Textile Notes related to fiber, yarn, fabric knowledge, spinning, weaving, processing, projects, knitting, Indian Traditional Textiles and denim manufacturing
100x120 quality of voile is a misnomer.Actually the count of the fabric is 64 x 80 or 64 x 90. The construction is the same as that of 92 x 80. It is a greige construction. Finished construction will be 104 x 80.
To understand it, there are various varieties available in the market. I am just giving a brief list in the decreasing order of qualities. In the first column I have given the popular name, in the second column I have given the reed and pick ( All Greige) corresponding to that quality.
100 x 120 92 x 104 ( A typical 100 x 120 quality has count of 56 x 90, Reed pick of 91 x 101)
100 x 120 92 x 88
100 x 120 92 x 80 ( A typical 100 x 120/92 x 80 has a count of 60 x 80 and Reed x pick of 90 x 76)
100 x 120 92 x 72
80 x 72 80 x 72 (A typical 80 x 72 quality has a count of 60 x 80 and Reed pick of 80 x 64)
100 x 100 76 x 68 ( A typical 100 x 100 quality has a count of 60 x 80 and reed pick of 76 x 60)
80 x 100 76 x 66
70 x 90 66 x 52 ( A typical 70 x 90 quality has a count of 60 x 90 and reed pick of 66 x 50)
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If Teal color needs to be obtained. Then indigo dyed fabric is first dipped into myrobalan solution and then treated with water of Iron. (Teal Background)
If Green color is desired then indigo dyed fabric is first treated with solution of Haldi and then treated with Alum. Please remember to dry in the night or dry upside down to get a green color.
To Get Red and Black as Motif, Green as background- Block 52 and 52A
a. The Fabric is first Dipped in Myrobalan
b. Then it is Printed With Red Process( Alum Paste) as explained earlier
c. Then it is Printed With Black Process (Iron Paste)
d. Then it is Washed and Boiled with Alizarin ( To get red on 1st Block)
e. Then it is Dyed in Indigo
f. Then it is Dipped in conc. solution of Pomegranate Chilka + Haldi ( For Green Back ground)( Green Process)
If the color is dark indigo is added
Remember if the indigo is not properly mixed then it will smear on the block color.
To Get a Brown Color in the Background
There are two methods
1.In one method after the green process, the fabric is dipped in alum and then boiled in Alizarin ( Green +Redà Brown). The motif being resisted by Dabu.
2.In other method the indigo dyed fabric is dipped in alum and then boiled in Alizarin ( Blue + Red-à Brown).
The two tones of brown are different.
Green Motif (with Dabu)
To get Green Motif, in white process, some Haldi is added in the paste ( Means: kaali Mitti, Gum, Jaggery, Hydrate of Lime, Haldi)
Black Background with Hira Kashish ( Ferrous Sulphate – Hara thotha)
1.Fabric is treated with Myrobalan and Dabu Done
2.Hira Kashish is then mixed with water.
3.The fabric will then turn to brown except dabu
4.Then it is put to Alizarin boiling process it will turn to black
5.Then it is washed properly.
To get a darker color, the fabric is again dipped in myrobalan after finishing. For example to get a darker brown fabric is dipped in Myrobalan.
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Black color is obtained with the help of "iron water". To prepare iron water, Take 25 kg Iron Scrap+ water + Baajre ka aata + 2 kg ( Gud- Jaggery) . Close the lid from the top and keep it aside for 15 days.
Take out the iron, boil the water and then cook with Tamarind seed flour to prepare the iron paste for mixing with Iron. ( Black Process- NO Dabu)
To Apply it, first prepare the fabric using myrobalan. Then apply the paste to the fabric using printing blocks to give deep black color
Indigo Dyed Dabu
First of all fabric is desized just like the previous process.
Then it is treated with Castor oil in water to increase its absorbancy.
Then the dabu printing is done just like the earlier process.
After that the fabric is dried and then the fabric is put into indigo pot
The potis very old and the water is never changed. New indigo is kept on adding in it. It is generally 10 feet deep. Hydrate of Lime ( Ca(OH)2) is added time to time to keep the potency intact.
Generally there are two vats; one has 50% indigo and the other has 100% indigo. At a time two thaans are taken. The than is taken folded and gradually all the layers are exposed.
After that it is dried into the sun.
Another two dippings and dryings in the sun are done to get a dark tone.
If one wants to have one design with light and the other as a dark tone, the after printing the fabric is dipped into 50% indigo first and then dried.
After that dabu printing is done with the second design and the fabric is dipped twice into 100% indigo pot. The first type of dabu retains its whiteness, whereas the second type of dabu will become slightly less blue.
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Dabu is a mud-resist hand-block printing practiced in Rajasthan of India. The prints have a sublime quality and appearance. In making of the printed fabrics, a lot of manual process and hard work is involved and the process of uses lots of natural dyes and vegetable pastes. Here is a brief outline of the process.
1. First of all Fabric is received from the mills. Traditionally mill made cloth of 30s, 60s and Mull is used.It is heavily sized. For that it needs to be desized.Desizing is done by repeatedly beating the wet fabric against a hard surface (stone). It is frequently kept for a day after such beating so that enzymatic reaction can loosen the size. Next day it is again beaten and so on. This process continues for three days.
2.After that the fabric is dipped in Myrobalan (Tanning) agent. The myrobalan paste is prepared about three hours in advance by mixing about 2kg paste for 100 m of fabric.
3.After that the fabric is dried in the sunlight
4. After that fabric is printed once with a paste of Alum+ Tamarind Seed+Direct dye to distinguish. (Red Process-No Dabu)
5. After that fabric is washed once, and then it is dried and then go for boiling.In boiling we boil the fabric with Dhauri Ke Phool ( Jaloor)+ Alizarin ( Madder)+Mahi for 1 hour at 100deg Celcius. The fabric is circulated about 5 times using Bamboo Poles. If the color required is dark then some iron water needs to be added.
6. After it is dried and then the next process of Dabu is done. Printing paste is made using ( Jaggery, Hydrate of Lime, Kali Mitti and Gum ( Nigeria). The paste is then spread over a coir to give it a base. The printing is done using blocks. (White Process-Dabu).
Saw dust is sprinkled over the fabric as it is printed so that the block applied should not smear the other sides
1.Then it is dried in the sunlight.
After that the fabric is treated with Myrobalan again.
3.Then it is dried and then dipped completely in Alum + Water.
4.Then it is dried and washed and again boiled with Alizarin+ Mahi( Sakur)+ Dhawdi. Then it is dried in the sun and washed to reveal the dabu resist .
Want to see something modern in Dabu ?? Klick here.
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If your reasoning goes like this that since single yarn strength of airjet/ rotor or friction yarn is less than that of ring yarn so fabrics made from ring yarn will be stronger than those made from airjet/rotor or friction yarn, than you are in for a Surprise.
The fabric made from ring yarn will be weaker than those made from the other yarn as mentioned above.
A study done by scholars of IIT and Behrampur University suggests this conclusion.
The presence of wrapper fibers inside the rotor/airjet/friction yarns increase the frictional force inside the fabric and therefore resist rupture, among other factors such as the rupture of wrapper fibers inside the fabric for these yarns are more than ring yarn, which enhance further frictional force.
A study on cotton yarn was done to answer the question mentioned above. It was done by Muhameet Akaydin of Pamukkale University, Turkey. The following are the conclusions from the study:
1. Compact fabrics absorb more dyes and thus have vivid colors than the ring fabrics.
2. They have higher abrasion resistance and lower pilling tendency than ring fabrics.
3. They show higher bursting strength than ring yarns.
These are some of the standard value addition norms
Fibre to Spun Yarn: 75%
Yarn to Grey: 40%
Grey Fabric to processed fabric for apparel consumption: 80%
Grey Fabric to non apparel textile items: 100%
Processed fabric to apparel: 110%
Retail value addition for Apparel: 100%
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Coated Denim: Why Some Jeans Look Like Waxed Cotton or Leather
One reader recently asked about coated denim. This is a very interesting surface treatment used in denim garments, especially jeans, to give them a different handle, appearance, and fashion value.
Coated denim refers to denim fabric or denim garments that have been given a special surface coating. This coating may make the denim feel as if the cotton has been waxed. In black denim, the effect can be even more striking: the jeans may shine almost like leather pants.
This is why coated denim is often used in fashion jeans, biker-style jeans, premium denim collections, partywear denim, and garments where a sharper, more polished look is required.
What Is Coated Denim?
Denim is normally known for its rugged cotton character, twill weave, indigo fading, and casual appearance. In coated denim, a thin layer of coating material is applied on the surface of the fabric or garment.
This coating changes the surface behaviour of the denim. It may improve lustre, create a waxy touch, give a leather-like effect, reduce fading, or provide some resistance to stains and dirt.
Simple Explanation:
Coated denim is ordinary denim whose surface has been treated with a thin film-like layer. This layer may be pigment-based, acrylic-based, polyurethane-based, or resin-based, depending on the effect required.
Common Types of Coating Used on Denim
The coating on denim is generally done using materials such as:
Pigment coating
Acrylic coating
Polyurethane, or PU, coating
Resin coating
1. Pigment Coating
Pigment coating gives denim a new surface appearance. It can create colour effects, dusty effects, worn effects, and fashion finishes. One interesting feature of pigment-coated denim is that it may change its look after washing and wearing.
With every wash, the coating may abrade slightly, producing a new appearance. This gives the garment a lived-in, evolving, and vintage character.
2. Acrylic and Polyurethane Coating
Acrylic coating and polyurethane coating are often used as transparent or semi-transparent coatings. These coatings form a thin protective layer on the denim surface.
Unlike pigment coating, acrylic and PU coatings may preserve the colour and fading properties of denim to some extent. They can also improve the lustre, surface feel, and handle of the garment.
Acrylic and PU coatings may provide:
A smoother surface feel
A mild glossy or leather-like appearance
Protection against surface abrasion
Some stain-resistant properties
A breathable protective layer, depending on the formulation
3. Resin Coating
Resin coating is another method used to create special effects on denim garments. It is commonly used when a leather-like appearance or firm surface handle is required.
In one method, resin is applied with the help of a wooden handle and a rubber squeezer. The rubber squeezer helps to extract and spread the resin under pressure, allowing the coating to form a leather-like effect on the denim garment.
The resin material used for such coating may be a neutral cream-coloured paste, with a pH of around 7. It is miscible in cold water and may show resistance to heat up to around 200°C, depending on the product formulation. Some resin coatings are self-catalysed and resistant to chlorine.
Technical Note:
The exact behaviour of resin coating depends on the chemical formulation supplied by the manufacturer. Temperature resistance, chlorine resistance, handle, gloss, and wash durability may vary from product to product.
How Is Coating Applied on Denim?
Coating can be applied either on denim fabric before garment making or directly on the finished garment. In fashion denim, garment coating is quite common because it allows special effects to be created on selected areas.
The coating may be applied by different methods, such as:
Screen coating
Brush application
Knife-edge coating
Rubber squeezer application
Machine coating
Each method gives a slightly different surface effect. For example, brush application may create a more uneven handcrafted appearance, while knife-edge or machine coating can give a more uniform surface.
Drying and Curing of Coated Denim
After the coating is applied, the denim fabric or garment must be dried and cured. Curing helps the coating film set properly on the surface of the fabric.
A commonly used curing condition is:
Curing Temperature: 150°C Curing Time: 5 minutes
However, the exact drying and curing conditions should always be decided according to the chemical supplier’s recommendation, the type of denim, coating thickness, garment construction, and final performance requirement.
Why Is Coated Denim Popular?
Coated denim is popular because it gives denim a more fashionable and premium appearance. It allows ordinary denim to be transformed into a garment with a glossy, waxed, or leather-like surface.
Some of the important benefits of coated denim are:
It gives denim a new fashion look.
It can create a waxed or leather-like appearance.
It improves surface lustre.
It can improve the feel and handle of the garment.
It may provide stain resistance.
It can protect the fading character of denim, depending on the coating used.
It adds value to basic denim garments.
Durability and Washing
Coatings on denim are normally designed to be reasonably permanent. A good coating should be able to sustain multiple launderings without completely disappearing from the surface.
However, coated denim should still be washed with care. Harsh washing, strong bleaching, high mechanical action, and aggressive tumble drying may reduce the coating effect over time.
Care Note:
Coated denim should preferably be washed inside out, with mild detergent, and without strong bleaching agents. This helps preserve the coating and surface shine for a longer time.
Coated Denim vs Ordinary Denim
Feature
Ordinary Denim
Coated Denim
Surface
Natural cotton twill surface
Film-like coated surface
Appearance
Casual, rugged, indigo look
Glossy, waxed, polished, or leather-like look
Handle
Dry cotton feel
Smoother, firmer, or waxy feel
Fading
Fades naturally with wear and wash
Fading may be protected or modified by coating
Fashion Value
Classic denim look
Premium, fashion-oriented look
Conclusion
Coated denim is a value-added denim finish that changes the surface character of jeans. It can make denim look waxed, glossy, polished, or even leather-like. Depending on the chemical used, the coating may be pigment-based, acrylic-based, polyurethane-based, or resin-based.
Pigment coating gives denim a changing and evolving fashion effect after washing. Acrylic and PU coatings form a transparent protective layer that can improve lustre, handle, breathability, and stain resistance. Resin coating can be used to create a stronger leather-like appearance.
In short, coated denim allows a basic cotton denim garment to move from casual wear into fashion wear. It is a good example of how surface finishing can add both aesthetic and commercial value to textiles.
T500: Means number of threads per square inch of the cloth are 500. This is also known as the thread count.
To calculate. Cut a square inch of the fabric. Count the number of weft threads in that region and count the number of warp threads in the region and add the two. Thread count = Number of warp threads+ Number of Weft threads.
100% cotton: Is Self Evident. The fabric is made of 100% cotton.
100x100: It is the English count of warp and weft.
185 x 195 : This indicate the number of ends ( warp threads) and number of Picks ( weft threads) per inch. Incidently 185+195= ~500 which is the thread count.
118" is the width of the fabric in inches.
4PI(1/1) : It means that the weave is one-up-one-down but four picks are inserted at a time. If two picks are inserted at a time it is called DPI ( Double pick Insertion) if single pick is inserted it is called SPI ( Single Pick Insertion).
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Workers involved in sewing activities such as manufacturing garments, are at a risk of developing musculoskeletal disorders. Therefore it is imperative that the design of sewing station, stitching, finework,scissor work and material handling should be ergonomically appropriate. This site talks about ergonomical solutions for the same. A lot of sketches and diagrams are given for easier understanding. Some very quick rules of thumb can be derived from the sketches:
1. Chair Height is correct when the work surface is at elbow height and the sole of the foot should rest on the floor.
2. Schedule frequent and short breaks to stretch and change position.
3. Height and Tilt adjustable tables help employees access their work without using awkward postures.
4. Edges of work surfaces should be padded or rounded, so that the workers can rest their arms against them.
5. Use of Adjustable task lighting and magnifying glasses at workstation can take care of fine work inspection.
6. Shorter width table should be used for scissorwork so that the workers dont have to bend and reach so far.
7. Lifting of weight should be done at waist level.
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The Following are the basic differences on the basis of which we can distinguish Linen from cotton:
1. Linen is about 20% more heavy than cotton.
2. It has a leathery feeling that is absent in cotton .
3. Cotton feels warmer(about 15-30% warmer) and holds heat better than linen.
4. On holding linen against light, the threads and the fibers composing the threads appear uneven and streaked as it is not possible to make linen yarn as uniform as cotton yarn.
5. On burning a linen thread, the fibers lie in the same position as before with no change except the scorched appearance. Burning a cotton thread causes the fibers to spread like a tuft.
6. Linen absorbs oil much better than cotton. To distinguish Linen with cotton in a piece of fabric, first remove all the impurities by washing and boiling. Then when if the fabric is dipped in oil, the linen fibers look transparent if held against the light. The Cotton remains nearly opaque.
7. Linen stands the action of sulphuric acid better than the cotton. To check a blend, first remove all the impurities then dip in con. sulphuric acid for a minute or two. Wash in water and dry on a blotting paper. All that remains on the blotting paper is linen. The cotton almost immediately dissolves in acid.
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Is Indigo Natural or Synthetic? How Was Indigo Produced?
The answer to the first part of the question is simple: both. Indigo began its textile journey as a natural dye obtained from plants. Later, with the development of modern chemistry, the same blue colouring substance began to be manufactured synthetically.
Today, most of the indigo used in the textile industry, especially in denim, is synthetic. But historically and culturally, indigo is deeply associated with natural dyeing traditions of India, China and many other parts of the world.
Indigo belongs to the category of water-insoluble dyes. More specifically, it is a vat dye. This means that indigo, in its blue form, does not dissolve in water and cannot be applied to fabric directly like many other dyes. It has to be chemically converted into a soluble form before dyeing, and then converted back into the blue insoluble form on the fibre.
Indigo is one of the oldest dyes known to human civilization. It is believed to have been used for dyeing in India and China from very early times, possibly as far back as 2000 BC. The name “indigo” itself is connected with India. The Greeks and Romans referred to it as a blue dye coming from India, often described as “Indian blue.”
Originally, indigo was obtained from plants, especially from species such as Indigofera tinctoria. The leaves of the plant contained the precursor of the dye, but not the ready-made blue dye in a simple usable form. The blue colour had to be developed through fermentation, reduction and oxidation.
This is what makes indigo so fascinating. It is not merely a colouring matter extracted like juice from a plant. It is a dye that requires chemical transformation before it becomes useful.
Chemical Structure of Indigo
The main colouring compound in indigo is called indigotin. Its molecular formula is:
\[
C_{16}H_{10}N_2O_2
\]
The structure of indigo consists of two indole-like units joined together through a central double bond. It also contains two carbonyl groups \((C=O)\) and two nitrogen atoms. A simplified way to understand the molecule is:
The indigo molecule is highly conjugated. This means that electrons are spread over a large part of the molecule. This extended conjugation is responsible for the absorption of visible light and the characteristic deep blue colour of indigo.
Visual 1: Chemical structure of indigo, \(C_{16}H_{10}N_2O_2\).
This structure also explains why indigo is stable and water-insoluble. For dyeing, the molecule has to be temporarily converted into another form.
How Natural Indigo Was Produced
Natural indigo was traditionally obtained from the leaves and stems of indigo plants. The harvested plant material was placed in a vat filled with water. In older traditional processes, urine or other alkaline fermenting materials could also be used. Fermentation was then allowed to take place.
Inside the plant, the main precursor of indigo is indican, a colourless glucoside. During fermentation, indican breaks down into indoxyl and glucose.
This step is important because the plant does not directly give a strong blue dye. It first gives indoxyl, which is the immediate precursor of indigo. When the fermented liquid is stirred or beaten with poles, oxygen from the air enters the liquid. This oxygen oxidises indoxyl into indigo.
As indigo is insoluble in water, the blue particles begin to separate out and settle at the bottom of the vat. The liquid above is drained off, and the remaining blue sludge or mash is collected. This mash is then dried in the open air and sold in the form of pressed cakes, lumps or powder.
This traditional method explains why indigo production was both an agricultural activity and a chemical process. The farmer grew the plant, but the dyer or processor had to understand fermentation, aeration, settling and drying.
Visual 2: Natural indigo production from leaves to indigo cake or powder.
Indigo as a Vat Dye
Indigo is insoluble in its blue form. Therefore, to dye fabric with indigo, it must first be reduced into a soluble form called leuco-indigo. This reduced form is pale yellowish or greenish and can dissolve in an alkaline dye bath.
In this reduced form, indigo can enter or deposit onto the fibre. When the yarn or fabric is removed from the dye bath and exposed to air, oxygen converts leuco-indigo back into blue indigo.
This is the magical moment in indigo dyeing. The material may come out of the vat looking yellowish-green, but slowly turns blue as it reacts with oxygen in the air.
Practical textile point: This conversion from insoluble blue indigo to soluble leuco-indigo, and then back to insoluble blue indigo, is the heart of vat dyeing.
Visual 3: Indigo vat dyeing cycle: reduction, dyeing and oxidation.
Why Stirring Was Important
In traditional indigo production, the fermented mass was stirred or beaten with poles. This was not merely a mechanical operation. It had a chemical purpose.
During fermentation, the precursor compounds were converted into reduced or reactive forms. When the liquid was stirred, air entered the vat. The oxygen in the air converted indoxyl into indigo. Since indigo is insoluble, it appeared as blue particles and settled at the bottom.
\[
\text{Fermentation develops the precursor}
\]
\[
\text{Stirring introduces oxygen}
\]
\[
\text{Oxygen converts the precursor into blue indigo}
\]
\[
\text{Insoluble indigo settles at the bottom}
\]
This is why the process required both patience and skill. Too little fermentation, too much fermentation, insufficient aeration or poor settling could all affect the quality of the final dye.
From Natural Indigo to Synthetic Indigo
Thus, indigo began as a natural dye. For centuries, India was one of the important sources of natural indigo. Indigo was exported as a valuable dye material, and the term “Indian blue” became associated with it.
However, in the nineteenth century, European chemists began studying the structure and synthesis of indigo. Adolf von Baeyer made major contributions to the chemistry of indigo and succeeded in synthesising it in the laboratory. Later, in 1897, BASF began industrial-scale production of synthetic indigo.
This changed the dye industry completely. Synthetic indigo gave manufacturers a more consistent, predictable and scalable source of blue dye. Natural indigo depended on crop quality, climate, fermentation conditions and extraction skill. Synthetic indigo could be produced in large quantities with more uniform strength and shade.
Over time, synthetic indigo almost completely replaced natural indigo in large-scale textile production.
Natural Indigo vs Synthetic Indigo
Point
Natural Indigo
Synthetic Indigo
Source
Plant-based, mainly from indigo-bearing plants such as Indigofera tinctoria.
Manufactured chemically.
Main colouring compound
Indigotin.
Indigotin.
Molecular formula
\(C_{16}H_{10}N_2O_2\)
\(C_{16}H_{10}N_2O_2\)
Consistency
May vary from batch to batch.
More uniform and predictable.
Scale
Suitable for craft, heritage and natural dyeing.
Suitable for industrial denim production.
Process control
Depends on fermentation and extraction.
Depends on chemical manufacturing controls.
Present use
Niche use in natural dyeing, handcraft and sustainable fashion.
Dominant in denim and industrial textile dyeing.
The important point is that the main blue molecule is the same: indigotin. The difference lies mainly in the source, impurities, production method, consistency and environmental profile.
Indigo and Denim
Today, indigo is most strongly associated with denim. Cotton warp yarns are dyed with indigo, while the weft often remains undyed or lightly coloured. In denim dyeing, yarns are repeatedly dipped into the reduced indigo bath and then exposed to air for oxidation.
This repeated dipping and oxidation builds up the blue shade gradually. One interesting property of indigo dyeing is that the dye often remains more concentrated near the surface of the yarn rather than penetrating fully into the core. This is one reason denim fades beautifully with wear.
As the outer surface of the yarn is abraded, some of the indigo is removed, revealing lighter areas. This gives denim its characteristic worn, faded and aged appearance. So, in denim, fading is not always a defect. It is often part of the desired aesthetic.
A Small Correction to Understand the Old Process Better
In older descriptions, it is sometimes said that hydrogen was created by microorganisms and acted as a reducing agent. This is a simplified way of explaining the process. More accurately, fermentation creates reducing conditions in the vat. These reducing conditions help convert dye precursors into forms that can later be oxidised into indigo.
Similarly, when the liquid is stirred, the aim is to introduce oxygen. Oxygen converts the soluble or reduced precursor into insoluble blue indigo. The blue particles then settle at the bottom.
\[
\text{Reduction during fermentation}
\]
\[
\text{Oxidation during beating or aeration}
\]
This reduction-oxidation cycle is also central to indigo dyeing on fabric.
Conclusion
Indigo is both natural and synthetic. Historically, it was obtained from plants and processed through fermentation, aeration, settling and drying. Later, chemists discovered how to produce the same blue colouring substance synthetically. With industrial production by BASF in the late nineteenth century, synthetic indigo gradually replaced natural indigo in most commercial textile applications.
The beauty of indigo lies in its chemistry. It is a water-insoluble vat dye. It must first be reduced to a soluble leuco form, then applied to the fibre, and finally oxidised back to the blue insoluble form.
This is why indigo is not just a dye. It is a story of plants, fermentation, chemistry, trade, denim and textile technology.
Related Reading on Indigo, Natural Dyes and Dyeing
This article is intended for educational and general textile knowledge purposes only. The chemical reactions shown are simplified to explain the main principles of natural indigo formation and vat dyeing. Actual indigo extraction, dye reduction, denim dyeing, effluent treatment and chemical handling require proper technical knowledge, safety precautions, process control and laboratory or mill-level validation.
Textiles have function of a 'second skin', substituting for the biological properties that other animals have evolved to cope with specific environments on this planet. Thanks to textiles, humans have even been able to enter the most extreme and inhospitable environments, such as interplanetary space.
At the same time, however, dermatologists and consumers have become increasingly aware of the risks garments may cause to human health.
Contact dermatitis is the name given to localised rash or irrittion of the skin caused by the contact with a foreign substance.
When an allergen is involved there is an immune system reaction. The rash can show up a day or two after contact with the allergen. It will usually disappear in a few weeks, even if it is not treated.This is called Allergic Contact Dermatitis ( ACD)
When an irritant is the cause, the rash usually appears right away, possibly damaging the skin. The longer the skin is exposed to the offending substance, the more it will be damaged. The hands are often affected by this type of rash when harsh chemicals and substances are handled. This is Called ICD ( Irritant Contact Dermatitis).
Irritant dermatitis is one concern, but allergic contact dermatitis especially to certain colors used in textiles and to textile finishers even more so. The treatment of textiles or their raw materials with insecticides has alarmed authorities and prompted the industry to set safety standards known as 'eco seals'.
Textile is rated at number 5 of the top ten skin-unfriendly occupations.
At each stage their are irritants or allergens that are a potential cause of dermatitis.
Fibers commonly cause ICD and rerely ACD. The synthetic and wool fibers tend to be the irritants.The process of making yarns and preparation exposes to the irritants such as spinning oil, heat and polyvinyl alcohol.
During weaving the same irritants as in case of spinning apply.
Preparation process also exposes the workers to irritants.
It is dyeing, however, which is the principal cause of Occupational Skin Disease in the industry.The two groups of dyes i.e. reactive and disperse are the most frequest sensitisers.Chemicals and metals used are modants to give color their permanence can be irritants or allergens.
A complete list of Irritants and Allergens in the textile industry is given here.
To conclude, As This site says - "The interaction between textiles and the skin is a close and reciprocal one. Therefore, a mutual exchange must be established between those who create textiles and those who treat skin. Thus a textile engineer must understand basic skin anatomy and microbiology. Similary a demermatologist must need to know about the structure of fibers, fabrics, dyes and finishes."
Traditionally Natural pumice stone is used in denim washing process. It has the following disadvantages:
1. Residual pumice is difficult to remove from washed fabric/garment.
2. There is always a danger of damage to the equipment by overload of tumbling stones and material.This can also clog the drains and sewer lines.
Thus enzymes like cellulase are used to achieve the desirable appearance and soft handle for the fabric.
The problem with using enzymatic treatment is that the removed indigo dye can be redposited on the white yarn of the denim fabric. this process is called back staining and it can mar the look of garment.
Industrially cellulase is used along with Pumice stone for stone washing.
The cellulase can be at ph=7, when it is called the neutrual cellulase or at a pH of 5.5, when it is called the acidic cellulase.
In general the cellulase added is for 60min at 55 deg C as a percentage of the weight of the garment. It can be 3%, 6%, 9% or 12% depending upon the appearance required.
Pumice stone is generally taken as equal in weight that of the garment.
According to a study , the best stone washing ( as measured by the lightness of the sample is achieved for treatment with Neutral cellulases with pumice stone, acid cellulases with pumice stone, neutral cellulases, acid cellulases and pumice stone, in that order.
In the same order tensile strength of the sample decreases.
However, degree of back staining increases in the order of treatment with pumice stone, acid cellulases, neutral cellulases, acid cellulases with pumice stone and neutral cellulases with pumice.
which means a balance needs to be achieved- and where the effort to increase one desirable leads to increase in another undesirable one.
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Colors are an inseparable part for any Textile enthusiast. It is therefore, important, to understand the colors as a physical and psychological phenomena. Equally important is to understand the effect of various color patterns on an overall experience.
This site presents a three-part series on color theory. Here the meanings behind the different color families are discussed , and some examples of how these colors are used (with a bit of analysis for each) are given.
In Part 2 there is a talk about how hue, chroma, value, saturation, tones, tints and shades affect the way we perceive colors.
Third part discusses color pattern for designers.
The treatment of the subject is done keeping a web-designer into mind. The implications are true equally for any textile situation.
This brilliant text is written by Cameron Chapman, who is a professional Web and graphic designer with over 6 years of experience.
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Silk is sold by weight. By means of weighting the manufacturer can increase the weight of silk by 3 to 4 times. The weighting substances in the silk includes tannins such as salts or iron, tin (mostly used), chromium, sodium, magnesium and barium. Also sugar (mostly used), glucose, gelatin, glycerin and paraffins are used.
How weighting is done
Silk has great absorptive power. It can take upto 50% of tannin. Once that is applied the tannin itself can attract salts of iron and tin by another 50% without any visible indication of being changed in character. For dark colored silks, iron salts are used, for light-colored silks, tin salts are used.
For applying weighting, the silk is first degummed. During degumming process, silk loses approximately one-fifth of the weight. This is done prior to weaving. Then it is immersed in a solution of catechu or some other substance rich in tannin. Then it is tranferred from tannin vat to iron or tin baths. After this cloth is taken out and washed in pure water.
Effects of Weighting
Weighting causes the fabric to lose its strength as soon as the weighting is applied. Heavily weighted silk must be made into garments as soon as it is made. Spots develop in the dyes. Saltswater, perspiration and tears cause spots to be formed which seems as if the silk is eaten by acids. Sunlight also attacks weighted silk and can cause silk to fall to pieces.
How to Detected Weighting in Silk :
Weighting of silk can usually be detected by the burning test. Separate threads from the warp and the weft are set on fire with a burning match. Pure silk burns very badly and stops burning as soon as the burning match has been removed. Practically no ash is formed (less than one per cent), and the end of the fiber left unburned takes the shape of a little bulb.
Weighted fibers, when burned, leave a considerable amount of ash, and the entire thread may keep its shape after being burned. When only the filling or the warp is weighted, applying the flame to a sample of the cloth seems to consume only one set of threads, the unweighted ones, the others keeping their form because of the heavy ash content.
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This Article written in early 1900s is a superb treatise on everything about Mercerization:
Here is a list of FAQ that this articles seeks to clarify:
1. Why Mercerization ?
Mercerization was evolved to get over the limitation of silk. It is the high price of silk and low production. On the other hand, a product was needed which could imitate the high lustre, steel-like strength, its attractive smoothness and softness, its elasticity and and its quality of taking the most delicate tints and shades in the dyeing process.
2. What is Mercerization
Mercerization is a process applied to cotton yarn or fabrics which gives to the cotton fiber a silk-like luster, greater strength than ordinary cotton and a greater affinity for dyes.
3. How it is done
The cotton is soaked in strong caustic soda or caustic potash solution for a few moments under stretch and then washing in pure water to remove the caustic.
4. What happens to the structure of cotton during Mercerization
In natural condition the cotton fiber is a flat, twisted, ribbon-like filament. When immersed in caustic solution it swells out and takes on a round and a hair like appearance, and becomes plump instead of flat.
5. What happens to the chemical structure of cotton during Mercerization
The cellulose is changed into hydro-cellulose or cellulose-hydrate.
6. Why mercerized cotton takes dyes so quickly.
Cellulose cannot be dyed so easily. Hydro-cellulose on the other hand, absorbs almost any kind of dye readily. Mercerised cotton takes dyes so fast, that chemicals are added in the dye bath to check the process in order that the dyes may not enter so rapidly as to render the shading uneven.
7. What is role of stretch during mercerisation.
Stretch causes the luster, the more the stretch the more the lustre. However, after a certain point, the stretch causes a decrease in strength.
8. How mercerization is done actually ? What are the chemicals added and other process parameters.
9. Apart from Caustic Soda, what other chemicals can be used for Mercerisation, what are their limitations.
10. Why sometimes Carbon disulphide is added in mercerisation.
11. Should bleaching be done before or after mercerisation
12. What pre-processes ensure better luster in Mercerisation processes
13. What type of Cottons are suitable for Mercerisation
Longer cottons are more suited to get as much natural luster as possible. Similarly combed cotton lend themselves better to Mercerisation than carded cottons.
14. What is part Mercerisation. How it is used in produces various fabrics.
Taking a cotton blend, and then mercerising will produce an effect called as crepon effect. Similarly, mercerisation can be used to produce seersucker effect by Mercerising only certain stripes on the warp direction by covering the rest of the cloth by suitable means.
15. How to identify Mercerised Cotton
(This method has not been tried by me. Please take all precautions including consultation from a chemical scientist before attempting)
Mercerized cotton may be determined as follows: A solution is prepared by dissolving 140 gms of potassium iodide in about 475 ml of water. To this solution add 30-60gms of iodine, and mix with another solution made by dissolving 850 gms of zinc chloride in 350 gms of water. The cloth sample should first be soaked in water, immersed in this prepared solution for three minutes, and then rinsed in water. Mercerized cotton will have a deep blue color, while unmercerized cotton will wash out white. The blue of this solution on mercerized cotton will show through quite heavy dyes.
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