Histories of UK potters and pottery manufacturers

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Last updated: 1st August 2011

GLOSSARY - POTTERY PROCESSES

Bat printing

An over-glaze printing process using a flexible material to transfer a design from an engraved plate to the ware

Calcine

Roast by application of strong heat in order to make some chemical or physical change to a material. Animal bones were calcined as part of the process of making the bone ash used as a component of the paste used for bone china.

Calcination is used to remove unwanted volatiles substances from a material or to convert it to a different state. Materials are ground after calcining ready for addition to a paste.

Casting

Technique of making articles by pouring liquid or molten materials or metals int0 a mould.

Encaustic

Method of decorating by burning in pigments to earthenware, usually in a brick red, often on a black stoneware body.

Glaze

Application of a smooth, impervious, glassy coating to ceramics primarily to make the body hygienic and non-porous. A glaze may be transparent, translucent or opaque, white or coloured, and highly glossy to matt in surface texture.

Glost firing

A term relating to the glazing of ceramics. The glost firing is the firing applied after the glaze material has been applied with the purpose of fusing it to the body of the ware. Thus, glost house, glost oven etc.

Hand-thrown

Wares, generally hollow ware, produced by hand on a potter's wheel.

Incise

Ato form a decoration by cutting into the surface with a metal tool.  See scraffito .

Jiggering

A process for forming pottery on a lathe or wheel. A profile describing the outside shape of the ware is used to force the soft clay against a rotating plaster mold describing the inside shape. Flat ware is often made by jiggering.

Raku

A low-temperature-fired earthenware where the body is composed of a previously fired clay that has been broken up and pulverised. Of Japanese origin.The word can refer to the finished ware or to the process of manufacture.

Reduction Firing

Firing a kiln for part of its cycle with an atmosphere having no free oxygen to induce special effects in the chemistry of the glaze. A reduction kiln allows the operator to restrict the flow of incoming air to only that required for combustion so that the atmosphere becomes oxygen deficient.

Slip casting

A manufacturing technique where slip is poured into a porous mould which absorbs the water and leaves a layer of solid clay on the inside. The excess slip is poured out and the object left to dry.

Turned

A manufacturing technique were the leather-hard wares were turned on a lathe prior to the biscuit firing.  The lathe could be used to thin the wall thickness of the ware and/or could be used to incise decoration or trim the rim and foot-rim of hollow wares.

Vitrification

'Vitrification' is the process of converting an alumino-silicate-rich paste into a semi-porous or non-porous glass-like material by application of intense heat. Some clays will only vitrify at close to their melting point and wares must supported in the kiln to avoid slumping or deformation. Stoneware is generally fired to a non-porous, semi-vitrified state, whilst hard-paste porcelains are strongly vitrified.