I just resprayed one side of my engine bay as I wasn't happy with it....too many nibs and some runs in the clear coat. I fixed it and sanded 600. A week later I tried to respray it. A few minutes after spraying the base it started to wrinkle in a few spots. Was this caused by the clear coat being a bit thin in these areas? It was the areas I did not work on. I'm not sure what to do. Can I sand and respray or am I going to need to sand and shoot sealer first? Thanks.

Can you post a picture?

My guess is you sanded through the clear and the solvent in your fresh clear reached the underlying base coat.

'68 Coronet R/T wrote:Can you post a picture?

My guess is you sanded through the clear and the solvent in your fresh clear reached the underlying base coat.

I left my phone in the garage so I can't I hadn't sprayed the clear yet. I sanded out the wrinkles which seemed to work out ok and I sprayed more base over top. I had some left over. We will see how that works out. I have nothing to lose.

ok photo was blurry. The respray attempt didn't pan out either.

These are pics after the touch-up...basically looks the same. Its limited to an area near the firewall and along the top line before the inner fender turns down. Everything else I have sprayed turned out nice when going over 2K primer.

looks like your base coats solvent is attacking the none hardened / activated product your going over .
what your going over is called reversible meaning when a solvent gets on it it wants to return to a liquid state.
the wetter your putting on the base the worse the winkles get.
you would need to sand what's on there and then spray a isolating product down like bar coat or a waterborne primer.

Will a primer sealer work?

This is one of the reasons I put clear coat activator in my base coat mix.

You can sand that area flat and then scuff the rest of the panel with a gray Scotchbrite pad just to dull the shine. Then apply an inter-coat clear, which is basically a clear base coat over the blend area.
After that you spray a light coat of base just over the sanded area, follow that with a coat slightly larger than the first in all directions and repeat with a third coat. If everything looks good, I like to shoot one more light coat over the entire panel. Then you can move on to your clear coat.

If you don't have access to inter-coat clear you can use the following formula to reduce clear coat.

This is how I mixed the clear 3:1:9..... 3 parts being the clear; 1 part activator; 9 parts reducer (slow is preferred).

I used this mix to fix this sand through on my signature car.


After clearing the whole panel:

Fixed. I'm pretty happy with the result now. Live and learn. I resprayed with my 2K primer, sanded and resprayed. Its a Mopar engine bay. It has to look good!

The urban myths are flying strong here.

First thing to understand is that it is primarily hardened, not unhardened, paints that are subject to this problem. Some thermoplastic paints suffer from it too, but generally unhardened paints like acrylics (aka lacquer) do not. On older paint substrates the issue usually manifests in edge mapping and this is where the solvent(s) in the base coat being applied soften feathered edges on the substrate, causing wrinkling as the solvent gets under the exposed (usually) primer.

It can happen with fresher hardened paints as well. Although clears (for example) are hardened they take some time to fully harden and cure, especially lower down in the layer. So the surface may appear hard but underneath it still has some solvent and that solvent may take a few months to fully evaporate through the surface layers. This is why we never seal fresh paint.

In this case the clear was only a week old. Now some clears won't present a problem for recoating even after a day but others take much longer and care needs to be taken. See your TDS for more information on recoating times.

So, what's happened is that you probably put it on a bit thick - hence the runs. Thicker means slower curing. Then you sanded back with P600. This is too coarse even on a much better substrate but on relatively fresh clear it really opens up the underlying part of the clear and increases the surface area for the solvent in your base coat to attack. Add subsequent application of the base way too heavy and you're just asking for it to fry up.

Sand it back smooth using quite fine sandpaper - I like to use P1500 but you could go down to P1000. Now apply either a sealer or a little primer. But apply in multiple very light coats with lots of time in between for flashing off of the solvents. It must never appear wet. You may need 8, 10, 15 of these super light coats and the surface may appear overly dry once done. Don't worry. Allow to fully dry/cure and then sand back gently (again with fine grade papers) making sure that you don't get any rub throughs. Now re-apply your base coat, but lightly. It might take a few coats but never wet enough that the paint looks wet on the surface, yet not as dry as you did with the primer/sealer. You don't want a sandpaper like dry finish. Once you've done a few light coats your last coat can be a little heavier, but only just enough to get the application even. If it sits wet then the solvents may soak through and you'll be doing it all again.

Allow to flash thoroughly then reclear.

Edit: Oh good, two replies since I started typing this. 68's solution works, too but it looks like you've achieved the result by isolating the substrate with primer. Obviously works, too.