Textile Notes related to fiber, yarn, fabric knowledge, spinning, weaving, processing, projects, knitting, Indian Traditional Textiles and denim manufacturing
Important Factors in Judging Cotton Yarn Industries in India
1. Cost Management
Raw material cost forms about 50-55% of sales, in a cotton spinning company. The ratio of indigeneous to imported cotton affects the cost, as imported cotton depends upon international cycles.
Power cost forms a fair component of cost (about 10% of sales) and the power expenditure becomes very critical. Players using captive generation have an assured uninterrupted supply of power.
Efficient cotton procurement strategies like contract farming, proficiency in estimating the future trends in the cotton market, proximity to the cotton cultivation areas and optimal quantity of cotton procurement would help players in minimizing costs and achieving profitability.
2. Inventory management
Cotton is a seasonal crop and is harvested from October to February every year. Inventory management thus plays an important role as companies procuring optimum quantities of crop and stocking raw material
requirement for a considerable time can ensure availability of good quality raw materials at reasonable prices.
3. Economies of scale
As the industry is characterized by low margins, profitability depends on volume of sales and companies having high capacities can register satisfactory growth. High capacities can also help players in bagging huge
orders. Further, companies having the capacity to manufacture on multiple lines can take the advantage of simultaneous production of different counts.
4. Labour relations
Labour cost constitutes about 6% of sales. Given the labour intensive nature of the industry, the companies having cordial labour relations are better placed in terms of labour productivity and smooth operations.
5. Expansions / Modernization
Opening up of global markets in the post quota regime, requires companies to undertake expansions and modernisations at the appropriate time so as to gain advantage of the growing markets and the demand-supply gap. Ability of spinning units to replace obsolete machines with modern state-of-the-art machines will enable companies to cater to the export marketsand offer better quality products. Further, players foraying into downstream expansions can benefit from integrated operation.
6. Diversification
Product diversification
Players having finer count yarn in their product mix, cater to the elite market segment where demand is relatively price inelastic and margins are high. Companies having capacity to produce double yarn have better product flexibility. Further, companies producing blended yarn rather than only cotton yarn, can efficiently tackle the cyclicality in the cotton yarn demand. Also,companies focusing on value added products can further improve their profitability.
Geographical diversification
A player catering to both domestic as well as export markets can diversify the risk of sluggishness in a particular market. Export oriented companies catering to various countrieshave lower country specific risk. However, a large composition of exports calls for foreignexchange management policies as fluctuations in the foreign exchange market can adversely affect such players.
There is frequently a need to describe the textile yarn concisely in the language which a laymen can understand. Also there is a need to write concisely the description of the textile yarn. ASTM has an elaborate system to describe spun, filament and a yarn made from a combination of these i.e. ply and cable yarn.
In yarns such as ply or cable yarn which are made from components, it is essential to describe the components and the resultant from those components. Thus in describing such yarns, there have to be two groups; one of them describes the components and the other describes the resultant yarn. Accordingly there are two ways to write a yarn description.
First method is called single to fold or ply notation. In this system, the single component of yarn is described first and only then the resultant yarn is descibed. This system is used in indirect numbering system.
Second method is called fold or ply to single notation. In this system, the whole structure is described first and then the components are described. This is frequently used by yarn buyers.
The full treatment of the topic is given here. Some general guidelines and examples are given in this article.
The notation
24 Ne Z 15tpi (Cotton, 1 1/6 inch, SLM, 4.3 Micronaire Reading)/5 S 9 tpi/3 Z 5tpi; R 1.4 cc
represents a yarn made from 24 Count twisted in z direction with 15 twists per inch which is then again twisted 5 fold in s directions with 9 tpi and three such yarns are again twisted in Z direction with 5 tip which give a resultant cotton count of 1.4.
The filament single yarn is described as
11 tex f40 s 2.5tpi( nylon 2.5 dtex)
For yarns where linear density gets increased on bulking or texturising, we describe it by symbol B.
70 den f34 t0(Nylon 2.97den); B 80 den
B 80 indicate that the denier of yarn is increased from 70 to 80 after bulking.
Multiple wound yarns are described as:
25 tex Z 15 tpi ( Cotton ) x 2 t0
Here t0 indicate zero twist and describes that 2 yarns of 25 tex cotton with 15 tpi in z direction are wound together.
Difference between Cold Peel and Hot Peel in Heat Transfer Printing
Heat Transfer printing is an indirect printing method where, rather than printing inks directly on to a garment, inks are printed on to paper (called transfer paper), dried, then ‘transferred’ under a heat press on to the garment. Transfers are produced basically in two ways: these are Cold Peel (cold-split) transfers, and Hot-Peel (hot-split) transfers. Cold Peel method is where the transfer paper is allowed to cool down completely after application and before removing. This gives a semi-glossy, rubbery feel to the print. Hot peel method is where the transfer paper is peeled off the hot transfer immediately after the transfer is applied. When the paper is peeled hot, a portion of ink remain on paper and the rest on the fabric. Hot peel transfers feels just like screen prints.
There is an excellent article about how to do the transfer printing here. To know in general about heat transfer printing one can go here .
Excalibur Product Manual is a trasurehouse of information about screens and heat transfer printing
An amazing introduction to Screen printing is done in comic style here
Warp is always 20/22 denier ungummed, silk called Japani. Normally is is natural in color but it is also dyed by partially degumming the fiber. This silk is obtained chiefly from Varanasi. The main source of this silk is China. In weft different types of fibers of different thickness can be used. Thus Mercerised cotton ( which is always twisted 2/120s or 2/100s) count is used. Generally, in weft 2/120s count is used for heavy saris, 2/100s for dress material with Buti and 2/80s for fabrics. If 2/70s is used it is generally a blend. The Kanni is always in cotton. This can be used as a way to identify if chanderi contains any synthetic. If kanni is not cotton, there are chances that the weft used is synthetic as using cotton in kanni will cut it.
Similary Katan ( which is two ply twisted 2 x16/18 denier silk) can be used. Sometimes they degum the Katan and make it look very soft. This is called Puna Resham. Some times single folded, two folded or three folded 100s cotton yarn is used. Zari is Half Fine Thread obtained from Surat, and is used in warp or weft for border, ornamentation in the body or at palla. Normally six zari colors are employed: Silver, Vine, Copper, Gold, Black and Green. Zari comes in bundle of four gittis ( cops ) of 240 grams each.
Production Details
Chanderi is a Silk cotton fabric woven on handloom. The production is 3-4 meters per day for plain weave, it can be upto 1 meters per day where butis are required. The length of the weavers beam is from 60 m to 100 m (Image- Weaver’s Beam). When changing the beam, simple knotting is done with the threads of the previous beams. The EPI is 100 per inch ( 50 dents) the PPI is 66 picks per inch.
However length of fabric on roll is kept at 12m to 13 m. The Border is inserted using dobby or Jacquard. (Image: View of Jacquard- Notice the two Jacquard, one is for Palla and the other for Body, the image on the middle is Dobby Mechanism, image on the extreme right shows the Lingos for Jacquard Mechanism)
The image below represents the fabric woven on two jacquards ( Image above at the left):
Similarly Palla can be woven. The dobby is of 24, 60 or 64 levers. Reed used can be of 2500 dents or 2600 dents. Normally two ends per dent are used, however to give stripe effect to the fabric , 4 ends per dents are used after every 8-9 ends- which are dented in the regular fashion. Reed width is of 50 inches which gives a 46 inches wide cloth. Reed used is 100s which is number of dents per 2 inch. Thus for a 50 inch read, a maximum of 2500 dents are there which accommodate the warp. Generally in a 12.80 m warp, 12 m of fabric can be obtained. Design is counted by the number of Tillis used to produce it. Tillis are small yarn holders used to hold the ornamentation yarn. ( Image- left: Tillis, Video- How design is inserted, Image at right showing warp sheets for two looms).
Ends for Tillis are lifted separately by a mechanism called as Nakka. Image ( Nakka). According to the design after every one or two normal picks the prescribed ends are lifted and held by means of peg and then the tillis are taken under those threads.
Generally in one inch 33 tillis are used. Thus if a graph is of 330 picks, it will take 10 inch of space on fabric. ( Image – Graph and its Replica on Chanderi Fabric)
One inch has got 100 ends and 50 dents. The tillis can be inserted after every one pick of normal yarn or after two picks of normal yarn. After warping the rope form of silk yarn is prepared called as Gundi. It contains 5300 ends. If 500 ends are used for making border, The rest 4700 are divided equally among 2350 dents. The warp beam is ordered like (2300=78)/931, which means warp meant for 2300 dents of 78 yards of 931 grams. The yarns in the warp sheet are prevented from entanglements with the help of lease threads which are inserted in the warp sheet after regular intervals ( Image- Lease Threads).
The warp beam is prevented from sloughing off by means of nylon ropes tightly twisted ( Image- Rope to hold the warp beam)
When weaving with Single yarn is weft, water is used whereas when folded yarn is weft is used it is used as is. A typical dotted effect called Kirkita is produced using a flat wooden strip called Chapetan or rod. It is inserted in the warp end after every 6 ends depending upon the design. Then wherever the dotted zari effect is required to be produced, it is made to stand and the pick is inserted. In chanderi they have started using vat down. However black is still Sulphur black. As told earlier, the acid dyes are used in the silks. The yarn is first wetted using 30-40 C. Then it is dyed at 60 deg Celcius. The color Is matched and then acidic acid is added in requisite amounts. Then it is heated for 15-20 minutes and dried. Chanderi can be hand washed but because of Zari, it has to be dry cleaned. In a loom called Tara loom(Please see here), the amount of beat up is controlled using cam in the loom. In most of the looms take up mechanism is employed to avoid banding and even picks per inch (Image: Take up mechanism in left and Tara Loom on the right).
Warp is obtained in bales of 60 kg containing 12 bundles of about 5 kg. Weft is obtained in 2 kg bundles. Warp is always obtained which is dyed according to the requirements. Now in more and more looms Katan is used in weft instead of cotton. The cotton weft , when bought in dyed from Mills in Mumbai or Coimbatoor is mostly obtained already Reactive dyed from the source, which are semi fast colors. However vat dyes are increasingly being done to get the best colorfastness. ( Image on the left: Vat Dyes Stored by BVSC in Chanderi- It also shows the dyeing rate). Cabinet dyeing is also practiced at some places ( Images: Inside of a Cabinet dyeing machine at Handloom Institute, Chanderi).
Most of the cotton is bought through NHDC rather than private suppliers. Zari is obtained in 1kg bundles with 4 gittis or cops in it each of about 240 gram. The zari that glitters more is inferior in quality.
To hold the fabric while looming, instead of temples a narrow strip with three pointed nails at both its end is used. Once the fabric is woven to some length, the strip is then shifted forward suitably.
Motifs and Colors used
An excellent treatment on the motifs and colors used in Chanderi fabrics can be found here.
The dyeing process of Silk in Chanderi Fabric according to MSME is as follows:
The process of Dyeing silk in chanderi fabric as per MSME website is as follows:
1. Water is heated at 40 degrees.
2. A hank of yarn is soaked for about 4-5 minutes.
3. The hank of 20/22 deniers is for 12 saris and is not degummed because degumming would take away
the basic crispness of the Chanderi fabric. This however reduces the degree of colour penetration.
4. The dye is prepared in a separate utensil.
5. Amount of dye to be used (say 50 gms in this case) is measured by hand.
6. The dyes in use vary from good quality dyes to the local ones.
7. The hank is soaked in the dye for 3-4 minutes.
8. Ascetic acid is added to the container containing the dye and the hank is kept in this solution for
almost 20 minutes.
9. The hank is then delicately squeezed with the help of wooden rods and dried.
10. The dyeing process takes about 45 minutes.
11. The normal charges are Rs. 4o/- per hank of12 saris.
12. This process enables colors, which are fast to 40 degrees.
Bamboo is a regenerated cellulosic fiber. There are three types of bamboo fibers:
1. Pure Bamboo
2. Bamboo Charcoal
3. Bamboo Viscose
1. Pure Bamboo
Pure bamboo is produced by physical and mechanical process like linen and hemp. It has high strength and is environment friendly. However it suffers from poor spinnability properties and high cost.
2. Bamboo Charcoal- An application of Nano Technology
In making this fiber, the bamboo is dried and heated at 800 deg. C until it becomes bamboo charcoal. Then the charcoal is sent for further processing to turn it to nano particles. These ultra fine bamboo particles are then embedded into viscose or polyester fiber. The fiber is then drawn into yarn and processed as usual.
Generally nano-bamboo charcoal powder is added during the process of spinning solution.Thus polyester, nylon and viscose fibers can be manufactured embedded with bamboo charcoal fiber.
This fiber has strong adsorption capacity. It can adsorb bad odor and chemicals. It shows an excellent anti-pilling tendency and the material washes well. It has strong anti-microbial properties. In an actual test of a pair of socks, after wearing without washing for a week, the socks not only have no odor, they were also dry. The disadvantage with this fiber is that it is only available in grey and black colors.
Some Notes on Indigo Dyeing using Fermentation Vat
1. Indigo itself doesn not exist as such in nature. It is easily formed by oxidation of a a part of plant called IndigoFera by exposure to air.
2. Simply speaking, Indigo itself is a blue solid. It is insoluble in water, acid and alkalies. If Hydrogen is added to it, or chemically speaking it is "reduced" by many reducing agents- It changes to "Indigo White" which is colorless. This indigo white can dissolve in water, in presence of alkalies, to a bright yellow liquid. When Textile substance is dipped in it and exposed to air, white indigo takes up oxygen and get converted into blue coloring matter.
3. In fermentation method water is made alkaline with the the addition of Lime or Alkali. Then substances are added which can ferment easily in the presence of alkali, for example wheat bran (madder is added to expedite the fermentation). It takes about two to three days to ferment and then indigo is added. This bath can be used for several days or even weeks. Fresh indigo and other ingredients are added from time to time. The color of bath is light greenish yellow in color with a blue or bluish green scum. Goods immersed in this bath turns yellow. When they are taken out and exposed to air, the yellow color quickly changes to blue.
3. The color of the bath is very important. If it is bright yellow, it means too much alkalanity and more indigo should be added. If the color is too dark, it needs more lime or other alkali.
4. After the color has changed, the goods should be rinsed well in two or three waters. After that should be boiled for several minutes in a soap bath to washoff the loose dyestuff and prevent rubbing. Rubbing can also be prevented by building up deep shades by successively dippings in the moderately weak vats, rather than obtaining the shade once for all.
1. Keep the vat covered. The level of water in the pot should be to the brim.
2. Wet out your fibers well. Any air remianing in the fiber will oxidise the indigo in the vat.
3. Enter the fiber into the vat very carefully, to avoid any air in the wet.
4. Always work under the vat.
5. For greens, dye with indigo first. Then rise well and overdye with alum mordant and any yellow dye ( traditionally Turmeric). For purples, dye the Indigo first, rise well, mordant and dye with any red dye.
Remember, you can use various chemicals to reduce the indigo vat. The alkalnity of these chemicals vary from Soda Ash ( Sodium Carbonate), Slaked Lime ( Calcium Hydroxide), Sodium Hydrosulphide to Caustic Soda ( Sodium Hydroxide) in that order(from low to high).
There are four main processes in the Denim washing
- Pretreatment
- Stone or Enzyme Wash- To adjust the surface effect
- Bleaching- To adjust the color
- Finishing- To adjust the handfeel of the garment
Pretreatment involves removal of impurities from the garments and desizing the garment. It also involves prevention of creases in the garment. Wetting Dispersing agent is used in desizing process. It should be able to rapidly wet the jeans so that it can prevent white lines of creases and prevents back staining. Back staining is the redeposition of indigo dyed short fibers, or loose indigo, removed during desizing, stone-washing or enzyme washing. Backstaining reduces the contrast of warp and undyed weft. It also stains pockets and labels and it is more prone ot ozone and yellowing. An anticrease agent is added to prevent crease formation during the washing process.
Enzyme in garment Industry
Enzyme is a kind of protein. They help the chemical reaction but themselves do not take part in chemical reaction. The starting molecule in a reation is called substrate and the yield molecule is called substate. Enzymes and substrate work like lock-key model so only one enzyme is useful for one type of substrate. Enzymes are better than chemical catalyst because they act in mild conditions such as room temperature. They are also biodegradable. Many enzymes are used in garment washing. An enzyme called Amylase is used in removing starch in desizing. Celullase is used in breaking and removing cellulose fibers. Laccase is used in biobleaching and catalase is used as an anti peroxide.
Stone and Enzyme Wash
Cellulase weaken the surface fibers which are then mechanically torn off during processing, taking with them indigo. However, they need mechanical action to work. Hence they are used with stones. Cellulase is also used in biopoloshing, which removes surface fibers and make the surface smooth.
Bleach
Laccase enzyme decolorises indigo without using bleach. It provides very good contrast and since it attacks only indigo dye and not the fiber so it gives excellent tensile strength.
Yellowing
The discolouration of textiles, i.e. a change of shade or loss of whiteness, giving a yellow tint, is commonly known as YELLOWING.Yellowing is due to many reasons. Cotton, yellows with age. However aging cannot make severe yellowing happen. Certain lubricants used in weaving and knitting can cause yellowing. The Anti oxidants present in these oils can cause a type of yellowing called as phenolic yellowing. The anti oxidants are also present in packaging materials and silicon softeners. Also temperature of drying and curing during processing can scorch the fibers and cause yellowing.
Indigo dyed fabrics are more prone to yellowing. Indigo when exposed to NOx or Ozone can produce yellow colored compounds. Indigo itself through simple oxidation can transform into yellow colored compounds.
There are specialised anti-yellowing softeners available. This work by either forming a protective filem, or by reacting the pollutants to form colorless compounds.
The source of these notes this presentation. This also contains images and chemical reactions. You can also view images of various denim washes here. One more resource is here.
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If you are a student of textile technology, you will find this site very useful. The owners of the sites are themselves textile students who have put together all the resources at one place.
While surfing I came across one more site, again very useful for textile students.
This is important for nightwear as they are finer and thinner than regular wear and are more prone to flammability than other fabrics.
In the testing, among other things time required for the flame to travel a certain distance is determined. It is now mandatory to have a flammability test if the fabric GSM is less than 88 grams.
Samples are tested both as submitted and after one cycle of washing and dry cleaning to obviate any instance of flammbility finish that might get washed of after one washing. Also iginition behaviour of the fabric is observed. Normally 5 specimens are tested. If they do not get ignited than 10 specimen are tested.
Butane gas of specified parameter is used. Based on the ignition behaviour, fabric is classified into Class I, class II and Class III. You can learn about the classification here.
You can read some facts about fabric flammability here.
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-Colorfastness to Light: In this the samples is exposed to a light source along with blue wool sample. The fading is observed and the rating is given. The main difference between American and European Standards is that American standard is time bound. In European standards it is not a time bound test but fading bound test- means you have to keep on exposing the sample till the sample fades to that of blue scale. Factors affecting lightfastness are the type of dyes used, depth of shade, surface structure and finishing chemicals.
-A cotton pigment printed fabric cannot be dry cleaned . In dry cleaning solvent called Perc- Perchloro Ethylene or Tetrachloroethylene. Pigments are very susceptible to dry cleaning- they will come out. Perc is the only solvent that do not blast. In exports they use MTO . The problem with perc is that it damages Ozone layer. Perc will take out the pigments from the print. However, if you dry clean with MTO, nothing will happen. Perc does not smell as much as MTO does. To test for dry cleaing, a bag is prepared where instead of steel balls, stainless steel discs are added.
-To remove smell from pigment printed fabric, it has to be cured well. To do it, maintain a temperature of 150 deg and allow the fabric for 10 minutes. It will cause phosphoric acid to get liberated and pigment get fixed- for that Diammonium phosphate needs to be added – so fixation takes place under acidic condition.
-When testing for shrinkage, the fabric is conditioned for 24 hours. Then it is subjected to washing process for 45 minutes to 1 hours. Then it is dried and reconditiond before remeasuring.
-When testing for shrinkage, soft water is used. Alum can be used for softening. Just move the alum on the upper surface for a few times. Now decant the upper portion and use the rest of the water for testing. One can also use wetting agent.
-Drying can be line drying, wet drying, tumble drying or drip drying.
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