Investigation of the recycling of Han Chinese bronze mirrors into Japanese imitation mirrors

We revisit the chemical data on imitation Japanese bronze mirrors of the Kofun period (c. 300–538 CE), which Hisao Mabuchi (馬淵久夫) has used to suggest that these mirrors were made from broken imported Han-style mirrors diluted with additional copper. Using a different approach, we confirm that the composition of these mirrors is consistent with Mabuchi's suggestion. In addition, we can use data from our model to take this analysis further, by combining the elemental and lead isotope data, determining how much each source contributes to the lead in the mirrors, and calculating the possible isotope composition of the lead in the imported mirrors and in the added copper. This shows that both the mirrors and the added copper are unlikely to contain Japanese lead. As Mabuchi suggested, there appears to have been a trade in both Han-style mirrors and copper ingots from China to Japan in the Kofun period. Not only does this work support the previous conclusions, but it also sets out a new methodological approach that can be used to further such research.