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Seeking the Cold Truth on Lagering Times

The lager-brewing tradition is full of received wisdom and rules of thumb about how long it’s supposed to take to condition a beer. In reality, however, there’s no magic formula.

Michael Stein Jan 15, 2024 - 14 min read

Seeking the Cold Truth on Lagering Times Primary Image

Photo: Matt Graves/mgravesphoto.com

“A lie can travel halfway around the world before the truth puts on its shoes” is wisdom as applicable to brewing as it is to any other 13,000-year-old pursuit. There is nobody quite like experienced brewers, however, to help you sort the scientific fact from myths and apocryphal history.

You may have heard this one: Lagers need one week of lagering time per degree Plato. So, a 10°P lager would need 10 weeks, an 18°P bock would need 18 weeks, and so on.

Says who?

“I’m sure it was accurate in the 1800s before modern refrigeration,” says Chris Lohring, founder of Notch Brewing in Boston and Salem, Massachusetts. “But currently that’s just not a good rule of thumb. I don’t know why you would follow that. It doesn’t make a lot of sense because [there are] a lot more analytical tools we have to determine if the lagering phase is complete, based upon goals.”

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Those goals may include passing a polymerase chain reaction (PCR) test, testing negative for diacetyl precursors, or satisfactory sensory testing for sulfur compounds, acetaldehyde, or other thresholds.

Producing a clean and tasty lager is the end, while cold and time are the means—and there’s no perfect formula for how long that takes.

Selling the Long Lagering

Consider this 1904 Hamm’s advertisement, which offers a window into the conditioning process. The copy reads, “Beer aged under three months is what is known as ‘green’ beer—that is to say, the yeast has not had sufficient time to properly work on the other elements.” The ad continues, “Hamm’s Beer is aged from four to six months.”

If 120 to 180 days seem like a lot of time in the cellar for maturation, that’s indicative of a paradigm shift that’s occurred over the past century of American lager brewing.

The rationale offered by the Hamm’s ad is true enough, Lohring says. In green beer, “there could be sulfur compounds, there could be acetaldehyde, there could be a number of things going on with the beer that would benefit from aging and lagering. And the reduction of these [things] that are classified as off-flavors could be reduced, and [you] would have a more pleasant beer on the back end.”

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Okay. But eight months? “Unless you understand everything that happened upstream, the question is irrelevant,” Lohring says. “And unless you understand what the intent of the brewer is, it’s irrelevant.”

Practical concerns may affect how long you’re cold-conditioning or how much time you have for maturation. Maybe the canning date is etched in stone, or maybe the sales team needs that packaged beer by Opening Day—there are valid real-world issues that often dictate how long we can afford to lager a beer. Despite what some breweries might have told their customers more than a century ago, there is no hard-and-fast rule for how long a beer must be aged.

While four to six months was proudly advertised as a great deal of time in 1904, two to three months seems like a long time today. It might even feel like forever.

“Lagered Forever”

In recent years, as more small breweries have dabbled in lager, many have been mentioning the lagering times on their packaging or social media. After all, if it’s expensive to keep beer in tanks for that long, you might as well get some marketing benefit out of it.

The team at Notch began noticing those labels—and then they put “Lagered Forever” on their own. “I have to give full credit to Brienne Allan for that phrase,” Lohring says. (Allan, who previously brewed at Notch, is now cofounder and head brewer at Sacred Profane in Biddeford, Maine.) “We’re kind of poking other brewers,” Lohring says. “‘Lagered forever’ is not really a statement of Notch pounding their chest like, ‘We lagered the beer for three months!’ It was just a fun thing to say.”

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If it’s a cold-conditioning arms race that you’re after, you’ll need about a year. Consider Schloss Eggenberg’s Samichlaus, a strong dark lager at 14 percent ABV. It mellows for 10 cool months in their Austrian cellars.

Back in 1907, Christian Heurich Brewing in Washington, D.C., was advertising two beers, Maerzen and Senate, as being six to 10 months old. Heurich, however, was a large brewery with a massive footprint, able to produce 200,000 barrels a year.

Local brewery Right Proper revived the Senate Beer brand in 2019—but their lager is certainly younger than Heurich’s. Right Proper cofounder Thor Cheston says their target is 35 days.

“The time from brew day to package for Senate Beer is especially important for us, given the limited amount of physical space we have,” Cheston says. Given Senate’s current production time and sales velocity, Right Proper can currently produce about 6,500 barrels per year. “However, if we were to increase the lagering time by even a week, we would shave more than 600 barrels of production off of our annual capacity.”

In case you need further proof that your beer doesn’t need 10 months in the tanks, consider Chicago’s Dovetail—one of the country’s most stubbornly traditional breweries.

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“Our shortest lagering time of three weeks belongs to our Hefeweizen, Grodziskie, and Hopfenweisse,” says Brittany Gedwill, Dovetail’s production manager. She says that the “longest lagering time for any of our beers is 13 to 15 weeks, which is a profile shared [among] our Maibock, Festbier, Holiday Bock, and Rauchdoppelbock.”

The idea that your beer may need only 21 days—or it may need up to 105 days—is exactly why the production team should be as intentional as possible about why they keep beer in the tank for the time they do. “Figuring out what works just right to result in the best beer you can make takes time and, unfortunately, some trial and error,” Gedwill says.

The question of how long to lager hinges on what works best for you and your brewery.

“It’s the time that’s the big question mark for everyone,” Lohring says. “The Czechs are like the British, and they love to say, ‘We’ve always done it this way.’ Or, you could be more analytical like the Germans, and say, ‘We’re going to measure for these components, and upon the reduction of these components, lagering is complete.’ I’m not saying either direction is the proper one.

“At Notch, we have taken both German fermentation and Czech fermentation processes and melded them together to suit what I want to produce—not what I think the Germans or the Czechs want to produce.”

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Times and Temperatures

Let’s say your lager is fermented and ready for cold conditioning. Should you do so right away? Should you do some cooling but then raise the temperature before dropping it even lower? There are many regimes out there—infinite permutations of time and temperature. Tweaking your own process through trial and error is a given, but where to start?

Dovetail’s Gedwill recommends giving yourself plenty of time in the tank and letting the beer tell you when it’s ready. “Obviously, reaching final fermentation is a main goal, but I’ve found some beers still need some warm time after that to clean up any off-flavors still lingering,” she says, citing diacetyl and acetaldehyde as examples. “Beyond that, it is then giving the beer enough cold time in the tank for clarity purposes and an added depth and melding of flavors which usually comes along with it.”

Practices also differ on whether to raise the temperature for a diacetyl rest—much more common in North America than it is in Europe. “I never had diacetyl issues because I felt like I was pitching appropriately, so I never did the raise in temperature,” says Daniel Terrones, most recently head brewer at Other Half’s production facility in D.C. “We start dropping temperature based on fermentation profile, fermentation curve. Even if you’re not quite cleaned up on diacetyl, you’ll still get the cleanup [during conditioning].”

At Other Half, he says, they mainly use two lager yeast strains from BSI—one German (34/70), the other meant for Mexican-style lagers (BSI-940). Typically, they knock out at 46°F (8°C) and ferment at 48°F (9°C) for the German strain, while with the Mexican strain they knock out at 48°F (9°C) and ferment at 50°F (10°C). “We like to be cold and keep it there,” he says. “And we never raise temperature—we really just drop after that.”

The Mexican strain is what they use for Poetry Snaps, a rice lager hopped with Saaz and Saphir. “The Mexican strain is a more robust strain that just rips,” Terrones says, adding that they brew more Poetry Snaps than any other lager. “Sometimes it has to fit in these manipulated windows of four [or] five weeks—or whenever I can eke it out, I’ll get six weeks out of it—and that strain just plays ball. We know it has repeatability. It’s just a workhorse.”

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At Notch, they start with “open” fermentation in unsealed, non-pressurized vessels before transferring to a closed tank and then to lagering tanks when they still have one or two degrees Plato left to ferment. That process aids clarity while allowing natural carbonation via spunding. Also, once in the tanks, they maintain fermentation temperatures until terminal gravity—their way of doing a diacetyl rest—and then gradually drop to 32°F (0°C) for lagering. “That process has worked really well for us from a practical standpoint and in terms of flavor stability,” Lohring says.

He views the open fermentation—in a vessel as wide as it is tall, and thus with less hydrostatic pressure on the beer—as beneficial to the flavor and aroma, encouraging more expression from the yeast. Meanwhile, he says, the spunding helps to provide smoother carbonation and better head formation and retention.

Brewers also need to consider the vessels that they have available. “That’s going to impact your lagering regime, and they’ll yield different results based upon your goals.” A horizontal tank for lagering, for example, allows yeast and protein to drop out sooner, while the yeast get more exposure to the beer than in a tall cylindroconical. Even if you’re lagering at 32°F (0°C), those yeast are still active in reducing off-flavors.

Patience, in Moderation

Realistically, there’s not necessarily a clear dividing line between fermentation and lagering. Where does one end and the other begin?

“Different brewers will have different answers for that,” Lohring says. At Notch, after terminal, they typically hold the beer between fermentation and lagering temperatures—say, 41°F (5°C)—for a week. “Is that lagering?” he asks.

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When lagering actually starts may seem philosophical, but it’s relevant to the question of how long you lager. The fact that there’s no clear answer is just more evidence that there’s no one-size-fits-all formula.

It would be great if it were as simple as saying, “My favorite Bohemian lager takes 12 days to ferment and three months of maturation, so that’s how I’ll make the best Czech-style lager I’ve ever made.” But it’s likely not that simple, and you might be surprised to find your best-ever lager needs 10 days of fermentation and just 21 days of maturation.

So, if you have the time, take it—but remember, you may not need it to make your best lager. And you may well find that attention given to fermentation is much more important than that given to cold time in the tank.

“It seems really backwards to me to talk about how long you lager, when what you really should be looking at is how long your fermentation is,” Lohring says. “In our process, what we found is the more relaxed [we are] and [the more] time we take in fermentation to complete the beer, the less lagering time you need. But there’s a qualitative step there, too—if you rush that fermentation, it’s quick, you’re never going to get that [quality] on the back end. Lagering is not going to help that.”

For all the things in life that feel rushed, lager need not be one of them. Yet if we have an intentional approach to brewing great beer, there’s no need to put stock in old rules of thumb or crazy-long conditioning times. You might well find that the missing ingredient is patience—or, it might be a more outcome-driven approach. Test the beer, taste the beer, and figure out a lagering process that works for your system—and for you.

Michael Stein is president of Lost Lagers, Washington, D.C.’s premier beverage research firm. His historic beers have been served at the Smithsonian National Museum of American History and the Polish Ambassador’s residence.

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