Trying to keep my cool

With the summer solstice behind us and 3-digit temperatures facing Central Texas, I’ve been giving lots of thought to fermentation temperature control. Fermentation temperature is the most important variable a brewer can control during fermentation, and has a huge impact on flavor. Ales should be kept between 65-72°F during active fermentation, and ideally between 66-68°F for most yeast strains. Too hot and you start to get banana, clove, and bubblegum flavors from esters produced by the yeast (hotter than 80°F and you get fusel alcohols, which give that acrid “firewater” taste associated with cheap spirits). Too cold and ale yeast start go dormant, so fermentation may not complete – although lager yeasts ferment best between 45-55°F.

Here in Texas, “too cold” has never been a problem – with sympathy for my friends in Minnesota and Canada – but “too hot” frequently is. So I use a “swamp cooler” to keep my fermentations cool. This is where you place the fermenter in a big tub filled with cold water, and keep the water cold by periodically swapping out frozen ice packs. I also cover the fermenter with a T-shirt to wick cold water up the sides – some brewers even add a fan to the system. Whatever specific variation you go with, it’s a great way to keep fermentation cool on a budget: for the price of a $7 plastic tub at Target, a decent-sized collection of ice packs (or frozen water bottles), an old shirt and that broken fan in your garage that stopped oscillating in 1998, you can easily keep your fermenter 10°F colder than the room it’s in. My Weiss Blau Weiss Bavarian Hefeweizen didn’t get above 73° all last week, despite ambient temperatures in the house of up to 80°. And the only reason it got that high was because I wanted it to.

But this method has its drawbacks. For one, temperatures fluctuate quickly, and you need to be able to swap out ice packs every few hours. I work from home, so I can do this; but I can’t imagine making this work with a job outside the house. And overnight, the temperature usually goes up 5-7° by morning (sorry, beer: I love you, but not enough to wake up every 2 hours during the night for you) and it takes time to bring it back down.

It’s also messy. Keeping a few gallons of stagnant water in a dark closet for 7-10 days isn’t always a pretty sight. Sometimes, the T-shirt develops mildew and needs to be changed out – unpleasant at best, and a contamination risk at worst (though not a huge one if the fermenter is closed and the airlock filled). And when primary fermentation is done … well, let’s just say that if you’ve ever lifted a plastic bucket containing 5 gallons of liquid wrapped in sopping wet cotton out of a larger plastic bucket, you know how much fun it isn’t.

So I think I’m ready to graduate to a chest freezer with a Johnson temperature controller. It’ll be cleaner, easier, and will give me new power as a brewer. No longer will I be tied down brewing wheat beers during the sweltering Texas summer – I can make crisp APAs and blonde ales, knowing I’ll be able to keep the fermentation cool enough to get a good clean flavor. I’ll also finally be able to make some decent Belgian-style ales, which require gradually ramping up the temperature with better precision than I can get in my swamp cooler. Someday, if I get really crazy, I may even try my hand at making a lager.

I just need to find a freezer that’s big enough for my 8-gallon fermenter but small enough to fit through the door of the Harry Potter closet. It’ll cost a bit of money, but it’s an investment in better beer and more versatility. And really, isn’t that what being a homebrewer is all about?