What is a coolship? The term coolship, from the Flemish koelschip, is a large shallow vessel made of stainless steel or copper, used to cool wort. Coolships are often housed in large rooms, where they lie open to the elements allowing for airborne yeast to flow in and inoculate the beer. This type of fermentation is referred to as “spontaneous fermentation” because the microbes come at random, rather than using a controlled addition of cultured yeast strains. Predominantly used to create sour beers, a renewed interest in coolships for brewing has been inspired by Brasserie Cantillon, a world-renowned lambic producer …