The pressure does collapse. I fill the mold and as it cools, the level drops a little bit. Where should I add the sprew/riser? Thanks for your insight
I would add a sprue to the largest end. if you do the smaller flat end you will catch air in the undercuts of the mushroom shaped end, unless you add vents. That sprue can also be your sprue for your investment mold further simplifying your process. You can add the sprue to your already existing mold by cutting it with a round punch like a sharpened pipe or something along those lines. As for the pressure, 40psi should be plenty.
