On May 7, 2017 Dr. David Schiering presented a talk entitled The Application of a New FTIR Microspectroscopy Accessory for Far-IR Analysis of Artists’ Pigments at a meeting and workshop pertaining to the use of FTIR in the fields of Archaeology and Art Conservation. The talk was co-authored by Ron Rubinovitz (Thermo Fisher Scientific), Anthony W. DiDomenico (Czitek), Beth Price (Philadelphia Museum of Art), and Kate Duffy (Philadelphia Museum of Art).
The analysis of artists’ materials by infrared (IR) spectroscopy is well-known. Analyses are broadly performed in the mid-IR region of 4000-400 cm-1. The 400 cm-1 low frequency cutoff is due to KBr optics typically employed in the Fourier transform infrared (FT-IR) spectrometer. The mercury-cadmium-telluride (MCT) detectors employed in FT-IR microscopes further limit the spectral low frequency cutoff to 700-500 cm-1. Many inorganic materials, such as pigments found in artworks, have diagnostic spectral absorption bands in the far-IR, while others yield bands exclusively in that region. Opening the far-IR to pigment identification in microscopic samples should provide a wealth of new chemical information for museum scientists and conservators, as well as academics. Advances in optical materials and design have opened the far-IR region, typically defined as 600-10 cm-1, for application in materials characterization. This presentation will concern the use of a new FT-IR microspectroscopy accessory in the far-IR analysis of artists’ pigments. This accessory allows the collection of spectra in transmission, reflection, and attenuated total reflection (ATR) modes and interfaces to the instrument mounted detector. There are no optics in the accessory that limit the spectral range. The utility of this new optical accessory will be demonstrated in the far-IR analysis of artists’ pigments. Reference spectra of pigments will be measured in the far-IR and these spectra will used to identify pigments in artworks. Data collected in transmission and ATR modes will be compared and discussed.