| ■Tokyo National Research
Institute for Cultural Properties |
■Center for Conservation
Science |
| ■Department of Art Research,
Archives and Information Systems |
■Japan Center for
International Cooperation in Conservation |
| ■Department of Intangible
Cultural Heritage |
|
Conference venue
Presentation scene (poster session）
Presentation scene (oral session）
From May 6 to May 9, 2025, three members of the Center for Conservation Science―Dr. AKIYAMA Junko (Head of Preventive Conservation Section), Dr. Chi Chih Lien (Associate Fellow, Analytical Science Section), and Ms. TERASHIMA Kai (Research Assistant, Analytical Science Section)—participated in the International Conference on Analytical Techniques for Heritage Studies and Conservation – TECHNART 2025, held in Perugia, Italy.
TECHNART is an international conference focused on scientific approaches to the analysis of cultural heritage. The 2025 program featured the latest developments in non-invasive, imaging-based analytical techniques such as Macro X-ray Fluorescence Scanning (MA-XRF), Macro X-ray Powder Diffraction Scanning (MA-XRPD), and Reflectance Imaging Spectroscopy (RIS), as well as studies on image analysis using machine learning and the development of environmentally sustainable conservation materials. (See: TECHNART 2025 program.pdf)
Dr. Chi presented a poster entitled “Analysis of Green Coloring Materials in the Takamatsu Matsudaira Family Illustrated Book on Natural History Using Hyperspectral Imaging.” Focusing on a designated tangible cultural property of Kagawa Prefecture, the study employed hyperspectral reflectance data and principal component analysis (PCA) to classify and identify the green colorants used. This approach, which integrates large-scale spectral datasets with statistical methods, proved effective for gaining insight into painting materials and techniques. Discussions and exchanges during the session further underscored the importance of developing comprehensive pigment databases and advancing multidimensional data analysis as shared international challenges.
Ms. TERASHIMA gave an oral presentation titled “Investigation on the Use of Smalt in 17th–18th-Century Japanese Illustrations Using MA-XRF and RIS-VNIR,” focusing on two-dimensional spectroscopic analysis of Edo-period paintings. This presentation highlighted the use of smalt (blue pigments made from cobalt-containing glass), commonly seen in Western oil paintings, in Japanese artworks, and discussed its unique application and coloring effects. Presentations by participants from the United States and Portugal on similar topics reflected international interest, providing valuable opportunities for comparative perspectives and deeper discussions.
Many of the international research teams included not only experts in conservation science and cultural heritage science but also developers of hardware and software for analytical instruments, demonstrating an interdisciplinary approach. While cross-disciplinary research is advancing in Japan as well, further expansion of venues for diverse presentations will be key to future development. Insights gained through participation in this conference will be integrated into ongoing and future research activities.
Injecting nitrogen into the bag set in the display case
Extracting the air from the bag using a pump
The Center for Conservation Science investigates the conservation environments of museums. Recently, the Kanagawa Prefectural Museum of Cultural History requested us to investigate the air quality in their exhibition cases. They detected some organic acids, however, the emission source was not identified. The emission source was needed for taking appropriate counter-measures. Moreover, the ratio of acetic acid and formic acid is called for as the current measurement was taking them collectively as organic acids.
Therefore, the Preventive Conservation and the Analytical Science Sections decided to investigate the emission source by applying the air quality investigation methods developed by the Analytical Science Section. Five points including the floors of two wall display cases (big and small size), the display surface of a tabletop case, the display stand, and the back panel, were targeted. As shown in the photos, the targeted measurement points were covered with bags made of airtight film and the 4.5 kg lead rings were set to seal them. Then, after replacing the air inside the bags with nitrogen and leaving them for 24 hours, the air was extracted from the bags using a pump, dissolved in ultrapure water, and analyzed using ion chromatography. Consequently, we measured the amount of acetic acid and formic acid emissions. Simultaneously, we checked the sealing degree by the measurement of CO2 density change inside bags over time.
We have identified the density of acetic acid and formic acid at each measurement point and will leverage these outcomes for future air quality improvement.
Investigation at Kangetsu-do Hall of the Kotoku-in Temple
The Kotoku-in Temple, famous for its Great Buddha, has a hall called Kangestu-do Hall, transferred from Gyeongbokgung, a Korean royal palace. Kangetsu-do Hall faces various issues for its conservation and utilization, such as aging roofing tiles and outer walls as well as damage by wild animals. Dancheong were the original coloring pigments used in Kangetsu-do Hall at the time of its construction. This is very valuable because they exist in their original state. Their elements have not yet been elucidated; therefore, it is important to understand their status. Through these examinations and discussions, we decided to collect basic information related to the coloring pigments used in Kangetsu-do Hall.
Responding to the request by the Kotoku-in Temple (chief priest: Prof. SATO Takao), INUZUKA Masahide, HAYAKAWA Noriko, HAGA Ayae, and CHI Chih lien of the Center for Conservation Science of Tokyo National Research Institute for Cultural Properties (TOBUNKEN) conducted on-site investigation of coloring pigments on the building components of Kangetsu-do Hall using portable analytic equipment on July 6th and 7th, 2022.
As this investigation’s first step, reflectance spectrometry was conducted using a hyperspectral camera to investigate two-dimensional color information, focusing on the places where the original paintings from the construction time were presumed to remain. We then selected some places that were academically interesting based on the reflectance spectrometry data and performed further detailed analysis using X-ray fluorescence analysis. We plan to analyze in detail the data obtained by these two types of analysis methodologies, further investigate the unique coloring pigments used in the Joseon Dynasty, and use this information for future conservation and utilization.
Preparation for the survey
Discussion about the investigation parts
Department of Art Research, Archives and Information Systems has been engaged in a series of surveys on Rakan-zu (a painting of Arhat, an enlightened Buddhist high priest) painted in the Yuan Dynasty, owned by the Baijōsan Kōmyōji Temple in Minato Ward, Tokyo. Please refer to our online monthly report for this survey. (https://www.tobunken.go.jp/materials/ekatudo/910616.html)
Near-infrared imaging and fluorescence imaging produced by optical survey suggested that the new artificial iwa-enogu (mineral pigment used in paintings) could have been used to add colors on several parts of this painting.
It is expected that, in addition to the observation on the imaging data including high-definition imaging, scientific analysis survey can provide additional data from the different approaches. Then, we, INUZUKA Masahide, CHI Chih lien, TAKAHASHI Yoshihisa from the Center for Conservation Science, and EMURA Tomoko, YASUNAGA Takuyo and MAIZAWA Rei from the Department of Art Research, Archives and Information System conducted a survey on Rakan-zu by reflectance spectrometry at the Baijōsan Kōmyōji Temple on January 19th, 2022.
Reflectance spectrometry can identify the kinds of coloring materials used in the work by reflectance spectrometry formation, how the reflectance of the surface against wavelength of light. Furthermore, hyperspectral camera, which we used this survey, shows the distribution of the same reflectance spectra in two dimensions simultaneously.
We plan to identify the materials and places for adding color by analyzing the data which we have gathered in this survey.
Investigation using X-ray fluorescent analyses
The Protection of Tumuli and Wall Paintings Project Team consisting mainly of researchers from Tokyo National Research Institute for Cultural Properties（TOBUNKEN）and the Nara National Research Institute for Cultural Properties has been working on research studies to preserve and restore the wall paintings of Takamatsuzuka Tumulus and Kitora Tumulus. Compared with the wall paintings of Takamatsuzuka Tumulus, the wall paintings of Kitora Tumulus are characterized by the twelve signs of the zodiac, depicted as animal heads on human bodies, three of which are featured on each wall along with the Four Divine Creatures and Star Atlas and others.
While six figures out of twelve—the Rat, Ox, Tiger, Horse, Dog, and Boar—have been identified, the Rabbit, Sheep, and Rooster are completely lost since the plaster where the paintings should be is missing. The rest, that is, the Dragon, Snake, and Monkey, are not yet identified because the surface of the walls is covered with mud. These three pieces of walls that could contain those paintings are currently not reassembled, but are preserved in the facility for conservation and restoration of Takamatsuzuka Tumulus wall paintings.
The material investigation group and restoration group of this project team worked together on an investigation using X-ray radiography in 2018 and found some radiographic images that seemed to show something drawn in the space where the Dragon was expected to be, but many questions remained. Then, in December 2020, X-ray fluorescent analyses were performed on the parts of the walls where the wall paintings of the Dragon and Monkey could possibly exist. Some mercury was detected, indicating that the figures might be present.
Following this outcome, on August 11th, 2021, further X-ray fluorescent analyses were conducted on the part of the wall where the Snake artwork was suspected to be. Three members of the Center for Conservation Science, TOBUNKEN—INUZUKA Masahide, HAYAKAWA Noriko, and CHI Chih lien—participated in this investigation. X-ray fluorescent analyses were conducted at spots distanced 2 cm apart where the Snake painting was expected to be. The detection of mercury indicated that the painting was indeed present.
These results were reported in the “29th Committee on Preservation and Utilization of Tumulus Wall Paintings” held on August 31st, 2021 by the Agency for Cultural Affairs.
X-ray image of the piece of the wall where the Snake painting could be present (left) and distribution of mercury signal strength (right)
