There’s no question that imperial (or double) styles have a devoted audience. Whether or not you personally enjoy them, you’ll probably end up making one sooner or later, and there are some good rules-of-thumb to follow when you do! I wish I could tell you it’s as simple as doubling all of the ingredients, but I can’t. Don’t get me wrong: that’s an option, but it’s probably going to yield a pretty wild beer. This week, we’re going to take a relatively straightforward style—Helles—and “upscale” it into a double/imperial version, so that you can get a sense of the kinds of considerations in play and an approach to dealing with them.
Style
Helles is a light lager that is described in the style guidelines as “a Pils malt showcase.” To make an imperial version, we’re not only going to want more alcohol, we’re going to want to turn up the volume on that key style characteristic. This will both ensure that it comes through clearly, at a minimum, but hopefully also gives the beer an “intense” style effect. We’ll also still want that floral, noble hops flavor and aroma, and some balancing bitterness appropriate to our new malt and alcohol levels. But more Pils malt is key here, just as increased hopping is key to Imperial IPA.
Ingredients
First, we need to set our target. Ordinarily, you find Munich Helles in about the 5 percent ABV range. While we could literally double that, a 10 percent pale lager might be a bit much; when “doubling,” I like to increase to 7.5 percent or add 2.5 percent to the normal ABV, whichever is higher. Doing so ensures that it’s a meaningful increase to justify the new name and also ensures that we add a dose of soft, warm alcohols to the flavor and feel because this should be a key flavor of any imperial beer! For Helles (typical ABV of 5 percent), we’re shooting for 7.5 percent ABV using either measure (convenient, isn’t it?).
Base grist usually follows that number up, in proportion. In this case, we’ll increase from 50 to 75 points of gravity (a 50 percent increase). Most of that is coming from base malts, so 12 lb (5.4 kg) of Pilsner and 1.5 lb (680 g) of Vienna will get us most of the way there.
When it comes to specialty grains, I like a simple metric of a “half-scale” increase. In this case, we’re adding about 50 percent to the overall ABV, so I’d increase any remaining specialty malts by 25 percent. In this case, that means 6 oz (170 g) of Victory. Why only half? Because specialty malt flavors increase their presence at a disproportionate rate to their percentage of the grist. Five percent Melanoidin malt is enough for almost any recipe; increase it to 7.5 percent of the grist, and you’ll get something that’s absurdly rich and bready, even though the increase was proportional to that of the base grist. Then there are chocolate/black malts. We aren’t using them, but if there are chocolate malts in use in your “imperial-ed” style, you want to increase them very slightly, and maybe not at all—what I call just a “bump” of a few percentage points of the original total, say 3–5 percent. You get more bang for your buck out of dark roasted malts in terms of flavor, and adding too much can create all kinds of flavor and mouthfeel problems.
The “full” increase on base grains, “half” increase on specialty grains, and “bump” increase in chocolate malts are a solid starting-point strategy for most doubled recipes. It helps ensure proper attenuation and the right contribution of specialty-grist flavors and avoids harsh flavors from the black malts. You will probably need to adjust in subsequent recipes, but this will get you neatly in the ballpark.
Then there’s hopping. Increase your bitterness by more than the overall ABV increase. My Helles recipe calls for about 20 IBUs. A linear increase there would move us to 30 IBUs. That might be enough to offset the increased malty flavors, and it might be enough to offset the additional sweetness from the alcohol, but in my experience, it isn’t quite enough to do both. I increase proportionally, then add another 10 percent. In this case, we increase to 30 IBUs, then add 3 IBUs more. That means 1.5 oz (42 g) of Hallertau at 60 minutes, then 1 oz (28 g) at 15 minutes.
Finally, in terms of yeast, just be sure you’re accounting for the increased alcohol volume in the pitch rate, and you’re choosing the greater-attenuating and/or more-alcohol-tolerant yeast strain, if you have more than one that can do the job. In this case, Wyeast 2308 (Munich Lager) is still the best choice.
Process
There’s little change in the process, but take care to really drive your fermentation. Many lighter beers are set-and-forget with maybe a slight increase in temperature to clean up diacetyl, but higher-ABV beers do better with some actual temperature ramping of a degree or so a day. For our imperial Helles, that means we still start at 50°F (10°C), but rather than just waiting until fermentation is almost complete to bump up to just over 60°F (16°C), you should start slow-walking it up to that about 4–5 days into fermentation, then hold there to minimize diacetyl. The same logic applies to most “big” beers—start them cool and slowly increase to minimize off-flavors, which are more prevalent in higher-ABV beers because of the increased alcohol toxicity of their environment.
Package as usual, even for bottle conditioning. Yeast are robust little buggers, and I’ve had them bottle-condition a months-old Eisbock at 14 percent ABV.
In Closing
One final note: this is a pretty simple double/imperial recipe and style. Others will add more variables. The two keys to always keep in mind are to factor in the changes caused by increasing the relative volume of different ingredients—whether grain, hops, or yeast—and to ensure that your fermentation accounts for the more-challenging ABV level. Enjoy your bigger beers!