Vicksburg National Military Park - Bronze and Metal Preservation (U.S. National Park Service)

General Lloyd Tilghman Statue before cleaning

NPS Photo

General Lloyd Tilghman Statue Prior to Cleaning

Preservation of bronze sculptures in the park entail a thorough cleaning and application of hot and cold wax to bring out the deep bronze color of the metal. Untreated surfaces become covered with a dull green patina from several years of oxidation of the copper in the alloy.

After using a pressure washer to loosen the dirt and grime on the metal, xylene is applied with a sponge to reverse the chemical process of oxidation. Restoration workers must use protective gloves and masks, and once the xylene evaporates, a tac rag is used to clean the surface and remove any left-over particles.

NPS Photo

General Lloyd Tilghman Statue After Cleaning

The next step involves treatment with an application of hot wax. The wax is a mixture which is heated, mixed, then allowed to cool into a thick paste-like substance which can be applied easily with a brush.

A final treatment of a cold wax forms a hard protective barrier to isolate the metal from the effects of weather, sunlight and airborne contaminants.

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