Moisture Tensile Strength Measurement Scene of Hanji

- National Research Institute of Cultural Heritage Registers Patent for Wet Hanji Resistance Measurement Method

The National Research Institute of Cultural Heritage under the Cultural Heritage Administration completed the registration of a patent for a new test analysis method called the "Traditional Hanji Moisture Tensile Strength Measurement Method" in March to scientifically evaluate the durability and quality of Hanji paper. The patent registration for a test analysis method for Hanji is the second one following the "Hanji Internal Bond Strength Measurement Method" registered on June 9, 2023.

So far, the quality evaluation of Hanji has been conducted using the "General Pulp Paper (Mechanical Paper) Test Method" specified in the Korean Industrial Standards (KS). However, due to the differences in raw materials and production methods between Hanji and machine-made paper, also known as Yangji, there is a need for the development of specialized test methods for Hanji that distinguish it from Yangji.

The National Research Institute of Cultural Heritage had previously measured the internal bond strength by applying a load of 4.91~14.72N to a 15mm wide specimen cut for quality measurement through folding or bending. However, when applying this method to individually produced Hanji sheets made by hand, there was a problem of significant variation in results for each specimen. To address this issue, they developed the "Hanji Internal Bond Strength Measurement Method" consisting of a specimen width of 10mm and a load of 4.91N, which is most suitable for testing the internal bond strength of Hanji, and obtained the first patent registration related to Hanji test analysis.

Following the registration in 2023, the newly patented "Traditional Hanji Moisture Tensile Strength Measurement Method" measures the stress that Hanji can withstand when pulled in a wet state. It involves immersing a 50mm wide specimen cut into water for at least 3,600 seconds, then pulling the specimen from both sides at a speed of 20mm per minute to measure its resistance.

The moisture tensile strength of Hanji is an important measurement criterion for evaluating the quality of Hanji used for the conservation and restoration of paper cultural heritage items such as ancient documents, records, and paintings. Hanji used for conservation purposes is not only utilized for reinforcing damaged parts but is also used in wet cleaning operations to remove contaminants and foreign substances on the surface of artifacts that cannot be resolved through dry cleaning methods using tools like brushes. Therefore, measuring the tear strength of Hanji when wet is crucial.

The development of the moisture tensile strength measurement method following the internal bond strength measurement method for traditional Hanji is significant in establishing a scientific and standardized evaluation basis for assessing the quality of traditional Hanji, which is globally recognized for its excellent properties, preservation, and artistic value. Furthermore, being able to measure the strength of Hanji in both dry and wet conditions can contribute to significantly expanding the utilization of traditional Hanji in various fields such as construction, daily goods, and art through consistent quality management in the future.

This patent is a result of the "Research on the Characterization and Applicability Evaluation of Traditional Materials" project being carried out as part of the "Research on Quality Standards for Hanji Used in Cultural Heritage Conservation and Restoration" by the institute from 2022 to 2026.

The National Research Institute of Cultural Heritage under the Cultural Heritage Administration plans to enhance the utilization of the patented test method by collaborating with relevant research institutions, industries, cultural heritage restoration sites, and strengthening cooperation with international standardization organizations. They also intend to pursue the development of additional test analysis methods.