They use bacteria to “clean” Miguel’s sculptures …

A group of Italian scientists showed that bacteria release the dirt accumulated in the sculptural groups of the Medici Chapel in Florence, created in the 16th century by Michelangelo. They proved it by an experiment to counter the effects of the deterioration of the marbles of the crypt.

The experiment was conducted in secret by the researchers and focused on the sculptures that line the crypt of the families of patrons and former rulers of Florence which is today part of the tourist and historical complex of this city and known as the Medici Chapel Museum.

The statues were sculpted by Michelangelo Buonarroti (1475-1564), the famous Renaissance sculptor, author of the frescoes in the Sistine Chapel, the monumental sculpture of Moses located in Rome o Pity in the Vatican. For centuries, the statues in the crypt have accumulated layers of dirt that are difficult to remove.

The commission from Michelangelo was carried out by Giovanni di Lorenzo de Medici (son of Lawrence the Magnificent), once Pope Leo X became Pope, in 1513. The problems started in 1595 with the appearance of stains and discoloration in one of the sarcophagi, Alexandre de Medici, murdered by his cousin Lorenzo in 1537, and whose body was wrapped in a carpet and not eviscerated, the decomposition of which eventually spread through the Carrara marble sculptures. Over time, the plasters used to copy the sculptures that embellish the ensemble have also left their mark. Alexander is buried next to his father Lorenzo II de Medici and the group is distinguished by the allegories of Aurora and Twilight at the foot of the statue of the sovereign.

The novelty of the experiment was marked by the use of the bacterium Serratia ficaria SH7, which feeds on glue, oil and phosphates., “as a biological weapon against centuries of coloring”, as detailed The New York Times. This is how before the pandemic and during the second wave in Italy, they used the bacteria to “eat” the stains, although the first test was carried out in the tomb of Giuliano di Lorenzo, Duke of Nemours, whose group was also sculpted by Michelangelo.

Already in 1988, a restoration of the complex had been carried out, which took almost a decade. Most of the stains had been removed (walls marred by centuries of damp and handprints, damage to plasters, and marks from wire brushes used to remove oil and wax), but dirt on the grave and other lingering stains required a different kind of attention, something observed in 2013 by the museum’s former director, Mónica Bietti.

The idea to use bacteria came from a 2016 conference organized by Anna Rosa Sprocati and her team, titled “An Introduction to the World of Microorganisms”, which restaurateur Marina Vincenti attended. Bacteria (strains isolated from wastewater from Sardinian mines) had cleaned the resin residues from the frescoes of Baroque masterpieces in the Carracci gallery in the Palazzo Farnese in Rome.

Previous infrared spectroscopy studies, carried out by the National Research Council of Italy in 2019, revealed traces of calcite, silicate and the like in the sculptures and the two tombs facing each other in the New Sacristy. On this basis, biologist Sprocati from the Italian National Agency for New Technologies, selected the correct strain, from those used to break down petroleum in spills or reduce the toxicity of heavy metals.

The team, made up of Donata Magrini, Sprocati, Daniela Manna, Paola D’Agostino, Bietti and Vincenti, performed limited tests with 8 strains (non-dangerous and spore-free) and after selecting the correct one, they shed some gels with SH7 bacteria on the sarcophagus of Lorenzo di Piero, Duke of Urbino, buried next to his murdered son.

Now, returning tourists can admire Michelangelo’s sculptures and the tomb of Lorenzo II without the grime caused by the hasty burial of the murdered Alexander.