An Introduction to Cask Conditioning Homebrew

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Who says you can’t have your own “Firkin Friday” at your homebrewery? We took a look at what makes beer “real ale,” how to cask condition and serve your real ale and a heated debate that surrounds the real ale campaign.

What is Real Ale?

By definition, “real ale” is a name for draught (or bottled) beer brewed from traditional ingredients, matured by secondary fermentation in the container from which it is dispensed, and served without the use of extraneous carbon dioxide. To the homebrewer, this may sound like any bottle conditioned beer is technically real ale, but the British-based group Campaign for Real Ale (CAMRA) uses the term to specifically refer to traditional British beer styles (bitters, stouts, pale ales, etc.) that were served at cellar temperatures (52-57° F) and a specific low level of carbonation (<1 vol. of CO2).

The push for authentic real ale is much less of a matter in the United States compared to Great Britain, but the interest in serving cask-conditioned beer is becoming more and more prevalent at state-side watering holes and among homebrewers.

How to Brew Real Ale

CAMRA’s definition of real ale is specifically in regard to traditional British styles, but really any style of beer can be cask conditioned and served as such. The brewing process is exactly the same as any other homebrew day, with the difference occurring after primary fermentation.

As fermentation nears completion, the wort is transferred to the vessel in which it will be served from to undergo secondary fermentation and ultimately the “cask conditioning” process. It is crucial to carry over enough viable yeast from primary into the serving vessel to ensure secondary fermentation will complete. Depending on the style and when the beer is racked, some brewers will add a bit of sugar in the secondary to give the yeast something to ferment and condition the beer. Fining agents, like isinglass, are also common to help further promote beer clarity, which is a hallmark of real ale. Dry hops and other ingredients, like fruit, are sometimes added to the cask, too.

The length of time in the cask before serving will vary depending on the beer style. Some beers may only need 24 hours, while others require weeks or even months. A good rule of thumb is the higher-strength the beer, the longer the maturation period should be. This duration not only allows for the conditioning to complete, but also the beer to have time to drop clear.

Real ale should be carbonated to one volume of CO2 or less, but contrary to what some believe, real ale is never served flat (non-carbonated).

Selecting a Serving Vessel

Cask conditioning can be conducted in a few different vessels, allowing for some flexibility to the homebrewer who may have space or equipment restraints. As the name eludes, the traditional means utilizes an actual cask. Casks were traditionally made of wood, but these days are normally stainless steel or plastic since they are easier to clean and sanitize compared to its wooden forefather.

The most common cask is a firkin, which is 9 imperial gallons and shaped like a mini-barrel. Chances are you’ve seen one of these at your neighborhood brewery. There are also kilderkins (18 imperial gallons), barrels (36 imperial gallons) and hogsheads (54 imperial gallons), though these tend to be much less common.

Casks have become much easier for homebrewers to obtain, though they can be a bit pricey sometimes. But don’t let that discourage you! Many homebrewers have had great success using a Cornelius (aka “corny”) keg in a slightly unconventional way to achieve the same cask conditioned profile, which is discussed in more detail below.

With both casks and kegs, it is important to have the ability to vent off excess gas during maturation, if needed. Over-pressurizing can result in a higher carbonated beer that is not in the spectrum of real ale, or worse cause a geyser of beer to shoot from the vessel! Controlling this aspect of cask-conditioning can be quite tricky, and it takes some experience to dial in. That’s why some breweries have people who specialize in casks, typically known as the cellerman. If you have a means to gauge pressure, maintaining 7-9 PSI is typically ideal.

Of course, conditioning in bottles or growlers will also technically create real ale, as long as the volumes of CO2 are in line with real ale specifications and the beer is served at cellar temperatures.

How to Serve Cask Beer

How beer is served from the cask will primarily depend on the type of vessel being used, but the goal is to always pour crystal clear beer at cellar temperatures without using any additional CO2, though some brewers contest to the value of not using additional CO2, which will be discussed in the breather section below.


When serving from a cask, it’s important to understand the different components needed to serve beer, since casks don’t come equipped with a dispense valve or connects for the modern keg fittings. Instead, casks have a 2-inch opening on the belly of the vessel and a smaller round opening on the rim at one of the ends. The larger hole is where the cask is filled, and the smaller one where the beer will be served. When preparing the cask for beer, the smaller hole is plugged with a “keystone.” After the beer is racked, the larger hole is plugged with a plastic or wooden stopper called a “shiv.”

Once the cask is ready to be tapped, it is “stillgated,” meaning it’s securely placed in the location it will be tapped. A cask is stillgated on it’s side with the large whole on top and the smaller whole facing the bartender. Stillgating also allows for the yeast and other sediment to drop to the bottom of the cask so it does not cloud up a patron’s pint.

Then, a wooden peg is driven through the shiv with a mallet. This allows for air (or CO2 in some non-traditional instances) to enter the cask as beer is poured, which helps regulate the serving pressure. Next, a tap is driven through the center of the keystone, which is intentionally weakened to allow this process, from where the beer will be served.

This setup is gravity-fed, meaning the serving pressure is achieved by good ol’ fashion gravity.


Casks might not be a typical piece of beer making equipment, but many homebrewers have corny kegs readily available. With a little homebrew ingenuity, a corny can achieve the same real ale character as a cask when set up properly.

One option is to simply rack the beer to a corny, along with some additional sugar to stoke secondary fermentation if need be. Once the conditioning and maturation period is through, position the keg horizontally, some will put a block under the bottom end of the keg to get a bit of a tilt going, with the liquid post positioned at the top. In this method, the typical roles of the gas and liquid posts are reversed.

Attach a picnic tap to the gas-in fitting, and then attach a bare liquid fitting to the liquid-out fitting to allow air in. This method also relies on gravity to pour the beer.

The one pitfall of this method is the potential for leaks through the lid due to the low level of pressure. Dave Carpenter developed a simple solution to this issue by building a beer engine-like pump to work with his corny that allows the beer to be served while the corny is upright. For step-by-step instructions, check out his article “(Un)real Ale: A Free Thinker’s Guide to Cask Conditioning” in the July/August 2013 Zymurgy, which can be accessed instantly online.

Beer Engines

You’ve likely seen a beer engine at a pub or brewery. This hand pump allows cask beer to be poured without the use of gravity. This is particularly useful for bars and breweries who store all their casks in a cellar and need to pull the beer up to the bar to serve to patrons. Beer engines can be pricey and are not essential to the homebrewer serving cask ale, so we won’t focus too much on that. If you do wish to pursue a beer engine, you might be able to find a used one for a reasonable price.

The Breather Debate

According to CAMRA, real ale cannot have any sort of extraneous CO2 at the time of serving. The reason being that CAMRA believes allowing air into the cask improves the real ale’s flavor. On the flip side of the debate, some will rig up a low-pressure feed of CO2 or use a “breather,” which allows CO2 into a cask as it’s emptied.

But why the debate? Those who oppose CAMRA’s strict guidelines are wary of the staling properties that occur when allowing air, specifically oxygen, into the cask. If a cask is to be completely enjoyed and emptied in day, than staling caused by the air may not be an issue. But for commercial breweries who question their ability to empty a firkin in a day or homebrewers who don’t burn through 5 gallons in a session, it is key to find a way to preserve the quality of the real ale for more than a day or two.

By bringing CO2 instead of air into the head space of the cask, these worries of stale beer are eliminated, but CAMRA says that the addition of the extraneous CO2 will change the flavor and texture of real ale. A CO2 breather is rigged up to a CO2 tank to allow sterile gas to be replaced in the cask as beer is dispensed, which helps lengthen the shelf life of the cask before it starts to turn south.

In the end, the decision is up to you. If you are interested in exploring the breather debate even further, check out this research project funded by the AHA’s Research & Education Fund.

Sources: Radical Brewing by Randy Mosher; The Oxford Companion to Beer by Garrett Oliver et al; “(Un)real Ale: A Free Thinker’s Guide to Cask Conditioning” by Dave Carpenter (July/August 2013 Zymurgy).

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