If you’ve never had good Eisbock, you’re letting one of the best beer styles in the world pass you right by. Most of the time, if we want high-alcohol, high-ABV beer, we need to get it the “honest” way, by providing more fermentable sugars and exposing our yeast to a much more alcohol-toxic environment. It can lead to incomplete fermentations, lots of hot and solventy off-flavors, and, well, an “alcoholic” flavor profile. Eisbock, though, uses a freeze-concentration process to increase the relative level of alcohol but does so without requiring your yeast to work overtime to get up into the double-digits.
The result is a smooth, rich, intense beer that is perfectly suited to sipping on a cold winter night. To be on the safe side, though, you’ll want to start brewing it at the beginning of summer.
Style
Eisbock is a German lager in the Bock family, and it can prove to be devilishly hard to find, commercially. There aren’t many on the market, and the market for them is fairly small, but you can sometimes source them from larger beer vendors. The beer itself is an intensified version of Doppelbock, amplifying its typical bready richness and warm (but smooth) alcohols. It also tends to have more noticeable fruit flavors than Doppelbock and can also give a greater impression of light roast, depending on the base recipe.
What’s key to remember is that what might be less-noticeable (or even below the detectable threshold) flavors in the base beer might come to the fore in a finished Eisbock because all of the flavors are being concentrated. This means that we can’t simply make our standard Doppelbock, freeze it, and call it an Eisbock. The freeze-concentration of flavors must be accounted for in the base recipe so as to avoid a beer that is overly sweet, overly bitter, or overly alcoholic, because the Eisbock is none of those.
Ingredients
Brewing a great Eisbock requires restraint. Don’t try to make the beer intense, rich, or high in alcohol: let the freezer do the work.
When brewing Doppelbock, I usually go with near-100 percent Munich malt, but with a couple of small add-ons to round out some specific flavors. One of the best things about Eisbock is that I don’t even need those! This grist is as simple as can be: 100 percent Munich malt (make sure it’s the 9L variety) to a predicted starting gravity of 1.080 at pitching. Depending on your efficiency, that should be somewhere in the neighborhood of 18 pounds (8.2 kg). Don’t worry if you miss by a couple of points high or low: predicting the real final gravity here is challenging in any case, and a few points in either direction won’t matter.
I like to use nothing but German noble hops for this recipe: one ounce (28 g) of Hallertau (about 5% AA) at the start of the boil and 0.5 ounces (14 g) of Tettnang with 20 minutes to go will yield about 20 IBUs, which should be sufficient to balance the residual sweetness and add some good earthy, floral flavors to the finished product.
Again, thinking of the finished product, I use Bavarian lager yeast here (Wyeast 2206). It will give you solid attenuation, which is important to avoid a beer that’s too heavy, post-concentration.
Process
In the initial fermentation, it’s important to pitch a sufficiently large quantity of yeast and give it plenty of oxygen to minimize off-flavors and esters that will be heightened downstream. You also want to be sure to give the beer a thorough diacetyl rest, which has the added benefit of ensuring a more-complete fermentation/attenuation. After primary fermentation, the beer should taste bready and a bit thin, and maybe not like much else.
Now for the fun part!
Transfer to a keg for the freeze, or if you don’t have a keg, you can use a BetterBottle plastic fermentor, and I’ve heard tell of people using plastic bottling buckets (though I’ve never done so myself). The important thing is to rack the beer into something that won’t crack when the beer starts to freeze, so no glass carboys.
Put the vessel in a freezer and leave it alone. Give it a little shake every few hours, but don’t be surprised if it takes a while to begin to develop that “slushy” sound! After about 10 hours, you should finally be getting some noticeable freezing. Once you do, your goal is to freeze out a volume of water that reduces the total liquid volume by about 25 percent. I’m afraid there’s no definitive answer on just how long that takes, but for me it seems to take about 16 hours from the time I put the beer into the freezer. Keep checking, keep shaking, and trust your gut. It may take a few attempts before you get the hang of it, but no one ever said this style was easy!
When you think you have about 25 percent ice to 75 percent beer, rack the beer out from underneath the ice and package it. You’ll end with a gravity of about 1.100, and if you like, you can melt down the ice to get a sense of how close to the 25 percent mark you are (in a 5-gallon/19-liter batch you should end up with about 1.25 gallons/4.7 liters of melted ice).
I’ve straight bottle-conditioned this with no additional yeast, but it’s the one beer where I don’t think pitching in some additional yeast at packaging is overkill. However you do it, though, carbonate to about 2.25 volumes, then let this beer age for a while to mellow out. Most versions will be a little rough around the edges at first (though not always) and can benefit dramatically from a long (3–4 months) lagering!
In Closing
This is a challenging style. Even when brewed conscientiously, the additional steps can create issues. One of my first attempts accidentally over-concentrated by a mile, leaving me with a 13.4% “beer” that was, paradoxically, so clean that I ended up having to enter it as a Traditional Bock in competition because the judges kept dinging it for being “too clean” and without enough alcohol character. I’d love to have given them a full pint of it and watched them try to walk across the room.
The moral of the story, though, is that if brewing is about “practice makes perfect,” then Eisbock is arguably the pinnacle that we should be practicing to reach. Take on the challenge. Don’t be intimidated: be inspired!