July 1999 Issue 32
Not So New Methods of Cleaning
All MA students on the RCA/V&A Joint Course in Conservation undertake a ten-week research project in their final year. My research project took the form of a literature review of two of the innovative cleaning techniques for painted and decorated surfaces introduced by Richard Wolbers in the mid 1980s. The dissertation evaluates the literature published in response to Richard Wolbers' introduction of resin and bile soaps and Carbopol™ solvent gels in order to assess how claims made for these materials compared with experimental results reported in the conservation literature1.
Many of the concerns raised about Wolbers' cleaning methods have focused on their potential or actual impact on oil paint surfaces. Although his methods can be applied to a wider range of materials, my dissertation took this substrate as its starting point, outlining the drying and degradation of linseed oil paint films. Traditional methods of cleaning using solvents and alkaline reagents and their effect of on an oil paint layer were discussed in order to provide a context for the development of Wolbers' methods and materials.
The theoretical basis of two of Wolbers' innovations resin and bile soap gels and Carbopol solvent gels were considered, followed by a review of studies which examine aspects of the activity or clearance of these materials. The literature review summarised significant findings and evaluated experimental methodology in order to compare results which were sometimes contradictory and thus find a way through the maze of claims and counter claims surrounding the methods and materials Wolbers introduced.
Wolbers introduced both new techniques for use with traditional materials, such as solvent gels, and adopted an aqueous approach for solvating layers which had proven resistant to solvents or alkaline reagents, or when the use of such traditional cleaning materials represented a significant risk to the paint layers underneath. These methods were intended to allow a more controlled cleaning process and to facilitate the selective removal of unwanted layers from the underlying decorative surface. Wolbers set out the theoretical basis and discussed the use of these materials in a booklet2, which originally accompanied a two-week programme of lectures and practical workshops in 1988.
These 'Notes', reissued in 1989 and 1990, have been the primary written source of information for conservators seeking to understand or test Wolbers' methods. The 'Notes' were divided into sections on case histories, fluorescence microscopy, surface coatings and cleaning materials. Nine case histories of complex cleaning problems set out how and why Wolbers used his 'new methods' to solve practical problems which would have been insuperable using traditional cleaning methods. The results were inherently empirical and offered no experimental confirmation of the mechanism or effects of such cleaning treatments.
Concern about Wolbers' cleaning methods has focused around three primary issues - the possible deposition of residues of non volatile components from cleaning formulations, the complexity of aqueous cleaning formulations and the role of individual components, and the possibility that fatty acid compounds may be leached out of oil paint films. Research over the last ten years has shed some light on these issues and has allowed for the original claims made for resin and bile soaps to be evaluated.
The literature review highlighted problems in some of the research which has been undertaken to evaluate Wolbers' methods. The complexity of the theoretical foundation of these methods has not been fully grasped by some researchers and this has produced contradictory conclusions. Other researchers have limited the application of their findings by using non standard formulations with the result that their experimental data cannot be used to inform conservation practice. Some papers were characterised by a lack of rigour researchers drew broad and occasionally specious conclusions from narrow experimental data.
Some of the confusion which is evident in the literature has been a result of the haphazard dissemination of both basic principles and changes to formulations and clearance procedures. The 'Notes' intended to accompany a two-week programme of lectures and practical experience of the methods have been the primary source of information. These were never formally published and as a result bootlegged photocopies have circulated the profession as conservators have tried to come to grips with new approaches to cleaning.
Wolbers is planning to publish a book on his methods in the near future, which will at least partly address this problem. Communicating changes as these new methods evolve remains problematic. Although clear and logical guidelines for clearance procedures for aqueous cleaning solutions and solvent gels were published in a conservation newsletter in 19903, it is apparent from the literature that this has been insufficient to ensure they are widely known and understood.
More than ten years after the introduction of Wolbers' cleaning methods it is still not possible to make an informed and objective comparison of the potential damage from a traditional cleaning treatment and that which may occur as a result of using Wolbers' methods.
Wolbers has made a significant contribution to conservation. Whether individual conservators adopt his methods or not, he has facilitated and extended the theoretical basis for cleaning which has had an inevitable impact on conservation practice. Many of the materials used by Wolbers are not new to conservation. Enzymes have been used in paper conservation, wax pastes in paintings conservation, gels in furniture conservation.
However, perhaps Wolbers' most significant contribution to conservation practice has been to propose a coherent cleaning strategy based on a general chemical characterisation of both the substrate and overlying layers which can be used to formulate a conservation treatment as controllable and selective as possible. This general approach may prove to be as important as the new materials introduced to solve individual cleaning problems.
1. Lang, S., A Review of Literature Published in Response to Wolbers' resin Soaps, Bile Soaps and Solvents Gels, Final Year Research Project, RCA/VA Joint Course in Conservation, 1998.
2. Wolbers, R., Sterman, N. and Stavroudis, C., Notes for the Workshop on New Methods in the Cleaning of Paintings, Getty Conservation Institute, 1990.
3. Stavroudis, C. and Blank, S., Author's Reply, WAAC Newsletter, No.12, 2, pp31, 1990.