramics The decorating and glazing of ceramics is considered by some ceramicists to be the most important part of the creation process. The surface of a ceramic object may be decorated or changed using a number of methods.

Glaze is a type of glass that sticks to the surface of clay when fired in the kiln. There are many different types of glazes, and the glaze used must be compatible with the type of clay employed. Glazes come in many colours and textures. Some glazes are transparent while others are opaque. Glazing ceramics makes them water-resistant and more durable. The clay surface is often treated with an underglaze, usually made of coloured slip, before it is glazed. Underglaze can be used to paint pictures, patterns, or decorations onto clay before it is fired. Underglazes come in a wide range of colours and can be used in a variety of ways. Unlike glaze, underglaze will not make a pot more durable or water-resistant.

Ceramic surfaces can also be altered by using methods that are inspired by two-dimensional art forms, such as drawing and printing. Incising or scratching into hard clay before applying glaze, impressing objects into very soft clay, or sprigging (applying relief moulded objects onto the clay surface with slip as the glue) are all traditional and popular techniques. Sgraffito is a method whereby the coloured slip is scratched to reveal the true clay colour underneath. Slip trailing and drawing with slip on wet clay gives a raised pattern. Burnishing produces a smooth shiny surface. The effect is achieved by rubbing hard clay with a hard smooth object, such as the back of a spoon, to compact the clay particles.