New Insights into the Cleaning of Paintings

194 • smithsonian contributions to museum conservation
Table 4. Roughness variation as measured by CSM and main damage observed on the painting surfaces. Roughness
variation is the average value of measurements taken in 10 areas 1.46 × 1.10 mm 2 in size. W = water; V = Vulpex; WS
= white spirit; FG = fluid gel; FGP = fluid gel applied on barrier paper; RG = rigid gel.
General roughness variations
Treatments
Roughness variation
(%) Main damage
W 0.60 Movement of particles
VW 0.5% –1.46 Flattening of the surfaces and particle removal
VW 1.0% –1.81 Flattening of the surfaces and particle removal
VWS 1.0% 0.30 Slight particle movement
VWS 5.0% 0.33 Slight particle movement
VFG 1.0% 2.46 Particle detachment and accumulation and appearance of deep cracks
VFGP 1.0% –5.22 Flattening of the surfaces, particle dragging, and appearance of deep cracks
RG –1.87 Flattening of the surfaces and appearance of thin cracks
VRG 1% 1.05 Flattening of the surfaces and appearance of deep cracks
although they were fewer in number than with the previous system
(Figure 6).
The cleaning with clear agar gel (RG) showed surface flattening
that was caused by the joint action of two factors. First, the
water softened the paint, and second, the slight pressure applied
to keep the gel in contact with the paint caused a reduction in
the roughness. In this case, only thin cracks were found. Adding
Vulpex to the rigid gel (VRG 1.0%) would produce an increase in
the roughness because soap causes deeper cracks to open.
CONCLUSIONS
The methodology used in this study served to evaluate the
residues of the Vulpex commercial soap on the surface of paintings
after cleaning. The study showed mainly qualitative differences
between the various cleaning treatments.
The results suggest that Vulpex is not appropriate to eliminate
dirt in young unvarnished paintings because of the deterioration
induced by this product on the paintings, as had already been
highlighted in other studies with different paintings and at different
concentrations. All the surfaces treated with aqueous solutions
of Vulpex had residues after the cleaning except when treated with
a 1% soap solution in white spirit; the application was carried out
at this same concentration in water but was applied as fluid or
rigid gel, or the fluid gel was applied with a barrier paper.
In general, all the paintings treated with Vulpex in this study
showed surface damage. This was linked to the effect of the soap,
the application method, and the rinsing processes. The main
damage observed was cracking, surface flattening, and paint particle
removal. Rigid gel systems were the least damaging, and
they seemed to be more practical for local treatments.
A good correlation was found between the results of the P1
test samples and those obtained with the painting cleaned by the
professional restoration team (P2). Furthermore, the results from
the restorers did not present important variations. Instead, variations
seemed to stem from the area of the painting on which the
treatment was applied. The inclusion of the results of these studies
in the technical files of companies specializing in restoration
product distribution is a positive measure to reduce risks related
to the use of commercial soaps.
Acknowledgments
The authors thank Luis Alberto Angurel at the Instituto de
Ciencia de Materiales y Fluidos, Universidad de Zaragoza, for
his contribution to the CSM studies; restorers Raquel Sáez, Susana
Pérez, Alejandra Martos, Juan Alberto Soler, Marta Palau,
and Susana Lozano for assisting with the cleaning treatments
carried out in conjunction with the experiments; the distributors
specializing in restoration products, Agar- Agar SL, C.T.S. España
Productos y Equipos para la Restauración S.L., Productos de
Conservación SA, and STEM Servicios Técnicos y Equipamiento
para Museos; and, in particular, Ubaldo Sedano, Jorge García,
and Pilar Sedano, the heads of the restoration departments at
the Museo Thyssen Bornemisza, Museo Nacional Reina Sofía,
and Museo Nacional de Prado, respectively, for supporting this
project.
APPENDIX A: INSTRUMENTAL
OPERATION CONDITIONS
GC- MS. An Agilent Technologies GC- 6890N–MS
5973 chromatograph, with a HP- 5MS (5% phenyl, 95% dimethylpolysiloxane)
capillary column (length: 30 m, internal
diameter: 250 mm × film thickness: 0.25 mm) and with a flow
of 1 mL/min of helium as the carrier gas, was used. The oven