Glassfiber repair and moisture

Anything goes in the world of fiberglass and plastic



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PostPosted: Mon Mar 11, 2019 4:09 pm
I am fixing a glassfiber car.
I am not stripping to the fibers.
I am concerned about moisture.
If i use a primer immediately after resin has cured, I hope I am ok.
Sorry, I dont know what type brand of primer, or paint yet.

Am i being overly cautious. Or do I need to have it in a controlled environment until primer is dry?

Kind Regards
James

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PostPosted: Mon Mar 11, 2019 10:28 pm
Priming over "fresh" fiberglass work is can be a recipe for disaster. If I make a part or do repair work involving several layers of mat, cloth, whatever.....I'll give a minimum of a week before I put anything on it. Also, I almost always use epoxy as a barrier coat before moving on to regular or high build primers. When you prime over fresh laid fiberglass you are locking in escaping gases. Even if those gases don't try to escape immediately by creating pinholes they will eventually try to gas out creating larger bubbles when enough direct sunlight/heat get on the area. Guy at a car show last year had a beautiful paint job done on his Fiero but the painter rushed the nose work on the front. He had bubbles the size of quarters and 50 cent pieces on that nose. At least a dozen or so...,.
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PostPosted: Tue Mar 12, 2019 9:44 am
Ok, good stuff. Thanks
I had some bubbles the size of quarters in the trunk lit. Initially I thought it was vapours from fuel or ...
The local body shop said strip it, and keep it warm for a month.
Repainted. And new bubbles.
My best guess is after I warmed the lid, moisture hurried back in there.

My hope is to get it right this time!
Thank You

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PostPosted: Tue Mar 12, 2019 1:04 pm
Yeah, bubbles are "something" trying to gas off. Water/water vapor can indeed do the same thing as solvent vapors. It usually just takes longer for water type bubbles to show themselves. Not sure how you might be heating but many types of "ventless" heaters dump a ton of moisture in the air. I'm talking gallons of water a day. That vapor saturates the air and although it may be pulled out when vent fans are on, the real damage has occurred many times because the surface fillers have already loaded up with it and airborne moisture is literally being trapped while you are shooting.
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PostPosted: Wed Mar 13, 2019 9:19 pm
It’s for sure the problem, as the bubbles took months to show up.
Heating with wood in the winter. So I better find a solution.
Thank You very much

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PostPosted: Thu Mar 14, 2019 8:10 am
Generally, wood heat is very dry heat however because it can let your shop "cycle" up and down in temps depending on how it is fired you could still be getting excess moisture in the air. You might consider picking up a used dehumidifier and see if it has any impact on the shop environment.
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PostPosted: Thu Mar 14, 2019 11:42 am
Ah, great
I have a couple dehumidifiers
Maybe I need to make more of an environment of my shop. It has some gaps in garage door etc
I suspect with wood heat, and the dehumidifier running for 4-5 days might do it?

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PostPosted: Thu Mar 14, 2019 1:03 pm
Yeah, that's definitely the next thing I would do. If you ever get a chance try picking up a digital Thermo-Hygrometer. They are a small device with a digital screen that shows both temperature and relative humidity. Most also keep a running record (until you push reset) of the highest and lowest values for both humidity and temp. I think I got my last one for like $15 or so. We use these for tracking levels in our wood finishing shop as well as the humidity checkers that plug directly into our woods. The more control you have over your materials and environment the less problems you will have.....
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