I just completed a beer on Saturday and I am using a bucket fermenter (brand new from NB with a grommeted lid). I went to check on the bucket today and the krausen had begun pushing out through the air lock. No big deal, happens a lot even though I wasn't expecting such an aggressive fermentation. I know it was technically still an air lock, just with krausen instead of sanitizer in there.
But as I cleaned up the mess and inserted a blow-off tube instead, I noticed something about the lid of the bucket. It sounds like it's pissing air and the lid seems to have some play to it. I am 100% certain that the lid is on as far as it can go, I know it clicked on each side as I closed the lid, and I put my entire body weight on top of the lid just now and couldn't get it to sit any differently. However, if I push down, the lid will move maybe 1/16" down, and then when I release it will come back up that same distance. There's no rubber grommet inside the lid for a seal, but it could very well be just the way the lid works. Also, no idea if this would continue to be the case after the fermentation slows down and finishes. I'm just trying to avoid oxidation at all costs.
Any thoughts? Has anyone ever experienced this? It never happened on my old bucket fermenter so I'm curious.