HOW TO MAKE A TWO-PART RUBBER MOLD
OF A COMPLICATED MODEL, PAGE 4
10) Let the rubber set until cured, then
remove the foam board walls and the clay. Remove the
foam board carefully, because you will want to reuse
it for the second half of the mold.
Your funnel and vent wires may pull out of
the rubber. They need to be replaced, so the funnel
and vents are formed in the second half of the mold as
well as the first half.
Clay may stick to the first half of the mold,
and your model. Every bit of clay needs to be removed.
If there is clay on your model, the second half of the
mold will reproduce the clay instead of your model. If
there is clay on the first half of the mold, the
second half of the mold will not sit directly against
the first half, creating a void where casting material
may go and create “flashing” that will need to be
cleaned off every casting made in the mold.
The only exception is for the funnel and vent
wires. If you need to use clay to connect the funnel
or vents to the model, that is OK.
11) Reassemble the foam board walls around
the first half of the mold. Apply release agent to
keep the second half of the mold from sticking to
the first half. Add braces to the foam board.
Mix and pour rubber for the second half of
the mold, just like the first half. Wait until the
rubber is cured, then remove the foam board walls and
separate the two halves of the mold. Remove the vent
wires and the funnel, and clean the mold completely.
This is the finished mold.
12) This type of mold can be held together
with two flat boards and any sort of clamps or bands.
The clamps in the photo look very powerful, but they
are actually applying only light pressure - just
enough to keep the two halves of the mold together. In
the photo, the funnel opening and the ends of the vent
holes are visible.
a PDF source list
Includes 26 suppliers of all mold making and
casting materials mentioned in ALL the demonstrations
on this web site, including silicone rubber,
polyurethane rubber, latex rubber, polyurethane
plastic, epoxy resin, polyester resin, molding clay,
foam board, release agents, pottery plaster, Hydrocal,
metal powders, other plastic resin fillers, and
gelatin molding compound. With company names,
addresses, phone numbers, and web sites. Downloads to
your computer as a PDF file.