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Instead of talc?

I am wondering if anyone has had success with an alternative to
talc or mica for wax injection. I use several different injectors,
mostly on vulcanized silicon, and have tried all the various
combinations of parameters, pot and mold temp, pressure, excess of
relief cuts etc. Much of my work has areas of texture surrounding
raised flat areas which are highly polished. I have found that I
get the sharpest details on my waxes if I use an excess of talc on
my molds. The excess of talc causes surface porosity, which I sand
off the raised areas, but becomes a problem on any area I can’t sand
flat. If there is a different powder available that would aid in
evacuating air from the mold without degrading the surface of the
wax, such a product would greatly help. In particular it would
enable us to inject and tree multiple pieces as one, reduce wax temp
shrinkage etc. If I win the lottery I will get a vaccum injector
and the rotary table from Gesswin, in the mean time…

Martin

Martin,

I use Talc for my molds except I only powder them after about 20 or
30 injections and I use very little powder. The best waxes come
after shooting a number of times.

I have also used the cooking spray called PAM with success on some
molds.

Good Luck
Greg DeMark
email: greg@demarkjewelry.com
Website: www.demarkjewelry.com
Custom Jewelry - Handmade Jewelry - Antique Jewelry

I use baby powder. It is just cornstarch with a scent.

I have been using arrowroot powder which if I remember correctly was
reccomended by someone on Orchid . I also find it seems to let
difficult moulds fill well and either washes away when invested or
burns off . I have not noticed any flaws from it yet . Also it does
not seem to suffer from the damp.

Tim Blades.

Corn starch works just fine.

Dear Martin,

Non lab grade Magnesium Carbonate has been the main mold talc I have
used for many years. Used in my casting experience for over 40
years.

Currently though I have been in love with Gerber Baby powder for my
mold talc. It is mostly corn starch, about 98%. They don’t make it
any more so I bought every bottle I could find. After you powder your
molds you should always use an air jet to blow all the excess powder
away. I get good waxes every time with great detail. I understand
Arrow root powder is also excellent mold talc. I’ve not tried it.

I would speculate if you can’t get the detail in your waxes you may
either be using the wrong kind of injection wax or not venting your
mold properly. The injection machine is also a concern.

Every place air will run into a dead end should be cut for vent and
wax release. Think of the finger of a glove. If wax were injected
into this kind of mold the end would have to be vented to allow the
displaced air someplace to go.

On gum rubber molds I do prefer silicone spray. But spray and let
dry for a few minutes before injecting.

What material mold are you using? This may impact the powder choice.
Silicone, gum rubber or metal molds all have varying working
properties.

Best Regards.
Todd Hawkinson

Hello Martin;

You can use corn starch instead of talc. Talc will not burn cleanly
away in the investment, but corn starch will. But as for your
problem of degraded surfaces from the talc, here’s my advice, for
what it’s worth. You shouldn’t really need to have any talc (or corn
starch) on the surfaces of the mold which come in direct contact
with the wax in order to get details to fill properlly. The secret is
in cutting vents in the mold for air to escape. This takes a little
more instruction that I can give here, but in short, here’s what I
mean.

Suppose there’s an area on a mold that is not filling. If you make a
cut in the rubber leading from the point at which the wax is not
filling the mold, not too deep, and lead this cut out a ways,
sometimes to the edge of the mold, that’s a vent. Pry open this
cut, dust it with talc, then let it close, trapping the talc in the
cut. Now brush away the talc that’s on the surfaces where the wax
will be. What has happened is that the cut in the rubber is filled
now with a slight bit of talc, which is permeable to air. The air
trapped in the mold can escape into the talc/vent, allowing the wax
to more completely fill the cavity. Hope this helps. What would be
best would be for you to watch an expert cut a mold. All kinds of
factors are involved, including the selection of injection wax, the
mold rubber, the spruing, wax/air pressure, wax temperature, etc.
Takes a little experimentation.

David L. Huffman

Hi - I stopped using talc and I use the talc baby powder alternative
and I think it’s made of cornstarch and think it works great. I
brush it on with a very soft brush and then blow the excess away into
my dust sucker. My pieces have a lot of texture and polished areas
too and have not had problems with surface porosity.

Right now I use the teal Kerr wax - what do you like to use?

Best, Jennifer Benusis

In my experience Talc is best used to separate molds when
vulcanizing…saves the hassle of cutting the halves apart.
Thereafter, when shooting waxes, I use a liberal amount of silicone
spray on both halves of the rubber mold. The use of the silicone is
most important for the first injection; thereafter an occaisional
treatment works best. A judicious use of the talc for the separation
of the mold is called for. There is a tendency for the dusted talc to
accumulate in the crevices and I try to redistribute the talc with a
very small oil painting brush before vulcanizing. Works for me !

Ron Mills at Mills Gem Co. Los Osos, Ca.

Martin, Use cornstarch. Won’t give you lung cancer, burns off
during burnout and doesn’t give you that “surface porosity”. Just
keep it dry.

Tino Volpe Quality Assurance Manager,
Metallurgist Tiffany & Co.
300 Maple Ridge Drive Cumberland,
RI 02864-8707
401-288-0124
@Volpe_Constantino1

hi martin

as an alternative to breathing talc and mica all day long which is
not supposed to be good for you; I know of one commercial caster
that uses plain old corn starch with good results. However I do not
know if it would specifically address your porosity problems. Are you
sure the porosity is from the powder and not other factors like
overheating the metal? Happy experimentation.

Mark Kaplan
Providence, Rhode Island
markaplan AT hotmail. com

Gerber Baby powder for my mold talc. It is mostly corn starch,
about 98%. They don't make it any more so I bought every bottle I
could find. 

Todd, you might be happy to know that Johnson & Johnson makes both
talc and cornstarch baby powders (as well as powder with aloe, which
I doubt will much affect its efficacy as a mold release :slight_smile: Plus,
your molds and waxes will have that special clean-baby smell…

Cheers,
Jessee Smith
www.silverspotstudio.com

Dear Jesse,

I’ll use Gerber until it’s gone. Johnson & Johnson is not quite 98%
cornstarch. I can’t honestly say I can tell the difference anyway. I
do include the small traveler’s size Johnson & Johnson in my CAD ring
mold kit.

Best Regards,
Todd Hawkinson

Hi and thanks to those that responded to my question about
alternatives to Talc (a poreosity causing mineral) for aiding the
evacuation of mold air in the wax injection process. After reading
the responses I am going to experiment with arrowroot and
cornstarch.

What would be best would be for you to watch an expert cut a
mold.

We own the Rio mold cutting videos which show how to use the choppy
waters technique for ring molds. A good video. Does anyone make a
video that covers bracelet molds?

I have also used the cooking spray called PAM with success on some
molds. 

For production molds we mostly use vulcanized silicon, today Rio’s
belcone clear, because it is much easier to both fill the mold and
cut, does not need to be sprayed, does not react with the copper in
our masters, and there is less wax sticking at the nozzle, so there
are comparitively less wax slivers getting into the patterns. But I
have noticed that silicon does not vent as easily as natural rubber.
I have ordered some of the new Castaldo VLT 160 F to see how that
works vulcanized on green wax.

Right now I use the teal Kerr wax - what do you like to use? 

I am using Rio pink, and Rio carvable, but was thinking of
switching, I will ask for advice on this in a seperate question.

 In my experience Talc is best used to separate molds when
vulcanizing.....saves the hassle of cutting the halves apart. 

Ditto, I have yet to become an expert at getting the parting lines
where I want them or getting the mold alignment to work as well as
the choppy waters cutting technique. Does anyone have experience
with Castaldo parting cream? I was thinking of trying some for
separating some sections of a mold while cutting other sections to
achieve better parting lines, or to aid in setting up more
complicated spruing systems etc.

 if you can't get the detail in your waxes you may either be using
the wrong kind of injection wax 

Advice on different waxes welcome.

I would speculate...not venting your mold properly. 

I usually start injecting a new mold with as few relief cuts as
possible, starting from the sides at first and then adding cuts as
needed to get complete fills. I at times resort to stabbing through
the bottom of the mold to relive a particularly difficult area. I
was told by one of the experts that this was wrong, but it works for
me and can result to less clean up in the metal. Usually I talc
these cuts with a dull blade. Still I have found that my flat
pieces with deep detail inject the best with excess talc.

After reading the responses to this question I have come up with a
new (to me) technique. I am going to try cutting “through the
backside” vents with a thin ex-acto #4 and then thread the cuts with
thin sewing thread and pull the thread back just out of the cavity.
And maybe build air ducts into the mold with wires, which when cut
to, will increase air expulsion.

Thanks again for the responses,
Martin

Martin,

I have made well over 4000 molds, and I have never had to do
anything like what you mentioned above.

And I use talc, and have no porosity, gold or silver. Not using the
right amount can give you a grainy surface, but not what I would
call porosity. If you can file down and get to a polishable surface,
it is not porosity.

I have used a needle to put a hole thru a mold to create an escape
for air in a difficult place about 3 times in 20 years. If you know
how to cut molds properly, you do not have to spend time being
creative about something that is basic and simple. Save that for the
jewelry. There is an art to it, but it common sense rather than trial
and error once you know several factors. Model thickness is
important, and usually not to try and get wax to go from a thick
part thru a thin part back to a thick part.

If anyone is visiting Denver and wants a lesson in moldmaking,
contact me. Send me a metal piece that you are having trouble with,
and I will make a mold for you, for free. You might be able to learn
from how I cut and vent my molds. My molds produce waxes that are very
easy to clean up, minimal parting lines, complete fills, no
flashing.

Richard Hart