FTIR imaging investigation in MIR and in an enlarged MIR–NIR spectral range

Abstract

The study of polished cross sections is a well-assessed and practical method to investigate the stratigraphy of paintings and multilayer polychromies on works of art, in general. Analyses on cross sections allow us to characterize, at once, all the layers in the stratigraphy, giving information about the artists technique, the number of layers and their composition and sometimes about the conservation history of the artefact. In this paper, the application of an imaging detector focal plane array (FPA) coupled to an infrared (IR) microscope has been studied, focusing on the characteristics and potential of the different working methodologies (attenuated total reflectance (ATR) and total reflection). FPA detector coupled with ATR crystal can "localize" IR information coming from a 30 × 30 μm sample area, in a 64 × 64 dot matrix detector. In particular, an innovative analysis methodology has been tested for the total reflectance measurements in order to obtain maximum information with single measurements. Micro-infrared total reflection measurements have been carried out in an extended IR range (from 1,000 to 5,266 cm(-1)) exploiting the broad spectral response of mercury cadmium telluride detector in order to include overtones and combination bands from near-infrared spectral range without any modification of the standard mid-infrared micro-FT instrumentation. The potentialities of this new approach have been successfully transferred in the imaging/mapping investigations with a minimal tuning of the apparatus. Results obtained on a polished cross section coming from a modern painting and on a micro-sample of a wood polychromy from an undated historic polyptic are shown for demonstration.

Surface characterization of medieval silver coins minted by the early Piasts: FT‐IR mapping and SEM/EDX studies

“…Nowadays, due to the need for high sensitivity, reliability and non‐destructiveness, several analytical methods are continuously been developed to study cultural heritage objects, including numismatic collections. Vibrational spectroscopy methods (infrared absorption spectroscopy and Raman spectroscopy), X‐ray fluorescence (XRF), and ion beam analysis techniques (particle‐induced X‐ray emission [PIXE], particle‐induced γ‐ray emission, and Rutherford backscattering spectrometry) are the most commonly used in this area and allow for high sensitivity and reliable identification . These kinds of studies are useful to enrich the discussion on many historical aspects, such as coinage production, provenance of raw materials, forgeries, and conservation treatments .…”

Methodology for infrared spectroscopy analysis of sandwich multilayer samples of historical materials

“…The first step is the creation of cross-section for observation under a microscope before other analysis. The sample is usually embedded in synthetic resin (polyacrylic [1], polyesters [1][2][3][4] or epoxy [2,5,6]).…”

Studies on paint cross sections of a glass painting by using FT‐IR and Raman microspectroscopy supported by univariate and hierarchical cluster analyses

“…However, Fourier transform infrared (FT‐IR) imaging and Raman mapping overcome this limitation providing information on the distribution of a compound over an entire cross‐section surface. According to the literature, Raman mapping has not been yet extensively performed on artworks contrary to FT‐IR imaging . Furthermore, to our best knowledge, both methods have not been yet employed simultaneously in studies on paint cross sections.…”

“…Despite this fact, this technique allow for chemical characterisation of individual paint layers of <10 µm thickness. Until now, both external reflection and ATR techniques of FT‐IR imaging have been used in investigations of paint cross sections. Among these reports, the studies of Spring et al .…”

“…According to the literature, Raman mapping has not been yet extensively performed on artworks [5][6][7] contrary to FT-IR imaging. [8][9][10][11][12][13][14][15][16][17][18][19] Furthermore, to our best knowledge, both methods have not been yet employed simultaneously in studies on paint cross sections.…”