Keeping up with new materials, techniques and, of course, technology is an important part of being a conservator. Until recently, cleaning acrylic painted surfaces was problematic, as little was known about the behaviour of acrylic films when water or solvents were introduced to the paint film. Most conservators used dry cleaning methods or experimented with water or saliva to remove imbibed grime. The results were often disappointing, and the use of water often risked unwanted alterations of the surface texture of the painting.
In August 2014, the Canadian Conservation Institute (CCI), in part with the Getty Conservation Institute, hosted a workshop on the cleaning of acrylic painted surfaces (CAPS). Over four days, an intimate group of conservators gathered from around the world in Ottawa to hear several of the top conservation scientists discuss their latest findings.
The mornings were spent in lectures, learning about the molecular structures and physical properties of acrylic paint films, as well as about new cleaning solutions and their mechanisms of action. The afternoons were spent in the CCI laboratories, with participants watching demonstrations by expert painting conservators and trying out the new cleaning methods themselves.
The foundation of the CAPS system is that the conservator must first understand the properties of the paint film with which he or she is working and develop cleaning solutions customized to that structure. Participants reviewed the behaviour and aging properties of acrylic paint as well as the response of paint to water-based cleaning systems.
Participants also learned how to measure properties such as the pH and conductivity of painted surfaces knowledge that would prepare them to tailor their cleaning solutions to a specific painting. Choosing aqueous or solvent-based cleaning systems, conservators can then alter the pH or conductivity and add chelating agents or surfactants, depending on the desired effect.
Each participant was given large samples of acrylic paint that had been aged for several years and artificially soiled to mimic the grime often found on the surface of indoor paintings (including grime from tobacco smoke, dust, fingerprints, and food and beverages). The group was then encouraged to experiment with combinations of new and old cleaning solutions, making note of qualities such as whether the solutions were efficient cleaners, changed the texture of the painted surface or mistakenly removed paint.
The cleaning systems detailed at the CAPS workshop, however, now provide conservators with solutions and emulsions that are more easily customized to the paintings being worked on. The result of these advances means safer conservation practices and more brilliant outcomes.