Bubbling paint on a 71, causes?
Thread Starter
Team Owner
Joined: Jan 2004
Posts: 22,185
Likes: 65
From: NJ
Bubbling paint on a 71, causes?
I am looking at a 71 coupe that was recently (2 years ago) painted. The paint is bubbling in a few spots and I was curious as to the causes of bubbles in a fiberglass car. I’m not a bodyman so I was wondering is it mainly a uncured filler or moisture thing? Going forward can it generally be expected that other areas will start to pop? I am looking at it from the point of view that the car will need to be brought down to glass to repair properly, is that generally correct?
Racer
Joined: Feb 2006
Posts: 428
Likes: 1
From: West Des Moines Iowa
where is it bubbling??? If it is between the back of the headlamp housing and the front part of the hood, then it is the "ever popular" rivet pop problem. this occurs with just the 68 through 72 chrome bumper cars and can be expensive to repair. Need to replace with quality aluminum rivets underneath the fiberglass bodywork. I am not sure of any other places that bubbling can occur on vettes...Hope this helps. 
Johnny B
Johnny B
Le Mans Master
Joined: Jul 2005
Posts: 5,752
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From: Austin Texas
Bubbling paint is caused by trapped moisture or solvents. This can be from paint stripper residue, uncured bondo or filler, water in the primer, oil contamination from the compressor etc. You may never find what caused it. The best approach is to strip it down all the way and start over. 
Safety Car
Joined: Oct 1999
Posts: 4,101
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From: NorCal
Another source of problems is oil residue soaked into the fiberglass, typically on the hood and fenders from the engine compartment. When I got mine, I removed four layers of old paint and found the hood soaked with refrigerant oil from a leaky A/C compressor seal. I have yet to successfully get it all out and it may never happen, but it's the original 427 hood and it fits perfectly, so I'm not giving up!
Hans
Hans
Melting Slicks
Joined: Mar 2005
Posts: 2,094
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From: Midlothian VA
Originally Posted by Wrencher
Another source of problems is oil residue soaked into the fiberglass, typically on the hood and fenders from the engine compartment. When I got mine, I removed four layers of old paint and found the hood soaked with refrigerant oil from a leaky A/C compressor seal. I have yet to successfully get it all out and it may never happen, but it's the original 427 hood and it fits perfectly, so I'm not giving up!
Hans
Hans
Melting Slicks
Joined: Mar 2003
Posts: 2,512
Likes: 49
From: Franklin IN
it happened to me
Originally Posted by big_G
Bubbling paint is caused by trapped moisture or solvents. This can be from paint stripper residue, uncured bondo or filler, water in the primer, oil contamination from the compressor etc. You may never find what caused it. The best approach is to strip it down all the way and start over.
To any one repainting a Corvette DO NOT WET SAND A BARE FIBERGLASS PANEL. It wicks in water and after it's painted and the car sits in the sun the water expands and cannot find a way out that is one of the causes of blisters. If you are stripping the car and are using chemical that needs to be washed after striping the bare glass should sit out in the sun for a week or two the hotter and dryer the better. Dry sanding or the razor blade method would be my choice for paint removal. I am not an expert in paint removal or painting these are things I've learned by expirence with my wifes 79.
Thread Starter
Team Owner
Joined: Jan 2004
Posts: 22,185
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From: NJ
Thanks for all the input. The bubbles on this car are on the rear deck behind the rear window along the the inside of the sail panels and a bit on top above the back window. If its already happening after 2 years I would think there is more to come. So a complete strip down would be in order.
Racer
Joined: Mar 2005
Posts: 263
Likes: 0
From: Creswell OR
Same problem here.My car was just painted when I bought it.It really looked good,and I loved the color.It was probably the main reason for pulling the trigger.Now I've got bubbles in a lot of places.I'm hoping that it is only a moisture issue,and not leftover stripper.I'm wondering if it is stripper,will it be possible to take it back down,and resand,will you not have the bubbles show up again?
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Pro
Joined: Feb 2006
Posts: 718
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From: Jacksonville , NC
Having (had) the same issue with my 80. Bubbled area on fenders down both sides of hood. Wound up hand sanding down to gel coat the entire front clip. Found, if you can believe it fingerprints and something that looked to be unset primer/sealer. Hopefully going to the booth this weekend for fresh paint.
Burning Brakes
Joined: Aug 2004
Posts: 971
Likes: 7
From: roanoke va
Originally Posted by big_G
Bubbling paint is caused by trapped moisture or solvents. This can be from paint stripper residue, uncured bondo or filler, water in the primer, oil contamination from the compressor etc. You may never find what caused it. The best approach is to strip it down all the way and start over.
Also I would like to add that vettes were never gelcoated from the factory. Different people on the fourm suggest using epoxie primer to help seal the fiberglass. I have a paper here from the maker of replacement press molded fiberglass that strongly suggest only to use true gelcoat on top of the fiberglass. And to make sure you have a min. of 20 mil. thickness of gelcoat after sanding. Then you can apply the primer.
I have been doing the body work on my car for some time now and trying everything possible to keep it dry. I am planing on applying gell coat to my car before too long. and sanding down the first coat. Then I am going to pull it outside in the hot sun over the summer and hopefully let any shrinkage of body work occur. Then I am planning on applying another coat of gelcoat this fall and then after a final sanding it should be ready for some primer.
Instructor
Joined: Apr 2005
Posts: 226
Likes: 0
From: lakewood (tacoma/seattle) washington
With every one and would like to expand on one thing............gel coat is not a product it's a term like primer,finish,paint etc. etc. Gel coat is a smooth layer that hides the fiber glass strands. So be very carefull on what you use. Gel coats are made of 3 major types ,polyester, epoxy,and vinyl ester and come in clear,colors,and primers. some gel coats are not designed to air dry.(beware) with out additives or p.v.a over them. More important is the substrate (smc,fiberglass,etc.) have a good profile for the gel coat to adhere to.Now this being understood most all marine or automotive primers can be a gel coat . Some can be wet sanded and some canot, so it is very important to follow the mfg. instructions on the data sheet. There should be no problems . The data sheets also cover fingerprints ,oil it tells you how to prepare the surface. My prefrence is polyester primer over 80 grit. IM not saying this is the best ,this what I choose to use.
Burning Brakes
Joined: Feb 2006
Posts: 1,024
Likes: 1
From: AL
The "gelcoat" that Eckler's sells comes with a MEKP hardener exactly like the hardener used in polyester resins (used for f/g repair). That stuff has worked well for the last 8 years. I wish I know who really makes that stuff for Eckler's.
Heed the notice on shelf life; go buy it when your ready to use. Get a really accurate measuring tool, like the old 10 ml graduated tubes we used in science class. Too much MEKP and your cleaning and rebuilding your gun.
I've had experienced painters tell me they can get the same results with brand name epoxy primers. These have been out long enough now that we should hear some long term success stories.
Heed the notice on shelf life; go buy it when your ready to use. Get a really accurate measuring tool, like the old 10 ml graduated tubes we used in science class. Too much MEKP and your cleaning and rebuilding your gun.
I've had experienced painters tell me they can get the same results with brand name epoxy primers. These have been out long enough now that we should hear some long term success stories.
Safety Car
Joined: Oct 1999
Posts: 4,101
Likes: 10
From: NorCal
Originally Posted by murvette
:....The data sheets also cover fingerprints ,oil it tells you how to prepare the surface. My prefrence is polyester primer over 80 grit. IM not saying this is the best ,this what I choose to use.
On the bubbles on the back deck, mine had those. I attributed it to fuel or some such contaminant as it was worst around the filler. I used laquer thinner to clean it after I sanded it, let it dry completely, then sealed it.
Hans
Last edited by Wrencher; Mar 22, 2006 at 01:59 PM.
