New Insights into the Cleaning of Paintings
SCMC-0003 SCMC-0003
212 • smithsonian contributions to museum conservation blue were used to allow optical comparisons with series II). Samples were soiled as in series II. Dry Cleaning Tests Cleaning tests were performed under ambient temperature and humidity (±22°C at 50% RH) at the ICN laboratories. After each test the paint samples were brushed and vacuumed. Test results were first observed visually (normal light, UV fluorescence, raking light) and then with light microscopy (polarized light, UV fluorescence, raking light), followed by electron microscopy (low vacuum, acceleration voltage from 1.7 to 20 kV, backscattered electron and low- vacuum secondary electron at magnifications of 100× to 2500×). Gloss measurements were performed to complete microscopic visual assessment. The following pieces of equipment were used: a ZEISS Axioplan 2 light microscope with ZEISS neofluar lenses and Axiovision 4.4 software, a Jeol JSM 5900 lV scanning electron microscope (SEM), a Tri- glossmaster 20- 60- 85 glossmeter from SHEEN, and a Sony Cybershot DSC- F505V digital camera. Observations were recorded in evaluation tables (Table 2) with attention to six criteria: topography integrity, gloss integrity, removal of residues, cleaning power, stability of the paint surface after testing and after artificial aging, and (if applicable) UV fluorescence changes. The syntheses of the results were then represented in star diagrams (Figure 1). RESULTS The results of the experiments on the water- sensitive oil and gouache paints are presented in Table 3. Table 2. Example of the evaluation table used in this study: Results of the Absorene tested on the cadmium red gouache. Grades are from 0/10 (null) to 10/10 (excellent). — = no data Tested materials Topography integrity Gloss integrity Change under UV light Clearance of residues (per cm 2 ) Cleaning power Stability with aging Number 3: Absorene b Abrasion (10/10) 5/10 (significant decrease in gloss) None Quantity on the picture spot (film Evenness (5/10) Change in color: more cloudy and gray deposit) Polishing 5/10 (significant None Color (—) Paint layer Change in color: (9/10) decrease in gloss) (6/10) more cloudy and gray Flattening 5/10 (significant None Size (—) Crumbs Change in gloss: (8/10) decrease in gloss) (—) more matte Cracks and holes 5/10 (significant None Tenacity (—) Material Other: thin, hard skin (10/10) decrease in gloss) (3/10) impregnated into the paint layer Global evaluation: Global evaluation: Global evaluation: Global evaluation: Global evaluation: Global evaluation: 9.4/10 5/10 None 1/10 5/10 1/10 a Increase or decrease, observed with the naked eye. b Cleaning achieved for a 2 minute application and 5 s vacuuming and brushing (if no dust remains, it becomes stickier). T Ag 10 9 8 7 6 5 4 3 2 1 0 Cr T Ag 10 9 8 7 6 5 4 3 2 1 0 Cr Cp G UV Cp G FIGURE 1. Star diagram examples. (left) Not filled in. Note that 0/10 corresponds to an extremely poor result, and 10/10 corresponds to an excellent test result. T = topography integrity; Ag = stability of paint surface after testing and artificial aging; Cp = cleaning power; Cr = clearance of residues; G = gloss integrity. (right) Example of a star diagram with Absorene scores from tests on gouache (see Table 2).
number 3 • 213 Table 3. Average dry cleaning test results on oil paint (sample II) and gouache (sample III). T = topography integrity; Ag = stability of paint surface after test and after artificial aging; Cr = clearance of residues; G = gloss preservation; UV = preservation of the paint layer aspect under UV fluorescence; Cp = cleaning power. See Table 1 for materials images. Material class Material name Average result on series II (oil paint layer sensitive to water) a Average result on series III (underbound gouache paint layer) a Handling remarks Observations after aging (indication of aging tendencies of residues) Malleable Absorene The “pink plasticine” became rock hard; an oily substance was leached out T Cr T Cr during the aging process, mixed with a very hard translucent substance (gray crystals) Groom/stick T Cp Cp Ag Ag UV Cr G Cr G T Cp Cp Rolled around wooden stick for ease of use Much stickier after aging and still glossy; it has softened into a liquid shape; on very thin areas, it became translucent and matte, like a little gray skin (this corroborates its aging on paint surfaces) Erasers Edding R10 A little bit yellower and less flexible Ag Ag Ag G G Cr T Cr T G Cp Cp Ag G Pentel ZF11 Not tested It generated a little bit of oily substance during aging; the eraser is also slightly T Cr less flexible Ag Cp G Bic Galet Not tested No change T Cr Cp G Cloths Yellow microfiber cloth T Cp Ag UV Cr G T Cp Ag G Cr Cloth with velvety characteristics, quite thick; produces threads when cut off No change Sponges Smoke sponge T Cp Ag UV Cr G T Cp Ag G Cr Greasy surface becomes harder and unusable within months; store protected from air More compact, less flexible, harder, and yellower than before aging. (continued)
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Table 3. Average dry cleaning test results on oil paint (sample II) and gouache (sample III). T = topography integrity; Ag = stability <strong>of</strong><br />
paint surface after test and after artificial aging; Cr = clearance <strong>of</strong> residues; G = gloss preservation; UV = preservation <strong>of</strong> <strong>the</strong> paint layer<br />
aspect under UV fluorescence; Cp = cleaning power. See Table 1 for materials images.<br />
Material<br />
class<br />
Material<br />
name<br />
Average result on<br />
series II (oil paint layer<br />
sensitive to water) a<br />
Average result on<br />
series III (underbound<br />
gouache paint layer) a<br />
Handling<br />
remarks<br />
Observations after aging (indication<br />
<strong>of</strong> aging tendencies <strong>of</strong> residues)<br />
Malleable Absorene The “pink plasticine” became rock<br />
hard; an oily substance was leached out<br />
T<br />
Cr<br />
T<br />
Cr<br />
during <strong>the</strong> aging process, mixed with a<br />
very hard translucent substance (gray<br />
crystals)<br />
Groom/stick<br />
T<br />
Cp<br />
Cp<br />
Ag<br />
Ag<br />
UV<br />
Cr<br />
G<br />
Cr<br />
G<br />
T<br />
Cp<br />
Cp<br />
Rolled around<br />
wooden stick<br />
for ease <strong>of</strong> use<br />
Much stickier after aging and still<br />
glossy; it has s<strong>of</strong>tened <strong>into</strong> a liquid<br />
shape; on very thin areas, it became<br />
translucent and matte, like a little gray<br />
skin (this corroborates its aging on paint<br />
surfaces)<br />
Erasers Edding R10 A little bit yellower and less flexible<br />
Ag<br />
Ag<br />
Ag<br />
G<br />
G<br />
Cr<br />
T<br />
Cr<br />
T<br />
G<br />
Cp<br />
Cp<br />
Ag<br />
G<br />
Pentel ZF11 Not tested It generated a little bit <strong>of</strong> oily substance<br />
during aging; <strong>the</strong> eraser is also slightly<br />
T<br />
Cr<br />
less flexible<br />
Ag<br />
Cp<br />
G<br />
Bic Galet Not tested No change<br />
T<br />
Cr<br />
Cp<br />
G<br />
Cloths<br />
Yellow<br />
micr<strong>of</strong>iber<br />
cloth<br />
T<br />
Cp<br />
Ag<br />
UV<br />
Cr<br />
G<br />
T<br />
Cp<br />
Ag<br />
G<br />
Cr<br />
Cloth with<br />
velvety<br />
characteristics,<br />
quite thick;<br />
produces<br />
threads when<br />
cut <strong>of</strong>f<br />
No change<br />
Sponges<br />
Smoke<br />
sponge<br />
T<br />
Cp<br />
Ag<br />
UV<br />
Cr<br />
G<br />
T<br />
Cp<br />
Ag<br />
G<br />
Cr<br />
Greasy surface<br />
becomes harder<br />
and unusable<br />
within months;<br />
store protected<br />
from air<br />
More compact, less flexible, harder, and<br />
yellower than before aging.<br />
(continued)
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