|■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
A scene from the workshop
The 2nd workshop for specialists on the new insecticidal treatment for historical wooden buildings, known as “humidity-controlled warm-air treatment,” was held on May 9th, 2019.
Pest-borne damage to historical wooden buildings risks not only the loss of important wooden materials but also building safety, as the wooden materials can become hollow, thus weakening the strength of the lumber construction material and the building itself. In response to severe pest-borne damage, the Rinno-Ji Temple at Nikko has undergone closure and repair. Fumigation with sulfuryl fluoride gas, which is known to have almost no effect on cultural properties, was performed to eradicate all noxious pests in the building. However, there are huge health and safety risks associated with the use of mass fumigation with poisonous chemical substances, and such treatment can also dissuade neighboring institutions from opening to the public.
To address this issue, humidity-controlled warm-air treatment was developed as a new insecticidal treatment. This method eliminates pests by increasing the temperature to 60 degrees Celsius while regulating the humidity without altering the water content of the wood, thus minimizing any damage to the wooden content. Two successful domestic cases have been reported with no significant damage found in buildings containing Urushi (Japanese lacquer) decorations. Subsequent examination of these cases indicates that the technology used in this new treatment is nearly ideal. Nevertheless, concerns have been raised regarding the number of technicians required and the cost involved, which must be addressed before formally establishing humidity-controlled warm-air treatment as a valid insecticidal treatment. Also, since this a newly developed treatment, its long-term performance is difficult to evaluate; there may be as yet unknown effects inherent in the use of this treatment.
Several issues must be resolved before humidity-controlled warm-air treatment can be considered to be an established insecticidal treatment method. We look forward to working over the long-term in cooperation with related organizations.
“Humidity-controlled high-temperature treatment for the bell tower of Chuzen-ji Temple in Nikko (branch temple of Rinno-ji Temple) and on-site inspection”
On September 10th, 2018, we visited Chuzen-ji Temple to inspect the “Humidity-controlled warm air treatment ” for its bell tower. This treatment method aims to expel noxious insects harming pillars and beams of wooden structures under a high temperature (around 60°C). Usually, as the temperature increases, wooden building materials crack or strain. However, it is possible to increase the temperature inside the wood almost without affecting its physical property, since the temperature rises while the humidity in the treated space is controlled with the wood water content maintained at a certain level. The conventional yet sole insecticidal method for historical wooden structures is fumigation treatment, where a structure sealed with covering is filled with vaporized pesticide to exterminate noxious insects inside the wood. However, vaporized gas also affects human health, thus, requiring safety measures against greater risks. Accordingly, it was hard to implement such large-scale treatment for wooden structures continually. This Humidity-controlled warm air treatment is expected as a new approach to overcome such a challenge.
So far, a research team comprising the Association for the Preservation of the Nikko World Heritage Site Shrines and Temples, Kyoto University, Kyushu National Museum, Total System Laboratory Co., the Japanese Association for Conservation of Architectural Monuments, National Museum of Ethnology, Natural History Museum and Institute, Chiba, and Tokyo National Research Institute for Cultural Properties has been proceeding with the studies from basic research for application to old wooden buildings to establishment of application technique. In the basic research, we verified the humidity distribution in the treated space during the test with a chamber, as well as the temperature distribution inside the wood, measured surface strain, and effects on wooden materials. Then, following the treatment testing with a model structure by using a pilot unit manufactured to control the temperature and humidity of actual structures, we finally realized on-site treatment testing of a historical wooden structure for the second time in Japan after Aizendo Hall of Chuzen-ji Temple. We would like to move ahead with this research toward the dissemination as one of new insecticidal methods while organizing these two treatment test results obtained from two buildings of Chuzen-ji Temple.
installation of FIT
The Center for Conservation Science has been moving forward the basic research on “hot-air processing” as one of the new ways of exterminating insect pests in historical wooden architecture. It heats a structure while maintaining a steady moisture content so that wood or coloration sustains no damage, thereby exterminating insect pests that perforate members inside the building, such as columns and beams, or cause feeding damage to them.
In research such as this, it is ideal to use insect pests that actually cause damage when evaluating insecticidal effects. However, it becomes necessary to identify ways of collecting living insect pests efficiently or to establish an artificial rearing method to ensure their steady availability. To that end, we here discuss ways of capturing them.
In the case of ordinary sticky traps for capturing flying insects, because an adhesive substance adheres to the insect pests captured, it is difficult to catch them alive. We therefore looked into how they are captured by applying a method called a Flight Interception Trap (FIT). The FIT utilizes the characteristic that a flying insect shrinks its wings or legs and falls when hitting an obstacle and thus is made up of a transparent collision plate and a trapping container installed underneath.
When we conducted a survey on insect pests captured by using a FIT at a temple on Mt. Nikko this fiscal year, we succeeded in capturing the intended insect pests (mainly deathwatch beetles) alive. Being able to capture them alive can not only provide clues to elucidating their biology or life history but also lead to artificial rearing.
We believe that it is important to accumulate the results of such basic research activities as the foundation underpinning the development of new ways to exterminate insect pests in historical wooden architecture.
The venue for a lecture at the forum
The scene of the satellite venue 1
The Center for Conservation Science and Restoration Techniques held the “IPM (Integrated Pest Management) Forum: 10 Years after the Abolition of Methyl Bromide Use: The Current Situation of IPM for Cultural Properties” on July 16, 2015. This event was jointly hosted by the Japan Society for the Conservation of Cultural Property, and was also held as a regular meeting of the society. This year marked the 10th anniversary of the abolition of methyl bromide use in and after 2005 decided by the Meeting of the Parties to the Montreal Protocol on Substances that Deplete the Ozone Layer. In this milestone year, we held the forum to review past activities, share information about the current IPM activities in the field of cultural properties, their progress and problems, and consider current challenges and the future direction. On the day of the forum, Mr. Takamasa Saito of the Cultural Affairs Agency, Ms. Rika Kigawa of the National Research Institute for Cultural Properties, Tokyo (NRICPT), and Mr. Sadatoshi Miura of the Bunkazai Chukingai Kenkyujo (research institute on insect and bacterial damage to cultural properties), respectively introduced fumigation techniques and subsequent IPM practices in Japan as well as countries around the world. In addition, various measures by individual museums were introduced from various perspectives by Ms. Mitsuko Honda of the Kyushu National Museum, Ms. Natsuko Nagaya of the Aichi Prefectural Museum of Art, Ms. Naoko Sonoda of the National Museum of Ethnology, Mr. Shingo Hidaka of the National Museum of Ethnology, Ms. Akiko Saito of the Natural History Museum and Institute, Chiba, and Ms. Mutsumi Aoki of the National Institute of Japanese Literature. Furthermore, Ms. Miyuki Asakawa of Ninna-ji temple introduced concrete examples of IPM activities in temples, while Mr. Yoshinori Sato of the NRICPT introduced an example of IPM practices at a conservation and exhibition facility for a decoratedtumulus, which is an environment for burial.
The forum was attended by 200 participants, and we set up two satellite venues at a meeting room (see photo 2) and a lobby in addition to the main venue at a basement seminar room of the NRICPT (see photo 1). In the lobby, we displayed copies of articles on IPM for cultural properties and measures against biological deterioration as well as related materials, and allowed participants to take them home for free. While it was regrettable that there was little time for discussion due to a series of heated presentations, we again appreciate that we could end the forum on a high note thanks to the cooperation from those concerned.
Keynote speech by Dr. Piero TIANO from Italy
Growth of microbes causes substantial deterioration of cultural properties, regardless of whether they are outdoors or indoors. Memories of the Great East Japan Earthquake are still fresh. The effects of water damage can soon lead to microbial deterioration of cultural properties that have been damaged by a disaster like an earthquake or tsunami. Surveys to ascertain the extent of damage and countermeasures against that damage are crucial. Thus, the Center for Conservation Science and Restoration Techniques hosted a symposium on the Microbial Deterioration of Cultural Properties at Heiseikan of the Tokyo National Museum from December 5 (Wed.)–7 (Fri.), 2012. Different departments of the Institute take turns hosting a symposium each year, and this year’s symposium marked the 36th International Symposium on the Conservation and Restoration of Cultural Properties.
The opening day of the symposium featured two keynote speeches by foreign experts, followed by a session on the biodeterioration of disaster-damaged cultural properties. The second day of the symposium featured a session on the biodeterioration of stone monuments and wooden structures outdoors. The final day of the symposium featured sessions on techniques to ascertain biodeterioration of cultural properties indoors and environmental factors for deterioration. The 3 days of the symposium featured 15 lectures as well as 23 poster presentations by presenters from Japan and abroad. The symposium encouraged an active discussion among the 232 participants (421 participants in total). The symposium was attended by numerous foreign experts from countries such as Italy, France, Germany, Canada, China, and South Korea. Symposia on the specific topic of microbial deterioration of cultural properties are seldom seen, and many of the experts from Europe who attended did so at their own expense. The symposium was truly an international symposium, allowing a substantial exchange of information. Sincere thanks are extended to the presenters and participants who enthusiastically collaborated with the Center for Conservation Science and Restoration Techniques.
Microbial Biodeterioration of Cultural Property
Degradation by microorganisms significantly affects cultural properties, regardless of whether they are indoors or outdoors. In addition, cultural properties that have been damaged by an earthquake, tsunami, or other natural disaster are soon susceptible to biodegradation due to water damage. Surveys of the extent of damage and steps to combat it are vital. The National Research Institute for Cultural Properties, Tokyo will hold an International Symposium on the Conservation and Restoration of Cultural Property on Dec. 5 (Wed.)–7 (Fri.), 2012 in Heiseikan of the Tokyo National Museum. In addition to guest lectures, the symposium will feature 22 poster presentations on biodegradation of cultural properties and steps to counter it. The symposium provides a forum for active discussion and exchange of information by domestic and foreign researchers and individuals who work with cultural properties, so numerous attendees are expected, including individuals involved in the protection of cultural properties, researchers, and students interested in the area of cultural properties. Applications will be accepted until Oct. 20th. For details, see http://www.tobunken.go.jp/~hozon/sympo2012/. Please direct inquiries to firstname.lastname@example.org.
Mold growing on areas painted oyster shell white
An on-site exposure test with a fungicide
As part of a commissioned study on Development of Techniques to Prevent Color Paint Peeling at Kirishima Shrine and Work to Implement Those Techniques, the Center for Conservation Science and Restoration Techniques has studied biological deterioration of traditionally painted areas of Kirishima Shrine. Traditional painting techniques used organic substances such as animal glue and are usually susceptible to biological deterioration by microbes like mold. If mold grows, it can seriously mar a building’s appearance. Moreover, mold degrades the proteins in animal glue that serve as a binder, causing pigments to separate from the painted surface. Metabolites also cause pigments to discolor and dissolve. As a result, the physical deterioration of painted areas accelerates.
Kirishima Shrine has suffered damage, i.e. extensive growth of mold, in areas that were painted traditionally with oyster shell white paint or ochre paint including walls of breezeways, the covered stone stairway, and the worship hall. This year, a microbiological study was conducted to identify the mold responsible and ascertain the impact of that mold on painted areas. Temperature and humidity changes on-site were also monitored and an exposure test with fungicides was also conducted to help devise optimal control measures.
Environmental measurements revealed that the Shrine’s air temperature is lower than the air temperature of level ground and the Shrine has a relatively high relative humidity of about 70% as an annual average. The Shrine was found to have an environment conducive to the growth of indigenous microbes. During the on-site exposure test with fungicides, several agents were found to have fungicidal action, but some of the fungicides chemically reacted with the white paint and could lead to deterioration. One hundred and thirty-three fungal strains have been isolated from damaged areas. These strains were grouped based on colony morphology and analyzed phylogenetically and physiologically. Results indicated that 3 groups had highly prevalent fungal strains (i.e. they had the most strains isolated). These groups are presumed to play a major role in microbial deterioration of traditionally painted areas of Kirishima Shrine. Plans are to perform a more detailed analysis of the isolated strains and continue exploring measures to prevent and control microbial deterioration of areas with traditional oyster shell white paint and ochre paint in conjunction with exposure test results.