Development of restoration technique for paper corrosion in paper artifacts

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K16342
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Cultural assets study and museology
• Research Institution: Independent Administrative Institution National Institutes for Cultural Heritage Tokyo National Research Institute for Cultural Properties
• Principal Investigator: Kida Keiko (貴田啓子) 独立行政法人国立文化財機構東京文化財研究所, 保存科学研究センター, 客員研究員 (20634918)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 紙の劣化 / cellulose / 緑青焼け

Outline of Final Research Achievements

Regarding the deterioration phenomenon of "corrosion of paper" caused by Gunjo or mud of Shintyu, discoloration of paper and a decrease in molecular weight of cellulose proceeded slowly with the use of Gunjo pigment. On the other hand, when mud of Shintyu was used, both deterioration phenomena proceeded faster than the Rokusho pigment. It was also suggested that the discoloration and the molecular weight of cellulose show different behaviors, and that discoloration and deterioration accompanied by the decrease of the molecular weight of cellulose proceed by different mechanisms.
The amount of water-soluble copper ions in the Rokusyo pigment depends on the particle size, the type of pigment, and the nature of the glue, which is the medium. Since there was a strong correlation between the amount of copper ions and the degree of paper corrosion promotion, by selecting different glues, we found the possibility of controlling the attack of corrosion.

Free Research Field

保存科学　文化財保存

Academic Significance and Societal Importance of the Research Achievements

緑青焼けの主要因である銅イオンが紙の劣化に及ぼす影響を調べる上で、緑青のみならず銅含有顔料として群青顔料および真鍮泥の劣化現象に着手し、これらを比較検討することにより、「緑青焼け」との類似点、相違点が見つかった。一方、紙の劣化を促進する顔料由来の銅イオンについて、顔料－膠分散液中の銅イオン濃度を測定することにより、彩色材中の水溶性銅イオン溶出量が、顔料の粒度、種類、または膠の性質により異なることを見出し、文化財の修復処置では確実な除去が必要であることを示した。また、性質の異なる膠を修復処置に用いて、銅イオン溶出量を制御できる可能性を見出し、処置方法改善に寄与する結果となった。