This is something that I've thought about for years, but have never actually conducted experiments (other than thought experiments) with.
It seems to be that an airlock (either three piece or one piece) that is properly sanitized and then left dry might actually be more sanitary and safe than an airlock filled with water.
My reasoning comes from the classic Louis Pasteur gooseneck flask experiment where a flask with a curved neck was left exposed to air, but because of the curved neck, sterile broth in the flask never becomes contaminated. (click here for a description of the experiment.)
It seems that water in the airlock might give a medium for the bacteria to travel through, making it less sanitary than it would have been if left dry. This would be especially true if the airlock were filled with water and affixed prior to the wort fully cooling. The cooling wort actually shrinks creating a bit of a vaccum effect, which can suck the liquid in the airlock back into the wort.
I understand that having a bubbler for an airlock is reasurring to brewers, because it gives an indication of fermentation activity, but I'm wondering if it isn't somewhat counter-productive when looked at from a sanitization point-of-view.
I usually put a shot of my wife's vodka in my airlocks, and will probably continue to do so. But simply thinking about it logically, I think it might be better to leave it dry.
-Bob D.
I saw this on another forum and I thought that it was such and interesting idea, that I'd share it with you guys. Kinda unique approach to it.
The only thing that I can think of is maybe the positive pressure keeps things out.
