The San Giovanni Baptistery in Florence (Italy): assessment of the state of conservation of surfaces and characterization of stone materials

During the last restoration campaign of the Baptistery of San Giovanni in Florence (Italy), the assessment of the state of conservation of external surfaces was performed, with a multi-analytical approach, in order to support the conservation and restoration treatments. Black crusts, red staining, sulphation, and organic patinas were identified. Moreover, a complete characterization of marble cladding, bricks, and mortars was carried out. A geochemical and minero-petrographic approach was used in order to classify and assess the provenance of marbles, and define raw materials and technologies of the production for bricks and mortars. Provenances from Italy (Carrara and Lasa marbles) and from Greece (Hymettus and Pentelicum marbles) were identified and attributed to different construction phases, restoration interventions, and re-use of ancient materials. For mortars, the obtained data suggested the use of local materials and traditional technologies for the production. Overall, two different minero-petrographic typologies were identified for the analyzed bricks.