To a mainstream beer drinker, the list of featured beers at a recent Washington-area festival might sound like a weird beer geek's Christmas list: a crisp, briny gose that gets its flavor from local oyster liquor -- the liquid you slurp from the half shell -- and is fermented with yeast cultured from the shells of oysters; tart Berliner weisse-style beers brewed with blood orange, mango and passion fruit, or a mix of cucumber and mint; and a sour Beligan-style brown ale with half the spices in your local supermarket, including star anise.
Yet hundreds of people paid $60 to $75 each to wander around the Make It Funky Festival last month at Denizens' Silver Spring, Maryland, brewery, sampling almost 100 wild-fermented and sour beers from 36 breweries.
The popularity of this event is a sign of the growing power of the sour, which remains a niche style in terms of overall beer consumption but is of increasing importance to brewers who are trying to differentiate themselves.
And as sours find more devotees and space in taprooms, the variety of styles is also helping to expand craft beer's consumer base beyond stereotypical hopheads: According to a 2016 Nielsen survey of craft beer consumers, women are 75 percent more likely to prefer sour ale than men.
Sour beers are one of the most unlikely success stories in the current American craft scene. Traditional German and Belgian styles, such as gose and lambics, are centuries old. Their trademark sharp, acidic flavors come from the presence of lactic bacteria during fermentation. Modern brewers approach the creation of these beers in different ways: Some allow wild yeast and bacteria to enter the wort, a process known as spontaneous fermentation, while others carefully control the yeasts. Some brewers make sour beers with these wild organisms only in the brew kettle, while others prefer to leave fermenting beer in tanks or wooden vessels for months.
Hannah Gohde, a brewer at Free Will Brewing in Pennsylvania, remembers her first taste of oud bruin, a tart brown ale from Flanders. "At first I was like, 'I'm not so sure about this,' and then I took another sip, and I was like, 'Yeah, this is so cool.'"
When Free Will began brewing sours a few years ago, Gohde says, it was "from a selfish standpoint. It was hard to find a great sour that was available for a decent price on the market." More than that, she enjoys the process. "I like the creativity that goes into sours," Gohde says. "It's more of an art form than a science."
Jun Rossetti admits she didn't know what sour beer was when she first visited Denizens a few years ago. But after she told a bartender about her love of vinegar and citrus flavors, he steered her toward a sour ale. Now she's spreading the gospel: "My husband doesn't like sour beer -- he's a hoppy IPA guy. He didn't get why I like it. He came (to the Make It Funky festival) last year and tried some beers and said, 'I get it now.'"
One barrier might be the terminology: "Sour" is not always a positive descriptor for beverages. And so many different styles now fall under the umbrella of sour that it's hard to know what's meant without context: A tart gose, made refreshing by the addition of coriander and sea salt? A lemony, face-puckering Berliner weisse? The sweet, woody tartness of barrel-aged blond Belgian ale? Or something else entirely?
"I think it's a challenge with all the terms," says Allagash brewmaster Jason Perkins. The Maine brewery has made some of the more interesting wild ales in the United States and was the first on this side of the Atlantic to use a large, open pan called a coolship to brew tart, complex Belgian-style ales. "I think it's a confusing thing for the consumer. But I wouldn't want to tell a brewer, 'If you want to call it this, it has to go into one of these boxes.' That goes against craft brewing, frankly."
At the same time, "I don't love the term 'sour beer,'" Perkins says. For some beers, "to say, 'That's a sour beer,' it doesn't really describe that beer, it doesn't do that beer justice."
Whatever you call them, supermarket sales of sour beers tripled between 2015 and 2016, according to market research firm IRI, says Bart Watson, the economist for the Brewers Association trade group. He thinks that is probably underselling the style's popularity, because many sours are most popular in brewery taprooms.
Sours are still a niche, Watson says, "but a fast-growing style and one that a lot of brewers think is going to be important in the future."