2K question? Solvent pop or contaminant issue?

[Dpate]

So I didn’t see this while clear coating, but noticed it after the 2K was drying for a bit. Did this happen being too impatient between coats or somehow something was on the paint of the hood, and I didn’t notice it or something? Just wanna figure this out for non future mistakes. This actually first time this has happened as well. 

[Ace-Garageguy]

The divot is a fisheye due to contamination. Could be a single piece of dust that has silicone residue on it, or even a piece of pollen.

And it's nothing remotely like "solvent popping".

But boy howdy...that clear sure looks like you hammered it on thick and fast...and that IS a good way to get solvent pop...which the divot is NOT.

Edited May 28, 2024 by Ace-Garageguy

[Ace-Garageguy]

"Solvent popping", by the way, looks like extra metallic particles, or sometimes light areas in the clear, particularly where it's heaviest.

What it actually IS is thousands of tiny bubbles trapped in the clear, bubbles of solvent vapor that couldn't evaporate because too many coats were hammered on too fast with insufficient flash time, or in elevated temperature and humidity that made the material "kick" before solvent evaporation was complete.

The bubbles will NOT sand out, and the only fix is to remove the entire coating and do it right.

EDIT: I've been using "2K" products since they were first introduced to the automotive body repair and paint industry decades ago...on full-scale things and models.

EDIT 2: Worst case of solvent-pop I ever had to deal with was on a Superformance Cobra repair I did for Chuck Gutke at Cobra Restorers. The temps were in the high 90s, as was the humidity for days on end. Every shop in town was shooting their paint late at night, because in many cases, even the slowest reducer and hardener wasn't enough to keep clearcoats from popping. I shot the car twice in the daytime, it popped horribly...and I had to sand it all off. I finally shot the thing at 04:00, and it was OK.

I've pretty much seen it all. The chemistry and problems are identical.

Edited May 29, 2024 by Ace-Garageguy

[Dpate]

3 hours ago, Ace-Garageguy said:

The divot is a fisheye due to contamination. Could be a single piece of dust that has silicone residue on it, or even a piece of pollen.

And it's nothing remotely like "solvent popping".

But boy howdy...that clear sure looks like you hammered it on thick and fast...and that IS a good way to get solvent pop...which the divot is NOT.

Picture making it look thicker than it really is. Only 4 coats with last coat being thinned more. One of my better 2K jobs with no orange peel just few dust specs, and now this fisheye issue.  Can that spot be sanded carefully, and re cleared? Or we’re talking about a complete redo? If so I’m just gonna sand, compound etc as normal. 

[Ace-Garageguy]

12 minutes ago, Dpate said:

Can that spot be sanded carefully, and re cleared? 

Honestly, it looks to me like you might be able to sand most (maybe all) of the divot down flat, then polish it as usual.

You'll need to cut the divot flat, so you'll need to use a sanding block of some sort.

I'd recommend hard rubber. Just sanding with no block, you'll ride over the divot without knocking it down, and there's also the likelihood you'll make a wave.

Work carefully and don't get in a hurry...because you don't want to go all the way through the clear. If you DO, you'll have to reshoot the blue too, so stripping it would be best if that happens.

Use plenty of water and squeegee it off frequently to see if it's flat.

4 coats of clear will most likely be enough to sand that out without even having to shoot more clear.

Still, the worst case will be having to shoot the whole hood, which really isn't too bad.

AND...the problem with trying to only airbrush the sanded area is that with 2K, you'll get a "blend edge" that won't polish out, because catalyzed clear doesn't re-wet like lacquer.

 

 

 

[Michael jones]

I had something like this once, and just put a drop of 2k clear into the "hole" and let it cure. Then sanded it flat. Worked pretty well. If your compressor uses oil, this might be the reason why.