A Top Brewmaster Tells Us What’s Up with Spontaneously Fermented Beer

By Noah Kaufman |

© Mat Trogner, Allagash Brewing Company

Spontaneous or wild fermented beers occupy an odd niche in the world of American craft beer. Because they take so much time to perfect and are not always the most predictable beers, they remain a rarity among American breweries. That has allotted them a sort of white whale status among many beer geeks. But that same scarcity—and the fact that the beers themselves can taste a bit funky—has kept the style from catching fire among casual craft beer drinkers. But at Allagash Brewing Company in Portland, Maine, they are true believers in wild beer. They were the first American brewery to use a coolship—a wide, shallow vessel that exposes unfermented beer to wild yeast in the air. And they have used that coolship with great success. Allagash’s Coolship series rates between 95 and 100 among the picky palates on Beer Advocate.

We chatted with Allagash brewmaster Jason Perkins about his coolship, his wild beers and what the future might hold for spontaneous fermentation.

How did people begin using coolships?  
Historically speaking, they have been around for a very long time, but they weren’t invented for what they’re used for now. They were invented to cool wort (sugary unfermented beer), because even though people didn’t understand all the science of fermentation, they knew if they cooled their wort faster they got better results.

Why do you think coolships aren’t more common in the United States?
The [brewing] literature says spontaneously fermented beer can only be made on the Seine somewhere around Brussels. There is a belief that there is magical yeast that exists there but nowhere else.

So what made you guys add it to the brewery?
Belgian beer has always been our focus, and we were curious about a process that is so tied to Belgium. We wanted to see if we could bring it here. Rob [the brewery owner] came in one day and just said, 'We’re doing it.' There wasn’t even a way to pilot it, because we needed the actual room and the vessel. 

And how does your natural Maine yeast compare to the “magic” stuff they have in Europe?
I actually think the beers are pretty similar. In my opinion, the flavors we have are unique to us, but the differences are no more different than the differences in individual producers in Belgium. 

How long does it take to brew using a coolship?
Generally, it takes somewhere between two and three years. Coolship Resurgam, for example, is a blend of 1-, 2- and 3-year-old beers. The fruited beers we make with raspberries or cherries use a 2-year-old base and then an addition of fruit for another four to six months.

As more brewers have begun to experiment with wild fermentation, what do you think are the challenges they face?
I have similar concerns about people getting into this as I do about brewing in general. Make sure to take the time to know what you’re doing. One bad wild or sour can dissuade someone forever.

I’m also a little worried it could turn into a race to see who can make the most sour beer in the same way there was a race to make the hoppiest beer. It’s a delicate thing for me. Sourness is such a cool tool. But it’s not like more sour is better. 


Anyone looking to get their hands on a beer from Allagash’s Coolship series will have to make their way up to Maine. For the time being, the brewery only sells the bottles at the brewery and limits them to two per person. But if you’re looking for a beer road trip, this is one worth taking.

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