September 22, 1986 12:00 PM

Walking into the backyard of Mark Antrobus’ modest Victorian house on a quiet Denver side street is like time-traveling back to the ’60s. Stereo speakers pump Oriental music out of the windows, incense spikes the air, and the 20-odd men and women moving around in various states of undress seem to be reenacting Day Two of the Woodstock Festival. That was the day when the rains fell and blissed-out Aquarians made full body contact with a river of mud.

Actually, the mud in this case is a whitish potter’s clay, which the guests pat and smear on every inch of bare skin while their host—a 40-year-old ex-Hindu ascetic who now runs a tiling business—serves up gin and tonics.

Next come the embellishments. One man dips into a pot of tinted clay and begins planting black handprints on his colleagues. Others paste leaves and feathers to their loincloths while a woman tries to fashion a breastplate from a refrigerator shelf. Crude, outsize papier-mâché masks complete the costumes, each one embedded with gewgaws and personal totems: pistachio nuts, pottery shards, auto springs and, in Antrobus’ case, tile spacers.

Several neighborhood kids on bikes wheel up to the edge of the yard and yell, knowingly, “Mudmen, Mudmen!” As Antrobus will later explain to bemused bystanders in Civic Center Park, “We’re a Denver tradition.”

But of what? Does it help to say that the Mudmen, a fluid troupe that makes three or four public appearances a year, practice primitivist performance art? Not really; group founder Antrobus is reluctant to wrap the scantily clad Mudmen in artistic mumbo jumbo. Instead, he tells a simple tale: In 1981 Antrobus began seeing photos of the Mudmen of New Guinea—in a book of Irving Penn photos and on a record album. They got him thinking about what it might be like to strip down and “mud up.” Somehow, “without trying to create a philosophy about it,” he managed to persuade some friends on the Denver performance-art scene to join him in the experiment. “I guess people trust me,” he says.

Certainly Antrobus, the son of two peripatetic British journalists, can claim more of a kinship with primitive culture than most of us. At age 19, in 1964, he forsook art school in London for a life of Zen meditation, sequestering himself in a hut in Ireland. He eventually traveled to a Hindu monastery in southern India, where he stayed eight years, meditating eight hours a day and living at “lower than a peasant level.” Then in 1975, Antrobus decided it was time to be a “normal person, have a family.” A friendly correspondence with Chogyam Trungpa Tulku, of the Naropa Institute in Boulder, drew him toward the Buddhist community, and soon he was settled in Denver with a wife, a mortgage and a construction job, all very normal. The marriage failed, however, and Antrobus’ relationship with mud—which he first encountered as drywall clay—developed in an interesting if not quite normal way.

“Mudding up,” Antrobus and his friends have discovered, can unleash all sorts of odd, primal impulses—to dance, to chant, to beat sticks. The performances, he says, just “grew out of the chaos,” though an unkind critic might say they didn’t grow very far.

“I like the primitive look and feel of it, but I don’t know what it means,” says a woman in Civic Center Park while the Mudmen brandish vacuum cleaners, old car fenders, snowshoes and other “20th-century trinkets,” as Antrobus classifies them, in a loosely choreographed public ritual. The toddler set appears most absorbed by the skit, though a few beady-eyed adolescent boys watch intently to determine whether the Mudwomen are topless. (Two are.)

The dreamlike apparition of aborigines among city buildings rarely fails to elicit some response, be it smile or grimace. The Mudmen seem to have tapped into a very basic urge. “There are a lot of people who’d like to do this, who’ve wandered through the woods on their vacation and thought, ‘I want to be like these animals are,’ ” says Antrobus in explanation.

But it takes a Mark Antrobus to get them to give it a try. On a recent trip to Vancouver, Antrobus, who’d brought along a Mudman mask in a hat box, contemplating a solo turn somewhere or other, asked directions from a local artist. Much talk and a few beers later, he’d talked the man into joining him in a mud à deux in Stanley Park.

How long can he keep on in this way? “I want to do this the rest of my life,” the missionary of mud says firmly. “I guess I’m dedicated to repaganizing the Western world.”