Dean Yoder Conservator of Paintings
Light Fantastic Museum photographer Howard Agriesti worked with paintings conservators to shoot the exact same portion of the painting in three conditions of visible light: “normal” natural light, raking light (light source at an oblique angle to show surface texture), and specular light (light source adjusted for maximum reflection into the camera lens). Then the same view was done in the non-visible range using infrared, ultraviolet, and x-ray wavelengths. All of these views are in perfect register in a single multilayer Photoshop document. The conservator then created additional layers of that same document to mark areas where his experienced eye detected different kinds of modifications to the surface.
One Image, Many Layers The image used for this project comprises 15 digital layers superimposed. The researcher can turn on or off the visibility of any combination of layers to view specific information.
The condition of a work of art and how it has been interpreted through restoration can affect our aesthetic perceptions of quality, technique, color, and form. The capacity to separate original condition from past restoration leads to a more in-depth understanding of an artwork.
The Cleveland Museum of Art’s Portrait of a Woman (subject of a special conservation study room in the Rembrandt exhibition) is a good example of how original condition and restorative treatments combine to limit the proper aesthetic reading of a painting.
The museum is in the initial stages of examining this portrait and planning for a possible treatment after the exhibition closes. The conservator and curator are using this exhibition in part as a laboratory to study and compare our painting to others by Rembrandt. The study gallery demonstrates several photographic and scientific tools: high-resolution images of the painting are shown under different energy sources and lighting conditions and a video guides the viewer as one imaging technique morphs into another. Programmed iPads on the study table allow visitors a more self-directed discovery.
These features are designed to illustrate how imaging technologies allow museum conservators and curators to separate a painting’s current condition from the added layers of its treatment history. Once this information is understood, we can better evaluate how these previous interventions influence our aesthetic interpretation of the painting.
Each of the three lighting conditions and three energy sources offers different information about the construction and condition of the paint layers. None of these techniques are new to the field of painting conservation, but what separates this analysis from others before is that all the images are annotated and are overlaid in perfect alignment—thus, observations unique to each image can be compared to subsequent images. This flexibility increases our ability to visualize the aesthetic impact of former treatments to the original painting.
Armed with such knowledge, the museum can make the most informed decision about how to proceed with future treatment and gauge the degree of improvement that can be anticipated.
Ultraviolet Mapping The ultraviolet photograph reveals areas where the painting was recently retouched as a darker reddish violet color (because the newer retouching paint absorbs UV light). Yoder then outlined these areas in yellow.
Map Transferred to Normal Light By switching back to the natural light image and superimposing the yellow retouching map, the viewer can see where these retouched areas are in the context of normal viewing conditions.
Work History The areas marked above show parts of the painting where modifications to the original paint have been made over the past few hundred years, as revealed through different photographic modes.
Green Ultraviolet light, showing older retouching
Magenta Raking light, showing areas of previously tented paint
Blue Dotted Ultraviolet light, remnants of much older varnish
Orange Normal plus infrared light, showing abraded glazes
Red Dotted Infrared light showing most notable abrasion to the original paint
White Natural and ultraviolet light, showing retouching with white zinc paint
Teal Ultraviolet light, showing recent varnish masking retouching
Yellow Ultraviolet light, showing recent retouching
Cleveland Art, March/April 2012