Fabric faults produced during weaving & knitting production

Weaving fault:
Warp way defect:
I. Warp stitching : Occurred due to want of interlacement between warp & weft yarn which happen:
   Ø If the warp threads of one shed goes to another.
   Ø Faulty dobby or jacquard mechanism.
   Ø Warp yarn if loose.
   Ø Height of the harness card if not equal.
   Ø Warp is not properly sized.

a) Long float: causes due to
   Ø If the warp yarn does not take part in interlacement.
   Ø Tappet is not properly tied.
   Ø Peg if dobby displaced.
   Ø Jacquard harness or cord cutting if defective.
   Ø Worn out Reed if used.

b) Wrong warp threads: due to drafting & lifting.
Missing warp: causes due to:
   Ø Wrong denting.
   Ø Broken warp yarn in the beam.
   Ø Out of order warp stop motion.

d) Double warp: warp way marks on the fabric due to:
   Ø Wrong reed count used.
   Ø Wrong denting in the reed.

e) Loose warp: Causes due to
   Ø Loose warp exist on the beam in loop form.
   Ø Yarn tension in the dropper.
   Ø Size picks up unequal.

f) Knot in the warp yarn: If there are any knots in warp yarns.

g) Selvedge effect: Causes due to :
   Ø If the body and selvedge warp yarns tension is unequal.
   Ø If the reed space is greater but the width of the fabric is les.
   Ø Sharp temple ring spikes.

h) Weft cut at the selvedge: due to
   Ø Absent of weft yarn in the selvedge
   Ø Defective ring temple.
   Ø If the temple not properly set.

i) Temple mark: Mark on the selvedge of the fabric due to: light fabric if course temple is used.

Weft way fault:
1. Miss pick or broken pick:- Causes Due to
   Ø Broken pick.
   Ø Yarn of pirnoooo is finish.
   Ø If weft yarn breaks at the middle.
   Ø Picking much uniform occurred by empty shuttle.

2. Broken design: If the lifting mechanism is defective.

3. Thick & thin place which is called bar on the fabric.

4. Shuttle mark:
   Ø Shuttle flies.
   Ø Shuttle box is not properly set.

Defective of knitted goods to be unspected:

1. Broken ends: If the yarn breaks, holes create in the fabric.
   Ø During loop formation if the yarn previously broken in the needle.

2. Drop stitch:
   Ø Due to defective needle.
   Ø Yarn feeder not properly set.
   Ø Wrong take up mechanism.
   Ø Stitching tension if not proper.

3. Slugging.
   Ø Only occurs in continuous filament yarn.
   Ø Occurs due to mechanical strain in the next process stages.

4. Tuck & doable stitch: Occurs due to badly oooo or knitted loop. It results the formation small brads or thick & thin places in large ascoooo.

5. Bunching up: Visible knots in the fabric eyes known as beads.

6. Vertical stripe: Vertically shown streaks on the Wales which causes due to:
   Ø Gauge is not done according to count.
   Ø Stitch size.
   Ø Course density.

7. Horizontal stripe: unevenness along the course direction.
   Ø Yarn feeder if not properly set.
   Ø Tension if not uniform.

Wish You Good Luck..................................
You Should Interested to read RELATED POST on the topics

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Warp Knitting, Production of warp knitted fabric

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Knitted fabrics are divided into two general types: (1) those produced by weft knitting, where one continuous yarn forms courses across the fabric; (2) those produced by warp knitting, where a series of yarns forms wale’s in the lengthwise direction of the fabric. 

Warp Knitting 

This form of knitting is very different from standard hand knitting; the earliest warp knitting machine was Crane’s tricot machine (England), built about 1775. In warp knitting, a yarn is fed to each needle from the lengthwise direction. A bar guiding the yarns to the needles can move from side to side, or to the front or back of the needle, so that the loops can be interlocked in a zigzag pattern. Very wide (over 400 cm, nearly 170 in.), flat fabric can be produced by warp knitting, at speeds in the order of 1,000 courses per minute, giving almost 3 m2/min (3.6 sq. yds./min). The two main machine (fabric) types are tricot and raschel. 

Diagram of simple warp knit fabric. 

Tricot warp knitted fabric: Tricot is a machine with one needle bar (spring beard type) and one to three guide bars, +0 3++most are two-bar or three-bar. The spring beard needle, accepting mainly filament yarns, has limited the depth of texture that can be achieved in tricot fabrics; some fine spun tricot, produced on machines with hybrid needles, was introduced many years ago, but does not seem to have taken hold in the market place. Tricot does not ravel, can curl somewhat, and has almost no stretch or “give” lengthwise but a little crosswise. 

Raschel warp knitted fabric: Raschel is the other main warp-knitting machine. Fabric from these machines may be of any weight or thickness from lace to carpet; the one feature they share is a pillar-and-inlay effect; Wales like hand crochet chains forming the “pillar” with other yarns laid in to form patterns or the main body of the fabric, usually making up the right side. Raschel machines have one or two needle bars (usually latch, but may be spring beard), set horizontally on wide or narrow machines with 1 to over 30 guide bars. The multi guide bar types are used mostly for laces; most of our moderate-priced laces are knit on this type of machine. They do not have the depth of texture that the twisted Leavers laces or the embroidered Schiffli laces have. Powernet, knit on the raschel machine, incorporates elastomeric yarn to give one- or two-way power stretch for contour fashion Variations on raschel-type machines include crochet, ketten raschel, and Cidega machines. The latter, similar to raschel, can knit various fabrics side by side, and so is used for many narrow trims called “braids,” such as gimp and ball fringe. 

Minor Warp Knits: Simplex is a machine with two horizontal needle bars and two guide bars, producing a double tricot type of warp knit in a fine gauge, with two threads to each loop. The needles in one bar are directly behind those in the other, in much the same way that needles in the weft knit interlock are aligned; like interlock, simplex looks like plain-stitch jersey on both sides. The fabric is very firm and stable, used for its greater firmness in lounge wear, uniforms, and gloves.

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Weft Knitting, Produce weft knitted fabric

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Weft Knitting 

There are three fundamental stitches in weft knitting: (1) plain knit stitch, (2) purl stitch, (3) rib stitch. Novelty stitches are variations of these three stitches. The hand method of knitting is weft knitting. On a knitting machine, the individual yarn is fed to one or more needles at a time 

1. Plain-knit Stitch: The plain knit is the basic form of knitting. It can be produced in flat-knit or in tubular (or circular) form. The flat knit is also called jersey stitch because the construction is like that of the turtleneck sweaters originally worn by English sailors from the Isle of Jersey; it is sometimes called balbriggan stitch after the hosiery and underwear fabrics made in Balbriggan, Ireland. Plain flat knits may be shaped or full-fashioned. The knitting is done with a row of latch or beard needles arranged in a linear position on a needle plate or in a circular position on a cylinder. All the needles are evenly spaced side by side and are moved by cams, which act on the needle butts. The spacing of the needles is referred to as the gauge, gage, or cut. As applied to many flat knits and some circular ones, gauge refers to the number of needles in 11/2 inches; for example, a 60-gauge machine would have 40 needles per inch. 

2. Purl Stitch: This construction is also referred to as the link-sand links stitch after the German word “links,” or on the left). It is made on flat-bed and circular machines by needles using hooks on both ends to alternately draw loops to the front of the fabric in one course and to the back in the next course. It is a slower and more costly technique. The fabric looks the same on both sides and resembles the back of the plain knit. Like the plain knit, the purl knit will run up and down if a loop is broken. But a purl knit fabric will not curl at the edges. 

3. Rib Stitch: Rib-knit fabrics have alternating lengthwise rows of plain and purl stitches constructed so that the face and back of the fabric appear alike. This may be produced either on a flat rib machine or a circular rib machine. In the flat rib machine, one set of needles is placed opposite the other set of needles is placed opposite the other set of needles in an inverted V position of 45 degrees to the horizontal; in the circular rib machine, one set of needles is placed vertically in a cylinder and the other set of needles is placed horizontally on a dial. In both machines, one set of needles pulls the loops to the front and the other set pulls the loops to the back of the fabric. Each set of needles alternately draws loops in its own direction, depending upon the width of the rib desired. 

For example, rib stitches can be 1 x 1, 2 x 2, 2 x 1, 3 x 1, and so on. A combination of 1 x 1 and 2 x 2 is called an accordion rib. Rib construction is costlier because of the greater amount of yarn needed and the slower rate of production Rib knits are made on a two-bed machine with one set of needles forming the loops for one wale and the other set of needles forming the alternating wale.Rib knits have greater elasticity in the width than in the length. They are stable and do not curl or stretch out of shape as do the jersey knits. For this reason, they are often used to make cuffs and necklines on weft knitted garments. Rib knits are reversible unless the number of stitches in the alternating wales is uneven, as in a 2 X 3 rib.

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Gauge and Quality; Knitting machine element to produce knit fabric

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Gauge and Quality 

The size of the needle and the spacing of the needles on knitting machines determine the number and size of the knit stitches and their closeness those are known as knitting element. Each wale is formed on one needle. The number of needles is equal to the number of Wales. The closeness of the stitches determines whether a knit fabric will be lightweight and open or heavier and more dense. The term gauge is used to describe the closeness of knit stitches. Gauge is the number of needles in a measured space on the knitting machine. Higher-gauge fabrics (those with more stitches) are made with finer needles; lower gauge fabrics are made with coarser or larger needles. 

The term cut is also used to designate the number of needles per inch in the needle bed of a circular weft knitting machine. To describe the stitch density of a single or double knit fabric, the fabric may be designated as an 18-, 20-, 22-, or 24cut fabric. The higher the cut, the closer the stitches; the lower the cut, the coarser the fabric. 

Varying types of knitting machines measure gauge over different distances on the machine. For example, circular knit hosiery measures the number of needles in 1.0 inch, fullfashioned knitting in 1.5 inches, and Raschel knits in 2.0 inches. 

Because of these differences, it is best to keep in mind the generalized principle that the higher the gauge, the closer the stitches. 

The quality of needles used in manufacturing knit goods is related directly to the quality of the fabric produced. Needles of uneven size and quality will produce knit fabrics with unevensized stitches and imperfect surface appearance. 

In warp knits, those knits in which the yarns interlace in the long direction, one or more yarns are allotted to each needle on the machine, and those yarns follow the long direction of the fabric. For weft knits, those in which the yarns interlace crosswise or horizontally, one or more yarns are used for each course, and these yarns move across the fabric. In weft knits, one yarn may have from twenty to several hundred needles associated with it. To summarize, weft knits can be made with one yarn, but warp knits must have a whole set of warp yarns, that is, one or more for each needle. 

Once the basic distinction between warp and weft knits has been made, further subdivisions of knit classifications are usually based on the types of machines used in their production. The majority of knit fabrics are named after the machines on which they are constructed. For this reason, the discussion of knitted fabrics that follows is organized around the types of machines used in manufacturing knit fabrics and the types of knit fabrics made on these machines. 

1. Flat or circular jersey, or single knit, machine: one needle bed and one set of needles. 

2. Flat or circular rib machine: two needle beds and two sets of needles. 

3. Flat or circular purl, or links-links, machine: two needle beds and one set of needles.

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Loop Formation in knit fabric structure

Loop Formation 

The spring beard needle is formed from one piece of thin wire. One end of the needle is drawn into thinner dimensions and is curved to form a hook. The flexible outer side of the hook can be pressed against the stem of the needle to close the hook for sliding a formed loop off and beginning a new loop. In 1847 Matthew Townshend invented a different type of hook known as the latch needle, which has come to be the most widely used type of needle. Its operation s similar to that of the spring beard needle, except that instead of having to mechanically press the flexible wire of the needle closed so that the forming yarn loop will not slide off, a latch closes to hold the yarn in place. 

1. The old loop is held on the stem of the needle. The latch is open (a). 

2. The hook grasps the yarn to begin forming a new loop (b). 

3. The needle falls, the old loop rises, closing the latch of the needle (c). 

4. The old loop is cast off (d and e). 

5. The needle tises, and the new loop slides down to the stem of the needle, pushing the latch open again, and the needle is ready to repeat the cycle (f).

Loop formation in knit fabric

Yet a third type of needle, the compound needle, is used almost exclusively for warp knitting. The compound needle has two components, a tongue and a hook Its motion is as follows: 

1. The old loop encircles the hook; the tongue is in such a position as to leave the hook open. 

2. Both tongue and hook rise; a new yarn is fed to the hook. 

3. Both tongue and hook descend, but the tongue descends more slowly, thereby closing the hook. 

4. As the needle descends, the held loop slides off, forming a new loop. 

5. The needle returns to its initial position, the hook ascending more rapidly, thereby opening the hook again. 

For weft knitting with either needle type, a cam system provides the action for lifting the needles as the yarn is fed in. A small projection called a butt is located at the bottom of the needle. The butt is held in a groove formed by a system of cams or shaped pieces. The movement of the butt in the grooves between the cams causes the needle to rise and fall. 

The engaging by the needle of a new piece of yarn is called feeding. Devices called feeders are located to introduce the yarn to the needles. The number of feeders can vary, but obviously the more feeders a machine has, the higher will be the speed of fabric forming on the machine, since each needle produces a loop each time it is activated and if many needles are activated more frequently, many courses can be formed at the same time. 

Another important element of some knitting machines is the sinker. The already formed fabric may need to be controlled as the subsequent knitting action takes place. A thin steel device called the sinker may be used to hold the fabric as the needle rises, support the fabric as the needle descends, and push the fabric away from the needle after the new loop has been formed. Sinkers are generally mounted between the needles. Some machines, however, do not use sinkers but instead use the tensions placed on the completed fabrics for control.

Construction of Knit Fabric

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The construction of knitted fabrics is evaluated by the number of stitches or loops. When the interlocking loops run lengthwise, each row is called a wale. A wale corresponds to the direction of the warp in woven fabrics. When the loops run across the fabric, each row is called a course. A course corresponds to the filling, or weft. Thus, a knitted fabric having 40 loops or stitches in 1 inch of width, and 50 loops in 1 inch of length, is said to have 40 Wales and 50 courses.

Construction of Knit Fabric

The major difference between knitted and woven structures lies in the way the yarns are interconnected geometrically. In weaving, two sets of parallel yarns are interconnected by interlacing them at right angles. Different woven structures are produced by varying this basic principle In knitting, the yarns are initially formed into loops, and then these loops are interconnected in order to produce a textile structure. The term interlooping is used to describe this technique of forming fabrics. Based on this principle, a textile fabric is produced by using only one set of yarns. Thereby, a horizontal set of yarns (weft) could be interlooped to produce a weft knitted fabric, and a vertical set of yarns (warp) could be used to produce a warp knitted fabric. As a result of this interlooping of yarns, the surface of a weft or a warp knitted fabric is more open when compared to the surface of a woven fabric. Due to this interlooping of yarns a knitted fabric could be stretched more than a woven fabric, even when a small force alone is applied. 

Once this force is eased the fabric slowly returns to its original dimensions. In fact, weft and warp knitted fabrics have higher elongation values than woven fabrics due to their structure, and their elastic behaviour generally exceed the elastic properties of the yarns used to knit the fabric. 

Yarns have poor bending and tensional properties compared to their longitudinal elastic properties, and so once a knitted fabric is stretched and then released, it would slowly go back to its original state. The absolute elongation and the elastic behavior of the fabric are both determined by the knitted structure and the mechanical properties of the yarns used to knit the fabric. Due to the structure and good elastic behaviour of knitted fabrics, garments made of knitted fabrics (knitted garments) are comfortable to wear. The air trapped in the loops of a knitted garment insulates the human body against cold. At the same time the relatively loose and open structure helps the perspiration process of the human body, especially when the knitted fabric is made of yarns spun from natural fibers. Due to the interlooping of yarns, the knitted fabrics also have better crease recovering properties compared to fabrics woven from similar yarns. 

The term binding can be used to describe the connection of one or more yarns in a textile fabric. The structure of a knitted fabric can be evaluated by studying how the yarns in weft and warp knitted fabrics are bound or interconnected, and this can be illustrated using stitch (loop) diagrams (charts). The actual interlooping of yarns in order to produce knitted structures depends on the knitting principle that was adopted to produce the structure, i.e. weft or warp knitting, and on the patterning elements. Knitting is the process of making cloth with a single yarn or set of yarns moving in only one direction. Instead of two sets of yarns crossing each other as in weaving, the I single knitting yarn is looped through itself to make a chain of stitches. These chains or rows are connected side by side to produce the knit cloth” (American Fabrics and Fashions Magazine 1980, 370). The interlocking of these loops in knitting can be done by either vertical or horizontal movement. When the yarns are introduced in a crosswise direction, at right angles to the direction of growth of the fabric, and run or interlock across the fabric, the knit is known as a weft knit. (Some sources may refer to these knits as filling knits, but the term weft knit is used in the knitting industry.) 

When the yarns run lengthwise or up and down, the knit is known as a warp knit. In knitting terminology, the rows of stitches that run in columns along the lengthwise direction of the fabric are known as wales. This corresponds to the warp direction of woven fabrics. Crosswise rows of stitches or loops are called courses. The direction of the courses corresponds to the filling of woven goods. 

Both warp and weft knits are made by machine. Knitting machines may be either flat or circular. The flat-type knitting machine has needles arranged in one or two straight lines and held on a flat needle-bed. The cloth is made by forming stitches on these needles. The resulting fabric is flat. Machines with flatbeds are used to make both warp and weft knits. 

The circular knitting machine has needles arranged in a circle on a rotating cylinder. The resulting fabric is formed into a tube. Circular knitting machines produce weft knits almost exclusively. For nearly two hundred years after its invention in 1589, Lee’s machine was used without further improvement. Using a spring beard needle, Lee’s machine produced flat knitted fabrics by mechanically passing one loop of yarn through another.

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Care of Knit Fabric

Care must be taken for Knit Fabrics 
Although there is a great variety in the quality of knitted goods sold, and the performance of any individual knit may differ markedly from that of other knits, some general guidelines for the care of knitted goods can be observed. The problems that consumers seem to encounter most often in the performance of knitted fabrics are in the areas of dimensional stability, snagging, and pilling.

Dimensional Stability
One reason for the popularity of knits for wearing apparel is their comfort. The looped construction of knit fabrics permits the fabric to give with the body as it moves. But the stretchiness of knits also results in lessened dimensional stability. Consumers have complained about shrinkage, stretching, and distortion of knits, although interlock and double knit fabrics are usually more stable and display little or no shrinkage. Similarly, fabrics with weft or warp inserted yarns are more stable. Shrinkage control treatments, heat setting of synthetics, and special resin finishes can provide good dimensional stability for knits. Unfortunately, not all manufacturers provide such treatment for their products. Consumers should check labels for percentage of shrinkage or for other special treatments to judge potential dimensional stability. (About 3 percent shrinkage is one garment size.) If products fail to live up to specified performance standards, items should be returned to the retailer or the manufacturer.

Knits are considered to be easy-care fabrics, and many care labels recommend machine washing. Some labels will also specify that the fabric can be dried in an automatic dryer. In general, however, knits will shrink more in the dryer than if air dried. Knits maintain their shape best if they are dried flat. The weight of a wet knit, hung on a line, may cause the fabric to stretch out of shape. The dimensions of knits usually will be retained best by professional dry cleaning. Hand knits, sweaters of wool or animal hair fiber, and other knits with an open construction may require special hand laundering and blocking (stretching back into shape). Such items should be laid on a sheet of wrapping paper before washing, and the outlines traced. After washing, the garment should be stretched out on the paper to dry. While still damp, the garment should be gently stretched to fit the outline of the original dimensions.

Aside from stretching or shrinking, an additional problem with knitted items is skewing or twisting as the fabric is relaxed during laundering. Side seams of garments may pull to the front or back and hems may hang unevenly. In general, knits made of synthetics will have better resistance to stretching out of shape than will cotton, acetates, and rayons. Blending of synthetics with cottons, acetates, and rayons will improve the resiliency and dimensional stability of knitted fabrics made from these fibers. Price is a good guide-especially for children’s knits.

Mechanical Damage
The loop structure of knitted fabrics makes them especially susceptible to snagging. If a loop catches on another object, it may be pulled up from the fabric surface and a long snag, or pull, of yarn may be formed. If the yarn that has been snagged is not broken, it can be pulled to the back of the fabric. It may be possible to gently stretch the fabric and work the pulled yarn back into place. This is difficult to do with tightly knitted fabric structures. If the yarn has been broken, the snag may produce a hole in the fabric. A few hand stitches with needle and matching thread should be made to secure the yarns so that the hole does not become enlarged during wearing or laundering. Synthetic double knits or knits made from loosely twisted yarns may be subject to pilling. Weaker fibers, such as cotton, rayon, acetate, and wool, generally break off the fabric, but the stronger synthetic fibers cling to the fabric, making an unsightly area on the fabric surface. The use of textured yarns for knitting synthetics decreases the likelihood of pilling. Knits may be damaged by sharp objects puncturing the fabric. If yarns are cut, a hole will result, and further pressure and strain on the fabric may enlarge the open area, as loops are dropped in the interlocking structure.

Effects of Knit Structure on Knitted Fabric Performance

Knit fabrics are most comfortable, durable and make most flexible effect on human body. I am going to describe the effect of knitted structure on knit fabric performance in details. 

Durability Factors 

Strength of knitted fabrics is considered to be less important for durability than it is in woven goods. Knitted fabrics are easily stretched to accommodate changes of shape as a result of stresses imposed in wear and care. When knits are made from resilient fibers and yarns, the ability to stretch and recover from stretching will be enhanced. In comparison to knitted fabrics, woven fabrics are generally firmer and have less elongation. In knits the loops in the structure can be deformed horizontally or vertically, increasing the stretch in both directions. But, as noted earlier, variations in knitting techniques can increase or decrease extensibility of knitted fabrics. Double knit fabrics and warp knit fabrics are usually less extensible than single knit fabrics.A major problem in the durability of knits is the runs that can develop in weft knits when one of the loops is broken. If stronger fibers and yarns are used in these knits, they will be less likely to run. 

Appearance 

Shear ability, discussed in chapter 15, is an important factor in the appearance of textiles. In general, because of the ways in which yarns are combined, woven fabrics have higher shearability than do knitted fabrics. Knitted fabrics have good flexibility and are easily extended. Warp knits do not shear as easily as weft knits. 

These qualities must be taken into account by designers, although they may not be aware of the technical terminology used to describe the fabric properties. For example, a warp knit tricot fabric with low shearability would not be used to make a bias-cut garment in which the intention is to take advantage of high shearability. Instead, the designer would be likely to use a soft, gathered construction where the high flexibility of the fabric would work to good advantage, but where most of the draping would fall in the vertical direction of the fabric. In general, knits wrinkle less than do other fabrics. This is because loosely constructed fabrics generally allow more fiber redistribution and motion. However, knitted fabrics, because of their greater extensibility, are more likely to lose their shape in laundering. The stresses applied in knitting distort the shapes of the loops rather than just stretching the yarns as in weaving. On relaxation, the loops broaden, shrinking the fabric length and increasing the width. As with woven fabrics, the tighter the structure, the higher the shrinkage until the structure becomes so tight that further shrinkage is not possible. Such fabrics may, however, buckle. 

Knitted fabrics tend to have lower cover than do woven fabrics, with weft knits having substantially more porous structures than warp knits, unless the fabric is deliberately made to have an open, lacy construction as in some Raschel knits. Use of thinner or thicker yarns can increase the cover of knitted fabrics. 

Comfort Factors

Knits usually entrap more air than woven fabrics, although the tightness of the knit is a factor as well. Pile or napped knit constructions are especially good for cold weather because the yarns or fibers perpendicular to the surface provide numerous spaces for dead air. This effect is maximized if such fabrics are worn with the napped or pile surface next to the body, or if they are covered with another layer. The flexibility of knits contributes to a feeling of fabric softness. Fibers and yarns used can enhance or detract from the smoothness of knitted fabrics. 

Elongation and Recovery 

The majority of bathing suits for women, and many for men, are tight fitting, with stretch required for getting the garments on and off. Since knits have much higher elongation than woven or nonwoven fabrics, they are the preferred fabric construction for bathing suits that fit tightly to the body. Fibers too play an important role in achieving tightness of fit. Those with lower modulus and high resilience will enhance the stretch and recovery properties of knits. Not only elastomeric fibers but also nylon have low modulus and good recovery. Nylon and spandex are often chosen for swimwear because of these properties. Polyester is not usually used because it has a higher modulus and therefore does not stretch as easily. Knitted fabrics of nylon blended with elastomeric fibers, such as spandex or rubber, will provide the highest amount of stretch. The elastic fibers also have high recovery from stretch. 

Colorfastness 

Bathing suits are exposed to sunshine, chlorine and other chemicals in swimming pools, and salt water in oceans. Fibers and yarns are both important in maintaining the colorfastness of swimming suits that are often made of bright-colored fabrics. Light-fastness of dyed spandex is fair to good, while that of nylon dyed with acid dyes is good. Spandex normally makes up only a small percentage of the fiber content of swimwear fabrics and is often used in core-spun yarns wrapped with nylon. This helps to protect ir from sunlight. Colorfastness of nylon and spandex exposed to pool and salt water is fairly good but these fabrics will show some loss over time. 

Absorbency 

Since bathing suits are worn while swimming in water, the absorbency of the fabric is a consideration. If a material absorbs and retains a significant amount of water, the weight of the suit will increase, affecting its comfort and function. Synthetic fibers have low water regain and are more appropriate for bathing units than the natural fibers that were used many years ago. 

Environmental Resistance 

Light, chlorine, and salt water can also degrade textile fibers. When this occurs, bathing suit fabrics may lose some of their recovery from stretch. Nylon and polyester are more resistant to ultraviolet light and chlorine than spandex. That is another reason why spandex is usually used in small percentages blended with nylon. The use of rubber as an elastomeric fiber in swimwear has decreased because of its susceptibility to degradation by light and other environmental conditions. Because resistance of nylon to degradation by light is higher for fibers that have not been delustered, brighter nylons are usually used in swimwear.

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