Revealing the Fugitive Palette of the Early American South: A SERS Study of Eighteenth-century Oil Paintings

Abstract

ABSTRACT The identification of organic colorants in traditional oil paintings is an important and challenging area of conservation research. Since many organic dyes and pigments are fugitive, the detection of these materials is crucial for the proper assessment of fading, conservation treatment, and the prevention of further photodamage. While numerous methods exist to characterize colorants, recent advances in surface-enhanced Raman scattering (SERS) methodologies have enabled the unambiguous identification of various organic dyestuffs in oil paintings in a minimally invasive manner. Here, we apply a collection of SERS-based protocols to identify the organic pigments used in a number of oil paintings that were made in the Southern British colonies of North America during the eighteenth century and are being prepared for exhibition at the Art Museums of Colonial Williamsburg. Questions arose during the painting examinations that would appear to involve color shifts and possible fading. The SERS results reveal the identity of several organic pigments (i.e. carmine lake, madder lake, Reseda lake, indigo, gamboge) in these eighteenth-century portraits, within the broad-scale quantity-rich areas of the composition as well as the more challenging flesh tones and small, yet important, detail regions. We discover the continued use of carmine lake in seven of the ten paintings and identify the blue and yellow organic pigments used in this group, both of which contribute to our understanding of pigment availability and artists’ choices, as well as supporting the more accurate assessment of condition and the artists’ original intent.