Shrinkage

What I imagine happened is the edge was lifting the lacquer, and not the epoxy. Thinner softened the lacquer, swelled the scratches, and didn't soften the epoxy. Two different materials next to each other tend to do that, especially something as different as lacquer and epoxy.
Bingo..i saw this today.
I had a spot on the side and can see the elevation diff from original laquer to our epoxy...if tgat makes sence. Tge line horizontaly showed us tge laquer loiked raised compared to epoxy side, not ebough tgat i could feel it but i could see the raised edges.
From now on we will be priming full panels if using old laquers to prevent this, or at least seal whole panels before painting, personaly not a fan of using sealers unless i realy have to. Ratger spend my time on metal work and fillers to not burn through.
My next project was done in base clear so shouldnt be any issues..
 
Agree with TK it was the lacquer lifting/moving about rather than the epoxy. Like your buddy said that's typical for trying to spot repair lacquer, especially NC lacquer. Acrylic you have a slightly better chance but NC is very susceptible to swelling when spotting it in like that. Let it dry a few days, lightly wet sand with 1000 grit or so in the mapping area, then blend out further with more coats (hopefully you have more paint). Don't go crazy sanding the area just get it down some then spray more coats extending out past the problem area. Then cut and buff.

In the future don't spray it as heavy as you did. That greatly increases the likelihood that something like this will happen. Spot repair you have to creep up on it. both with the sealer and the color/clear. Ideally spot repair with NC or Acrylic you would use a single stage acrylic sealer and dust it on. Especially as you get to the edge of the repair. Dust it, two coats of sealer if you have too, because of how light you are spraying it. Nib sand between coats if neccesary to knock any roughness down. Then light coats of lacquer until you get coverage. Then let it dry for a few days and go back and spray several more coats (3-6) still pretty light but slightly heavier than before. Then you should have enough to cut and buff, but you still don't want to get to aggresive with it. Sand the minimum amount to try and preserve the amount of millage on the panel. Don't hammer it with the buffer either.

And remember a (nearly) undetectable spot repair in NC or acrylic is a completely different animal than when doing a blend using modern materials. You have to allow a lot of flash time between coats. That is critical. A proper spot repair on NC or acylic will take 2 or 3 times as long as doing a blend using modern materials.

I love epoxy as much or more than most anyone but the time to use epoxy under lacquer is when you are doing a complete bare metal job.
 
I'm following this discussion but even as an "oldtimer" I have very limited experience with lacquer. When I did use it, it was with other lacquer materials, at that time I had barely heard of epoxy primer! I do remember being really surprised once about 10 years ago, we primered some scuffed jambs on a virgin 1970 C10 survivor truck with some epoxy, and I will be damned if the blue GM lacquer didn't bleed through and stain the epoxy! It was crazy. From now on it's strip all old finishes, no exceptions!
 
Starting out I was fortunate enough to work with several old guys who had a lot of experience. One man in particular taught me a lot. He was right at 70 (he didn't want to retire) and had been in the trade since he was 16. He started in 1937! He knew a lot and could do anything.

Even in 1991 when I was starting out, lacquer was not being used very much, but you could still get it and even NC lacquer pretty easily. GM though used lacquer on some cars right into the early 90's! Caprice's were one that was lacquer until they changed body styles in 1991. I did quite a few blends on those Caprices using lacquer. Shop we were at did a lot of old stuff that was originally NC lacquer (Packards, old Fords etc) and I got a little experience doing those. I miss that Shop and those old bastards:))) but I don't miss blending lacquer. Or lacquer primer. :)
 
You guys are making me feel old.................Wait I am old and I do not miss the lacquer primer. When working at at a Oldsmobile dealership 1973 era, lacquer was standard finish and very touchy but would blend very well over the GM original finish ( sometimes ) The painter use to wipe off a panel and blend then right out in the sun. With Crash now even a hint of lacquer on an older car will strip to bare metal.
 
I'm following this discussion but even as an "oldtimer" I have very limited experience with lacquer. When I did use it, it was with other lacquer materials, at that time I had barely heard of epoxy primer! I do remember being really surprised once about 10 years ago, we primered some scuffed jambs on a virgin 1970 C10 survivor truck with some epoxy, and I will be damned if the blue GM lacquer didn't bleed through and stain the epoxy! It was crazy. From now on it's strip all old finishes, no exceptions!
This one would have been fine if we primed full panels. He mentioned to do it that way but i mentioned it was a waste of materials. No swnce priming fulk undamaged panel to repaibt. But in laquer i find you do have to now lol. Or at leaat blast it in a sealer to full cover any laquers.
 
This was only spot in primer on repairs. Got a complete repaint.
When laquers were used i was still only doing metal/body work. Didnt get into paibting till acrylic enamel days..another pain to blend out
This was only my second laquer paint job, first was on the 32 model A we also just completed a month or so ago. . Sitting a bit till we final sand and polish.
Next one im doing i think is a 34, all done in base clear. My world lol
 
It is a finiky paint to use. Personaly i hate it and see why its a thing of the past.
Its always moving being non activated and only reduced, or thinned. It did settle down a bit when i walked in yesterday after sittibg overnight. Hope its not to bad today when i go to work.
I point to the paibt being the issue and is what it is. It will be fine once sanded out for polishing.
Just thought maybe someone had issue similar and a solve for it other than having to epoxy full panels if using old school laquers
What solvent did you use in the Nitro? Whenever a soluable product like that old lacquer gets a chance to pull in some solvent it will swell and in extreme cases turn liquid again while the nonsoluable products like 2K urethanes and epoxies won't-you'll see mapping because of this. And when it's really bad some 2K products will lift or wrinkle up.
 
What solvent did you use in the Nitro? Whenever a soluable product like that old lacquer gets a chance to pull in some solvent it will swell and in extreme cases turn liquid again while the nonsoluable products like 2K urethanes and epoxies won't-you'll see mapping because of this. And when it's really bad some 2K products will lift or wrinkle up.
We used valspar thinners on this one.
 
Ive began my colour sand on my previous project. This ones a 32 model A. Also in nitro laquer.
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