I scheduled my arrival in Belgium to coincide with a relatively rare brew day at Cantillon. Lambics can only be brewed in the winter when the air is cool enough to chill wort overnight. Because lambics spend years in wooden casks, lambic brewers are confined to annual outputs equal to the cask space their breweries allow; Cantillon, a small brewery in a small building in downtown Brussels, has a strictly limited capacity. So brewer Jean Van Roy brews only enough beer to fill his available cask space. (Important tip: if you want to see Van Roy in action, visit between November and March and watch the Cantillon Facebook page about brewing dates.)
Lambic brewing is by design an ancient practice, but even among lambic breweries, Cantillon is the most insensitive to time. The equipment, the brewery, the methods--everything could have come straight from the 19th century. (With one caveat: Germans stole all Belgium's coppers in World War I, so the oldest coppers anywhere only dates to about 1920.) Cantillon has a museum at the brewery as well, but you'll find if you visit that this is a bit redundant. Cantillon is a museum.
Unlike that easy pale ale that goes from whole malt to fermenter in a few hours, a lambic is an all-day grind. The turbid mash, designed to create a wort that can stand up to years of munching by wild yeasts and bacteria, takes hours. Cantillon's equipment is steampunk old, and very hands on. When I arrived, Van Roy was pumping the finished boil through a thing that looked a bit like a hop back, except that it's purpose was to remove hops, not add them. Hops are used in lambics as an anti-microbial, to keep the wilder elements of the wild yeasts from getting out of hand; breweries age them so they're leached of all alpha acids and add no bitterness or flavor. (Except in a beer like Iris, where Van Roy jumps off the road of strict tradition.)
The wort becomes a template for feral yeasts, invited to join the party during the next phase of the process, when it goes up to a vessel called a koelschip (cool ship) that looks like an enormous cake pan. Van Roy has a disarmingly democratic approach to visitors: me brasserie su brasserie. He told me to just go wander around if I wanted to see the rest of the place (he was elbow-deep in the hop-catcher). The koelschip is on a loft above the brewery's top floor, where open windows let in the Brussels air. On a chilly day, the steaming wort creates clouds of ethereal mist that waft through the rafters, and I spent probably fifteen minutes communing with this scene. For an American lambic fanatic, this was ground zero for one of the most remarkable events in brewing.
In the romantic story of lambic brewing, you always hear about the pastoral Zenne Valley, laden with fruit trees and farmers smilingly working the fields. My mind conjured a kind of rural preserve where the wild yeasts were pristine and untroubled by modern life. Wrong. Cantillon is in the city of Brussels (it's called a "suburb," though to American eyes this is a bizarre characterization--the city sprawls unending for miles and miles, and Cantillon is in the middle of a gritty urban tableau.) The wild yeasts have definitely been slumming with some street-wise elements, from which I conclude that it's not mandatory to have untrammeled rural wonderland to make lambic--potentially good news for Americans willing to risk experimenting with spontaneous fermentation.
The most important part of the process happens in the wooden barrels, which themselves have their own ecosystems. What develops in the casks is straight lambic, some of which breweries may sell without blending. You get interesting but variable character from straight lambic. The real triumph of this style of brewing comes when lambic-makers blend the barrels and then add younger, fresher year-old lambic to add liveliness and effervescence to the sharp, dry, and completely still lambics that result after three years.
I followed my visit to Cantillon with a trip to Brouwerij Boon the next day. It was a fascinating contrast of styles. Frank Boon is emphatically not a museum brewer; in fact, he's one of the most microbiologically sophisticated brewers I encountered in Europe. He currently has a traditional old brewery, but Boon is in the process of upgrading everything--well, almost everything. He will install the world's first modern lambic brewhouse, purpose-built to accommodate the rigors of turbid mashing, but designed to create absolutely consistent worts batch after batch. The traditional part of the process--koelschip, wood aging, and blending--will continue as it has for centuries.
The Boon brewery is located in Lembeek, the historic capital of lambic brewing--the famous Zenne is just a stone's throw away. (It's tiny.) This is a much more rural location than Cantillon's, but it's still just 13 miles from Brussels' Grand Place--in what Americans would actually call a suburb. Boon told me that valleys were important for lambic brewers--and dangerous to regular breweries, which like to locate themselves on high ground. Valleys create pools of still air, and microfauna collect there. River valleys are even better, because the fog and humidity help keep the wild buggies from drifting away. Even though it's just around the corner from Cantillon, the wild yeasts are definitely different near Boon--as anyone who's tasted beer from the two can readily attest.
Another area where Boon and Cantillon differ is their casks. Cantillon uses wine barrels, but Boon uses vats. They aren't as big as Rodenbach's but they're in the ballpark--and 20-40 times bigger than wine barrels. This has a substantial effect on the beer. The volume of beer exposed to wood is greater in a smaller barrel, which affects the density of resident microfauna and amount of air that permeates the staves. I mentioned to Frank that I've seen Raj Apte's analysis of which yeasts become active in the life-cycle of lambic and asked if his followed the same pattern. Boon has been working with a university microbiologist to learn more about his yeasts--likely the most far-reaching studies into the biology of lambic ever done. He gave me a Cheshire Cat grin and said that Apte's charts don't apply to his yeasts--but he wasn't prepared to divulge how Boon lambic differs.
As with Rodenbach, my tour of Boon was spent disproportionately in the impressive cellar. We sampled lambic at different ages to see what character it would give to a gueuze. On their own, they were all less complex than the finished gueuze--one two-year-old batch was pretty tart and sharp, one was more fruity. The year-old lambic was sweet and uncomplicated.
Just before I left Cantillon, Jean pulled out a bottle of 2006 Gueuze, which was one of the highlights of the trip. It was practically glowing with sharp lemon notes. Boon makes a gueuze called Mariage Parfait, which has always been among my very favorite beers in the world--it's got layers and layers of fruit and sour flavors, a tiny bit of saltiness, and a towering effervescence. Drie Fonteinen, which is in between breweries, uses Boon's lambic in its blends, and that brine really pops. It's actively salty, but also has a kind of umami note.
Lambics, and especially gueuzes, live in that strata of artistic accomplishment that includes stinky cheeses, opera, and abstract art. It's very difficult to come to a gueuze cold and appreciate what's going on with it. If I had three beer wishes, I'd ask that people try several different gueuzes in at least ten sessions--different brands and ages. Unlike a lot of American sour beers, gueuzes don't have super challenging flavors--there's no band-aid, solvent, or burning tire. Because of the blend of young and old beer, they're not intensely dry nor sour, and the effervescence nudges them toward sparkling wine. Once you get past the shock of the experience, you begin to understand the flavors and how they work together. Moreover, sampling a bottle from different breweries makes it instantly clear what role the wild yeasts play. Gueuzes are a bit like dog breeds--they are distinctive and unique, and people have their preferences. I'm a Boon man, but I know people so devoted to Cantillon, Drie Fonteinen, or Girardin that they consider the preference for others a minor blasphemy. That kind of devotion is a testament to just how profound these beers can be.
Below are a few more photos:
The undisturbed cobwebs at Cantillon.
Faro, a sugared, low-alcohol, young lambic, is now all but extinct. (Even Cantillon's is well stronger than the traditional 2-3% ABV.) Still, Jean Van Roy serves it from the clay pitcher that at one time would have been found in cafes all around lambic land.
The soon-to-be-replaced mash tun at Boon.
Every lambic brewer has a mark that identifies a cask of their beer when they send it out to blenders. The stylized "L" at the top is Boon's.