Started casting aluminite clear slow in HDPE molds as well as PVC pipes. I use Stoner mold release on the molds. The blanks come out very nice but very hard to get out of the molds -- I've had to pry them out of the square molds with a chisel, and for the PVC I had to turn the PVC off on the lathe. What am I doing wrong? I thought I was being generous with the mold release but maybe I need more?