Why Natural dyes are important? (Detailed Guide)
Welcome to our blog, where we will delve into the world of natural dyes and the crucial role they play in our daily lives. Natural dyes are derived from natural sources such as plants, insects, and minerals and have been used for centuries to color fabrics, textiles, and other materials. Today, natural dyes are becoming increasingly popular as they are environmentally friendly, non-toxic, and offer an array of unique and beautiful colors, unlike synthetic dyes. In this blog, we will explore the benefits of natural dyes, how they are made, and how to use them in your own projects, join us as we discover the world of natural dyes and why they are so important.
After the advent of synthetic dyes by Scientist Henry Perkin in 1856, the production of synthetic dyes started on a mass industrial scale. The ultimate commercialization of a number of synthesis of various categories leads to production in tons of volume. The environmental toxicity by virtue of effluent discharge and pollutants as contaminated color water rose to alarming levels.
In the early 21st century, the market for natural dyes in the fashion industry started experiencing a resurgence. Moreover, Ayurvastra or ayurvedic textiles which involve herbal medication through the dyeing of fabric with natural powders and extracts, are gaining more importance nowadays. For instance, Turmeric- the most popular natural dye does not only have coloring ability but also has anti-inflammatory, anti-microbial, anti-parasitic, and some other significant activities. A bed sheet dyed with turmeric thus becomes an Ayurvastra that can increase metabolism and helps to get rid of toxins when human skin comes in contact with this fabric.
Natural dyes have been used pretty much since the existence of mankind. Natural dyes or organic dyes are colors that are extracted from natural resources surrounding our environment; they are extracted from insects, and mineral components such as iron ore, plants, or parts of a plant.
Currently used synthetic dyes are soluble, disperse, and pigment category & being non-degradable comes under the non-eco-friendly class. In the natural dyes, azo groups (-N=N-) are absent. So the carcinogenic amines are absent. Twenty-two such aromatic amines are reported to be harmful & banned according to the EU directive of 2002.
The present-day synthetic dyes made out of all classes involve intermediates and chemicals of hazardous and non-eco-friendly nature. They pollute the river, and soil and also are carcinogenic to the human & animal kingdom. The pollution thus generated is of far-reaching consequences and recycling of contaminants & removals are cumbersome and cost imperative.
Though much stricter legislation is placed from time to time by pollution control boards; and federal regulatory authorities. The courts have announced the closure of many textile manufacturing units spreading such pollutants in the environment for decades without check & control.
The time is now ripe to accommodate natural dyes in the business model to support the “save the earth” initiative to make consumers protected by the ill effects of synthetic dyes. It is evident from the historical places like Ajanta, Ellora, Sithannavasal, Mithila wall paintings (mural art), and Egyptian pyramids which had been exclusively used with natural colorants.
Moreover, at the Spanish caves of Altamira and Elcatillo and the French Pyrene caves of Niaux, mineral earth and other inorganic pigments like ferric oxide for red, ferrous oxide for yellow and copper carbonate for blue have been used extensively in their mural paintings.
Vedas also mentioned red, yellow, blue, black, and white as main dyeing colors and expressed that, the ancient craftsmen dyed blue from indigo, yellow from turmeric and saffron, brown from cutch, and red from lac, sunflower, and madder.
Thus natural dyes are part of human civilization since time immemorial. The advantages of using natural colorants are manifolds as they are eco-friendly, safe for body contact, unsophisticated and harmonized with nature, obtained from renewable sources, and also their preparation not required added chemical reactions.
Though some limitations are held by natural dyes in terms of the scale of quantity manufacturing, consistency in shade reproducibility, and limited color band. The certain obvious advantages are their friendliness with human skin and health as stimulants in cure of some deceases and protection over microorganisms.
The conscious environmental minds started advocating sustainable and renewable sources of material in manufacturing through nature.
Advantages of natural dyes
The use of natural dye started reviving with sustainability ground with some inherent advantages.
- No health hazards with renewable sources
- Easily extractable/purifiable
- Some health protective properties added
- No effluent generation and the residue are biodegradable
- Milder applicability
Disadvantages of natural dyes
Though some disadvantages are also associated as per below,
- Inferior color fastness
- The high volume of manufacturing
- Use of metallic mordant
- Mostly applicable to natural fibers
Classification of natural dyes based on chemical structure & group
- Indigoids
- pyridine
- Flavonoids
- Carotenoids
- Quinonoid
- Dihydropyran
- Betalains
- Tannins.
- Indigoids- indigo blue + Tyrian purple -these are blue pigments extracted from leaves of Indigofera species (I. Tinctoria). Indigo blue and Tyrian purple are representative examples of indigoid colorants, which have a high affinity for cellulosic and protein fibers.
- Pyridine-based dyes consist of isoquinoline alkaloid units with bright yellow color. Berberine yellow (natural yellow 18, C.I 75160) is the only natural dyed from this class. It is extracted from b.aristana, b. vulgaris, and p.amurence & r. coptidis.
- Carotenoids are extracted from various plants such as carrots and tomatoes. It can be applied to food colors also which contain vitamin A that function as an antioxidant scavenger. Carotenoids are divided into two types carotenes and xanthophylls. Orange, red, and yellow colors are derived from it.
- Quinonoid are generally found in flowering plants and their color ranges from yellow to red. Further classified as benxoquinones + anthraquinones + Alpha-naphthoquinones. It imparts antibacterial properties along the color. Some common examples are lawsone, jaglone, and emodin. Lawsone is the main active ingredient in henna (Lawsonia inermis). Based on the staining properties of lawsone, it is mainly used as a hair dye, but also applied to the body. Lawsone corresponds to 2-hydroxy-1,4-naphthoquinone (CAS n. 83-72-7) and is present at 1 to 2% in the dried leaves of the plant.
- Flavonoids-allius cepa is a very soothing color providing yellow to red and blues and orange. The performance of these colorants is also enhanced by the use of mordants. Luteolin, 3′, 4′, 5, 7-tetrahydroxyflavone, is a common flavonoid that exists in many types of plants including fruits, vegetables, and medicinal herbs. Plants rich in luteolin have been used in Chinese traditional medicine for treating various diseases such as hypertension, inflammatory disorders, and cancer.
- Di-hydropyrans closely related in chemical structure to the flavones is substituted dihydropyran viz haematin and its leuco form, hematoxylin. These are important natural dyes for dark shades on silk, wool, and cotton. Logwood, Brazil wood, and sappan wood are common examples.
- Betalains –beta Vulgaris (beet) are nitrogen-containing pigments comprising yellow & violet colors. Due to bioactive components, they are rarely used in textiles as they are temp, and ph sensible. Betalains from red beetroot are natural pigments, which mainly include either yellow-orange betaxanthins or red-violet betacyanins. However, betalains are quite sensitive to heat, ph, light, and oxygen, which leads to poor stability during processing and storage.
- Tannins–Proanthocyanidins-(polyphenols) + pyrogallol are high molecular weight water-soluble compounds found in various plant parts like fruits, leaves, barks, roots, etc. Tannin extract has been used to dye wool and its general fastness properties along with light fastness are improved by using different metal salts as mordants.
Mordanting:-
Basically, natural dyes will not adhere to natural fibers without the use of a mordant or fixative.
Mordants not only give the dye an affinity, but in many cases, they produce different colors and improve the fastness of a dye. There are many plants that may yield a color that is brilliant and pleasing but fades easily unless fixed by using a mordant.
However, mordants can also be used with dyes which may be applied directly. In this case their function is to form an insoluble compound with the dyestuff within the fiber itself, thereby improving the fastness properties of the dyed material. Mordants can broadly be classified into three categories:
1. Metal salts or metallic mordants
2. Tannins and tannic acid
3. Oils or oil mordants.
Table -1Mordant used for different natural dyes and hues developed.
| Dye | Mordant | Hue |
| Lac | Stannic chloride | Red |
| Ferrous sulphate | Black | |
| Bougainvillea | Tin | Yellow |
| Ferrous sulphate | Brown | |
| Alum + ferrous sulphate | Green | |
| Cochineal(Carmine red) | Alum | Pink |
| Chrome | Lilac pink or purplish red | |
| Cutch | Chrome | Black brown |
| Copper | Brown | |
| Henna | Unmordanted | Yellow |
| Alum | Golden yellow | |
| Tin | Orange |
Various dyes class with their pollution impact, which is categorized as 1 to 5, from lowest to highest polluting numbers.
