44th Annual Meeting – Research and Technical Studies, May 17, "Binders and pigments used in traditional Aboriginal bark paintings” by Narayan Khandekar

This was the last talk I saw at the meeting and was a perfect way to wrap things up, with a travelogue-slash-fascinating research project on the materials and techniques of Aboriginal paintings from the northern part of Australia. Narayan traveled to various art centers and museums to look at and sample pre-1960s paintings, talk to artists and gather local materials. He took about 200 samples from 50 paintings (including some from Harvard’s collection), the oldest from circa 1878. He also obtained materials from artists working today, some of whom took him around to gather materials from local sources, including the beaches of Bathurst Island (part of the Tiwi Islands off the coast of the Northern Territories – thanks Google Maps!). Back at Harvard, he and his colleagues (co authors were Katherine Eremin, Daniel P. Kirby & Georgina Rayner) gathered information on pigments, binders and other materials present that may indicate previous treatments. Narayan pointed out that only two samples of similar paintings had been analyzed and published before, such that this study presents entirely new information.

Australia map

Of particular interest was the investigation into possible binders. Oral histories and documentary evidence recorded various possible binders, including turtle eggs and orchid mucilage, but it was generally thought that paintings made before the arrival of missionaries in the 1920s didn’t have binders at all (a similar question has been on my mind regarding the paintings made in the Sepik River region of Papua New Guinea). Binders were present in 77% of the samples analyzed. No proteins, waxes, fats or blood were detected. The analysis of the oldest paintings did reveal the presence of orchid juice, confirming that binders were in use that early. The techniques of using orchid mucilage could vary; the sticky juice could be mixed with the pigment, or laid down first before applying the pigments mixed in water.
As expected the pigments were largely ochres, and Narayan noted that the trace elements present in the samples provide a fingerprint that can in theory be used to begin to trace the occurrence of different ochres in different areas, but that more study and sampling is necessary to pursue this.

Colorful ochres on the beach

Other interesting findings included the use of dry cell batteries as a source for black manganese and zinc pigments on paintings from Groote Eylandt (yes a very great big island off the east coast of the Northern Territories); this area also shows the use of natural manganese-rich ores and charcoal for black pigments. A curious silver oil-resin paint on two paintings from the 1920s turned out to correlate with the roof repainting of a nearby lighthouse at the same time. The presence of DMP (dimethyl phthalate) in some paintings prior to 1957 resulted from the liberal use of insect repellent (FYI this is the main ingredient in Avon’s Skin-so-Soft; it fell out of use when DEET was invented). The presence of nitrocellulose on Groote Eylandt paintings was connected to records from the 1948 expedition suggesting that they had been consolidated with Duco.
As always, research continues, and Narayan mentioned that they would be looking further into the use of gums and of bloodwood, though I didn’t get down any details on that (I hadn’t actually planned to blog the talk, so apologies for any lacunae!). Also, I’m pretty sure there was a crocodile sighting mentioned, but that too didn’t make it into my notes, so here’s one of my favorites for good measure…

43rd Annual Meeting – “Investigating Softening and Dripping Paints in Oil Paintings Made Between 1952 and 2007” by Ida Antonia Tank Bronken and Jaap J. Boon, May 14

Issues encountered during analysis and treatment of contemporary artworks by conservation scientists, conservators, and other professionals have been brought into the limelight during recent years. Both in the United States and throughout the world, contemporary art collections have introduced new concerns regarding the use of modern materials, artists’ intent, and so on. Even the modern use of materials such as oil paints have demonstrated conservation issues. During this presentation, Bronken described her team’s research into oil paintings (created after 1950) which have exhibited softening and dripping media. The team’s research was conducted on works produced by Jean-Paul Riopelle (Canadian, 1923-2002), Pierre Soulages (French, b. 1919), Georges Matthieu (French, 1921-2012), Paul-Émile Borduas (Canadian, 1905-1960), Frank Van Hemert (Dutch, b. 1956), Paul Walls (Irish, b. 1965), Jonathan Meese (German, b. 1970), and Tal R (Danish, b. 1967).
Softened paint shows decreased surface gloss in normal light and drip material fluoresces in ultraviolet light (sometimes misinterpreted as fluorescing varnish). Softening/dripping impasto and thickly applied paints are easier to identify, but analysis has demonstrated the presence of softening in thinner paint layers as well. Possible causes of this phenomenon are the use of semi-drying oils in recent decades and the development of fatty acids in paint. In their abstract, the authors mention: “There is ample evidence from a number of paints studied by mass spectrometry that the exudates are rich in polar fractions with triglycerides with moieties of mid-chain oxygen-functionalised stearic acids and azelaic acids . . . observations led to the hypothesis that exudation is caused by a loss or absence of anchor sites for the acidic fractions that develop over time.”1
Details from Peinture (1954) by SoulagesTest area from the Seven Series (1990-1995) by Van Hemert
Lead II acetate and europium II acetate were tested by brush and gel application. These compounds treated the softening and dripping oil paint at the molecular level by penetrating into the sample to create carboxylates and forming a hard crust on the paint surface. Brush application was determined to be the most effective method. At this time, the only disadvantage appears to be the lack of reversibility.

About the Speakers

Ida Antonia Tank Bronken, Touring Exhibitions Coordinator, The National Museum, Norway
Bronken graduated from the University of Oslo with a Candidata Magisterii in Fine Art Conservation (2002) and a Masters in Conservation (2009). Bronken has been working for the Touring Exhibitions Department at the National Museum of Art, Architecture and Design in Norway since 2011. Her main interests are collection management and chemical change in modern paint. Bronken has cooperated with Boon since 2007 on different studies on softening and dripping paint, and has contributed to four papers since 2013 about dripping paint (currently at different stages of publication and review).2
Jaap J. Boon, JAAP Enterprise for Art Scientific Studies
Boon, PhD was trained in Geology and Chemistry at the Universities of Amsterdam, Utrecht and Delft Technical University (1978). He became Head of Molecular Physics at the FOM Institute for Atomic and Molecular Physics (1987) and Professor of Molecular Palaeobotany at the University of Amsterdam (1988). His first survey studies on painting materials and traditional paints were performed in 1991, which resulted in collaborative research with Tate Gallery London, the Rijksmuseum in Amsterdam, the Limburg Conservation Studio (SRAL) in Maastricht and EU supported development projects. His research focus changed gradually from identification of constituents towards chemical microscopy and spectroscopic imaging of pigments, binding media and their interactions in paintings. Boon was Professor of Analytical Mass Spectrometry in the University of Amsterdam (2003-2009) and is presently author/coauthor of about 400 research papers and supervised 33 PhD theses. Boon received the KNAW Gilles Holst Gold Medal for his innovative work at the cross roads of chemistry and physics in 2007.3
1 Bronken, I., & Boon J. J. (2015). Investigating Softening and Dripping Paints in Oil Paintings Made Between 1952 and 2007 [Abstract]. AIC Annual Meeting 2015 Abstracts, 81-82.
2 Bronken, I. (2015). Ida Bronken – AIC’s 43rd Annual Meeting [SCHED Speakers]. Retrieved from https://aics43rdannualmeeting2015.sched.org/speaker/ida_antonia_tank_bronken.1t1j0ku0
3 Boon, J. J. (2015). Jaap J. Boon – AIC’s 43rd Annual Meeting [SCHED Speakers]. Retrieved from https://aics43rdannualmeeting2015.sched.org/artist/boon1