Fermentation Anywhere: Brewers Experiment with Portable Coolships

May 1, 2017 By John Holl

Brandon Jones was standing on the loading dock of Yazoo Brewing Co. in downtown Nashville, Tennessee, looking over the coolship that had just been delivered. It would soon go into the upper reaches of the brewery building, but Jones was already thinking about getting it out.

While most coolships are built to stay in place, this custom-built unit for Yazoo is designed to be mobile, to fit onto the back of a truck and let yeast inoculate the wort around the region.

“With a pop of sours and wild and funky beers on the market now, and kettle sours becoming more popular, this is another way to differentiate our beers,” says Jones, who runs the brewery’s barrel program.

Coolships have been a part of brewing tradition for centuries They’re large shallow containers, typically in the attics or tops of breweries—most notably in Belgium—that are exposed to open air. Wort is pumped in hot and allowed to cool, and natural microflora, wild yeasts that live in the area or happen to be floating by, land in the liquid and begin the fermentation process.

There’s a static nature to these beers, with equipment rooted in place and microbes taking up residence in nearby wood and other surfaces waiting for a new batch to be pumped in. More and more brewers, like Jones, are breaking away from the brewery and taking the coolships on the road, sometimes quite literally.

In March of 2016, if you happened to be driving along the stretch of 1-25 between Denver and Colorado Springs on a particularly cool night, you might have spotted a flatbed truck with a metal tub strapped down, from which a copious amount of steam was escaping. It was the culmination of months of planning by TRVE Brewing Co. in Denver and Trinity Brewing Co. in Colorado Springs. A collaboration beer—a method gueuze—was made at Trinity, and wort was loaded into the brewery’s already mobile coolship (affixed with wheels; brewer Jason Yester would expose it to the air when the temperatures were just right) that was strapped to the back of the truck. For this trip, the coolship was outfitted with a custom-made baffle to prevent the liquid from sloshing out.

After carefully making it to TRVE, the wort was pumped into barrels. A new batch of wort was made at the brewery and then trucked down to Colorado Springs for a similar barrel treatment. The beer has yet to be named, and no release date has been announced.

“Because it’s spontaneous beer, we’re waiting for it to tell us when it’s ready,” says Nick Nunns, the owner of TRVE.

Traveling with a coolship also allows brewers to break up the normal brewing routine. Derrick Morse, the founder and owner of Mantra Artisan Ales in Franklin, Tennessee, recently acquired a 15-barrel coolship that can be transported on the bed of a truck. During the first weekend in March, the brewery rehydrated and steamed some barrels, brewed a gueuze at the brewery and brought both about 45 minutes east to a farm it purchased in Murfreesboro.

With a homebrew-level pump that could handle about seven gallons per minute and a portable generator, they pumped the wort that evening into the coolship. The next morning, starting around 6:30, they began transferring the wort from the coolship into the barrels that had been loaded onto a box truck.

“Ultimately, 80 percent of the process is just hanging out, camping, drinking beer and waiting while wort is cooling off overnight,” says Morse. Starting next winter, he’s hoping to work with state officials and use his coolship at every state park. “I think it would yield some cool stuff as far as flavors are concerned.”

As to whether portable coolships will become commonplace, “no one has complete answers at this point,” says Jeffrey Stuffings of Jester King Brewery. “Right now everyone is just experimenting.”

His brewery, on the outskirts of Austin, Texas, is celebrated for its spontaneous and wild ales, most of which come out of a coolship in the eaves of the brewery building. Last year, however, Jester King took an old coolship and 15 barrels of wort to La Cruz de Comal Wines, about an hour drive south of the brewery, and set it up in the vineyard.

“We try to time it to bud break, just when the plants are starting to sprout and break because, presumably there’s a little voodoo in the air as the grapevine gets growing for the year,” Stuffings says. “We thought there might be some nice microflora, and we wanted to see what different climates could do.”

Having recently tasted the beer, he professed to being “pretty darn happy with it” and returned to the winery again this past February. “By next year we’ll have two years to blend from; batches 18 to 24 months is where I like to be with these. And we can get to blending and bottling.”

Jones of Yazoo Brewing says he was inspired by Jester King’s movable feast and, with brewery owner Linus Hall, commissioned his custom-made fully mobile coolship to get new flavors into Yazoo beers. It can hold about 600 gallons per batch, can fit onto the back of a trailer—when it’s not in use in the brewery’s attic—and even has a specially built immersion chiller to go inside if the wort needs a little help cooling down.

“The idea is to use ambient temperature as much as possible,” he says. Typically ambient temperatures in the 30s and 40s are what brewers look for.

There are trade-offs to leaving home, although mostly aesthetic.

“It’s a pretty magical thing. … You start pumping wort into the coolship and you can see real well in the room, and within 45 seconds it’s just a dense cloud of steam that has this amazing aroma, and it’s a pretty cool thing to experience,” explains Rob Tod, the founder of Allagash Brewing Co. in Portland, Maine. “It’s also really cool to come in the next morning. It’s a very peaceful, serene experience because it’s cooled overnight, there’s no more steam, the wort is maybe 72 or 74 degrees Fahrenheit and ready to go into oak, and spend a couple of years in oak.”

Tod’s brewery was one of the first in the United States to install a coolship, he said during a recent recording of “After Two Beers,” the interview podcast from All About Beer Magazine.

“It’s a cool experience, and we’ve been making more and more of those beers, adding space for more barrels. I think we brewed about a dozen batches this year of the coolship.”

Talking with brewers around the country, static coolships are becoming a regular part of brew house planning and expansions. But in an age of beer experimentation, expect to see more offerings that got their spark far from the brewery walls.

“I think pulling in different characters, from farms, flower fields and beyond is going to give us extremely unique beers,” says Jones, “with characters that we could not get from the brewery.”