A crash test for Michelangelo’s David: results from small-scale centrifuge modeling

It has been noted since the mid 1800s that the Michelangelo’s David, the standing marble male nude representing a masterpiece of the Italian Renaissance, is affected by small cracks on both legs that threaten its stability. Understanding the characteristics and the conditions under which these lesions developed is thus critical for the preservation of this universal masterpiece. In this study, we use an analogue modeling approach to test the conditions that led to the development of fractures in the David’s legs and to get insights into its stability. The experiments were performed by using the centrifuge apparatus at the Tectonic Modeling Laboratory of the Institute of Geosciences and Earth Resources (CNR-IGG) settled at the Earth Sciences Department of the University of Florence. 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 (a), the more unstable the statue becomes under its own weight, confirming existing finite element modeling (FEM). In a vertical position, rupture of the statue typically occurs in the lower portions of the legs, while ruptures tend to develop progressively higher along the legs as forward inclination 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. These simple, preliminary models are characterised by many important simplifications, and can be thus improved in the near future. However, our results support the applicability of small-scale centrifuge modeling to problems of conservation of Cultural Heritage. At least in principle, through the analogue model approach, any feature of the original work of art, including anisotropies, aging, restoration etc., could be simulated by a suited model. Analogue modeling may thus represent a powerful technique to analyze the stability and deformation of other masterpieces, providing complementary information to the more classical FEM approach.