7CHAPTER Processing: from Gin to Fabric

GINNINGCotton gins are factories that complete the first stage ofprocessing cotton – separating the lint from the seed. Gin isshort for en-“gin”. In Australia gins are located in cottonareas to avoid costly transport.

Before the gin was invented, the lint and seed were separatedby hand. It took one person a whole day to separate only halfa kilo of the lint from the cottonseed. Modern gins can separateand bale about 230,000 kilograms of cotton in one day.

THE GINNING PROCESSThe seed cotton arrives at the gin in round bales or modules.

The first step in the ginning process is where the cotton isvacuumed into tubes that carry it to a dryer. Cotton must beginned with a moisture level of 5%. The cotton is dried out if it is too wet or water is added if it is too dry to ensure thecorrect moisture level. Next, the cotton goes through severalstages of cleaning equipment to remove leaf trash, sticks,dirt and other foreign matter.

After cleaning, the cotton is then ready for separation in the ginstand. The gin stand removes the seed from the lint. In Australia,most cotton is ginned with saw gins where fast moving circularsaws grip the fibres and pull them through narrow slots.

The raw fibre, now called lint, has any remaining trash removedand makes its way through another series of pipes to a presswhere it is squashed into bales under very high pressure.Each bale weighs 227kg. Samples are taken from each balefor classing and the bales are wrapped in stretchy white cottonfabric to protect the lint. They are now ready for transport toone of the ports for shipping into overseas markets.

Cotton being fed into the ginphoto by Andrew Patton

Gin is shortfor en-“gin”

•LOCATIONOF COTTON

GINS

Cotton is pressed undervery high pressure by a bale press into balesweighing 227kg each

Cotton gins like this one are mostlylocated in cottonregions to cuttransport costs

THE SEEDS MAKE UP ABOUT 55% OF THE SEED COTTON WEIGHT

THAT COMES FROM THE FARMS.THEY ARE VERY VALUABLE AND

ARE USED FOR A VARIETY OFPRODUCTS SUCH AS OIL, PLASTICS,

STOCK FEED, COSMETICS ANDMARGARINE. THEY MIGHT ALSO BE USED AS SEEDS FOR THE NEXT

COTTON CROP.

PRODUCTS FROM GINNINGWHEN THE SEED COTTON IS PROCESSED IN THE GIN, THREE PRODUCTS RESULT — COTTONSEED, LINT AND TRASH.

SEED

Fuzzy Seed

LINT MAKES UP APPROXIMATELY35% OF THE SEED COTTON

WEIGHT. ONCE THE LINT HAS BEEN SEPARATED IT IS COMPACTED

INTO BALES FOR EASYTRANSPORTING. THE COTTON

BALES ARE THEN MOSTLYTRANSPORTED DIRECTLY TO

AUSTRALIAN PORTS FOR EXPORTTO OTHER COUNTRIES TO FURTHER

PROCESS (SPIN) THE COTTON.

Cotton Lintphoto by Pete JohnsonBales of Lint

THE REMAINING 10% OF THE SEEDCOTTON IS CLASSED AS WASTEPRODUCT OR TRASH. COTTON

FIBRE WASTE CAN BE USEDIN ETHANOL MANUFACTURING

OR IN PRODUCTS THAT CLEAN UPOIL SPILLS. IT CAN ALSO BE USED

AS A FERTILISER.

Cotton Trash

LINT TRASH

TRADITIONAL CLASSING METHODThe more traditional method of testing cotton quality involves using speciallytrained ‘classers’ who manually examine the cotton fibres. This testing involvesthe classer taking a sample from each bale of cotton and assessing it by:

Colour (bright or dull, white or grey)

Trash content (the amount of stalk, leaf or dirt)

Character (whether the sample has a smooth or lumpy appearance)

Staple (length of fibre)

Strength of the fibres

Manual classers still largely determine the leaf, extraneous matter and preparationgrades of cotton.

Sunflower seed Soybean Raspeseed Cottonseed Peanut

COTTONSEED VERSUS OTHER OILSEEDSWorld Oilseeds Production source: USDA

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Cottonseed is separated from thelint during the ginning process.Before the seed can be crushed foroil extraction or used for plantingfuture crops, it must be delinted.This means removing any excess lint still attached to the seed. These final short fibres (linters) areused to make many industrial anddomestic products.

After the linters are removed, the hull (the hardshell covering the seed) is removed. Inside thehull is the kernel – the really valuable part of theseed. To produce oil, the kernels are flattenedusing rollers and then cooked at very hightemperatures.

The kernels are squeezed and crushed and theoil flows out. This oil is then processed andrefined further, turning it into a light yellow,tasteless, odourless oil. Cottonseed oil is used inthe manufacture of products such as vegetableoil, margarine, soap and cosmetics.

The excess hulls and leftover kernels can beused to feed animals such as pigs, cattle andpoultry.

PROCESSING COTTONSEED

AFTER THE COTTON ISGINNED, A SAMPLE ISTAKEN FROM EACH BALEAND SENT AWAY TO CLASSING ROOMS TOHAVE IT GRADED FOR ITSQUALITY. THE COTTONFIBRE IS SORTED INTODIFFERENT QUALITY-BASEDGRADES (OR CLASSES). THE HIGHER THE CLASS,THE BETTER THE QUALITYOF THE COTTON FIBRE, AND THE HIGHER THE PRICETHAT WILL BE PAID.

CLASSING

Andrew Hammond, cotton classer, Dunavant Enterprises

● MEDIUM 41% ● LOWER 4%● LOW 11%

● PREMIUM 24%● HIGH 20%

MODERN CLASSINGMETHOD - HVI TESTINGHigh Volume Instrument (HVI) testing is a machine-based method that can quickly and accuratelycheck the quality and exact value of cotton fibres.The technique originated in the USA and Australiancompanies have also contributed to the world’sknowledge about HVI testing.

An HVI test print-out includes information relating tothe following areas:

Colour grade (relating to any visible impuritiesand the degree of whiteness)

Length (the price of cotton is roughlyproportional to staple length. Australian cropstypically produce 28mm (1.15 inch) staple ifirrigated, but shorter from a dryland crop).

Micronaire (the fineness of the cotton that affectshow quickly it can be spun)

Trash and dust (the number of trash and dustparticles that are in the cotton)

Strength (if the cotton is stronger it can be usedin smaller quantities)

Length (fibre length)

At the end of the classing process each 227kg baleof cotton carries a classing description. This gradewill decide whether the cotton is sold for a higher or lower price, known as premium or discount.

THE QUALITY OF THE AUSTRALIANCOTTON CROP

Grading categories are set in eachindividual country and are revised andupdated, usually on an annual basis. In Australia, the classing grades aredetermined by the Australian CottonShippers Association.

Australia has an enviable reputation onthe world market as a reliable supplierof very high quality cotton, and cancommand a premium price for thisreason. A recent study found newvarieties from CSIRO’s cotton plantbreeding program had improved yield,HVI quality and are showing superiortextile performance attributes.

HVI Classing machinerycan accurately test for a number of cottonquality parametres

SHIPPING THE COTTON TO MARKETOnce the cotton is ginned and pressed into bales it isloaded on to trucks and trains and sent to port for shipping,mostly to overseas markets. Over 99% of Australia’scotton is sent overseas, with only a very small spinningindustry left in Australia – it’s almost non-existent.

SHIPPING THE COTTON TO MARKETOnce the cotton is ginned and pressed into bales it isloaded on to trucks and trains and sent to port for shipping,mostly to overseas markets. Over 99% of Australia’scotton is sent overseas, with only a very small spinningindustry left in Australia – it’s almost non-existent.

SPINNING TOPRODUCE YARN OPENING, BLENDING

AND CLEANINGThe bales are laid down in a row (called alaydown), opened and blended through a range ofmachines. This ensures a consistent blend offibres. The blended fibre is then put through moremachines to loosen the fibre tufts and to removeleaf, sticks, boll parts, bark and seed fragments.

Historically, cotton was spun by hand using spinning wheels – thispractice is no longer used to produce commercial quantities of cotton

yarns, but the method is still practiced as an artisan craft by some.

Cotton arrives at a spinning mill in bales. Most often these millsprocess a range of different types of fibres including cotton and

man-made fibres including polyester and nylon.

At the textile mill, the cotton is put through a number of processes,depending on the setup in the spinning mill and the desired quality

of the yarn to be produced.

Australia is the fourthlargest exporter ofcotton in the world

Cotton is warehousedbefore it is shipped

The main ports for Australian cotton are in Brisbane andSydney. The cotton bales are warehoused, and oncethey’re sold and ready to be shipped are loaded intolarge shipping containers.

The main customers for Australian cotton are spinningmills located in south east Asia – China is Australia’slargest buyer of cotton. Cotton Carding Machine

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CARDINGNext, the fibre is fed into a carding machine whichis often referred to as “the heart of the spinningmill.” The carding machine individualises, alignsand further cleans the fibres before pulling theminto a single, continuous, loose rope called sliver.

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Nan Yang Textile Mills

Opening Cleaning

Cotton Carding

DRAWINGDrawing is the process where the fibres areblended, straightened and the number of fibresreduced to achieve a desired density. It alsoimproves the evenness of the sliver.

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COMBINGThis process removes any final waste from thecotton and makes it finer, stronger, smoother andmore uniform compared to carded yarns. Combedyarns are also more expensive than carded yarnsbecause there’s an extra processing step andthere’s more waste.

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Carded yarn Combed yarn

ROVINGIn preparation for ring spinning, the sliver iscondensed into a finer strand know as a roving,before it can be spun into yarn. The roving framedraws out the sliver to a thickness of a fewmillimetres and inserts a small amount of twist tokeep the fibres together. This is then wound on toa bobbin in readiness for spinning yarn.

5SPINNINGThere are three main spinning systems usedcommercially to produce cotton:

RING SPINNINGRing spinning was perfected as a process bythe end of the 19th Century. There arecurrently 213 million ring spindles installedworldwide that account for about 60% of allshort-staple yarn production.

Ring spinning draws out the roving andinserts a twist into the fibres by a rotatingspindle and winding the yarn onto a bobbinsimultaneously. It’s a comparativelyexpensive process due to slower productionspeeds and additional processes.

ROTOR SPINNING (also known as open-end spinning)

This was introduced in the mid-1960s. Today, there are over 9 million rotors installedworld-wide which account for about 30% ofshort-staple yarn production.

Sliver is fed into the machine and combed andindividualised by the opening roller. The fibresare then deposited into the rotor where aircurrent and centrifugal force deposits themalong the groove of the rotor where they areevenly distributed. The fibres are twistedtogether by the spinning action of the rotor,and the yarn is continuously drawn from thecentre of the rotor. The resultant yarn is clearedof any defects and wound onto packages.

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AT THE TEXTILE MILL, THE COTTON IS PUT

THROUGH A NUMBER OFPROCESSES, DEPENDING ONTHE SETUP IN THE SPINNING

MILL AND THE DESIREDQUALITY OF THE YARN

TO BE PRODUCED.

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IBRE

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Drawing

Ring Spinning Rotor Spinning

AIR-JETSPINNINGThis was developed in the 1960s but wasnot commercially successful until the1980s. There are currently about 500,000airjet spinners installed world-wide.

Sliver is fed into the machine and is furtherdrawn out to the final count and twist isinserted by means of a rotating vortex ofhigh pressured air. The resultant yarn iscleared of any defects and wound ontopackages ready for use in fabric formation.(These spinning processes are summarised from theFIBREpak, a guide to improving Australian CottonFibre Quality)

Figure 1, 2 and 3 – courtesy of short Staple Manufacturing,McCreight, Feil, Bosterbaugh and Backe and FIBREpack

MANUFACTURING FABRICSAFTER THE COTTON LINT HAS BEEN SPUNINTO YARN IT IS THEN WOVEN ORKNITTED INTO FABRIC.

Woven FabricsWeaving is the oldest method of making yarn intofabric. While modern methods are more complexand much faster, the basic principle of interlacingyarns remains unchanged.

Weaving is done on a machine called a loom. Beforethe weaving can start, the loom needs to be set upwith warp yarn. Warp yarn runs up and down theloom. Weft yarn is then woven (or sewn) over andunder the warps from side to side. A torpedo-likeimplement at very high speeds does the weavingand can produce an almost endless variety offabrics. Some of these machines carry the yarns

across the loom at rates in excess of 2,000 metersper minute! The resulting fabric is particularly strong.

There are three basic weaves with numerousvariations, and cotton can be used in all of them.The plain weave, in which the filling is alternatelypassed over one warp yarn and under the next, isused for gingham, percales, chambray, batistes andmany other fabrics.

The twill weave, in which the yarns are interlaced toform diagonal ridges across the fabric, is used forsturdy fabrics like denim, gabardine, herringboneand ticking.

The satin weave, the least common of the three,produces a smooth fabric with high sheen. Used for cotton sateen, it is produced with feweryarn interlacings and with either the warp or fillingyarns dominating the “face” of the cloth.

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FABRIC FINISHINGMost fabrics are finished to make them look and feel moreattractive. This is the final step in the manufacturing process.

Cotton fabrics, as they come from the loom in their rough,unfinished stages, are known as greige goods. Most undergovarious finishing processes to meet specific end-use requirements.

Some mills, in addition to spinning and weaving, also dye or printtheir fabrics and finish them. Others sell greige goods to converterswho have the cloth finished in independent plants.

Cotton finishing processes are numerous and complex, reflectingtoday’s tremendous range and combination of colours, texturesand special qualities. In its simplest form, finishing includes cleaningand preparing the cloth, dyeing or printing it and then treating it toenhance performance characteristics.

There are literally hundreds of ways to finish off cotton fabrics tochange its look and feel. More than one finish can be applied to asingle cotton fabric and there are more innovations introduced allthe time.

Some examples of cotton finishes include:

SCOURING this process removes microdust

BLEACHING this produces an off-white colour

GASSING this produces a smooth finish to thefabric

STENTERING this prevents the shrinkage andwrinkling of knitted or woven fabrics

SANFORISING this prevents the shrinkage of wovenfabrics

CALENDERING fabric is given a final press to producedifferent effects

DYEING colour can be added to the yarn or the fabric. Fabric can also be printedto apply colours and patterns

PERMANENT PRESS this finish prevents the need for frequentironing

WATER REPELLENCY this finish ensures water is repelled notabsorbed

FIRE RETARDANT finishes such as cotton proban

KNITTEDFABRICSKnitting fabric from cotton yarn is asimpler process than weaving. Knittinginvolves forming loops with one or moresingle continuous yarns and joining eachloop to its neighbours to form a fabricthat’s stretchy, like t-shirt material.

Lengthwise rows of loops, comparable tothe warp yarn in woven goods, are calledwales. Crosswise rows, comparable tofilling yarns, are known as courses.

Most cotton is knit on circular machineswhich have needles fixed to the rim of a rotating cylinder. As the cylinder turns,the needles work their way from stitch tostitch producing a tubular fabric.

Depending on the width of fabric desired,a modern knitting machine might use over2,500 needles. The number of needlesvaries according to the type of machineused and the fabrics produced.

The flat knitting machine is another basictype. Designed with a flat bed, it hasdozens of needles arranged in a straightline and produces a knit fabric that is flat, similar to woven fabric. A flat knittingmachine makes over one million stitches a minute, and can be set to drop or add stitches automatically in order tonarrow or widen the fabric at certainpoints to conform to specific shapes.Knitting machines can be programmed to produce a wide variety of fabrics and shapes.

Cotton is woven intolong reams of fabric

MOST FABRICS ARE FINISHED TO MAKE THEM LOOK AND FEEL MORE ATTRACTIVE. THIS IS THE FINAL STEP IN THE MANUFACTURINGPROCESS.

Weaving

Warping

Raw Cotton

Fibre Preparation YarnFormation

FabricFormation

WetProcessing

Fabrication

Spinning

Knitting

Preparation

Dyeing

Finishing

Cutting

Sewing

Sizing

Weaving

Printing

Finished Goods

GENERAL STEPSIN MANUFACTURING COTTON TEXTILE GOODS

Fact Sheet: Processing, Exportingand Marketing Australian Cotton

FIBREpak: A guide to improvingAustralian Cotton Fibre Quality

This is textile dyeingmachinery, one of themany finishes that can be applied to cotton

Cotton is the world’s most widelyused natural fibre and still theundisputed “king” of the globaltextiles industryphoto by Hayley Caccianiga

CASE STUDY: THE STORY OF DENIM

A BRIEFHISTORY OF DENIMDenim was first made in the 16th Century at a place called Nimes in France. The name ‘denim’ comesfrom the French words ‘serge de Nimes’(fabric of Nimes). Indian sailors werewearing a similar fabric at about thesame time. It is also said that Columbuswas using denim sails when he firstdiscovered America.

For a few hundred years denim wasmainly used as durable work clothing.Around the 1940s denim started to beused in different clothing forms such aswet weather gear and sports clothes. It was not until the 1970s that denimstarted to become fashionable,particularly with American youth.

Cool denim facts

The making of Denim at Cone Millsfor Self Edge Jeans

Case Study: Storm Denim Technology, new ways with denim

ONE BALE OFCOTTONCAN MAKE266 PAIRSOF DENIM JEANS The making of weSC Denim Jeans – cutting,

sewing, stitching and manual treatment

Momatoro Jeans Japan