DEPARTMENT OF THE NAVY -- NAVAL HISTORICAL CENTER
805 KIDDER BREESE SE -- WASHINGTON NAVY YARD
WASHINGTON DC 20374-5060

Conservation of Spanish 12 Pounder

Cannon before conservation treatment. Conservator removing dirt and surface corrosion with low-pressure water jet.  Conservation treatment of cannon completed.

A thorough examination of the cannon was the first part of the conservation process. Photographs, drawings and exact measurements were made to document existing conditions. Recording and examining the corrosion and degradation of the cannon was particularly important as it helped determine the cause of decay. The polluted urban atmosphere in Washington, DC, was determined to be the main cause of the powdery light green corrosion found on the cannon El Alano. Many outdoor sculptures and monuments undergo similar corrosion in an urban environment. The cannon was power-washed with a low-pressure water jet to remove loosely adhering corrosive elements and bird droppings, and then air-abraded with walnut shells. This removed the loosely adhering corrosion without damaging the protective patina. After walnut shell blasting, the surface finish became more uniform; streaks and run-marks were not as easily detected once the bright green corrosion was removed. In order to protect the cannon from future environmental risks, it was coated with a high melting point wax. Even though the wax is very stable, the protective coating will not last forever - annual maintenance will be necessary. The cannon is scheduled to be returned to the Washington Navy Yard in the Fall of 2001.