New Insights into the Cleaning of Paintings

76 • smithsonian contributions to museum conservation
two regions: b < 0.32 and b > 0.52. In the range of b values between
~0.32 and ~0.52, most solvents, mainly aliphatic ketones,
esters, and ethers, are low- moderate swellers, as are solvents with
b > 0.62 and p* < 0.60, which are the aliphatic alcohols.
CONCLUSIONS
This study has demonstrated that the interaction of organic
solvents with artists’ oil paints to cause swelling is more complex
than the existing models (Stolow, 1963; Hedley, 1980) suggest
and that the complexity of this interaction is not faithfully described
using the Teas fractional solubility parameter diagram
approach. It has been found that better discrimination of the
swelling power of solvents can be achieved using other descriptors,
of which the KAT parameters (a, b, p*), Reichardt normalized
polarity E TN
, molar volume V m
, and refractive index n D
appear the most significant. Similar interpretation of the swelling
action on oil paints of mixtures of solvents remains an outstanding
task, but productive lines of enquiry will probably lie in the
use of empirically determinable descriptors, such as Reichardt
polarity (E T
30, E TN
), which can be applied to mixtures as well
as pure solvents (Reichardt, 2003:425–428; Bosch and Rosés,
1992; Catalán et al., 2000). Finally, and perhaps most usefully
for the practicing conservator, this work has offered a broad descriptive
vocabulary for the respective actions of different organic
solvents and mixtures in terms of ultimate swelling power
(∆A max
% values) and rate of swelling (t ½
values).
Acknowledgments
Special thanks go to Emma Richardson, GCI postdoctoral
fellow, for assistance with multivariate statistical analysis of the
swelling results.
REFERENCES
Bosch, E., and M. Rosés. 1992. Relationships between E T
Polarity and Composition
in Binary Solvent Mixtures. Journal of the Chemical Society, Faraday Transactions,
88(24):3541–3546. http://dx.doi.org/10.1039/ft9928803541.
Catalán, J., C. Díaz, and F. García- Blanco. 2000. Characterization of binary solvent
mixtures. Journal of Organic Chemistry, 65:9226–9229. http://dx.doi
.org/10.1021/jo001008u.
Cremonesi, P. 2000. L’uso dei solventi organici nella pulitura di opere policrome.
[The Use of Organic Solvents in the Cleaning of Polychrome Objects.] Padua:
Il Prato.
Fuesers, O., and S. Zumbühl. 2008. “The Influence of Organic Solvents on the Mechanical
Properties of Alkyd and Oil Paint.” Paper presented at 9th International
Conference on NDT- Art 2008, Jerusalem, Israel. http://www.ndt.net/
article/art2008/papers/219Fuesers.pdf. (accessed 3 December 2012).
Gramatica, P., N. Navas, and R. Todeschini. 1999. Classification of Organic
Solvents and Modelling of Their Physico- chemical Properties by Chemometric
Methods Using Different Sets of Molecular Descriptors. Trends in
Analytical Chemistry, 18(7):461–471. http://dx.doi.org/10.1016/S0165
- 9936(99)00115- 6.
Hedley, G. 1980. Solubility Parameters and Varnish Removal: A Survey. The Conservator,
4:12–18. http://dx.doi.org/10.1080/01410096.1980.9994931.
Marcus, Y. 1999. The Properties of Solvents. Chichester, UK: John Wiley.
Phenix, A. 1998. Solubility Parameters and the Cleaning of Paintings: An Update
and Review. Zeitschrift für Kunsttechnologie und Konservierung, 12(2):387–
409.
———. 2002a. The Swelling of Artists’ Paints in Organic Solvents. Part 1, A Simple
Method for Measuring the Inplane Swelling of Unsupported Paint Films.
Journal of the American Institute for Conservation, 41:43–60. http://dx.doi
.org/10.2307/3179896.
———. 2002b. The Swelling of Artists’ Paints in Organic Solvents. Part 2, Comparative
Swelling Powers of Selected Organic Solvents and Solvent Mixtures.
Journal of the American Institute for Conservation, 41:61–90. http://dx.doi
.org/10.2307/3179897.
———. 2003. The Swelling of Artists’ Paints by Organic Solvents and the Cleaning
of Paintings: Recent Perspectives, Future Directions. In Postprints of Annual
Conference of the American Institute for Conservation, Paintings Specialty
Group, Miami, June 2002, ed. H. Mar Parkin, pp. 71–86. Washington, D.C.:
American Institute for Conservation.
Pietsch, A. 2002. Lösemittel: Ein Leitfaden für die restauratorische Praxis. VDR-
Schriftenreihe zur Restaurierung 7. Stuttgart, Germany: Theiss Verlag.
Reichardt, C. 2003. Solvents and Solvent Effects in Organic Chemistry, 3rd ed.
Weinheim, Germany: Wiley- VCH.
Stolow, N. 1963. Application of Science to Cleaning Methods: Solvent Action Studies
on Pigmented and Unpigmented Linseed Oil Films. In Recent Advances in
Conservation, ed. G. Thomson, pp. 84–88. London: Butterworths.
Zumbühl, S. 2005. Illusion mit System. Das Lösemitteldreieck in der Praxis. Aspekte
zur Charakterisierung der Wirkung von binären Lösemittelmischungen.
[The Solvent Triangle in Practice. Characterization Aspects of the Effect of
Binary Solvent Mixtures.] Zeitschrift für Kunsttechnologie und Konservierung,
19(2):253–263.
Banik, G., and G. Krist. 1984. Lösungsmittel in der Restaurierung. [Solvents in
Conservation.] Vienna: Verlag der Apfel.