Colouring Characteristics of Neem (Azadirachta indica) Bark Dye on Silk

The colours extracted from neem bark with different concentrations of mordants were tested on silk for the shades and colour fastness properties. The mordants tested were CuSO₄, Al₂(SO₄)₃, alum and citric acid. The colours of the fabrics were studied with a Hunterlab colour scale and the maximum ÄE* value (51.48±0.60) was observed for 1% CuSO₄ mordant treated samples. However, the values were not significantly different from 2% and 3% CuSO₄ treated samples. The unmordanted samples were also statistically acceptable in terms of ÄE* values. The change in chroma values were maximum for the 2% citric acid mordant (37.22±0.69), though the change in chroma offered by 2% and 3% alum, 3% citric acid and unmordanted samples were not significantly different. All the mordanted samples had fair to good (3–4) fastness to washing. The staining on undyed silk fabric with citric acid mordant showed excellent (5) fastness followed by alum and CuSO₄ mordanted samples, which had good to excellent fastness. CuSO₄ mordant offered good fastness to washing. The alum, Al₂(SO₄)₃ and citric acid mordants exhibited excellent dry rubbing fastness whereas the CuSO₄ mordant showed good to excellent (4–5) fastness. In case of wet rubbing, alum, citric acid and Al₂(SO₄)₃ mordanted samples showed good to excellent (4–5) colour fastness. Colour fastness in case of CuSO₄ mordant was good (4). The CuSO₄ mordant offered fairly good (4) colour fastness to sunlight and all other mordants showed moderate (3) colour fastness. The samples without mordants exhibited poor fastness (2). In view of the colour fastness, viz. fastness for washing, rubbing and exposure to light, the neem bark dye should be applied with any of the mordants used for the study at 3% level.

The neem bark has a good potential to be used as a natural dye and the resultant colour shades and intensities vary with the type of mordant and concentration thereof.