Injection vulcanized molds

Jewelry Discussion
1

I have made thousands of vulcanized milds, I never tried using an
injection molded plastic part. will the part withstand the heat?

Richard Hart G.G.
Jewelers Gallery
Denver, Co.

2

I have made vulcanized rubber molds using miniature sandalwood
carvings as models. The wood models were darkened slightly but not
destroyed. The molds worked great.

One way to find out if injected molded plastic parts can be used to
make rubber molds is to try it.

Lee Epperson

3

It depends on the type of plastic the original part was created
from. One thing you might want to try is a batch of Castaldo’s
“Rapido” – vulcanizes at 200F for 15 mins per 1/2inch. Excellent
quality results and the lower temp expands the range of things that
can be molded with it.

If that doesn’t work, try the VLT (165F vulcanizing), also from
Castaldo.

Good luck!
Karen Goeller
No Limitations Designs
Hand-made, one-of-a-kind jewelry
www.nolimitations.com

4

I used to make vulcanized molds of injection molded plastic model
car parts. The shape of the parts were usually a bit distorted, but
they came out reasonably intact detail-wise, and with a little gentle
persuasion in either wax or metal, most were usable. Problems were
usually associated with using too much rubber, causing too much flow
out of the vents, which of course made the piece move around. When I
needed a dimensionally sound part, I invested the plastic part,
burned it out like a wax, cast it and then made a mold from the metal
piece.

But with the currently available RTV mold compounds, why would you
not just make an RTV mold and not worry about the heat/pressure
issue?

Dave

5 
But with the currently available RTV mold compounds, why would you
not just make an RTV mold and not worry about the heat/pressure
issue?

I TOTALLY agree with Dave’s last statement. Actually I don’t really
understand why jewelers continue to use vulcanized molds at all. I
continually shake my head when there is discussion abut it.

John Dach

6 
Actually I don't really understand why jewelers continue to use
vulcanized molds at all. I continually shake my head when there is
discussion abut it.

Uh, because they last longer.

Elaine

7

Hi John,

I TOTALLY agree with Dave's last statement. Actually I don't
really > understand why jewelers continue to use vulcanized molds
at all. I continually shake my head when there is discussion abut
it.

I use both. If I want a mold to last forever and it’s a complicated
piece that is difficult to cut, I prefer traditional vulcanized Gold
Label rubber. I like it because it is so tear resistant, I can
strrrrrrretch a thin little bit quite far before I cut it and it
won’t tear. Or I can pull a bigger piece through a smaller hole and
not have a tear. Or cut a corkscrew, so it unwinds out of a tight
spot. You really can’t do that stuff with the current RTV compounds.
The shrinkage is the only real issue I have with it and if you plan
ahead it’s easy to deal with.

So if I have something that I need a bullet proof mold of, something
for a line that will be reused many many times for instance, I use
the traditional rubber. If I just need to use the mold a few times
or if it’s a relatively simple mold to cut, I use the RTV.

Mark

8

So if I have something that I need a bullet proof mold of, something
for a line that will be reused many many times for instance, I use
the traditional rubber. If I just need to use the mold a few times
or if it’s a relatively simple mold to cut, I use the RTV.

I agree, also rubber mold is quicker and easier for me to make. I
also cut corkscrews to pull large pieces of rubber through small
holes.

Richard Hart G.G.
Jewelers Gallery
Denver, Co.