Making Pottery

Potters start their work with lumps of moist clay and end it with finished pieces of pottery. The means by which such ends are accomplished vary widely and what follows should be regarded as an outline of one sequence of operations sometimes followed, chosen from the many that are practised.

Preparing the clay. A portion of clay is kneaded until it is thoroughly mixed and of even moisture content throughout. If at this stage the clay is too dry to use, water is added, and if the clay is too wet, it is allowed to dry out to the condition required. After mixing, the clay is wedged to remove entrapped air. When wedging clay by hand a ball of the material is thrown repeatedly onto a hard surface, to drive out the air. The progress of the operation may be checked periodically by cutting the clay with a wire and checking the cut surface for bubbles of air. Mixing and wedging are operations that can be carried out by hand, or mechanical mixers and wedging machines may be used. Machines used for wedging clay are called pug-mills.

Shaping the wares. Wares may be shaped by hand, by using the hands in conjunction with a machine such as a potter's wheel or by mechanical means alone. Other methods of shaping are also used, including slip-casting and pressing.

Drying and finishing. After shaping it is common for pottery wares to be air-dried to a leather-hard condition and finished by trimming off unwanted clay on a wheel, in an operation analogous to turning wood on a lathe, or perhaps by sandpapering the surface of the ware to a fine finish. Shaped but still unfired pottery is called greenware.

First or bisque firing. Greenwares are fragile and are sometimes given a first or bisque firing to harden them for convenient handling and to reduce the risk of breakage during glazing and decorating. In this condition the ware is called biscuit-ware or bisque-ware. Temperatures used for bisque-firing may be either higher than those used for final firing, or lower, depending on the characteristics of the materials used and the preferences of the potter.

Glazing and decorating. After bisque-firing the wares may be coated with a layer of glaze, often applied by dipping.

Second or glaze firing. The glazed wares are re-fired to melt the glaze and bond it to the clay body, thus forming a glassy covering on the surface of the pieces.

Enamelling. Glazed wares are sometimes decorated with coloured enamels and re-fired in a glaze kiln or muffle-furnace.

History

It is believed that the earliest pottery wares were hand-built and fired in bonfires. Firing times were short but the peak-temperatures achieved in the fire could be high, perhaps in the region of 900 degrees Celsius, and were reached very quickly. Clays tempered with sand, grit, crushed shell or crushed pottery were often used to make bonfire-fired ceramics, because they provided an open body texture that allowed water and other volatile components of the clay to escape freely. The coarser particles in the clay also acted to restrain shrinkage within the bodies of the wares during cooling, which was carried out slowly to reduce the risk of thermal stress and cracking. In the main, early bonfire-fired wares were made with rounded bottoms, to avoid sharp angles that might be susceptible to cracking. The earliest intentionally constructed kilns were pit-kilns or trench-kilns; holes dug in the ground and covered with fuel. Holes in the ground provided insulation and resulted in better control over firing.

It is believed that the earliest known ceramic objects are Gravettian figurines such as those discovered at Dolni Vestonice in the modern-day Czech Republic. The Venus of Dolní Věstonice (Věstonická Venuše in Czech) is a Venus figurine, a statuette of a nude female figure dated to 29,000–25,000 BCE (Gravettian industry). [1]. The earliest known pottery vessels may be those made by the Incipient Jōmon people of Japan around 10,500 BCE[2] [3]. The term "Jōmon" means "cord-marked" in Japanese. This refers to the markings made on clay vessels and figures using sticks with cords wrapped around them. Pottery which dates back to 10,000 BCE have also been excavated in China.[4] It appears that pottery was independently developed in North Africa during the 10th millennium b.p.[5] and in South America during the 7th millennium b.p.

The invention of the potter's wheel in Mesopotamia sometime between 6,000 and 4,000 BCE (Ubaid period) revolutionized pottery production. Specialized potters were then able to meet the expanding needs of the world's first cities. Pottery was in use in ancient India during the Mehrgarh Period II (5500 - 4800 BCE) and Merhgarh Period III (4800 - 3500 BCE), known as the ceramic Neolithic and chalcolithic. Pottery, including items known as the ed-Dur vessels, originated in regions of the Indus valley and has been found in a number of sites in the Indus valley civilization.

In the Mediterranean, during the Greek Dark Ages (1100–800 BCE), artists used geometric designs such as squares, circles and lines to decorate amphoras and other pottery. The period between 1500-300 BCE in ancient Korea is known as the Mumun Pottery Period.

Pottery

Pottery is (1) the ware made by potters; (2) a place where pottery wares are made; (3) the business of the potter; and (4) a ceramic material.

Pottery is made by forming clay body into objects of a required shape and heating them to high temperatures in a kiln to induce reactions that lead to permanent changes, including an increase in strength and the setting of their shapes.

There are wide regional variations in the properties of clays used by potters and this often helps to produce wares that are unique in character to a locality. It is common for clays and other minerals to be mixed to produce clay bodies suited to specific purposes; for example, a clay body that remains slightly porous after firing is often used for making earthenware or terra cotta flower-pots.

The term pottery is sometimes taken to include ceramic materials such as stoneware, faience and porcelain.