Weekly Publication of

Cotton Association Edited & Published by Amar Singh

of India 2020-21 No. 11 25th August, 2020 Published every Tuesday

Cotton Exchange Building, 2nd Floor, Cotton Green, Mumbai - 400 033 Phone: 3006 3400 Fax: 2370 0337 Email: [email protected] www.caionline.in

Cotton - A Living Art

Dr. T.R. Loknathan has a Ph. D. in plant breeding. is quite ancient, existing in many civilizations. He is currently working as a Principal Scientist in With the development of yarn, fabric and cloth- the Division of Crop Improvement at ICAR-CICR, making, dying became more popular as plain white gained an ornamental Nagpur. He is pursuing his research value once they were coloured. on genetic enhancement of cotton. History of Dyeing Introduction The word originated in the There is always a certain amount 12’th century AD and is derived of colouring matter prevalent in from middle English ‘diei‘ and the form of endochrome (colour from the ancient English ‘dag’ imparting organelle) located in and ‘dah’. The primary source the walls of the fibre immediately of has been natural dyes surrounding the inner extracted from plants, cavity or lumen. In animals and insects Egyptian cotton it is since ancient times. more pronounced, assuming a reddish Dyes have been brown or golden prevalent in old colour. It turns whiter in colour when exposed to civilizations viz., Peruvian (red dye), Indus sunlight and darker when exposed to moist heat Valley civilization (indigo) in Mohenjo-dharo, like the steaming process involved in doubling. Harappan remains (purple, etc). Dr.Schunk, after a careful examination of the colouring matter associated with the Egyptian Plant extracts used as dyes were common and East Indian cotton, noticed two kinds, one from plants like madder, woad (northern indigo, of which is readily soluble in alcohol which he indigo (tropical woad) American logwood, called A and the other soluble in boiling water, Brazil-wood (source of most of the dyes in the which he termed B. middle– ages). The American Quercitron barks gave the colour yellow. Various shades of the These natural colour manifestations were same colour are produced from various barks limited and man the need to resort to artificial creating variegated shades. Basically, four colouring. Dyeing is the application of dyes colours viz., Red, blue, yellow and brown are in (colouring matter) to the yarns, fabrics, cloths existence. The combination of these four colours and attain . The practice of dyeing create various patterns and shades. 2 25th August, 2020 Cotton Statistics & News

Insect Dyes: These are extracts from insects The essential process of dyeing has changed a like Cochneal , (mostly used in Europe), little over time. The dyeing material is put in a pot and also fish dyes used in Byzantine during of water for extraction. The to be coloured ancient times. is added to it and a slight heat is applied till you get the desired result. may be added The earliest known dyeing of flax fibres to achieve colour fastness. The dyeing can be was discovered in an ancient prehistoric cave achieved depending on the dye in various fibre in the Republic of Georgia which dates back to processing stages. Dyeing can be done before 34000 BC. More evidence of textile dyeing in spinning or (dyeing of wool), after the Neolithic period was discovered in the city spinning ((yarn dyeing) and dyeing in pieces of Catalhuyk in Southern Anatolia as traces of (fabric). red dye (ochre), an iron oxide pigment obtained from clay. In China, dyes extracted from plant Dyeing may be done to the entire fabric or parts, barks and insects have been in use for 5000 in patches on the fabric by printing. Printing years. Early evidence from the Sind province in application is achieved by block printing, an Pakistan - cotton dyed with a vegetable dye - was ancient art practised by skilled artisans endowed found in Mohenjo-dharo remains (3rd millenium with a hereditary legacy. It is a process creating B.C.). This colour was obtained from madder and patterns on textiles, selective dyeing on textile, in combination with a blue dye obtained from not the whole of it. Some of the traditional indigo was introduced to other regions through Navajo printing still exist in USA. Block printing trade. is widely prevalent in various parts of India, like Jaipur in Rajasthan and kalamkari printing Cochneal dyes and Kermes from insects and in . Few people have come and plant dyes like woad and madder were part of learnt the art of Jaipur block printing emerging the main economies of Asia and Europe until as able textile designers in USA. The few artisans the discovery of synthetic dyes in the mid -19th still remaining are dwindling in numbers, century. Types of dyes: The first synthetic dye was William Perkin’s These are classified as Natural dyes and mauveine in 1856 followed by another important Synthetic dyes based on their origin. synthetically designed dye duplicating red dye from madder. another dye obtained from Natural dyes: coal tar was designed in 1869. The advent of these These are obtained from vegetable and synthetic dyes led to the collapse of the art of plant parts like roots, berries, barks, leaves and dyeing with natural dyes in the textile economy of wood; Cochneal insects and Kermes and other Britain and Europe in the mediaeval times. With biological matter like fungi. Natural mordants the rising domination of the commercial dyeing ((used as colour fixatives or colour binders processes, began the decline of the art of dyeing to the fibre) like tannins are derived from oak and the numbers of skilled artisans practising the galls, pigments and a wide range of other plant ancient art block print also dwindled. parts; pseudo-tannins like plant-derived oxalic acid and ammonia from stale urine. Plants that Concept of Dyeing: bio-accumulate aluminium have been used like Dyeing is the application of colours or club mosses. Symplocus genus used for dyeing pigments to textile fibres, yarns or fabrics, are an endangered species in Europe. Plant dye ensuring an element of colour fastness. It is done producing plants like woad, indigo, and by using a chemical solution where the fibre madder, etc. have been in cultivation since ages expresses affinity depending on the dye and in the commercial trade economies of Africa, particular chemical material. Dyeing is achieved Europe and Asia and America. by absorption, diffusion and bonding of the pigment in the fibre, depending on time and Many available local dyestuffs have temperature. The bond may be strong or weak been used in different places. Some scarcely depending on the dye or chemical used. available dyes from natural invertebrates, Cotton association of india 25th August, 2020 3

plants (Haematoxylum campachianum.), Tyrian plants, their geography and the blue and Kermes (crimson red) are valued as native craft dyers (tribes as stakeholders : luxury ones due to their brilliant colour and permanence. The natural dye colours like red and pink, yellow, blue, purple, violet, green, brown, black Mordants are often used with Natural dyes. are distributed in many diverse species, genera of the word originates from the Latin invertebrates, plants, animals, insects, lichens, etc. word ‘mordere ‘ meaning to bite and improves These diverse genera are to be found in different colour fastness. Mordants are metal salts which ecological regions. The diverse dye producing form stable molecular complexes with natural plant species within a genera are endemic to these dyes and natural fibres. Most commonly used regions. Ancient dyeing techniques were practised mordants are alum (a metal salt, potassium by the natives inhabiting the region. These native aluminium silicate) and iron (ferrous sulphate). tribes flourished in their art of dyeing and block But many other metal salts in use earlier have printing (creating patterns) and the local textile now been abandoned due their toxic nature and industries developed, taking on the distinctive ecological health. Many non - metal mordants characteristic of their respective domestic regions. like pseudo - tannins were also used as apt These local textile industries continued to flourish binders to these dyes. in the mediaeval 18th century till the entry of the synthetic dyes. In natural dyes there are ‘fast’ dyes which bind very strongly to the molecular structure Some of the plant species cited here like of mordant and fibre. Another group are the madder, alkanna, indigo, dyer’s broom, Juglans, ‘fugitive’ dyes which do not bind and fade away ochre, logwood , Brazil wood, many more species after being treated with the fibre. Natural dyes like lichens, molluscs, snails, lac insects, Cochneal are obtained from all berries, beets, cabbage, have been explored. Some are widespread and spinach and most of the flowers (although a few some are endemic. The native tribes, like, Navajo flowers are used as natural dyes). basket and rug weavers, Japanese printers, European craft dyers, Indonesian cloth Common natural dyestuff has been obtained weavers, native Indian craft dyers (Jaipur block from various dye yielding plants belonging printers, Ponduru craft dyers, Himalayan madder to different genera and species distributed in dyers, etc), flourishing in Asia have all put the tropical, sub- tropical and temperate regions in dyeing industry on the global map. diverse geographical habitats, spread across the continents of both the New and the old words. Different fibres require different mordanting. They have flourished within various tribes in They are broadly classified into two categories. different countries as craft weavers (ancient dyeing art preservers). 1. Cellulose fibres: Cotton, , hemp, ramie and . The natural dyestuff in existence were red, pink, blue, purple, brown, black, green, yellow, 2. Protein fibres: Angora, wool, , pink, etc. Each of them was characteristic cashmere, , soy, leather and suede. and manifested in diverse plant species. A combination of few produced diverse shades Both the fibres require different mordants for practised since ages. dyeing due to their differing molecular structures, differing in their binding abilities. Cellulose fibres The various natural colour dyes viz. Red and have less affinity for dyes as compared to Protein pink, yellow, orange, blue, purple, green, brown, fibres. The best thing for a cellulose fibre is to first black are manifested in different plant species use tannin and then add alum. and different genera distributed across the world (To be continued...) in diverse habitats. These have been utilised by a diverse sect of craft dyers of differing ethnicity (The views expressed in this column are of the in different parts of the world. author and not that of Cotton Association of India) ------4 1st September, 2020 COTTON STATISTICS & NEWS Cotton Dyeing - A Living Art Contd. from Issue No. 11 dated 25th August, 2020

Dr. T.R. Loknathan has a Ph. D. in plant breeding. The binding of the dyes to the fibres are based on He is currently working as a Principal Scientist in solubility and chemical properties of the chemical. the Division of Crop Improvement at ICAR-CICR, Acidic dyes: These are mostly the water-soluble Nagpur. He is pursuing his research anionic dyes which combine with on genetic enhancement of cotton. the cations of the fibres resulting in a dyed fibre. Some popular natural dyes prevalent amongst craft dyers and These dyes are used for dyeing fashion industry are: of wool, silk, and mostly modified acrylic fibres in a neutral Animal based - or acidic bath. Acidic dyes are not cellulosic in nature. Examples are 1. Cochneal insects (red). aniline, alizarin pure blue 88, etc. 2. Cow urine (Indian yellow) 3. Lac insect (red and Basic dyes: These violet) dyes are water- 4. Murex snail (purple) soluble cationic mostly 5. Octopus / cuttle fish combining with salts. (sepia brown) They are mostly applied to nylon fibres. Plant based – 1. (brown) Dyes have been further classified into various 2. Gamboge tree resin (dark mustard yellow) types based on their mode of action on fibres. 3. Chestnut hulls (peach to brown) 4. Himalayan rhubarb root (bronze and yellow) Direct or substantive dyes: 5. Madder roots (yellow and orange) Direct dyes are basically treated in a neutral 6. Indigofera leaves (blue) or slightly alkaline bath using potassium chloride 7. Kamala seed pods (yellow) or potassium sulphate or potassium carbonate. 8. Mangosteen peel (green, brown, dark brown, These are used for treating cotton, paper, leather, purple, crimson) nylon, etc. They are also used as pH indicators 9. Myrobalan fruit (yellow, green, black, source of and biological stains. tannin) 10. Pomegranate rind (yellow) Mordant dyes: 11. Teak leaf (crimson to maroon) 12. Weld herb (yellow) These dyes require mordants which 13. or black walnut hulls (brown, improve colour fastness against water, light and black source of tannin) perspiration. Natural dyes are mostly mordant 14. Rhus typhina or Sumac tree (brown, source of dyes which have been described a lot in history. tannin). Thirty percent of the mordant dyes or chrome dyes are used for wool especially for black and Many hundreds of mordants are being used with navy shades. The choice of the correct mordant many dyes resulting in viable dye combinations. is very important as different mordants can The traditional craft dyers prefer natural dyes since change the final colour. The mordant potassium they are multi - coloured and permanent in nature, di - carbonate is added after dyeing. Most of unlike the single coloured synthetic dyes. the metallic mordants of a slightly heavy metal category are hazardous chemicals. 2. Synthetic dyes: These are known as coal -tar dyes, since they were mostly produced from coal- Vat dyes: tar in earlier years. They are organic molecules These dyes are insoluble in water and are synthesised artificially to suit the various fibres. incapable of dyeing. However, the reduction in They are of single colour types and more of a alkaline liquor often produces a water- soluble permanent nature. They are mainly of two types alkaline salt solution. This takes the form of a - acidic dyes and basic dyes - in a broader sense. colourless solution. Hence it is known as leuco dye. COTTON ASSOCIATION OF INDIA 1st September, 2020 5

It has an affinity with the textile fibre. Subsequent The essence of theory of dyeing revolves oxidation reforms the original insoluble dye. The around the fact why and how the desired reflecting iconic blue colour of the is due to indigo, surface is obtained or by what we really mean as the original . fixation of colour on various fibres and fabrics.

Reactive dyes: But this has become a matter of controversy These dyes utilise a chromophore substituent over a period of time. It was thought by some which gets attached to the substrate of the fibre. chemists that there is a true chemical combination The covalent bond of the formed between the colouring matter and the fibre and makes the dye the most permanent and stable this occurs in equivalent proportions. Others amongst the dyes. Cold reactive dyes viz., believed that the combinations arise from a special MX, Cibacron F are easy to handle since they work action in which the usual chemical proportions at room temperature. Reactive dyes are best used equivalent are not obtained by the catalytic action at home or at art studios. of the fibres. While some were of the opinion that chemical action had little to do with the matters Disperse dyes: and colours are fixed upon or within the surface of the bodies by molecular attraction alone; others These dyes are specifically used to dye were vehement in their belief that the absorption cellulose acetate. They are used along with is altogether mechanical and the colouring matter dispersing agents. They are ground into a powder is absorbed into the pores and cells of the fibres and used as a paste. They can also be used to dye and held there simply as a pigment. nylon, cellulose tri-acetate and acrylic fibres. Their main use, however, is to treat . A dyeing After all these debates, three theories viz., temperature of 133 degrees Centigrade (266 Mechanical theory, Chemical theory and Chemico- degrees Fahrenheit) is required and a pressurised Mechanical theory were propounded. These have dye bath is used. The very fine particle size, been described in detail in the book, ‘Textile provides a large surface area which helps to Fibres’ by J.F. Barker in the 1920s. dissolve and allow uptake by the fibre. The dyeing rate can be influenced by the dispersing agent Recent Research Trends used in grinding. After a decade of research, Eric Leite Pados Azoic Dyeing: This is a technique in which and his group has recently come up with new an Azo dye, an insoluble dye is formed onto or findings that natural red pigments like betalains within the fibre. This is achieved by the combined in beetroots can be changed to blue by changing use of diazoic and coupling components. the molecular structure of carbon bonds. This Appropriate bath adjustments with the reaction exciting new research could open the door for the of the two components will result in an insoluble advent of new pseudo-synthetic dyes, that have azo dye. This is a unique dye as the final colour been obtained by changing the pathways of the is dependent upon the choice of the diazoic and natural pigment processes. coupling components. The use of this technique for dying cotton is declining due to the toxic Knowledge of natural dyes and research nature of the chemicals used. in search for new dyes could help evolve a new range of textile fibres by going back and referring Sulphur dyes: to ancient dyeing history. This will enable the dyeing profession to continue to live its heritage These dyes are used in cotton to give dark and preserving the diverse ethnicities of the world. colours. This dye is made by heating the fibre in a solution of organic compound, a nitrophenol a Some of the books that give an exhaustive and nitrophenol derivative and a polysulphide. The detailed account of ancient dyeing history are as sulphide produces a dark colour. Sulphide Dark follows: ‘Textile Fibres’ by Mathews (1929), ‘The black is a popular dye selling widely, though it Structure of Cotton Fibre ‘ by Bowman( 1908 ) and does not have a well-defined chemical structure. ‘Textile Fibres ‘ by J.F. Barker.

Theory of Dyeing. (The views expressed in this column are of the The properties attributing to the expression author and not that of Cotton Association of India) of dyes are the nature of colour (as revealed by the reflection of light on the cotton fibre); ------polychromatic light or monochromatic light, nature of dyeing, conditions of dyeing, importance of investigation and simple and compound dyeing.