Yeast & Fermentation

The koelschip, known in English as coolship, is a large, shallow pan in which hot wort cools overnight. The name comes from Dutch and literally means cooling ship. Because the wort sits open to the air, microorganisms fall into it from the surrounding environment. That's exactly the point: no yeast is added, and fermentation begins on its own. Experts call this spontaneous fermentation.

Allagash was, by its own account, the first brewery in the US to install a coolship, in 2007. Rob Tod had previously traveled through Belgium with a group of brewers, including Sam Calagione of Dogfish Head and Vinnie Cilurzo of Russian River. The morning after cooling, the wort goes into French oak wine barrels, where it ferments and ages for one to three years.

The result resembles Belgian lambic, which is native to the Senne Valley and the Pajottenland. The name lambic has been an unprotected EU designation since 2023; only Oude Geuze and Oude Kriek carry protected status. That's why people speak of beer brewed in the lambic style. Coolship Resurgam—Latin for 'I shall rise again'—blends one-, two-, and three-year-old barrels.

Witbier works in an entirely different way. Here, a top-fermenting yeast is deliberately added. Top-fermenting means the yeast collects at the surface and ferments at temperatures around 20 degrees Celsius, considerably warmer than for a lager. Geary's and Shipyard Export follow the same principle, since both are ales in the English tradition and therefore also top-fermented.

The contrast between these two approaches is really the full span of what Maine has to offer. On one side stands yeast as a tool, precisely selected and kept under control. On the other, the cold of a coastal night and a mix of microorganisms that no brewer fully controls. Both happen in the same city.