When the choice of pigments affects the stability of paint materials: the case of manganese violet in contemporary paint mixtures

This thesis project "When the choice of pigments affects the stability of paint materials: the case of manganese violet in contemporary paint mixtures" was conceived within the collaboration between Ca’ Foscari University of Venice, the Academy of Fine Arts in Vienna, the University of Applied Arts in Vienna, and the Academy of Sciences in Prague, and was developed under the framework of Erasmus+ for traineeships programme. The project dealt with the stability of modern synthetic paints mixed with manganese violet pigment (PV16) (NH4MnP2O7) when exposed to weathering agents, specifically high relative humidity and sulphur dioxide (SO2). In particular, the study focuses on the capability of PV16 to enhance the degradation processes of modern synthetic binders. The aims of this project are, therefore, the study and evaluation of the chemical changes involving PV16, the investigation of the degradation processes occurring in the various organic matrices (Oil, alkyd resin, acrylic and styrene-acrylic emulsion) and the comparison between self-made and commercial synthetic paint stability. The paints were investigated using the main diagnostic techniques commonly applied in the Cultural Heritage field. Specifically, 3D Optical Microscopy, ATR-FTIR Spectroscopy, μ-Raman Spectroscopy, SEM-EDS, XRD, and Py-GC/MS were employed. Preliminary results showed that when exposed to high relative humidity and SO2, PV16 changes colour from violet to grey and forms crystals on the surface. This study, considering the susceptibility of manganese violet pigment to certain conditions, can therefore provide an important contribution in defining appropriate conservation and prevention strategies for artworks containing this specific pigment.