The Brewer

Eisbock Brewing Guide: Freeze Distillation

Eisbock: Ice Cold Concentration

Eisbock is not brewed; it is distilled. But not with heat. By freezing a strong beer (Doppelbock), the water turns to ice, but the alcohol and sugars remain liquid. Removing the ice concentrates the beer, boosting the ABV from 7% to 12%, 15%, or even 40% (like BrewDog’s Tactical Nuclear Penguin). Legend has it that a lazy apprentice left a barrel of Bock outside in winter. The master brewer, furious, made him drink the oily sludge at the bottom as punishment. The apprentice loved it.

1. Safety and Legality

  • Legality: In the USA and many countries, freeze distillation is technically a grey area. Since you aren’t using a still, it’s often tolerated for home use, but check your local laws.
  • The Hangover: Freeze distillation concentrates everything, including fusel alcohols and methanol. Drink Eisbock in small quantities (2-4 oz), or you will have the worst headache of your life.

2. The Base Beer

You need a flawless Doppelbock.

  • Why?: Freezing concentrates off-flavors. If your base beer has a tiny hint of butter (diacetyl), the Eisbock will taste like movie theater popcorn oil.
  • Recipe: Use a standard Doppelbock recipe (Munich malt, melanoidins, low hops).

3. The Process

  1. Brew & Ferment: Make 5 gallons of Doppelbock. Ferment it fully. Carbonation is optional (it will be lost anyway).
  2. The Keg Method:
    • Put the beer in a keg.
    • Put the keg in a chest freezer set to -5°C (23°F).
    • Wait 24-48 hours. You want it slushy, not a solid block.
    • Invert the keg or use a floating dip tube. The concentrated liquid (alcohol/sugar) will remain at the bottom/center.
    • Rack the liquid off the ice.
  3. The Bottle Method (Small Scale):
    • Fill a 2L plastic soda bottle. Freeze it solid.
    • Invert it over a jar. Let it drip as it melts.
    • The first 50% that melts is the Eisbock. The white ice left behind is water.

4. The Result

If you start with 5 gallons at 8%, and remove 1.5 gallons of ice, you end up with 3.5 gallons at approx 11.5%. The flavor is intense: molasses, dark fruit, brandy, and warming alcohol.

Conclusion

Eisbock is the alchemy of brewing. It turns a humble lager into a spirit-like elixir.