In some lucky parts of the world, mercury is beginning to rise to that little point on the thermometer that says "iced coffee time". Yet with all the options available nowadays, from bottled, grab-and-go varieties to easy, overnight at-home methods, have you ever considered taking your iced coffee and just...slowing...it...down?
Japanese slow-drip cold coffee brewers do just that, brewing a concentrate of patiently wrought coffee one drip at a time. These handsome towers use the variable of lots of time, not lots of temperature, to extract a brew that's more subtle and aromatic than cold brew methods that require steeping grounds completely in water.
While cold brewing in the Toddy/Filtron/pitcher in your house method is easy as pie, Japanese slow-drip cold-brewers (like the ones Blue Bottle uses to produce their "Kyoto" cold brew, or this Yama model for your home) require special equipment to pass individual drops of water over top of a bed of coffee grounds.
Different slow-drip brewers will require slightly different doses of coffee, water, and time, but the essence of the method is this: coffee ground to a medium/filter setting is put into a grounds chamber, over top of a filter (many prefer paper for clean taste, but some models come with a metal filter included). Water is put into a water chamber some distance above—and while some accept room temperature water, some brewers are designed for cold water, and have reservoirs roomy enough for you to add a mixture of water and ice. (More decorative drippers will have coils through which the water travels as part of its slow journey, adding to the theatrical nature of the brewing process.)
Via a valve that you can attenuate for drip speed, you'll release the water over top of the bed of coffee grounds, which will travel, drop by drop, into the coffee, eventually saturating the grounds and ultimately extracting into the lower chamber. Depending on which kind of brewer you have, this can take anywhere from 6 to 24 hours before your coffee concentrate is ready to dilute and drink.
What's the advantage? We asked Northwest Regional Barista Champion Laila Ghambari of Seattle's Cherry Street Coffee House, one of the few professionals we know that's owned one of these models at home as well as tested it on the competition stage.
"The difference that I experience from Toddy, or other full immersion cold brew methods, versus the drip, is specifically in the flavor, aromatics, and the body," said Ghambari. "I tend to get these heavy chocolate-like qualities from full immersion cold brew methods. It seems regardless of the coffee it always tastes the same to me." In contrast, with the Japanese-style slow-drip Ghambari says "the coffee tends to be more aromatic and have more delicate or nuanced flavors and have a lighter body."
Ghambari's tested the limits of her slow-drip brewer: it appeared for a time on the bar at Portland's BARISTA cafe, and alongside her in competition in 2012 when she used it for a coffee signature drink by slow-dripping hot water with lemon zest over top of oranges and peaches to complement her espresso creation. (Nowadays, alas, Ghambari's brewer—she says it's difficult to clean—is serving time as a multi-tiered terrarium.)
Beauty aside, a slow-drip tower is likely only practical if you run a cafe, or have a beautiful kitchen that's lacking just that one thing that would bring your life together, decoratively and cold-brew coffee-wise, all at once. And with entry level prices beginning in the hundreds, you'll be making quite a commitment time-and-money-wise. But will you appreciate that next cup of slow-drip a little more next time you get the chance to try one? Darn right you will.