An evaluation of cold paste waxes used in conservation for outdoor bronze sculpture

Julie Wolfe, Christina L. Simms, Alessa Gambardella, Rosie Grayburn, Arlen Heginbotham, Herant Khanjian, Joy Mazurek, Alan Phenix, Katrina Posner, Michael Schilling, Magdalena Solano, Maria Olivia Davalos Stanton, and Hope Welder


The J. Paul Getty Museum has experimented with different paste wax coatings over the past decade for the protection of outdoor bronze sculptures. Various commercial waxes have been used with noticeable changes in their performance over the years. A preferred home-made mixture was developed, starting with a blend developed by the National Park Service, and modified to raise the melting point, substituting solvents, and subtraction of the polyethylene
component. Evaluating the tactic of fine-tuning a custom blend has turned into a more systematic evaluation of the pros and cons of proprietary products, lab-made paste waxes, and varying application techniques. This paper will present a candid summary of observations made in the performance of various wax coatings used on the Museum’s collection and introduce a pilot study that compares over twenty-three paste waxes applied to metal coupons. In collaboration with the Getty Conservation Institute, the study includes a range of isolated wax types (natural, petroleum-based and synthetic), proprietary products, as well as lab-made paste waxes. The waxes were brush-applied cold to polished brass coupons, buffed, and naturally aged following ASTM standard protocol G50-10. The coupons were evaluated before and after
aging using spot colorimetry and digital image analysis. The physical properties of the pastes and the effects of aging were characterized using direct melting point determination, acid
value assay, solubility testing, and Fourier transform infrared spectroscopy. Given the expectation that waxes perform differently depending on application, preliminary results for cold application have nonetheless provided some useful comparisons between the various coatings.


2017 | Chicago | Volume 24