Non-destructive Raman investigations on wall paintings at Sala Vaccarini in Catania (Sicily)

In the framework of the restoration works carried out under the supervision of Superintendence of Catania at the Libraries “Civica and A. Ursino Recupero”, part of the 16th century monumental complex of Benedictine Monastery (Catania, Sicily), an archaeometrical investigation of the Sala Vaccarini wall paintings has been carried out. Sala Vaccarini is one of the historical Libraries of the Benedectine Monastery and preserves unique manuscripts collected by the monk Niccolò Riccioli e Paternò (1695-1783), who financed the realization of the Monastery Libraries. It was built by the architect Giovanni Battista Vaccarini in 1773, during the reconstruction works performed after the 1693 earthquake that partially destroyed the city of Catania. The well-known Sicilian painter Giovan Battista Piparo (1730-1754), who realized splendid medallions representing the Virtues, the Arts (Figure 1 (a)) and the Sciences, decorated the vaults of the library. In view of the exceptional value of these wall paintings, a campaign of in situ measurements has been performed in order to investigate aspects as pigmenting agents, preparation layers and deterioration processes. In detail, spectroscopic analyses by using portable Raman equipment have been performed, considering the effectiveness of the method in characterizing pigments in non-destructive and non-invasive way [1-5] and the availability of a large number of databases for the identification of ancient and modern pigments [6-9]. Raman spectra were collected by a portable EZRAMAN-I-DUAL Raman system (Enwave Optronics, Irvine CA, USA) equipped with a near-infrared diode laser (785 nm) and a green Nd:YAG laser (532 nm), and a BWTek instrument equipped with 1064 nm line. Finally, additionally measurements have been carried out on small fragments sampled from the vaults by using the laboratory micro-Raman apparatus Jasco NRS-3100, equipped with laser excitation sources at 785 nm and 532 nm. The obtained results (Figure 1(b)) allow us to achieve a complete characterization of the pigments used in the paintings of the vaults, supplying fundamental information to the restorers, useful for planning appropriate conservation and preservation actions. Moreover, the campaign offered the possibility to compare the efficiency of different laser lines in both portable and laboratory Raman spectrometers. References: [1] D. Bersani, P.P. Lottici, G. Antonioli, E. Campani, A. Casoli, C. Violante. Journal of Raman Spectroscopy 2004. 35: 694. [2] D. Bersani, M. Berzioli, S. Caglio, A. Casoli, P.P. Lottici, L. Medeghini, G. Poldi, P. Zannini. Microchemical Journal 2014; 114: 80. [3] D. Lauwers, A.G. Hutado, V. Tanevska, L. Moens, D. Bersani, P. Vandenabeele. Spectrochimica Acta Part A 2014; 118: 294. [4] P. Vandenabeele. Journal Raman Spectroscopy 2004; 35: 607. [5] E. Aquilia, A. Giuffrida, C. Ingoglia, P. Mazzoleni, S. Raneri. Rendiconti Lincei 2015; doi: 10.1007/s12210-015-0419-0 [6] I.M. Bell, R.J.H. Clark, P.J. Gibbs. Spectrochimica Acta - Part A 1997; 53: 2159. [7] L. Burgio, R.J.H. Clark. Spectrochimica Acta Part A 2001; 57: 1491. [8] P. Vandenabeele, L. Moens, H.G.M. Edwards, R. Dams. Journal of Raman Spectroscopy 2000; 31: 509. [9] RRUFF Project, Department of Geosciences, University of Arizona, Tucson, USA. http://rruff.info/. Accessed 01 October 2015.