1.8 Protection of Works of Art from Damage Due to Photochemical Smog
 

California Institute of Technology
The Getty Conservation Institute
Daniel Grosjean and Associates
Mellon Institute, Pittsburgh, PA

Glen R. Cass
Paul M. Whitmore
William Nazaroff
Cynthia Shaver Atherton
Kaitlin Drisko
C. Pam DeMoor
Mark Adams
Lisa Cummings
Cynthia Wittman
Christine Tiller
James R. Druzik
Daniel Grosjean
Department of Civil Engineering, University of California,
633 Davis Hall, Berkeley, California 94720
Period of Activity: 4/84 to 4/89

Project Abstract
The objective of this research program was many fold, including:

a.) establishment of ozone as a damaging factor to sensitive colorants

b.) establishment of nitrogen dioxide as a potentially damaging factor to sensitive colorants

c.) measure indoor ozone, nitrogen dioxide concentrations in a selec tion of museums and art galleries in the Southern California area

d.) determine protective strategies shielding sensitive objects physically from exposure

e.) mathematically model indoor air quality for the museum environment

f.) determine the protective effects, if any, of a wide assortment of binders and coatings on a broad selection of paint media

g.) determine as well as possible mechanisms of ozone damage to a few of the larger classes of colorants-specifically those based on Alizarin and like compounds and the Indigo system.

Primary Publications
Cass, G. R., W. W. Nazaroff, D. Grosjean, P. Whitmore, and J. R. Druzik, "Protection of Works of Art from Damage Due to Photochemical Smog," progress report through September 1985.

ABSTRACT-Experiments conducted in the early 1980s on a very small selection of modern artists' pigments showed that several pigments fade dramatically if exposed to ozone at the levels found in Los Angeles photochemical smog. The objective of this research project is to provide a comprehensive assessment of the full scope of this fading hazard to works of art, and to determine the methods that can be used to protect works of art from damage due to photochemical oxidants. In order to achieve this objective, research is progressing on several fronts. Accomplishments to date are summarized briefly, followed by several appendices that provide more detailed information on some aspects of the research.

Cass, G. R., J. R. Druzik, D. Grosjean, W. W. Nazaroff, P. M. Whitmore, and C. L. Wittman, "Protection of Works of Art from Photochemical Smog," Final Report to the Getty Conservation Institute, June, 1988.

ABSTRACT-This final report has twelve chapters and runs a total of 282 pages of text, tables, and figures. The chapter titles are:

1. Introduction

2. The Ozone Fading of Traditional Natural Organic Colorants on Paper

3. The Ozone Fading of Traditional Japanese Colorants

4. Fading of Alizarin and Related Artists' Pigments by Atmospheric Ozone: Reaction Products and Mechanisms

5. Ozone Fading of Natural Organic Colorants: Mechanisms and Products of the Reaction of Ozone with Indigos

6. Ozone Fading of Organic Colorants: Products and Mechanisms of the Reaction of Ozone with Curcumin

7. Ozone Fading of Triphenylmethane Colorants: Reaction Products and Mechanisms

8. The Fading of Artists Colorants by Exposure to Atmospheric Nitrogen Dioxide

9. Mathematical Modeling of Chemically Reactive Pollutants in Indoor Air

10. The Measurement and Model Predictions of Indoor Ozone Concentrations in Art Museums

11. The Ozone Fading of Artists' Pigments: An Evaluation of the Effects of Binders and Coatings XE "Binders and Coatings"

12. Protection of Works of Art from Damage Due to Atmospheric Ozone;

Cass, G. R., J. R. Druzik, D. Grosjean, W. W. Nazaroff, P. M. Whitmore, and C. L. Wittman, Protection of Works of Art from Atmospheric Ozone, Research in Conservation, N 5, 1989.

ABSTRACT-Condensed version of the Final Report. (See above abstract).

Drisko, K., G. R. Cass, P. M. Whitmore, and J. R. Druzik, "Fading of Artists' Pigments due to Atmospheric Ozone," Wiener Berichte Uber Naturwissenschaft in Der Kunst, eds. A. Vendl, B. Pichler, J. Weber, Doppelband, 2/3, 1985/86, pp. 66-87.

ABSTRACT-Recently it has been shown that several artists' pigments fade in the absence of light if exposed to atmospheric ozone at the levels found in Los Angeles photochemical smog. In this study, a large number of organic artists' pigments have been examined to further assess the scope of this fading hazard to works of art. It was found that all of the alizarin-derived pigments are susceptible to fad ing in the presence of ozone. Several organic red pigments were identified that are much more ozone-resistant than the alizarin lakes, including quinacridone reds and BON arylamide reds. The question of ozone exposure in museums is reviewed. It is shown that indoor ozone concentrations may be as high as 50% to 70% of those outdoors, and that long-term average outdoor ozone levels in many parts of the world are nearly as high as those found in geographic locations with well-known pho tochemical air pollution problems.

Druzik, J. R., M. S. Adams, C. Tiller, and G. R. Cass, "The Measurement and Model Predictions of Indoor Ozone Concentrations in Museums," Atmospheric Environment, Vol. 24a, N 7, pp. 1813-1823, 1990.

ABSTRACT-During the summers of 1984 and 1985, two matched ultraviolet pho tometric ozone monitors were used to take simultaneous indoor/outdoor ozone measurements at eleven institutions housing cultural properties over a period totaling thirty-eight days. These sites were picked to represent a wide range of building types in the Los Angeles area and 100 miles to the south in San Diego, California. Each building and its ventilation system was documented. A hot wire anemometer was used to measure air flow into and out of ventilation ducts, doors, and windows at each site. In stagnant areas, air exchange rates were evaluated from standard engineering estimates for air infiltration. From the accumulated information, the air exchange rates and retention times for ozone destruction by reaction with building surfaces could be determined.

Grosjean, D., P. M. Whitmore, C. P. De Moor, G. R. Cass, and J. R. Druzik, "Fading of Alizarin and Related Artists' Pigments by Atmospheric Ozone," Environmental Science and Technology, Vol. 21, 1987, pp. 635-643.

ABSTRACT-The colorants alizarin and Alizarin Crimson (a calcium-alu minum lake pigment) and their simple structural homologues anthra-quinone were deposited on silica gel, cellulose, and Teflon substrates and exposed in the dark to ozone in purified air (0.4 ppm O3 for 95 days). Exposed and control samples were analyzed by mass spectrometry . Alizarin Crimson reacted with ozone on all substrates, yielding phthalic acid (major), benzoic acid (minor), and other minor and unidentified products. Anthraquinone did not react with ozone irrespective of conditions. Alizarin did not react on Teflon or cellulose but reacted on silica gel to yield phthalic acid (major) and other products. A chemical mechanism responsible for the fading of these alizarin-based colorants by ozone is suggested that is consistent with the products distribution, the observed reactivity sequence, and the observed substrate-specific effects. The possible application of this work to predicting the ozone fastness of other alizarin-related pigments is discussed briefly.

Grosjean, D., P. M. Whitmore, C. P. De Moor, G. R. Cass, and J. R. Druzik, "Ozone Fading of Organic Colorants: Products and Mechanism of the Reaction of Ozone with Curcumin," Environmental Science and Technology,Vol. 22, 1988, pp. 1357-1361.

ABSTRACT-The organic colorant curcumin [1,7-bis(4-hydroxy-3 methoxy-phenyl)-1,6-heptadiene-3,4-dione] was exposed to ozone in purified air in the dark, and the exposed samples were analyzed by mass spectrometry. The major reaction products included vanillin (4-hydroxy-3-methoxybenzaldehyde ) and vanillic acid (4-hydroxy-3-methoxybenzoic acid) . These products and the corresponding loss of chromophore (i.e. fading of curcumin) are consistent with a reaction mechanism involving electrophilic addition electrophilic addition of ozone onto the olefinic bonds of curcumin. Vanillin and vanillic acid did not react with ozone under the con ditions of this study.

Grosjean, D., P. M. Whitmore, G. R. Cass, and J. R. Druzik, "Ozone Fading of Natural Organic Colorants: Mechanisms and Products of the Reaction of Ozone with Indigos," Environmental Science and Technology, Vol. 22, 1988, pp. 292-298.

ABSTRACT-Indigo , dibromoindigo , and colorants containing thioindigo and tetrachlorothioindigo were exposed in the dark to dry, purified air containing ozone (10 ppm) for four days, and the exposed samples were analyzed by mass spectrometry. Under the conditions employed, indigo and dibromoindigo were entirely consumed, and the major reaction products were isatin and isatoic anhydride from indigo and bromoisatin and bromoisatoic anhydride from dibromoindigo. Thioindigo and its chloroderivative also reacted with ozone, though at a slower rate; the corresponding substituted isatins and anhydrides were tentatively identified as reaction products.

Grosjean, D., P. M. Whitmore, and G. R. Cass, "Ozone Fading of Triphenylmethane Colorants: Reaction Products and Mechanisms," Environmental Science and Technology, Vol. 23, N 9, 1989, pp. 1164-1167.

ABSTRACT-Triphenylmethane compounds were exposed in the dark to ozone in air (10 ppm for 4 days), and the exposed samples were analyzed by mass spectrometry. There was no evidence for reaction between ozone and triphenyl-methane and between ozone and the triphenylcarbinol pararosaniline base . In contrast, the triphenylmethane cationic dye Basic Violet 14 yielded substituted benzophenones and other aromatic compounds. These products are consistent with a mechanism involving ozone addition on the unsaturated carbon-carbon bond. The results are briefly discussed in terms of the ozone-fastness of triphenylmethane dyes used as artists' pigments and industrial colorants.

Nazaroff, W. W., and G. R. Cass, "Mathematical Modeling of Chemically Reactive Pollutants in Indoor Air," Environmental Science and Technology, Vol. 20, 1986, pp. 924-934.

ABSTRACT-A general mathematical model is presented for predicting the concentrations of chemically reactive compounds in indoor air. The model accounts for the effects of ventilation, filtration, heterogeneous removal, direct emission, and photolytic and thermal chemical reactions. The model is applied to the induction of photochemically reactive pollutants into a museum gallery, and the predicted NO, NOx-NO, and O3 concentrations are compared to measured data. The model predicts substantial production of several species due to chemical reaction, including HNO2, HNO3, NO3, and N2O5. Circumstances in which heterogeneous chemistry may assume particular importance are identified and include buildings with glass walls, indoor combustion sources, and direct emission of olefins.

Whitmore, P. M., G. R. Cass, and J. R. Druzik, "The Ozone Fading of Traditional Natural Organic Colorants on Paper," Journal of the American Institute for Conservation, Vol. 26, 1987, pp. 45-58.

ABSTRACT-This report details the results of an ozone exposure experiment per formed on a large number of traditional natural organic colorants applied to watercolor paper with no binder. These colorants were exposed in an environmental chamber to an atmosphere containing 0.397-0.007 parts per million (ppm) ozone at 72 F and 50% RH in the absence of light for 12 weeks. This ozone concentration is typical of that found in the Los Angeles atmosphere during a heavy smog episode. The total ozone dose delivered to the samples is equivalent to about four years of exposure to outdoor air in Los Angeles or to about eight years inside a typical air-conditioned building in Los Angeles. The ozone sensitivity of these colorant systems was evaluated by monitoring the color changes which occurred during the exposure. Almost all colorant systems tested showed some degree of fading after ozone exposure, and a few of these (curcumin, dragon's blood, indigo, and madder lake) should be considered very ozone-fugitive.

Whitmore, P. M., and G. R. Cass, "The Ozone Fading of Traditional Japanese Colorants," Studies in Conservation, Vol. 33, 1988, pp. 29-40.

ABSTRACT-The colorfastness of several traditional Japanese colorants upon exposure to atmospheric ozone was tested in a chamber exposure experiment. Samples, in the form of colorants applied to paper, dyes on silk cloth, and colorants on a 19th century Japanese woodblock print, were exposed to an atmosphere containing 0.40 part per million ozone at 22 C and 50% RH, in the absence of light, for 12 weeks. Color differences, calculated from the measured diffuse reflectance spectra, were used to assess the rate and extent of the ozone fading. Of the colorants applied to paper, orpiment was the only inorganic pigment that showed severe color loss after ozone exposure. Several organic colorants on paper also reacted, including the widely used plant colorants ai (indigo) and ukon (turmeric). The wood block print, produced using the plant-derived colorants beni (safflower), ai (indigo), shio (gamboge), and aigami (dayflower) showed significant ozone fading only in the blue and green areas, which contain ai. Several of the dyed silk cloths also exhibited some color change in this experiment, suggesting that prolonged exposure to atmos pheric ozone could pose a risk to these materials as well.

Whitmore, P. M., and G. R. Cass, "The Fading of Artists' Colorants by Exposure to Atmospheric Nitrogen Dioxide," Studies in Conservation, Vol. 34, 1989, pp. 85-97.

ABSTRACT-Nitrogen dioxide is a common air pollutant formed in the atmosphere from the nitric oxide emissionsfrom fuel combustion sources. Samples of organic and inorganic pigments, iron inks on paper, and traditional Japanese tex tile dyes mordanted onto silk were exposed to 0.50 ppm NO2 in air for 12 weeks. Ten of the traditional natural organic colorant samples on paper tested showed mea surable color changes (DE>2) as a result of the NO2 exposure, as did several of the an thraquinone-based synthetic organic pigments. The arsenic sulfide pigments orpiment and realgar and the iron inks tested showed considerable color changes (DE >5) over the 12-week period. Nine of the 23 Japanese dyed silk cloths changed color by at least two DE units. An NO2 dose (concentration times duration of exposure) of the magnitude employed in this experiment would be experienced in side an unprotected museum in downtown Los Angeles over about a two-year period, and in many other cities within a period of five to six years.

Wittman, C. L., P. M. Whitmore, and G. R. Cass, "The Ozone Fading of Artists' Pigments: An Evaluation of the Effect of Binders and Coatings," Technical Report, Protection of Works of Art from Photochemical Smog, The Getty Conservation Institute Scientific Program Report, June 1988, pp. 228-252. AATA, Vol. 27, 1990, 1993, p. 196.

ABSTRACT-A chamber exposure experiment has been conducted to examine the effect of binders and coatings that might be used to protect artists' pigments from oxidation by atmospheric ozone. Alizarin Crimson pigment was used as a sensitive colorimetric detector of the penetration of ozone or its reaction products through the binder and coating systems tested. Binder systems studied in cluded acrylics, beeswax, casein, egg tempera, oils, and varnishes. Coatings tested included acrylic emulsions, methacrylates, beeswax, varnishes, shellac, and ethulose (a consolidant). Alizarin Crimson dry pigment airbrushed onto a white painted background with no binder or coating typically faded severely (DE <15) under the conditions of this experiment (0.40 ppm O3 for 12 weeks at 22 C and 52% RH). In contrast, many of the binder and coating systems tested were capable of limiting the fading of an equivalent Alizarin Crimson sample to a color change of DE < 1 during identically the same exposure conditions. Several binders and coatings did prove to be less effective than others. In particular, many of the acrylic emulsion coatings failed to offer adequate protection to the Alizarin Crimson pigment samples tested.

Grosjean, D., P. M. Whitmore, P. C. DeMoor, J. R. Druzik, D. K. Sensharma, and G. R. Cass, "Products and Mechanisms of the Reactions of Gas Phase Ozone with Organic Colorants," Preprints, American Chemical Society, Division of Environmental Chemistry, Los Angeles, California, September 25-30, 1988, pp. 132-135.

ABSTRACT-Organic colorants that have been shown to be ozone-fugitive, such as curcumin, indigo, alizarin lake, and triphenylmethane dyes, were exposed to 0.3-0.4 ppm of ozone for 12 weeks in purified air. Exposed and control samples were analyzed by mass spectroscopy using a Kratos Scientific Instruments MS25 hexapole mass spectrometer operated either in chemical ionization (CI) or electron impact (EI) modes. The data from the investigation are reported here.

Cass, G. R., "Protection of Works of Art from Damage Due to Air Pollution," American Chemical Society, Division of Environmental Chemistry, Miami, Florida, September 10-15, 1989.

ABSTRACT-Damage to works of art can occur due to the intrusion of outdoor air pollutants into the museum environment. In this presentation, mathematical modeling approaches are described that can be used to evaluate the effect of ventilation system redesign on indoor pollutant levels. Other methods for protection of collections from damage due to air pollution include the use of display cases, framing under glass, pigment substitution, and application of coatings over the works of art. A quantitative comparison will be presented, with examples drawn from experience gained in studies of indoor ozone and airborne particulate matter abatement.

Secondary Publications
Cass, G. R., and N. Baer, "Environmental Criteria." In Preservation of Historical Records, Committee on Preservation of Historical Records, National Materials Advisory Board, National Research Council, National Academy Press, Washington, D.C., 1986, pp.11-31.

ABSTRACT-Long-term preservation of the paper-based collections at the National Archives requires that damage caused by environmental conditions and atmospheric pollutants be prevented. Because these documents, or at least their in formation content, must be retained indefinitely, even very slow rates of deterioration caused by air pollution could lead to unacceptable levels of accumulated damage over a period of several hundred years. The problem of protecting the National Archives inventory is thus quite different from the question of protecting common consumer products from premature deterioration over their short service lifetime. Standards adopted for acceptable air quality outdoors therefore are not applicable, and separate air quality objectives must be set that are suited to the problem of long-term preservation of archival materials.

Preusser, F., and J. R. Druzik, "The Environmental Research at the Getty Conservation Institute," Paper presented at the National Archives and Record Administration, April 12, 1988.

ABSTRACT-Having recognized that control of the collection's environment is the best preservation strategy, the Scientific Program of the Getty Conservation Institute began in early 1984 to concentrate the main part of its resources on research in the museum environment. This research is done in the laboratories of the GCI and through research contracts awarded to other institutions. The following main areas of research are presently being pursued: comparative measurements of indoor and outdoor con centrations of industrial and domestic air pollutants (ozone, PAN, NOx, HNO3, HCl) and airborne particulates (soil dust, road dust, sea salt H2SO4, aerosol, sulfate, nitrate, and organic and elemental carbon). A mathematical model has been developed for the calculation of the infiltration of these pollutants into a building in relation to its architecture and ventilation strategy.

a.) Survey of indoor generated air pollutants (at present carbonyls and organic acids) in museums in the United States.

b.) Strategies for the control of pollutants in buildings, rooms, and storage and display cases.

c.) Assessment of the damage to museum objects and archival materials caused by outdoor- and indoor-generated pollutants.

d.) Passive and active methods for the control of relative humidity in storage and display cases.

e.) The evaluation of the current generation of temperature and humidity monitoring equipment.

Preusser, F., and J. R. Druzik, "Environmental Research at the Getty Conservation Institute," Restaurator, 10, N 3/4, 1989.

ABSTRACT-In 1984, the Getty Conservation Institute (GCI) embarked on a program of museum environmental research museum covering outdoor-generated air pollution, indoor-generated pollution, and microenvironmental studies. These three branches are further divided into surveys of pollutant concentrations in buildings containing cultural and natural history collections, materials damage assessments, and control strategies. In the microenvironment, the targeted issues are humidity control and monitoring, low-cost sealed display cases, biological control, and selected topics in lighting. In separate but related areas the GCI con ducts research in vibrational and shock effects, fumigation research, and on bringing the conservator and mechanical engineer closer together in the process of designing and retrofitting building air conditioning systems. In this paper, for each area of research, a brief background is presented in addition to where the GCI has built upon it.

Druzik, J. R., D. C. Stulik, F. Preusser, and G. R. Cass, "The Presence and Transport of Ozone in the Museum Environment," Poster and Extended Abstract, Science, Technology, and European Cultural Heritage, Bologna, June 13, 1989.

ABSTRACT-Air pollution has been known to cause damage to museum objects for at least one hundred years. However, until recently, little was known about the indoor concentrations of photochemical oxidants in the museum environment or the potential risks they might pose to museum collections. For this reason we began in the early 1980s to measure the indoor/outdoor (I/O) concentration ratios of ozone in a selec tion of buildings which represented a range of ventilation, architectural, and collection types. A computer model was developed which predicted indoor ozone concentrations based on a combination of building parameters, pollutant sources, and loss mechanisms. In parallel, experiments were established that exposed natural and synthetic colorants, on various substrates, to ozone at concentrations found in Los Angeles photochemical air pollution.

Cass, G. R., W. W. Nazaroff, C. Tiller, and P. Whitmore, "Protection of Art from Damage Due to Atmospheric Ozone," Atmospheric Environment, Vol. 25a, N 2, 1991, pp. 441-451.

ABSTRACT-Ozone at the concentrations found in the indoor atmosphere of many museums poses a fading hazard to the pigments used in works of art. The ozone control problem faced by museum personnel is unusual because indoor ozone exposure must be reduced to very low levels in order to protect the collections from accumulated damage over periods of 100 years or more. In the present study, methods that can be used to protect museum collections from ozone damage are evaluated. Control measures examined include pollutant removal via ventilation system redesign, con struction of display cases to protect the works, framing of paintings, prints, and water colors behind glass, selection of ozone-resistant pigments, and application of binder and coatings that protect ozone-sensitive pigments.