× Expand Robin Shepard The new wild fruit cave at New Glarus Brewing's Riverside Brewery is up and running.

The first beers from the new wild fruit cave at New Glarus Brewing are set to be released. "People have been moving to hoppy beers, and now IPAs are sort of mainstream," says brewmaster and co-owner Dan Carey. "The next cutting-edge thing is sour beer."

Despite sounding like he's just now riding the next craft beer wave, Carey has actually been making sour beers since opening New Glarus Brewing in 1993. What is new is his wild fruit cave, a specialized addition to the original brewery location that takes advantage of wild yeasts and other microorganism for making beer. That facility is referred to as the Riverside Brewery, as opposed to the Hilltop Brewery, which is where New Glarus concentrates its production.

"There's been steady interest in sours over the past 20 years," states Carey. "But in the last year or two, it's really taken off."

An Oud Bruin (old brown) will be the first release from Carey's emerging lineup of American sours and Belgian lambic-style beers, and is expected out this week. This style is similar to the brewery's Enigma, its Old English Porter, and the highly sought after Wild Sour Ale, which was first released last summer and quickly evaporated from store shelves amidst national acclaim.

New Glarus has made an Oud Bruin before, but this new version is significant because it's the first beer to come out of the new wild fruit cave at the Riverside Brewery.

Perhaps even more importantly, this Oud Bruin is expected to become the base beer for an increasing and evolving selection of New Glarus fruit beers. "I don't think of it as its own brand yet, because the beer kind of goes its own way with flavors the way it wants," says Carey. "The challenge with these beers is that I'm not really in charge -- they are wild, and I go were the beer leads me."

Carey's second beer from the wild fruit cave will be a Belgian lambic-style blonde ale, which is termed a gueze when not made with fruit. But this sour blonde will be used as the base for certain fruit beers, and is slated to provide the background for this year's New Glarus Cranbic, which is planned to be released in September. Both the Oud Bruin and Cranbic are sold in four-packs as part of the brewery's Thumbprint line of limited release beers.

Carey adds he's planning a special release from his wild fruit cave for the Great Taste of the Midwest on Saturday, August 9. He hasn't decided just yet what that beer will be, though. In part, that's because making sours and lambic-style beers takes months of fermentation, and the final beer is often blended by taste.

"In other words, you have a barrel that is really sour and a barrel that is really sweet and then you blend them together to come up with something," Carey explains.

The Oud Bruin and lambic-style blonde were initially brewed back in February, and have been aging in oak ever since. "I want to go down to the Riverside Brewery and taste some barrels, put them all out, and see what I can come up with," he says, referencing his planned special beer for the Great Taste.

New Glarus has long been known for making sour ales and lambic-style fruit beers. Its Wisconsin Belgian Red and Raspberry Tart have won numerous awards and enjoy a cult-like following among craft beer enthusiasts. That reputation outpaces their scale, though, as sours, lambic-style and specialty fruit beers from New Glarus represent only about 4% of the brewery's overall output.

The wild fruit cave, designed by Carey's daughter, Katherine, who works for Potter Lawson architects in Madison, allows New Glarus to increase the amount and variety of these unique beers. Its approach is built upon Old World traditions developed over centuries by Belgian brewers to produce beers that rely on open fermentation processes involving fruits along with wild yeasts and bacteria. Many of these beers are known for their sour, tart and even acidic flavors.

At the heart of the wild fruit cave is a coolship (termed a koelschip in Flemish) used to cool fresh wort, gradually, in open air. It is a large, shallow, square, stainless steel tub that has no cover. The coolship sits in its own room with windows on either side; these are left open to slowly cool the wort and allow wild yeasts from the outdoors to find their way in. Such cooling of the wort in this manner usually happens overnight, and during cooler months of the year. The ceiling above the coolship is a combination of concrete and exposed wooden beams and slats that increases the room's humidity and collects moisture, making for a ready home to microorganisms essential to this type of brewing.

Modern breweries do everything possible to clean and sterilize their facilities to prevent "infections" of their equipment. However, in making beer that relies on wild fermentation, these microorganisms are nurtured. For breweries like New Glarus that have an extensive commitment to making such beers, this process is often kept separate from other brewing operations because of concerns over cross-contamination by those wild yeasts and bacteria. At New Glarus, those who attend to the wild fruit cave do not go back-and-forth between it and the main production brewery during the same work day. (For anybody interested in visiting the wild fruit cave, this summer it's accessible only during the Hard Hat Tour held on Friday afternoons; reservations are required.)

As part of developing his wild fruit cave, Carey has increased the number of large oak tanks, called foeders, which are used to age these special beers. Each foeder can hold nearly 2,800 gallons of fermenting beer. As his dream for the wild fruit cave took shape over the last couple of years, Carey contacted and traveled to wineries from California to France looking for foeders. Last winter, New Glarus even brought in a cooper (barrel-maker) from California’s Napa Valley to help teach brewery workers how to maintain and care for these large wooden vessels.

New Glarus has been using foeders since 1994, and was actually the first U.S. brewery since Prohibition to install them in its facility. For visitors who get access to the Riverside Brewery and its wild fruit cave, it's like taking a step back in brewing history. With all of the oak foeders, the walls of stone and brick punctuated with arched doorways sporting heavy wooden doors, and the coolship room itself, the overall setting is unique to the U.S. craft brewing scene, perhaps even worldwide. The wild fruit cave may be all new construction, but it has the look and feel of breweries centuries ago.