An analytical survey of zinc white historical and modern artists’ materials

Abstract

This study is the first systematic survey of a large corpus of zinc white (ZnO) artists’ materials. Zinc white is a white pigment developed within the wave of 19th-century technological developments in the paint industry. The composition, particle morphology and size, and luminescence of 49 zinc white samples from artists’ materials were characterized, including three references of known synthesis methods (indirect and direct) and synthesized by the authors (ZnO nanosmoke). The corpus included historical and modern zinc white pigment powders and paint materials from the leading European and American color manufacturers. The study aims to characterize and evaluate the variability of the properties of zinc white and its paint formulations. The reference materials presented properties in agreement with the literature: indirect ZnO exhibited submicron prismoidal blue-luminescent particles of higher purity than direct ZnO, which had larger acicular green-luminescent particles. ZnO nanosmoke presented acicular (tetrapod-like) blue/green-luminescent nanoparticles. Composition, particle morphology, size, and documentary sources suggested a production via the indirect method for the analyzed corpus. However, the luminescence behavior was more complex to interpret. The fundamental emission of ZnO was not always detected, even in pure ZnO powders. Three trends were identified: smaller ZnO particles for the most recent samples; green luminescence connected to larger particle size; fewer trace elements, and of the same type (i.e., lead, sulfur) for historical materials. Another interesting finding was the detection of hydrozincite in some powders, likely a degradation product of ZnO. In terms of methodology, cathodoluminescence proved a valuable tool for pigment identification. The study provides a database of zinc white references for pigment and artwork analysis.