Near-Infared Imaging of Paintings

Near-infrared (NIR) imaging can be used as a discovery-based investigation of how the interaction of light with pigment and dyes changes with wavelength. The investigation has three primary pedagogical goals: (1) extending the student’s previous experience with color to the whole of spectroscopy, (2) introducing diffuse reflectance as a useful analytical tool, and (3) emphasizing quantitative skills. The experiment utilizes readily available equipment and materials. The imaging aspect aids the students in bridging the divide between visible color and optical spectroscopy, because the features in the images remain largely the same. The investigation is designed to span a single four-hour general chemistry laboratory. The topic can be extended to upper division courses by further investigation of the visible-NIR diffuse reflectance spectrum and the spectral response of the imaging system.