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Pottery: the story on HearLore | HearLore
Pottery
The oldest known pottery vessel, discovered in Xianren Cave in Jiangxi, China, dates back to 20,000 to 19,000 years before the present, shattering the long-held belief that pottery only emerged after the invention of agriculture. This ancient vessel, found alongside fragments from the Yuchanyan Cave in southern China dated to 16,000 BC, proves that hunter-gatherers were shaping clay into containers long before the Neolithic revolution. These early potters utilized whatever clay was available in their geographic vicinity, often tempering it with sand, grit, crushed shell, or crushed pottery to create an open-body texture that allowed water and volatile components to escape freely during firing. The coarser particles in the clay also acted to restrain shrinkage during drying, reducing the risk of cracking in these primitive bonfire-fired ceramics. The earliest forms were hand-shaped from slabs, undecorated, and unglazed, fired at low temperatures achievable in open pits or bonfires. The shapes were typically rounded at the bottom to avoid sharp angles that might be susceptible to cracking, serving primarily as weights for looms or fishing nets before evolving into storage vessels for wild cereals and small game.
The Wheel And The Kiln
The invention of the potter's wheel in the 5th millennium BC revolutionized pottery production, transforming it from a solitary family craft into an industry capable of feeding growing cities. The earliest potter's wheel, dated to the middle of the 5th millennium BC, emerged from the Cucuteni, Trypillia culture in western Ukraine, while the wheel was invented in Mesopotamia sometime between 6,000 and 4,000 BC during the Ubaid period. This mechanical innovation allowed for the mass production of standardized shapes, enabling potters to create specialized cooking utensils, pot stands, and even rat traps beyond simple storage vessels. As the region developed new organizations and political forms, pottery became more elaborate and varied, with glazing commonly used and decoration becoming a primary focus. The development of kilns, specifically pit-kilns or trench-kilns, provided better control over firing temperatures, allowing wares to be fired to higher temperatures than open bonfires could achieve. These kilns were holes dug in the ground and covered with fuel, providing insulation that resulted in more consistent chemical changes within the clay body. The transition from individual production to small groups of potters working for small cities marked a significant shift in social organization, where the potter's wheel became a tool of economic power and cultural expression.
The Science Of Fire
Firing pottery produces permanent and irreversible chemical and physical changes in the body, transforming soft clay into a hard, durable ceramic through a process known as vitrification. The temperature at which pottery is fired dictates its classification, with earthenware fired as low as 600 °C and porcelain requiring temperatures between 1,200 °C and 1,400 °C. In lower-fired pottery, the changes include sintering, the fusing together of coarser particles in the body at their points of contact with each other. In the case of porcelain, where higher firing-temperatures are used, the physical, chemical, and mineralogical properties of the constituents in the body are greatly altered, leading to the formation of the mineral mullite within the body. The atmosphere within a kiln during firing can affect the appearance of the body and glaze, with oxygen concentration influencing the type and relative proportions of iron oxides. An oxygen-deficient condition, called a reducing atmosphere, is generated by preventing the complete combustion of the kiln fuel, causing carbon monoxide to react with oxygen in iron(III) oxide and reduce it to iron(II) oxide, resulting in much darker colors. The time spent at any particular temperature is also important, the combination of heat and time is known as heatwork, and modern kilns can be monitored by pyrometers, thermocouples, and pyrometric devices to ensure the maturity required in the body of the wares.
Common questions
When was the oldest known pottery vessel created?
The oldest known pottery vessel dates back to 20,000 to 19,000 years before the present. This vessel was discovered in Xianren Cave in Jiangxi, China, and proves that hunter-gatherers shaped clay into containers long before the Neolithic revolution.
Where did the potter's wheel originate?
The earliest potter's wheel emerged from the Cucuteni, Trypillia culture in western Ukraine during the middle of the 5th millennium BC. The wheel was also invented in Mesopotamia sometime between 6,000 and 4,000 BC during the Ubaid period.
What temperature is required to fire porcelain?
Porcelain requires firing temperatures between 1,200 °C and 1,400 °C. Earthenware is fired as low as 600 °C, while the higher temperatures for porcelain alter the physical, chemical, and mineralogical properties of the body to form the mineral mullite.
Which city is known as The Potteries?
The city of Stoke-on-Trent is widely known as The Potteries because of the large number of pottery factories or Pot Banks. As early as 1785, two hundred pottery manufacturers in this region employed 20,000 workers.
What is Potter's rot?
Potter's rot is the colloquial name for silicosis, an occupational lung disease caused by inhaling large amounts of crystalline silica dust. Workers in the ceramic industry developed this condition due to exposure to silica dust in raw materials, with negative effects noted less than 10 years after calcined flint was introduced to the British ceramics industry in 1720.
How does modern 3D printing work in pottery production?
Modern 3D printing involves the layered deposition of soft clay body similar to fused deposition modelling. The technique uses powder binding where clay body in dry powder form is fused together layer upon layer with a liquid.
Pottery may be decorated in many different ways, with some decoration done before or after the firing, and may be undertaken before or after glazing. Glaze, perhaps the most common form of decoration, serves as protection to the pottery by being tougher and keeping liquid from penetrating the pottery, and may be colourless, especially over painting, or coloured and opaque. Crystalline glaze is characterized by crystalline clusters of various shapes and colours embedded in a more uniform and opaque glaze, produced by the slow cooling of the glost fire. Carving is a common technique in Chinese porcelain of the classic periods, where pottery vessels are decorated by shallow carving of the clay body, typically with a knife or similar instrument used on the wheel. Burnishing the surface of pottery wares prior to firing by rubbing with a suitable instrument of wood, steel, or stone produces a polished finish that survives firing, though wares in this condition are extremely fragile and the risk of breakage is high. Terra Sigillata is an ancient form of decorating ceramics that was first developed in Ancient Greece, while lithography, also called litho, is used to apply designs to articles through a three-layer process comprising the colour, or image, layer, the cover coat, and the backing paper. Gold decoration, used on some high-quality ware, includes methods such as Best gold, Acid Gold, Bright Gold, and Mussel Gold, each requiring different levels of skill and firing techniques to achieve the desired luster and permanence.
The Global Pot
The city of Stoke-on-Trent is widely known as The Potteries because of the large number of pottery factories or, colloquially, Pot Banks, and it was one of the first industrial cities of the modern era where, as early as 1785, two hundred pottery manufacturers employed 20,000 workers. Josiah Wedgwood, who lived from 1730 to 1795, was the dominant leader of this industry, and in North Staffordshire hundreds of companies produced all kinds of pottery, from tablewares and decorative pieces to industrial items. The main pottery types of earthenware, stoneware, and porcelain were all made in large quantities, and the Staffordshire industry was a major innovator in developing new varieties of ceramic bodies such as bone china and jasperware, as well as pioneering transfer printing and other glazing and decorating techniques. By the late 18th century, North Staffordshire was the largest producer of ceramics in the UK, despite significant hubs elsewhere, and large export markets took Staffordshire pottery around the world, especially in the 19th century. Production had begun to decline in the late 19th century, as other countries developed their industries, and declined notably after World War II, with employment falling from 45,000 in 1975 to 23,000 in 1991, and 13,000 in 2002. The industry faced significant challenges, including the development of new technologies and the changing tastes of consumers, but it remained a major economic force in the region for centuries.
Notable risks to pottery workers include silicosis, heavy metal poisoning, poor indoor air quality, dangerous sound
The Industrial Revolution
levels, and possible over-illumination, with silicosis being an occupational lung disease caused by inhaling large amounts of crystalline silica dust, usually over many years. Workers in the ceramic industry can develop it due to exposure to silica dust in the raw materials, and colloquially it has been known as Potter's rot. Less than 10 years after its introduction, in 1720, as a raw material to the British ceramics industry, the negative effects of calcined flint on the lungs of workers had been noted. In one study reported in 2022, of 106 UK pottery workers, 55 per cent had at least some stage of silicosis. The type of dust linked to a higher risk of lung cancer is harmful, and exposure to siliceous dusts is reduced by either processing and using the source materials as aqueous suspension or as damp solids, or by the use of dust control measures such as local exhaust ventilation. These have been mandated by legislation, such as The Pottery (Health and Welfare) Special Regulations 1950 in the UK, and the Health and Safety Executive in the UK has produced guidelines on controlling exposure to respirable crystalline silica in potteries. The British Ceramics Federation provides a guidance booklet, and the first legislation in the UK to limit pottery workers exposure to lead was included in the Factories Act Extension Act in 1864, with further introduced in 1899, addressing the
The Health Of The Potter
significant health concern of lead poisoning, or plumbism, which was recognized at least as early as the nineteenth century.
Modern pottery production has evolved to include advanced techniques such as 3D printing, which involves the layered deposition of soft clay body similar to fused deposition modelling, and the use of powder binding techniques where clay body in dry powder form is fused together layer upon layer with a liquid. Pressure casting, developed in the 1970s for the production of sanitaryware, allows for much faster casting rates and faster production cycles, with specially developed polymeric materials allowing a mould to be subject to application external pressures of up to 4.0 MPa. Injection moulding, adapted for the tableware industry from the method long established for the forming of thermoplastic and some metal components, allows the production of a cup, including the handle, in a single process, and thereby eliminates the handle-fixing operation and produces a stronger bond between cup and handle. The feed to the mould die is a mix of approximately 50 to 60 per cent unfired body in powder form, together with 40 to 50 per cent organic additives composed of binders, lubricants, and plasticisers. The technique is not as widely used as other shaping methods, though it has been developed, though it has yet to be fully commercialised. The future of pottery lies in the balance between preserving traditional techniques and embracing new technologies, with the industry continuing to innovate in the face of environmental and health challenges, while maintaining the rich cultural heritage that has defined pottery for thousands of years.