Bret Kimbrough, brewmaster at Growlers of Gaithersburg, uses converted kegs to make the brewpub's pilot beer. (Eric Gleason/For The Washington Post)

The beers have names like Cereal Killer, Uber Tuber and Windbreaker White Bean Ale. Their ingredients tend to be even odder: Honeycomb breakfast cereal, sweet potatoes and, yes, white beans, plus bacon-perfumed malt and hickory wood. Oddest of all, though, may be their place of origin: Growlers of Gaithersburg, a brewpub that used to be, in the words of head brewer Bret Kimbrough, “pretty much a cookie-cutter brewery.”

Now, thanks to a small pilot brewing system that complements the Montgomery County brewpub’s eight-barrel brew house, many of Kimbrough’s beers would fit right in among the off-center stuff at the nearby Dogfish Head Alehouse. What’s more, Kimbrough and his assistants, Eric Gleason and Thomas Vaudin, can’t keep up with demand. In a matter of months, Growlers has quietly revitalized itself by brewing some of the most experimental beers in greater Washington: beers, it turns out, that are often really good.

“Basically, the rules of the pilot system are that there are no rules,” Kimbrough says. “We have ideas and we brew them and we see what happens.” Still, he adds, “we do try to make good decisions. We’re not going to make ham-and-cheese beer or anything like that.”

Kimbrough did, however, brew an amber ale with sunflower seed butter and blackberry preserves: PB&J apparently is fair game.

Breweries typically use pilot brewing systems, often less than one-10th the capacity of their usual equipment, to test new recipes. But Kimbrough’s rig has taken on a life of its own. Since his first pilot beer last June — Lillian’s Lavender Ale, which celebrated the birth of his daughter — Kimbrough has brewed more than 60 others, and he estimates that pilots will make up about 15 percent of his output this year.

There’s a certain mad-scientist quality to the whole project, an air of home-brew-style romance embodied by Kimbrough’s original pilot brew kettle: a keg with the top cut off. Old kegs also serve as his fermentation vessels. He has since graduated to a proper 55-gallon brew kettle, but he still boils the unfermented beer using a portable 210,000-BTU propane burner, a hazard that one Growlers regular quickly brought to Kimbrough’s attention.

The man said, “ ‘You can’t do that in here,’ “ Kimbrough recalls. “And I said, ‘Who the hell are you?’ And he said, ‘I’m the fire marshal.’ ” Much of Kimbrough’s mad science now takes place on the brewpub’s outdoor deck.

There are also occasional excursions onto the pavement out back to make German-style steinbiers — “stone beers” — which Kimbrough heats to a boil using red-hot hunks of granite. “We’re like 5-year-olds out there, screaming and jumping up and down,” he says.

The pilot beer program has generated a similar sort of excitement among the brewpub’s customers, creating so much buzz, according to Kimbrough, that last month Growlers served nearly 50 percent more beer than usual.

“It’s obviously helped the business tremendously,” says co-owner Jon Silverman. Within the next year, Silverman and his partner, Chuck Blessing, intend to convert a private dining room into additional brewing space.

Why do patrons love beers like Turkish Delight (scented with rose water and preserved lemons) and Rye of the Tiger (brewed with 100 percent rye)? The creative ingredients and silly names help, Kimbrough says, but even more important is the sense of constant experimentation. He also credits his previous career. Before arriving at Growlers, Kimbrough studied bread-baking and pastry at the Culinary Institute of America in Hyde Park, N.Y., and spent a decade in professional kitchens. “Having an understanding of how ingredients work in food gives you a really good understanding of how they’ll work in beer,” he says.

Kimbrough’s beers, particularly those that rely heavily on spices, fruits or other added ingredients, are surprisingly balanced and fresh-tasting, even as his home-brew-style brewing methods make quality control more difficult than usual. He decided not to serve some of his white bean ale, for example: The beans added a pleasant acidity, but one keg was too sour.

As the beers themselves attest, such issues are rare. A Belgian-style saison brewed with peppercorns and lemon is aromatic and refreshing, without the overwhelming bite that can mar peppercorn beers. A creation inspired by Grand Marnier, brewed with orange marmalade and orange blossom honey, has a candylike aroma, full flavor and an appropriate boozy warmth.

“I don’t want to be necessarily remembered as eccentric,” Kimbrough says. “I want to be remembered as making good beer.” But ideally, he adds, “I’m remembered as eccentric and making good beer.”

Fromson, a freelance writer, lives in Washington. Follow him on Twitter: @dfroms.