"Lasers Used in the Study and Treatment of Pigment Degradationon Artwork"

Abstract:

Basic lead carbonate [lead white, 2PbCO3•Pb(OH)2] is one of the earliest synthetic artists’ pigments and was used almost universally as the principle white colorant until the advent of synthetic, brilliantly white titanium dioxide. Although stable to light and humidity, lead white is known to suffer from a variety of darkening reactions, the most common being discoloration from sulfurous pollution to form black lead(II) sulfide (galena, PbS). Because of the variety of potential black reaction products that can be formed – and the different conservation treatment used to restore the white appearance in each instance – a molecularly specific technique is required for identifying the degradation product prior to any intervention. Lasers are gaining wider acceptance in art conservation as a tool for materials characterization and for the cleaning of artwork. This talk will highlight the role of laser Raman microscopy in palette studies of artwork and its use in the identification of pigment degradation products. Recent studies are exploring the potential application of lasers to the treatment of blackened lead white pigments.