Introduction of dyes:
Definition of Natural dyes:
Natural dyes are dyes derived from animal or plant material without any chemical treatment. They are obtained from sources like flowers, leaves, insects, bark roots etc.; however, they are not readily available and involve an extraction process.
Types of Natural Dyes:
There are three types of natural dye which must be applied in fabric with appropriate technique.
These are as follow:
1. Plant dyes: obtained from leaves, flower, skins of fruit, bark, roots, wood etc.
2. Insect Dyes: obtained from various dried bodies of insects.
3. Animal Dyes: obtained from created from shellfish Carmine, Cochineal and so on.
Sources of natural dyes:
Specialist plant and animal sources Many plants and some animals have been identified for making natural dyes. A range of parts of plants like roots, stems, barks, leaves, fruits and seeds are generally used.
By-products (Particularly lac dye): The lac industry provides lac dye as a by-product, which is taken from the effluent. Likewise from cassia tora, utilized in gum production, a brown dye is obtained as a by- product.
Chemical mixture: It is a mixture of dyes of molecular structure similar to those of natural dyes.
Cell or tissue culture by DNA transfer technology: A few fungi such as Drechslera and Trichoderma make anthraquinone derivatives. Anthraquinone is a significant type of dye, where exploiting the fungi would be helpful over their chemical mixtures.
Application of natural dyes:
Natural dyes have been and can be used for many aesthetic and utilitarian purposes. Since they are nontoxic, their use as food coloring or substrates is much safer for human consumption and are preferable to artificial dyes. They’re used in the makeup industry for similar reasons, can be used as pH indicators, and are also popular in art, textiles, and leather making.
There are some technical issues and disadvantages related to the application of natural dyes
which reduced its applications that are:
Mostly applicable to natural fibres (cotton, linen, wool and silk)
Poor colour fastness properties
Poor reproducibility of shades
No standard colour recipes and methods available.
Use of metallic mordants, some of which are not eco friendly.
Advantages and disadvantages of Natural Dyes:
Advantage:
The shades produced by natural dyes/colourants are usually soft, lustrous and soothing to the human eye.
Natural dyestuff can produce a wide range of colours by mix and match system. A small variation in the dyeing technique or the use of different mordants with the same dye (polygenetic type natural dye) can shift the colours to a wide range or create totally new colours, which are not easily possible with synthetic dyestuffs.
Natural dyestuffs produce rare colour ideas and are automatically harmonizing.
Unlike non-renewable basic raw materials for synthetic dyes, the natural dyes are usually renewable, being agro-renewable/vegetable based and at the same time biodegradable.
In some cases like harda, indigo etc., the waste in the process becomes an ideal fertilizer for use in agricultural fields. Therefore, no disposal problem of this natural waste.
Many plants thrive on wastelands. Thus, wasteland utilization is an added merit of the natural dyes. Dyes like madder grow as host in tea gardens. So there is no additional cost or effort required to grow it.
This is a labour intensive industry, thereby providing job opportunities for all those engaged in cultivation, extraction and application of these dyes on textile/food/leather etc.
Application of natural dyes has potential to earn carbon credit by reducing consumption of fossil fuel (petroleum) based synthetic dyes.
Some of its constituents are anti-allergens, hence prove safe for skin contact and are mostly non-hazardous to human health.
Some of the natural dyes are enhanced with age, while synthetic dyes fade with time.
Natural dyes bleed but do not stain other fabrics, turmeric being an exception.
Natural dyes are usually moth proof and can replace synthetic dyes in kids garments and food-stuffs for safety. Despite these advantages, natural dyes do carry some inherent disadvantages, which are responsible for the decline of this ancient art of dyeing textiles.
Disadvantages:
It is difficult to reproduce shades by using natural dyes/colourants, as these agro-products vary from one crop season to another crop season, place to place and species to species, maturity period etc.
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 materials.
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 time and excess cost for mordants and mordanting.
Scientific backup of a large part of the science involved in natural dyeing is still need to be explored. Lack of availability of precise technical knowledge on extraction and dyeing techniques.
The dyed textile may change colour when exposed to the sun, sweat and air.
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.
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 ratings are inadequate for modern textile usage.
Cost – A larger amount of natural dyes may be needed in order to dye a specific amount of fabric as opposed to synthetic dyes. For instance, one pound of cotton may be dyed with just five grams of synthetic dye, whereas 230 grams of natural dye are needed to dye the same amount of material. Since that is the case, using natural dyes is more expensive than synthetic dyes.
Materials and Methods:
Collection of plant material
The floral parts of Clitoria ternatea L., Ixora coccinea L., Tagata erecta L., Impatiens balsamina L., Peltophorum pterocarpum.(Dc.)., Lawsomia inermis L., Rosa rubi ginosa L. and the leaves of Croton versicolor (L) R.Br., and fruits of red chili (Capsicum annum L.) and tubers of Beetroot (Beta vulgaris L.) were collected from in and around Madurai.
Dye extraction
The collected plant materials used for extraction dye. The cleaned samples (50g) were crushed, dissolved in deionized water (500 ml) and then boiled for 2 hours in a hot water bath for quick extraction. At the end of 2 hours, the total color was extracted. The solution was then double filtered and used to carry out our study.
Dyeing materials
Cotton (2mm size), jute (0.5 cm size) and woolen (3mm size) yarns were used to test the dyeing ability of extracts.
Pre mordant Dyeing
Different mordants like cooking salt, vinegar and potassium dichromate were used as mordants. The extracts obtained were filtered and used for dyeing textile material. The textile materials used for dyeing were first washed with water.
Natural Dyes Extraction Process:
In the process of extraction / preparation of natural dye solution needs to be adjusted with the weight of the material to be processed so that the amount of the natural dye solution is produced can be sufficient to dye the textile material. Number of natural dye solution which depends on the amount of textile material to be processed. Comparison of solution dye with textile materials commonly used is 1: 30. For example, the weight of textile materials which is processed 100 grams then the need of natural dye solution is 3 liters.
The following is measures extraction process to explore natural dye in a scale laboratory
1. Cut into small size – a small part of the plant you want, for example: leaves, stems, skin or fruit. Materials can be dried first or direct extracted. Take the piece weighing 500 gr.
2. Insert the pieces into the pan. Add water with comparison 1:10. For example if the weight of the material extracted 500gr then the water 5 liter.
3. Boil the ingredients until the water volume becomes half (2.5liter). If desired dye solution so thicker the volume of residual boiling can be reduced for example to one-third. As an indication that the color pigment is inside plants have come out shown with water after boiling into color. If the solution remains clear then the plant is almost certainly not contains color pigments.
4. Filter with the filter solution screen the extraction process results to separating with the remaining material extracted (residue). Solution extract the results This filtering is called a natural dye solution. After chilling the solution is ready used.
Definition of synthetic dyes:
A human-made organic dye. Synthetic dyes are manufactured from organic molecules.
Types of Synthetic Dyes:
Acid Dyes
Azoic (or Naphthol) Dyes
Basic Dyes
Chrome (or Mordant) Dyes
Developed (or Diazo) Dyes
Direct Dyes
Disperse (or Acetate) Dyes
Reactive (or Fiber-reactive) Dyes
Sulphur Dyes
Vat Dyes
Advantages and Disadvantages of synthetic dyes:
Advantage:
Synthetic fibers are strong so they can take up heavy things easily.
Synthetic fibers retain their original shape so it's easy to wash and wear.
Many synthetic fibers create highly attractive fabrics. Modern synthetic fabrics can look and feel as luxurious as silk or wool.
Fibers like Acrylic fibers are resistant to chemical and biological degradation hence can be used in filters and artificial wool in sweaters.
Synthetic fibers are more durable than most natural fibers and they readily pick-up different dyes
Many synthetic fibers offer consumer-friendly functions such as stretching, waterproofing and stain resistance
Disadvantages:
Synthetic fibres do not absorb water or sweat. In hot and humid weather therefore the clothes made of synthetic fibre stick to the body and make the wearer uncomfortable.
Synthetic fibres melt and burn easily.
Synthetic fibres on catching fire shrink forming beads which stick to the skin. Therefore it is not advisable to use clothes made from synthetic fibres while working near flam/fire, such as,in kitchen.
Synthetic fibres are nonbiodegradable. Therefor they cause soil pollution.
Different between natural and synthetic dyes:
The different between natural dyes and synthetic dyes is largely that synthetic dyes are chemically manufactured whereas natural dyes are purely developed from nature. Natural dyes, although pure from chemicals, are often times more expensive than chemical dyes. This is why for the most part many textile industries have shifted to chemical dyes. Still, however, natural dyes are still valued for their purity and are still used for food, drugs, and cosmetics that have human ingestion components.
Natural vs. synthetic dyes: which is better?
Natural dyes are derived from plants, animals, fruits, insects, minerals and other natural resources. That’s why natural dyes are usually perceived as harmless and safe for the environment. However, that’s not the case all the time. Some natural dye sources such as logwood and bloodroot can be toxic. Logwood can produce a range of colors, but the active ingredients in it, which are hematein and hematoxylin, can be harmful when it enters the body through inhalation, ingestion, or skin absorption. Meanwhile, bloodroot can also be harmful because it may cause irritation and inflammation when inhaled. Most natural dyes are safe and harmless. However, they can be toxic due to the mordant used for their application. Mordant are substances used to make the natural dye stick to fabrics such as aluminum, copper, iron and chrome. More so, natural dyes are scarce and expensive, because producing it requires a vast area of land. Sustainability is also an issue because their pigment may wash off overtime. synthetic dyes have harmful effects on the environment and human beings. First off, synthetic dyes are made up of chemical compounds that can be harmful to humans, especially those who work in their production. Some of the chemicals found in synthetic dyes are mercury, lead, chromium, copper, sodium chloride, toluene, and benzene. Exposure to large doses of these substances can be toxic and can have severe effects in the human body. Water pollution can also result from manufacturing synthetic dyes when untreated dye effluent is dumped directly on bodies of water.
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