In this article we review how to improve the colour fastness properties of natural dyes with 5 dye fixing agents. Eco-friendly mordants such as alum, stannous chloride and ferrous sulphate are used. Annato dye is selected because this source produces fugitive colours on cotton. A pre-treatment with myrobalan has been given for better dye uptake. After dyeing, the sample is post treated with 5 dye fixing agents such as alum, ammonia, lime juice and calcium chloride for better colourfastness of natural dyes on cotton.
The dye extraction and treating procedures are standardized based on the procedures suggested by AICRP- Home science (1997). Treatment was given to the cotton samples and evaluation of treated samples in terms of colour fastness to washing, before and after treatment was undertaken by following the standard procedures laid down by Bureau of India Standard Test Series IS 768-1956 for colour change. The result is 769-1956 for staining using geometric grey scale. The results were analyzed based on the colour fastness of control samples to find out the impact of the treatments.
Alkaline method is suitable for extraction of dye from Annato. The optimum time for extraction of dye liquor from the seeds was 60 minutes. A dye material concentration of 4 percent (2g/g of fabric) was selected. The optimum time for dyeing was 45 minutes for both the dyes. Cotton fabric was pre-treated with 20 per cent myrobalan concentration to 9in cease the tannin deposition which in turn increased the depth of the shade obtained.
To improve the colour fastness 5 per cent solution of fixing was selected. Depending on the absorption values, depth of the shade and appearance, three concentrations for each mordant was selected. In case of alum 5, 10, and 15 per cent and 1, 2, and 3 per cent concentrations of stannous chloride and ferrous sulphate mordants for cotton were selected for pre-mordanting cotton fabric.
Materials and methods
It deals with the selection of materials, preparation and implementation of experimental procedures. The cotton fabric was selected due to its easy availability and popularity in use. Then, the fabric is dyed with natural dye i.e. is annto seeds, using different eco-friendly mordants. To improve the colour fastness of the shades, fixing agents are employed. The treated samples are evaluated for colourfastness.
Natural dyes have emerged as prime colorants for textiles globally. Very few studies have been conducted to improve the colourfastness of these natural dye sources. Therefore, an attempt has been made in this study to improve the colour fastness of natural dye source i.e. annatto seeds by using five fixing agents.
Evaluation of colour fastness test:
Wash fastness properties of Annato (Bixa orellana) dye on cotton
TABLE: Wash fastness properties of Annato (Bixa orellana) dye on cotton
Wash fastness of Annato dye on cotton:
The wash fastness grades of vinegar post-treated cottons showed good resistance to colour change in all mordanted samples. Almost all samples showed good resistance to staining on silk. Post-treatment with alum produced shades that showed varied fastness as per the mordant used. While alum and ferrous sulphate mordanted samples exhibited good resistance to colour change, stannous chloride samples showed only fairly poor to fair resistance. Ferrous sulphate mordanted cotton showed good resistance to staining on cotton and very good resistance on silk fabric over control.
Ammonia post-treatment did not show much effect on the wash fastness of annato dye on mordanted cotton. Alum and ferrous sulphate mordanted cottons showed only fair resistance to colour change due to washing over control. Lime juice post-treated cottons did not register much improved wash fastness over its control. Very fair to fair resistance to colour change was shown in stannous chloride mordanted sample.
Post-treatment with calcium chloride had not exhibited much improvement. Slight increase in resistance to colour change was observed in alum mordanted cottons. The improved resistance to staining was observed on both cotton and silk in all mordanted cottons due to washing fastness over control.
Among the mordanted and post-treated cottons, vinegar post-treated samples showed increased depth of the shade on cotton mordanted with alum, stannous chloride and ferrous sulphate, besides providing leveled shades over control. Resistance to colour change and colour staining on silk was improved due to the washing over control. Increased wash fastness in majority of the samples due to alum post-treatment, when compared to control. The lime juice post-treated samples exhibited increase in depth of the shade and contributed for level dyeing in all mordanted samples with wash fastness. Calcium chloride post-treated cottons had registered the same as fairly good especially, in case of stannous chloride mordanted samples on cotton over control.
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R. Prabhavathi is a lecturer in Department of Home science, J.M.J. college for women, Andhra Pradesh.