Hey guys, well I made my first ever successful negative head mold last night and plan on pouring soon. However, what I have to pour the positive is a type of plaster of paris. Now, I've had some experience with plaster of paris, i even made a teeth cast and it breaks easy. I'm planning on being able to model prothstetics on this so I need a stronger material. Preferably some that I can pick up at a lowes or walmart. Suggestions?