The interface of art and science provides a broad range of educational and collaborative projects at various learning stages. Therefore, the use of historic artists’ materials for teaching chemistry is receiving more attention. We prepared and used copper acetate (verdigris pigment) for a series of interconnected, lab-based activities, which can be applied to high-school-level chemistry, to undergraduate general chemistry, and further to heritage conservation science research for emerging art conservators. The synthesis and degradation processes of artists’ materials like this pigment allow instructors to illustrate scientific concepts like redox chemistry, while extending the vision of science to arenas beyond the classroom.

Copper-containing materials such as verdigris are commonly found in historic and artistic works of art, often at advanced states of decay. Applied on paper as inks and watercolors, many of which needed a binder such as gum arabic, the intrinsic instability of this pigment was known since the medieval period. The decay of verdigris (a mixture of copper acetates) as a pigment, as watercolor, and as a dye, was studied using a combination of vibrational (Fourier transform infrared) and X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) instrumental techniques. Changes in the copper oxidative states and the formation of copper oxide were monitored during accelerated degradation as powdered solids and applied on mockup samples (with and without binder). Accelerated aging of both commercially available and synthesized verdigris pigments showed the presence of an intermediate species, Cu(CH3COO)2•3Cu(OH)2•2H2O, which points to the beginning of the decay processes, that culminates in the formation of Cu(II) oxide. However, the presence of gum arabic seems to delay deterioration, by temporarily reducing Cu(II) to Cu(I), even when the final product includes Cu(II). This novel application of XPS and supporting techniques has significant implications in art conservation, as the identified behavior helps explain the better preservation state of some works of art.