As former geology students, rocks were what brought Lisa and Brandon Boldt together. But these days, yeast and hops are more their passion as they rigorously craft Belgian-inspired, lambic-style beers at their sunlit, high-ceilinged brewery, Primitive Beerin Longmont.

We all know that brewers across the Centennial State experiment with a diversity of styles. And some devote a bulk of their energy into brewing specific quaffs, such as German beers or saisons. But no other brewery in Colorado, and probably in the United States, has devoted itself so fully to lambics as Primitive.

The Boldts closely follow the myriad rules for producing these beers, a style born in the Pajottenland region of Belgium, as well as in Brussels. The complex approach includes utilizing a “coolship,” a broad, shallow, flat-bottomed, 10-foot by 10-foot vessel that holds “wort,” the sugary soup that turns into beer after fermentation. The coolship’s shape encourages wild yeasts floating around in Primitive’s brewery to settle on the wort and kickstart fermentation—the Boldts eschew commercial yeasts. It’s a far more rigorous process, spanning 14 to 16 hours of open fermentation as the wort cools, and there are temperature restrictions, too. But for the Boldts, the pleasures of beer brewed the lambic way, with wild yeasts, surmount the challenges. Among other things, the wild yeast delivers a pleasing funk, one not attainable through commercial yeast.

Once the wort has cooled to the required 68 degrees, the Boldts pump it into neutral oak barrels where fermentation continues for at least nine months. Finally, they add fruit—Colorado cherries, peaches, plums, and other fruits, each in their own season.

The result: Beer so complex and aromatic that it carries itself more like wine. Swirl a glass of Disgraced Nuclear Physicist, made with golden Rainier cherries and aged in a barrel that formerly held Barolo. Inhale, and submit to cherry perfume. Take a sip, and notice—the Boldts don’t carbonate their beer, per the rules for making lambic. It will taste flat. It might not be your thing. But if you can get past the lack of effervescence, rewards await. Namely, beautiful flavors that reflect Colorado: the grains in the wort, the water, the hops, the fruit, and even the yeast.

If sparkle is a must, wait a few months. While Lisa and Brandon reject the injection of carbon dioxide into their beers, this year they anticipate introducing a line that has undergone secondary fermentation in the bottle, resulting in a gentle fizz.

And be forewarned: Even though their entire brewery revolves around these time-intensive lambics, you won’t see that word on Primitive’s boxes or bottles. Only beers made in those regions in Belgium that adhere to lambic rules can put the word “lambic” on a label. So, instead of lambic, Primitive and others like them use the term “Méthode Traditionnelle.”

Scoring sips of Primitive Beer’s lambics requires heading to the brewery’s beautiful wood-meets-iron-meets-cement space in Longmont’s Prospect New Town neighborhood. (Pro tip: It’s right across from the new Babettes Pizza & Pane.) Primitive typically has between eight to 10 beers on tap, all of them poured by way of English handpumps (no C02-fueled kegs or taps there). Order them by the glass or the one-liter ceramic pitcher, as is traditional in Belgium.

Lisa and Brandon both work full-time for other breweries—Odd 13 Brewing and 4 Noses Brewing, respectively—but Primitive is their passion. “This is what we geek out on,” Brandon says. “We went all in.”

If you go: The brewery is only open on weekends, and not all of them; it’s best to check the website or call for details before you visit.