(C4) Tiny Bubbles, old paint? (1990 coupe)
06-16-2010, 07:10 PM
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(C4) Tiny Bubbles, old paint? (1990 coupe)
Before I owned this car I had a 1986 Coupe that I bought from a junkyard. It had a ruined interior and a lot of peeling paint. I had a vocational school paint it for me. A year later I had tiny bubbles in the paint, but only in two spots - the "ridge" or curve where the hood bends and becomes fender right above the front tires.
I took it to two different body shops to have those bubbles sanded out and repainted. But those bubbles kept returning.
After talking to twenty pros, someone suggested that the school had inadvertently sanded through the gelcoat and exposed some of the fibers in the fiberglass. The curved ridge above the tires is a high point on the body and its easy for someone inexperienced using a power sander to go a little too deep. Then they unknowingly painted over the exposed fibers. Anytime it got hot out, the air in the fiberglass strands would push the paint making a bunch of tiny bubbles. When it cooled off they went away. This of course was just a suggestion as to what had happened.
That car got wrecked in 2001 and I replaced it with a 1990 coupe.
Early last year the paint on the hood began to oxidize. I buffed it repeatedly but the oxidation kept returning. I soon found myself wearing through the clear coat and decided to stop. I put a car cover over it in October, and left Florida for business in California.
Three weeks ago I uncovered my Vette. Most of the clear coat is GONE. The top half of the car looks terrible, the bottom half looks brand new. I'm going to get the top repainted.
Right on that same spot where I had trouble with my 1986, I have tiny bubbles pushing up the paint!
It might be just that the aged paint and clearcoat are seperating. But I'm worried that I'll have a repeat of the paint job I had with my 1986.
What could cause those tiny bubbles? More importantly, what do I need to tell the body shop so that the hood is properly prepped for new paint, especially if they end up sanding down to the fiberglass?
ZIP Corvette told me I need to make sure to use an Epoxy based paint instead of polyester, because polyester paint won't stick to SMC. I don't know what SMC is.
I took it to two different body shops to have those bubbles sanded out and repainted. But those bubbles kept returning.
After talking to twenty pros, someone suggested that the school had inadvertently sanded through the gelcoat and exposed some of the fibers in the fiberglass. The curved ridge above the tires is a high point on the body and its easy for someone inexperienced using a power sander to go a little too deep. Then they unknowingly painted over the exposed fibers. Anytime it got hot out, the air in the fiberglass strands would push the paint making a bunch of tiny bubbles. When it cooled off they went away. This of course was just a suggestion as to what had happened.
That car got wrecked in 2001 and I replaced it with a 1990 coupe.
Early last year the paint on the hood began to oxidize. I buffed it repeatedly but the oxidation kept returning. I soon found myself wearing through the clear coat and decided to stop. I put a car cover over it in October, and left Florida for business in California.
Three weeks ago I uncovered my Vette. Most of the clear coat is GONE. The top half of the car looks terrible, the bottom half looks brand new. I'm going to get the top repainted.
Right on that same spot where I had trouble with my 1986, I have tiny bubbles pushing up the paint!
It might be just that the aged paint and clearcoat are seperating. But I'm worried that I'll have a repeat of the paint job I had with my 1986.
What could cause those tiny bubbles? More importantly, what do I need to tell the body shop so that the hood is properly prepped for new paint, especially if they end up sanding down to the fiberglass?
ZIP Corvette told me I need to make sure to use an Epoxy based paint instead of polyester, because polyester paint won't stick to SMC. I don't know what SMC is.
06-17-2010, 06:05 PM
#2
Race Director
SMC is the material that makes up a majority of your body panels. Both of your cars did not and do not have a "gelcoat".
Bubbles can be caused by a contaminent getting into the SMC and working its way to the top. I know that tire shine can do it to your rear quarters if it is used too much or applied heavily and allowed to splatter to the underside of the quarter panel ...just above the tire...where it is NOT protected by the plastic splash shield.
The shop will carefully have to prep this area and try to find out what is causing it to bubble up.
Many views on what to apply to SMC when it comes to painting. Many feel that epoxy based products are what is required for good adhesion...others do not see it that way.
I do not understand this thought in this area....because those who believe that epoxy is the only way to go...will also be the first ones to apply a polyester based product ( body filler or catalyzed glazing putty) to the bare SMC before they epoxy it. I am not saying EVERYBODY...but many do this. I do not use an epoxy primer on SMC....but that is just me.
Hope the shop can determine what is causing the bubble issue. I also HATE car covers for outside use. They can often times restrict air flow and actually create a "greenhouse " effect...not allowing moisture to evaporate off quickly enough....thus trapping this moisture and you can start a problem. Just be careful in using your car cover when you get your car re-painted....regardless if it one designed for outside use. Your paint will need time to cure and be allowed to breathe and have good air flow around it. SO sticking it in a rentable storage building is not a good idea due to lack of good air flow. I would much rather have one of my customers leave it out in the weather if that is all they have....versus "bagging" it up. May take a bit more regular maintenance ( applying poilish and washinig)...but that sure beats having to deal with a problem due to it not being allowed to cure properly.
Just my opinion.
"DUB"
Bubbles can be caused by a contaminent getting into the SMC and working its way to the top. I know that tire shine can do it to your rear quarters if it is used too much or applied heavily and allowed to splatter to the underside of the quarter panel ...just above the tire...where it is NOT protected by the plastic splash shield.
The shop will carefully have to prep this area and try to find out what is causing it to bubble up.
Many views on what to apply to SMC when it comes to painting. Many feel that epoxy based products are what is required for good adhesion...others do not see it that way.
I do not understand this thought in this area....because those who believe that epoxy is the only way to go...will also be the first ones to apply a polyester based product ( body filler or catalyzed glazing putty) to the bare SMC before they epoxy it. I am not saying EVERYBODY...but many do this. I do not use an epoxy primer on SMC....but that is just me.
Hope the shop can determine what is causing the bubble issue. I also HATE car covers for outside use. They can often times restrict air flow and actually create a "greenhouse " effect...not allowing moisture to evaporate off quickly enough....thus trapping this moisture and you can start a problem. Just be careful in using your car cover when you get your car re-painted....regardless if it one designed for outside use. Your paint will need time to cure and be allowed to breathe and have good air flow around it. SO sticking it in a rentable storage building is not a good idea due to lack of good air flow. I would much rather have one of my customers leave it out in the weather if that is all they have....versus "bagging" it up. May take a bit more regular maintenance ( applying poilish and washinig)...but that sure beats having to deal with a problem due to it not being allowed to cure properly.
Just my opinion.
"DUB"
06-17-2010, 08:37 PM
#3
Instructor
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Member Since: Oct 2000
Location: Sacramento, CA USA
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SMC is the material that makes up a majority of your body panels. Both of your cars did not and do not have a "gelcoat".
Bubbles can be caused by a contaminent getting into the SMC and working its way to the top. I know that tire shine can do it to your rear quarters if it is used too much or applied heavily and allowed to splatter to the underside of the quarter panel ...just above the tire...where it is NOT protected by the plastic splash shield.
The shop will carefully have to prep this area and try to find out what is causing it to bubble up.
Many views on what to apply to SMC when it comes to painting. Many feel that epoxy based products are what is required for good adhesion...others do not see it that way.
I do not understand this thought in this area....because those who believe that epoxy is the only way to go...will also be the first ones to apply a polyester based product ( body filler or catalyzed glazing putty) to the bare SMC before they epoxy it. I am not saying EVERYBODY...but many do this. I do not use an epoxy primer on SMC....but that is just me.
Hope the shop can determine what is causing the bubble issue. I also HATE car covers for outside use. They can often times restrict air flow and actually create a "greenhouse " effect...not allowing moisture to evaporate off quickly enough....thus trapping this moisture and you can start a problem. Just be careful in using your car cover when you get your car re-painted....regardless if it one designed for outside use. Your paint will need time to cure and be allowed to breathe and have good air flow around it. SO sticking it in a rentable storage building is not a good idea due to lack of good air flow. I would much rather have one of my customers leave it out in the weather if that is all they have....versus "bagging" it up. May take a bit more regular maintenance ( applying poilish and washinig)...but that sure beats having to deal with a problem due to it not being allowed to cure properly.
Just my opinion.
"DUB"
Bubbles can be caused by a contaminent getting into the SMC and working its way to the top. I know that tire shine can do it to your rear quarters if it is used too much or applied heavily and allowed to splatter to the underside of the quarter panel ...just above the tire...where it is NOT protected by the plastic splash shield.
The shop will carefully have to prep this area and try to find out what is causing it to bubble up.
Many views on what to apply to SMC when it comes to painting. Many feel that epoxy based products are what is required for good adhesion...others do not see it that way.
I do not understand this thought in this area....because those who believe that epoxy is the only way to go...will also be the first ones to apply a polyester based product ( body filler or catalyzed glazing putty) to the bare SMC before they epoxy it. I am not saying EVERYBODY...but many do this. I do not use an epoxy primer on SMC....but that is just me.
Hope the shop can determine what is causing the bubble issue. I also HATE car covers for outside use. They can often times restrict air flow and actually create a "greenhouse " effect...not allowing moisture to evaporate off quickly enough....thus trapping this moisture and you can start a problem. Just be careful in using your car cover when you get your car re-painted....regardless if it one designed for outside use. Your paint will need time to cure and be allowed to breathe and have good air flow around it. SO sticking it in a rentable storage building is not a good idea due to lack of good air flow. I would much rather have one of my customers leave it out in the weather if that is all they have....versus "bagging" it up. May take a bit more regular maintenance ( applying poilish and washinig)...but that sure beats having to deal with a problem due to it not being allowed to cure properly.
Just my opinion.
"DUB"
I've learned my lesson on Car covers. The only way I'll ever use one again is if I have to leave my car somewhere that is extremely dirty, like under a tree leaking sap.
The cover I used is a breathable fitted "cloth" cover I bought from Performance Corvette's catalog for about $120. In Ohio the cover was perfect. In Florida it was a disaster. It was OK when I used it to cover the car for a week or two, but this time it was on there for eight months. There was a very very fine layer of sand on the entire car. I'm guessing superfine sand soaked through the breathable fabric. It looked like someone had taken 1000 grit sand paper and gently brushed the top half of the car with it.
