i've been reading all the posts on here for the past few weeks, to try to find a solution to the problem i'm having. i have an 86 coupe that had a crack on the upper front corner of the door. we used panel bond to mend the crack, sprayed epoxy primer, put on a coat of bondo body filler, sprayed on a coat of catalized primer, base coat, clear coat. then a few days later, the paint popped. not sure if doing it again and letting it dry longer between steps would help prevent this from happening again. any info would be greatly appreciated. thank you.

 

Im' no Pro but they say you should wait, and let the solvents evporate,
from the sealer/primer, or you get solvent pop ?

 

I am not a pro either but I have recently painted my '80 and I suspect 69Vette is correct. My bet is that one of two things is going on.

First guess, you have some sort of surface contamination of which solvents are the most common problem. I cleaned mine with an alcohol and water mix and then washed the bare glass twice with an Ivory dish wash soap solution, rinsed it and let it dry thoroughly before spaying on a polyester primer. This was per the primer manufacturer's instructions.

Second guess, there is an incompatibility between the surface you are trying cover and the product you are using. Of course I can't tell from your description if the paint let go at the bare glass or at some intermediate coat. You just say it popped. Look at where the paint separated and back at the preparatory steps you took on that layer.

Perhaps it was solvents. Perhaps you didn't know or pay attention to the flash times required for the different coats. For instance, if you sprayed on the primer coats too thick and too fast you might well have trapped solvents below your base and clear coats. Maybe reread the manufacturer's instructions and make sure you followed them to the letter.

 

thank you for the responses. that was my suspicion too. i have seen on here that porchdog, as well as others say to let the epoxy primer dry for at least 12 hours. the guy that was helping me, put a heat lamp on it and then we only let it sit for 6 or 7 hours. i don't think that was quite enough. i am going to go out in the morning and cut the bubble out, to see just how many layers popped. thanks again.

 

I'm not discounting what the others have said, they are on the right track, but I might be able to narrow it down to 2 items. Remember to always state the products you use for more accurate diagnosis.

What was the panel bond that you used? When painting over adhesives, you need to make sure the adhesive is paintable.

As long as you follow the tech sheets for the dry times between paint products and you apply the products correctly you won't have problems with the minimum times. Yes, it's better to let them cure longer, but they won't lift if you follow the tech sheets. However, most epoxies have 2 different recoat times. One for applying paint and another for applying body filler. Body filler usually requires that the epxoy set overnight.

If you only let the epoxy cure 7 hours before applying the filler, your problem is most likely due to applying the filler to soon. You could also have a problem with the panel bond.

 

ahoover, thank you so much for your reply. you may have totally hit the nail on the head. the majority of the bubbling is right over the area where the panel bond was applied. the process was, panel bond, then epoxy. so if the panel bond is not paintable, then the epoxy wouldn't stick to it. that's one more thing i will have to check in the morning. if by chance the panel bond is not paintable, is there something i can put over that before applying the epoxy? perhaps epoxy resin?

 

Let us know what the panel bond was so that can be ruled out and make sure it is the right product to use. I think there is a stronger possiblility of failure when applying filler over the epoxy too soon.

 

the product was 3m automix 8115. i can't see anywhere yet if it is paintable, or not. if anyone knows, please advise.

 

Yes 8115 is paintable, and at 70 degrees (F) it needs to cure at least 4 hours before coating it. So you should have allowed about 24 hours between the 8115 and the filler.