| ■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 |
|
Confirmation of paint stain removal status
Confirmation of surface using microscope
3D model obtained by SfM-MVS
Unlike ancient cultural heritage items created using traditional materials and techniques, many modern cultural heritage items were created using relatively new technologies brought to Japan after the Meiji period (1868-1912). Furthermore, modern industrial products created for mass production and mass consumption are generally difficult to preserve over the long term. One of the research themes of our laboratory is how to preserve cultural heritage from such a relatively recent era for the future.
In March 2023, we conducted a survey of aircraft components from the 1910s stored and displayed at the Matsuiya Sake Brewery Museum (松井屋酒造 Tomika-cho, Gifu Prefecture). The survey aimed to collect information about the appropriate preservation method and the direction of utilization of the materials, following an actual inspection of and discussion about the materials with the Tomika-cho Board of Education, the Matsuiya Sake Brewery Museum, and others in May 2022.
The surveyed part is believed to be the horizontal tailfin of a French Salmson Model 2 double-seat reconnaissance aircraft (Salmson 2A2), manufactured by another company in France under license from Salmson(YOKOKAWA Yuichi, “On the Salmson 2A2 Fuselage Parts Remaining at the Matsuiya Brewery,” Aviation Fan, December 2021). In 1918, at the end of World War I, the Japanese Army purchased 30 of these planes, and it is estimated that the material kept at the Matsuiya Sake Brewery Museum comes from one of them.
The paint is visible on the entire front and back of the tailfin. It is highly likely that it is the original paint from the 1910s, and if so, it may be the only aircraft component in the world that still has the original paint from that period (YOKOKAWA, above).
To examine the possibility of conservation and restoration and its methods, we checked stain removal status with partial dusting and the removal of dirt using water and other methods. With the cooperation of the repair technician, we confirmed that there was a high probability that the original paint was still extensively in place and discussed specific cleaning methods.
Although the survey confirmed which cleaning method is to be used, many points still need to be considered in its implementation. We will continue to work with the Matsuiya Sake Brewery Museum, Tomika-cho Board of Education, and other concerned parties to find solutions for the preservation of the aircraft components.
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.
Lid delivery
Lid in place (east wall)
The Kitora Tumulus Mural is a national treasure that depicts the four deities, the twelve signs of the Chinese zodiac with beast heads and human bodies, and astronomical images. It has been repaired after it was removed from the inside of the tomb, and is now stored with the mural face up at the Kitora Kofun Mural Conservation and Management Facility in the “Hall of Four Deities” located in Asuka Village, Takaichi County, Nara Prefecture. Until now, dust has been prevented from entering the storage room using a dust remover in the front room. However, the visible dust on the wall painting that was brought into the room and could not be removed has been an issue for many years. As there is risk of damaging the mural when removing dust, the installation of a lid to prevent the accumulation of dust on the mural was considered. The Agency for Cultural Affairs, Tokyo National Research Institute for Cultural Properties, Nara National Research Institute for Cultural Properties, and the Association for Conservation of National Treasures (ACNT) have discussed the elements required for the lid, which does not adversely affect the mural, is easy to handle, allows the mural to be seen with the lid in place, and made of a material that does not attract dust. At the Kuroda workshop (Representative: Mr. USUI Hiroaki), a manufacturer of traditional fittings, whose technique is designated by the government as one of the Selected Conservation Techniques, a wooden frame covered with a transparent antistatic sheet was made as a prototype lid. Because it was confirmed in FY2021 that there is no difference in temperature and humidity inside and outside the lid, the possibility of adverse effects on the mural is extremely low. Thus, the finished product, with improvements in terms of strength, was delivered on March 24, 2023, and the lid was installed on the Kitora Tumulus Mural. We plan to confirm the effectiveness of the installation of the lid and discuss with the relevant parties how to handle the lid during mural inspections, public openings, and inspections.
Investigation of " Hayate"
The air quality Investigation
Filming of the former Chiran Airport water tower
Investigation of the former Aoto Airfield pillbox
Tokyo National Research Institute for Cultural Properties (TOBUNKEN) worked with Minamikyushu City for “memorandum concerning the conservation and restoration of cultural properties designated by Minamiyusyu City”, and recently started joint research in July, 2022.
（https://www.tobunken.go.jp/materials/ekatudo/996061.html）
The following surveys and investigation were conducted in Minamikyushu City in February, 2023.
Investigation and advice on preservation and restoration of the former Japanese Army Type 4 fighter “Hayate”
The “Hayate” (designated cultural property of Minamikyushu City), which is stored and exhibited at the Chiran Peace Museum, was captured by the US military in the Philippines during the Asia-Pacific War and is the only surviving aircraft.
After a test flight by the US military, it was sold and passed through multiple owners before it was returned to Japan in 1973. When the town of Chiran (now Minamikyusyu City) was established in 1995, the aircraft was transported there and has been on display at the Chiran Peace Museum since 1997.
Since 2017, Minamikyushu City has been conducting a conservation survey, and TOBUNKEN has participated in the survey from 2018. Our findings suggest that overall, the fuselage is in good condition, but some parts have worn out or been replaced because of the post-war test and demonstration flights. We will continue to check the status of the remaining original parts and consider the restoration policies. In this investigation, we mainly targeted the engine, checked the original parts, and the condition inside the engine and oil tank, among other things. Some parts removed from the aircraft were entrusted to TOBUNKEN for cleaning and component analyses.
The research was conducted in the exhibition room. Since the exhibition room was not closed during the research period; visitors were able to observe it at that time. Additionally, a report on the state of preservation was published in March, 2022.
Air quality investigation of exhibition rooms and storage in the Chiran Peace Museum
In this study, we conducted an air quality investigation (inspection of organic acids, aldehydes, and volatile organic compounds [VOC]) in the exhibition room and storage room along with a survey of ” Hayate.” In the future, we plan to consider a more stable exhibition and storage environment based on the results of this investigation.
Records of the current state of concrete structures during the Asia-Pacific War in Minamikyushu City
Minamikyushu City has there are cultural assets related to numerous wars and the former Chiran Airfield. They have remained in the city since the Asia-Pacific War period. Many of them are concrete structures, but nearly 80 years have passed since the end of the war, and they are deteriorating and falling debris. In this study, we recorded the current situation by obtaining actual measurements and photogrammetry (three-dimensional models were created from multiple photographs) of the former Chiran Airfield water tower (a city-designated cultural property) and two pillboxes (defensive positions) of the former Aoto Airfield as concrete structures in the city during the relevant period. In the future, we will analyze the progress of deterioration based on regular records and consider measuring concrete strength.
With participants
Lecture on basic chemistry using molecular models
Practical session for the selection of organic solvents
The Center for Conservation Science continues scientific research on the conservation and restoration of cultural property. Since FY 2021, based on our research, we have held workshops on basic science for conservators who have diverse experiences in the restoration of cultural property and museum curation and archiving.
In 2022, the workshop was held for three days from October 31st to November 2nd. We provided lectures and practical sessions on basic scientific knowledge essential for conservation and restoration, including basic chemistry, science of adhesion and adhesives, chemistry of paper, pest damage control, and usage and disposal of chemical agents. Researchers of the Tokyo National Research Institute for Cultural Properties delivered lectures based on their expertise.
We received 45 applications across Japan for 15 seats. In 2022, we invited 19 applicants from across Japan with varied backgrounds to the workshop; by contrast, in 2021, considering the COVID-19 pandemic, we accepted only those applicants who either resided in or commuted to Tokyo. Workshop content was carefully aligned with requests from the previous year. Participants expressed their appreciation for this workshop through the questionnaires provided. We received specific requests for disseminating scientific information used in actual conservation and restoration cases. We intend to continue this workshop series to meet these expectations.
Measuring the surface temperature of the rock
Measuring the moisture penetration status above the rock
Measuring the surface temperature of the honden
The Center for Conservation Science conducts investigations for the conservation environment of wooden architecture built in rock caves.
The Natadera Temple in Komatsu City, Ishikawa Prefecture is a temple of the fusion of the Indigenous Hakusan Faith (the faith for Mt. Hakusan), and Buddhism. Its wooden honden (main shrine), which is an Important Cultural Property, was reconstructed in 1642 in a rock cave created via natural erosion. In recent years, aseismic reinforcing works have been installed. Since then, moisture condensation has often occurred during spring to summer time, which is problematic because it causes wood decay. Therefore, it is desirable to reduce the frequency of moisture condensation to conserve the shrine and its decoration in good condition.
To tackle this, the Center is conducting an environmental investigation to identify the occurrence factors of moisture condensation and to determine the appropriate countermeasures to reduce them. Rainwater, outer air, and heat capacity (ability to store heat) of the rocks affect the environment inside the cave. Therefore, the temperature and humidity in the cave, moisture penetration into the rocks, and surface temperature of the rock and the honden are being measured. We plan to pursue our investigation by continuous measurements of environmental data and analysis.
Moisture condensation causes many problems at many masonry constructions and stone chambers of burial mounds. In recent years in particular, the rise of temperature and absolute humidity in the summer season increases the condensation occurrence risk. There is an urgent need to tackle the global environmental challenges. However, for now, we suggest the achievable countermeasures in everyday management.
Participants at the opening ceremony
Practical work
In recent years, the investigations of conservation and restoration for cultural properties have expanded their targets not only to traditional cultural properties but also to modern artifacts and documents made of various types of materials. The Restoration Materials Section of the Center for Conservation Science invites experts from overseas and conducts workshops to meet these needs. In 2022, we invited Mr. Remy Dreyfuss-Deseigne, an expert who conducts research and application of nanocellulose films for conservation and restoration, to conduct a three-day workshop beginning on October 5th, 2022. Nanocellulose films are a kind of cellulose made from natural materials, which are transparent and stable. Therefore, nanocellulose films can be applied to transparent materials such as tracing paper and photo film with which traditional conservation materials do not work well.
We received applications more than double the official capacity of 15 seats for this workshop from conservators. This indicated high expectations for the workshop. We accepted all applicants to the lectures for the morning sessions, but we needed to limit participants for the practical sessions in the afternoon. The workshop began with an inauguration ceremony, with opening remarks by SAITO Takamasa, Director General of TOBUNKEN, and then the lecturer, Mr. Dreyfuss-Deseigne was introduced. During the workshop, the lectures were held in the mornings and practical sessions in the afternoons. On the last day, a tour of TOBUNKEN was conducted to see TOBUNKEN equipment related to the workshop.
This workshop with a lecturer invited from overseas was held for the first time in 3 years since the last one. The “face-to-face workshop” encouraged participants to raise very active questions and discussions. Participants said that they could build mutual collaboration among the workshop members. We recognized again the significant impact of in-person workshop, which could not be achieved online. We believe that our workshop helped in the actual reconstruction of cultural properties and conservation of archives.
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.
SAITO Takamasa, Director General of TOBUNKEN and Mr. NURUKI Hiroyuki, Mayor of Minamikyushu City holding the signed MoU
Meteorological observing station now installed close to the water tower of the former Chiran Airfield site (cultural heritage designated by the city) – right hand side in the fence
The Tokyo National Research Institute for Cultural Properties (TOBUNKEN) and Minamikyushu City of Kagoshima Prefecture have jointly conducted research on conservation and restoration of individual cultural properties located in the city from around 2008. Now, we decided to conclude “MoU for Research on Conservation and Restoration of Cultural Properties Designated by Minamikyushu City” and explore further collaboration as joint research. Taking this opportunity, we conducted the conclusion ceremony of this MoU in the city office of Minamikyushu City on July 20th, 2022. At the ceremony, the project details were explained and SAITO Takamasa, Director General of TOBUNKEN and Mr. NURUKI Hiroyuki, mayor of Minamikyushu City signed them, after the explaining the project overview.
Minamikyushu City has total 191 designated cultural properties. Among them, modern cultural heritage, including the buildings at the former Chiran Airfield site of the Imperial Japanese Army, as nation registered cultural properties and The Army Type-4 Fighter Aircraft, “Hayate”, a cultural property designated by the city are well known as mandatory materials in Japanese modern history. However, the modern cultural heritage’s characteristics differ from those of traditional cultural properties in volume, materials, functions, and others. Therefore, it often requires new methodologies for conservation and restoration.
This joint research aims to solve technical issues related to conservation and utilization of these cultural properties, develop new conservation methodologies, vitalize research activities, and contribute toward promotion of public awareness of local cultural properties by collaboration of TOBUNKEN and Minamikyushu City. We will also provide information beneficial to other local governments who have the same or similar challenges by disseminating the research outcomes.
Visiting the Analytical Science Section
Lecture on conservation of Modern Cultural Heritage
The Tokyo National Research Institute for Cultural Properties (TOBUNKEN) held the “2022 Training for Museum Curators in Charge of Conservation (Advanced Course)” for five days, from July 4 to July 8, 2022.
This training is an application version of the trainings for museum curators in charge of conservation, which were held from 1984 to 2020 for curators in charge of material conservation to master basic knowledge and techniques necessary for environmental management, evaluation, and improvement.
From 2021, we reorganized the training into two courses: 1) basic course, focusing on conservation of environment by the National Center for the Promotion of Cultural Properties, and 2) advanced course, focusing on curators who attended the course before and/or who have similar experiences, by TOBUNKEN.
We provided lectures and workshops mainly based on research outcomes of each research area of the Center for Conservation Science, along with lectures from external lecturers related to various conservation and restoration in the advanced course. We are pleased to have organized face-to-face training with 18 participants, with thorough prevention measures for COVID-19 pandemic. We believe that the participants made their networks there.
Based on questionnaires after the training, we understand that the participants were well satisfied. We could know their voices: “I will try various techniques from this training in our museum,” “I could review my understandings and obtain new knowledges. It was very beneficial for me,” and “It was a very useful week for me.” Henceforth, we will work to provide more useful training to curators in charge of conservation.
Video and photo documentation of the chisel manufacturing process
Manufacturing chisels for sculpture
Understanding the manufacturing situation of tools and raw materials used for restoration is extremely important to continue sustainably restoring cultural properties. However, “the Research Project on Preservation and Restoration of Tools and Raw Materials,” commissioned to the Tokyo National Research Institute for Cultural Properties (TOBUNKEN) by the Agency for Cultural Affairs since FY2018 revealed that the manufacture of tools and raw materials for cultural property restoration faces many challenges rooted in the following two factors. The first is the human factors of aging manufacturers and a shortage of successors, and the second is factors caused by shifts in social structures, such as deteriorating business and the unavailability of raw materials. Considering this research outcome, the Center for Conservation Science initiated a project to collect fundamental physical property data and to document tools and raw materials necessary to preserve and restore cultural properties. The Center has worked on this project with the Department of Art Research, Archives and Information Systems and the Department of Intangible Cultural Heritage. This monthly report presents the documentation survey of chisels for sculpture, the manufacture of which will cease.
Chisels and saws are key tools to restore wood carving cultural properties because new timber materials may be carved and used as repair materials. Konobu Ltd. (Konobu), founded in the early Shōwa era (early 20th century) by the Takiguchi family, specialized as carving tool smiths. Since then, this smith has manufactured chisels for sculpture; Mr. SAITO Kazuyoshi succeeded their manufacturing techniques. Their products have been favored by many in charge of wood carving restoration and wood carving itself. However, Konobu stopped accepting new orders in October 2021 and expressed that they would soon close their business. TOBUNKEN used videos and photographs to document their full manufacturing process of chisels for sculpture, as well as their equipment and smith tools in interviews from May 23rd to 27th, 2022. Mr. KADOWAKI Yutaka of BIJYUTSUIN Laboratory for Conservation of National Treasures of Japan and the Agency for Cultural Affairs cooperated in this documentation survey.
Unfortunately, it became almost impossible to experience and observe in person the Konobu chisel manufacturing process. We plan to organize the survey records to serve as a clue for future generations who want to reproduce chisels for sculpture.
Presentation by HAYAKAWA Noriko
HAYAKAWA Noriko of the Center for Conservation Science spoke about the relationship between techniques and materials for cultural property restoration in Japan titled The Relationship Between Traditional Painting Materials and Techniques in Japan from a Scientific Perspective in a talk at the symposium held in Bard Hall, New York City, United States, on May 6th and 7th 2022.
This symposium titled Conservation Thinking in Japan and India was held both in person and online by Bard Graduate Center with support from the Andrew W. Mellon Foundation. There, experts on restoration of Japanese cultural properties and fine art history introduced their latest research from Japan and other countries.
HAYAKAWA introduced two primary points among research in the Restoration Materials Section: the fact that furunori (aged paste) used for restoration of paintings is corelated to fringe materials and techniques, and an assumption that changes in the manufacturing process for silk, a support material of paintings, altered its string forms and preservability, which then impacted painting expression.
Tours around related facilities and other meetings were held before and after the symposium, where useful discussions were conducted based on actual restoration cases.
Scientific elucidation of materials and techniques is required even during everyday operations in restoration and material production. Opinion exchanges with other experts triggered further research. This presentation was a precious opportunity to disseminate our research outcomes to a wider audience.
Seminar in the meeting room
A series of seminar on the survey and management of conservation environment is organized annually, targeting the curators in charge of conservation for materials in museums and researchers engaged in conservation of cultural properties. These seminars aim to share common understanding on the surveys, assessment methods and improvement of conservation environment, and materials and tools for safe storage. The first and second seminars were organized by the National Center for the Promotion of Cultural Properties (CPCP) and the third was held with a co-sponsorship of CPCP and the Tokyo National Research Institute for Cultural Properties (TOBUNKEN.)
In the first seminar, titled the Survey and Assessment of Air Environment Using Kitagawa Detection Tubes, usage and appropriate assessment methods of Kitagawa detection tubes, which were widely used for quantitative analysis of chemicals in the air in the exhibition and storage rooms, were explained. In the second seminar, titled Neutral Papers as Materials Used for Document Conservation, the scientific character of paper, characteristics and standards of neutral paper, and appropriate usages of conservation containers made of neutral paper were explained with hands-on practice. Neutral paper is widely used as a material to create document conservation containers in storage and stack rooms.
The theme of the third seminar was chemical substance absorbent. Recently, concerns about chemical substance emission from the building and interior materials and its impact on the documents, as well as methods to improve the situation have attracted people’s attention. However, we are still exploring the best possible ways to clean the air in exhibition and storage rooms. Therefore, we invite a company that develops chemical substance absorbent to explain methods of selecting appropriate chemical substance absorbent, as well as the adsorption phenomena, principle and structure of absorbent, and environmental factors related to adsorption efficiency.
We conducted this seminar with eight participants in person and distributed it online for the prevention of the spread of COVID-19 infection. A total of 30 people participated in the seminar. Participants provided their opinions on the usefulness of the seminar because they could learn from the principle to the practice, stating, “I could well understand the types and mechanisms of gas adsorption,” and “as I understood the principle of gas adsorption and measurement methods, it would get easier to assume the solutions.”
We plan to continue the seminars by setting themes that are necessary for daily practices, from the viewpoint of conservation science.
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.
Method to identify cultural property pests using DNA as an identifier
Collecting frass from buildings
Damages caused by cultural property pests are a serious and global threat to cultural property conservation because they result in significant losses of cultural property materials and largely reduce their values. Thus, it is critical to identify and take appropriate measures as soon as the cultural properties start showing signs of damage to prevent further loss. However, we may encounter a situation in which it is difficult to identify “criminal” species even by experts, as we cannot find living insect pests but only their frass. To overcome these difficulties, the Biological Science Section has identified cultural property pests using DNA extracted from frass as an identifier.
As the outcomes in FY2021, we succeeded in establishing a method to identify species by frass for the major pests boring bamboo, which are used as part of cultural property buildings and to create craft works. The method includes collecting bamboo-boring pests, extracting the DNAs, and determining a short section of sequence from a specific gene. The datum is registered in the international databases, combining the morphological characteristics and the DNA sequence. Then, DNA is extracted from frass collected at rearing containers and outside buildings, determining their target sequence. The resulting sequences are compared to the reference databases to find the matching species. Before the establishment of the method, it was difficult to determine the base sequence, because the DNA extracted from the frass was either too small or contaminated by DNA of other species. However, specific primers for PCR constructed in this study enabled us to succeed in identifying “criminal” species using anonymous frass collected in the cultural property buildings, rather than being limited to laboratories. Please refer to “Science for Conservation” #61 for further details.
In the future, we plan to further develop specific primers to identify species by frass of cultural property pests in various phyletic lines, and enable easy usage in the field by upgrading the base detection system, including standardization and simplification of methods. We will continue to proceed with the study to achieve these objectives.
Adherence sample setting for exposure test
Water content meter setting to measure the amount of water in the rock
Usuki Stone Buddhas, a National Treasure, are a group of “magaibutsu” (Buddha statues directly carved into rock face) sculpted niches that were carved on ignimbrites between the late Heian period and the Kamakura period. They consist of the following four clusters: the Hoki First Cluster, the Hoki Second Cluster, the Sannosan Cluster, and the Furuzono Cluster.
Weathering has partially progressed in these Buddha statues. Although protected by the niches from rainfall and winds, their surfaces have been impacted by repeated frosting and melting of underwater and rainwater during winters, and by flaking and granulating as a result of salt deposition due to evaporation in dry season. Therefore, weathering prevention methods such as building protective shelters, controlling river-bed water running behind the statues, and remounting falling pieces were adopted in the past. Tokyo National Research Institute for Cultural Properties (TOBUNKEN) has been engaged in these efforts for a long time.
A new joint research with Usuki City has now started to preserve and restore the Stone Buddha Statues. The surfaces around one knee of the seated Amitabha Tathagata Buddha statue in the Hoki Second Cluster have rebegun flaking and falling despite early preservation and restoration efforts. Via environmental research, we plan to monitor the change in temperature and humidity in the newly built protective shelters and review the water content in the rock, in addition to studying materials and implementing methods to strengthen and remount falling pieces. In preparation, we set the measuring equipment and adhesive samples for outdoor exposure testing on October 18th and 19th.
We plan to regularly review the measured data and observe the efficacy of adhesive samples against the weather, while continuing to discuss appropriate actions for the preservation and restoration of the Usuki Stone Buddha Statues with the Agency of Cultural Affairs, Oita Prefecture, and Usuki City.
Lecture on how to handle lab instruments
The Center for Conservation Science conducts scientific research on the conservation and restoration of cultural property. In 2021, we introduced a workshop on basic science, based on our research, for conservators who have diverse experience in restoration of cultural properties and museum curation and archiving.
The workshop was held for three days from September 29th through October 1st, 2021. We provided lectures and practical sessions on basic scientific knowledge that is important for conservation and restoration. It included basic chemistry, science of adhesion and adhesives, chemistry of paper, and pest damage control. The researchers of Tokyo National Research Institute for Cultural Properties delivered the lectures, based on their areas of expertise.
We received 44 applications from across Japan for 15 seats. Fifteen applicants, who either resided in or commuted to Tokyo, and had the desirable expertise, participated in the workshop keeping in mind the on-going COVID-19 pandemic.
The participants expressed their appreciation for this workshop through the questionnaires that were provided. We received requests for further scientific information on more advanced conservation and restoration cases. We intend to continue this workshop series to meet these expectations.
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)
Lecture on the Types and Characteristics of Restoration Materials
A Visit in Pest Control Practical Training
During a five-day period of July 5–9, 2021, we held the 2021 Training for Museum Curators in Charge of Conservation (advanced course). Last year, we held this training jointly with the National Center for the Promotion of Cultural Properties. In order to clarify the content of the training and to make it more beneficial for museum curators in charge of conservation, this fiscal year, we decided to divide the training into the “Basic Course,” implemented by the National Center for the Promotion of Cultural Properties, and the “Advanced Course,” implemented by the Tokyo National Research Institute for Cultural Properties.
The Tokyo Metropolitan Government has been implementing intensive measures to prevent the spread of COVID-19, and we thoroughly conducted temperature inspections, sanitization, and mask-wearing policies during the training.
Each laboratory of the Center for Conservation Science led the training on a one- or half-day basis, providing lectures and practical training in accordance with their respective specialties. Since advance-level courses are offered to people who have already received training for curators in charge of the conservation of museums, most of the attendees had an awareness of the issues and challenges faced by their own museums. On the last day, a lecture on disaster prevention and the mitigation of damage to cultural properties was given in light of recent natural disasters. This was a valuable opportunity to consider how to deal with and implement measures against natural disasters in museums, as well as the roles of the institutions in disaster prevention with regard to cultural properties.
In questionnaires, many participants stated that the training was helpful, such as by increasing the knowledge and skills that would be helpful in carrying out their work in the future.
This was the first time the training was held as an advanced course, but since the issues of the training have been clarified, we would like to improve it next year and in the future.
