barbotine (Fr.) Colored liquid slip applied by piping or trailing for raised decorations, first used on Rhenish pottery before A.D. 300. In France designated 19th-century French majolica with or without raised flowers made of slip. The term also refers to such flowers on English and American majolica.

biscuit Unglazed porcelain or earthenware that has been fired only once. Such ware is sometimes erroneously termed "bisque" in England and the United States. Ware deliberately left unglazed include porcelain introduced in the 1750s at the Sèvres factory in France for modeling figures and groups, perhaps because it resembled marble. Biscuit was later made elsewhere on the Continent and at the Derby factory in England about 1770.

biscuit firing A preliminary firing of unglazed pottery and porcelain that transforms the ware into the biscuit state. That is followed by glazing and decoration, unless the ware is intended to be left unglazed.

cailloux de Tours Literally "pebbles from Tours".(See Stoneware).

crazing Unintentional crackling of the glaze due to the differences in the rates of expansion and contraction during firing and cooling. Crazing may also occur any time after the pottery is made and will destroy the impermeability of the glaze.

decoration The enhancement of the basic form of a piece of ceramic ware by any of several techniques such as painting, enameling, gilding, burnishing, applying relief work, transfer printing, and others. The term "undecorated" in factory parlance refers to glazed but unpainted ware. In appropriate cases it is said to be "in the white."

delftware Tin-glazed earthenware made at Delft, Netherlands, and also in England, where the industry was introduced by immigrant Dutch potters. The latter ware is best termed English delftware to separate it from that made in Holland. The term is synonymous with maiolica, which is Italian tin-glazed earthenware, and is often used interchangeably (though technically incorrect) with faience, tinware, and majolica.

earthenware Pottery that is not vitrified and is porous unless glazed.

enamel An opaque or transparent pigment of a vitreous nature colored with metallic oxides and applied to ceramic ware as decoration over the glaze by low-temperature firing. Enamel colors often sink deeply into the glaze of artificial porcelains, but they do not penetrate the feldspathic glazes of true porcelain; rather, they remain on the surface and are readily palpable.

faience Tin-glazed earthenware, especially made in France, Germany, and Scandinavia. The term is of French derivation and probably comes from the sixteenth-century popularity in France of ware originating in the fifteenth century at Faenza, Italy. The technique is exactly the same as that used for maiolica and delftware, the only difference being the place of origin. In Portugal, the term also refers to majolica, lead-glazed and/or tin-glazed porous earthenware decorated with transparent metallic pigments.

figulines rustiques (Fr.) Sixteenth-century term used by Bernard Palissy for rustic earthenware; derived from Latin figulus for potter.

firing The process of transforming a clay body into pottery or porcelain by exposing it to heat in a kiln. The necessary temperature varies according to the type of ware, usually ranging from about 800°C for earthenware to 1450°C for oriental true porcelain. According to the type of ware, there may be several firings before the manufacturing process is complete.

flux A substance added to glass, glazes, or vitrifiable bodies, such as porcelain, to lower the fusion point during firing. Fluxes are commonly added to enamel colors to lower their fusion point to slightly below that of the glaze to which they are applied, although some softening of the glaze is essential to bind the enamels to it.

glaze A coating of glass applied to a porous body to seal it against the penetration of liquids. Glazes are made by fusing silica and alumina, after a flux has been added to the silica to decrease its melting point.

impressed Indented, as distinguishable from incised or cut in, by means of a stamp while the clay is still soft. Many factory marks are impressed.

jasper technique A technique developed by Bernard Palissy around 1545 to imitate the surface of jasper (a type of quartz) by mingling various colored lead glazes with metallic oxides.

kaolin A white clay, first discovered by the Chinese, derived from decomposed granite rocks and formed by water acting on the feldspar in the granite. An essential ingredient for all types of porcelain.

kiln Oven used for firing all ceramic ware.

Glossary continued