DAR -- Constitution Hall is made of limestone and was built in the 1930's.
The main damage on this limestone building, built in the 1930's, is the blackening of the side balustrade from algae or fungi. The stone is porous and therefore retains moisture, thus encouraging growth of organisms. The limestone in this building is quite uniform and shows little preferential dissolution, except in a few places. On the top of the balustrade along C Street, for example, some of the calcite matrix has dissolved from around the fossil fragments, and some holes are filled with calcite crystals.
|Some of the blackening on limestone surfaces may be from algae or fungi that readily grow in the rough surface in Washington's warm, humid climate.|
Map of All Sites on the Tour [102 K image]