Hyperspectral imaging for heritage: from books to bricks

Thesis

In heritage science one important line of enquiry is the pigmentation of an artefact. Imaging methods have been developed for this purpose and have had success in the investigation of colourants. In particular a great deal of information has been gained by looking at the spectra outside of the visible region, however, visible and near infrared hyperspectral imaging (VNIR HSI) equipment has been developed at a price point that could see widespread use across heritage institutions. This thesis addresses how VNIR HSI is best utilised for the analysis of colourants and evaluates the efficacy of VNIR HSI for characterisation, detection, and monitoring. Advantages and drawbacks of this new technique are highlighted.

VNIR HSI was used to characterise the colouration in illuminated manuscripts from the Bodleian Libraries. VNIR HSI was restricted in its capacity for characterisation by its spectral range but it could analyse a surface more rapidly than Raman spectroscopy. In the case of characterisation VNIR HSI could be useful for mapping heterogeneity of colourants, or to highlight areas of interest to investigate.

To investigate the ability of VNIR HSI to detect traces of pigmentation the shrine of Taharqa, in the Ashmolean Museum, was scanned. VNIR HSI was capable of mapping pigmentation not obvious to the eye. It could therefore act as a useful aid in the reconstruction of works of art, however as it was limited to mapping only pigmentation that it could detect, X-ray fluorescence (XRF), and data from past experiments, were used in conjunction with VNIR HSI in order to more fully evaluate the surface.

To investigate the abilities of VNIR HSI as a method for the monitoring of pigmentation in an artefact, an illuminated manuscript on short display at the Bodleian Libraries, and a partially faded silk robe now in the collection of The Ashmolean Museum, were analysed and it was found that a colour change value was obtainable, and that VNIR HSI could afford the advantages of being non-contact, full-field, and capable of digitising the scan in comparison to presently used methodology.

Authors: Maybury, IJ

• DOI: 10.5287/ora-aejkpzgz6
• Type of award: MSc by Research
• Level of award: Masters
• Awarding institution: University of Oxford
• Language: English
• Keywords: hyperspectral imaging
• Subjects: Hyperspectral imaging