Starsan getting sucked into fermenter?

[TheHumanSwing]

So I am two weeks into fermenting a five gallon batch in a 6.5 gallon glass carboy, and today I noticed that my airlock started sucking in the starsan in it. Why is this happening?

 

[highgravitybacon]

So I am two weeks into fermenting a five gallon batch in a 6.5 gallon glass carboy, and today I noticed that my airlock started sucking in the starsan in it. Why is this happening?

Your beer sucks.

Because it's cold and that creates a vacuum in the fermenter because the volume of air decreases. And there's no CO2 pushing out on the airlock.

It's fine. I've spilled enough StarSan in a beer before to count it as a dry hop addition.

 

[iaefebs]

Is the carboy getting colder?