Pottery may have grown out of basket-making, and certainly could not become an important factor in human affairs until Neolithic man had adopted a settled mode of life: game had been roasted on a spit, but the cereals and pulses which now made up a large part of his diet required slow cooking in a container which could stand heat. Then, and only then, would he have occasion for large-scale use of containers which were as easily broken as made. They are easily manufactured, since clay is plentiful and the hardening effects of fire upon it could be discovered whenever primitive man happened to use a patch of clay for a hearth. The fact that pottery is fragile, readily discarded, and yet ultimately imperishable, is, of course, the combination of qualities that has given it so large and prominent a part in the archaeological record. But although pottery occurs in Neolithic settlements before the growth of urban cultures, its development is primarily associated with the latter; it was a product that settlers and colonists introduced to remoter areas, and that commonly suffered a setback when the urban influence declined. Britain, for example, in the second millennium B.C. had much good pottery of Mediterranean origin; for the greater part of the next millennium, very little.

Nevertheless, pottery deserves pride of place among the domestic arts as one in which the product and its uses have changed comparatively little in the course of the ages. One great invention, that of the potter's wheel, was made about 3000 B.C., but no further technical advance of revolutionary importance was made until the nineteenth century A.D. The potter has always had three main tasks to perform: the selection, mixture, and moistening of clay; the forming and shaping of the vessel; and the execution of the drying and firing processes by which the finished product is made hard and durable. Very little is known about early methods of selecting, washing, and kneading the raw material with water. It is the second process, the shaping, that was transformed by the invention of the potter's wheel.

The lump of clay which the potter is ready to shape, when placed in the centre of the fast-turning wheel--at least 100 revolutions a minute--will rise easily and assume any desired circular shape at the lightest pressure of the potter's hand. The potter with the wheel can do in a few minutes what would take an amateur without it several hours, at the same time achieving perfect symmetry. Thus the momentum of the spinning wheel, which reduces the muscular effort on the part of the potter to almost nothing, gave man one of the first of the long series of laborsaving devices out of which modern industry has been developed. No early wheel survives complete, and we have no means of determining how the device originated, though it may have grown out of the practice of using a turn-table so as to have all sides of a pot under modeling conveniently to hand. In its simplest form the wheel turned on a pivot which fitted into a socket in a stone. Spun by hand, such a wheel could be given sufficient momentum for the shaping of one pot, but enlarging it to increase the momentum caused the small disk in the centre, on which the pot itself was supported, to be placed less conveniently for the potter's hand. Hence the practice, which seems to have grown up by 2000 B.C., of deriving the necessary momentum from a second wheel placed under the first and generally turned by the foot of the potter, or possibly with a stick, or by an assistant using a band. By the sixth century B.C. the wheel was also being used as a lathe, for instance to cut grooves and moldings.

In order to make the vessel less porous it was usual to cover it, when dried but not fired, with a slip of a finer clay which could be burnished with a pebble or other implement to close the pores and make the product watertight. From a very early period, large pots were commonly made in two sections, in order that their weight should not cause them to sag before drying; when partly dried they were fitted together with a slip. The same method was used for pots with narrow necks.

During the firing a complex series of changes occurs in the clay, the nature of these depending upon many factors, but particularly  upon the final temperature reached. Primitive man probably had to be content with firing-temperatures in the range of 450 to 700 degrees C., which did no more than drive off all the moisture from the clay. At rather higher temperatures (750 to 800 degrees C.), such as can be attained in large open fires or simple kilns, chemical changes take place in the clay, making it stronger and less porous. At higher temperatures still it is vitrified (fused into a glassy substance), but such a degree of heat is readily attainable only with furnaces of comparatively modern type: in ancient times firing-temperatures above 1,000 degrees C. were very rare. Firing is a long process and consumes much fuel, and a good supply of the latter is essential for any sort of large-scale work. Wood must have been the principal fuel, but dung, peat, and grass were also used when appropriate. Some pottery may have been sold or bartered unfired, the purchaser completing the process himself.

Pots must originally have been dried on the domestic hearth, then in a special fire of brushwood, and later in a fire burning for several days under cover of earth or other air-excluding matter, after the pattern of the charcoal-burner's fire. It is believed that this last type of fire could attain a temperature of 750 to 800 degrees C., about 150 degrees below what was required for the kiln-fired Athenian vases. When the kiln began we do not know, but examples can be traced from the fourth millennium B.C. Until modern times the vertical kiln was commoner than the horizontal: it was developed, mainly in brickusing countries, as a domed structure, from which the hot gases generated in the hearth escaped eventually through a chimney. The pots to be fired were placed on a perforated clay floor and the kiln was then sealed: indirect heating prevented them from being contaminated by smoke and smuts from the fuel. The two problems, of retaining the hot gases long enough for them to be fully effective and of equalizing the temperature at the top and bottom of the kiln, were partly solved in the horizontal kiln, where the flue is laid horizontally between hearth and chimney, which are at opposite ends of the kiln. Specimens are found in Roman Britain, but the vertical kiln remained commoner until modern times, except in China.

The nature of the processes made the potter at a very early stage a whole-time specialist. The aesthetic sense which he developed, and which gives such interest to the study of early pots, was both a result and a cause of his special position. Painting was one early form of decoration, mixtures of natural earths being used before firing, and either organic or inorganic colors at a later stage. Shapes were, to some extent, an imitation of wood- or basket-work, and later there was sometimes a rather odd imitation of sheet-metal products. It is claimed that the pleasurable excitement of the spinning process and the ease which it imparted to the potter's work had much to do with the development of a sense of form; indisputably, pottery developed with remarkable speed both as art and as craft. First at Corinth and later at Athens, pottery manufacture for a wide overseas market achieved a degree of industrial concentration which almost rivals those of modern times, while the beauty of the best Attic products has remained unequalled. The achievements of some of the early metal-workers, for instance at Ur, were also dependent in part upon the skill of the potter, who supplied the casters with moulds made of fired clay. . .

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