Conservation by Fire and Ice

The public conservation of Saint-Gaudens’s Labor Supported by Art and Science and Law Supported by Power and Love was an opportunity to use a relatively new, environmentally friendly technique that began with icy blasts of carbon dioxide and ended with a searing application of hot wax.

Developed in 1986, CO2 cleaning was introduced in art conservation only a few years ago. It is a technique that “blasts” pellets of frozen carbon dioxide (dry ice) through a nozzle, safely removing build-up from surfaces. In the case of the Saint-Gaudens bronzes, this meant removing accumulated dirt, bird droppings, and failing wax coatings. CO2 blasting is an ideal technique for museum conservation because it is nonabrasive and nonconductive. When the ice pellets hit the surface of the sculpture, the warmth from it immediately sublimates the ice. (Sublimation is the process of a solid changing into a gaseous state without becoming a liquid first.) The ice freezes unwanted soiling, and the gas separates it from the artwork. This results in a smooth, clean surface ready for a fresh protective wax coating. Although outside temperatures were in the upper nineties during the conservation treatment, the conservators nevertheless applied additional heat to the bronzes, using blow torches to ensure that the wax coating went on smoothly.

An added benefit of this form of conservation is that it is environmentally friendly. Since carbon dioxide is a naturally occurring gas found in our atmosphere it produces no toxic fumes. And because the blasting process returns the gas it to its natural state, it leaves no hazardous materials to dispose of after the conservation treatment.

Watch the video to learn more.

Art conservator cleaning sculptures with CO2 blasting method