From the tombs of the Medici family to St. Peter’s Basilica, Michelangelo designed several structures in his native Italy that have endured the threat of earthquakes. But the artist wasn’t anticipating the rumblings caused by hordes of tourists and automobile traffic when he erected his 17-foot statue of David in a public square outside Florence’s Piazza della Signoria in 1504.
It now seems the sculpture could be just a few trembles away from tumbling down, just like Goliath, according to a report published last week in the Journal of Cultural Heritage by the National Research Council (CNR) and the University of Florence.
Visible micro-fractures in the statue’s left ankle and the tree stump on which it stands have compromised the stability of the biblical figure, whose ankles are now too slender to support its six-ton marble physique. Experts warn that the vibrations caused by crowds, car traffic, and construction, as well as the possibility of an earthquake (Florence has 127 recorded minor quakes), could threaten it further.
To reach their conclusions, scientists used an analogue modeling approach to discover the conditions that first led to the fractures and to better understand how stable it is now. The report’s abstract states:
Small-scale (10 cm-high) gypsum replicas of the statue were deformed in a centrifuge, where the models were affected by a body force stronger than gravity but otherwise playing the same role. Analysis of the model results suggests that both the stability and the resulting deformation of the statue are highly sensitive to its attitude. A forward inclination promotes destabilization: the higher the angle of inclination (α), the more unstable the statue becomes under its own weight, confirming existing FEM modelling. In a vertical position, rupture of the statue typically occurs in the lower portions of the legs, but ruptures tend to develop progressively higher along the legs as α increases. Comparison of these results with the lesions detected on the actual David suggests that a long-lasting, small forward inclination (likely close to ∼ 5°) of the statue may have represented a critical driving factor for the development of the observed damages.
According to Gazzetta del Sud, the cracks developed because the statue spent over a century leaning forward in the main city square. Experts first noted the fissures in the mid-19th century, and in 1873, the statue was moved indoors to the Galleria dell’Accademia.
It’s interesting to note that when Michelangelo was still working on the sculpture, a committee of 30 Florentine citizens including Michelangelo’s rival Leonardo da Vinci convened to choose a site for the sculpture. Da Vinci thought that because of the poor quality of marble that Michelangelo used, the statue should be placed out of the elements under the roof of the Loggia dei Lanzi. In the end, the figure was placed outside as a symbol of the city-state’s strength. Five centuries later, it looks like da Vinci may have been right.