On May 10, Threes Brewing posted a photo of a dozen or so 750 mL bottles of Wandering Bine, a beer the Brooklyn-based brewery has been making since its opening more than four years ago. There was something different about these bottles, however, that Threes’ observant followers spotted immediately—where once the saison came in standard brown bottles, this release was packaged in vibrant kelly-green glass.

“Young Matty fresh on the green bottle tip,” cracked Dan Suarez (of the acclaimed Suarez Family Brewery) in the comments section, poking good-natured fun at Threes’ head brewer, Matt Levy. “Is this the first green bottle?” asked another commenter. For a Heineken or Beck’s drinker, a green bottle might not seem all that interesting, but in the world of craft beer—where 16-ounce “pounder” cans once indicated you were an of-the-moment brewery—it makes a serious statement, especially if a saison is inside.

Around the time of World War II, due to a shortage of brown glass, many European lager makers started using green bottles, and continued using them for the way they stand out on a shelf. But American craft breweries, like Threes, have begun using them for a reason beyond aesthetics; green glass typically leads to flawed beer. Unlike brown glass, lighter-colored glass does not protect a beer from UV light, which, when it comes into contact with hops, produces a sulfurous compound. This “skunked” flavor might be gross (and considered a brewing flaw) in export lagers, but can be pretty interesting in a funky farmhouse ale. Some brewers even think the skunkiness should be inherent.

“I’ll sometimes compare a green bottle saison to caviar or linen,” explains Bob Sylvester of Florida’s Saint Somewhere Brewing Company, citing two products whose typically undesirable qualities are intrinsic to their appeal. “Caviar is salty, linen wrinkles. Neither would be the same without those properties.” Sylvester packages all his farmhouse ales in green bottles.

Green bottles were first used for farmhouse beers in the birthplace of the style, Belgium and France. The archetypal Saison Dupont has used them since at least 1992, when they began exporting to America. Brasserie Thiriez and Brasserie Au Baron, masters of the bière de garde style (a slightly maltier, French farmhouse ale), also favor green glass.

Most admired is the avant-garde Brasserie Fantôme (a who’s who of beer cool), which has used green bottles since opening in Soy, Belgium in 1988. Some of Fantôme brewmaster Dany Prignon’s beers are so skunked by the time they reach America that they’re downright revolting—imagine an aroma of tire fire mixed with rotten eggs. Still, they are always one of a kind, creating an inconsistency that beer geeks crave.

Only this century have Americans started exploring green glass in earnest. Sylvester was the first to unleash a version stateside when he opened Saint Somewhere in 2006. Though his beers were well regarded, the green bottles themselves didn’t catch on. “I received quite a bit of backlash from the start [from consumers], and actually changed to brown bottles around 2010,” explains Sylvester. He wasn’t happy with the sans-skunk versions, however, and switched back to green for good in late 2012. Ahead of his time, Sylvester laments how little credit he seems to get now that the trend is finally taking off. “Now, any US saison or farmhouse brewery looking for authenticity—which is rare these days among the multi-fruited kettle sours and lactose milkshake IPAs—is packaging in green glass.”

If any brewery made green glass definitively cool, it was Jester King, which, in February of 2015, started putting its Le Petit Prince table beer in green bottles. One of the country’s most rustic breweries, Jester King’s endorsement of the green bottle was like Dylan and Brandon growing their sideburns long on 90210; a zeitgeist had been tapped into. But, like those sideburns, green glass is not easy to pull off, and today perhaps only two dozen breweries are using it.

Those who do are part of a murderers’ row: Oklahoma’s American Solera, Pennsylvania’s Forest & Main Brewing Co., California’s Homage Brewing, Connecticut’s Fox Farm Brewery, Wisconsin’s Funk Factory Geuzeria, North Carolina’s Zillicoah Beer Company and South Carolina’s Birds Fly South Ale Project, who recently collaborated with Sylvester for the green-bottled Skin & Bone.

Even home brewers, who once resorted to bottling in any old empties, have taken note. Dave Martin of the cult garage brewery Mindful Ales, uses green glass for his mixed fermentation farmhouse ales like Elemental and Dreams (Whatever They May Be). A lower hops utilization (essentially: how much, percentage-wise, hops impart their aroma and flavor into a beer) means they don’t get overwhelmingly skunked. “But I’ve found the minimal reactions that happen actually add a pretty cool layer of complexity,” notes Martin.

Acquiring the green bottles, though, is another matter. Most breweries seem to use United Bottles’ “Method Traditional” model, which runs about $1.50 a bottle (before labels, corks, cages and crowns), but they’re impossible to purchase in small quantities—a pro brewer friend hooks Martin up at the moment. They still cost him around 75 cents more per bottle than the typical brown glass. With green glass, you’re investing with the hopes of creating a more flawed beer—a strangely calculated risk.

Of course, trends evolve quickly in the beer industry, and it seems one brewery has already moved beyond green bottles. At a recent beer festival, I came upon the booth of Half Acre Beer Company, which has used green glass in the past. The lauded Chicago brewery was offering Bon Hut, a blueberry, plum and black currant wild ale. Before they had even poured me a glass, I noticed its stunning purple color—because the bottle was crystal clear. In theory, as the sun pounded down upon us and the bottles, the skunk would manifest in spades.