Application of Advanced Analytical Techniques in Organic Cultural Heritage: A Case Study of Ancient Architecture Relics in the Palace Museum (Beijing)

Multilayer objects with different interfaces are quite typical for architectural heritage, and from them may be inferred the age, production process, and deterioration mechanism through analyzing characteristic compositions with advanced analytical techniques. The Meiwu ceiling in the Hall of Mental Cultivation of the Palace Museum was found to contain many paper-based layers during conservation. Once several surface strata were detached, a colorful layer of printed fabric textile was discovered integrally. Through microscopic observation and micro-attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) imaging, the overall structure consisted of 11 layers, namely, bast paper, cotton wiring, xuan paper, cotton printed fabric, two yellow board papers, bamboo paper, three wood pulp paper and surface coatings, and starch was considered as an organic adhesive. For identification of the printed fabric’s color palette, ultra-performance liquid chromatography (UPLC) combined with high-resolution quadrupole time-of-flight (QTOF) technology, non-invasive macro X-ray fluorescence (MA-XRF) and desorption electrospray ionization mass spectrometry imaging (DESI-MSI) were applied in situ. Seven industrial synthetic dyes, including auramine O, malachite green, and eosin Y with corresponding by-products, as well as chromium-based pigments considered as dark draft line, were confirmed. By X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), and micro Fourier transform infrared spectroscopy (micro FTIR, other results showed chalk soil and talc for the outermost coating. According to the synthetic time of industrial dyes and degradation degree of paper, there were at least four occurrences and their specific time periods were speculated.