Freezing point of Star San?

I knocked the fermentation chamber temp down to 31 this morning and headed to the office... and then once at work I remembered that I have a jar of (mixed) Star San in there as a bubbler.

You think it is going to blow by the time I get home?

Im going to make a somewhat educated guess. If the air temp is 31, and there are bubbles present in the starsan, it may take longer to freeze, as water in motion (being agitated by the bubbles) will freeze at a lower temp, or take longer to get there.

Im just guessing though.

You're probably OK.
1. It'll take some time for the temperature to get to 31.
2. There is some thermal mass to the star san solution.
3. As foyt20 said, if the beer is in active fermentation the agitation will stave off freezing.

You'll probably see some ice crystals but I'd guess you're OK.

I am hoping you are right (and that is my guess too). Unless our beloved acidic cleaner somehow made the freezing temp higher. Some internet searches today taught me that some long chain alcohols and testosterone <insert joke about adding testosterone> can move that freezing point up a bit.

Just for clarification...it is not bubbling any more (sorry I can see how that could be read in my original post). Just sitting there with a tube in it.

I think you'll be ok. I keep mine in the brewshed in the winter and never noticed it freezing.

Hopefully the acid in star san lowered the freezing point one degree
How exact is your temp control? and where is the sensor placed?