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  • Writer's pictureJennifer McGlincheySexton

Test Panels and UV/Vis Documentation

Duke University recently hosted a FAIC workshop in my ongoing series for UV/visible fluorescence documentation of cultural heritage materials. In this workshop, I teach conservators how to best use UV radiation to bring out details such as, coatings, old restorations, information about pigments, and other attributes.

Each one of my workshops is different. The participants drive the workshop, especially the practice sessions, based on their interests and backgrounds. One of the topics that we discussed in depth this time - conservation test panels. Every conservation lab I've visited has a small collection of test panels. Varnishes, face-mounted photographs, pigments, adhesives, mounting methods - you name it. The panels usually serve a specific purpose - like pH of materials, dust accumulation, mounting systems, or pigment samples. They can pass as decoration, even as they're being naturally aged.

Test Panels by Rachel Penniman, Beth Doyle, and myself, as seen with UV/vis fluorescence

I always travel with my test panel when giving this workshop. I have been building and refining it over the last few years, adding materials as I get small amounts of them. Rachel's adhesive wheel is from a different AIC workshop in 2007. Beth's pigment panel provides examples of pigments in a variety of media.

Pigment, adhesive and support test panel as seen in visible light (normal light) and UV/vis (UVF, UV-vis, UV visible fluorescence)
Test Panel - Visible Light and UV/vis

These test panels give conservators vital information for understanding cultural heritage materials because they provide information about known materials. Many materials have visual differences, but changes in different wavelengths can begin narrow down the materials an artist or previous conservator may have used. My focus, naturally, is UV/Visible fluorescence, but this panel also shows some interesting things in IR or reflected UV. We were lucky to be able to image all three test panels using Duke's multispectral imaging system (MSI).

MSI at the Perkins Library, Duke University is accomplished by using Phase One IQ260 digital back in conjunction with an Equipoise filter wheel and light panels and Spectral XV software. WIth this system, 17 images that represent exposures at different wavelengths and wavelength/filter combinations can be compared and stacked. It is a powerful tool to use material differences to pull out details that may not be otherwise visible.

Pigment panel captured in reflected UV, reflected IR, and a composite visualization of MSI with false color.
Test panel - Mutilspectral images captured using Duke MSI equipment

In graduate school, our documentation professor, Dan Kushel, used a lot of tricks to teach us about imaging techniques. UV/vis was especially memorable because he had a painting that was made specifically for UV/vis. In normal light, it was white and boring. But, when the UV lamps turned on, the image of a clown was revealed. The trick relied on some known difference in the UV/vis fluorescence of white pigments. The clown painting inspired me to commission my own white painting.

White painting by Brett Andrus as seen in normal and UV/Vis
Painting executed in titanium, zinc and lead white by Brett Andrus. Left, the painting as seen with normal light; Right, the painting as seen with UV/Vis.

In a sense, this painting is a test panel as well, created for the express purpose of demonstrating material differences. I think it memorably illustrates the power of imaging techniques.

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