The following is a guest post by Meghan Wilson, a preservation specialist in the Preservation Research and testing Division of the Library of Congress.
The spark of inspiration and discovery spurred on by collaboration is always exciting to rekindle. In April, the Preservation Research and Testing Division hosted colleagues from Nottingham Trent University’s ISAAC Research Lab (Imaging & Sensing for Archaeology, Art History, and Conservation) as they explored the Library of Congress’ collection of pith paintings. Their international research project “From Lima to Canton and Beyond: an AI-aided Heritage Materials Research Platform for Studying Globalisation through Art” exemplifies collaboration on a multitude of different levels: between the cultures who produced the art, between institutions researching them in present day, between collections in multiple divisions within the Library, and even between different instruments for analysis.
Pith paintings were a new medium to me. Pith, the substrate onto which the paint is applied, is not like traditional paper. It’s made from hand-cutting thin sheets of the spongy tissue found in the stem of Tetrapanax Papyrifera, a plant native to southern China and Taiwan, and used to mimic silk that was used in traditional Chinese painting. The unique plant cell structure provides a soft and translucent surface, emphasized by thin washes of color and juxtaposed with areas of thick opaque pigment. Up close, the paintings look velvety, seeming to hover off the page.
The pith paintings are largely attributed to artists’ shops located on the Canton (now Guangzhou) waterfront, depicting scenes of everyday life in the early half of the 19th century. Simultaneously, the Costumbrismo genre of painting was flourishing in Peru, depicting the exotic identity of the Peruvian people in traditional attire. Both niche art forms had striking stylistic resemblance to one another, indicating a shared artistic influence between the cultures. As stated by project lead Professor Haida Liang, one of the goals of Lima to Canton and Beyond is to use these paintings as a lens to reveal details of global trade and information exchange networks among the Americas, Asia, and Europe ca. 1780-1850. Pigments, dyes, and paper are commodities that were traded extensively throughout history; their identity and the way they are used are often traceable to their geographic and cultural origins.
This project took us to collections in both the Manuscript Division and the Prints and Photographs Division to explore the Caleb Cushing Papers (a U.S. ambassador to China), the William Speiden Journals (a purser’s clerk on a U.S. naval expedition to Japan), paintings from the Sunqua Studio, paintings based on works by Peruvian artist Pancho Fierro, as well as a select collection of unattributed Chinese pith paintings. While these objects are well cared for, pith is inherently delicate. Sara Duke, curator in the Library’s Prints and Photographs Division, notes that because the pith support becomes so fragile over time, the Library has to balance the story that is being told with the future preservation needs of the object when choosing to acquire the paintings. Thus, there was significant internal curatorial support for the project. Analyzing the materiality of the paintings promotes the preservation and longevity of the objects and, as Barbara Bair, curator in the Library’s Manuscript Division, observes, allows a better understanding of their international underpinnings.
The paintings were analyzed in PRTD’s lab using a “multimodal” approach. Six imaging and spectroscopy techniques were used to study the paintings under a wide array of different parts of the electromagnetic spectrum, or different types of light. X-ray fluorescence provides information about the elemental composition of a material. Ultraviolet light provides luminescent information, causing some materials to glow as if under a black light. Visible light provides information about the material’s color and how it is seen to the human eye. Infrared light measures molecular vibrations, identifying things that are invisible to the eye like coatings or the binders the pigments were mixed with. These methods are safe and non-invasive, even to materials as fragile as pith. PRTD is fortunate to be well fitted with a range of instrumentation and Professor Liang brought a similar, complimentary suite of portable instruments developed in-house by the ISAAC Mobile Lab. This allowed work to proceed in parallel at the Library and the Smithsonian Freer Gallery of Art. While fundamentally using the same technique as instruments within our lab, it was a giddy moment for me as a scientist to be able to see a different perspective on data collection methods and how they rigged two instruments onto a single stage. Examples like this help me think of ways I can optimize and make my own workflows more efficient.
For three days the lab was full of scientists at different instrument stations performing round-robin analyses on the beautiful collections of paintings.
Professor Liang and her team travelled to additional institutions while in the U.S. including Yale and the Lilly Library at Indiana University. Though the analysis is still ongoing due to the significant amount of collected data, the Lima to Canton and Beyond project guarantees new insights for these unique paintings in the Library’s collections, both from a cultural and preservation point of view.
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The entire Speiden journals, including the original pith paintings that Speiden collected on the voyage, have been carefully conserved by the Library’s Conservation division, digitized by the Manuscript Division, and are available online internationally for view and further study through the Library’s digital presentation web site.
Kogou, S., Lucian, A., Bellesia, S. et al. A holistic multimodal approach to the non-invasive analysis of watercolour paintings. Appl. Phys. A 121, 999–1014 (2015). https://doi.org/10.1007/s00339-015-9425-4