I applied urethane primer on my front fenders today. Everything looked fine until I came back in to turn off the fan and lights. Then, I noticed a blister about the size of a quarter raised up in the middle of one of the fenders. I'm hoping that somebody can tell me what may have caused it. The fenders were sand blasted to bare metal, then Kirker's epoxy was applied. Some dents were hammered out and filled. Lots of sanding was of course done. Then today I applied the urethane primer. It all looks fine except for the one big blister. I'm sure that I did something wrong, but I have no idea what.
