I was just looking at my 67 original pinch weld blackout and was wondering how they got such a straight line on the rocker panel. What was the technique to apply the blackout and was it common to all plants?
Have "discussed" the subject with an engineer from the NJ plant but what they were designing never got applied at the plant. Never found one of the workers, yet, that did the job at San Jose or Dearborn but have a visit coming up that might provide an real response. Until that it appears from the evidence it was a mask that was held in place by a worker (main section from front wheelwell to rear wheel opening) while the paint was being applied and from the rear wheel well to rear valance it may have been a hand held mask since we've got a fair number of those examples that travel up the outer surface of the quarter panel rather than staying below. The longer mask may have been hung from above and swung into place during use.
Would have thought that this step might have been automated like the floor pan paint/primer application but the results appear to be different enough for this to not be the answer. Might have been a good idea for the long section but would create a challenge for the rear section IMHO but we'll ask and see what we find out.
Black paint overspray coated any panel that hung down (front frame rail, torque box, convertible seat support....) either a little or allot depending on the angle. In addition blow out into the rear wheelwell (front and rear) was typical as the gun stopped flowing at the front of the wheel well and started again at the rear
IF the pinch weld black out was missed or not done for another reason the paint brush and coffee can of black paint was put to use. We it it pop up from time to time in different years at different plants to make "things" disappear