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27KnitsStretch andShrinkage Factors

chapter

626

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 627STRETCH AND RECOVERY FACTOR . . . . . . . . . . . . . . 627

Stretch Factor . . . . . . . . . . . . . . . . . . . . . . . . . .627Recovery Factor . . . . . . . . . . . . . . . . . . . . . . . .627Variance in Stretch . . . . . . . . . . . . . . . . . . . . . .627

STRETCH AND RECOVERY GAUGE . . . . . . . . . . . . . . 628CLASSIFICATION OF KNIT FABRICS . . . . . . . . . . . . . . 629DIRECTION OF STRETCH . . . . . . . . . . . . . . . . . . . . . . . 629ADAPTING PATTERNS TO KNITS . . . . . . . . . . . . . . . . . . 630

The Shrinkage Factor . . . . . . . . . . . . . . . . . . . .630The Stretch Factor . . . . . . . . . . . . . . . . . . . . . . .631

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KNITSSTRETCH AND SHRINKAGE FACTORS 627

INTRODUCTIONKnits are some of the most popular fabrics in the market today, primarily for the following reasons: Structure: Knit fabrics are made of natural and synthetic fibers. Versatility: Knits are suitable for dressy, daytime, and activewear. Stretchability: Knits have the capacity to stretch in length, width, or both (in addition to the bias stretch

common to all fabrics).

Many manufacturers and designers devote part or all of their lines to knit designs. The patternmakershould be knowledgeable about the special characteristics of knits and their stretch and recovery factors sothat a good fit can be achieved with few corrections. This is accomplished by modifying the pattern beforecutting in knit. DuPont has launched a patented processSorona polymer (made from a petro chemicalsource and also from a renewable sourcecorn). The latest-patented process called Lycra 2.0-Xtra Life

Lycra fiber was developed for swimwear. The composition is mainly of elastomer and other stretch fibers. Itskey characteristics are: softness, stretch and recovery hand, stain resistance, crush resistance, quick and easydyeing, fast drying, and resistance to chlorine and ultraviolet degradation.

STRETCH AND RECOVERY FACTORThe ability of a knit fabric to stretch and return to its original shape (length and width) is referred to as thefabrics memory. (See the stretch and recovery gauge on page 628.)

Stretch FactorThe stretch factor is the amount of stretch per inch that occurs when the knit is stretched to its maximumlength and width. The stretch factors of knits range from 18 to 100 percent or more.

Recovery FactorThe recovery factor is the degree to which a knit will return to its original shape after being stretched. Knitswith good recovery are those that return to their original length and width when released. If the fabric doesnot return to its original dimension, or close to it, the garment will eventually sag on the body and lose someof its original shape.

Variance in StretchThere is a variance in the degree of stretch among knits and the degree of stretch between the length andwidth of each knit. Knits that stretch in both directions are two-way stretch knits.

If some of the stretch is not removed from garments made with a blended Lycra , the garment will sag onthe figure. To remove stretch, the pattern is reduced in its length and width as designated by the stretch of the fabric. To determine the stretch of knits, use the stretch gauge on page 628. Buy the type of knit appro-priate to the garments use.

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628 Chapter 27

STRETCH AND RECOVERY GAUGEThe ruler at the edge of the page is used to determine the stretch/recoveryfactor of knits. Suggestion: Copy the ruler, glue on cardboard, and take itwith you when testing and buying knits. To use the stretch gauge ruler,

follow the instructions.

5 "

Fold of lengthwise grain

Selvage

Selvage

5 "

Fold of crosswise grain

S el v a

g e

This method is used for close-fitted and contour-type garments (body-suit, leotard, swimwear) in which stretch is the most important factor. Theoriginal pattern is modified (reduced in length and width) to compensatefor the stretch. Read the classification of knits on page 629.

Determining the Stretch/Recovery Factor of KnitsFigure 1 Crosswise Grain Fold knit along crosswise grain. Pin-mark a space 5 inches

wide.

Place fold of the knit on the stretch gauge. Holding knit firmly at edge of the gauge, stretch without dis-

torting the fabric. If distortion (parallel folds) appear, relaxtension.

Note the distance the knit stretched beyond its originallength18, 25, 50, or 100 percent. Release the pulled end of the knit to determine its recovery factor. If the knit returnsto its original location, it has excellent recovery.

L Y C RA

L Y C RA

T e s t S am

pl eL en

g t h

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1 2 0 %

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1 1

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E L ON GA

S C A L E F ORME A S URI N GE L ON GA T I ON OF C OV E RE D

Y A RN ORE L A S T I C F A B RI C S

C ONT A I NI N GL Y C RA

Figure 2 Lengthwise Grain Repeat process used for crosswise grain.

Caution: If a knit does not have good recov-ery, 50 to 100 percent stretch factor in one orboth directions, do not consider using it for abodysuit, leotard, or maillot. It will sag ratherthan contour the body like a second skin.

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KNITSSTRETCH AND SHRINKAGE FACTORS 629

CLASSIFICATIONOF KNIT FABRICS

Knits come in many fibers: cotton, antron, and nylon,to name a few. When combined with Lycra spandexor Lastex latex, the fabric will vary in weight, texture,direction, and degree of stretch and shrinkage.

Lycra (spandex) is a manufactured fiber inwhich the fiber-forming substance is a long-chainsynthetic polymer comprised of at least 85 percentof a segmented polyurethane. The DuPont Com-pany introduced the first spandex fiber called Lycrain 1958. DuPont (the leader) has issued standardsfor Lycra spandex for activewear garments: Must have a minimum of 12.5 percent elongation Must withstand power of at least 0.6 pounds per

square inch to ensure good recovery under wetand dry conditions. Must have zero pullback after 3,000 flex cycles. Must have a Lycra content of at least 0.6 ounces

per square yard to ensure working stretch.

Lycra spandex may be combined with antron,nylon, and cotton for swimwear, bodysuits, and leo-tards. Spandex has the ability to spring back to itsoriginal shape when stretched (referred to as itsmemory). After repeated stretching, it shows only asmall increase in length.

Lycra allows the body to move with completefreedom when in a flexed position:

Across the back flex movement from 13 to 16percent

Elbow FlexLength35 to 40 percentCircumference15 to 22 percentSeat flex: Across4 to 6 percent

Knee FlexLength35 to 45 percentCircumference12 to 14 percent

There are single-knit and double-knit fabrics;however, knits can generally be classified in the fol-lowing ways:

Stable (firm) knits. A stretch factor of 18 percent onthe crosswise grain (example: 5 inches will stretch to5 7/8 inches). This type of knit has a limited degree

of stretch and will retain its original shape well. Fit

is similar to that of a garment cut in a woven fabric.Example: double knit in any fiber.

Moderate-stretch knits. A stretch factor of 25 per-cent on the crosswise grain (example: 5 inchesstretches to 6 1/4 inches). Combines characteristics

of both stable and stretchy knits. Generally used forsportswear when stretch is used for comfort and aclose fit but should not be used for garments con-touring the figure. Example: nylon tricot.

Stretchy knits. A stretch factor of 50 percent on thecrosswise grain with 18 to 50 percent on thestraightgrain. (example: 5 inches will stretch to7 1/2 inches). Because it is stretchy and light-weight,stretchy knit drapes well and is used for garmentsthat contour the figure. This type of knit is suitablefor bodysuits, leotards, maillots, and clingingdresses and tops (provided the knit has an excellentrecovery factor). Example: cotton/spandex, nylon/spandex, cotton/latex, nylon/latex, or any fabriccontaining spandex or latex.

Super-stretch knit. A stretch factor of 100 percentin the lengthwise and crosswise grain (example:5 inches stretches to 10 or more inches). Its excellentstretch and recovery make it suitable for bodysuits,leotards, and skiwear, as well as tops. The elasticfiber of this type of knit can stretch many times itslength and yet return to its original measurements.Examples: Any fiber blended with spandex or latex.

Rib knits. A stretch factor of 100 percent (1 1 ribswill stretch less than 2 2 or 3 2). Used for topsand banding (example: the knit two, purl two tra-ditional wristband stitch). Rib knits are dependenton the knit pattern as well as on the fibers used.

DIRECTION OF STRETCHKnits can also be classified by the direction of stretch in the following ways:

Warp stretch. Stretch yarns run lengthwise.Filling stretch. Stretch yarns run crosswise.

Two-way stretch. Stretch yarns run in both thelength and crosswise directions.

To utilize the built-in stretch of knits, the maxi-mum stretch should encircle the figure when knitsare used for dresses, jackets, pants, and tops. Themaximum stretch should go up and down the figurefor bodysuits, leotards, jumpsuits, and skiwear toallow for maximum mobility. See Chapter 29,

Activewear, and Chapter 30, Swimwear.

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ADAPTING PATTERNSTO KNITS

There are two reasons for adapting a pattern to knitfabrics: The shrinkage factor requires the size of thepattern to be enlarged, and the stretch factor re-quires the size of the pattern to be reduced. Thechoice is determined by the type of knit and the useof the garment.

White (C) enlarged pattern.Shaded (B) original pattern.White (A) cloth pattern.

The Shrinkage FactorFor loosely fitted garments, shrinkage is consideredto be the most important factor. Therefore, the pat-tern is enlarged to compensate for shrinkage. To dothis, the shrinkage factor must be known.

Enlarging the PatternFigures 1,2 Cut the garment parts. (The torso and sleeve are

used as the example.) Wash and dry the fabric. Place the cloth pattern

on top of the paper pattern. Place on paper,aligning the center line and waist of the torsoand the grainline and biceps line of the sleeve.Pin to secure. (White area indicates the garmentpart [A], the shaded area indicates the originalpattern [B], and the outside white area indicatesthe new enlarged pattern [C].)

Enlarging the pattern for shrinkage: Draw guide-lines out from the corners of the fabric patternand working patterns. Measure the distancesfrom the cloth pattern and the working patternat each guideline. Use these measurements to

mark the distances out from the working patternat each location. Draw the new pattern by con-necting lines from one mark to the next, blendingcurved lines. True the patterns when cut.

Reducing the pattern for stretch: Trace the A patterns.

Note: Placement of garment parts on the pattern may look different from the illustrations, but the process for developing the enlarged pat-tern remains the same.

Guideline

Guideline

Guideline

Guideline waist

GuidelineC

A

B

C ent er f r ont

TOP FRONT

Figure 1

C

BA

Guideline

Guideline

Guideline

Guideline GuidelineGuideline

Guideline

Guideline

SLEEVE

Figure 2

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KNITSSTRETCH AND SHRINKAGE FACTORS 631

The Stretch FactorKnits with varying stretch and recovery factors (firmknits and stretch knits) require different methods forreducing the pattern. Three methods are discussed.

Modifying the PatternTo determine how much a patterns length and widthshould be reduced, follow the examples and measure-ments given for knits with a stretch factor from 18 to25 percent. For knits stretching beyond 25 percent but less than 50 percent, add 1/8 inch to all measurements.The measurements are general and may require addi-tional adjustments at the time of the fitting. Knitsshrink when washed. Walk all seams and marknotches. The basic front bodice, skirt, sleeve, andpant are illustrated and should be used as guides for

all similar pattern modifications. (Broken lines indi-cate original patterns.)

Figures 1,2, 3, Bodice, Skirt, Pants Neckline: Raise 1/4 inch. Blend. The back neck is

not adjusted unless the neckline is deeply cut. Side seams: Remove 1/4 inch (parallel with origi-

nal line of the pattern). Repeat for the back.Remove 1/4 inch from the inseam of the pant.

Armhole: Raise 1/2 inch. Blend. Repeat for theback.

Dart points: Raise 1/4 inch where shown. Hemline and waistline: Remove 1/4 inch (parallel

with the original hem or waist of the pattern). Crotch: Raise 1/4 to 1/2 inch (amount depends on

style of the pant). Example: 1/2 inch for trouser,1/4 inch for slack or jean. Repeat for the back.

BODICE FRONT1/2 "

1/4 " 1/4 "

1/4 "

1/4 "

1/4 "

Figure 1

1/2 "

1/4 "

1/2 "

1/4 "

New biceps level

1/4 "

1/4 "

Figure 2

SKIRT

1/4 " 1/4 "

1/4 "

1/4"

PANT FRONT

New crotch level 1/2 "

1/4 "

Figure 3

Figure 2 Sleeve Biceps: Raise 1/2 inch. Blend. Underarm seam: Remove 1/4 inch

(parallel with the original line of the pattern).

Hem: Remove 1/4 inch (parallelwith the original hemline of thepattern).

Elbow dart: Reposition 1/4 inch up. Walk sleeve to armhole.

Figure 4