Focus

CARAMEL are our monuments getting blacker? by Cristina Sabbioni

It is known that changes are taking place in the composition of the atmosphere and in the resulting impact of multipollutants on the environment and land. Cultural heritage is particularly vulnerable to such changes.
The results of the EC-financed CARAMEL project, wound up in 2003, showed that carbonaceous particulate has now become the main damage factor on the architectural and archaeological heritage.
Measurements performed in a number of European cities (Milan, Rome, Paris, London and Seville), both in the atmosphere and on monuments, have proved that the blackening of surfaces is increasing and is attributable to automobile traffic.
The data were obtained thanks to an innovative methodology for the measurement of the carbon component in stone materials, monitoring campaigns in the proximity of monuments (such as Milan Cathedral and S. Maria del Fiore in Florence) and assessments of the visual perception of monument blackening by the public (tourists and inhabitants).
It has also been demonstrated how the composition of the damage layers responsible for the blackening of the architectural heritage is changing, which imposes the need for suitable cleaning techniques.
The results achieved underscore the urgency of adopting air quality thresholds that are compatible with the preservation of the Cultural Heritage, in order to avoid irreversible damage, escalating restoration costs, and the gradual disappearance of our monuments under a cloak of blackness.