A recent Sunday, 10:04 a.m.: With morning services in full swing seven floors below, two beekeepers prepare a pair of hives and 70,000 bees for the annual honey harvest on the roof of Glide Memorial Church. Congregants are soon heading up a winding staircase to watch.

Later, a lucky few chosen for a hands-on workshop with resident beekeeper Paul Koski learn about extracting nature's divine sweetener.

"I met him at a coffee shop, and I found him to be this amazing mix of character," said Konrad Bouffard, 44, founder of Round Rock Honey of Texas, whose company runs beekeeping classes several times a month on the San Francisco rooftop. "He wasn't in it for himself. ... He does work that very few people do. He's an amazing individual."

Koski maintains both the hive he gave to Glide five years ago and one Bouffard donated a short time later. His interest is in keeping the bees happy and humans safe. An out-of-control swarm in the Tenderloin would cause quite a stir.

"Keeping bees in an urban area can be a little bit problematic," Koski said.

Workshop attendees watch as Koski and Bouffard, wearing their bee suits, carefully pull frames full of honey from the two hives. The men expect at least 60 pounds of honey from this season's harvest.

All will be bottled and sold to congregants who share coffee and snacks during social hour after church services. Proceeds go directly back into the hives and Glide's Graze the Roof garden, which not only produces food, but also is used as a educational and community building tool. The food grown there goes directly to Glide's basement soup kitchen.

Every year the honey sells out fast.

"People want a taste of it," Koski said. "You can't go to Safeway to get it. It's nowhere else to be found except here at Glide."

Koski, 69, who retired after 39 years of teaching high school science in San Francisco, doesn't eat a lot of honey - just a bit in his morning coffee, and sometimes on his yogurt. Unlike many who get into beekeeping, it wasn't the sweet stuff that got him interested in bees as an entomology student at UC Berkeley 40 or so years ago.

"I've always been interested in insects and honeybees because they have this very complex social structure," said Koski, who also has three hives in his backyard. "I wanted to understand social interaction within a colony and the colony life cycle over a year and several years.

"If you keep bees, you have to get rid of the honey. A lot of people start with an interest in honey. I started with an interest in bees."

The framed combs collected on the Glide roof are brought down to a room two stories below, where Koski shows workshop students how to remove the honey. Soon it's the students who are doing the time-consuming work. They walk away with a better understanding of bees, and the work gets done more quickly than if it were just Koski.

"It's just really cool to see the actual structure and to see what the bees do," said workshop attendee Adalyn Naka of San Francisco. "We're in the middle of the Tenderloin. ...Once you get to this roof it's like this oasis, and you look down at the city and it's just so strikingly different from everything around it. There are plants, there is community - there are bees."

Koski isn't a member of the Glide congregation, but for five years, he says, volunteering with the Graze the Roof program has been one of the most valuable uses of his time.

"As a teacher I enjoy not only showing people what to do, but to have them do it," he said. "That's one of the great things about science. It's a hands-on activity.

"If they understand the honeybee life cycle and the colony life cycle, then they have a greater appreciation for what they see," Koski said. "Knowledge gives them freedom to know what's going on around them. It's demystifying. It's empowering."