I recently made a plaster mold of a rabbit head (raw). It was frozen solid when I put it in. I coated it in mold release. After pouring the second part, I went to bed, woke up the next morning and took the head out. Plaster usually cures in 30 minutes to an hour so I expected the mold to be solid by this point, but it wasn't. The inside of the mold was very chalky, and the outside was cold and over all it didn't feel very solid. I could easily scratch marks into the surface with a tool. I decided to put it in the sun for a couple of days, taking it inside at night or whenever the sun wasn't out, but after a week it was still like this. I poured the polyurethane foam into it anyways to make a cast. It kind of destroyed the mold but this was ok with me since I was just casting this head to be able to sculpt over it and make a nice change out head sculpture, so I didn't need any more than one. I just want to be able to make permanent molds of said change-out head sculptures with the plaster instead of silicone. Does anyone know what went wrong? I assumed it was the iron in the blood of the rabbit head that messed with the sulfur of the plaster, but I've seen other people carcass cast in plaster before with no issues.