Natural Dyes: Definition, Characteristics, Classification, Uses, Advantages & Disadvantages

Natural Dyes: Definition, Characteristics, Classification, Uses, Advantages & Disadvantages

Arna Datta
B.Sc. in Textile Engineering
Textile Engineering College, Zorargonj, Chattogram

What are Natural Dyes?
Natural dyes are dyes, pigment or colorants that are derived from natural sources such as plants, animals, or minerals. They are more sustainable and eco-friendlier compared to synthetic dyes. These dyes are obtained from renewable resources and are often considered more environmentally friendly. These dyes have been used for centuries to color textiles, food, leather, and other materials.

Characteristics of Natural Dyes:

1. Natural dyes are organic and derived from natural sources.
2. They are sustainable and eco-friendly.
3. They are biodegradable and easily broken down by microorganisms, making them environmentally friendly.
4. Natural dye is generally less toxic and allergenic.
5. They have lower color fastness compared to synthetic dyes, but they can create a more natural and unique spectrum of colors.
6. They work well with natural fibers like cotton, linen, wool, and silk but don’t work well with synthetic fibers without mordants.

Classification of Natural Dyes:
Natural dyes can be classified based on their source, chemical structure, and application.

a) Classification on the basis of sources:

i. Plant-based Dyes:
They can be extracted from a variety of plant parts, including seed, root, stem, berries, bark, leaves, flowers and wood.

Some common examples are given below:

ii. Animal-based Dyes:
These dyes can be obtained from various animals like insects, shellfish, and fish.

Some examples are:

iii. Mineral-based dyes:
These dyes are obtained from minerals. Compared to plant and animal-based dyes, they typically provide more limited colors.

Some examples are:

iv. Microorganisms-based dyes:
These dyes can be extracted from fungi, bacteria and algae.

Some examples are:

b) Classification on the basis of chemical structure:

1. Indigoid-based dyes: Indigo dye is obtained from Indigofera tinctoria. Indigo blue and Tyrian purple are the most important dyes of this group.
2. Anthraquinone-based dyes: Dyes like alizarin and purpurin are obtained from plants and insects. Most of the red natural dyes are obtained from them. Madder, lac, kermes and cochineal have anthraquinone as a common structural element.
3. Alpha naphthoquinone-based dyes: Lawsone (henna) is the most important dye of this class. And another one Juglone is obtained from the shells of unripe walnuts.
4. Flavonoid-based dyes: Yellow dyes obtained from this group and can be classified under flavones, isoflavones, aurones and chalcones. Many plant-based dyes extracted from this, including quercetin (yellow), kaempferol (yellow), and myricetin (brown). The natural dye weld also derived from this.
5. Anthocyanidins-based dyes: Orange and blue dyes are obtained from this. From the leaves of Bignonia chica, Carajurin is obtained which gives the orange shade.
6. Dihydropyrans: Logwood and Sappanwood produces dark black shades on silk, wool and cotton are belong to this.
7. Carotenoid-based Dyes: Red, orange and yellow dyes are extracted from this and can be found in various types of plants and flowers like sunflowers. Saffron and Annatto are the most important natural dyes of this group.

c) Classification on the basis of application:

1. Direct dyes: Turmeric, pomegranate rind and annatto used in direct dyes. Soda ash and common salt is used in this dyeing method. The dyeing temperature is 70-100°C. They are water soluble and have a long planar molecular structure.
2. Vat dyes: The solubilisation of natural indigo can be carried out with the help of sodium hydrosulphite and sodium hydroxide. After solubilisation, it is applied on cellulosic fiber like cotton, jute, hemp, flax etc.
3. Acid dyes: Dye molecules contain sulfonic or carboxylic groups in their structure, which form affinity for wool and silk fibers. The dyeing is carried out at an acidic pH of 4.5–5.5. The dyeing of wool and silk with saffron can be done by acid dyeing method. Common salt is used for levelling effect.
4. Basic dyes: The dye molecules contain –NH2 groups and form an electrovalent bond with the carboxylic group of wool and silk. Berberine is classified as a basic dye.
5. Mordant dyes: Mordant dyes are organic or inorganic materials that are attached to textile fibers by a fixing agent “mordant”. Mordant dyes are sometimes called chrome dyes because of using chromium widely.
6. Disperse dyes: Disperse dye which has low aqueous solubility and low molecular weight requires post mordanting treatment with chromium, copper or tin salt.

Uses of Natural Dyes in Textile:
Some of the important and common natural dyes that are widely used for dyeing textile materials (fiber, yarn, cloth) are given below

1. For dyeing fabrics, natural dyes are widely used. They provide a wide range of colors.
2. By using natural dyes, bed linens, curtains, and other home textiles can be dyed.
3. Ethnic clothing, traditional clothing, and formal textiles are dyed using natural dyes to maintain authenticity and cultural significance.
4. They are also used in the color of accessories such as scarves, shawls, hats, and gloves.
5. They can also be used to dye handmade textiles, textile arts, and crafts for organic coloring.
6. Due to the natural, non-toxic and perceived softness of natural dyes, they are often used in the color of children’s clothing.
7. They are also used by artisans and craftsmen to create unique patterns and designs.

Advantages of Natural Dyes:

1. They are sustainable and eco-friendly.
2. They are generally biodegradable
3. They are Non-Toxic and Hypoallergenic
4. They are not harmful to health
5. They provide a wide range of shades.
6. They are soft and relaxing.
7. They are renewable
8. They have high UV ray absorption capacity
9. Some natural dyes offer potential health benefits e.g. turmeric.
10. Reduced water pollution as they use less chemicals

Disadvantages of Natural Dyes:

1. Natural dyes are expensive as the source is limited.
2. They are not suitable for man-made fibers.
3. They are sensitive to pH
4. Colors may fade quickly
5. Many natural dyes depend on mordants & mordants can be toxic & harmful to the environment.
6. Many times the dyeing shade changes due to mordanting.
7. It’s a complex and time-consuming process.
8. There is no standard dyeing methods.

Conclusion:
Increasing knowledge about different natural sources providing beautiful colors is expanding the shade cards of different fabrics. Despite their limitations, natural dyes are sustainable, eco- friendly and an intriguing alternative for coloring textiles, food and other materials. So we need to do more research on natural colors to improve their consistency and color fastness to protect the environment from pollution. Overall, natural dyes represent a significant step forward to embrace a more sustainable and eco-conscious approach to coloration

FAQ

Q1. How are natural dyes different from synthetic dyes?
Ans: Natural dyes are derived from natural sources such as plants, animals, minerals and are environment friendly while synthetic dyes are chemically produced and the environment unfriendly.

Q2. What are common sources of natural dyes?
Ans: Common sources of natural dyes are plants, animals, insects, minerals, and microorganisms. Different parts of these sources, such as leaves, roots, or insects, can be used to extract pigments

Q3. Are natural dyes environmentally friendly?
Ans: Due to their renewable sources and biodegradability, Natural dyes are often considered more environmentally friendly.

Q4. Are natural dyes safe to use?
Ans: Natural dyes are generally safer than synthetic dyes, but some natural dyes may be harmful to health. So it’s best to research the specific dye before using.

Q5. Do natural dyes fade faster than synthetic dyes?
Ans: Natural dyes may fade faster compared to synthetic dyes.

Q6. Can natural dyes be used on all types of fibers?
Ans: Natural dyes can be applied on cotton, linen, wool, and silk. But they may not be effective for synthetic fibers without the use of mordants.

Guest Author

This article is written by a guest author and reviewed, revised and edited by Tariq Bin Mutalib, Editor in Chief, TextileFact.com.

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