How a Cask of Real Ale Is Prepared before Serving Any Beer
When a cask of real ale arrives at its destination, the landlord or cellarman is now in charge of seeing that the cask is properly cared for before serving that beer to the public. Doing so requires much more than simply putting the beer on tap. Suffice it to say that the cellarman’s role in the quality of real ale is just as crucial as the brewer’s.
When the cellarman determines that the beer has dropped bright — which means the finings have clotted yeast cells and other organic matter and dragged them to the bottom of the cask, where they have settled and formed a jelly-like mass of sediment — and is about ready for serving, he knocks a soft spile into the shive, which is located on the side of the cask. The soft spile — sometimes called a peg — is made of porous material that allows air to pass through it, thus allowing the cask to breathe.
Because carbon dioxide is allowed to vent off through the soft spile, the cellarman can gauge conditioning activity by the bubbles that form around the spile. After wiping the spile clean, the cellarman can watch how fast the bubbles reform. If the bubbles reform slowly, it means the yeast is settling down, and the ale carbonating is near completion. If the bubbles reform quickly, it means the yeast is still active, and the ale isn’t yet fully carbonated.
When the beer has reached the desired clarity and carbonation level, the cellarman replaces the soft spile with a hard spile, which doesn’t allow gases in or out of the cask. The beer is then allowed to settle for about 24 hours before serving.
The cask has to be open and breathing (with a soft spile in place) while drawing a beer, or you’ll create a vacuum in the beer line (and cask), which is why cask ales have such a short shelf life (about three days). You not only draw air into the cask with each pour — which hastens the staling process — but you also have a vessel that isn’t under any pressure, so the beer will eventually lose all its carbonation.
Real ale should be consumed within three days of drawing the first beer from the cask, because it begins deteriorating immediately thereafter. With this in mind, some landlords insist on using a cask breather, which allows a small amount of carbon dioxide to replace the oxygen in the cask. Cask breathers don’t release enough carbon dioxide to carbonate the beer or push the beer through the beer lines but just enough to blanket the beer to keep it fresher tasting for longer.