On the upcoming November 28th, the restoration of the Church of Santos Juanes will be inaugurated, and the cleaning of Palomino’s frescoes covering the vault has been crucially aided by bacteria, bacteria trained to complete in three hours a task that would have taken a restorer hours of scalpel work. Bacteria trained in just 24 hours to obtain the carbon they need from the material aimed to break down; in the case of the Church of Santos Juanes, bacteria trained to destroy rabbit glue applied more than sixty years ago, solidified, insoluble, and impenetrable without the help of microorganisms.

The origin of biocleaning is water bioremediation, the fight against oil spills with microorganisms capable of degrading tar. Pilar Bosch, with degrees in Biological Sciences and Fine Arts, comes from a long line of restorers and successfully tackled the problems faced by professionals trying to restore the vault of the Santos Juanes.

Pilar Bosch has an office at the Polytechnic City of Innovation, where, surrounded by flasks and bacterial culture plates, she explains: “The frescoes of Santos Juanes were removed in the 1960s because they had suffered a fire during the Civil War. At that time, removal was in fashion. It was a way of intervening in that era. To remove them, they would place a cloth and a layer of rabbit glue, a material that sticks to the fabric, and when removed, the paint layer comes off, leaving only the wall. It was a team from Barcelona. They took it to Barcelona and worked on it there. They placed the paintings on panels and then brought them back here.

On the round trip, a lot of information was lost and the methods at the time were not the best. When the intervention proposal reached us, the paintings were full of glue residues and also soot, the result of the fire. If you remove the glue immediately after detaching the paint, it is very simple; it is soluble and dissolves in hot water. But when many years have passed, several interventions have taken place, and numerous physico-chemical processes have occurred, the glue hardens and becomes insoluble. There was no way to remove it with normal physical and mechanical methods because it had to be scraped and it was a very complex process. I was conducting a study on the biodeterioration of the church when I was informed about the matter. It happened that I went to Barcelona for a conference where Giancarlo Ranalli, a very prominent Italian researcher and biologist, presented his work with bacteria on paintings detached from the Camposanto Monumentale in Pisa, which had suffered a fire in World War II.

This is what happens to me, I told myself. I went to talk to him. Then I went to Pisa, learned the technique, and then adapted and improved it to apply it here in Valencia. I had to change the application system because we work on-site. We kept perfecting the system, and now we use it as just another restoration technique.”

How does biocleaning start?

“We look for microorganisms in nature that produce metabolic reactions that can benefit us to clean certain substances. For example: There are organisms that eat glue, others that eat inflorescences, others that eat paper. They don't eat directly; they produce enzymes that deteriorate those substances, excreting enzymes that break down the chains making up that glue, cutting it into little pieces, and then it is very easy to remove. To apply biocleaning, we use some seaweeds that are used in cooking to make jellies or jams, and this product allows us to apply the bacteria and keep them moist that they need to stay alive without moisture penetrating the deep layers of the paint and affecting the wood."

Those are trained bacteria.

"Bacteria learn to eat glue. I put them to grow in a flask with a basic mineral medium and tail. So they have the minerals they need to grow and the source of coal they have to pull out of the tail. We have also cleaned salt inflorescences in the church, which are mainly nitrates, and then I use denitrifying bacteria, bacteria that are capable of transforming nitrates into nitrogen. To grow, I give them another growing medium that forces them to eat nitrates. With this formula, bacteria do their job in three hours. We are not using toxic chemicals or aggressive physical, chemical or mechanical means. The alternative is a restorer with a scalpel removing it. And it must be taken into account that the vault of the church of Santos Juanes is almost 500 square meters."

The inauguration of the rehabilitation of the Church of Santos Juanes will be the debut of the technique developed by Pilar Bosch, but similar systems promise future interventions. In Valencia, the same technique has been applied to some lunetos of the Church of San Nicolás, which were also removed using rabbit glue. Pilar Bosch's team has carried out biocleaning tests on the Serranos and Trinidad bridges to combat salt efflorescence, as they have also done in Santiago de Compostela. “At the moment,” she explains, “we are developing a project funded by the ministry to find bacteria capable of cleaning graffiti and resins. We are in an early stage. Graffiti is very complex. Its composition includes different resins, pigments, additives… Among the resins, there are acrylic, methylcellulose, and a wide variety. We have to find a microorganism capable of degrading these substances, one that is not pathogenic and does not sporulate, that does not produce spores to to prevent them from reproducing later.”

Other researchers have paved the way: “There is a lot of literature on microorganisms capable of degrading different products.” “There was a time when a lot of a resin called Paraloid was used, but over time it yellows,” she continues, “we have found bacteria in the Paraloid that we now cultivate because we already know they are good for removing that layer.”

And she explains that “in Italy, these biocleaning systems are used to remove black crusts on monuments, crusts that form from pollution, the sulfates in the environment. Bacteria capable of degrading sulfates are used, but they have to work for several days.”

Her team is now working with products designed to protect monuments exposed to the elements, and the Ciudad Politécnica de la Innovación allows her to access a nearby chemical laboratory where they supply nanoparticles as easily as a neighbor asking for sugar. “The possibility of restoring Goya's canvases is complicated because pigments can be harmful to bacteria,” he adds. The public does not quite grasp the virtues of bacteria; people think they are harmful, “which is why I like to remind them how healthy probiotics can be,” she concludes.

THE PROBIOTICS FROM ART