Cast in Stone: Brewers Experiment with Equipment that Has Winemaking Origins

Tools of the Trade by | Aug 2016 | Issue #115
Bent Water’s head brewer John Erik Strom with the brewery’s two concrete fermentors. | Photo by Michael Shaughnessy

“I learned about concrete fermentors through the wine world, and thought if they make great wines, they might make great beers as well,” says Hair of the Dog founder and head brewer Alan Sprints. “Concrete was a great way to change a beer’s flavor only because of the shape and material of the fermentor.”

Since the bright red, egg-shaped, 15-barrel concrete tank arrived at the Portland, Ore., brewery in April 2015, Sprints has filled it with many of the iconic recipes he usually ferments in stainless, like Blue Dot, an Imperial IPA, Cherry Lila, a Pale Bock, Fred, a Golden Strong Ale, and even a Barleywine, Doggie Claws.

Sprints says making recipes he knew well helped him understand the vessel’s potential. “Before I started using it, I thought of it as a big barrel,” he says, “and for the first few beers I used it only for maturation.” Like any new process, it took some trial and error to get the flavors dialed in. “I was not happy with the level of minerality imparted to the beer and started using it only for fermentation. Now I am very happy with the flavor and mouthfeel changes we get from the fermentor.”

So, how exactly does concrete change the beer? It’s subtle. “In general, the beers have a softer, smoother mouthfeel and more lush flavors,” Sprints maintains.

Although concrete tanks are new to the beer world, the vessel’s use dates back centuries to vintners in Europe. Most of California’s pre-Prohibition wineries used large concrete vessels for fermentation and storage, too, before the material fell out of favor. In California wine country, the practice has regained popularity over the past 10 years, spurring local manufacturers like Vino Vessel in Templeton and Sonoma Cast Stone in Petaluma to begin selling the tanks in the US.

The vessel’s porous material and smooth shape aids in fermentation and flow. Micro-oxygenation (concrete’s ability to breathe) helps to jumpstart the fermentation process, creating a round mouthfeel with a purity of flavor that’s difficult to achieve with oak. The organic shape, without any soft or hard corners, prevents stagnation and encourages movement.

“Concrete reacts to the beer-making process in a manner very similar to oak,” explains Sonoma Cast Stone owner Steve Rosenblatt, who supplied Hair of the Dog’s concrete egg. Since appearing at the 2015 Craft Brewers Conference Expo in Portland, Ore., Rosenblatt has sold five tanks to breweries across the US, with an “overwhelming response,” he says. “Although many styles of beer can successfully be made in concrete, it is the range of sour beers that appears to be working the best.”

In Oxford, Conn., OEC Brewing founder and head brewer Ben Neidhart says concrete “allows for more oxygen exchange compared to stainless steel, but less than oak,” offering a new fermentation profile to work with. “Also, concrete adds an interesting minerality.”

To create Tempus, a blended sour Saison, Neidhart brews a “minerally version of a Saison without any spices” that’s aged in barrels for six months and makes up 15 – 20 percent of the final blend. “The concrete fermentor gives it more minerality and a fruitiness that we are not able to achieve in other vessels,” Neidhart explains.

Fermenting in stone does have its challenges, though. The porous material makes the vessels much harder to clean than their stainless counterparts. “The biggest challenge I have faced is forgetting about the way we normally clean,” says Hair of the Dog’s Sprints. “I have not had any problems with off flavors but never feel quite safe.” The extra labor might turn off some brewers, says OEC’s Neidhart, who uses a baking soda solution to clean the stone. “They are much harder to work with than stainless steel, so from an ease-of-use perspective I don’t think it will become mainstream.”

Meanwhile, in Lynn, Mass., two charcoal-colored concrete eggs have been part of the brewhouse at Bent Water Brewing since it opened early this year. So far, head brewer John Erik Strom has brewed three stone-fermented beers, building each recipe on what he learned from the last.

“Since we were unsure of how the concrete would affect the beer, we steered clear of making an over-flavorful beer, where the effect of the concrete might get lost,” Strom says. In his opinion, the dry and drinkable German-style Altbier Altogether Now allowed the concrete to express itself. “We found that the concrete highlighted the bitterness of the beer and added a very unique, stony minerality to the flavor.”

In Bent Water’s Concrete Evidence, an English-style Brown Ale, the concrete mimicked the bitterness-enhancing mineral flavors imparted by England’s limestone bedrock, while Barba, a tart Blonde Ale, uses salt, tartaric acid, and rhubarb to add complexity to the vessel’s minerality.

Despite the positive results to date, Strom is still learning. “Concrete is so new to the brewing industry and very little information is available for guidance on how best to use them, both in terms of fermenting and cleaning,” he says.

But thanks to a few pioneers, beer drinkers have new flavors to explore. “We hope concrete catches on among craft beer drinkers. We love the taste it imparts,” says Strom, adding that Bent Water’s patrons either love or hate the polarizing flavor. “We believe that with more experimentation and exposure, concrete beers will find a nice little niche for themselves in the world of craft beer.” 

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