Last week I painted the front fenders and SS hood for my 70 malibu. Here's my problem the hood had developed bubbles (up to the size of a quarter) in a couple different places, the paint and self-etching primer have both raised from the bare metal. This was after only the first coat of paint. the bubbles weren't in the primer.What could cause this and how do I prevent it when I sand and re-shoot?

sounds like either mismatched paint brands reacting, or contamination. After you strip this down, make sure to use a good wax and grease remover before painting. I usually use it BEFORE sanding, to keep anything from getting sanded into the metal or surface being repainted, but it sounds like its too late for that now. I also always use a sealer coat between the primer coats and finish coats, PPG DAS80 grey I believe was the number. No problems with this method so far.

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Dave (NY)
70 chevelle ss396 conv
66 chevelle ss396 hdp/conv
55 chevy prostreet
69/71 camaros
TC member #493

This is a very odd problem, I would look at the heat of the panel when you applied the etching primer. Or the heat after the primer was applied. I have been a painter for 20 years and am now for the last four a paint rep for a major company and I have never seen ecthing primer do that, what brand is it? I don't think it was the brand of the primer, I just am curious. Is it an acid etching primer or an epoxy (which is not an etching primer, but some call it that) I have seen epoxies do that, they hold moister and air more than any acid etching primer would, which are actually very porous which allows for the air or moister to excape. Cleaning the panel is very important but make sure you wipe it very dry and don't prime it to soon, you don't want to trap any solvents under the primer.

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1965 Buick Gran Sport Convertible
1965 Buick Skylark H/T

Self-etching primer was acid etching
all prep and paint products I am using are PPG
Thanks for your imput

Was it D831 or DPX171? and are you positive that it pulled up off the bare metal, or was it the next product that came off the etching primer? What was the next product that you applied on the etching primer? If you used some sort of conversion coating like Metal Prep, that could be your problem, any kind of metal conditioner that leaves a phosphoric acid coating can really cause problems with an acid etching primer that is trying to do the same thing.

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1965 Buick Gran Sport Convertible
1965 Buick Skylark H/T

The only time I ever saw this happen was when a guy who was taking an auto body class had his girlfriend help him do the final prep work before painting. The lotion on her body and hands got all over the car and thrashed the new paint job. Had to take it back down to metal.

The Paint seperated from the Primer(DPX171) I went to strip it and it peeled off the primer easy with a razor blade This really has me puzzled any idea of the problem.
This primer and the paint were supose to be compatible.
http://www.chevelles.com/forum/confused.gif

I am not real hep on PPG but I don't think there are any recommendations to paint directly over the DPX171. By the by this is a "normal" problem, I knew the acid primer whouldn't come off the metal. This is also a much easier fix! I think that you either applied the paint to soon and the solvents were still flashing off, or you waited too long to paint it and the surface had "closed up" too much. Either way, you will need to take all the paint off and sand, then reapply the primer. I would put a urethane primer over the DPX171 and then sand it with 500 (or 600 if the color has a lot of mica or pearl in it) Then paint right on the urethane primer.

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1965 Buick Gran Sport Convertible
1965 Buick Skylark H/T

I just looked at a PPG Product data sheet, The only top coat that they recommend is two different polyurethane enamel single stages. It says one or two coats MAX and 30 minute min dry time to top coat. Then after 24 hours scuff sand before top coat.

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1965 Buick Gran Sport Convertible
1965 Buick Skylark H/T

Hey.CR Martinsr is correct. You CAN NOT topcoat the DPX171 primer directly with most paints. You need to use another primer surfacer or primer sealer in between. Take it off and start over I would recommend. I am a tech. rep for a PPG Platinum Distributor. I hope this helps. The jobber that sold you the products should be able to guide you through this. Ed