Here you see a mother made out of plaster.  I usually use hydra stone as it is far harder/stronger than plaster so the mother can be much thinner, lighter and stronger.  I like fiberglass as a mother material the best, as it is very strong and lightweight.  More on this as I get the site up.  With plaster, hydra stone and the like, I insert sisal fiber into the mother material for strength and in case the mother gets cracked, the fibers will normally keep the mother usable and the parts together.  You can glue broken mother molds if it occurs, I like Gorilla Glue as it foams and “pushes” into the mother material for a better bond, but use what ever you like.

        Make the plaster or hydra stone mixture somewhat thick so it is easy to build up as needed, but not so thick it will not work into and around the rubber to make good contact.  As it just starts to set up, wet your hands and smooth the mother.  A smooth mother is much nicer to work with, the wax doesn’t have rough spots to stick to etc.  Once the mother on the first side has hardened, the mold is turned over in preparation for the 2nd side of the mold making.