INSIDE THE CASK:
HOW TO BREW, CONDITION, SERVE, AND ENJOY CASK ALES!
What is a firkin? What is real ale? And, for the love of all things good and holy, what on earth is ullage? Discover the answers to these questions and more as we explore the naturally carbonated world of cask-conditioned ale.
“THE BRITISH ARE SO
easy to please. It is the most extraordinary thing. They actually like their pleasures small.” —Bill Bryson in Notes from a Small Island
Whether served directly from the cask or via an elegant swan-necked beer engine, a brilliantly clear pint of sparkling cask-conditioned beer is one of the simplest, most comforting pleasures an ale aficionado will ever know. When treated with care and reverence, so-called real ale easily ranks among the world’s finest expressions of malt, hops, water, and yeast. Mistreated cask ale, however, simply reinforces the misconception that British beer is warm and flat.
The United Kingdom’s Campaign for Real Ale (CAMRA) offers as concise a definition of cask-conditioned—or “real”—ale as one could hope for:
Real ale is a beer brewed from traditional ingredients (malted barley, hops, water and yeast), matured by secondary fermentation in the container from which it is dispensed, and served without the use of extraneous carbon dioxide. Real ale is also known as “cask-conditioned beer,” “real cask ale,” “real beer,” and “naturally conditioned beer.”
If you brew and bottle condition your beer, you’re already drinking real ale. That yeast sediment at the bottom of the bottle is living proof. The term “cask conditioned,” however, is reserved for draft beer dispensed from a cask, often manifest as a firkin.
In North American craft-beer culture, a firkin usually means a stainless-steel cask of beer that is served at room temperature and gravity dispensed. However, the word itself doesn’t necessarily imply either of these. A firkin is simply a unit of measurement derived from the Middle English ferdkyn, itself from the Middle Dutch veerdelkijn, roughly meaning “a cute little quarter” of something. A cute little quarter of what? In the case of beer, a cute little quarter of a barrel. Today, a firkin is universally understood to mean 9 imperial gallons, which is 10.8 U.S. gallons, or 40.91 liters.
There’s nothing that says that serving a firkin of beer has to mean gravity dispense, room temperature, dry hops, vanilla beans, banana peels, or any of the other trappings that have come to be implicitly associated with the term on the western side of the Atlantic. In fact, sometimes you’ll run across an American brewery that advertises “firkin beer” dispensed from a pin, which is actually half a firkin (4.5 imperial gallons, 5.4 U.S. gallons, 20.5 liters). For our purposes, we can assume that a firkin refers to a stainless-steel cask with a volume of 9 imperial gallons.
To refer to a vessel as a cask implies a certain woodsy, romantic rusticity, but most casks today are made from high-quality stainless steel, not wooden staves. Your typical cask has a more rounded, curvaceous, barrel-shaped silhouette than the standard Sankey keg. Two holes in the cask permit access. The bung hole, which is located along the circumference at the cask’s fattest point, is the orifice into which fresh beer is racked before being sealed with a shive, a stopper made of wood or plastic. One of the two flat ends (heads) of the cask also features an opening that is sealed with a smaller stopper known as a keystone.
Fresh beer is racked into the cask along with a small amount of priming sugar, which is what the yeast cells in the unfiltered beer feed upon to create the carbon dioxide that will carbonate the beer during conditioning. In some cases, dry hops are added to further enhance the aroma of the finished ale. The shive and keystone are placed at the brewery before the cask is delivered to its destination pub.
Once at the pub, the cask is stillaged (stored horizontally in a slightly inclined