SMYDA! Confused, questions about porosity, and chemical reactions.

enkeivette

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Joined
Mar 30, 2008
Messages
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I get conflicting info on the autobody forum, and if I ask for clarification I get scolded for asking more than once.

I've been told that after chemically stripping a vette the best thing for it is to let it sit outdoors to let the body leech out. Even washing it with soapy water to clean out the pores. But then I read that filler should not be wet sanded because if it gets wet, it will absorb the water which could later come through the paint. And my vette is sitting outside every night, getting soaked with condensation. I even planned to pressure wash it after all the body work was done to get all of the dust and dirt off. So what's the deal with getting filler wet?

Secondly, I'm told that you should not epoxy primer over laquer paint because it can have a funny reaction with the new paint. (Although I would think that the epoxy primer would seal whatever was underneath it) But it's never been explained to me why the original primer must come off. So must it? If so why? I prefer not to use the DA anymore than is necessary because I don't want to damage the body. And taking off the very last layer of primer will leave me no indication as to how badly I'm waving the body. So do I NEED to take off the factory primer?
 
I can only give you the info that I got and know.

I have personally seen cars that were stripped completly and then sprayed with a filling primer (don't know the exact term in English but it was a bodyfiller that could be sprayed). After painting it and then heating it to dry in the paint booth, the car started showing blisters all over the place. The reasoning there was that the filler absorbs water. I guess the same applies for regular fillers. I have been told that fiberglass does exactly the same thing..absorb water. I have been told to stay away with water from the car as far as possible as long as it hasn't been properly primed. They suggested that I thouroughly painted the underside of the panels also to prevent water from penetrating via the underside. Don't know if this last thing is true, but just to be sure, I did mine on the inside also (which was easy because my body was completly apart at the time).

As far as stripping the car, I always had the advice to do it completly, that is remove the factory primer also, then prime with a epoxy type primer and then finish it off with regular primer.

Regarding the removal of the factory primer : i read an article on the net that said that smc panels in my car where made with some sort of release agent that was incorporated in them. These agents would surface when doing some bodywork or could surface after/during baking the body in the booth. It supposedly (!) could cause the blisters we see a lot on these cars. Epoxy primer would not suffer from them, or at least not as muchSince paintwork is so expensive I never took the risk and completly removed the paint and started from scratch there. The other advantage to removing is that you can see every little problem the bodypanels might have and repair them properly.

The problem with some epoxy paints is that they get really hard and don't allow for much flex, which could be a problem when there is some other kind of paint underneath. It presumably (not from experience) could start to show a landchart type of cracks in the epoxy. Over at CF I saw a post from a guy that had this problem.

A lot of bodyshops here strongly advise against stripping the car chemically, so I never tried. I used a sander to get rid of most of the paint, untill i saw the primer coming through. Then i stopped and did the rest by hand. A hell of a job but it was worth it.
 
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I agree with the above and strongly advise you to never let the raw 'glass get wet. Blow off the body panels and just prior to doing any body-work, wipe the body down with lacquer thinner or acetone. Both will flash off quickly, even from any porous areas. I never paint over any top-coats, unless blending. You can't trust old paint to adhere or not crack. Epoxy will seal down the body fine, but still remove all old paint. On rough bodies, I use a product called "Slick-Sand", directly over the 'glass (no epoxy primer). It is a high-build primer-surfacer, and is a cousin (IMO) to gel-coat, as it is polyester based and uses MEK for a catalyst.
 
So both of you guys would agree that it's ok to leave the factory primer on the car as long as I'm using an epoxy primer?

And since the car has been sitting outside, what's the best course of action to remedy this? I was thinking about parking it in the garage till it's ready for paint, maybe even putting a heater in there to help the water evaporate.
 
Adam,

Sorry for the slow response.....got your PM :thumbs: that will always make me take a look. :D
Been really busy with the new place and getting things ready for Deer season..:hunter:
not to mention we're headed out for our Oregon vacation/holiday in 2 weeks. :yahoo:
(The Wife picked up our VetteMod T's today so we're all set ;) )

Just to add a little to the good advice posted above.

Early C3s originally came with Bias-Ply tires......but nobody uses them anymore
because there are tires made today that are far superior.
Your car was originally painted with Lacquer products.......the products today are
also far superior to Lacquer. IMO....I would remove ALL of the inferior Lacquer
products from your car.

You would not want to spend $10,000 on suspension upgrades just to slap inferior tires
on your ride........the car would only be as good as what enables it to contact
the road. Top coating the Lacquer with expensive products is doing the same
thing. The job will only be as good as the layer that is directly against the body.
Paint that has been applied over Lacquer has always been known to peal.

Next.........get the car OUT of the weather.
Most all body filler will absorb moisture.
Putting a heater in the garage with the car is a good idea.
Do Not top coat any of the body work that has been exposed
to water till it has had plenty of time to dry out. Just to be safe
give it a week or more.

Just a Note: Even Epoxy Primers will absorb moisture if exposed long enough.
UV rays will also make them brake down quickly.....so don't think that if it has
Epoxy Primer on it that it can set outside for several months before being painted.






JMHO others may vary. :thumbs:
 
Thanks SMYDA, so the original primer was lacquer based? I did not know this, I'll take it off then. :drink:

It turns out the filler around the doors was done to get the doors aligned with the body. Seems ridiculous to me that someone would grind the body for this reason. I would much rather have had slightly misaligned doors and no filler. I'm going to leave the old filler by the doors alone, unless you strongly object. The biodegradeable stripper that I used never ate past the primer surfacer, or the original paint/ primer coat. So the filler was never in direct contact with the stripper.

And check out the 10lbs of filler that had been used to mold my 82 bumper in. After taking it all off moving the groove down, my spoiler is about an inch longer.

348lu9d.jpg
 
On my son's car I'm having him remove everything.......old filler included.
(The prior filler work was horrible anyhow :huh: ) I would rather start new
than fix old.

Since your not concerned with alignment.........take it off.
You also mentioned some time back about racing the car ....
so there is no need for the added weight either. ;)



:bounce:
 
Even after wetsanding primer/high build primer or filler/bondo or whatever I'd let it sit in a hot dry Florida garage for a day or two to make SURE the moisture is gone before topcoating that wet area....

Now that your car was out in the weather it really doesn't matter right now, just make sure you dry it for a few days before you shoot sealer and base/clear coat :thumbs:

You have to slow yourself down as hard as it is: right before you're getting ready to spray is when you're getting impatient.... been there done that....
 
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