The Cumulus Machine Review: Fast and Frothy Cold Brew

A first-of-its kind cold-brew machine that can make fridge-chilled nitro or “cold espresso” in a minute flat. Beautiful froth and crema. Easy use and cleaning. Succeeds significantly better than previous automatic cold-brew machines.

Expensive. Large. Requires proprietary capsules. Cold-brew flavor is still not quite there.

For maybe the first time in my life, I have received expert praise for my “foam situation.”

The foam in question was the bubbly top to a frigid espresso martini I’d just made in my home kitchen. And the “situation” was that there was a lot of it. The cocktail brimmed with satisfying crema as thick as the head on a Guinness—leading to kind words from an esteemed cocktail pro of my acquaintance.

This was surprising for lots of reasons. One was that I didn’t even have to shake the drink to get it frothy. The other was that the espresso in my drink had never touched heat.

Espresso, by definition, requires heat and high pressure to make. But the espresso in my martini was instead a novel substance called cold-brew espresso, made by an innovative new device called The Cumulus Machine that is certainly the most talked-about cold-brew machine in recent memory.

The dedicated cold-brew machine, which retails for a heady $700, was created by some big names in coffee. Mesh Gelman, former innovation head at Starbucks, spearheaded the thing. Howard Schultz, Starbucks’ erstwhile CEO, helped fund it.

The Cumulus promises a unicorn. Perhaps miraculously, the device makes genuine cold brew—not just iced coffee in disguise—within about a minute, in a somewhat hulking countertop machine that looks a bit like a Dell PC from the early 2000s. The Cumulus will also make frothy nitro brew, using nitrogen sucked from naked air.

It’ll likewise whip up cold espresso with a weirdly persistent crema, which makes for an impressive-looking foam-topped martini.

Some Like It Cold

The Cumulus came after an epiphany, Cumulus CEO Gelman told me in a conversation this fall—one that arrived after he saw that 75 percent of drinks ordered at Starbucks were now cold.

The popularity of cold brew has quadrupled since five years ago, according to coffee industry stats. There are Zoomers, industry legend goes, who don’t even think of coffee as a hot drink.

But there’s a problem. Cold brew, prized for its low acidity and smooth expression of a bean’s character, famously takes as long as 24 hours to brew the old-fashioned way. Not everyone has the patience or the foresight to make it at home. (Check out WIRED's guide to the best home cold-brew devices.)

And so a flood of fancy machines has entered the world, each one designed to short-circuit the long path to cold caffeine. Most fast-chill hot coffee or use pressure or agitation to speed up extraction. WIRED reviewers have not always been kind to such attempts.

The Cumulus is something different: It starts with genuine cold brew, extracted in cool water over the course of hours from high-altitude coffee beans specifically selected for cold extraction. The cold brew is then condensed, using a proprietary process of vacuum distillation that can pack a double-shot’s worth of coffee into a recyclable capsule the size of a light bulb’s bottom.

Cumulus makes a variety of these capsules, light roast and dark roast and decaf and espresso, retailing for around $2.50 a pop. You’ll need them to use the machine. Plunk a capsule into the Cumulus, select your style of cold brew among “still,” “nitro” or “espresso,” and press a glowing button on the device. That's pretty much the end of the usage instructions.

The Cumulus will then pressurize and chill and hydrate the result into 10 ounces of still or nitro-bubbled cold brew, or perhaps a wildly foamy 2-ounce double-shot of coldspresso.

Each drink arrives fridge-cool, 34 degrees Fahrenheit. The device is easy to clean, mostly by removing and rinsing a tray at the bottom. The front-loading water reservoir is just as easy to fill and replace. The ease and intuitiveness is a bit astonishing for a first-generation device.

Who’s Got the Flavor?

But though it is made with genuine cold brew, the flavor of Cumulus coffee does not quite have the character of classic cold brew.

The device avoids the acrid bitterness, acidity, and tepidity that have marred most other machines that hurry up cold brew. But from light to dark, the various flavors of coffee made with the Cumulus tend to taste mostly like … other coffee made with the Cumulus.

The capsules tend “smooth,” not robust or roasty, with an unplaceable flavor or tang that remains consistent across capsules. Some have described the Cumulus' unique character as falling between espresso and cold brew, with floral pep unknown to cold brew’s customary gentleness. Less charitably, one could describe the note as sharp, even a bit phenolic or rubbery, especially on lighter roasts. The dark comes on smoothest.

The vacuum distillation process used to condense the cold brew is proprietary, so it's difficult to ascribe causes. But what I do know is that coffee is a complicated thing, full of hundreds of substances—esters, acids, oils, things with funny names—which vaporize at different rates and under different conditions. Distilling and condensing it fully is, presumably, as much art as science.

I’ve asked person after person to taste the Cumulus Machine's cold brew. Some houseguests, ranging from my mother to a Jersey-Italian coffee lover, preferred the Cumulus' frothy nitro to the best packaged equivalent and couldn't believe this bubbled heaven could arrive so immediately.

Others, me included, have puzzled at its somewhat idiosyncratic flavor, as a peek into an uncanny valley of cold coffee. It's cold brew, sure. But it's also something else.

A Fine Froth

Where the Cumulus succeeds wildly and unequivocally is froth and texture.

The nitro function on the Cumulus is the foamiest vision of nitro coffee I’ve yet encountered, whether in cafés or at home: a micro-pressurized riot of tiny bubbles that pervades the whole substance of the coffee. Mix a nitro cup with milk and sugar, and it’s a carnival of fat and sweetness and fine-structured air. This is air that doubles as architecture.

But, a word on oxygen. The device essentially pumps pure air (79 percent nitrogen, 20 percent oxygen) into the coffee rather than fuss with nitro cartridges. This is cool, but oxygen exposure is the known enemy of fresh-tasting coffee. After the nitro evaporated, side-by-side taste tests did show more flabby oxidation flavors in the nitro than the basic non-nitro.

But fresh off the machine, this doesn't show up much. What you notice is bracing, fun bubbles that also add perceived sweetness. Those bubbles cover a lot of sins, building a dense head atop cold brew that looks for all the world like a well-poured Irish stout.

A WIRED editor, looking at a photo of Cumulus’ abundant nitro, jovially suspected chicanery. “I’d swear they used Guinness for the promo shots,” he wrote.

The espresso is likewise effervescent—endowed with a thick and genuine crema, formed through the pressure exerted by the device’s powerful compressor. It was the Cumulus espresso’s own natural frothiness that led to my handsomely foam-topped martini—a result that eluded me with chilled hot espresso.

A strong hat tip to cocktail consultant and educator Josh Seaburg, of Virginia’s Model Citizen Cocktails, for a good espresso martini recipe to try this stuff out on. For the record, this involved 1.5 ounces of vodka, 0.75 ounces of coffee liqueur such as Mr. Black, and a half-ounce of simple syrup, mixed with an ounce of cold espresso. Mix, shake, pour. The device makes only double shots, so one capsule provides enough cold espresso for two cocktails.

Who’s the Cumulus For?

On the one hand, the Cumulus is an impressive piece of engineering—one that succeeds on multiple fronts where other device makers have failed.

But it is not a device for coffee snobs. It lends itself best to those who prize the convenience of a Keurig and aren't overly fussy, or those who'd naturally load up their cold brew with milk and sugar or other flavors. Cumulus doubles down on this with flavored syrups ranging from Orange Piloncillo to Cinnamon Demerara.

That said, the device’s high price tag and demand for counter space, its nonnegotiable coffee capsules, and its single-minded devotion to cold coffee can make it a tough sell. This is true especially when Cumulus capsules cost about $2.50 a pop, and adequate packaged cold brew can start at just a dollar more.

The home quaffer who'd stand the best chance of getting their money’s worth out of a $700 cold-brew device is likely someone who already regularly pays around $7 for complicated cold-brew concoctions at Gelman’s alma mater, Starbucks—but who could now find frothy luxury at home with oat milk and cinnamon syrup. That, or those who’d rather sip extra-foamy espresso martinis at home than pay $15 at a hotel bar.

Still, that's a lot of martinis, and you have to buy the booze.

Intuitively, the math seems to pencil much more easily for businesses. When we asked, Gelman said some of the device’s preorders went to places like luxury car dealerships that want to offer a special treat to showroom browsers, and that the device is a godsend for high-volume bars turning out scads of espresso martinis per hour.

The Cumulus is an intriguing proof of concept and a feat of user-friendly design. But it's also a device I suspect may need to go through another generation before it finds a large audience.