For generations, the classic Italian stovetop moka pot has often been referred to as an “espresso maker,” though traditional espresso aficionados tend to scoff at the designation.
Building upon the domestic-friendly promise of the little steam brewers is the 9Barista brewer, which has emerged from the United Kingdom. Bearing some resemblance to a classic moka pot, the 9Barista introduces a dual-boiler design that actually yields an espresso akin to what’s made on commercial coffee bars, according to its makers.
Invented by Cambridge-based jet engineer Will Playford, the 9Barista features a high-pressure boiler on the bottom that, when heated to accumulate precisely 9 bars of pressure, sends super-heated water through a calibrated spring-loaded valve into a heat-exchanger coiled inside a second, upper boiler.
The upper boiler is not pressurized, and freely allows steam to escape through a little exhaust chimney on one side.
“That’s key to what is unique — and patented — about 9Barista,” Playford told Daily Coffee News. “The upper boiler uses the property that boiling water open to the air must be at 100°C, at sea level.”
Playford said users can warm their espresso cups over the steam chimney if they want. Meanwhile, after passing through the central coil where it drops from 179°C (354.2°F) to 100ºC (212°F), the water then passes through a third chamber in which another heat-exchanger, this one of a cool-looking exterior fin design, further dissipates the heat down to an ideal 93°C (199.4°F) before at last the water completes its journey upward through a finely ground, 53-mm bed of tamped coffee.
The device is physically split into three parts. At the bottom is the lower boiler that the user fills with water to a fill line, amounting to 120-ml. Next comes the middle assembly that contains the upper boiler and the fin heat exchanger, and when screwed down onto the lower part, automatically divides the water between the lower and upper boilers.