Brussels, 28 Jul 2006
Physicists in Italy have developed a new microwave-based technique for analysing the moisture and salt content of fresco paintings without damaging them - something that was previously impossible. The technique will help restorers to preserve these works of art.
Frescoes - works of art that were painted directly onto walls during the Renaissance period between the 14th and 17th centuries face two main hazards: moisture from the atmosphere and the salt in plastered walls. 'Moisture and salts are the nemesis of frescoes, and their presence should be detected before damages become too serious,' says Roberto Olmi, who developed the new technique with colleagues from the National Research Council in Florence.
Knowing how much of both are present in a fresco indicates the best approach to restoration. Until now, restorers had to drill a hole in the fresco in order to extract plaster and establish moisture and salt content. Holes could not be drilled everywhere, and samples were usually taken from the edge, away from the part whose preservation was considered most important.
The new technique involves a computer-based portable sensor system that can 'feel' below the surface of a painting. A sensor device scans the surface of the painting, sending out microwaves that are absorbed by the water and salt molecules if they are present. A signal is then sent from the scanner to a computer, indicating how much moisture or salt is present.
The tool is called SUSI - Sensore di Umidita e Salinita Integrato, or 'integrated sensor for humidity and salinity'.
SUSI has already been tested on the Paradise Wall fresco in the chapel of Santa Maria Maddalena de Pazzi, and on the frescoes in the cloister of St Antonio at the Convent of St Mark. Both are in Florence.
The technology could be versatile, according to Dr Olmi. 'We have also started to refine the device for use on other types of art. For example, we have used SUSI to measure the humidity and salt content of the famous Robbiane ceramics in the sanctuary of La Verna in Arezzo. However, paintings and old parchment are too thin for the device at the moment and we will need to refine it before we can use it on these kinds of works,' he says.