Cask Ale

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Cask ales are unfiltered and unpasteurised. When the bartender feels the beer has settled, and he is ready to serve it, he will knock a soft spile into a bunghole on the side of the cask. The major difference in appearance between a keg and a cask is the bunghole. A keg does not have a bunghole on the side.

The soft spile in the bunghole allows gas to vent off. This can be seen by the bubbles foaming around the spile. The bartender will periodically check the bubbles by wiping the spile clean and then watching to see how fast the bubbles reform. There still has to be some life in the beer otherwise it will taste flat, but too much life and the beer will taste hard or fizzy. When the beer is judged to be ready, the bartender will replace the soft spile with a hard one (which doesn’t allow air in or gas out) and let the beer settle for 24 hours. He will also knock a tap into the end of the cask. This might simply be a tap if the cask is stored behind the bar. The beer will then be served simply under gravity pressure: Turn on the tap, and the beer comes out. But if the cask is in the cellar, the beer needs to travel via tubes, or beer lines, up to the bar area using a beer engine.