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Vulcanized VS. RTV


#1

I have some vulcanized molds done in Castaldo Gold and some in
White, that are about 30 years old, They still have very good detail
and have all yielded several hundred parts, But they have been well
cared for, I have some that are 10 to 15 years old that were done in
Kerr White and their soft formula as well, These have not held up as
well as the Castaldo rubber, I have also used the Castaldo No Shrink
Pink embedded in Castaldo white label and are still going strong
several of these have had a few thousand parts run through, Down side
is they eventually need some type mold release, I prefer silicone
spray (in very moderate quantities) I have used the Castaldo RTV and
I like it BUT it doesn’t seem to have the durability of the
vulcanized molds, I have used Belicold RTV which I like, but is no
longer available, I also tried Rio’s Ditto formulas and while they
are very good at first the seem to deteriorate rather quickly, ( I do
watch my wax Temp. and pressure closely )I would say if a person is
going to only make 50 or 100 pieces then the silicone RTVs work
well, But I have to tell you, I LOVE the Castaldo Silicone
vulcanizing material , It so far has held up very well, over 1,500
parts on one run 3 molds, 500pcs per mold and no degradation of
detail, and as a good silicone should, requires no mold release. Plus
side of RTV is the range of things you can mold, I also like the
ability to mold directly off of a wax pattern or a plastic pattern
with 0% shrinkage, and that being said I really think there is a
definite purpose for both, but for high production Vulcanized for me
is better or so it seems

Kenneth Ferrell


#2

Dear Ken; I have too, a lot of molds of Castaldo goldlabel and i make
it for a large production of pieces in gold and silver.i have used
no shrink-pink ,and a silicone from a company of my country. when i
want a o% shrinkage i used too RTV but ONLY works well in little
number of pieces but for this cases is the solution.in this moment i
find the rubber of my dreams,this rubber works very well and the
cost is less than the castaldo rubber and i have a very fine cut
with my x-knife and very good priable,this rubber is the rubber from
"ZERO D-PRODUCTS"(www.zerodproducts.com) and they have too a very
good silicone,i’m very happy with this,in this moment is the only
rubber that i cut.I think too that for a large production the rubber
is the better solution.thanks for your coments.


#3

Although you can make one material work for most every design, one
mold material isn’t the best choice for every design. These are the
pros and cons as I see 'em:

RTV. Perfect for molds of wax, organic and plastic originals, or
where shrinkage is a problem. The clear RTV’s make cutting easy
since you can see where you are going. Waxes release beautifully.
It’s a little more expensive. I find it less than ideal where lots
of flex is necessary on an oft-used mold. You have to wait for it to
cure. You need a vacuum.

Vulcanized silicone. Shrinks less than vulcanized rubber, for the
most part. Packs very quickly. You can use powder separation. If
you are new to cutting molds, the fact that there are nearly
see-through varieties is a plus. Where a rubber mold might stick in
a design, vulcanized silicone will, most often, release beautifully.
It doesn’t oxidize silver masters (better for duplicate molds). It’s
a hair more expensive than rubber. You need a vulcanizer that will
get hot enough. You need a metal master.

Vulcanized rubber. Inexpensive. Powder separation is an option.
There are some good kinds out there that release well without having
to overuse spray or powder. You need a vulcanizer. You need a metal
master.

If we are supplied with a metal master, we’ll almost always use a
vulcanized mold. They’re less expensive and we can be injecting
waxes that very day.

Dana Carlson
The Alchemist Casting Shop - platinum, gold, silver, bronze