Investigation of Conservation Environment for Wooden Architecture in Rock Caves

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.

Air Quality Investigation in the Museum Display Cases

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.

2020 Training for Museum Curators in Charge of Conservation

Lecture on measures against biodeterioration

Lecture on scientific research on cultural properties

　The abovementioned training was held from October 5th to October 15th, 2020. Although we have received many applications, the training was provided to 17 curators and others (or half the usual number) as a measure against the spread of COVID-19. Starting from last year, the training is implemented jointly with the National Center for the Promotion of Cultural Properties (CPCP). The CPCP took charge of the training sessions in the first week and Tokyo National Research Institute for Cultural Properties (TNRICP) in the second week. During the training, various control measures were thoroughly implemented to prevent the spread of infection: body temperature checking, sanitizing, and avoidance of the “3C’s.” Moreover, the participants wore gloves during hands-on training sessions. Furthermore, training materials were distributed to each trainee.
　During the first week when the CPCP was in charge, participants learned the basics of the conservation environment through classroom lectures. In addition, reports were made on the instruction and advice regarding the “Virus Removal and Disinfection Work at Museums, etc.” addressed jointly by three organizations, namely the Agency for Cultural Affairs, CPCP, and TNRICP. During the second week, certain sections at the Center for Conservation Science provided separate half-day sessions and provided classroom lectures and practical workshops with a variety of topics such as the concept of conservation and restoration of cultural properties, the method of addressing on-site issues with the application of basic natural science knowledge, and other topics. Participants appreciated these sessions, commenting that they were informative and useful. On the last day of the training, Dr. KOUZUMA, Director of the Cultural Heritage Disaster Risk Management Center established in October 2020, was invited to give a lecture on the “Disaster Risk Management of Museums,” which turned out to be a valuable occasion to think about the role played by museums in protecting cultural properties from disasters.
　We will keep working to provide better trainings to suit the needs of the time in 2021.