Researching historical beer styles can be a bumpy ride. Saisons in particular tend to be a very broad, fraught framework of beers to dive into, and I’ll frequently head to the chapter in Phil Markowski’s Farmhouse Ales titled “A History of Saison,” which was contributed by Brasserie de la Senne’s co-founder Yvan De Baets—both a great brewer and a well-regarded historian.

In the context of this month’s featured 100%-Brett beer via De La Senne, this chapter notes how crucial the impact of Brettanomyces yeast was to old-school saisons (before things shifted away from frequent sourness, in favor of the more bitter-forward interpretations of saison). De Baets, in compiling a profile of these older saisons, writes, “An important characteristic was their wine-like character, a sign of aged beers that were properly made. This vinous and sour side [corresponded] to the ‘taste of the North’ (Belgium and Northern France), and was the ‘must have’ of the era. The nose of old saisons was clearly marked by Brettanomyces.”

In concluding his historical deep dive into classic saisons, the De La Senne brewer added, “An authentic saison has a small ‘wild’ side, rustic, indefinable, far from the clean aspect of certain engineered beers of today. In one word, it must have an extraordinary character.”

Libertine Brewing Co.’s Aubree is one of an increasing number of beers being spontaneously fermented through the use of a coolship—a wide and shallow stainless-steel vessel, typically, that allows brewers to expose in-progress beer to the ambient air. This process, once limited to the traditional methods of Belgian lambic, is pretty much the opposite of how one usually brews today: pitching a single homogenous vial (or vat, bucket, etc.) of yeast from one of the main yeast labs, and using a monoculture with near-uniform genetics to reliably ferment said beer. If you’re looking for a challenge, though, fermenting with local yeasts can provide one.

Michael Tonsmeire’s American Sour Beers has a particularly helpful section on using coolships. “The isolated strains of brewer’s yeast that we pitch into our ales and lagers,” he said, “have characteristics that took untold generations for brewers to select for, important properties like alcohol tolerance, flocculation, and desirable flavor profile. Finding a wild yeast strain with all of these same attributes is as likely as dropping a net onto a prehistoric field [!] and having the first animal you catch be as easy to raise and delicious to eat as a modern cow.”

The next time you’re sipping on a spontaneously fermented beer, whether from Libertine or Allagash or Russian River or Jolly Pumpkin, or myriad other international brewers aiming to coax cow-equivalents from the local air, keep in mind the unseen effort that went into them. The dumped batches. The ones that end up too lactic or too acetic, or worse. The months or years of fingers crossed… Digging any new coolship beers lately? Hit us up @RareBeerClub.