What sort of plague is this...

[Discseven]

The surface you’re looking at was painted about 7 years ago. The finish was excellent all around when the car was completed back then.

Over time, welting has appeared in varying degrees in limited areas. The front hood has it the worst. The rear hood comes in second place. The rear fender flairs come in third.

Front fenders as well as the doors and remaining parts have absolutely none of this. All these parts look excellent.

For the painting 7 years ago, I replaced the front hood with a good condition used one because it was less costly doing so as compared to dealing with the dings and rust presented by the onboard hood. Based on the original appearance of the dampening and paint on the inside of the replacement hood, I have to rule out that hood having been in a fire. The fact that "the plague" is occurring on the car's existing metal areas and on the replaced metal... this might suggest something.

I'm not a paint & body expert so when I had the car painted last, I had to leave it to them to decide how to do it. The shop came with a good friend's recommendation, they do all kinds of vehicles from new to classic, and I looked over the cars in-house before proceeding --- everything suggested a quality shop.

I’ve spoken with the same manager now as I dealt with years ago to see about getting this situation corrected. (Why not give them a chance to make it right.)

They’ll get the front hood as a test.

Before delivering the hood…

I’d like to know what I’m dealing with and if you have any recommendations.

(The body shop suggested I replace the hood. Not happening again because… while that might solve the hood problem, there’s still the issue of the rear hood and rear fenders --- the point of doing the front hood is to see if they can correct the problem. If so, they can treat the other parts to the same procedure.)

Various views from front hood:

[962porsche]

it looks to me that they did not us a etch or epoxy primer over any bare mater spots . if you don't use a E-type primer over bare matel the finish will start to blister later on down the road . you may see at as soon as a year on car that are out in the elements every day to years if you only use the once and a while .
any bare metal spot bigger than a quarter you really shoud spray a coat of E-primer down 1st before you spray any filler type primer .
in my shop i make it mandatory to spray E-primer over any bare metal no matter how big the spot is of bare metal . on cars that are in for a resto it really is a must for the simple fact that for the most part cars like that do not get driven every day so insted of the 5 years the paint should last on daly drivers it's more like 10 to 15 for restored cars that the finish has to last .
paint CO's only for the most part warranty finishes for 5 years at the most . after that it's up to the shop to warranty the finish .

[slcarr]

That is what it looks like to me also, etching is something no body seems to do, I do a 2 part, metal cleaner and then a conversion coating with metal conditioner ( I think it is phosphoric acid). I chemically strip everything that has been repainted, if it is original paint you can not get a better substrait. I have been restoring cars 43 years and have never had a come back because of problem with primer over bare metal, and yes I do use epoxy primer before primer surfacer, but in the old days I never had a problem using red oxide or grey lacquer type primers as long as it was etched. In your case if you are in a high humidity area that could be a issue or if the air compressor was not purged it could cause the same problem even if epoxy primer was used. Steve

[962porsche]

yes when we were only using lacquer base products they did stick to bare metal substraights . the big reason for that was that the primers back then had a alkaline base to them . there is also the fact that ferromagnetic ( red oxide ) is a iron base product . iron will bite into it's self ( the metal substraight ) .
the old gray lacquer primers would bite into metal but not as good as a a red oxide would . the main reason is that there was no iron oxide in the gray primers there was only a alkaine . alkaline is a acid the down side to the old products is health .

with the panels in this post i would guess that the hole panel was not stripped to bare metal but only were there was a chip or other imperfection that needed to be sanded out . but like always it's hard to tell from a photo .