BILBAO, Spain - Rarely has a new building enjoyed as much acclaim as the Guggenheim Museum's newest branch did when it opened on the esplanade along the River Nervion here in 1997.
Its shining fish-scale exterior was lavishly praised by international critics, putting this industrial port city on the map for thousands of tourists. Architect Frank O. Gehry's bold design earned him near-mythic status in his profession, and one of his most eminent rivals, architect Philip Johnson, called it the "greatest building of our time."
But now, three years after opening, the spectacular $100 million building whose corrosion-proof titanium exterior was created to shine for centuries has started to resemble the rusting hull of an abandoned barge.
Experts have conflicting theories about what is happening to the building, but one thing seems clear: This creation of space-age glimmer and technology is also a monument to the law of unintended consequences.
Gehry chose titanium for its light weight, its durability and the warmth and character created by its muted reflective properties. The element is extracted from sand crystals, notably from Australian beaches, and is commonly used to build aircraft parts, high-performance bicycle frames, golf clubs and replacement bones and joints. When rolled flat into panels, it forms an oxide on the surface that gives it a warm glow.
Gehry had never used the mineral before, and he and his team of designers relied on a computer program developed for the French aerospace industry to experiment with the building's curvaceous shapes.
He picked it instead of a more traditional building material such as stone, because, as he wrote: "Stone deteriorates in the pollution of our cities whereas a third of a millimeter of titanium is a hundred-year guarantee against city pollution."
Vincent Scully, a retired professor of architectural history at Yale University, said, "Titanium, to Gehry, does just what he wants. It looks absolutely weightless. and it shines. Because the plates are small, the entire wall can undulate. But how it's going to hold up is a question."
Scully visited the museum not long after it opened and said he thought then that the titanium panels looked very fragile.
"They just didn't look very permanent," Scully said. "It's very possible, I would think, that a lot of water is getting in between those sheaths and that rust is getting in there."
Gehry declined to comment on the building's condition from his office in Los Angeles.
The source of the discoloration depends on whom you ask. Museum officials blame the problem on the manufacturing process. The U.S. titanium supplier defends its product and said that some of the 33,000 panels used in the building were contaminated during construction.
While pollution has not bored through any of the 2-by-4-foot panels, it is apparently playing some role in the deteriorating aesthetic condition of the Guggenheim Bilbao's exterior.
A spokeswoman for the museum, Nerea Abasolo, said that about 20 percent of the building's titanium panels were erroneously manufactured with a protective film that accumulates rusty runoff from the metal understructure.
As soon as the museum discovered the problem, she said, it asked the manufacturer not to add the film to the remaining panels.
"It's the film that has become dirty," Abasolo said. "We are very happy about the building, except for this small problem that we detected very early."
The titanium supplier, Titanium Metal Corp. of Denver, Colo., or Timet, said the problem is that parts of the building were contaminated by fireproofing sprayed at the dirty former industrial site throughout four years of construction. The building just needs a good cleaning, Timet maintains.
"Those chemicals and compounds tufted into the air and onto the building," said Gary Nemchock, an architecture and design consultant to Timet who has worked to find a solution. "It changes the reflectivity due to the physics of light."
Though the Japanese have made increasing use of titanium in their architecture, Gehry's use of it in Bilbao was then highly novel in the West. The architect plans to use it again in the expansion branch that the Guggenheim proposes to build on a pier jutting into the Hudson River in New York.
Not since Frank Lloyd Wright's Fallingwater, a house built atop a waterfall, began taking on water has a celebrated building suffered as unusual a fate as the Guggenheim Bilbao.
Millions of dollars in repairs have been needed to reinforce Fallingwater's cantilevered decks and prevent it from falling into a stream.
Wright designed the Bear Run, Pa., house, completed in 1937, for Pittsburgh department store magnate Edgar Kaufmann. He also designed the original spiral-shaped Guggenheim Museum on Fifth Avenue in New York.
Architects and engineers, well aware that titanium does not rust, have been quick to notice the change in the Bilbao museum's complexion, Abasolo said. They call her office baffled by what they have seen.