Lager is one of two overarching families of grain-based beverages that comprise “beer.” The other family is ale. See ale. Although there are countervailing views on terminology, it is generally accepted that all of the world’s beer styles belong to one of these two families. Under these families lie further differences that split the world of beer into more than 100 styles, some distinct and some with decidedly fuzzy borders. See beer style. Lagers are the young upstarts of the beer world, but over the past 150 years lager beer emerged out of central Europe and conquered with amazing speed. Today, approximately 9 of 10 beers consumed around the globe are lagers. Technically, there is only one core difference between all ales and lagers: the type of yeast used to ferment the wort into beer. Simply put, ale yeasts (Saccharomyces cerevisiae) make ales and lager yeasts (Saccharomyces pastorianus) make lagers. See ale yeast, lager yeast, and yeast. Although most ale yeasts ferment wort at relatively warm temperatures, usually between 15°C and 24°C (roughly between 60°F and 75°F), lager yeasts can ferment at relatively cool temperatures, usually between 6°C and 13°C (roughly 42°F and 55°F). Lager yeasts also ferment much more slowly than ale yeasts, produce fewer fermentation by-products, and are considered “cleaner and crisper” tasting than ales by most drinkers. Lager yeasts also tend not to throw a thick, rocky head on top of the fermenting wort during primary fermentation; instead they tend settle to the bottom. This is why lager yeasts are also called “bottom-fermenting” yeasts as opposed to “top-fermenting” ale yeasts. See bottom fermentation and top fermentation. If wort has a warm, fast primary fermentation by an ale yeast, it becomes an ale. If it has a cold, slow fermentation by a lager yeast, it becomes a lager. The brewer surely has an intention, but the wort itself is agnostic as to its destiny—it is the yeast that decides its future as a beer.

A pre-Prohibition lager label from The Christian Heurich Brewing Company in Washington, DC. During Prohibition the company managed to stay afloat thanks to its ice plant, which supplied ice to homes, commercial refrigerators, and even, for a time, Congress and the Supreme Court. pike microbrewery museum, seattle, wa

The name lager comes from the German verb lagern, which means “to store.” This is because lagers are usually matured after fermentation, on the yeast, between several weeks and several months, often near or even below the freezing point. See maturation.

Other than a temporary closure during Prohibition, the Quandt Brewing Company in Troy, NY, operated from 1859 to 1942. pike microbrewery museum, seattle, wa

This maturation period, therefore, is also called “lagering.” See lagering. During lagering, unwanted flavor and aroma compounds are reabsorbed and transformed by the yeast, which settles to the bottom of the beer, leaving it clear. There is a common perception that lagers are golden, light on the palate, and lower in alcohol, whereas ales are darker, heavier, and stronger. In fact, there is no truth to this whatsoever. The color of a beer has nothing to do with whether it is a lager or an ale nor does its alcoholic content. There are dark and strong lagers just as there are pale and light ales and any combination of these attributes in between. Lagers come in a wide variety of flavors. There are very opaque, almost black, chocolaty lagers; there are smoked lagers; thick, heavy, sweetly malty lagers; amber lagers; deep golden rustic lagers; golden aromatic lagers; straw blond and malty lagers; blond, hoppy, spritzy lagers; and very thin and light quaffing lagers, usually mass-produced with adjuncts. See adjuncts, bock beer, doppelbock, helles, light beer, märzenbier, pilsner, rauchbier, schwarzbier, and vienna lager. For the consumer of beer, the difference between ale and lager is one of flavor and aroma. Lager flavors tend to be ingredient driven rather than yeast driven. The main players on the palate and the nose are grains and hops. Fruity esters and spicy flavors tend to be muted and the flavors direct and focused. Notable fermentation character is usually limited to a fresh whiff of sulfur and often not even that. Ales can be more complex, but well-brewed lagers can be beautiful in their relative simplicity. For virtually all of human history, until roughly the mid-1800s, and unbeknown to the brewer or drinker, beers became either ales or lagers more or less by happenstance, depending on the ambient temperature and overall climate. In temperate environments, ale yeasts tend to become dominant in the fermentation before slower-growing lager yeasts can establish themselves. In cooler climates, especially in the winter, ale yeasts would simply remain dormant, leaving only lager yeasts active in the fermenting wort. Because bacteria would also be dormant during the winter months, beer brewed during the cold season would also be less likely to be infected—cold-fermenting lager yeasts could outcompete bacteria. As a result, winter-brewed beers lasted longer than summer-brewed beers, which often went sour very quickly. This fact did not escape the attention of brewers in central Europe during the Middle Ages. For this reason, Duke Albrecht V of Bavaria decreed in 1553 that henceforth in his realm, all beer brewing had to stop between April 23 and September 29. It was with this decree—perhaps much underappreciated even by beer historians—that Bavaria, with its cold winters in the foothills of the Alps, was moved firmly into the development of lager beer. From then on, by necessity, any beer style developments in Bavaria had to be in lagers. This is why virtually all lager styles brewed the world over today, whether classical or industrial, have Bavarian roots. Eventually ale yeasts largely faded from the scene in Bavaria’s cold-brewing culture. The beers made in the run-up to the April shutdown date, now known as märzenbiers (March beers), had to last through the summer until the autumn brewing season and were thus stored, or “lagered,” in cellars and caves packed with blocks of ice cut from lakes during the winter. This laborious practice of cold beer storage in central Europe was abandoned only in the last quarter of the 19th century, after Carl von Linde invented mechanical refrigeration for beer storage tanks in 1873. See linde, carl von. Since the advent of refrigeration, it has been possible to make lager beer anywhere in the world and in any season. Lager beers, despite being more costly to brew and age, stored and traveled better than ales. By the late 1800s, the new railroads spread lager beer throughout Europe, and from there this once-obscure type of beer was poised to dominate the world of brewing.