Basic Research for Preservation and Restoration of Usuki Stone Buddhas, a National Treasure
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.