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The Brews of Summer is a series spotlighting the area’s best summer beers.

Today, our beer is UNION Craft Brewing gose Old Pro, a 4.2% German-style sour wheat ale brewed with salt and coriander.

There are two questions Kevin Blodger hears most frequently from UNION Craft Brewing patrons.

“It’s what do you have hoppy?” the brewmaster shares. “And it’s what do you have sour?

The first query is hardly surprising. Consumer enchantment with hops has been the thread running through – driving, even – modern American craft beer’s growth over the last 30 years. But the latter descriptor’s popularity is a far newer phenomenon.

Gose, Berliner weisse, fruited kettle sours (or, ahem, American-Style Fruited Sour Ale) – a decade ago, these styles were scarcely found in beer bars or populating the refrigerators of American consumers. In fact, a decade ago, when Blodger brewed his first gose, he did so based almost entirely on what he had read about the tart German wheat ale. He says he “figured out the rest by taste.”

At the time, the DC-area native was working in suburban Chicago for brewpub chain Gordon Biersch. As head brewer, he got to choose what he produced, albeit with one not insignificant limitation: All beer had to fall within the German tradition.

“When they said German, they were thinking standard lagers and a few ales – you know, kölsch, hefeweizen, altbier,” Blodger remembers. “I loved brewing those beers, I love German lagers, but I wanted to do something cool, so I said, ‘Hey, I wonder if I can get away with brewing this sour beer.”

The brewer came across the subject of gose in Stan Hieronymus’s 2010 guide Brewing with Wheat. As a style, it scanned as a bit of an oddity. Descended from North Germany’s lineage of funky wheat beers (which stretches back at least five centuries and contains myriad brews that have since gone extinct), gose is a pale straw yellow ale soured with lactobacillus bacteria, much like the Berliner weisse. But in contrast with its less-alcoholic counterpart, gose is distinguished by the addition of coriander and salt, which lend it zesty lemon notes and a finish that’s evocative of the ocean. One thing was for sure: None of Blodger’s regulars would confuse it with a Helles lager.

Importantly, Blodger’s interest in gose coincided with the emergence of kettle souring (or “quick souring”) as a technique to produce tart beers. Historically, beer could be soured a handful of ways, including spontaneously fermenting wort, pitching bacteria and wild yeast during fermentation, or adding fruit with naturally occurring microbes on its skin. These processes were invariably long (it takes months upon months, often years, for bacteria to produce rounded, complex flavors within a wooden vessel) and risky for a brewery not specializing in sour beer production (live bacteria in one part of a brewery is a threat to contaminate “clean” beer elsewhere). Thus, for an operation like Gordon Biersch, producing a gose the old-fashioned way was not a realistic proposition.

So, Blodger called the Brewing Science Institute in Colorado fishing for ideas. They told him about kettle souring, a technique that allowed brewers to efficiently, carefully sour a beer prior to fermentation. To do this, brewers could pitch lactobacillus to wort in the brew kettle, then allow the bacteria to lower the liquid’s pH over the course of 24 to 48 hours, and, once sufficient tartness had been achieved, boil the wort to kill the bacteria. From there, the beer could safely be treated – hopped, transferred, fermented – like any other beer.

Blodger did all the research he could on kettle souring. At the institute’s encouragement, he reached out to Tampa’s Cigar City, which had been experimenting with the process. He read what little he could find in online forums. Finally, he pitched his boss, Tom Dargen, the company’s director of brewing operations, on the idea.

“He thought it about it for a while,” Blodger remembers. “Then he said, ‘OK, you can do it, but if you infect the brewery with lacto, I’m going to fire you.’”

Thankfully, no pilsner was harmed in the process, and Blodger maintained his employment. The 15 barrels of gose, meanwhile, were greeted with curiosity.

“I think people thought it was weird,” he says. “It definitely took a while to sell through. But some people really ‘got it.’ The good thing about the Chicago market is that there are a lot of really mature, experienced beer drinkers. So, they understood what it was and were cool with it, even though there weren’t too many other goses floating around.”

Not long after, Blodger moved back to Maryland, where he took the reins of Rockville’s Gordon Biersch. He brought the gose recipe with him, too. And after making a splash locally during DC Beer Week, his Goze captured a bronze medal at the 2011 Great American Beer Festival.

With the spring of 2012 came the opening of UNION Craft Brewing, a venture co-founded by Blodger and Baltimore locals Adam Benesch and Jon Zerivitz. The brewery led with two flagships: the now-ubiquitous pale ale Duckpin and Balt, a rich altbier that drew, like many UNION Craft beers, from Blodger’s formidable familiarity with malt and the German tradition. As the weather warmed, the trio contemplated a summer seasonal. Blodger floated the idea of a gose: “I was like, ‘Hey, I’ve got this beer – it just won a bronze medal. It’s a weird beer, but I think it’s perfect for the summer.”

By 2012, gose had been gaining traction among discerning craft beer drinkers. That April, South Carolina’s Westbrook Brewing released its Gose, another seminal American iteration of the style. But it’s hard to overstate how bold the decision was for a Baltimore production brewery to roll out a tart, salty beer as its summer seasonal at that point in time. Nevertheless, UNION Craft debuted its Old Pro gose in late July.

“I’d say 60% to 70% of people turned their faces up, like, ‘What is this?’ or ‘Something’s wrong with this,’” Blodger recalls of the initial reaction in the taproom, which was still limited to serving tasters. “But one or two of every ten people were like, ‘Damn, this is pretty good.’”

The brewery stuck with Old Pro as a summer seasonal, convinced of its untapped, broad appeal. Bolstering its case, Old Pro took home a silver medal at the 2014 Great American Beer Festival. Once the tasting room could serve pints, the co-founders noticed increased enthusiasm surrounding the odd 4.2% beer. But nothing prepared them for the public’s reaction when Old Pro first went it into cans in May 2015.

“That’s when it really exploded on the scene,” says Blodger. “Old Pro kind of became this cult Baltimore summer beer.”

When the brewery initially ordered Old Pro cans, with its now-instantly recognizable miniature golf motif, UNION Craft believed the supply would be sufficient for three summers.

“We thought, ‘This is a weird beer. We’re not going to sell this beer in cans,’” recalls Zerivitz.

Those cans didn’t even last one summer.

“People really ‘got it’ as a hot weather, summertime, thirst-quenching beer,” Benesch says. “People were crushing it.”

Old Pro’s popularity wasn’t a passing fad, either. The gose is UNION Craft’s second best-selling beer – a remarkable feat for an offering available only half the year.

“As much Duckpin as we sell, Old Pro is really our signature beer,” Blodger admits. “Everyone does a gose now, but I do think Old Pro stands out amongst other beers like that.”

There are indeed a plethora of goses in the market these days, particularly as they’ve been utilized as vehicles for heavy fruit additions. (To wit, The Veil’s Tefnut series, fermented on mountains of purée and clocking in at over 10% alcohol, is billed as a “cosmic Imperial Gose.”) Yet Old Pro’s reign as one of the country’s best goses – bright, approachable, deceivingly delicate – remains unchallenged.

“One thing that makes Old Pro stand out amongst kettle sours is that it’s a lot tarter,” observes Blodger. “I think that tartness adds a lot of character and complexity. I like that puckering sourness. At first, it can be alarming, but after you get used to it, it’s refreshing and inviting and draws you in for another sip.”

I ask Blodger what the secret is – how he’s been able to unlock a depth of flavor in kettle sours where most others haven’t been able. It’s not a question he hasn’t heard before.

Part of it, he explains, is adding the right balance of salt. (He won’t share the exact amount with other brewers, but he’ll give them a range.) Part of it is using a small amount of acidulated malt to kickstart the lactobacillus in the kettle. But, perhaps most of all, it’s about honing the tartness that comes from kettle souring, and the development of complimentary flavors around it.

“You can get a much more well-rounded sour using a traditional process, but Old Pro is about capturing the one lactic note that’s perfect for the beer,” he shares. “And then we add complexity with salt and spices and our process and how we mash. So, the lacto and tartness are very present, but they’re complimented by all these other flavors that help round everything out.”

As if to underscore Old Pro’s respect in the brewing community and Blodger’s role in revitalizing the style, the UNION Craft brewmaster was invited last year to participate in an “All Things Gose” seminar at the Craft Brewers Conference. Sitting alongside him: Edward Westbrook (of Westbrook Brewing notoriety, naturally) and Fal Allen, who has used a variety of goses to breathe new life into Anderson Valley Brewing with the introduction of The Kimmie, The Yink and The Holy Gose Ale in late 2013.

“Honestly, I think Kevin invented gose,” jokes Zerivitz.

Despite its success, Blodger says he and his team will never stop trying to improve Old Pro. Through the years, they’ve continued to tweak how its made. They’ve changed how the coriander is processed. When the salt is added. How the wort is cooled. These adjustments have impacted UNION Craft’s entire kettle sour program, which now includes a rotating anniversary sour ale, the recently introduced winter seasonal Cold Pro (with cranberry and cinnamon), and its highly sought-after series of Older Pros, for which Blodger ages the summer gose with fruit in wine barrels.

“Old Pro kind of led us to perfecting our kettle sour process,” says Blodger, “and now we use that for other beers, as well.”

The one thing that hasn’t changed is UNION Craft’s insistence that Old Pro remain a summer seasonal, despite calls from across the industry to make it a flagship.

“There is pressure to turn your seasonals into year-rounds when they hit,” says Zerivitz, who notes the beer crosses over particularly well with wine drinkers. “There’s a niche that loves Old Pro. There are people out there who love us only for Old Pro.”

That’s still not enough to change their minds.

“We’ve always come back to the idea that Old Pro is a summertime beer,” says Benesch. “When I find a stray can at home and I drink it in the colder months, I still love how it tastes… but it just doesn’t feel right.”

In the end, their resistance is only appropriate for a beer whose story has always been about puckish defiance of the expected.

“We’re not chasing anything,” adds Blodger. “We can say, ‘This beer is for the summer.’ Maybe we could sell more of it year round, but we want to stay true to what we want to do.”

Follow writer Philip Runco on Twitter.

View more of Clarissa Villondo’s beer photography at Karlin Villondo Photography.

Read other entries in The Brews of Summer on Bluejacket’s Pattern Skies, Crooked Run’s Coast, Astro Lab’s Fresh As, and Ocelot’s Sunnyside Dweller.