Determination of pigments in paintings by FT-IR spectroscopy
On May 3, 2010 Signe Vahur from chair of analytical chemistry defended her doctoral thesis “Expanding the possibilities of ATR-FT-IR spectroscopy in determination of inorganic pigments”.
ATR-FT-IR has been used by conservation scientists for a long time. This technique enables to identify the binder materials and fillers. At the same time its usefulness in identification of pigments – a most important component of a painting – has been limited because the mid-IR (4000–400 cm–1) region of the IR spectrum of many of them is not characteristic enough and also there are many pigments that either do not absorb in that region at all (oxides, sulphides, etc) or have absorptions that are at the low wavenumber end of that region and are not characteristic enough for pigment identification.
At the same many pigments absorb IR radiation in the far-IR region (below 500 cm–1).
Signe developed a method how to use the low wavenumber region (550-230 cm-1) for identification of pigments and demonstrated that with this advancement ATR-FT-IR spoectroscopy firmly established as a pigment analysis technique.
The work provides a comprehensive overview of the inorganic pigment identification possibilities using ATR-FT-IR as well as a collection of reference spectra in the low wavenumber range (550-230 cm-1) and is expected to be a useful reference material for conservation practitioners and material scientists. The usefulness of ATR-FT-IR in the region of 550-230 cm-1 for identification of inorganic pigments is demonstrated by 5 case studies on art objects (several of them are important in Estonian history).
Full text of the thsis is available via the electronic storage of the UT library: “Expanding the possibilities of ATR-FT-IR spectroscopy in determination of inorganic pigments”.