Effect of Physiochemical Properties of Seokganju on Functionality and Light Fastness

The purpose of this study is to evaluate the functionality and lightfastness of the natural pigments according to the type of Seokganju used as Dancheong. The commercially available red iron-oxide-based natural pigments that are called Seokganju and Daija manufactured by traditional methods in Korea and Japan were selected. The analysis of the constituent minerals and constituents of 8 kinds of collected Seokganju showed that most of them contained hematite. There are two types of Seokganju according to the Fe2O3 contents. The type of Seokganju can be characterized not only using the main component but also from the burn-out processing. The chromaticity results for Seokganju with a high Fe2O3 concentration indicate dark red or grayish brown, while those for Seokganju with a low Fe2O3 concentration indicate yellowish red or yellowish brown. Samples were prepared by mixing with a glue solution and functional properties were evaluated based on the opacity and spreadability. Coated samples were used in the lightfastness test. The spreadability and opacity of the pigments were measured differently depending on the main component. Most Seokganju samples a showed slight color change until 9,000 kJ/m 2 but rapid color changes were detected after 18,000 kJ/m 2 . In particular, burnt Seokganju showed superior lightfastness.