UV-Vis-NIR reflectance spectroscopy: its application to the study of plastic heritage

Reflectance spectroscopy is a well-established technique for the study of traditional artworks on parchment, paper, textiles, stained glass/windows, wall, canvas, and panel paintings. For the analysis of plastic heritage, its application is still a pioneering line of research. It poses new challenges due to the inherent complexity of plastics and a lack of experimental protocols for the reflectance analysis of these materials. Being a non-destructive technique (sampling is not required) and thanks to the possibility of in situ applications, reflectance spectroscopy might be used as a preliminary tool for the detection of possible discolouration in the plastic heritage caused by polymer and colourant degradation (e.g. yellowing, darkening and fading). In this work, the application of Fibre Optic Reflectance Spectroscopy (FORS) and colourimetry for the discolouration assessment of plastic heritage is presented. The spectroscopic techniques successfully characterised the discolouration, and results of yellowing and fading measurements of naturally aged historical plastic objects are discussed.