At 2,250 degrees Fahrenheit the fire burns lime green. Embers and scraps of molten bronze skitter onto the concrete floor of an open-air shed housing the furnace.

"Sweep it up," commands sculptor Steve Tobin, and ten assistants—shouting and brandishing shovels—rush forward and spring into a kind of dance. They've done this hundreds of times and are casual about protection. Some are dressed in shorts. Others wear scorched leather jackets, gloves, a mask. Tobin's concession is sunglasses.

As usual, there are several projects under way in Tobin's Bucks County, Pennsylvania, studio, and everyone seems to be doing everything at once. The molten bronze is for casting bones—deer, coyote, mountain lion—that the 47-year-old artist is welding together into a 7-foot-high, 12-foot-long sculpture called Bone Wave. The bronze bones—some 3,000 so far, with a thousand more to go—fit together like lace.

"Some of the pieces we do take 2,000 or 3,000 man-hours, which is a whole year's labor," says Tobin, who has made art out of a forest floor, tree roots and African termite hills. For an exhibition of 50 of his huge sculptures at the Natural History Museum of Los Angeles County and its sister Page Museum earlier this year, "we sent 150,000 pounds of artwork in five tractor-trailers." (That show has now been broken down into three smaller exhibitions—at the Laumeier Sculpture Park in St. Louis, Missouri, Florida International University's Margulies Collection in Miami and the College of the Atlantic in Bar Harbor, Maine.)

Tobin calls what he does—turning aspects of nature into sculpture—"visual science." Art and science are often "regarded as mutually exclusive," he says, "because science is considered to be about deductive reasoning. But science defines the universe starting from basic assumptions. Art is trying to do the same thing using a different language."

With a degree in theoretical mathematics from Tulane University, Tobin is particularly interested in string theory, which proposes that everything in the universe is composed of vibrating loops of energy. In that spirit, he created a spiny organic work he calls Uni, Japanese for sea urchin, out of junked fireworks-launching tubes. The piece appears to be in throbbing motion, like string theory's loops of energy.

More recently he's been working on "Exploded Clay" sculptures (made by detonating fireworks in blocks of wet clay), which, at least in theory, pay homage to the Big Bang that most scientists believe created the universe. Open or closed, upright or hunched, concave or protruding, the sculptures appear ageless, as various in their frozen moment of creation as anything in nature. The Earth, Tobin points out, is also exploded clay.

Steve Tobin has always seen himself as odd man out. Growing up in suburban Philadelphia's tradition-bound Main Line, "I felt like a wild animal in the house," he says. "Everything was ordered, everything was structured. I felt out of place, like a piece of lint in a clean environment."

His father, Sylvan Tobin, is a second-generation manufacturer of men's and boy's clothing. His mother, Fran, raises orchids. When he was 10, his father built a treehouse, and that became the place where the boy hung out. "I felt more in harmony with nature," he says. "Nature is not as rigid. I was wild. I never really drank or stole cars. I was conversing with the birds and the butterflies. I was sleeping in the woods. They call it antisocial." Not much has changed. He still casts himself as the outsider who never went to art school. "I did pottery," he says, "I did glass blowing, but I never formally studied art." In fact, it's his study of physics and math—his passion for science—that forms the basis of his art.

"Even as a child I used to see sets of things, and I would know how many there were," Tobin tells me, as we tour his 14 disheveled acres. "Sometimes when I'm swimming, I'll see a pattern of rocks and know how many red ones there are." It wasn't until he saw the 1988 film Rain Man (for which Dustin Hoffman won an Oscar for his role as an autistic savant) that Tobin realized that his facility for grasping patterns was not widely shared. "In mathematics I would know the answer and not know the method," he says, "and that got me in trouble in school."

Tobin made his reputation creating sculptures out of glass that were at once both delicate and monumental. He was introduced to glass blowing in junior high school, but didn't take it up until 1977 when he was at Tulane and glass artist Gene Koss arrived to teach there. Tobin and Koss built Tulane's first glass furnace, and Tobin had his first exhibition in 1979. His early pieces were modest in scale, but he would go on to produce such works as the 41-foot-high Waterfall he created out of scrap glass tubing for an exhibition at the American Craft Museum in New York City in 1993. That same year, he suspended scores of handblown, 15-foot-tall glass "cocoons" from the ceiling of a cave for an exhibition at the Retretti Art Museum in Finland. "The engineers at Corning said I couldn't blow glass pieces 15 feet high because they wouldn't support themselves," he says. "But I blew them."

Tobin hasn't worked with glass for almost a decade and doubts that he ever will again. "I'm not loyal to any particular material," he says. "I invent processes that create pieces." He takes particular pride, for instance, in the method he came up with for casting a leaf in bronze through its stem. "I'd like to cast a spider web in bronze," he says. "I'd like to make clay pieces that are 20,000 pounds and explode them the size of a large room."

To that end, on this day Tobin is making what he estimates to be at least the ten thousandth "experiment" in his "Exploded Clay" series, testing various "what if" scenarios. What if he uses more clay, or less? What if he increases the amount of explosives? What if he textures the surface with bronze dust or packs the unfired clay with glass?

This time he has loaded a 3,000-pound block of clay onto a large metal plate. The clay has been scored on the exterior with a grid and coated with glass and bronze sweepings. Copper wires connected to embedded explosives protrude from the center. "We're ready," someone yells. Tobin's assistants scramble up a hill to watch at a safe distance. Tobin, wearing industrial earmuffs and a protective visor, takes the detonator behind a door. "Fire in the hole," he cries.

There's a tense silence. The clay explodes, not with a bang but a pop. Tobin shoves up the visor and grins. For him, this is what passes for elation. "I'm working my way up to that 20,000 pounds of clay," he says. "I'll make monumental outdoor pieces that you can walk inside. I've already made some that you can hold in your hand. It's like in mathematics: What happens in the smallest case? What happens in the largest case? What is your relationship to the size of the piece and the relationship of the piece to the environment?"

Tobin lives alone in an 1820s house that reflects his having worked, over the years, in 20 different countries: African Dogon house posts flank the entrance; kente cloth from Ghana hangs from a ceiling; fossils are grouped near the fireplace. "I like to surround myself with things mysterious in themselves," he says. "I'm a bit of a hermit." He craves quiet, he says, because "my work really comes from my own heartbeat. If my life gets too frenetic, I can't feel my pulse and don't know what I'm doing."

There was a time when he had to grow his own food to support his art. Now he can sell a single work for as much as $400,000; he estimates it costs $45,000 a month to pay his crew and keep the furnaces fired. It helps that for the past six years he's had a partner, Kathleen Rogers, who helps arrange and promote his exhibitions. "Kathleen is really my muse," he says. "She put together the Los Angeles show."

Tobin saw his first termite hills—the craggy mounds that termites construct out of earth and saliva—in 1994, when he visited one of his assistants in Ghana. Fired with the urge to cast them in bronze, Tobin mortgaged his house to finance the $600,000 project. He then hired Ghanaian villagers to make rubber-and-plastic molds of abandoned mounds. Of the resulting bronze termite hills—there are 12 in all, ranging in height from 8 to 14 feet—and of Tobin's work in general, critic William Warmus wrote: "His anarchic art is largely there to jolt us into seeing the result of power: insect power, explosive actions, the terror of dreams."

The termite mounds, like the bone walls, are examples of what Tobin calls his "Earth Bronzes" series. Bone Wave, which was made for the Los Angeles show, is now on display at Florida International University, along with one of Tobin's arched, upright eight-foot-high Forest Floor bronzes. To make them, he dug up sections of the forest floor and took them back to his studio on sheets of plywood. He then cast the sections exactly the way he found them—leaves, bark, spiders and all.

Similarly, for his bronze sculptures of tree roots—one of which was recently installed in Chicago's Lincoln Park—he excavated dead roots as large as 30 feet in diameter, then cast them in bronze. ("Maybe 200 castings to make a single piece," he says.) He welded them together and applied a patina of iron oxide. Then he set them on the ground like baroque domes to be walked under and looked up through.

"When you walk away from the roots and go on with your life, hopefully the next time you look at a tree, your mind will travel underground and see things not readily apparent," he says. "We all have roots. We all have histories. We all have mysteries below the surface."

Tobin's bronze roots are reminiscent of artist Louise Bourgeois' giant welded spiders, but drained of the terror and the humor. To Tobin, emotions are fleeting; he aspires to something more lasting. "I look at how pieces will function in 500 years," he says. "I look at Easter Island, Stonehenge, the Pyramids. At different times they're integrated into different cultures in different ways. I’m trying to make icons."