Ever since the prehistoric time, mankind took delight in coloring the objects of daily use by employing natural pigments of vegetable, animal, and mineral origin. These coloring substances, known as natural dyes, are the chemical compounds used for coloring fabrics, hair, leather, plastic, paper, food items, cosmetics, and medicines, etc., and to produce artistic colors and inks for paintings and printing.
People always prefer natural dyes and pigments because of their brightness, soothing and non-toxic nature. But after the discovery of synthetic dyes by William Henry Perkin in 1856, the natural dyes gradually lost their utility value in most parts of the world. However, people lately have come to realize the toxic effects of synthetic dyes, especially the azo dyes and benzidine derivatives. Therefore, it has become imperative to revert to the natural dyes as they are user-friendly and eco-friendly, and are harmless to health and environment. Further, natural food colors are more desirable than synthetic dyes from their nutritional point of view as few of the carotenoid pigments are helpful in prevention of few forms of cancers and few are vitamin A precursors, which may be effective antioxidants.
Recently conducted National and International conventions and workshops on natural dyes were of the opinion that there is a great need for the revival of the use of natural dyes in Asia, particularly in India. Therefore, efforts should be made to promote the use of natural dyes, extend the range of their application, and encourage their commercial use rather than restricting them to small scale cottage industries. There is a need to carry out research and development on natural dyes by using modern technology to develop extraction techniques, standardize applications on synthetic as well as natural fibers, leather, and also evaluate their toxicity.
In India, National Handloom Development Corporation (NHDC), Indian Institute of Technology (IIT), New Delhi, Forest Research Institute (FRI), Dehradun, National Botanical Research Institute (NBRI), Lucknow, Alps Industries, Sahibabad, Ghaziabad, U.P., etc., have developed technologies for the extraction of natural dyes from plant materials. These technologies are being marketed through National Research Development Corporation (NRDC), New Delhi.
Keeping the above in view, this book attempts to revive the glory of natural colors. The book, written in technical style, is profusely illustrated, contains information on 86 natural dyes derived from 350 plant species, 5 animal dyes, and 11 mineral pigments arranged in alphabetical order of their chemical names. The book is mainly focused on sources of natural colors of Indian subcontinent. It will be useful for students, teachers, scientists, researchers, industrialists like textile, food, pharmaceutical, cosmetics, etc.
Dr. G.P. Phonke, former Director, CSIR-NISCAIR, conceptualized the idea to bring out a book on natural dyes and pigments. He bestowed his faith in the senior author of this book for this task. We are thankful to him for this. The authors are grateful to Prof. B. R. Chauhan, Department of Textile Engineering, IIT, Delhi, and Prof. C.R. Babu, former Pro Vice Chancellor, Delhi University, Delhi, for going through the manuscript and providing their valuable suggestions for the improvement of the book. The authors also want to express their thanks to Dr. M. V. Viswananthan, former head, Raw Materials Herbarium and Museum Delhi (RHMD), for his critical comments and valuable suggestions. We also express our gratitude to Dr. Anand Kumar and Dr. Anant Kumar, Botanical Survey of India, Kolkata, and Dr. Rajesh Kumar, Bareilly College, Bareilly, U.P., for providing good photographs of Acacia catechu, Curcuma amada, Haldina cordifolia, Mallotus philippensis, Persicaria hydropiper, Rumex dentatus, Terminalia chebula, and Equisetum arvense. We are grateful to Dr. G.V.R. Joseph, Assistant Director, Central Council for Research in Ayurvedic Sciences (CCRAS), New Delhi, for providing photograph of Crocus sativus L. printed on the cover page. We are also thankful to all those who, directly or indirectly, have contributed towards the completion of this book.
Ever since pre-historic time, man has been fascinated to color the objects of daily use employing inorganic salts or natural pigments of vegetable, animal, and mineral origins. These coloring substances, known as dyes, are the chemical compounds used for coloring fabrics, leather, plastic, paper, food items, cosmetics, etc., and to produce inks and artistic colors. Dyes are of two types, i.e. synthetic and natural. Synthetic dyes are based on petroleum compound, whereas natural dyes are obtained from plant, animal, and mineral matters.
Natural dyes are always preferred because of their brightness, soothing and non-toxic nature. But after the advent of synthetic dyes by William Henry Perkin in 1856, the use of natural dyes has gradually gone out of existence from most part of the world. However, natural dyes are traditionally used in certain parts of India despite synthetic dyes insurgency. Lately, people have come to realize the toxic effects of synthetic dyes, especially the azo dyes and Benzedrine derivatives. They release harmful amines, allergens, carcinogens, and other poisonous compounds that caused cancer, allergy and are detrimental to human health and environment. Consequently, many developed countries of the world have imposed a ban on the import, stock, and sale of commodities manufactured from such azo- and Benzedrine-based dyes that came into effect from April, 1996. Therefore, no textile, leather or food products which contain azo or Benzedrine based dyes are to be found in the markets of America, Canada or other Western countries. As a result, the countries’ manufacturing and exporting azo based products are losing its sizeable export earnings.
Moreover, to preserve public health and to protect the environment, the Union Ministry of Environment and Forests, Government of India, has also imposed a ban through a gazette notification on manufacturing and using of 118 azoand Benzedrine-based dyes from June 23, 1997. Furthermore, 38 pigments of this category have also followed suits in April 1998. Therefore, it has become imperative to revert to the natural dyes as these dyes are said to be userfriendly and eco-friendly and are harmless to health and environment.
India is harboring enough potential raw materials for manufacturing natural dyes. It is believed that out of 47,000 plant species occurring in India, coloring matters. Besides animal and mineral, raw materials are also available in abundance in India for obtaining natural dyes. Thus there are enough natural resources in India for manufacturing natural dyes, provided that they are judiciously and efficiently exploited.
There is a belief that natural dyes are fugitive and do not produce brilliant and deep shades as synthetic ones. It may be because the natural dyes have been used in the crude form. The crude extract may be a mixture of several coloring matters. So that each coloring matter gives its own hue. Therefore, the color of the natural dyes may not be as brilliant and deep as synthetic one, which is based on a single chemical compound. For example, the natural indigo contains indigotin, indrubin, indigobrown, an amorphous substance of under mined constitution, gluten, the flavonol kaempferol (indigo yellow), and mineral matters. Because of this composition, the natural indigo does not produce as brilliant and deep color as that of synthetic indigo, which in contrast is a hundred percent pure indigotin. Similarly, the crude extracts of the roots of the madder (Rubia cordifolia L.) contains about 19 anthraquinone pigments in which alizarin, purpurin, and pseudopurpurin are the major coloring matters. If these coloring matters are not separated, each and every coloring matter produces its own hue. Therefore, the crude extracts of the plant should be subjected to isolation of principal coloring matter in pure form using modern methods of analytical chemistry such as spectroscopy, and chromatography. The coloring matter, thus obtained, would be in no way inferior in shade, depth, tone, etc., to the synthetic one.
Considering the similar approach in mind, the Indian Institute of Technology, Delhi, and Forest Research Institute, Dehradun, have developed a technology for manufacturing natural dyes from vegetable raw materials. By using the same technology, Alps industries of India has set up the world’s first vegetable dyes manufacturing unit at Sahibabad, Uttar Pradesh, India, with collaboration of Park. B. Smith Inc., USA.
Keeping the above view in mind, the present book has been written. Hope this would fulfill the aspirations and needs of the industrialists, entrepreneurs, traders, researchers, students, and those who are interested to acquire knowledge in natural dyes.