Research study on the conservation and restoration of trowel paintings on the earthen storehouse of the former Kina-Saffron-shu-Honpo (Part 3)
The Tokyo National Research Institute for Cultural Properties is conducting ongoing research on the conservation and restoration of trowel paintings that decorate the earthen storehouses of the former Kina-Saffron-Shu-Honpo in Nagaoka City, Niigata Prefecture, as part of A Research Survey into Stucco Decorations and Clay Statues. By fiscal year 2024, studies had been carried out on consolidation treatments using inorganic restoration materials for the plaster layers that constitute the reliefs, as well as on retouching techniques, and conservation treatments were implemented based on the findings.
Following these treatments, an on-site investigation was conducted from April 20 to 23, 2026, to confirm the post-treatment condition of the reliefs. These trowel paintings are exposed to particularly harsh environmental conditions, including the hot and humid summers characteristic of the Sea of Japan coast, as well as heavy snowfall and freezing conditions during the winter months. During this survey, detailed observations focused primarily on the treated areas. As a result, no major deterioration, new detachments, or losses were observed in the reliefs themselves, confirming that the areas consolidated with inorganic restoration materials have remained in stable condition.
Until now, repairs to these trowel paintings had been repeatedly carried out in response to damage as it occurred. However, many of these interventions were intended as short-term repairs, and in particular, treatments using synthetic resin-based materials were found to harden and discolor over time, in some cases causing additional stress to the reliefs themselves. In response to these issues, the present study aimed to establish treatment methods based on established cultural heritage conservation, principles, considering both the distinctive environmental conditions of the region and the material characteristics of the reliefs. In particular, the introduction of highly durable and stable inorganic restoration materials represents the first full-scale application of such methods to the conservation of trowel paintings in Japan, and the present follow-up survey provided important findings demonstrating their effectiveness.
The Institute plans to continue long-term monitoring the condition of the reliefs while further evaluating the research results. It is hoped that the outcomes of this study will contribute to the conservation and restoration of trowel painting cultural properties throughout Japan and serve as a new guiding approach for their preservation in the future.