Macromolecular oxidation was detected in proteins by the colorimetric measurement of Advanced Oxidation Protein Products (AOPP) and in lipids by the colorimetric quantification of malondialdehyde (MDA). Standard curves were run with chloramine-T and 1,1,3,3 tetraethoxypropane (TEP) for AOPP and MDA methods, respectively [29], [30], [31]. Values were normalized to initial protein content in samples, measured with Bradford reagent [32]. The standard deviation of at least six measures was calculated and p-value < 0.05 were considered significant.

The author thanks Marco Leona, Scientist-in-Charge of the Department of Scientific Research at the Metropolitan Museum of Art for conducting fluorescence spectrometry on Wheel of Fortune and a valuable discussion of the research, as well as Silvia Centeno, Research Scientist at the Metropolitan Museum of Art, who performed Raman analysis on the watercolors and also contributed her insight. The phenomenon of the phosphorescing lithopone was originally discovered during the author's fellowship in the Sherman Fairchild Center for the Conservation of Works on Paper, funded by the Andrew W. Mellon Foundation. The author thanks all her colleagues for their ideas and support during the research of this paper, and special thanks to Rachel Mustalish for her assistance in editing this work.