Paint Crazing

Mach10 · Post by **Mach10** » Thu May 24, 2007 10:58 am

I learned a new word the other day... It's what has happened to the paint on my car.

None of that lame "clearcoat peeling off" or fading...

Just that up-close, the paint on my car looks like a dried-out riverbed. tiny geometric cracks that cover probably 2/3 of the car's surface. After buffing the car handily for several hours, it looks alright from a distance, but up close you can see where dirt has literally sunk into the paint via these millions of cracks.

I spoke to an automotive painter who gave me two scenarios that depend entirely on how GM prepares their panels:

1) Standard primer: Crazing will go right down to the substrate; i.e., right to the panel. ALL the paint has to be stripped clean off, or the new paint will do the same thing.

2) "Gel-coat" epoxy-based primer that bonds directly to composite panel: Crazing will go down through the clear and the base, but probably leave the primered coat alone.

Anyone have any input? I know I'm going to wear my arms down to stumps either way when sanding... but the less material I have to take off, the better. As it is, I'm probably going to have to sand off nearly 1/16" of paint... And since I'm going with an extremely dark paint, I have to be very mindful of ripples...

Does anyone know of any stripping materials that won't warp the panels (either the composite shell or the "enduraflex")?

Dirty Sanchez · Post by **Dirty Sanchez** » Thu May 24, 2007 12:55 pm

You need an air compressor and some power sanding tools. You might be able to rent these at a rent-all center. You should be able to sand the car in a day with the right tools.

Mach10 · Post by **Mach10** » Thu May 24, 2007 1:03 pm

I've got a big random-orbit sander that will do the job...

What I'm worried about is getting the panels nice and smooth. With metal, it's easy, since the grit won't bite steel quite as easily as paint.

Composite is a little trickier, since it isn't much harder than the paint. Last thing I want to do is spent 3 weeks filling the dips and ripples with putty and glazing compound :noway

Darrelk · Post by **Darrelk** » Thu May 24, 2007 4:11 pm

Biggest problem with Fieros is the many different type of plastic you're looking at. You've go RIM, RIMM, SMC, and the flexy bumper stuff. If you've got saponification of your coating now (that cracking you're talking about) there's enough paint on there to seriously look at using chemicals to break those topcoats at least.
Here was an excerpt from a pro painter that does a lot of Fiero's over at the Old Europe site...

You don't *have* to sand it. In fact, with that much paint on it using chemical stripper will probably be a LOT quicker. Just do a small area (about 2 square feet) at a time, & make sure you don't let the chemical soak into the material the parts are made of. Use a good name brand (I use "Aircraft Stripper") on the SMC, & a "bumper stripper" (usually comes in a spray can) on the bumpers. You *may* get away with the strong shtuff on the plastic parts, untill you get most of the paint off, then go to the bumper stripper. Follow the instructions (well ventilated area, etc.), & once you get down to the original paint, stop. It may take one application for each layer of paint, but it may come off quicker than that. Once down to the original paint, make *sure* you clean off all the stripper & you're ready to sand everything smooth. This all makes a big mess: have a cardboard box ready to scrape the shtuff into as you go (cardboard on the floor dosen't hurt either).
What I would do is try sanding it first to see how well that goes, & if that's slow as hell then try the chemicals. You may also want to consider buying new (used) panels in some cases, 'cause things like fenders & door skins (& 1/4 panels & decklids & hoods....) can be bought cheap sometimes.
With that much paint on it I'd say it would cost you about a grand for a shop to strip it.
~ Paul
aka "Tha Driver"

Just really watch that random orbit sander. A lot of guys assume that just because it's a tight orbit that they are not that aggessive. I'd be inclined to turn my speed down and use rougher grits to "break" the original coating, then turn my speed up a little with finer sandpaper for further removing. Remember, that original paint GM paint package is about 6 mils thick or roughly twice the thickness of a heavy duty trash bag. It doesn't take much to rough into those plastics.
Even as careful as you can be with this stuff you're probably still going to have to use a hgih build polyurethane surfacer to get the plastics mostly level.

Mach10 · Post by **Mach10** » Thu May 24, 2007 4:24 pm

So basically, "no" all paint strippers will affect the body panels, so I have to step through the stripping, but if I do it carefully, I *might* not ruin anything.

Sanding will probably be the way to go. I'll probably have help with that, so it's not going to be just me sanding continuously for 96 hours. The trick--of course--is keeping shit flat. I guess the best technique is to sand the entire car clear down until the primer is peaking through, go over the high-spots until it's uniform, then proceed taking down the primer to bare plastic...

I know the bumpers are black... What color are the rest of the bare panels?

I'm pretty sure the paint on this car IS original, although I guess I could run a razor over a corner and see if I can lever up any layers... If it WAS an aftermarket paint-job, then it was done REALLY well, because there isn't a hint of overspray anywhere on the car.

6 mils? Is that it? I thought it was much thicker due to the flex agents they added... That's the best damn news I've heard all week!

Thanks for the info.
:salute:

Darrelk · Post by **Darrelk** » Thu May 24, 2007 4:32 pm

You sound like you've got a plan. As for colors I know the SMC stuff is white ( if you start getting a powdery look to it stop!., that's the mold release IN the SMC), I looked at broken fender on my parts car and it has a yellowish cast, just not sure on the rest of everything.
As for that thickness, yep, that's straight from the Finish Engineer's mouth at a GM plant I toured in 1989. Although flex is added it actually evaporates out of the mix after time so there is no real "thickness" to it.
Hope it goes well for you, post back if you figure out any tips from this, I'm sure other guys could use the info.

Mach10 · Post by **Mach10** » Thu May 24, 2007 5:28 pm

I meant that I thought that "flex" enhanced paint had to be laid on thicker.

Thanks again for the info!

I_wear_pants · Post by **I_wear_pants** » Thu May 24, 2007 10:01 pm

I'd say using a chemical stripper is the way to go. I spent countless hours sanding on my car (easily 50+) trying to get through all of the repaints the car has had over the years. Then when I took it to the paintshop the guy just used stripper to get them completely cleaned off. Don't waste your time with sanding, it sucks and its too hard to get to alot of places on the body without doing it by hand.

greengoblin0129 · Post by **greengoblin0129** » Fri May 25, 2007 9:45 am

bead blasting

p8ntman442 · Post by **p8ntman442** » Fri May 25, 2007 1:49 pm

greengoblin0129 wrote:bead blasting

no. for plastic panels you would need a very soft medium, which probably would not work on the paint.

Darrelk · Post by **Darrelk** » Fri May 25, 2007 3:39 pm

Only two mediums I've heard of for the mix of plastics on a Fiero is deformable plastic pellet blasting and soda blasting. Even at that, you've got to have a very experienced operator or he can still do some damage if he doesn't keep moving.

cactus bastard · Post by **cactus bastard** » Sat May 26, 2007 4:16 pm

FWIW, the door skins are made out of the same yellow stuff as the fenders.