S. MOREL, HORIBA Jobin Yvon S.A.S, France

For the non-destructive characterization of works of art and archaeological materials, a range of methods can be used, depending on the degree to which the material under investigation can be sampled, is accessible for analysis and the structural complexity of the compound of interest. Since often highly heterogeneous materials need to be investigated, methods allowing the information to be extracted from selected areas with a good spatial resolution are strongly favored. Likewise, instruments that can be employed in galleries, in store rooms or directly in the field where large artifacts are displayed or preserved offer additional flexibility.

Among the methods offering elemental information, micro-XRF (X-ray fluorescence) spectrometry is one of the few techniques with which it is possible to obtain spatially resolved information in a non-destructive manner on major and minor constituents of a variety of materials. On the other hand, by means of micro-Raman spectrometry, in a similar manner, highly-specific identification of molecular species is possible.

In recent year, a number of technological developments have favoured the improvement of spectroscopic systems which have become very efficient and flexible for a very wide range of applications, including Art.

X-ray microscopy with a resolution as low as 10 microns, will inform the specialist on the elemental composition of the pigments or materials. This technique is used to determine the quantity and repartition of Au, Pb, Hg, Cu etc in painted manuscripts, ceramics, jewellery or pottery. No vacuum is used, thereby preserving the integrity of invaluable objects.

Especially, there have been more and more contributions using Raman spectroscopy to the analysis of art-history items for conservation, restoration, or even forensic field work.

Raman spectroscopy permits the chemical identification of a very large range of compounds (polymer, minerals, pigments,…) without destruction, on a micro or macro scale, beneath glass or other types of transparent covers. A new compact, rugged and more affordable micro-Raman system, the XploRA, now allows micro Raman studies at different excitations to be carried out with an easily transportable unit. Indeed, fluorescence interferences faced in the investigation of art items often makes the use of different laser sources mandatory. Moreover remote analysis can be carried out thanks to efficient probes connected through fibres to the laser and the spectrometer.

In addition, a new route for mapping large paintings without the need for moving them will be described.

Recent case studies are presented to show the interest of these new developments for the application to Art and Cultural materials.