Researches on 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 in 1782 it was moved 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 to identify mortars related to different interventions occurred in the past. Scientific results together with information obtained from historical sources, have been used in order to decide the selective removal of the materials which 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 aesthetical point of view.