Slipcasting is an easy technique for the mass-production of pottery, especially for shapes not easily made on a wheel. A liquid clay slip (technically a slip) is poured into plaster moulds and allowed to form a layer, the cast, on the inside cavity of the mould.
The slip can be formulated to mature at a variety of temperatures. In a solid cast mold, ceramic objects such as handles and platters are surrounded by plaster on all sides with a reservoir for slip, and are removed when the solid piece is held within. In a pour mold, once the plaster has absorbed most of the liquid from the outside layer of clay the remaining slip is poured off for later use, and the item is left to dry. Finally the finished item is removed from the mould, “fettled” (trimmed neatly), and allowed to air-dry. This produces a greenware piece, which is generally fired to harden it by a process of sintering.
It is commonly used for smaller decorative pieces, such as figurines, which have many intricate details. In the United States, moulds and their slipcast pieces are primarily an industrial product, and are usually called “ceramics” to distinguish them from other pottery. In recent years, slipcasting has become a process used by artists and independent designers to produce editions of objects, play with the aesthetics of mass production in ceramics, or manufacture ceramic ware on a small scale. ware on a small scale.