What are coolships primarily used for in brewing?

Coolships are traditional shallow vessels used primarily in brewing, especially in the production of lambic beers. Their main function is to cool wort rapidly after boiling, but the process involves exposing the cooled wort to ambient air, allowing it to come into contact with natural wild yeast and bacteria present in the environment.

When wort is pumped into a coolship, it spreads out and cools more efficiently due to its larger surface area. This exposure to air not only allows for rapid cooling, but it also invites spontaneous fermentation, which is crucial for styles like lambic. The process of allowing wild yeast and bacteria from the environment to inoculate the wort is what leads to the characteristic flavors found in sour beers.

Although fermentation of clean beer types may happen in other types of fermentation vessels, coolships are not designed for this purpose. They are specifically associated with the fermentation of sour beer types, where the interaction of the cooling process with wild yeasts is essential.