Real ale was the term used by the Campaign for Real Ale in the early 1970s when it set out to rescue England’s great contribution to world beer. Brewers prefer to call it “cask-conditioned beer.” At the end of fermentation, beer is left to condition for a few days in the brewery and is then run into pot-bellied casks in an unfiltered state. A handful of hops is often added to give additional hop aroma to the beer. Sometimes liquid sugar is added to encourage a powerful second fermentation. Finings [isinglass] are also added to slowly clear the beer.
The casks are taken to pubs where they are set up, or “stillaged,” on their sides in deep, cool cellars. Some publicans or their cellar managers prefer to leave a cask for several days or even a week or more before venting it. A spile, or venting peg, made of porous wood is knocked into a shive hole on top of the cask to allow the conditioning beer to give off excess carbon dioxide as a slow secondary fermentation takes place.
When fermentation has slowed, the porous peg is replaced with a hard one that prevents further escape of gas. The natural CO2 gives the beer its sparkle and condition.
Depending on the strength and eccentricities of the beer, it may take from a day to several days for a beer to come into perfect condition. During secondary fermentation and conditioning, a beer will improve in aroma and flavor, and will gain a small amount of additional alcohol as remaining malt sugars undergo fermentation.
The finings attract yeast particles and proteins and drag them to the bottom of the cask. When clarity is achieved, the beer is said to have “dropped bright.” A tap is then knocked through the bung hole at the front end of the cask, pipes or “lines” are attached and connected to beer engines in the bar, where they are operated by the familiar tall levers known as hand pumps or hand pulls.
Pubs that do not have cellars may keep casks in a cool room at ground level and serve the beer straight into glasses without the use of beer engines. Many pubs serve winter warmers from small casks known as “pins” that are simply placed on the bar.
The recommended cellar temperature for cask ale is between 52 and 56 degrees F. Old ales, barley wines and winter warmers should be served at between 58 and 60 degrees. There is a growing movement among brewers to produce cooler ales, especially summer ales, at lower temperatures of around 48 degrees.