We now ferment in a chest freezer using a Ranco ETC temperature controller.

I've long since retired the fermenation chamber; however, I'll leave this up for those interested in this very inexpensive and easy to build box.

The Fermenation Chamber

It gets rather hot during the summers in Texas so we need some way of ensuring the beer stays at a temperature suitable to the yeast we're using. The beer will stay in our fermentation chamber for about a month.

A disaster with an oatmeal stout convinced use we needed better control over the temperature of our fermentations. Actually, Sean quite enjoyed our "Butterscotch Stout". I found it undrinkable.

The butterscotch flavor comes from diacetyl. This chemical is secreted by the yeast and is usually reabsorbed toward the end of primary fermentation. We dropped the temperature with a bunt-cake mold ice ring at the wrong time and caused the yeast to settle out before it reabsorbed the diacetyl. Some people like the flavor and in some beers its a desirable characteristic.

Our chamber varies from the Internet plans in a couple of ways. First, it uses a digital thermocouple reader as opposed to an analog thermostat. Second, we had planed on using a larger fan, something we had on-hand, so the divider between the ice chamber and fan chamber (for lack of a better term) had to be reduced. We eventually decided the original plan of a small 12 volt computer fan was superior but kept our modifications.

In this batch we've 10 gallons, five in each of a 6.5 gallon carboy and 5 in a corny keg with an airlock set into the oval opening. The long beer-out tube has been replaced with a shorter gas-in tube.

Construction Details

Plans abound, click here and you'll find the original Son of Fermentation Chiller.

The Process

After pitching our yeast, the carboy with airlock goes into the chiller. We typically ferment ales at 69°. When the carboy first goes in, the system cycles quite a bit. It takes a long time to chill ten gallons of liquid!

We typically put 2 gallons of ice in the ice chamber at a time. The ice will last about a day. We've found gallon milk jugs make poor ice containers. They rupture when frozen. Of course, we could fill them a bit less and lie them on their sides so the ice expands in the handle, but who wants that? Juice containers seem to work better -- especially those without handles.

Our chiller frequently keeps our fermenting beer at 69° in a South Texas garage over 110°! Admittedly, we often fight the first few hours as getting the near-beer down to temperature in that kind of heat takes some time and runs through the ice. We've found we can augment the other chamber with a bit of dry ice to help us get to our target. Once the beer is at temperature, the whole system cycles much more slowly.