MIR Spectroscopy results on the Scream (1910?)

Reflection mid-FTIR spectroscopy is widely used in the field of cultural heritage for the characterization and identification of organic and inorganic materials. Being a vibrational molecular spectroscopic technique, it provides information concerning the functional groups constituting the molecules ultimately aiding a molecular identification of unlimited materials under exam (from any painted surface (ancient, modern, contemporary), manuscripts, monuments etc). It is particularly adapt for the recognition of inorganic pigments (with some limitations from metal oxides) as well as limited synthetic and natural organic pigments classes. This technique can also be used to characterize the organic materials present in associated binding media or varnishes as well as provide information concerning any surface contaminations, alterations and products/processes of degrade.

The portable ALPHA spectrometer collects infrared radiation reflected from a surface located at 1cm distance. This instrument consists of an infrared source and a Globar DLaTGS detector. It exploits a range from 7500 cm-1 -400 cm-1 and a spectral resolution of 4 cm-1 with a spatial resolution of about 28 mm2.

The portable JASCO VIR 9500 spectrophotometer is equipped with a mid-infrared fiber optic sampling probe. It observes a good signal-to-noise ratio is very good in the range 900 to 4000 cm-1 with the exception of the 2050-2200 cm-1 region, with a spectral resolution is of 4 cm-1. The non-contact probe (4 mm diameter) is maintained perpendicular to the painting surface (0°/0° geometry) at a distance of about 6 mm. Owing to the probe geometry, reflectance mid-FTIR spectra can present large distortions, both in band shape and absorption frequency, due to the presence of both specular and diffused components. Interpretation of spectra is possible through a wide specific database created ad hoc.