New York — From a distance, she looks as impressive as ever. But on close inspection, she may be overdue for some major structural and cosmetic repair. Wear and tear, acid rain, and other pollutants have caught up with the 98 -year-old Statue of Liberty, which hasn't had a major inspection and overhaul in more than 40 years.
Erosion of the statue's copper skin, fatigue of its steel skeleton, and decay of the fasteners that hold skin to skeleton worry conservators and metallurgists with the National Park Service. Its condition, they say, is not critical -- nor is the statue unsafe for visitors. But expensive preventive measures should be taken soon.
"I don't know how much time we have before the damage is irreparable," said David Moffitt, Park Service superintendent at Liberty Island. "I've heard estimates of 1,000 years and another of 500 from our preservation people, based on the thickness of the copper now vs. when it was installed."
But this measure may be misleading, Moffitt pointed out, because most of the erosion has happened in the past 20 years. The most suspected culprit: rain acidity.
Acid rain, although not fully understood, is thought to be caused by increased sulfur oxide air pollution. Combined with water in the atmosphere, sulfur oxides form acids which fall to earth and erode stone and metal and kill fish in lakes.
Exposed to years of a nonacidic environment, the statue's copper skin formed a coating of the green mineral brochantite, a protective patina. But showered with acid rain, the brochantite is converting to antlerite, which is less protective because it is water soluble and washes away. Given enough time, acid rain would dissolve the statue's skin into New York Harbor.
Actually, the acid rain problem is more than skin deep. Acidic water, combined with the salty air, is an excellent conductor of electricity. It catches on the interface between the steel fasteners and the copper underpinnings. A spontaneous electrical charge passes from steel to copper, gradually dissolving the fasteners. Left unchecked, the skin might pull away from the skeleton and wind stress would deform the copper, according to E. Blaine Cliver, the Park Service regional chief of historic preservation.
The skeleton, although protected from weathering, has never been tested for fatigue. Structural engineers make visual inspections every 12 to 18 months, but a more thorough study is needed, according to Moffitt.
Park Service officials first discovered the statue to be in serious need of help when they surveyed damage done by two political protestors who scaled the monument with mountaineering gear in May 1980. This damage was found to be minimal compared with the ravages of air pollution.
"Repairs cost less then $200," Moffitt said. "They pried open a few seams that had to be recaulked and put back flat." corrosion was the real problem.
Also, for $54,000, the Park Service erected scaffolding to remove a climbing chock the protestors had left in the folds of Liberty's gown. From the analysis of scrapings of corrosion taken during the operation, "we found that the existing environment is extremely hostile -- more so than it's ever been," said Edward McManus, an architectural conservator with the Park Service.
From the scrapings and the first up-close scrutiny of the statue in years, a movement grew in the Park Service for a detailed, inside-out, torch-to-toe look at the monument.
A thorough study, which is awaiting funding, will involve detailed chemical analyses of corrosion products to find ways to halt or stabilize the damage. The study will also use ultrasonics -- high frequency sound waves -- to measure how much of the copper skin has eroded from its original 3/32-inch thickness -- about the thickness of two pennies. X-ray analysis will also help determine whether parts of the skeleton need reinforcement or replacement.
The first step, according to Frank Matero, a Park Service conservator, will be to map the surface of the statue, breaking it up into grids to record corrosion conditions in small areas. There appear to be several different kinds of corrosion that may need separate treatment.
Once the corrosion products are identified, the next step is to find a way to stabilize them and seal off the skin from further corrosion. There is some disagreement over how this should be done.
Some chemists and metallurgists say corrosion inhibitors could be applied directly to the statue, without cleaning the familiar green coating. Others doubt that the inhibitors could work without cleaning the copper first.
The leading candidate for corrosion inhibitor is benzotriazole, a chemical developed by the copper industry for keeping copper roofs shiny. The chemical works by combining with copper ions and forming a new compound that locks up the ions, preventing corrosive pollutants from gaining a foothold. There is some evidence, according to Edward McManus, that benzotriazole also combines with the corrosion on top of the copper, so that the statue might not need a cleaning before the treatment.
In addition to the corrosion inhibitor, a protective coating of synthetic wax , plastic, or a combination of the two would also be applied. This sealant could be mixed in with the corrosion inhibitor, making the task a more economical, single- step process.
Would the chemical bath change the statue's appearance?
If plastic is used, according to Arthur Beal, head conservator at Harvard University's Fogg Museum, the surface might take on a slight gloss. Synthetic wax would pick up dirt in the air that might discolor the statue.
But the sealant's effect on the statue's appearance isn't the only consideration. The sealant must form a tough barrier against pollutants and salt air; it must be easy to apply and maintain. Because it washes away, new sealant would have to be reapplied every two to seven years.
Copper and bronze statuary have been treated with corrosion inhibitors and sealants for decades, but none present as big a challenge as the 151-foot-tall Statue of Liberty.
"We don't even know how we'd apply the stuff," Blaine Cliver of the Park Service said, "maybe with a fire hose."
In anticipation of the monument's centennial in 1984, some patriots have suggested shining the copper back to its original penny-bright color.
"there are a number of ways you could safey clean it up," McManus said. "But then you'd have to decide whether the green has achieved some significant status , or whether we want to go back to the original copper-brown."
"It's an esthetic question," said Moffitt. "I'm getting letters 20 to 1 saying the patina is a thing of beauty and that the copper would be gaudy. . . . I suspect we'll never see that statue shine, but for the primary reason of preserving its structure."