Shedding Light on Korean Natural Dyes: Chemical Composition and Fading Behavior

The study investigates the lightfastness of traditional Korean textiles dyed with six natural dyes: sappanwood, Sophora japonica, rhubarb, myrobalan, gallnut, and persimmon. The research aimed to determine how variations in temperature and relative humidity (RH) affect color fading, specifically under ultraviolet (UV) and non-UV lighting conditions. Silk, ramie, hemp, and cotton fabrics were tested in a series of controlled light aging experiments in a Xenotest. Colorimetric analysis revealed that fabrics dyed with sappanwood and S. japonica exhibited significant color loss, while those dyed with myrobalan and gallnut demonstrated high lightfastness. Temperature and RH separately barely had any effect on the rate of color fading. In addition, high temperatures combined with high RH accelerated fading. Under UV exposure, rhubarb and persimmon dye showed unique darkening behavior, likely due to tannin-based oxidation. HPLC analysis showed that chebulic acid was present in myrobalan and could serve as a marker to distinguish between myrobalan and gallnut, which are both tannin-based natural dyes widely used in Asia. This study provides valuable insights for the preservation of naturally dyed textiles in museum collections, suggesting possible strategies for more sustainable management of dyed textiles. The findings also contribute to the broader understanding of how environmental factors affect the durability of natural dyes on various textile substrates.