Revered building losing luster

Museum: The titanium panels that cover the Guggenheim's branch in Bilbao, Spain, are showing signs of deterioration.

Bilbao architects Carlos Perinat and Luis Dominguez were standing outside the museum on a recent afternoon and sympathized with the dilemma facing Gehry: "In architecture, these are eternal problems," Dominguez said. "This is a very risky design. We think it's a really good building, but it's a really risky building.

"When you are playing cards, you take risks, and Frank Gehry took risks."

Some tourists coming here express concern when they see the mottled condition of the swooping elements that attracted them to the international landmark.

"It does look bad," said Donna Schneider, a teacher from Connecticut who traveled by overnight train from Barcelona just to see the building. "It definitely has streaks. I'd hate to be the one to clean it."

Museum maintenance workers will rappel down the sides of the building next month to begin the cleaning, Abasolo said, much as 90 construction workers did while installing the panels during an 18-month period. They will use a grunge removal process that Timet has spent several years developing.

Nemchock declined to provide details about the cleaning process because the company is seeking patent protection for its formula. The process should strip off soil and contaminants and restore the building's luster, he said, but Timet has not used it on a large scale and cannot be certain it will work.

"We hope we can get rid of it," he said. "This building is now really the icon in the world for titanium."