Fourier transform Raman spectroscopic study of pigments present in decorative wallpapers of the middle nineteenth century from the Santa Isabel factory (Vitoria, Basque Country, Spain)

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Abstract
One of the earliest wallpapers manufactured by the Santa Isabel factory (Vitoria, Basque Country, Spain) (1845) was found at the Torre de los Varona (near Vitoria) during restoration work on the building. As part of this cleaning and restoration work, the identification of the wallpaper's pigments was carried out by Fourier transform (FT) Raman spectroscopy. Fragments of paper were set in a sampler kit for planar surfaces. By moving the paper samples, it is possible to locate the laser beam's spot at the point that it is going to be analysed with a spatial resolution of about 0.5 mm. With this method it is possible to map a surface of several square centimetres without the need for an optical microscope. As FT‐Raman analysis is totally non‐destructive, the samples were restored and integrated with the whole wallpaper at the end of the analysis. Small particles of pigment were collected for the analysis of the pink and green colours by atomic absorption spectrometry (AAS). In both cases, the damage caused by the pigment sampling was minimal and non‐visible. BaSO4, CaCO3, Pb3O4, PbCrO4, PbO, Prussian Blue, gypsum and an organic black pigment were detected. It is important to take into account the laser beam's penetrative power in order to interpret the spectra correctly. The identification of only eight pigments to make 12 different colours, mostly in two different shades, shows the ability of the wallpaper manufacturer to create a rich palette at low cost. This type of primitive industrial decorative work has become real artwork that it is necessary to preserve and restore. Copyright © 2002 John Wiley & Sons, Ltd.