Photographic Services: Ultraviolet Fluorescence
Exposure to ultra violet light can cause some substances to fluoresce. This is particularly useful to distinguish between varnish types and to indentify retouching. Some pigments have particular characteristic fluorescence. Madder for instance fluoresces bright orange. Ultraviolet light can therefore be used to identify a number of characteristics.
The inscription becomes clearly visible under ultraviolet lighting as are areas of retouching in the figures hands.