Further comparative investigations are carried out on other aspects of the wrapping manufacture, including the nature and spatial distribution of the dyes present on the bandages. The non-invasive proposed protocol for this study couples multispectral imaging techniques (MSI) with fibre optic reflectance spectroscopy (FORS) to ensure suitable identification of colouring matters used in the dyeing process. MSI methods are a system of broadband images captured using selected ranges of wavelengths of light extended beyond the capabilities of the human eye to record reflectance and luminescence properties of the organic and inorganic materials, including dyes. This allows the identification of the spatial distribution and, in some cases, the chemical nature of colorants present on the mummy wrappings and facilitates comparisons between objects. The detection of dyed yarns is challenging since they are mostly degraded due to bleaching agents, used to obtain a better dyeing result, and the combination of different materials used in mordanting, especially iron compounds and tannins to reach a very dark color. The usual fading of textiles and the huge layer of soiling often present further affect the recognition of coloring matters.
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This non-invasive, cost-effective and portable methodology is carried out through a full-spectrum modified camera, different radiation sources and a set of filters to produce reflectance (Visible-reflected [VIS], Infrared-reflected [IRR], Ultraviolet-reflected [UVR], False-colour reflected [IRRFC, UVRFC] and luminescence, including Ultraviolet-induced luminescence [UVL]) images, that reveal emitting materials and their reflectance and absorbance properties, which often help in identify and characterize dyes as well as to assess their condition.
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