The Stovebolt Site Forums The Shop Area Paint and Body Shop Blister in the middle of my primer

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.

Is it on a horizontal surface, or vertical surface?

Either way, pop it, wait till full cure, take a blow gun, and try to blow right inside the popped bubble and see if more paint will come off. Really pick at it. If it sticks, its good.

If it blows strips off, obviously theres a contamination issue.

It was on a horizontal surface, although the fenders are not on the truck, so I can position them however I need to. Thanks, I'll do as you instructed. and THANKS

Pre-spray prep? Did you do a final wipe with a degreaser, using latex gloves so the oils in your hands wouldn't contaminate things? Did you let a drop of sweat hit your fender before applying paint?

Agree with the above. Sounds like not keeping things like a hospital surgery room. No bare hands allowed on surfaces you want to paint. Don't learn to paint watching shows like overhauling, with bare hands all over everything they are going to paint.
Latex gloves may not be a good idea they dissolve in the thinners and solvents.

You guys are right on. I wiped the fenders down with prep sol when I started the whole process. But I did use bare hands and did not wipe them down prior to primer. I assumed that it would be OK after all of the sanding & etc. That's what happens when amateurs get involved. I'm pretty old to be learning, but I'm learning (the hard way) just the same. Thanks for the help.

Sorry, should've said powder free nitrile gloves.

Back in the late 1990's I was teaching collision repair in a big high school in Nashville Tennessee. Lots of my students lived in the inner city housing projects. We started getting an epidemic of "fish eye" blemishes in several of the jobs we were doing- - - -both spot repairs and all-over paint jobs. I was using all the routine precautions popular at the time to avoid contamination of the surfaces prior to painting, yet the problems persisted. Wearing Nitrile gloves hadn't yet come into general use at that time. Quite by accident, I discovered the source of the problem. Some of my students of a particular ethnic group were using Vaseline Intensive Care lotion as "ash killer"- - - -slathering the stuff liberally onto their skin to give it a shine instead of the gray appearance caused by dead skin cells sloughing off. Sand some Bondo or primer,- - - -rub a palm over the surface to check for roughness- - - -any guess where the body lotion ends up? I solved the problem by explaining- - - -very delicately to avoid accusations of "racism"- - - -what was happening, and having the kids scrub down with soap and water like a surgeon prepping for the operating room before going into the shop!
Jerry

Sounds like the lotion would cause that, alright.
But, also, any lubricant with silicone, in the shop could contaminate inadvertently.
I’m always afraid to have that stuff around.

The urethane primer is likely less expensive compared to what yet remains to be sprayed. Do you err on the side of caution and strip the fenders completely as added insurance that a repeat bubble performance doesn't occur after all the expensive paint goes on? Food for thought...

Had that happen to me due to a drop of sweat while I was priming recently. ticked me off something fierce. I sanded well and had some 2k rattle can I went over a bunch of times to build it back up.