Porcelain
Porcelain, also called china, is a ceramic material made by heating raw materials, generally including kaolinite, in a kiln to temperatures between. The greater strength and translucence of porcelain, relative to other types of pottery, arise mainly from vitrification and the formation of the mineral mullite within the body at these high temperatures. End applications include tableware, decorative ware such as figurines, and products in technology and industry such as electrical insulators and laboratory ware.
The manufacturing process used for porcelain is similar to that used for earthenware and stoneware, the two other main types of pottery, although it can be more challenging to produce. It has usually been regarded as the most prestigious type of pottery due to its delicacy, strength, and high degree of whiteness. It is frequently both glazed and decorated.
Though definitions vary, porcelain can be divided into three main categories: hard-paste, soft-paste, and bone china. The categories differ in the composition of the body and the firing conditions.
Porcelain originated in China, the result of centuries of ceramic experimentation by Chinese potters. Depending on the definition used, the technology matured between approximately 200 and 800 CE. It later spread to other countries in Asia, then to Europe, and eventually to the rest of the world. The European name, porcelain in English, comes from the old Italian porcellana because of its resemblance to the surface of the shell. Porcelain is also referred to as "china" or fine china in some English-speaking countries, as it was first seen in imports from China during the 17th century. Properties associated with porcelain include low permeability and elasticity; considerable strength, hardness, whiteness, translucency, and resonance; and a high resistance to corrosive chemicals and thermal shock.
Porcelain has been described as being "completely vitrified, hard, impermeable, white or artificially coloured, translucent, and resonant". However, the term "porcelain" lacks a universal definition and has "been applied in an unsystematic fashion to substances of diverse kinds that have only certain surface-qualities in common".
Traditionally, East Asia only classifies pottery into low-fired wares and high-fired wares, the latter also including what Europeans call "stoneware", which is high-fired but not generally white or translucent. Terms such as "proto-porcelain", "porcellaneous", or "near-porcelain" may be used in cases where the ceramic body approaches whiteness and translucency.
In 2021, the global market for porcelain tableware was estimated to be worth US$22.1 billion.
Types
Hard paste
Hard-paste porcelain was invented in China, and it was also used in Japanese porcelain. Most of the finest quality porcelain wares are made of this material. The earliest European porcelains were produced at the Meissen factory in the early 18th century; they were formed from a paste composed of kaolin and alabaster and fired at temperatures up to in a wood-fired kiln, producing a porcelain of great hardness, translucency, and strength. Later, the composition of the Meissen hard paste was changed, and the alabaster was replaced by feldspar and quartz, allowing the pieces to be fired at lower temperatures. Kaolinite, feldspar, and quartz continue to constitute the basic ingredients for most continental European hard-paste porcelains.Soft paste
Soft-paste porcelains date back to early attempts by European potters to replicate Chinese porcelain by using mixtures of clay and frit. Soapstone and lime are known to have been included in these compositions. These wares were not yet actual porcelain wares, as they were neither hard nor vitrified by firing kaolin clay at high temperatures. As these early formulations suffered from high pyroplastic deformation, or slumping in the kiln at high temperatures, they were uneconomic to produce and of low quality.Formulations were later developed based on kaolin with quartz, feldspars, nepheline syenite, or other feldspathic rocks. These are technically superior and continue to be produced. Soft-paste porcelains are fired at lower temperatures than hard-paste porcelains; therefore, these wares are generally less hard than hard-paste porcelains.
Bone china
Although originally developed in England in 1748 to compete with imported porcelain, bone china is now made worldwide, including in China. The English had read the letters of Jesuit missionary François Xavier d'Entrecolles, which described Chinese porcelain manufacturing secrets in detail. One writer has speculated that a misunderstanding of the text could possibly have been responsible for the first attempts to use bone-ash as an ingredient in English porcelain, although this is not supported by modern researchers and historians.Traditionally, English bone china was made from two parts of bone ash, one part of kaolin, and one part of china stone, although the latter has been replaced by feldspars from non-UK sources.
Materials
Kaolin is the primary material from which porcelain is made, even though clay minerals might account for only a small proportion of the whole. The word paste is an old term for both unfired and fired materials. A more common terminology for the unfired material is "body"; for example, when buying materials a potter might order an amount of porcelain body from a vendor.The composition of porcelain is highly variable, but the clay mineral kaolinite is often a raw material. Other raw materials can include feldspar, ball clay, glass, bone ash, steatite, quartz, petuntse and alabaster.The clays used are often described as being long or short, depending on their plasticity. Long clays are cohesive and have high plasticity; short clays are less cohesive and have lower plasticity. In soil mechanics, plasticity is determined by measuring the increase in content of water required to change a clay from a solid state bordering on the plastic, to a plastic state bordering on the liquid, though the term is also used less formally to describe the ease with which a clay may be worked.
Clays used for porcelain are generally of lower plasticity than many other pottery clays. They wet very quickly, meaning that small changes in the content of water can produce large changes in workability. Thus, the range of water content within which these clays can be worked is very narrow and consequently must be carefully controlled.
Production
Forming
Porcelain can be made using all the shaping techniques for pottery.Glazing
is unglazed porcelain treated as a finished product, mostly for figures and sculpture. Unlike their lower-fired counterparts, porcelain wares do not need glazing to render them impermeable to liquids and for the most part are glazed for decorative purposes and to make them resistant to dirt and staining. Many types of glaze, such as the iron-containing glaze used on the celadon wares of Longquan, were designed specifically for their striking effects on porcelain.Decoration
Porcelain often receives underglaze decoration using pigments that include cobalt oxide and copper, or overglaze enamels, allowing a wider range of colours. Like many earlier wares, modern porcelains are often biscuit-fired at around, coated with glaze and then sent for a second glaze-firing at a temperature of about or greater. Another early method is "once-fired", where the glaze is applied to the unfired body and the two fired together in a single operation.Firing
In this process, "green" ceramic wares are heated to high temperatures in a kiln to permanently set their shapes, vitrify the body and the glaze. Porcelain is fired at a higher temperature than earthenware so that the body can vitrify and become non-porous. Many types of porcelain in the past have been fired twice or even three times, to allow decoration using less robust pigments in overglaze enamel.History
Chinese porcelain
Porcelain was invented in China over a centuries-long development period beginning with "proto-porcelain" wares dating from the Shang dynasty. By the time of the Eastern Han dynasty these early glazed ceramic wares had developed into porcelain, which Chinese defined as high-fired ware. By the late Sui dynasty and early Tang dynasty, the now-standard requirements of whiteness and translucency had been achieved, in types such as Ding ware. The wares were already exported to the Islamic world, where they were highly prized.Eventually, porcelain and the expertise required to create it began to spread into other areas of East Asia. During the Song dynasty, artistry and production had reached new heights. The manufacture of porcelain became highly organised, and the dragon kilns excavated from this period could fire as many as 25,000 pieces at a time, and over 100,000 by the end of the period. While Xing ware is regarded as among the greatest of the Tang dynasty porcelain, Ding ware became the premier porcelain of the Song dynasty. By the Ming dynasty, production of the finest wares for the court was concentrated in a single city, and Jingdezhen porcelain, originally owned by the imperial government, remains the centre of Chinese porcelain production.
By the time of the Ming dynasty, porcelain wares were being exported to Asia and Europe. Some of the most well-known Chinese porcelain art styles arrived in Europe during this era, such as the coveted "blue-and-white" wares. The Ming dynasty controlled much of the porcelain trade, which was expanded to Asia, Africa and Europe via the Silk Road. In 1517, Portuguese merchants began direct trade by sea with the Ming dynasty, and in 1598, Dutch merchants followed.
Some porcelains were more highly valued than others in imperial China. The most valued types can be identified by their association with the court, either as tribute offerings, or as products of kilns under imperial supervision. Since the Yuan dynasty, the largest and best centre of production has made Jingdezhen porcelain. During the Ming dynasty, Jingdezhen porcelain had become a source of imperial pride. The Yongle emperor erected a white porcelain brick-faced pagoda at Nanjing, and an exceptionally smoothly glazed type of white porcelain is peculiar to his reign. Jingdezhen porcelain's fame came to a peak during the Qing dynasty.