Deconstructing Rattan: Morphology of Biogenic Silica in Rattan and Its Impact on Preservation of Southeast Asian Art and Artifacts Made of Rattan

Abstract

ABSTRACTRattan, a climbing palm of the tropical region of Southeast Asia (SEA), supplied material for objects of myriad purposes including ceremonial, religious, utilitarian, and artistic as exemplified by the collections at the National Museum of Singapore, Asian Civilization Museum, and the Singapore Art Museum. The aim of this analysis of rattan is to further the understanding of rattan, in particular its surface, and to propose a protocol-enabling positive identification of rattan in artifacts, thus guiding conservation decisions. The rattan surface defines an artifacts esthetic appearance and stability, and understanding its characteristics is essential to the development of an informed preservation strategy. Rattan epidermis morphology, topography, and cellular structure were characterized by a multi-scale and a multi-sensory approach using optical microscopy, confocal laser scanning microscopy, and field-emission scanning electron microscopy (FESEM). The chemical composition was analyzed with energy dispersive X-ray spectroscopy and macro-X-ray fluorescence spectroscopy (m-XRF) and indicated the presence of a siliceous compound, biogenic silica, in the epidermis and phytoliths in vascular tissue. A parallel analytical protocol was applied to samples extracted from museum artifacts (nineteenth-twentieth century) and contemporary objects acquired during field studies in Indonesia, Malaysia, Myanmar, and Cambodia. The methods of processing rattan have a direct impact on the siliceous layer thus leading to a better understanding of surface patterns found on artifacts. An attempt to find correlations between the percentage of silica and thickness of the siliceous layer did not produce conclusive results; both varied greatly in all studied examples. Darkening of rattan was clearly associated with aging but did not indicate any distinct effect on the chemical composition of the outer layer. The chemical analysis of the biogenic silica layer combined with recording methods of processing rattan observed during field studies in SEA provide a basis for a better understanding of rattan collections in the museum context.