If you want to know what a lager is, there’s an easy place to start.

“In one word? Yeast”, said Brian O’Reilly, Master Brewer at Sly Fox Brewing in Phoenixville, PA, where many a lager is brewed in the German traditional style. “It can be simple as, if you want to brew a lager, use lager yeast, and if you want to brew an ale, use ale yeast.”

And brewing a lager really does depend most of all on that simple little sugar-metabolizing creature. But that definition proves simple, straightforward, and insufficient if you want to really dig into the complexity and history of a greatly misunderstood, greatly important beer.

ALES VS LAGERS, AT A GLANCE

INGREDIENTS: Lagers and ales share the exact same list of potential ingredients (hops, malt, wheat, fruit, coffee, etc.), save one: yeast. Ales are brewed with ale yeast (Saccharomyces cerevisiae), lagers with lager yeast (Saccharomyces pastorianus).

FERMENTATION: While ales ferment for roughly two weeks at warmer temperatures (roughly 65 to 75 degrees Fahrenheit), lagers are fermented for anywhere from four to 10 weeks at colder temperatures (46 to 59 degrees F).

FLAVORS: Just like ales, lagers come in a wide variety of styles, each with unique and broad flavors. However, lager yeast tends to offer more subdued flavors than ale yeast; ale yeast produces more esters in a beer, chemical compounds that produce fruit, honey, and spice notes. Because it lacks these esters, the lager tends to feature a more obvious interplay between hops and malts.

Here’s another way to look at it: the lager is not a beer style, but a major family of beers. There are a few exceptions, but by and large a beer is either a lager or an ale. People often mistakenly believe the lager is a specific style or equate it solely to the mass-market lagers they know rather than understanding the lager as a major family of beers, according to Jack and Sam Hendler of Jack’s Abby Brewing, based out of Framingham, Massachusetts. The Hendlers should know: theirs is one of the first and only breweries to make only craft lagers. “We’re [visiting] Pennsylvania right now”, said Jack, “and if you go into a bar and order a lager, they give you a glass of Yeungling. And that’s just not what a lager is.”

So the best way to define the lager might be comparing it to the ale. That involves the aforementioned yeast, but it’s not so straightforward. Lagers are the relative newcomers in the beer world and come from the Germans, who named their beer after their verb for “to store”. While ales have been made using the domesticated yeast strain Saccharomyces cerevisiae fermented at warm temperatures for going on 6,000 years, it was only about 250 years ago that the Germans started using a hybrid yeast strain, Saccharomyces pastorianus, to ferment their beers in cool caves and, later, in refrigerated tanks. The reasoning was several-fold, but one advantage was that lagers, because of their different yeast strain (called “bottom fermenting” because it sinks to the bottom of fermentation tanks, whereas ale yeasts tend to float to the top) and long-time fermentation at cold temperatures, created high natural carbonation and smooth, complex flavors, whereas ales at that time and before had relatively low carbonation.

American craft drinkers, Jack Hendler said, still yearn to be “smacked upside the head” with flavors. That’s not really the lager’s wheelhouse.

We take carbonation in beer for granted today, but before “force carbonation” — pushing CO2 and nitrogen through beer to create those refreshing bubbles and head that we so associate with beer — these bubbles were a major bonus for the lager style over the ale. Today, although ales use force carbonation to match the lager’s refreshment, the difference between yeasts, fermentation temperatures and aging length remains. Lagers are still fermented colder; they’re left to ferment for between four and ten weeks, versus an ale’s two weeks and warm-temp fermentation.

This longer timetable is a large part of why lagers have lagged behind ales in the craft beer scene today. Ales are more affordable to make, turning a profit around in half the time for a small brewery in need of fast cash. Another reason for the ale’s proliferation among craft beer brewers and drinkers is its broader range of full flavors, the result of more phenols from its yeast, which produces fruity and spicy notes, as opposed to the lager’s subtler nuances. These have made the vibrant ale the perfect foil to boring mass-produced lagers, and hence the perfect champion of craft beer.

“Ales have a nuance from the esters from the yeast. So [the esters’ flavors in an ale] could be very dramatic, like a weissbier (German for ‘wheat beer‘), which has a banana and bubblegum phenol, or it could be just a little nuance to a British bitter that has a mineral-y, kind of peach aroma to the yeast”, O’Reilly said. Lager yeast, on the other hand, yields a much “cleaner” character because it results in fewer esters.

The result for the lager is a higher dependence on the interplay of the remaining active ingredients, hops and malts. “An ale brewer would rely on the essence from the yeast as well as far as the palate of the beer”, O’Reilly said — say, those banana and clove notes of a Bavarian wheat beer — where the brewer of the Bavarian lager would highlight “just that honey-malt character in the minty, fresh-mowed-lawn character of noble hops.”

Lacking the boldness that craft drinkers expect of those big ale flavors — ale reviews frequently cite grapefruit and citrus, and even “cat piss” and “fresh-cut PVC” — remains one of the lager’s biggest hurdles. American craft drinkers, Jack Hendler said, still yearn to be “smacked upside the head” with flavors. That’s not really the lager’s wheelhouse.

But drinkers (and writers) need to be careful here. When comparing the flavors of lagers and ales, one inches narrowly along a deep pit of misinformation and misunderstanding. In fact, the flavors and taste profiles of lager styles abound, just like in the different styles of ales — for example, an IPA versus a stout. Or, as Jack Hendler cautioned, the lager is far from typified by a Yeungling.

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Again, there’s deception at play here, because in naming their lagers, the Germans have lent their stolid dichotomy to two major types: on one side are your helles or “bright” lagers, and on the other, the dunkel or “dark” lagers. But that’s just the tip of the bier-berg the Germans built. There are the bocks and doppelbocks, possibly named after the German word for “goat” and which abound in ABV and maltiness; the eisbock, a bock that’s had much of its water frozen off to concentrate flavors and its ability to get you drunk; the amber lager, made by the boatload by American brewers especially. The kellerbier is a hazy, unfiltered lager; the rauchbier is a “smoked beer” that often tastes like a delectable liquid ham sandwich; an Oktoberfest or Märzenbier is dark amber in color and perfect in autumn. And don’t forget the star of the lagers and the front-runner in the American craft lager boom, the pilsner or pilsener, which can be made in the German or in the Czech style, and, though often loaded down with hoppiness, also has one of the crispest finishes of any beer.

Where the uniqueness of the ale’s styles have been canonized by American craft drinkers, lager styles have been left in the dark. That’s beginning to change.

“When craft beer started to blossom, [labels] all just said ‘ale’, or maybe ‘red ale’ or ‘copper ale'”, said Sam Hendler of Jack’s Abby. “And now, no one thinks of ale in that way. The same thing’s happening with lager.” Jack’s Abby and others are leading the lager style charge by presenting their different styles for what they are — and by pushing the beer’s traditional boundaries. There’s the IPL or “India Pale Lager”, heavily hopped and high on ABV a la the IPA; Jack’s Abby is also leading the way into the Double and Triple IPL, the biggest of which tops out at 10% ABV; they also make wheat lagers, hoppy lagers, sour lagers, barrel-aged lagers and wine lagers, inside and outside of the German tradition. “It all falls within lager”, Sam Hendler said. “And it really does not limit us much.”

Perhaps this duality is the best way to define the new craft lager: made by brewers who are increasingly unafraid to expect more out of an educated, mature craft drinker, but who are also looking to pull in drinkers who’ve never liked craft beer before.

This explosion of lager styles among top craft brewers is having a profound effect on the lager’s role within craft beer. Though mass-market beers have long been ruled by the lager — each of the top 10 beers sold worldwide is one — in American craft beer, ale has long been king. But now there are rumblings that the light (or more accurately, “pale”) lager may be partaking in the great liquid comeback story of the century. The New York Times recently heralded the “lager Renaissance”; so did the Brewers’ Association’s Chief Economist; and so have drinkers, who’ve boosted pilsner sales (a leading style of lager; more on that later) by 56 percent from this time last year.

The Hendlers and many other craft brewers also see the lager as a gateway beer for drinkers of traditional American mass-market pilsners like Budweiser. The familiarity — smooth hops, mellow malts — might just make the switch to craft beer that much smoother. How many times have you heard your older relatives say they just can’t drink the damn craft beer with its huge, bitter hops?

“There’s gonna have to be some transition from Budweiser to super hoppy double IPAs”, said Jack Hendler. “As these beers get put out, there’s a better chance that mainstream Bud drinker will decide to try a pilsner from their local brewery, and it’s a good way to get more people drinking craft beer.”

Perhaps this duality is the best way to define the new craft lager: made by brewers who are increasingly unafraid to expect more out of an educated, mature craft drinker, but who are also looking to pull in drinkers who’ve never liked craft beer before. In the end, ardent drinkers and first-timers can both agree that while understanding the lager is great, drinking it might be the best education.