If murals or street art are defaced with graffiti, restoring them can be a challenge. But now there is a hydrogel that can remove a layer of graffiti within minutes, without altering the work underneath – even when the art and overlying graffiti use the same type of paint.
Michele Baglioni at the University of Florence in Italy and his colleagues have developed a system that allows cleaning agents to remove just the top layer of paint, which is only a few microns thick.
The team’s technology comprises a cleaning fluid held in a hydrogel, a material that consists of long molecules forming a network that is hydrophilic, meaning it has an affinity for water.
Unlike other gels – such as jam and hair gel – which can spread, change their shape and leave residues in their wake, the hydrogel the team used is made from a network of polymers with a fixed shape.
“The strength of these kind of gels is that they do not leave residues on the surface they clean, which is something that is different from the majority of gels which are used also in [art] conservation,” says Baglioni.
The hydrogel allows only small amounts of cleaning fluid to seep out when it is applied to a painted surface. “This helps in controlling very finely the cleaning action,” says Baglioni.
The cleaning fluid consists mainly of water, with nano-sized droplets of organic solvents as well as detergent-like surfactant materials.
The solvents are targeted at three classes of polymers that are commonly used as paint binders: acrylic, vinyl and alkyd polymers. The solvents cause the paint to swell, allowing it to be removed from a surface.
Depending on the thickness of the paint and its age…
