The detection of copper resinate pigment in works of art: contribution from Raman spectroscopy

Year: 2014

Authors: Conti C., Striova J., Aliatis I., Possenti E., Massonnet G., Muehlethaler C., Poli T., Positano M.

Autors Affiliation: Istituto per la Conservazione e la Valorizzazione dei Beni Culturali (ICVBC), Consiglio Nazionale delle Ricerche (CNR), Via Cozzi 53, 20125, Milano, Italy;
Consiglio Nazionale delle Ricerche (CNR), Istituto Nazionale di Ottica and LENS, Università di Firenze, Via Nello Carrara 1, 50019, Sesto Fiorentino, Italy;
Dip. DIFEST, Università di Parma, Parco Area delle Scienze 7/A, 43124, Parma, Italy;
School of Forensic Science (ESC), Institut de Police Scientifique, University of Lausanne, Batochime, UNIL-Sorge, CH-1015 Lausanne-Dorigny, Switzerland;
Università degli Studi di Torino, Dip. Chimica I.F.M., Via Giuria 7, 10125, Torino, Italy;
Emmebi Diagnostica Artistica s.r.l., Via S.Francesco di Sales 80, 00165, Roma, Italy

Abstract: Copper resinate is a green pigment widely used by the 16th century painters, as many surveys on Italian and European paintings proved. The pigment is a transparent green glaze, and its color is due to copper salts of resin acids. The oldest recipes suggest the preparation of copper resinate by mixing verdigris with terpenic resins as Venice turpentine (conifer resins) on hot ashes. The detection of copper resinate in paintings is up to this time an analytical challenge. We examined the Raman features of copper resinate (powder and in a mock paint film with linseed oil) and compared them with verdigris. Six laser sources (488, 514, 532, 633, 785, and 830nm) were used in different laboratories to highlight the drawbacks and advantages of a specific excitation source. The obtained results were applied in the analyses of a famous Caravaggio’s painting. For a detailed interpretation and full exploitation of the Raman spectra, Fourier transform infrared spectroscopy measurements were carried out as well.

Journal/Review: JOURNAL OF RAMAN SPECTROSCOPY

Volume: 45 (11-12)      Pages from: 1186  to: 1196

KeyWords: copper resinate; verdigris; Raman spectroscopy; green painted layers; Caravaggio
DOI: 10.1002/jrs.4455

Citations: 27
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