Back to Ganoksin | FAQ | Contact

Getting fine detail raised text in wax mold to fill


#1

I’m trying to reproduce the front of an antique button in wax so I
can make it into a pendant. The design contains a scroll with raised
Latin text that’s about 1mm in height. I can see the text clearly in
the mold (made of Castaldo Gelato silicone mold rubber). It’s a very
clean, crisp mold of the design. But when I inject it, I can’t get a
good wax of this button.

Either the letters don’t fill and just look blurry, or tiny air
bubbles fill in the tops of some of the letters (only the ones
nearest the center of the design), leaving pin holes that are just
too small for me to fill without destroying the surrounding letters.

I’m currently using Kerr purple accu-carve wax in my injector, and
I’m using a spring-loaded mold clamp to hold it while injecting. I’ve
got half a dozen vents cut in both the front and back of the mold.
There is talc in the vents. I do not have any vents cut right up to
the lettering because the surface surrounding the scroll is mirror
smooth. I don’t want to put parting lines across it – I know I
could not get the surface perfectly smooth again if I cut it.

I’ve tried filling it right side up, upside down, smacking it on the
bench to loosen the air bubbles after I fill it, standing the mold
clamp up on end so the fill hole points upward as it cools–no
changes. I still get the little pin holes in the text. I’ve tried
injecting at different pressures–no improvements.

I get slightly more readable results when I heat up the mold with a
hair dryer before I inject it, but the pin holes still happen.

There has to be a way to get raised text like this to fill
cleanly–I see it all the time on class rings.

How can I get the text in this mold to fill?

Kathy Johnson
Feathered Gems Jewelry
http://www.featheredgems.com
http://www.fgemz.com


#2
I get slightly more readable results when I heat up the mold with
a hair dryer before I inject it, but the pin holes still happen. 

Try putting the mold into the freezer for a good moment and then fill
longer. I have found that cold molds have a better fill. My
explaination is that the first wax that enters freezes instantly, and
shrinks. The then entering wax fills around and can not shrink as
much.

I am curious what others suggest,
Andreas


#3

try adding some surgical precise vent cuts behind the cavities for
the lettering you may need to reshape the blade of the scalpel to a
fine point to be as accurate as possible.

i cant be very specific on the exact where to’s becaause i cant see
the mold but if you can cut in to the rubber around the lettering
then you can push the blade fromth cavity of the lettering outward to
make " micro venting "(did i just coin that term?)

that will let the air out so the wax can fill up the void. in my
experience ive had some great success with fine detail but the key
to success was planning the model ahead to exaggerate the letting on
the original to allow for shrinkage however slight so that things
come out looking normal on the copies you may end up doing touch up
on the waxes- goo


#4

Hello Kathy, If you put a piece of masking a little bigger thant the
button on the outside of the mold over the button, you can increase
the wax pressure by a lot. It sometimes helps a difficult mold to
fill without blowing wax out the side.Don’t have the wax any hotter
than you must. More pressure helps more than increasing the heat.

Tom Arnold


#5

Kathy,

You would be best off with shallow powdered vents in the text. The
vents should not show on the injected waxes unless your temperature
and pressure are really wrong.

There is another technique I have used for injecting carving wax
(blue nasty stuff) into molds with raised/depressed text. Almost a
standard air injector only with a 2 way valve on the air line. Vac or
pressure. Seal the mold with silicone spray, turn on the vac and
pretend to inject. You will hear and feel the air being removed from
the mold, flip the valve to pressure. Not a real fancy $K machine,
and not perfect but the odds of getting a good wax are better than
nothing.

jeffD
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand


#6
There has to be a way to get raised text like this to fill
cleanly--I see it all the time on class rings. 

Two ways. The classic class rings don’t use rubber molds, or normal
wax injectors. Metal molds and high pressure injectors where the wax
is not as hot, almost pasty, will fill, simply because the high
pressure will compress any tiny bubbles down to the point where they
don’t matter. The lower temp pasty wax solves some problems with wax
shrinkage pulling back from details, etc.

But that info doesn’t help you much.

The second method that works, and with rubber molds, is a more
complex injector that pulls a vaccuum on the mold before injecting it
with wax. The problem you’ve got is air trapped in little blind spots
in the mold to which you can’t cut a vent. Either compress the air
bubbles down to nothing via high pressure (doesn’t work with a rubber
mold), or remove the air prior to the wax entering. Yasui wax
injectors or similar machines do this, and for that exact reason.

Again, this doesn’t help much for you.

The closest I ever came to getting molds like this to fill is
tricky, and doesn’t work all that well, but you can get it to work
with some waxes, some of the time. Manually fill those details with a
low melting wax, like a dental inlay wax, using a wax pen, before
injecting the molds. You can worry loose any bubbles from the
details. Once those details are filled, you then inject the mold.
But this too has it’s problems, getting the injected wax to then
seamlessly bond with the wax you filled the details with.

Good luck. It’s not an easy problem. There are a few neat designs we
tried to manufacture from models made from detailed CAD/CAM designs
which proved simply impossible for us to get good waxes from, for
this exact same reason. There are limits, as you state, to just how
many vents you can cut into a mold without the quality of the image
deteriorating too much from the resulting faint marks on the wax.

If it’s a critical issue, then learn how to make, or have made, a
metal mold of your design. Your ordinary wax injector will work at
higher pressures and reduced temperature settings if you’ve got a
good metal mold. That’s the only way I know to get the quality of wax
the class rings typically are made from, other than spending the
large amounts of money for a vacuum wax injector…

Peter


#7

Hi Kathy

If you have the original button to mold again, try HD Jewelery model
material. Stuller has it. It will do exactly what you are try to do.
I tried to do what you are doing for years with no luck. Injection
wax in rubber molds just won’t do it.

Dave


#8

Hi Kathy;

the mold... But when I inject it, I can't get a good wax of this
button. 

I’ve had this problem myself. Unless you want to cut lots of vents
into the deepest recesses of the letters (spoiling the smooth surface
you want to keep), the only option I can think of is a vacuum wax
injector. These aren’t cheap, but my guess is you could call a few
casting houses and I’d wager the better equipped one’s have these
machines. Try AU in Detroit, they are top shelf. Ask for Linus or one
of the guys in the shop. You can reach AU at 800.637.2278.

Seems to me it would be advantageous to have them do the casting as
well, as you may encounter another set of issues when it comes to
casting these things.

David L. Huffman


#9

Kathy,

If you’re truly using talc you might try cornstarch instead. Much
slicker and better for your lungs as well. I assume you’ve cut vents
from the edge of the object cavity out into the surrounding mold
area. It is possible that you’re clamping the mold too tightly
constricting wax flow in the critical areas.

While the previous comment that you’re detail may just be too fine
is a possibility I wouldn’t give up yet. For every difficult mold
there is a “best” ratio between mold temp (warmer is better),
injection pressure, and clamping pressure.

Is there a reason you have to use the wax you’re using? You might
try one of the formulations available for better flow.

And finally, if your clamp allows (I use an ancient Rio clamp) hold
the assembly so that you can give more pressure with your fingers to
the front end (end where the injection nozzle inserts). I have found
this allows even higher injection pressures without the wax blowing
out of the mold or creating flashing around the model.

Les Brown
L F Brown Goldwork, Inc
www.goldwork.com


#10

I have experienced this problem. I can’t say my solution will work
for you because several variables are different in my case. I use a
common pin to poke a hole from interior to exterior in the corner of
the letters. The pin hole vents were filled with talc as best as I
could. When you resolve your problem, please post the solution. Best
regards, Kevin

Kevin Lindsey
lindseyjewelers.com


#11
The classic class rings don't use rubber molds, or normal wax
injectors. 

Or much of anything else most of us are familiar with - they have
their own technology, by and large.

Like others, we have found this to be one of the toughest nuts to
crack. We have some certain clients that just insist on molding
lettered rings, and other things, and then they hit everybody with a
wax pot trying to get a single wax or two.

One thing that helps is to not make the sides of your letters
straight - make them angled on the sides like a pyramid. That makes
the flow much smoother and accessable. You can’t do it in silicone,
but you can burn away the bottoms of letters in a standard mold, if
you must, angling at least the bases, a bit. One of those things
that’s funky to have to do, but it’s better than 0% waxes, sometimes.
Or have them made that way to begin with…


#12

Hi there, I sometimes have this issue with thin patterns having fine
detail, and have found that lots of vents and finely dusting the
entire inside of the mold with cornstarch can make all the
difference. Talc in the wax is no good since it doesn’t burn out but
cornstarch is no problem. Usually I dust the mold, shoot one
"throw-away" wax, then I get several good waxes before I have to dust
the mold again. Patterns like turks’ head knots originally done in
string that would not fill completely by any other method are now
some of my most popular designs.

Hope that helps. Douglas


#13
Or much of anything else most of us are familiar with - they have
their own technology, by and large. Like others, we have found this
to be one of the toughest nuts to crack. We have some certain
clients that just insist on molding lettered rings, and other
things, and then they hit everybody with a wax pot trying to get a
single wax or two. 

I’d forgotton about it when I wrote my first reply, noting the metal
molds and all, but Dave Mereski’s suggestion does indeed truely solve
the problem, and at an acceptable cost. The system consists first of
making your molds of what I seem to recall is a standard transparent
silicone RTV or cold mold material. Several are available I think.
The main innovation is the mold material itself, which is used
instead of injection wax. It’s a liquid polymer that you can pour
into the mold (clamped shut during this). Because it’s liquid, you
can allow it to fully fill at your leasure. Bump it jog it, or
whatever. You might even be able to vacuum it (not sure of that) When
demonstrated, the method was to put the mold in the bottom of a
stocking or bag or something like that and swing it around in a
circle, so centrifugal force would cause the resin to fully fill,
and any bubbles to be dislodged and float “up” to the sprue. The
transparent mold lets you carefully examine the mold to be sure it’s
filled, visible because the resin is nicely red colored. When you’re
sure it’s filled, you then expose the mold to sun lamp type bulbs,
and the ultraviolet light cures and solidifies the resin. When that’s
done, you remove your casting model which is now a durable and
accurate resin/plastic model instead of wax.

While purchasing this system requires mold material, a standard
glass side RTV type mold frame, the resin, and the sun lamp bulbs,
this whole system, last I saw it, cost a couple or few hundred, not
the thousands you’d pay for a vacuum wax injector. And it really does
make even the most complex mold fillable. At that point, your limits
become not whether you can get the mold to fill, but rather if you
can manage to actually cut a decent mold in the first place to allow
the original model and later, the resin models, to be removed from
the molds. But you don’t need to cut vents in the mold, and the resin
models are more durable than wax, so if you can pull the original
metal model from the mold, likely the resin one will come out too.

As I recall, it was marketed in response to some of the rapid
prototyping methods that can produce such detailed and delicate
models that people can find it hard to get proper casting wax models,
and this system solved that.

It does, of course, then cost more per resin/wax model that
injection wax, and is slower than normal wax injection, but like I
said, from what I saw, it’s very effective. And problems of wax model
shrinkage within a rubber mold are also eliminated.

Peter


#14
If you have the original button to mold again, try HD Jewelery
model material. Stuller has it. It will do exactly what you are try
to do. I tried to do what you are doing for years with no luck.
Injection wax in rubber molds just won't do it. 

I agree Dave the HD pattern material is a neat innovation and will
allow you to do this kind of project. It uses a clear RTV mold and a
liquid photopolymer that you fill the mold with. Once the mold is
filled and the bubbles are tapped/coaxed out you cure the
photopolymer to a flexible solid state by exposing it to UV light.
Because you can see the bubbles and work them out before you cure the
pattern it always makes for a good pattern. This system allows for
making patterns that are just too difficult to get in wax a simple
project. It has some limitations but is a neat trick to have in your
kit.

Jim

James Binnion
James Binnion Metal Arts


#15

Its witchcraft I tell you. Its Witchcraft!!!

I have many molds of buckles and pendants which are long and thin.

I use Pink Buckle wax at around 155 degrees F and a pressure of
around 10 to 15 PSI into a room temperature mold.

Anything less and the sharpness is lost.

I have read that warmer molds work better. I find the first shot
into a cold mold gives me the best fill with sharper corners of my
engraved wax. If I don’t let the mold cool between shots the
sharpness gets less with each shot.

There are lots of suggestions. The best bet is to try them all.
Experiment with wax, temperature of wax and mold, mold relief, vent
cuts and pressure.

Somewhere in all that witchcraft will work… You just have to find
the solution.

Sometimes I use wires stuck into the mold to provide air release at
the end of a long mold. See my Blog entry:
http://leessilver.ganoksin.com/blogs/

Lee Epperson


#16
The closest I ever came to getting molds like this to fill is
tricky, and doesn't work all that well, but you can get it to work
with some waxes, some of the time. Manually fill those details
with a low melting wax, like a dental inlay wax, using a wax pen,
before injecting the molds. 

Wow! I thought of this one on my own before you posted it. I must be
absorbing the Orchid out-of-the box way of solving problems. I did
exactly this with a few waxes–I melted Wolf ivory repair wax into
the text and picture of the design, then I melted some thin green
sheet wax (scrap from the scrap wax box on my bench) on top of that
to cover it completely.

Then when it was all cool, I injected the mold to fill it the rest
of the way (the button is a dome that’s 1/2" thick in the center).
The
resulting waxes were beautiful–no bubbles at all. And they looked
like green and ivory cameos! It’s a shame that I can’t use them as-is
for something. I hollowed out the backs and made them into pendants.

They’re sprued and invested now, waiting to be cast after I get more
casting grain tomorrow. I’ll report when I have finished results in
hand.

Kathy Johnson
Feathered Gems Jewelry
http://www.featheredgems.com
http://www.fgemz.com


#17
I have read that warmer molds work better. I find the first shot
into a cold mold gives me the best fill with sharper corners of my
engraved wax. If I don't let the mold cool between shots the
sharpness gets less with each shot. 

this makes sense if you think about the mold being cool the air in=
side the mold would be cool as well taking up less space and easier
to compresss.

warm mold and warm air would take up more space inside the mold. when
i use natural rubber i have a similar experience as the above quote
with cold molds or the first try after cutting a mold the thing will
shoot what i consider a perfect wax then it never works again until i
spend a bunch of effort nipping, tweaking, dusting, etc. the best
molds i found that i like are made with silicone rubber from zero-d
some people think its too much trouble to use johns method of making
molds with extreme cleanliness and putting a piece of paper into the
mold frame but to me it is good craftmanship and since i started
using zero-d exclusively ive had a 100% positive increase in the
quality of my mold results. what most people dont realize is that
john makes his own silicone rubber from raw ingredients and it takes
alot of time to make the batchs and its expensive and he tests each
batch himself to make sure it is done right i know i went to his
factory and saw him do it

goo


#18

Thank you Peter. You are way better at explanations than I am. I have
used this mold system lots with extreme satasfaction. The results are
amazing. A couple of small items to add. I decommisioned and old wax
injector and converted it. It serves as a pressure vessel to cure my
RTV molds as well as de-bubble the polymer in the molds as well. If I
am molding metal, I will heat the wax injector ( with no wax in it of
course ) to 160 degrees. It will put the RTV mold in the injector and
pressurize to about 60-70 psi. The mold will cure in about 2 hours,
and there is not a single bubble ANYWHERE in the mold. The mold
however is a tiny bit off color when cured with heat, but not enough
to effect its function. If I am molding a wax, I will keep the mold
in the vessel at the same pressure for about 11 - 12 hours and let it
cure at room temp. The mold is very clear and precise. It is a bit
odd cutting the mold as it is see through. One would think it is
easier, but it is like reaching under clear water with a stick to
move a pebble. The end of the stick is not where your eyes think it
is.

After I fill the mold with the polymer, I return it back to the
pressure vessel for another 5 minuites at 50 psi. The kits comes with
a sock that you can use to spin the mold…and it works good, but I
find the pressure vessel works better. A 5 minute cure under the
lamps, and you have a model that is RP quality. Durable and highly
detailed. I use the process to do multiples of items I have milled
with the finest lettering right off the wax, and the second
generation models are as good as the milled ones.

One thing I did find out is that you should follow a slightly
different casting burnout. I use an investment that is designed for
casting in place called Diamante. Plastic-cast is also recommended.
Normal investment proceedure. You should use the following burnout
cycle. 300 degrees for 2 hours, ramp up to 350 for 1 hour, ramp up
to 1350 over 5 hours, hold at 1350 for 3 hours, and cool to casting
temperature. You are ready to go. I use centrifugal, vaccum, and
induction casting and have amazing results with all 3.

Stuller has the kit, and I want to say it is about $400. It is very
worthwhile investment and will do what you need to have done. Good
Luck.

Dave Mereski


#19
When that's done, you remove your casting model which is now a
durable and accurate resin/plastic model instead of wax. ... 

Which you can use on its own as a jewelry element? Or not THAT
durable? This whole thing sounds so cool, it makes me want to do it,
even though I seldom use castings, and have Dan Grandi do them for
me. Is the burnout especially toxic?

Noel


#20
If I am molding metal, I will heat the wax injector ( with no wax
in it of course ) to 160 degrees. It will put the RTV mold in the
injector and pressurize to about 60-70 psi. The mold will cure in
about 2 hours, and there is not a single bubble ANYWHERE in the
mold. The mold however is a tiny bit off color when cured with
heat, but not enough to effect its function. 

You’ve turned it into an autoclave. Good idea. You could also use
such a system to cure acrylic plastic resins if you wanted. The one
note I’ve got is that many wax pots out there are not built for more
than about 15 psi, and higher pressures might not be safe, so some
caution is indicated here. The other thing that occurs to me is that
while modest heat will speed the cure, more than modest heat can,
with some RTV’s slightly increase the mold shrinkage. Not much, but
for some uses, worth mentioning. For those without a pressure vessel
setup, the rubbers can also be debubbled by vacuuming them for about
five minutes or so. With some, you need to “cycle” the vacuum, as it
initially rises up a lot, so you release the vac and let it settle
down, then repeat several times like that.

After I fill the mold with the polymer, I return it back to the
pressure vessel for another 5 minuites at 50 psi. The kits comes
with a sock that you can use to spin the mold..and it works good,
but I find the pressure vessel works better. 

I’m a little surprised that it always works. The pressure works when
maintained during the cure, but that isn’t the case here. Releasing
the pressure to remove the mold prior to light curing the resin would
allow any bubbles trapped there, and which had been crushed down in
size by the pressure, to return to their original size. The sock
centrifuge by contrast forces resin down, and forces bubbles to float
out, so they don’t remain in the mold. It’s the centrifugal force
working there, not just pressure. But if it works for you, then
cool. Perhaps some other mechanism is working that doesn’t occur to
me, to actually eliminate the bubbles. Pressure would be fine if you
could mount the U.V. bulbs inside the wax pot, maintaining pressure
until after the model is cured… But like I said, since it’s working
for you, obviously I’m overlooking something. Maybe the resin is
simply liquid enough that trapped bubbles just float out anyway once
"disturbed" by the pressure…

Peter