A Spectroscopic Study of Brazilwood Paints in Medieval Books of Hours

Abstract

In this work, microspectrofluorimetry was for the first time applied to the identification of the red organic lakes that are characteristic of the lavish illuminations found in 15(th) century books of hours. Microspectrofluorimetry identified those red paints, ranging from opaque pink to dark red glazes, as brazilwood lakes. An unequivocal characterization was achieved by comparison with reference paints produced following recipes from the medieval treatise The Book on How to Make Colours, and was further confirmed by fiber optic reflectance spectroscopy (FORS). For these treasured cultural objects, microspectrofluorimetry and FORS proved to be the only techniques that could identify, in situ or in microsamples, the chromophore responsible for the pinkish hues: a brazilein-Al(3+) complex. Additionally, a multi-analytical approach provided a full characterization of the color paints, including pigments, additives, and binders. Microspectroscopic techniques, based on infrared and X-ray radiation, enabled us to disclose the full palette of these medieval manuscripts, including the elusive greens, for which, besides malachite, basic copper sulfates were found; Raman microscopy suggested a mixture of brochantite and langite. Infrared analysis proved invaluable for a full characterization of the additives that were applied as fillers or whites (chalk, gypsum, and white lead) as well as the proteinaceous and polysaccharide binders that were found pure or in mixture.

Silver paints in medieval manuscripts: a first molecular survey into their degradation

“…5b. This blue colour construction was also observed in other books of hours analysis studied [4]. In the pink pigment lake, depicted in layer 3, Table 3, potassium and sulphur were identified by SEM-EDS analysis, which could be associated to the additives of the organic pigment.…”

“…A recent investigation, on the systematic study of the colour materials applied in the illumination of the books of hours preserved in Portuguese institutions, showed that silver is lavishly applied in backgrounds, highlights and minute details [2][3][4][5][6][7][8][9][10][11][12]. In most of the cases, silver colours present dramatic blackening, but in some manuscripts, the metal brightness is still present.…”

“…The metallic leaves could be applied over the parchment surface, previously burnished, or over a ground layer. In the cases that we analysed, the grounds were prepared with gypsum, calcium carbonate or a mixture of both, combined with proteinaceous or polysaccharide binders [4,52]. Yellow ochres and vermilion could be applied over the ground as a bolus layer [52].…”

Hyper-Spectral Acquisition on Historically Accurate Reconstructions of Red Organic Lakes

“…FORS measurements of the paints in the 350-1000 nm range were performed using the same apparatus and conditions as that described in [14].…”

“…This study will indeed provide useful information that will ensure access to the best documentation of works of art, enhancing their understanding and helping their long-term preservation. Moreover, the preparation of such accurate references enables the creation of a database of materials that, not only helps the interpretation of the data obtained, but can also be used to compare with case studies [14].…”