Hand-held Xrf for the Preliminary Screening of Early Romanesque Frescoes in Slovakia

Within the investigation of historical paintings, portable X-ray fluorescence (XRF) can successfully be used for a non-invasive screening that involves basically describe inorganic pigments and locate repaints, retouches and surface alterations. In combination with imaging techniques, e.g., IR-reflectography, such a screening could effectively reduce further sampling and select areas important for detailed investigations. In a case of paintings, the description of layer stratigraphy and painting technique is limited when using only non-invasive tools. Elements located in underpainting and ground layers are usually found as accompanying in whole measured area. Within our study, hand-held XRF was used for the screening of a cycle of Early Romanesque frescoes in the single nave church of St. George at Kostoľany pod Tribečom, Slovakia. After the first stage of the prerestoration research coming out from non-invasive measurements and microanalysis of very limited amount of samples, we were able to distinguish the relics of full-area 19 century re-paints by zinc and barite whites and also partly re-established the original colouring of paintings based namely on the detailed screening of Cu and Pb. Copper-based pigments were almost totally washed-out from the painting and the original green and blue colours turned to yellow and light grey, respectively. Low concentrations of Cu can now be detected only by portable XRF when integrating the measured area of ca 2mm or more. Blackened parts containing lead was finally interpreted as conversion of red lead (Pb3O4) to plattnerite (PbO2) and cerussite (PbCO3). INTRODUCTION Unique wall paintings at Kostoľany pod Tribečom, Slovakia, were uncovered in the sixties of the 20 century. Archaeological, construction-historic, art-historic and restorer research were taken out within the reconstruction of the church in fifties of 20 century [2, 5, 7]. It was found out that the single nave church with rectangular presbytery was not built later than in the 1st half of the 11th century. The wall paintings, probably painted shortly after the church was built, were badly damaged during a thousand years of their existence. According to literature, they had been several times over-painted. In the 16th century the church burned out and it had not been repaired for a long time so rainwater poured in and most of the top cycle of paitings fell off. After the last building reconstruction in fifties of 20 century, the wall paintings were further faded, damaged by varying humidity and smudged by candle smoke, because of their insufficient preservation and unfavourable climatic conditions. The relative humidity inside the church, still regularly used for services, is high even during dry periods of the year and fluctuation in temperature plays an important role as well. Within the first stage of our investigation, visual inspection of the frescoes was combined with imaging techniques (UV luminiscence, IR reflectography) and non-invasive analytical measurements. In limited amount, microsamples were then taken to describe the layer stratigraphy in areas of the most importance. The aim of the work presented here was to distinguish original paints and re-paints and to describe the alteration processes causing numerous colour changes of frescoes. 1 9th International Conference on NDT of Art, Jerusalem Israel, 25-30 May 2008 For more papers of this publication click: www.ndt.net/search/docs.php3?MainSource=65