Natural dyes refer to those colourants which are obtained from plant, animal and mineral resources. These are used for colouration of textile, food, drugs and cosmetics. Small quantities are also used for colouration of paper, leather, shoe-polish, wood, candle etc. The main natural dyes used in India have been extracted from the roots, barks, flowers and fruits of various dye producing plants. Mollotus phillipinensis is a small evergreen tree belonging to the Euphorbiaceae family, mostly natives of tropics of old world, flourishing in the forests of tropical Asia from India to Malaysia and Phillipines, China and Australia. The tree bears fruits in the form of pods. The dye is an orange-red powder, which occurs as a glandular pubescence on those pods and is gathered by shaking the ripe capsules harvested in the month of February-March. The colouring matter of Mollotus phillipinensis comprises of several chalcones, the structures of which are given in the literature. Rheum emodi, commonly known as dolu, is a stout herb of 1.5-3 m in height, distributed in the Himalayas from Kashmir to Sikkim at an altitude of 3300-5200 m. The stout roots are the chief source of Himalayan rhubarb and finds application chiefly in medicine as a purgative and astringent tonic and can also be used for colouration of wool and silk fibre. The chief colouring component of Rheum emodi is chrysophanic acid and the structure of which is given in the literature. Ratanjot (Onosma echoides) has traditionally been used as a food colourant. The bark of roots contains several naphthoquinone pigments, which give a violet-red colour. The main pigment is believed to be alkanin. Alkanin is insoluble in water but has been used to dye wool, silk and cotton with addition of alcohol for one hour at 400C and its alkaline solution is deep blue coloured.
Natural dyes are mostly used to dye natural fibres like, cotton, wool, silk, jute etc. But very little information is available on dyeing of synthetic fibre like polyester with natural dyes. In this study an attempt has been made to dye polyester fabric with those above mentioned natural colourants in absence and presence of different inorganic salts or mordants. The dyed fabrics were assessed in terms of depth of shade and different colourfastness properties.
About the Author
Sankar Ray Maulik is Lecturer at Visva Bharati University in the Department of Silpa Sadana (Textile section), Sriniketan, Dist. Birbhum, West Bengal.