Artificial aging of modern organic pigments in presence of reactive inorganic whites

The investigation of aging processes and degradation mechanisms in the materials that artists commonly use is important for developing the right conservation strategies and preventing aesthetic variations. This Ph.D. focuses on establishing effective artificial aging procedures to study the interactions between modern organic pigments and highly reactive white inorganic pigments. During the Ph.D., different aging experiments were designed and tested through exposure of pigments to different conditions of light (solar, ultraviolet, visible), temperature, and relative humidity. A multi-technique analytical approach was employed to investigate the surface-level and molecular variations induced by aging. These techniques include colorimetry, Fourier transform infrared spectroscopy, Raman spectroscopy,X-ray diffraction, and time-of-flight secondary ion mass spectrometry. Due to the complexity of the multi-component samples, the use of complementary techniques was fundamental to studying the aging-induced variations. The study focuses mainly on three modern organic pigments, commonly used in modern and contemporary works of art, belonging to the monoazo, isoindoline, and phthalocyanine classes. Their stability was studied in interaction with three different white inorganic pigments, lead white, titanium dioxide, and zinc oxide. Two main case studies were reported with the aim of investigating the photostability of selected modern pigments in samples that combine organic and inorganic pigments in paint or powder forms. Surface color variations were the first indicators of Chemical and physical degradation. Vibrational techniques were used to investigate molecular changes in pigments and binder, whereas X-ray diffraction analyses provided insight into the role of crystalline nature in the degradation process. In particular, ion mass spectrometry enabled high-sensitivity surface analysis, allowing a detailed investigation of the degradation effects underlying the observed color changes. This research sheds light on pigment-metal oxide interactions in paint systems, providing valuable insight into their stability over time in modern and contemporary artworks, laying the groundwork for future studies on organic-inorganic pigment mixtures.