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Epoxy resin and eliminating bubbles

4K views 24 replies 12 participants last post by  Sundownsailing 
#1 ·
I've tried nearly every combination imaginable and still get these consarned bubbles! I've even done a fairly decent search here (even via Google), and haven't read anything very convincing that's different than what I've already tried. I'm beginning to think it might just be a temperature issue (it is getting into the upper 80's here by late morning). I'm mixing West System resin with both speeds of hardner (slow and fast), and no matter which additives I stir in, I still get them. The best method I've seen so far is to limit the thickness, but then if you are filling a large gap using fairing compound, then what's the point. Is there a trick to eliminating bubbles? So far, I'm finding myself going back 3 or 4 times, sanding and filling, sanding and filling... There's gotta be a quicker way, but I'm not discovering it on my own... puzzling.

Any ideas would be most welcome-

Ray
 
#3 ·
should I fill them with helium?? Another thing I thought of was the insane amount of humidity here-- although it's not as bad as Florida, I guess.. Even the slow stuff starts kicking very quickly, and I think that factor is at least partially responsible for creating bubbles.
 
#7 ·
what additives? if it is a filler then mix it and put it on thick in one pass and do not over work it. over working is a sure way to get bubbles. when filling large areas you can cover with peel ply or poly plastic sheet to help hold in place. clear plastic over the top will allow you to work the bubbles out.
 
#9 ·
Bubbles when you mix or when you apply? If your using a cup to mix, quickly put it in a shallow container.. don't wait until it kicks. Mix your cabosil or fairing powder to get the thickness you need. My guess is it's getting hot in the pot. (cup your mixing in)
 
#10 ·
They appear after I apply. I can smooth it all on-- thick like peanut butter as I've done on a keel, or a bit thinner like mayonnaise for the cabin top I'm currently working on. I can take just one look away (like a plane flying overhead), look back, and they're there.
 
#21 ·
what is the air temp and the cabin top temp . is it in the sun. if it is bubbling after you spread it on then it is heating up from the surface temp being to high. try mixing it even thicker. also the thicker the easier it is to sand and the lighter in weight it is. if you mix it to the same consistancy every time it is easier to fair as there are no hard and soft spots. put it on a dry as you can thick a with one swipe and sand with 40 grit to shape until fair. then go over with the same consistancy and fill the holes then same with 100 grit. paint some epoxy high build primer or squeegy on some resin and wipe off excess with a cloth. this is just to fill the pin holes and sand to 240 for paint primer or gelcoat
 
#11 · (Edited)
Is the substrate warming up from the sun and outgassing? (air and or water vapor would make bubbles) that's a problem with fiberglass in general.. it holds that moisture until it's very warm. the epoxy is not going breath so the air (outgas) will bubble through it. Maybe if you try applying the epoxy when the temp is dropping instead of rising you may get less bubbles. just thinking aloud... :rolleyes:
 
#14 · (Edited)
Kicks Brian in the shins

"Maybe if you try applying the epoxy when the temp is dropping instead of rising you may get less bubbles. "

"Warm the surface first with a heat gun before applying and it should eliminate the problem. " = meaning as the temp drops.
 
#18 ·
This will work with thinner mixes don't know about the thick.

Apply as normal. Using one of these small pencil butane blow torches gently heat up any bubbles. They pop and the surface clears. Repeat if required.

Done this many times with no probs but have an extinquisher to hand.
 
#19 ·
Now you're gonna' think this sounds nutty as Hell, and I've never used West System to try this out, but it worked extremely well with several, clear, epoxy resins I've used years ago.

In the late 1980s I used to make some really neat tables from slabs of black walnut, most measuring 7 to 8 feet long and 18 to 24 inches wide. The walnut was sanded with 400-grit wet/dry automotive sand paper, vacuumed, then tack-ragged to remove the tiniest particles, which is imperative.

The epoxy resin was then mixed, poured on the table's surface, and squeegeed to an even consistency on the entire top. Within a few minutes, bubbles began rising to the surface, thousands of them. The next step, which the first time I did this scared the hell out of me, was to fire up a propane torch and play the flame lightly over the surface. Each and every bubble popped, the finish layed down flat, no dimples were created and the surface dried bubble free. The guy that taught me how to do this said what occurs is the bubble quickly expands and pops before the epoxy is anywhere close to being cured.

I'm not sure if West System is flammable, therefore I would suggest trying this on a small patch of metal or fiberglass somewhere where it's safe to test. If it is, the technique may still work using a heat gun, but I've never tried using one for this purpose.

I don't believe heating the surface prior to applying the paint will do anything, but it may be worth a try, again on a small test strip of fiberglass or metal.

Hope this helps,

Gary :cool:
 
#22 ·
The epoxy resin was then mixed, poured on the table's surface, and squeegeed to an even consistency on the entire top. Within a few minutes, bubbles began rising to the surface, thousands of them. The next step, which the first time I did this scared the hell out of me, was to fire up a propane torch and play the flame lightly over the surface. Each and every bubble popped, the finish layed down flat, no dimples were created and the surface dried bubble free. The guy that taught me how to do this said what occurs is the bubble quickly expands and pops before the epoxy is anywhere close to being cured.
This exact technique was discussed favorably in the most recent edition of Epoxyworks, which is provided by West. Here is a link (go to the article entitled Bubble-free Coating). Lots of other good hints in the article, including those already mentioned regarding the temp of the substrate (shout out to Denise):
EPOXYWORKS
 
#20 ·
Epoxy is Highly flamable, and very toxic while burning. And you cannot use water to extinguish it, or it kicks off highly dangerous fumes.

The general recomendation is to first seal the substrate with unthickened neat epoxy. Just a very thin layer just to seal the surface, then come back with the thickened filleting mix. As mentioned the likely problem is from out gassing from the surface. Worrying about surface temprature is just going to cause other problems, like accelerating the kick of the epoxy.

When dealing with very large quantities of epoxy for infusion, it is typical to degass it by applying a vacume, but that it pretty extreme for simple filets.


If you are using slow hardner already, and you need an even slower open time, try storing the resin and hardner in a cool fridge. Something around 60 degrees is ideal. To cold and it can thicken and be hard to mix, it will still kick, but you may need to let it warm up a little before working it. And don't move it directly from a fridge to outside air, if it's to cold water can condense in it, and cause other problems.

You can also switch to West 209 (it's what I use in New Orleans). It will give you about 45 minutes to an hour working time, but it will take a while to cure (about a day).
 
#25 ·
It is temp. Get your work and workspace as warm as it will be and work and cure on the cool down. I am betting that the side you are working on is oposite a finished/ air tight side?
I have had this issue in the past with several cold molded projects that temp control resolved. Let me know if it works.
 
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