PHILADELPHIA Amid a crowd of face-painted children and noshing parents, a small knot of old-timers gathered Sunday to gossip and reminisce at the 40th birthday party of the Weavers Way co-op.

They had seen the cooperative Mount Airy grocery store go from new age to middle age, from a small buying group in a church basement to a 5,000-member cooperative with two thriving stores and a farm.

And now a couple of hundred stalwarts held a picnic at Cliveden, a historic mansion in Germantown, followed by - what else? - a membership meeting.

David Baskin, a past president, recalled the first store, with room for just six shoppers to peruse the shelves while others waited their turn in a separate room. Abby Weinberg said her mother, Sheila, newly divorced and leaving Scranton, chose to move to Mount Airy because of the co-op; she used to send Abby, at age 8, down the street with a grocery list and a blank check.

Linda Schatz recalled meeting her future husband, then a purchaser at the store, when she came to put in the work hours required of co-op members. The marriage lasted three years before they separated, but Schatz is a member still.

Her mother, Vivian, told how her husband, Albert Schatz, a scientist renowned for discovering the antibiotic streptomycin, took off his lab coat and rolled up his sleeves for years to sharpen the co-op's knives. He learned the skill as a child on his grandparents' farm.

Baskin summed up the conversation: "From packing bags in the basement of Summit Church to having a hundred employees and $18 million of business a year, I'd say things have changed a little bit."

At the party with grilled sausages and burgers, local beer and wine, and live music by several local artists, other longtime members commented on the changing values evident on the store's shelves. The original goal, Vivian Schatz said, was saving money by buying groceries as a community. Later, she recalled members boycotting produce from certain regions of the country and the world to protest workers' treatment.

The foods available for sampling Sunday spoke to a new set of ideals, in a vernacular unheard of 40 years ago. Organic. Locally sourced. Fair trade.

The display included egg-free egg salad made of tofu; antibiotic-free cheese made by a co-op in Holland; and dark chocolates with Hawaiian ginger, Pennsylvania berries, or Sri Lankan tea.

Amy Zitelman offered tastes of the tahini she and her sisters began marketing to restaurants and stores in April.

"My sisters and I found a really unique sesame seed," she said, that was sweeter than that harvested in China, India, and South America.

The natural focus extended beyond food. Carly Dougherty of Philadelphia recently began producing aluminum-free deodorant in her kitchen. She was delighted when Weavers Way contacted her about stocking it.

"Stores that are committed to really buying local, it makes me feel so much more confident that I can get a business off the ground," she said. When a founding member of Weavers Way stopped by to check out her product, which she sells under the brand name Stinky Girl, Dougherty gushed, "You mind if I get a picture of you? You guys really are like rock stars."

Cherron Perry-Thomas, a member of Weavers Way since 1996, brought along a stationary bicycle for her display of Vega nutrition shake mix. Passersby young and old tried pedaling the bike, which operated a blender to make the shakes.

"It takes a lot of energy," Perry-Thomas said as she took a turn pedaling. "Sometimes you don't realize. You just flip on a switch. When you start using your own power and your energy, you start to appreciate it."

A co-op member tried a sip of Vega's dairy-, soy-, gluten-, and whey-free drink. "Is this a complete meal?" she asked. Perry-Thomas said it was, and responded to the shopper's question about what sweetener it used. "Usually I can taste stevia, but I don't taste it," the shopper said approvingly.

A decade ago, Weavers Way was rocked by the revelation that its bookkeeper had been concealing failing finances, including more than 4,000 bad checks she had written from the organization's account. Weavers Way suddenly found itself facing $600,000 in unexpected debts and losses.

"That was an important moment in the organization's growth. In a lot of ways, it was a gut check," said John McGoran, who worked at the co-op for 30 years. Members rallied around the store to provide loans and paid an extra surcharge on their groceries. When the bookkeeper, Andrea Sheaffer, agreed to pay $30,000 in restitution to avoid jail time, the board instituted better practices for managing its money.

The scare was a turning point, McGoran said. "It helped demonstrate to the members and the community how important Weavers Way was to them. And it helped demonstrate to the leaders of the co-op that we needed to make major changes."

The birthday party Sunday marked a moment of triumph as the store celebrates several years of record growth. In 2010, the co-op opened a second location, in Chestnut Hill, and added about 2,000 members there. Next week, it will open a small shop carrying vitamins and hygiene products next to that branch.

"I love that it feels like a really good institution to be part of," said Rona Pietrzak, a longtime member. "It just feels like part of living in Mount Airy."