Perhaps it’s the aura of mad scientist cool, or perhaps it’s the fascination of watching an unusual process unfold, but vacuum brewing coffee is really fun for those who like to tinker. There’s another reason, though, that this manner of making coffee is likely to be the next big thing among the over-caffeinated set: it makes a really delicious cup that’s unusual in some significant ways.
Making coffee in a drip machine, with its paper filter, removes oils that appear to elevate cholesterol. It does, however, make a difference in the taste that some coffee connoisseurs won’t stand for. That leads a lot of people to employ a French press or a moka pot. But both methods, while they leave oils in, can produce coffee gone crunchy with the grounds that inevitably remain.
That’s where a vacuum brewer (or coffee siphon) comes in. It makes coffee of decided clarity, completely free of grounds (if, that is, you want it that way), but leaves in those oils. Users also control the length of brewing time in most cases, allowing for much stouter or weaker coffee.
Vacuum brewers have been around a long time—patents for them go back as far as the 1830s, and they remained popular in many parts of Europe for decades. The first machines consisted of a heat source, a stand and two glass vessels with a filter in between. Lots of improvements got added to the first, fairly simple designs, creating baroque machines that would loook more at home in a Victorian museum than a modern kitchen. (Versions employing some of those fancy improvements can still be found, and can run into four-digit prices.)
In America, vacuum brewing entered the scene in the late 1800s, and its popularity continued unabated until the 1950s. Even now, a visit to a thrift store can often turn up a vintage brewer.
If you don’t know what they are, these machines appear quite mysterious, as if they are missing something. Vintage brewers often look like the pot portion of a drip machine, but with a second, lidded glass vessel on top and a piece of glass extending down into the first vessel. Usually no heat source or electric component is along for the ride. That’s because vacuum brewing takes place on a stovetop, or with a spirit lamp in some cases.
Here’s how they work. The bottom vessel holds water. The top holds coffee grounds. A filter of some kind—usually cloth or plastic—fits into the bottom portion of the top vessel. The top fits into the bottom snugly, held in place by a rubber gasket. The whole contraption is placed on a heat source.
When the water below turns to vapor, the vapor exerts pressure that sends nearly all the water up through the tube into the top chamber, seeming to defy gravity. Up top, it mixes with the grounds, just as in a French press. As long as the heat continues, air from the bottom chamber bubbles up through the brewing coffee (though it’s not actually boiling). Electric vacuum brewers exist, but don’t allow for customizing the brewing time in this step. With a stovetop brewer, the bubbling can go on as long as you wish. Three minutes produces a fine cup, and five or six minutes produces coffee that’s truly stout.
Once the brewing time is reached, the whole setup is removed from the heat source. As the vapor down below cools, it takes up less space in the chamber. Since nature abhors a vacuum, the rest of the space quickly gets filled with the water (now coffee) from the top chamber. The top chamber empties of coffee, and the filter keeps the grounds at bay. Those who want some of the grounds in the cup sometimes employ a glass filter, which is basically a rod with a roughened bulb that fits between the chambers. The rough grooves on the bulb keep most of the grounds out, but it’s inefficient enough that the finished product still contains some crunchiness.
Once the coffee has all drained to the bottom, the top chamber is removed. It contains grounds that are almost dry, thanks to the force of the vacuum-induced pull from below. What’s left is a modest-looking carafe of particularly tasty coffee.
The strength of this brewing method is that it reveals the flavors of coffee in unmuddied fashion, offering a strong cup with almost no bitterness. The essential character of a particular variety or roast is revealed in stark fashion. If you’ve got a batch of fresh-roasted beans to enjoy, you’d be hard-pressed to find a better way to bring out their flavors. Plus you get to bask in the air of Frankensteinian creation as you watch the process unfold. A true win-win.
Although high-end vacuum brewers can readily be found, the low end of the price scale (for new ones) is inhabited by two main devices. The Bodum Santos, which employs a plastic filter, is a stovetop brewer that resembles a pair of stacked glass globes. Its list price is $89.95, and it’s available at many places, including online at bodumusa.com.
The brewer in the pictures is a 5-cup Yama Coffee Siphon (also available in a larger size), a sturdy choice that clocks in at $28.50 and employs a cloth-wrapped metal filter. It’s sold by Northwest Glass, and can be found at northwestglass.com. Yama also makes a reproduction of an older-style vacuum brewer that comes complete with an alcohol-burning lamp for making coffee at the table.
