the body of my vette started to blister. the car has been painted about 1.5 year ago (blistering showed up already after 4 months). specially the hood shows the blistering. i had sanded the corvette mostly down to the original red paint (had 5 layers of paint on it) as prep for the paintjob

Depending on what you're calling "blisters", there could be several reasons for the paint to "bubble up" on a fiberglass body.
First is usually oils, or some other contaminant in the glass itself. Fiberglass is absorbent, naturally, since it is a porous material. Any oils, or silicons, etc. that settle on the body will eventually get soaked up into the panels. For instance. In A/C cars, the compressor leaks from the front area, where the pulley is. This freon/oil mixture gets slung on the bottom side of the hood. Eventually, this oil will seep it's way to the top side of the hood. So, later on, when the car gets painted, this contaminated area of the hood winds up with oil underneath the paint layer(s). Paint doesn't stick to oily surfaces too well, so it starts to bubble up, or blister.
The best way to solve an issue like this is to clean the bottom side of the hood(or other body panels) with a strong lacquer thinner, and let the panel dry completely, sometimes for weeks.
Sometimes, there are other contaminants that get onto the surface of the body just by airborn pollutants, as in when someone else in the area is using a spray type lubricant such as WD40. Even body oils on your fingers can create paint problems.
Spraying, or otherwise applying a new gelcoat on the painted surface will help, but it won't do much good unless the surface is clean to start with.

I'd be interested in what the paint Rep has to say...

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Joel Adams
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Most good painters I have talked to agree that you should leave the original paint if is solid.  Blistering is quite often caused by just not cleaning the surface well enough just before painting (I say from sad experience).  If they remove the bad paint and properly scuff, clean and seal, I bet you will be fine. 

Be sure to post what the DuPont guy says, although you know he is going to say the product was fine, but the use was wrong.

[QUOTE=art-corvette]...i had heard that best was to sand it down to the bare polyester and than have a new layer of gelcoat on it .... the painter told me that was not necessary and just sanding it down to the original paintlayer would give a solid base to build up the new paint layers...[/QUOTE]

Is it true that having a Corvette media blasted before painting is a good idea?

I was under the impression that they always applied a gel coat to the original fiberglass, then primer, then base coat. The Bowling Green ones got a clearcoat as the final layer.

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Art-

to remove the old layers of paint i haven't used chemical strippers... i did it all by hand.. just sanding. The car has been in garage for years so it was not submitted to rain or watever. the underside of the hood was already painted before . At the paintshop they did go through the standard procedures of preparing before painting. i have been checking regularly so i know it wasn't done as a rushjob.

I had a few spots appear on the blacray after the same process. The car was sanded down to the original primer / gelcoat. Primer applied, drying time, base coat, more drying time, clear coat, more dring time etc. Alot of care was taken to keep contaminants out of the paint booth during this time.

I can only surmise that it was either something that in the one area worked its way back throught the primer. In the other area there are very small bubbles (pinhead size). I bellieve these are as Joel described as airborn contaminants.

Only one fix was to sand it off and go again. Fortunitly base coat clear coat blends really well and dries fast so the repair process is quick. Unfortunitly it is a PITA and I didn't want to go through that exercise.

Probally not what you wanted to know but I doubt that you find the magical answer unless your painter recalls something odd that occured while the prep work / painting took place.

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I was told that my Vette was painted about 14 years ago. On the right side of the front of the hood there is small little blisters located above the side with the A/C unit.. Also alot of small tiny blisters on the rear deck lid. I do not know when these appeared, but overall the paint job looks pretty good for being painted so long ago, the prep must have been very good with all the jams looking good with the knowledge available back then. So I agree that prep is the key and you need to remember that the bodies are old and may have stuff from years ago hiding there.

Aaron19762008-03-02 16:10:30

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Aaron

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an update of what the dupont guy has told .
first question he made was if after the old paint removal there was already some blistering that went into the fiberglass... and yes it was... here and there it looked like there were tiny "needle holes".. or "woodworm" holes that were in the fiberglass.
with that knowledge he said it probably won't help if the hood was completely redone since the problem is in the fiberglass.. best solution is polishing and seal it off again  with layer clear coat..... if it comes back just redo the process.. and hope that the chemical reaction has worked out.
( i hope that that has already happened since the paintjob was done about 1.5 year ago)

monday they will start treating the hood..... will see how it turns out

art-corvette

Hope it works out for ya, Art! Be sure to let us know how it turns out.

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Joel Adams
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