Paint bubbles

I painted my truck yesterday. I thought I had taken all the precautions, but apparently not. The paint bubbled where I had bondo. I used a tack cloth to wipe it all down, it was 70° I’m thinking although I left it set overnight, it retained moisture somehow? Oh well I sanded it down and shot some primer on it, see how it goes tday.

Are you sure the primer is compatible with the paint? Sometimes a paint won't adhere well to some primers. Then sometimes especially if bondo isn't cured primer will resist adhering to it. Anyway, I think your bubbles are a result of putting too much paint on too fast. It was either applied too thick or a second coat was applied before the first was dry enough for it. Could it have been painted in direct sunlight? That sometimes will make paint bubble. The solvents create vapors and the paint film bubbles up because the solvent can't escape fast enough.

It looks to me like solvent evaporating out of what is underneath. What did you have for primer over your filler?

I used all Endura products for priming and painting. I applied the paint at approximately 1-1.5 mils and waited 30 minutes between coats. We have a tent set up for sandblasting and painting, so no direct sun. The truck looks great except where I added some bondo. A little on one door and the hood. The temp was 70° and the paint says it’s ok above 60°
I sanded it down in those spots, added a little filler and put some primer on it yesterday, so I’ll see how it goes t’day.
We sandblast and paint quite a bit, but never really had this particular problem. I was thinking maybe the bondo sucked in some moisture overnight before we painted. I don’t know. We paint industrial equipment with epoxies mostly.
Here’s a picture of how nice 3 coats of epoxy looks on the frame and the good side of the cab.

Just hard to say without being there. The reason I thought the paint may have needed to be thinned is I'm seeing what looks like orange peal in your first pictures. 1 to 1 1/2 mills is a lot to lay down in one shoot on a vehicle. It's why automotive paints are thin as water. It would probably take 6 to 8 coats of automotive paint to make a mill thickness. I know you aren't using paint a body shop would but I think the thickness is the reason for bubbles. It may be the bondo spots just held a little too much solvent.

Yes, even a morning dew can cause paint not to adhere to bondo. It's very porous so if I do any wet sanding and sand through to bondo I will take a hair drier and thoroughly dry the spot before re-priming. Then if the bondo didn't get quite enough hardener it could still have wet resin in it which can cause the primer to not adhere. It does look like the surface dried before the paint below did and trapped solvent fumes underneath which caused the bubbles.

Now, the problem is what to do with the bubble spots. If the paint isn't dry underneath and you start sanding, it's liable to peal the paint off in sheets. If you think this might be the case it might save you a lot of grief to allow the paint that is there to fully cure before you fix it. That would take about a month.

I was wrong about the primer. We used Ferro Con grey

Thank you for your insight to my problem. You are probably right that it’s either one of two problems or maybe both.



I’m using industrial paint and adding a few drops of reducer to lay the paint down a bit. Maybe not enough because yes there is some orange peel.

Check all your water filters and drain compressor