Clay pigment structure characterisation as a guide for provenance determination—a comparison between laboratory powder micro-XRD and synchrotron radiation XRD
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Application of X-ray diffraction (XRD)-based techniques in the analysis of painted artworks is not only beneficial for indisputable identification of crystal constituents in colour layers, but it can also bring insight in material crystal structure, which can be affected by their geological formation, manufacturing procedure or secondary changes. This knowledge might be helpful for art historic evaluation of an artwork as well as for its conservation. By way of example of kaolinite, we show that classification of its crystal structure order based on XRD data is useful for estimation of its provenance. We found kaolinite in the preparation layer of a Gothic wall painting in a Czech church situated near Karlovy Vary, where there are important kaolin deposits. Comparing reference kaolin materials from eight various Czech deposits, we found that these can be differentiated just according to the kaolinite crystallinity. Within this study, we compared laboratory powder X-ray micro-diffraction (micro-XRD) with synchrotron radiation X-ray diffraction analysing the same real sample. We found that both techniques led to the same results.
KeywordsPowder X-ray micro-diffraction Synchrotron radiation Kaolinite Wall painting Pigment provenance
The authors thank restorer Václav Potůček for providing artwork samples and versatile cooperation. The authors also acknowledge Lubomír Smrčok from the Institute of Inorganic Chemistry SAS, Bratislava, Slovakia, for his valuable help in preparing this paper. This work was supported by the Academy of Sciences of the Czech Republic (AV0Z40320502 and M200320901) and by the Ministry of Education, Youth and Sport (MSM 6046144603).
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