Unraveling Color Transformation and Material Degradation in Munch's Artworks: Ultramarine Blue and Cobalt Blue Industrial Oil Paints

Abstract

This thesis project has its start in the fruitful collaboration between Ca’ Foscari University and MUNCH, the Oslo’s Museum dedicated to the famous Norwegian expressionist Edvard Munch, under the framework of Erasmus+ Internship programme. Moving from the necessity of understanding the dynamics regulating darkening and degradation phenomena of Ultramarine and Cobalt blue- based oil paints in three real case studies by Edvard Munch (namely, Old Man in Warnemunde, The Drowned Boy and The Death of the Bohemian), 20 oil paint tubes from Edvard Munch’s material collection owned by MUNCH were investigated , together with the case studies themselves. After an in-depth review of the conditions and previously performed studies on the selected paintings, a multi-analytical approach was adopted, involving non-invasive (Hirox 3D microscope, pXRF, performed inside MUNCH’s facilities) and micro-invasive (ATR-FTIR, micro-Raman, GC-MS, performed at Ca’ Foscari University) techniques. The objective was to determine the composition of these industrial blue oil paints, identify any resemblances in composition from paints’ samples to real case studies, and examine the potential implications for the observed darkening in the paintings. Binding media admixtures, pigments and additives present in the manufactured formulations were assessed. The samples from both the paintings and industrial paints displayed intricate mixtures, featuring a significant presence of additives such as non-drying or partially drying oils, metal soaps, and preservatives. Additionally, the industrial paint tubes contained extenders, among others clay minerals, white and other blue pigments. In certain instances, the compositions diverged from what was indicated on the labels. Hypothesis regarding the possible cause of the deterioration mechanisms observed in Cobalt blue and Ultramarine blue paints was presented, and future perspectives outlined.