Danger: Don't breathe on the dinosaurs

Moisture from the breath of museum visitors is eating away the bones of a triceratops

February 13, 2000|By Malcolm W. Browne | Malcolm W. Browne,New York Times News Service

WASHINGTON -- For 65 million years, the fossil triceratops now displayed at the National Museum of Natural History in Washington lay protected in its rocky cocoon, immune to the ravages of the outer world.

But for the last 95 years, the hot breath of museum visitors has been eating away this valuable dinosaur, and now, like some of its fossil neighbors, it is threatened with destruction.

The museum, part of the Smithsonian Institution, hopes to save its most endangered fossils by removing them from display and exhibiting only their plastic casts.

The fossil that has suffered the most serious environmental damage, said Fred Grady, a museum preparator, is that of a triceratops that has been on view since 1905. Conservators have also found areas of damage in the museum's stegosaur and in various extinct mammals, including a mastodon and an Irish elk.

The biggest problem, Grady said, is "pyrite disease," a condition hastened by moisture, in which sulfur and iron combine as pyrite (fool's gold), which replaces and greatly weakens the mineralized bone in fossils. Ivory tusks and antlers, which are not mineralized, develop cracks and fall apart under their own weight, and have therefore been replaced by lightened plastic replicas.

Restoration of the museum's prized triceratops has begun and will continue well into the next year, Grady said. A cast will replace the fossil, which will be placed in air-conditioned storage out of public view. The real skull, however, will be kept in a sealed glass case next to the cast.

The preservative varnishes applied to fossils over the years have deteriorated and in some cases have hastened deterioration, Grady said.

"Another problem stems from the vibration that damages fossil bones in contact with metal supports and framework," he said. "Conservators detected some serious bone damage at those contact points, some of it caused by jack- hammers while the museum was being renovated. We have installed seismometers near some of the fossils to monitor the threat, and pads are being installed in the fossil mounts to cushion the shocks."

The museum's largest dinosaur fossil, a diplodocus, was found to be undamaged, Grady said, but experts will keep an eye on it.

Although damage caused by the breath of visitors is relatively rare in museums, it is a big problem in caves decorated by Cro-Magnon artists some 15,000 years ago. During most of the years since these artists embellished the walls of Altamira cave in Spain and Lascaux in France with beautiful images of animals, the caves were sealed against the elements, and pigments remained fresh and bright.

But with the arrival of floods of tourists in the 20th century came moisture from breathing, and algae and bacteria tracked in by the shoes of visitors. That marked the beginning of rapid deterioration in the form of faded pigments and smudged images. All these caves are now closed except for specially authorized visits. The caves most tourists visit today are replicas.

Eugene S. Gaffney, curator of vertebrate paleontology at New York's Museum of Natural History, said he deplored the substitution of casts for real fossils.

"Visitors to the museum come to see the real thing, not replicas," he said. But that is easy for him to say, because the Museum of Natural History is more or less immune to the problems besetting its counterpart in Washington.

"All our halls are air-conditioned, and we recently completed an overall renovation and remounting of all our dinosaur fossils," Gaffney said. "We once encountered a mildew problem in a glass case, but we cured it by drying the fossil."

"The only thing we have to deal with now is lint -- lint from the clothing of museum visitors," he said. "So periodically we get out the vacuum cleaners and go over the dinosaurs. It's nothing serious, though, and our dinosaurs are in good health."

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