paint bubbles

[1970 FM3 Cuda]

Looking for some paint bubble help. I am getting ready to paint my convertible challenger. This car had a complete rotisserie in 1991 with whatever type of paint they used back then. I am not taking this car completely down and performing a rotisserie. I am just looking to paint jams, trunk, under the hood, and outside. The question I have are these bubbles should I dustless blast this? Should I just sand it to metal? The bubbles are between the primer and paint I think they are from the clear plastic they put on the car to store it, when I got the car, it had sat for 15 years in a barn with clear plastic on it. Under the hood, in the truck, and under the car no bubbles just on the sides and tops of the flat surfaces. The top of the truck lid looks like goosebumps the sides have bubbles that you would think are rusted-out metal. I have popped these bubbles on the side and the metal below is good, I had sanded the primer off to get to the metal.

So, my question do I blast this car? Do I just sand it to bare metal? do I take the engine bay, door jams, and truck to bare metal even though it doesn't have bubbles on it?

I have been told this happens because of water in the paint job.

Open to your thoughts. Thanks in advance.

[Mr Cuda]

 Oh man, where to start. 
40 years of auto body  experience.  Yes, plastic can cause paint bubbles.  Usually very small pimples,  from moisture being caught under the plastic.  So not a problem inside as much as covering a car outside in the rain.
But those are not paint bubbles.  That is massive blistering,  and the one blurry picture shows rust underneath,  with what looks like a pinhole.
So the answer to your question about how to prep means taking a small grinder to the bubbles,  and to a good area.  Is there rust under every bubble?
And is the paint bonded well under the "good" area?
I would say with that much defect, blasting will be required.
If you are trying to preserve any work underneath the surface (metal work), then you will have to mechanically strip the car and blast the bad areas.
So get some better pictures,  and grind into one of those areas.

[torredcuda]

  The whole car needs to be stripped to metal as there is rust, very poor prep or moisture underneath before or during priming/painting, if you don`t strip to metal you may have the same issue again. How you strip is your choice - media blast, dustless blast, mechanical strip (grind/sand) etc.

[tparker]

I'm not a paint guy, but I did paint my car. After lots of research one thing that stuck in my head is your relying on the quality of work someone else did as the foundation to your paint. Do you trust that paint? I don't think good paint should bubble like that, but what do I know, as I said I'm not a paint guy. There could be water and perhaps rust up under that paint. Plus that paint is already coming up. If you fix the problems you see, then paint over the rest, will other areas have problems in 2, 5, 10 years? Probably best to sand to whatever is under, metal or original paint if it's still there. Not sure if there is any reason to sandblast it. might be easier, but probably messier. I kinda enjoyed sanding mine down to metal. There was something satisfying about it. 

[71vert340]

 I saw this once on a car that had been stored with a plastic cover on it and a blue poly tarp over that. It seems the moisture from condensation built up under the plastic, since it couldn't breathe, and did this same thing to the paint. Had to take it down and treat the rust pits and repaint. No easier way to take care of the problem. When I store a vehicle now in a non-heated environment, I always use a breathable cover.
Terry W.

[anlauto]

The question sounds simple, and I think you already know the answer, you just don't really want to hear the answer....
However, the answer is a large YES !!! The entire metal surface that you intend on painting should be stripped to bare metal and start from scratch.

With the high cost of body work products, primers, sealers, base coats, clear coat....you're only throwing money away by not doing it the correct way...