Quantitative chemical near-infrared hyperspectral imaging of Islamic paper

Heritage objects are well known for their compositional inhomogeneity due to materials and processes used in their production. Hyperspectral imaging is gaining importance in the field of heritage conservation by expanding spectroscopy to the examination of an entire surface of an object. This paper focuses on the application of near-infrared hyperspectral imaging to the characterisation of Islamic paper using a pushbroom HSI scanner in the 1000–2500 nm range to collect hyperspectral datacubes. A calibration target was devised using 105 samples from the well-characterised reference Islamic paper collection of the UCL Institute for Sustainable Heritage. Two material properties of Islamic paper were of interest: starch sizing and degree of polymerisation (DP). In addition to the developed discrimination and regression models using multivariate data analysis methods, a quantitative chemical map of the DP of an Islamic paper was generated as a case study for improved visualisation of the inhomogeneity of material properties, of value to researchers and conservators. As a case study, this research shows the wealth of valuable chemical information that near-infrared hyperspectral imaging could provide for diverse heritage applications in the future.