Coolship

A coolship (also known as a koelschip in Flemish) is a type of shallow, open-topped vessel used in traditional brewing, particularly in the production of lambic and other spontaneously fermented beers. Its primary purpose is to rapidly cool wort (the sugar-rich liquid extracted from malted barley) and expose it to wild, airborne microorganisms that initiate fermentation.

Function and Design:

Coolships are typically broad and shallow, maximizing the surface area of the wort exposed to the ambient air. This design facilitates:

• Rapid Cooling: The shallow depth allows the wort to cool down much faster than in closed vessels. Rapid cooling is crucial in controlling the microbial ecosystem that will ferment the beer.
• Inoculation with Wild Microorganisms: The open top exposes the wort to a variety of airborne yeasts and bacteria, including Brettanomyces, Pediococcus, and Lactobacillus. These microorganisms are responsible for the unique flavors and characteristics of spontaneously fermented beers.

Coolships are typically made of copper, stainless steel, or, less commonly, concrete. The material should be inert and easily sanitized to prevent contamination from undesirable microorganisms.

Location and Environment:

The location of a coolship is critical to the success of spontaneous fermentation. Breweries that utilize coolships are typically located in areas with a specific microbial terroir, meaning the local air contains a diverse and desirable population of wild microorganisms. Breweries often build their coolships in open-air rooms or on rooftops, allowing for maximum exposure to the ambient air. The time of year and weather conditions also play a significant role in the fermentation process. Lambic breweries, for example, traditionally cool their wort only during the cooler months of the year (typically October to May) to ensure the correct microbial activity.

Significance:

The coolship is a defining piece of equipment for breweries specializing in spontaneously fermented beers. It represents a commitment to traditional brewing methods and a reliance on natural processes. The coolship is not merely a vessel for cooling wort; it is an integral component of the brewing process that directly contributes to the unique and complex flavor profiles of these beers. The success of a coolship fermentation hinges on a combination of proper design, a suitable location, and the brewer's understanding of the local microbial environment.