Identification of dyes is of great importance for the protection of textiles artefacts, as well as for further understanding the manufacturing process of ancient dyes. Moreover, the evaluation of degradation status can help conservators to reconstruct the original appearance of historical textile objects and predict the stability of their colors.
Natural organic dyes on textile are usually detected through molecular analytical methods. In particular, liquid chromatography (LC) and gas chromatography (GC) have been widely used in the dye analysis with high accuracy. However, they are invasive methods, as they are based on the analysis of organic extracts.

Recently, non-invasive methods based on spectroscopy technology, such as reflectance spectroscopy and fluorescence spectroscopy, received great attention. Reflectance spectroscopy is used for the characterization of paint films and pigments. In addition, Kubelka-Munk’s theoretical reflectivity of diffuse medium provides chances to quantitatively analyze mixtures of pigments by reflectance spectroscopy. When the scattering coefficient is independent of the wavelength, the typical absorption spectrum measured by the reflection can be used as a substitute indicator for the actual absorption spectra.