Inert material: Material which is passively resistant to any change. In ceramics, we particularly refer to materials which are relatively unaffected by the action of heat or water.
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Bentonite
Bentonite: A highly plastic collodial clay-like material which is a useful plasticiser and suspender
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Ball clay
Glossery of Pottery Terms
Ball clay: A plastic secondary clay, usually quite refractory, and firing to a fairly pale, off-white colour.
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Refractory
Refractory: Resistant to high temperatures.
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Ceramic Change
Ceramic change: The point at which chemically combined water is driven off from clay molecules, so that the clay becomes pot, and can no longer be slaked down. This change is permanent and irreversible, and is widely said to take place at 573degrees C..although it is, in fact, an ongoing process which may begin as low as 350C., and may still be taking place a temperatures as high as 700C
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Scumming
Scumming: Unwanted deposits of soluble salts which sometimes appear on the surface of a raw dry pot, or more significantly, on bisc-fired ware. After bisc firing, areas where scum is apparent may be slightly fused and therefore resistant to glaze take-up. Scum is unlikely to resist glaze take-up on a raw pot.
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Slipcasting
Slipcasting: A method of making objects by pouring a dense, deflocculated slip into a mould.
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Feldspar
feldspar
One of a group of rock-forming minerals, the most abundant group in the Earth´s crust. They are the chief constituents of igneous rock and are present in most metamorphic and sedimentary rocks. All feldspars contain silicon, aluminum, oxygen, linked together to form a framework; spaces within this structure are occupied by sodium, potassium, calcium, or occasionally barium, in various proportions. Feldspars form white, gray, or pink crystals and rank 6 on the Mohs´ scale of hardness. The four extreme compositions of are orthoclase, KAlSi3O8; albite, NaAlSi3O8; anorthite, CaAl2Si2O8; and celsian, BaAl2Si2O8. These are grouped into plagioclase feldspars, which range from pure sodium feldspar (albite) through pure calcium feldspar (anorthite) with a negligible potassium content; and alkali feldspars (includingorthoclase and microcline), which have a high potassium content, less sodium, and little calcium. The type known as moonstone has a pearl-like effect and is used in jewelry. Approximately 4,000 metric tons of feldspar are used in the ceramics industry annually.
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Dunting
Dunt: A crack caused by firing and /or cooling
stress in a pot.
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Pyrometric Cones
Pyrometric cones: These are used to accurately measure the amount of heat work that has taken place in the kiln. They are made from precisely measured combinations of clay and flux materials which reliably begin to ruse and bend at a predetermined heat.
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What is a Binder?
Binder: A polymetic substance(e.g. starch-based adhesives) used to strengthen unfired glaze surfaces
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Raku
Raku: A Japanese word which loosely translates as ´enjoyment´, and which strictly only refers to pottery by the potter who holds the Raku title. In the West, however, the work has become associated with a particular technique which generally involves placing pots into the already hot kiln, and often then carbonising the pots by removing them directly from the hot kiln to a bin of combustible material such as leaves or sawdust.
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Suspender
Suspender: A material added to a glaze slop in order to facilitate the suspension of heavy particles in water. Suspenders usually act by the creation of a macrostructure which hold particles in dispersal.
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Pyroplastic
Pyroplastic: The condition of a clay body in the kiln when heated to vitrification. At this point, any impact upon the pot may alter its shape, and, ultimately, it may begin to sag under its own weight.
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Engobe
Engobe: The word engobe is often used to refer to decorative (as oppossed to casting) slips, but may also refer to any material which is neither a pure clay slip nor a glaze but which is used to cover clay.
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What is Siccative
Siccative: A drying agent; any material which tends to take up moisture from a slop or body.
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Crazing
Crazing: a glaze fault caused by excessive shrinkage of the glaze in relationship to the body, and which is characterised by a network of fine cracks all over the fired surface.
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Flocculent
Flocculent/flocculant: Acids (or salts which in solution behave as acids) which alter the electrostatic charges of fine particles in a suspension, reducing their mutual repulsion, and thus increase their forces of attraction. This causes particles to floc together, increasing friction and viscosity, thus apparently thickening the suspension without removing any water from it.
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‘pipe'
A ‘pipe' is the metal rod that runs through the center of lamps through which the cord passes and it is threaded on each end.