You may not be aware of this, but not all beer comes in bottles or kegs. Some beer is served up in a special container called a firkin. A firkin, which is derived from the Middle Dutch word vierdekijn (meaning fourth), is actually a small barrel of beer that is one-fourth the size of a regular barrel of beer. As opposed to a standard beer barrel, which contains 117.34 liters or roughly 30.96 gallons, a firkin full of cask ale will contain a volume of 40.91 liters or 10.79 gallons. These volume sizes are provided in U.S.-based gallons.
Besides its smaller size, what makes the firkin so special? It is the fact that the firkin is typically dedicated to housing Real Ale (i.e., cask-conditioned ale), or beer that has not been cold-filtered, pasteurized and carbonated by outside equipment. The ale beer that is housed inside the firkin is naturally carbonated by its resident yeast and its ingredients have not been processed in any way outside of simple fermentation by the yeast. In essence, firkin-contained Real Ale is comparable to the ale beers that were produced hundreds of years ago, before industrialization subjected them to processes that removed and/or killed the yeast, stripping the beer of many of its inherent vitamins (especially the B vitamins), minerals, and perhaps most importantly, taste.
How is the Real Ale produced inside of the firkin? When wort, which is the cooked mixture of water, barley and hops, has yeast added into it, fermentation of that wort into beer begins. This process is typically termed primary fermentation. After primary fermentation has run its course (i.e., the yeast are spent), the immature beer is transferred to another vessel for secondary fermentation. In this way, the yeast can get a fresh start on the immature beer and raise its alcohol percentage. Once secondary fermentation is complete, the beer is filtered and bottled or kegged.
In some cases, however, secondary fermentation of the immature beer occurs inside of a firkin instead of a vessel like a steel tank. This immature beer then takes on the characteristics of the firkin, such as its wood flavor, for example. Once secondary fermentation is completed inside the firkin, the beer matures there and is not transferred out for filtration, pasteurization and bottling or kegging.
Once the beer has matured inside of a firkin, the discovery process begins. Because secondary fermentation and maturation of the beer have both occurred inside of the firkin with no outside testing conducted, there is just no telling how the final product might look, feel, or taste. Also, individual yeast strains work differently depending on the firkin wood type, temperature, ingredients, length of fermentation, etc. Thus, when tapping a finished firkin for the first time, you just never know what you're going to get.
Aside from buying a firkin and making your own Real Ale, you can also try it at area bars and certain festivals. Generally, firkin-conditioned beer goes by the name of cask ale. This cask ale will be warmer (roughly 55F) than your standard beer simply because the yeast cannot carbonate the beer very well if the surrounding temperature is too low (i.e., the yeast become dormant). You'll know which bars have firkins because these containers will typically be suspended above the bar and have a tap inserted into them, along with a separate hose that lets air into the firkins so a vacuum is not created during the pour. Alternately, if there is no room at the bar for a firkin, a special hand engine will be placed nearby the beer taps; it needs to be pumped several times in order to draw beer from the firkin and into your glass. As a result of this pumping, your cask ale may have a significant amount of head.
The Great Dane Pub & Brewing Company, based in Madison, Wisconsin, is one place that often carries firkin-based cask ale. The accompanying photo that I provide in this article actually shows one of the Great Dane's suspended firkins at its downtown bar location. This particular firkin contains the cask-conditioned Black Watch Scotch Ale beer.
There is also a well-known annual firkin festival in Milwaukee, called the Milwaukee Firkin Craft Beer Festival, that features over 20 firkins from many area breweries, including several in Madison, for sampling. This festival lasts only one day and tickets sell out fast, so if you'd like to try some Real Ale, you should purchase those tickets ahead of time and not at the festival gate. Ticket sales start on March 19th. The Milwaukee Firkin Craft Beer Festival is on July 21st of this year and will be held in downtown Milwaukee at Cathedral Square Park. For more information, please go to the Milwaukee Firkin Craft Beer Festival home page.