1) The Historical Foundations

An historical study of the documents conserved in various Florentine archives (and in particular the Archivio Storico Comunale di Firenze and the Archivio dell'Accademia di Belle Arti, the city's historical municipal and the Accademia's archives) brought to light the following data concerning the conservation history of the David:

  • the first damage to the David was caused by a arrow that struck its base in 1512;
  • the statue's left was broken to pieces during the popular uprising against the Medici;
  • between 1808 and 1815 a patina of hot wax, known as encaustic, was applied to the David to protect it from atmospheric agents. We do not know if the surface had any other type of protective coating prior to this;
  • at the same time, the restorer, Stefano Ricci remade the middle finger of the right hand;
  • in 1843 Aristodemo Costoli cleaned the surface o the David with a 50% solution of hydrochloric acid;
  • on that same occasion Costoli also remade the little toe of the left foot, and this was repeated in 1851;
  • in 1847 Clemente Papi made a complete cast of the David;
  • in 1873, when the David was moved from Piazza della Signoria and placed inside the Galleria dell'Accademia, the many cracks that had developed at the ankles created great concern about its stability;
  • finally, there was the act of vandalism in 1991 that smashed the tip of the second toe of the statue's left foot. The damage was repaired by the Opificio delle Pietre Dure.

2) The Scientific Foundations

 The fact that the David needed more than “ordinary maintenance” was already evident in the early nineteen eighties when Giorgo Bonsanti was the director of the Accademia.
The Opificio delle Pietre Dure began working on the scientific studies back then, and restorer Gugliemo Galli prepared a detailed project report.
A preliminary series of tests on samples of deposits taken from the statue was done by the Opificio delle Pietre Dure laboratories, along with close-up visual (naked eye) observations and an initial photographic campaign.
In 1992 Editech made a photogrammetric survey of the statue and conducted preliminary tests under ultraviolet light to pinpoint the degraded areas that required monitoring. These tests made a further contribution to determining the statue's state and to planning the restoration program.
The gammagraphs taken by E.N.E.A. (Ente per le Nuove Tecnologie e l'Ambiente. Progetto Tecnologie per la Salvaguardia del patrimonio Artistico – Agency for New Technologies and the Environment - Technologies for Protecting the Artistic Heritage Program) in 1993 made it possible to identify a series of metal pins that were placed inside the left arm and hand to rejoin the parts that had been shattered in 1527 during an uprising in Piazza della Signoria. Unsightly filler is still visible on that portion of the statue.
All of this led to a preliminary assessment of the state of conservation of Michelangelo's masterpiece in 1995, that we can summarize as follows:

  • prolonged outdoor exposure left evident marks on the marble surface, especially those parts that were washed by rain water; there is widespread erosion and loss of shape on the toes on the left foot;
  • the widespread presence of gypsum revealed by the tests leads us to believe that the sulfation of the marble that occurred in the past is still ongoing and is a risk factor for the future integrity of the material;
  • the cleaning done before the David was removed from Piazza della Signoria left consistent residues of gypsum-rich incrustations from atmospheric deposits in some undercuts (armpits, thighs, hair);
  • finally, the tests confirm uneven amounts of waxy, partly yellowed substances that create unsightly streaks and stains.

3 ) The Restoration

Restoration of the David was begun on 16 September 2002.

Preliminary Phases

The restoration, in its preliminary phases, was started by the art restorer Agnese Parronchi and was directed by Antonio Paolucci, Superintendent of the Polo Museale Fiorentino, and Franca Falletti, Director of the Galleria dell'Accademia, with general consulting assistance from Annamaria Giusti, Director of the Stone Materials Section of the Opificio delle Pietre Dure. The physical and chemical tests undertaken prior to the restoration and monitoring the statue's physical state that will continue at periodic intervals are directed by Mauro Matteini, former director of the Scientific Laboratories of the Opificio delle Pietre Dure and currently director of the National Research Council's (CNR) (Istituto per la Conservazione e la Valorizzazione dei Beni Culturali - Institute for the Conservation of Cultural Heritage ). The static tests were coordinated by Luciano Marchetti, Regional Superintendent for Umbria, with the assistance of Eugenio Chellini
The cost of the restorations (€165.000,00) is being completely covered by Ars Long Stichting, a Dutch non-profit foundation.
The diagnostic and monitoring programs are sponsored by Friends of Florence that is also producing a DVD and a Website about the project.

The restoration and testing programs have been planned so as not to interfere with the view of the statue: the Centro Ricerche Fiat designed a special, raised mobile platform and FIAT S.p.A. donated it to the Galleria dell'Accademia.

The restoration also calls for a long-term maintenance program relative to the statue and the room where it stands.

The first phase of the project consisted of historical research. The results are presented in a detailed, chronological report and some summaries arranged by subject (corrosion and surface deposits – stability – breaks).
The project used an avant-garde tool: a three dimensional computerized model built using the data obtained from the laser scans done within the context of the Digital Michelangelo Project and then adapted to the specific needs of the restoration work. This tool was used to store the data and results (e.g. archive of the data obtained from the mapping and the individual tests) and as a base to acquire specific knowledge of the statue's dimensional and geometric features (e.g. determining the center of gravity, volume, weight and height) and finally for simulations with specific goals (e.g. simulations of the areas with greater and lesser exposure to rain for the surface roughness analyses).

The second phase, of mapping the state of degradation was done by the restorer via direct visual inspection.
After having identified the five main views of the three dimensional model (Front – Back – Right – Left – Top) the surface of the David was divided into 68 areas that were photographed with a digital camera.
Four transparencies were made for each A3 format photographic print, showing the four different types of damage found (original defects in the marble – surface deposits – breakage – traces of carving); all the transparencies were then transferred from paper to computerized supports using the 68 areas of the three dimensional model.

The third phase consisted of actual scientific analyses.
The testing program comprises three different sections: tests on the environment, on the surface of the statue and on the fragments of marble from the toe that was shattered in 1991. The surface tests were performed on ten sampling areas. The exact positions of the sample areas were documented on photographic and digital images and by making casts of the area in order to be able repeat the tests on the same points in the future. Many tests were also conducted on numerous other points that were considered significant.
Each research team produced an analytical report of its work and findings. Then two maps were constructed on each of the five main views: one showing all the test points and the types of tests and analyses performed, the other showing the results concerning the three main substances found on the surface (gypsum – wax – oxalates).
Then, a final report was written when the tests were completed.

A separate analysis dealt with the static problems of the sculpture and its base. This study, which is not yet complete, has – thanks to the three-dimensional model – acquired data concerning the statue's weight and center of gravity.

Operational Phases

The second phase of actual work on the statue began on 1 September 2003. The restorer, Cinzia Parnigoni is currently doing the light surface cleaning as planned.
The Superintendent of the Opificio delle Pietre Dure, Cristina Acidini and the Director of the Stone Materials Department, Laura Speranza are providing general consulting on the project.
The work, that is being done mainly between 2:00 and 9:00 p.m. on the days the museum is open to the public and all day Mondays, is scheduled for completion by May 2004.
When visitors are in the museum the restorer works on scaffolding situated on one side and towards the middle of the statue's back in order to be as unobtrusive as possible. When the museum is closed she uses the mobile lift that was designed and donated by FIAT and already used during the first phase of the restoration in order to work on the front of the statue.

Cleaning Tests Performed Since 1 September 2003

Michelangelo's David does not have conservation problems that would be a cause for major concern. However, during the course of its long history it has suffered a series of damages of various types and origin that visibly mar the surface. There are three main types of alterations: incoherent dust deposits on the entire surface, sulfatation residues consisting of gypsum, many small streaks of yellowish wax. Even in the dust deposits there is gypsum, albeit in limited quantities, but it is still a hazard and a threat to the future conservation of Michelangelo's masterpiece.
In order to be able to eliminate these three categories of foreign substance safely, cleaning assays were performed on various parts of the surface that differ as to state of conservation (highly abraded and smooth areas) and type of workmanship (finished and unfinished areas).

Dust deposits and gypsum residues

To remove these substances, the restorer uses only distilled water and develops the most appropriate methods to obtain optimum results for each area.
The poultice consists of cellulose pulp and sepiolite, The combination of the two materials and their respective merits guarantees good absorption and high malleability which, in turn, improves adhesion and makes it possible to reduce the thickness of the poultice. A sheet of Japanese paper is used between the poultice and the statue to prevent the cellulose and pulp from coming into the direct contact with the marble and leaving residues on it. The poultice is left in place for 15 minutes and then is removed. The application time was tested on 3 March by the restorer Cristina Samarelli of the Opificio delle Pietre Dure. The scientific analyses confirmed a consistent reduction in the amount of gypsum and therefore, it is the minimum time that guarantees the attainment of the project's priority goal in terms of conservation.
The still damp surface is then gently wiped with a small, absorbent cotton swab according to how much dirt there is and the desired level of cleaning. Swabbing is not needed where the poultice alone has achieved sufficient cleaning.
This is the phase in which cleaning must be fine measured.

Wax Stains

There are wax stains on very small areas of the David's surface and required totally circumscribed treatment.
After the dust and gypsum are removed, the area with wax stains is wetted to saturate the marble's pores. This is a precautionary measure to prevent even a minimal part of the wax from penetrating the stone when it melts. Then the stain is cleaned with a small swab saturated with petroleum ether , taking care not to go beyond the perimeter of the stain.

  Photo 1 - The first test was done on the left arm between the area that was highly corroded by rain and the smooth area. The results show that with identical treatment the rougher part retains more dirt than the smooth part. This happens because the poultice does not adhere to the rough surface as well as it does to the smooth portion. For the time being these slight differences will be left as they are; decisions will be made later as to whether or not to continue cleaning with additional distilled water swabbing.
  Photo 2 - This area consists of surface corroded by leaching and a section (on the strap) that was carved in steps. Therefore, it is a matter of testing the response to the poultice on adjacent parts with different surface features.
The cleaning results were quite satisfactory. The careful swabbing made it possible to eliminate the unsightly black stain without excessively cleaning the surrounding area.
  Photo 3 - The area (upper left part of the back) has rainwater stains in the form of alternating light and gray streaks of dusty deposits. The goal is to attenuate the different tones insofar as possible and to eliminate the stripe effect. This is achieved by swabbing only the lines of the deposits and not the clean area.
  Photo 4 - The area (the trunk supporting the right leg) has some unsightly wax drippings. Here the surface is very rough, due to leaching and the fact that Michelangelo used a different sculpting technique. Like the slingshot, the trunk was probably gilded. Here the solvent has to remain in place longer because the stain is very thick. Upon completion the residues are barely noticeable.
  Photo 5 - A poultice is applied to the surface over a sheet of Japanese paper.
  Photo 6 - The poultice has just been removed. Note how the cleaning is so minimal that the moisture stain is still visible.
  Photo 7 - To eliminate the traces of the moisture stain, it is sufficient to wipe it gently with an absorbent cotton swab.