Pigment-medium Interactions in Oil Paint Films containing Red Lead or Lead-tin Yellow
Catherine Higgitt, Marika Spring and David Saunders
Technical Bulletin Volume 24, 2003
Translucent white lumps or inclusions in red lead and lead-tin yellow type I paint layers are discussed in detail. These lumps are described as varying in size. Most often visible under the microscope and sometimes to the naked eye, the inclusions impart a gritty texture to paint films. Inclusions are found to be ubiquitous in European oil paintings with red lead and lead-tin yellow type I pigments. The earliest example of a lead soap inclusion has been identified in the 13th-century Westminster retable.
Inclusions commonly are made up of lead carboxylates and lead carbonate and are formed by the interaction of the lead-containing pigments and oil-binding medium. Certain characteristics of the inclusions, such as the fluorescence of the particles in ultraviolet light and the reduced azelaic acid content, are proposed to be responsible for the misinterpretation of aged oil paint layers as being bound in protein.
Techniques of analysis of inclusions presented in this article include energy dispersive X-ray analysis in the scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and thermally assisted transmethylation gas chromatography-mass spectrometry. The analysis of inclusions in paint layers is presented in tables that identify the paintings the samples are taken from, describe the paint layers, and list the content of the inclusions. An appendix details the preparation of lead fatty acid soaps and presents characteristic infrared frequencies for lead soaps of palmitic, stearic, and azelaic acids.
lead-tin yellow, oil paint, oil paintings, paint layers, pigment, red lead, scientific analysis
To cite this article we suggest using
Higgitt, C., Spring, M., Saunders, D. 'Pigment-medium Interactions in Oil Paint Films containing Red Lead or Lead-tin Yellow'. National Gallery Technical Bulletin Vol 24, pp 75–95.
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