On a molecular scale, there are surprising similarities between the outer shell of a golf ball and the white oil paint used by Van Gogh and his contemporaries. In both cases, the interactions between zinc ions and polymer chains are at the basis of important material properties. In a recent publication in the scientific journal Science Advances, Rijksmuseum and University of Amsterdam researchers describe the role of zinc ions in the molecular network of oil paint. Their studies could explain why paintings made with zinc white pigment are so sensitive to high humidity conditions.
Vincent van Gogh and other painters of his day often used zinc white (zinc oxide, ZnO), a white pigment that yields a good opaque oil paint. However, zinc white can easily react with the oil binder as it polymerises and transform into a network of molecular chains during paint drying. As a consequence, zinc ions nestle themselves between the molecular chains of the oil. Previous research showed that this process is not without danger—the ions can speed up the breakdown of the oil, and they form problematic chemical compounds with the degradation products.