Problem with big bubbles in epoxy

[Mike S]

Can anyone suggest what causes dime-sized and bigger bubbling when coating the bottom of a 10 year old cedar-strip canoe with West System epoxy? And maybe a fix for the problem? I removed the old epoxy, which had delaminated. (This should have given me a clue that there was a problem....) I did not use any abrasives or cloths - I just cut out the old material and reapplied
SOMETHING is reacting and off-gassing, but I have not a clue what is going on. I know that rising temperatures can cause some bubbling, but this is silly. And I do admit that the first try was done in the morning. The second try was at noon, though, so it was not cold. Same result.

[Noah's]

Bubbles are usually caused by something on the surface that will not allow the epoxy to bond properly, such as water, oil, silicone, wax, etc. Basic prep for any epoxy application is degrease surface first with acetone or TSP, then sand with 80 grit. New epoxy will not stick to old unsanded cured resin or contaminated surfaces. Use a clean rag dampened with water to remove dust, be sure the surface is dry before applying the new epoxy.
Out gassing usually occurs if has been raining at lower temperatures, even if you are working indoors in an unheated shop. The wood absorbers moisture then bubbles the epoxy as the water tries to get out when the temperature rises. Not a good idea to use epoxy, paint or varnish when it is cold and damp.