1.
Types of Bottoms
Mainly we can categorize as 1. 2. 3.
Men’s Women’s Kids
And by Styling / Construction
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2. Type of Fabrics ( Discussion only about Woven Fabrics) Fabric
is made from yarns, which i n turn are ar e made from fibres fib res . Fibres and yarns are interlaced (woven),
interlooped
(kni (knitt tted ed))
or bond bonded ed t o g e t h e r
(non (nonwo wove ven) n) to make make fabr fabrics ics.. Each Each me meth thod od o f join joinin ing g
t h e yarn yarnss or fibe fibers rs togeth er c r e a t e s a diff differ eren entt type type of fab fabri ric. c. Diff Differ eren entt f a b r i c types are avail availab able le for you you to use. •
woven fabrics
•
knitted f a b r i c s
•
Nonwoven f a b r i c s .
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Woven Fabrics Woven fabrics a r e produced b y the process of weaving. Weaving is the int erla cing of two or more yarns, us in g a loom. Generally, wov en fabric s ar e strong fabri cs. To weave yarns together, the loom is first set up with yarns running lengthwise, from the top to the bottom of the loom. These are called warp y a r n s .
A
second yarn is then threaded from side to side,
over and underneath warp yarns, to make fabric. This is called th e
weft yarn .
Warp yarn: yarns that go down the length of the fabric Weft yarn: yarns that go across the woven fabric Selvedge:
the edge of the fabric that does not fray
Water Jet Loom Machine
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Denim Fabrics
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3. Denim Jeans
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3.1 Denim Wash – The Process Washing processes impart the following effects on denim garments:
Appearance / colour change Softening Dimensional stability Different handle
The degree of the above effects depend on processing conditions such as time, temperature, liquor ratio of washing batch and chemicals used. Steps in the Denim Wash Process Denim wash is a sequential process, which consists of many steps. Some of the major steps discussed here are: 1. 2. 3. 4.
Pre-treatment Wash Tinting and Dyeing Softening
Pre-treatment This process is the first and most important part of denim washing, which includes: 1. 2. 3.
Removing impurities Desizing Reducing the risk of creasing
1. Removing impurities Impurities from the fabric or garment manufacturing stages can be oil-based or chemical-based. They can cause problems during the washing steps that follow, and hence are removed. 2. Desizing During this stage, sizing material applied during weaving are removed to make it suitable for further processing. 3. Reducing the risk of creasing Anti-crease agents are used to avoid creasing that can occur due to machine parameters like rotating speed, chemical reactions, production of the fabric and storage. Different Types of Denim Wash After pre-treatment, denim garments may be subjected to different types of wash. Some of the commonly used wash types are: 1. 2. 3. 4. 5.
Stone Wash Acid Wash Rinse Wash Enzyme Wash Bleach Wash
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3.1.1 Stone Wash This is the most common and basic process for producing a washed-down look on denim garments. Towards the end of the seventies, pumice stones were discovered to accelerate the ageing process of indigo dyed denim garments. Wash Components The stones in widespread use today are pumice stones, which have numerous pores. These pores have very sharp edges, facilitating a very high degree of abrasion. The Process
A typical stone wash process is as follows:
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The degree of colour fading and change of garment feel depends very much on the ratio of weight of the stone to the fabric weight, which can vary from 0.5:1 to 3:1. During the treatment, the outer most layer of the indigo-dyed yarn is partially separated and the portion of the fibre inside, which is undyed, comes to the surface. The surface gets a softer handle through the mechanical process with pumice stones. The degree of the wash-down effect depends upon several factors – the size of the stone, stone ratio, liquor ratio, duration of treatment, garment load, etc. Size The size of pumice stones available for stone washing vary from 1 cm to 7 cm in diameter. Pumice stones, around 2 to 3 cm in diameter, are used for finer denim qualities. The common size employed for normal denim qualities is 3 to 6 cm in diameter. Variants Different wash names like sand wash, golf ball wash, micro wash and micro-sand wash — which are types of stone wash — refer to the use of very small size pumice s tones. Equipment Drum washing machines are used for stone washing. The capacity of drum washing machines can be up to 200 kg. Some of these machines are equipped with tilting facility to empty the washed garments. Stone Wash Effects
Under normal circumstance (fabric-stone ratio at 1:2), colour fading is irrespective of the fabricstone ratio. Smaller stones give slightly better fading effect, but this would reduce the colour c ontrast due to more uniform abrasion. Fading effect increases with the stone wash time. However, increase of the effect becomes insignificant when the washing time exceeds 90 minutes.
3.1.2. Acid Wash (Moon Wash)
Acid washing or ice washing is usually done by dry tumbling the garments with pumice stones presoaked in an acid solution, such that localised bleaching is effected in a non-uniform sharp blue / white contrast in the garment.
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Wash Components Pumice stones pre-soaked in sodium hypochlorite (5 to 10%) or potassium permanganate (3 to 6%).
A typical acid wash process is as follows:
The process involves soaking of pumice stones in a net or mesh fabric in solutions of potassium permanganate for at least one or two hours and then draining off the excess liquor. This treatment results in a very strong bleaching effect at the raised parts whereas the lower parts remain dark. The selection of sodium hypochlorite or potassium permanganate depends upon the dyestuff and the required effect.
Drawbacks
Acid washing or moon washing is a tedious and dirty bleaching process, si nce the manganese dioxide formed out of the potassium permanganate must be removed from the trousers after the process. The hypochlorite bleaching process is fast, efficient and cheap, but it also suffers from a number of disadvantages. The process is relatively difficult to control because it is difficult to obtain the same level of bleaching in repeated runs.
Furthermore, hypochlorite is a harsh chemical that can damage cellulose, resulting in severe strength loss, breakages and pinholes at the seams and pockets. Since hypochlorite is a hazardous chemical, precautions should be considered while using it in the production floor.
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3.1.3 Rinse Wash or Mill Wash
The objective of rinse washing is to keep the fabric appearance as dark as possibl e. The denim is desized width wise in open-width washing machine and t he dye is not washed out.
Variants
One variety of the rinse wash is desizing ready to wear trousers in drum washing machines. The disadvantage in this process is very poor rub fastness.
3.1.4 Enzyme Wash As denim is made of cotton, it too consists of cellulose. Cellulases can be used to give denim a worn look. Enzymes have opened up new possibilities in denim finishing by increasing the variety of finishes available. For example, it is now possible to fade denim to a greater degree without running the risk of damaging the garment. Cellulases are the enzymes commonly used in enzyme wash. As the name suggests, it degrades cellulose. Wash Components Enzymes are molecular proteins which accelerate biochemical r eactions within a short span of time. The most commonly used enzymes in the textile industry include alpha amylases, proteases, catalases and cellulases. Multi-component enzymes are cellulases introduced by leading manufacturers whi ch contain a range of different cellulases which affect different parts of the cellulase. Mono component enzymes have only one component, and are precise in their action. The Denimax range of products belongs to this category.
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Advantages of Cellulase (Enzyme Wash) over Pumice (Stone Wash) The most widely used application of cellulases (neutral and acid cellulases) is the replacement of pumice stones in the ‘stone washing’ process to produce the aged appearance of denim garments. Some of the advantages of enzyme wash are:
The use of cellulases instead of pumice stones pr events damage by abrasion to washing machines and the garments, eliminates the need for disposal of the used stones, and improves the quality of the waste water. The load of garments may also be increased by as much as 50% since stones are no longer added. Depending on the finishing effect required, a mixture of cellulases and pumice may be used, which causes the surface fibres to weaken and later be removed when subjected to either fabric to fabric abrasion or fabric to stone abrasion during the washing. The temperature and the pH used must be specific to the type of cellulase employed. For enzymatic stone washing, acid cellulase and neutral cellulase are available. While pumice stones are effective on the fibre surface, cellulases react inside the fibre as well.
The Process
A typical enzyme wash process is as follows:
Acid Cellulase: These enzymes are applied at an acid pH value of 4.5 to 5.5 at 50 - 60ºC. At the beginning of enzymatic treatments negative effects on the tensile strength could be observed. The application of acid cellulases reinforced the ‘backstaining’ problem. Backstaining is the result of soiling of the weft thread and the pocket li ning by the detached indigo dyestuff. Neutral Cellulase: neutral cellulose is used in denim washes. It i s applied at pH value of 6 to 7 at 50 to 60ºC. Compared to acid cellulases, neutral cellulases have a less negative effect on the tensile strength. For improved surface abrasion, higher quantities are required in the case of neutral cellulase. An enzyme dose of 2 to 4 grams per litre is normally sufficient. In general, the colour of the enzyme washed goods are more uniform, particularly when stone is not used. Since cellulases are only reactive on cellulose, any sizes or other impurities must be removed before the cellulase treatment. Neutral cellulase is still more widely used in denim wash than acid cellulase. The reason is that the tendency of indigo dye to redeposit on the surface of the fibre is much higher in acid medium than that in neutral medium. 15 | P a g e
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Enzyme Wash Process Parameters
For neutral enzyme, the best performance is obtained at pH 6 - 7. A satisfactory result can be obtained when enzyme dosage is in the range of 0.5 - 2.0 g/l cellulase.
Neutral cellulase is still more widely used in denim wash than acid cellulase. The reason is that the tendency of indigo dye to redeposit on the surface of the fibre is much higher in acid medium than that in neutral medium.
3.1.5 Bleach Wash In bleach wash, a strong oxidative bleaching agent is added during the washing, with or without pumice stones. The purpose of the bleaching is to decolourise the dark blue shade by destroying the indigo dye molecules with oxidative bleaching chemicals. Wash Components Sodium hypochlorite is generally used as an agent. As on date, ‘Chlorine Bleach’ is the most effective bleach agent for indigo since all shades can be obtained from it. Drawback The problem with this bleaching method is the fact that the fibre is damaged and there i s emission of polluted waste water.
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A typical bleach wash process is as follows:
Variants Ecologically less harmful methods such as laccases, potasium permanganate, potasium persulfate, sodium caustic, peroxide have been tried. However, they cannot be compared with chlorine bleach as far as the effect and looks are concerned. The ‘White Bleach’ method is a variation of the normal bleach in which, chlorine bleach is carried out two to three times one after the other in different treatment baths. Bleaching with hypochlorite
Optimum Dosage: 40 g/l when using a hypochlorite with 12% available chlorine. Increase in hypochlorite dosage effectively increases the colour fading to a certain limit. pH: At 7 or lower, the rate of bleaching is rather fast which may present difficulty in controlling t he shade. It is suggested that the bleaching bath should be slightly alkali by adding soda ash to pH 9-10 such that bleaching effect could be effectively monitored by the bleaching time. Chlorine Bleach: 15 ml (150 g/l active chlorine) Temperature: 50 - 60ºC. A higher temperature increases the bleaching action and hence the colour fading. But for the temperatures above 70ºC, the effect would be si milar. Time: 15 minutes Rinse: cold
Dechlorination After every chlorine bleach, the remaining chlorine must be removed by dechlorinating with sodium bisulphite. Dechlorination can also be carried out with h ydrogen peroxide instead of sodium bisulphite.
Sodium Bisulphite: 3 g/l Temperature: 40-50ºC Liquor Ratio: 1:5 Time: 10 minutes Rinse: warm or cold
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Common Process Parameters
Desizing Denim garments that are made from indigo or sculpture slashed-dye will have sizes that are water-soluble and insoluble in nature. Starch-based sizes are most commonly used. Methods employed to desize them are washing with alkaline ag ents, acidic agents, oxidative chemicals and with enzymatic amylase. The most effective and preferred method is enzymatic desizing using amylase. The typical parameters are as follows:
Amylase: 1 - 2 g/l pH: 6 - 7 Temperature: 60 - 70ºC Time: 15 mins Liquor Ratio: 1:6 to 1:8 Rinse: cold
Note: Addition of detergent accelerates the wetting process.
Tinting and Dyeing
After wash, a garment is tinted or dyed. Tinting is used change the hue or tone of indigo. It gives the denim garment a worn or used look. This process takes from 5 to 15 minutes, and is followed dye-fixing and clean-up of superficial dye. Comparison of Different Dye Types Dye Type
Cost
Shade Options
Cycle Time
Process Effects
Direct Dyes
Economical
Wide range of shades
Short Cycles
Ease of application
Reactive Dyes
Costly
Wide range of shades
Long Cycle
Water Consumption High
Short to Long Cycle
Machine contamination, but hard to obtain consistency, harsh hand feel
Pigment Dyes
Cost Efficient
Limited to dull shades
Softening Since denim is a heavy fabric, it needs softening. A major problem encountered during this process is yellowing, which is the change in shade or loss of whiteness. All organic polymers (like cotton) are prone to yellowing. Indigodyed fabric, in particular, is very prone to yellowing. Cause: It is difficult to pin-point the exact causes of yellowing. Among the many causes is exposure to light, impurities, incorrect process temperatures, or a combination of the same. Reducing the risk of yellowing: It is impossible to eliminate yellowing.
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However, it can be minimised by keeping in mind the following:
Ensure bleaching and bleach neutralisation residues are minimised or eliminated Minimise back staining Avoid the use of chemicals which create yellowing Avoid leaving garments damp any longer than necessary Control drying and curing conditions
Other Fashionable Denim Washes
Overdyed: A stoned trouser is over dyed to create variety of shades and effects. Damaged: Trousers are partially destroyed. This can be done by very aggressive chlorine bleach or by the American variation of shooting at the trousers with bullets. As part of the proof, some jeans manufacturers incorporate the empty bullet cartridge in the trouser pocket. Scrubbed: The surfaces of the trousers are scrubbed with brushes in this process, to effect suede and partially fluffy appearance.
Wash-down Effect on Different Types of Sewing Thread Critical Wash Process Bleach wash – mild wash with sodium hypochlorite
Spun Polyester Thread
Corespun Thread
Minor fading in shade. Some grey shades can have complete change in tone under unstable wash conditions.
No colour change in vat dyed cotton cover.
Bleach wash – strong Bleach Most disperse dyed colours fade completely with calcium hypochlorite under strong bleach conditions.
Unaffected in most cases. Mild fading observed in selected dark shades under strong bleach.
Pumice stone washing
Seam weakens by 5%. Some degree of seam abrasion at waist belt and pockets. The looper thread abrades at a noticeably higher rate and can cause broken stitches.
The high tenacity polyester filament core provides complete protection for seams against abrasion. Seam appearance is excellent.
Enzyme wash with pumice stones
Severe seam abrasion at waist belt, back rise, back york and bottom line seams. Poor seam appearance. 30% chance of total seam breakage at stress points.
Seam strength and seam appearance remain intact. Vat dyed cotton cover retains the shade under normal conditions.
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5. Bottom Garment Zones 5.1 Defect Classification – Zones When inspecting garments for cleanliness and fabric flaws, the location of the defect and its effect on the appearance and performance of a garment must be taken into consideration. Size and severity also have an impact on the acceptability. Defects which are noticeable on a garment but are not in the focal area of the garment may not be a cause for garment rejection if the garmen t’s performance, fit or general appearance is not impaired. Our standard defect classification for all merchandising categories; Fabric, Appearance, Color, Shade, Workmanship & Construction, Cleanliness and Packing is classified using zones.
Critical Defect: A defect likely to result in a hazardous or unsafe condition for an individual using the product or fails to meet Government mandatory regulations. One Critical Defect found during the inspection would cause the final QA audit to fail. The failure will be resulting in a 100% inspection by factory to remove all critical defect items prior to re-inspection again by a 3 rd party auditor
Zone A - Where the visual appearance of the garment is considered a MAJOR area of critical importance. Major Defect: Anything that adversely affects the appearance, performance including fit or customer satisfaction to a degree that would provide a discerning customer with justification for no purchase, a return or complaint. Zone B – Where the visual appearance of the garment is considered a MINOR area of importance but not critical. This is not as noticeable to the person wearing the garment or to an observer at first glance. Minor Defect: Any variation from the standard that is not sufficient in degree to be classified as major, and that would not provide a discerning customer with justification for non-purchase, a return or complaint.
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Long Pants
Zone B areas are identified in illustrations, All other areas Zone A
Short / Capris / Bermudas
Zone All
B will
not apply to inseams that are shorter than
A bove the Knee
“
”
Other Inseam Lengths will follow the above illustr ation.
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6. Common Defects in Denim Jeans Sewing 6.1 Broken Stitches – Needle Cutting Description: Where the thread is being broken where one seam crosses another seam (ex: bartacks on top of waistband stitching, seat seam on top of riser seam) resulting in stitch failure.
Recommended solution
Use a larger diameter thread on operations where the thread is being cut.
Make sure the proper stitch balance is being used. On a chain stitch seam on denim, you normally would like to maintain a 60%/40% relationship of Needle thread to Looper thread in the Seam.
Use needles with the correct needle point.Change the needles at regular intervals on operations where the Needle Cuts are occurring frequently. Use a higher performance T h r e a d
6.2.
Broken Stitch – Abrasion :
Description: where the thread is broken during stone-washing, sand blasting, hand sanding, etc. Broken stitches must be repaired by restitching over the top of the stitch-line.
Recommended Solution:
Use a larger diameter thread on operations where excessive abrasion is occurring (ex: use T-120 on Waistband);
Make sure stitches are balanced properly.
Use a Magic air entangled thread in the looper due to its lower seam profile making it susceptible to abrasion (ex: use T-90 or T-135 Magic in loopers of the Yoke, Seat and Waistband seam);
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6.3.
Broken Stitches : Chemical Degradation :
Description: where thread is being compromised by the chemicals used during laundering resulting in loss or change of color and seam failure.
It is recommended to go to larger thread sizes when the Denim Garments will be subject to Harsh Chemical washes.
To achieve the best laundering results make sure that the water temperatures and PH Levels are correct and that the proper amounts and sequence of chemical dispersion are within guidelines. Make sure the garments are being rinsed properly to neutralize the chemicals in the fabric. Monitor the drying process, cycle times, and temperatures to make sure they are correct so that the best possible garment quality can be achieved
6.4.
Unravelling Seams :
Description: where either the stitch has been broken or a skipped stitch has occurred. This will cause seam failure unless the seam is Restitched. Recommended Solution:
This may include going to a higher performance thread designed to minimize sewing interruptions.
Observe sewing operators for correct material handling techniques.
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6.5.
Sagging or Rolling Pockets:
Description: where the pocket does not lay SAGGIN G OR ROLLING POCKETS flat and rolls over after laundering.
Recommended Solution:
Make sure the sewing operators are not holding Pockets back excessively when setting the front pocket. Make sure the hem is formed properly and that excess ive fabric is not being put into the folder that will cause the hem to roll over.
Check to make sure pocket is cut properly and that pocket curve is not too deep .
Use a reinforcement tape on the inside of the pocket that may help prevent the front panel from stretching along the bias where the front pocket is set.
The type and weight of denim, along with the fabric construction, may contribute to this problem. Contact your fabric supplier for assistance.
6.6.
Skipped Stitches
Description: where the stitch forming device misses the needle loop or the needle misses the looper loop. Skips are usually found where one seam crosses another seam and most of the time occurs right before or right after the heavy thickness.
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Recommended Solution:
Use corespun thread.
Use minimum thread tension to get a balanced stitch.
Use the ideal foot, feed and plate that helps to minimize flagging.
Training sewing operators NOT to stop on the th ickness.
Make sure the machine is feeding properly without stalling.
Make sure the machine is not back-feeding.
6.7.
Ragged – Inconsistent Edge
Description: where the edge of the seam is either extremely “ragged” or “rolls” inside the stitch.
Recommended Solution:
Make sure the sewing machine knives are sharpened and changed often.
The knives should be adjusted properly in relationship to the “ Stitch tongue” on the needle plate to obtain the proper seam width or width bite.
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6.8.
Wavy Seams on Stretch Denim
Description: where the seam does not lay flat and is wavy due to the fabric stretching as it was sewn or during subsequent laundering and handling operation.
Recommended Solution:
Use minimum presser foot pressure.
Instruct sewing operators to use proper handling techniques and not stretch the fabric as they are making the seam.
Where available, use differential feed to compensate for the stretch of the fabric.
6.9.
Ropy Hem
Description: is where hem is not laying flat and is skewed in ROPY HEM appearance.
Recommended Solutions:
Instruct the sewing operator to make sure they get the hem started correctly in the folder before they start sewing.
Also, make sure don’t hold back excessively as the seam is being sewn.
Use minimum roller or presser foot pressure.
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6.10. Twisted Legs: Description: is where the side seam twists around to the front of the pant and distorts the appearance of the jeans .
Recommended Solution:
Instruct the sewing operator to match the front and back properly so they come out the same length. Sometimes notches are used to insure proper alignment. They should NOT trim off the front or back with scissors to make them come out the same length.
Make sure the cut parts are of equal length coming to the assembly operation.
Check fabric quality and cutting for proper skew.
Make sure the sewing machine is adjusted properly for uniform feeding of the top and bottom plies
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6.11. Disappearing Stitches in Stretch Denim Description: is where the thr ead looks much smaller on seams sewn in the warp direction than in the weft direction of the fabric
Recommended Solution:
Use a heavier thread size (T-120, ON STRETCH DENIM T-135, T-150) on topstitching.
Go to a longer stitch length (from 8 to 6 spi). 3) Make sure the thread tensions are as loose as possible so the thread sits on top of the fabric rather than burying in the fabric on seams sewn in the warp.
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6.12. Thread Discoloration after Laundry Description: is where the thread pics up the indigo dyes from the fabric giving the thread a ‘dirty’ appearance. A common discoloration would be the pick-up of a greenish or turquoise tint.
Recommended Solution:
Use thread with proper color fastness characteristics. Correct PH level (too low) and Water Temperature (too low) during laundry.
Use the proper chemicals & laundry cycles.
Do not overload washers with too many garments at one time
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