My plaster of paris molds never work
I tried making one part and also two part (push) molds with plaster of paris. I followed the directions and mixed two parts of plaster to one part of cool water and poured into a box (dunno the technical name for it) over my shape. But the plaster sticks to my shape no matter what. I can't get my shape (positive) out without breaking my mold b/c it won't release. I've tried mineral oil, silicone release spray, and vaseline. The vaseline has worked the best but I can't use it on every part. I've tried making a mold of a piece of wood and a concrete paver and neither of which worked.
I don't know what I'm doing wrong. It seems fairly straight forward. Lubricate the positive (what I want to make a mold of), put a slab of clay down, put the box around the positive and imbed into the clay to prevent leaking from the bottom, and then pour the plaster over the positive.