Non-destructive X-ray fluorescence and Raman micro-analytical study of coffee drawings by Lagoa Henriques

Lagoa Henriques (1923–2009), the well-known Portuguese Sculptor, was also Drawing professor at the Lisbon School of Fine Arts. The sculptor is known for drawing on paper tablecloths during coffee chats. Some of these drawings have become part of the collection of the Faculty of Fine Arts from the University of Lisbon, and like many contemporary artworks that are not carried out with materials conceived for this purpose, pose relevant conservation issues. To ensure the future preservation of the drawings with scientific-based knowledge, non-destructive micro-analytical characterization of the supports and drawing materials was carried out. Micro-Raman spectroscopy enabled the identification of calcite and anatase as fillers in the paper support, carbon black in the ink, and contributed to the diagnostic of the state of conservation of the drawings based on the obtained Raman cellulose spectra. Furthermore, micro-X-ray fluorescence spectrometry (μ-XRF) allowed the identification of clay fillers and sizing materials in the paper support, as well as the chemical identification of coffee characteristic elements on the drawings. The 2D elemental maps obtained by μ-XRF indicates an accumulation of phosphorus, sulphur, potassium and calcium in the coffee stains.