1

S. Lakshmi Manokari

INTRODUCTION

Colour is everywhere; the clothes we wear, our surroundings are abundant with Colour. Colour is one of the key aspects by which the consumer judges the quality of textiles. So knowledge of dyeing will be helpful for the practioners of textiles. This module provides information about history of dye, evolution of synthetic dye, dyeing terminologies and classification of dyeing.

LEARNING OBJECTIVES

To get an overview of history of dyeing To Understand the Dyeing terminologies To Know the broad classification of dyes

HISTORY OF DYEING

Dyeing is colouring that imparts beauty to Clothing. It is a very old art since time immemorial. This attraction continued through the Egyptian, Greek and roman eras and grown up to the present day. From the very earliest times man desired to colour the fabrics from natural products such as Brazil wood, logwood, kermes, lac insect, cochineal, Persian berries and madder.

3.1. Archaeological evidences of Textile dyeing

There are some evidences excavated by archaeologists’ which reveals that textile dyeing dated back to the Neolithic period. Ochre a red dye from Iron ore was found in excavation at Çatalhöyük in southern Anatolia. Fragments of earliest textile were kept at Museum of Anatolian Civilizations, Ankara, Turkey. It is understood that the natural dyes were used by Chinese 5000 years ago. Cotton fabrics dyed with madder were found in Mohenjo-Daro an archaeological site which is now Sindh, Pakistan. In Sanskrit, this plant name is Manjistha. It was found that Saffron dyed clothes were worn by Hermits. Insect dyes such as Tyrian purple and kermes and plant-based dyes such as woad, indigo and madder were key elements of commerce of Asia and Europe.

EVOLUTION OF SYNTHETIC DYES

Efforts have been made in ancient times to extract dyes from brightly coloured plants and flowers but most attempts failed because most natural dyes are not highly stable, limited colours, crude methods of extractions. These limitations of natural dyes led to the development of synthetic dyes which dominated the market by 1900. Sir William Henry Perkin was an English chemist discovered a new compound Mauveine which produced a purple dye while he was preparing quinine, the anti malarial drug at the age of 18. Perkin, who had an interest in painting, carried out further experiments with his friend and his brother. Their first experiments indicated that it dyed silk which was stable when washed or exposed to light. They sent some samples to a dye factory in Perth, Scotland and received a very hopeful reply from the company. At the age of 18 Perkin filed for a patent in August 1856. At the time, all natural dyes were expensive, labor-intensive, lacked fastness. The colour purple, which had been a mark of royalty since ancient times, was expensive and difficult to produce and so Perkin and his brother realized that they had discovered a possible alternative whose production could be commercially successful

DYEING TERMINOLOGIES

1. Dye

Dye is a natural or synthetic substance that affix colour to textiles, paper, leather and other materials. When the dye is applied to a substrate, it must be fast to washing, dry cleaning, perspiration, light and heat. Dyes are molecules which absorb and reflect light at specific wavelengths to give human eyes the sense of colour. Permanence of dyes depends upon the chemical structure of the fibre and the type of dye used. There are two types of dyes – natural and synthetic dyes. The natural dyes are extracted from natural substances such as plants, animals, or minerals. Synthetic dyes are made in a laboratory.

5.2. Pigment

Pigments are water insoluble colouring material mostly from mineral origin and used for colouration of metal, wood, stone and textile materials. The insoluble coloured particles are held on the surface of the fabric with a binding agent. The application of dye and pigment will be different. The dye is applied in the form of a solution whereas the pigment is applied in the form of a paste

5.3. Dyeing

Dyeing is the method of colouring textile materials by immersing them in a solution of dye called dye liquor. The dye liquor consists of dye, water and an auxiliary. To improve the effectiveness of dyeing, heat is applied to the dye liquor. Dyeing can be done at fiber, yarn, fabric and garments stage. The temperature and time should be controlled during dyeing. Excellent Colour fastness depends upon two aspects- selection of proper dye and selection of the method for dyeing the fiber, yarn or fabric.

5.4. Difference between Pigment and Dyes

The term dye and pigment are interchangeable, both dyes and pigments are powerful colourants. The Basic difference between them is that dyes get dissolve in the substrate, while pigments tend to leave residues. The differences are shown in Table-1

5.5. Dye Affinity

Attraction between the dye and fibers is called dye affinity. In simple terms, dye affinity is the dye absorbing capacity of textile fibers, yarn and fabrics. A number of factors are involved in this process, e.g. dye liquor ratio, dye physical and chemical characteristics, dyeing auxiliaries used, time, temperature and Quality of dyes

5.6. Binder:

It is a material like a gum nearly colourless that is used to attach a pigment

5.7. Mordant:

It is a chemical that helps the binding of dye or dyestuff to the fibers for both fiber and dye

5.8. Fastness:

These are the properties of the dyes which indicate the tolerance of the dyes on the fiberstowards the action of various foreign agencies like light, washing, heat, rubbing and perspiration. That means the dyed or printed fabric for example garment, curtains, fabrics should not fade or change its colour

6. CLASSIFICATION OF DYES

Common classifications of the dyes are based on the sources from which it is taken. They could be classified as: Natural and synthetic dyes (Figure-1) Natural dyes are classified into 1. Plants 2. Animal 3. Mineral 4. Microbes and FungusSynthetic dyes are classified into 1. Direct, 2. Vat, 3. Sulphur, 4. Azoic, 5. Reactive, 6. Acid, 7. Disperse, 8. Basic 9. Mordant

6.1. Natural dyes

Natural dyes are dyes derived from plants, animals or minerals. The luxury dye of the ancient world was Tyrian purple or royal purple, Indigo was highly prized for its colour and light fastness, Kermes carmine was used as a dye and a pigment in ancient Egypt, Greece, and the Near East and is one of the oldest organic pigments, Madder has been cultivated as a dyestuff since antiquity in central Asia and Egypt, where it was grown as early as 1500 BC.

6.1.1. Plant origin:

The majority of plant natural dyes are from vegetables. Different parts of plants are used to make dyes, for example, the leaves, the skins of fruit, the bark, roots or wood (Table-2)

6.1.2 Animal origin: Insects were the main source of natural dyes of animal origin and most of these provided red colours. The most highly prized ancient dyestuff and one concerning with much interest has always been felt, was the so called Tyrian purple. This was obtained from the juices of certain species of snails found in the water of Mediterranean Sea .

The dye Tyrian purple is extracted from Sea snails and shell fishes which gives violet colour The Carmine dye is from Cochineal-Insect which gives Crimson red The Kermes dye is from Kermes ilicis which gives Red The Lac dye is extracted Kerria lacca which gives Scarlet

6.1.3. Mineral origin

Natural pigments are found in rocks and soils. Mineral dyes such as Ochre, Malachite, Manganese, Cinnabar, Azurite, Minium, Aragonite, Ultramarine blue are extracted from different minerals which are listed in the Table-3

6.1.4. Microbial and Fungal Origin

1. Lichens

Lichens are plant like that grow on bark, leaves, rocks, roofs and walls. They produce dyes for textiles There are many colours of lichens that make dyes. They are a mutualistic symbiosis. The plant body consists of two quite different organisms together in an intimate association; a fungus and a microscopic green plant, an alga. Lichen dyes are substantive, meaning no mordant is needed.

Mushrooms

Mushrooms can be used to create colour dyes with a solvent. Mushroom dyes are simple to extract and yield a wide range of bright, fast colours.

6.2. SYNTHETIC DYES

Direct or substantive dyes

Application is simple, Available in full colour range, Moderate colour fastness, It has affinity for cellulosic fibres.

Vat dyes

These are insoluble in water and an important dye for dyeing and printing on cotton and other cellulosic fibres. These cannot be used on silk and wool. The dyeing in this case is a continuous process and is carried out in large scale called vat. For this reason these dyes are termed as vat. The vat dye has excellent fastness properties to washing, light, perspiration, chlorine and rubbing.

Sulphur dyes

Sulphur dyes are most commonly used dyes, manufactured for cotton in terms of Volume They are cheap, generally have good wash-fastness, and are easy to apply. They are like vat dyes, brightly coloured, water insoluble, have to be converted to water soluble, before application to textile materials. Sulphur dyes are predominantly used for black, brown and dark blue.

Azoic dyes

They are not ready made dyes. These are supplied as napthols and bases. Method of application is complex. Comes with Limited colour range. Azoic dyes produce bright or brilliant colours such as deep reds, violet, yellows and oranges. They have excellent colourfastness to washing and have good to poor light and chlorine fastness. Suitable for cellulosic fibers 5. Reactive dye

These dyes are soluble in water. There are two types of reactive dyes-Hot and cold method, cold dyeing is used in batik printing, Not Suitable for synthetics. It has excellent fastness to laundering, crocking and dry cleaning

Acid

Commonly used for Silk, wool, nylon and modified acrylic. It has no affinity for cotton celluloses. Acid dyes are water soluble, and have better light fastness than basic dyes.

Disperse

Disperse dyes are water insoluble dyes that dye synthetic polyester and acetate fibres and sometimes nylon and acrylic fibers. These are non-ionic dyes having low molecular weight. It dissolves in organic solvents. There is a uniform dyeing but limited to pale shades. Require skill in application

Basic

The most brilliant dyes among all synthetic dyes are found in this class of dyes. However they have poor light fastness (they fade in sunlight quickly) Basic dyes have direct affinity for wool and silk but not unmordanted cotton. For dyeing cotton the basic dyes require a mordant such as tannic acid or some synthetic organic substances 9. Mordant dyes

Before the development of synthetic dyes, it was found that dyeing of wool becomes wash fast with the addition of some metallic salts. These salts were named as mordants.The word mordant is derived from the from French word ‘modre’ which means to bite. A mordant is an acidic or basic salt of chromium, iron, aluminium or tin, which helps through penetration of colour into fabrics. The dye that has affinity for one type of fibre may not have affinity for another type of fibers. This problem can be overcome by the use of mordants. There are three methods of mordant dyeing, namely,1. Chrome method, 2. Meta chrome method, 3. After chrome method.

OTHER IMPORTANT DYES

A number of other classes have also been established, based among others on application that includes the following:

Leather Dyes: Leather dyes are usually azo-aniline group dye that fix firmly to the leather Optical Brighteners: It is used for textile fibers and paper. They are fluorescent whitening agents that are colorless to weakly colored organic compounds. It was discovered in 1929 by

Krais, the whiteness of viscose rayon and semi bleached flax yarn was increased by treatment with an aqueous solution of esculin and drying. Esculin was obtained by extracting horse chestnut bark
Fluorescent Dyes: A very innovative dye. Fluorescent dyes have the important property of absorbing in the UV range and emanating in the visible range of the color spectrum. The main use of fluorescent dyes is in the coloration of synthetic fibers like polyester, polyamide and acrylics especially for sportswear use.
Sublimation Dyes: It is used in digital printing that gives strong light fastness characteristics. The dyes can potentially use to print textiles for commercial, architectural or outdoor application.

CONCLUSION

Dyeing is the craft of imparting colors to textiles by treatment with a dye. Throughout history, people have dyed their textiles using natural dyes. Plant-based dyes such as woad, indigo, saffron, and madder were raised commercially and were important trade goods in the economies of Asia and Europe. In 1856 the whole art and dyeing was completely revolutionized by the discovery of the artificial dyestuff named mauveine. This discovery of Synthetic dyes superseded natural dyes for the commercial textile production. Still natural dyeing techniques are preserved by artisans in traditional cultures around the world.

you can view video on Introduction to Dyeing

WEBLINK: