How toCreate

the

Perfect 100%

CottonKnit

A Technical Guide to Improving Your Knit Products

PRODUCE FIRST QUALITY KNITS

REDUCE SURFACE FUZZING

INCREASE COLOR RETENTION

CONTROL SHRINKAGE

100% Cotton

About 60% of all garments sold at retail in the United States are knit products. In order to engineer the performance

your customers expect in a knit garment at the price they are willing to pay, it is important to make the right

decisions about each stage of the manufacturing process. Today’s customers have myriad choices in

apparel, so they often show little brand loyalty, and if a purchase fails to meet their expectations, they are

often willing to try something different.

The consumer’s garment care practices can significantly affect the overall appearance and performance

of a cotton knit garment. Improper care results in disruption of the fabric surface, causing the garment to lose its

new appearance and to wear out prematurely. If a knit product has a tendency to fuzz easily or lose

its color quickly, this only makes the problem worse.

Consumers average 5 loads of

laundry per week and expect

to wash a dark garment 15

times before it fades.

For over 25 years, Cotton Incorporated has conducted research examining the various cotton knit manufacturing processes and their effects on the

performance and overall quality of the resulting consumer products. The quality of the final product is directly affected by decisions made about the

manufacturing process with respect to fiber selection, yarn spinning systems, fabric construction, fabric preparation, and dyeing and finishing. Decisions

about any of these manufacturing steps can give rise to problems downstream that may not be easily remedied, resulting in a less-than-optimal product.

Such problems can be anticipated and prevented if you make well-informed decisions to engineer a product that meets both the retailer’s performance

specifications and price point and the consumer’s expectation of quality. Savvy choices will result in a product that is a good value and performs well in

terms of color retention, fabric appearance, and shrinkage. Armed with knowledge of the various manufacturing operations and how each step affects

the next, your company can make better-informed decisions that will help you

How to Create the Perfect KnitA Technical Guide to Improving Your Knit Products

• save time and money at each manufacturing stage, by reducing costly mistakes and off-quality goods,

• deliver a higher-quality product, resulting in fewer customer returns and greater consumer satisfaction, and

• develop value-added products that garner higher margins.

1 0 0%C o t t o n

Fiber Selection

Fiber Selection CardingCarding

CombingCombing

Conventional Ring SpinningConventional Ring Spinning

RovingRoving Compact Ring Spinning

Compact Ring Spinning

Open End Spinning

Open End Spinning

Murata Vortex Spinning

Murata Vortex Spinning

Type of Product Being Made?

Type of Product Being Made?

Yarn Quality?

InterlockInterlock

No Bio-PolishNo Bio-PolishBio-PolishBio-Polish

Type of Fabric to be

Knit?

Type of Fabric to be

Knit?

DrawingDrawing

JerseyJersey

PiquePique

ScourScour BleachBleach

Product Color?Product Color?

ReactivesReactives DirectsDirectsVatsVats

Chemical Finishing

Mechanical Finishing

Cost?

Fabric Characteristics?

Performance?

Cost?

Fabric Characteristics?

Performance?

Cost?

Fabric Characteristics?

Performance?

Cost?

Fabric Characteristics?

Performance?

Cost?

Fabric Characteristics?

Performance?

Cost?

Fabric Characteristics?

Performance?

Understanding the interactions between manufacturing stages, the influence of one step on another, and

the trade-offs that can be made will increase both the profitability and quality of your knit products.

This guide will walk you through the manufacturing process, step by step. Each important decision, from

choice of spinning system to dye selection to choice of finishing process(es), will be addressed in terms

of the effect it has not only on the final product, but also on downstream manufacturing steps.

Cotton Incorporated offers unmatched industry knowledge and expertise, based on decades of

experience and a comprehensive understanding of every step of the knit manufacturing process. The

information presented here provides a head start to creating a high-quality knit garment. However, to

truly create the perfect 100% cotton knit for your company’s purposes, please consult one of our experts

in any of the fields addressed in this guide. Our experts will discuss with you the particulars of your

manufacturing process and tailor the answers to meet your specific needs.

Decision Chart for Production of Knit Garments

It is important to note the above symbols are assigned to each alternative in relation to other options at that particular point in the manufacturing process, and are meant to be used strictly as a guideline in making decisions. The actual amount of increased time or cost will depend on the specifi c manufacturer.

$

Processing Time: Processes with this symbol will require additional manufacturing time.

Cost: Processes with this symbol will require additional expense.

+/- Fabric Appearance after Consumer Laundering: A plus (+) denotes positive appearance characteristics (less fuzzing and pilling, greater color retention) while a minus (-) indicates the fabric will show greater amounts of pilling and fuzzing, and less apparent color retention. See photo below

Hand of fi nal knit garment: Processes with this symbol create a favorable hand to the end product.

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Throughout this manual four different symbols will be used to indicate probable outcomes for

options at each step.

Below are the defi nitions and parameters of each symbols.

Key Learnings from this Guide:

The yarn spinning system can have

a direct effect on fuzzing during home

laundering, though it has little effect

on color performance itself.

Bio-polishing is an option to control

fabric fuzzing

Surface fuzz on knit fabrics can create

the appearance of color loss.

Colorfastness is signifi cantly affected

by dye selection, as well as consumer

care, including detergent selection.

Selection of dyestuffs is a critical

step; reactive dyes maintain their color

strength and shade better than direct

or sulfur dyes.

Resin fi nishing is an alternative to

bio-polishing for control of fabric

fuzzing.

Softener selection infl uences surface

appearance and color retention.

The overall sequence of

manufacturing processes can affect

color performance.

Consumer care practices can affect

fabric surface appearance

Fiber Processing and Yarn Spinning

Cotton fiber properties directly affect a knit garment’s quality, appearance, and

performance. It is important to select cotton fiber with the appropriate properties for

each specific end product. It also is important to choose the appropriate spinning system

to produce cotton yarn that will yield the desired fabric characteristics. The three current

spinning systems have different effects on the yarn structure and therefore on the final

product. Sourcing companies must determine which combination of fiber and spinning

system will result in a knit product with the desired key characteristics. Decisions made

about yarn spinning will affect appearance, softness (which depends on yarn hairiness and

twist), color retention, yarn strength for performance, and cost factors related to spinning.

Ring Spinning (Conventional & Compact)

Conventional ring spinning is the oldest production

method used today, yet incorporates many of the

latest technologies. It is also the most expensive and

time-intensive system, because of the roving step at

the beginning and the winding step at the end. This

system allows for the largest range of yarn counts

and is capable of spinning especially fine counts.

Compact ring spinning differs from conventional

ring spinning by using suction in the bottom roller

to control the fiber in a more uniform manner. As a

result, the fibers are more tightly condensed when

exiting the front roller. (See the photo above right.)

Conventional spun yarn shown on the left, compact spun yarn on the right in both photos

StrengthFlexible yarn count S and Z twist yarnsHigh yarn hariness Fabric fuzzing Soft fabric handHigh costLow production rate

StrengthLow yarn harinessLess bulky yarnLess soft fabric handLow production rate

Lower costHigh production rateLowest yarn harinessYarn evennessLimited yarn countsLess soft fabric handStrengthZ twist only

High production rateYarn evennessResistance to abrasionStrengthLow yarn harinessLess soft fabric handCritical system to operate

ConventionalRing Spinning

Vortex Spinning

Open End Spinning

CompactRing Spinning

Yarn Character ist ics Note: Ring spinning is used as a benchmark for comparison of spinning systems

$$$(Conventional & Compact) (Conventional & Compact) (Conventional & Compact) (Conventional & Compact)

$$$$$$(Conventional & Compact)

Open End Spinning

Open-end rotor spinning has a production rate up

to ten times that of ring spinning. Open-end rotor

spinning begins with sliver fed into a combing or

opening roller. This process separates the sliver

into individual fibers, which are transferred into a

rapidly spinning rotor where the sliver meets the

tail of the feeder yarn. Twist is inserted into the

exposed yarn end. The yarn package is ready to

be used right off the machine. Open-end spinning

produces a smaller range of yarn counts than ring

spinning.

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Vortex Spinning

$$

Vortex spinning, a form of air-jet spinning, has the

highest production rate of all the spinning systems.

It begins with sliver fed into a high-speed roller

and apron drafting system. An air vortex imparts

twist to the leading fibers as the fibers leave the

front roller; the air wraps the leading fibers around

the core fibers. Yarn packages are ready to use

right off the machine.

$$$$

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Fabric Construction

Proper fabric construction is essential to creating a well-

engineered garment. Fabric construction must be engineered

from the start of the manufacturing process, through selection

of the right fiber, the appropriate yarn for the specific knitting

machine, and the right stitch length. At the next step of the

process, dyeing and finishing can either improve or impair the

performance of any given fabric construction. To produce a

knit fabric that delivers the best performance at the desired

cost, well-engineered construction must be combined with the

appropriate dyeing and finishing processes. A knitting mill should

have knowledgeable staff who can engineer the fabric to the

performance specifications provided by the customer.

Cotton knit products must be engineered for performance. This means they must be planned, constructed, and managed correctly at each step of the knitting process. Many factors

relate directly to the performance of cotton knits, including fi ber selection, yarn type and knitting parameters. The most critical considerations in engineering a cotton knit are the con-

struction variables and the length processing tensions.

Construction variables:Factors relating to construction include fi ber type, yarn type, machine gauge and diameter, stitch length, and type of stitch. This section focuses on the elements that are selected and

controlled by the knitter.

Yarn:

Four main factors determine a yarn’s performance: size, type, twist multiple, and twist direction. The size of cotton yarn relates to its yield, width, and performance. Yarn size usually is

measured by a cotton count system, which is an indirect numbering system; by the English cotton count system (Ne), the higher the yarn number, the smaller the yarn. Yarn type captures

the spinning process used, how the yarn was assembled (e.g., single or plied), and whether it is a spun yarn or a fi lament yarn. Finally, yarn type and twist determine the hand, appearance,

and strength of the fabric, and they are the main factors affecting skew or torque.

TM (Twist Multiple) =

Engineering Cotton Knits

Stitch Length:

Stitch length is the amount of yarn in one stitch repeat, and course length refers to the amount of yarn used

in one revolution of the knitting machine. Stitch length affects the weight, width, and shrinkage of the fabric.

If the stitch is too short, excessive stress on the yarn and knitting elements can result in holes. If the stitch is too long, dropped stitches are

more likely. It is important to determine the proper stitch length for the desired fabric properties. As shown in the chart to the right, short

and long stitches affect the fabric’s performance in very different ways.

A measurement related to stitch length is the tightness factor, a number that indicates the relative tightness of knitting, taking into

account both the thickness of the yarn and the length of the loops. The tightness factor is important because when this number is out of

range, the machine can operate at lower effi ciency and produce a fabric with defects or a harsher hand. In addition, knitting costs can be

higher, because higher-quality yarn is needed than for the same type of fabric knit with a lower tightness factor.

Type of stitch:

Three basic stitches are available to a knitter: jersey, tuck, and fl oat. These three stitches

are combined to create a multitude of design and performance characteristics in

knit fabrics. Illustrations of these stitches can be seen to the far right.

The shorter the stitch length:

the less yarn in a stitch

the tighter the stitch

the less the length shrinkage

the more the width shrinkage

the narrower the fabric

the heavier the fabric

the fi rmer the hand

The longer the stitch length:

the more yarn in a stitch

the looser the stitch

the more the length shrinkage

the more the width shrinkage

the wider the fabric

the lighter the fabric

the softer the hand

TURNS PER INCH

√NE

Suggested Tightness Factor Ranges

Normal Limits

Single 14-18 12-20

Interlock 10-14 8-16

1X1 Rib 14-18 12-20

Single Pique 14-18 12-20

Six-Thread Pique 14-18 12-20

9.567L in √NE

English

L cm

√TEXMetricTF (Tightness Factor) =

Machine Gauge:

The machine gauge or cut is determined by the number of needles and the diameter of the machine. When

selecting a machine gauge, you are also selecting a range of yarn sizes. Only certain yarn counts can be used

on each type of knitting machine, and this factor determines the types of knit products that can be produced

from a given machine. Generally, the higher the machine gauge, the fi ner the yarns that can be knitted.

Controlling Shrinkage

Controlling Shrinkage

Relaxed stitchLength stretched

Width stretched

Above and right are illustrations of a regular

fabric and fabrics that have been stretched. Relaxed Drying and CompactingRelaxed drying and compacting are two methods used for shrinkage control in knit fabrics. On the opposite page is a photo of a compacting machine. Below is an illustration of the

relaxed drying process and a photo of the actual drying machine.

In today’s competitive markets, where high quality is expected at a low price, apparel companies are demanding low shrinkage. Furthermore, shrinkage must be consistent from garment

to garment in the same style and fabric construction. The term “shrinkage” is commonly used to mean any dimensional change in a fabric or garment - either shrinkage or growth - caused

by the application of force or a change in environment. For a cotton garment, shrinkage characteristics affect parameters such as seam puckering, torquing, and overall garment fit.

Shrinkage during the manufacturing process is caused by two types of factors: those relating to the construction of the fabric or garment and those relating to how the fabric or garment

is processed.

Construction Shrinkage:

Dimensional changes during construction occur as a result of such parameters as fiber, yarn, machine gauge, total number of needles, stitch or course length, and type of stitch. This type

of shrinkage is controlled by careful selection of construction parameters to meet fabric specifications.

Processing Shrinkage:

Dimensional changes during processing can occur during any dyeing or finishing step (whether chemical or mechanical) and usually affect both the length and width of the fabric. Keys

to reducing shrinkage and improving fabric performance are processing the fabric with minimal tension and using compacting or relaxed drying steps.

In this illustration, fabric is fed in from the left into the dryer where it is dried with slack in the fabric to allow it to return to its pre-engineered shape.

Various wet processing techniques have different effects on shrinkage. In general,

batch processing (in a jet dyeing machine) applies less linear tension on the fabric

than continuous processing. Processes such as napping, sanding, and merceriza-

tion apply high tension, while others such as relaxed drying apply low tension.

Weft knits can be processed either open width or in tubular form. Each process

applies tension in different ways, and different processes used on the same greige

and dyed fabric will result in different performance. Resin treatment also has a

huge effect on both fabric strength and shrinkage.

Fabric PreparationIn the preparation stage, the greige cotton fabric is scoured

and/or bleached to remove impurities, thus increasing its

whiteness and absorbency. This step prepares the fabric

to receive dye or other wet processes. One additional step

that can be performed before dyeing, to ensure an end

product free of surface fuzz, is bio-polishing. Bio-polishing

is a cellulase enzyme treatment that removes cotton fibers

protruding from the yarn or fabric surface to create a less

hairy knit fabric with clear stitch definition. Bio-polishing is

one way to clean up the surface of a fabric made of lower-

quality yarn, but it should not be considered a cure-all for

poor-quality, excessively hairy yarn.

The photo to the right shows a

Jemco Bleaching machine

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$No Bio-Polish With Bio-PolishFabrics not treated with cellulase enzymes tend to have more surface

fuzzing after 20 home launderings.

However, if fabric is to be finished with a resin treatment, bio-polishing

may not be necessary, because the resin will inhibit fuzzing during home

laundering and tumble drying. Choosing a less hairy yarn also could

eliminate the need for bio-polishing.

Bio-polishing can reduce fabric surface disruption on a garment

during home laundering. Applied correctly, it can impart an “as

new” appearance that is maintained for the life of the garment. The

combination of bio-polishing and a resin finish was most effective in

reducing shade change after multiple launderings. However, using

both bio-polishing and resin adds an extra bath, which translates to

extra processing time and cost.

+-

The photos show non-enzyme treated (below) and enzyme treated

(right) knit fabrics after laundering, as well as a close up of the fibers.

How are fabrics bio-polished?Manufacturers use a bath or series of baths to bio-polish fabrics. Depending on other factors in the manufacturing process, this step can be done before or after

dyeing. Bio-polishing parameters must be strictly controlled to avoid damage to the fabric as a result of the process. Processing time, temperature, pH, and the

amount of enzyme in the bath must all be coordinated to achieve the desired result. If these factors are not at the correct levels, the fabric may have excessive

loss of weight and strength.

Dye SelectionFabric appearance and color retention are significantly affected by dye selection.

It is essential to select dyes that have the right fastness properties for the desired

end product. Within a class of dyes, quality and price can vary. Use of high-quality

dyes, from reputable suppliers, will improve fastness. It is important to understand

the different types of dyestuffs available for cotton and to understand the

trade-offs between performance and cost. Decisions made at this stage directly

affect the garment’s colorfastness when laundered by the consumer.

Another important factor is the process used to dye the fabric. Knits fabrics are

most commonly jet dyed in sealed vessels. Jet dyeing can be used with various

dye classes. In the dyeing process, it is essential to avoid excessive abrasion of the

fabric surface, which will affect the appearance of the end product.

Choosing a Dye

CharacteristicsTo achieve a quality end product, dyes should have:

Good cold water bleed characteristics Good colorfastness to levels of chlorine in municipal systems Shading components with good performance properties Durability to multiple home launderings

ProcessIn jet dyeing machines, both the fabric and dye liquor are moved simultaneously. Fabric is moved through a venturi

tube, and dye is pumped through the tube as the fabric moves by. The photo to the right shows unloading of the

machine after a dyeing cycle.

Benefits of using a jet dyeing process: The greatest benefit is the versatility of being able to use the same machine

to bleach, enzyme treat, and dye. In addition, jet dyeing uses a low liquor ratio; using less water saves on energy for

heating the water and reduces the amount of waste water that must be treated and disposed of. New machines can

use a ratio of water to dye as low as 5:1.

Dye Class

Reactive

Direct

Vat

Shade Brightness

ApplicationTime

Wash Fastness

Light Fastness

Crock Fastness

Sulfur

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Dye selection for cotton knits is an important part of the manufacturing process. As illustrated below, each dye class has both advantages and disadvantages. It is

necessary to understand these differences in order to select the dye that is best for your product.

FinishingAlthough the finishing of a knit fabric can make or

break the final product quality, the other steps in the

manufacturing process can have just as great an effect.

In determining how to finish a product, it is essential

to understand that decisions in the manufacturing

process are cumulative. Finishing is not a cure-all,

and it cannot overcome limitations resulting from

earlier steps in the process. In fact, finishing can even

have counterproductive effects if the manufacturing

process has not been thought through all the way

to the end. Engineering of the product should start

at the end of the manufacturing process and work

backwards. Identifying and understanding the

specific properties desired in the final product will

allow you to make better-informed decisions for

each stage of the process, ensuring that the finished

product has the characteristics you intended.

ResinResin treatment can be used in place of bio-polishing to reduce fuzzing. Its effects

can be similar; however, resin alone does not improve the color performance of knit

fabrics. Although resin can help maintain a knit fabric’s dimensional stability and control

shrinkage, it can also weaken the fabric. The amount of resin added to the fabric should

be carefully determined to achieve a balance of performance and strength.

$

SoftenerSome silicone softeners can make fabric more prone to fuzzing during laundering, causing

the perception of color loss. Choice of softener is key to minimizing surface fuzzing due

to repetitive laundering.

$-

Finishing Options:The options for fi nishing knit products are seemingly endless. Everything

from water repellent to soil release to fl ame retardant properties can be

incorporated onto the fabric. In addition, surface fi nishes such as sanding,

sueding, napping, and shearing offer ways to dramatically alter the hand

or appearance of the end product. It is important to remember that all of

these processes will affect the visual characteristics of the fi nal product,

including the color and shade. To ensure that the fi nal product has the

desired properties, plans for fi nishing need to be taken into account when

the choices are made for every earlier step in the manufacturing process.

$

Napping Shearing Water Repellent

To the left is an illustration and a photo of a

tenter frame. Fabric is fed through rollers (here

shown from the right) and set into a frame to

hold it in place. The fabric then enters several

ovens, where the processing occurs. Tenter

frames are used for many purposes, including

drying and curing and controlling skew.

Consumer Care

Garment LabelingGarment care labels are an important factor in maintaining the quality and appearance of a knit garment once it leaves the store.

Understanding consumer laundry habits and how clothes are washed helps manufacturers to reduce problems resulting from

improper laundering, to prolong an “as new” appearance.

Two thirds (67%) of consumers “always” or “usually” refer to the care label before washing.

If a shirt fell apart in the laundry, only 17% of consumers would hold themselves responsible for not reading the instructions. More than 70% would blame the manufacturer.

Simple actions by the consumer can preserve the appearance of a knit fabric and lengthen the life of a garment:

Turn garments inside out before laundering, to reduce fabric surface abrasion.

Use detergents with chlorine scavengers, to reduce fading due to chlorine in the water.

Set the right water level in the washer for the amount of clothes, to reduce fabric surface abrasion.

Prevent over drying in the tumble dryer by checking progress frequently, to reduce abrasion and shrinkage.

What Happens in the Laundry?

Why did my shirt shrink in the dryer?

Only 20% of consumers were aware that the dryer, not the hot water or the fiber type, causes shrinkage. However, many of these

consumers incorrectly identified the heat from the dryer as the reason their shirt went down a few sizes. In fact, the culprit is not the

temperature; shrinkage actually is caused by the dryer’s tumbling action.

Does abrasion happen in the washer or the dryer?

Abrasion can happen in either machine as a result of overloading. When clothes do not have enough room to move around, they

rub against each other and machine components constantly. Consumers can decrease abrasion-related fuzzing by not overloading

machines, as well as by turning garments inside out for laundering.

Cotton IncorporatedWorld Headquarters

6399 Weston Park way Car y, NC 27513

Tel . (919) 678-2220 Fax (919) 678-2231www.cottoninc.com

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