Pottery is made by forming the 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 increasing their strength and hardening and setting their shape. There are wide regional variations in the properties of raw materials used for the production of pottery, and this can lead to wares that are unique in character to a locality. It is common for clays and other materials to be mixed to produce clay bodies suited to specific purposes. Prior to some shaping processes, air trapped within the clay body needs to be removed. This is called de-airing and can be accomplished by a machine called a vacuum pug or manually by wedging. Wedging can also help to ensure an even moisture content throughout the body. Once a clay body has been de-aired or wedged, it is shaped by a variety of techniques. After shaping it is dried before firing. There are a number of stages in the drying process. Leather-hard refers to the stage when the clay object is approximately 15% moisture content. Clay bodies at this stage are very firm and only slightly pliable. Trimming and handle attachment often occurs at the leather-hard state. Clay bodies are said to be “bone-dry” when they reach a moisture content at or near 0%. Unfired objects are often termed greenware. Clay bodies at this stage are very fragile and hence can be easily broken.
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 °C, 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 allows 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.
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). The earliest pottery vessels found include those excavated from the Yuchanyan Cave in southern China, dated from 16,000 BCE, and those found in the Amur River basin in the Russian Far East, dated from 14,000 BCE.
Other earlier pottery vessels include those made by the Incipient Jōmon people of Japan from around 10,500 BCE have also been found. The term “Jōmon” means “cord-marked” in Japanese. This refers to the markings made on the vessels and figures using sticks with cords during their production. It appears that pottery was independently developed in North Africa during the 10,000 BCE and in South America during the 10,000 BCE. In several cultures, the earliest vessels were made either by hand-shaping or by rolling the clay into a thin round cord which was then coiled round on itself to form the vessel. The earliest history of pottery production in the Near East can be divided into four periods, namely: the Hassuna period (5,000-4,500 BCE), the Halaf period (4,500-4,000 BCE), the Ubaid period (4,000-3,000 BCE), and the Uruk period (3,500-2,000 BCE).
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, including areas now forming Pakistan and northwest India, during the Mehrgarh Period II (5,500-4,800 BCE) and Merhgarh Period III (4,800-3,500 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 have been found in a number of sites in the Indus Valley Civilization.
In the Mediterranean, during the Greek Dark Ages (1,100–800 BCE), amphoras and other pottery were decorated with geometric designs such as squares, circles and lines. The period between 1,500-300 BCE in ancient Korea is known as the Mumun Pottery Period. In the Chalcolithic period in Mesopotamia, Halafian pottery achieved a level of technical competence and sophistication, not seen until the later developments of Greek pottery with Corinthian and Attic ware. The distinctive Red Samian ware of the Early Roman Empire was copied by regional potters throughout the Empire.
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