Why does ceramic slip stick to plaster mold?
The plaster mold is very, very dry. When you pour, the clay slip is mostly water and the plaster mold sucks up the moisture quickly, creating a coating inside the mold. It’s like pouring gravy onto a sponge…the water is absorbed, but the solids stay on top of the sponge if you leave it long enough. It’s the same way with a plaster mold..it’s a sponge. That’s the reason you watch the pour opening and pour out the excess when it is the thickness you need. The plaster will continue to absorb until the clay pulls away from the mold naturally, yet it is still green.
