**Dyeing of Textiles with Natural Dyes**

Ashis Kumar Samanta and Adwaita Konar

*Department of Jute and Fibre Technology, Institute of Jute Technology, University of Calcutta India* 

#### **1. Introduction**

14 Will-be-set-by-IN-TECH

28 Natural Dyes

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(in Japanese).

Textile materials (natural and synthetic) used to be coloured for value addition, look and desire of the customers. Anciently, this purpose of colouring textile was initiated using colours of natural source, untill synthetic colours/dyes were invented and commercialized. For ready availability of pure synthetic dyes of different types/classes and its cost advantages, most of textile dyers/ manufacturers shifted towards use of synthetic colourant. Almost all the synthetic colourants being synthesized from petrochemical sources through hazardous chemical processes poses threat towards its eco-friendliness.

Hence, worldwide, growing consciousness about organic value of eco-friendly products has generated renewed interest of consumers towards use of textiles (preferably natural fibre product) dyed with eco-friendly natural dyes. Natural dyes are known for their use in colouring of food substrate, leather as well as natural fibres like wool, silk and cotton as major areas of application since pre-historic times. Although this ancient art of dyeing textiles with natural dyes withstood the ravages of time, but due to the wide availability of synthetic dyes at an economical price, a rapid decline in natural dyeing continued. However, even after a century, the uses of natural dyes never erode completely and they are being still used in different places of the world. Thus, natural dyeing of different textiles and leathers has been continued mainly in the decentralized sector for specialty products besides the use of synthetic dyes in the large scale sector for general textiles/apparels.

Recently, most of the commercial dyers and textile export houses have started re-looking to the maximum possibilities of using natural dyes for dyeing and printing of different textiles for targeting niche market. Natural dyes produce very uncommon, soothing and soft shades as compared to synthetic dyes. On the other hand, synthetic dyes, which are widely available at an economical price and produce a wide variety of colours, sometimes causes skin allergy and other harmfulness to human body, produces toxicity/chemical hazards during its synthesis, releases undesirable/hazardous/toxic chemicals etc.

For successful commercial use of natural dyes for any particular fibres, the appropriate and standardized techniques for dyeing for that particular fibre-natural dye system need to be adopted. Therefore to obtain newer shade with acceptable colour fastness behaviour and reproducible colour yield, appropriate scientific dyeing techniques/procedures are to be derived. Thus, relevant scientific studies and its output on standardization of dyeing

Dyeing of Textiles with Natural Dyes 31

ix. Some of its constituents are anti-allergens, hence prove safe for skin contact and are

xii. Natural dyes are usually moth proof and can replace synthetic dyes in kids garments

Despite these advantages, natural dyes do carry some inherent disadvantages, which are

i. It is difficult to reproduce shades by using natural dyes/colourants, as these agroproducts vary from one crop season to another crop season, place to place and species

ii. It is difficult to standardize a recipe for the use of natural dyes, as the natural dyeing process and its colour development depends not only on colour component but also on

iii. Natural dyeing requires skilled workmanship and is therefore expensive. Low colour yield of source natural dyes thus necessitates the use of more dyestuffs, larger dyeing

iv. Scientific backup of a large part of the science involved in natural dyeing is still need to

v. Lack of availability of precise technical knowledge on extraction and dyeing techniques.

vii. Nearly all-natural dyes with a few exceptions require the use of mordants to fix them on to the textile substrate. While dyeing, a substantial portion of the mordant remains unexhausted in the residual dye bath and may pose serious effluent disposal problem. viii. With a few exceptions, most of the natural dyes are fugitive even when applied in conjunction with a mordant. Therefore, sometimes their colour fastness performance

Natural dyes can be classified (Gulrajani & Gupta, 1992) in a number of ways. The earliest classification was according to alphabetical order or according to the botanical names. Later, it was classified in various ways, e.g. on the basis of hue, chemical constitution, application

a. In "treatise on permanent colours" by Bancroft, natural dyes are classified into two groups: 'Substantive Dyes' such as indigo, turmeric etc. which dye the fibers directly and 'Adjective Dyes' such as logwood, madder etc. which are mordanted with a

b. Humme classify the colouring matter as 'Monogenetic Dyes', those produce only one colour irrespective of the mordant present on the fibre or applied along with the dye and 'Polygenetic Dyes', those produce different colour with different mordant applied,

c. In the colour index the natural dyes are classified according to the hue (Predominating

colour). The number of dyes in each hue are as follows in table-1:

vi. The dyed textile may change colour when exposed to the sun, sweat and air.

x. Some of the natural dyes are enhanced with age, while synthetic dyes fade with time. xi. Natural dyes bleed but do not stain other fabrics, turmeric being an exception.

mostly non-hazardous to human health.

responsible for the decline of this ancient art of dyeing textiles.

**3.2 Limitation/ disadvantages of natural dyes/ colouants** 

time and excess cost for mordants and mordanting.

ratings are inadequate for modern textile usage.

**4. Classification of natural dyes/ colouants** 

and food-stuffs for safety.

to species, maturity period etc.

materials.

be explored.

class etc.

metallic salt.

e.g., alizarin (Dedhia, 1998)

methods, dyeing process variables, dyeing kinetics and test of compatibility of selective natural dyes have become very important, however the information on which is insufficient. That is why, this chapter is very much relevant to the current need of the textile dyers. An attempt has been made here to give scientific overview on dyeing of textiles with natural dyes and related issues.
