Technology and repairs in castelli e ponti di mastro Nicola Zabaglia (Rome, 1743)

The construction of St. Peter's in Rome can be considered as having been completed at the end of the XVII century. Concurrently, with the closing of the Vatican building yard, a number of important actions to maintain the Basilica were started and continued for a long time up to the XIX century, on the vault and the dome first, on the porch and the obelisk later. Both editions dated 1743 and 1824 of the treatise Castelli e Ponti written by Nicola Zabaglia (1664-1750), the "sampietrino" building foreman, are an excellent compendium of technical and mechanical achievements of the Roman Baroque in the field of building construction. Due to the technical and operational difficulties encountered to carry out most of these repairs, it was necessary at that time to design and erect suspension scaffolds, either fixed or moving, as well as special machines and temporary structures which were really innovative. The instruments and techniques of repairs developed in Rome in the XVIII century can be highlighted through analysis of the Zabaglia treatise Castelli e Ponti. There are so clearly detailed pictures of these techniques shown in this document that their understanding and use has been possible up to the beginning of the XX century. Even today, the works of Zabaglia can provide the specialists with new elements to be used for developing a more comprehensive and realistic history of repairs.