Artwork to be studied via non-invasive spectroscopy

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Precious works of art could soon be studied and preserved by a non-invasive laser technique developed by UK and Italian scientists. The method, known as micro-Spatially Offset Raman Spectroscopy (micro-SORS), allows layers of paint to be analysed without causing any damage to the artefact. It is anticipated to have a huge impact on cultural heritage, as precious pieces of art could be preserved and authenticated without being harmed.

Scientists from both the UK’s Science and Technology Facilities Council’s (STFC) Central Laser Facility and Italy's Institute for the Conservation and Valorisation of Cultural Heritage (ICVBC), have tested this laser technique on artwork dating back several centuries. Tiny flakes of paint were analysed from religous murals and sculptures housed in devotional chapels in Northern Italy. Known as Sacred Mounts, these chapels were built several centuries ago and are currently undergoing restoration.

Last year, the international team demonstrated that the non-invasive method could analyse artificially prepared layers of paint, but this is the first time they have successfully applied it to real objects of precious art.

Micro-SORS is derived from traditional Spatially Offset Raman Spectroscopy (SORS), which was developed by UK researchers at the STFC’s Central Laser Facility. Not just useful for studying artwork, the technique has also been demonstrated to detect bone diseases non-invasively, as well as analyse the contents of opaque bottles without opening them

‘What [SORS] allows us to do in addition to just doing ordinary Raman spectroscopy, is to probe opaque media − by that I mean diffuse scattering media such as skin tissues, powders, or opaque bottles that you cannot see through − and to probe them in depth or through the wall barrier,’ explained Professor Pavel Matousek, a STFC Senior Fellow who origionally developed the technique. ‘Conventional Raman would be only applicable to the near surfaces of these objects,’ he said.

The new micro technique combines SORS with microscopy concepts, allowing scientists to analyse the chemical composition of artwork at a greater depth than has been possible before. Laser light is used to probe through the surface layers, and a small number of photons will scatter back with changed colour, according to the different paint components they represent.

Crucially, the technique can identify any areas of decay in the materials beneath the paint, and also pinpoint any earlier conservation work that may have been carried out.

According to the researchers, the technology would have a major impact on the area of conservation of artwork, where no effective tools for analysis currently exist. The team hopes to develop a portable piece of equipment able to test precious works of art without needing to take samples.

‘Micro-SORS promises to make a major contribution to the knowledge and conservation of artworks. We will continue to work with our colleagues at the STFC to take forward this important research. Our ultimate goal is to turn the micro-SORS technology into a portable device that can be also used in the field,’ Dr Marco Realini from the ICVBC said.

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