Natural Dyeing of Cotton Fabric Using Amaranthus tricolor Extract: Influence of Extraction Method on Colourimetric, Fastness, and Antioxidant Properties

Natural dyes have emerged as promising alternatives to synthetic colorants owing to their biodegradability and environmental compatibility. The present study investigates the dyeing performance of Red Amaranth (Amaranthus tricolor) leaves on cotton fabric and evaluates the resulting colorimetric, fastness, comfort, and antioxidant properties. Dye extracts were prepared through both hot and cold aqueous extraction techniques and applied to alum-mordanted cotton fabrics using an exhaust dyeing method. The dyed fabrics were assessed for color characteristics, wash and rubbing fastness, air permeability, and antioxidant activity using the DPPH free-radical scavenging assay. Results revealed that extraction conditions significantly influenced pigment stability and shade development. Alum-mordanted samples exhibited bright pink shades with improved color retention, while ferrous sulphate mordant produced darker greyish-brown tones. The fabrics demonstrated good dry rubbing fastness (Grade 4-5), moderate wet rubbing fastness (Grade 3–4), and an air permeability value of 147 mm/s, indicating satisfactory comfort performance. The DPPH assay showed 47% antioxidant activity, confirming the retention of bioactive compounds from the natural dye source. The study establishes Amaranthus tricolor as a viable natural dye source for sustainable textile coloration and highlights its potential for developing value-added functional textiles.