From construction to maintenance. The history of the wooden chain encircling the dome of Santa Maria del Fiore

The present paper aims to illustrate the events that shaped the wooden ring surrounding the dome of Santa Maria del Fiore from its very construction until the present day. Indeed, among the architectural elements of Brunelleschi’s masterpiece, this probably represents the least analysed, especially in reference to its history. The encircling tie rod was already included in the first Cupola Programme (1420), which stated that the structure was to be provided with «chains of great oak beams between one spur and the next which bind the said spurs (together) and encircle the vault(s) inside» . Such chains, to be positioned every twelve braccia along the height of the vault, were only one of the several expedients developed by the designers to overcome the typical collapse mechanism of masonry domes. Although empirically, Brunelleschi must had in fact acknowledged the risks connected to the vaults’ horizontal trust and tried his best to avoid it. However, since «in building only practical experience will teach that which is to be followed» , the original plan was changed along the way, and only one of the intended four wooden chains was actually realised. For this and other reasons, ever since its construction, this device has been the subject of a debate concerning its original role and current contribution to the monument’s equilibrium. Even though over the years numerous scholars [1-9] formulated hypothesis to address these issues, a systematic historical study of the artefact had not been yet conducted. The primary objective of the present research was hence to retrace the construction and maintenance history of the wooden chain, which, beside the authentic elements, currently shows signs of transformations occurred after the XV century. After a throughout examination of previous literature that somewhat dealt with the topic of its construction [10-13], the study resorted to the historical documents stored in the Opera di Santa Maria del Fiore’s archive, shedding light on long-lost pieces of information in this regard. The newly found data, spanning several centuries (XVII-XX), allowed to reliably date most of the elements comprising the chain. The complete understanding of the gathered information were however only achieved by comparing the historical data to the object in its current state, as well as to the accurate geometric survey of the encircling tie commissioned by the Opera in 2018. In fact, while rather detailed, the blacksmith’s and carpenter’s expense records rarely offered spatial references. Thus, the mere analysis of archival documents would not have enabled to certainly locate the described maintenance interventions along the wooden ring. The visual and dimensional crosschecking of information highlighted quite precise matches, allowing to attribute the different beams and joints to specific years, or broader timeframes. In this process, the consultation of historic architectural treatises also proved fundamental, as did the comparison with similar examples whose construction date was known.