Eisbock: The Legendary Beer Style Discovered By Accident

History of Eisbock

Eisbock is the summit of the bock beers. It is the strongest rendition of the bock tune; the first mysterious verses of which were hummed back in the 1300s in the town of Einbeck. From these first strains the music spread taking on different subtle notes along the way bringing to the world a series of songs all firmly sequestered within the framework of that earliest music; Traditional bock/Dunkles bock, Maibock/Helles bock, Doppelbock, and Eisbock.

Eisbock is, put simply, a strong Bockbier made stronger by freezing. Exactly how and when this first happened is unknown, but a tale about it has been passed down throughout generations. It goes a little like this.

The Legend of How Eisbock Was (Accidentally) Discovered

Our story takes place at the end of the 1800s. It is a winter evening at the Reichelbrau Brewery in Kulmbach, Bavaria. A young brewery worker is finishing a long hard day of shoveling spent grain, lugging barrels into storage, and cleaning. His arms feel heavy and his eye lids are drooping. He has just finished sweeping, when the head brewer — we’ll name him Gregor — comes around the corner.

“Ah, Klaus. Zere you are. Please, brink in zat last barrel of bock before you leafe.”

Klaus huffs and hangs his head, but finally nods. The head brewer is in too much of a hurry to get home himself and does not notice the young man’s hesitation. Klaus leans the broom in a corner and shuffles down the long room to the back door. He opens it and the cold air of a cold winter evening makes him hunch his shoulders and shiver fiercely. The barrel sits just off the last step. He looks at the barrel a moment, walks over to it and gives it a cursory tilt. It seems this barrel has taken on 200 extra pounds, propped against his draining shaky strength.

He shakes his head slowly. No. He rights the barrel. Not tonight. One night outside isn’t going to hurt it any, better to leave it then to lose control of it on the way, and smash it open. Yes, better to just come fetch it in the morning. He nods, having convinced himself of his reasoning, locks up and heads home for the night.

Morning comes gray and cold. Klaus dresses quickly, planning to get to the brewery and have the barrel safe inside before the Brewmaster appears. He exits his family’s home and sprints through a world newly minted with bright crystal frost. Travel is an odd light footed run, inter-mixed with a series of haphazard, barely controlled, slides every time his feet find new ice. His breath hangs and steams behind him.

He makes the last turn to the brewery and skids to a halt. At the brewery door sits the barrel, but the barrel head is canted upward on one side and a single stave protrudes oddly. He can see trails of frozen liquid issuing from the unbound joint.

His stomach seizes than falls away to a terrible dread. He walks stiffly to the barrel and examines the damage. The cold night has frozen and expanded the barrels contents, popping the head and cracking the week stave joint. He shakes his head angrily. Why hadn’t he thought of what would happen if the beer froze last night? Now a whole barrel of bockbier was wasted and he was in trouble.

He sits on the step and waits, seeing little reason to go in and start his morning chores when he knows Gregor will probably fire him as soon as he arrives. Five minutes later Gregor arrives. Klaus watches the man’s face darken as he surveys the barrel and the boy sitting beside it.

“Vat hafe you done? Are you so lazy?!”

Klaus rises and tries to speak boldly but his voice comes low and trembling. “I vas so tired. I vas afraid of tryink to mofe it and losink control and…” he indicated the barrel with a small gesture, “breakink it open.”

Gregor looks back and forth between the barrel and the defeated lad. “Broken! You were afraid of breakink it! It’s broken now, isn’t it?”

“Yes Herr, Gregor.”

“You shtay here.”

Gregor disappears inside. Angry murmurs and loud bangs of tossed tools issue from within. Moments later Gregor storms out a heavy hammer and chisel clutched in his hands. He walks to the barrel and begins to take it apart. The barrel head goes flying, exposing a sold covering of ice. Gregor looks across at Klaus accusingly, then starts to hammer at the ice and staves. Frozen shards and wood splinters flicker through the air and Kluas ducks his head behind an arm as chunks fly past. After several minutes the rythmic icy whack of hammer on ice suddenly give way to a squishy splash of slush.

“Vat is zis?”

Kluas peeks out from behind his arm. Gregor is leaning over the partially destroyed barrel, glaring at some new offense buried in the wreckage. A moment passes. Gregor stomps back inside to return almost instantly with a clay mug.

“Come. Now.”

Klaus steps forward without thought, summoned by the uncompromising iron behind the man’s words. Gregor slaps the mug against Klaus’s chest and indicates the barrel. “You vill drink all zat is left of your laziness.”

Klaus raises his hand to the cup and tilts his head to look down inside the top barrel hoop. There, nestled within an icy recess is a murky brown-colored liquid.

“Drink or leafe. Is simple.” Klaus licks his dry lips. The pool sits; a dark smear against the clean ice around it. It looks much like the old dregs found at the bottom of some casks. He looks up at Gregor then tilts the cup down until a little of the liquid breaks the lip and swirls into the bottom.

“More.” Gregor growls. He let more spill into the cup then lifts it free. He stops the cup when the liquid is only inches away from his lips. The strong scent of malt-sweetness and the low spicy sting of high alcohol drifts.

“Drink!” He cringes and sips. A fiery sweetness slides across his tongue; magnified dark fruit and thick malt. He swallows, feels a warmth issue mid-chest and radiate outward. He smacks his lips and stares into the empty cup, then enthusiastically reaches into the ruined barrel again and pulls out another cup-full. Gregor’s triumphant smile fades slowly as he watches the boy’s tentativeness turn to eagerness. As Klaus dips a third time Gregor pulls the cup away and raises it to his own lips….

Tall Tale or True Origin?

That’s the tale. Whether it’s tall or not is a question we may never be able to answer. The above is obviously my own imagined retelling, bad German accents and all. However, some version of these events have become widely accepted as Eisbock’s origin.

Today, Eisbock may be one of the rarest beer styles around due to the expense and effort that goes into producing it. This style is also rarely found in the U.S. because of alcohol laws that put freeze distillation or fractional freezing in the same category as other forms of distillation.

This seems rather silly as these days, it’s legal to brew a 20% ABV beer, yet you cannot freeze a beer and concentrate it down to between 9 and 14 percent to make an Eisbock. I know, I know, makes no sense to me either. I talk about the legal stuff more in the “Freezing” part of the “How To Brew Eisbock” section below.

It is also important to note the difference between Eisbock and the commercial ice beer craze that took hold among American macro breweries in the mid 1990s. These are not the same thing. Though the freezing process may be the same, the results are worlds apart.

Macro breweries used this more as a marketing gimmick than anything else. It allowed them to light up TV screens all across America with exploding ice blocks and slow-motion ice shards spinning through the air. Where “Big Beer” freezes their already dull lifeless beer and removes very little water to create a, supposedly, smoother dull lifeless beer; the result of a frozen strong bock beer is, not only nicely warming alcohol, but also a much smoother, deeper, and richer complexity of malt flavors.

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Style Profile & Characteristics

The guidelines for the Eisbock beer style are set by the Beer Judge Certification Program (BJCP) Style Committee. The below details are a summary of what an Eisbock should represent.

The BJCP classifies the Eisbock beer style as an “Strong European Beer” and it can be found in their guidelines as category 9B. Similar beer styles within this category include: Doppelbock (9A) and Baltic Porter (9C).

Appearance:

Color will range from a rich reddish copper to dark brown. Ruby highlights often appear when held to good light. Beer should display superb clarity. Head will be off-white to ivory in color with moderate to poor retention. Noticeable legs may build due to the high alcohol content.

Aroma:

Shows a definable alcohol presence, but should never be harsh. This is mostly balanced by intensely deep malt profile. Strong dark fruit esters from the malt and no hop aroma.

Mouthfeel:

Should have low carbonation and display a full to very full body, buoyed by a smooth warming alcohol. Alcohol should not be hot or solvent-like and bitterness or fusels should not contribute any harshness to the velvet-smooth feel.

Taste:

Malt can be a heavily sweet presence, though should be balanced enough not to be cloying. Should have toast, caramel, possibly even chocolate qualities. May have considerable dark fruit esters. Alcohol should never be hot. No flavor from the hops and bitterness is only enough to help the alcohol balance the huge malt. Should have a clean lager character with some remaining malt and alcohol character. Alcohol may create a perception of dryness in the finish, which should never be syrupy or overly sweet.

Food Pairings:

First, Eisbock could be considered brother to brandy or port. It is great as a before meal apèritif or after meal digestif… pair it with a favorite after dinner cigar and your golden.

The rich deep character of Eisbock pairs will with the rich dark flavors of many heavy meat dishes. Think venison in a dark fruit reduction or fatty slow cooked pork. Game birds such as smoked duck or slow roasted peasant also make an excellent pairing to the complex depth of Eisbock.

Look for strong cheese to pair here such as; Limburger, aged Gouda, or Camembert.

Eisbock’s sweetness and richness makes it an excellent accompaniment to German Chocolate Cake, crème brulee, candied fruit, or any of the myriad of other rich desserts.

Serving & Storage:

For best presentation and greatest appreciation, an Eisbock should be served at around 55-60°F in a snifter glass. They are best stored at cellar temperatures away from light and can be aged for many years.

*Reference: The 2015 BJCP Style Guidelines

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Examples of the Style

Note: In most brewing competitions, Doppelbock and Eisbock are in the same category. And because Doppelbocks are more popular, they are entered, and win, at a much higher rate than Eisbocks.

• Aventinus Eisbock from G. Schneider & Sohn (Year-Round)

• Kulmbacher Eisbock from Kulmbacher Brauerei (Year-Round)

• Raspberry and Blueberry Eisbocks from Kuhnhenn Brewing Company (Limited)

• Fire & Eisbock from Mammoth Brewing Company (Winter Seasonal)

• Blood Stains from Merciless Brewing Company (Unknown Availability)

• Freeze Ray Eisbock from Strangeways Brewing Company (Rotating)

• Eisbock from High Point Brewing (Draft Only)

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Tips to Brewing Eisbock

Though an Eisbock can be made from just about any strong Bock recipe be it Dunkles/Traditional, Helles/Maibock, or even a Weizen-Bock, the most common recipes tend to follow the Doppelbock style. This is something that is noted in the BJCP guidelines for Eisbock, but as we’ll see, this may not yield the best examples.

Brewer’s may like to consider Eisbock as just a bock recipe that’s been freeze-concentrated. And some great Eisbocks have been made following these assumptions, but in their book, Brewing Classic Styles, Jamil Zainasheff and John Palmer maintain that to brew a truly great Eisbock you need to do some serious tweaking to that Doppelbock recipe.

What’s sort of cool about making an Eisbock beer is it’s a very easy way to get two markedly different beers from the same batch. You can split your batch, only freeze-condition a part of it, while conditioning the other portion the same way you would a Doppelbock. This not only gives you two distinct beers and is easier to handle due to the smaller volume that has to be frozen, but it also allows a comparison of before and after the freeze-concentration.

Grain Bill:

In the Doppelbock grain bill, I talk about my belief that one of the best ways to get the malty depth for a doppelbock is to go heavy on the Munich malt (up to 90%) and, if any is used, go light on Pilsner (10-20%).

This sort of straight up Doppelbock grain bill can work for an Eisbock. But depending on the bill, you may end up with a beer too cloyingly sweet. Jamil Zainasheff and John Palmer note that because of the higher concentration of flavors in an Eisbock the maltiness of the grain bill needs to be reduced somewhat.

So, we end up with a pretty ambiguous sliding scale between the Pilsner and Munich. Each can make up anywhere from 30% to 60% with the other countering, but, generally, you’ll want the Pilsner at the higher percentage. Beyond this, how far the scale is tipped one way or the other is going to depend a lot on how sweet and malty you want the finished beer. You may want to start with relatively small batch sizes until you find the best recipe for your taste.

To this, a single or a couple shades of crystal or cara-Munich might be added at up to 10 percent. I’ve also seen Vienna, carapils, chocolate, and melanoidin malts used in some recipes. If using chocolate, find a pale chocolate and only at about 1 to 2 percent.

Extract brewers should be looking for a good German pilsner extract, along with a Munich extract, and steep a selection of the above specialty grains. Alternatively, you could go with just a pilsner extract and do a large mini-mash with the Munich and any other specialty grains you choose. I’m inclined to believe the second option makes a more complex malt profile.

Hops:

The hopping of an Eisbock won’t change much from a good Doppelbock recipe. Hops are used to help the alcohol balance the malt. They should not be a distinguishing element themselves.

One bittering addition an hour before flame out is the standard. A second, though largely unneeded, small aroma addition within the last 20 minutes can be added.

German hop varieties are best suited for the Eisbock style, with likely choices including Northern Brewer, Magnum, Perle, Hallertauer, and Saaz.

The Mash:

The mash profile for an Eisbock and Doppelbock is exactly the same. Here a decoction mash would be traditionally used.

To perform a decoction mash, you would boil a portion — generally the thickest 3rd — of your mash for 20 to 30 minutes and then add it back into your main mash to “step up” the temperature to its next resting point. Boiling the mash causes maillard reactions (caramelization) which adds complexity and color to be beer.

A double or triple decoction can be performed. You’ll want a mash thickness of about 1 qt./1 lb. of grain. Mash-in at about 100°F and have rests at ≈122°F, 149-158°F, and a final mash out of 168-170°F. If doing a double decoction, the first “step-up” is performed by adding hot water.

This is a labor intensive process because any part of the mash being boiled needs constant stirring to keep from burning. Many brewers will say that this is an obsolete process, what with modern grain and the ability to add complex caramel flavors through the use of specialty malts.

I’m not here to argue either way. It’s a brewing tool, an option, that’s all. If you want to add some old brewing authenticity to your beer, give it a shot. Decoction mashing, when done right and with the right grain bill, has been making excellent beer for a long, long time.

These days the mash can also be performed as a single infusion mash with a saccharification temperature around 155°F. There is the option here of putting a bit of old authenticity into even this mash by doing the mash-out temperature climb as a decoction. To do this, just pull the thickest 3rd of your mash after its been at 155°F for 20 minutes or so, boil it for 30 to 40 minutes while the rest of the mash continues on at 155°F, then add it back in. This will add a bit of color, malt complexity, and tradition to your Eisbock.

Sparge with 170°F and finish with a starting gravity between 1.078 and 1.120.

Yeast:

For yeast, you want a German lager strain that attenuates slightly higher — about 80 percent — than you might look for in a Doppelbock. This is another preventative measure to ending up with a beer too sweet. Remember, in an Eisbock everything is concentrated. Some decent choices include the following:

• Wyeast: Bohemian Lager (2124) or Bavarian Lager (2206)
• White Labs: German Lager (WLP830) or German Bock Lager (WLP833)
• Dry Yeast: With an attenuation of ≈82 percent, Saflager S-23 is a solid choice.

Fermentation:

You want a very clean fermentation because, as with the malt profile and alcohol, any flaws resulting from sub-par fermentation conditions will be concentrated in an Eisbock. Plus, the higher gravity will be hard on your yeast. So, pitch two to three times the amount of yeast you would regularly and aerate the wort extremely well.

Pitch the yeast when the wort temperature has dropped to around 45 to 48°F and try to maintain a fermentation temperature not much above 50°F and definitely not above 55°F. If your yeast strain calls for a diacetyl rest, raise the temperature to around 60°F at the end of fermentation. A longer, slower, cooler — up to 4 weeks — fermentation will reduce esters, phenols, fusel alcohol, and other potential off-flavors.

It’ll be here, after fermentation is complete, that you can split your recipe if you’d like; concentrating whatever portion you want to turn into eisbock while letting the other portion lager and, under the right conditions, become whatever bock style you started with.

Concentration Process:

Alright, first a quick, but important, side note: According to the Bureau of Alcohol Tobacco and Firearms (ATF) Ruling 94-3 freezing a beer and removing more than 0.5% of its volume is illegal without a license. There’s an email exchange between someone at the Alcohol and Tobacco Tax and Trade Bureau and a brewer, posted in a Reddit r/homebrewing discussion that makes this pretty clear.

So, making Eisbock by removing more than 0.5% water volume is basically illegal. But, it is also openly brewed by several craft breweries, and it seems the TTB knows about this craft beer level production, but has chosen not to act (PDF) on said knowledge.

Make of this what you will. But, this article is, obviously, for informational purposes only.

Ok, now that we’ve got that cleared up…

The reason freezing is part of the process is to make the beer stronge, not only in alcohol but also the complexity and flavor of the beer’s profile, by removing water content. This can be done by freezing because alcohol freezes at a much lower point (-173°F) than water. Thus, we can remove ice as it forms, leaving behind alcohol. In most cases, less than 10% of the water volume is removed. Removing more than 20% may make the alcohol too harsh.

After fermentation is complete, let your beer lager for at least a month. If you have very good temperature control you may even try doing this right at freezing, so that as your yeast begins to stall, finishing a secondary fermentation, the beer will start to freeze. The slower and longer this transition from secondary/lagering to freezing takes, the more volatiles you’ll drive off. If done this way, it can take up to a couple months to get actual ice.

If you just stick to a regular lagering — no fancy stuff — you’ll drop the temperature below freezing (28-30°F) after you’ve determined the regular lager period is over.

Ice will form on top of the liquid. As ice forms, you either need to remove it or have your beer in a container that transfers from the bottom such as a bucket with a spigot or a keg. However you do it, it’s not a bad idea to melt and measure the volume of the ice you take out or is left behind. This will give you a percentage of the total volume removed.

Numerous different vessels have been used as freezing containers. Kegs work well. There is a good write up, pictures and all, of one homebrewer’s process here. Using a keg is straight forward. It also may be the most sanitary and in-line with “good brewing” practices, e.g. less worry about oxygenation, etc. The problem of course comes if you don’t keg.

If you don’t keg, some thought should be put into what sort of vessel you transfer the beer to for freezing. Everything from an unused plastic fermenter, to plastic milk jugs, to liter soda bottles, even big mouth carboys will work. If using soda bottles or milk jugs, try to freeze them on end so that the part that’s gonna remain liquid is closer to the opening and easier to transfer.

A Couple Things to Remember:

1. First, no matter what type of container you chose always remember water expands when it freezes. Though this really shouldn’t matter because the point is to remove the ice as it forms, just in case your vigilance lapses: Fill them only about 2/3rds full. This is especially important if you’re using glass and even then there is a slight possibility of them busting.
2. Container choice may be dictated by the amount of room you have in your freezer. Rather than putting it all in one 5 gallon bucket it may be necessary to split your brew over several smaller containers.

Allow at least another month of lager time after the concentration is complete.

Estimating ABV After Freezing

To get a general estimate of your new ABV, you can multiply your Total Volume by the Pre-Freezing ABV (as a decimal) and divide by your Post-Freezing Final volume. So, it would look like this:

As a quick example, let’s say you started out with a total volume of 3 gallons and a pre-freezing ABV, using your hydrometer readings, of 9%. You then freeze the beer and remove 1 gallon of ice leaving a final volume of 2 gallons. This would look like:

This will not be completely exact because it is assuming that you are only removing water and no alcohol at all from your beer, which in most cases will not be wholly accurate, but it does give you at general ballpark.

Packaging:

Once the freezing process is complete, you can package your beer as you would any other. Though it is unlikely, there is a possibility of not having enough viable yeast for bottle conditioning. If you believe this to be the case, you can always pitch some fresh yeast at bottling time.

You are looking for around 2.4 volumes of CO2.

If you keg, I’d recommend doing a few bottles too, so that you can easily age them. The Eisbock style is one of the best for cellaring. It’s high ABV and huge malt profile means it can be saved and enjoyed over many, many years.

Cheers!