More Than Just Copper: The Materials That Make Up Lady Liberty
The Statue of Liberty is one of the world’s most recognized landmarks, a towering figure of hope and freedom. While her iconic green colour is famous, many people wonder what lies beneath the surface.
The statue is not a solid block of carved stone but a brilliant feat of 19th-century engineering, composed of three main components: a thin copper exterior, a strong iron skeleton, and a massive pedestal of concrete and granite.
Let’s break down each element.
The Famous Green “Skin”: A Shell of Copper
The part of the statue we see, her flowing robes, face, and crown, is an exterior shell, or “skin,” made of pure copper.
- How Much Copper Was Used? Approximately 31 tons of copper were used to create the statue. The copper sheets are only about 3/32 of an inch thick, which is less than the thickness of two pennies combined.
- The Repoussé Technique: To create the statue’s intricate shape, French artisans used a technique called repoussé. This involved heating the copper sheets and then hammering them by hand into large wooden moulds. This method allowed sculptor Frédéric Auguste Bartholdi to create a detailed and artistic form without the immense weight of a solid cast metal statue.
- Why It Was Originally a Shiny Brown: When the statue was unveiled in 1886, it was not green. It had the radiant, reddish-brown lustre of a brand-new penny, gleaming in New York Harbor.
The Hidden Skeleton: Gustave Eiffel’s Iron Framework
Lady Liberty’s thin copper skin couldn’t support its own weight, let alone withstand the harbour winds.
It needed a strong internal support system, and for this, Bartholdi turned to one of France’s most brilliant engineers: Gustave Eiffel, the man who would later design the Eiffel Tower.
- The Engineering Marvel Beneath the Surface: Eiffel designed a revolutionary internal skeleton made of wrought iron. This structure consists of a massive central pylon, similar to a modern skyscraper’s core, from which a secondary framework extends.
- How the Skeleton Supports the Skin: Hundreds of flat iron bars, known as “saddle bars,” are riveted to the inside of the copper skin. These bars are, in turn, connected to the secondary framework. This design allows the copper skin to “breathe”—expanding in the summer heat and contracting in the winter cold—without cracking or buckling. It also allows the statue to sway slightly in strong winds.
- Why an Insulating Layer Separates the Iron and Copper: To prevent a chemical reaction known as galvanic corrosion between the dissimilar metals (iron and copper), Eiffel and his team used an insulating layer of asbestos cloth soaked in shellac between the iron supports and the copper skin. During the 1980s restoration, this was replaced with a more modern Teflon-based material.
The Foundation: The Massive Pedestal and Its Composition
The agreement for the statue was that France would provide the figure, and the United States would provide the pedestal it stands on. The result is a monumental structure in its own right.
- The American Contribution: The pedestal was funded by the American people, largely through a passionate fundraising campaign led by newspaper publisher Joseph Pulitzer.
- What Is the Pedestal Made Of? The pedestal is a massive structure composed of concrete and faced with granite. It was one of the largest concrete structures ever poured at the time of its construction. It stands on a foundation built within the star-shaped walls of the existing Fort Wood.
The Golden Torch: A Unique and Replaced Component
Lady Liberty’s torch has a unique history and material composition compared to the rest of the statue.
- What Was the Original 1886 Torch Made Of? The original torch was primarily made of copper with sections of glass. However, modifications in the early 20th century to light it from the inside led to leaks and significant corrosion damage over the decades.
- Why the Original Torch Was Replaced: By the 1980s, the original torch was damaged beyond repair. During the major restoration project for the statue’s centennial, an entirely new torch was created.
- The Materials of the Modern Torch: The new torch, installed in 1986, was built to match Bartholdi’s original design. It is made of copper and covered in 24k gold leaf. This allows it to gleam in the sun during the day and be illuminated by external floodlights at night. The original torch is now on display in the Statue of Liberty Museum.
Why Is It Green? The Science Behind the Patina
The statue’s iconic green colour is a natural result of its environment.
- The Natural Process of Oxidation: When the copper skin was exposed to the oxygen in the air, it began to slowly oxidize, changing its colour from shiny brown to a dull black.
- How Air, Rain, and Pollution Turned it Green: Over about 30 years, further chemical reactions involving rain (water) and sulfur in the air (from natural sources and pollution) on the oxidized copper created a new layer of minerals. This protective layer is called a patina.
- Why the Green Patina is a Protective Layer: The green patina that covers Lady Liberty is not a sign of damage. In fact, it acts as a durable shield that protects the underlying copper from further corrosion, preserving the monument for centuries to come.
Summary: A Breakdown of the Statue’s Materials
| Component | Primary Material(s) | Key Designer(s) |
| Exterior Skin | Copper | Frédéric Auguste Bartholdi |
| Internal Structure | Wrought Iron | Gustave Eiffel |
| Pedestal | Concrete and Granite | Richard Morris Hunt |
| Torch (Modern) | Copper with 24k Gold Leaf | French Artisans (1986) |
Conclusion: A Monument Built to Last
The Statue of Liberty is a testament to the masterful combination of art and science. The graceful, sculpted copper skin gives her a powerful presence, while the ingenious iron skeleton provides the strength to endure.
The solid granite and concrete pedestal literally and figuratively provides the foundation for the ideals she represents. By understanding what she is made of, we can better appreciate the genius of her creators and the enduring power of this global symbol.
Takeaway
The Statue of Liberty is a composite structure: a thin copper skin attached to a flexible wrought iron skeleton, all resting on a massive concrete and granite pedestal. Its green colour is a natural protective patina formed by oxidation.
For more detailed information, visit the official National Park Service website for the Statue of Liberty.