The Great American Beer Festival now has a wild, weird, and undeniably cooler younger sibling: the What the Funk?! Fest, held on Saturday, October 11 in Denver, which featured more than 40 breweries pouring wild, sour, funky, and barrel-aged beers for a sold-out and sour-beer crazed crowd.

Organized by Denver's Crooked Stave Artisan Beer Project and presented with sour beer group Funk'n Wild, the fest came together after many breweries were shut out of GABF because registration filled up in record time.

Breweries from all corners of the country were represented, from Vermont (Hill Farmstead) to Oklahoma (Prairie Artisan Ales) to Tennessee (Yazoo Brewing Co.). Veterans like Goose Island, regarded as one of the first to barrel age beer with their Bourbon County Stout, poured across the room from J Wakefield Brewing, a Florida brewery-in-planning who was pouring his sought-after Berliner Weisses that he brewed at Tampa's Cigar City.

The fest was a celebration of what some of the best breweries in the country are doing right now—cultivating native yeast, experimenting with fruits and fermentation, and putting their beer into barrels and seeing what comes out.

Time consuming, not very cost effective, and requiring a great deal of patience and skill, barrel aging, sour brewing, and blending is as much an art as it is a science, so I talked to a few of these brewers to find out what the funk is going on.

On patience and unpredictability

"We have a lot of beer sitting," said Jolly Pumpkin lead brewer Sean Brennan, who has been at the Dexter, Michigan brewery since they opened in 2004, working under founder and brewmaster Ron Jeffries. He estimates they have somewhere around 1,500 barrels of beer in their inventory, "aging, doing nothing, just sitting."

Jolly Pumpkin practices open fermentation, a traditional, time-consuming technique that creates complex flavors. They age all of their beers in oak casks, and blend different batches of the same beer that have been aging for varying amounts of time.

"That's the fun part about barrel aging," said Brennan. "We can brew standard beers, but with barrels, it's almost stressing because you're kind of hands-off. Once you put it in the wood, it could go bad, but then that's the excitement and the fun is maybe something doesn't taste quite like what you're looking for, sometimes you can just let it sit, and a year later, it could be the best thing in the world."

On dumping beer

"Every brewery that does a lot of barrel-aged beer will end up dumping a lot of beer," said Ryan Fields, barrel manager at Lost Abbey in San Marcos, California. "It's not a majority that gets dumped, but it's definitely a percentage. You don't know what the barrels are going to do. You're not in control of it."

Barrels can be dumped for a variety of reasons—non-sour barrels can get infected and infected barrels can turned into vinegar, said Fields.

"There will be bad barrels—there are bad barrels in our barrel room," said Ron Extract, co-owner and brewer at Austin, Texas Brewery Jester King. "And if we commit to packaging everything we brew, then we commit to making bad beer and that's not what we want to do. I think that self-editing is one of the hardest things to do as a brewer and it's also one of the most important things, especially as a brewer embracing wild yeast and bacteria and rolling the dice really, with this type of process."

On defining sour and wild beer vocabulary

While sour, wild, and funky beers are growing in popularity, consumers—and brewers—are still sorting out how to describe and categorize them.

"I think there's a lot of gray area that I hope eventually can be cleaned up," said Cory King, head brewer of Perennial Artisan Ales in St. Louis, and founder/brewer of 100 percent barrel-aged gypsy brewery, Side Project Brewing.

"The term American wild ale I think is too broad still," said King. "If you have a beer and you throw Brett in it, people label it as American wild ale. That Brett strain pitched in that beer is no more wild than any yeast strain you bought from a lab," said King. "When I say wild ale, there will be wild yeast in it."

King plans to do a series of 100% Brettanomyces-fermented beers; the first was released at the end of September and is fermented with a single isolated Brett strain from a bottle of Cantillon that a home microbiology hobbyist has isolated, he said. He's also working with native yeast and wild ales—look out for his Black and Wild, a black American wild ale, fermented and aged on tart Michigan cherries in whiskey barrels.

On consumers embracing sour and wild beers

"When we started, we heard from a lot of people that the only way we were going to be able to sell beer in Texas is if our core lineup consisted of a red, a blonde, a bock, an IPA, and a wheat," said Ron Extract of Jester King, which was founded by brothers Michael and Jeff Steffing in 2010.

While they didn't go that route, they do incorporate several simpler fermentations into their lineup—an imperial stout, a rye IPA, a table beer. Then there's the funkier stuff: multi-strain fermentation with souring bacteria and Texas Hill County native yeast and local wildflowers. Their Atrial Rubicite, a 5.8% ABV wild ale refermented in oak barrels with raspberries, won bronze in the Belgian-style lambic or sour ale category at GABF and was a big draw at What the Funk!?

"There is a real strong interest in these beers in Texas, much stronger than a lot of people realize," he said.

On the future and looking back

Rob Widmer, co-founder of Oregon's Widmer Brothers Brewing, recalled, with a laugh, his first sour beer as "probably some of my homebrew or some of my uncle's." Widmer, who will be celebrating the brewery's 30th anniversary next year, reflected on how the sour and wild beer experimentation fits into the larger American craft beer landscape.

"Twenty years ago," he said, "it was different beer styles. And then it was different hoppy beer styles. We could go back 20 years and have the same thing going on, only it would be, 'Wow, I just tasted a beer called a pale ale.' ... Who knows what the future holds? There was a fellow brewer who has been in it a long time, he has a lot more technical training than I do, but he said he still feels like we're just scratching the surface of what beer can do."

About the Author: Heather Vandenengel is a nomadic beer writer and the News Editor for All About Beer. You can follow her on Twitter @heathervandy.

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