I was over at a friends shop the other day and was looking at his 68 vette in his paint booth and noticed bubbles on the hood, when i asked him about them he said that in the summer it would settle down but in the winter the fiberglass
"breaths" and creates the bubbles. Ive never heard this before and am just learning to work with fiberglass and making coustom glass scoops..
is this a common problem and is there a way to get around it?

I just spent a couple of minutes in the garage with my 'vette and I didn't hear any breathing except my own. smile.gif

OK...on a more serious note, I have heard of troubles with bubbling paint (assume that's what you mean) if the glass is cracked, crazed, or had moisture on it before the paint was laid down. Some guys have also reported troubles when the AC compressor slings oil on the fiberglass and that seeps through.

On properly laid-up fiberglass, with a good gel coat and finish I don't think it should be a problem.

I think that is one of those lines like "The color will match after it fully dries" or "The plastic takes the color differently that is why it looks different", "the painter will finish blocking it out" smile.gif That is the BS of a guy trying to get out of a re-do.

It is caused by air trapped in the fiberglass in the form of a air bubble that the glass cured around. OR a pin hole that he painted over. The air in the bubble or pin hole expands when it gets hot, plain and simple.

Now, a number of years ago I did a '69 Vette complete lacquer job. It was a near perfect original car with some "stress cracks" around the rear window like all of them. I repaired them with resin and mat. After painting there were bubbles there. The town Corvette specialist (his shop is called "Corvette City") said that it was "Uncured resin". I ground it all out, bought new hardener and just mixed up some resin and brushed it over the repaired area. Primed and painted and it never came back. Now, looking back, I would put money on it that all I did was seal off some pin holes or break the air bubbles and then fill them with resin. THAT is what fixed them, not some "Uncured resin". I say this because now understanding the chemistry of the product a lot more, you need AIR to make a bubble. "uncured resin" is not going to CREATE air.

Take a quarter and tap (lightly) from a solid appearing area across the bubble. Notice how the sound of the tap changes. That is what is called a void. You can sand that area down exposing the void then fill it with resin mixed with some chopped mat(mixed to make a thick slurry) This will fill the void and eliminate all further worry.
By leaving the void in there you run the chance of water finding its way in there and causing further delamination

MartinSR is right, the only way to stop them is redo it with another coat of resin. One other trick is mix resin 25% with filler(BONDO) and hardner and sand this rock hard mixture.

Incorrectly cured fiberglass will cause the paint to get bubbles. They usuallly look like small pimples. Trust me I do know about this problem. I paid 12K to get my 68's fenders replaced and the car painted. The fenders got "pimples" below the weld line for the top surround. ( A corvette front end is about 10 pieces glued together.) The corvette shop redid the paint after pulling the fenders and putting them under a set of paint booth heat lamps. You could atually see resin spots come up and they put a new gel coat on them. They reshot the front end and about 18 months later a few pimples returned.

They were not pleased and the manufacturer agreed to replace the fenders completely. Reshot the front end yet again and for two years now......... no pimples. My experience is why I advise anyone putting a lot of money into repairs of a corvette to have the work and paint done at a shop with an excellent reputation and that will guarantee the work. I never paid a penny for the work required to correct the problem.