Natural Dyes ( Kyun Ki)

In Hindi Kyun Ki means “because”.

According to scientists, textile production using synthetic dyes is one of the most polluting of all industrial sectors and is considered the second-largest source of water pollution in the world after agriculture.

Rinse water from the dyeing process is still blamed for contaminating many of India’s rivers

Natural dyes have an older, more romantic heritage. Indigo, the most commonly known natural dye, is traced back to the days of ancient India’s Indus river valley civilization.

The use of natural dyes on cotton was India’s unique gift to the world,

Natural Dye sources are not only biodegradable but also have

medicinal properties

Definition of a Natural Dye

Natural dyes are dyes or colourants derived from plants, invertebrates, or minerals. The majority

of natural dyes are vegetable dyes from plant sources- roots, berries, bark, leaves, and wood

and other organic sources such as fungi and lichens.

Classification of Natural Dyes

Natural dyes can be classified: in a number of ways. The earliest classification was in

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 class etc.

Natural dyes are classified into two groups:

1 ‘Substantive Dyes’ such as indigo, turmeric etc. which dye the fibres directly and

‘Adjective Dyes’ such as logwood, madder etc. which are mordanted with a metallic salt.

2 ‘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

On the basis of hues, natural dyes can be classified as follows:

i. Red colour dyes: most red dyes are hidden in roots or barks of plants. They are almost invariably based on anthraquinone and its

derivatives. These dyes are stable to light and washing.

ii. Yellow colour dyes: Yellow is the liveliest and perhaps the most abundant of all hues in

nature. About 90% of the yellow dyes are flavonoids-Generally, they produce pale shade with quicker fading except for turmeric, which produces a dull deep shade but are considered to be susceptible to light as they emit fluorescence. Wash fastness rating of natural yellow dyes

ranges from fair to excellent, e.g., tesu, turmeric, Kapila.

iii. Blue colour dyes are indigo and woad and give excellent fastness to light and washing. 

iv. Black colour dyes: Black shades, generally obtained from rich plant

natural dyes and are appreciably substantive towards cellulosic and protein fibre imparting good overall fastness properties. Examples – logwood, custard apple etc.

Parts of the Plant generating Colour Dyestuffs

Root ….Turmeric, Madder (Manjistha), Onions, Beetroot

Bark/ Branches….. Purple bark, Sappan wood, Shillicorai, Khair, Red, Sandalwood

Leaf …….indigo, Henna, Eucalyptus, Tea, Cardamon, Coral Jasmine, Lemon Grass

Flowers (Petals).... Marigold, Dahlia, Tesu, Kusum

Fruits/Seeds…. Latkan, Pomegranate rind, Beetle nut, Myrobolan (Harda)

Natural dyes can also be classified on the basis of their

chemical constitution 

I. Indigoid dyes: Indigo and Tyrian purple are the most

common examples of this class. Another blue dye, woad

also possesses indigo as the main dyeing component.

ii. Anthraquinone dyes: Almost all the red natural dyes are

based on the anthraquinone structure having both plant

and mineral origin. Examples are Madder, lacs, kermes. These are

generally mordant dyes.

iii. Alpha Naphthoquinones: Typical example of this class is

lawsone (henna), cultivated mainly in India and Egypt.

Another similar dye is juglone, obtained from the shells

of unripe walnuts. These dyes generally disperse dyes

and give shades of orange.

iv. Flavonoids, which yield yellow dyes, can be classified

under flavones, isoflavones, aurones and chalcones.

Flavones are colourless organic compounds. Most of the

natural yellows are derivatives of hydroxyl and methoxy,

substituted flavones and isoflavones. Common example

is weld (containing luteolin pigment) giving brilliant and

fast colours on both wool and silk.

v. Di-hydropyrans: Closely related in chemical structure to

the flavones are substituted dihydropyran, viz.

haematin and its leuco form, haematoxylin. These are

important natural dyes for dark shades on silk, wool and

cotton. Logwood, Brazilwood and sappan-wood are the

common examples.

vi. Anthocyanidins: The naturally occurring member of this

class includes carajurin, a direct orange dye for wool and

cotton.

vii. Carotenoids: The class name carotene is derived from

the orange pigment found in carrots. In these, the colour

is due to the presence of long conjugated double bonds.

Another method of classifying natural dye is on the basis of

the method of application.

i. Mordant dyes are dyestuffs which require a mordant in

their application as they have no affinity for the fibre

being dyed. A mordant dye should have electron-donating

groups capable of forming a complex with the transition

metal salt, e.g., madder, fustic, Persian, berries, kermes,

etc.

ii. Vat dyes are water-insoluble dyes which are first

converted to their water-soluble form (reducing with Hydrosulphite and then solubilising it with alkali) and

then applied to the fibres. The true colour is produced

only on oxidation followed by treatment with a hot soap

solution, e.g., indigo.

iii. Direct dyes are those dyes that have a tremendous affinity

for the cellulosic fibres. They are dyed from a boiling dye

bath. Turmeric, pomegranate rind etc. are the few

of the direct natural dyes.

iv. Acid dyes are applied from an acidic medium. The dye

molecules have either sulphonic or carboxylic group (s)

which can form an electrovalent bond with amino groups

of wool and silk. An after treatment with tannic acid

known as back tanning improves the fastness of these

type of dyes, e.g., saffron.

v. Disperse dye has a relatively low molecular mass, low

solubility and no strong solubilizing groups. Disperse

dyes can be applied on to hydrophobic synthetic fibre

from neutral to mildly acidic pH. They can also be

applied to silk and wool. These natural dyes can be post mordanted with chromium, copper and tin salts, e.g.lawsone and many other flavone and anthraquinone dyes.

vi. Basic or cationic dyes on ionization give coloured cations

and form an electrovalent bond with the –COOH group

of wool and silk. These dyes are applied from neutral to

mildly acidic pH. These dyes have poor light fastness,

e.g., berberine.

Advantages of Natural Dyes

While common textile dyeing processes are responsible for 

a large number of residues in the wastewater from textile

finishing companies, dyeing with natural dyes averts this crisis. In this way, not only water can be saved and water pollution avoided, but a broad spectrum of

colours can be reached, opening new possibilities for textile

designers. 

On the other hand, natural dyes are usually less

intense and more prone to bleaching due to mechanical

impact, washing or UV irradiation. 

Sustainability of Natural Dyes

Natural dyes are compounds which are abundant in nature and have eco-friendly characteristics. These dyes are recyclable, biodegradable or compostable in nature and are easily composed

in the soil after end-use due to their sustainability.

1. Disposing natural dyes does not cause pollution.

2. Natural Dyes do not damage human health.

3. Some natural dyes are cheaper

than synthetic dyes.

4. Nature dyes come from renewable sources.

5. Mild shades: Natural dyes are materials that provide mild

shades to the textile materials like fabrics, yarns and fibres etc. they

produce shades soothing to human eyes.

6. Generally harmless to Skin.

7. Natural dyes are easily available in nature..

8. Natural dyes have a unique vibrancy.

9 have the characteristics of antimicrobial that make them safer for children in

specific. Fabrics dyed with natural dyes can be used in hospital beds

due to their excellent antibacterial capabilities.

10 are Non-Toxic

11. Production of natural dyes is safe,

12 Less Waste is produced in the manufacture of Natural Dyes

13 Lays the foundations of feeling nature

14. UV Absorption: Natural dyes are dyes those can absorb

a higher amount of UV radiation

15 Propogate Harmony 

16 Are Decomposable

17 Fungus Resistance: Natural dyes are fungus resistant and

provide good protection against antibacterial germs 

Credits

Robert Wright

[Illustrations of Indian Botany] February 1838

hand coloured plates

International Journal of Home Sciences

The Guardian