KFKI Research Institute for Particle and Nuclear Physics of the HAS

H-1121 Budapest, Konkoly Thege út 29-33 – Hungary

Tel. +36 3959289 - Fax: +36 3959151

E-mail address: sznagy@rmki.kfki.hu

The preservation and conservation of our cultural heritage has become one of the main concerns today all over the world. In particular there is an increasing need for non-destructive investigations, as sampling from the unique and precious objects of art and archaeology. In addition to the conventional analytical procedures, techniques utilising nuclear instruments and methods play increasing role in this field. The small, portable X-ray fluorescence (XRF) spectrometers using radioisotope excitation allow in situ analysis in museum, galleries, on even on field.

Utilising this elemental analytical technique selected areas of the object are exposed to the primary X-rays emitted by the radioactive excitation source. As the consequences of the interaction of these X-rays with the material of the object so called characteristic X-rays are induced. By accurate measurement of the energy of these secondary X-rays the chemical element composing the sample can be identified, while careful analysis of the X-ray intensities can provide quantitative data about their concentrations. Due to the very small energy given to the irradiated volume, not any deterioration, damage or destruction of the analysed surface can be observed. This non-destructiveness together with its multi-elemental character, that is numerous elements can be detected simultaneously, makes this method so promising.

In this talk the main features and performance of our portable XRF spectrometer is described and illustrative applications are presented with special attention to the study of paintings. Taking the elemental map of regions of different colour conclusions on the composition and kind of the paints used by the artists can be drawn. The detailed knowledge of the “palette” of a painter could certainly be very important and useful for artists and art historians, but the most frequent question of the public that is whether a particular painting is a forgery, or an authentic one, can not be answered in general on the basis of the elemental compositions. There are, however, a few special cases, when the presence of a particular paint provides unanimous evidence for the age of the painted spot. One of the most known example is the identification of the presence of titanium at white coloured spots. Taking into account, for instance, that titanium white (TiO2) is available since about 1920, only, its presence provides an indisputable indication for either forging or later repainting. The decision, however, is not always easy even is this “simple” case. The difficulties caused by the simultaneous presence of Ti and Ba (a very frequent component white paints) are also discussed.

Z. Szőkefalvi-Nagy, I. Demeter, A.Kocsonya, I. Kovács: Non-destructive XRF analysis of paintings, Nuclear Instruments and Methods B 226 (2004) 53-59.