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Meet the Local Breweries Riding the Coolship Wave

The centuries-old brewing tool is wildly unpredictable, yet can produce unique, terroir-driven beer.

On a night next winter when the temperature dips below 30°F, you might spot Jeff Hardesty driving down U.S. 67 in St. Louis with a miniature house in tow. Peek inside one of the windows, though, and you’ll spot an unlikely inhabitant: a 6-by-12-foot stainless steel coolship – which essentially resembles a giant brownie pan – plus a stainless steel IBC tote tank full of wort (the sugary liquid that ferments into beer). That night, Hardesty – who owns acclaimed Narrow Gauge Brewing Co. in Florissant, Missouri – will be on his way to Sioux Passage Park near the Missouri River, where he’ll park the trailer, load the coolship with wort and wait for the magical process known as spontaneous fermentation to happen overnight.

So why is a brewery with a national reputation for juicy New England-style IPAs investing in an ancient tool famous for producing Belgian lambic beers? Because coolships are currently the, well, coolest tool in craft brewing.


Calling coolships trendy might be a little disingenuous – use of the traditional vessel dates back centuries. The tool takes its name from the Flemish koelschip; in medieval times, brewers cooled down boiled wort in a hollowed-out tree trunk resembling a boat (today, most coolships are made of stainless steel or copper). Before modern refrigeration, the shallow, open-top rectangular vessel was used to cool hot wort naturally prior to fermentation, as the large surface area allows the liquid to cool quickly. And because coolships are uncovered, they also pick up airborne yeast and microflora, which inoculates the wort. This process, known as spontaneous fermentation, produces funky, sour beers with a distinct sense of terroir that simply can’t be replicated by using commercial yeast strains developed in a lab.

As alternative – and more reliable – methods for cooling wort arrived starting around the mid-1850s, coolships became less popular, though not entirely extinct. Arguably the most famous Belgian lambic producer, Cantillon Brewery in Brussels, has continued to use coolships over the past century to produce its acclaimed spontaneously fermented sour ales.

Inspired by these European lambic producers, American craft breweries including Allagash Brewing Co. in Portland, Maine; Jester King Brewery in Austin, Texas; and De Garde Brewing in Tillamook, Oregon; have ushered in a new era of the coolship over the past decade.

In the St. Louis area, Foeder Crafters of America, which has become the country’s leading producer of traditional foeders (massive oak fermentation tanks), began producing coolships about four years ago. Co-owner Matt Walters jokes that he was simply trying to come up with a way to make the company “cooler,” but demand has quickly skyrocketed. Foeder Crafters sold just three coolships in its first year producing them, and now produces about 30 per year for breweries across the country.

The size of the vessel itself depends on the size of each brewery’s own brewing system, ranging from a tiny 2-barrel coolship (like the one at White Rooster Farmhouse Brewery in Sparta, Illinois) up to a 30-barrel coolship comprised of three 10-barrel coolships stacked on top of each other. (Wisconsin’s New Glarus Brewing Co. is said to own the country’s largest coolship – the 25-by-160-foot coolship can hold 100 barrels of wort.)

“With coolships, you’re waiting for some magic to happen – for some [wild yeast] to land in your coolship,” Walters says. “And some wild yeast just tastes terrible. But every once in a while, you’ll find one that’s just mind-blowingly good. Once you’ve caught this wild, beautiful animal, you want to put it in your zoo. And that’s what the foeder is; the foeder is the zoo that will hold that bacteria or wild yeast strain and let it work.”

Among the first breweries in the country to use a coolship was the acclaimed Side Project Brewing in Maplewood, Missouri, which started working with one in 2013. The brewery specializes in old world-style, Belgian-inspired beers, so head brewer Cory King, who owns the brewery with his wife, Karen, says using a coolship was a no-brainer.

Side Project has predominantly used its 10-barrel coolship, which is stored outside and brought into the brewery when in use, to produce components of its blended beers. Because of the nature of spontaneously fermented beers, which are produced using wild, airborne yeast, no two beers will ever be exactly alike.

“If you rely too heavily on [the coolship], the things that come out of it are just all over the place,” King says. “People expect Side Project to taste like Side Project – that’s the importance of the blending that goes with it.”

The recent Pulling Nails Blend #8, for instance, featured beer that was cooled in the coolship overnight before being aged in French oak puncheons (larger wine barrels) for three years. It was then blended back with a 1-year-old Missouri saison and refermented on raspberries and cherries before being bottle-conditioned.

And now, after several years of navigating the wild nature of working with coolships, Side Project is gearing up to release its first line of 100-percent coolship-produced beers – in other words, coolship beers that haven’t been blended. The first was put into Side Project’s coolship in early winter of 2016, then moved to a horny tank (a mixing tank) and blended before being racked (or transferred) to Danish cherry wine barrels and fermented for two years. It was then finished with fresh cherries and bottle-conditioned. The beer, which King says is the most traditional lambic-inspired beer Side Project has produced yet, is scheduled for release sometime this year.

On the flip side, the brewery also collaborated with Jester King on an entirely nontraditional coolship beer. Typically, most breweries use coolships for either wheat malt, blonde beers or Pilsners; Side Project and Jester King, meanwhile, put a brown beer through the coolship and then fermented it on cherries and blackberries. The as-yet-unnamed beer is also slated for release this year.

While brewing another recent collaboration with friends from a few sour-focused breweries in Ohio, California and Pennsylvania, King says the group soon came to the same realization: “We were like, ‘Did you notice that everybody and their brother has a coolship now?’ he says with a laugh. “The consumer gets excited about everything from coolships to – I don’t know – Oreo cookies in their beer. People are always trying to do something different.”

Coolships are indeed popping up at breweries across the country, including City Barrel Brewing Co. in Kansas City, as well as Narrow Gauge Brewing Co., Perennial Artisan Ales and Wellspent Brewing Co. in the St. Louis area.

Wellspent’s coolship is far from traditional: owner Kyle Kohlmorgen says the small brewery didn’t have a coolship in the budget, so he built an alternative. Kohlmorgen bought two oak barrels, and on each, removed the head off one side. The barrels sit side by side on concrete blocks outside the brewery and are filled to the very top with wort when used for cooling.

Similar to the desire for terroir in wine, coolships allow breweries to produce beer with a distinct sense of place and time. Mobile coolships, like the trailer Hardesty built for Narrow Gauge, take this idea to the next level. Although Narrow Gauge is best known for New England-style IPAs, Hardesty says his favorite beers to brew during his homebrewing days were sour and mixed-fermentation styles. As the brewery has scaled up production, Narrow Gauge has started diving into other styles, including a few quick-soured beers like sour IPAs, Goses and Berliner weisses. Next, Hardesty plans to use the brewery’s new mobile coolship to produce some traditional Belgian-style beers, such as lambic-inspired beers, saisons and a Belgian gueuze, which blends 1-year-old, 2-year-old and 3-year-old coolship beers.

“It being mobile will essentially give us the availability to coolship the wort anywhere,” Hardesty says. “We could coolship at the brewery, at my house or drive it down to the river. We should be able to pick up different microbes wherever we do it, so as we use it more, we’ll build up a library of different beers that will be better for blending, so we may be able to capture more complexity in that style of beer. It will also give us the opportunity to do some collaborations with breweries that don’t have a coolship.”

In Kansas City, City Barrel Brewing Co. employs a similar technique. The brewery, which opened in the Crossroads Arts District in late February, specializes in wild, sour and hoppy beers, and works with a 15-barrel coolship that’s about 6 feet wide by 14 feet long. True to its name, City Barrel is committed to keeping things as local as possible – the tanks in the brewery are all named after neighborhoods in Kansas City – and that’s precisely the idea behind the brewery’s series of coolship beers.

City Barrel’s Neighborhood Spontan series features beers inspired by the different microflora of Kansas City’s neighborhoods. Just like Narrow Gauge, the brewery pumps wort out of a kettle and into a stainless steel tote tank, then loads the tote full of wort, along with the coolship, onto a trailer. Stutsman and the rest of the City Barrel team will then drive the coolship to different neighborhoods in Kansas City, unload the coolship, pump the wort back in and, in Stutsman’s words, “let the natural microflora do its thing overnight.” The next morning, the wort is pumped back into the tote, taken back to the brewery and racked to barrels, where the beer is aged.

Fittingly, City Barrel kicked off its Neighborhood Spontan series with a Crossroads-inspired beer. In mid-March, the team unloaded its coolship in the brewery’s front dining room, opened up the garage doors and invited the public in for a party as the fermentation process got underway. After its turn in the coolship, the resulting beer, a golden sour made in the traditional lambic style, will be ready for release sometime next year. Next up in the series, City Barrel aims to produce a beer inspired by the wild yeast captured in the Brookside neighborhood.

“The cool thing about coolship beer is that it’s the most local beer you can possibly make,” Stutsman says. “It’s just one place in time that created that mixed culture.”

The greatest advantage of a coolship, though, may also be its greatest disadvantage. Since the vessel is open (though some breweries will use a screen similar to a fish net), the beer is exposed to any number of airborne yeast and microflora. This process can produce wonderfully unique wild beers, but it also opens brewers up to a great deal of risk – wild yeast is, after all, wild, and can act in unpredictable ways that lead to off flavors.

Missouri’s climate also makes the process extremely tricky – most of the time, it’s either too hot or too cold, so the window to use a coolship is narrow. Most breweries in the area use their coolship in the winter months, as the ideal temperature range is about 20°F to 40°F. If it’s too hot outside, the wrong type of yeast and microflora can inoculate the wort. During Missouri’s famously warm summers, for instance, more acid-producing yeast can find their way into the beer, producing sour or acetic flavors that make the beer taste more like vinegar.

Yet if the weather is too cold, the coolship won’t catch enough wild yeast and bacteria for the beer to ferment properly. Over the years, King says Side Project has had to dump entire batches of beer when there’s not enough yeast, as the yeast that is captured gets stressed out and overworked, leading to undesirable flavors.

“It’s a tough tool to use,” King says. “There’s a reason why people stopped using them when we started getting refrigeration and other ways to chill beer. With coolship beer and the spontaneity, you throw a lot of what you’ve learned out the window. You’re letting nature take more hold of the beer than we do. With that comes a lot more risk and a lot more loss. But when everything comes together, they produce some beautiful, unique beers – that’s for sure.”

City Barrel Brewing Co., 1740 Holmes Road, Crossroads Arts District, Kansas City, Missouri, 816.298.7008,

Foeder Crafters of America,

Narrow Gauge Brewing Co., 1595 N. U.S. Highway 67, Florissant, Missouri, 314.831.3222,

Side Project Brewing, 7458 Manchester Road, Maplewood, Missouri, 314.224.5211,

Wellspent Brewing Co., 2917 Olive St., Midtown, St. Louis, Missouri, 314.328.0505,

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