Sources and Applications of Natural Dyes

Md. Imran Hossain

Introduction:

Natural dyes are colourants obtained from plants, invertebrates, insects, fungi or minerals.  Most natural dyes are vegetable dyes, the main sources of which are various parts of plants such as roots, stems, seeds, barks, leaves and wood. There are also other biological sources such as fungi, snails, insects, etc. Natural sources were the main source of textile dyes before chemically dyeing. Our ancestors extracted and prepared dyes from these natural sources. Although, all-natural materials can’t produce color but there are some elements except plants that produce some expensive colors like sea snails, Cochineal insects etc.

History of the Origin of Natural Dyes

Exactly when the use of this natural color began is not yet known. However, the first natural dye use was found around 2600 BC. On the other hand, the colorful cave paintings discovered inside the “El Castillo” cave in Spain show that these cave paintings were painted about 40,000 years ago. The oldest colored flax fiber was found in a Prehistoric Cave in the Republic of ‘Georgia’ around 34,000 BC. Further evidence of textile dyeing is from the ‘Neolithic period’ in Southern Anatolia, where iron oxide dyes obtained from the head, probably with red markings, were found on the top. Data show that dyeing was done by plants, barks and insects in China about 5000 years ago. Also, the earliest evidence of dyeing came from the ‘Sindh’ province of Pakistan, a piece of coats dyed with vegetable dye was recovered from the archaeological site of Mohenjo-Daro.

Classification of Natural Dyes Based on Sources

1. Vegetable sources
2. Biological or Animal sources
3. Mineral sources

Vegetable Sources of Natural Dye

The best source in this case is the plants and the different parts of the plants. Most natural dyes are taken from different parts of plants, for example- Plants, Seeds, Roots, Stems, Barks, Leaves, Flowers etc.

Biological Sources of Natural Dye

Uses of Natural Dyes in Textile Fashion

Due to the different molecular structures, different mordant treatments are required to prepare cellulose and protein fibers for natural dyes.

Cellulose fiber: Cotton, Linen, Flax, Bamboo, Rayon etc.

Protein fiber: Wool, Angora, Mohair, Kashmir, Silk, Leather etc.

Cellulose fibers have less affinity for natural dyes than protein fibers. The most common method of preparing cellulose fibers is to use Tannin first, then use Aluminum metal salts. The most common method of preparing protein fiber is to use Alum. However, there are hundreds of different mordanting methods for both protein and cellulose fibers in the historical record. Mordant dyeing is required for the weak attraction of natural dyes to textile fibers.

Below are some of the important and common natural dyes that are widely used for dyeing textile materials (fiber, yarn, cloth).

1. Jack Fruits

The wood of the jackfruit plant is finely chopped and then boiled in water to extract the dye. After the treatment of mordanting, it gives the color of the fabric from Yellow to Brown shade. It was used for dyeing cotton and jute fabrics. The color molecule responsible for this yellow-to-brown color is ‘Morin’.

2. Indigo Tree

Indigo dye, which is obtained from Indigofera tinctoria and gives a shade of Blue. Color is found in 0.4% of the total weight of the Indigo tree. Proper reproduction of natural Indigo shades is difficult. Various natural Indigos are used to get Blue shades on cotton. It is a kind of VAT dye and therefore vatting is required for dyeing. It is known as the oldest and most widely used dye.

3. Onion Skins

Onion skin is the main source of dyes. It is boiled to remove the color from the onion skins and can later be dyed without mordanting the fabric. The result is a shade of Orange to Brown on the fabric. Pelargonidin is the color molecule responsible for the dye in onion skins.

4. Madder Roots

Red dye prepared from herb called Madder. Madder’s color molecule is Alizarin. Cotton, Silk and Wool fibers can be dyed with Madder at a temperature of 100^oC. It gives bright Red shades on wool and silk and Reddish to Purple shades on cotton.

5. Tumeric

Tumeric seems to be the most common dye found in nature. The Tumeric obtained from the roots of the plant is first dried, then crushed into powder and boiled with water to extract the dye. The result is a bright Yellow shade. It is commonly used for dyeing cotton, Wool and Silk. The color molecule responsible for this yellow color is ‘Curcumin’.

6. Henna Leaves

The leaves of the henna tree are dried and ground and then boiled with water to get the dye out of the leaves. Mordanting fabrics range in color from Brown to Mustard yellow. It is a dispersed dye-type color. Therefore, polyester and nylon can be dyed by henna.

7. Logwood

The color is extracted by boiling the stem of the Logwood tree in small pieces for an hour. Logwood is used to create Black shades on wool. Logwood trees are commonly found in Mexico, Central America and the Caribbean islands. Haematoxylin is the pigment of the Logwood natural dye.

8. Lac Insects

Lac dye is made from a special insect (Coccus Lacca). It mainly produces shades of Scarlet to Crimson Red. This pigment produced by insects is called stick lac.

Some Luxurious Dyestuffs:

1. Tyrian Purple from Sea Snails:

Although these dyes are available and readily available in nature, the preparation of these dyes is very time-consuming and at the same time expensive. Tyrian Purple is also called Royal Purple, it is made from the glands of sea snails. Sea snails are certainly readily available. But the problem is, the amount of dye extracted from about 12,000 snails will be only 1.4 grams. For this reason, this dye is very expensive and the Royal family of that time used this dye to color their dresses.

2. Crimson and Scarlet Dye from Cochineal Insects:

This dye is derived from Cochineal insects. It creates beautiful Crimson, Scarlet and Pink colors on cotton, wool and silk. But after mordanting with chromium, iron or copper, grey color is produced from purple. Cochineal is a type of insect from which the natural colorant ‘Carmine’ is produced. Only 1 kg of carmine dye can be prepared from the dry bodies of about 150,500 Cochineal insects.

History of Prussian Blue Dye

In the 18^th century, the German chemist ‘Johann Jacob’ was working in a laboratory with ‘Carmine’ dye obtained from the Cochineal.  At one time he came to the conclusion that if he mixed Alum or Iron or Potash with this Red Carmine dye, a kind of faded red color would be obtained. With Alum and Iron, he got a fairly accurate color. But after mixing potash, he noticed that a more valuable ocean blue color was created. After mixing the potash, it underwent a chemical change in the carmine dye to a blue color. The blue color is very rare in the natural environment. The appearance of this blue color there is really amazing and known as ‘Prussian Blue’, discovered by Dizbach.

Natural Dye has some special benefits:

1) Not harmful to health.

2) It is possible to easily extract and purify dyes from various natural sources.

3) There is no effluent generation.

4) The durability & sustainability of natural dyeing is very high.

5) Has mild dyeing condition

7) Natural dye is a renewable source.

6) Natural Dye has no Allergic, Carcinogenic or Toxic reactions.

6) Natural dye has high UV ray absorption capacity.

Although natural dye has several advantages, it has some technical problems-

1) Natural dyes are suitable for most natural fibers (cotton, linen, wool and silk), but not for man-made fibers.

2) Its color fastness properties are not good.

3) It has less affinity to the fiber and forms a weak bond with the fibers.

4) There is no standard coloring recipe and method.

5) Mordant is used when dyeing with natural dye, which is harmful to the environment.

6) Due to mordanting, many times the dyeing shade changes.

6) Natural dyeing is very expensive & time-consuming.

Conclusion

We use natural dyes to dye fabrics because we want something non-carcinogenic and that is not harmful to our environment. Toxic and allergic reactions to synthetic dyes are forcing people to think about natural dyes again. Natural dyes are a renewable source of color materials. Natural dyes are being used in food, medicine and handicraft items in addition to textiles. Synthetic dyes have many harmful effects, constantly polluting the environment.  So many researchers are currently researching natural dyes to protect them from harmful effects. Many fashion houses and boutique houses are even using natural dyes. There are many types of natural dyes that are beneficial for the human body when using dyed fabrics.  So, we need to do more and more research on natural dyes to protect ourselves from environmental pollution.

References:

1. https://www.intechopen.com/books/chemistry-and-technology-of-natural-and-synthetic-dyes-and-pigments/fundamentals-of-natural-dyes-and-its-application-on-textile-substrates
2. https://en.m.wikipedia.org/wiki/Natural_dye
3. https://maiwa.com/pages/natural-dyes
4. https://www.diynatural.com/natural-fabric-dyes/
5. http://www.allnaturaldyeing.com/

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