Bubbles in wax injector waxes?

Hi all,

I have been getting tiny bubbles in my injected waxes. It’s driving
me bats and I can’t figure out why I’m getting them. I have enough
wax in the machine (well enough to cover where the nozzle is), I’m
using KERR superpink wax (which I don’t like… but that’s another
story), I have the temp set to exactly 150deg (what the superpink
requires), and I’m using around 10-12 pounds of pressure.

Any thoughts as to what I’m doing wrong?

Any thoughts as to what I'm doing wrong? 

I’m not positive but my first thought is water in the wax caused by
wet air. Second thought…are you sure aboout the150deg? I have half a
dozen devices to meaasure temp and none pf them agree :slight_smile:

Demand Designs
Analog/Digital Modelling & Goldsmithing

Dear Cheyenne,

If you are using an air compressor you might be getting water in
your air line, which would show up as water vapor bubbles. You need
to check the compressor’s condensate filter.

If your environment is humid you might also be getting atmospheric
moisture in your wax pot. A desiccant (drying) filter would help if
that’s the case.

You also might not be getting a good fit between your injector
nozzle and the matching part of your mold. A bad fit lets air get
sucked into the mold along with the wax. If that’s the case you need
to get sprue button formers that more closely match your injector

Just a few of the things that might cause this problem.

Michael Knight

HI Cheyenne,

I believe this will be a little trial and error but lower your
pressure on the air. It sounds way too high. Usually on filling a
mold with tiny intricate areas you want a little bit more pressure,
but for larger fill lower pressure. Get it down to about 6 or 7 and
see what happens…good fill? bubbles? Is the temperature on the pot
correct? I know what the wax temp. calls for but the pot might not be
to spec…Lower the temp a bit as well.


Russ Hyder
the jewelry cad institute…

No thoughts of “wrong doing” but why don’t you try a different
injection wax, especially since you evidently do not like the super
pink? Contact Kerr and ask them what is going on and what "they"
recommend you do to get ride of the bubbles?? So now you have a
couple of “ways” to deal with your problem… Also, are you sure that
your thermometer/thermostat on your wax pot is correct? Check the
temp with another thermometer to make sure the temp is correct…

John Dach

Sometimes air compressors create moisture in the line. Try an in line
filter for moisture. That may be the problem. I would switch to a
blue plastowax instead. You will love it! Steve


Air bubbles in pattern: the causes & the cures are listed. Usually
caused by Cured by Air pressure too high. Adjust air pressure. Wax
pot low on wax. Add wax. Be sure that wax pot is more than full. Wax
too hot or cold. Adjust temperature and stir wax to release trapped
air. Mould held at wrong angle to nozzle. Hold mould on same plane as
nozzle. Hope this helps.

Warm regards

Hi Cheyenne,

you are perhaps trying to get the wax into the mould too fast and it
is causing turbulence as it shoots in. Try dropping the pressure
lower and lower and see if that solves the problem.

If you find that the mould does not fill a solution to that is to
warm it up. I have a few delicate moulds that I had problems with, I
made a small hotplate, a wooden box with an aluminium top and a 25W
soldering iron poked in the side. That gave me about 30Deg C and
completely solved the poor fill.

Or perhaps better venting. You still have to give the air time to
get out.

Tim Blades.

Any thoughts as to what I'm doing wrong? 

When is the last time you tested to see it if your temp. is correct?

A good solution for lots of was injector problems is using bottled
nitrogen, it is very dry and inert.


Thanks all for the comments. I ‘calibrated’ the temperature and put
in a new kind of wax and no bubbles at all. YAY! I think I wasn’t
realizing just how long it took to melt all that wax; my gauge would
read up to temp and the thermostat would click off but only half the
wax would be melted.

Now I am having trouble with fill. Low pressure or high pressure,
there are spots in my waxes that never seem to fill properly. I
can’t imagine why now though. Should I cut some slits in it where
it’s not filling for air to escape or something? (Thanks again!)

Should I cut some slits in it where it's not filling for air to

Yes, and dust a little bit of talc into the slits.


Now I am having trouble with fill. Low pressure or high pressure,
there are spots in my waxes that never seem to fill properly. I
can't imagine why now though. Should I cut some slits in it where
it's not filling for air to escape or something? (Thanks again!) 

Sounds like trapped air pockets, or the wax not hot enough. More
likely the first, since you’ve already paid some attention to the
temp. If the air is being trapped in the mold, first try powdering
it. Talcum powder (the drug store stuff is fine, even tho it’s not
actually talc.) Or use the actual talcum powder sold for molds, or a
similar mica powder. All will prevent mold cuts from closing down so
hard and tight as to prevent air escape. Normally, you make sure
those cuts are powdered, use compressed air to blow off any excess,
and throw away the first wax you pull, which will get the powder off
the interior of the actual mold surface (that first wax will be
rougher because of that powder). Subsequent injections will still
have enough powder in the cuts to allow air escape. If you use
silcone mold sprays, be aware that overuse can also impede air
escape, since it helps those mold cuts seal up more, the opposite of
powder. If this still doesn’t help, you may need to cut more vents
(those slits you mention). But do take a look at the bad waxes, and
try to see if the misfills are because the wax froze too quickly, or
if it just didn’t make it into the recesses of the mold, even though
liquid and hot enough. The two effects are similar, but not
identical. Not hot enough will show up as areas that did fill, will
not have completely sharp edges and details. Hot enough, the areas
that filled will have filled all details, but it just won’t get into
those blind alley spots. Too hot shows up as excess shrinkage, which
shows as surfaces that should be flat, end up sunken in, as thicker
interior areas shrink, pulling the surface down in the middle.


It may be the air vents to be needed where the filling is
incomplete, or you may use little corn flour to dust sparingly on the
mold for easy air escape.

I melt the wax in a wax pot and vacuum it and then fill up my
injector,one more suggestion for the air bubble free waxes.

Hope this helps.
May all be happy, be peaceful, be liberated…

Hi Cheyanne,

Your comment about injectors and time reminded me of something.
Injectors take a LONG time to get the wax up to temp, and get the
temp evened out. Long being on the order of 8 hours or so. Most of
the production shops I’ve seen either leave their pots on 24/7, or
have them on timers so that they kick on in the middle of the night,
so they’ve got plenty of time to get up to temp. (Energy costs being
what they are, I suspect that most shops have them on timers these

It’s possible to get molten wax out of them within 20-30 minutes,
but the temp will be all over the map, from shot to shot, so it’s no
wonder you’re having trouble. Give the pot enough time to melt the
whole load, and then get the temperature evened out across the whole
load, and you’ll be a much happier camper.


Should I cut some slits in it where it's not filling for air to

You can also use silicon spray as a releasing agent.

Try not holding the mold so tight. Allow some of that nice, scalding
wax to leak out onto your hands.

  1. If pressure in the pot is more that a few pounds, lower the
    pressure to 2-3 lbs. You may be getting “dissolved gas” bubbles from
    high pressure air releasing when the pressure is taken off.

  2. Use a mold clamp to hold the mold together and so you don’t get
    any way on you skin if a leak.

  3. If bubbles are forming in “dead end voids” on the mold, try
    "punching" a hole thru the rubber with a sharp pick dusted in talc
    (better yet, include a relief wire ((tiny)) at these dead ends when
    making the mold so the wire can be removed to make a hole for gas

Keep the wax at as low a temperature as possible (in the pot) so
that the mold fills well. Higher than such a temperature is just
asking to wax degradation, burns, excessive wax shrinkage, etc.

Just a couple of ideas to help you out.
John Dach

I don’t think the spray works as well as some kind of powder for
helping air get out of the mold.


The spray is to release the wax from the mold, that’s why it’s
called a RELEASING agent. To remove the air, cut vents.