Wax pattern thicker than model

Hi there,

I recently made a master model which is thin pendant, about
0.9mm,weight 2.6g, I vulcanized using castaldo rubber and then
injected it just find the wax pattern is thicker than my master
model, 1.2mm thick, and weight is 3.5g, I tried several rubber mold
by vulcanizations, but the same problem in the result, I hardly to
find the solution, can anybody help ?

Thanks in advance,

Do it with RTV room temperature vulcanizing. I think heat and vents
may be your problem in the conventional way of using the vulcanizer.


Try backing off the pressure of your wax. It is possible to get
waxes of different weights and thicknesses out of the same mold. I
have noticed this difference even from my professional caster who
does my silver production work. It is certainly something to watch
when estimating prices, particularly with gold!


Dear Peter,

This can happen if you inject at too high a pressure. The mold may
balloon a bit, resulting in a larger mold cavity.

Try less pressure or perhaps a harder rubber, which will resist
balloooning. Try our White Label, Titanium Label or Econosil, all of
which are harder than Gold Label.

Michael Knight

From what I understand about injection wax devices is that they use
pressure to fill the mould.

I’m assuming this is what’s blowing out the model, I’d be interested
to know from someone more experienced if I was on the right track.

Have you tried a gravity pour, with a high definition gravity pour
wax. There’d be no pressure, and the viscosity is much lower.

Regards Charles

Hello Peter, I have had this happen occasionally with a product
called “no- shrink pink” vulcanizing rubber. If it is a problem for
you, switch to something like castaldo gold. It will then shrink a
bit. I’m not affiliated with the company.

Have fun.
Tom Arnold

Its wax injection problem. Either air pressure too high or wax pod
too hot and timing during shooting. Pink castaldo do helps


Too much injection pressure, the mold is swelling and distorting.
When properly injected it should actually be smaller than the master
due to mold and wax shrinkage.


James Binnion
James Binnion Metal Arts

One way to prevent the mold from blowing up when wax is injected is
to back the mold with pieces of wood the size of the mold. Place the
wood on the front and back of the mold.

There is also a clamping device on the market that can be used to
clamp the mold.

I inject wax into molds for ranger and presentation buckles. The wax
has to travel around 3 inches to reach the back of the mold. After
reading the posts on the subject I tried using an injecting pressure
of 5 PSI. That did not work for me. Wax never reached the back end of
the mold.

I normally inject Rio Grande’s Pink Buckle wax with around 12 to 15
psi and a temperature of just under 160 degrees. That seems to be
the only conditions that produce satisfactory waxes for me.

I am not satisfied with talcum powder as a means of venting the
mold. On my long waxes I place 18 gage wires into the very edge of
the back end of the mold. See the following Orchid Blog for a
description and photos.


Lee Epperson

I have been making rubber molds for over 30 years. When someone posts
their problem with a rubber mold, there are many variables.

If I said I had a rash and asked for opinions as to what was causing
it, there are too many causes for anyone to make an educated guess.
Making a silicone mold most likely will not be the answer if you do
not know why the wax is turning out thicker than the original. A
vulcanized mold does not increase the chances of having a thicker

Temperature of the vulcanizer, mold plates held correctly, pressure
wax is injected are some of the first considerations. Are there
noticeable parting lines? Flashing? Not tightening the platens
enough, not waiting for 10-12 minutes with light pressure and then
tightening down hard.

Without a picture of the mold and the wax, I can make guesses, one
of them might be right, but might not.

I think the guys at Zero D Products or Castaldo are available to
help trouble shoot problems if you call them.

Making mold after mold without knowing the problem reminds me of the
saying that the definition of insanity is when you do the same thing
over and over and expect the results to be different.

Richard Hart G.G.
Denver, Co. 80210

Yes, this is very common with either high pressure or light clamping
pressure. You can actually use this to your advantage sometimes if
you need a thicker piece

Zero D products has a gray low shrink vulcanizing rubber that I have
been extremely happy with, I have made over 4000 molds and have
moved away from the other fine vulcanising rubber that Zero D
produces to use this one exclusively. Flexible and really good
filling qualities.

Richard Hart G.G.
Denver, Co. 80210