Relationship and Source of Whitings Used as a Painting Ground in Icons From Polish Museum Collections Based on Their Calcareous Nannofossil Content

ABSTRACT In icon painting, chalk whiting is key to creating a gesso ground, providing a smooth, absorbent surface for paint. Calcareous nannofossils, tiny marine skeletons found in chalk, are an ideal tool for analyzing the origin of an icon's chalk ground, often the only reliable information about where the icon came from. This paper summarizes an analysis of nannofossil assemblages from calcareous whiting in the collections of the National Museum in Krakow, previously analyzed, and the National Museum of Przemyśl Land, where new studies were conducted on 34 samples from icons and 1 from chalk in Mielnik on the Bug River. Nannofossil assemblages from the Przemyśl icons came from the Upper Cretaceous, mainly from the lower Maastrichtian. They showed a predominance of Arkhangelskiella cymbiformis and Micula decussata , while one sample was characterized by the predominance of Watznaueria barnesiae and the presence of the endemic Nannoconus truitti . Comparative studies of calcareous nannofossil assemblages from gesso in Przemyśl and Krakow collections reveal two main groups. Over half of the analyzed icons contain boreal assemblages that are highly similar to those found in Chełm's chalk, suggesting the most probable source due to historical mining activities. The remaining boreal nannofossil assemblages do not match chalk from Chełm or Mielnik. A separate group of icons features Tethyan assemblages, while others used pre‐Campanian–Maastrichtian Tethyan sediments for their gesso. The research methods detailed in this article can be applied to analyze whiting backgrounds in panel paintings, including those beyond museum icons. This allows for pinpointing the material's origin and connecting artworks to specific artistic environments.