It is frequently necessary to document a restoration process with photos. Then it is foremost about clarity: accurately depicting as many of the existing inadequacies as possible in an artwork or structure. Because restorers are usually not in a position to call on a professional photographer anytime they desire, they tend to shoot lots of so-called ‘before and during treatment’ photos themselves. The client or restorer often engages a professional photographer to take high-resolution (‘after treatment’) photo(s) once the restoration is completed.
But how do you go about making good photographs during a restoration, using diffused or UV light? If you work as a restorer and have specific technical questions, in many cases an advisory consultation can significantly improve the quality of your work-in-progress photos. As a result, these photos will provide an even better record of the entire restoration process.
Below we see restorer Lieve d'Hont removing the old varnish layer from the Self Portrait of Paul Moreelse (c. 1630, Mauritshuis, The Hague). Followed by two photos of the painting with the varnish partially removed, shot with 'plain light' and UV light. Lastly, we see the elements Earth and Air —two of The Four Elements by Giovanni Antonio Pellegrini (1718) from the so-called Gouden zaal (Golden room) in the Mauritshuis —in UV light and after being restored.
Lieve d'Hont explains: ‘Ultraviolet radiation (UV light) reveals the fluorescent properties of materials. Old yellow varnishes, based on natural resins, are perceived by the camera as yellowish-green—pigments often have a characteristic fluorescence as well. The white lead pigment used in the man’s collar is seen as white, while zinc white pigment fluoresces bright green. (Zinc white started being used at the end of the eighteenth century). These photos were made during the removal of earlier varnishes and retouchings. The old varnish layer fluoresces transparent green. Where the varnish has been removed, the yellow-brown fluorescence of the original background and the bright-green fluorescent retouching with zinc white are easy to distinguish. In the restored paintings of Pellegrini, the bright-green colour is also caused by zinc white.’