Painting materials and Microanalysis of Fine Arts

Contact person: D. Hradil, Centrum instrumentálních technik, ALMA laboratory (http://www.alma-lab.cz/eng)

Laboratory ALMA is a joint workplace of the Institute and the Academy of Fine Arts in Prague. In the laboratory we study historical as well as contemporary painting materials, processes of their preparation, natural localities of origin and also historical context of their use. We examine their technological properties and chemical interactions in colour layers. In materials themselves and in procedures of their preparation we are able to find specific signs characterizing different regions and periods. These characteristics are thus helpful in the tracing of the artwork provenance.

We are still searching new ways how to find out these materials signs of artworks in a manner friendlier to the painting. Particularly, it includes an application of portable analytical methods with no need of contact with the artwork and no need of sampling. Thus we can collect data more effectively and cheaper, directly at the location of the artwork (not only in relation to its restoration).

In the field of laboratory instrumental analysis of microsamples we pay attention to development of such procedures that minimize the risk of misleading interpretations, which is a common phenomenon in analyses carried out on a purely service basis. Thanks to close collaboration with restorers and art historians we know how to compare and integrate materials, technological and artistic signs within interdisciplinary discussion. Then we are able to relate the artwork with a certain historical period, to interpret its original colouring, or to propose the best possibilities of its further protection and evaluation. 

Legend to figure:

Clay minerals with layered structures represent a common component of traditional earthy pigments. They give very useful properties to the pigment, e.g. the adhesive force to different surfaces. They are also reactive and can be chemically modified. They react with organic binders in the colour layer and thus form organo-clay complexes. Thanks to their structural and chemical variability they also represent sensitive indicators of natural processes of their formation and therefore they can be used as one of indicators of the provenance of materials used by the artist. In our laboratory, we apply an unconventional method of X-ray powder microdiffraction to characterise different clay structures found in microsamples of colour layers. On the figure, there is an example of attribution of one anonymous painting to the Italian provenance based on the presence of characteristic mixed-layered clay structure. A microsample casted in a polyester resin (A), and polished in the cross-section (B) is subjected to non-destructive analysis and the resulting diffraction pattern is then compared with a ground of reference painting of known authorship.

Project Funding

This work is supported by research projects of both institutions that established the joint workplace, e.g. by the project of international cooperation of the Academy of Sciences M200320901 (2009-2011), project of the Ministry of Culture of the Czech Republic DF12P01OVV048 (2012-2015) and Czech Science Foundation project P103/12/2211 (2012-2014).

Selected Papers

•  Švarcová S., Klementová M., Bezdička P., Łasocha W., Dušek M., Hradil D.: Synthesis and characterization of single crystals of the layered copper hydroxide acetate Cu₂(OH)₃(CH₃COO)·H₂O. Crystal Research and Technology 46/10 (2011), 1051-1057.
• Hradil D., Píšková A., Hradilová J., Bezdička P., Lehrberger G., Gerzer S.: Mineralogy of Bohemian green earth and its microanaytical evidence in historical paintings. Archaeometry 53/3 (2011), 563-586.
• Švarcová S., Bezdička P., Hradil D., Hradilová J., Žižak I.: Clay pigment structure characterisation as a guide for provenance determination – a comparison between laboratory powder micro-XRD and synchrotron radiation XRD. Analytical and Bioanalytical Chemistry 399/1 (2011), 331-336 (Paper in Forefront).
• Švarcová S., Kočí E., Bezdička P., Hradil D., Hradilová J. Evaluation of laboratory powder X-ray micro-diffraction for applications in the field of cultural heritage and forensic science. Analytical and Bioanalytical Chemistry 398 (2010), 1061 – 1076.
• Kotulanová E., Bezdička P., Hradil D., Hradilová J., Švarcová S., Grygar T.: Degradation of lead-based pigments by salt solutions. Journal of Cultural Heritage 10 (2009), 367-378.
• Švarcová S., Hradil D., Hradilová J., Kočí E., Bezdička P.: Microanalytical evidence of origin and degradation of copper pigments found in Bohemian Gothic murals. Analytical and Bioanalytical Chemistry 395 (2009), 2037-2050.
• Hradil D., Hradilová J., Bezdička P., Švarcová S.: Provenance study of Gothic paintings from North-East Slovakia by hand-held XRF, microscopy and X-ray microdiffraction. X-ray Spectrometry 37 (2008), 376-382.
• Hradil D., Grygar T., Hradilová J., Bezdička P., Grűnwaldová V., Fogaš I., Miliani C.: Microanalytical identification of Pb-Sb-Sn yellow pigment in historical European paintings and its differentiation from lead tin and Naples yellows. Journal of Cultural Heritage 8/4 (2007), 377-386.