Blister or bubble under clear appeared after buffing

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PostPosted: Tue Jul 03, 2012 11:58 pm
First post and I could use a little help from the watchful and experienced eyes here...

Not new to painting but this is something I've actually never encountered before. This is a new hood on my Charger that I just sprayed with Dupont Chromabase mixed to paint code PXR. Cleared with ChromaPremier 72500S. Came out great, no issue and nearly zero orange peel. 2 coats of base over 2k primer and 3 coats of clear on a thoroughly cleaned fiberglass hood. No chance of contaminants unless the ghosts decided to play a trick.

While buffing out the wet sand scratches (finished with 2000) I went over the hood with 3M Perfect-It 3000 Rubbing Compound and a orange LC pad. Looked great, I was hungry and hot as hell ( I live in Oklahoma after all) so I took the rest of the afternoon off and left the car outside to get some sun. Today, I come back to it and find this:
Image

Image

To the right of the penny:
Image


I would call this a blister I suppose. Wasn't there (or at least I didn't see it) after I finished compounding.

My question is, can this be sanded out or do I need to go remove the clear and re-clear? And if I re-clear, would blending it with the rest of the hood be fine or should I just redo the whole thing.

I have a gallon of HOK UFC35 clear that I will be using on my next project so I've got more than enough to recover this hood if necessary.

Thoughts/Ideas?

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PostPosted: Wed Jul 04, 2012 9:16 am
What did you spray the sanded fiberglass with first?
1968 Coronet R/T


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PostPosted: Wed Jul 04, 2012 9:42 am
'68 Coronet R/T wrote:What did you spray the sanded fiberglass with first?


DuPont ChromaSurfacer 7704S. 2 coats and let it dry in the Oklahoma sun for 3 days before reblocking, cleaning and putting down sealer and base coats.

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PostPosted: Wed Jul 04, 2012 10:32 am
I would cut a blister off with a razor blade and look at the back side of it. Try to evaluate at which step the problem occurred. The back of the chip will have the color of the last layer it adhered to.
Generally it is an adhesion problem that the heat of the buffer brings to light. I had it happen on a car roof that I treated with Dupont Metal Prep. Everything looked great until I was buffing it and then this blister started rising up. When I cut it open I found the adhesion had failed at the metal prep layer. Since then I don't use any metal treatments on surfaces I plan to paint. I also use epoxy primer for a foundation on all surfaces.

I don't use DuPont products so maybe there is something I am missing but no matter what you will need to know where it failed and why.
1968 Coronet R/T


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PostPosted: Wed Jul 04, 2012 1:19 pm
put the hood in the sun and see if any more blisters come up.it being a fiberglass hood ,it could have very small pin holes in the fiberglass.or even moisture trap .i think you will find you have trapped pin holes in the fiderglass hood.
fail to prepare ,prepare to fail.



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PostPosted: Wed Jul 04, 2012 10:19 pm
paintpot wrote:put the hood in the sun and see if any more blisters come up.it being a fiberglass hood ,it could have very small pin holes in the fiberglass.or even moisture trap .i think you will find you have trapped pin holes in the fiderglass hood.


It's been in 100 plus degree heat for the past several day. Nothing else has popped up. The rest of the hood looks great.

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PostPosted: Thu Jul 05, 2012 8:27 am
I feel your pain, it's heartbreaking to have something like this appear.
68 Coronet gives great advice, listen to him.

Fiberglass can have a lot of problems from contaminates from down in.
Especially new parts that often aren't cured enough.
I've heard it's preferred to let new fiberglass parts sit in the sun a week to off gas
before painting. You may have a problem that has nothing to do with
your work or products. Even if the new part is primed, it's subject to
being rushed and should be allowed to final cure.
Usually it still has a strong fiberglass smell it if it's to new to paint.
I hope that's the end to your problems and you don't get anymore.
JC.

(It's not custom painting-it's custom sanding)

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PostPosted: Thu Jul 05, 2012 9:32 am
What's strange is that the blisters formed in a line, and only in a small area.
It could be a void inside the fiberglass layers that has trapped gas. Take a
look at the underside of the hood directly under the bubbles; that might
give a clue...?
"If you can't move it, paint it." - U.S. Army

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PostPosted: Thu Jul 05, 2012 11:12 am
Sure agree with what the guys are telling you. Unfortunately a lot of the aftermarket open lay up fiberglass stuff is just not that "tight" in its' lamination. It's more like an English muffin with lots of nook and crannies. When you paint, your solvents actually back down into those spaces. When you add heat the liquids will start forming the gas and then you have your blister. I started giving glass parts about 2 weeks in the sun before I'll even start working them. I continue to sun the parts during each stage looking for those blisters. I did all that and STILL had one blister that came out on an edge almost 3 years later on my last hood.... :knockout:
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!

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PostPosted: Thu Jul 05, 2012 12:18 pm
One of the most important things with new fiberglass, keep it dry.
Don't get it wet with anything.
Soaking it with wax and grease remover can create a nightmare. :mrgreen:
JC.

(It's not custom painting-it's custom sanding)
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