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How does slip casting create a hollow clay object in a plaster mold?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Stages in the slip casting of a thin-walled whiteware container. Clay powder is mixed in water together with a dispersing agent, which keeps the clay particles suspended evenly throughout the clay-water slurry, or slip. The slip is poured into a plaster mold, where water is drawn out by capillary action and a cast is formed by the deposition of clay particles on the inner surfaces of the mold. The remaining slip is drained, and the cast is allowed to dry partially before the drain hole is plugged and the mold separated. The unfinished ware is given a final drying in an oven before it is fired into a finished product.
traditional ceramics Stages in the slip casting of a thin-walled whiteware container. Clay powder is mixed in water together with a dispersing agent, which keeps the clay particles suspended evenly throughout the clay-water slurry, or slip. The slip is poured into a plaster mold, where water is drawn out by capillary action and a cast is formed by the deposition of clay particles on the inner surfaces of the mold. The remaining slip is drained, and the cast is allowed to dry partially before the drain hole is plugged and the mold separated. The unfinished ware is given a final drying in an oven before it is fired into a finished product.

Slip casting is a specialized forming technique used to create hollow ceramic objects by utilizing the porous nature of plaster molds. The process involves the following steps:12

  • Preparation: A clay-water mixture, known as a slip or slurry, is prepared by adding dispersing agents to ensure the clay particles remain in a stable, liquid suspension.1
  • Absorption: When the slip is poured into a porous plaster mold, the mold’s capillary forces draw water out of the suspension.12
  • Deposition: As the water is absorbed, a layer of clay particles is steadily deposited in a dense, face-to-face packing against the interior surface of the mold.1
  • Drainage: Once the clay deposit reaches the desired thickness, the remaining liquid slip is poured out or drained from the mold.12
  • Removal: After the cast has stiffened, the mold is opened to reveal the freestanding, hollow clay piece, which is then ready to be dried and fired.12

This method allows for the creation of surprisingly complex shapes that would be difficult to achieve through other forming techniques.1