The Methods of Making Joseon and Daehan Empire Royal Seals Varied by Era
National Palace Museum Issues 'Scientific Analysis of Royal Seals' Report
Detailed Analysis of 155 Gold Seals and 167 Jade Seals...Production Techniques, Materials Identified
Eobo (御寶) is a ceremonial seal symbolizing the authority of the royal family. It was produced over a period of more than 500 years, from the Joseon Dynasty to the Korean Empire. It was made during court ceremonies such as royal weddings or investitures to inscribe posthumous titles, honorific titles, or calligraphy. Recognized for its authenticity, originality, and global significance, the "Joseon Dynasty Royal Seals and Royal Documents" were designated as a UNESCO World Heritage in 2017.
On the 15th, the National Palace Museum published three volumes of the "Scientific Analysis of Eobo" report, analyzing 322 seals (155 gold seals and 167 jade seals). Volume 1 contains an overview of the scientific analysis of the seals and four papers summarizing the manufacturing techniques, materials, and characteristics of the gold and jade seals. Volumes 2 and 3 present the analysis results of the gold seals and jade seals, respectively.
Gold seals were made by plating seals with an amalgam of copper and zinc alloys. Amalgam plating is a technique where gold dissolved in mercury is applied to the metal surface, and then the mercury is evaporated to leave a gold coating. Analysis showed that the zinc content varied by era. From the 15th to 17th centuries, it was around 10%, but after the 18th century, it ranged from 10% to 30%. In the 19th century, most contained more than 20% zinc.
The differences were also found in the appearance. In particular, patterns engraved with dots and the tortoise shell motifs decorated by chasing (engraving patterns by hammering metal) appeared only on gold seals with tortoise-shaped handles (Gwinyu, 龜紐) made between the late 17th century and mid-18th century.
Jade seals were mostly made from the Sarmunam (a type of marble) series, but after the 19th century, some were made from dolomite and baegunam (white cloud marble) series. Twenty-five seal handles had characters such as '王 (Wang, meaning king)' engraved on them. Eleven had tortoise eyes painted black.
The red cords attached to the seals, called bosu (寶綬), were usually made of silk. However, one seal made in 1740 (Yeongjo Posthumous Title Jade Seal) and five seals made after the 1900s used rayon, a synthetic fiber. Rayon was introduced to Korea in the early 1900s. A museum official explained, "The use of rayon on the bosu of the Yeongjo Posthumous Title Jade Seal is presumed to be due to its replacement with a newly made cord after the 1900s."
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This analysis was conducted over two years from 2018 to last year. The National Palace Museum independently analyzed the gold seals, while the jade seals were analyzed jointly with the Conservation Science Research Division of the National Research Institute of Cultural Heritage. The results will be distributed to national and public libraries, museums, and research institutions. They are also accessible on the National Palace Museum’s website.
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