Materials in historical paintings, their provenance and causes of degradation
During the history, painters used various materials (both natural and artificial) and applied them in specific ways, witnessing the historic period and also the region where they worked or they were trained in painting. Each genesis leaves traces such as contamination by by-products formed during the manufacturing process, specific combination of minerals, their kind and crystallinity corresponding to the conditions of their geological formation and depositing, accessory minerals typical for some type of geological locality, or typical morphology. Knowing the historical context of the use of painting materials and their specific signs, we contribute significantly to tracing of artwork’s provenance. As an example we can mention the so far neglected clay-based pigments, which were often obtained from local sources due to their cheap availability in nature. According to clay structures, admixtures and also microfossils in carbonates, it is possible to prove Italian provenance of anonymous Baroque paintings.
Another aspect of investigation of materials in paintings we focus on is the systematic study of their secondary alterations which represent a serious problem especially in cases when they result in the undesirable changes of the original appearance of an artwork, such as colour changes or loss of cohesion of paint layers. Within these studies, we combine the detailed investigation of artworks’ microsamples with model experiments simulating the reactions of particular components under various conditions, reflecting the factors effecting the paintings (e.g., temperature, humidity, light, UV radiation, salt solutions, metabolites of microorganisms, conservation agents and treatments, etc.). In case of missing appropriate reference data for identification of secondary products, we also prepare and characterize these compounds, in close cooperation with colleagues specialised in syntheses. Besides stability of painting materials in murals which represent the most affected paintings, being often exposed to unsuitable climate and aggressive agents from the environment, we study the pigment-binder interactions. Recently, we focus on saponification of oil-based binders resulting in neo-formed metal carboxylates which can lead to the translucency of paint layers or their mechanical damages caused by the extension of protruding aggregates of soaps.
Hradil D., Hradilová J., Lanterna G., Galeotti M., Holcová K., Jaques V., Bezdička P.: Clay and alunite-rich materials in painting grounds of prominent Italian masters – Caravaggio and Mattia Preti. Applied Clay Science 185 (2020) 105412, https://doi.org/10.1016/j.clay.2019.105412
Švarcová S., Kočí E., Bezdička P., Garrappa S., Kobera L., Plocek J., Brus J., Šťastný M., Hradil D.: Uncovering lead formate crystallization in oil-based paintings, Dalton Transactions 49 (2020), 5044-5054, https://doi.org/10.1039/D0DT00327A
Garrappa S., Kočí E., Švarcová S., Bezdička P., Hradil D.: Initial stages of metal soaps` formation in model paints: the role of humidity. Microhemical Journal 156 (2020), 104842. doi.org/10.1016/j.microc.2020.104842
Kočí E., Rohlíček J., Kobera L., Plocek J., Švarcová S., Bezdička P.: Mixed lead carboxylates relevant to soap formation in oil and tempera paintings: the study of the crystal structure by complementary XRPD and ssNMR, Dalton Transactions 48 (2019), 12531-12540.5044-5054, https://doi.org/10.1039/C9DT02040C
Hradil D., Hradilová J., Holcová K., Bezdička P.: The use of pottery clay for canvas priming in Italian Baroque – An example of technology transfer. Applied Clay Science 165 (2018), 135-147, https://doi.org/10.1016/j.clay.2018.08.011
Hradil D., Hradilová J., Bezdička P., Serendan C.: Late Gothic / Early Renaissance gilding technology and the traditional poliment material „Armenian bole“: truly red clay, or rather bauxite? Applied Clay Science 135 (2017), 271-281, https://doi.org/10.1016/j.clay.2016.10.004
Hradil D., Hradilová J., Bezdička P., Švarcová S.: Differentiation between anonymous paintings of the 17th and the early 18th century by composition of clay-based grounds. Applied Clay Science 118 (2015), 8-20, https://doi.org/10.1016/j.clay.2015.08.038