BREWERS of barrel-aged sour beer take risks and practice patience. They wait as long as three years to see whether the cloudy liquids resting in oak ripen into shades of gold or raspberry and develop the ideal tart, tangy flavors, or become undrinkable, ravaged by aggressive yeasts. It’s an expensive gamble.

And even if they succeed, they may still have to persuade people to drink them.

“We still get customers who call to let us know a bottle of our barrel-aged beer had gone bad because it tasted sour,” said Vinnie Cilurzo, owner of Russian River Brewing Company in Santa Rosa, Calif. “Sour beers will never become the pale ales of craft brewing.”

But for the brewers of sour beer, and its fans, the wait is worth it.

"I almost regret that we call them sour beers,” said Tom Nickel, owner of O’Brien’s Pub in San Diego. “The word ‘sour’ requires a bit of a leap of faith.” The best of some sour styles, such as gueuze, he said, have flavors like champagne or fresh lemonade. “You may not like the idea you’re drinking sour beer, but your mouth will like it."

While the umbrella of “sour ales” includes many styles, traditional sour beers are most popular in Belgium, home of lambics, gueuzes and Flemish sour ales. But in the last few years American brewers have been trying their hand at imitating and riffing off those styles by fermenting with special yeasts and lactic acid bacteria. Sometimes they age the beers in wood or stainless steel and add raspberries, cherries, apricots and other fresh fruit for flavor, before blending the end results.