동화사 비로암 삼층석탑 출토 사리외함 밑면 유물 일괄품과 목제소탑의 과학적 조사 및 보존처리(보고서)

Base side of outer sarira reliquary and miniature wooden pagoda found from the Three-story Stone Pagoda at Biroam Hermitage of Donghwasa Temple: scientific survey and preservation treatment

We conducted scientific survey and preservation treatment of the following objects unearthed from the Three-story Stone Pagoda at Biroam Hermitage ofDonghwasa Temple: Base side of the outer sarira reliquary, and Miniature wooden pagoda currently kept at the Dongguk University Museum. We took X-ray photos to grasp the internal structure of the relics. To ascertain the ingredient of an organic matter assumed to be pine resin, we carried out Fourier-transform infrared spectroscopy (FT-IR) and Pyrolysis-Gas Chromato graphy/ Mass Spectrometry (Py-GC/MS). We analyzed the ingredient of the base metal plate of the outer sarira reliquary and the galvanized surface layer of the miniature wooden pagoda using X-Ray Florescence Spectrometry (XRF). To determine the type and characteristics of textile left at the base of the relic, we checked its twist, thickness, density, and structure using a microscope. The base metal plate of the outer sarira reliquary contained Cu 99.39%, Ag 0.49% and a small amount of Pb, Sn, Pb, Fe, Sn, and Ni. Thus, the base plate was thought to be made of pure copper with very high Cu content. The galvanized layer of the miniature wooden pagoda was judged to be Au with some Cu content. With regard to the material applied to the outer surface of the base side of the reliquary, which we assumed to be pine resin, we conducted FT-IR and Py-GC/MS analysis. As a result of the comparison analysis by setting pine resin powder and lacquer as control group, we ascertained an IR pattern similar to that of pine resin composed of abietic acid and fumaric aid. The Py-GC/MS-based analysis produced camphene and terpene alcohol. Thus, we judged that it was pine resin containing essential oil and resin. As for the textile, we found multi-knit fabric and single-knit fabric. Most of it appeared to be densely knit plain weave fabric. The textile seemed to have lost the bending/drape property unique to fabric. The exposed base side textile displayed diagonally placed warp yarns and weft yarns. Warp and weft yarns are untwisted yarns with similar thickness and status. The density of the fabric was about 31*32/km. The density ratio of the yarns was about 11 with thickness of 0.25 - 0.35mm. As for its cross section, it had a triangular shape or the like without hollowness as a feature of fibroin consisting of silk fiber. Accordingly, the fabric that is fixed to the bottom of the outer sarira reliquary is believed to be silk fiber. With regard to the base side metal plate of the outer sarira reliquary, we dry-washed it with a soft brush. We wet the washed foreign material that was not removed with dry washing using distilled water mixed with alcohol. After a process of natural air drying, we stabilized it using a method of natural immersion with alcohol mixed with 396 diluted benzotriazol. Then, we reinforced it by applying 10% acetone mixed with 5% paraloid-B72 twice to its surface. We dry-washed dust and foreign material on the surface of the fabric and what was assumed to be pine resin with a brush and reinforced it with hydroxylpropylcellulose 196 solution. For the galvanized layer (showing severe peeling off) of the surface of the miniature wooden pagoda, we fixed the layer with hydroxypropyl cellulose 1% solution and reinforced the entire surface by coating it with the solution using a brush.