Sharon Cather

Stratigraphic analysis of organic materials in wall painting samples using micro-FTIR attenuated total reflectance and a novel sample preparation technique

Wall paintings typically contain low concentrations of organic materials within a largely inorganic matrix and are characterised by their high porosity and long-term exposure to severe environmental conditions. The identification of organic materials within specific paint or plaster layers is challenging and the inherent characteristics of wall painting samples present further complications. Embedding materials (such as epoxy, polyester and acrylic-based resins) used to produce cross-sections often infiltrate porous and leanly bound samples, and compromise the interpretation of Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectra and the qualitative identification of natural organic materials. An alternative method for the preparation of cross-sections of wall painting samples was developed using cyclododecane (C12H24) as a temporary consolidant and barrier coating to encapsulate the sample, and to provide necessary support to produce a cross-section through microtoming. Impacts of traditional and novel sample preparation techniques on the identification of organic materials with micro-FTIR-ATR were examined for both replica and real wall painting samples.

Analysis of Protein-Based Media Commonly Found in Paintings Using Synchronous Fluorescence Spectroscopy Combined with Multivariate Statistical Analysis

The spectrofluorimetric analysis of protein-based binding media, which are commonly found as painting materials, is based on the detection of emissions from amino acids, as well as fluorescent degradation products that develop with aging. Laser-induced fluorescence spectroscopy, fluorescence excitation emission spectroscopy, and time-resolved fluorescence spectroscopy have all been employed in efforts to discriminate between commonly found proteinaceous binding media, including egg white, egg yolk, milk, and casein, as well as collagen-based glues from rabbit skin, ox bone, parchment, and fish. However, synchronous fluorescence spectroscopy (SFS), a rapid means of recording fluorescence properties of samples, has not been reported for the differentiation between binding media. This work focuses on the analysis of a large set of naturally aged films of different protein-based binding media using SFS with a range of different offsets between excitation and emission monochromators between 30–60 nm. An interpretation of synchronous fluorescence spectra of binding media is presented and is followed by an assessment and classification of a database of recorded spectra using multivariate analysis. Importantly, following SFS analysis of films of binding media, principal component analysis is used to differentiate among all the proteinaceous media considered on the basis of clustering of data. This application is thus a novel and nondestructive means for differentiation between protein-based binding media.

Vast and dispersed: Developing portable facilities for non-invasive analysis and recording of heritage sites in China

Context China’s cultural heritage is vast. Among over 400 000 immovable heritage sites and relics, there are 4295 highly significant nationally listed sites, 45 World Heritage sites and some hundred historical and/or cultural towns. There are also 30 million objects in museums, increasing by 100 000 each year. The sites are geographically dispersed and many are in areas of challenging (though improving) infrastructure. In Gansu province alone, there are over 20 significant grotto sites, and many are remote from both conservation resources and advanced technology. Along with increases in emergency excavation, triggered by economic development, archeological sites are at risk whether excavated or unexcavated. Those responsible are challenged by heavy workload, time constraint, outdated equipment, experience in mainly older methods, lack of professional conservators, and other issues. Furthermore, some dramatic changes have occurred on many artifacts in a very short time, during excavation. How to reduce the loss of valuable information has long been explored by archaeologists. China is responding to preserving its vast and dispersed archaeological heritage in various ways, through research, education and policy-making. As the nationally designated Expert Center for the Conservation of Ancient Murals, the Dunhuang Academy has a daunting remit, one that also extends to archaeological sites. The Academy’s Conservation Institute has been embracing new approaches and technologies, with a clear emphasis on non-invasive 背景

Conservation research at Dunhuang: The pivotal role of Cave 260 for conservation education and policy

China’s ‘unbroken’ cultural heritage has, nonetheless, suffered from large cracks. At the World Heritage site of Dunhuang [1], with some 500 rock-cut painted Buddhist cave temples begun in the fourth century, the historical rift occurred when the site was abandoned in the fourteenth century, and was only bridged at the end of the nineteenth century [2]. Since the establishment of the Dunhuang Academy (DA) in 1943 as the body responsible for preservation of the site (and many others in the surrounding region), the process of preservation has evolved, reflecting changing attitudes to conservation. International interest in Dunhuang’s treasures began in the late nineteenth century and has gathered momentum since the ‘foreign devils’ who arrived in the late nineteenth century [3], their plundering only curtailed in the 1920s, to the numerous international scientific collaborations of the DA today. As the legal guardian of the site and the principal repository of knowledge of its history and condition, the Academy has an unparalleled ‘institutional memory’, matched by the depth and breadth of its documentation and publications. We propose to tell the story of the Academy’s collaborative approach to ensuring long-term evidencebased conservation, through the extraordinary tale of one cave, Cave 260. A sumptuous Northern Wei period cave, recently re-dated to the third quarter of the fifth century, it was selected in 2004 from among 中國歷史文化雖然源遠流長,但當中仍有不少裂