‘Miracle’ microbes restore gleam to Michelangelo marbles in Florence
IN THE darkest months of the pandemic, a team of scientists and art restorers in Florence unleashed a bacteriological bioweapon on Michelangelo masterpieces in the Medici Chapels to clean them of centuries of grime.
A trio of oil, glue and consuming microbes employed by the team have successfully eaten away at stains and residues on the marble sculptures inside the mausoleum that Michelangelo designed for the Medici at the Basilica of San Lorenzo.
On Tuesday, Medici Chapel officials will release new details about the experiment’s efficacy, disclosing how innovative biological technology can help restore delicate art marred by the passage of time.
The little-known bacteria used to clean up the works were sourced from humble surroundings.
One was Serratia ficaria, known as SH7, which had been isolated in an abandoned Sardinian lead and zinc mine, another was Pseudomonas stutzeri CONC11, which came from a tannery near Naples, and the third was Rhodococcus sp. ZCONT, discovered in diesel-contaminated soil near Caserta.
After just two overnight sessions, the microbes had removed grime present for 500 years in the New Sacristy, which houses the largest concentration of Michelangelo’s works in one location.
“In theory, we believed it would work because we were using microorganisms that we know have certain applications,” said Annarosa Sprocati, who led a team of microbiology researchers from the Italian National Agency for New Technology.
“But it was beautiful when we took the xanthan gel packs off the statues and could see the packs were no longer white but had turned a horrible colour. We knew it had been successful.”
It took the team of scientists, museum officials and restorers eight years of analysis, diagnosis and testing to determine how best to solve the problem inside the funeral monument.
Diagnostic tests such as infrared spectroscopy helped researchers determine that contaminants were originating from the tomb of Lorenzo, Duke of Urbino, and were made up of silicate, calcite and various organic phosphates.
Researchers determined that the culprit was the corpse of Lorenzo’s son, Alessandro de Medici, who had been assassinated by a cousin and then improperly buried in his father’s tomb, without removal of his internal organs.
As the Duke of Florence decomposed, stains seeped into the white Carrara marble favoured by Michelangelo. The miracle microbes, however, made quick work of him.
“They basically ate Alessandro,” Ms Sprocati told The Sunday Telegraph. “But of course more than 500 years have gone by, so there was a transformation over time of these organic liquids that had completely traversed the marble.”
The reduced hours of Florence’s museums during the Covid-19 crisis gave the team of scientists and art experts the perfect opportunity to carry out a top-secret experiment – they arrived in lab coats and white gloves to apply the microbes on an obscure patch of marble behind the sarcophagus in the Medici Chapel.
After seeing positive results, they later applied the microbes to entire sculptures. Today, tourists eager to put the pandemic behind them will have the bacteria to thank for the new gleam on Michelangelo’s marble masterpieces.