Well, I am back with some results and I think they are very encouraging.
Here are the test conditions,
Temp: 70 F
Solution: 20 ml NaOH 25% solution in distilled water
UUT: 2.5 inch x 1/2 inch strip of PET, approx 12 mils cut from a food container (cherry tomatoes if it matters)
Procedure: Using a kitchen shot glass, 1/2 of the PET strip was dipped in the NaOH solution and evaluated at 5 minute intervals up to 30 minutes with the exposed part of the PET serving as control. A further check was made at 60 minutes and a final at 6 hours (360 minutes). At the end of each interval the strip was rinsed in clean water and dried. Clarity and wettability (is that a word?) was evaluated against the untreated portion of the strip.
Clarity: The clarity of the strip did not show a noticeable change throughout the test. It appears a clarity change takes longer than 6 hours.
Wettability: At 0 minutes, wettability was nil. Water dropped onto the strip beaded and ran right off. At 5 minutes, wettability was clearly improved although there was still significant beading. At each 5 minute interval wettability improved up to 30 minutes. However, there was still (but much less) beading even at 60 minutes. Wettabilty might have been acceptable for coating at 60 minutes, though. (Had to leave home for some other business at this point.) Last check at 6 hour point: Beading was nil at this point and water dropped on the PET strip spread into a smooth layer. While wettability might continue to improve, the strip compared favorably to the overnight sample, without the cloudiness.
The NaOH is granular lye drain cleaner from the hardware store. It's reputed to be quite pure. The ingredients are listed as 100% NaOH.
At this point, I believe you would want a 6 hour soak in the NaOH to prepare PET for subbing. While higher temperature might reduce the soak time, I think we can see why this wouldn't compare well to corona discharge for an industrial process. But for home brewing, if we're just making a few feet at a time, I see no reason why this method could not be used.
Any chance someone else can try this to see if the results can be repeated? I do not have any unsubbed PET film on hand. If anyone has some could they give it a try? I am thinking about getting a small roll of Graphix Dura-Lar but I don't think I'd be able to get to it before next week.
(Wow, I love this stuff!)