The fall of the Berlin Wall in November 1989 was a seminal moment in 20th century history, paving the way for German reunification. Many segments, both large and small, were preserved for posterityβincluding portions covered in graffiti or murals. A team of Italian scientists used a combination of spectroscopic analysis and machine learning to study paint chips from wall fragments to learn more about the chemistry of the paints and pigments used, according to a new paper published in the Journal of the American Chemical Society.
There has been increased attention in recent years to preserving street art, which is vulnerable both to degradation over time as well as deliberate vandalism. For instance, in 2021, Italian chemists figured out how to use hydrogels to remove added graffiti from vandalized murals in Florence. (Over-painting by vandals is so chemically similar to the original painting underneath that it is difficult to selectively remove just the over-painting without damaging the original.) Unlike most classic masterpieces of the past, created with paints designed to last centuries, street art is more ephemeral in nature, using materials that lack such longevity.
In many cases, like the Berlin Wall, the painters didn't bother to document the specific materials they used, their application techniques, or other useful information that conservators could use to restore or conserve street art. Modern painting materials are also much more complex, and manufacturers typically do not report specific information on the composition of those materials.
Β© Thierry Noir/CC BY-SA 3.0
The US Capitol building in Washington, DC, is adorned with multiple lavish murals created in the 19th century by Italian artist Constantino Brumidi. These include panels in the Senate first-floor corridors, Room H-144, and the rotunda. The crowning glory is The Apotheosis of WashingtonΒ on the dome of the rotunda, 180 feet above the floor.
Brumidi worked in various mediums, including frescoes. Among the issues facing conservators charged with maintaining the Capitol building frescoes is delamination. Artists apply dry pigments to wet plaster to create a fresco, and a good fresco can last for centuries. Over time, though, the decorative plaster layers can separate from the underlying masonry, introducing air gaps. Knowing precisely where such delaminated areas are, and their exact shape, is crucial to conservation efforts, yet the damage might not be obvious to the naked eye.
Acoustician Nicholas Gangemi is part of a research group led by Joseph Vignola at the Catholic University of America that has been using laser Doppler vibrometry to pinpoint delaminated areas of the Capitol building frescoes. It's a non-invasive method that zaps the frescoes with sound waves and measures the vibrational signatures that reflect back to learn about the structural conditions. This in turn enables conservators to make very precise repairs to preserve the frescoes for future generations.
Β© Nick Gangemi
