North Extension Stone Restoration

US Capitol Building, Washington, DC
The United States Capitol Building houses the two branches of Congress, the House of Representative on the south and the Senate on the north. On September 18, 1793, President George Washington laid the cornerstone for the original building which has been greatly expanded over more than two centuries since. Marbles from Lee, MA and Cockeysville, MD were used in the mid-19th century expansion of the Senate House Extension.
EverGreene is very proud to have contributed to the restoration of the North Extension of the US Capitol exterior stone work. We performed chemical consolidation and laser cleaning on the carved marble cornice, columns, pilaster capitals, and window and door surrounds during a major exterior restoration of the Senate wing. After general cleaning (performed by others), we used two 100-watt and one 500-watt, Q-switched lasers operating at 1064 nm to ablate remaining black sulfate crusts and soiling without damaging the weathered stone substrate. The laser effectively reduced black crusts and soiling on the marble, leaving a substantially cleaned surface. Chemical consolidation of friable stone followed to help slow deterioration of the carved details. This work was completed from 2015 – 2017.