VIS-NIR Spectrophotometry

Sebastian Bosch

Spectrophotometry measures the reflection or transmission properties of a material as a function of wavelength. In the field of cultural heritage, spectrophotometers are mainly used to record the reflection of a surface with the help of a fibre probe. In such a configuration, this method is called fibre optic reflectance spectroscopy (FORS) and ideal to analyse objects of any size on-site in a noninvasive manner. Depending on the used radiation, different material features can be detected. In the visible range of the electromagnetic spectrum (380 nm - 730 nm) this method is a convenient tool for the analysis of coloured materials (e.g. to classify pigments and dyes). Spectrophotometers with visible and infrared detectors are suitable to detect even more features of some colourants, and are also used for the analysis of paper or binding materials. By comparing the raw, first derivative and logarithmic spectrum with a database, it is possible to identify most of the organic and inorganic colourants.

Limitations: pigment mixtures; copper green pigments