Brewing High-Gravity Lagers: Tips from Pros
Brewing a high gravity lager (with an original gravity above 1.070) takes a lot of patience and a lot of yeast. These pros have brewed award-winning examples, and with their advice you can too.
Brewer: Brian Destree, Capital Brewery in Middleton, WI
All of our high-gravity lagers undergo a long, slow fermentation for about 10-12 days at 53 °F (12 °C). They have a similar diacetyl rest as our other lagers: As fermentation nears its terminal gravity we allow the fermentation to free rise to about 62 °F (17 °C) and hold it there for about 36 hours. That being said, diacetyl should not be of too much concern for these beers because they are lagered for so long and some yeast is still present in the lagering tank that any diacetyl present at the end of fermentation will be re-metabolized by that yeast prior to the end of lagering. After the rest, the fermenter is then crash cooled down to 35 °F (2 °C) and the beer is transferred to a lagering tank and held at that temperature for a minimum of another five weeks. Ideally, our doppelbocks are lagered six or seven weeks, but that is not always feasible depending on the production demands of the brewery.
Thankfully, our proprietary yeast strain can handle the high gravity lagers with ease. However, we do increase the pitch rate for these fermentations and we also use some additional yeast nutrient supplements that we do not use for our regular lagers. To keep it simple for brewing at home, I would recommend increasing your pitch rate by 50–100%.
Challenges with high-gravity lagers are usually related to pushing the physical constraints of your brewing system. It is very likely that you will have to reduce the size of your brew. For instance, in our brewhouse a typical 12-13 °P (1.048–1.053 SG) wort will yield 35.5 barrels. For our doppelbocks, which run about 19 °P (1.079 SG), we only yield about 19.5 barrels.
For homebrewers, one thing to be mindful of is mash density (i.e. lbs. malt/gallons water). The easiest thing to do is decrease the batch size; however, if you really prefer not to do that, add some rice hulls to the mash to help with the lauter. Another thing to consider is fermentation temperature. I believe low and slow is the way to go, and especially at home. Since there is so much sugar there to start with, if your fermentation gets too warm (and as a result too vigorous) you are very likely going to blow the top off your fermenter and all of your hard work to date will be for naught. Increasing the size of your blow-off tube can help alleviate any additional head pressure in your fermenter.
Once you have mastered the art of producing and fermenting high gravity worts, and you really want to test your skill as a brewer, here is what I recommend: Make a recipe that is 15-16 °P (1.061–1.065) with roughly the following ingredients: 60-65% blend of 2-row and 6-row base malt, 25-30% flaked corn or rice, and 5-10% caramel 60 °L malt and target about 15-20 for the IBUs. Ferment and lager for a total of four weeks. Prior to finishing (racking or bottling) dilute by 1⁄3 with carbonated water (you should boil and cool the water prior to carbonating to sterilize it).
At this point, you just brewed yourself a nice premium American lager. Conversely, enjoy at full strength and you are drinking a good old American malt liquor. Lastly, if you substitute dextrose or candi syrup for the corn or rice in the mash bill, ferment and lager the same way, and dilute by 1⁄3 with carbonated water prior to finishing; you’ll have yourself an authentic American light lager.
If you can brew those styles without any perceivable flaws you can truly brew anything.
Brewers: Sean Piel and Jeff Pasquale, Thomas Hooker Brewing in Bloomfield, CT
High gravity lagers have the same challenges as any lager but they are amplified. More time, more yeast, more oxygen, and more patience are needed to get the perfect brew. Higher gravity lagers tend to have a thicker grain to water ratio so we can fit extra grain in the mash/lauter tun. The result is more water is used during the sparge and a reduction in overall efficiency. We typically do a single infusion mash and let it rest for 40 minutes before starting a 20-minute vorlauf. The temperature of the mash is going to depend on various things such as yeast strain and desired characteristics (dry or sweet, clean or fruity). If using a high-attenuating yeast, we like to mash in at the 154–156 °F (68–69 °C) range, to ensure the beer doesn’t get too dry or boozy.
For lower gravity lagers like our Munich Helles (5.5 % ABV) we pitch about 1.5 million cells per mL per degree Plato. For higher gravity lagers like our Liberator Doppelbock (8.5%) we use the same yeast strain but pitch anywhere from 2–2.5 million cells per mL per degree Plato. For homebrewers, try brewing a lower gravity lager first as a propagation and collecting yeast from that batch. For aerating wort, splashing it into a bucket won’t be enough. I suggest attaching a barbed diffusion stone to an aquarium pump with an air filter and aerate for 30 minutes before pitching yeast.
Our typical diacetyl rest is at fermentation temperature for 1–2 days after fermentation completes. The beer must pass a diacetyl test where a sample is heated to transform all VDK (diacetyl precursor) into diacetyl. If any buttery notes are still present, it needs more time. If it passes this sensory test, we start cooling the beer for lagering. As a general rule with this style you should taste your brew at every step until you are sure your beer is ready for the next step.
Lagering times tend to be longer for higher gravity lagers because more esters and higher alcohols are produced during fermentation and more time is needed to smooth out and balance these flavor compounds. For us, the difference is six to eight weeks, compared to four to five weeks for the lower gravity beers.
