Rigorous analysis was performed to identify the structure and materials of the murals to study techniques used on mural tombs of ancient Daegaya era(6th century). The murals were painted by applying mortar on the walls and the ceiling after building a stone chamber and creating ground layers on mortar layers. Mud was applied on most of the mortar layers on four sides of the walls except the ceiling. Sand was not used in mortar but was made of materials with pure calcium substances. In addition, shells in irregular sizes with incomplete calcination were mixed; and the mortar's white powder was inferred as lime obtained by calcination of oyster shells. Kaolinite(Al2Si2O5(OH)4) was used in the ground layer, Cinnabar(HgS) was used for red pigment, Malachite(Cu2CO3(OH)2) for green and Lead white(PbCO3·Pb(OH)2) for white. Mud plaster was applied on the mortar and was composed thinly and densely using clayey of particle size smaller than that of medium sand. It was assumed that the finishing was for repair after long time had passed since the mortar layer came off. Using lime made with oyster shells as mortar is unprecedented in ancient Korean mural tombs and its durability was very poor, suggesting that Gaya's mortar production technique was relatively 458 | 보존과학회지 Vol.30, No.4, 2014 behind compared to that of Koguryo's in the same era.

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Study on the Manufacturing Technology of Mural Tomb in Goa-dong of Daegaya Period

This study used morphological analysis to identify the materials used for the wall plaster in the Goa-ri Tomb and elucidate the wall manufacturing techniques by determining the processing conditions for the plaster ingredients through a calcination experiment. A glossy nacreous layer (or folia layer) and an adductor muscle scar were identified on the ventral of the shell. The shell section was confirmed in the form of a lens-like prismatic layer (or chalky layer) inserted between the nacreous layer (or folia layer). The calcinated samples showed clusters of polygonal particles of different sizes. The experiment confirmed a process of particles in plate-type–bedded structures converting into shapeless particles followed by recrystallization. The samples calcinated at 650 °C and 750 °C mostly showed plate-type–bedded structures. According to the results of the study, the plaster used on the Goa-ri Tomb walls was confirmed to be made of oyster shells. The existence of many incompletely calcinated shell particles in the plaster indicates that the calcination temperature was not high enough or the heat was not evenly distributed. The Goa-ri Tomb used weaker and less durable plaster made of incompletely calcinated shells, which seems to have caused the extensive exfoliation of the plaster from the wall surfaces.

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Wall Materials and Manufacturing Techniques for Korean Ancient Mural Paintings (Great Gaya, 6th Century)—Discovery of Shells Used in Wall Plaster and Identification of Their Processing Status

조남철

Papers

Scientific Analysis of Ancient Mural Pigments (Focus on Mural Pigments at Daeungjeon Hall of Bongjeongsa Temple and Ancient Tomb in Goadong)