AIC’s 39th Annual Meeting – Joint Paintings/Research and Technical Studies Session, June 3, “Developing Cleaning Systems for Water Sensitive Paints by Adjusting pH and Conductivity” by Tiarna Doherty

As a fitting end to a conference full of great talks, Tiarna Doherty, from the J. Paul Getty Museum, wrapped up the final session of the joint PSG/RATS session at the annual meeting on Friday evening with an incredible talk about new developments in cleaning water-sensitive paintings. The project was a collaboration between herself and two others, Chris Stavroudis, conservator in private practice, and Jennifer Hickey, Graduate Intern at the Metropolitan Museum of Art, that aims to develop a methodological approach to cleaning water sensitive works by measuring the pH and conductivity levels of the surface of the artwork and cleaning solutions in use.

Doherty began her presentation by introducing us to the Modular Cleaning Program (MCP), a database system that has been developed to assist conservators in their approach to cleaning artworks. The MCP performs valuable computations which assist the conservator in creating cleaning solutions that take into consideration, pH, ionic strength, HLB, and the functions of surfactants, buffers, and chelating agents, within aqueous cleaning solutions. Using MCP workshops given by herself and Stavroudis as an example, Doherty highlighted how practical experience with the MCP has helped them to understand how paints interact with cleaning systems, and thus aided in their current research.

She continued by concisely explaining why they focused on pH and conductivity. First, recognizing that the pH of something as simple as water may vary widely, Doherty notes that even exposing de-ionized to air over a long period of time eventually causes the pH to lower. Likewise, carbonated water also has a low pH, but since an acrylic paint film swells at a pH of 7 and higher, the use of carbonated water has been shown to successfully clean some water sensitive acrylic artworks. Doherty finished her introduction on pH with a brief explanation of buffers and the use of acetic acid and ammonium hydroxide to adjust the pH of water for cleaning, noting that both of these components of the solution will evaporate over time without leaving a residue on the surface of the artwork.

Next, Doherty continued her talk by segueing into an introduction on conductivity. Conductivity, the ability of a solution to transfer (conduct) electric current, was recently explored as a means to evaluate the surface of an artwork during cleaning and to create/develop useful cleaning systems. In a simple manner, the conductivity of a painting’s surface can be measured by placing a small drop of water on the surface of the painting, and then transferring it to a conductivity meter after a short period of time. Doherty reported that recent research in the field has concluded that there is less swelling of a water sensitive paint surface when it is cleaned with a solution that has a of pH of 6 or lower and a conductivity of 6000 micro-Siemens.

The talk continued with two in-depth cleaning case studies on an oil painting and an acrylic painting, which were both painted in the 1960’s, and had proven to be sensitive to water. Using solutions with adjusted pH, various conductivity levels, and the addition of materials such as chelators, surfactants, and even an emulsion system containing a proprietary material called Velvasil®, Doherty’s team tested and successfully developed systems for cleaning each of the two artworks (which, to ensure accuracy of content, I will point you in the direction of the post-prints for the details of).

As Doherty concluded her talk, I couldn’t help but be a little excited about possible implications of this and future research on these topics. This talk not only raised many interesting considerations about the cleaning of paintings, but, it also revealed the practical application of a new a tool set for conservators who face the challenge of water-sensitive paintings.

Bravo Tiarna (and team), I look forward to hearing more as this project progresses.

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.