The limited edition Sigtuna Ace of Spades Imperial Stout is brewed with fresh figs, dates, raisins and heather honey. An additional 2.5 kg of dark chocolate from Ecuador and star anise are added to the brew, which uses Columbus and green bullet hops.
"I got the idea to brew Sweden's strongest brew from other breweries from around the world, like Scotland's BrewDog, which has brewed 55 percent, 41 percent and 32 percent beers," head brewer Mattias Hammenlind told The Local. "They also have a beer called Tokyo which is also an Imperial, a similar style."
He added, "We settled at 18.5 percent. Above that is a little bit too much. I want it to be drinkable."
The new brew is only slightly higher than Sweden's previous strongest brew at 17 to 17.5 percent. The brewery has made 1,500 bottles that will be available starting next Friday at the Stockholm Beer and Whisky Festival. After this batch, they will give the brew a rest until June or July next year to be ready for November and Christmas sales.
"We first fermented it with a British ale yeast strain to about 13 percent ABV, then added 25 kg of muscovado sugar and fermented it again with an American super-high gravity yeast," Hammenlind told BeerSweden.se. "Then we matured it in steel tanks with French oak chips (heavy roast) for three months."
Hammenlind joined the brewery last year. In his spare time, the brew master is also a drummer in the band SuperJudge.
"My brewing style is a mix of classical British and US innovation," he told BeerSweden.se. "All our beers at Sigtuna have a distinctive character of their own, but every one is made with the emphasis on quality, complexity and taste."
The brewery is located in a business park 3 kilometres from Stockholm Arlanda airport. In 2008, the brewery produced 35,000 litres of beer, a volume that doubled to 100,000 litres last year and is expected to reach 250,000 this year. Hammenlind added the brewery can increase capacity to 1 million litres a year.