Photography
Photography with visible light is the simplest way to record an object’s appearance. Adjusting photographs digitally or photographing the object under a range of light wavelengths, however, can provide more information.
Multi-spectral Imaging is a technique where an object is exposed to different wavelengths of light, from visible light we can see ourselves, to light we can’t see such as ultraviolet and infrared. Options for examining the charter with Multi-spectral Imaging were limited due to lack of equipment (special light sources are required to produce a set of photographs taken with a wide spectrum of wavelengths), but examination of the text with an infrared digital microscope showed the ink was probably an iron-gall ink – other black inks, such as those made with carbon, are transparent to infrared light and do not appear when photographed using infrared wavelengths (Jones et al., 2020, p. 340).
Multi-spectral Imaging has been used on other manuscripts to recover text lost through ageing, deliberate erasure, and even fire damage – traces of text in the parchment’s surface, invisible to the eye, can be revealed under different wavelengths of light (Duffy, 2018).
‘Alternative colour spaces’ offer the possibility of similar results by digitally manipulating normal photographs. A photograph is usually depicted with red, green and blue (RGB) components. These components can be altered – for example, by removing one of the components or altering their ratios – to reveal invisible features such as watermarks in paper or lost text (Tonazzini et al., 2019, pp. 37-38). Photographs of the charter were explored in this way, but no hidden features were revealed.
Infrared digital microscope image of the ink.