stylistic:style_transfer, information:filtering, structural:summarization
Conservation

Officials responsible for the artistic heritage of Florence had become concerned about the David' s physical state by the middle of the 19th century. A cleaning of the statue had apparently occurred about 1746, and in 1813 the sculptor Stefano Ricci gave the statue a gentle cleaning and applied a thin coat of encaustic, consisting of beeswax, possibly mixed with linseed oil, to its surface as a protective coating. The sculptor Lorenzo Bartolini recommended in 1842 that a thorough conservation of the statue should be performed, and, like most of the advisory committee formed in 1504, that the David be moved to the Loggia della Signoria for its protection. In 1843 the sculptor Aristodemo Costoli cleaned the statue with a 50 per cent hydrochloric acid solution that removed the encaustic coating and left the marble surface pitted and porous, damaging the statue far more than the weathering it had suffered in the previous 400 years.

During World War II, David, along with Michelangelo's other sculptures in the Accademia, was packed in sand and entombed in brick to protect it from being damaged.

In 1991, the left foot of the statue was damaged by an unemployed Italian man named Piero Cannata, who was carrying a hammer he had hidden under his jacket and broke off the tip of the second toe. The samples obtained from that incident allowed scientists, utilising spectroscopic, isotopic and petrographic analysis simultaneously, to determine that the marble used was obtained from the Fantiscritti quarries in Miseglia, the central of three small valleys in Carrara. The chemists and spectroscopists who conducted these tests say the marble of the David consists entirely of the mineral calcite.

Because of the marble's surface degradation, on the eve of the 500th anniversary of the sculpture's unveiling in 2004 the statue was given its first major cleaning since 1843. A scientific committee was formed to advise in the restoration. The committee was composed of university professors and scientists from the Consiglio Nazionale delle Ricerche (National Research Council) and the Opificio delle Pietre Dure, a government art-restoration department. They carried out tests and analyses and determined that the statue should be cleaned by poultices soaked in distilled water and applied to the sculpture's surface. Agnese Parronchi, the restorer originally selected by Florentine museums superintendent Antonio Paolucci, assessed the David' s condition herself by examining hundreds of photographs and performing a series of tests. Consequently, she opposed the committee's pre-specified method, fearing further deterioration, and insisted that it should be cleaned dry, with soft brushes and motorized erasers. Paolucci demanded that she use the wet pack method instead, but Parronchi refused. After Parronchi resigned, restorer Cinzia Parnigoni undertook the job of restoring the statue under the direction of Franca Falletti, director of the Accademia Gallery.

Researchers at the University of Siena (Università di Siena) performed an investigation of the small cavities, about a millimetre in diameter and of irregular distribution, with which the marble surface of the David is covered. Their macroscopic examination determined that the cavities have not resulted from deterioration of the stone, but rather that they can be attributed to the mineralogical structure of the marble taken from quarries in the Apuan Alps. The local quarrymen in their dialect call those less than a millimetre in size taròli and those several millimetres or larger they call tarme. Observation with optical fibres and magnifying lenses shows that the marble immediately surrounding the cavity may present milky white or greyish "halos" averaging a few millimetres wide. Many of them are completely or partly filled with various substances; this deposition is caused by the statue's exposure over centuries to atmospheric agents or to past restoration processes.

As of 2024 temporary scaffolding is erected around the statue every two months and in an operation that takes a half a day, dust and spider's webs are removed using soft-bristled brushes of various sizes and a bristle tipped vacuum cleaner.