Reflectance Spectroscopy (RS) has become a powerful portable technique for the analysis of polychrome artworks, particularly for pigment identification. Compared to other commonly used spectroscopic methods such as XRF and Raman, a key advantage of RS is that its instrumentation can be assembled using relatively low-cost components.

RS measures, at each wavelength, the ratio between the intensity of reflected light and incident light relative to a standard white reference (reflectance). The resulting reflectance spectra provide characteristic information that can be used to identify pigments.

As a non-invasive analytical method, reflectance spectroscopy is especially suited to the examination of artworks. It is based on the principle that materials interact with light in different ways: specific wavelengths are absorbed while others are reflected. By analyzing these spectral responses, it is possible to obtain a diagnostic “fingerprint” of the materials present and thereby determine their composition.