The Shaw Memorial, America's first monument to African-American soldiers, became an important part of American art and history. A plaster cast of the memorial, stored outdoors for decades, suffered the effects of weather until restored to life by 20th-century conservators. For millennia, each has been used to make sculptures, jewelry and structures large and small. Artists often work with alloys like bronze, steel or brass because of their durability and color.
Steel is made of iron and carbon.
Alloys are used to make coins, jewelry, sculptures and other items. When exposed, metals can become damaged. After many years of exposure to humidity and the sulfur compounds in acid rain, copper in the statue oxidized to form copper compounds that are blue-green in color. You may also see this on copper roofs and pennies. This same process of oxidation similarly affects silver.