Researchers at the Institute of Heritage Restoration (IRP) and the Polytechnic University of Valencia, Spain, are cleaning 17th-century frescos using what the professional cleaning industry knows as bio-enzymatic cleaners.
Bio-enzymatic cleaners are formulated with specific enzymes and "good" bacteria that essentially digest soils. These products, which are available in different formulations, are typically used to clean restrooms, showers, kitchens, as well as to eliminate odor-causing bacteria in grout and urinal drain pipes.
According to IRP's researchers, these bio-enzymatic cleaners are able to clean works of art "in a fast, specific, and respectful way, as well as being nontoxic for the restorer and the environment."
This project came about because the IRP was having difficulty restoring several murals damaged in a 1936 fire at the Church of Santos Juanes in Valencia, Spain.
The murals had been improperly restored during the 1960s, so the goal of the cleaning project was actually twofold: removing residue left behind by the prior restoration and restoring the murals to their original condition.
"This is a new and obviously very delicate way to clean works of art," says Mike Sawchuk, Vice President of Enviro-Solutions. "But it shows the possibilities available using these [bio-enzymatic] products."
So far, the bio-enzymatic cleaners have been tested on two interior walls of the church, with promising results.

"We will continue the process and improve the technique," says one of the researchers. "In nature, [we find] different species of bacteria that can feed on almost anything" — including, apparently, the grit and soil that can build up on priceless works of art.