Tue Jun 03, 2008 5:10 am
From BYO:
"T-shirt method
If you donât have the room or the budget for a brewing fridge, there is a low-tech way of cooling your fermenter. If you place a wet T-shirt over the fermenter, it will cool down the wort inside the fermenter. The wet T-shirt method works because as water evaporates from the T-shirt, heat goes with it. To keep the T-shirt wet, set a pan of water next to the fermenter and dip part of the shirt in the water. As water evaporates from the shirt, water from the glass will wick up to replace it. You can also circulate water over the shirt with a garden-type pump.
You can increase the cooling power of the T-shirt method by pointing a fan at the fermenter. The air flowing past the fermenter displaces the air next to the fermenter. This air, laden with water vapor from evaporation, is replaced by drier air. This allows further water to evaporate from the T-shirt. And, of course, you can always add ice to the water pan. [This works even better if you put a garden-type pump in a bucket and pump water over the tee-shirt. The excess water flows back in the bucket and is recirculated by the pump.]
Another way to further the cooling power of the T-shirt method is to decrease the surface-to-volume ratio of your fermenter. Basically, if you split the wort in your 5ö7 gallon carboy into two smaller carboys, youâve increased the amount of surface area per unit of wort volume.
The T-shirt method is cheap, but only moderately effective. You can decrease the temperature of your wort by 5ö15¡ F, depending on a number of factors. These factors include temperature of the water in the pan, relative humidity, and surface-to-volume ratio of the fermenters."
