Bob Wall and Margaret Rinkevich are never alone at their Russian Hill home. When they're at the dining room table, a Bamileke sculpture from Cameroon peers down at their meal. At Wall's desk, a Fang female from 19th century Cameroon joins forces with Dogon figures from the 13th, 15th and 16th centuries to keep him feeling youthful; on Rinkevich's desk, a chi wara headpiece from Mali bids (so far unsuccessfully) for a more prominent place in their collection.

On the wet bar, Kaka strongmen carved in wood guard the remains of last night's wine, stored in the cooler behind them. Assorted tribal masks line a shelf behind the headboard in the master bedroom. And in the bathroom, a Suku mask from the Congo presides over the corner just inside the door.

Wall and Rinkevich didn't spend millions of dollars on what dealer Jim Willis describes as the biggest, deepest collection of African tribal art in San Francisco to lock their prizes away under glass. Everything is reachable, touchable, accessible -- and the couple invites visitors to hold up a mask, try a headpiece, caress a figure that's sweating palm oil leftover from some ancient ceremony.

"Not only do we have it in the bedroom, we have it in the bathroom," said Wall, who with Rinkevich is co-chairing Thursday's Gala Opening Preview for the weekend's San Francisco Tribal & Textile Arts Show. "I mean, if you're going to live with it. ... We get up in the morning and we look at that Suku mask and it makes us feel better. Because we look better than that does. So, we think it can pretty much go anywhere."

Wall's two-story space had a history of housing art collections even before he moved in 21 years ago. Previous resident John Berggruen is a well-known San Francisco art dealer.

"Everything was beige," Wall said. "He didn't want anything to compete with the art that he sold. So we remodeled about six years ago, and added a lot of stone and colors and textures. Which I think goes well with the African art. Besides, I like rocks."

Wall's father was a geologist, which partly explains his attraction to three-dimensional objects. In Wall's undergraduate days studying business at DePauw University, a professor showed off a collection of perhaps a dozen African tribal masks that, Wall said, "blew me away."

But, he said, "Other than going into the occasional museum, I didn't do anything about it, because I didn't have any money to collect anything. Finally, back in the early to mid-'80s, I thought, OK, I'm starting to have a little bit so that I could maybe buy something, and I went in and talked to a couple of dealers."

Wall made that money as a CEO for high-tech startups and companies including Theatrix Interactive and Clarity Wireless. But this artistic startup intimidated him.

"A dealer would say, 'That's a great piece, that's a great piece, those two are fakes,' " he said. "And I couldn't tell the difference. And I went to another dealer and it was basically a similar thing, and it freaked me out. I didn't buy anything at that time. I couldn't tell the difference between an authentic piece and one that wasn't, a so-called fake. Some people would go out and get an adviser to tell them. That's not my nature."

So Wall instead went out and got a library, embarking on a collection of volumes on African art that now totals more than 5,000. (Yes, there are a lot of shelves in this Russian Hill home. The couple's recommended reading for beginners: "The Art of Africa," by Jacques Kerchache, and "Tribal Arts of Africa" by Jean-Baptiste Bacquart. They also recommend this weekend's Tribal & Textile Arts Show for a rare chance to chat informally with dealers.)

It took, Wall guesses, about 10 years of research before he bought his first piece. In 1998, he said, he really got going.

"It's remarkable what they have collected in such a short period of time," said Willis, a dealer for 35 years. "They've bought very important and, in our field, relatively expensive objects. In the Bay Area, I'd be hard put to think of anybody who has collected as assiduously."

Willis said it's not unusual for collectors to share their passion with a significant other; rather, he noted, "When you're going to be that devoted and have your environment that filled with it and spend that kind of money, it's unusual to find only one in a couple who likes it."

And in 2001, in a Santa Fe gallery specializing in contemporary art, Wall found Rinkevich.

"I loved the art," said Wall, who keeps the paintings he bought that day in his house in Telluride, Colo. "I also was attracted to the person. It's an open question whether I would have bought four oils from somebody else."

Rinkevich asked Wall if he collected contemporary art, and he revealed that his true passion was African art, and the two were off and running.

"In college, I had taken a few African art classes and really liked them," said Rinkevich, who studied art history at the University of Arizona. "But I didn't really know what to do with it, and was really thrilled to return to it when I met Bob."

They made the first of what Wall describes as their "really significant" (synonym: really expensive) purchases together at a 2002 Christie's auction in Paris, a fiercely sought-after Boyo figure from the Congo for which Wall paid "about half a million."

"It was the one and only time I've seen him say, 'I'm getting it,' " Rinkevich remembered.

"Then we went out in search of a really strong drink," Wall said.

Both say they are attracted to the same sorts of objects, mostly strong or abstract figures from Nigeria, Congo, Gabon and Cameroon. They have no textiles, for example, and few of the Baule and Yoruba masks that are popular among other Americans.

Aesthetics grab Wall, while Rinkevich finds more excitement in discovering how a piece was used. During The Chronicle's tour, there was no discussion about value or investment: He'd pick up a piece, offer touches and comment on patina, while she'd explain that it had been an ancestral figure whose nose was rubbed for luck, or a headrest that was used during circumcision.

Oh, did we mention, not all of this stuff is for the kiddies? (There aren't any living with the couple, and Coco the dog seems unintimidated.)

"I've heard people say, 'I'm not sure I could live with that,' " of some objects, Wall said. Rinkevich remembers a Janus mask that had been in the guest bedroom in Telluride that had to be moved so that one guest could sleep.

"It was a helmet mask that fit all the way over your head, with the outer part skin -- typically hyena skin, or in some cases, not this one, missionary skin -- and it's peeling away and, yeah, it's pretty intense," Wall said.

Said Rinkevich, "I don't know if the guest didn't like it, but it was powerful and ..."

"Didn't want to sleep with it," Wall concluded.

They've got a similarly scary skull on a shelf in their Russian Hill living room. Wall, by the way, does the dusting -- it's problematic for a housekeeper to overclean, he said.

Conditions in San Francisco generally are ideal for preserving this mostly wood collection because the humidity is constant. So 60 percent of the collection is on Russian Hill, the other 40 percent in Telluride, where the bigger house has to be humidified.

"A lot of museums will put it in cases that are hermetically sealed, where they maintain a constant temperature and constant humidity," he said. "We don't do that."

It would spoil so much of the fun.

"One of the wonderful things we do and expect everybody to do is pick up the pieces," Wall said. "You want to feel the weight, you want to look at it a little differently, you might want to smell it.

"I heard of one guy who would lick a mask. I'm not going there, I'll tell you. But what he was looking for was the taste of salt."

Chimed in Rinkevich, "With a mask, this is how he would tell if it had been worn or not."

"Because if it had been," Wall said, "with the rest of the costume of raffia or cloth or whatever, in a hot climate, there would have been a lot of perspiration, and if you like it, you can tell, it would taste salty. I don't do that."

"There's the line," Rinkevich concluded.