Development of carbon extraction method from verdigris and demonstration of effectiveness of carbon-14 dating for bronzeware

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K20718
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 3:History, archaeology, museology, and related fields
• Research Institution: Nagoya University
• Principal Investigator: Oda Hirotaka 名古屋大学, 宇宙地球環境研究所, 助教 (30293690)
• Co-Investigator(Kenkyū-buntansha): 山田 哲也 公益財団法人元興寺文化財研究所, 研究部, 研究員 (80261212)
• Project Period (FY): 2020-07-30 – 2024-03-31
• Keywords: 青銅器 / 緑青 / 炭素14年代測定法

Outline of Final Research Achievements

Verdigris is produced by the reaction between Cu in bronzeware and CO2 in the atmosphere. Once verdigris has formed, it inhibits the formation of new verdigris. Therefore, if it becomes possible to extract carbon from verdigris and measure its 14C dating, it will be possible to determine the age of formation and use of bronzeware. In this study, we determined reaction conditions that yield accurate ages with high yield through thermal decomposition of verdigris in vacuum. In addition, since the amount of verdigris that can be analyzed is limited, we investigated a cementite synthesis method that allows measurement of small amounts. As a result, it was pointed out that this method had lower measurement precision than the conventional graphitization method. We also conducted measurements on bronzewares of known age and demonstrated that the verdigris is suitable for the 14C dating method.

Free Research Field

文化財科学

Academic Significance and Societal Importance of the Research Achievements

従来，青銅器は14Ｃ年代測定法の対象とされてこなかった．これは青銅器自体が炭素を含んでいないためである．しかし，青銅器の表面に緑青が発生する際に，大気中の炭素を固定するところに着目し，緑青の14Ｃ年代測定法の開発を試みた．分析する緑青の量に限度があり，従来の試料調製法では測定ができないことがあるため，新たな試料調製法についても検討を行った．その結果，測定精度が低くなるという問題点が示されたが，この解決は今後の課題である．
青銅器の年代が自然科学的手法により明らかになれば，考古学・文献史学等に新たな情報をもたらすことになり，より精緻な歴史観，また全く新しい歴史観を導き出す手法となるであろう．