In A Nutshell
We often see beers labeled as lager or ale, but what’s the difference? It’s all in how they’re made and what they’re made with. Both types use yeast to encourage the fermentation of other ingredients. In brewing an ale, the yeast that’s used floats on the top of the brew—that’s what creates the foamy head. When making lager, a yeast that sinks to the bottom is used. Lagers are also brewed cold.
The Whole Bushel
Fermentation is the process that makes beers of both types alcoholic. Whether it’s grain, hops, or barley that’s used, it’s fermented into alcohol and carbon dioxide. Yeast is the ingredient that causes this reaction, and ales and lagers use different types of yeast in their processes. The yeast used in the process of brewing an ale floats on the top of the liquid, fermenting there first. This creates the light foam head that floats on the top of an ale when you pour it. A lager, on the other hand, uses a type of yeast that sinks to the bottom. That’s why there’s typically no large head on a lager if it’s poured correctly at the correct temperature.
Ales are the more traditional style of beer, and include stouts and porters. (For a good example of the head characteristic of an ale, look at a well-poured pint of Guinness.) Ales can be finished in one of two ways. “Real” ales are a beer brewed in a cask that is taken directly to the place it’s going to be served. The yeast in it is still active, and the fermentation process continues. That means that it has a limited shelf life and must be served before the fermentation goes on for too long. Ales can also be chilled at a certain point and have the yeast filtered out to stop the fermentation process and prolong shelf life.
Lagers are brewed with a different kind of yeast than ales. One of the most important steps in brewing a lager is dropping the temperature; most types of yeast used in the fermentation of ales will stop working at low temperatures. Lager yeast will continue to work, very slowly. This means that it generally takes longer for the fermentation process of a lager to complete; most of the process takes place at low temperatures, but raising the temperature near the end ensures that the process is complete. Also unlike ales, lagers are kept in cold storage after the process is complete in order to further condition them. This gives lagers their traditionally clear appearance.
Historically—and not surprisingly—ales are the traditional alcoholic drink of choice since well before the Middle Ages. Since lagers require strict temperature control and a way to store them cold, they’re a relatively new invention in the overall scheme of things. Throughout medieval Europe, ale and beer were the main styles of brewed, alcoholic drink. The difference is that ale was made from grain, while beer was made with the addition of hops.
The process for creating an ale has changed considerably in the 700 years or so they’ve been around, so much so that an ale created from a medieval recipe will bear little resemblance to the ales of today. Not only is equipment very, very different (medieval ales were made without modern luxuries like thermometers), but liquid would not always be boiled before or after fermentation. Ales were traditionally served “fresh,” or what we now call “real.” As it was a common drink, batches seldom lasted long enough to worry about whether or not they had a self life. In medieval England, it was average that a family of five would consume about 9 gallons of ale each week.