Scientific Examination of Art Modern Techniques in Conservation and Analysis (2005) / Chapter Skim
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The Scientific Examination of Works of Art on Paper--Paul M. Whitmore
The Scientific Examination of Works of Art on Paper--Paul M. Whitmore
Pages 27-39
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From page 27... ...
Paper can be characterized easily to an extent, in identifying a watermark or the risk of deterioration from a high acid content, but the monitoring of the condition and degradation of paper remains an extremely difficult challenge. The assessment of light sensitivity, which is not easy to determine by merely identifying material composition, has been made straightforward by the development of a device that allows rapid, essentially nondestructive fading tests.
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From page 28... ...
Another distinction between paper-based objects and traditional paintings is the use of the paper substrate as part of the image itself. Particularly with such graphic art as drawings and prints but also with printed text or even thinly painted watercolors, the paper substrate is exposed and is part of the image.
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From page 29... ...
SURVEY OF EXAMINATION AND MATERIAL IDENTIFICATION TECHNIQUES The most common technical investigation for paintings or colored prints on paper involves identification of the pigments in the paint. For this, the routine analytical tools of polarizing-light microscopy, X-ray diffraction, and elemental analyses by X-ray fluorescence are commonly employed, usually on samples of the paint that have been removed from the artifact.
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From page 30... ...
Watermarks, the decorative patterns often woven into the wire molds or embossed on the cast sheets, are also the most obvious characteristic patterns of the paper manufacture. The evidence of chain and laid lines and watermarks can be captured in any of a number of ways, with transmitted light photography or with beta or soft X-ray radiography, and various image processing tools have been applied to enhance such records (erasing interferences from the printing, for example)
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From page 31... ...
Chemical degradation breaks cellulose chains, which reduces the average molecular weight but more importantly also breaks the connections between the highly crystalline cellulose zones. This progressive rupture of the tie chains, the amorphous cellulose chains connecting the crystallites and imparting the cohesive strength to the fiber, is the underlying aging chemistry leading to physical failure of the paper sheet.
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From page 32... ...
so that they do not suffer from fading damage caused by inappropriate display. These same tests, done with filtered illumination, can also be used to test the effectiveness of different lighting in reducing fading rates.
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From page 33... ...
FIGURE 2 Fading test results for selected Winsor & Newton gouache paints. "Blue Wool 1" designates fading test results for the ISO Blue Wool no.
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From page 34... ...
. In addition to these fading tests designed to evaluate individual artifacts, current studies are measuring the fading rates of particular colorants in Japanese woodblock prints from different eras, printed at different depths of color, and of varying degrees of prior fading.
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From page 35... ...
1, showing no difference in fading rate in anoxic environment. Reprinted from the Journal of the American Institute for Conservation, vol.
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From page 36... ...
CONCLUSION The scientific examination of works of art on paper utilizes tools from the very simple to state-of-the-art analytical instrumentation, depending in large part on the question that is the objective of the investigation. Identifying pigments or paper fibers is relatively easy, while inks are more challenging because of the lack of pronounced chemical differentiation between the ink types and because of possible interferences in the analyses from the paper substrate.
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From page 37... ...
"BW2" and "BW3" denote the color change produced in ISO Blue Wool fading standards nos. 2 and 3, respectively, after a five-minute exposure in the fading tester.
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From page 38... ...
1995. Journal of the American Institute for Conservation 34:173-186.
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From page 39... ...
1998. Journal of the American Institute for Conservation 37:294-311.
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