A coolship 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 Stainless Steel for better thermal conductivity.