Mr. Robb, 35, is the senior conservator of photographs at the Library of Congress.

"We really need to figure out what we have to do with them," said Tania Passafiume, senior conservator of photographic records.

Karen Clark, a senior conservator, oversees all treatments in the laboratory, including those for the flags.

In addition, Peter Stetler works downstairs, constructing frames for some of the textiles, while quietly in the background, the senior conservator, Karen Clark, does paperwork.

"It's a Caravaggio," said Mr. Benedetti, the gallery's senior conservator.

The museum said that two sculptures had been removed for "review," pending the return of the senior conservator.

Sarah Wagner, a senior conservator with the National Archives in Washington, said, "If you spot that new-car smell, the material has probably got PVC."

"They create a sense of scale," said Catherine Nicholson, senior conservator at the National Archives.

Richard Stone, the Metropolitan Museum of Art's senior conservator, spoke admiringly last week of the unlikely precision of the multistep process.

He also met with Mr. Noel; Abigail Quandt, the senior conservator of manuscripts and rare books; and specialists in imaging techniques.