Quote:
Originally Posted by Complex01
These are not the same colors as the Tower Life Building, The TLB is green at the top
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The Tower Life Building is green at the top because the top (the dome) is made of copper. Copper oxidizes from a chemical reaction between the metal itself and the oxygen in the air which causes it to turn green. Copper can also be forced to turn green by adding a chemical compound to get the desired "patina".
More here.
http://en.wikipedia.org/wiki/Patina
About copper.
http://en.wikipedia.org/wiki/Copper
One very well known hunk of copper resides in New York harbor, the Statue of Liberty. Also pennies made from before about 1981 are made of copper. The newer ones made after that time however, are made of zinc. They stopped making pennies out of copper because copper prices have risen over the years to make the amount of copper in a penny worth more than the penny itself. Zinc is a much cheaper material, however, it doesn't last nearly as long if left to the elements. My dad and I used to go screening for old coins and jewelery in the creeks downtown and you could always tell the difference between a copper penny and one made of zinc. The copper one would be black or green, while the zinc penny would just be an unidentifiable disk and would actually crumble in your hands. The reason pennies are still that familiar copper color is of course because they're plated/coated with it over the zinc.
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