What is "coolship"

A coolship (Anglicized version of the Dutch/Flemish koelschip) is a type of fermentation vessel used in the production of beer. Traditionally, a coolship is a broad, open-top, flat vessel in which wort cools. The high surface to mass ratio allows for more efficient cooling. Contemporary usage includes any open fermentor used in the production of beer, even when using modern mechanical cooling techniques. Traditionally, coolships were constructed of wood, but later were lined with iron or copper for better thermal conductivity.

While Anchor Brewing Company is the oldest continually-operated brewery in the United States to employ open fermentation, coolships in the traditional sense were first used in the United States by Allagash Brewing Company. Several craft breweries have followed, including Logsdon Organic Farmhouse Ales, LIC Beer Project, Earlybird, Funk Factory Geuzeria, Jester King, De Garde, Blue Jacket, Crooked Stave, Russian River Brewing Company, Oxbow, New Glarus, Side Project, Anchorage Brewing Company, Block 15, Beach Brewing, OEC Brewing, Peekskill Brewery, Pen Druid Brewing, Burley Oak Brewing Company and Wander Brewing.