Balancing the risks associated with restoring the world’s masterpieces and frescoes is an art in itself. But a mixed group of experts from Italy and Spain demonstrate that injecting a bit of life — in this case, bacteria — into a painting can work wonders in removing unwanted features a piece gathers over time.

With the help of experts in Italy, researchers at the Polytechnic University of Valencia in Spain used the method on a series of frescoes by the 17th century artist Antonio Palomino in the Church of Santos Juanes in the same city.

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Frescoes lining the church’s walls were nearly destroyed after a 1936 fire and were later restored in the 1960s, according to one press release. But the previous restorers did not anticipate that the dried salt left on the walls from the fire would migrate to the paintings over the years, creating a white, grainy crust over the work. They also failed to remove an excess of hardened glue from where the murals were previously detached.

Seeing the salt layers and glue as threats to the art’s longevity, restoration specialists and scientists sought the help of a team in Italy that used bacteria to gently remove hardened glue from other works. While collaborating, they selected for a species of Pseudomonas bacteria capable of removing and breaking down the dried salt layer.

Other options to restore the frescoes would have required using chemicals to remove the unwanted layer or using physical means to scrape it off. It’s clear that both measures would increase the risk of further damage.

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But the bacteria treatment, placed on the works’ surfaces via a removable gel, did not allow moisture to penetrate or alter other layers of the paintings. Without the gel, scientists say, the bacteria die off. And unlike other restoration approaches, the bacteria pose no toxic threats to individuals using them.

It’s suggested the team also used another type of bacteria to break down the leftover globs of glue as well.

After the bacteria remove the salts, experts clean and dry the surface of the paintings to preserve them for years to come.

Photo by Asociación RUVID via Alpha Galileo