2023 IMEKO TC-4 International Conference on Metrology for Archaeology and Cultural Heritage Rome, Italy, October 19-21, 2023 Analytical investigations on polychrome artworks from the wooden ceiling of “ex-Ospedale San Matteo” in Pavia Giacomo Fiocco 1,2 , Francesca Volpi 1,2 , Tommaso Rovetta 1 , Chaehoon Lee 1,3 , Michela Albano 1,2 , Chiara Delledonne 1 , Maduka L. Weththimuni 3 , Mario Colella 4 , Anna Letizia Magrassi Matricardi 5 , Curzio Merlo 6 , Marco Malagodi 1,2 , and Maurizio Licchelli 1,3 1 Arvedi Laboratory of Non-Invasive Diagnostics, CISRiC, Università di Pavia, Via Bell’Aspa 3, 26100 Cremona, Italy, giacomo.fiocco@unipv.it, francesca.volpi@unipv.it, tommaso.rovetta@unipv.it, chaehoon.lee1@universitadipavia.it, michela.albano@unipv.it, chiara.delledonne@unipv.t, curzio.merlo@unipv.it, marco.malagodi@unipv.it, maurizo.licchelli@unipv.it 2 Department of Musicology and Cultural Heritage, Università degli Studi di Pavia, Corso Garibaldi 178, 26100 Cremona, Italy 3 Department of Chemistry, University of Pavia, Via Torquato Taramelli 12, 27100 Pavia, Italy, madukalankani.weththimuni@unipv.it 4 Centro Studio e Conservazione Piccolo Chiostro, Via Riviera 20/22, 27100 Pavia, Italy, centrorestauropiccolochiostro@gmail.com 5 Museo di Archeologia del Sistema Museale d’Ateneo di Pavia, S.da Nuova 65, 27100 Pavia, Italy, annaletizia.magrassi@unipv.it 6 Laboratorio di Diagnostica applicata ai Beni Culturali, Scuola di Restauro Cr.Forma, C.so Matteotti 17, 26100 Cremona, Italy, curziomerlorest@crforma.eu Abstract – The ex-Ospedale San Matteo in Pavia, constructed in 1449, featured wooden ceilings adorned with unique angelic decorations. Restoration efforts began in the late 1980s, with some panels completed in 2001. Currently, ten restored panels are on display and the Museum of Archaeology of the University of Pavia is initiating a new conservation project to restore the entire wooden ceiling, starting in 2024. The main aim of this preliminary project was the characterization of the colour palette, as a support for the restoration procedures. Non-invasive analysis using XRF and ER- FTIR spectroscopies revealed a colour palette, including cinnabar, azurite, copper-based greens, white lead, calcite, iron-based reds, yellow ochre, and organic-based black. I. INTRODUCTION The construction of the ex-Ospedale San Matteo in Pavia was completed in 1449 with a roof characterized by flat wooden ceilings decorated with hundreds of angels, one different from the other, to give a heavenly and consoling vision to the sick (Fig.1). The construction of a Baroque dome in 1770, about 30 meters high, resulted in the breaking through and loss of the central section of the 15th century wooden ceiling, of which only a few sections remain visible. Given the poor condition of preservation, from the late 1980s, restoration of some sample wooden panels was begun. The project was completed, although only on some bays, in 2001. Currently, 10 panels restored during the 1990s campaign are properly preserved and on public display at the Museum of Archaeology of the University of Pavia. In the wake of the latter project, completed more than twenty years ago, the Museum of Archaeology is starting a new conservation project to make this extraordinary and unique heritage, planning the restoration of the entire wooden ceiling from 2024 [1,2]. The current conditions of degradation of both the wood substrate and the painted layers, due to fires and water infiltrations that occurred over the centuries required strong maintenance and restoration procedures, as well as a preliminary diagnostic campaign that could support the first approach to the artworks. Under this scenario, an analytical campaign on 4 wooden polychrome panels (Fig. 2) was performed. The main aim of this preliminary project was the non-invasive characterization of the colour palette used in the paintings, as a support for the first restoration procedures. For this purpose, Visible-Ultraviolet-Infrared (Vis-UV-IR) 33