Earthenware.—All ware that, in contradistinction to porcelain, is not translucent.
Glaze.—The glassy substance applied to the surface of pottery and porcelain.
Lead Glaze.—The porcelains of Bow, Chelsea, and other early factories contained as much as 40 per cent. of oxide of lead. Modern chinas contain less than half that, and some glazes are “leadless.” As to the terrible results of the use of this glaze on the health of the potters, see Report of Professors Thorpe and Oliver to Home Office on subject (C. 9207, 1899).
Over-Glaze Decoration.—Decoration after the surface has received its transparent glaze. This decoration admits of a wider range of colours. On hard paste, such as Plymouth, it stands flat on the surface; on soft paste, such as Bow, it is partly incorporated.
Under-Glaze Decoration.—Decoration applied to the unglazed surface when in biscuit state; the whole is then covered with transparent glaze and refired.
Ironstone China.—A term invented by Mason, who took out a patent for his ware. It is not china, but is a heavy class of earthenware highly decorated. It was generally adopted by other Staffordshire makers.
Moulds.—The models from which china is made. These are of plaster of Paris.
Opaque.—Incapable of transmitting light. This distinguishes pottery from porcelain.
Paste.—The body or material of which porcelain is made.