We all know that Belgium is full of great brewers, but usually we're thinking of that other kind of brewer, you know, the one who makes the delicious golden stuff that goes in decorative goblets. But if a cup of theatrically created coffee in an historic and fragile device is what you seek, you might be curious about the Belgian Balance Brewer.
The Belgian brewer (a.k.a balance brewer) is a type of coffee siphon. These laboratory-esque devices came shortly on the heels of the vertical siphon brewers of the mid-18th century. (Sound familiar? Those vertical siphon brewers resembled the stovetop models of the mid-20th century, as well as the Japanese siphon brewers somewhat popular these days.)
How does the Belgian brewer work? It helps first to understand a traditional vertical siphon. Siphon brewers are two-chambered devices, one of which holds ground coffee and another of which holds water over a heat source. In a vertical siphon, one bulb-shaped chamber with coffee in it is stacked over top of another with water in it, with a heat source placed beneath the lower bulb. The vapor pressure causes the water to 'head north' and enter the chamber with the coffee, where the coffee begins to brew. Once brewing time is achieved, the heat source is cut, and the imbalance of pressure in the lower chamber causes the brewed coffee to siphon down from the upper chamber into the lower, typically through a cloth or paper filter.
In a Belgian-style, or balance brewer, the process is more elegant not only because of the tradition of decorative craftsmanship displayed (here are some lovely examples in copper, modern chrome and gold plated!) but also because of the suave kinetics of the brewer itself.
The chambers in a Belgian balance brewer are side by side, and the process works best if you're using a heat source such as an oil burner that comes with a spring-loaded lid, as you can see in action in various YouTube videos like this one.
Coffee grounds are placed in the glass chamber, while the water is placed in a metal chamber over the heat—this chamber is affixed to a weighted arm, which is where the balance comes into play.
As the water in the heated chamber begins to boil, it escapes through a thin tube into the chamber with the coffee grounds. The coffee brews in this chamber while the water supply exhausts itself, at which point the metal chamber, now lighter, will rise up against its counterweight—triggering the spring on the burner, which then extinguishes its heat source. As in the vertical siphon, the withdrawal of heat will cause the liquid in the glass chamber to escape back into the metal chamber, and voila! Coffee!
Balance brewers have, until fairly recently, been the largely the domain of international gear-hunting geeks and antiquarians. Nowadays, though, a company called Royal, who credit the invention not to the commonly attributed Belgians but to the French, sell a full array of these devices, in rather a full array of prices as well (luckily for those still looking for a birthday gift for me, the $2,995 Deluxe Gold was out of stock at press time.) You can find a more affordable "household" version online if you'd like to try one out yourself.
How does balance-brewed coffee taste? Temperature control can be a tricky thing in siphons, so you may find your results are less precise and reproduceable in these handsome machines than in many other modern implementations. That said—no matter how this coffee tastes, you're going to look unbelievably cool making it.