Jason, those are fantastic test ideas; thank you very much!

Here's the test from patent 2,014,547:

The stripping test usually comprises two parts, namely, dry stripping and wet stripping. The wet stripping test is carried out as follows: A strip of the emulsion coated film of convenient size, say 6 to 40 inches, is soaked in water at 70°F for ten minutes. It is then removed from the water and fixed on a flat surface with the emulsion side up. The emulsion is then gouged or creased with the finger nails at points near the middle and end of the strip. Each nail scratch tears the emulsion away from the support to a certain extent. The scratched places are then rubbed with considerable force with the balls of the finger tips for several seconds. A film is said to have satisfactory wet stripping (emulsion adherence) properties when no peeling, or substantially no peeling, of the emulsion occurs as a result of this rubbing action. Wet stripping is said to be unsatisfactory when an appreciable or large amount of the emulsion comes off. For most types of film it should not be possible thus to remove pieces wider than 1/4 inch by this test.

Is the terphthalic acid coming from the PET and "poisoning" your NaOH subbing bath? What about the ethylene glycol, where does that come from? It's a very clever theory, and seems like a good explanation if you're discovering that the peeling sheets are those which were treated in this potentially compromised bath.

Unfortunately my coatings have no hardener in them, so I might have to harden them or lower the temp° of any wet tests.