Hello,

I have been reading up on the site and had a couple of questions that may open up a pandoras box.

I was reading on the site and found two possible problems in particular with painting fiberglass; spider-stress cracks & paint bubbles.

For the first one for cracks, I read as long as the body was prepped correctly cracks shouldn't appear on the paint.

But for the second part paint bubbles, I've been reading that others out there have had to repaint certain parts several times because of contaminated fiberglass.

My question is for the paint bubbles b/c of contaminted fiberglass, is this something that can be prevented with proper prep work or is it something of a gamble that even with prep work it may still show and end up require a replaced body panel?

 

It's all about the proper prep work. Every paint job looks great when new...the big question is time and how it looks later.

 

All about the prep work! The paint on my '73 is 24 years old, but you would think it might be closer to 4 or 5 years with just a few nicks and chips. I am hoping to get another 8 or 9 years out of it before getting her ready for her 50th!

 

from what I understand making sure the fiberglass is clean and any possible previous paint stripping chemicals are properly neutralized is the most important thing... I belive you can use a baking soda mix or I'm sure there are other more expensive solutions out there to use to make sure it doesn't return... Then its just a matter of using the correct primer and sealer over the top.

 

I'm pretty sure most use dawn soap and wash everything really well then let it sit in the sun and dry thoroughly.

Then you use a TON of wax/grease remover before doing any painting.
Spray it on, it works for a few seconds, brings all the bad stuff to the surface. Then you wipe it off with a clean dry cloth. Repeat till it's clean.


I'm no expert but I'm pretty sure star cracks are from weak fiberglass areas or ones that flex too much. Like a rock hitting the wheel well or something pushing on the 1/4 panel. fiberglass flexes and the paint doesn't....= cracks

 

Hi jc,
I think people often confuse cracks in the paint, both random and 'spider', with fiberglass problems, rather than paint problems.
Many cracks that are seen in paint are caused by too much primer, sealer, and top coat, being applied.
The cracks seen in the front corners of the opening for the hood in the hood surround for example are often 'stress' cracks. While the cracks sometimes seen in 'valleys' like along the top of the rear fenders at the sail panels on coupes is the result of too much material.
95% of the LABOR in a paint job is in the preparation, while 5% is in the spraying.
BUT 95% of the necessary EXPERIENCE is in that spraying.
Regards,
Alan

 

About Paint: I drove the car to a local Corvette body shop with a good reputation. Actually I've used them in the past for parts, mechanical repair and everything was very reasonable. For the 68 Convertible, their basic repaint cost was about $10,500. A little sticker shock here, but I agreed. What do you get for the $10,500? First of all they de-chrome the car...all the chrome pieces are removed including the door lock surfaces on the door, door handles, etc. The only thing they don't remove is the stainless steel trim around the window. Also, they removed the convertible top. Next they removed all the paint/primer down to bare fiberglass. For the relatively large flat expanses of the body surface, the used pneumatic orbital sanders. For the nooks and crannies it was all hand sanding. Included in the $10,500 is labor and material to grind out and re-seal the original body panels seams For example, the front "clip" ...the body work in front of the doors is comprised of about 6 or 7 panels bonded together. Similarly several panels behind the doors. They grind out the seams and re-epoxy them. Next, for the $10,500, they use say...a Windex spray bottle filled with alcohol. Now they are looking for micro-cracks in the fiberglass surface. The entire surface gets spritzed with alcohol about 1 foot in diameter. The wet surface on the car now looks a dark grey. A towel is rubbed across the surface, and the surface alcohol soon evaporates.....but the wet alcohol in the micro-cracks is still observable. Areas on the surface where the micro-cracks are highlighted with a black felt pen. Of the $10,500, the cost of repainting itself is about $3600...Forget exactly the brake down, but I think it's about $1600 for paint and materials and about $2000 for labor. They do fine sand the final paint surfaces.

Also, as a part of this very intrusive examination of the 68 surfaces it was pointed out that the hood didn't match all that correctly. This was the result of a front end collision repair in the late 60's. Also, the doors did not match exactly with the rear quarter panels and the convertible lid.......this was a production fault ...not accident repair. The door skins did not exactly match up with the front clip either.

I agreed for the extra body work. For the front hood alignment problem, they broke the inner front wheel wells free from the front clip and also broke the front clip loose in the front. They shifted all the pieces around, added some fiberglass/resin were needed and ground down the fiber/glass resin.

Adding fiberglass/resin and shaping..the rear of the doors, the rear quarter panels, and the convertible lid now all match perfectly. The door skins now match up with the front clip. This makes up for factory miss-matches.

About those micro-cracks. They grind down the area where the cracks are and splot the area with a fiberglass/resin patch. Later they grind it back to the original surface contours...some artistry is involved here.

In addition to micro-cracks, there's a WD-40 problem! To protect all the chrome pieces I kept them covered in WD-40. Every few months I'd clean off the WD-40...it'd attract dust...and re-apply the stuff. I'd just spray it on the chrome and wasn't concerned about overspray on the painted surfaces. Unfortunately the paint had cracks in it I couldn't see, and WD-40 has in places soaked into the fiberglass. The areas of soaked fiberglass aren't to large, so they too have been ground out and covered with a larger fiberglass/resin patch that will have to be ground down...From now on I'll use a wax to protect the chrome. I have 69 factory sidepipe housings and I don't want them to corrode ($2500 replacement cost.)

With regard to the WD40 problem....I'd be leery of using a chemical stripper. The old bare fiberglass will soak up liquids and it's impossible to really remove the soaked in fluid...IMO. Also, engine oil mist had penetrated the rear valance panel...the panel the tail lights are in. This entire panel had to be replaced because of oil contamination.

There's just a tremendous amount of hand work involved...a lot of it is probably tedious. So far they are doing a good job....the weeks roll by, but i don't drive the car that much anyhow.

I never realized that painting a 46 year old fiberglass car would involve the expenses of repairing fiberglass aging.

Here in Cali it's water based paint which is what a lot of original car manufacturers use anyhow. Light Bright metallic blue...aka Le Mans Blue.

 

PROFESSIONALLY SPEAKING:

AS for you question on 'cracks". It all depends. Where the crack is located....and how bad the crack actually is. Usually the location is my primary concern. Some cracks in high stress areas will require a completely different set of repair procedures....versus a crack in a headlight bezel (for example).

Question 2 about 'paint bubbles'. What I read about how someone did 'this or that'...and still had problems... often times makes me laugh and shake my head. WHY you ask??? Because in most cases....these are people who do not do this for a living...because any person who does this for a living will know how to do 'this or that'...even it if requires a panel to be replaced due to extensive contamination. Many people have found a procedure that worked for them at one time or another....and when 'other people' try it...and it fails....they wonder what they did wrong.

I have so many different procedures to remove contaminates from fiberglass that NOT one way does them all. Sometimes....I run into an issue where the panel NEEDS to be replaced. So...PROPER PREP means nothing...if you have a panel that is literally ruined. AND I still have customers who want me to save it. And I tell them..."I lost my magic wand....and I do not have a crystal ball". So it ALL DEPENDS!

Then it also comes down to what is applied on the raw fiberglass to protect it. Many views on this subject also.

I am VERY OPINIONATED in my views on how I prep and repaint a Corvette. I do not waver at all. WHY...Because the procedures that I currently employ have NEVER caused me to have a problem. If I leave out one process...I open up the possibility for a failure....which I have experienced in the PAST. I do not have time to wait for fiberglass to dry out and 'wonder' if a unapproved cleaner on the fiberglass did not actually migrate into the fibers and NOW will cause me problems....when IF I stayed with my process...I KNOW it would not fail.

Like I wrote...many people found ways that work for them. And I can say..I would NEVER do them ( regardless if it worked for them)....And they may feel that they would never do it my way...which is fine. All I know is that I have to warranty MY WORK....and I know what works....and I do not have to do something twice.

Like previously written. The PREP is EVERYTHING...and I AGREE. But also taking in consideration factory flaws and knowing when it is time to decide to replace a panel or not is something else.

DUB

 

Both my '67 and '69 had problems with this. Coinsidently, they were centered on the drivers side front top and side fender. The '69's were "minor" (if there is such a thing), the '67's severe enough that I ground the panels down and laid in layers of West Epoxy and Fiberglass matte. If you're interested enough, you can search my prior posts and easily find out what sort of problems I had and how I (hopefully) corrected them. If you have contaminated glass, you simply cannot just repaint over it.

 

DUB

 

OK. What can you do to work around this problem? I have a perhaps a bare fiberglass 2 inch by 4 inch spot on my door panel were WD40 has contaminated the fiberglass. Plans are to ground down this area and the surrounding area and then splot on a fiberglass/resin patch and when hardened, grind down the fiberglass/resin patch to match the original door skin surface.

In my previous post did you read the comment where engine oil mist was blowing on the rear valance panel..the panel that the tail lights were on..had completely saturated the panel. When exterior paint was ground off, oil contamination was immediately seen. The entire panel has had to be replaced....$$$

 

Wise move on replacing the panel.....This is why on the exhaust filler panels...I gelcoat them on the inside when I do one.

DUB

 

Thanks for the reply. I'll talk to the body shop Friday about the perhaps 2 inch by 4 inch WD40 contaminated fiberglass. A problem is that this area is on the door down near where the factory sidepipe shroud was mounted. Getting to this area from the other wide is difficult since the steel door "pan" is in the way.

 

Here's another "little" tip. Years ago I did a strip and paint. I couldn't figure why I was getting little "fish eyes" or bubbles showing up in the paint. Turns out I was using paper towels to wipe the surface with solvent to clean it. DON'T USE PAPER TOWELS or other commercial paper products for cleaning. Part of their production process is using release agent to make the paper easier to process. It is a serious contaminant.