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Published January 7, 2010 | Submitted
Report Open

Protection of works of art from photochemical smog


Air pollution has been suspected as a possible cause of damage to museum collections for at least one hundred years. As early as 1888, concern over pollution in the London atmosphere led to a systematic investigation of whether or not direct exposure to the combustion exhaust from a burning gas jet would cause artists' pigments to fade. Since that time, a number of studies have examined the effects of sulfur oxides air pollutants on leather, paper, calcareous stone, textiles and a few pigments. Much less has been said about the effects of photochemically-generated air pollutants like ozone, which is found in Los Angeles, Athens and other cities that experience intense solar radiation in the presence of high population densities. Ozone is one of the most powerful oxidants found in nature. High levels of atmospheric ozone (O_3) in outdoor urban atmospheres are known to be caused by the combined interaction of sunlight, oxygen, oxides of nitrogen and hydrocarbons. Many effects of ozone on materials have been reviewed by Jaffe and by the National Research Council. Accordingly, damage to materials has been reported for rubber, exterior paint binders and textile fibers. Ozone attack on cellulose has been investigated by Katai and Schuerch. Within the textile industry, ozone has been implicated in the fading of anthraquinone dyes on nylon and cellulose acetate. In the early 1980's, a pilot study was conducted to determine whether or not artists' pigments are affected by exposure to ozone at the concentrations found in urban atmospheres. In the first exploratory test, seventeen artists' watercolor pigment samples and two Japanese woodblock prints were exposed to 0.40 ppm ozone in a controlled test chamber for three months. A second study followed in which the ozone-fastness of 27 modern organic watercolor pigments was examined. It was found that several artists' pigments when applied on paper will fade in the absence of light if exposed to an atmosphere containing ozone at the concentrations found in photochemical smog. Alizarin-based watercolors containing 1,2-dihydroxyanthraquinone lake pigments were shown to be particularly sensitive to ozone damage, as were the yellow pigments used in the Japanese woodblock prints tested. Indoor-outdoor ozone measurements made at that time in a Pasadena, California art gallery confirmed that ozone concentrations half as high as those outdoors can be found in art galleries that lack a chemically protected air conditioning system. The identification of ozone-sensitive artists' pigments plus the existence of high ozone levels inside at least one museum argued that further investigation of the hazard to works of art posed by exposure to photochemically-generated air pollutants was warranted.

Additional Information

© 1988 Environmental Quality Laboratory. California Institute of Technology. Thanks are due to Dr. Frank D. Preusser and the staff of the Getty Conservation Institute for technical advice throughout the course of this project. The natural colorants used in this work were made available with the cooperation of a large number of individuals. Eugene Farrell and Richard Newman of the Harvard University Art Museums, and Gary Wade Alden of the Balboa Art Conservation Center provided pigments used traditionally in Western pictorial art. The Japanese silk cloths were dyed by Mr. S. Yamazaki and were made available through Dr. K.M. Kashiwagi of the Kyoritsu Women's University, Tokyo. Dr. Takeo Kadokura and Dr. Kunio Yoshizumi are also to be thanked for their help with sample acquisition in Japan. The aigami sample and woodblock prints from an illustrated poetry book were provided by Mrs. Keiko Keyes. The Munsell conversion calculations were performed using a computer program supplied by Max Saltzman and Dr. Fred Billmeyer. Discussions with Mr. Saltzman were helpful in the spectroscopic analyses of the pigments. The authors also wish to acknowledge the assistance of Dr. Helmut Schweppe, whose advice and reference materials aided the thin layer chromatographic identification of the natural colorants. Solvent extractions needed to prepare samples for mass spectrometry analysis were carried out by Dr. Scott Boyce of the California Institute of Technology. The mass spectrometry analyses were performed by Drs. Dilip K. Sensharma and John Wells, Department of Chemistry, University of California, Los Angeles. The XRF analyses of the inorganic constituents of the pigments tested were performed at NEA, Inc., Portland, OR. The program of indoor/outdoor ozone concentration measurements in southern California museums was conducted with the help of Mark Adams and Christine Tiller of the California Institute of Technology. The assistance of the staff of each of the museum sites tested is sincerely appreciated; without access to these facilities, this research project could not have been completed. Dr. Fred Shair of Caltech made available the laboratory facilities needed for the SF6 tracer tests used to determine the air exchange rates between display cases and the room air. This project final report and the accompanying eleven journal articles were typed by Dixie Fiedler and Christina Conti. Nancy Tomer drafted the figures.

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Submitted - EQL-Report-28.pdf


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