Agate – earthenware made to resemble the semi-precious stone agate. It is created by building up irregular layers of white, green, blue and brown clay.
Atelier – the studio of an artist or designer.
Basalt – a type of hard, unglazed, black stoneware that is uniformly and densely grained.
Bas Relief – a type of relief in which figures or shapes protrude only slightly from the background.
Biscuit – the first firing of clay. From the French “twice fired,” a reference to the preliminary firing involved in the production of the glassy frit used in French soft-paste porcelain. Biscuit firing hardens the clay in preparation for glazing. Some sculptural biscuit pieces are deliberately left unglazed and undecorated.
Bisque Ware – ceramic pieces that have undergone their first firing. In this non-porous state, the ware will no longer dissolve in water and cannot be turned back into malleable material.
Blue-and-White Ware – porcelain and other white ware that has a decorative blue pigment beneath the glaze. The pigment is derived from cobalt.
Body – the name used to describe the physical composition of any type of ceramic ware, as opposed to its decoration or glaze.
Bone Dry – describes raw clay that contains little moisture. At this stage, the clay cannot join other pieces and cannot be carved, but may be suitable for some other decorative processes and biscuit firing.
Bone China – combines bone ash with the hard-paste porcelain ingredients kaolin and china stone, in a formula of 50% bone ash, 25% kaolin and 25% china stone. This formula is still used today.
Burnishing – the process of rubbing the surface of a leather-hard or dry clay object with a hard object, such as a stone or a piece of glass or metal. This creates a polished look and reduces the piece’s porosity, making the clay more resistant to water absorption.
Caneware – unglazed, tan-coloured stoneware with a dry look, occasionally decorated delicately with light-blue enamel.
Celadon – stoneware with a feldspathic glaze that gives it a bluish-green colour.
Ceramic – the word “ceramic” is traced to the Greek term Keramos, meaning pottery or potter. Ceramics are defined as products made from inorganic, non-metallic materials with a crystalline structure, usually processed at a high temperature at some time during their manufacture.
China – a term commonly used to describe ceramic wares, named after the country of origin.
Chinese Export Porcelain – Chinese ceramics produced specifically for export to the West. During the 18th century, English potters duplicated the decorations of this type of porcelain, while the Chinese duplicated some European artwork, making it difficult to ascertain the origins of certain motifs.
Clay – the basic material for all ceramic ware is clay, a soft earth that is plastic, or may be molded with the hands, consisting of hydrated silicates of aluminum. It is the result of the wearing down and decomposition, in part, of feldspathic rocks containing aluminous minerals, such as granite.
Clobbering – porcelain that is originally white or blue and white that is touched up with various other colours.
Cobalt – the blue pigment used in the decoration of blue-and-white ware.
Coiling – creating the walls of ceramic forms by melding together rolls of clay.
Combed Ware – clay objects decorated with dots or lines made by pressing a comb into damp clay or by dragging a comb across surface of the clay.
Commedia dell’Arte – this movement began as a disrespected, improvised form of street theatre in 16th-century Italy. It is best known for its high-spirited characters, including Harlequin, Columbine, Pantalone, Scaramouche and Pulcinella. These characters have been represented in porcelain sculptures, paintings and engravings for centuries.
Crackle – the intentional creation of a fine network of cracks in the glaze on a clay surface, sometimes darkened for accentuation. Crackle occurs during the cooling process when the clay and the glaze contract at different rates.
Crawling – a part of the underlying clay surface that is exposed when the glaze separates from the body.
Crazing – the unintentional cracking of glaze on a clay surface. This occurs during the cooling process when the clay and the glaze contract at different rates.
Creamware (or Queensware) – a type of earthenware developed in the 18th century that came to dominate western ceramic tastes during that time.
Delft – a type of tin-enameled earthenware produced in the early 17th century in Delft, Holland. It is glazed with a lead-based glaze, and turns white when tin-oxide is added as a flux. Delft was a key producer of this type of pottery, hence the name, although it originated in England during the 16th century.
Delftware – this is the original English version of Delft. It is more vitreous (glasslike), less evenly enameled and denser than the Dutch version.
Dipped Wares – ring-shaped or banded decoration. Called “dipped” because they are dipped in a container holding coloured slip.
Earthenware – an opaque, porous and coarse ceramic ware that is fired at a relatively low temperature (700º–1200ºC).
Enamel – overglaze enamels are low-fired metallic oxides used to decorate ceramic wares. The frit, suspended in an oily medium, is painted on the glazed surface, and the suspension material is burnt away.
Engine Turning – a technique developed in 18th-century England in which a vessel in the leather hard or greenware state is incised with a decoration while rotating on a lathe.
Engobe – liquid clay slips that are applied to the surface of either wet clay, leather-hard clay, greenware or bisque ware. Its purpose is varied; it can be added to change the colour or texture of a piece or to prepare it for additional decoration.
Faïence – this is the French version of tin-glazed earthenware that was popular in 16th, 17th and 18th century Europe. The name is derived from the Italian town Faenza, where maiolica was produced.
Famille – this is the French word for “family.” In the 19th century, French ceramic collector Albert Jaquemart divided the ceramics of the Qing Dynasty into categories based on their predominant colour. The categories are: famille verte (green), famille rose (pink), famille jaune (yellow) and famille noire (black).
Feldspar – an abundant group of rock-forming, hard crystalline minerals containing potassium, sodium, calcium, silicates of aluminum and sometimes barium. It is used widely to produce stoneware, porcelain and glazes as a flux.
Feldspathic Glaze – used on hard-paste porcelains, this glaze is made of the same kaolin and petuntse as the body but in different proportions. It fuses into a type of natural glass when heated to a very high temperature
Fireclays – these clays contain a slightly higher percentage of fluxes than does pure clay. They usually fire to a grey colour and mature at between 1371º–1482ºC, which are higher temperatures than that typically used in firing pottery and glazes. Fireclay is often used to make muffle, firebrick and kiln linings.
Fire – to bake clay in a hot kiln or oven. To harden clay, the temperature must be high enough to fuse the clay particles. High firing (1200°–1400°C) is used for porcelain; moderate firing (1200°–1280°C) is used for stoneware; and low firing (800°–1100°C) is used for earthenware.
Flux – a base oxide that lowers the melting point of vitrification, the fusion of particles that occurs in stoneware, porcelain and overglaze enamels. Fluxes include alkaline materials such as sea salt, feldspar, soda, potash, bones, ferns, seaweed and lead.
Frit – a glassy frit is composed of silica (found in sand or quartz), a flux (potash or soda) and metallic-oxide pigments. The mixture must be calcined (melted) and ground to a powder before being added to soft-paste porcelain or overglaze emanels.
Geochemistry – the study of the crust of the earth, its chemical composition, and the chemical changes that occur within it
Gilding – the application of gold to the surface of an object for decorative purposes. An early technique was unfired lacquer gilding, in which a gold powder mixed with lacquer was painted on a glazed vessel, but the result was fragile and easily worn off. Honey gilding involved ground gold leaf mixed with honey, which was fired at a low temperature and could be chased and tooled. This was replaced with mercury gilding in the 19th century.
Glaze – a glassy coating fused with a ceramic body by firing, creating a water-tight surface. The glaze consists of silica, stabilizers (alumina) and various fluxes, the latter added to lower the required melting temperature.
Greenware – this refers to hard clay objects that have not yet been fired. In this state, moisture can be added to turn the clay back to a malleable form. Despite its name, it may be grey, turquoise, yellow, or blue.
Grog – usually made of fireclay or a comparable type of clay that has already undergone the firing process, grog is added to clay to diminish shrinking and cracking as the clay dries; to increase durability, workability and strength; to protect against thermal shock and to add texture. Grog is often added to wares such as Raku and flameware because of their vulnerability to thermal shock.
Handbuilding – creating ceramic pieces using only the hands and simple tools as opposed to the potter’s wheel.
Hard-paste Porcelain – “true” or Oriental-type hard-paste porcelain is made from white china clay (kaolin) and china stone (petuntse or feldspar, a silicate of potassium and aluminum). These two ingredients are fired together at a high temperature (1250º–1350ºC) to produce a glassy matrix.
Hausmauler – freelance artists who ran independent decorating studios in Germany, Holland and England. They painted on a variety of materials including porcelain from China, Meissen and Vienna.
Inlay (or “Mishima”) – a decoration technique that involves pressing coloured or contrasting clay into incisions made on a clay object. The excess clay is scraped off when it has partially dried.
Insizing – decorating by cutting designs into the clay with a sharp tool or wire.
Ironstone – a dense, durable, hard white pottery first produced in England during the 18th century. It contains a high percentage of clay and a low percentage of non-clay materials, and is fired at a high temperature.
Istoriato – an Italian term meaning story. Refers to imagery on ceramic surfaces that tells a story.
Jasper Ware – white, fine-grained, vitrified stoneware developed by Josiah Wedgewood in the 18th century. It was unglazed but was often stained with a variety of colours, typically blue, black, lilac and green.
Kaolin – this very fine, pure, white-firing natural clay is used to make porcelain paste. Kaolin forms when the mineral feldspar decays, and is sometimes called “China clay” because of its prevalence in China.
Kick Wheel – a manual potter’s wheel that is powered by the artist’s foot, which kicks or pushes a stone or concrete base.
Kiln – a furnace or oven used to fire pottery and fuse glass. Kilns can be powered by electricity, natural gas, propane, wood, coal or fuel oil.
Lead Glaze – a clear glaze in which lead oxide serves as the principal flux. Lead glazes can be pigmented with a variety of metallic oxides.
Leather Hard – the stage between plastic and bone dry in which unfired pottery is firm enough to handle without being distorted, but pliable enough to add more clay.
Low-Fire Kiln – a kiln that heats to a temperature high enough to fuse the clay into a solid mass, but too low to make the clay totally non-absorbant.
Lustre – the technique of applying an iridescent decoration to ceramics by depositing a metallic film onto the glaze. Oxides of silver, copper or gold are dissolved in acid, combined with an oily medium and painted onto the ware. The object is then fired in a reduction (oxygen-starved) kiln, causing a metallic film to adhere to the ceramic surface that becomes iridescent when burnished.
Maturing Point – the temperature and time during firing at which the clay or glaze attains its ideal state of solidity and density.
Mocha Ware – this glazing technique was first developed in 18th-century England. An acidic solution called “tea” was originally made of hops, herbs, and tobacco juices, with oxides added for colour. Small amounts of this solution are dropped onto an alkaline slip, forming a unique dendritic (treelike) pattern.
Muffle – a kiln or a compartment in a kiln in which pottery can be fired without exposure to direct flame.
Opaque Glaze – a non-transparent glaze that conceals the clay beneath it.
Overglaze – the application of low-fire coloured glazes to clay pieces that have already been glazed and have usually already been fired.
Oxidation – a kiln firing in which the pottery is exposed to a full supply of oxygen. Electric kilns perform these firings, and oxidation occurs between 704º and 1149ºC. All pottery goes through an oxidation stage during firing, although it is called “oxidation” firing only when the complete process is fulfilled; otherwise, it is known as “reduction” firing.
Oxides – pigments derived from metallic oxides and used to decorate ceramic bodies and glazes. Pure metallic oxides include cobalt for blue, copper for green, iron for brown, manganese for purple, antimony for yellow and various other compounds to produce red and black. Metal-oxide pigments are called underglaze colours when painted over the glazed surface and refired. In-glaze pigments are painted onto the unfired tin-opacified lead-glazed ware, which fuse together during firing. Overglaze enamel colours provide the greatest range of colours because of their low-firing requirements.
Paper Clay – any clay that has had paper added to it. This makes the clay piece stronger and more pliable, and can be added to, cut apart, reassembled and mended even after it has dried.
Parian Body – this soft, translucent porcelain made from feldspar is commonly used for making statuettes and figurines. It is in the form of liquid clay, and has to be poured into moulds. Parian ware was especially popular in the mid-19th century.
Paste – clays and other materials that compose the clay body, exclusive of the glaze. Paste can be described as coarse, medium- or fine-grained and in terms of its porosity.
Pate-sur-Pate – an elaborate and expensive style of decoration in which successive coats of porcellaneous slip are applied to a contrasting body, then carved to create a cameo-like, low-relief design. This technique was developed in the mid-19th century at the French factory Sevres.
Pearlware – this refined earthenware contains a large percentage of kaolin, making it whiter than creamware. It was developed by Josiah Wedgwood in the late 18th century.
Petuntse – a type of feldspar that is sometimes mixed with kaolin to create Chinese porcelains.
Pinch Pot – a clay form created by manually pinching and manipulating a mass of clay into the desired shape.
Plasticity – the ability of moist clay to be malleable and impressionable without cracking.
Porcelain – a white, translucent, vitrified clay body fired at a very high temperature (1250º–1450ºC).
Porcelaineous Stoneware – a high-fired white ware that is similar to, but not as glassy as, true porcelain.
Porosity – the state of being porous. This is an important factor in the creation of ceramics. Clay can be too porous or not porous enough, which may result in cracking. Clay can be combined with flint, grog, or another type of clay to adjust its porosity.
Potter’s Wheel – a flat, rotating disk used for throwing clay. Can be either electric or manual.
Pottery – refers to any type of ceramic ware or the workshop where ceramic ware is produced.
Pouncing – a fine powder, such as powdered charcoal, that is sprinkled over a stencil to create a design on the underlying clay piece.
Raku Ware – a type of earthenware that originated in Kyoto, Japan, in the 16th century. Raku (meaning “pleasure”) has a rough, handmade and unpredictable appearance. The technique involves heating bisqued work to a red-hot temperature, removing it from the kiln and allowing it to burn in wood shavings, newspaper or a similar combustible material.
Reduction – a kiln firing in which there is an intentional absence of oxygen. This type of firing produces carbon monoxide, which functions to extract oxygen from the clay and glaze, resulting in colour changes to the piece.
Redware – a type of earthenware made from clay that contains a large proportion of ferrous oxide, giving it a red color.
Relief – the protrusion of figures or shapes from a background.
Salt Glaze (or Soda Glaze) – a glaze formed on stoneware by throwing common salt into the kiln at peak temperatures, which vaporizes into sodium and chlorine. The sodium combines with the silicates in the clay stoneware to form a thin, colourless glaze that resembles the texture of orange peel.
Scratch Blue – a process whereby a design is incised into pre-fired stoneware clay and a blue pigment is rubbed into the incised design.
Sgraffito – a decorative technique of scratching through a coloured slip to expose another colour underneath.
Slipware – a decorative technique using slip, a liquid mixture of fine clay and water. The slip can be coloured with oxides or coloured clays and applied to the vessel by dipping or painting, or trailed on like icing on a cake.
Soft-paste Porcelain – sometimes referred to as “artificial” porcelain, soft-paste porcelain is made without kaolin. France was the first to successfully manufacture this type of porcelain in the 17th century.
Spatterware – a crude, inexpensive pottery that is spattered or sponged with colour and decorated freehand with brightly coloured designs. Found on creamwares and sometimes ironstone.
Stoneware – a dense, fine-grained, non-translucent, vitrified clay body that is impervious to liquids and fired at a high temperature (1200º–1350ºC). The clay contains significant amounts of aluminum silicates.
Terra Cotta – a lightly fired, unglazed earthenware usually reddish in colour. It has frequently been used by sculptors and modellers to produce models or studies for more finished pieces in other materials.
Tin Glaze – a decorative technique invented in ninth century Mesopotamia for use on low-fired earthenware. Already-fired biscuit vessels are covered in a clear lead glaze with tin added as an opacifier to create a smooth white surface, imitating porcelain after a second firing.
Trailing – a decoration technique in which lines or dots of coloured slip are dribbled on the surface of a clay body.
Translucent – Permitting diffused light to shine through.
Transfer Print – an economical method of mass-producing intricately decorated earthenware. A pattern is etched into a copper plate, and the plate is then coated with a coloured enamel glaze. The excess glaze is printed onto thin paper, and the paper is trimmed to fit particular vessels. The wet paper is applied to the vessel and rubbed lightly, resulting in the transfer of the enamel pattern to the vessel. The vessel is then fired to set the enamel.
Underglaze Decoration – colour that is applied to greenware or bisqueware before it is glazed or fired.
Vitrification – the conversion of clay into a hard glass-like substance by firing it at a high temperature.
Wax Resist – a decoration technique in which warm wax is applied to pottery or to the pottery’s glaze so that subsequent layers of glaze do not adhere to the waxed areas.
Wheel Throwing (or Throwing) – using a potter’s wheel to produce pottery. A mass of clay is placed in the exact centre of the wheel head, forming an opening in the centre of the clay. The size of the opening gradually enlarges as the artist uses his or her hands to manipulate the clay into the desired form.