ANCIENT GLASS TECHNIQUES AND COMPOSITIONS BY X-RAY OPTICAL METHODS

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This study clarified chemical compositions and manufacturing technique of ancient glasses by using X-ray optics.1). To examine manufacturing technique of tubular beads, comma shaped beads, and beads, this study showed inside structure of the beads, using high energy X-ray computerized tomography for the first time in Japan.At the same time, beads that has simple structure were investigated by traditional X-ray photography accompanied with newly developed image processing.The result is that tubular beads, made of potash-silica glass and distributed in Yayoi period were hollowed, and that these glass objects were found in Fukui, northern part of Kyoto, Tottori, Shimane prefectures, raging from Hokuriku to Sannin districts, not in Kyushu district.Meanwhile, tubular beads made of lead-barium glass and distributed in the same Yayoi period were fabricated by molding, which is different from the manufacturing process of tubular beads made of potash-silica glass.2). As for glass compositions in Yayoi period, the majority was lead-barium glass and potash-silica glass. From the latter half of the Yayoi period to the beginning of Kofun period, soda-lime-silica glass appeared, and became at its best in the Kofun period.By the content of alumina, there are two types of soda-lime-silica glasses distributed in Japan.It is said that the glasses with various colors appeared in the Kofun period, which were brought by the use of soda-lime-silica glass containing a large amount of alumina.Further investigation showed that mentioned above were already observed in the northern part of Kyushu from the late Yayoi period.What is more, mixed-alkali-silica glass was excavated in the relic of Kofun period, being needed further investigation, such as from where the manufacturing technique was brought to.