NTK Institute of Science and Technology in Art; Academy of fine Arts Vienna; Schillerplatz 3 A-1010 Vienna
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Historical Pigments:
A Collection analysed with XRD, XRF and FTIR in order to create a Database

This work presents a systematic characterization of historic inorganic pigments with respect to their crystallographic structure, main components, and trace elements. The results are compiled in a computer database containing the experimentally obtained information.

The specimens examined in this study originate from the collection of 19th and 20th century pigments, dyes, and binding media with a wide variety of colours and materials present in our institute. Approximately 400 different inorganic pigments were analysed for this study of its kind by combining x-ray diffraction (XRD), x-ray fluorescence (XRF) and Fourier transform infrared spectroscopy (FTIR). The experimental work has focused on x-ray diffraction to detect the main components and to perform phase analysis for the identification of the crystallographic structure. XRF measurements were carried out and complemented by FTIR-spectroscopy to facilitate the analysis of the diffractograms and investigate differences in the elemental composition. The combination of XRD and XRF has enabled phase analysis, whereas FTIR supports primarily the identification of the non-crystalline organic components of the samples.

In some cases, the obtained results show remarkable differences in the composition of the pigments with the same trade name. These differences are either caused by the chemical composition or added components, such as pure white pigments. However, in most cases the chemical structure of the phase determining the colour of the relevant pigment group was similar.

In order to help identifying pigments, a database of the experimental results obtained in this study was created. It is supplemented by additional information about the pigments as found in literature. Additionally, two libraries for XRD and FTIR analysis were compiled containing the measured spectra of all pigments, which can be combined with conventional databases (ICDD, IRUG). This allows extended and direct access to the original information and eases the identification of unknown samples.

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