Hard top paint issue

[Sparra]

I recently purchased a dark blue hard top. I set about prepping it to paint to a colour more suitable to my BRG NA6, which really only included roughing the surface for the primer/filler to adhere correctly and ensuring there were no surface irregularities. Once happy with the surface, it was cleaned with a wax and grease remover.
Four coats of primer/filler and two coats of base colour went on without any problems.

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The third base coat however was another matter entirely. (I haven't included actual photos of the base coats at this point, but take my word, they were fine.)

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As the image shows, there is something in one of the original layers of paint that is reacting with the acrylic paint. No idea why it only started after 6 successful coats of primer and base!
Initially I cleaned all of my spray equipment from top to bottom in case I had a contaminant in the base paint mix. I then cut back a section of the crinkled paint and cleaned the surface with the wax and grease remover again. I then hit that section with a coat of primer/filler. It immediately started to 'bloom' around the edge, where the offending layer of original paint is visible.
I realize that I am going to have to strip all paint off, back to bare and start again. I was just interested in knowing if anyone had seen this before?

[Mr Morlock]

what I would do is talk to a paint supplier- some business like the Bodyshop. I think the answer will be related to what was the base paint and then what primers base coats etc that you added. You can test the base paint by rubbing with thinners etc - you can lookup tests as well. My guess is simply that it is a reaction of a thinner over a base paint with a different paint type eg. The paints you have used will almost surely be compatible with each other but not necessarily with the base system. There is a lot of info on line but either a book on painting or better still talking to someone supplying and solving probs everyday will save you time. If you are using a 2 pack system that might even complicate it further.

[Drek]

I agree with Mr Morlock, and I have also had this happen at times because I was in a hurry and didn't let the primer dry for long enough between coats - or put a coat on too thick. It was easy enough to fix.

[Sparra]

I would possibly agree with you Drek, based on the info provided, however.......

I took this video this morning. Note that the crinkle is only happening around the perimeter of the area sanded back, and then only in a very narrow section. This says to me that the sanding has uncovered a layer of existing paint, which is reacting with the paint(s) I am attempting to spray.
The first spray is the acrylic primer/filler used in the photos posted. Second was a generic spray putty, also used prior to the problem occurring. The third is an etch primer, not really required for this job, however, like the putty, is suitable for both acrylic and enamel based paints.

http://www.youtube.com/watch?v=8GsoqXhLR6g

Had this issue occurred with the first coat, I would have accepted it and moved on, by doing what I am having to do now, ie sand it all the way back to bare. As stated in the OP, this problem didn't surface (sic) until after 4 coats of primer and 2 coats of base. Now, I can only paint the areas that have either been sanded back to bare, or those sections that have remained unaffected after I painted them. Anywhere there is an exposed edge of the original blue paint, the paint being applied bubbles.

Sorry about the noise in the background, it is the exhaust fan. Turn the sound down/off, as there is no commentary.

[bigdog]

The problem most likely relates to your use of etch primer. Self etching primers contain an acidic solvent designed to adhere to bare metal, and are meant to be be sprayed very lightly over said bare metal to provide adhesion for subsequent paint layers. You should not use them on fibreglass or similar surfaces, and they are not meant to be used on previously painted surfaces. At this point I would sand it all off and give it to a panel shop to rectify after explaining the problem to them.

[Sparra]

I didn't use the etch primer on the actual job, just the demo video.
Thanks for your thoughts!

[bigdog]

OK, I have watched your demo video now and see some basic mistakes that could be part of your problems.

When you apply wax and grease remover you wipe on with a clean cloth, then immediately wipe off with a separate clean cloth - your rubbing is with the 2nd cloth, not the first, and you turn it repeatedly to present a clean face to the paint. When either cloth gets stained, replace them. It takes plenty of clean cloths to wipe down a panel properly. Avoid touching the can with the cloth - tip the liquid onto the cloth so you don't contaminate the can with any silicone etc you might have picked up on the cloth.

Next, make sure the panel is completely dry before you apply the first coat of primer. Your demo shows the WGR is still damp on the panel when you apply the primer. WGR is a solvent and it will react with paint. I would normally use compressed air to blow over the panel and into all the nooks and crannies to chase out any moisture, and either heat lamps or direct sun to warm the panel before applying paint. Use a tack cloth to give the panel a final once over to remove dust before you paint.

I would remove all the previous paint on the panel and start from scratch given the issues you're facing. Talk to your paint shop about using a sealer on the fibreglass as your base coat to act as a barrier to any residual issues.

[Ross]

A bit late, but you should try this,
http://www.hichem.com.au/hicheminfo/PIDS/Misc/Iso.pdf
I have used it over acrylics before applying 2 pack urethanes. Works well.