Forty years ago, Ken Vavrek, a ceramics professor at Moore College of Art, got together with four former students to open a shared studio space, the Clay Studio, in Old City, then still a warehouse district.

But they needed support - which required obtaining nonprofit status, which in turn required creating programming to serve the community, such as pottery classes.

"We kind of invented it as we went along," Vavrek said.

Since 1974, the organization has evolved into something Vavrek never envisioned: A $1.7 million-a-year nonprofit serving 35,000 artists, students, and gallery visitors annually. "One thing we did not envision was that we would have visiting artists from around the world, some of the best artists from other countries, coming to spend time at the Clay Studio," Vavrek said.

This weekend, the Clay Studio celebrates that trajectory with a 40-hour 40th-anniversary blowout, including cocktails and silkscreening in the gallery, clay-instrument-making and jam sessions, wheel-throwing battles, and "muggings" (volunteers will flag down people carrying disposable cups and swap them for handmade ceramic vessels).

It will also host Occupation, an endurance art challenge by artist and Iraq war veteran Ehren Tool, who, with fellow artist and vet Jesse Albrecht, will turn a 700-pound bunker of clay into hundreds of handmade cups to give away.

More than an excuse for a party, the studio's anniversary comes at a pivotal moment: After four decades in Old City, its favorable 30-year lease on its home at 137-139 N. Second St. is winding down.

So, it will soon have to reinvent itself again, likely in a new location and possibly even in a new neighborhood. To do that, it will also need to continue to grow, through a multimillion-dollar capital campaign and broad outreach efforts to attract an even larger audience.

It could be good timing, said Garth Johnson, who joined the Clay Studio in December as curator.

"Every generation has had a big craft movement," he said. "And we're in the middle of the next great craft explosion: the DIY movement and the maker movement."

After all, the organization was, like many other artist cooperatives, born out of the last crafting boom, which began in the late '60s.

"The thing that set the Clay Studio apart was they were, early on, very ambitious artistically. They decided to open a gallery even though it was a pain to do, they decided to start a residency program even though those things took away from studio time."

Over time, they added more classes and studio-share programs; a Claymobile that visits schools, detention centers, and homeless shelters; and a series of date nights where couples can sip wine, throw pots, and make gratuitous Ghost references.

The studio also became an anchor for Old City's revitalization as an arts hub.

"We were one of the lead founders in 1990 when First Friday began," Clay Studio president Chris Taylor said. "We had three or four different arts organizations, and they just coordinated their openings. First Friday was born."

He said that the studio has helped Philadelphia's creative community grow through its residencies for emerging artists, who apply from around the world. Many put down roots and stay in the city.

A current resident artist, Chase Folsom, arrived in September just out of graduate school in Colorado. "I've been wanting to come here since I started in ceramics 12 years ago," he said. "The Clay Studio is sort of a career launching pad."

Johnson said the studio is already known internationally; his next goal is to reach more people in Philadelphia. That means leaving the white walls of the gallery behind - or at least getting them a little dirty.

"I'm actively trying to mix things up as much as possible, and get artists in front of the public as much as possible - and to get people to realize that a handmade cup is made by an artist in a certain way and it wasn't just born in a gift shop," he said.

For example, in August, Philadelphia textile artist Andrew Dahlgren will set up a knit shop in the exhibition space (dipping the textiles in clay, of course).

More immediately, for the anniversary event, there's Tool and Albrecht's marathon cup-making session in the gallery. Tool has made and given away 13,600 cups since 2001, many to veterans; it's become a ritual.

"In times of economic or other stress, you want to protect your community," he said. "The temptation is to build walls, and protect your community that way. But another way to protect your community might be to expand your community, to destroy your enemy by making him a friend. We can take the wall down and make cups - and make some kind of abstract community with the cups."

That's just what Johnson wants to do: Build a community with cups.

"Ceramics has always had a social role," he said.

Still, where that community will be, and what it will look like over the next 40 years, remains unclear.

Taylor said the studio, now 21,000 square feet in two buildings, needs to grow to about 35,000 square feet to add essential classrooms and studio space (never mind wish-list items like a demonstration kitchen to showcase the link between food and functional pottery).

The search has taken them to Callowhill, South Philadelphia, Kensington, the Delaware River waterfront, and, yes, Old City. About eight neighborhoods are being considered for relocation when the lease is up in 2018.

Taylor said, "I'm proud to say we might be able to do it again - help another neighborhood the way we've helped Old City."

CLAY FETE

Fired Up at Forty

7 a.m. Friday to 11 p.m. Saturday, The Clay Studio, 137-139 N. Second St. Information: www.theclaystudio.orgEndText

smelamed@phillynews.com

215-854-5053

@samanthamelamed