Chanderi Fabric - Process and Specifications

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.



Now you can watch this amazing video on Chanderi:

Bamboo Fiber- I

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.

Source 1 2 3 4

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Indigo Dyeing using Fermentation Vat

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. 

Here are some tips (Source)

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). 

Sources

http://www.archive.org/stream/dyesdyeing00exmorich/dyesdyeing00exmorich_djvu.txt

http://www.aurorasilk.com/info/indigo_tutorial.shtml

http://www.pburch.net/drupal/?q=node/909

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Some Notes on Denim Washing

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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