Monica Galeotti

Non-destructive and non-invasive analyses shed light on the realization technique of ancient polychrome prints.

Five polychrome prints representing famous painters, such as Albrecht Dürer, were analyzed using a non-destructive and non-invasive methodology as required by the artwork typology. The diagnostic strategy includes X-ray fluorescence (XRF), reflectance micro-infrared (microFTIR) and micro-Raman (microRaman) spectroscopy. These prints were realized with a la poupée method that involves application of the polychrome inks on a single copper plate, before the printing process. A broad range of compounds (i.e., cinnabar, red lead, white lead, umber earth, hydrated calcium sulfate, calcium carbonate, amorphous carbon, and Prussian blue) was employed as chalcographic inks, using linseed oil as a binding medium. Gamboge was identified in the delicate finishing brush touches realized in watercolor.

Brownish alterations on the marble statues in the church of Orsanmichele in Florence: what is their origin?

IntroductionThe paper describes the complex investigations carried out to understand the sources of the brown chromatic changes that have occurred on ten marble statues dated back to the first half of the 15th century and now located in the Church of Orsanmichele in Florence, Italy. When the statues were removed from the outdoor niches for restoration in the 1980s, they appeared covered with a dark brown patina (called ‘bronzatura’) that dated to interventions occurred just after 1789. Archival documents confirmed that they had been carried out to make the marble statues look like bronzes. Because of the removal of the dark patina carried out by the Opificio delle Pietre Dure in the 1990s, the marble almost regained its distinguishing clear tonality even if darker areas remained. After the statues were placed indoors at the end of restoration, brownish discolorations started to appear on their surfaces.ResultsResearch began by using various non-invasive analyses (photographs under ultraviolet illumination, fluorescence lifetime imaging, x-ray fluorescence). The results of UV fluorescence tests and FLIM showed that the fluorescence emission’s distribution map does not have distinctive and homogeneous characteristics in relation to the areas with the discoloration. Therefore, it is not a superficial film, but rather a phenomenon affecting the marble structure. Then we performed invasive analyses on samples from some statues. The results of optical microscopy, ATR-FTIR and Raman spectroscopy on cross sections, pyrolysis-gas chromatography/mass spectrometry on powdered samples from the surfaces and/or the bulk of the marble allowed the identification of the various substances involved in the chromatic alteration. Most important was the detection of weddellite and gypsum on the surface and within the marble. This finding, combined with the presence of lipids inside the stone, suggests that mineralization of treatments have occurred, causing discolorations.ConclusionsEven though the study focuses on the statues from Orsanmichele, their issue nevertheless should not be considered specific to them. Marble discolorations are a widespread phenomenon whose complete understanding needs a complex series of analyses and only the combination of non-invasive and invasive analyses can fulfill this goal.

Ancient and New Repair Mortars for Conservation: Application to the Case of San Leonardo Pulpit (Florence, Italy)

The San Leonardo pulpit in Arcetri (12th century) is an unicum in Florence. The first documents place it in the Church of San Pier Scheraggio, from where it was moved in 1782 to the Church of San Leonardo in Arcetri. Inside the church the pulpit was again dismantled and reassembled in 1921 by Opificio delle Pietre Dure, with the addition of new parts. In this work, different restoration mortars have been characterized mineralogically by x-ray diffraction (XRD), chemically both by Fourier transform infrared spectroscopy (FT-IR) and by scanning electron microscopy (SEM-EDS), and petrographically by optical microscope observation in transmitted light (OM). Compositional data allow the research team to identify mortars related to different past interventions. Scientific results, with information obtained from historical sources, have been used in order to decide the selective removal of the materials that could give rise to further decay. Therefore mortars suitable for restoration were also developed by specific tests, in order to obtain materials compatible with the substrate by chemical, physical, and aesthetic point of view.