The story
According to a much-loved tale from Kulmbach in northern Bavaria, a brewery worker once forgot to bring barrels of bock beer inside on a freezing winter night. By morning some of the water in the barrels had turned to ice. His furious boss cracked open a cask, found a thick, dark liquid under the frozen crust, and — so the story goes — discovered it was delicious. Whether the accident happened exactly like that is unknowable, but freezing beer to concentrate it became a Kulmbach tradition.
What it tastes like
Eisbock is essentially a doppelbock turned up to full volume. It pours deep copper to dark brown, often with little head retention because of its high alcohol. The aroma is rich with toffee, caramel, dark bread, and dried fruits such as plum, raisin and fig. On the palate it is full-bodied, sweet and dense, but a well-made eisbock stays smooth, with alcohol showing up as a warming glow rather than a harsh burn. Sip it slowly, like a dessert wine.
How it’s made
Brewers start with a strong, fully fermented bock or doppelbock. The beer is then chilled until some of its water freezes. Because alcohol freezes at a much lower temperature than water, removing the ice leaves behind a liquid that is more concentrated in alcohol, sugar and flavour. This technique is called freeze concentration (sometimes loosely called freeze distillation). The process is repeated or controlled to reach the target strength, and the beer is then conditioned before release.
Fun fact
Freeze concentration has been used to push beer to astonishing strengths. In the early 2010s, a handful of breweries in Germany and Scotland competed for the title of world’s strongest beer, with some freeze-concentrated releases topping 40% and even 50% ABV — territory usually reserved for spirits. A traditional eisbock, thankfully, is a lot more drinkable.