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[French porcelaine, cowry shell, porcelain, from Old French, from Old Italian porcellana, from feminine of porcellano, of a young sow (from the shell's resemblance to a pig's back), from porcella, young sow, diminutive of porca, sow, from Latin, feminine of porcus, pig.]
porcelaneous por'ce·la'ne·ous (-lā'nē-əs) adj.Background
The term porcelain refers to a wide range of ceramic products that have been baked at high temperatures to achieve vitreous, or glassy, qualities such as translucence and low porosity. Among the most familiar porcelain goods are table and decorative china, chemical ware, dental crowns, and electrical insulators. Usually white or off-white, porcelain comes in both glazed and unglazed varieties, with bisque, fired at a high temperature, representing the most popular unglazed variety.
Although porcelain is frequently used as a synonym for china, the two are not identical. They resemble one another in that both are vitreous wares of extremely low porosity, and both can be glazed or unglazed. However, china, also known as soft-paste or tender porcelain, is softer: it can be cut with a file, while porcelain cannot. This difference is due to the higher temperatures at which true porcelain is fired, 2,650 degrees Fahrenheit (1,454 degrees Celsius) compared to 2,200 degrees Fahrenheit (1,204 degrees Celsius) for china. Due to its greater hardness, porcelain has some medical and industrial applications which china, limited to domestic and artistic use, does not. Moreover, whereas porcelain is always translucent, china is opaque.
Hard-paste or "true" porcelain originated in China during the T'ang dynasty (618-907 A.D.); however, high quality porcelain comparable to modern wares did not develop until the Yuan dynasty (1279-1368 A.D.). Early Chinese porcelain consisted of kaolin (china clay) and pegmatite, a coarse type of granite. Porcelain was unknown to European potters prior to the importation of Chinese wares during the Middle Ages. Europeans tried to duplicate Chinese porcelain, but, unable to analyze its chemical composition, they could imitate only its appearance. After mixing glass with tin oxide to render it opaque, European craftspeople tried combining clay and ground glass. These alternatives became known as soft-paste, glassy, or artificial porcelains. However, because they were softer than genuine porcelain, as well as expensive to produce, efforts to develop true porcelain continued. In 1707 two Germans named Ehrenfried Walter von Tschimhaus and Johann Friedrich Bottger succeeded by combining clay with ground feldspar instead of the ground glass previously used.
Later in the eighteenth century the English further improved upon the recipe for porcelain when they invented bone china by adding ash from cattle bones to clay, feldspar, and quartz. Although bone china is fired at lower temperatures than true porcelain, the bone ash enables it to become translucent nonetheless. Because it is also easier to make, harder to chip, and stronger than hard porcelain, bone china has become the most popular type of porcelain in the United States and Britain (European consumers continue to favor hard porcelain).
Raw Materials
The primary components of porcelain are clays, feldspar or flint, and silica, all characterized by small particle size. To create different types of porcelain, craftspeople combine these raw materials in varying proportions until they obtain the desired green (unfired) and fired properties.
Although the composition of clay varies depending upon where it is extracted and how it is treated, all clays vitrify (develop glassy qualities), only at extremely high temperatures unless they are mixed with materials whose vitrification threshold is lower. Unlike glass, however, clay is refractory, meaning that it holds its shape when it is heated. In effect, porcelain combines glass's low porosity with clay's ability to retain its shape when heated, making it both easy to form and ideal for domestic use. The principal clays used to make porcelain are china clay and ball clay, which consist mostly of kaolinate, a hydrous aluminum silicate.
Feldspar, a mineral comprising mostly aluminum silicate, and flint, a type of hard quartz, function as fluxes in the porcelain body or mixture. Fluxes reduce the temperature at which liquid glass forms during firing to between 1,835 and 2,375 degrees Fahrenheit (1,000 and 1,300 degrees Celsius). This liquid phase binds the grains of the body together.
Silica is a compound of oxygen and silicon, the two most abundant elements in the earth's crust. Its resemblance to glass is visible in quartz (its crystalline form), opal (its amorphous form), and sand (its impure form). Silica is the most common filler used to facilitate forming and firing of the body, as well as to improve the properties of the finished product. Porcelain may also contain alumina, a compound of aluminum and oxygen, or low-alkali containing bodies, such as steatite, better known as soapstone.
The Manufacturing
Process
After the raw materials are selected and the desired amounts weighed, they go through a series of preparation steps. First, they are crushed and purified. Next, they are mixed together before being subjected to one of four forming processes—soft plastic forming, stiff plastic forming, pressing, or casting; the choice depends upon the type of ware being produced. After the porcelain has been formed, it is subjected to a final purification process, bisque-firing, before being glazed. Glaze is a layer of decorative glass applied to and fired onto a ceramic body. The final manufacturing phase is firing, a heating step that takes place in a type of oven called a kiln.
Crushing the raw materials
Cleaning and mixing
Forming the body
Bisque-firing
Glazing
Firing
Quality Control
The character of the raw materials is important in maintaining quality during the manufacturing process. The chemical composition, mineral phase, particle size distribution, and colloidal surface area affect the fired and unfired properties of the porcelain. With unfired body, the properties evaluated include viscosity, plasticity, shrinkage, and strength. With fired porcelain, strength, porosity, color, and thermal expansion are measured. Many of these properties are monitored and controlled during manufacturing using statistical methods. Both the raw materials and the process parameters (milling time and forming pressure, for example) can be adjusted to achieve desired quality.
The Future
High-quality porcelain art and dinnerware will continue to enhance the culture. Improvements in manufacturing will continue to increase both productivity and energy efficiency. For instance, a German kiln manufacturer has developed a prefabricated tunnel kiln for fast firing high-quality porcelain in less than 5 hours. Firing is achieved by partly reducing atmosphere at a maximum firing temperature of 2,555 degrees Fahrenheit (1,400 degrees Celsius). The kiln uses high-velocity burners and an automatic control system, producing 23,000 pounds (11,500 kilograms) of porcelain in 24 hours.
Manufacturers of porcelain products may also have to increase their recycling efforts, due to the increase in environmental regulations. Though unfired scrap is easily recycled, fired scrap poses a problem: mechanically strong and therefore hard to break down, it is usually dumped into landfills. However, preliminary research has shown that fired scrap can be reused after thermal quenching (where the scrap is reheated and then quickly cooled), which makes it weaker and easier to break down. The scrap can then be used as a raw material.
Porcelain appears to be playing a more important role in technical applications. Recent patents have been issued to Japanese and American companies in the area of electrical insulators and dental prostheses. NGK Insulators, Ltd., a Japanese manufacturer, has developed high-strength porcelain for electrical insulators, whereas Murata Manufacturing Co. has developed low-temperature-sintering porcelain components for electronic applications.
Where To Learn More
Books
Campbell, James E. The Art and Architecture Information Guide Series, vol. 7:Pottery and Ceramics, A Guide to Infonnation Sources. Gale Research, 1978.
Camusso, Lorenzo, ed. Ceramics of the World: From Four Thousand B.C. to the Present. Harry N. Abrams, 1992.
Charles, Bernard H. Pottery and Porcelain. Hippocrene Books, 1974.
Jones, J. T. and M. F. Bernard. Ceramics, Industrial Processing and Testing. Iowa State University Press, 1972.
Periodicals
Shashidhar, N. and J. S. Reed. "Recycling Fired Porcelain." Ceramic Bulletin. Vol. 69, No. 5, 1990, pp. 834-841.
Wilson, Lana. "Charcoal and Metallic Salts." Ceramics Monthly. October, 1987, p. 36.
[Article by: L. S. Millberg]
A high-grade ceramic ware characterized by high strength, a white color (under the glaze), very low absorption, good translucency, and a hard glaze. Equivalent terms are European porcelain, hard porcelain, true porcelain, and hard paste porcelain. See also Glazing; Pottery.
Porcelain is distinguished from other fine ceramic ware, such as china, by the fact that the firing of the unglazed ware (the bisque firing) is done at a lower temperature (1800–2200°F or 1000–1200°C) than the final or glost firing, which may be as high as 2700°F (1500°C). In other words, the ware reaches its final state of maturity at the maturing temperatures of the glaze.
The white color is obtained by using very pure white-firing kaolin or china clay and other pure materials, the low absorption results from the high firing temperature, and the translucency results from the glass phase. See also Ceramics.
A material formed by the fusion of feldspar, silica, and other minor ingredients. Most dental porcelains are glasses and are used in the manufacture of artificial teeth, facings, jackets, and occasionally denture bases and inlays.
For more information on porcelain, visit Britannica.com.
A glazed or unglazed vitreous ceramic whiteware used for electrical, chemical, mechanical, structural, or thermal components.
A fine form of pottery which is fired to a very high temperature in order to vitrify the clay.
Benjamin Franklin viewed the domestic manufacture of porcelain as an important step toward economic independence from England, and it ultimately became intimately linked with the industrialization of the nation. However, its production in the United States was never as crucial as stoneware and redware production.
Porcelain, first made in China during the Tang dynasty (618–907 A.D.), remained a Chinese secret sought by the West for many hundreds of years. It was not until 1708 and 1709, after the German ceramist Johann Friedrich Böttger had discovered its secret, kaolin, that true hard-paste porcelain was produced outside of China. In 1738, Andrew Duché of Savannah, Georgia, made the first recorded piece of porcelain in North America, "a small teacup … very near transparent."
Around 1825 some twenty skilled craftsmen from England and France were employed to make porcelain for the Jersey Porcelain and Earthenware Company in Jersey City, New Jersey. Other ventures followed in Philadelphia. In 1853, when the Crystal Palace Exhibition of the Industry of All Nations was held in New York City, work by the Haviland Brothers, who had a china shop there, was much praised. By the mid-1860s, Parian ware, a type of porcelain having the appearance of marble, became so popular that no fashionable Victorian parlor would be without a piece or two. Ott and Brewer of Trenton, New Jersey, sold a wide line of Parian ware. From the 1880s on, Belleek, a light, marvelously thin, ivory-colored porcelain variant of Parian, named after its Irish town of origin, became the greatest American ceramics success story.
After the influential Centennial Exhibition in Philadelphia, art pottery became a serious business in America. Porcelain, while a minor branch of the industry, had its champions in M. Louise McLaughlin (1847–1939) and especially Adelaide Alsop Robineau (1865–1929). By the 1930s, porcelain found wide application in industry and began to be studied at colleges, universities, and art schools such as Cranbrook. An intense interest in porcelain continues.
Bibliography
American Ceramics: The Collection of Everson Museum of Art. New York: Rizzoli, 1989.
Frelinghuysen, Alice Cooney. American Porcelain, 1770–1920. New York: The Metropolitan Museum of Art, 1989.
Bibliography
See G. Savage, Porcelain through the Ages (1955, repr. 1963); F. Litchfield, Pottery and Porcelain (6th ed. 1953, repr. 1967); S. Valenstein, A Handbook of Chinese Ceramics (1989).
Common clay must go through the heat and fire of the furnace to become porcelain. But once porcelain, it can never become clay again.
— Unknown
Porcelain is a ceramic material made by heating selected and refined materials, often including clay in the form of kaolinite, to high temperatures. The raw materials for porcelain, when mixed with water, form a plastic body that can be worked to a required shape before firing in a kiln at temperatures between 1200°C and 1400°C. The toughness, strength, and translucence of porcelain arise mainly from the formation at high temperatures of glass and the mineral mullite within the fired body.
Porcelain was named after its resemblance to the white, shiny cowry, called in old Italian porcella (little pig), because the curved shape of its upper surface resembles the curve of a pig's back. Properties associated with porcelain include low permeability, high strength, hardness, glassiness, high durability, whiteness, translucence, resonance, brittleness, high resistance to the passage of electricity, high resistance to chemical attack, high resistance to thermal shock and high elasticity.
For the purposes of trade, the Combined Nomenclature of the European Communities defines porcelain as being "completely vitrified, hard, impermeable (even before glazing), white or artificially colored, translucent (except when of considerable thickness) and resonant." However, the term porcelain lacks a universally agreed definition and has "been applied in a very unsystematic fashion to substances of diverse kinds which have only certain surface-qualities in common" (Burton 1906).
Porcelain is used to make table, kitchen, sanitary and decorative wares, objects of fine art and tiles. Its high resistance to the passage of electricity makes porcelain an excellent insulating material and it is widely used for high-voltage insulators. It is also used in dentistry to make false teeth, caps and crowns.
Porcelain has many uses but this article is concerned mainly with its employment as a material used to make objects of craft and fine art, including decorative and utilitarian household wares. A difficult line to draw is that which divides high-fired stoneware from porcelain because this depends upon how the terms porcelain and stoneware are defined. In this article the term porcelain is taken to encompass a broad range of high-fired ceramic wares, including some that might according to some systems of classification fall into the category of stoneware.
The material used to form the body of porcelain wares is often referred to as clay, even though clay minerals might account for only a small proportion of its whole. The porcelain clay body, unfired or fired, is sometimes spoken of as the paste and porcelain clay is itself sometimes described as the body (for example, when buying materials a potter might order such an amount of porcelain body from a vendor).
The composition of porcelain is highly variable, but china clay, comprising mainly or in part the platy clay mineral kaolinite is often a significant component. Other materials mixed with china clay to make porcelain clay have included feldspar, ball-clay, glass, bone ash, steatite, quartz, petuntse and alabaster.
The clays used by potters are often described as being long or short according to plasticity. Long clays are cohesive (sticky) and of high plasticity and short clays are less cohesive and are of 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 facility with which a clay may be worked. Porcelain clays are of lower plasticity (shorter) than many other clays used for making pottery and wet very quickly, which is to say that small changes in the content of water can produce large changes in workability. Thus, the range of water contents within which porcelain clays can be worked is very narrow and the loss or gain of water during storage and throwing or forming must be carefully controlled to keep the clay from becoming too wet or too dry to manipulate. This property also contributes to porcelain's use as a slipcasting body.[dubious ]
The article on Pottery provides much useful background information on methods used for forming, decorating, finishing, glazing and firing ceramic wares.
Forming. Porcelain wares can be formed by any of the shaping methods listed in the Pottery article.
The relatively low plasticity of the clays used for making porcelain can cause difficulties for the potter, particularly in the case of wheel-thrown wares. To the spectator, throwing is often seen as pulling clay upwards and outwards into a required shape and potters often speak of pulling when forming a piece on a wheel, but the term is misleading, clay in a plastic condition cannot be pulled without breaking. The process of throwing is in fact one of remarkable complexity. To the casual observer, throwing carried out by an expert potter appears to be a graceful and almost effortless activity, but this masks the fact that a rotating mass of clay possesses energy and momentum in an abundance that will, given the slightest mishandling, rapidly cause the workpiece to become uncontrollable.
Glazing. It has been speculated that the first glazes were accidental and resulted from the presence in the kiln of lime-rich wood ash [citation needed] , which acted on the surface of the wares as a flux. 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. Great detail is given in the glaze article.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 wares may be decorated under the glaze, using pigments that include cobalt and copper, or over the glaze using colored enamels. In common with many earlier wares, modern porcelain wares are often bisque-fired at around 1000 degrees Celsius, coated with glaze and then sent for a second glaze-firing at a temperature of about 1300 degrees Celsius, or greater. In an alternative method of glazing particularly associated with Chinese and early European porcelains the glaze was applied to the unfired body and the two fired together in a single operation. Wares glazed in this way are described as being green-fired or once-fired.
Firing. Firing is the operation of heating green (unfired) ceramic wares at high-temperatures in a kiln to make permanent their shapes. The porcelain is fired at a higher temperature than earthenware or stoneware so that the clay can vitrify and become non porous.
Western porcelain is generally divided into the three main categories of hard-paste, soft-paste and bone china, depending on the composition of the paste (the paste is the material used to form the body of a piece of porcelain).
One of the earliest European porcelains was produced at the Meissen factory and was compounded from china clay kaolin, quartz and alabaster and was fired at temperatures in excess of 1350-degrees Celsius to produce a porcelain of great hardness and strength. At a later date the composition of Meissen hard paste was changed and the alabaster was replaced by feldspar, lowering the firing temperature required. China clay, feldspar and quartz (or other forms of silica) continue to this day to provide the basic ingredients for most continental European hard paste porcelains.
Its history dates from the early attempts by European potters to replicate Chinese porcelain by using mixtures of china clay and ground-up glass or frit; soapstone and lime were known to have also been included in some compositions. As these early formulations suffered from high pyroplastic deformation, or slumping in the kiln at raised temperature, they were uneconomic to produce. Formulations were later developed based on kaolin, quartz, feldspars, nepheline syenite and other feldspathic rocks. These were technically superior and continue in production.
Although originally developed in England to compete with imported porcelain, Bone china is now made worldwide. It has been suggested that a misunderstanding of an account of porcelain manufacture in China given by a Jesuit missionary was responsible for the first attempts to use bone-ash as an ingredient of Western porcelain (in China, china clay was sometimes described as forming the bones of the paste, while the flesh was provided by refined porcelain stone). For what ever reason, when it was first tried it was found that adding bone-ash to the paste produced a white, strong, translucent porcelain. Traditionally English bone china was made from two parts of bone-ash, one part of china clay kaolin and one part of Cornish china stone (a feldspathic rock), although this has largely been replaced by feldspars from non-UK sources
The earliest porcelains originated in China possibly during the late Eastern Han dynasty 25-220 AD). The reader is referred to the article on Chinese porcelain where the history of early porcelain is discussed.
Porcelain was first made in China, and it is a measure of the esteem in which the exported Chinese porcelains of the seventeenth and eighteenth centuries were held in Europe that in English China became a commonly used synonym for the Franco-Italian term porcelain. After a number of false starts, such as the so-called Medici porcelain, the European search for the secret of porcelain manufacture ended in 1708 with the discovery by Ehrenfried Walther von Tschirnhaus and Johann Friedrich Böttger of a combination of ingredients, including Colditz clay (a type of kaolin), calcined alabaster and quartz, that proved to be suitable for making a hard, white, translucent porcelain, first produced at Meissen. It appears that in this discovery technology transfer from East Asia played little part.
William Cookworthy is credited with discovering china clay in Cornwall which made a considerable contribution to the development of porcelain and other whiteware ceramics in the United Kingdom. Cookworthy's factory at Plymouth established in 1768 used Cornish china clay and Cornish china stone to make a form of porcelain the body of which in character closely resembled the Chinese porcelains of the early eighteenth century.
Tschirnhaus and Böttger worked at Dresden and at Meissen, in the German state of Saxony, for Augustus the Strong. Tschirnhaus had a wide knowledge of European science and had also worked on the search for porcelain for more than a decade. In 1705 Böttger was appointed to assist him in this task. After training as a pharmacist, Böttger turned to alchemy and it was his claim that he knew the secret of transmuting dross into gold that attracted the attention of Augustus. Imprisoned by Augustus as an incentive to hasten research, Böttger was obliged to work with other alchemists in the futile search for transmutation, but his work in this area ended in 1705, when he was appointed to assist Tschirnhaus in the search for the secret of making porcelain. However, one of the first results of the collaboration between Tschirnhaus and Böttger was the development of a red stoneware that resembled the red wares of Yixing, and a factory was established to make these wares at Meissen, in 1707.
A workshop note records that the first specimen of hard, white European porcelain was produced in January, 1708. At this time the research was still being carried out under the direction of Tschirnhaus, who died in October of that year. It was left to Böttger to report to Augustus in March, 1709 that he could make good, white porcelain and for this reason credit for the European discovery of porcelain is traditionally given to him, but unjustly, in the view of many of those who point to the essential role played by Tschirnhaus.
The Meissen factory was established in 1710, following the development of a kiln and a glaze suitable for use with Böttger's porcelain, which required firing at very high temperatures to achieve translucence (greater than 1350 degrees Celsius). Meissen porcelain was once-fired or green-fired in the Chinese manner and was noted for its great resistance to thermal shock; so much so that a visitor to the factory in Böttger's time reported having seen a white-hot teapot being removed from the kiln and dropped into cold water, without damage. Evidence to support this widely disbelieved story was given in the 1980s when the procedure was repeated in an experiment at the Massachusetts Institute of Technology.
Heinrich Schmidt, a designer from the Meissen factory, went on to establish his reputation in America when he joined the Knowles, Taylor & Knowles factory in East Liverpool, Ohio in the 1890s. Schmidt was the creative force behind KT&K's famed Lotus Ware, commonly acknowledged to be the finest porcelain ever produced in the United States.[dubious ]
In unusual modern cases porcelain has also been used as a building material for exterior surfaces. Generally the porcelain is formed into large rectangular panels . An award winning building using porcelain is the Dakin Building, Brisbane, California. An older example is the Gulf Building, Houston, Texas, built in 1929, which had a seventy-foot long logo of porcelain [1]
For a short time in America, porcelainized steel homes were produced in a Columbus, Ohio factory and constructed throughout the US. These Lustron homes had porcelain coated steel ceilings, walls, exterior siding and roofs. About 2500 were built and many remain standing today. The homes were advertised as maintenance free, never needing painting.
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Nederlands (Dutch)
porselein, porseleinen
Français (French)
n. - porcelaine
Deutsch (German)
n. - Porzellan
Ελληνική (Greek)
n. - πορσελάνη
adj. - πορσελάνινος
Italiano (Italian)
porcellana, di porcellana
Português (Portuguese)
n. - porcelana (f)
adj. - de porcelana
Español (Spanish)
n. - porcelana, de porcelana
Svenska (Swedish)
n. - porslin
adj. - porslins-
中文（简体） (Chinese (Simplified))
瓷器, 瓷
中文（繁體） (Chinese (Traditional))
n. - 瓷器, 瓷
العربيه (Arabic)
(الاسم) خزف صيني (صفه) صيني
עברית (Hebrew)
n. - חרסינה, כלי חרסינה
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