Fermentation Temperature Control, Part I: The Wet T-shirt Method

One of the things that will greatly increase quality of your homebrew is fermentation temperature control. If fermentation temperature gets too high, it will increase the ester profile and produce fusel alcohols, affecting the taste of your homebrew. If it gets way too high, it will even kill your yeast. If it goes too low, it can put your yeast to sleep, causing a stuck ferment.

There are several ways to effectively control you temperature. The first one is quite simple. If your temperature it getting too high, you can put the fermenter in a tub of water. You can then throw a t-shirt over it, which will wick up the water. The evaporation will cool the fermenter down up to 10° F, or more. For even better cooling, a small fan will get air moving over the thing.

I used to do this, not with a t-shirt, but rather with a white towel. One thing that I noticed, however, is the towel would get slightly discolored with tan water spots after a while. It would also smell kind of mildewy, like clothing that was left wet in the washer for too long before drying. As a result, I started putting a little chlorine bleach in the water so it would keep it fresher longer. The odd smell never affected the brew, though it always concerned me every time I'd do it.

Using this method, I was able to get the fermentation temperature down to about 65° F. This was down from about 78° F ambient temperature of the room it was in. This made summer brewing possible, even in the desert, where I live.

NEXT TIME: Part II, Using Ice to Control Temperature.