This work is getting a bit complicated. I have tried both positive and negative corona, with different power levels and distances. I have read many old patents now and they describe a very easy way to measure the level of hydrophobicity; place a drop of water on the surface and look it carefully from the side and measure the angle of water drop at the point it separates from the film. Well then, I've looked these water drops with microscope and the angle is around 70...80 degrees, not quite enough according to patents. With this method, I don't have to make test coatings every time.

Now comes the interesting part; as I was making tests, one sample, to which I had given negative corona discharge for a minute or so, did show a significant difference compared to unprocessed sheet; the angle of many of the drops was something like 60 degrees, which would be enough for coating. But, I wasn't able to repeat this results, no matter what I tried -- longer or shorter treatments, different distances, both polarities.

Well then, I've read patents and they describe quite well the apparatus used. I'm going to try that next. They describe an AC voltage with a large DC offset level and positive corona; well, that's exactly what I've been doing. But they describe a totally different type of electrodes than just a wire and plate.

Kirk, grounding the plate gets rid of most of the static charge but there still remains so much. At least it's fun. You can stick the sheets to walls and give them to your friends so they can get funny static jolts etc . And when you take the sheets near to any galvanometer, the needle dances around. The sheets have such a high electric field.

PE; I searched for patents by Yost and found many, and they were good resources, but didn't find the one about corona discharge causing fog. I found patents that describe corona discharge causing mottling in color coupler materials if the corona treatment is fresh. Maybe I'm just blind, or the search engine I use at my university lacks some patents? Do you have the patent number?

I also found patents about purely chemical subbing layer for PET, but it included components not readily available.