First I softened plasticine in the microwave, then built it up around my model. I leveled it out right at midline, and I poured the first half of the mold in plaster.
After curing I removed the plasticine and poured the second half. After letting the mold halves dry for a couple of days I held them together with large rubber bands, and filled the cavity with the liquid neoprene. The plaster absorbed moisture from the rubber and a thin wall of solid material built up.
I emptied out the liquid neoprene and let the casting dry overnight before removing it from the mold. Here I am preparing for the final assembly, with the neoprene hose connecting the leather mask and the pressure gauge.
