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Exploring David: Diagnostic Tests and State of Conservation
edited by S. Bracci, F. Falletti, M. Matteini, and R. Scopigno
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| Before cleaning | Another view | A closeup | After cleaning | A closeup |
In September of 2002, the Galleria dell'Accademia began cleaning Michelangelo's giant statue of David for the first time in 130 years. Here's a web page describing the restoration in more detail. By March 2004, the cleaning was almost finished, and despite some controversy about how best to clean him, he looks great: lighter-colored, reasonably homogeneous, and with a "healthy glow" caused by subsurface scattering through the now-dirt-free surface. Compare the images at left and right above. (I don't guarantee the color balance; the images at right seem a bit too yellow.)
In preparation for this restoration, the Galleria dell'Accademia undertook an ambitious 10-year program of scientific study of the statue and its condition. Led by Professor Mauro Matteini of CNR-ICVBC, a team of Italian scientists studied every inch of the statue using color photography, radiography (i.e. X-rays), ultraviolet fluorescence and thermographic imaging, and several other modalities. In addition, by scraping off microsamples and performing in-situ analyses, the mineralogy and chemistry of the statue and its contaminants were characterized. Finally, finite element structural analyses were performed to determine the origin of hairline cracks that are visible on his ankles and the tree stump, to decide if intervention was necessary. (They decided it wasn't; these cracks arose in 1871, when the statue briefly tilted forward 3 degrees due to settling of the ground in the Piazza Signoria. This tilt was one of the reasons they moved the statue to the Galleria dell'Accademia.)
The results of this diagnostic campaign are summarized in the book Exploring David, whose front cover is shown at the top of this web page. The book, written in English, also contains a history of the statue and its past restorations, a visual analysis of the chisel marks of Michelangelo as evident from the statue surface, and an essay by museum director Franca Falletti on the difficulties of restoring famous artworks. The book is on sale in the museum bookstore and can be ordered online from Giunti Press. Its ISBN is 88-09-03325-6.
Aside from its sweeping scientific vision, what is remarkable about this book is that many of the studies employed a three-dimensional computer model of the statue - the model created by us during the Digital Michelangelo Project. Although we worked hard to create this model, and we envisioned 3D models eventually being used to support art conservation, we did not expect such uses to become practical so soon. After all, our model of the David is huge; outside our laboratory and a few others in the computer graphics field, little software exists that can manipulate such large models. However, with help from Roberto Scopigno and his team at CNR-Pisa, museum director Franca Falletti prodded, encouraged, and cajoled the scientists working under her direction to use our model wherever possible. We contributed a chapter to this book, on the scanning of the statue, but we take no credit for its use in the rest of the book. In fact, to us at Stanford University, the timing of our scanning project relative to the statue's restoration and the creation of this book seems merely fortuitious. However, Falletti insists that she had this use of our model in mind all along! In any case, this is a landmark book - the most extensive use that has ever been made of a 3D computer model in an art conservation project.
Reproduced below are some of the images from the book that were created using our 3D model. The images have been cropped and slightly edited to look good on this web page. The captions are my own. An article summarizing some of these uses also appears in an article by R. Scopigno et al. in IEEE Computer Graphics & Applications, March/April 2004.
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Figure 1:
Exposure of the statue surface to nearly vertical (± 5 degrees) deposition of
rainwater, dust, and other contaminants.
(Image from the chapter by
R. Scopigno and P. Cignoni.)
Figure 2:
Locations of analyses carried out on the statue surface
(Image from the chapter by M. Matteini.)
Figure 3:
Hypothetical placement of gilding reported to have been applied in the 16th
century.
(Virtual reconstruction by Artmedia Studio.)
Figure 4:
Buttress proposed in the 19th century when cracks were observed in David's
ankles.
(Virtual reconstruction by Artmedia Studio.)
Figure 5:
Calculation of the statue's center of gravity.
(Image from the chapter by
R. Scopigno and P. Cignoni.)
Figure 6:
Tensile stresses in the left leg with the statue tilted 3 degrees forward, as
it was in 1871.
(This and the next image are from the chapter by A. Borri,
A. Grazini, and L. Marchetti.)
Figure 7: Tensile stresses in the tree trunk supporting the right leg. Superimposed are branching red lines indicating the location of hairline fractures that are still observable today.