SlipCasting

Slipcasting is a ceramic forming technique in which liquid clay slip is poured into a plaster mold. The plaster draws water from the slip, causing a layer of solid clay to build up on the mold’s interior surface. After the desired wall thickness forms, the remaining slip is poured back out, leaving a hollow casting that will dry and harden into greenware.

Most slipcast pieces use two-part plaster molds, though some complex forms employ multiple sections. A release agent may be applied to the mold to ease demolding. The slip’s viscosity and the mold temperature are controlled to achieve even wall thickness; sometimes the mold is rotated or tilted to distribute the slip. When the piece has stiffened, the mold halves are opened and the greenware is removed. It is then left to dry before firing; afterward glaze is applied and the piece is fired again to maturity.

Slipcasting has long been used in mass production of tableware, figurines, and sanitaryware, especially in porcelain and fine earthenware. The method became prominent in the 18th and 19th centuries with the development of plaster molds and successful commercialization of bone china and similar wares.

Its advantages include high reproducibility, the ability to produce complex shapes and thin walls, and reduced labor compared with wheel throwing. Limitations include dependence on plaster mold life, shrinkage and cracking during drying, and the need for careful drying to avoid warping. Contemporary practice may combine slipcasting with hand finishing and glazing to produce varied results.