Investigation of mineralization products of lead soaps in a late medieval panel painting

Elena Platania; Noëlle L W Streeton; Anna Vila; David Buti; Francesco Caruso; Einar Uggerud

doi:10.1016/j.saa.2019.117844

Investigation of mineralization products of lead soaps in a late medieval panel painting

Spectrochim Acta A Mol Biomol Spectrosc. 2020 Mar 5:228:117844. doi: 10.1016/j.saa.2019.117844. Epub 2019 Nov 22.

Authors

Elena Platania¹, Noëlle L W Streeton², Anna Vila³, David Buti⁴, Francesco Caruso⁵, Einar Uggerud⁶

Affiliations

¹ Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, 0315 Oslo, Norway; Conservation Studies, Department of Archaeology, Conservation and History, University of Oslo, P.O. Box 1008 Blindern, 0315 Oslo, Norway. Electronic address: elena.platania@kjemi.uio.no.
² Conservation Studies, Department of Archaeology, Conservation and History, University of Oslo, P.O. Box 1008 Blindern, 0315 Oslo, Norway. Electronic address: n.l.w.streeton@iakh.uio.no.
³ Statens Museum for Kunst, Centre for Art Technological Studies and Conservation, Sølvgade 48, 50, 1307 Copenhagen, Denmark. Electronic address: anna.vila@fundaciolacaixa.org.
⁴ Statens Museum for Kunst, Centre for Art Technological Studies and Conservation, Sølvgade 48, 50, 1307 Copenhagen, Denmark. Electronic address: DBU@smk.dk.
⁵ Conservation Studies, Department of Archaeology, Conservation and History, University of Oslo, P.O. Box 1008 Blindern, 0315 Oslo, Norway; Department of Art Technology, Swiss Institute for Art Research (SIK-ISEA), Zollikerstrasse 32, 8032 Zurich, Switzerland. Electronic address: francesco.caruso@sik-isea.ch.
⁶ Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, 0315 Oslo, Norway. Electronic address: einar.uggerud@kjemi.uio.no.

PMID: 31784229
DOI: 10.1016/j.saa.2019.117844

Abstract

Metal soaps pose significant concerns in the preservation of paintings made with oil as a binding medium. In highly alkaline environments, metal soap aggregates may undergo mineralization processes with the formation of new phases, such as carbonates, chlorides, oxides and sulfates of the metal cations that are present in pigments or paint additives. In this work, we report new examples of the mineralization of lead soaps in paint-cross sections taken from a late-medieval panel painting owned by the Museum of Cultural History at the University of Oslo. Scientific analyses were carried out with optical microscopy under UV and visible light, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and Raman spectroscopy to investigate and characterize the nature of the compounds present in the samples. Lead (II,IV) oxide, which is presumed to be a secondary product in the mineralization of lead soaps, has been identified in lead-based paint.

Keywords: Lead oxides; Metal soaps; Mineralization; Paint cross sections; Raman spectroscopy; SEM-EDX.