denim basics doc 7
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DENIM
The word Denim is believed to have evolved from a French fabric known as “serge de Nîmes.” The
cloth from Nîmes was a twill woven cloth made of a silk-wool blend; however; the fabric mix of this
cloth casts some doubt on this origin since Denim has always been made from cotton. Since the mid-
1950’s Denim Garments has become a mainstay in the wardrobe of American youth. Denim represents a
rugged cotton twill textile, in which the weft passes under two or more warp fibers, producing the
familiar diagonal ribbing identifiable on the reverse of the fabric, which distinguishes denim from cottonduck. Denim was traditionally colored blue with indigo dye to make blue jeans though jean represents a
different, lighter cotton textile. Although Denim jeans are favorites among the American youth, it has
changed style and significance throughout the years. Globally, Denim designers are experimenting with
fabric and garment details including embellishments in order to add value to its garments.
PROCESS FLOW
WEAVING
The process of producing a fabric by interlacing warp and weft threads is known as weaving. The
machine used for weaving is known as weaving machine or loom. Weaving is an art that has been
practiced for thousands of years. The earliest application of weaving dates back to the Egyptian
civilization. Over the years, both the process as well as the machine has undergone phenomenal changes.
As of today, there is a wide range of looms being used, right from the simplest handloom to the most
sophisticated loom.
BASIC WEAVE DESIGNS
There are three basic weaves:
1) Plain weave
2) Twill weaves
3) Satin Weave
Most of the other weaves are derived from these three basic weaves.
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FINISHING OF DENIM
“Finishing is the process done on denim fabric; causing them to change in appearance, texture
and performance.”
The term finishing covers all those treatments that serve to impart to the textile the desired end-use
properties. These can include properties relating to visual effect, handle and special characteristics such
as waterproofing and non-flammability. Finishing treatment is done to achieve the ultimate customer
requirements.
These are mostly value added processes.
Finishing may involve
• Mechanical Finish
• Chemical Finish
MECHANICAL FINISHING:
Mechanical Finishing is defined as any operation performed to improve fabric appearance or function by
physical manipulation. Steam or water may accompany the physical manipulation; however, chemicals
other than lubricants are seldom used. Fabric luster, smoothness, softness, residual shrinkage and hand
are examples of the properties that can be altered by mechanical finishing.• Compacting (Shrink-proofing)
• Calendaring
• Raising (Napping, Sueding)
• Shearing
• Polishing
• Corduroy Cutting
CHEMICAL FINISHING:
Among chemical treatments one can further distinguish between treatments that involve a chemical
reaction of the finishing agent with the fiber and the chemical treatments where this is not necessary
(e.g. softening treatment). Some finishing treatments are more typical for certain types of fibers like easy
care finishes for cotton antistatic treatment for synthetic fibers and mothproofing and anti-felt treatments
for wool. In case of fabric the finishing treatment often take place as a separate operation after dyeing. In
more than 80% of cases the finishing liquor, in the form of an aqueous solution/dispersion, is applied by
means of padding techniques. The dry fabric is passed through the finishing bath containing all the
required ingredients, and is then passed between rollers to squeeze out as much as possible of the
treating solutions before being dried and finally cured. Washing as final step, tends to be avoided unless
absolutely necessary.
Following are some of the Finishes:
• Flat finish (singeing – mercerizing- padding- sanforizing)
• Regular finish (singeing –padding- sanforizing)
• Coating
DENIM WASHES ARE OF TWO TYPES:
1. Mechanical washes
- Stone wash
- Microsanding
2. Chemical washes
- Denim bleaching
- Enzyme wash- Acid wash
Other chemical washes:
• Ozone fading
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• Snow wash
• Over dye
• Sun washing
BACK STAINING OR RE-DEPOSITION:
The dye removed from denim material after the treatment with cellulose or by a conventional washing
process may cause "back staining” or "redeposition”. Re-coloration of blue threads and blue coloration
of white threads, resulting in less contrast between blue and white threads.
REMEDY OF BACK STAINING ---
- Adding dispersion/suspension agent to wash cycle.
- Intermediate replacement of wash liquor.
- Using alkaline detergent like sodium per borate with optical brightener as after wash.
INSPECTION
Quality is ultimate concern; every single yard of the denim goes through inspection department and
rated by a point count system to ensure that quality is up to standard before packing. Defective fabric
pieces are rejected and sold as seconds and relatively minor defective points are marked clearly using
stickers to alert cutters.
Defects
• Removable defects
• Non-Removable defects
REMOVABLE DEFECTS
Removable defects are those defects which are removed by washing and by cutting.
Defects are:
_ OIL STAINS
Fabric gets spots of oil lubrication from any part. _ SLUBS
It is the collection of the threads at the surface of the fabric. Similarly fibers present in the form of bunch
at the fabric are called slubs. This defect is removed by combing.
_ HOLE
When fabric passes through temple it produces holes on the fabric due to its wiry surface.
NON REMOVABLE DEFECTS
Those defects which cannot be removed by mending and these are count in fabric grading. These are:
JALA
In warp and weft direction there is a gap, it looks like that some warps or wefts are missed.
CRACKS
During weaving when m/c stops and again starts running then there is a gap between the two wefts. It
seems like that the beating is not done properly.
PATTI
It is the dark color or thick weft lines in the fabric.
DOUBLE PICK
The two or more threads are inserted at the same place. It is somewhat emboss and occur at the full
length of the fabric.
BROKEN PICK
If the double or thick yarn is inserted 1/4 or ½ width of the fabric then it is known as cut or broken pick.BROKEN END
When the warp end is broken.
KNOT
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It comes due to knotting of broken warp end.
WRONG DENTING
When more yarns are passed through dents.
TIGHT END
When warp end becomes tight due to tension in dyeing.
COARSE END
It comes when warp end is coarse.MISS PICK
If the weft yarn is missing from any place of fabric then it is known as miss pick.
REED MARKS
The lines are formed on the fabric due to reed movement and this defect is called reed marks.
STARTING MARKS
That mark which is due to the beating motion of the loom is called starting mark.
A GRADE FABRIC
If 30 points come in meter fabric it is considered as A grade fabric.
B GRADE FABRIC
If more than 30 points comes in fabric then it is considered as B
grade fabric.
Skewness in twill Fabric
The skewness in denim fabric, particularly in twill weave creates
a serious problem in subsequent garment manufacturing and its
washing. Leg twist is a major problem in denim manufacturing.
Due to this problem the leg is rotated in the opposite direction of
the twill of the fabric after laundering. Leg twist is assumed to be
happen due to the directional yarn stresses. These are inherent in
regular twill weave fabrics and developed during weaving.During washing the yarn stresses is relaxed which change the
regular position of interlacement between warp and filling yarns.
Due to this reason the legs are twisted. Normally leg twist not
shown on garment stage. It only observed after laundering of the garment. Although leg twist appears
after first laundering and it increases progressively with repeated launderings.
Shrinkage:
Denim twill fabric is with a warp yarn consisting essentially off 20-95% cotton and balance0 -5% other
synthetic fibre based on the end use and the fill yarn consisting essentially of 20 -100% cotton and from
0-2% of other synthetic fibre. Warp yarn having been sized. The finished woven fabric will have a warp
shrinkage varying from 5 -12% and 3-5% in the filling direction. If the term pre-shrunk is used then the
warp shrinkage will be 3-5% and weft shrinkage will be 0-3%.
TESTING
The fabric shrinkage is determined by measuring the dimensions of the fabric before and after three
wash/ dry cycles. The wash/ dry cycle consists of washing the fabric according to the desired look
(process recipe) and drying in a conventional tumble dryer to a maximum dryness at a final maximum
Temperature of 71°C. Usually drying time of 30 minutes is required.
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GLOSSERY
Abrasion The process of making garments look worn and aged by scraping or rubbing the surface of the
fabric causing abrasion.
Acid Wash The finish that gives indigo jeans sharp contrasts by soaking pumice stones in chlorine and
letting the stones create the contrast.
Bartack Stitching that reinforces places on jeans such as flies and pocket openings.
Bleach A chemical used to make denim fade.Broken twill denim was first used by Wrangler in 1964 as a way to combat the twisting effect
characteristic of regular twill denim (at the time considered a "fault" by many).
Cotton After blooming, this plant turns from white to purple, providing the well-known textile that
withstands high temperatures, accepts dyes well, and increases in strength when wet. The quality of
cotton is determined by the length of fibres; the longer the fibres, the higher the quality.
Crocking A term used to describe how dye rubs off fabric on skin or other fabric.
Denim The word denim is believed to be a derivative of the French term, serge de Nîmes, rugged cotton
twill textile, in which the weft passes under two or more warp fibers, producing the familiar diagonal
ribbing identifiable on the reverse of the fabric distinguishing denim from cotton duck.
Double Needle A common seam on jeans where two stitches run parallel to each other for
reinforcement.
Enzymes Proteins that speed up chemical processes. They are used in textile processing, mainly in the
finishing of fabrics and garments.
Enzyme Wash A more environmentally sound way to create a stone wash, organic proteins are used to
eat away at the indigo.
Finishing The overall processes performed on a garment giving it its unique look.
Five Pocket Jeans Most frequent design for denim: two back pockets, two front pockets and a coin
pocket inside the right front pocket.
Hand The term used to describe how denim feels.Indigo A blue dye obtained from indigo plants. The chemical structure was synthetically produced in
1987. Indigo's inherent features are good colorfastness to water and light and a continual fading. This
allows the blue color in jeans to always look irregular and individual.
Jean Possibly derived from the French work "genes", it was first used to describe the type of pant worn
by Genoan sailors.
Laundry A facility that takes unwashed jeans and processes them; i.e. stone wash, sandblasting,
finishing, etc. It is essential in creating commercial denim and has become as important as fabric
development.
Laser technology, initially used by the military, has developed dramatically in the last few years as a
textile treatment with laser finishes. Used with automated Tonello machines, lasers can be directed
vertically or horizontally and used to create both-specific detailing or a textured all-over effect. The
frequency of the laser is set to erode the indigo surface in order to either alter the color or burn through
the cloth. Laser treatments are used exclusively in the upper end of the denim market and are considered
a more environmentally acceptable process than the traditional methods of finishing.
Left-Hand Twill A weave in which the grain lines run from the top left-hand corner of the fabric
towards the bottom right. Usually in piece-dyed fabrics, left-hand twill fabrics are woven from single
piled yarns in the warp. They often have a softer hand feel to them after washing.
Loop Dyed One of three major industrial methods of dyeing indigo yarn.
Open-End Spinning A spinning process in which individual fibers are fed into a high-speed rotor
shaped like a cup where they begin to accumulate. The yarns produced using this method is not as strong
as the ring-spun yarns of the same size.
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Overdye A dying process in which additional color is applied to create a different shade or cast on the
garment.
Oxidation In denim manufacturing, when indigo yarn comes out of the dip and joins oxygen,
penetrating the fibre.
Pigment Dyes Dye that lack the ability to grab onto the fibers and must be held to the fabric with resins.
Pima Cotton Originally grown in the 1900's in Peru, Pima Cotton is known for its long fibres, making it
a very high quality, luxurious cotton. Pima Cotton was brought to America and got its name from thePima Indians, who harvested this particular type of cotton.
Polyurethane Provides a chemical resistance in the washing and dying process in order to achieve the
desired denim wash/ color. It is the basis of a novel type of elastomeric fiber known generically as
spandex. It is a man-made fiber (segmented polyurethane) able to stretch at least 100% and snap back
like natural rubber.
Pumice Stone Lightweight and strong, this stone is used in the process of stone-washing apparel.
Right hand twill, also know as "z twill", was made famous as Levi's jeans standard fabric and now is
the most common twill weave used for denim fabrics. Right hand twill can be recognized by the upward
direction of the diagonal twill on the face of the fabric as it runs from lower left toward upper right.
Right hand twill is known to have a flatter and smoother surface compared to other twill fabrics.
Ring Dyeing Describes a quality unique to indigo dye in which only the outer ring of the fibers in the
yarn is dyed while the inner core remains white.
Rivet A metal accessory that is used for reinforcement of stress points as well as nonfunctional
ornamentation.
Sanding Process that makes the surface of a garment soft by rubbing aggressively with paper containing
small loose grains of worn rock.
Selvage The edge of a fabric that is woven so that it will not fray or ravel. Old 28 to 30 inch shuttle
looms produce denim where selvages are closed, whereas on the larger modern weaving machines the
weft yarn is cut on every pick, creating what is called a fringe selvage.SPI Stitches per Inch
SPI for Denim garments is around 7 – 8 as Fewer stitches per inch generally will give a more contrast
stitch appearance.
Spraying & Staining: Spraying color can be added at various stages in the finishing cycle, either by
hand or by automated robot. The effect adds to the aged look of a garment by introducting stained areas,
color contrast or blotched tints. These appear more “natural” following laundry treatment. Overdyeing
and tinting is carried out in giant washing machines, where a dirty or stained effect is achieved via the
use of a pigment dye. The more subtle and sophistocated effects are hand-applied to individual areas.
Stone Washing Process that physically removes color and adds contrast using pumice stones. The
longer the denim and stones are rotated the lighter the color becomes and more contrast occurs. The
denim is then rinsed, softened, and tumble-dried.
Sulphur Bottoms: Many manufacturers apply a sulphur dye before the customary indigo dye. This is
known as Sulphur Bottom Dyeing. It can be used to create a grey or yellow “vintage” cast.
Warp: Yarn that runs parallel to selvedge. In denim, it’s dyed indigo.
Weft The un-dyed crosswise filling yarns used in denim weave.
Weight: Denim is traditionally graded by its weight per yard of fabric at a 29-inch width. Early jeans
were nine-ounce Levi’s, increasing to 10-ounce in 1927. Lee Cowboy Pants were introduced in the
much heavier 13-ounce weight, and most modern jeans are now 14 ounces.
Whiskering Term used to describe a denim that has a fading of the ridges in creases in the crotch area
and back of the knees giving the appearance of aged denim.