Fermentation Temperature Control, Part II: Son of Fermentation Chiller

As I mentioned last time, the easiest way to drop your fermentation temperature is using the t-shirt method, where you put your carboy in a tub of water with a t-shirt over it, and evaporation cools the fermenter. The problem with this method is that it only drops the temperature; it does not control the temperature.

The reason why temperature control is important is that most yeast strains have a ideal temperature that they work at. These temperatures can vary from yeast strain to yeast strain. For instance White Lab's California Ale (WLP001) yeast has an ideal fermentation temperature of 68-73°F, while White Lab's English Ale (WLP002) yeast's ideal fermentation temperature is 65-68°F. Both of the yeasts mentioned above are ale yeasts. It gets even more strict when you get to lager yeasts.

Using the t-shirt method you cannot set the temperature you want to ferment at. You are still at the whim of the environment to set the temperature. The temperature can change depending upon ambient temperature and humidity. For instance, if you are fermenting say an English bitter at 65°F, but a storm moves in pushing up the humidity causing the fementer to warm up to 71°F, you could end up with off-flavors. This is where the ice comes in.

A homebrewer could simply add ice to the tub of water mentioned above, but that is similar to the t-shirt method in that is does not control temperature. What you really need is a way to set a temperature.

There is a method that is popular among homebrewers that uses ice that can strictly control temperature and it works like this: Using an insulated box with two chambers, the brewer places the fementer in one chamber and the ice in another chamber. He or she can then rig up a system that blows air into the ice chamber, cooling it, and then through the fermenter chamber, via a computer fan hooked up to a thermostat. This can keep the fermenter's chamber at an exact temperature set by the thermostat.

Ken Schwartz, a homebrewing gadget pioneer, published plans on the internet for building such a contraption in the late 1990s, which he called Son Of Fermentation Chiller. Homebrewers around the world built this chiller box according to his plans, giving them exact temperature control for the first time, including myself. I used it for several years before moving to refrigeration.

Below are pictures of the thing:

A picture of the fermentation chiller closed up, facing the left side. You can see the thermometer and running LED mounted on the upper right corner.

Another view of it closed up. The plans called for dowels to hold the thing shut. However, I never did that. I used books to weight it instead.

This is a close-up to the thermometer and running LED on the outside. The thermometer is an indoor/outdoor thermometer from Radio Shack. The LED indicates that the fan is running.

This is a view of it with the top and front removed.

This is a view from the top and behind, showing the ice chamber. The ice is kept in bleach bottles filled with water which are then frozen.

This is a picture of me placing a bleach bottle filled with ice in the ice chamber. The ice needed to be changed every three or four days.

This is a view from the front with a carboy sitting in it. You can see the thermostat and fan above the carboy.

This is a close-up of the computer fan and thermostat. Unlike the directions, I use a digital thermostat that is battery powered. The plans called for an analog thermostat, which I found not to work well.

This is a picture of the thing in use. Here, I am pitching yeast into the carboy.

NEXT TIME: Part III, Refrigeration