What’s the difference between an ale and a lager? Like scotch and bourbon are both whiskies, ale and lager are both beer. By definition, an ale is brewed with a top-fermenting yeast that thrives at mid-range room temperatures. For this reason, ales are typically stored between 60° and 78° Fahrenheit during the fermentation stage. This type of yeast, and the fermentation temperature tend to give ales a fruitier and spicier flavor than lagers. Generally speaking, ales are more robust and complex. A few common styles of ale include pale ale, India pale ale, amber ale, porters, and stouts. In contrast, lagers (In German, Lager means, to store away) are made with bottom-fermenting yeast that work best at cooler temperatures, usually between 35° and 55° Fahrenheit. Fermentation happens a bit slower at cooler temps making the beer more stable, so it can be stored (or “lagered”) for longer periods than ales. This yeast tends to have less characteristics presence in the finished beer. As compared to ales, lagers have a cleaner and crisper quality with emphasis on the hops and malt flavors. The lager family includes but is no limited to, pilsners, bocks, and dunkels.
Now you may be wondering what top fermentation and bottom fermentation are. The top-fermenting versus bottom-fermenting yeast distinction likely originated in the observation that ale typically features a large, fluffy kräusen (Pronounced kroy-ZEN – it is the foamy head that develops on top of fermenting beer. It is used by brewers to gauge when the fermentation process is going strong and when it is complete) on top of the fermenting beer. Lagers have a kräusen as well, but it is usually smaller and less vigorous. This has less to do with any particular positional preference in the vessel than it does with the simple fact that cool fermentations are more subtle than warm fermentations. Yeast works slower when it’s cold than when it’s warm, which is why you’ll get less to no fruity esters with lagered beer. Observe an active fermentation for any length of time and you’ll immediately notice that yeast activity is distributed throughout the liquid. As billions of yeast cells multiply and feed upon the available sugars, initially clear wort becomes rather cloudy. Bubbles rise to the top from all points in the fermenter, and the whole mass appears to churn violently. When fermentation is over, those yeast cells drop out of solution, and the beer becomes clear once again. Most yeast cells, ale and lager alike, flocculate and end up on the bottom of the fermentation vessel, at least to some degree.
Here is where it all gets a bit tricky…some brewer’s yeasts fall into a grey area that blurs the clear distinctions between ale and lager. Some ale yeast can be fermented at lager temperatures and vice versa. For example, beer styles like Kölsch and altbier are fermented with ale yeasts at low, almost lager-like temperatures. And California common beer is fermented with a lager strain that has adapted to warm, almost ale-like temperatures.
So ultimately, Ale fermentation falls on the warm side of the scale, with yeasts that prefer a general range of 60 to 78°F. Clean fermenting beer styles, like those of English and American “origin” (think pale ales, porters, stouts, etc) tend to stay under 68–70°F. As fermentation temperature creeps above 70°F and approaches 80°F or warmer, ale yeasts can lend complex esters and phenols to beer. When intentionally created, these compounds add interesting complexity and are hallmarks of many Belgian, French, and some German styles. That peppery finish in your favorite French saison, or the notes of banana and bubblegum in your German wheat beer, are results of yeast activity and can be manipulated based on the fermentation temperature (yeast can lend tons of flavor!). And on the other side of the coin, lagers are fermented at cooler temperatures than ales, but not as cold as you might think. Typically, lager fermentation is conducted in the range of 48–58°F, and because some lager yeasts can ferment more kinds of sugars than ale yeasts, the final beer is often crisper on the palate. The cold fermentation temperature also means that yeast-derived flavors like esters and phenols are rarely present. Fermenting lager, however, has one additional step compared to ale fermentation: lagering. Many beer drinkers assume lagers are fermented near freezing, but what they are actually thinking of is the extended cold lagering period during which the beer is aged for at least 2 to 3 weeks near 32°F. This cold aging period allows lager yeasts and other proteins to precipitate out, which helps deliver the signature smooth, crisp lager drinking experience.
Hope this clears up any confusion you may have had between the two.