Hello all, I had something happen to me a couple hours ago that has never happened before. I am re-painting the front bumper of my 2016 Hyundai Elantra and am planning on using OEM touch up paint (as made by touchupdirect.com). I didn't want to sand all the way (or chemically strip) down to the plastic for fear of marring the plastic, so I thoroughly wet sanded the existing clear with 400 grit, 600 grit, 800 grit.
I then sprayed a layer of Dupli-color Primer Filler (Pic 1), cured for 20 min under IR lamps (plus another 15-20min air dry period)... no problem. I did a very light/brisk wet sand with 800 grit. Looking smooth with no burn through.

I then sprayed a layer of Dupli-color Sandable Filler Primer. Again, cured for 20min under IR lamps + 20min air dry and a brisk/light wet sand with 800 grit and 1000 grit. Looking smooth, no burn through.

I then sprayed a layer of Dupli-color Primer Sealer (pic 3) in preparation for the color coat. Whilst I was misting on the tack coat and watching for any reactions, I see some crazing (at least I think that's what it is) and strange long scratch marks that just appeared out of nowhere! (see Pics 4-7; the last being "color enhanced" to make the defect more pronounced). I stopped spraying and let it sit for a couple of hours, then took the aforementioned pics.
I have sprayed this Dupli-color "3 primer combo" MANY times in the past with no problems at all, let alone this reaction. All three are lacquers, so I have no clue what is going on here. Any thoughts?!?!?

Looks to me the top coat dissolved the underlying coats.
Maybe it wasn't dry enough between coats?
Maybe the top coat was applied to wet?
Lacquers can take a long time to dry, was it colder this time?
I'm just guessing here but something was different.
You're going to have to sand down past the problem,
once you do, try and get it sealed before moving on.

First, are you sure all products are lacquer? I'm not familiar with DUplicolor products, (don't like them) and I know their colors are lacquer, but are the primer and sealer?
If so, I've NEVER had a reaction of lacquer on lacquer. I don't think it's possible. Lacquer always dissolves the layer under it, and melts into it. That's it's chemistry.
More likely it's whatever's UNDER the lacquer that is reacting. Freshly sanded urethane clear often wrinkles at the edges. COld makes the problem worse, as it takes longer for the thinner to evaporate, and gives it time to attack whatever is under it. The sealers, I don't believe are very good at preventing this, they're more for having a uniform color under the paint, and perhaps to keep the hardener in bondo from leaching up into the paint, and staining it.
I used to spray lacquer all the time, up until the mid-late 80's.

you've got something under there that's reacting to the lacquer. i have found that doing TINS its best to strip all the old paint. its not that big of a job and your problems are over.
Jay D.

Thanks so much for the insight all.
Yes, I'm sure they are all lacquer, according to the TDS on Dupli-color's website.
Yes, it did happen to be pretty cold when I was spraying, so perhaps I didn't wait long enough for the previous layers to dry.
Will sand down and try again! (story of my painting life...

I thought that the Koreans had given up using that thermoplastic rubbish on plastics. Seems maybe not.

When I get something that has been finished in that stuff the only option is to remove it all, back to bare plastic.