Cask-Conditioned Ale: Natural Flavor One Pint at a Time

Come along as we explore the naturally carbonated world of cask-conditioned ale.

Dave Carpenter Apr 18, 2017 - 11 min read

Cask-Conditioned Ale: Natural Flavor One Pint at a Time Primary Image

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.


The Cask

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 position) in the cellar and allowed to sit undisturbed for a few days so that suspended yeast and finings can drop to the bottom of the barrel. A day or so before the beer is to be tapped, a wooden spile is driven through the bung to allow excess carbon dioxide to vent.

Tapping the Cask

The word tap is tossed about rather loosely these days and may refer to a keg coupler or even the faucet from which draft beer is poured. The question “What’s on tap?” is taken universally, at least in North America, as an inquiry concerning any beer served from a keg and not from a bottle or can.


But when one speaks of cask-conditioned ale, the tap is unambiguous. It is the piece of hardware that is physically hammered (tapped) into the cask by way of a mallet and determination. The ritual may be performed with great fanfare in the case of very special ales, but in most cases, the act is more mechanical than ceremonial. Regardless, the tap is the spigot through which beer is extracted from the cask.

As beer is drawn from the tap, the slight vacuum created within the cask allows oxygen to enter through the soft spile, which is typically made of porous wood or cork. Because the beer is displaced with air, and not carbon dioxide, some oxidation of the beer occurs over the lifetime of the cask. It is this oxidation that many real ale aficionados claim leads to the unique character of true cask-conditioned ale.


The tap does the job of getting beer out of the cask, but some force is needed to ultimately move said beer into a customer’s glass. In the United States, that force is very frequently supplied by good old gravity. Placing a cask on the counter of a bar lets gravity pull beer from the inclined cask and into the glass.

In traditional pubs of the United Kingdom, however, a beer engine is frequently the mechanism of choice for filling pint glasses. Casks are stored in cellars, which maintain a fairly uniform temperature of 50–55°F (10–13°C), but customers tend to prefer the somewhat warmer climes of the ground-level pub itself. Therefore, some means of moving beer from the downstairs cask to the upstairs bar are in order.


The beer engine supplies said means. Unlike most modern systems, which rely on top pressure carbon dioxide to push beer through a dip tube, out of the keg, through a beverage line, and into a faucet, beer engines instead make use of the suction generated from a hand pump to pull beer from the cask and into the customer’s glass. These are the swan-necked faucets that you see in the most traditional of English pubs.

Depending upon the geographical location of your particular pub, the beer engine may include a sparkler, which is a kind of restrictor plate that forces carbon dioxide out of solution as beer is pumped into the nonic pint. Customers in southern parts of England maintain that a sparkler destroys much of what makes a proper pint worth fussing over, while those farther north, notably in Yorkshire, insist that the sparkler promotes smoothness and drinkability. Ultimately, it’s a matter of personal preference and, to some degree, beer style.

Cask-Conditioned Ale: A Traditional Pint with a Future

Until the mid-1970s, it appeared as if cask-conditioned ale in the United Kingdom might be replaced by industrial, mass-produced lagers. It took the grassroots efforts of groups such as CAMRA to rekindle support for traditional methods and serving styles, not unlike the craft-beer movement in the United States that emerged around the same time.

A few enlightened pubs in the United States and Canada have taken the time to create an authentic cask-ale experience and maintain traditional cellarmanship practices. In many cases, however, it pays to be skeptical. A typical Firkin Friday may consist simply of a brewer’s normal beer that has been racked into a cask, left on top of the bar, and “dry hopped” with any range of additives, from vanilla beans or cacao nibs to mushrooms or chile peppers. In some cases, the beer is dry hopped with actual hops, an occasion that is cause for celebration, indeed.


Ultimately, there’s nothing inherently right or wrong with choosing to serve beer one way or another. Instead, it’s about selecting a method that best enhances the qualities of the beer itself and, most importantly, the drinker’s experience thereof. A mild ale may very well seem lifeless and uninspired served at 38°F (3°C) with the same effervescence as a Czech Pilsner. But the very same beer, dispensed with just over 1 volume of carbon dioxide at 55°F (13°C) will seem fuller in body and richer on the palate.

If you’ve yet to taste truly authentic cask-conditioned ale, then I urge you to seek it out at your earliest opportunity. Real ale is to industrial beer as fresh homemade bread is to a shrink-wrapped, sliced white loaf: different experiences altogether.

Oh, and as for ullage, that’s just the term for the last bit of unsellable, sediment-rich beer that remains in the cask. But, because it’s British, it automatically sounds more refined, don’t you think?

From ingredients to equipment, process, and recipes—extract, partial-mash, and all-grain—The Illustrated Guide to Homebrewing is a vital resource for those who want to brew better beer. Order your copy today.