J.CAC VOLUME 24 (1999)

A Starch-based Ground Layer on a Painting Attributed to Louis Dulongpré

Kate Helwig, Debra Daly Hartin

Technical examination of an oil painting on canvas attributed to Louis Dulongpré has provided insight into the nature of the ground layer responsible for the poor condition of the work. The paint and ground layers exhibited extensive cracking, cleavage, cupping and loss throughout. Cross-sections from several areas of the painting were examined and components were identified using a combination of X-ray microanalysis, X-ray diffraction, Fourier transform infrared spectroscopy and polarized light microscopy. The examination showed that three distinct ground layers were applied to the canvas before the portrait was painted. Cross-sections and X-radiographs provided evidence that these ground layers had cracked even before the application of the paint layers. The first ground layer applied to the canvas was found to be composed of starch, protein, gypsum and a red iron oxide pigment. The presence of a high concentration of starch granules in this layer indicated that the material was not heated sufficiently to form a paste. This explains the lack of cohesion within the ground layer and the ensuing cracking and cleavage. Although the use of pigmented, starch-based preparatory layers is mentioned in documentary sources, this type of ground has rarely been identified in a painting.

Download: JCAC24 Helwig & Daly Hartin