AIC's 53rd Annual Meeting

Guqin is a Chinese plucked musical instrument with profound symbolic, aesthetic, and socio-cultural meanings. It consists of seven silk strings and a rectangular wooden soundbox painted with multi-layers of Asian lacquer-based coatings. The art of guqin has been inscribed on the UNESCO Intangible Cultural Heritage List since 2003, and the collecting of antique guqin instruments has been an important and active part of Chinese material culture since the eleventh century. Mostly resulting from natural aging processes due to playing and chemical and mechanical deteriorations of the compositional materials, craquelure appears on guqin’s surface coatings with time. Interestingly, instead of being viewed as defects or ugly, these craquelures are highly valued as cultural beauty, a sign of authenticity, and a key criterion for appraisal in the guqin collecting tradition. As the connoisseurship of guqin craquelure developed from the eleventh to the nineteenth century, various craquelure patterns were recognized, named, and associated with specific production periods.

However, these seemingly self-explanatory pattern names, such as snake-belly, ice-cracking, and plum-blossom craquelure, have never been clearly defined or illustrated in historical documents or guqin treatises. Although these terms continue to be widely used in contemporary catalogs, auctions, and museum practices, the lack of clarification and in-depth understanding of guqin craquelure patterns has caused issues like arbitrary naming, miscommunication, controversial dating and valuation, and thus puzzling the decision-making of guqin conservation treatments. 

This research used non-destructive imaging techniques, including normal and raking light photography, reflectance transformation imaging (RTI), multi-band imaging, and digital microscopy, for over fifteen historical guqin instruments in both public museums and private collections in China and the US. The goal is to document the cracking surfaces at different magnifications and lighting conditions, and segment the most characteristic visual features to re-define and distinguish those traditional pattern names. From this imaging, four comparable attributes are summarized that best differentiate the guqin craquelure patterns in planar: 1) degree of cross-linking, 2) shape and size of networked islands, 3) direction and distribution of disconnected patterns, and 4) formal features of individual cracks. Additionally, we used micro-CT to scan detached coating samples from five historical guqin to study the depth profile of the cracks and fine crackles, the stratigraphic structure of the coatings, and the distribution of the binder and filler in the ground layers. Although often disturbed by later restoration and re-lacquering layers, the micro-CT analysis proved to help study the more complex areas and distinguish craquelure patterns developing top-down that were potentially initiated by light damage, versus patterns developing bottom-up that were more likely caused by mechanical stress in between the wood substrate and the coating. 

We hope the results of this ongoing project can contribute to building a more scientific classification system of guqin craquelure and clarifying its crack-forming mechanism, which ultimately could improve current restorative and preventive conservation practices and bring more attention to the understudied category of East Asian musical instruments in the context of global collecting and cross-cultural conservation.