MatraSport Forum

I recall i one time bought a set of wheels (for my old manta) from a guy who had used them on his corvette 7.4 litre v8
Ofcause we had to speak a bit about cars when i picked them up, and ofcause we had to have a look (and listen) of the 'vette..
I noticed that the car (witch also has a fiberglass body) had small bubbles in the paintwork here and there.... just like it would have, had it begun to rust from the inside.
The owner told me that it was caused by the giberglass giving off "fumes" over time.. and particular when heated up.. (by the sun etc..)

Has anyone here ever heard, or experienced anything simmilar?..

The corvette was black, so i recon it would have been particularly vulnable if this fenomenon is indeed true..

This is called "glasfiberpest" in Danish and is a well known phenomenon (I'm told) to people with glass fiber boats. The problem is that the glass fibers are in fact capillary tubes and they will suck in moisture if left exposed to free air (or water). This will work out as bubbles under the paint eventually, when the sun heats up the water which then needs to expand.

There is nothing to do about it, except cut away the infected piece plus a good deal around it, and replace it with new glassfiber. That's what I've been told.

I know the problem from my Espace '87 where one of the doors has it. You won't notice unless you look carefully. Repainting will not help. Maybe it's possible to cure it by removing all paint and baking the panel for a proper amount of time?

- Anders

Yes it is moisture in the panel blistering through the paint, but it is not a problem as long as the panel is primed and painted correctly.

Hmmm.. would a coat of rustproofing on the inside of the panels, help keeping the moisture at bay ?

I think the problem occurs when the lacquer peels off and the paint becomes thin. Moisture enters through the remains of the painted surface, not from the underside.

It's usually worse on the roof and bonnet panels of a Murena where water can sit, rather than the door or side panels where the water rolls off.

My car had think problem a few years ago, really badly. My father owned the car before me, he bought some car polish, which gave fantastic results but shortly after the car seemed to bubble everywhere. It was a nightmare! He claimed against it but nothing conclusive was found by the inspectors. The inspectors put it down to contamination, though couldn’t say that it 100% from the polish. Anyway we took the car to a local car painter with a great local reputation, he used some form of undercoat that was from boat makers, I’d say its 95+% cured.

I am not sure I understand you fully - please clarify.

I assume "under" coat doesn't mean it was aplied to the underside of the panels, but rather that you had the car completely sanded down and resprayed - correct ?

/Lennart

Thats correct.

No not really.  Paint is porous, so the moisture gets in to the glass fibre through the paint.  This is why a metal painted panel can have surface rust form under the paint.  Any coating on the underside of a panel will possibly protect that surface.  The bubbles are caused by the moisture that has got in to the outer surface under the paint.  If you sealed the outer surface before painting it would help, but with an already painted car, you would have to strip off the paint/primer first.