“If you make a stout or an IPA or lager, typically, you brew your beer and then you buy a cultured yeast strain from a lab. And it’s a single homogenous strain of yeast that makes one very clean beer,” Martin explained. That’s what Cascade Brewing does for their own beers -- which is why Martin, who has travelled to Belgium and seen traditional lambic production, doesn’t consider their beers to be lambics at all. “Spontaneous fermentation is sort of an old-world method that’s probably how beers were made for thousands of years that basically heats up some wheat or barley in water and then just kind of expose it to the open air.”

Making lambics is an ancient tradition. At the core of this tradition is what is called “spontaneous fermentation,” which is what really sets lambics apart from most other beers. Spontaneous fermentation is a process in which the heated up wort, the base of the lambic that is essentially unfermented beer, is left out in what is called a coolship (a fancy word for a giant vat) to, well, cool. But during this time, the liquid is also collecting random bits of bacteria that are floating about.

“There has generally been an agreed upon set of rules out of respect for the tradition,” Martin says. “And so, for the most part, if you’re seeing ‘lambic’ on a bottle, it’s probably going to be from Belgium -- the Flanders region of Belgium.”

There are many different arguments out there for what actually constitutes as lambic. Some tie the name to the region, in the same manner that Champagne comes from the Champagne region of France (everything else is considered sparkling wine). Though there isn’t any stuffy legal backing of a similar manner for lambics.

As more breweries embrace sours, and as the American palate continues to become more and more intrigued by foreign imports and specialties, lambics, which are nuanced and layered, should definitely have a spot in your beer rotation.

“Lambic beers are kind of renowned for their funkiness. They can be hay-like or cheesy or musty, cider-y,” Martin explains. “People use terms that sound off-putting, like barnyard… when you describe it, it doesn’t sound appealing. But it’s really complex and really unique.” That's what makes them more fun to drink than say a lager or and IPA -- you never totally quite know what you might get when you crack open a lambic.

Lambic beers are a little bit like blue cheese, or maybe more like fish sauce. At least that’s what Kevin Martin, the director of brewery operations at Portland, Oregon-based Cascade Brewing (one of the West-Coast’s most celebrated purveyors of sours and fruit beer), tells me. And no -- it’s not because the flavor necessarily mimics the creamy stinkiness of blue cheese, or the boldly pungent fish sauce (though some have been described as tasting cheesy and musty). It’s because lambics, like many of the best things in life, are an acquired taste.

Do they have to be made in Belgium?

Belgian brewers don’t believe lambics can be made anywhere outside of Belgium. The beers are specifically brewed within the Zenne river valley, where seasonal wild yeasts flavor the quintessentially Belgian beer. But even though the term lambic is protected, that hasn’t stopped American brewers from trying to replicate the ancient method.

“Can this product be made in America or is this truly something that is unique to the microflora in and around Brussels and therefore can only be made there?” Andrew Holzhauer, the head of operations at Funk Factory Geuzeria in Madison, Wisconsin -- a brewery that primarily makes American-style lambics -- questioned. “I didn’t quite subscribe to that and wanted to kind of explore and see if making those beers was possible in this country.”

He, alongside other American brewers, met with HORAL (the High Council for Artisanal Lambics -- an association of Belgian lambic producers) to create an insignia for American breweries who follow the highly specific requirements to make lambics. The group came up with the term “Méthode Traditionnelle” -- if you see that term on your beer bottle, that means the lambic-style beer went through the same processes that have been around Belgium for centuries, though it wasn’t made in Belgium. Instead of calling their beers lambics, they’re referred to as “lambic-style beers” or “spontaneously fermented beers.”

'Spontaneously fermented' sounds intense. How do brewers ensure each batch is good?

The process for making lambics seems like it’d make for wildly inconsistent brews since it’s impossible to control what kind of microflora drifts into the coolship. But Brett Willis -- a marketing specialist for Portland, Maine’s Allagash Brewing Company, which specializes in Belgian beers -- assures me that the entire process is (somewhat) under control. “The beer is certainly exposed to all sorts of funky stuff, since it's basically just sitting out in the open air. But we have a solid handle on what's happening to it while it's out there,” he said.

There are three different aspects that you must pay attention to if you want to insure the beers will be consistent: temperature, bacteria control, and blending the finished products. “We're putting our beer outside only in a narrow temperature window,” Willis explained, adding that November is the month Allagash typically leaves their boiled wheat and barley blend out to cool. “This makes sure every batch cools consistently, and is exposed for a similar amount of time.” In terms of the random bacteria landing in the exposed coolship, Allagash brews “the beer a specific way to only help certain yeast and bacteria thrive.”

At the end of the day though, for spontaneously fermented beers, it’s near impossible to ensure that every single batch will taste exactly the same. “We mitigate this drift in flavor year-to-year by how we blend the beer at the end of the process. Meaning, a little more from this barrel, a little less from that barrel, until we have it tasting just right,” Willis said.

What’s unique about the process is that different locations inevitably make for different flavored-beer. It’s almost as if lambics, when left outside in say, Chicago, have captured the flavor of Chicago air. Or when brewed in the woods of Wisconsin, have zeroed in on what that may taste like -- in beer form.

“Every single beer we brew is essentially from the same recipes. So the flavors you get are coming from diversity,” said Holzhauer, citing his own brewing excursions. Funk Factory’s model includes a trailer-mounted coolship, which travels to different breweries across state lines to collaboratively create spontaneously fermented beers.

What kinds of lambics are out there?

Lambic is an umbrella term. It’s the base for a lot of interesting beers; a gueuze, for example, is a blend of different aged lambics to achieve the perfect, tart profile. Framboises are lambics that are later aged with fresh raspberries for three to six months. Krieks are the same, but with cherries. Brewmasters work with different fruits -- depending on seasonality -- to create an array of refreshing, tart, and fruit-forward beers. There’s peach (pêche), apple (pomme), and even lambics made from something called cloudberries: a sweet, yet tart, berry found in temperate regions. One of the most accessible brands of lambic out there is Lindemann’s, which is carried by both Trader Joe’s and Target.

Are they expensive?

Though the process behind making lambics is complicated and steeped in tradition, you won’t be encountering a price point that compares to, say, Dom Perignon. Instead, you can find bottles of lambic at Trader Joe’s or Target that will set you back about $9 for a 750 mL bottle. Craft versions, like those from Cascade Brewing or Allagash Brewing Company, may climb up to $30 or more -- depending on batch size and availability -- but for a refreshing beer made from the bacteria of the world, it's worth dropping some cash.