Nanofluids confined in chemical hydrogels for the selective removal of graffiti from street art

The main challenge in the conservation of street art is the selective removal of graffiti (i.e. tags, writings and overpaintings) from the original artwork. Nowadays, the effective methods available for this intervention involve risking damage to the original. The novel combination of nanofluids with highly retentive pHEMA/PVP chemical hydrogels is proposed as a controllable cleaning method for selective removal of graffiti from street art. Nanofluid-loaded hydrogels were tested on laboratory models simulating street art paintings covered in graffiti. The outcome of cleaning tests was investigated by means of visual, photographic and microscopic observation, and micro-reflectance FTIR spectroscopy. It was shown that the proposedmethodology is effective in removing acrylic-, nitrocellulose- and alkyd-based graffiti without damaging the underlying paint. This can be achieved by means of a gradual swelling action performed by the nanofluid, which is limited to the surface layers by the retentive power of the hydrogel.