Combining in situ elemental and molecular analysis: The Viceroys portraits in Old Goa, India

The Vice-Roy's Portraits Gallery hosted at the Old Goa Museum of the Archaeological Survey of India in Goa, India, is a unique panel painting collection, spanning from the 16th till the 18th centuries, and representing the Portuguese Viceroys and Governors who administrated the Portuguese provinces in the coastal region of the Indian Ocean. During the Old Goa Revelations project (a collaborative inter-institutional consortium between Evora University HERCULES Lab, Lisbon University Fine Arts Faculty, Archaeological Survey of India and Ghent University), this important collection of panel paintings was examined in-situ using a non-invasive approach with mobile analytical instrumentation. Next to a series of imaging techniques, point analysis has been performed, using both, elemental and molecular spectroscopic methods. On the one hand, handheld X-ray fluorescence analysis and macro X-ray fluorescence imaging was used to obtain the elemental composition and its distribution on pictorial support, while on the other hand mobile Raman spectroscopy was implemented to obtain molecular information. These non-invasive techniques were used to determine the composition of the paint layers and to study the different treatments (e.g. overpainting, changes in compositions, etc.) that the artworks have witnessed since their creation.