Coolship

Copper Coolship at a brewery in Prague

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.

Homebrew Coolships

"Mini-coolship" by Devin Bell

Boil kettle coolship by Gail Ann Williams. Cheese cloth was used to keep out debris, and a chair was carefully placed to keep out wild raccoons.

Many homebrewers will construct a "mini-coolship", as seen by Devin Bell's picture. Devin has reported good results from using his makeshift coolship . The benefit of building one is that a ball valve can be installed near the bottom of the coolship, which will make transferring the wort easier. Another option that some people have reported trying is purchasing a large stainless steel pans from a restaurant supply store, as well as food grade plastic trays.

The third option is to use your boil kettle. At the 2015 National Homebrewer's Conference in San Diego, James Howat's presentation, Wild and Spontaneous Fermentation at Home, showed that using a boil kettle as a coolship is equal for replicating a large commercial coolship when comparing the surface area to wort ratio. James showed this by figuring out the volume of the wort in cubic feet for a large coolship, and the volume of wort in cubic feet for a small coolship. He then compared the surface area of the top portion of the wort that is exposed to the air for each coolship. There is a greater surface area to wort ratio in a scaled down smaller coolship. This same idea applies to how there is a greater surface area to wort ratio in small wooden barrels versus large wooden barrels. .

Example of a 36 bbl coolship:

Dimensions of the example coolship: 10 ft x 10 ft x 1.5 ft.

Wort volume = 1122 gallons = 150 cubic feet.

Surface area of the top surface of the wort = 100 square feet.

Surface Area to Volume ratio = 100/150 = 0.67 square feet of top surface area per cubic foot of wort.

Example of a 10 gallon coolship:

Diensions of the example "mini-coolship":2.5 ft x 2.5 ft x .020 ft (2.4 inches).

Wort volume: 9.35 gallons = 1.25 cubic feet.

Surface area of the top surface of the wort = 6.25 square feet.

Surface Area to Volume ratio = 6.25/1.25 = 5 square feet of top surface area per cubic foot of wort.

Surface area effects both the microbe collection and the cooling rate. The smaller surface area to wort ratio of large production coolships is obviously adequate for collecting microbes, and more importantly it allows the wort to cool slowly. Using a boil kettle, while it still might not be as close to the 0.67 surface area to wort ratio of a large commercial brewery coolship, will be closer than a "mini-coolship". The boil kettle method only takes into consideration surface area to air ratio. It does not take into consideration cooling rates. For more information on the process of brewing with a coolship, see Spontaneous Fermentation.

See Also

Additional Articles on MTF Wiki

• Spontaneous Fermentation
• Lambic

External Resources

• King's Coolship, BrewingTV Episode 42.
• Lambic and Wild Ale blog; Cool Ship posts.
• The Sour Hour, Episode 11 with Rob and Jason from Allagash, Jean Van Roy from Cantillon, and Vinnie from Russian River.
• Koelschip, Lambic.info.
• Amos Browne (Browne and Bitter blog) shows that not all coolship projects succeed.
• Amos Browne's second attempt (Browne and Bitter blog) with lessons learned from the first attempt.
• Slow Learning: Sour Beer Experiments, by Gail Ann Williams.