|■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
As cultural properties attract more attention, conservation and restoration measures have been required for works comprised of various materials in recent years. Under the circumstances, conventional measures are inapplicable in many cases. It is of particular importance that we clean the works without diminishing their value.
To meet these growing needs, the Center for Conservation Science invited Dr. Paolo CREMONESI, conservation scientist from Italy, to organize a workshop on basic scientific knowledge of cleaning and usage of gels from October 8th through 10th, 2019. On October 11th, a seminar on restoration measures for cultural properties was also held to raise on-site issues and introduce the latest research on cleaning of Japanese and Western cultural properties.
With regard to the workshop, lectures were delivered in the seminar room in the morning (to 56 participants). During the afternoon training in the conference room, 21 trainees learned how to prepare cleaning solutions used for the restoration of cultural properties and how to actually clean them.
At the seminar, Dr. Cremonesi delivered a lecture on “Cleaning Methods in Western Countries –Application of Gels and the Latest Cases,” in addition to “Cleaning of Oriental Paintings” by Ms. YAMAMOTO Noriko, Representative Director of the Association for Conservation of National Treasures, and “Potentiality of Gels Applicable to Paper and Photo Works” by Ms. SHIRAIWA Yoko, photo restorer. They introduced the current state of restoration sites in the East and the West. TORIUMI Hidemi and HAYAKAWA Noriko from the Center for Conservation Science gave lectures on the “Historical Background of Cleaning Methods Developed for Western Paintings” and the “Development of Cleaning Solutions for Cultural Properties – Introduction of Recent Studies,” respectively.
Conducting Research at the Okinawa Prefectural Museum & Art Museum
Fibers used in cultural properties come from a variety of sources including hemp, ramie, kudzu, and bashō (Japanese banana). As discussed in the May 2017 monthly report (Takuyo YASUNAGA, “Historical Position of ‘Hakubai-zu byobu’ by Goshun－A workshop is organized by the Department of Art Research, Archives and Information Systems”), we have learned in the more recent years that in addition to silk and paper, fiber is also used as the support medium in paintings. There are no well-defined, established methods of identification, however, in part due to the difficulty of discerning the characteristics of individual fibers once in textile state. Tokyo National Research Institute for Cultural Properties (TNRICP) is working to find a solution to these and other problems, in a cooperative research effort into fiber identification among the Department of Art Research, Archives and Information Systems; Center for Conservation Science; and Department of Intangible Cultural Heritage.
As a part of this research, the three-dimensional forms of fibers in a calligraphy work and a dyed article made of bashō-fu (textile woven from banana plant fiber) were examined using a digital microscope at the Okinawa Prefectural Museum from January 22nd to 23rd, 2019.
Bashō-fu is textile developed in Okinawa and Amami Islands and has been designated an important intangible cultural property, with Ms. Toshiko TAIRA recognized as an individual practitioner and Kijōka Bashō-fu Preservation Society recognized as a heritage protection organization. Of the work examined this time, the calligraphy work is known to have been created in a particular year and the dyed article is an item whose wearer can be guessed at. The examination showed that despite being all works thought to be made of bashō-fu, the look and the feel of the textiles varied due to differences in yarn density and yarn processing method.
While it is difficult to judge whether the differences are rooted in regional variation within Okinawa and Amami Islands or due to differences in use, we were able to conclude that many kinds of bashō-fu were created through different processes.
Accurate identification of fibers goes to the most basic data on a particular work, and is a key element in considering the circumstances of production. It is also a pressing issue in the organization of basic data for use in the present repair or the passing on to future generations of intangible cultural heritage.
We hope to continue furthering the research into identification of fibers through field investigations into techniques in conjunction with examination of exhibits at museums and art museums.
Ongoing general discussion
In recent years, cultural properties have been attracting more attention. In response to their promoted utilization, the number of cultural properties that need restoration has been increasing. Under the circumstances, conventional restoration approaches and concepts are not applicable in many cases. In the light of the current situation, the “Seminar on the Current Status of Restoration of Cultural Properties and Its Issues” took place on November 22nd, 2018. Sharing a restoration overview of the past, experts specializing in cultural property areas introduced the issues identified during the current restoration process.
Guest Professor Toshikazu SASAKI from Hokkaido University, who specializes in historical materials, delivered a lecture on the conservation of historical materials and issues of conservation of folk materials under the title of “Thoughts on Restoration of Arts and Crafts” based on his vast experience accumulated in the Tokyo National Museum, the Agency for Cultural Affairs, and the National Museum of Ethnology. Senior Specialist Tomohiko JINUSHI from the Agency for Cultural Affairs reported “Achievements and Issues in Recent Restoration of Historical Materials” including detailed cases under the existing conditions. Curator Hitomi KITAMURA from the National Museum of Modern Art, Tokyo presented the details of recent restoration of the collection and the issues in that process under the title of the “Current Status of Restoration of Cultural Properties and Recent Issues -With a Focus on ‘Twelve Hawks’-.” Chief Noriyuki NAKANO from the Kyoto Prefectural Government reported what kinds of discussions are actually conducted in restoration and how necessary decision-making should be done. During the general discussion, the audience asked many questions, which resulted in an active Q&A session. The seminar attracted 104 people, who expressed expectations for our continually providing an opportunity to exchange information on the restoration of cultural properties on a large scale through a post-seminar questionnaire survey. The details of this seminar will be published as a report next year.
The Center for Conservation Science has been developing materials required for the restoration of cultural property. One of the items subject to our research is glue. Glue, an animal collagen hydrolysate, has been used as an adhesive since ancient times. According to the information found, the kinds of animals used for producing glue vary and different measures have been used to find better ways to manufacture it. On the other hand, it has not been scientifically defined whether the raw materials and manufacturing methods have any effect on the properties of glue. In recent years, research on the raw materials of glue and its manufacturing methods has finally been carried out. Based on these results, the Restoration Materials Section has been conducting research studies on the characteristics of glue as a restoration material.
On the case of the restoration of a famous Japanese-style painting, “Jo-no-mai (Noh Dance Prelude,” designated as an Important Cultural Property, the suitable glue was selected based on the outcomes of the studies. It is notable that by using glue which keeps whiteness of shell chalk, restoration, which minimizes the possibility of changes in original works, was implemented.
These outcomes were displayed in the Chinretsukan Gallery of The University Art Museum, Tokyo University of the Arts for the Exhibition “Animal Glue and Conservation – To Keep ≪Jo-no-mai≫ -.” The exhibition was co-organized with the Conservation Science Laboratory, Graduate School of Conservation, Tokyo University of the Arts from October 14th to 19th, 2018. In cooperation with Nikawa Labs as one of the organizers, the exhibition displayed the actual glue used for restoration, scientific data, and numerous images including enlarged ones taken during the restoration process. In addition, a visiting researcher, Kentaro UDAKA, delivered gallery talks. This exhibition provided a valuable opportunity for visitors to gain a broad understanding of the relations between research outcomes and the workplace for the restoration of cultural properties.
The lecture about solvents using molecular models
Practical work of removing stains on a painting
To conserve Japanese paintings, calligraphic works and other pictorial artifacts, we are now increasingly required to have some knowledge of conservation science. To meet these demands of conservators Tokyo National Research Institute for Cultural Properties and the Association for Conservation of National Treasures (ACNT) jointly conducted a workshop with a training program for conservators from July 31st to August 1st, 2018, which included lectures on basic knowledge and practical work sessions. The workshop aimed to provide hands-on knowledge that can be applied to actual conservation works. To achieve this purpose, we designed a curriculum that would help participants accurately understand the chemical properties of organic solvents and enzymes as well as the proper handling of basic laboratory instruments and chemicals for more effective and safer restorations. The workshop has been held once a year since 2016.
A total of 11 people, one from each corporate member of ACNT, participated in the workshop. Dr. Sano, Director of the Center for Conservation Science; Dr. Sato, Head of the Biological Science Section; and I provided lectures on the safe handling of organic solvents; integrated pest management (IPM) for cultural properties at restoration studios; and removal methods of adhesives and stains, respectively. Based on these lectures particularly using models of the molecular construction of solvents, the participants practiced removing various types of stains on the sheets of paper that we prepared, by using suitable solvents and enzymes. The practical work session also covered other topics such as the use of cyclododecane as a temporary protective coating for water-sensitive colorants. Mr. Kimishima, ACNT’s Senior Conservator, taught in the work session and provided hands-on training to the participants.
The program ended with a lively Q&A session and discussion. We will continue to hold such workshop in the future.
Lecture by Ms. Sano on the safe handling of organic solvents
Workshop by Mr. Kimishima on how to remove stains
To conserve Japanese paintings, calligraphic works and other pictorial artifacts, we are now increasingly required to have some knowledge of conservation science. To meet these demands of conservators who wish to learn how to handle chemicals, particularly those that have recently become more popular in restoration sites, and how to apply them in conservation and restoration works, the Tokyo National Research Institute for Cultural Properties and the Association for Conservation of National Treasures (ACNT) jointly conducted a workshop with training program for conservators from August 8 to 9, 2017, which included lectures on basic knowledge and practical work sessions. The workshop aimed to provide hands-on knowledge that can be applied to actual conservation works. To achieve this purpose, we designed a curriculum that would help participants accurately understand the chemical property of organic solvents and enzymes as well as the proper handling of basic laboratory instruments and chemicals for more effective and safer restorations.
A total of 11 people, one from each corporate member of ACNT, participated in the workshop. Dr. Sano, Director of the Center for Conservation Science; Dr. Sato, Head of the Biological Science Section; and I provided lectures on the safe handling of organic solvents; integrated pest management (IPM) for cultural properties at restoration studios; and removal methods of adhesives and stains, respectively. Based on these lectures, the participants practiced removing various types of stains on the sheets of paper that we prepared, by using suitable solvents and enzymes. The practical work session also covered other topics such as the use of cyclododecane as a temporary protective coating for water-sensitive colorants. Mr. Kimishima, ACNT’s Senior Conservator, taught in the work session and provided hands-on training to the participants.
The program ended with a lively Q&A session and discussion. We will continue to hold such workshop in the future.
Packing for transportation
The Tokyo National Research Institute for Cultural Properties (Tobunken) has been conducting the project “Work on the investigation of the preservation measures for Kitora Tumulus, a special historic site” since 2004. As the mural paintings in the tumulus required conservation treatments, it was decided that they would be removed from the tumulus and currently conserved externally. Three types of conservation treatments were conducted: maintaining the mural paintings in the tumulus, removing the mural paintings from the tumulus stone, and reconstructing the mural painting fragments. The removal of the mural paintings had been conducted for over 6 years, and the paintings were separated into 1143 fragments. The paintings have been reconstructed in the restoration facility in Asuka-mura, Nara prefecture. The Tobunken team has developed conservation techniques and performed experimental checks for this project, and the Association for the Conservation of National Treasures, an association of conservators for Japanese paintings, has applied the developed techniques.
On August 24th and 25th, 2016, three reconstructed mural paintings, the south wall with suzaku, west wall with byakko, and the ceiling with an astronomical chart were moved from the restoration facility to “Shijin no yakata”. This museum opened on September 24th, and the three mural paintings was exhibited for a month.
A lecture underway
A post-conference workshop
From April 8 to 10, 2015, a conference entitled “Adapt & Evolve: East Asian Materials and Techniques in Western Conservation” took place mainly at the Brunei Gallery at the University of London. The conference was organized by the Book and Paper Group of the Institute of Conservation (colloquially known as ICON) in the UK.
The conference consisted of tours of relevant institutions in the City of London, group events (presentations and question-and-answer panels), and various workshops. MASUDA Katsuhiko (an emeritus researcher at the Institute, currently a professor at Showa Women’s University), HAYAKAWA Noriko (a senior researcher at the Institute), and KATO Masato (a head of the Resource and Systems Research Section at the Institute) reported on the results of projects such as international training in Conservation of Japanese Paper (JPC) and the Cooperative Program for the Conservation of Japanese Art Objects Overseas as well as studies of the materials used to restore cultural properties. In addition, post-conference workshops were conducted after the conference. HAYAKAWA Noriko and KUSONOKI Kyoko (an associate fellow of the Institute) explained the traditional adhesives used in the field of conservation in Japan, and showed how to make starch paste and they instructed attendees in its application.
According to the conference organizer, the conference was attended by about 300 people from around the world. During the question-and-answer session, the conference chair asked the audience about the JPC, and the answer revealed that 30 or more individuals who had completed the training were in attendance. Individuals who had completed other workshops organized by the Institute were also in attendance. Thus, the Institute plays a major role in introducing East Asian materials and techniques to Western conservation. In addition, many of the attendees asked that the Institute continue to provide information about conservation.
Test application at Itsukushima Shrine
The Center for Conservation Science and Restoration Techniques conducts investigative research on restoration materials for cultural properties. Various types of restoration materials are needed in a diverse range of fields such as architecture, and fine and applied arts.
At Itsukushima Shrine, the center is involved in continuing investigative research on restoration materials for the large “Torii.” Itsukushima Shrine is located on the sea, in a severe temperature and humidity environment, directly exposed to wind and rain, and the effects of salts must also be taken into consideration. For such reasons, there are stringent conditions on the selection of restoration materials. Working time is also limited due to factors such as rise and fall of the tide. In selecting restoration materials, two types of testing are done in parallel: accelerated deterioration testing under various conditions in the laboratory, and exposure testing at the actual site.
Specifications of filling material were finalized through research studies up to the last fiscal year, and surface finishing materials are currently being studied. Based on the results achieved to date, test application of a selected material was carried out on October 22 and 23. Going forward, the center plans to make follow-up observations, and continue investigations to enable proper selection of materials.
Exposed test pieces under an open platform (stage)
The Center for Conservation Science and Restoration Techniques studied materials to restore the Otorii gate of Itsukushima Shrine. The study selected materials for use in a coastal setting with harsh conditions such as high temperature and high humidity, immersion in water, and the presence of salts. Forced degradation tests are currently being performed in the lab and an exposure test is being performed on-site. Exposure on-site began in June 2010, and the water content in test pieces is being measured and deterioration is also being observed, in every 2 months. These tests will continue in the future, and plans are to verify deterioration via a strength test in 2011. Forced degradation tests in the lab include a UV irradiation test and temperature cycle test, and plans are to conduct a salt spray test in 2011.
Inside the stone chamber with all plaster walls removed
The Center for Conservation Science and Restoration Techniques has been removing the wall paintings of Kitora Tumulus as part of a project called the Investigation on Conservation for special historic site Kitora Tumulus, commissioned by the Agency for Cultural Affairs. We had aimed to complete the removal in the next spring term following the intensive removal of the paintings in the spring and autumn of 2009. However, we removed all plaster from the stone chamber walls during this term earlier than the planned schedule (autumn 2010). This work was attributed to the proficiency of the engineers in removal, as well as to the development and improvement of the machines, tools and materials promoted by Tobunken. The work in the stone chamber was finished in a series of conservation projects of Kitora Tumulus Wall Paintings, starting with the removal of Seiryu (blue dragon) in 2004. We will begin treating and mounting the wall paintings in the conservation facility.
The damage caused by bark beetles and shipworms
The Center for Conservation Science and Restoration Techniques is also examining the extent of deterioration of wooden buildings in the project “Study on assessment of influence of ambient environment on cultural heritage and countermeasures.” Among the wooden buildings subject to a severe outdoor environment, particularly the Itsukushima Shrine in Miyajima-cho, Hatsukaichi City, Hiroshima faces stern conditions, such as harsh weather and the influence of seawater. It is affected by intense UV rays, wind, rain, seawater and waves, and was also heavily damaged by gribbles and shipworms under the sea. We are now studying how to prevent the wood from deteriorating in this situation, and how to restore the deteriorated wood and what restoration materials to use. Therefore, we are conducting physical tests such as a strength test, curing test and exposure test in various forms at the local site. In this way, we are investigating the optimum techniques to use. We hope that the results obtained by such examinations will be adopted for other wooden buildings.
Removing plaster on side wall
Removed plaster piece
The Center for Conservation Science and Restoration Techniques has been removing the mural paintings of Kitora Tumulus as part of a project “Investigation on Conservation for special historic site Kitora Tumulus” entrusted by the Agency for Cultural Affairs.
Following the first work of removing in May, we continued the work in two periods of three weeks each, from October 19 to November 6, and from November 16 to December 4. Although the work in autumn took longer than that in May, performing the removal over periods of three weeks each enabled efficient removal progress. All plaster on the ceiling was detached by this latest work, and we will be able to resume removal of the plaster on the side walls for the first time in two years. We will continue to inspect the in side of the tumuls periodically, while irradiating UV-C to control microorganisms, and conduct removal again next year.
Presentation by a participant
Studying folk materials associated with urushi and collecting of urushi sap
Evaluation Seminar, 2007 of the International Course on the Conservation of Japanese Lacquer was held for a week from September 10. This international course on conservation is a joint project with ICCROM, whose headquarter is in Rome. Courses on urushi (Japanese lacquer) and Japanese paper are held in alternating years. Since this year was the fifth year of the course on urushi, the format was changed; instead of the regular course, past participants met to hold an evaluation seminar. On the first two days, 11 participants made presentations concerning how they are utilizing what they learned in the course in their current work while on the last 3 days, the participants went on a study tour to deepen understanding about urushi. Presentations by participants revealed cases in which the experience and knowledge obtained during the three-weeks’ course in the past are being put to use in the conservation of cultural properties made of urushi in various nations. This and the exchange of diverse information concerning urushi were extremely meaningful not only for the participants but also for us in conducting future courses.