Clay
Clay is the basic material of pottery and has distinctive characteristics. It can be moulded and will retain its shape and it hardens on firing to form a brittle but otherwise virtually indestructible material that is not harmed by any corrosive agents that attack metals or organic materials. 

Clay is a refractory substance and will vitrify only at temperatures of about 2,900F (1,600C). It can be mixed with a substance that will vitrify at a lower temperature when the clay will hold the object in shape while the other substance vitrifies. This forms a nonporous, opaque body known as stoneware.

When feldspar or soapstone is added to the clay the vitrified product is translucent and is known as porcelain. Pottery that is not vitrified is referred to as earthenware and is slightly porous and coarser than vitrified materials.

China clay naturally contains kaolin which provides the whiteness, hence its use in bone china. Perfectly pure kaolin is necessary for the manufacture of porcelain and other fine china, whilst less pure varieties are used in making pottery, stoneware etc.

Pottery
Pottery is made of clay that is permanently hardened by firing in a kiln. The nature and type of pottery is determined by the composition of the clay, the way it is prepared, the temperature at which it is fired and the glazes used. Depending on the clay used earthenware, when fired, can be buff, red, brown, or black. Earthenware is the oldest and simplest form of pottery.

Stoneware is a pottery compound that is fired at a sufficiently high temperature to cause it to vitrify and become extremely hard whilst porcelain, finer than stoneware and generally translucent, is made by adding feldspar to kaolin and then firing at a very high temperature.

Throughout history pottery objects have been produced by different cultures using local materials and traditional techniques. Undoubtedly the most sophisticated pottery culture was in China, where it has been made since the Neolithic Period. Porcelain was made in China as early as the 9th century, but its secret was not discovered by Europeans until the 18th century. Chinese porcelain, or "china" as it is commonly called, was widely exported to Europe where it had a influence on European manufacture and taste.

European wares made before the 19th century fall into six main categories: lead-glazed earthenware, tin-glazed earthenware, stoneware, soft porcelain, hard porcelain, and bone china.

Two other types of ware, less common than those already discussed, are slipware and lusterware.

Earthenware
Earthenware was the first kind of pottery made, dating back about 9,000 years and in the 20th century, it is still widely used.

Earthenware is usually glazed to overcome its porosity, which makes it impracticable for storing liquids in its unglazed state. The fired object is covered with finely ground glass powder suspended in water and is then fired a second time. During the firing, the fine particles covering the surface fuse into a glasslike layer, sealing the pores of the clay body.

There are two main types of glazed earthenware. When the earthenware body to which this glaze is applied has a cream colour it is covered with a transparent lead glaze, the product being called creamware. The second type, covered with an opaque white tin glaze, is called tin-enameled, or tin-glazed earthenware.

Lead-glazed earthenware was made from medieval times onward but fell out of favour when tin glaze became widely used towards the end of the 15th century. It returned to popularity with the advent of Wedgwood's creamware around the middle of the 18th century.

The first important tin-glazed wares came from Italy during the Renaissance, and manufacture spread rapidly, through Europe to England. Under the name of majolica, faience or delft it enjoyed immense popularity until the advent of Wedgwood's creamware, after which the fashion for tin-glazed ware declined rapidly.

Nearly all ancient, medieval, Middle Eastern, and European painted ceramics are earthenware, as is a great deal of contemporary household dinnerware.

Delftware
Also simply called Delft, it is a tin-glazed earthenware and was first made early in the 17th century at Delft in Holland. Dutch potters later brought the art of tin glazing to England along with the name Delft, which now applies to wares manufactured in The Netherlands and England, as distinguished from faience, made in France, Germany, Spain, and Scandinavia, and majolica, made in Italy.

Stoneware
Stoneware is a vitrified pottery and is very hard and, although sometimes translucent, it is usually opaque. The colour of the fired material varies considerably from red, brown, gray, white to black.

Fine white stoneware was made in China as early as 1400 BC, the first production of stoneware in Europe not being until the 16th century in Germany. By the end of the 17th century English potters were making a salt-glazed white stoneware that was regarded by them as a substitute for porcelain. In the 18th century, the Englishman Josiah Wedgwood made a black stoneware called basaltes and a white stoneware called jasper. A fine white stoneware, called Ironstone china, was first produced in England early in the 19th century.

Porcelain
Porcelain is a vitrified pottery with a white, fine-grained body that is usually translucent. The word is derived from porcellana, used by Marco Polo to describe the pottery he saw in China.

The distinction between porcelain and stoneware, the other class of vitrified pottery material, is less clear. In China, porcelain is defined as pottery that is resonant when struck, whilst in the West it is a material that is translucent when held to the light. Neither definition is totally correct as some heavy porcelains are opaque, while some thinly potted stonewares are translucent.

The three main types of porcelain are hard-paste porcelain, soft-paste porcelain and bone china. The terms soft and hard refer to the properties of the two materials; soft porcelain can be cut with a file, whereas hard porcelain cannot.

Porcelain was first made in a primitive form in China between AD 600 and 900 whilst the familiar Western porcelain was not manufactured until after the late 1200's. It was made from kaolin (white china clay) and petuntse (a feldspathic rock), the latter being ground to powder and mixed with the clay. 

The manufacture of soft porcelain started in the 16th century in Italy but it was not until the late 17th and 18th centuries that it was produced in quantity. The secret of true porcelain, similar to that of China, was discovered about 1707 at the Meissen factory in Saxony. Later, at the end of the 18th century, Josiah Spode the Second added bone ash to the hard porcelain formula to make the standard English bone china.

Bone China
A hybrid hard-paste porcelain containing bone ash. The initial development of bone china is attributed to Josiah Spode the Second, who introduced it around 1800. His basic formula of six parts bone ash, four parts china stone, and three and a half parts china clay remains the English standard . Hard porcelain is strong but chips fairly easily and, unless specially treated, is usually tinged with blue or gray. Somewhat easier to manufacture, bone china is strong, does not chip easily, and has an ivory-white appearance. It has since become the standard English porcelain. Bone china is popularly used for table services in England and the United States.