bubbles from heat

Alright well i did my hood work on my truck, and i keep having the same problem. I pieced a tundra hood to my s-10 hood to get the curve in the front and a little cowl. where the weld seam is on the hood i used long strand hair. alright got everything straight, on the hood primed and painted. Well it started to bubble where some of the long strand was. So i though it might just be the filler or the prime. So i chipped and sanded everything off of the hood completely then i went back with a brand new can of short strand to make sure it was mixed well. Primed with some good prime. sprayed the sealer and i just noticed this weekend once i got the truck out in the sun, a few tiny bubbles started to pop up about the side of a dime. It is starting to frustrate me after all the hours i have in the hood. Does anybody have a clue what it could be? 

It happens on fiberglass parts and fiberglass worked areas sometimes. Solvents trying to escape the surface. Usually the best bet is to epoxy prime the area or panel 1st, then proceed with the rest of the paint process. The Epoxy seems to seal it and solve the problem. Also if you're using a baking booth, don't bake it, let it dry overnight instead.

is your welded section completely welded, or just spotted. It could be getting air and moisture from the backside if it is not completely welded. -Brad

make sure u give it enuff time to dry between ur work. and it cud b air pockets in ur glass work coming up in the heat.

if there is no weld, its gona crack/bubble

thanks for the comments. pretty much all steps have been followed, I'm almost 100% positive the short strand has minimal pockets in it, this go around. It was never baked or anything just sat and cured for a few months. took it to spring fling it was good waited till scrapin the coast took it out to load it up and noticed them coming up. I know i am going to have to sand it down. what kind of prime would you guys recommend for this application?