Five years ago, standing over a urinal in his office restroom, Clark Sorensen found his porcelain muse.

"I kept thinking, 'Here's something that we use every day. I wonder if I could make it into some kind of new form,' " recalls Sorensen, 47, a San Francisco artist.

Bathroom trips aren't usually nature's call to inspiration, but some artists like Sorensen are transforming the mundane into works of creative expression. Sorensen's "Nature Calls" series is a line of one-of-a-kind, handmade, porcelain fixtures in the shape of gigantic flowers - art that can actually be plumbed and used in a bathroom.

Sorensen's work has a historic pedigree. Ninety years ago, the French artist Marcel Duchamp shocked the art world when he submitted a signed, ordinary urinal for a New York exhibition presented by the Society of Independent Artists. Though the artists claimed they would display every item submitted, the controversial piece, called

Fountain

, was never shown to the public. Now, the work is considered groundbreaking in overturning conventional notions of art.

In 2004, 500 leading art experts voted

Fountain

the most important work of modern art. The piece paved the way for provocative modern artists such as Andy Warhol and British conceptual artist Damien Hirst, famous for displaying dead animals (sometimes chopped up) suspended in liquid.

"Duchamp has had the single greatest influence on art today," says Kenneth Silver, an art-history professor at New York University who specializes in 20th-century American and French art.

While Duchamp's work may have provided Sorensen with a precedent, the sculptor contends he's saying something different from Duchamp.

"Flowers are beautiful, delicate and feminine," Sorensen says, "but urinals are considered ugly, something we hide away - so for me it became the perfect combination, the perfect contradiction."

Sorensen says he found inspiration in the large-scale, close-up flower paintings of Georgia O'Keeffe. And unlike Duchamp, he always envisioned his artworks as functional, not just something to be mounted on a wall.

"I created them from the standpoint of an artist, but I think it's cool that they can be used," he says. "It's a unique blend of form and function."

Unlike some other lavatory-inspired artwork, Sorensen's pieces haven't stirred up much controversy. A Dutch designer, Meike van Schijnde, was criticized for her

Kisses

urinal, which was shaped like a woman's open mouth, with full red lips.

In March 2004, Virgin Atlantic Airways canceled plans to install the urinals in New York City's John F. Kennedy International Airport clubhouse after women's-rights groups and a few politicians protested, calling the fixtures degrading to women.

Sorensen, who grew up in Salt Lake City, has a fine-arts degree in sculpture from the University of Utah, but he worked as a computer animator in the video-game industry for more than 15 years.

His sculpting was a part-time passion until he started creating his urinals five years ago. Sorensen takes weeks to sculpt each flower by hand, adding a little porcelain clay each day. Typically, he works on a few pieces at a time, because each can take several months to fully and evenly dry.

The urinals are then fired and glazed, creating a sturdy structure that "should last a lifetime," says Sorensen. The finished products, which include pink orchids, yellow tulips and red hibiscus, range in price from $4,000 to $10,000 (information:

).

So far, most of Sorensen's customers are homeowners wanting to add something unique to their luxury master bathroom. Kathy Dorfman, 36, says the pink orchid urinal she purchased from Sorensen for $10,000 is the perfect complement to the marble bathroom in her newly renovated Englewood, N.J., penthouse.

"Now, I have this gorgeous piece of art that I love," says Dorfman, "and my husband and I never have an issue with the toilet seat. It's always down."

Sorensen has also been commissioned to create a series of flower urinals for the restrooms of the Barton Grange Botanical Centre in Preston, England, as well as a restaurant in Bermuda. His pieces have been displayed in a handful of galleries in California, as well as in international design expos. He is currently preparing a series of orchid urinals for display at the San Francisco Orchid Society's Pacific Orchid Exposition in early March.

During his exhibitions, the urinals work, and visitors are encouraged to flush the fixtures, but not to use them.

Mary Brooks, curator of the Patrick Moore Gallery in San Diego, where Sorensen had a show this summer and still has several pieces on display, says the urinals provide a unique and beautiful experience for patrons.

"They're simply marvelous, and people absolutely love them," says Brooks. "I hope it inspires others to be more creative with everyday, functional items."

Sorensen, who also produces a few seashell-shaped urinals, says he loves the reactions people have: smiles, giggles, and stunned faces.

"I'm becoming known as the urinal man," he says. "But I'm fine with that."