Until 1842, bottom-fermented lagers were mainly dark and murky. Think of the roasty, full-bodied dunkels from Germany's Ayinger or Pottstown's Sly Fox.
Groll's landmark innovation was to use pale malt for a light color. The region's soft water and Bohemia's distinctively herbal Saaz hops created a remarkably smooth, light-bodied beer with a gentle, sweet flavor balanced by tongue-snapping bitterness.
And it was gorgeous. Held up to the light, a clear glassful looked like a golden beacon of sunlight.
It was a sensation, quickly spreading through Europe and - with the wave of German immigration - to America. By the last half of the 19th century, Bohemian pilsner and its German copycat sister, helles lager, nearly wiped out dark beer to become the most popular style in the world. Today, it would be hard to dispute estimates that nine out of 10 beers consumed worldwide are at least inspired by the pilsner style.
You might say that imitation is the sincerest form of flattery. Or you might say that the sequel is never as good as the original.
Some of the blandest, cheapest, lowest-common-denominator beer today is ostensible pilsner: PBR, Natty Light, Old Mil, Tsingtao, Heineken, Sapporo, Fosters, Molson Canadian.
Americans, in particular, have abused the style. We've added rice, corn, extracts and chemicals. We've watered it down and sacrificed most of the hops.
It was American pilsner that, years ago, newspaper columnist Mike Royko famously said tasted like it had been run "through a horse."
Mercifully, small brewers have since created authentic Bohemian-style pilsners. Try Victory Braumeister Pils, Samuel Adams Noble Pils or Oskar Blues Mama's Little Yella Pils.
Or try the first pilsner. You know it as Pilsner Urquell, meaning "pilsner from the original source."
As the brewery celebrates its anniversary this month, its current master brewer flatly says the current version tastes "practically the same" as the original. I had Vaclav Berka on the phone earlier this week as he was wrapping up anniversary festivities in the Plzen town square.
How does he know that today's Pilsner Urquell tastes the same as it did 170 years ago?
"We have brewing records, and we're using the same ingredients at the same parameters," Berka said. He acknowledged brewing technology has improved and so has the quality and stability of ingredients. "But the methods are the same."
That includes traditional triple decoction, a painstaking method in which the mash temperature is raised in stages to extract the proper amount of fermentable sugar. Few breweries bother with decoction today because of improved malting techniques. But that's science; what about flavor?
Pilsner Urquell runs batches past in-house panels of more than 70 judges, including one group of old-timers in their 80s who presumably have clear memories of how the beer tasted long ago.
Berka is obviously proud to brew such a seminal beer. But I wondered: Is he proud of his beer's many imitators?
"There's a lot of splitting of the pilsner style," he said. "You have Bohemian pilsner, German pils, and more. The ground is basically the same, and I'm happy our Pilsner Urquell is the founder of the category."
Sure, but what about light beer? Josef Groll also begot Miller Lite, a lifeless bottom-feeder (coincidentally owned by Pilsner Urquell's parent, SABMiller) whose label until recently declared it was a "true pilsner."
"I've tried it. It's . . . different," he said. Berka isn't just a master brewer, he's a master diplomat.
"Joe Sixpack" is by Don Russell, director of Philly Beer Week. E-mail: email@example.com.