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Treatment of Portrait of a Man
Posted By Beatriz Centeno On December 6, 2011 @ 9:00 am In Arts of Asia,Conservation | 6 Comments
In preparation for the paper rotation that recently went on view in our second floor, the works were examined and, if necessary, stabilized before going on view. Portrait of a Man is a Western-style painting of a man standing in a landscape and it is one of the pieces that required examination and treatment. This Indian miniature painting is composed of opaque watercolors and gold paint on a cream, Western, laid paper.
Following the identification of its materials, a condition assessment was carried out with the aid of a stereomicroscope (for low magnification) and illumination techniques to accentuate features of the piece that are not visible in plain sight.
At the time of condition assessment, the piece was in poor condition. There were dents and abrasions, but the most disfiguring problem was an uneven, yellowed coating on the image. While the coating was thin and spotty in some areas, it was thick and cracked in others. I took a look under the stereomicroscope and noticed that this coating was strong and had pulled up pigment with it where it was cupped and cracked, mainly on the upper right corner. In addition extraneous white fibers attached to the surface coating were visible throughout the image and can clearly be seen in raking illumination (light source coming from one side). It is thought these fibers became entrapped during a previous and unsuccessful restoration attempt to swell and reduce the coating by rubbing it with cotton.
I also examined the piece under long-wave ultraviolet (UV-A) irradiation, which brings out other features that are not evident to the naked eye. A mottled orange-yellow fluorescence coincided with the yellowed coating that was visible in plain sight. Also, the upper right corner of the image was absorbant to UV-A irradiation, which is a common reaction of modern materials under UV-A. At this point, an educated guess made me believe that the fibers embedded in the surface and the loss of media (watercolor) and overpaint on the upper right corner were most likely the result of a failed attempt to remove the coating with cotton and restoring the color.
After discussing the treatment plan with the curator, Joan Cummins , it was decided that the main goal was to minimize only the most distracting damages affecting the readability of the image. I proceeded with chemical spot testing to determine the solubility of the coating.
Localized testing using 100% ethanol and 100% deionized water was done to test the solubility of the coating. The coating did not swell with ethanol; it swelled with deionized water. Since natural resins are insoluble in water and soluble in alcohol and other organic solvents, I could eliminate dammar or shellac as the coating. As the coating did swell with water, it suggested a gum or glue material. A tiny sample of the coating was taken for technical analysis with the Biuret test. The results indicated that the coating is protein-based and thus probably an animal glue (i.e. adhesive derived from animal tissues). Ironically, water can also solubilize the gum Arabic binder in watercolors. This represented a limiting factor for removing the fibers on the surface as well as reducing the thicker and discolored areas of the coating. However, the application of a small amount of water would not disturb the original media if readily blotted from the surface. I brushed deionized water on the white fibers, removed them with a dry brush, and lightly blotted the surface.
The small areas showing flaking of the paint layer needed to be secure in place and flattened as much as possible before reducing the coating. I applied a suitable consolidant (an adhesive) under the flaking coating and carefully flattened the cupped and cracked areas with a microspatula. When the paint was reattached and secure, I thinned the areas of thick coating mechanically using a scalpel, while viewing under the stereomicroscope. Our main goal was accomplished, making way for the completion of other steps in this treatment, like mending minor tears, and filling and inpainting small losses of support.
Portrait of a Man will be on view until May 2012, so don’t miss the rotation!
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 Joan Cummins: http://www.brooklynmuseum.org/community/blogosphere/author/cumminsj/
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