After eight years of work, the cleaning of the New Sacristy of the Medici Chapels, designed and conceived by Michelangelo, was completed., and which is located in the Basilica of San Lorenzo in Florence, and in which a team made up of women used an innovative bio-cleaning technique with colonies of bacteria to remove dirt accumulated.
Cleaning work has given a new light to one of the masterpieces of Michelangelo, which began in 1520, at the will of the second Medici pope, Clement VII, and lasted until 1534 to build the tombs of Lorenzo, Duke of Urbino and Juliano, Duke of Nemours and in which two of the most powerful stand out. and dramatic sculptural groups sculpted by the genius of the Renaissance representing Day and Night and Dawn and Twilight.
This intervention stands out from the group of the Bargello Museums, which manage these spaces, “has allowed recover color values of the walls of the New Sacristy, the sculptures and deepening technical knowledge that today allow us to better understand the construction phases and the method that Michelangelo applied in carrying out the work “.
For this restoration that they define as “long and complex” was vitally important “a campaign of specific investigations and the use of an innovative bio-cleaning technique developed by the ENEA group, used for the first time in the masterpieces of Buonarroti (… ) So what uses bacteria colonies to clean the marble of the signs of aging “.
The restoration of the Sacristy had a brief first phase of intervention on the marble vestments in 2013, but it was between 2016 and 2020 when the most conspicuous works were carried out, they explain. In collaboration with the National Research Council (ISPC-CNR), significant areas in each sculpture for colorimetric and reflectance measurements of the marbleFor example, the sarcophagus of Lorenzo Duque de Urbino was altered by dark spots that extended throughout the entire base, identified as oxalates and organic materials and traced to organic liquids leaked to the outside of the sarcophagus in correspondence with these points, which It dates back to the burial of Alejandro de Medici (son of Lorenzo Duque de Urbino), who after being assassinated was buried without being gutted, as was the custom at the time of the Medici dynasty.
For the removal of these organic stains and others of diverse origin, such as phosphates, gypsum, traces of silicates, traces of calcium oxalate, some bacterial strains have been identified that are capable of selectively removing these deposits, without influencing their action on marble. After testing eleven different bacterial strains on small test pieces, the three “best” ones were chosen to proceed with the biological cleaning of the sarcophagus, they explained.
In the different points of the sarcophagus, packets of cells of the strains Serratia ficaria SH7, Pseudomonas stutzeri CONC11 and Rhodococcus sp Z-CONT have been applied, immobilized in a special gel that maintains adequate humidity for the bacteria and gives a correct consistency to apply and remove it easily, leaving no residue.
“They applied very hungry bacteria to support their appetite for organic substrates to eliminate and to make the bio-cleaning treatment more effective “, they added.” After cleaning we can once again enjoy Michelangelo’s exceptional use of sculptural technique: expression of his intimate relationship with marble and its capacity to transform it into light. The constant change in the texture of the marks left by the tools used gives life and throbs “, commented restorer Marina Vincenti.