The primer is obviously not adhering to the resin properly. Here are a few possible causes in order of likely hood.


The two chemical bases are not compatable. Alot of high build primers are polyester based. If you add MEKP to the primer as a hardener it is polyester and cannot be used over epoxy.

The epoxy was not fully cured adn was still gassing when the primer was applied. I usually wait a week before sanding and priming and never let the part see a temp less then 65 degrees during cure. The mix ratio could have been off, West Systems is one of the more ratio critical epoxies out there. You must always mix by weight.

Surface contamination. Epoxy surfaces should be wiped down with acetone before painting or having something else epoxied to them. Never handle with bare hands. Skin oils are disasterous contaminates.



The really bad news is that it really can't be fixed at this point. your options are to strip it and start over, the paint should peel off in sheets so it won't take long. Live with it or each time a blister forms, mix up some epoxy and inject the blister. You will have to squeeze any excess out then put down a square of chromite tape, some release film, some bagging film and then apply vacuum. This will apply enough pressure to glue the blister back down to the epoxy surface.