Clay ground in paintings: from Northern to Southern Europe

The use of clay grounds containing quartz was first observed in the Netherlands in artworks from Rembrandt’s workshop after 1640 [1, 2]. In addition, contemporary written sources outside the Netherlands mention this practice in Italy and Spain [2]. However, the reason for using clay as a constituent in paintings has still not been much investigated, neither with regard to the processing nor the trade of the material. Did it give a particular colour/structure in order to achieve a specific final effect of the painted surface? Was clay cheaper than chalk, calcium sulphate or earth pigments? Did it give more flexibility to the painting support? Was it connected to the tile industry? Was it a waste/reuse from the ceramic production?
To better understand the role of clay ground as a material and its influence on painting techniques, a number of Danish and Italian 17th century paintings from the Statens Museum for Kunst (SMK) collection were surveyed by means of SEM-EDX analyses, FTIR and Raman spectroscopy in order to characterize the materials employed in the red ground layers. The results indicate that these Danish and Italian grounds consist mainly of clay and quartz mixed with iron-based compounds. The investigation is demonstrating how widespread the use was of clays as constituent in paintings when comparing the analytical results performed on artworks from Northern and Southern Europe.
This preliminary study will lead to further research focused on the link between artistic schools of the period, the transmission of technology and knowledge of employing this type of clay grounds and, possibly, tracing the origin of the raw materials employed in the grounds.

[1] K. M. Groen, ArtMatters - Netherlands Technical Studies in Art, 3, 2005, 138-154. Waanders, Zwolle.
[2] K. M. Groen, "Grounds in Rembrandt´s workshop and in paintings by his contemporaries", in E. van de Wetering et al. A Corpus of Rembrandt Paintings, 2011, 318-334 + 660-677. Springer, Dordrecht