Bubbles in my Epoxy?

[Bigjim]

The other day I mixed some thickened West Systems epoxy. I was using the high density filler. When I came back after it set up the epoxy had lots of bubbles in it.

Since then, I've noticed my thickened epoxy has more bubbles in it.

The weather has been warm 70-80 degrees. I mix the epoxy first and then add the filler material.

Any ideas what's happening? I have not had this happen to me before.

[thinwater]

Originally Posted by Bigjim

The other day I mixed some thickened West Systems epoxy. I was using the high density filler. When I came back after it set up the epoxy had lots of bubbles in it.

Since then, I've noticed my thickened epoxy has more bubbles in it.

The weather has been warm 70-80 degrees. I mix the epoxy first and then add the filler material.

Any ideas what's happening? I have not had this happen to me before.

404 is colloidal silca (memory) and is mostly air as mixed. No matter how you blend it, if you put it under a microscope it's all bubbles. These bubbles can combine and get bigger.



But I'm guessing what you are actually seeing is exotherm. It got hot, which creates even more bubbles, even more so when thickened. If you used the fast hardener this is difficult to avoid, particularly filling holes and the like. The cure is to use slow hardener.

[Jammer]

May also be outgassing from the substrate. If you're bonding wood (or any porous material), then it will emit gas when warmed. The warming can be caused by sun, changes in air temperature, or the exothermic reaction that occurs in the epoxy. Solution is to be sensitive to surrounding temperature and do your epoxy work late in the day when the temperature is falling.

[Lepke]

I 404 all the time and probably 500 gallons of West Systems resin. It's the wrong temp hardener or wrong mix.

[Chotu]

Originally Posted by Bigjim

The other day I mixed some thickened West Systems epoxy. I was using the high density filler. When I came back after it set up the epoxy had lots of bubbles in it.

Since then, I've noticed my thickened epoxy has more bubbles in it.

The weather has been warm 70-80 degrees. I mix the epoxy first and then add the filler material.

Any ideas what's happening? I have not had this happen to me before.

This is probably due to the exothermic reaction going off too hot. How much epoxy/filler did you pile up onto the project and what are the local temperatures? What speed hardener are you using?

[gulfstar37]

Have you tried calling West Epoxy technical team a call. They are very responsive and are the experts in epoxy. Number is 866 937 8797. Monday through Friday business hours. Found on website.

I'm sure they know what has happened and how to prevent from happening. Best part its free tech service.

[Bigjim]

Thanks for all the replies. I think it was the fast hardener. I switched to fast this spring when the weather was cooler. I just finished a can the other day.

[Eigenvector]

It's really a combination of set up time and entrained air.

Slower set up time allows more time for the bubbles to migrate to the surface and disappear.


Not really practical in the field but in the shop we cast water clear epoxy all day long but we pull a vacuum on it after mixing to suck the air out.


Anything related to the term "exothermic" is minimal.

[Chotu]

Originally Posted by Eigenvector

.


Anything related to the term "exothermic" is minimal.

I beg to differ.

He said he used a fast hardener in the hot summer temps. That's going to cause a huge exothermic issue depending on how much he was trying to do at once.

[Eigenvector]

Originally Posted by Chotu

I beg to differ.

He said he used a fast hardener in the hot summer temps. That's going to cause a huge exothermic issue depending on how much he was trying to do at once.

The root cause of the bubbles is not the exothermic reaction.

[Chotu]

Originally Posted by Eigenvector

The root cause of the bubbles is not the exothermic reaction.

Yeah. Actually it is.

Assuming a 2:1 mix ratio, take 2 cups of resin and a cup of FAST hardener. Put that into a soda bottle in an 80F+ environment and tell me what happened.

[Eigenvector]

You're missing the point



The exothermic reaction does not cause out gassing. The air is entrained during the mixing process.


If it solidifies after all the air has migrated out your ok.
If is solidifies before the air migrated out you get bubbles and foam.


Cure times via accelerants and ambient temperature are independent from the above.

[model 10]

[QUOTE=Eigenvector;
Not really practical in the field but in the shop we cast water clear epoxy all day long but we pull a vacuum on it after mixing to suck the air out.[/QUOTE]



Wow! I want to cast a pad for the depth finder, I could use the shop vac to pull a vacuum on it.

[MarkSF]

My suggestion :


Using slow hardener, mix the epoxy and without adding filler, wait 20 minutes for the air to come out. Then mix in the filler.

[Eigenvector]

Originally Posted by Ecos

Wow! I want to cast a pad for the depth finder, I could use the shop vac to pull a vacuum on it.

Use slow cure and run a test sample. Find a cap that will fit on you shop vac hose. Use that as the mold. Apply Johnsons wax or similar for a mold release. Pour and connect to vac. The other method is with a centrafuge, but I don't have one either. A vacuum bagger works well also.



Picture is a 2 part pour of clear around a strobe light with the second pour being safety orange.