Is there a reason you other jewelers use vulcanized verses RTV
molds. Just curious......
I have a fair bit of experience with both kinds of molds, and there
are very good reasons to use vulcanized. The true rubber is much
much stronger than RTV. If you are going to use a mold a lot the
danger of damage is much less with real rubber. When cutting a mold
that has undercuts and complexity, the ease with which RTV tears can
ruin a mold easily. Vulcanized rubber is more flexible than RTV, so
a mold that is fairly involved is easier to work around details.
When cutting a mold for a basket type mounting it is necessary to
pull the rubber away from the mounting in order to get the cut line
where it needs to be to allow the wax to cleanly come out of the
mold. When doing this with RTV the likelihood of the material
tearing is very high. I cut molds in a very specific pattern to make
removal of the wax as easy as possible (reduces distortion), and the
tendency of RTV to tear in front of your cut adds an element of
unpredictablity. RTV is great when you need to mold a piece of wax,
or cannot use heat. It is also easier to avoid shrinkage, which is a
factor if you are copying an existing piece rather that something
that was designed to mold in the first place.