The original roof on the capital had to be replaced in 1979 because it was no longer waterproof. At the time, it was over 100 years old.
Flat copper blanks were shaped individually on a custom-made rolling machine. Each panel fit the double curvature of the dome, interlocking with adjacent panels to form the watertight covering - sort of like putting together a 4-ton jigsaw puzzle.
Over the period of many years, the color of the dome would turn into an antique green, but historians and investigators did not plan on waiting that long and instead planned on turning it green using chemicals.
Watch the full clip from 1979 in the video player above.