Sometime before 600 BC, Mayan artists painted one of the few frescoes–still in existence–that displays the domestic life of normal people in this ancient civilization (other Mayan frescoes display the lives of deities and rulers). The frescoes were found in a pyramid at the Calakmul archaeology site in Mexico. Calakmul is one of the biggest Mayan sites around, but it hasn’t been excavated to the same extent as say, Tikal, which had a cameo in “Return of the Jedi” as the Ewok planet and is also host to a constant throng of tourists.
As they work, archaeologists at Calakmul have tried to protect the wall frescoes from the subtropical climate of Mexico, but a mixture of light, temperature, humidity and sulfate-based pollution was starting to hurt the precious frescoes. That’s where Piero Baglioni comes in. He’s a physical chemist at the University of Florence, who has earned a certain amount of fame for his development of nanoparticles that can clean up frescoes harmed by pollution or by other restoration attempts. In particular, the nanoparticles can deal with the salts that lead to pigment deterioration and flaking of the frescoes. (Baglioni’s nanoparticles can also help reverse ill-thought-out attempts to protect frescoes by covering them with vinyl or acrylic polymers, a problematic restoration technique that can cause complete powdering of a painting. As recently as a decade ago, polymers were widely applied to give frescoes some water repellency but they’ve caused havoc at other Mesoamerican sites, including Tehotihuacan and Mayapan, Baglioni says.)
In the case of Calakmul, the frescoes were suffering from sulfate salts, but six months after application of a “humble” calcium and barium hydroxide nanoparticle solution, flaking of the frescos was reduced (Chem. Eur. J. 2010, 16, 9374).
See the before (left panels) and after (right panels) below.