Most cask beers are delivered to the pub ready to be prepared for serving. In instances where a freshly casked beer is delivered the cask may have to be cellared for up to a week to let the secondary fermentation finish. It should be noted that cellar temperature is around 10° C plus or minus a couple of degrees, considerably warmer than the sub-zero taste of “cold”.
Cask-conditioned beers usually have “finings” added to the cask to help settle the yeast. Finings are most commonly made from a seaweed called Irish moss, which is processed into carrageenan, or Isinglass, which is derived from the swim bladder of various fish. Finings attract particles floating in the beer and drop forming a somewhat gelatinous cake at the bottom of the cask and leaving the brew clearer.
After the cask has been cellared it has to be rolled to distribute the finings through out the brew. The cask is then put into its final serving place and is vented. In the traditional rack setup the cask is vented by knocking a “spile” into the “shive” on the side of cask. When using a spear the cask is vented through the keystone. The cask is left to set for 24 to 48 hours to allow the excess carbon dioxide to vent and the finings to drop. Once the beer has dropped “bright” it is ready to be served.