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'''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. See also the [http://www.milkthefunk.com/ccc/ MTF Coolship Cooling Calculator]. See [[Spontaneous_Fermentation#Cooling|Spontaneous Fermentation]] for information on dissolved oxygen in wort that is cooled overnight in a coolship.

Some homebrewers prefer to purchase or repurpose from the home suitable shallow, food grade containers used in cooking or catering. These include stainless steel or aluminum baking pans, large glass baking pans, food grade plastic trays and storage containers. These vessels are often cheap and may already be available in the home. It can be tough working with large vessels with no valve to drain the coolship into a fermentor. One must make sure the selected vessel is designed for use with hot liquids so it does not crack or melt. Cooling boiling wort in plastic containers that are not rated for boiling temperatures may leech chemicals from the plastics plastic depending on what they contain, even if they are food grade.

Abbreviated '''SA:V''', the surface area to volume ratio is the proportion between the surface area of the wort (the dimensions of the wort exposed to the sides of the vessel), and the volume of the wort. The SA:V affects the cooling rate of the wort. In addition to this, the surface area of the top of the vessel which is exposed to air in proportion to the volume of wort potentially affects the inoculation rate of the vessel.  ====Cooling Rate====The cooling rate of the exposed wort is influenced by a number of factors including the ambient temperature, the [https://en.wikipedia.org/wiki/Thermal_conductivity thermal conductivity] of the coolship material(for example, Jester King Brewery noted a faster, more preferable cooling rate for a 30 bbl coolship made from copper versus stainless steel because copper is a better thermal conductor <ref>[http://www.thebrewingnetwork.com/session-jester-king-brewery/ "Jester King Brewery"; Interview with Averie Swanson from Jester King Brewery. Brewing Network Session Podcast. 01/30/2017. ~1:22:00 minutes in.]</ref>), and the surface area to volume ratio <ref>[http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/heatingandcooling/heatingrev6.shtml ''Energy transfer by heating''. BBC website, Bitesize section. Retrieved 7/24/2015.]</ref>. The most important factor is the ambient temperature, but the easiest variable to control is the surface area to volume ratio. The greater the surface area of a given liquid the faster it will cool <ref>[http://www.fmf.uni-lj.si/~planinsic/articles/Cheese%20cubes_EJP.pdf The surface-to-volume ratio in thermal physics: from cheese cube physics to animal metabolism. Gorazd Planinsic and Michael Vollmer. European Journal of Physics. 29 (2008) 369–384.]</ref>. For example, imagine 100 liters of hot liquid is in a very wide and flat container. It will cool much faster than if it was in a perfectly square container, and even faster still than if it was in a spherical container. See [http://wordpress.mrreid.org/2011/10/20/spherical-ice-cubes-and-surface-area-to-volume-ratio/ this article for another explanation of how surface area to volume ratio affects cooling]. The surface area to volume ratio also affects the inoculation rate. The more surface area to volume ratio, the more microorganisms that will be collected in the coolship for the given volume of wort <ref name="Howat">[http://www.homebrewersassociation.org/how-to-brew/resources/conference-seminars/ ''Wild and Spontaneous Fermentation at Home''. Presentation by James Howat at 2015 NHC.]</ref>.

Scaling a commercial-sized coolship down to homebrewing volumes will produce a coolship that does not match the surface area to volume ratio of the larger coolship. For this reason, the surface area to volume ratio should be the driving factor in determining how to design the shape and depth of a homebrewing coolship. In his 2015 National Homebrewer's Conference presentation, Wild and Spontaneous Fermentation at Home, James Howat provides a comparison of the surface area to volume ratios between a 36 BBL coolship and a 10 gallon coolship scaled down linearly from the 36 BBL coolship <ref name="Howat"></ref>.  <code>:Example of a 36 bbl coolship:::Dimensions of the 36 coolship: 10' x 10' x 1.5'.::Wort volume = 1122 gallons = 150 cubic feet. ::Surface area (2wl + 2lh + 2wh) = 260 sq. ft.::Surface Area to Volume ratio = 260/150 = '''1.73''' sq. ft. per cubic foot :Example of a 10 gallon coolship:::Dimensions of the 10 gallon coolship: 2.5' x 2.5' x 0.20'::Wort volume: 9.35 gallons = 1.25 cubic feet.::Surface area (2wl + 2lh + 2wh) = 14.5 sq. ft.::Surface Area to Volume ratio = 14.5/1.25 = '''11.6''' sq. ft. per cubic foot</code> This example indicates a substantially lower ratio for the 36 BBL coolship. At the lower ratio, the wort will cool considerably slower. As a result difference in cooling rate between the two coolships, the inoculation rate and ratio between microorganisms will differ. Designing a coolship for homebrew volumes may result in a coolship that does not appear similar to its larger companions. To keep get as close to the comparison simple1.73 ratio of the 36 BBL coolship with our 10 gallon example, it compares the dimensions would have to be as close to a cube as possible with dimensions approximately 1.1' x 1.1' x 1.03'. This still only on gives a SA:V of 4.9 sq. ft. per cubic foot. A homebrewer desiring a more shallow vessel may insulate the surface area of wort exposed coolship to slow the air because cooling rate although this may affect the inoculate rate. A typical homebrew-volume boil kettle is where closer to the larger coolship (estimated 1-2 sq. ft. per cubic foot) and insulating the most heat escapes from kettle when using it as a coolship may slow the wortcooling rate closer to that of a commercial-volume coolship. (A comparison including the total  ====Inoculation Surface Area====The ''top'' surface area to volume ratio affects the inoculation rate. Some brewers may want their coolship inoculation rate to be somewhere near what commercial coolships are. An example to find the SA:V ratio of wort would show an even larger difference between just the top surface using the examples.)same two coolship dimensions follows:

::Surface area of the top surface of the wort (w x l) = 100 sq. ft.

::Surface area of the top surface of the wort (w x l) = 6.25 sq. ft.

</code>  The example above shows that the shallow 10 gallon coolship also has a much larger ''top'' surface area to volume ratio. ====Coolship SA:V Calculator==== Mark B. Fry's coolship SA:V calculator will calculate the SA:V for cylindrical kettles (updated by Joe Idoni to include a second tab for rectangular coolships). In order to use the files they must be downloaded. Click "File", "Download as", and select "Microsoft Excel (.xlsx)":* [https://docs.google.com/spreadsheets/d/1HFBTCt99OQ9-jSGI9jBZXwC6SqtZZVwlpXYw2rjLO4k/edit#gid=90184859 Original spreadsheet by Mark B. Fry (download and save a copy to use).]* [https://docs.google.com/spreadsheets/d/1gB4347cP70Sw6topMoOvDydMYQcS2PF7M0Yl0vgbZbk/edit#gid=1777054704 Updated version by Joe Idoni with tab for rectangular coolships (second tab; download and save a copy to use).]

This example indicates ==Commercial Coolships=====Manufacturers===Any metal tank manufacturer can generally build a substantially lower ratio for the 36 BBL coolship<ref>[https://www. At the lower ratiofacebook.com/groups/MilkTheFunk/permalink/1327576813937196/?comment_id=1327588103936067&comment_tracking=%7B%22tn%22%3A%22R3%22%7D Conversation with Joe Wells on MTF. 06/11/2016.]</ref>. However, the wort will cool considerably slowerbelow are manufacturers that specialize in their construction for commercial breweries: * [http://www.foedercrafters. As a result difference in cooling rate between the two coolships, the inoculation rate and ratio between microorganisms will differcom/koelschip/ Foedercrafters.]* [http://www.metalcraftfabrication.com/ Metal Crafters Fabrication.]* [http://nsibrew.com Newlands (copper coolship).]

Designing a coolship for homebrew volumes may result in a coolship that does not appear similar to its larger companionsSome commercial brewers have reported positive results from using industrial maple syrup boil pans. [https://www. To match the 0facebook.67 ratio of the 36 BBL coolship with our 10 gallon example, the dimensions would have to be approximately 0com/groups/MilkTheFunk/permalink/1459172714110938/?comment_id=1459763314051878&comment_tracking=%7B%22tn%22%3A%22R2%22%7D See this MTF thread] for more information.915' x 0===Miscelaneous Information===* [https://www.915' x 1facebook.49com/groups/MilkTheFunk/permalink/1637570519604489/?comment_id=1637600782934796&reply_comment_id=1637627056265502&comment_tracking=%7B%22tn%22%3A%22R%22%7D James Howat' with a surface area s comparison of 0.8375'. A homebrewer desiring a more shallow vessel may insulate the coolship to slow the cooling rate although this may affect the inoculate rate. A typical homebrew-volume boil kettle is closer to the larger coolship copper versus stainless steel coolships on MTF (estimated 1-2 sq. ft. per cubic footmultiple subreplies) and insulating the kettle when using it as a coolship may slow the cooling rate closer to that of a commercial-volume coolship.]