The Statue of Liberty
Through one hundred years of biting sea winds, driving rains and beating sun, the copper skin of the Statue of Liberty not only has grown more beautiful but also has remained virtually intact.
While a glance at the Statue’s rich, green patina provides proof of copper’s enduring good looks, closer analysis shows that weathering and oxidation of the copper skin has amounted to just .005 of an inch in a century.
For this reason, the copper skin was one of the few major elements of the Statue that did not need to be significantly rebuilt or completely replaced when the Statue was renovated for its centennial.
The only copper part of the Statue that required renovation was the torch section, which was rebuilt with new copper and patinated before installation to match the rich, green color of the existing copper – testimony to copper’s unique ability to grow more attractive over the years.
Copper played a key role in the restoration of the Statue inside, as well as outside. High-alloy copper saddles and rivets now secure the copper skin to the skeleton underneath. The copper fastenings ensure structural integrity and, as part of the total materials system, guard against any galvanic reaction problems.
The copper and brass industry provided technical advice on restoration of the copper components of the Statue, and it performed a similar service for these components at the adjacent Ellis Island restoration project. New copper replaced the missing copper domes and roofing, plus other features like globes, flashing, cornices, gutters, downspouts and the louvers of the long-abandoned Great Hall.
The most dramatic part of the restoration was the recladding of the Beaux-Arts domes of the Great Hall. That project alone called for 8,000 square feet of copper sheet. More up-to-date techniques made the copper installation easier and more enduring.
Copper clearly was a good idea a hundred years ago. With technological advances, copper is still a great idea today.
Facts & Figures
In 1886, Miss Liberty was:
Tallest iron structure ever erected.
Largest concrete pour ever made.
Used one of the first passenger elevators.
And, contained one of the first indoor lighting systems ever installed.
Significantly, it was the largest use of copper in a single structure at that time.
First, a little background. Most people probably know that the Lady was designed by Auguste Bartholdi. But, many of us may not know that the model for the face was his mother, Charlotte. The model for the arms and torso was his wife, Jeanne-Emilie, and the model for her stance was an 1830 painting by Delacroix. The statue was commissioned by the Franco-American Union in 1874, and was to be a gift to the American people from France to celebrate friendship and freedom on the 100th anniversary of America’s independence. By the way, the Lady’s full name is: The Statue of “Liberty Enlightening the World.”
To support his colossal sculpture, Bartholdi called upon the structural engineering skills of Gustave Eiffel, who designed the skeleton for its skin of copper. This was sort of a trial run for Eiffel’s Tower, which was to come about five years later.
The Lady’s skeleton is made from about 250,000 lbs of puddled iron. It’s spine is a pylon containing a double-helix stairwell. Four legs support the pylon, each connected by nine levels of horizontal struts and diagonal cross braces.
There is also a secondary frame, or armature, that conforms to the outer contour of the statue. The armature consists of about a mile’s worth of puddled-iron bars, more than 1300 of them, 2″ wide by 5/8″ thick and weighing about 20 lbs each.
Some 80 tons of copper sheet, originally about a quarter-inch thick, were cut into 300 odd pieces and then hand hammered – a process called repoussé. The hammering reduced them to about 3/32nds of an inch thick.
Now, here’s where the neat part comes in. The copper skin sections are attached to the armature by 1500 U-shaped copper saddles, using some 300,000 copper rivets. Now, Eiffel knew about Galvanic corrosion between the dissimilar metals – copper and steel. The first consideration, apparently, was to let the American’s worry about that when it happens.
That was quickly followed by discussion of using a red-lead barrier and cloth-covered copper plates that would go between the copper skin and the iron armature.
Ultimately, it was the Americans who came up with the barrier system finally used when the stature was reassembled. They isolated the junction of the copper and iron with a layer of shellac-impregnated asbestos cloth.
The saddle design was ingenious. Copper and Iron expand and contract at different rates. So, the free movement of the separate metals allowed them to accommodate the changes in temperature as well as other weather conditions.
Read more on the history of The Statue of Liberty by visiting Copper Development Association site at the following link: http://www.copper.org/education/liberty/