Tart, tangy, and technically contaminated, kettle sours are an increasingly popular craft beer category. But the term “kettle sour” is not a beer style; rather, it’s a means to an end.

Kettle souring, also called quick souring, is a production method that gives us beer styles like gose and Berliner weisse, along with what we like to call Warhead beers — the quick-soured puckerers that tend to be as bright in color as they are in acidity.

“Kettle” refers to the brew kettle, meaning the beer is soured in a stainless steel mash tun and fermented in a similar tank. This denotes the key difference between kettle sours and traditional sours: steel over barrel.

Souring in a steel “kettle” is faster and easier than the traditional sour beer method. The latter often involves aging in wood with a mix of microbes, and, most of all, time. Traditional sours can take several months or even years to create, while a kettle sour can be turned around in a matter of days. It’s a great way for busy brewers to get their tart on.