| Résumé | The remote-sensing technique of spectroscopic imaging has been adapted to the non-destructive examination of works of art. The principle of near-infrared reflectance spectroscopic imaging is explained, and our instrumentation for art examination described. The technique allows the art materials to be distinguished by their composition, and under-drawings revealed. The initial results indicate that even over limited wavelength ranges (650–1040 nm) and with relatively coarse spectral resolution (10 nm) a number of pigments can be distinguished on the basis of variations in spectral properties such as spectral slope and the presence or absence of absorption bands. Software adapted from the remote-sensing image-processing field has been used to successfully map areas of different brown and black pigments across a drawing. Non-destructive identification of pigments can be used to address issues of attribution, age dating, and conservation. An additional advantage of this technique is that it can be performed off-site using portable instrumentation, and under relatively benign lighting conditions. The technique has been applied to the examination of a 15th-century drawing, Untitled (The Holy Trinity), in the collection of the Winnipeg Art Gallery. Multivariate image analysis produced a set of principal component (PC) images highlighting different materials’ aspects of the drawing. A color composite image produced from the PC images provided a direct visualization of the compositional characteristics of the work. Features of the under-drawing have been exposed, and its material tentatively identified as charcoal, by comparison with reference data. |
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