Chemical analysis of the 5th and 12th century metal doors in the Lateran, Rome

Abstract

For the first time, the three bronze doors of the Lateran Baptistery and Cloister of the Archbasilica of St John Lateran in Rome have been studied to determine their chemical composition and to obtain further information about their manufacture. The doors studied include two made at the end of the twelfth century by Pietro and Uberto from Piacenza, Italy, and one made by an unknown master in the fifth century. This door now leads to the Oratory of St John the Baptist in the Lateran Baptistery. One of the 12th-century doors is now in the Chapel of St. John the Evangelist, and the second 12th-century door is in the cloister of the Archbasilica. High-resolution photographic documentation and a 3D model of one of the door wings complete the detailed documentation of the three medieval doors. The chemical analysis of the doors permits a detailed reconstruction of the alloys used in their manufacture. All doors were made of leaded tin bronze, and the resulting data provides a valuable contribution to the history of their construction and the processes employed in their manufacture.