Inside the secret Philly sour-beer brewery you need to know about

This doesn't look promising, I thought as I made my way down the narrow, Dumpster-lined alley framed with chain-link fence festooned with yellow caution tape. My search for Fermentery Form, one of the region's only breweries specializing in farmhouse ales and barrel-aged beers, had led me to a dead end, in every sense of the term: nothing but cinder-block buildings with tight-shut grates, not a cozy beer bar in sight.

But it turns out I was in the right place, just at the wrong time. Fermentery Form — only open one day a week — had taken the day off, announcing the closure in a last-minute Instagram post.

So I return for a second try. I find the door down at the end of the alleyway — look for the green lightbulb — and enter a tiny tasting room that's packed to capacity (and then some). Though the seven-month-old brewery produces only about 250 gallons of beer a month, its sour, funky, complex creations clearly have a cult following.

"We've had to figure out a way of working that made sense with the kind of beer we make and the amount of it we make — which is unusual and not very much," says Ethan Tripp, who was a graphic designer until his love of sour beers took him on a different path. He wanted to sample more varieties of wild-fermented and cask- and bottle-conditioned beer but found them unaffordable. So he started making them himself.

On this long-awaited Saturday opening, thirsty customers are seated along salvaged church pews, around communal tables, at the bar. A few fight their way in, curse quietly upon observing the thick crowd and instead opt to buy large bottles to take home. Others stand around barrels to sip one of the four options available on draft. I try the Origins/Barberra, a wild golden ale with a sour fruity flavor from the wine barrels in which it's conditioned.

This is not technically a brewery — the beer is brewed to Tripp's specifications by a contract brewery off-site, and then fermented, aged, and bottled here — but I definitely feel like I'm drinking in a brewer's workspace. A tall  stack of barrels partitions the tasting room from the business end of the space, but even so, people end up sipping beers while leaning against a utility sink where utensils used in brewing are drying. I find a tight corner near the water heater, atop which a jar of something bacterial-looking sits, bubbling.

Tripp says the bar is styled after Belgian tasting rooms and is meant to feel more like a family room than a brewery.

"I feel like I'm in someone's basement bar at a party and they're not terribly happy to see me," a friend tells me grumpily after fighting her way to the bar for a glass of Merry Merry dark strong ale. But as she takes a sip of the beer, a complex and slightly sour brew aged in white wine and bourbon barrels, her mood improves. At least it doesn't taste like home brew.

Fermentery Form

1700 N. Palethorp St., 267-518-3676, fermenteryform.com

When to go: Hours vary but include most Saturdays from 2 to 8 p.m. Check Instagram or Facebook for up-to-date information. If the idea of a thick crowd scares you, wait a few months until the patio, shared with the neighboring mini-golf place, opens.

Bring: Anyone who loves sour beers and farmhouse ales. The crowd tends toward hipsters with statement facial hair, but there are also neighborhood old heads in hoodies, the occasional man with a toddler in one arm. (Also, bring cash, as there are no credit-card sales.)

What to order: Many customers prefer draft beer, but Tripp advises that a bottle is a more ideal vessel for his carefully calibrated fermentations. It's also probably a better deal, as the bottles ($10 to $18) are large enough to share among a few friends. My favorite was the Origins/Barberra barrel-aged golden ale ($7 for a nine-ounce pour).

Bathroom situation: The spacious, clean, single-stall bathroom is a nice escape from the crowd in the tasting room.

Sounds like: About what you'd expect 30 people crammed into a tight space to sound like — 98 decibels of chatter, with soft alt-rock playing in the background.