Saturday 20 February 2010

What is Coated Denim

One reader has asked about coated denim.

Such jeans have a coating that feels like as if the cotton of the denim is waxed. If black in color, the jeans shines up like leather pants.

The coating is generally done using pigment, acrylic or polyurethane coating. Pigment coating provides the denim a new look and experience after every wash. Acrylic and PU, however, act as a transparent coating. This protects the fading properties. It also gives the fabric a protective breathable layer with stain resistant properties. The luster and feel of the fabric are also improved.

Resin Coating is generally done with the help of wooden handle. A rubber squeezer is used to extract resin under pressure to form leather effect on denim garment. It is a neutral ( pH 7) cream-colored paste that is miscible in cold water and resistant to heat upto 200 degree
Celcius. It is self catalysed and chlorine resistant.

The coating can be applied on the garment by screen, brush or knife edge. Machine coating is also possible.

After applying coating the fabric is dried and cured at 150 degree Celcius of 5 minutes.

Normally the coating are permanent in nature and able to sustain multiple launderings.

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Wednesday 17 February 2010

What is the Meaning of T500 100% Cotton 100x100 185x295 118: 4PI (1/1)

I was recently asked this question by a reader.

Let me explain this to you:

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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Tuesday 16 February 2010

Ergonomics in Apparel Industry

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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Monday 15 February 2010

Distinguishing Linen from Cotton

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 it manufactured earlier

The answer to the first part of question is "Both".

Indigo belongs to the category of water insoluble dyes.

It was first mentioned in a book in 13 BC by the name of Indian Blue. It is said that it has been used for dyeing in India and China 2000 BC. 

Originally it was made from Indigo plant.  The plant came to Europe in the 16th century via India. The leaves and stalk were kept in a vat filled with water and human urine. During this process, hydrogen was created by micro-organisms and acted as a reducing agent. It transformed the dyestuff in a water insoluble form. 

This fermented mass was stirred with poles. The reason for doing this was to transform the indigo into its water insoluble form again by oxidation. These water insoluble particles could then deposit on the bottom of the stationery vat. 

Then the liquid standing above was drained and a thin mash was left which was dried in open air and was put on the market in pressed or powder form.

Thus indigo started as a natural dye. However later it got manufactured using synthetic means.  In 1880  Adolf von Bayer succeeded in carrying out the first synthetic production of Indigo. In 1897, BASF was able to carry out the industrial scale production of Indigo. Now synthetic dyestuff has replaced the natural one almost completely. 

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Saturday 13 February 2010

Health Hazards in Textile Industry- Skin

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."


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How to Stonewash Better

How to Stonewash Better

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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Wednesday 3 February 2010

How to think in colors or Color Theory for Designers

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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Monday 1 February 2010

Chemical Identification of Silk

Please see the following link for details on chemical identification of silk.

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