The San Giovanni Battista is one of the three bronze statues from the Decollazione del Battista (1571) by Vincenzo Danti which have been exposed for more than four centuries in the south side facade of the Baptistery in Florence. Aim of this work is the characterization of the casting core and its interaction with the internal bronze surface of the sculpture in order to investigate the artist’s technique and to guide some aspects of the conservation. The core fills almost the whole internal volume, that is of particular importance for a Renaissance bronze statue. Samples of the casting core have been taken through few suitable apertures, the main of which is located at the bottom. Particular attention has been paid to the study on corrosion products at the interfaces of the core with both bronze and iron structural elements. The application of complementary analytical techniques (observations of thin section to polarised light microscope OM, XRD, FT-IR and SEM-EDS) provided meaningful information on ceramic paste (matrix and framework constituted by sand and organic temper ) as well as on the bronze alteration products. The detection of calcite suggests that the core has reached temperatures below 850°C. Most of the core was heated in an oxidizing environment giving a red color due to the presence of iron (III) while a thin layer, which was in contact with the wax, shows a brownish tone because of the reducing conditions. Besides the inner part of the core shows a framework with variable grain size and bad sorting respect to the outer one, indicating a different manufacturing of the ceramic paste. Some samples showed the presence of elongated pores related to organic materials added to the casting and carbonized during the heating process. The identification of the corrosion products of the bronze alloy and iron structure at the interface with the core contributed to assess the effects of removing the casting core.
The casting core study of a XVI century bronze statue:manufacturing and conservation aspects of San Giovanni Battista by Vincenzo Danti / Della Schiava E.; Agnoletti S.; Cagnini A.; Porcinai S.; Benvenuti M.; Pecchioni E.. - STAMPA. - (2008), pp. 379-380. (Intervento presentato al convegno 37th International Symposium on Archaeometry ISA, Siena tenutosi a Siena nel 12-16 Maggio 2008).
The casting core study of a XVI century bronze statue:manufacturing and conservation aspects of San Giovanni Battista by Vincenzo Danti
BENVENUTI, MARCO;PECCHIONI, ELENA
2008
Abstract
The San Giovanni Battista is one of the three bronze statues from the Decollazione del Battista (1571) by Vincenzo Danti which have been exposed for more than four centuries in the south side facade of the Baptistery in Florence. Aim of this work is the characterization of the casting core and its interaction with the internal bronze surface of the sculpture in order to investigate the artist’s technique and to guide some aspects of the conservation. The core fills almost the whole internal volume, that is of particular importance for a Renaissance bronze statue. Samples of the casting core have been taken through few suitable apertures, the main of which is located at the bottom. Particular attention has been paid to the study on corrosion products at the interfaces of the core with both bronze and iron structural elements. The application of complementary analytical techniques (observations of thin section to polarised light microscope OM, XRD, FT-IR and SEM-EDS) provided meaningful information on ceramic paste (matrix and framework constituted by sand and organic temper ) as well as on the bronze alteration products. The detection of calcite suggests that the core has reached temperatures below 850°C. Most of the core was heated in an oxidizing environment giving a red color due to the presence of iron (III) while a thin layer, which was in contact with the wax, shows a brownish tone because of the reducing conditions. Besides the inner part of the core shows a framework with variable grain size and bad sorting respect to the outer one, indicating a different manufacturing of the ceramic paste. Some samples showed the presence of elongated pores related to organic materials added to the casting and carbonized during the heating process. The identification of the corrosion products of the bronze alloy and iron structure at the interface with the core contributed to assess the effects of removing the casting core.
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