I have no idea what happened but during cold crash my blow off tub did a reverse siphon and sucked in the sanitizer from the blow off bucket. I also have another layer that I think might be clarifier solution? Pretty sure this is one too dump… would appreciate any insight on what I did wrong.
Details: after secondary I put in a clarifier and set the fermenter to 3.5 degrees Celsius. Sat for seven days and came out like this. I know one layer is santizer solution because the santizer in the blow off bucket was all but gone.
When warm wort cools it sucks. Literally. All you did was learn that suck back occurs because, as the air in the headspace above the wort cools, the air contracts. The contracting air pulls the liquid backwards through the lock. The same effect will happen when crash-cooling beer post-fermentation, if using a liquid air-lock.
I chill as much as possible then drain to a fermenter and cover the blowoff port with foil. Once to pitching temp, I pitch yeast and hook up the blow off tube. When I remove the tube I always remove the blowoff jug side before the fermenter side which seems to reduce issues.
A S-style air lock would have been better than the blow off tube assembly. Hind sight though. How much sanitizer and what was the sanitizer? A blow off tube assembly can be fitted with a reservoir in the middle that is larger than the volume of the sanitizer to prevent this. More work and cumbersome when moving a fermentor.
You don’t need any type of air lock when cold crashing. Just plug the air lock hole. Pressure inside the fermenter will drop below the pressure outside the fermenter but that is okay.
I switched to using cheap vodka or rum in my airlocks. I don’t seem to have as much loss to evaporation or bubbling as with starsan. Plus when I chill and get suck back there’s a lot less to worry about. 1/2 oz of vodka isn’t going to hurt anything in a 5 gallon batch.