New studies on Lorenzo Lotto‘s pigments: Non-invasive and micro-invasive analyses

In the frame of large research project, also related to the exhibition “Lorenzo Lotto” (Venezia, 1480 – Loreto, 1556-57) held at the Scuderie del Quirinale in Rome in spring 2011, more than 50 paintings of Lotto spanning from 1505 to around 1556 were studied by means of scientific examinations. The University of Bergamo coordinated and carried out non-invasive analyses using portable instruments: IR reflectography in different bands, false colour IR, reflectance spectrometry in the visible range (vis-RS), X-ray spectrometry (EDXRF), sometimes UV-induced fluorescence and X-ray radiography. On the basis of the obtained results some areas of four paintings undergoing restoration treatments were subjected to micro-sampling in order to be mounted in cross-sections and studied by optical microscopy (OM) and SEM/EDX by the University of Urbino e by micro-Raman spectroscopy by the University of Modena and Reggio Emilia. Non invasive exams allowed to know the evolution of Lotto’s palette during all the periods of his activity, as well as his underdrawing, the nature of painting changes and his pictorial technique. Among the most interesting results, the use of lapis lazuli and azurite in different combinations , and their mixture with red lakes. About these lakes, Lotto shows a peculiar use of madder, also alternated with carmine-type lake, according to desired effects. About yellows, he uses both lead-tin and lead-antimony (Naples yellow) pigments, the latter found by XRF in works starting from 1530 to the last years: it can be related to the “zalolin da vasarj” cited by Lotto in 1541 in his account book (Libro di spese diverse). Micro-invasive analyses (Raman and SEM/EDX) stated also the presence, among yellows, of litharge, of a high tin content “giallorino” (lead-tin yellow) and of saffron, as well as the use of grinded transparent glass in the pictorial layers, the existence of coloured priming and – in one case – of an iron-oxides coloured ground, the complexity of some stratifications and mixtures. This kind of analyses were carried out on a few selected samples of four works painted during different periods of Lotto’s career, from 1508 (Recanati) to 1522 (Bergamo)