The outside of the Statue of Liberty is constructed of copper, and it got that colour of green due to oxidation. Copper is a noble metal, which means it does not easily react with other elements. But it can oxidise when exposed to air, water, heat and light.
In 1884, an American engineer named Thomas Hovenden created a patent for a process called "photolithography" which is used today in microchip manufacturing. The statue was built using this process.
The photolithographic process starts with a thin layer of gold over the entire surface of the statue. This is then covered with an image-receiving sheet using silk screening technique. After removing the gold foil from the back of the sheet, it is placed in contact with a strong acid that removes the gold from those areas where light struck the film. The remaining acid reacts with the copper to form a negative image. The next step is to remove the gold from the areas where light didn't strike the film, leaving behind the pattern of the original design.
It's estimated that the statue requires replacement of its eyes and nose annually because they are made of glass, and they're easily shattered when hit by a ball bearing or small stone. However, replacement parts are now available in case they need to be replaced later on.
When exposed to air again, it rapidly reacts, forming the dull greenish copper oxide coating. The Statue of Liberty is covered with a thin coating of green copper from interactions with air and water. This explains the color of the Statue of Liberty!
In addition, the copper used for the statue was recycled from old electrical equipment. This also accounts for its black color.
Finally, the copper inside the statue comes from mining operations in America and all over the world. These mines use various processes to extract copper from rock. The most common method is called "hydro-mining". This process creates acid mine drainage that can harm local ecosystems if not contained properly. However, alternative mining methods have been developed to reduce these negative effects; for example, open-pit mining can destroy habitat but it uses technology to minimize damage to the environment.
These are just some of the many reasons why the Statue of Liberty is covered in a thick layer of green copper oxide. No matter what your reason may be for visiting New York City, don't miss out on seeing this beautiful monument!
Malachite, the green substance that covers the Statue of Liberty, is formed when copper is subjected to salt, acid, and weather. With pennies, you can replicate Liberty's metamorphosis from copper to green. Only 50% of each coin is copper; the other half is zinc with traces of other metals.
Zinc, like gold and silver, is an element used in making coins. But instead of being mixed with gold or silver, it is mixed with copper. The ratio between the two elements is always equal parts, but some coins may have more zinc than copper. Some coins may even have some silver or mercury added to make them weigh more. These special coins are called "bullion" coins.
The British Empire was the largest source of copper until 1845, when the California Gold Rush started a major new source. By 1900, American coins were made almost entirely of copper.
Until 1967, one-tenth of all U.S. coins were made up of silver. This was required by law in order to keep the value of our coins steady against foreign coins. From 1792 to 1968, the total weight of copper and nickel in U.S. coins varied between 92.5% and 93.4%. Silver coins ranged in value from 1c to 5c (29-146 grams). Today, only 9% of U.S.