Agate ware Pottery made from clays of two differing colours, not completely mixed. The result is a streaked effect resembling agate
Ash glaze A glaze made with ground ash, usually wood ash and sometimes mixed with other materials. Bone ash - Animal bones that have been baked and ground to a powder, used in the production of bone china
Banding Wheel A turntable used for applying lateral decoration to a pot.
Bisque, Bisque Firing -Clay that has been given a preliminary firing to render it hard enough for further work such as decoration and glazing. The higher the temperature of the bisque firing, the harder will be pot, resulting in reduced reaction between glaze and body in the final firing. Usual Bisque firing temperature is around 950c
Bizen glaze named after the Japanese city of Bizen produced by a long wood-firing, with resulting heavy ash deposits and some beautiful accidental glazing effects.
Body - The substance from which a pot is made. A mixture of one or more clays, grog, feldspars, etc., to give a material suitable for shaping and firing.
Bone china - A china made white and translucent by the addition of calcined animal bone to the body.
Burnish To smooth the surface of a pot by rubbing with a hard object to give a finish with a polished effect.
Cast - To produce shapes by pouring fluid clay into moulds. The 'negative' moulds are usually of plaster of Paris, and made from a 'positive' so that when they wear out, new ones can be made.
Celadon - Chinese technique making a 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.
China- Porcelain -The first porcelain imported into Europe was from China.
China clay - Kaolin. A white clay made from pegmatite
China stone - Pegmatite. A type of feldspar.
Chuck Tube-like form to hold a pot upside-down on the wheel for trimming the foot.
Chun A pale blue glaze used on stoneware.
Cobalt oxide - Used to produce a blue colour in glazes.
Colourants - Coulourants in glazes form a whole field of research and experimentation within pottery. Most colours in glazes come from metal oxides and carbonates such as cobalt (blue or pink), Iron (red, brown black), manganese (purple, brown) titanimum (white) copper (red, green, celadon). This website provides great information on glaze colourants
Coiling - Rolled clay in flat form or with a rounded section that welds to itself when fired to make a solid form.
Cone - Cones are temperature indicators inserted in the kiln to indicate to the potter when a certain temperature has been reached. They are made of various glaze materials of known melting point. Two examples of cones are Seger cones, named after Hermann August Seger, and Orton cones, manufactured by the Orton Ceramic Foundation in the USA.
Copper oxide Used to produce green colours in glazes. When used in a reducing atmosphere it produces a red colour.
Crackle -Cracks in the glaze formed intentionally as a decorative feature. (See also - Crazing)
Crawling - Shrinkage or retraction of the glaze during firing, causing exposed areas of underglaze or clay body.
Crazing - A fine network of cracks in the glaze usually caused by uneven contraction and expansion of the body and the glaze during changes of temperature. In some pottery this is a design feature rather than a fault (See - Crackle), but in earthenware pots the cracks can allow moisture to penetrate to the porous body leading to further damage.
Delft - Opaque lead glazed earthenware with a pattern or design painted in metal oxides on the glaze before firing.
Earthenware Pots that are porous when unglazed. Usually fired at low temperatures. Earthenware is softer than stoneware. The clay does not vitrify and needs to be glazed to make it non-porous. The temperature range is somewhere between 850c-1100c. Earthenware also refers to clay suitable for clay firing at low temperatures.
Enamel - Low-fired coloured glazes.
Engobe Slip - wet fluid clay used for decoration or for covering a base coloured body. This term is most often used to describe coloured slips.
Faience/Fajance - Tin glazed European earthenware, usually from France.
Feathering -Effect obtained by trailing a feather or brush through wet slip decoration.
Flashing – changes to colour and texture caused by the flow of flame over a piece during firing in a wood-fired or gas kiln
Fire (to) - To heat pots in a kiln to a specific temperature for a specific time.
Flambé -A flame-like effect produced by a reduced copper oxide glaze.
Flatware - Plates, saucers, trays, etc.
Fluting - Grooves cut into the clay in parallel lines running in any direction.
Foot - The base of a pot.
Frit - A vitreous composition used in glazes and enamels.
Glaze - A vitreous substance used to decorate pottery and render it impermeable to moisture.
Glaze firing - The last firing of a pot when the glaze is applied.
Greenware - Pottery that has not been fired.
Grog - Gritty material added to clay to modify its behaviour in firing. It is usually ground clay that has already been fired, and can be course or fine depending on the type of work for which it is being used.
Hakeme - Oriental technique of applying white slip directly to a pot with a stiff brush.
Handbuilding - Constructing pots from pre-made parts. The components might be moulded, coiled or fashioned by hand.
Hollow ware Cups, jugs, bowls, etc.
Impressed (design) - Stamped into the leather-hard clay with a tool or die.
Impressed (mark) - Stamped into the leather-hard clay with a tool or die.
Incised (design) - Pattern cut into the clay with a sharp tool.
Incised (mark) - Maker's name, monogram or mark cut into the clay with a pointed tool.
Jigger - Mould or profile used when uniform shapes have to be made repetitively on the wheel. See also -
Jolley- Mould or profile used when uniform shapes have to be made repetitively on the wheel. See also - Jigger
Kiln - The oven in which pots are fired. Kilns can be fired by wood, coal, oil, gas or electricity.
Kiln Furniture - The various items made of refractory materials that are used in the kiln to support or protect the pots. Shelves, posts, stilts, saggars, etc.
Kiln Wash - Kaolin solution applied to kiln furniture to facilitate the easy removal of glaze drips.
Leach, Bernard - The father of 20th Century Studio Pottery. This short clip is about 60 years old but well worth viewing. Bernard is talking about the "Humanity" of pottery. Enjoy.
Leather-hard - Clay that has dried to the point where it is stiff enough to retain its shape but wet enough for further work to be done on it.
Lustre - Metallic oxide film applied to pots after glazing and firing to produce pearly finish after a further firing in a reducing atmosphere.
Majolica - The technique of applying coloured pigments to an unfired glaze, traditionally glossy and whitened with tin oxide, and then firing to earthenware temperatures.
Neriage neriage is the ancient japanese technique of layering, cutting and recombining different colors of clay, creating an intricately patterned loaf that is sliced and applied to the clay body
On-glaze decoration Decoration applied after the pot has been glazed.
Overglaze decoration A decoration applied over an already glazed finish.
Oxidation Firing with a good supply of oxygen so that combustion is complete as opposed to Reduction firing which oxygen is extracted chemically by the flame resulting in different colouring.
Plastic (adj) Capable of being formed into a shape or moulded.
Porcelain Hard, fine, high-fired material made from china clay, feldspar and silica. It is white and translucent. Also known as hard paste.
Pugmill A machine to take the hard work out of 'wedging'. It is similar in operation to a domestic food mincer, The clay is put in at the top and comes out of the mouth at the bottom in the form of slices or wedges.
Pyrometer A thermometer able to measure the very high temperatures found in kilns.
Raku Originally a Japanese 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 container containing combustible materials. These ignite and create a reduction atmosphere. The smoke also turns any unglazed clay black. If the container 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.
Reduction - Firing in a reducing atmosphere. This is when there is insufficient air for the flame to burn off its carbon content. The result is a smoky atmoshere that causes metallic content in the glaze and clay to change colour.
Refractory - Capable of withstanding very high temperatures. The kiln furniture has to be able to remain stable at temperatures in excess of the normal firing temperature an must be made of refractory materials.
Rib - A shaped tool to facilitate the forming of pots.
Saggar -A fireclay box used to protect pottery while it is being fired.
Salt-glaze - a 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. Soda ash is also used by potters as it is less toxic.
Sang-de-boeuf Ox-blood. Used to describe deep red colours in glazes.
Sgraffito --The technique of scratching through a coating of slip to reveal the contrasting colour beneath.
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.
Slab building - A building technique where flat sheets of clay are formed and jointed. Used to good effect by Troika and by Bernard Rooke.
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.
Slip decoration - the application of slip to a pot. This can take the form of an all-over or partial coating, or a trailed, feathered, combed or brushed design.
Slip trailing - Method of decoration where slip is trailed onto a pot through a fine nozzle.
Slipware - Slip decorated earthenware pottery.
Slurry - Slip with a thick consistency.
Sprig - Decorative pieces, usually press-moulded, applied to pot when it is leather hard.
Spur marks - The marks left by the stilts used to support pottery in the kiln. Usually seen as three dots in the form of an equilateral triangle.
Stoneware Pottery fired at high temperature which is inherently non-porous. The clay vitrifies during firing and the surface will not absorb moisture. Stoneware can be left unglazed and still be usable for holding water, but it is more usual to glaze the inside of the vessel, at least. Stoneware is more durable than earthenware, and capable of resolving finer detail. Fired at 1200- 1300c. Also refers to a heavy large grained clay suitable for firing at high temperatures as opposed to eg. earthenware.
Tenmoku - A Japanese name for a Chinese glaze containing iron oxide. Tenmoku glazes are characterized by their black to reddish brown colour which is lighter in colour where the glaze is thinner and darker where it is thicker.
Terracotta Red earthenware, usually unglazed, usually only fired to Bisque temperatures.
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.
Throw - To make a pot on a potters' wheel. The wheel revolves and maintains a fairly constant speed as would a flywheel. The clay is thrown onto the centre of the wheel and the potter shapes it by hand to the desired form.
Tin-glaze – see Fajance - White opaque glaze containing tin oxide.
Transfer printing -Method of decoration where a pattern or picture is printed onto the gelatin coating of paper and then, when wet, is slid onto the surface of a pot. The gelatin can be sensitized with silver halide allowing the same process to be used photographically.
Tube-lining - A decorating technique where soft clay is piped from a bag via a fine tube onto the body of a pot. This creates an outline for a design that can later be enhanced by further painted decoration.
Underglaze decoration - A decoration applied to a biscuit or once-fired pot for subsequent covering with a transparent glaze.
Vitrification - To change to a glassy state.
Wax-resist - Wax applied to a pot to prevent adhesion of slip or glaze and produce a decorative effect.
Wedging - The cutting of clay into wedges in the process of mixing and kneading it to an even consistency. See also - Pugmill
Wheel - A heavy horizontal wheel onto which clay is thrown and shaped. The weight of the wheel gives momentum to preserve continuity of speed. Potters' wheels can be powered by the potter's foot, an assistant, electricity or in the factory environment from mid-19C to mid-20C a belt from a shaft driven by a steam engine.
Wire Length of wire with a handle at each end for cutting clay. Used in throwing and wedging.
YYunomi - A drinking vessel on a raised foot of smaller diameter than the body. Usually of a basically cylindrical shape. Sometimes seen spelt 'unomi'.
Zettlitz kaolin A pure kaolin found near Carlsbad in Germany used for making high temperature Seger cones.