Belgian lambic is the oldest surviving descendant of ancient, prehistoric brewing, which exposed wetted grains to the open air, allowing wild yeasts and bacteria to settle on the mixture and convert the grains’ dissolved sugars into alcohol. Traditional lambics originate in the Pajottenland (or Senne Valley), an area Southwest of Brussels, and may more closely resemble a dry wine, champagne, or cider than beer.

The brewing process is fairly straightforward: unmalted wheat and “pilsner” malted barley are milled and mashed with water of increasing temperature; it reaches a boil at which point aged hops are added as a preservative, and the mixture boils for a few hours to get the desired extraction from the grains. This resulting not-yet-alcoholic grain and hop infused water is called wort. In conventional beer production, the wort would then be chilled rapidly through a heat exchanger and sent to a fermentation vessel where pre-cultured commercial yeast is added. In lambic however, nature takes hold of the wort immediately. The boiling wort is pumped into a coolship—a large, shallow pan in a room with open windows—and the airborne bacteria and yeasts settle on the wort in the coolship as it cools overnight. The next day, the primed wort is racked into wooden barrels, where it ferments and matures with time.

The microflora from the inoculated wort and barrels now proliferate and out-compete one another, fermenting and acidifying the beer. After a few months, the barrels’ contents are enjoyable and resemble lambic, but for up to four full years the yeasts and bacteria jockey for dominance, imparting different characteristics to the finished beer. Because each barrel is wholly distinct, the real art of lambic production lies in blending barrels to produce the desired combination, and carrying some essential aspects from batch to batch of the same brands.

The Referend Bier Blendery is based upon the Belgian geuzestekerij (or geuze-blendery) in which pubs, individuals, or commercial producers purchase young lambic from local brewers, age in oak casks and blend and package to taste. In order to execute this model in America, where coolships are scarce, we bring our mobile coolship to a local host brewery. There, we collect the wort brewed to our specification and send it to the coolship where the wort cools overnight in the ambient cold air before being brought back to the blendery to begin its extended aging in oak.

We approach these naturally fermented beers with a distinctly modernist sensibility: take the best of the ancients, and make it new.