Back to Ganoksin | FAQ | Contact

Vulcanizer for lost wax mold making

I am looking for on Vulcanizer For Lost Wax Mold Making.

The main question I have right now is how thick of a mold is

I seems that 1" seems to be some standard.

What would be the thickness or height of a object that a mold could
be made.

Is there a outfit that can make a thicker mold for me.

Thanks Jerry


The thickness of a rubber mold ( or the mold frame) will have a lot
to do with the size of the piece you are molding. Sure, you could
mold most jewelry-sized objects in a one inch thick mold frame, but
molding a very small thin object in a one inch thick mold frame
wastes a lot of rubber! Also, the hand strength needed to separate a
1 inch thick mold while cutting it is no fun at all, even with a mold

In our studio, we have an assortment of thicknesses and sizes of
mold frames which allows enough rubber for an effective mold, but one
that conserves that expensive mold rubber. Fortunately, one of my
students has the ability to make us custom-sized mold frames out of
heavy welded aluminum stock, so we can successfully mold even giant
belt buckles or bracelets.

I’d recommend the 8 in. square vulcanizer, which will be able to
handle almost any size of mold frame.

I would also recommend a low or no-shrink mold rubber. My current
favorite is Zero-D Products Low Shrink Gray mold rubber strips.

Have fun!
Jay Whaley


Pros and cons of RTV (room temperature vulcanized) verses HV (heat
vulcanized) rubber molds

I like and use silicons RTV’s a LOT (mostly) and I primarily use Tin
Catalyzed silicon because of costs and lower "contamination"
problems verses platinum catalyzed silicon. Platinum silicon does
have a near unlimited mold life while tin silicons usually are
stated to have a 5 to 10 year life. Either of these have good shelf
life for the rubber base but the catalyzers can go be bad after a
few years but new cat. can be purchased if needed. There are a
number of other “rubber type” RTV’s each having pros and cons
themselves and too much to go into here, but there are many other
RTV mold materials besides silicon. Silicon molds release wax very
well compared to rubber heat vulcanized molds. Releases do eliminate
sticking waxes in heat vulc. molds but it is one more thing that can
cause wax surface “problems” and one more think that HAS to be done
when injecting waxes.

Heat Vulcanizing rubber now is available in rubber (many different
ones) as well as silicon. Heat vulcanized molds (rubber) have GREAT
mold life (decades if stored out of sunlight and heat) silicons I do
not have much experience with. Heat vulcanized molds have been a
mainstay in the jewelry industry for decades while RTV materials are
being used by some but it seems that the “old fashioned” heat
vulcanized molds still hold a major place by many.

I got into mold making over 20 years ago making molds for my wife’s
(ultimately) bronze sculptures. Her masters were done in an oil clay
(non hardening) and there was often a lot of fine detail (she was a
goldsmith and master model maker for 30+ years before we met, I was
an organic apple farmer and fruitstand operator). When I started
making molds for her sculptural pieces, I/we did use a number of
different RTV materials. Some were very cheap (compared to silicons)
but some had short mold life or poor mold stability, or lack of good
detail and wax finish and/or other

What I found as a problem with HV (heat vulcanizing materials) is
one HAD to have a “mold master” (to me this is different that the
actual “master”) in a somewhat high temp material, usually metal, so
as to withstand the heat of making the heat vulcanized mold. This
would require and master made in, say wax, to be cast to metal
before making the mold. Two problems here, at least to me, 1) being
you could loose your wax master in the casting process if you had a
problem, and 2) you had to make the wax oversized to account for the
loss is size that occurs in casting it into metal.

There is another a loss is size when making the mold (except
silicons have almost NO shrinkage when making the mold but this is
not true with other RTV’s or heat vulcanized rubber (not including
HV silicon here, it does not shrink) AND another loss when making
the wax and again a loss when casting.

So if one is making a wax master that is ultimately going to be
molded with a heat vulcanized rubber (not silicon), it has to be “up
sized” to account initial casting loss, detail loss during cleanup
of the casting master, mold making loss, wax loss and casting loss.
Additionally, there WILL BE a detail loss every step of the way.

If one uses an RTV material to make the mold, the mold can be made
directly from the wax master. Now there is going to be potential
size and detail loss occurring only at the mold making, wax
injection and casting steps, only occurring 3 times with an RTV
verses 5 “losses” in the sequence for a heat vulcanized mold.
Additionally, with an RTV mold, one STILL has the master wax in it’s
original state so additional molds can be made if needed from the
original wax master. To me, this fact of having the “original wax
master” after the mold is made, makes RTV molds very advantageous in
many situations.

You do not need a heat vulcanizer and mold making plates for RTV
materials either, just one more thing to consider when thinking
about RTV verses HV mold making. We have both but we haven’t used
the vulcanizer for many years, but Cynthia has not been making
jewelry either…

Just my thoughts, maybe some will help and maybe they won’t.
John Dach

John, Thank you for all this great info. I just tried using the
platinum silicon for the first time this week. The rep at Tap
Plastics told me that I could do a two part mold easily without
worrying because silicon sticks to nothing. However, even after
letting the first half cure for a day, the two parts of my mold
fused together and I was stuck trying to cut them apart. Do you have
any advice on how to make a two part silicon mold so that the two
halves actually stay separate’

Carina Rossner

Do you have any advice on how to make a two part silicon mold so
that the two halves actually stay separate' 

ABSOLUTELY!!! get some Teflon spray and use it as a parting
application. I get mine (by the case) from Miller-Stephenson’s

but their site is currently messed up, I sent them an e mail
about it, but their products are great (MS 122-DF)!!! It is a
teflon material and works GREAT… There are other releases for
silicon, but the teflon has proven, for me, to be the best and most
reliable. In a pinch, I have used teflon spray lubricants from the
auto parts store and “Home Depot” like places, but the Miller
Stephenson’s product works the best… I order it by the cast (12)
as needed and always have cans on hand. I do not want to run out of

If you need any other info “right now” my phone number is
360-681-4240. We are in the NW part of Washington State (PST) and
you are welcome to call if you need more info. etc.

Good luck. You might check out my website, the section on mold

for “some” info on mold making for foundry applications (bigger than
jewelry) but if folks want some info on smaller molds, let me know
and I will put that info up too. I know that there are some blank
pages on the site, I am working on them and putting them up as I get
them together… For you cooking folks, be sure to check out the
cooking section, there are some GREAT recipes there. Some of you
might want to see what other “art” we are doing and to see that, go
to and click on the section that interests you. Have
a GREAT day making “your” art, every day!!!

Best all…
John Dach

Carina, after making the first half of your mold dust it with a
separating powder such as corn starch then pour the second half of
the mold. They will not fuse together.

Frank Goss

Dear Jerry,

One inch is a common thickness, but there is no technical reason
that molds need to be limited to that dimension.

Vulcanized rubber molds are limited only by the size of the opening
of the vulcanizing press.

Liquid rubber molds are limited only by the size of the mold frame
that you can buy or make yourself.

Michael Knight

Dear All,

May I add a quibble to this discussion about rubber mold materials?

The rubber many people have been referring to is properly known as
siliCONE, not siliCON.

Silicon is the 14th element on the period table and is a grey
metallic, crystalline material. It is most commonly found combined
with oxygen to make silica, the main ingredient in common sand and
many other products including jewlery casting investment powder.

Silicone is made from silicon ore and can be either an oil, a liquid
or a gum, which when chemically cross-linked and vulcanized, is what
we know as silicone rubber.

Just FYI.
Michael Knight

John - I have the best Focaccia recipe in the world – straight from
Genoa. Differs from yours a lot - includes wine (can this ever be
wrong?) and Extra Virgin Olive Oil. The recipe is started by making
a short sponge. It’s available for the asking – I don’t hoard good
stuff and keep it from other foodies.


The rubber many people have been referring to is properly known as
siliCONE, not siliCON. 

Chuckle. I’m reminded of my own almost unreasonable irritation upon
hearing, all too often, the number of people who cannot seem to
correctly pronounce the names of Iraq and Iran. Despite invading
Iraq, and people dying and fighting over there, all too many,
including and especially the former president and most of his
administration, not to mention all too many of the military folks
who did the hard work over there, simply didn’t seem to know the name
of the place. For the record, they are not pronounced “eye rack” and
"eye ran". The “I” is a “short” i, like the “e” in “eek” or the "i"
in “if”, and the second sounds are like “rock” or the name “Ron”. In
both names, the accent is on the second sound, not the initial vowel,
and the initial vowel is clipped and short, a single vowel sound, not
a drawled diphthong (a vowel sound that starts as one sound and
blends into another, effectively two vowel sounds, not just one.
English is full of these. Most other European origin languages are
not.) One has to wonder, just peripherally, whether the appearance of
ignorance that is conveyed by the mispronunciations, just might
contribute in some slight way, with difficulties in getting the
people of Iraq and Iran to take the possibility of sincere good
intentions of at least some of us, seriously. After all, how would
we feel if they pronounced “America” as “Aye-meer-i-Kaye”, and seemed
to relish the mangling of our countries name instead of at least
trying to say it right…

Sorry for the rant. Spelling the word silicone versus silicon is so
much simpler…


Do you have any advice on how to make a two part silicon mold so
that the two halves actually stay separate' 

I use Castaldo’s Mold Separating Cream.


Barbara, Count me as one of the “foodies,” Hope you will share with
others Would love to have your recipe for Focaccia…

Thanks, Alma

Thanks Peter for the clarification of the pronunciation of Iran and
Iraq. I am glad that I am not the only one irritated by the
mispronunciation Also, to be added to the list is calling
Italians,“eyetalians.” I shudder each time I hear these
mispronunciations. Alma

Jeesh… years ago Mayor Yorte of Los Angeles couldn’t
pronounce the name of the city/county HE was located in. But then,
get off of the West coast and San Jose, La Jolla, Tijuana, etc. are
mangled by most. But then most “foreign” words through out the world
are mis pronounced by “non locals”. I must say that silicon vs
silicone is something I will be much more careful of…

John Dach


I would be most interested in what/how your recipe reads. I imagine
that what you are referring to as a “short sponge” is what the
Italians refer to as a Biga, a well fermented, highly active yeast,
water and flour mixture. I often make Focaccia and often the Ciabatta
doughs with a Biga, but as I am making bread about 3 times a week, I
have pretty much switched to using the "all in the mixing bowl"
recipe on my web site.20

Hoarding good should be a jail able offense!!! I
really do not believe it does anyone any good any good (well I guess
there are times, but in general and especially in cooking, Share,
sHare shAre. For those who don’t know but are interested, I have a
small recipe section on my website

If you think I might have something that you want, let me know and if
I have it, you got it and/or I will post it on the site…

Good eating!!! Great jewelry makin!!!

John Dach

While working for a community college, when Michelin opened a center
on campus, the college president informed the audience that the
Michelin representative had graduated from the University of

I tried to hide under my chair as I cringed.


We have both but we haven't used the vulcanizer for many years,,, 

My vulcanizer hasn’t been plugged in for at least eight years now.
RTV is definitely the way to go, unless the molds are expected to be
used many times. Much less shrink, no expensive frames, no vulcanizer
with all of their idiosyncrasies and fussiness, but best of all, you
can gate a metal master with wax wire and make molds of just about
anything, including as John says, wax patterns. I make RTV molds of
just about every wax that takes more than about six hours to carve.
Saved my hide more than once, I assure you.

Most of my molds are either 1/2 inch or 5/8. One inch or thicker
only when absolutely necessary. As John pointed out it cramps the
hands, makes cutting much more difficult and increases the risk of
slipping with the knife. Speaking of mold knives, always use a brand
new blade. If the tip touches a metal master (or anything else harder
than wax), grab a new one. Even a brand new blade with an invisible
nick in the tip will make cutting a lot harder and increase the risk
of a slip tremendously.

The only issue I have with molds parted with the various methods
described such as the cream or powder, is that parting lines and
alignment of the two halves can become a real problem. If mold making
is going to be a part of your adventure more than a couple times a
year, I would really recommend learning how to cut. When locks or
just uneven alternating up and down cuts are cut into the mold (it
looks like waves), the halves mate up and stay aligned much better.
When done well, parting lines can become almost invisible. Mold
cutting is an art unto itself, but it’s not really all that hard to
do, especially if you start with half inch molds.

Dave Phelps

Thank you , Peter for commenting on this. I’ve always been reluctant to wade into this topic for fear of looking grumpy.

For the record, SILICON is an element on the period table, symbol “Si”. It is the major ingredient in sand.

SILICONE is a man-made material made from SILICON. Some common forms include silicone oil, silicone grease, silicone rubber, silicone resin, " silicone implants" and silicone caulk.