Art Conservation Using Mid-IR Spectroscopy

Abstract

This research is intended to provide a baseline for infrared spectroscopy of art in the mid-IR range, 2.5 µm to 10 µm, using Fourier Transform Infrared Spectroscopy (FTIR) analysis of pigment samples. Infrared spectroscopy is a non-damaging way to identify and classify materials such as pigments by measuring their absorbance spectra and comparing them with known values and figures. It can be used to detect trace elements that might be results of corrosion, wear over time, or contamination. It can also be used to determine anachronisms in pigments used to detect forgeries, if a pigment was not available in the time or place from which a painting purports to be. This method has been done primarily using the visible spectrum of light or near-IR light. This experiment expanded that into the mid-IR range to determine what wavelengths are particularly useful in distinguishing between pigments at that range. By analyzing pigments of a similar color in the visible spectrum, a qualitative analysis of their absorbance spectra in the mid-IR range was catalogued. In particular, the areas around the wavenumbers 1250 cm-1 (wavelength 8 µm) and 2000 cm-1(wavelength 5 µm) stand out as areas of large magnitude differences between the absorbance spectra of various pigments. Using this information, further research into IR-spectroscopy using methods that do not require depositing the samples onto clear crystals, but instead can be measured directly on the canvas or other backing surface of paintings, can be conducted.