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A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, and brick.
Pottery is the process and the products of forming vessels and other objects with clay and other raw materials, which are fired at high temperatures to give them a hard and durable form. Major types include earthenware, stoneware and porcelain. The place where such wares are made by a potter is also called a pottery. The definition of pottery, used by the ASTM International, is "all fired ceramic wares that contain clay when formed, except technical, structural, and refractory products". In art history and archaeology, especially of ancient and prehistoric periods, pottery often means vessels only, and sculpted figurines of the same material are called terracottas.
Raku ware is a type of Japanese pottery traditionally used in Japanese tea ceremonies, most often in the form of chawan tea bowls. It is traditionally characterised by being hand-shaped rather than thrown, fairly porous vessels, which result from low firing temperatures, lead glazes and the removal of pieces from the kiln while still glowing hot. In the traditional Japanese process, the fired raku piece is removed from the hot kiln and is allowed to cool in the open air.
Earthenware is glazed or unglazed nonvitreous pottery that has normally been fired below 1,200 °C (2,190 °F). Basic earthenware, often called terracotta, absorbs liquids such as water. However, earthenware can be made impervious to liquids by coating it with a ceramic glaze, and is used for the great majority of modern domestic earthenware. The main other important types of pottery are porcelain, bone china, and stoneware, all fired at high enough temperatures to vitrify.
Pottery and porcelain, is one of the oldest Japanese crafts and art forms, dating back to the Neolithic period. Kilns have produced earthenware, pottery, stoneware, glazed pottery, glazed stoneware, porcelain, and blue-and-white ware. Japan has an exceptionally long and successful history of ceramic production. Earthenwares were made as early as the Jōmon period, giving Japan one of the oldest ceramic traditions in the world. Japan is further distinguished by the unusual esteem that ceramics holds within its artistic tradition, owing to the enduring popularity of the tea ceremony.
Celadon is a term for pottery denoting both wares glazed in the jade green celadon color, also known as greenware or "green ware", and a type of transparent glaze, often with small cracks, that was first used on greenware, but later used on other porcelains. Celadon originated in China, though the term is purely European, and notable kilns such as the Longquan kiln in Zhejiang province are renowned for their celadon glazes. Celadon production later spread to other parts of East Asia, such as Japan and Korea as well as Southeast Asian countries such as Thailand. Eventually, European potteries produced some pieces, but it was never a major element there. Finer pieces are in porcelain, but both the color and the glaze can be produced in stoneware and earthenware. Most of the earlier Longquan celadon is on the border of stoneware and porcelain, meeting the Chinese but not the European definitions of porcelain.
Donabe are pots made out of a special clay for use over an open flame in Japanese cuisine, and in the case of semi-stoneware Banko ware of high petalite content. Often, the food is cooked at the table on a gas burner for various nabemono dishes such as shabu-shabu and dishes served simmering including nabeyaki udon. They are sized by sun, one of the Japanese units of measurement.
Salt-glaze or salt glaze pottery is pottery, usually stoneware, with a glaze of glossy, translucent and slightly orange-peel-like texture which was formed by throwing common salt into the kiln during the higher temperature part of the firing process. Sodium from the salt reacts with silica in the clay body to form a glassy coating of sodium silicate. The glaze may be colourless or may be coloured various shades of brown, blue, or purple.
A saggar is a type of kiln furniture. It is a ceramic boxlike container used in the firing of pottery to enclose or protect ware being fired inside a kiln. The name may be a contraction of the word safeguard.
Slipware is pottery identified by its primary decorating process where slip is placed onto the leather-hard (semi-hardened) clay body surface before firing by dipping, painting or splashing. Slip is an aqueous suspension of a clay body, which is a mixture of clays and other minerals such as quartz, feldspar and mica. The slip placed onto a wet or leather-hard clay body surface by a variety of techniques including dipping, painting, piping or splashing. Slipware is the pottery on which slip has been applied either for glazing or decoration. Slip is liquified clay or clay slurry, with no fixed ratio of water and clay, which is used either for joining pottery pieces together by slip casting with mould, glazing or decorating the pottery by painting or dipping the pottery with slip.
Craquelure is a fine pattern of dense cracking formed on the surface of materials. It can be a result of drying, aging, intentional patterning, or a combination of all three. The term is most often used to refer to tempera or oil paintings, but it can also develop in old ivory carvings or painted miniatures on an ivory backing. Recently, analysis of craquelure has been proposed as a way to authenticate art.
Slip casting, or slipcasting, is a ceramic forming technique for pottery and other ceramics, especially for shapes not easily made on a wheel. In this method, a liquid clay body slip is poured into plaster moulds and allowed to form a layer, the cast, on the inside walls of the mould. The process usually takes at least 24 hours per piece. It gives very precise and consistent shapes, and is now the most common technique used for commercial mass-produced pottery, although it began in Europe as a technique for fine wares such as porcelain by the 1750s.
Architectural terracotta refers to a fired mixture of clay and water that can be used in a non-structural, semi-structural, or structural capacity on the exterior or interior of a building. Terracotta pottery, as earthenware is called when not used for vessels, is an ancient building material that translates from Latin as "baked earth". Some architectural terracotta is actually the stronger stoneware. It can be unglazed, painted, slip glazed, or glazed. A piece of terracotta is composed of a hollow clay web enclosing a void space or cell. The cell can be installed in compression with mortar or hung with metal anchors. All cells are partially backfilled with mortar.
Paper clay is any clay body to which processed cellulose fiber has been added.
Ceramic glaze is an impervious layer or coating of a vitreous substance which has been fused to a pottery body through firing. Glaze can serve to color, decorate or waterproof an item. Glazing renders earthenware vessels suitable for holding liquids, sealing the inherent porosity of unglazed biscuit earthenware. It also gives a tougher surface. Glaze is also used on stoneware and porcelain. In addition to their functionality, glazes can form a variety of surface finishes, including degrees of glossy or matte finish and color. Glazes may also enhance the underlying design or texture either unmodified or inscribed, carved or painted.
Glaze defects are any flaws in the surface quality of a ceramic glaze, its physical structure or its interaction with the body.
This is a list of pottery and ceramic terms.
The room-temperature form of quartz, α-quartz, undergoes a reversible change in crystal structure at 573 °C to form β-quartz. This phenomenon is called an inversion, and for the α to β quartz inversion is accompanied by a linear expansion of 0.45%. This inversion can lead to cracking of ceramic ware if cooling occurs too quickly through the inversion temperature. This is called dunting, and the resultant faults as dunts. To avoid such thermal shock faults, cooling rates not exceeding 50 °C/hour have been recommended.
In pottery, leather-hard is the condition of a clay or clay body when it has been partially dried to a consistency similar to leather of the same thickness as the clay. At this stage, the clay object has approximately 15% moisture content. The clay is still visibly damp but has dried enough to be able to be handled without deformation. The body is able to be gouged or incised without breaking.
References
- ↑ Frank Hamer, Janet Hamer (2004), "Crack", The potter's dictionary of materials and techniques, University of Pennsylvania Press
- ↑ Frank Hamer, Janet Hamer (2004), "Dunting", The potter's dictionary of materials and techniques, University of Pennsylvania Press
- Fraser, Harry. Ceramic Faults and their Remedies. A and C Black. London. 1986.