Collagen is fluorescent, so parchment usually fluoresces when exposed to UV radiation, appearing bright bluish white. The charter appeared bright when exposed to a UV light source as expected. Sometimes parchment does not fluoresce, because it has been treated with vegetable tannins – the same chemicals used to tan leather – which ‘quench’ the natural fluorescence of the skin (Reed, 1972, pp. 252-258). That the charter’s parchment fluoresced shows that this manufacturing method was not used.

 

As the ink does not fluoresce, it appears in much greater contrast to the parchment than under normal light. UV is an important aspect of Multi-spectral imaging for this reason – text and traces of text become much more visible under UV light, allowing recovery of lost text (Pottier et al., 2019, pp. 185-186). The thin, difficult to read text on the reverse of the charter became more legible under UV light. The small dots covering the surface which may be traces of hair follicles described in the section on Magnification were also more visible, but did still not show a discernible pattern.

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Additionally, some areas of the wax seal fluoresced. The newer wax fluoresced, along with the tops of raised areas of the original seal, the areas most vulnerable to abrasion. This may result from a coating suppressing the natural fluorescence of the wax being rubbed off, or may indicate repairs with new wax to damaged parts of the original seal.