| ■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 |
|
Flyer for the symposium
The keynote lecture by Deputy Director General HAYAKAWA
The keynote lecture by Deputy Director General KOHDZUMA
Panel Discussion
In recent years, developments in analytical chemistry have led to the discovery of new values of cultural properties.
On March 4, a symposium was held to commemorate the retirement, in March 2023, of HAYAKAWA Yasuhiro, Deputy Director General of Tokyo National Research Institute for Cultural Properties (TOBUNKEN) and KOHDZUMA Yohsei, Deputy Director General of Nara National Research Institute for Cultural Properties (NABUNKEN) who have, for the long time, contributed to the scientific research and conservation of cultural properties. The symposium aimed to discuss the new world of cultural properties opened up by the development of analytical chemistry from the perspective of “color,” one of the most fundamental and important values of cultural properties. The event was organized by TOBUNKEN and NABUNKEN, and co-sponsored by Nittetsu Technology Co.
The symposium was held in the seminar room of TOBUNKEN, and many participants also gathered at the satellite sites of TOBUNKEN and NABUNKEN (Participants: 69 [TOBUNKEN seminar room], 36 [satellite site of TOBUNKEN], 26 [satellite site of NABUNKEN]). The symposium was also simultaneously streamed on YouTube, and was watched by many people.
In the keynote lecture by Deputy Director General HAYAKAWA entitled “Transition of White Pigments in Japanese Paintings,” the presentation showed the transition of white pigments (lead white, artists’ chalk, and white clay) used in Japanese paintings based on the results of his analytical surveys.
In the keynote lecture, “Across the Boundaries ,” Deputy Director General KOHDZUMA spoke about the importance of conducting research with a broad perspective and mutual understanding while honing one’s own expertise in the field of conservation science of cultural properties. In addition to the keynote lectures, there were seven research presentations related to the “color” of cultural properties and an exhibition of various analytical instruments during the lunch break. Also, the lecture was followed by a lively panel discussion that went beyond the topic of color analysis of cultural properties to include future prospects of the conservation science for cultural properties.
We are thankful for the leadership of the two Deputy Director Generals which greatly helped the staff of TOBUNKEN, NABUNKEN, and Nittetsu Technology to collaborate with each other effectively and plan and conduct a very successful symposium.
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)
Survey of Armor by X-ray Fluorescence Analysis
At the request of the Kariya city Museum of History, INUZUKA Masahide of the Center for Conservation Science, conducted an analytical survey of a suit of armor. As part of these materials, the helmet became a designated cultural property of Kariya City in 1984. The location of items other than the helmet, such as the torso of the armor, only came to light a few years ago. The degree of damage to these other parts of the suit armor is much more severe than to the helmet, but they were additionally designated as cultural heritage by Kariya city in 2019 and deposited at the Museum.
A project to preserve and restore these materials will be implemented in the future. To collect basic data for this purpose, a structural survey using X-ray radiography and a pigment analysis using X-ray fluorescence analysis were conducted at Tokyo National Research Institute for Cultural Properties on May 31, 2021.
Images taken with X-ray radiography provided information on the structure of the helmet and torso, the number of components that comprise the armor, the position and number of studs, and other information. We also conducted an X-ray fluorescence analysis of the pale orange-colored portion on the surface of the helmet, leveraging a device that specializes in analyzing cultural properties, which are large in size and have a three-dimensional structure, with high sensitivity, as shown in the photograph. The results of these surveys will be used as reference materials for future restoration work.
The seminar is underway
In the research project “Research on the Analysis of Materials, Structures and Conditions of Cultural Properties”, the Center for Conservation Science focuses on the physical and chemical characteristics of cultural properties based on the investigations of their materials and structures using various analytical methods. In particular, the Analytical Science Section has been studying the problem of the corrosion of lead composing cultural properties.
In order to summarize the research, a seminar on the “Corrosion of lead composing cultural properties and air environment” was held on December 14th, 2020. Invited were experts in art history (HASEGAWA Shoko of Seikado Bunko Art Museum and ITO Tetsuo of Agency for Cultural Affairs), conservation science (KOTAJIMA Tomoko of National Ainu Museum), and restoration (MUROSE Tasuku of Mejiro Institute of Urushi Conservation) were invited. At the seminar, lectures were presented on examples of art works consisting of lead, the current situation and problems concerning lead corrosion in art works, and basic knowledge of lead corrosion from a scientific point of view. In addition, the latest information about the relationship between lead corrosion and air environment and examples of restoration were shared and discussed. (Attendance: 20 individuals).
X-ray radiography of Kongo Rikishi statue
The Oiwayama Bishamonten in Ashikaga city, Tochigi prefecture is said to be one of the three major bishamontens in Japan in addition to those at Kurama-yama in Kyoto and at Shigi-san in Nara. Wooden Kongo Rikishi statues, which are cultural properties designated by Ashikaga city, are enshrined at Sanmon gate. According to recent research, there are concerns about the deterioration of these properties over time. In particular, the inclination of the head of Agyo statue has been pointed out. Considering this situation, the owner plans to embark on a restoration project.
To carry out the project, it is necessary to clarify the inner structure of the statues, especially how the parts are connected to each other. However, an in-situ and non-invasive investigation is required without transferring statues, which are about 2.8 meters tall, from Sanmon gate. At the request of the owner via Ashikaga city, Masahide INUZUKA conducted an investigation into the inner structure of the statues using X-ray radiography from September 9th to 10th, 2020.
As shown in the photograph, the X-ray was irradiated on Kongo Rikishi statues from an X-ray tube set on the scaffold assembled in front of the statues. Before conducting the investigation, important discussions were done to determine how imaging plates (IPs) should be set in the limited space behind the statues. For this research, we used the developing equipment, which is dedicated to IPs, and proceeded with the research by confirming the X-ray transmission images each time they were obtained.
From the X-ray transmission images obtained during the above research, the inner structure of the statues and the information about positions and numbers of nails used in past restoration works were revealed. Such information will be referred to during the restoration works in the future.
Discussion during IIC 2018 Turin Congress
The congress of the International Institute for Conservation of Historic and Artistic Works (IIC) was held from September 10th to 14th in Turin, Italy. From Tokyo National Research Institute for Cultural Properties, Dr. Masahide INUZUKA of the Center for Conservation Science participated in the congress.
The theme of this congress was “preventive conservation.” Therefore, as well as the specific topics about conservation environments, material analyses and restoration, the importance of preventive conservation, leadership required for experts, public engagement and other relevant subjects were discussed.
In the session about preventive conservation for historic sites, Dr. Inuzuka made a presentation on the condensation problems and their preventive measures in a conservation facility for a decorated tumulus in Japan. In the poster sessions, the history of the environmental inspection of museums conducted by the Preventive Conservation Section was reported and information was exchanged with attendants from other countries.
Damaged Baird’s beaked whale specimen being X-rayed for investigation
The Baird’s beaked whale specimen (Berardius bairdii : nickname “Tsutchy”) exhibited at the Rikuzentakata Sea and Shell Museum is a whale (total length is about 10m) that was stuffed to celebrate the meeting of the International Whaling Commission in Tokyo in 1954. The specimen was damaged by the great east Japan earthquake and tsunami on March 11th, 2011. After the primary inspection of damage at the museum on May 28th, 2011, the specimen was transferred to the Tsukuba Research Department of the National Museum of Nature and Science on June 30th, 2011. Currently, the project for restoration of the specimen is in progress.
In this project, it is important to understand the structure of the timberworks and the location of corroded nails inside the specimen. At the request of the National Museum of Nature and Science, Masahide INUZUKA and Midori HAMADA investigated the inner structure of the specimen using X-ray radiography from October 16th to 18th and from 23rd to 25th, 2016. For this research, we used the developing equipment, which is dedicated to imaging plates that were introduced to our institute in 2015. Accordingly, we proceeded with the research by confirming the X-ray transmission images each time they were obtained.
To investigate the overall inner structure of the specimen with the total length of about 10m, we obtained 375 X-ray images in total. The information about the structure of the timberworks and the location of corroded nails inside the specimen obtained from these X-ray images will be referred to during the investigation using an endoscope and the restoration works.
Research on Asuka-daibutsu using a portable X-ray diffraction device
In Asuka-dera Temple located in Asuka village, Nara prefecture, the statue of Shaka Nyorai (the so called “Asuka-daibutsu”), which is about three meters in height, is enshrined as the principal image of the temple. According to historical sources, the statue is considered to have been made by Tori Busshi in 606. It is an important statue because it is considered to be the first Joroku Buddha in Japan. However, there are various opinions as to which part of the statue was originally made by Tori Busshi because it was damaged by fire in the early Kamakura period.
After the opening time of Asuka-dera Temple on June 16th and 17th in 2016, research on the preserved state and production techniques of Asuka-daibutsu was conducted by experts in art history, conservation science, restoration and three-dimensional measurement. This research was managed as a part of the “Japan-South Korea Joint Research on Bronze Buddhist Statues of East Asia from the 5th through the 9th Century” (the research representative is Prof. Fujioka of Osaka University.). From the National Research Institute for Cultural Properties, Tokyo (NRICPT), Yasuhiro HAYAKAWA, Masahide INUZUKA and Mai SARAI participated in this research and conducted the investigation of materials on the surface of the statue by using a portable X-ray diffraction device (RIKEN KEIKI Co., Ltd., XRDF), which was introduced to NRICPT in the last fiscal year.
Scaffolding was constructed around the statue, and then we carried out the measurement on the surface of the head and body of the statue (the number of measured points was 10). Together with the 3 measured points on a fragment considered to have been a part of Asuka-daibutsu, the number of measured points was 13 in total during this research period.
The crystal structure of materials can be obtained by the portable X-ray diffraction device. The chemical compounds can be identified from the information about the crystal structure by combining the information about the elements constituting materials obtained by X-ray fluorescent analysis conducted by Osaka University and the National Museum of Korea. In this research, copper compounds existing on the surface of the statue can be identified and the comparison of chemical compounds on different measurement points will be possible.
We are now analyzing these data in more detail, and plan to report the results of the analysis within this fiscal year.
Research Using Image Plate Developing Equipment
On November 10 through 12 following the first survey in August, we conducted an investigation into a pair of six-fold screens of “Birds and Flowers of the Four Seasons” (an important cultural property) at the Suntory Museum of Art. To investigate the production techniques and materials of the folding screens, we conducted research using an optical survey, fluorescent X-ray analysis, visible spectroscopy, X-ray radiography and other approaches.
As for X-ray radiography, we obtained X-ray transmission images with imaging plates. For this research, we brought the developing equipment, which is dedicated to imaging plates and were introduced to our institute in November, to the Suntory Museum of Art. Accordingly, at the site, we proceeded with the research by confirming the X-ray transmission images each time they were obtained. These images gave us a variety of information such as types and thicknesses of the coloring materials and production techniques.
We will summarize these research outcomes to publish a research report within FY 2015.
The investigation conducted at the Izu-no-Chohachi Art Museum
For research on materials and structures of cultural properties, non-destructive and non-contact methods are required frequently. Therefore, investigation techniques using X-ray play an important part. With X-ray radiography, one of the techniques using X-ray, it is possible to investigate the inner structure and the layer of materials, both of which cannot be visually confirmed, in a non-destructive and non-contact way by using the difference in X-ray transmission levels resulting from a difference in density and thickness of the material composing cultural properties.
The latest research was conducted on works of Chohachi Izu, a kote-e (plaster relief) artist who was active from the late Edo period to the early Meiji era. Chohachi left a large number of statues and kote-e works – paintings drawn with plaster using a trowel, a tool used by plasterers to plastera wall. To investigate the techniques for producing these works, we conducted an investigation into the inner structures of these works using X-ray radiography on the second floor of the Izu-no-Chohachi Art Museum in the town of Matsuzaki, Kamo-gun District, Shizuoka Prefecture, on May 19 and 20, 2015. As a result of our research, we identified the layered structure of a kote-e work sets in frames, the inner structure of statues and their production techniques.
The seminar underway
For the conservation of cultural properties, it is important to maintain properly environmental conditions such as temperature, humidity, light, and air quality. Environmental conditions of temperature and humidity in facilities that exhibit and store cultural properties have been improved remarkably with the progress of technology of air-conditioning units. On the other hand, from the viewpoint of the change of climate conditions surrounding cultural properties on loan transported between regions of different climates and of the energy saving, the debates for discussing temperature and humidity conditions is recently being held more and more actively not only in Japan but also internationally.
The Center for Conservation Science and Restoration Techniques studies how the influence of temperature and humidity on cultural properties and methods to predict and control temperature and humidity levels. A seminar on Controlling and Predicting Conditions for Conservation of Cultural Properties was held on February 9, 2015. Researchers in conservation (MABUCHI Hajime of the Mie Prefectural Museum and KOTAJIMA Tomoko of the Tokyo University of the Arts) and experts in architecture (GONDO Takashi of the Kajima Technical Research Institute, KITAHARA Hiroyuki of Total System Laboratory Co., and ABUKU Masaru of Kinki University) were invited to do presentations at the seminar. The latest information on conditions for conservation of cultural properties was shared and discussed at the seminar. This information included examples of temperature and humidity control with air-conditioning units in museums, examples of the new systems that have been developed and installed, examples of studies of temperature and humidity levels and air quality in display cases, and comparisons of the measured temperature and humidity levels and those predicted by using computer simulations (attendance: 29 individuals).
On-site study of painted wall panels of the Yomeimon Gate
Positioning of a device for X-ray imaging
As part of the Study of Traditional Techniques and Materials Used in Cultural Properties, the Center for Conservation Science and Restoration Techniques is currently conducting a study in line with restoration of the paint pigments on the Yomeimon Gate of the Toshogu Shrine. Large Panels with a Relief Sculpture of a Peony Design that were created in 1796 are currently installed on panels on the east and west walls of the Yomeimon Gate. According to historical documents, however, the walls had contained paintings produced by a technique known as “tung oil sprinkled with Makie” in much earlier years, such as 1688 and 1753. During restoration of these Panels in 1971, the east wall was removed, revealing a painting of 3 Zebra Finches Perching atop a Japanese Plum Tree on a Crag with Bamboo Grass that is thought to have been produced in 1753. The painting was studied by the Department of Conservation Science at the time. In addition, X-ray imaging at the time also revealed a painting of Nesting Cranes in a Pine Tree atop a Crag with Bamboo Grass beneath the panels on the western wall. However, the wall panel overlaying it was not removed, so the actual painting was not visible. The current study removed the overlaying panel on the western wall in order to restore its paint. Its removal revealed the painting beneath for the first time in 218 years or so. However, the painting had deteriorated markedly, as was evident from its discoloration and peeling. Thus, the Center examined the painting’s materials and its deterioration in cooperation with the Nikko Toshogu Shrine and the Association for the Preservation of the Nikko World Heritage Site Shrines and Temples in order to prevent further deterioration. In addition, X-ray imaging was done so that researchers in the history of painting could verify that traces of paintings from earlier periods were beneath the painting (Photos 1 & 2). Results of this study will help to reveal the state of paint pigments that have adorned the Yomeimon Gate since the Nikko Toshogu Shrine was completed in 1636. Results will also help to maintain the works in somewhat better condition.
Conservation Science No. 49
The latest edition of the research bulletin Conservation Science issued by the Center for Conservation Science and Restoration Techniques and Japan Center for International Cooperation in Conservation of the National Research Institute for Cultural Properties, Tokyo was published on March 31, 2010. This bulletin includes the latest research results of various projects conducted by our Institute. It includes research information on the conservation of Takamatsuzuka Tumulus and Kitora Tumulus and other basic studies and investigation results concerning conservation science. Please visit our website to read the entire text (PDF version):
http://www.tobunken.go.jp/~hozon/pdf/49/MOKUZI49.html
A scene from the International Symposium
The 31th International Symposium on the Conservation and Restoration of Cultural Property was held in the Seminar Room of the National Research Institute for Cultural Properties, Tokyo from February 5 to 7, 2008. The Center for Conservation Science and Restoration Techniques was in charge of this year’s symposium on the “Study of Environmental Conditions Surrounding Cultural Properties and Their Protective Measures.” Lectures were given by 7 experts from abroad and 8 experts from Japan.
Presentations by Japanese experts focused mainly on environmental and biological control at Takamatsuzuka Tumulus, whose dismantlement was conducted this fiscal year. Experts from abroad spoke on the wall paintings of Lascaux Cave where they are faced with similar problems, and we were able to have a meaningful exchange of opinions. There were also exchange of information and opinions on conservation measures at other decorated tumuli, international activities in the conservation of cultural properties and non-destructive methods of examination.
