Coatings Research on the Stark Collection

Wax is one of the most common materials used in the maintenance of outdoor bronze sculpture. Getty used a commercial paste wax for years until its effectiveness began to decrease, which is a typical challenge due to the unknown changes in trade secrets that may impact application. A Getty lab-made wax blend was developed—based on recipes from the National Park Service—by modifying the wax melting point, substituting solvents, and changing the blended components to suit a hot California climate. Different proprietary products continue to be studied, however, and applied periodically.

One area of research involves evaluating protective coatings including cold wax and clear lacquers. A review of Incralac (a protective coating specifically for copper alloys, brass, and bronze) development and modification made over several decades was the springboard for experimenting with lab-made versions, which provides an avenue for conservators and scientists to determine the effects of formula changes. Lab-made and commercial products are applied to bronze coupons and naturally aged. Preparing acrylic coatings in the laboratory could also provide more control in treatments and studies.

Exploring different solvents could lead to less toxic formulations in order to reduce environmental and human health risks. Incralac has changed its solvents to comply with government restrictions, and Getty has observed a range of effectiveness across formulations. For example, when a water-based version of Incralac was released, Getty testing results show it is less effective than solvent-based formulations. But in testing lab-made acrylic lacquers, Getty found possible solvents that are less toxic and still protect outdoor bronze surfaces.