Their protest finally prodded Pilsen's small-scale beer-makers into action. They joined forces in a citizens' brewery and brought in a Bavarian brewer by the name of Josef Groll.
Until the mid-19th century, beer was made by mixing mashed barley, hops and water in an open vat at room temperature, with the alcohol-forming yeast floating on top.
The extremes of the central European climate, however, played havoc with fermentation.
The results were unpredictable and often undrinkable.
Since the 15th century, the Bavarians had been experimenting with fermenting their beer in caves, where the low temperatures made the yeast drop to the bottom of the vat (hence the term "bottom-fermented") resulting in slower, more controlled fermentation.
The caves also protected the beer from wild yeasts. The new lager beer - lager comes from the German word for storage, referring to the long ageing period - was an improvement but still nothing to get excited about.
Groll's breakthrough was to combine cold fermentation with local ingredients and a bit of tinkering with the brewing process. He poured the world's first glass of bottom-fermented golden lager on October 5, 1842, just as the Industrial Revolution made large-scale production possible.
The new beer was a sensation.
Copycat lagers sprang up across Europe, forcing Groll to change the name from Pilsner ("beer from Pilsen") to Pilsner Urquell (or Plzensky Prazdroj in Czech, meaning "the original source") to distinguish it from dozens of imitators.
To this day, you can order beer in many parts of Europe by asking for a pils or a pilsner.
Plzen today is a gritty, industrial city. It's no Prague but it is a compulsory stop on any serious beer pilgrimage.
Around 100,000 people a year visit the Pilsner brewery, not counting the tens of thousands who turn up for three days of free bands and 40,000 litres of beer during the Pilsnerfest every October.
The Beer World tour starts with a filmed history of Pilsner and a glimpse of the new brewing hall built after multinational SAB-Miller bought the business.
With its gleaming tiles and copper mashing-kettles controlled from a computer station, it looks like the Starship Enterprise crossed with an old-time brewery.
But the cellars are by far the best part of the tour, and not just because that's where the tasting happens.
Cut from sandstone beneath the brewery, this 9km labyrinth used to house thousands of oak barrels at a naturally chilly 5-6C.
Some beer is still brewed by the old method in open vats. After 12 days this beer is decanted into barrels, lagered for a month and quaffed by tourists.
This cloudy, unfiltered beer straight from the barrel is superb, yeasty and - because it has yet to be pasteurised - literally alive.
The next stop for the serious pilgrim is Plzen's Brewing Museum, in a 13th-century malt house, tracing the beverage's history from the first jar of fermented barley in Mesopotamia around 4000BC. Exhibits include a spiked collar of shame for merchants who sold bad beer or short-changed customers - a device that could come in handy in some present-day Prague bars - plus beer paraphernalia and beer records.
If you exit the museum by a side door you end up in the Na Parkanu "tap room" against the old city walls.
It's a traditional pub with simple wooden tables and dark panelling, tourist-friendly but geared to local drinkers.
It's also one of only a handful of pubs in the country serving beer straight from the brewery's lagering tanks. This is as fresh as beer gets: pre-filtration, pre-pasteurisation, slightly cloudy and with a hint of yeast.
Among the shaggy beards and curling cigarette smoke I spotted a pair of silver-haired gentlemen who looked like they knew their beer. I asked Jaroslav Heyda about the appeal of local beer.
"It's a very social drink, for whenever people get together - at weddings, the birth of children, even funerals. It's a drink from birth to death," he said.
Then they reminisced about the old days. Most Czechs agree that the communist era was crap, but beer cost three crowns (15 cents) a handle and every town had its own brewery.
"Now many of them have closed down," Navratil said glumly.
Navratil has a point - many small-town breweries have shut down or been swallowed up by multinationals - but there's no need for despondency just yet. Of the 71 breweries active at the time of the Velvet Revolution in 1989, at least 20 have closed.
However, that has been more than offset, in numbers anyway, by new microbreweries and brewpubs. Today about 90 Czech breweries produce more than 470 varieties of beer.
CHECKLIST
Getting there: Air New Zealand flies to London, from where a range of budget airlines connect to Prague, from where Plzen is about a one-hour drive.
Further information: See prazdrojvisit.cz.
