Extraction of natural dye from red calico leaves: Gamma ray assisted improvements in colour strength and fastness properties

• Natural dye from red calico leaves has been promisingly extracted using alkali medium.
• Gamma ray treatment of 15 kGy improves the extraction of colourant and dyeing of fabric.
• Gamma ray treatment also reduces the amount of mordants and time of dyeing application.
• Optimum dyeing conditions: Temperature 60 °C, Dyeing Time 50 min, pH – 7.0, Salt Conc. – 6 g/L.

The present study was conducted to explore the colouring potential of red calico {Alternanthera bittzickiana (Regel) G. Nicholson} leaves and to improve colour strength of dye using gamma radiations followed by mordanting process. The results showed that red calico plant leaves could be an excellent source of natural dyes for textile sector. Copper sulphate (1%) and tannic acid (1%) were the best pre- and post-mordants, respectively to improve the colour strength and colourfastness properties. The results from dyeing indicated that gamma ray treatment of 15 kGy was the effective absorbed dose for extraction of dye and surface modification of cotton fabric. Dyeing of cotton fabric with red calico leaf extract at 60 °C for 50 min using dye bath of pH 7.0 and salt concentration of 6 g/L produced good colour strength. Gamma ray treatment of cotton reduced the amount of mordants and improved the colourfastness properties.