Originally Posted by BarryK
I guess the question is how much of a sandblast beating would it take to see with naked eye?
Barry, are you saying you have never seen a panel damaged by sandblasting? Holy cow, they will warp beyond repair! I had a 1928 Buick Sedan door that I was going to make into a display for a marketing conference. It was super straight and only had some super minor surface rust on the jambs and some funky paint all over. I dropped it off at a sandblaster that I had do things for me for years. I gave it to him along with a couple 32 Ford truck doors. They were pretty rough to begin with so I didn't care much about them. But the Buick door was going to be epoxy primed, and painted with a SS urethane. I described how I wanted these doors just DUSTED. I don't car if all the stuff is off, just blast the jambs good and the outside just a dusting and I would sand the rest off.
I returned to find that his son had done the job. The doors were totally ruined. That Buick door was warped about two inches! No kidding, it would pop in and out like one or two inches. I shrank it with a torch and water just so it would maintain a shape. I then covered it with a LOT of filler, cut it flat with an 8" orbital and poly primed it. The end result was pretty nice, but boy was that thing heavy.
Here is just one of the threads I have seen where someone has ruined a car or panel.