Martine De Reu

Investigation of pigments in medieval manuscripts by micro Raman spectroscopy and total reflection X-ray fluorescence spectrometry

Analytical pigment investigation can reveal important information for art-historians. The use of two micro-analytical techniques, micro Raman-spectroscopy and total reflection X-ray fluorescence, is shown to be very successful. These techniques give complementary information: Raman spectroscopy allows the identification of the different materials the pigment grains consist of, and total reflection X-ray fluorescence gives the average elemental composition of the sample.The latter is helpful to distinguish between the different palettes used by different artists or workshops. Samples can be taken with cotton wool swabs (Q-tips), which cause no visible alteration to the artefact. Such a sample allows both Raman-spectroscopy and total reflection X-ray fluorescence to be applied using less than 1 μg of material. This approach is illustrated with the pigment investigation of seven late-medieval Mercatellis manuscripts, kept in the Ghent University Library.

A TXRF and Micro-Raman Spectrometric Reconstruction of Palettes for Distinguishing Between Scriptoria of Related Medieval Manuscripts

Assigning related medieval manuscripts to different workshops on the basis of codicological characteristics, is not straightforward. We present the first attempt to distinguish between scriptoria by means of a large-scale total reflection X-ray fluorescence (TXRF) analysis of pigment elements and an identification of pigment molecules with micro-Raman spectroscopy. We analyzed 324 colored items in 10 medieval manuscripts, of which 7 are folio-sized illuminated manuscripts, all ordered by Raphael de Mercatellis in the late 15th and early 16th century. Palettes in miniatures were not yet examined. Blue palettes are exclusively azurite-based and are easily differentiated by means of the respective amounts of Ti, Ba, and As. Differences for green palettes are also pronounced. The green Cu-based pigment was not yet identified, but it certainly is not malachite or verdigris. Red pigments used are HgS, vermilion, and Pb3O4, red lead. The Flemish gold-leaf technique is used. The 7 Mercatellis manuscripts show two different palettes, both different from the non-Mercatellis manuscripts. The grouping of the Mercatellis manuscripts according to date and to palettes is, in general, consistent with a grouping on the basis of a classical codicological analysis, although some conflicting results are obtained. A quantitative and qualitative reconstruction of palettes by means of TXRF- and Raman-spectra, provides with a complimentary and objective tool for distinguishing between scriptoria.