Determination of the pigments present in a wallpaper of the middle nineteenth century: The combination of mid-diffuse reflectance and far infrared spectroscopies

• Determination of the pigments present in a wallpaper of nineteenth century.
• Applicability of the combination of DRIFT and FIR.
• Validated by Raman spectroscopy and Electron Dispersive X-Ray Fluorescence (EDXRF).

In this work the determination of the pigments present in a decorative wallpaper of the middle nineteenth century from the Santa Isabel factory (Vitoria-Gasteiz, Basque Country, Spain) has been performed by a combination of mid-Diffuse Reflectance Infrared Spectroscopy (DRIFT) and Far Infrared Spectroscopy (FIR) in transmission mode. The DRIFT is a powerful infrared technique that is not widely used in the analyses of artworks in spite of being especially adequate for powdered samples. In this mode, sample pretreatment is not required and the obtained spectra are easier to solve than those obtained in transmittance mode. Those pigments which are not active in the mid-infrared region may be determined easily by FIR. In the last decade, in the field of painted materials very few studies performed by far infrared spectroscopy and mid infrared spectroscopy in diffuse reflectance mode can be found. In most of them the researchers have used one of these techniques, but in no case the combination of both. As we demonstrate in this work, combining these two techniques a complete characterization of the wallpaper can be carried out.Small samples were collected from the wallpaper for the analysis of the rose, brown, yellow and blue colours. In this way, minium (Pb3O4), calcite (CaCO3), barium sulphate (BaSO4), prussian blue (Fe7C18N18), iron oxide yellow (α-FeOOH), vermillion (HgS) and carbon black pigment from organic origen were detected. Finally, the validation was carried out by XRF and Raman spectroscopy getting the same results as with the combination of diffuse reflectance infrared spectroscopy and far infrared spectroscopy.

This work studies the combination of Diffuse Reflectance Infrared Fourier Transform (DRIFT) and transmittance Far infrared spectroscopy (T-FIR) to perform pigments determination in wallpapers, as alternative to Raman spectroscopy.In the Santa Isabel wallpaper, minium (Pb3O4), calcite (CaCO3), barium sulphate (BaSO4), Prussian blue (Fe7C18N18), iron oxide yellow (α-FeOOH), vermillion (HgS) and organic black pigment were detected.The results obtained are consistent with the literature and also they have provided a new pigment to the color palette used in the factory.Figure optionsDownload as PowerPoint slide