39th Annual Meeting – Joint Paintings/Research and Technical Studies Session, June 3, “Potential Cleaning Applications of Poly(vinyl alcohol-co-acetate)/Borate gels on Painted Surfaces” by Lora Angelova & Kristin deGhetaldi

Where to begin? First let me start by saying, if you missed this presentation during the joint PSG/RATS session, then you should be sure to check out the paper in post-prints once available. The details and future potential of this research cannot likely be given its due justice in a short blog post, but I will do my best to give you the major highlights.

On the final day of the annual conference Lora Angelova and Kristin deGhetaldi presented their findings regarding recent research on Borate gels, a new aqueous co-solvent gel system for use on painted materials. This collaborative project between Angelova, a Ph.D candidate in the department of chemistry department at Georgetown University and deGhetaldi, the Andrew W. Mellon Painting Conservation Fellow at the National Gallery of Art, along with Senior Conservation Scientist Dr. Barbara Berrie and Professor of Chemistry Richard Weiss at the NGA and Georgetown, respectively, resulted in the development of a new aqueous based gel system with great potential for use by conservators in the cleaning of paintings and painted surfaces.

The presentation was first introduced by Kristin deGhetadi, who immediately hooked the audience with the highly successful results of a case study, which utilized the cleaning gels in question.

The case study involved the cleaning of a painting titled Multiple Views, a 1918 work by Stuart Davis in the collection of the National Gallery of Art. After a brief history of the work, including an antidotal account about how Davis painted the work during a three-day contest in an “atmosphere of drinking and conviviality”, deGhetaldi described in detail the before treatment condition of the work. The painting, which suffered from extensive previous restoration, was waxed lined and covered with an extremely yellowed and degraded dammar coating that analysis revealed contained not only wax, which likely migrated to the surface from the lining, but protein, polysaacharides, drying oil, and, even nicotine.

Needless to say, deGhetaldi realized that this particular coating would prove to be challenging to remove. She described her methodical approach to the treatment using the Modular Cleaning Program developed by Chris Stavroudis. After exhausting the options of traditional free solvents, various aqueous cleaning solutions, and solvent based gels, she turned to the use of an aqueous emulsion that contained Pemulen TR-2 with 5% Benzyl Alcohol. While the latter worked very well to remove the coating over much of the painting there were still areas where a particularly tenacious dark coating remained. For these local areas the Borate gels being developed by Lora Angelova were tested and used for treatment.

Working together, Angelova and deGhetaldi performed a variety of tests with the gels and adapted them to the particular problem of cleaning Multiple Views.

deGhetaldi finished her portion of the presentation describing this treatment with numerous beautiful before, during, and after treatment images and a full description of the practical use of the Borate gels, before handing the podium over to her co-presenter.

Lora Angelova began her half of the presentation by describing in detail the formation, characterization, and modulation properties of the borate gels (and the chemistry involved).

The gels are composed of a partially hydrolyzed poly-(vinyl alchohol-co-acetate) polymer that combines by cross-linking with a very small amount of borate ions. The formation of the gel is immediate and proved to be thermally stable with soft elastic properties found desirable for use in treatment. Additionally, due to the acetate groups present on the polymer, the gels allow for the use of large amounts of polar organic solvents to be incorporated into the system. Which was utilized in the case study discussed by deGhetaldi.

Angelova continued by describing several properties of the gels that may make them useful in conservation, including the fact that the gels are transparent, pliable, and as mentioned, have the ability to hold large amounts of commonly used solvents. She then went on to describe how the gels are easy to remove, leave no detectable residue, and have the ability to clean a precise area with little solvent penetration into the paint layers. Which of course grabbed the attention of the conservators in the audience.

Using the results of from a number cleaning tests and further analysis, Angelova further described testing of the prior mentioned traits. She used residue tests conducted by attaching a naturally fluorescing molecule to the polymer in the gel. This allowed for testing regarding the removability of the gel and demonstrated that no detectable residue of the gel was left behind after removal.

Finally, Angelova eloquently concluded her presentation with a brief discussion of future work and the testing that is necessary in order to fully understand and develop the use of Borate gels in conservation.

So, while these gels may not be quite ready for use in the wider world of conservation yet, as was made clear by both the author’s conclusions and some of the thought provoking questions posed by audience members, they are definitely showing great potential as a tool for conservators already and I know many, myself included, who look forward to hearing more about the results that this project produces.