Bisque – preliminary firing given to pots to render them hard enough for further work such as decoration and glazing.
Bizen – glaze named after the Japanese city of Bizen produced by a long wood-firing, with resulting heavy ash deposits and other effects.
Celadon – range of green colours produced by firing an iron bearing glaze in a reduced oxygen atmosphere. Colours may vary from turquoise to olive depending on the amount and type of iron.
Earthenware – ceramic pieces made from clay fired to a relatively low temperature (700º–1200ºC). The clay does not vitrify and must be glazed to render it non-porous. Also used to refer to clay suitable for firing at low temperatures.
Engobe – liquid clay slip applied to the surface of a pot to give color, improve or add texture or provide a ground for further decoration. It may be applied to wet. leather-hard, dry or bisqued ware.
Flashing – changes to colour and texture caused by the flow of flame over a piece during firing in a wood-fired or gas kiln.
Foot ring – area at the base of a pot, separate from the body and sometimes left unglazed.
Greenware – pottery that has been air dried but not yet fired.
Hakeme – decoration technique in which a stiff brush is used to apply slip directly to the surface of a pot.
Leather-hard – stage in the process of drying where a ceramic piece can be handled without damage but still worked, for example, to trim the base, add a handle or alter the shape.
Maiolica – technique of applying coloured pigments to an unfired glaze, traditionally glossy and whitened with tin oxide, and then firing to earthenware temperatures.
Raku – process where glazed pieces are fired to around 1000°C, then removed while red hot and either left to cool, or plunged into water to cool them, or placed into a sealed bin containing combustible materials. These ignite and create a reduction atmosphere. The smoke also turns any unglazed clay black. If the bin is opened after a short time, this re-oxidises the piece, creating interesting glaze effects.
Raw glazed – process whereby the glaze is applied directly to the hardened clay body and the pot is then fired once only.
Salt glazed – process whereby salt is added to a kiln at the end of a firing. The salt volatilises and fluxes with the silicas in the unglazed clay surface, creating a glassy translucent effect with a slightly ‘orange-peel’ texture. Brown, blue or purple salt glazes are the result of applying a thin wash of iron, cobalt or manganese oxide before firing.
Sgraffito – decoration technique in which a pot is coated with an engobe or slip of contrasting colour and then a design is created by carving or scraping the slip to reveal the clay underneath.
Shino – decoration technique in which a thick white feldspar glaze is allowed to run down and crackle around the clay body, sometimes enhanced with oxide brushwork under or over the glaze. Modern shinos may include flashing, beaded or crawled surfaces. Iron-rich clays added to the glaze produce brilliant orange colours and pigments may be added for other colour effects.
Slip – suspension of clay in water used to bond together two pieces of leather-hard clay or as an engobe to decorate the surface of a pot or as a casting material.
Slip casting – process of creating multiple, identical ceramic pieces by pouring slip into a plaster mould. The water in the slip is absorbed by the plaster, leaving a layer of clay on the surface of the mould. This method may also be used to make forms that are difficult to throw or build by hand.
Soda glazed – chloride-free alternative to salt glazing developed in the 1970s, whereby sodium carbonate or bicarbonate is added to the kiln at the end of firing to create soda-vapor. The effects are similar to salt glazing but aesthetically different, with a higher potential for flashing.
Stoneware – ceramic pieces made from clay fired to a relatively high temperature (1200º-1350ºC). The clay vitrifies and is waterproof even without glaze. Also used to refer to a heavy, large-grained clay suitable for firing at high temperatures.
Tenmoku – iron oxide rich glaze resulting in an intense black surface. A range of effects is associated with tenmoku, including oil spots, hare’s fur, tortoiseshell, pig’s skin, tea dust and rust-coloured breaks where the glaze is thin.
Terracotta – red form of earthenware.
Terra sigillata – very smooth, lustrous coating of clay made by syphoning off the thin milky layer from a mixture of clay and water that has been left to sit for a day or so. The sub-micron size particles of clay align when the surface is polished, creating a silky effect.
Trailed glaze – glaze applied as a trail over the clay body or another glaze.
Wax resist – decoration technique in which parts of a pot are brushed with warm wax. so that subsequent layers of glaze do not adhere to the waxed areas.