Denim Basics Doc 7

8/3/2019 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.



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



• 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



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.



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.



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.

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Denim Basics Doc 7