The Eisbock type of beer holds a special place in the heart of many beer aficionados and it’s a beer that is avidly sought after. Not least because here in the US it is rarely seen due to alcohol laws that restrict the use of the freeze-distillation technique used to produce the beer.
That doesn’t mean you are never going to see an Eisbock on the shores of the US, it’s just going to be rarer than other beer styles. Even the other German Bock beers are easier to find.
The Federal Bureau of Tobacco Alcohol and Firearms (ATF) seems to turn a blind eye to craft brewers who produce their own Eisbock freeze-distilled beers, and there are even some produced by the more well-known Independent craft breweries on a seasonal basis.
If you are really lucky you may even come across a few bottles of commercial Eisbocks that have been imported from Germany, such as the original Kulmbacher Eisbock from the Riechelbräu brewery in Bavaria or the, incredibly popular with US wheat beer fans, Aventinus Eisbock, which is made with a Bavarian Weizenbock.
If all else fails, why not try brewing your own Eisbock? Although phrases like freeze-distilling may seem unsettling at first, and I won’t lie it can be a challenging style to get right, remember that practice makes perfect.
And who knows – you may brew a decent Doppelbock, Maibock, or another Bavarian beer specialty as you practice.
What is an Eisbock?
Put quite simply, an Eisbock is a super strong version of the classic Bavarian barley-based bock beer. An intense beer in both alcohol content and flavor, it still remains rich and smooth, perfect for sipping on a cold winter night.
It’s the strongest of all the bock beer styles and gets those extra strong flavors and higher ABV through a special freezing process.
“Eis” is German for ice so an Eisbock literally translates as an ice beer. Normally when you require a beer with a higher alcohol concentration you go about it the “honest” way, by using more fermentable sugars and exposing the yeast used to a much more alcohol-toxic environment.
Unfortunately, this way isn’t without its problems and can often lead to incomplete fermentations, some hot and solventy off-flavors, and a more “harsh” alcohol profile.
Eisbock, however, uses a freeze-concentration or distillation process which increases the relative level of alcohol but without the yeast having to work overtime to reach the double-digits.
Natural chemistry (there’s no magic here really) dictates that pure alcohol or ethanol will freeze at a much lower temperature than water. By removing the frozen water, the liquid which is left forms a higher-concentrated beer. More flavors and more alcohol.
It’s key to remember an Eisbock is a much richer beer than many of the base beers which are used to brew an Eisbock through freeze-distillation. What might be more subtle or less noticeable flavor in the base beer will come to the fore and shine through in a finished Eisbock due to the flavors all being concentrated.
Think of it as adding less water to a traditional squash drink, but this time you are reducing the water content by freezing the liquid and removing the ice.
Which Bock Bier is an Eisbock Closest to?
In theory, you could use just about any beer, lager, or ale and subject it to the freeze-distillation process for a stronger ABV beer. However, remember it’s not just the alcohol you are bumping up, you are also making the flavors more concentrated.
If beer is overly sweet, overly bitter, or already overly alcoholic, the Eisbock style will only ramp that up through the distillation process, often to uncomfortable levels.
Although higher concentrated than a normal beer, an Eisbock should still offer balance with just enough alcoholic warmth to cut through the residual sweetness of the malt.
In Bavaria, the original birthplace of the Eisbock style, traditionally the base beer for Eisbock used is a barley-based strong lager. Although many people would argue it should be a Doppelbock, you may find the already double flavors of the “double bock” too much after freezing the batch of beer.
Often a Maibock, a May Beer, will be used as in the recipe we look at below.
The only notable exception to using a barley-based beer is the choice of a wheat-based ale, Weizenbock. The most famous example of a wheat-based Eisenbock is the Aventinus EisbockSchneider which comes from the Schneider Weisse Brewery on the banks of the Danube. Aventinus Weizenbock bock already has an impressive alcohol by volume of 8.2% with the Eisbock version bumping that up to 12% ABV.
Tips for Brewing an Eisbock
All this talk of distillation and freezing may have you thinking the Eisbock is a difficult beer to brew. Yes, it is a bit more challenging, but, if you can make a German-style lager, then you can also make an Eisbock, with practice.
You don’t need any extra specialized industrial equipment, a domestic freezer could do the job (If you do have access to a commercial walk-in freezer, though, it could make the process much easier!).
One of my very first attempts at brewing this higher ABV brew ended up over-concentrating the beer, not just the alcohol content but also the flavors, and you could barely taste that alcohol character.
But practice makes perfect, and hopefully, with some of the hints I’ve listed below, you may have more success with your first Eisbock brew.
The Grain Bill
A lot of the base malt you choose to use will depend on what style of bock you are going to brew before freeze-distilling it to turn into an Eisbock.
For a Doppelbock, I would normally go with nearly 100 % Munich Malt with some specialty malts to round out some of the flavors. Adding a little pilsner malt can give the beer some nice, sweet, honey notes or subtle, biscuity notes that this beer can carry well.
A couple of specialty malts like Pale Chocolate malt or Carafa II will often be added to impart more color.
Fortunately, with an Eisbock and the intensity of flavors after concentration, you rarely need any extra specialty malts. A 100% Munich Malt grist (ensure you use the 9L variety) will have a predicted gravity of 1.080 at the time of pitching your yeast. Ideal for this style of beer.
If you want an Eisbock which is slightly lighter in color, you could always try brewing a Maibock rather than a Doppelbock as your base beer.
Eschewing the darker malts of traditional bocks, a Maibock is one of those lighter bocks which is perfect for sipping in beer gardens in early spring. Using German pilsner malt as the base malt, you could also add melanoidin malts, Carapils, Caramunich, and Carared for extra flavors and color.
The specialty malts should only make up 10% of the entire grain bill though.
For Extract Brewers
With an Eisbock able to use any bock-style beer as its foundation, there’s very little need for extract brewers to steep grains and add them to an extract. If you haven’t got the facilities to mash all grain then any bock-style malt extract will do the job.
There are a few good options out there including, from Muntons, a hopped liquid extract, but the one I would personally recommend is Weyermann’s Bavarian MaiBock extract.
A golden-brown unhopped extract, it’s produced from a two-step mash of 80% Vienna malt, 10% Carafoam, and 10% Carared with a sugar content of 72 % to 78%.
The Hops and Hop Schedule
Sorry hop heads, but we are not looking for an overpowering hop aroma or bitterness with this style. Hops are only used here to balance the higher levels of alcohol and malt sweetness.
As for the hop schedule, it is recommended to add 1 ounce of bittering hops such as Hallertau (with about 5% Alpha Acids) and half an ounce of aroma hops like Tettnang with 20 minutes left of the boil.
The sweet maltiness is what is meant to shine through here, with the hops taking a more subtle backseat.
German lager strains work best when they have a high attenuation level and can prevent the beer from being too sweet or overly heavy. Choices include:
- Wyeast Bohemian Lager #2124 or Bavarian Lager #2206
- White Labs German Lager WLP830 or German Bock Lager WLP833
- Imperial Yeast Harvest L17
- Dry Yeast Saflager S-23
Whatever yeast you choose, you will need to make up a starter. When used with a minute of aeration, a yeast starter will provide that extra bit of insurance of a clean fermentation and help minimize any off-flavors or esters that may be heightened when the beer is distilled.
You also want to ensure you give the beer a thorough dactyl rest for the added benefit of a more complete fermentation or attenuation. Simply raise the temperature of your fermentation to 68ºF(20ºC) for approx 3 days to remove much of the undesired diacetyl.
You should be aiming for as clean a fermentation as possible with any types of flaws or off-flavors often more exaggerated in the finished beer after distillation.
It’s important to pitch a larger quantity of yeast for the initial fermentation due to the heavier grain bill. Follow the directions on the yeast package for the premium temperature to ferment at, but most German lager strains tend to use a temperature of 50ºF (10ºC).
The initial fermentation will take about 3 weeks, and the beer should then be racked for another 3 – 5 weeks at close to freezing point.
Turning Your Brew into an Eisbock
Here comes the fun part!
Although most commercial breweries will keep their well-lager bocks in jacketed cylindrical stainless steel tanks for freezing, this is a luxury most homebrewers can’t afford.
Instead, homebrewers will tend to rely on ambient cooling in a domestic freezer to achieve the same effect.
You’re going to need to rack the bock beer into a plastic or stainless steel fermenting bucket, something which won’t burst as the liquid expands when freezing. Don’t use a glass carboy or a wooden barrel.
If you can’t fit the entire batch into the freezer in one container you could always split it between two or more smaller containers. Ideally, the buckets should have a spigot at the bottom making it easier to drain the Eisbock liquid as the ice rises to the surface.
You should always purge the container with CO2 to minimize any oxygen pick up, and always leave some extra head space in the vessel as the ice will expand upwards when it freezes.
Put the vessel or vessels into the freezer and initially leave well alone. After maybe 3 or 4 hours give it a little shake and listen to see if it’s developing that slushy sound.
It will probably take about 10 – 14 hours to get some noticeable freezing, depending on the efficiency of your freezer. Once freezing is evident, your goal should be to freeze enough of the beer to reduce the total liquid volume by about 25%.
Although there’s no hard and fast rule for how long this will take, I find a normal freezer will take about 16 – 24 hours. The longer you leave it, the stronger the resulting beer will be in both ABV and flavors.
It can often take a few attempts to get it right, but nobody ever said this style was easy!
After the ice has formed on the top of the beer you will either need to remove the ice from the top or draw off the beer from the bottom using a spigot and a sterilized siphon tube.
A Cornelius keg would be the ideal vessel to draw the beer off into, which, once purged with CO2, will prevent any pesky oxidation of the beer. Ensure your plastic tube reaches all the way down to the base of the secondary draw-off vessel.
Brewers who live in the snow belt with more severe winters can even make their Eisbock au naturale. Simply leave the stainless steel or plastic container of finished bock outside overnight in the freezing temperatures, or bury it for a few days in a mound of snow (just remember where you bury it!).
You should retrieve your container of Eisbock on a cold day or night and drain as described earlier, but try to do this outside in the cold to prevent the icy slush from melting before all the beer is finally drained.
How Do I Know How Strong My Eisbock Will Be?
A simple formula that takes the initial yield or liquid volume of the bock beer and its alcohol by strength, and then divides it by the liquid volume of the Eisbock after freeze-distillation will allow you to know how much stronger the finished beer is.
- V1 x ABV1 / V2 = ABV2
- V1 = The liquid volume of the beer before freezing.
- ABV1 = The alcohol by volume (as a percentage) of the bock prior to the freeze distillation process.
- V2 = The liquid volume of the drawn-off beer after freezing
- ABV2 = The alcohol by volume of the finished Eisbock when freeze distillation is complete.
- If a 5-gallon (19-L) batch of bock with 7% ABV yields 3.75 gallons (14.25 L) of finished beer after freezing, the ABV of this Eisbock is:
- 5 x 7% / 3.75 = 9.3% ABV
Eisbock Recipe – The All Grain recipe
The clone recipe below comes from one of my favorite Maibock base beer recipes but is before freeze-distillation.
Once the beer has been freeze-distilled, the Vital stats of the beer will also change depending on how much ice you decide to leave behind.
|YIELD||5 Gallons / 19 L (ALL GRAIN)|
The Grain Bill
- 12 lbs. (5.4 kg) German Pilsner malt
- 0.46 lb. (0.21 kg) Melanoidin malt
- 0.4 lb. (0.18 kg) Carapils® malt
- 0.4 lb. (0.18 kg) Weyermann Caramunich® I malt
- 0.4 lb. (0.18 kg) Weyermann Carahell® (10 °L)
- 0.4 lb. (0.18 kg) Weyermann Carared® (20 °L)
- 0.23 lb. (0.10 kg) Weyermann Caraaroma® (150 °L)
Hops and Hopping Schedule
- 3.6 AAU Tettnanger hops (0.9 oz./26 g at 4% alpha acids) – 85 minutes
- 3.8 AAU Hallertauer Mittelfrüh hops (0.9 oz./26 g at 4.25% alpha acids) – 5 minutes
- 1.4 oz. (40 g) Hallertauer Mittelfrüh hops – 0 minutes or flame out
- Wyeast 2124 (Bohemian Lager) or Wyeast 2206 (Bavarian Lager) or White Labs WLP830 (German Lager) or White Labs WLP833 (German Bock) or SafLager S-23 or Mangrove Jack’s M76 yeast
- Lallemand CBC-1 yeast and 2⁄3 cup corn sugar (if priming)
Mash in the grains at 126 °F (52 °C) and leave to rest for 15 minutes before raising the temperature tor to 144 °F (62 °C). Allow the wort to rest for a further 25 minutes before raising the temperature again to 162 °F (72 °C). Before mashing out, you need to leave the wort to rest for an additional 20 minutes before raising the temperature to 172 °F (78 °C). Lauter as normal.
Boil for a total of 90 minutes, adding the hops as indicated. At the end of the boil add the aroma hops and whirlpool for 15 minutes. Cool to 55 °F (13 °C) and pitch the yeast. After the beer reaches terminal gravity (should be approximately 1.014 after 7 to 10 days), reduce the temperature by 4 °F (2 °C) per day to about 32 °F (0 °C). Package about four weeks after brew day.
So far you have brewed a Maibock, but to turn it into an Eisbock you are going to need to freeze-distill the beer.
Start by purging your fermentation vessel with CO2 (preferably one with a spigot at the bottom) to minimize any excess oxygen pickup and freeze the beer as talked about above.
After 2 to 3 days, when hopefully enough of the beer has frozen to your liking, drain the higher concentrated alcohol liquid from below the ice into a receiving container like a Cornelius keg. It really should be a closed container to eliminate any chance of contamination. You should purge the secondary vessel with CO2 again to cut down the risk of oxidation. You should also add CO2 to the top of the discharging vessel as, when you drain the beer, the headspace will increase and so too does the chance of oxidation. Ensure your transfer or siphon tube is long enough to reach the bottom of the secondary receiving vessel.
Allow the beer to settle for a few days before racking the beer again to help filter or clarify the beer.
Rack to a keg and force carbonate, or add fresh CBC-1 yeast and priming sugar before bottling.