Glossary
A
Absorbency: The ability of a material to soak up water.
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Ark: Large storage tank or container, e.g. Glaze Ark, Slip Ark, etc.
B
Ball clay: A secondary clay moved from the parent rock, ball clay is often mixed with other clays and minerals, organic matter are frequently present. Ball clays commonly exhibit high plasticity and high dry strength.
Bat: Or "batt." Less commonly also known as a "batterboard", thin slab of wood, plaster, or plastic used to support pottery forms during throwing, attached to the head of the potter's wheel by clay body or "bat pins".
Bisque: This term may also be seen as bisc, biscuit, bisqueware, bisquefired, biscuit. Refers to the pottery piece that has fired but not yet glazed.
Blunging: Suspending ceramic raw materials in liquid by agitation.
Body: Name given to prepared clays.
Body Stain: Colourant used to colour clay body.
Bone China: A thin and translucent china - historically made from a body containing bone ash, china clay and Cornish Stone.
Bone-dry: The final stage of greenware dried to a completely dry state and ready to be fired. In this stage, the clay is very fragile, non-plastic and porous. Approximately 45-65% of moisture is retained within the clay body.
Burnishing: A process by which leatherhard or blackhard clay is made smooth by rubbing it with a hard smooth object like a stone, spoon or piece of glass. This procedure gives the piece a polished look.
C
Casting / Slip casting: Casting or slip casting is a ceramic forming technique for shapes not easily made on a wheel. In slip casting, 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.
Ceramic: Derived from the Greek ‘Keramos’ meaning ‘earthen vessel’. Today it applies to a whole range of products, i.e. bricks, tiles, pipes, porcelain, china, pottery, etc.
Cheesehard: The first stage in the drying process of a piece of pottery where it is still soft.
Clay: A group of hydrous aluminium phyllosilicate minerals. Often also used to refer to the clay body, which sometimes may only contain small amounts of clay minerals. It is the material used to form the body of a piece of pottery.
Coiling: A hand method of forming pottery by building up the walls with coils of rope-like rolls of clay.
Cones: Small, elongated, three sided pyramids made of materials designed to melt at a specific temperature. Designed to melt at the same temperature as the glazes used. Cones indicate the progress of the melting. Cones are placed just inside the kiln during a firing so they can be seen through a peephole.
Crackle glaze: A glaze intentionally containing minute cracks in the surface.
Crawling: Movement of glaze over the body surface during the gloss firing stage, due to dust or grease on the surface or over application of the glaze or excessive colloidal material in the glaze.
D
Decorative: A general term describing a non-functional ceramic piece that is intentionally for art purpose or decoration. Typical examples include sculptures, and wall hangings.
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Dipping: Glazing pottery by immersion in a glaze suspension.
Dunting: Cracks or cracking in the clay caused by the too rapid cooling or heating of ware, and due to thermal stresses set up in the body.
E
Earthenware: A type of moderately porous clay body that is fired in a low temperature. Typically 1060 to 1100 C.
Engobe: A white or coloured coating of slip applied to the clay, for decoration, before glazing.
Extruder: Tools that are available in many shapes, sizes and styles, ranging from small, handheld extruders to industrial, wall-mounted extruders. Usually used by putting the clay inside and forcing it through an aperture.
Extrusion: The process of forcing clay through an aperture or die. e.g. through a pugmill.
F
Fettling: The removal, in the unfired state of excess body left in the shaping of pottery-ware at such places as seams and edges.
Firing: The process of exposing ceramic pieces to high heat in order to convert them into durable finished pieces.
Functional: A general term that refers to any ceramics piece that is not purely decorative and has some intended use. Typical examples include teapots, bowls, mugs, and vases.
G
Glaze: A thin glassy layer formed on the surface of a ceramic article by the exposure of the glaze coated article to a high temperature. Glaze is usually applied in the form of a suspension of ground glaze in a liquid medium, to the clay or biscuit surface of the article.
Greenware: Unfired clay ware.
H
Hand building: Any one of various techniques for creating ceramic objects that do not involve the use of a potters wheel. These methods include coiling, slab building, and pinch pots.
I
Iron oxide: A common oxide in glazes and some clays that generally gives a reddish colour.
J
Jigger: A machine for the shaping of clay body into flatware by the differential rotation of a profile tool and mould. The process is called ‘jiggering.
K
Kiln: Pottery oven or furnace in which ceramic products are fired. May be fired by wood, coal, sawdust, electricity or gas.
L
Leather Hard: Partially dried clay ware. The ideal stage for turning, fettling, sponging, etc.
M
Matte glaze: A dull-surfaced glaze with no gloss.
O
Once-Fired: The making, glazing and firing of ware in one operation.
P
Pinching: A technique of building pots entirely by molding the clay with the hands. Called pinching because it usually starts by a potter inserting a finger into a ball of clay and pinching the walls to thin and shape the pot.
Porcelain: A vitreous ceramic material. Traditionally considered to be white and if, of thin section, translucent.
Porosity: The amount of pore space in a ceramic material, which may consist of both open and sealed channels.
Potter: A person who makes pots or other ceramic art and wares.
Potter's wheel: A device used by a potter to rotate a lump of clay on top of a disk, which allows a skilled craftsperson to create a variety of cylindrical shapes for a wide array of functional objects. This activity is called throwing.
R
Raw glazing: Refers to applying a glaze to an unfired ware and firing both in a "Once-firing".
Raku: Raku generally refers to a type of low-firing process that was inspired by traditional Japanese raku firing. Western-style raku usually involves removing pottery from the kiln while at bright red heat and placing it into containers with combustible materials.
Rib tool: A wide, flat handheld tool used to shape, smooth, and/or scrape clay surfaces.
S
Shrinkage: An irreversible reduction in the size/volume of a ceramic piece or glaze which is caused during the drying and firing process.
Slab: Any one of various techniques for creating ceramic objects that do not involve the use of a potters wheel. In this technique, the clay is pressed into thin slabs that are then cut, assembled, and shaped into the desired form.
Slip: The suspension of a clay body in water, used for casting ware in moulds.
Stain: A compound added to glazes to add coloring. Sometimes applied directly onto a clay body without mixing with a vitrifying glaze.
Stoneware: A strong, hard, vitrified ware, usually high-fired above 2,200 F.
T
Throwing or wheel-thrown: A process of producing pottery by use of a rapidly rotating disk referred to as a potter’s wheel. The procedure involves placing a lump of clay in the exact center of the wheel head, creating an opening in the exact center of the clay. The size of the opening is gradually increased and the sides are pulled up until a cylinder is formed.
Terracotta: A type of earthenware, is a clay-based unglazed or glazed ceramic, where the fired body is porous.
U
Underglaze: Decorative colours applied to ware before the application of glaze.
V
Vitrification: The process, induced by exposure to high heat, by which a material such as a clay or a glaze, melts and fuses together, thereby becoming solid and glass-like.
W
Ware: A generic catch-all term referring to ceramic pieces. It is usually combined with adjectives to form compound words such as kitchenware, dinnerware, earthenware, stoneware, and ovenware.
Wedging: A procedure for preparing clay or a clay body by hand: the lump of clay is repeatedly thrown down on a workbench; between each operation the lump is turned and sometimes cut through and rejoined in a different orientation.
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