Technical What's Going On Here with My Paint?

This is on my 47 coupe that was involved in a rear end collision. The shop replaced the trunk lid, straightened out panels and repainted the back of car extending up maybe over the full legnth of the top. Some time later I started to notice these grooves under the paint that were not there when I got the car back; and the issue seems to have gotten more pronounced over time. Is it possible that there is a thin layer of body filler under the paint that has shrunk, resulting in these grooves or scratches under the paint?

They are hard to photograph, but if you look closely you can see them in these photos of the back panel between the trunk lid and the rear window. The trunk lid does not show any of this, it looks good, just the panel below the rear window, and the panels on both sides above the rear fenders.

 

They are sand scratches showing through. The shop didn't get all the coarse grit scratches out before they primed then probably pounded on the primer to fill the scratches and it has now died back.

Those look like pretty coarse scratches to start with which is a no no these days. Poor work all the way around.

 

Yeah, something has shrunk, whether it's primer or bondo remains to be seen.

If it's single-stage paint, is there enough paint to cut and buff it out? Although you may want to wait to make sure it's done shrinking.

 

Assuming that's the blend out, or where each quarter repair would meet, It seem's as if the old paint got activated by solvents... Just a guess...
Sure it'll be two pages by tomorrow

 

Damn, hard to believe they would leave those scratches and fill them with primer.

 

I think they are too un-uniform to be sand scratches.
No mater what, it's not an easy repair. Likely the primer surfacer was too thick, and and wasn't allowed to fully dry before the topcoat was applied.
Will need to be stripped and redone.

 

I'm no pro, though I paint a car a week, in my opinion, that's lacquer primer cracking under the paint. Little too heavy on the primer in my opinion.

 

Shrinkage.
looks like some straight line sand scratch issues.
Or primer stacked up starting to crack or cracked primer not completely removed and painted over.
Also looks like a blend or feather edged area that has shrunk or the materials used are not happy with each other.

what looks like a very course scratch is often magnified when painted.

 

This is one where I'll say that WON'T buff out!

 

If it is sand scratches showing due to the primer shrinking, hit it with some 2000 wet and buff it.

 

If they are using lacquer primer in this day and age at a body shop I would have serious reservations about taking anything to them.

 

I have done that myself and I am no painter....

 

Those look like cracks to me. The primer is probably not compatible with whatever is underneath it.

 

That looks like primer too thick and not allowed to dry properly before being hit with colour. In 12 months time you will have some large areas of cracked paint. Take it back to the shop that did the work. (Yes, I was a spraypainter / panelbeater in a former life).

 

Happens more often than you would think or hope. The scratches are hard to see until the first coat of primer goes on then the paint shop doesn't want to waste time sending it back to the body shop as its in line for the booth so they hit it with a few extra coats of primer. Known as primer abuse in the collision industry.

Lots of other suggestions have been offered but in 18yrs of going to shops and not being able to see it in person I have never seen perfectly straight lines under paint caused by anything other than sand scratches.

 

This shop has done 3 repairs for me, 3 different cars, all insurance jobs, and besides this issue the work has been top notch. I will take it back to the guy and get his response. After the work I've brought him I think he'll stand behind his work.

 

And especially when they try to build or bridge the gap with it! I haven't bought lacquer primer in quite a few years. Quality urethane primer is too affordable to have to redo work due to being cheap

 

I'm sure they'll fix it man.

 

Someone was probably in a hurry and cut a corner. It happens a quality shop will stand behind their work.

Lol no kidding. We still sell a fair amount of Lacquer primer to our distributors but they sell it to guys doing work out of their garage and I cringe every time I hear someone bought some. It's not even cheap anymore if your not using gun wash for a reducer.

 

Oh no shit. I think the last time I bought lacquer primer, it was around $60 a gallon? And you could get a 2K urethane kit, 5 sprayable quarts, for $100. With the cost of everything else associated, base, clear, etc, it's not worth the gamble. That's why I stopped using it. A year of sitting in the sun would ruin an otherwise nice paint job, and I had to redo it for free. With that said, I have also seen urethane crack like this, it's still not meant to replace plastic filler lol

 

I retired from the smash industry 40 plus years ago to work in an industry that paid better with less stress so I went truck driving instead. I still do the occasional repair job for myself and still use lacquer primer. You can do a repair section, grab the primer gun and squirt a coat on and move onto the next bit without worrying about the neighbours complaining on the smell or covering surrounding areas to avoid overspray. Plus it can sit in the gun for weeks and just needs a stir and a bit of thinner and away you go. Just call me old school.

 

I don't think you can even mention the name Lacquer in California

 

There was an old man that ran a body shop in Ashland Kentucky named Denver Jobe. He was well known around these parts. He always used lacquer primer. I went in his shop about once a week or so doing glass and would always chat with him. I asked him about using lacquer primer and his reply was as long as you don't try to bridge the gap with it you'll be fine a lot of the shops was trying to fill 80 grit scratches with it, and that's what got them. I finish with 180 before I prime. I had a couple of jobs that I had to go back and redo because of the primer failure, and that's when I decided not to use it anymore. Everybody does things their own way, and there's nothing at all wrong with that

 

True. I wish you could still get it; best for an amateur painter...of which I am.

 

About the best part of it is working time. Since it started going up in price, it's not really that affordable anymore. Depending on the area you're repairing, you can buy a spray can of 2K Urethane fairly cheap, and other than cure time, you'll love working with it. I use Roberlo primer, and it's freaking amazing to sand.

 

Evercoat makes a VOC compliant lacquer primer and reducer. DuraBuild 2.1.
https://www.evercoat.com/product/dura-build-2-1-gray-gal/
We sell it up here in Canada where we have the same VOC laws.

 

I use a lot of the evercoat filler in the blue and white can, can you hook a brother up? Lol

 

The lines are straight but not parallel. I would guess it is a solvent issue. The top coat did not like what is under it. It might be too much or uncured primer, but I think it will be whatever is under the primer will be the issue. I have made a lot of dumb mistakes with paint jobs in my life to have a good idea what causes most problems.

 

The age and type of paint the car had is a part of the equation.
was it blended within a panel?

sometimes we had to get creative with existing finishes at feather locations. How we bridged the old with the new.

 

Looks like it's time for a sandpaper autopsy.