In 1968, it became obvious that bronze monuments suffer considerable damage from aggressive components of the air. A research project revealed the cause of corrosion, the reactions on the surface of the metal, and the formation of corrosion products. From these experiments it was possible to propose methods for cleaning and for coating the surface to protect the monuments from further damage. Since 1968, nine important monuments from the Middle Ages and the 16/17th centuries, a large number of monuments from the 19th century, and modern sculptures from the 20th century have been restored. For cleaning, mechanical removal of the crust from the surface by means of a scalpel is preferred, but cleaning pastes, which soften the crust, are also in use. For protection of the surface, acrylic lacquers and silicone products are preferred: waxes have not proved to have sufficient resistance against weathering.