Bai et al. Herit Sci (2021) 9:2 https://doi.org/10.1186/s40494-020-00471-3 RESEARCH ARTICLE Open Access Analytical study of Buddha sculptures in Jingyin temple of Taiyuan, China Xiaojian Bai1,3* , Chen Jia2, Zhigen Chen2, Yuxuan Gong3, Huwei Cheng4 and Jiayue Wang1 Abstract With exquisite design and unique style, the painted sculptures of Tutang Buddha and two attendants Buddha in Jing- yin Temple are precious cultural heritages of China. The sculpture of Tutang Buddha, which was carved from a mound and painted by ancient craftsmen, was rarely found in ancient China. However, due to natural and human factors, the sculptures were severely damaged. Obviously, they require urgent and appropriate protection and restoration. In this study, samples taken from the sculptures were analysed through multiple analytical techniques, including scanning electron microscopy with energy dispersive spectrometry (SEM–EDS), Raman spectroscopy, X-ray difraction (XRD), optical microscopy (OM) and granulometry. The analysis results enable us to infer the techniques used by the crafts- men in making the sculptures and provide a reliable evidence for the conservation and future protection of these and similar sculptures. Keywords: Painted clay sculpture, Jingyin temple, Micro-raman, XRD, SEM–EDS, Granulometry, OM Introduction Te sculpture of Amitabha sitting on a raised plat- Jingyin Temple, also known as Tutang Buddha Temple, form, is one of the tallest Buddha sculptures in China is located in Tutang Village, 20 km northwest of Taiyuan, that carved from earth mound and painted with natural Shanxi Province, North China. It had been built during pigments. Since it locates in Tutang Village, the sculp- the Northern Qi dynasty, rebuilt in A.D. 1205 during the ture is also known as “Tutang Buddha”. According to the Jin dynasty and then partially restored during the Ming earliest evidence of the origin of Tutang Buddha found in dynasty [1]. In addition, it had once been home to Fu the inscriptions on the stone tablets [1], there was a hill Shan, an outstanding Taoist scholar and calligrapher, piled with loess which suddenly collapsed into a cave. who lived in seclusion here for several times during the Inside the cave, a 33.3 m mound which was likely a Bud- Ming and Qing dynasties [2]. In 2006, Jingyin Temple dha was found. It was then sculpted into the Tutang Bud- was declared a Key Cultural Relics Site under the State dha, which is a bare-chested 9.46-m-tall Buddha wearing Protection. Te Buddha Pavilion is the most important a robe and sitting on a 6-m-wide lotus seat with his building in Jingyin Temple (Fig. 1a, b). Te pavilion, hands in his lap. Te sculpture was decorated with gold which built on a clif, is an east-facing two-story building foils while the belt was painted with exquisite blue pat- with multiple eave hiped-roof. Tere are three painted tern (Fig. 2a). Its intricate patterns at the edge of the dress sculptures in the hall of the Buddha Pavilion, where were drawn by the traditional Lifen technique (Fig. 2b). the Tree Western Saints are worshiped [3]: Amitabha Te Lifen technique, also called an embossed painting (Fig. 1c), Avolokitesvara (Fig. 1d) and Mahasthamaprapta technique, is a high-level painting technique that was (Fig. 1e). used widely in wall painting, sculpture and architectural painting in ancient China. According to the technique, the rubber powder is extruded by tools on the surface *Correspondence: [email protected] 1 Department of Cultural Heritage, Taiyuan University of Technology, to form a 0.2-cm-high line, which highlights the three- Taiyuan 030024, China dimensional sense of the pattern. Tus, these overall Full list of author information is available at the end of the article proved the preciousness of the sculpture [4]. © The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creat​iveco​ mmons​.org/licen​ses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creat​iveco​mmons​.org/publi​cdoma​in/ zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Bai et al. Herit Sci (2021) 9:2 Page 2 of 19 Fig. 1 General view of the temple and the sculptures. a The interior of the Jingyin Temple; b The interior of the Buddha Pavilion; c Sculpture of Tutang Buddha; d Sculpture of Avalokitesvara bodhisattva; e Sculpture of Mahasthamaprapta bodhisattva (The cross-scale was marked in the unit of mm) Bai et al. Herit Sci (2021) 9:2 Page 3 of 19 Fig. 1 continued Te sculptures of Avalokitesvara bodhisattva and Mahasthamaprapta bodhisattva are positioned face to face in a gentle and beautiful appearance. Both sculptures are 3.7 m tall, having pure white, broad, plump faces and wearing necklaces, bracelets and ornate clothes. Refer- ences [1] showed that the two sculptures were made using the traditional sculpturing technology during the Ming dynasty as below [5]: the basic structure of the sculpture was built with wooden sticks of the mortise- tenon joint or fxed by nails; the wood skeleton was then wrapped with reed poles and fxed with hemp ropes; the cover consisted of coarse muds containing soil, sands and wheat straws, etc.; the thin layer was made of fne muds; the surface was whitened and painted. Complex pattern- ing and gilding were applied onto the two sculptures to obtain the exquisite patterns. Due to the natural and artifcial deterioration, the sculptures were eroded severely, shown as facking and shedding of the paint layer, salt corrosion, some dam- ages found at the bottom of the sculptures, and detached and cracked fngers of the Avalokitesvara bodhisattva. Moreover, due to the pollutions such as surface dust and lampblack, the exquisite patterns became invis- ible. Tus, they require urgent preservation and restora- tion. In this respect, analytical studies become a reliable source for revealing the actual application of materials Fig. 2 a The exquisite blue pattern painting on the gold; b The and the technique, as well as ofering basic information intricate patterns at the edge of the dress for restoration. Bai et al. Herit Sci (2021) 9:2 Page 4 of 19 Although studies on the sculptures have been con- Horiba Jobin–Yvon, France) coupled with an Olympus ducted over the years [1, 2], only a few technical studies BX41 microscope. Point measurements were performed have been reported for the conservation of other sculp- using an argon gas laser at 532 nm and a 50 × working tures and there is no previous technical investigation of distance objective. Measurements were performed in the materials and techniques used in making the sculp- the LabSpec 5 acquisition software program at a spec- tures in Jingyin Temple. Considering all these modern tral resolution of about 1 cm−1. Scanning times were methods, the combination of Environmental Scanning determined for each sample separately, depending on Electron Microscopy with Energy Dispersive X-ray analy- the acceptable quality of the spectra obtained and also sis (ESEM/EDX), Raman spectroscopy and Polarized light to ensure the samples were not altered due to the heat- microscopy (PLM) has proved to be a powerful method- ing produced by the laser. In general, the scanning time ology to identify the pigments [6–8]. Application of X-ray varied between 10 and 60 s. Te samples were meas- difraction (XRD) is benefcial for accurately identifying ured over the spectrum range of 3000–100 cm−1 with crystalline structures in muds [9, 10]. Granulometric an accumulation number of 2. Te spot size was 1 µm. analysis is a well-established and powerful technique for Te system used a 1200 groove/mm dispersive grating analysing the particle sizes of caly samples [11]. Te com- [14]. At least fve measuring points were selected for bination of Herzberg stain and optical microscope is used each pigment. to distinguish the fber sources, which is efective for identifying paper fber [12]. In this work, micro-Raman spectroscopy, SEM–EDS, XRD, Granulometric analysis, Scanning electron microscopy with energy dispersive OM were applied to analyse the fragments containing spectrometry (SEM–EDS) pigments, clay and paper. Such documentation and anal- SEM (a Quanta 650 of the FEI Company, USA) with EDS ysis not only ofer basic information for the future con- (a X-MaxN50 of the Oxford Instrument, UK.) were used servation and restoration of the Temple, but also support for characterizing the elements of the pigment, which the future study of the art history, age and ownership of was a useful micro-destructive method for analysing the materials. samples of cultural relics. Each sample was put on the sample holder with conductive adhesive and gold sput- Experimental tering technique was not used in the samples. Aztec soft- Samples ware was used in the point & ID mode for micro-analysis. Samples were taken from the damaged areas of the three Samples were analysed with 20 kV acceleration voltage painted sculptures, mainly the pigment, paper, and fne and 10 mm working distance.