New Insights into the Cleaning of Paintings

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44 • smithsonian contributions to museum conservation fraction is only present on the surface, rendering it hydrophobic; this was attributed to a migration effect because of the nonpermeable support. Interestingly, more saturated fatty acids were removed than oleic acid, in spite of the fact that oleic acid is more abundant than stearic acid in egg tempera. This is not surprising considering that unsaturated fatty acids become less mobile when they take part in the polymerization process. The study on the sixteenth- century panel painting showed that the leaching phenomenon was greater for lipid components but that amino acids were also extracted. As expected, unsaturated fatty acids were not detected; in fact, in a 500- year- old painting the polymerization process is complete. The extraction content results were about 50 times lower compared to the laboratory samples. These results are unexpected because mild cleaning tests were believed to be safe and undamaging for a 500- year- old painting. These results might be regarded as guidelines for cleaning paintings. Further research with other organic solvents and water solutions at different pHs is being carried out on laboratory panels and will also be tested on ancient tempera paintings. Acknowledgments The authors are grateful to Giovanni Antonioli, Cinzia Bignamini, Elisa Campani, Sara Capretti, Clelia Isca, Remo Reverberi, and Laura Spina of the University of Parma for their contribution to this research, as well as to Anna Maria Guiducci of the Pinacoteca Nazionale in Siena. The authors gratefully thank Marion Mecklenburg of Smithsonian Museum Conservation Institute for providing the aged tempera samples. REFERENCES Annaratone, C., A. Caligiani, M. Cirlini, L. Toffanin, and G. Palla. 2009. Sterols, Sterol Oxides and CLA in Typical Meat Products from Pigs Fed with Different Diets. Czech Journal of Food Sciences, 27:219–222. Antonioli, G., F. Fermi, C. Oleari, and R. Reverberi. 2004. “Spectrophotometric Scanner for Imaging of Paintings and Other Works of Art.” In CGIV 2004, Second European Conference on Colour in Graphics, Imaging, and Vision, pp. 219–224, Aachen, Germany: Technology Center AGIT. Berzioli, M., C. Bignamini, E. Campani, A. Casoli, P. Cremonesi, and C. Isca. 2009. “The Study of Egg Tempera Binding Medium and Its Interaction with Organic Solvents: Characterisation of the Preliminary Stage.” In Chemistry and Conservation: Proceedings of the 2nd Residential Summer School in Palermo, ed. E. A. Varella and E. Caponetti, pp. 17–26. Rome: Centro Stampa De Vittoria Srl. Boon, J. J., S. L. Peulvé, O. F. van den Brink, M. C. Duursma, and D. Rainford. 1997. “Molecular Aspects of Mobile and Stationary Phases in Ageing Tempera and Oil Paint Films.” In Early Italian Paintings: Techniques and Analysis, ed. T. Bakkenist, R Hoppenbrouwers, and H. Dubois, pp. 35–56. Maastricht, Netherlands: Limburg Conservation Institute. Casoli, A., P. Cremonesi, G. Palla, and M. Vizzari. 2001. Application of Gas Chromatography- Mass Spectrometry Analysis to the Study of Works of Art: Paint Media Identification in Polychrome Multi- material Sculptures. Annali di Chimica, 91:727–739. Cennini, C. 1437. Il Libro dell’Arte. [The Craftsman’s Handbook] Reprint edited by F. Brunello, Vicenza, Italy: Neri Pozza editore, 1982. Karpowicz, A. 1981. Ageing and Deterioration of Proteinaceous Media. Studies in Conservation, 26:153–160. http://dx.doi.org/10.2307/1505885. Khandekar, N., A. Phenix, and J. Sharp. 1994. Pilot Study into the Effects of Solvents on Artificially Aged Egg Tempera Films. The Conservator, 18:62–72. http://dx.doi.org/10.1080/01410096.1994.9995086. Phenix, A., 1997. “The Composition and Chemistry of Eggs and Egg Tempera.” In Early Italian Paintings: Techniques and Analysis, ed. T. Bakkenist, R. Hoppenbrouwers, and H. Dubois, pp. 11–20. Maastricht, Netherlands: Limburg Conservation Institute. Thompson, D. V., Jr. 1936. The Practice of Tempera Painting. New York: Dover Publications. White, R., and A. Roy. 1998. GC- MS and SEM Studies on the Effects of Solvent Cleaning on Old Master Paintings from the National Gallery, London. Studies in Conservation, 43:159–176. http://dx.doi.org/10.2307/1506743.
Solvent Leaching Effects on Aged Oil Paints Ken Sutherland Abstract. This paper presents a survey of significant developments in research on the leaching of oil paint films by organic solvents, from the first systematic investigations carried out in the 1950s to more recent “clinical” studies involving the sampling and analysis of paintings during treatment. Key studies are discussed in the context of an improved knowledge of oil paint chemistry that has developed in recent decades and advances in analytical techniques that have allowed a more informed and precise analysis of the solvent- extractable components of aged oil paints. Current research related to solvent cleaning effects, including studies of the formation of metal soaps and their migration in oil paints and the leaching effects of aqueous cleaning systems on acrylic paint media, is considered. The challenges of interpreting experimental data in relation to cleaning practice are outlined and illustrated with reference to discussions of research on solvent effects in the conservation literature. There must have been many . . . who wishfully hoped the phenomenon [leaching] could be dismissed as an insignificant curiosity only of interest to the scientist, perhaps conveniently to be soon forgotten. —Rees Jones (1973:43) Ken Sutherland, Conservation Department, Philadelphia Museum of Art, Box 7646, Philadelphia, Pennsylvania 19101- 7646, USA. Correspondence: ksutherland@philamuseum.org. Manuscript received 19 November 2010; accepted 24 August 2012. Organic solvents have long been the most widely used materials for the removal of discolored or deteriorated varnish and retouchings from paintings, a complex operation prosaically known as “cleaning.” The leaching of oil paint films by solvents, that is, the extraction of soluble, non- cross- linked components of the binding medium, was first described in detail by Nathan Stolow in a series of influential publications in the 1950s– 1970s (Stolow, 1957a, 1957b, 1963, 1971). The findings of Stolow and other researchers were widely discussed by conservators and museum scientists and became a controversial component of the more general debate on cleaning (for a detailed review of solvent cleaning studies, see Phenix and Sutherland, 2001). The above remarks by Stephen Rees Jones were made in a review of the second edition of the book On Picture Varnishes and Their Solvents, in which Stolow summarized his research, and they convey the uncertainty with which the findings on leaching were initially received. Unlike the related phenomenon of swelling, which carries the acute risk of softening and disruption of paint, the risks associated with leaching are less immediately tangible to the conservator and have proved to be more contentious in discussions of cleaning. In the early experiments by Stolow and others, carried out on laboratory- prepared oil paint films, leaching was found to result in embrittlement of the films and optical changes (blanching or desaturation) of paint surfaces. Although highly significant, such risks are difficult to assess in practice. Changes
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Smithsonian Institution Scholarly P
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smithsonian contributions to museum
Page 5 and 6: Contents PREFACE ACKNOWLEDGMENTS
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Page 13 and 14: The Removal of Patina Stephen Gritt
Page 15 and 16: number 3 • 3 and conceals its bea
Page 17: number 3 • 5 REFERENCES Algarotti
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Page 29 and 30: Surface Cleaning of Paintings and P
Page 31 and 32: number 3 • 19 methods for cleanin
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Page 35 and 36: Extended Abstract—A Preliminary I
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Page 63 and 64: Oil Paints: The Chemistry of Drying
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Page 67 and 68: number 3 • 55 FIGURE 7. Formation
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Page 73 and 74: number 3 • 61 FIGURE 3. Mechanica
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Page 77 and 78: number 3 • 65 observation that co
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number 3 • 95 allows identificati
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Sensitivity of Oil Paint Surfaces t
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number 3 • 109 Analytical Methods
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number 3 • 111 The method for ass
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number 3 • 113 FIGURE 6. Secondar
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Extended Abstract—The Effect of C
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number 3 • 117 Table 1. Surface m
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Multitechnique Approach to Evaluate
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number 3 • 127 RESULTS AND DISCUS
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number 3 • 129 FIGURE 4. The SEM
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number 3 • 131 FIGURE 7. (top) St
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number 3 • 133 FIGURE 10. Stress-
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Extended Abstract—A Preliminary S
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number 3 • 137 Acknowledgments An
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Cleaning of Acrylic Emulsion Paints
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number 3 • 149 advocates of publi
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number 3 • 151 2.5, 3.5, 4.5, 5.5
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number 3 • 153 ethoxylate units i
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number 3 • 155 FIGURE 5. Golden A
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number 3 • 157 alien und Methoden
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Extended Abstract—The Removal of
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number 3 • 171 RESULTS AND DISCUS
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number 3 • 173 FIGURE 3. The SEM
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Extended Abstract—Cleaning Issues
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number 3 • 177 Acknowledgments Th
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Effects of Commercial Soaps on Unva
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number 3 • 187 The aqueous and or
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number 3 • 189 all tests. The res
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number 3 • 191 palmitic and stear
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FIGURE 5. Scanning electron microsc
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number 3 • 195 FIGURE 6. Confocal
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Extended Abstract—Tissue Gel Comp
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number 3 • 199 • The capillary
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Extended Abstract—Use of Agar Cyc
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number 3 • 207 FIGURE 4. The FTIR
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Extended Abstract—The Schlürfer:
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number 3 • 223 FIGURE 3. Removal
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Extended Abstract—Surface Cleanin
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number 3 • 227 Table 3. Cleaning
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Extended Abstract—Laser Cleaning
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Ending Note: Summary of Panel Discu
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Index TABLES in BOLD; Figures in It
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number 3 • 243 polyvinyl acetate
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