Investigation and Research on the Conservation of the Plaster Remaining in Stone Chambers and Sarcophagus in Tumuli
The Tokyo National Research Institute for Cultural Properties (TOBUNKEN) visited the Oichi No.1 Kofun (tumulus) in Fukuyama City, Hiroshima Prefecture and investigated the conservation status of the plaster remaining in the stone sarcophagus, in cooperation with the Culture Development Section, Economic Environment Division of Fukuyama City, on October 20th, 2022. Plaster, a type of construction material used for tumulus construction, requires specific knowledge and techniques regarding all processes from manufacturing to application. Therefore, it is a precious archaeological material which shows how technology was transferred when those tumuli were constructed. Hence, regardless of the coloring and/or decorations on it, plaster conservation is considered important and implemented in many cases outside Japan. Though there are more than 40 tumuli where plaster usage is confirmed in Japan, they are not widely known like Takamatsuzuka and Kitora Tumuli. While most of these tumuli were designated as cultural properties, plaster conservation measures are rarely taken up; the plaster is left to erode due to weathering and flaking every day.
The Oichi No.1 Kofun keeps the highest percentage of plaster in Japan. We wonder why it is not designated as a cultural property. Furthermore, it does not just keep the plaster, but we can even identify plaster application traces, which were considered to be made when the plaster was applied during the tumulus construction in the area, where the conservation status is good enough. It can be a precious clue to identify the tools used during the construction. In this investigation we discussed sustainable measures for plaster conservation based on the confirmation of its conservation status and environment, by considering the sense of morality on the cultural property conservation and restoration including material adaptability and aesthetic appearance.
Utilization of the cultural properties is required now more than ever. It is time to revise the methods of passing down the cultural properties to future generations in the given situation. The plaster remaining in tumuli is one of these cultural properties. We will discuss further the appropriate measures for conservation and methods to maintain and manage it for its future utilization by revising the current situation where the plaster has been decaying and lost, while also referring to the similar advanced cases in and outside Japan.