Laboratory analyses can’t identify anything special about the water Hangar One Vodka Distillery collects from Bay Area fog to produce its limited edition Fog Point Vodka.

But head distiller Caley Shoemaker can. She says it’s the taste of San Francisco.

At the height of summer, when inland temperatures soar above 90 degrees, San Francisco is shrouded in fog. The shifting gray mass pours in across the Golden Gate Bridge and over the hills, settling moodily throughout the city. It’s an ecological phenomena so alive and with such personality that it’s been given a name: Karl the Fog.

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Karl doesn’t take many days off. In late afternoons all year long, San Francisco’s western neighborhoods are foggy and cool. Between June and September, while the rest of the state soaks in the sun, Karl works overtime.

And Karl brings more than just its gray pallor to the city. Made up of tiny droplets 100 times smaller than raindrops, Karl comes bearing fresh, clean water.

There’s an unfortunate irony to San Francisco and Northern California’s coastal fog. The state is perpetually in a state of drought. Groundwater sources are depleting more quickly than they can be replenished and, thanks to warming temperatures, the winter mountain snowpack California depends on to provide water throughout the year is decreasing. The fog bank that forms the coastal marine layer is a consistent and abundant source of water, but one that is logistically challenging to tap.

California was deep into a statewide drought when Shoemaker took over as head distiller at Hangar One in Alameda, an island across the bay from San Francisco. Unfortunately, producing the distillery’s craft vodka depended on a substantial amount of water. The Hangar One team wanted to find a way to conserve water and increase the distillery’s sustainability and, after some research, it came up with a solution.

There was one source generating an abundance of fresh, local water: Karl.

Fog collection is currently being explored around the world as a means of providing dry regions with a sustainable water source. In Northern California, fog is generated from a high-pressure system that circulates warm air over the ocean. As it circulates, the air cools but, because cool air can’t hold as much moisture as warm air, tiny droplets are formed into a marine layer of fog. When winds pick up, that marine layer is pushed into the hills that line the California coast. The higher the elevation of the coastal hills, the more fog can be collected.

With San Francisco and the surrounding Bay Area boasting some of the largest hills along the Pacific, the potential for producing water for fog collection was high. With the help of FogQuest, a volunteer-run Canadian non-profit that has been working with water-insecure communities in Guatemala, Ethiopia, and Morocco since 2000, Hangar One commissioned a series of fog catchers constructed from sail-like vertical mesh made of polyethylene or polypropylene. They placed them at a handful of locations in San Francisco and the East Bay in 2015.

The result was the first version of Fog Point Vodka, released in 2016. In this version, the water collected from the fog catchers was mixed with vodka distilled from a robust red wine, the Chateauneuf-du-Pape-inspired, 2013 Le Cigar Blanc from the holistic, biodynamic Bonny Doon Vineyard in Santa Cruz, Calif.

“The response was overwhelming,” Shoemaker says. Ever the perfectionist, for the 2018 edition she wanted to make some changes.

Throughout 2017, FogQuest volunteer Chris Fogliatti tended the fog catchers at San Francisco’s iconic Sutro Tower and at Sweet Farm Animal Rescue in Half Moon Bay, 30 miles south of the city. This time around, FogQuest used a more advanced fog catcher. The 17-square-meter CloudFisher Mini, made by the German company Aqualonis, has two different mesh layers. It’s more efficient, requires less maintenance, and can collect fog at higher wind speeds, Fogliatti says.

It took Fogliatti and the rest of the FogQuest team a full year to collect enough water for Hangar One’s 2018 Fog Point Vodka. At peak season in the summer months, Fogliatti pulled approximately four liters of liquid per square meter of fog catcher per day from the Sutro Tower location.

After collection, Shoemaker mixed the water at Hangar One with vodka distilled from an 80-20 Chenin Blanc-Viognier blend from Napa’s Pine Ridge Vineyards. The resulting liquor is “beautiful,” Shoemaker says, with the smell of warm wet stones bouncing off “bright citrus flavors and the coco-caramel distillate.”.

“There’s generally this misconception that vodka is boring,” she says. “We really have set out to change that perception.”

Hangar One’s Fog Point does just that by providing an utterly local sense of place. It leans heavily on the terroir of Bay Area fog, giving the vodka “interesting flavors that we can truly ascribe to place,” Shoemaker says.

Vodka skeptics, prepare to be convinced. This uniquely San Franciscan spirit tastes like the cleanest, freshest iteration of the city itself.