In the Baroque period, coloured clays were largely used for painting preparations – the grounds, and as they were cheaply available in many places, it did not make any sense to transport them on a longer distance. In addition, at that time, painters usually bought the already primed (ready-to use) canvases in the place where they were working. The composition of the clay material may thus be regionally specific – and this factor has never been considered by anyone before. In the earliest study carried out in ALMA in 2010, the grounds of the 17th to 18th centuries were divided into five mineralogical types, which most frequently do appear.
Subsequently, thanks to this classification, it was possible to distinguish the regional origin of a number of anonymous paintings and differentiate artworks painted in Central Europe from those imported from Italy. Recently, the clays used in some northern Italian painting of the 16th to 17th centuries have been identified as identical to those previously used by Renaissance masters to create terracotta sculptures. The composition of the grounds is so specific that it is possible to distinguish neighbouring regions - works that Carravaggio and others painted in Italy and in Malta.
Recent publications:
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
Hradil D., Hradilová J., Bezdička P.: Clay minerals in European painting of Mediaeval and Baroque periods. Minerals 10 (2020), 255. https://doi.org/10.3390/min10030255
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
Pospíšilová E., Hradil D., Holá M., Hradilová J., Novotný K., Kanický V.: Differentiation of clay-based pigments in paintings by means of laser ablation inductively coupled plasma-mass spectrometry. Spectrochimica Acta Part B: Atomic Spectroscopy 158 (2019) 105639. https://doi.org/10.1016/j.sab.2019.105639
Hradil D., Bezdička P., Hradilová J., Vašutová V.: Microanalysis of clay-based pigments in paintings by XRD techniques. Microchemical Journal 125 (2016), 10-20. https://doi.org/10.1016/j.microc.2015.10.032
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. 243. https://doi.org/10.1016/j.clay.2015.08.038
Top cited:
Hradil D., Grygar T., Hradilová J., Bezdička P.: Clay and iron oxide pigments in the history of painting. Applied Clay Science 22/5 (2003), 223-236. https://doi.org/10.1016/S0169-1317(03)00076-0 (281 citations, 12 per year in average)
No visual difference between red-brown ground layers in visible light, but distinct mineralogical composition. Bohemian clay (top) and Italian clay (bottom).
SEM images with interesting details in Calcareous pottery clays in the ground of Italian painting. Framboidal pyrite (top) and nanofossils (bottom).