I make beer alot and I have plenty of 7.5 gallon glass jugs. When i make beer, I always ferment in those and use a simple tube over into a bucket of star-san for an air lock. I just never do it with corn mash.
I have been asking around and it seems that this film is common. I thought i had never seen this film before except.........now i do remember. I just did not think about it since it was in a post here.....viewtopic.php?f=39&t=7002
Now I can eliminate a few variables.
Maybe it is some form of aceto bacteria. Starting to turn the alcohol to vinegar? I have never tried to make vinegar, but I think we are seeing the start of this process. The start of a formation of a vinegar "mother".
I recently did something I have never done before. I let a batch turn to vinegar because I did not have time to run it. I was out of town and a friend checked it and she said it smelled like vinegar and I had her throw it out. But I did not see what it looked like. Now the film shows up......hmmmmhttp://hbd.org/cdp/vinegar/vinegar.htm
Isn't nature a miracle? Take corn and put it in a bucket of water. Lacto gets it , then yeast gets it and makes alcohol, then bacteria gets that and makes vinegar and then eventually bacteria turns that to water and co2. Amazing