Beer brewers have some early mornings, but not usually this early. It's about 2 a.m. one day in November at Indie Ale House, in Toronto’s Junction district, and as you approach the brewing kettles it gets more and more humid. Water drips from the ceiling in the brewing room.

A new shift of brewers comes in at 6 a.m. to relieve the overnight crew. One pours himself a beer from one of Indie’s taps when he arrives. Indie’s head brewer is sleeping on the floor, on an air mattress he'd brought in for the occasion. By the time he wakes up, around 9 a.m., the air is thick and smells of sourdough bread. The beer is almost ready to go.

The brewers are pulling this all-nighter for a very special reason: to make a “wildly fermented,” Belgian lambic-style beer. Soon they'll start transferring the beer into kegs and loading it onto a truck, at which point they'll drive the beer out to a winery in Prince Edward County and unload it into "coolships" — large, open vessels — to let it cool outside overnight. (The brewers will spend their night in tents nearby.) In this way, the brewers say, the beer can collect the wild yeasts in the air.

Lambic beers are a type of sour beer, a variety that has popped up on restaurant and bar menus across Ontario in the last year and is gaining in popularity. Sour beers are one of the oldest styles of beer in the world. Before we had modern sanitation, all beers were slightly sour, because “good” bacteria and wild yeasts were added during the beer-making process. They give the beer a slightly acidic or tart taste.

Lambic beers in particular taste “a bit like a goat smells and draws in your cheeks as if you’ve seen something saucy happening in the pantry,” according to two beer writers at The Telegraph. “With their dryness, sourness and acute acidity, they’re closer in character to cider or fine sherry, while the method of their production is closer to winemaking than brewing.”

It’s a risky, time-consuming, and labour-intensive process. But “the idea is to do something hard,” says Jason Fisher, owner of Indie Ale House.

“This is a beer like no other,” says Fisher. “The process is very different in all aspects. It replicates what brewers did in a small region of Belgium hundreds of years ago.”

It’s also unusual in that it wasn’t just Indie Ale House working on its own beer. Three other Ontario breweries — Amsterdam Brewing, Great Lakes Brewery, and Sawdust City Brewing — were there, too, collaborating on this once-a-year project.

Making sour beers is complex. “You can do them quick and easy or you can do them properly,” says Fisher. He says you can turn around a low-quality sour beer in eight days, but a quality sour beer takes three years. Doing it right produces an “order of magnitude of difference,” he says.

Sour beers done right have a complex flavour that can be likened more to the layers of flavour of wine, says Fisher. For this wildly fermented beer, the aging in barrels will be closer to four years.

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These breweries started doing this four years ago. Their beer from that first batch is ready to go now, Fisher says — it just has yet to be blended.

It’s a riskier proposition than traditional ales or IPAs; there are more things that could go wrong in the making. Fisher says his loss rate is much higher on sour beers because while usually you know what you’re going to get when you put certain ingredients together, with sours “you have no idea.” That’s because this beer style is almost anti-scientific: the brewers have little control over how the bacteria or yeasts will affect the final product. It’s difficult to predict and even harder to replicate.

That also means it’s a terrible way to make money. Out of the five barrels of beer they brewed four years ago, Fisher estimates, they will probably end up using two. One barrel, he says, “tasted like rocket fuel.”

But the collaboration among these four brewers means that they can share the risk.

Some brewers in the United States have tried this, Fisher says, but he is not aware of any others in Canada.

Sour beer is expected to keep growing in popularity in Ontario: the LCBO reports that sales are growing at a brisk 89 per cent, year over year.

“We have committed to increased quantities on some products we purchase each year," says Genevieve Tomney, a media relations coordinator for the LCBO. "We are also seeing more sour beers being produced locally.” During Toronto Beer Week in September, Indie Ale House had a sour watermelon beer on tap at the Summerhill LCBO. “It was delicious and sold really well,” Tomney says.

Photo: Sarah Reid Fermenting in a brew kettle is just a small part of the years-long process of making sour beer. Photo: Sarah Reid Old hops are put in cheesecloths and then soaked in the fermenting beer. Photo: Sarah Reid Brewers watch the beer kettles overnight; at 9 a.m. it will be ready to pour into kegs. Photo: Sarah Reid The kegs being filled will be shipped to a special location for an odd but important step in the sour beer process. Photo: Sarah Reid. From Toronto, the beer will head to a winery in Prince Edward County to cool outside in large, open vessels overnight. Photo: Sarah Reid. Sour beer is so difficult to produce, there's no guarantee at the end of the years-long process that the beer will be drinkable.

The popularity of sour beers started to rise sharply in 2012 in the United States, says Matthew Miller, creator of sourbeerblog.com. “When these beers were obscure, people simply never had the opportunity to taste good examples,” he says. “As they slowly gained popularity amongst brewers, the market eventually reached a tipping point where many craft beer fans got the chance to try good examples and in turn developed a love for these beers.”

“The balance of sourness against malt sweetness or graininess is a flavour combo that people can relate to," he says, "much like wine or lemonade.”

Ontario beer trends tend to track about six or eight years behind the U.S., says Jason Fisher.

But the flavour is polarizing. It seems that beer drinkers either love it or hate it, and there’s not much middle ground.

“Sour beers, I think, still shock people,” says Fisher. “There’s a joke amongst writers and beer experts that if a brewery makes a beer that’s gone off they call it Belgian, and if it’s gone really off they call it sour. And that’s not untrue to some extent. But even a really good, world-class sour beer will still freak a lot of people out.”

Brewing lambic beer “requires a lot of planning and very specific weather conditions so we get the right temperature range,” he explains.

But beyond that, Fisher says they don’t know much more now than Belgian brewers did hundreds of years ago. “You don’t have enough data as a brewer to know it all yet. The process is a lot more wild and subject to variables you can’t control. In brewing you try to control every variable,” he says. “Sours, you’re like, ‘Leave it open, let’s see what happens, don’t clean that.’”

It’s a brewing process unlike any other, where you’re meant to do everything wrong. It will be four years before we know whether, instead, they did everything right.

Sarah Reid is a freelance journalist and a recent graduate of the Munk Fellowship in Global Journalism at the University of Toronto.