NATURAL DYEING OF SILK: A REVIEW OF NATURAL SOURCES, DYEING TECHNIQUES, MORDANTS AND SUSTAINABLE APPLICATION

Abstract

Natural dyes have attracted renewed scientific and industrial interest as alternatives to synthetic colorants because of concerns about chemical pollution, resource consumption and the sustainability of textile wet processing. Silk, a protein-based natural fibre primarily composed of fibroin and coated by sericin in its raw state, offers considerable potential for natural dyeing owing to its functional groups, surface characteristics, and affinity for several classes of natural pigments. Natural colorants obtained from plants, animals, microorganisms, and agro-industrial residues can produce a wide range of colours on silk. However, their commercial application is often limited by variations in pigment composition, low or inconsistent colour yield, inadequate fastness and the environmental impacts associated with certain mordants and extraction processes. This review examines the major sources of natural dyes suitable for silk, their chemical characteristics, conventional and emerging extraction and dyeing techniques, and the role of metallic and bio-based mordants in colour development and durability. Particular attention is given to recent advances in ultrasound-assisted and microwave-assisted processing, agricultural-waste valorisation, statistical optimisation and multifunctional textile finishing. Recent research demonstrates promising results for plant-derived colourants, lac dye, and waste-derived extracts when appropriate dyeing and mordanting conditions are employed. The review identifies standardisation, reproducibility, fastness improvement, life-cycle assessment, and industrial scalability as important priorities for future research. Integrating renewable dye sources with efficient extraction methods and safer mordanting systems may support the development of more sustainable silk coloration.