New Insights into the Cleaning of Paintings

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38 • smithsonian contributions to museum conservation and easy way as well as the ability to store them in a database. This decision is also supported by the fact that new solvents can be added to the database and that, having the largest number of solvents, it offers far more variability in the mixtures that can be created. REFERENCES Burke, J. 1984. “Solubility Parameters: Theory and Application.” In AIC Book and Paper Group Annual, Volume 3, ed. C. Jensen, pp. 13–58. Washington, D.C.: American Institute for Conservation. http://cool.conservation-us.org/coolaic/ sg/bpg/annual/v03/bp03-04.html (accessed 15 February 2012). Coladonato, M., and P. Scarpitti. n.d. References of the Interactive Solvent and Solubility Triangle©. http://iscr.beniculturali.it/flash/progetti/TriSolv/TriSolv .html (accessed 15 February 2012). Cremonesi, P., and I. Bortolotti. 1999. Un approccio più scientifico alla pulitura dei dipinti. Triansol®: Il triangolo delle solubilità, un software per il restauro. [A More Scientific Approach to the Cleaning of Paintings. Tiransol®: The Solubility Triangle, a Software for Restorers.] Progetto Restauro, 10:42–45. Feller, R. L. 1976. “The Relative Solvent Power Needed to Remove Various Aged Solvent-Type Coatings.” In Conservation and Restoration of Pictorial Art, pp. 158–161. London: Butterworths. Ormsby, M. 2006. Solvent Solver: A Calculator for Working with Teas Fractional Solubility Parameters. http://cool.conservation-us.org/packages/solvent-solver/ solvent_solver.html (accessed 15 February 2012). Stavroudis, C., and S. Blank. 1989. Solvents & Sensibility. WAAC Newsletter, 11(2):2– 10. http://cool.conservation-us.org/waac/wn/wn11/wn11-2/wn11-202.html (accessed 15 February 2012).
The Chemistry of Egg Binding Medium and Its Interactions with Organic Solvents and Water Antonella Casoli, Michela Berzioli, and Paolo Cremonesi Abstract. The aim of this study was to gain a deeper insight into the properties of egg, used as a binding medium, and its interactions with water and organic solvents. The research focused on egg tempera films prepared in July 2007 and on a tempera layer prepared by researchers of the Smithsonian’s Museum Conservation Institute in 1995. It also included a sixteenth- century panel painting from the Pinacoteca di Siena. Two paint samples from this painting were analyzed by gas chromatography coupled with mass spectrometry and identified egg as the binding medium. Ethanol or acetone, isooctane, and water were used to test for leaching. In general, the main leaching occurs from the fresher samples: using solvents of different polarity (from isooctane to water), the lipid components are the most removed. It also was observed that pigmented layers are less affected by leaching phenomena than a layer without pigments, in particular for lipid components. Finally, it was noticed that unsaturated fatty acids were extracted mainly from fresh samples, with less from the 1995 tempera and nothing from the sixteenth- century painting. However, the study carried out on this painting showed that leaching is more pronounced for the lipid components, and amino acids were also detected. These results were unexpected because mild cleaning tests were believed not to affect a 500- year- old painting. These results might be regarded as guidelines to take into account for cleaning paintings. INTRODUCTION Antonella Casoli and Michela Berzioli, Dipartimento di Chimica, Università degli Studi di Parma, viale G.P. Usberti, 17/a, 43124 Parma, Italy. Paolo Cremonesi, Cesmar7–The Centre for the Study of Materials for Restoration, Via Lombardia 41/43, 35020 Saonara, Italy. Correspondence: Antonella Casoli, antonella.casoli@unipr.it; Michela Berzioli, michela.berzioli@libero.it; Paolo Cremonesi, paolocremonesi57@gmail .com. Manuscript received 19 November 2010; accepted 24 August 2012. Egg tempera techniques employ the whole egg, or egg yolk and egg white separately, for binding media purposes, in which pigments are dispersed, sometimes combined with other materials, i.e., fig latex and cherry gum, depending on the painter’s requirements. Egg tempera was traditionally used in the past, especially in the fourteenth and fifteenth centuries in Italian painting. Because detailed studies are available on this topic (Thompson, 1936; Boon et al., 1997; Phenix, 1997), only a general description will be provided. Egg binding medium is made up of proteins, lipids, polysaccharides, and inorganic compounds. Egg white is a diluted water solution of proteins (mainly ovalbumin) and a small fraction of polysaccharides. Once applied, this material becomes insoluble. Egg yolk contains mostly lipids (66% in terms of mass) and proteins, as well as small amounts of polysaccharides and inorganic compounds. Lipids are present in the yolk as triglycerides (neutral lipids), phospholipids, and cholesterol. Triglycerides, the main lipids, are the same type of compound as drying oils. However, in egg these lipids contain less unsaturated fatty acids compared to oils. The fatty acid distribution in yolk lipids is saturated 38%, monounsaturated 42%, and polyunsaturated 20%. Their drying properties are not as strong as oils, but they are subject to the same oxidative polymerization reactions that
Page 1 and 2: Smithsonian Institution Scholarly P
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Page 5 and 6: Contents PREFACE ACKNOWLEDGMENTS
Page 7: number 3 • v Extended Abstract—
Page 10 and 11: viii • smithsonian contributions
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
Page 33 and 34: number 3 • 21 not the varnish its
Page 35 and 36: Extended Abstract—A Preliminary I
Page 37: number 3 • 25 FIGURE 3. Detail of
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Page 45: number 3 • 33 FIGURE 2. Recording
Page 63 and 64: Oil Paints: The Chemistry of Drying
Page 65 and 66: number 3 • 53 FIGURE 3. Weight ch
Page 67 and 68: number 3 • 55 FIGURE 7. Formation
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Page 71 and 72: The Influence of Pigments and Ion M
Page 73 and 74: number 3 • 61 FIGURE 3. Mechanica
Page 75 and 76: number 3 • 63 FIGURE 7. Mechanica
Page 77 and 78: number 3 • 65 observation that co
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Characterization and Stability Issu
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number 3 • 91 FIGURE 2. Film form
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number 3 • 93 (Saunders, 1973). T
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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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