Type: Spectroscopic point analysis
NIR spectroscopy has become an increasingly useful analytical tool for non-invasive, contactless measurements by providing signals that are characteristic of infrared combination and overtone bands which have very low absorption coefficients. This technique is suitable for analysing organic and limited inorganic materials, by providing distinctive features regarding both chemical composition and physical properties (crystallinity, crystal shape and particle size). As the NIR radiation is particularly penetrating, it can typically pass through paint layers and reach the ground layer of paintings providing information of pigments and binders alike. Main drawbacks include however difficult band assignments which can be alleviated by the application of successive derivative transformations and multivariate data processing procedures.
The JASCO NIR spectrometer provides information across the spectral region of the near infrared (12500 – 4000 cm-1 ). It consists of a halogen lamp as source, an InGaAs detector and a 2m fiber optic sampling probe. The Y shaped silica-glass fiber optic probe contains of 14 fibers, 7 of which carry infrared radiation from the source to the sample, while the other 7 collect the radiation reflected off the surface. Spectral resolution is 4 cm-1 with a sampling area of about 12 mm2 and an artwork-probe working distance of about 6mm.
1. F. Rosi, C. Miliani, et al. An integrated spectroscopic approach for the non invasive study of modern art materials and techniques” Applied Physics A, 100; 2010 pp. 613.
2. M. Vagnini, C. Miliani et al. FT-NIR spectroscopy for non-invasive identification of natural polymers and resins in easel paintings. Anal Bioanal Chem. 395; 2009 pp. 2107-18.
MOLAB Italy: UNIPG S.M.A.Art