You might miss the magnetic sign outside Sweet Caffeine but there’s a big “Coffee” sign next to the window.
For the past three months, Dave Thornton has opened his sliver of a coffee shop on Capitol Hill, tucked into what used to be a Bank of America ATM alcove, less than 90 square feet of space directly across from Seattle Central.
“My model is more about discovery,” Thornton said on a recent Tuesday morning, pouring a small sample of something called Diamond Brew into a two-ounce beaker. “It takes a while. It’s a lot slower than if I just did a grand opening and really did a whole bunch of social media.”
The coffee lands smooth, concentrated, and complex, more like a very refined cold brew than anything espresso-adjacent, but with the depth and flavor brightness you only get from a hot extraction. It is, legitimately, unlike anything else being served on the Hill right now.
The little space, meanwhile, echoes with the history of small coffee on Broadway where names like Vivace began with carts and counters.
Thornton spent roughly a decade developing the Diamond Brew process, first in his office kitchen, where the smell reportedly spread across half a floor of his tech company, and later in his garage after his wife reclaimed the home kitchen. He had a 35-year career in technology, most recently 13 years at a company where he’d worked his way up to a comfortable salary. When he got laid off, he already had his business license.
“The timing was perfect,” he said. “I was at the point where I was gonna have to get started anyway. And then I got all my time to do it, got a good severance package to get me started.”
He will turn 55 this month. He figures he has about ten good working years left, and he is not interested in going back to the office.
The Diamond Brew process breaks most of the rules baristas are taught to follow. Where pour-over protocols call for water in the low 90 degrees Fahrenheit and a careful grind size, Thornton brews at up to 250 degrees using pressure to raise the boiling point, and grinds his coffee to near-Turkish fineness, approaching powder.
“Smooth like cold brew, strong like espresso, and nuanced like pour-over.”
The logic, as he explains it, is about extraction chemistry. Coffee compounds pull out of the grounds at different rates, caffeine fast, bitter notes slow. By maximizing heat, pressure, and surface area simultaneously while strictly limiting the amount of water in play, the water reaches full saturation with the desirable compounds before the harsh notes have a real chance to extract. Once the water is fully saturated, it simply stops absorbing anything further.
The result is a concentrate he doses at about 40 milliliters, roughly a double espresso, which he uses as the base for lattes, both hot and iced. He has also developed a technique of steaming the Diamond Brew concentrate on a wand, which emulsifies the oils and replicates the texture of a pulled espresso shot, but smoother.
He is currently deep into water chemistry, using different mineral profiles for different coffees depending on what flavor characteristics he wants to emphasize. “I’m at that stage right now with water where I am basically having to follow recipes,” he said. “I don’t really understand the chemistry of it yet. When I get to that point, it’ll really open things up.”
Sweet Caffeine occupies what the building’s landlord, Hunters Capital, converted from an ATM vestibule. Thornton was not initially looking for a retail spot, he had been operating as a cart at the Amazon Spheres on a street use permit and planned to scale by adding more carts. He stumbled onto the Capitol Hill space while scrolling listings for a production kitchen base.
“I felt like, man, this is the perfect size,” he said. The landlord has been unusually supportive, he added. Installing the service window themselves, asked Thornton for input on materials and design, and showed him samples before proceeding. The building also emailed residents and office tenants to introduce the new business.
Thornton sources from four roasters currently, including Naomi Joe out of Tacoma. He is about to add a fifth, a specialty Vietnamese roaster focused on Arabica from the Laos border region.
Despite running the current location solo, Thornton has already signed a lease on a second space in Belltown. The plan is to operate it Thursday through Saturday as a dessert bar at night, with coffee service during the day once it’s fully built out. All of his locations will be cart-based in format.
He has also secured a wholesale license and has developed a single-serve vial of Diamond Brew concentrate, one dose per vial, that he envisions selling retail and potentially licensing to other cafes, including high-volume operations like the in-building cafes on Amazon’s campus.
“Part of what I’m doing here is proof of concept,” he said. “If it works for me, then maybe it’ll work for somebody else.”
Sweet Caffeine is now open at 1620 Broadway where the ATM used to be. Follow @sweetcaffeine.me for updates.
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