Chapter 9: Sets for Animation Mold Release Once the mold has cured, it is flipped around and the water-based dam is removed exposing the ultra cal underneath. The clay sculpture is touched up to repair any slight damage from the casting process, and the plaster is coated with petroleum jelly (Vaseline) to act as a mold release. The Vaseline is critical to prevent the second half of the mold from sticking fast to the cured plaster. You must be careful to fully coat the surface of the cured plaster that will come in contact with the new batch. Before mixing and pouring the second half, you may consider placing thin clay slabs at the edge of the mold. Once the second half is cast, these slabs of clay will leave small gaps at the edge of the mold to allow you to insert a flathead screwdriver to pry the mold halves apart. Prepping the Mold Once the second half of the mold is cured, the two sides are pried apart and the original is removed and discarded. The two halves must be thoroughly cleaned of clay and residue and the interior of the mold inspected for air bubbles and repaired if need be. The interior is coated with another type of mold release specifically made for rubber. When dry, this release consists of a fine layer of powder. The armature is then placed within the mold and adjusted so that it fits and does not touch any of the mold surfaces. Mixing the Foam