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

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.

KEYWORDS:

• Surface-enhanced Raman spectroscopy (SERS)
• fugitive pigments
• lake pigments
• carmine
• madder
• indigo
• gamboge
• Prussian blue
• Reseda lake
• eighteenth century
• Charles Willson Peale

Acknowledgements

K. W. acknowledges the Henry Dreyfus Teacher-Scholar Awards Program for funding. S. S. acknowledges continuing support from Claudine Fall for the Paintings Conservation Laboratory at Colonial Williamsburg. Painting samples and images are courtesy of The Colonial Williamsburg Foundation and Museums at Washington and Lee University, Lexington, VA.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Camille and Henry Dreyfus Foundation through the Henry Dreyfus Teachers-Scholars Awards Program.