Connecting the campus to the community
Keg vs. Cask
By Dr. Paul J. Pope
What beer is packaged in is as important to the quality of that beer as the process of brewing it. The decision to use a bottle, can, keg, or cask is important. Each package choice impacts the beer in the glass and the drinker’s perception of that beer. Many brewers and beer lovers may argue the height of beer freshness is beer served on draught (or draft). The two main draught options for getting their beer to the customer is either keg or cask. For the sake of this article I will be excluding the option of serving directly from bright tanks and focusing only on transportable serving vessels.
What is the difference then between kegs and casks? Kegs are a relatively newer way of serving beer and are made of stainless steel or food grade plastic. Cask beer (sometimes called real ale) predates kegs. The earliest casks were made of wood. Today they are also either stainless steel or durable food grade plastic. Kegs come in a variety of sizes, the most common are 7 and 15.5 gallon (half barrel) sizes. The casks also come in several sizes, the 5 gallon pin and 10.8 gallon firkin are the most common. Kegs use a single coupler on the top and uses CO2 gas to dispense the beer through a tap. Casks are a bit more involved to serve. Casks are usually served on their side, but options exist for upright service. Cask beer is not served via gas pressure. First, casks can be served by gravity from a spigot hammered through a wood or plastic block called the keystone on one end. Just turn the nob and beer pours out. The second option is pumping the beer out with a hand pump called a beer engine. This is where the term “draught” comes from, it means to “pull.” Additionally, an angled piece of wood, called a spile, is hammered through the shive bung on one side. This allows for a tiny amount of air to enter the cask so the beer can be pumped out without creating a vacuum. However, this means the beer comes into contact with air, which stales the beer. Cask ale is therefore a more difficult prospect to keep fresh. Beer served this way typically only lasts about 3 days. One solution is to use a CO2 breather that keeps a blanket of CO2 in the cask at all times, but not enough pressure to push the beer out. This extends the shelf life of the beer. Cask purists turn their noses up at adding gas like this, and therefore not “real ale.”
Keg beer is ready to drink the moment it leaves the brewery. Cask beer on the other hand is usually not ready. When the brewer fills the cask through the bung hole on one side of the cask they add more sugar, yeast, and sometimes fining to clear the beer. Unlike keg beer, there is a second fermentation in a cask to carbonate (condition) the beer. Between the brewery and serving in the pub, cask beer is going through another small fermentation right in the serving vessel. This means cask beer is alive. Laying the cask on its side allows the yeast to drop to the cask belly, keeping it away from the tap. This allows for bright and clear beer to flow out.
Keg beer in the glass will have more carbonation and is usually served at or near 38 degrees Fahrenheit. Cask beer is traditionally served at cellar temperatures, 50-55 degrees. It may be served colder, but this is not the tradition. In the end, it is the choice of the brewer or drinker to which they prefer; cold and fizzy keg beer or cool and low carbonation cask beer.