Fermenting and Conditioning Lagers: Tips from the Pros

Three brewers brewing award-winning lagers share cool tips on fermenting and lagering that homebrewers can employ on their own homebrew setups.

Clint Lohman is the Co-Owner/Head Brewer of Working Draft Beer Company in Madison, Wisconsin

If you are looking for a “house” lager strain, you must consider a few key qualities.

  • It should meet your required attenuation level, fermentation temperature range and flavor profile for the lagers you’re looking to brew.
  • It should ferment reliably, predictably and consistently.
  • It should be easy to harvest and repitch

We use two different lager strains here at Working Draft. We use what is essentially the Pilsner Urquell strain for all of our Czech-style lagers and the Weihenstephan lager strain for everything else. These two strains are pretty distinguishable from each other. The Czech strain is a little less clean than the Weihenstephan strain in that it is less attenuative, creates more diacetyl, and seems to pull less bitterness from the wort; thus creating a maltier and more bitter beer with a little more complexity. This works perfectly for classic Czech-style beers. The Weihenstephan strain is the most widely used lager yeast in the world and it creates a very clean, crisp, and dry beer. Both strains create a nice sulfur note when fermented at cooler temperatures (50 °F/10 °C and lower), which I think is an important component to European-style lager.

We really try to focus on making our lagers as authentic to their European counterparts as possible so we employ a cold fermentation/cold maturation method. What this means is that we typically pitch yeast about 8 °F (4 °C) cooler than our target fermentation temperature, then when they’re 40–60% attenuated, we will cool the fermenter 2–3 °F (1 °C) per day back down to our pitching temperature and then hold it there for 7–10 days or until it passes a forced diacetyl test. After that we continue to cool 2–3 °F (1 °C) per day down to 30 °F (-1 °C) and hold there for 3–8 weeks depending on the beer. In general our pale lagers top out at 48 °F (9 °C) and our darker lagers top out at 52 °F (11 °C). Darker worts tend to have a more complex sugar profile and thus are a little tougher for the yeast to ferment, so that extra couple degrees helps them get the job done. Other instances in which we may ferment a touch warmer is when we’ll need to harvest a substantial amount of yeast for subsequent brews. Pitching and fermentation temperature has a direct effect on cell growth so if we need to harvest from a single brew tank to pitch into a double brew tank, we may fall a bit short if we ferment too cold. We also ferment a touch warmer with fresh pitches of yeast as it often takes first generation yeast a generation to acclimate to your brewery conditions.

The way in which most American brewers and European brewers define primary fermentation seems to differ. Americans view primary fermentation as being over when the beer has reached terminal gravity. However, many European lager brewers define it as when fermentation activity has slowed. Open fermenters were commonly employed by many European lager brewers in the past and some still use them today. Prior to the invention of the hydrometer, many European brewers used a visual assessment to determine when primary fermentation was done and when the beer needed to be transferred from the open fermenters into conditioning tanks. The goal with this was often to have a small amount of extract left in order to naturally carbonate the beer in the conditioning tanks. While we employ unitanks at Working Draft as opposed to open fermenters and conditioning tanks, we do naturally carbonate all our lager beer by closing up the tank 1–2 °Plato before the end of fermentation. This is the point in which we consider primary fermentation to be over. Typically it takes us about 7–12 days to get to this point depending on the beer.

We do not employ a diacetyl rest. With our Czech-style beers, a small amount of diacetyl is actually appropriate as it lends a little extra mouthfeel and complexity. With the German-style lagers, we will hold the beer at pitching temperature until we can no longer taste any diacetyl in a forced diacetyl test. By pitching and fermenting on the cooler side of the spectrum, the yeast actually creates less precursor for diacetyl so there is less to clean up in the first place. Also, by cooling the beer in steps we never shock the yeast into flocculating early so there are viable cells in suspension that will continue to consume carbohydrates and clean up/mature the beer (albeit very slowly) even during lagering at 30 °F (-1 °C).

On average, our lagers are in the fermenter 6–8 weeks from brew day to filtration. The break down goes something like this:

Day 1: Growth Phase (fermentation typically kicks off within 12–24 hours.

Days 2–3: Tank has come up to peak temperature and fermentation is fully underway

Days 3–5: Holding at peak temperature until we reach 40–60% attenuation, then start to cool 2–3 °F (1 °C) per day until we reach pitching temperature.

Days 7–10: We’re back at pitching temperature, somewhere in that ramp down we’ll bung the tank to naturally carbonate. Then hold at pitching temperature for 7–10 days.

Days 14–21: Forced diacetyl test is passed, start cooling 2–3 °F (1 °C) per day down to 30 °F (-1 °C).

Days 18–56: Let rest at 30 °F (-1 °C) until filtration

The length we lager is very much dependent on the beer style and starting gravity. In general, higher gravity beers will need more time to clean up and mature. For example, we will aim to have our doppelbock lagering at 30 °F (-1 °C) for 6–8 weeks whereas with a standard strength pale lager we’d be comfortable with lagering for only 3 weeks.

I would recommend lagering for the same amount of time on a homebrew scale assuming you’re performing a step cooling method to keep from shocking yeast. Homebrew will certainly clarify faster than commercially brewed beer simply because it’s in smaller vessels and there’s less distance for yeast to drop out, however, clarification is not the only goal of lager. Part of the objective for lager is letting the yeast slowly continue to mature the beer. When cooling your lager down in steps (2–3 °F /1 °C) you prevent the yeast from being shocked out of suspension so they can stay active even at 30 °F (-1 °C) to help clean up and mature the flavor of the beer. One caveat to this is that you don’t want too much yeast in your lagering vessel. At Working Draft we purge yeast from the cones of the tanks twice per week (after harvesting what we need) to ensure we don’t get any autolysis (dead/decaying yeast cells) off-flavors. Commercial breweries utilizing a two tank process and horizontal lagering tanks likely do something similar and/or target a certain cells/mL before transferring to conditioning tanks to avoid this issue. The old rule of thumb for German brewers was 1 week for every °Plato original gravity plus one. So a 12 °Plato beer would be layered (held at 30 °F/-1 °C) for 13 weeks. Most brewers are not lagering for that long these days but a typical lagering time for standard strength pale lager would be 5–6 weeks in most European breweries and going up from there based on strength and color of the beer.

Dry hopping lagers can be tricky because dry hopping at colder temperature can lead to less fruity notes and more harsh sulfur characteristics. We haven’t done a ton of dry-hopped lager at Working Draft but we have done a few. Because I really strive to naturally carbonate all our lagers, I’m usually dry hopping at the same temperature that I’d bung that tank at, which is typically our pitching temperature (40–45 °F/4–7 °C). However, I may choose to ferment a dry-hopped lager on the warmer end of the spectrum to still be able to naturally carbonate but hopefully help avoid too many sulfury characteristics from the dry hops. A cold ferment with a ramp up for diacetyl rest may be a better choice for dry-hopped lager for these reasons, although you will have a harder time achieving full natural carbonation at those elevated temperatures.

Great lager is the product of doing a million little things right. It’s getting pH, temperature, pitch rate, oxygenation rate, mash chemistry, yeast health, wort clarity, trub settling, etc., all dialed in. Great lager has much more to do with process and less to do with recipe. Keep your recipe simple and if you’re looking for really authentic European lager, use European ingredients. Homebrewers with a temperature-controlled fermentation chamber capable of sitting at lagering temperatures will have a huge advantage. Additionally, having a kegging setup and Corny kegs could allow you to perform a very traditional fermentation process.

Here are some key tips that can really step up your homebrew lager game:

1. Perform a decoction or step mash. Decoction mashing at home is much easier than it would be in our brewery. We have a two-vessel system that wasn’t really built for that style of brewing so it’s nearly impossible. On the homebrew scale all you need is a decent insulated mash tun, a kettle, heat-proof gloves, and a scoop/pitcher to transfer mash and you’re good to go. Step mashing with boiling water additions takes a little trial and error but once you figure it out it’s not so bad. We utilize this in our brewery for most of our lagers since we lack a heated mash mixer. These steps are certainly not necessary but are one of the small things that can take your lager from good to great.

2. Make sure you have a good vigorous boil to ensure proper volatilization of S-Methyl Methionine and Dimethyl Sulfide.

3. Take great care to minimize trub carryover from your kettle to fermenter. Excess cooked hop matter in your fermenter will lead to a harsher bitterness and less drinkable lager. There’s not much to hide behind in these beers and this is a small detail that I don’t hear people discuss often, however, dialing this in at Working Draft has made a substantial difference in the quality of our lagers. There are a number of ways to do this:

• Perform a whirlpool rest after cooling with an immersion chiller.

• Cool through a heat exchanger into a carboy and let the wort rest without yeast overnight, then rack into your primary fermenter and add oxygen and yeast. This can be a great way to get your wort down to a nice cool pitching temperature as well.

• Ferment in a bucket and skim the Kräusen off the beer once a day during the most active part of fermentation. The trub will rise to the top with the CO2 and you can simply remove it with a sanitized spoon.

• Rack from the primary fermenter into a Corny keg when you’re 1-2 °Plato away from terminal gravity, then seal the Corny keg and let it carbonate naturally.

• Let the beer sit in your Corny keg at 40–45 °F (4–7 °C) then step cool it down to 30 to 32 °C (-1 to 0 °C) and let sit for 5–10 weeks depending on the strength of the beer.

With these steps you can make a truly authentic European-style lager beer.

Adam Goodwin is the Owner/Brewer at Charles Towne Fermentory in Charleston, South Carolina

For nearly all of our lagers we use the Weihenstephan lager strain, which is a great option if you’re looking for a “house lager strain.” It can be super clean or you can push some nice character out of it when you really want it to shine. It is also a very forgiving yeast. We will push it as low as 48 °F (9 °C) and as high as 58 °F (14 °C) depending on the character we’re after. Then when we get a few points from terminal gravity, we’ll let the fermentation free rise for a diacetyl rest. When dry hopping any beer, I like to aim for 65 °F (18 °C) or higher and then crash and condition.

We average about four weeks of lagering after transfer to horizontals. For some of the cleaner lagers, like an American light lager, that time might actually come down a bit as it gets bright pretty quickly. Some of the more characterful or classic lagers may require a little extra time to clean up post-fermentation, so they may head closer to the 6–8 week mark or longer. At this point, it comes down to sensory. At a small commercial scale (or homebrewing) you have some wiggle room with your production schedule, so no need to rush it out before you are happy with it.

This schedule mirrors what I did as a homebrewer, but it doesn’t have to be done this way. Temperature control is crucial for these types of yeasts, and lagering is obviously a critical aspect of making lagers. Do I think you can still make great lagers, otherwise? Definitely. I am all for efficiency, especially when you are brewing just for yourself and friends to enjoy at home. I tend to ramp up the temperature of all of my lager fermentations throughout primary. If the beer tastes clean not long after crashing, then I’d say it’s ready to drink. That being said, if I’m making a classic lager style, I like to stick to the traditional processes as best I can, so it would be pretty hard to get a clean bright beer within a few days. At the end of the day, if the beer tastes how you want it to, that’s the most important thing.

The signs of a great lager brewer are often patience and consistency. Do your best to be true to classic style if that is your aim, but don’t be afraid to play around with methods and ingredients to get the characteristics that you want in the beer in an amount of time that you are willing to dedicate in your fermentation chamber or keezer.

Ryan Wibby is the Co-Founder and Brewmaster at Wibby Brewing in Longmont, Colorado

When looking for a “house” lager strain I want one that can ferment high- and low-gravity lagers in a relatively short period of time without producing tons of off-flavors. Our preferred yeast is a proprietary lager strain, but there are many from yeast labs that will do the job — Wyeast 2308 (Munich Lager) is a great one.

All of our recipes and processes started at the homebrewing level and everything has been scaled up from my homebrew setup to our commercial setup. I think the only difference between the two setups is that on the commercial scale we are able to lager the beer under CO2 pressure. 

We ferment our lagers at 52 °F (11 °C) for two weeks and then perform an extended diacetyl rest on all of our lagers, allowing the beer to free rise to 54–55 °F (12–13 °C) for a week or so.

Then we lager for at least two weeks.  We try to lager the beer longer if we are able to but with demand so high we generally need to package the products after two weeks of lagering. For our hoppy lagers we don’t lager for longer than two weeks as we have found that the hoppy aroma begins to deteriorate quickly during an extended lagering period. We don’t dry hop any of our lagers.

I am aware of the “fast lagering” methods homebrewers debate sometimes. In fact, I learned about them in school and know several international brewers who use these techniques.  However, I am of the belief that if you are trying to make a great lager you need to schedule the time to make a great lager.  Lager brewing isn’t about moving beer quickly but rather allowing the lager to tell you when it is ready.  Patience is the best characteristic of any great lager brewer.  A final piece of advice, if you have the capability, lagering horizontally is the best way to make crisp clean lagers.  Horizontal tanks allow for the yeast to floc out quickly and if you are filtering your lagers, using horizontal tanks will allow for much better efficiency during the filtrations.

Issue: January-February 2023