The patent info/description Bob provided is worth a look-see.
Rogers invented machinery for sand-blasting the tubes prior to the coating process. I always wondered how they got the paint to stick to glass, and now I know.
Grigsby-Grunow’s spray shielding must have been pretty primitive compared with Rogers. Some of my GG Majestic shielded tubes are losing large chunks of the coating.
Eric S.
