Whitish haze, soapy globules: micro-analysis of degraded burmese paintings on zinc supports

Abstract

Two Burmese oil paintings on zinc supports depicting portraits of royal families, dated to the early 20th century by Saya Aye and Saya Mya, showed interesting corrosion, efflorescence and soapy globules for analytical investigation prior to conservation for exhibition. The features and colours on the two paintings, one of which was in worse condition than the other, were obscured by a whitish haze. Paint rupture and losses due to corrosion of the zinc support were apparent. Using a combination of 3D digital microscopy, FTIR microscopy and SEM-EDS, the degradation, as well as the paint materials and artists' techniques were analysed and discussed. Zinc soaps, oxalates, silicates, hydroxychlorides, carbonates, wax and mould characterized the haze. Interestingly, brown outlines in Aye's painting appeared unusually dark. Upon analysis, this degradation phenomenon was attributed to micro-sized greenish soap globules that have developed around copper/zinc (brass) particles, causing the brown outlines to lose their intended luminosity. The other painting by Mya, in which the same brown outline was applied, did not show such formation of globules. Detection of oxalates in the corrosion of zinc support and brown outlines are discussed. This study shows the importance in understanding the artists' materials and techniques, which have consequential effects to the degradation observed.

Chemistry for cultural heritage: connecting past and future

“…Understanding deterioration mechanisms and measurement of quantifiable properties in order to assess the damage was the focus of the articles by Simoen et al [14], Chua [15], Vyskočilová et al [16] and Badea and Carşote [17]. The first concerned with a combined microand macro-scale X-ray powder diffraction mapping of degraded orpiment pigment in a seventeenth century still life painting by Martinus Nellius in which the authors demonstrated the in situ formation of secondary metal arsenate and sulfate species and their migration through the paint layer stack they originate from.…”