All sculptures begin to change from the moment the object leaves the artist’s studio. In the case of outdoor works, natural aging and the physical impact of light, temperature, humidity, air pollution, and handling all take their toll. Nonetheless, there are many benefits to viewing works of art outdoors; visitors can experience the works in a unique context in combination with foliage, architecture and even the weather. While viewing sculpture in an outdoor context can bring new meaning and depth to the visitors’ experience, these benefits must be navigated relative to the risks the works face from the effects of the elements, animals, and human interactions. Much of the Hirshhorn Museum’s outdoor sculpture conservation internship may at first sight appear to be routine, but the preventative measures that we carry out are essential in minimizing deterioration.
It may be surprising that massive sculptures made of steel or bronze are vulnerable to the elements. Yet, when bare metals are exposed to moisture and air pollution, corrosion can begin, gradually weakening and degrading the metal and putting the sculpture at risk from structural failure. Rain water can also pool in low areas and crevices and, as pools evaporate, they leave behind crusty areas of mineral deposits that are aesthetically disfiguring and difficult to remove. This is why a major part of the intern’s role is to ensure that these vulnerable works are suitably protected when on display. Regular cleanings of all of the sculptures and the application of thin, protective layers of wax to the bronze sculptures has become an essential part of the annual maintenance program of outdoors sculptures at the Hirshhorn. In some cases it is not necessary for us to apply the protective wax coating because an element of the artwork, such as a layer of paint, acts as the protective surface.
Figure 1. Corrosion, grime, and spider-webs on the underside of a painted steel sculpture
Figure 2. Corrosion on a painted steel sculpture
Although it is a delight to see creatures roaming throughout the sculpture garden, birds are rapidly becoming an unbeatable foe for this summer’s sculpture conservation interns. It seems just as quickly as a sculpture is cleaned of droppings; more birds come along to replace what has been removed. As aesthetically disrupting as bird droppings can be, they also pose a significant risk to the sculptures. Bird droppings are acidic and when left in place too long, they can etch into the metal, creating areas of uneven corrosion thus making the sculpture more difficult and complicated to treat. Bird droppings can also stain or etch painted surfaces, leaving disfiguring marks that are tough if not impossible to remove.
Figure 3. Bird droppings on a painted steel sculpture
The public also can erode sculptures, even if unwittingly. Despite explicit signage and a diligent security staff, sculptures can prove so enticing that some visitors are tempted to touch and even climb on them. While the sculptures are meant to be enjoyed by the public, human interactions can be very damaging. The cumulative impact of thousands of finger and hand prints can rub away the artist’s finish. Natural oils, sunscreen, and lotions react poorly with paints and waxes, and jewelry and clothing can easily scratch a sculpture’s delicate surface. Less common, but often more damaging is vandalism such as graffiti which can result in the need for major treatment. When these types of incidents occur they can penetrate the protective layer (wax or painted surface) which will allow the elements to interact with the underlying metal causing corrosion and possibly structural damage. Public outreach is proving to be a rewarding aspect of our time in the sculpture garden as we speak to inquiring visitors about our work. These conversations help educate visitors about the importance of conservation and the negative impacts of physical interactions with artwork.
Figure 4. Graffiti scratched into the surface of a painted steel sculpture
Figure 5. Scratches on the surface of a painted steel sculpture caused by the abrasive clothing of climbing visitors
With each sculpture we examine, document, and clean, as interns we are witnessing how each of these risks can be manifested in different ways, and how the work of past interns has successfully prevented damage and helped maintain the beauty of the Hirshhorn Museum sculpture garden.
Top: Alexander Calder, “Sky Hooks,” 1962