Characterization by Spectroscopic and Microscopic Techniques of Degraded Zinc White Pigment in <i>Las Dos Fridas</i>

<i>Las Dos Fridas</i>, 1939, is Frida Kahlo's most renowned achievement. This work now presents conservation problems, especially around white regions. In 2008, ten microsamples of <i>Las Dos Fridas</i> were studied by scanning electron microscopy with energy-dispersive X-ray spectroscopy. Recently, to understand its alterations, the microsamples were reanalyzed using nuclear magnetic resonance spectroscopy, micro-Fourier transform infrared spectroscopy, attenuated total reflection infrared spectroscopy, and electron microscopy. The analysis revealed a pictorial layer affected by metallic soaps and the presence of zinc lactate, which is typically associated with environmental contamination. A metal-catalyzed radical pathway is posited by this study. According to this hypothesis, the oxidative drying processes of linseed oil generate free radicals that degrade the cellulose of the cotton canvas. This hypothesis is based on the pictorial technique employed by Frida Kahlo, whereby the absence of a preparation base for her canvas is highlighted, which resulted in the transmission of the drying oil to the canvas fabric.