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Homebrewing Lagers: Chilling Out

Learn how to get your wort chilled and maintain the ideal fermentation temperature to turn out excellent lagers.

Taylor Caron April 26, 2017

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Homebrewers learn early on the importance of chilling their wort to the proper temperature and holding it there for a full, clean fermentation. Even for many ales, getting the wort chilled down and maintaining the ideal temperature can be a challenge without the proper equipment, but once you decide to tackle a lager, it becomes even more difficult. But with a bit of know-how and readily available equipment, the intrepid homebrewer can make lagers as good as any that are commercially available.

The first concern is getting the boiled wort chilled to the proper temperature for pitching the yeast. Most lager strains do great work in the 48–55°F (9–13°C) range, although there are some that give lager characteristics even a bit warmer. Here are some examples:

  • Wyeast 2035 American Lager: 58°F (14°C)
  • Wyeast 2124 Bohemian Lager: 68°F (20°C)
  • White Labs WLP810 San Francisco Lager: 65°F (18°C)
  • White Labs WLP862 Cry Havoc: 58°F (14°C)

But even when you’re aiming for the high-50s, the ice bath in the sink just doesn’t cut it. With an immersion chiller, you’ll still have a difficult time getting the temperature down to 50°F (10°C) except in the coldest months. Plate chillers truly shine in such instances. They are even more effective when you use one with an immersion chiller in a bucket of ice water to pre-chill the cooling water on the way to the plate chiller. Even in the heat of summer, this setup will quickly bring your wort’s temperature down to pitching range.

The Wort’s Chilled, Now What?

Once you have your wort chilled to the proper temperature, how do you keep it there? The best solution is a fermentation chamber, which is usually a small refrigerator or chest freezer with an external thermostat/controller to control the temperature. These external controllers are available at most local homebrew shops. They come in both analog and digital models, and they cost anywhere from $50 to $120. The controllers operate by overriding the internal thermostat in a refrigerator or freezer. Either analog or digital will do the job, but with a digital controller, it’s very easy to set the temperature and swing, raise the temperature to perform a diacetyl rest at the end of fermentation, and slowly lower the temperature to lager range before transferring the wort.

When you have your controller and your refrigerator/freezer, set the latter’s thermostat as low as it will go, plug it into the temperature controller, and plug the controller into the wall outlet. Set the controller to the temperature at which you’d like to ferment. Considering that yeast activity generates its own heat—maybe 2–4°F (1–2°C)—it’s a good idea to tape the controller’s probe to the side of your fermentor rather than to the wall of the chamber. Even better is to use a thermowell, a sanitary waterproofed tube that lets the probe be immersed in the wort itself. And given that 5 gallons of liquid can take some time to change temperature inside-to-outside, I consider a +/-2°F (1°C) swing perfectly reasonable for holding stable temperatures while not beating the compressor to death turning off and on.

Pitching the Yeast and Fermenting

Proper yeast pitching rates are critical for kicking off a 50°F (10°C) fermentation, so be sure you plan to have plenty of yeast—at least twice what you normally pitch for an ale of similar volume.

Many homebrewers pitch their lager yeast in the ale range (65°F/18°C) and then continue chilling the wort over the next day, but this can lead to increased yeast growth at warmer temperatures, giving an increased ester profile and possibly high acetaldehyde production. Best practice is to pitch at, or even just below, the desired fermentation temperature.

Consensus is that the first few days of yeast growth and fermentation are the most critical for producing a clean lager yeast character, so even if your fermenting wort rises above the ideal temperature after the first few days, you may be surprised at how clean a lager can result.

Most healthy lager yeast strains that have been pitched adequately and fermented at the proper temperature will reach final gravity within a couple of weeks without issue, but if you are unfamiliar with a yeast’s properties, a warm rest at the end of fermentation is a safe bet for staving off diacetyl, that buttery slickness that’s generally unwanted even at low levels. A diacetyl rest is simple. Raise the temperature of the nearly finished fermenting wort into the low- to mid-60s for two or three days to finish the final four or five gravity points before dropping the temperature again.

Cold Storage

Once fermentation is complete, you are ready for the true lagering stage—cold storage for anywhere from three to four weeks or more. One rule of thumb is to lager a standard-strength beer for four weeks and add a week for every five degrees original gravity for larger beers. For all but very strong lagers, cold storage beyond eight weeks may show undesirable age character.

This cold storage lets the beer drop bright, reduces any remaining diacetyl, reduces sulfur compounds, and generally matures the flavor. Ideal lagering temperatures are between 32 and 36°F (0 and 2°C). Best practice involves lowering the temperature of the fermented or very nearly fermented beer 3–5°F (2–3°C) every day until you reach your lagering temperature, which takes about a week. Gradually lowering the temperature prevents shocking the yeast into dropping out prematurely (it still has a bit of work to do).

According to George Fix in Principles of Brewing Science, a typical 5 percentish beer can even go down below 30°F (-1°C) before freezing, so if you can get a freezer warm enough, it will work great for lagering. A corny keg is a great vessel for lagering because it lets you purge well and won’t easily break should you dip below freezing.

Or if you have a kegorator you can simply make room in it and turn the temperature down a bit temporarily. Just don’t accidentally tap your lager prematurely! If you’re clever, you can even cut a dip tube short to sample your lager until it tastes ready, then—with perfect sanitation—swap to the full-length dip tube, pour off a pint for yourself to get past the trub and yeast sediment, then jump your brew into the serving keg. Prost!

If you’re ready to try your hand at lagers, check out our recipe for “You Can Do It! Dunkel.”

Lager without Refrigeration

Even if you lack the equipment I discuss above, you can still successfully brew a lager. First, chill the wort through your normal methods (an immersion, counterflow, or plate chiller is best) then make some room in the kitchen refrigerator for the wort for a few hours to bring the wort down even further. You might not see the best cold break, and your sanitation will have to be spot-on given the longer wait before introducing the yeast, but this approach can work. You want to be sure to pitch the yeast at the appropriate temperature if you want that crisp, clean lager effect. So, if it stays a bit too long in the refrigerator, no worries—just remove it from the refrigerator and monitor it for a bit as it warms to the appropriate temperature. Then pitch the yeast.

As far as fermentation goes, if you simply do not have the room for even a small refrigerator, you can still jury rig something for a one-off lager. If your house temperature is on the cooler side, place your fermentor in a large tub and move the setup to the coolest place in the house—a basement or an internal closet. Fill the tub with cold water and swap out blue-ice packs or frozen water bottles to manage temperatures effectively on the lower end. Trade out six ice packs twice a day and see how well it works. A wet t-shirt over the carboy with a fan blowing over it makes the tub even more effective. Depending on humidity and how often you change the ice packs, you could reach 10°F (6°C) or even more below ambient temperature, which makes all the difference in a 62°F (17°C) basement.

I’ve also had good results with an immersion chiller in the actual fermentor, using a thermowell temperature probe to operate a sump pump moving ice water as needed. According to John Palmer in How to Brew, because the acidity of fermenting wort can expose the yeast to unhealthy levels of copper, you need a stainless chiller. Unless you already have a stainless chiller and a sump pump and a temperature controller, the cost to purchase this rig’s components would not be much different than finding a good deal on a used refrigerator, so the idea’s usefulness is limited.

A lager that has been fermented as cool as you can manage, then bottle-conditioned, and cold-aged for a few weeks will produce a satisfactory brew, so don’t let anything keep you from taking your best shot. However you manage, get that wort chilled and avail yourself of one of the most delightful beer styles known to man.

How Big is that Fermentor?

When you’re shopping for a refrigerator or freezer to use as a fermentation chamber, size does matter—it needs to fit your fermentor with room for the airlock. Almost any chest freezer will work if your back doesn’t mind the lifting, and a chest freezer will hold the cold in when you open it. There are a few mini-refrigerators that work as well, but they often lack even the minimum depth for a bucket. The best thing to do is take this chart and a tape measure with you when you go shopping.

Plastic Bucket

21" tall x 12" wide

5-Gallon Better Bottle

24" tall x 11" wide

6-Gallon Better Bottle

25" tall x 11.5" wide

6-Gallon Glass Carboy

28" tall x 12" wide

6.5-Gallon Glass Carboy

28" tall x 13" wide

Want to learn more about creating crisp, cold-conditioned lagers at home? Sign up for Craft Beer & Brewing Magazine®’s Introduction to Lagering online class.

PHOTO: MATT GRAVES

Have you brewed this recipe? What did you think?