Early this month, the artist Judy Pfaff and a crew of assistants and union workmen applied the finishing touches to "cirque, Cirque," a vast, ceiling-suspended artwork she created for the new Pennsylvania Convention Center in Philadelphia. The materials and the outsize dimensions of the work - an airy system of steel and aluminum tubes and glass orbs that extends across 70,000 square feet of space - suggest a work of architecture rather than a sculptural installation. In fact, "cirque, Cirque," evoking the heavens, is one of the largest public-art projects in recent years.

Like so much public art - works commissioned for public places and largely financed by tax dollars - this sculpture by Ms. Pfaff took several years to complete. Because of the complexity of her project and the intricacies of the bureaucratic process, she confronted an array of problems unimaginable to most contemporary artists. These ranged from negotiating a 55-page contract for the piece, which cost $400,000 to produce and install, to devising methods for bending nine miles of tubing into jaunty spirals.

"It was like a roller-coaster," Ms. Pfaff, who is 48, said recently of her three-year experience. "Each time some new obstacle emerged, I worried that it was beyond my power - or control - to resolve it."

Every work of public art may be distinct, but daunting challenges are the norm for this genre in the United States. John Singer Sargent's murals for the Boston Public Library, done around the turn of the century, were public commissions that took more than two decades to complete. In the 1930's, artists were put to work by the Federal Works Progress Administration, painting murals in post offices, but after World War II, public art in this country all but disappeared. The leading artists of the 1950's and early 60's had determinedly private, often abstract esthetics and regularly took an adversarial stance toward the values embodied in such public-art staples as monuments to war heroes. With public institutions and corporations devoting money to cultural enhancement in the last 25 years, however, commissioned public art returned with a vengeance.

It returned with controversy, too. Artists simultaneously tried to avoid compromise and find a place for their visions in a public arena of conflicting expectations and, increasingly, resentment over the use of tax dollars. Although Maya Lin's Vietnam Veterans Memorial in Washington has come to be one of the most beloved American monuments, its abstract form at first proved so disturbing to veterans' groups that after its dedication in 1982, a conventional figurative sculpture was installed nearby.

And in 1989, Richard Serra's Tilted Arc was removed from a Federal plaza in lower Manhattan after a long, bitter debate over whether the abstract sculpture's aggressive bisection of the outdoor space marred people's use of it.

Ms. Pfaff's "cirque, Cirque" owes its existence to the proliferation in the last 20 years of Percent for Art programs, which require that one-half to 1 percent of a public building's construction budget be set aside for art. According to Tom Finkelpearl, director of Percent for Art in New York City, there are more than 180 such programs at various governmental levels in the United States. It is unclear whether tens or hundreds of millions of dollars are spent annually on public art, he said, because Percent for Art money generally comes from the capital budgets of police departments, boards of education and other agencies.

The city of Philadelphia and the State of Pennsylvania together sponsored the Pennsylvania Convention Center's Percent for Art program, whose $2 million budget paid for the commissions or purchase of works by 52 artists. Ms. Pfaff's was one of the two most expensive commissions.

The Conception: Meeting a Site After a Hurricane

The beginnings of "cirque, Cirque" date to spring 1992. Jacqueline Holmes, a Florida art consultant and a member of the art advisory committee for the Pennsylvania Convention Center, invited Ms. Pfaff, who was then teaching at Columbia University, to submit a proposal for a permanent work to be installed in the old Reading Terminal, an 88-foot-high train shed that was being transformed into the center. (When it was built in 1892, the train shed was believed to be the world's single largest room.)

"Not many artists could take on the challenge of dealing with this huge volume of space in a unique and creative way," said Ms. Homes, a longtime admirer of Ms. Pfaff's work.

Ms. Pfaff, who was born in London, lives in a loft in TriBeCa and usually works out of a studio in Williamsburg, Brooklyn. She is known for risky, improvisational work that is boldly decorative and labor-intensive. Shortly after receiving a master of fine arts degree from Yale in 1973, she attracted the art world's attention with dense abstract environments that suggested swirling undersea gardens, whirling tornadoes and Jackson Pollock canvases gone three-dimensional.

By the end of the decade, she had established a signature style, but she had sold little. "I had to give it up or starve," she recalled recently. As it turned out, she did not give it up so much as expand her repertory to include wall sculptures.

Ms. Pfaff's vividly colored, space-defining work is accessible and seems ideal for public places. Indeed, she has complete two other artworks for such sites in the 1990's: a sculpture for the GTE Corporation in Irving, Tex., in 1991, and a lobby installation for the Miami Beach Police Department, which was installed last fall. Compared with "cirque, Cirque," however, those two are modest in scale and creative scope.

Ms. Pfaff was not the only artist invited to compete for this particular Pennsylvania Convention Center commission. The advisory committee also invited the artists Alice Aycock, Albert Paley and Charles Phalen to prepare proposals; each artist was paid $5,000 to design and build a maquette for a presentation.

Ms. Pfaff was delighted by the unexpected invitation. "I needed the money and just wanted to be paid to do the maquette," she said. "Getting the commission was another matter entirely; I just fell into it."

She vividly recalls her first view of the eerily huge and empty train shed, seen through the rainy aftermath of Hurricane Andrew in August 1992. "There were 5-foot cranes and parts of the roof were missing, so it looked like Dante's 'Inferno,'" she recalled. "There I am standing in the rain, soggy plans in hand, when I'm told that I shouldn't use the ceiling or attach anything to the structure."

She immediately knew she would have to do both. "When you're a kid and you're in Grand Central Station, you want to look up, right?" she explained. "I still do."

The design that evolved from Ms. Pfaff's first impression resembles the romantic evocation of a night sky at Grand Central Terminal, but it is three-dimensional. Its 14 elements include two immense, swooping circular double-helix forms, one painted blue and the other gold; a variety of other comet-like trails of tubing, and "constellation" clusters whose stars are glass globes set into tubular nests. In addition to the miles of tubing, the work, which was originally called "Cosmography," required 120 handblown-glass orbs and more than 150 gallons of automobile paint and primer.

Ms. Pfaff's conviction that her piece had to be attached to the ceiling eventually passed muster with the center's engineers. Two months later, in October 1992, after she and the others made their presentations, the advisory committee awarded her the commission. Judith Stein, a committee member, described Ms. Pfaff's proposal as "far and away the most dynamic and inventive solution for art in this vast space."

Ms. Pfaff thinks that it was her newly acquired knowledge of fabrication costs and the bravado with which she presented this information that impressed the engineers and the committee members. In any case, she knew that her presentation had gone well. "I had the facts, so it was a coup," she said. "But from that moment on it was hell."

The Control Question: The Creative Act By Consensus

A lack of esthetic control is unavoidable in public art. "The need for consensus makes it a painfully slow process," Ms. Pfaff said. "You can't change your mind, because it's already been through so many committees. Then you realize you've grown beyond it."

She isn't the only artist who chafes at the inflexibility of the process. Christy Rupp, who specializes in ecological themes, has spent nine years planning a functional boardwalk-and-trellis sculpture for the Coney Island Water Pollution Control Plant in Brooklyn. Now she would prefer simply to help restore the neighboring wetlands to which the work will provide access, but she knows this is not politically feasible.

Government involvement also dictates that tax dollars be spent responsibly. Public financing transforms art into a form of procurable goods and services, and in 1993, Ms. Pfaff grew to understand this all too well as she spent much of the year simply working with her lawyer to hammer out a contract. And even though a contract wasn't in place, she had to go ahead and fashion an elaborate plan of attack, involving staff, materials and months of time without having seen dollar one in reimbursement.

Artists undergo frequent audits and quality-control assessments. Getting paid is especially complicated: contracts with public agencies call for outlays of money based on the status of a project, with a percentage paid when a work is one-quarter completed, a percentage when it's half finished and so on. Before her contract was signed, Ms. Pfaff had to gamble on its outcome and rent a suitable work space.

"The supervision drove me made," Ms. Pfaff said. "I had to spend months and thousands of dollars putting electricity into the barn we worked in, and to them it looked like no progress was being made."

At this point, she also realized that to complete "cirque, Cirque," she would have to leave her teaching job at Columbia. (As it turned out, she received an appointment as co-chairman of the art department at Bard College, to start in January 1995, just after the December 1994 delivery date for "cirque, Cirque.")

Making the Art: Learning in the Lab, And Lovett vs. Love

In May 1994, Ms. Pfaff and a crew of six assistants, most in their 20's and 30's, settled into an old 400-foot-long stone barn near Granite Springs, N.Y., in Putnam County, because they needed a work space larger than any New York City warehouse Ms. Pfaff could afford to rent.

Over the next seven months, each week seemed to bring an unexpected technical problem. Ms. Pfaff had planned to subcontract the production of some of the piece's elements, but the fabricators she had hired went out of business. She and her crew not only had to develop methods for bending the tubing, but also had to come up with computer drawings that could be followed later for installation. And because they were using highly toxic urethanes and lacquers, they had to assemble a painting booth that resembled a chemistry lab.

The project presented social challenges, too. Ms. Pfaff was as much den mother as employer and artist in residence. Parts of the stone building became a dormitory, and Ms. Pfaff slept in an office area. At night, she had the team gather in the office to watch videotapes. She also insisted that laundry be done once in a while.

As summer turned into fall, the novelty of living in an unheated building and cooking on a barbecue wore off. The only real problem, though, had to do with music. "People in their 20's liked to work to Courtney Love," said Rob van Erve, a crew member. "But the older ones liked Lyle Lovett."

Some of the crew members were former students of Ms. Pfaff. "Of course, I felt responsible for the crew," she said. "But I couldn't express my fears or they'd get unnerved. There were times I was so frightened about completing the piece that I had nightmares."

Down to the Deadline: Delay, by Contract, Then Up at Last

As the December 1994 delivery date approached, Ms. Pfaff and company rushed to apply finishing touches. A few days before the deadline, though, Mayor Edward G. Rendell of Philadelphia sent a message: he had decided to let the film director Terry Gilliam shoot parts of the movie "12 Monkeys" in the convention center. As exasperating as this development was, it fell within the terms of her contract. In the standard public-art contract, the commissioning agency reserves the right to delay installation - for any reason. "There wasn't anything I could do, although I should have been liable for a fine every day the piece was late," Ms. Pfaff said.

She futilely tried to persuade Mr. Gilliam to move his production. Then, after having "cirque, Cirque" trucked to Philadelphia in hundreds of pieces, she stored the work in an unused portion of the train shed that was provided to her at no cost, and went off to start her job at Bard.

In mid-June, Ms. Pfaff and her crew removed the pieces of "cirque, Cirque" from storage and gradually assembled it and touched up its lustrous paint job. Then, after a brief squabble between unions over jurisdiction, a crew of riggers slowly attached the sculpture to the ceiling, loop by loop, quirky sculptural element by element.

When the work was finally completed on July1, few Philadelphians seemed to notice. The convention center, and most of the art created for it, had been dedicated in June 1993. It had become old news. No one rushed to review "cirque, Cirque," although Ms. Stein was enthusiastic at the result. "To see it realized was thrilling," she said. "Set against the architecture, it was everything I had hoped for, and more."

Final Accounting: Drawbacks Beyond Dollars and Cents

Given working conditions like these, it's remarkable that so many artists want to compete for public-art commissions. And there's not much money to be made. "If artists think they'll break even, they're likely to lose money," said Mr. Finkelpearl. "The artists who've done public projects before come in with much more modest proposals." The painter Jane Hammond, a friend of Ms. Pfaff, recalled Ms. Pfaff's nervousness the day she was awarded the commission: "Judy said, 'I'm going to lose my shirt on this one.'"

The standard take-home fee for an artist on a large project like this is 10 percent of the budget for the work (20 percent for smaller projects). So, if all goes well in the final accounting, which is still not complete, Ms. Pfaff should make $40,000 on the $400,000 project. She estimates she lost a year's worth of time when she could have been producing work to be sold by her gallery. (Some large drawings exhibited in her show at the Andre Emmerich Gallery last year sold for $10,000 each; the occasional sale of a sculpture brings far more.) Now she hopes her final fee for the Philadelphia commission will cover a down payment on a chicken coop in Ulster County, N.Y. that she plans to convert into a residence.

The financial drawbacks are not the only ones. Making public art does not necessarily enhance a career, either. "It's a long, involved process whose outcome may not be visible," said Max Protetch, a dealer who represents a number of sculptors who make public art. "Artists have to have the right sensibility for it, too: the social skills and concerns and an interest in functional art."

Public art rarely attracts much critical coverage, and mainstream publications tend to cover it only after some brouhaha has erupted, as with Tilted Arc. As Ms. Holmes, the Florida art consultant, observed, "It's truly another art world."

Within that world, "cirque, Cirque" is likely to gain attention eventually for its scale and ambition. While many who saw the design proposal were enthusiastic - Ms. Stein said the maquette received a standing ovation from the Philadelphia Art Commission, which had to give its approval - Ms. Pfaff worried down to the wire about whether "cirque, Cirque" would work. Not working meant it would be swallowed up by its dramatic context. "Too many public artworks are invisible," she said. "They blend right into the architecture."

Despite the myriad problems, Ms. Pfaff believes "cirque, Cirque" works. And if she finds what she describes as a "perfect space," she might consider taking on another public-art venture. "We triumphed against the odds," she said. "I could build anything now."