Question

The domes of many building in Europe are made of copper. These domes now appear greenish in colour.

1. Why do the domes appear greenish though copper is orange-red in colour?
2. In your opinion, should the copper domes be replaced by iron domes to overcome the problem of change of colour of copper domes?
3. Domes used to be made from thin sheets of metals. Why did the ancient architects use copper to make domes?

Answer 1

1. Copper gets oxidised/corroded to basic copper carbonate which is greenish in colour.
2. No, iron will rust, and the reddish layer of rust will come off, exposing iron to air; the dome will not be stable. Copper, on the other hand, on corrosion forms a protective layer which does not allow further corrosion.
3. Copper is a highly malleable metal; its thin sheets can be used to give different shapes of roofs, like the shape of a dome.