Ash glazes are ceramic glazes made from the ash of various kinds of wood or straw. They have historically been important in East Asia, especially Chinese pottery, Korean pottery, and Japanese pottery. [1] Many traditionalist East Asian potteries still use ash glazing, and it has seen a large revival in studio pottery in the West and East. Some potters like to achieve random effects by setting up the kiln so that ash created during firing falls onto the pots; this is called "natural" or "naturally occurring" ash glaze. Otherwise the ash is mixed with water, and often clay, and applied as a paste.
Ash glazing began around 1500 BC, in China during the Shang dynasty, initially by accident as ash from the burnt wood in the kiln landed on pots. Around 1000 BC, the Chinese apparently realized that the ash covering the pieces was causing the glaze so they started adding the ash as a glaze before the pot went into the kiln. Ash glaze was the first glaze used in East Asia, and contained only ash, clay, and water. [2] [3]
One of the ceramic fluxes in ash glazes is calcium oxide (CaO), commonly known as quicklime, and most ash glazes are part of the lime glaze family, not all of which use ash. In some ash glazes extra lime was added to the ash, which may have been the case with Chinese Yue ware. [4] A relatively high temperature of around 1170 °C is required, high enough to make the body into stoneware or (above about 1200 °C and with the right materials) porcelain. [5]
The glaze has glasslike and pooling (buildup of glaze) characteristics which puts emphasis on the surface texture of the piece being glazed. When the glaze is mostly made up of wood ash, the final result is mostly dark brown to green. The pots with these glazes resemble the earth in color and texture. As the ash percentage decreases, the artist has more control on the color and the final glaze color, using wood, differs from light to dark shades of brown or green, if no other coloring agents are added. [6] Rice-straw ash glaze produces an opaque creamy-white glaze; it is high in silica. If the ash is very thick, there may be sufficient phosphorus to give an "opalescent blue"; [7] rice-husk ash is good for this.
"Natural" ash glaze from ash falling in the kiln tends to collect thickly on the shoulders of typical shapes of storage jar, and begin to drip down the walls of the vessel. This effect might be aided by tying plaits of straw around the shoulders before placing in the kiln. [8]
To create the ash, the material needs to burn completely in a kiln. Wood ash is around 1% the mass of the original wood, though some kinds of straw leave ash at a much higher percentage of the original weight. [9] Usually a large quantity of wood or straw is necessary to produce the ash. The ash is then put through a sieve to eliminate the excess clumps from the ash. At this point, artists can process the ash further to create a more uniform mixture or leave it unprocessed so there are more random final results. To process the ash, water is first added to the mixture and left to settle for a couple of hours. The solution is drained and dried and the result is ash containing less harmful chemicals like some soluble alkalis. [10]
A wide range of plants have been used, and their differing chemical compositions can give very different effects. [11]
Most wood ash is primarily made up of calcium carbonate (CaCO3), which is used in many glaze recipes. The ash also contains potassium carbonate (K2CO3), phosphates, and other metals; however, the ratio of these chemicals depend on the location, soil, and type of wood the ash came from. The varying chemical compositions of ashes used to make the glaze produce different results from batch to batch. Furthermore, two pieces with the same glaze batch can even have different results. If the ash is not cleaned or mixed thoroughly the glaze mixture may be inconsistent in chemical composition. [12]
Current ash glazes usually contain 50% less wood ash than they did when the majority of the glaze was ash. The decrease in ash percentage is to give the artist some control over the chemical make up and result of the glaze. Currently, ash glazes are mostly used by artists as a decorative tool, but some still use ash glaze ware. In Korea, the traditional ash glaze composed of only ash and water is used to make functional pottery such as bowls, cups, and teapots.
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. 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". End applications include tableware, decorative ware, sanitary ware, and in technology and industry such as electrical insulators and laboratory ware. In art history and archaeology, especially of ancient and prehistoric periods, pottery often means only vessels, 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.
Longquan celadon is a type of green-glazed Chinese ceramic, known in the West as celadon or greenware, produced from about 950 to 1550. The kilns were mostly in Lishui prefecture in southwestern Zhejiang Province in the south of China, and the north of Fujian Province. Overall a total of some 500 kilns have been discovered, making the Longquan celadon production area one of the largest historical ceramic producing areas in China. "Longquan-type" is increasingly preferred as a term, in recognition of this diversity, or simply "southern celadon", as there was also a large number of kilns in north China producing Yaozhou ware or other Northern Celadon wares. These are similar in many respects, but with significant differences to Longquan-type celadon, and their production rose and declined somewhat earlier.
Pottery and porcelain is one of the oldest Japanese crafts and art forms, dating back to the Neolithic period. Types have included earthenware, pottery, 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 hold within its artistic tradition, owing to the enduring popularity of the tea ceremony. During the Azuchi-Momoyama period (1573-1603), kilns throughout Japan produced ceramics with unconventional designs. In the early Edo period, the production of porcelain commenced in the Hizen-Arita region of Kyushu, employing techniques imported from Korea. These porcelain works became known as Imari wares, named after the port of Imari from which they were exported to various markets, including Europe.
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.
Salt-glaze or salt glaze pottery is pottery, usually stoneware, with a ceramic 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.
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.
Ding ware, Ting ware or Dingyao are Chinese ceramics, mostly porcelain, that were produced in the prefecture of Dingzhou in Hebei in northern China. The main kilns were at Jiancicun or Jianci in Quyang County. They were produced between the Tang and Yuan dynasties of imperial China, though their finest period was in the 11th century, under the Northern Song. The kilns "were in almost constant operation from the early eighth until the mid-fourteenth century."
Chinese ceramics are one of the most significant forms of Chinese art and ceramics globally. They range from construction materials such as bricks and tiles, to hand-built pottery vessels fired in bonfires or kilns, to the sophisticated Chinese porcelain wares made for the imperial court and for export.
Jun ware is a type of Chinese pottery, one of the Five Great Kilns of Song dynasty ceramics. Despite its fame, much about Jun ware remains unclear, and the subject of arguments among experts. Several different types of pottery are covered by the term, produced over several centuries and in several places, during the Northern Song dynasty (960–1127), Jin dynasty (1115–1234) and Yuan dynasty (1271–1368), and lasting into the early Ming dynasty (1368–1644).
Ceramic glaze, or simply glaze, is a glassy coating on ceramics. It is used for decoration, to ensure the item is impermeable to liquids and to minimise the adherence of pollutants.
This is a list of pottery and ceramic terms.
Sancai is a versatile type of decoration on Chinese pottery using glazes or slip, predominantly in the three colours of brown, green, and a creamy off-white. It is particularly associated with the Tang dynasty (618–907) and its tomb figures, appearing around 700. Therefore, it is commonly referred to as Chinese: 唐三彩 Tang Sancai in Chinese. Tang sancai wares were sometimes referred in China and the West as egg-and-spinach by dealers, for their use of green, yellow, and white, especially when combined with a streaked effect.
Shiwan ware is Chinese pottery from kilns located in the Shiwanzhen Subdistrict of the provincial city of Foshan, near Guangzhou, Guangdong. It forms part of a larger group of wares from the coastal region known collectively as "Canton stonewares". The hilly, wooded, area provided slopes for dragon kilns to run up, and fuel for them, and was near major ports.
Qingbai ware is a type of Chinese porcelain produced under the Song Dynasty and Yuan dynasty, defined by the ceramic glaze used. Qingbai ware is white with a blue-greenish tint, and is also referred to as Yingqing. It was made in Jiangxi province in south-eastern China, in several locations including Jingdezhen, and is arguably the first type of porcelain to be produced on a very large scale. However, it was not at the time a prestigious ware, and was mostly used for burial wares and exports, or a middle-rank Chinese market. The quality is very variable, reflecting these different markets; the best pieces can be very thin-walled.
Yue ware or Yüeh ware is a type of Chinese ceramics, a felspathic siliceous stoneware, which is characteristically decorated with celadon glazing. Yue ware is also sometimes called (Yuezhou) green porcelain in modern literature, but the term is misleading as it is not really porcelain and its shades are not really green. It has been "one of the most successful and influential of all south Chinese ceramics types".
Cizhou ware or Tz'u-chou ware is a wide range of Chinese ceramics from between the late Tang dynasty and the early Ming dynasty, but especially associated with the Northern Song to Yuan period in the 11–14th century. It has been increasingly realized that a very large number of sites in northern China produced these wares, and their decoration is very variable, but most characteristically uses black and white, in a variety of techniques. For this reason Cizhou-type is often preferred as a general term. All are stoneware in Western terms, and "high-fired" or porcelain in Chinese terms. They were less high-status than other types such as celadons and Jun ware, and are regarded as "popular", though many are finely and carefully decorated.
Guan ware or Kuan ware is one of the Five Famous Kilns of Song dynasty China, making high-status stonewares, whose surface decoration relied heavily on crackled glaze, randomly crazed by a network of crack lines in the glaze.
Yaozhou ware is a type of celadon or greenware in Chinese pottery, which was at its height during the Northern Song dynasty. It is the largest and typically the best of the wares in the group of Northern Celadon wares. It is especially famous for the rich effects achieved by decoration in shallow carving under a green celadon glaze which sinks into the depressions of the carving giving contrasts of light and dark shades.
A dragon kiln or "climbing kiln", is a traditional Chinese form of kiln, used for Chinese ceramics, especially in southern China. It is long and thin, and relies on having a fairly steep slope, typically between 10° and 16°, up which the kiln runs. The kiln could achieve the very high temperatures, sometimes as high as 1400 °C, necessary for high-fired wares including stoneware and porcelain, which long challenged European potters, and some examples were very large, up to 60 metres long, allowing up to 25,000 pieces to be fired at a time. By the early 12th century CE they might be over 135 metres long, allowing still larger quantities to be fired; more than 100,000 have been claimed.