Marco, after you have the necessary strips of rubber, divide the
amount in two stacks and stick the strips together except for the
last center strip that will be facing the opposite side.( I assume
you know how to prepare the center portion for ring, pendant, etc.
)With this piece, take a scissors and cut the four corners (approx.
10mm square or any shape) not off but still clinging onto the strip.
Now stick this on to the lesser stack and peel the cloth off the four
corners that would be facing the opposite side, press this side
against the opposite half and the four corners have been transferred
to the other side. You now have an interlocking mold that will
eliminate the need to cut it. Peel off the last partial cloth
covering and without the project in between, take a brush and lightly
paint both sides that would be facing each other with talcum or baby
powder. Blow excess powder off, since you want a minimum amount of
powder, take both sides in either hands and clap it together till
hardly any powder is visible. Don’t worry, you’ll never take it all
off. Put the two sides with your metal project in the center and
vulcanize. After it cools, the two sides will automatically split
apart, if not pull apart at the nozzle recess. If you’re in a hurry,
after vulcanizing you can plunk the mold into a bucket of water and
it’ll split. But best to let it naturally cool. Enjoy, Min
Azama in Tokyo.