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epoxy bubbles

john lucas

john lucas

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I'm trying to help a jeweler friend who fills her jewelry with color epoxy. She is spending way to much time repairing holes from bubbles. I've had the same problems using Inlace and various epoxies to fill areas in turnings.
We tried using a vacuum pump that her husband rigged up. It was a refrigerator compressor. It pulled the bubbles to the surface but they don't pop and level out so you still have the repair hassle.
Anyone have any solutions. Thanks.
 
What I've done:

1) When the bubbles are on the surface either breathe on them or fan them lightly with a torch. I was told that the heat and CO2 causes the bubbles to pop. (all the usual disclaimers about fire and flammables apply here).
I've also used a heat gun (on low) with success which wouldn't have any CO2, so maybe it's the heat and air pressure that pops the bubbles.

2) If the piece is small enough put it in a pressure pot at around 60psi. This really shrinks the bubbles down. The piece has to be really cured before removing the pressure or you will get bulges. DAMHIKT.

Ed
 
Ed I've tried the heat gun and also waving a flame over the top to produce CO2. Works Ok sometimes and sometimes it doesn't pull all the bubbles out. It probably has something to do with the viscosity of the epoxy and how fast it's trying to cure.
Another turner mentioned pressure. We can try that pretty easily so I'll get back with her after Christmas and we'll give that a try.
 
Bubbles

john lucas said:
I'm trying to help a jeweler friend who fills her jewelry with color epoxy. She is spending way to much time repairing holes from bubbles. I've had the same problems using Inlace and various epoxies to fill areas in turnings.
We tried using a vacuum pump that her husband rigged up. It was a refrigerator compressor. It pulled the bubbles to the surface but they don't pop and level out so you still have the repair hassle.
Anyone have any solutions. Thanks.
Click to expand...

John,

Chances are you're not pulling enough vacuum to overcome the surface tension of the epoxy "film" of the bubbles. Increasing the vacuum will help as will reducing the surface tension of the epoxy. You can add up to 20% alcohol to thin the epoxy and help the bubbles to break with no loss in strength on the plastic. You can also apply vibration to the vacuum container to help break the bubbles. Jewelers use a "debubblizer" to get the air bubbles out of their casting investments, so you should be able to do the same by strapping an orbital sander to the chamber to set up a standing wave vibration in the liquid to rupture the bubbles as well as break remaining ones loose from the surfaces of any embedments.
 
Bubbles

I get the bubbles out of pen castings using pressure, not vacuum. Clearly, the pressure does not remove them, but it shrinks them so small that there are "invisible". Alumilite has a video showing the difference between a casting done on the bench and one done under pressure. I used to have all kinds of problems, like the one you describe. Since going to a pressure pot, I've not had one bad blank.
 
http://www.epotek.com/SSCDocs/techtips/Tech Tip 4.pdf

Also, from:

http://www.epoxyproducts.com/bartop.html

"Most people would like a thick clear epoxy to apply to their table or bar top. Thick, unfortunately has trouble with trapped tiny air bubbles. Mixing and pouring the epoxy introduces lots of bubbles to the mixture. Fortunately most will rise to the surface and pop before the epoxy gets hard and traps them. Heating the poured epoxy with a hair dryer will aid the bubbles rising to the surface and popping. The heat the epoxy generates as it cures (if not too great) will also help the epoxy rise to the surface and pop.

Like most plastics, epoxies will soften with heat. Generally if you place something that is hotter than about 125 degrees F (such as a hot coffee cup) it might soften the epoxy to the point of leaving a dent, ring or depression in the epoxy that will not go away. Keep hot things away from your epoxy surface."
 
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This is from my sailboat epoxy days, but maybe it'll help. The longer the cure time, the better chance of getting rid of bubbles.
 
Thanks everyone. Keep them coming. I'm making a file and when we get back together after christmas we'll try everything.
 
Lower viscosity will help a lot. I have a specification for structural repair work around here someplace, but extremely hard to find it. Might not be available in clear in any event.

Blowing across the surface (either you or a compressor) also breaks up bubbles, by increasing local vacuum; called "Bernoulli effect," it's part of what pulls airplanes up. Works on brushed polyurethane varnish too.

Joe
 
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