Marble has been widely used in architecture and sculpture since antiquity, but is subject to several weathering processes likely to be accelerated by climate change. Current treatments that slow or prevent damage to these valuable cultural artefacts need refining.
The EU-funded HAP4MARBLE project is developing new approaches to tackle marble degradation which includes soiling, dissolution and bowing. The ‘biomimetic’ approaches are so-called because they imitate natural processes. They are based on hydroxyapatite (HAP), a calcium phosphate that is also found in bone and teeth.
“In spite of apparently being very durable, marble is actually sensitive to several deterioration processes,” explains Enrico Sassoni, a researcher at the centre of the project who is funded through the Marie Skłodowska-Curie actions programme. “Environmental temperature variations cause cracks inside the marble, and rain dissolves the carved surface.”
Sassoni is benefiting from high-level on-the-job support at three host institutions. He is under the supervision of leading figures in the field at the University of Göttingen, Germany and University of Bologna, Italy, with an 18-month stint at Princeton University in the US.
The new HAP treatment being further developed in the three-year project works a bit like glue, strengthening and holding the marble together. The researchers put down ultra-thin layers – a tenth of the thickness of a human hair – so that the protective coating is not visible.
The HAP formulations could help preserve precious monuments exposed to weathering for decades, such as those in Italy’s Certosa di Bologna cemetery. For example, the tombstone of Antonio Basoli, an 18th century artist, is crumbling around the edges in a characteristic pattern called sugaring.
Back in Bologna for the final year of his project, Sassoni is testing improved methods of applying the treatment, such as electrodeposition, which uses electric currents to apply thin HAP layers.
- Project acronym: HAP4MARBLE
- Participants: Italy (Coordinator)
- Project N°: 655239
- Total costs: € 244 269
- EU contribution: € 244 269
- Duration: September 2015 to August 2018