Stopping Bubbles in poured wax molds


Bramblebush ForumsFAQ

Posted by Derek, Dach and friends on October 24, 19100 at 08:36:11:

Hello all.

I"m having a problem with large (1/16" diameter) bubbles forming on the face of my wax patterns. I'm using silicone rubber with a plaster mother. After I pour the wax I clunk the mold on the floor until I no longer see bubbles coming to the surface. Unfortunately this is not releasing all of them.

Is there something I can spray in the molds or some technique I can use to reduce or eliminate them?




This may have to do with the temperature, (either too hot, or too cool) or the type of wax.

I find the best way to reduce bubbles though is by putting the mold under a pressure of about 25 PSI while it sets up or hardens.

You can do this easily with a rigged up canning pressure cooker modified to connect to an air compressor.

Needs a gauge,

a slow air feed and do leave the safety release mechanism in tact to work at any pressure over the limits specified by the manufacturer.

Also raise the air pressure slower than the release could release it if necessary.

I find the pressure stops most all bubbles and use mine regularly for small molds that can fit in.



Good question Derek

Another thought(s).........

Try different wax/wax mixes. I am currently using Remets waxes,

specifically their "victory brown" wanna be (a more highly refined version of regular VB) and one of their hardener waxes (pink pellets). Makes a great wax for slush molds and it has reduced bubbles, reduced/eliminated the little "freeze lines" created as the wax slightly cools as more wax is being poured making little lines on the wax surface, this wax doesn't delaminate (I used to have problems with one layer not sticking well to the next layer when making slush molds), it is also hard but easily softened to bend the wax, it is tacky to itself so pieces can be pressed together then "welded".

Lastly, with bubbles, I now heat my molds before pouring them. I

used an old freezer (electric with elec. defrost coils and a small circulating fan already installed) using the defrost coils for heat, the fan for air movement and I added a bulb thermostat wired into the defrost coil to maintain the set temp (100F). By heating the molds, I was able to reduce my wax temp. thus getting better wax life, better mold life and.................................... fewer bubbles.

Fewer bubbles because (I think!!!!!) the wax doesn't freeze

on the warmed mold surfaces so fast and there is time for the bubbles to float. Also the Remet wax blend is a godsend. They have some sort of debubbling agents in it that work great. Also, be sure to pour the wax into the mold so as NOT to create any bubbles. Releases MIGHT help, I haven't found any that really seem to work. Also, if you do have a few bubbles, you might try making a filler wax from say sprue wax, bees wax and Vaseline or mineral oil. Heat the wax(s) add the mineral oil/Vaseline and test to get a filler wax that will wipe into the bubble hole and fill it, be soft enough to be easily worked into the hole yet firm enough to stay in the hole.

Hope this helps a bit.

John Dach


I also use the Victory Brown quite a bit. Cheapest I found is about $2 per lb in 50 lb boxes (5 slabs per box). Addresses and additional info at the end of this in the listed Wax Chat....

I principally use plastics, styrofoams, wood and anything that burns out for the models and model direct in those and wax.

This can involve several hundred lb. at times and is a one shot cast pour.... Risky but so far, almost so good. (loose one every few years).

If the items need special burnouts (like oxygen injections while in the kiln... another subject) or are too thick to be cast directly or took too much time to ever want to remodel if lost or wanted for future use then a mold is pulled off. These are sometimes urethane rubber and this gets us to the bubbling question.

I always use the release agents regularly on the rubber molds (or fiberglas molds, or wax molds (see the Chat on Waxes from Waxes to make more waxes)and prefer a tried and true brand from Polytek ( called Pol-ease 2300 Mold release.

BUT IT DOES TAKE A DRY OR EVAPORATION TIME after each use or it will cause bubbles in the wax even though it is a very minute amount. Consequently I either re spray the mold after each wax is out and the mold goes back into storage, OR give it a good 15 minutes before another one is cast, OR force 'blow' it (actually suck it with a vacumn cleaner hose in the entrance).

Hope this helps.

bruce paul fink

See also

for many more hints on general wax use and sources.

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