New Insights into the Cleaning of Paintings

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192 • smithsonian contributions to museum conservation FIGURE 4. Fatty acids measured in the rinsing swabs used in paintings P1 and P2 after the treatments with water (W), soap in water (W0.5, W1.0, W5.0), soap in white spirit (WS1.0, WS5.0), fluid gels (FG1.0), and fluid gel applied on barrier paper (FGP1.0). flattening of the surface and detachment or removal of paint particles (Figure 5). In general, thin cracks were seen to become larger whenever aqueous or gelled solutions were applied. Apart from this, rigid gels (both clear gels and gels containing Vulpex) also caused small fissures. No surface cracks were found in test samples treated with the solutions of soap in white spirit. Flattening of the paint was evident in the treatments with aqueous soap solutions, in paintings that were cleaned with fluid gel, especially the one where Japanese paper was used, and in those treated with rigid gels. Particle detachment or material removal was clearly seen in test samples treated with fluid gels that were applied following both methods in the test. CSM One of the most common methods used in industry to quantify the roughness of a surface is based on recording height profiles by means of a roughness meter or profilometer. Data are treated statistically to determine parameters such as the average roughness R a , and they provide useful information on the quality of different processes, even if they cannot be considered properties of surfaces (Hinojosa and Reyes, 2001). Variations in the roughness profiles have been used in operations with cultural objects, especially to monitor changes after applying various cleaning systems (Blanco et al., 2008; van den Berg et al., 2008). Atomic force microscopy has also been useful for pinpointing topographical variations in paintings treated with different cleaning systems (Ormsby et al., 2006). The ability to measure the depth of the cracks and to obtain images with false coloring that illustrates other modifications, such as detachment and dragging of particles, is an important confirmation and complement to the SEM observations. The results of the modifications in the P1 test samples are presented in Table 4. The surface that was treated with water showed a slight increase in roughness because of the softening of the surface and the movement of particles, which led to an irregular topography. Aqueous soap solutions (VW 0.5% and VW 1.0%) caused flattening of the surface, and this was related to a decrease in roughness. In these cases, paint particles were removed in a medium that was already softer because of the water. The effect was increased with a greater soap concentration. The solutions of Vulpex in white spirit (VWS 5.0%) showed little roughness variations. This treatment only showed slight movement of particles on the paint surface. However, no damage was found on surfaces treated with a solution of 1% of soap in white spirit. The roughness variation values were different in the test samples treated with fluid gels directly on the painting or on the barrier paper. In the former case (VFG 1.0%), the roughness increased because of particle detachment and accumulation and the appearance of cracks of up to 15 mm in depth. In the latter case (VFGP 1.0%), roughness values decreased by more than 5% with the barrier paper because the surface became flatter and particles were dragged in the rinsing swab, as verified in the GC- MS analyses. Deep cracks were also found in this case,
FIGURE 5. Scanning electron microscopy images with examples of the damage observed on the painting surface. The images were taken (left) before and (right) after the cleaning. B (VWS 1.0%) does not present significant surface changes, D (VFGP 1.0%) shows increased cracking, F (VRG 1.0%) shows surface flattening, and H (VFG 1.0%) shows particle dragging and removal. number 3 • 193
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Smithsonian Institution Scholarly P
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smithsonian contributions to museum
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Contents PREFACE ACKNOWLEDGMENTS
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number 3 • v Extended Abstract—
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viii • smithsonian contributions
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The Removal of Patina Stephen Gritt
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number 3 • 3 and conceals its bea
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number 3 • 5 REFERENCES Algarotti
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8 • smithsonian contributions to
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Surface Cleaning of Paintings and P
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number 3 • 19 methods for cleanin
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number 3 • 21 not the varnish its
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Extended Abstract—A Preliminary I
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number 3 • 25 FIGURE 3. Detail of
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Extended Abstract—A New Documenta
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number 3 • 33 FIGURE 2. Recording
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Oil Paints: The Chemistry of Drying
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number 3 • 53 FIGURE 3. Weight ch
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number 3 • 55 FIGURE 7. Formation
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number 3 • 57 FIGURE 11. Differen
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The Influence of Pigments and Ion M
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number 3 • 61 FIGURE 3. Mechanica
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number 3 • 63 FIGURE 7. Mechanica
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number 3 • 65 observation that co
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number 3 • 67 • Not all pigment
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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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100 • smithsonian contributions t
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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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Page 154 and 155: 142 • smithsonian contributions t
Page 159 and 160: Cleaning of Acrylic Emulsion Paints
Page 161 and 162: number 3 • 149 advocates of publi
Page 163 and 164: number 3 • 151 2.5, 3.5, 4.5, 5.5
Page 165 and 166: number 3 • 153 ethoxylate units i
Page 167 and 168: number 3 • 155 FIGURE 5. Golden A
Page 169: number 3 • 157 alien und Methoden
Page 181 and 182: Extended Abstract—The Removal of
Page 183 and 184: number 3 • 171 RESULTS AND DISCUS
Page 185 and 186: number 3 • 173 FIGURE 3. The SEM
Page 187 and 188: Extended Abstract—Cleaning Issues
Page 189: number 3 • 177 Acknowledgments Th
Page 197 and 198: Effects of Commercial Soaps on Unva
Page 199 and 200: number 3 • 187 The aqueous and or
Page 201 and 202: number 3 • 189 all tests. The res
Page 203: number 3 • 191 palmitic and stear
Page 207 and 208: number 3 • 195 FIGURE 6. Confocal
Page 209 and 210: Extended Abstract—Tissue Gel Comp
Page 211: number 3 • 199 • The capillary
Page 217 and 218: Extended Abstract—Use of Agar Cyc
Page 219: number 3 • 207 FIGURE 4. The FTIR
Page 233 and 234: Extended Abstract—The Schlürfer:
Page 235 and 236: number 3 • 223 FIGURE 3. Removal
Page 237 and 238: Extended Abstract—Surface Cleanin
Page 239: number 3 • 227 Table 3. Cleaning
Page 249 and 250: Extended Abstract—Laser Cleaning
Page 251 and 252: Ending Note: Summary of Panel Discu
Page 253 and 254: Index TABLES in BOLD; Figures in It
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number 3 • 243 polyvinyl acetate
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