Andrea Cagnini

Spectroscopic analysis of works of art using a single LIBS and pulsed Raman setup

A nanosecond pulsed laser setup has been optimized to perform laser-induced breakdown spectroscopy (LIBS) and pulsed Raman spectroscopy measurements in the field of cultural heritage. Three different samples of artistic/architectural interest with different typologies have been analyzed. The results from the two techniques allowed the identification of the materials used in their manufacture or contaminating them, probably coming from atmospheric pollution and biological activity. No sampling and sample preparation was required before the measurements, and no visual or structural damage was observed. Depth profiling using LIBS was performed in one of the samples, providing elemental information along the different layers composing the object and covering its surface. The quality of the results and the rather short time needed for the measurements and for switching between techniques confirmed the instrument’s capabilities and specificity for dealing with objects of artistic or historical interest.

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.

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.

An unusual mortar with a magnesium binder in the Perseus of Giovan Battista Pieratti in Boboli Gardens (Florence)

The restoration of Perseus Boboli Gardens (Florence, Italy), a sculptural complex realized by Giovan Battista Pieratti in the 30 th of the XVII century mostly as reuse and reinterpretation of fragments of ancient Roman sculptures, offered the opportunity to face the problem of the structural consolidation of a fragmented sculpture. During disassembly of this sculptural complex it was possible to observe an overlapping of techniques and materials that covers more than three and a half centuries, from the first half of the XVII century until the 80 s of the XX century. One of the materials used as glue of the pivots showed an unusual composition, characterized by a magnesium hydroxide based binder (brucite) and brucite and barite as aggregate. It is probably an old mortar still in excellent conservation conditions.