Question #e85f6

1 Answer
Feb 3, 2018

Damages to the surface and progressive erosion.


Statues are mostly made of natural rocks and therefore are exposed to erosion as any other natural outcrop of the same composition.

A variety of rocks are used for sculptures including sandstone, granite, marble (that is a form of limestone undergone to metamorphosis), travertine (which is composed by calcium carbonate).

All these materials, when exposed to the environment, are affected by weathering of different intensity and velocity depending on their mechanical and chemical strength.

The resulting is a progressive damage to the statues starting from the surface and progressing until the features of the shape are lost.

This damage can be minimal and very slow in areas where the weathering is minimal due to local environmental conditions.

An example are the ancient statues and columns in Egypt. Here the arid climate minimizes chemical weathering (that requires rain) and the sand often buried the structures acting as further protection.

Once the statues are excavated and exposed to the atmosphere the weathering starts.

In the desert the sand blown by the wind can ac as a sand blaster causing strong mechanical erosion. This is the case of the Sphinx which face has lost most of the details due to the long exposure to wind and sand.

It is therefore important for the archaeologists to identify some kind of protective methods to avoid the damage.

In other areas,such as cities, the chemical pollution (mostly as acidic rain) strongly enhances the weathering process.

This is a very serious issue in cities with ancient architecture such as Rome, Paris, London or the Taj Mahal in India that is damaged by the acidic rain originated from the flumes of the industries in its surroundings.