Casting, joining and recycling. Use of lead and plumbers practices in Notre-Dame building yard (12th-19th c.) through historical, archaeological and chemical investigations

An interdisciplinary scientific project composed of different work groups was set up after the fire of Notre-Dame cathedral in 2019 which aims at studying all different aspects of the building and its evolutions from the 12th to the 19th century. One of them is the Metal work group who investigates the use of iron and lead in this monument and try for instance to trace the history of lead uses in the construction and restorations of cathedrals. The present paper focuses on the case of Notre-Dame de Paris, a jewel of French gothic architecture to question the role of this metal in its structure, to determine the quantities used and to investigate issues related to its provisioning and its recycling. Paradoxically, though the fire of 15th April 2019 melted almost the whole lead roof as well as decorative elements on the spire, lost forever for scientific investigations, it also enabled to reveal hidden parts of the cathedral where lead used as sealing became accessible thanks to scaffolding. A methodology combining archaeology, archive record study and archaeometry was implemented to study the remaining lead in the cathedral leading to a textual approach coupled with a material approach. Two case studies are considered in this paper as representative of lead uses at different periods of the cathedral's life: in medieval masonry with cramp's sealings in the tribunes, and on the sacristy's roof dating from the 19th century. For the first case, a chronology of the construction will be suggested and for the second a discussion between chemical analyses and archive records will be opened.