I got to work right away this morning opening up the mother molds. Using a chisel and a hammer, I tap away at the shim line gently to get the mother mold to open. Once I see a crack starting to form in the plaster, I can start trying to pry the mother mold open.
Once the mother mold is open, I remove the plastic wrap and all of the clay from the inside of the mother mold. To be extra thorough, I also wash the mother molds under water in the sink to be sure that the clay is all clear.
Above is an image of the cleaned mother molds, ready to be reassembled.
Putting the mother molds back into place.
The reassembled mother mold.
I model out of plastilene a little wall around the pour hole, as well as pieces of plastilene around the edges of the bottom of the mother mold. Next, I mix about 30 oz. of rubber which is then poured and distributed amongst the three molds. The purpose of this second layer of rubber is to seal and clog the bottom edges of the mother mold. If you try to pour all of the rubber all at once, sometimes the pressure of the rubber is too much and the rubber leaks out of the bottom of the mold, which is a disaster. That way when I pour the final layer of rubber, I don’t worry at all about the rubber leaking out, because the second layer has sealed the mold tight. (I learned this one the hard way many years ago)