When a fabric needs warmth, softness, or better next-to-skin comfort, the yarn structure matters as much as the fiber itself. Spun yarns are one of the oldest ways to turn staple fibers into usable yarn, and they remain central to textile production today. Different spinning systems change the yarn’s feel, strength, appearance, and insulating behavior. That is why spun yarns are still studied closely in textile education and manufacturing.
What Is Spun Yarn?
Spun yarns are continuous strands of staple fibers held together in some way. Mechanical twist often uses fiber irregularities and natural cohesiveness to bind the fibers into one yarn. The process of making yarn from staple fibers by twisting is very old, although spun yarns can also be produced without twist in some systems.
Spun yarns usually have a fuzzy surface, more twist than filament yarns, short fibers that can pull apart, and fibers that are only partly parallel. They also have protruding fiber ends, which keep the yarn from making close contact with the skin. For that reason, a fabric made from spun yarn is usually more comfortable next to the body than a fabric made from smooth filament yarn.
Spun Yarn vs Filament Yarn
Many of the insulating qualities of a fabric come from the structure of the yarns used in it. There is more space between fibers in a spun yarn than in a filament yarn, and those spaces trap air. Yarn with more trapped air insulates better than yarn with less trapped air.
A spun yarn with low twist has more air space than a spun yarn with high twist, so it usually has better insulating qualities. That is why most fabrics made for warmth use lower-twist yarns. If wind resistance is the goal, high-twist compact yarns with a high count are more desirable because they reduce air permeability.
The strength of the individual staple fiber matters less to spun yarn strength than it does to filament yarn strength. Instead, spun yarn strength depends on the fibers’ cohesiveness, or clinging power, and on the points of contact created by twist or other binding methods. The more points of contact there are, the more resistance the yarn has to fiber slippage. Fibers with crimp or convolutions create more points of contact. Friction between fibers also helps resist lengthwise slippage. A rough or irregular fiber surface, such as wool scales, creates more friction than a smooth fiber surface.
Key Properties of Spun Yarns
Spun yarns are valued for several practical properties. Their fuzzy surface, fiber ends, and internal air spaces give them comfort, warmth, and a softer hand than many smooth filament yarns. Their level of twist also affects insulation, compactness, air permeability, and fabric performance.
Ring-spun yarns are generally finer, smoother, and more uniform, while open-end yarns are more opaque and often bulkier in appearance. Combed yarns are smoother and stronger than carded yarns because short fibers are removed and the remaining fibers are more parallel. High-bulk spun yarns are designed to be essentially free from stretch and to give extra loft and bulk in the finished product.
History of Spinning
Mechanical spinning of staple fibers into yarn is one of the oldest manufacturing arts, and it has been described as an invention as significant as the wheel. The basic principles of spinning are still the same today as they were when yarn was first made, although engineering and technology have greatly increased speed and output.
Primitive spinning involved drawing out fibers held on a stick called a distaff, twisting them with a spindle that could be spun like a top, and winding the finished yarn. The spinning wheel was invented in India and introduced to Europe in the 14th century. The factory system began in the 18th century, when James Hargreaves invented the spinning jenny that operated more than one spinning wheel at a time. Later inventions improved the spinning process and helped lead to the Industrial Revolution, when power machines replaced hand processes and made mass production possible. Machines were eventually developed for each separate step in spinning.
Spinning continues to change. The number of steps has been reduced in many systems, the process has become more automated, yarn quality has improved, and production has become faster, simpler, and more economical through higher speeds and more user-friendly computerization.
How Spun Yarns Are Made
Spinning may be done by several systems, including cotton, woolen, worsted or long-staple, and flax systems. These are adapted to fiber characteristics such as length, cohesiveness, diameter, elasticity, and surface contour. They are used to process natural fibers, manufactured fibers, and blends of the two. Because the cotton system is the most widely used, it is discussed here in more detail.
Opening
Machine-picked cotton contains a high amount of trash and dirt. The fibers have been compressed tightly in a bale that may have been stored for many months. Opening loosens, cleans, and blends the fibers. Because cotton varies from bale to bale, blending fibers from several bales helps produce more uniform yarn quality. Manufacturers need yarns with steady characteristics and performance so basic fabrics do not change from season to season or year to year.
Material removed during opening includes very short fibers, soil, plant debris, and other foreign matter. This waste may be discarded, or the short fibers may be purchased and recycled into yarns, fiber batts, or other textile products. Recycling this waste improves spinners’ bottom line because they avoid landfill or hauling fees and sell a secondary output from the facility. It also improves sustainability because new fibers do not need to be produced for products made from these short fibers.
In large commercial facilities, the machinery is usually enclosed and processes fiber in long production lines. Smaller fiber mills, especially in local fiber settings, clean and process locally grown fiber with equipment that is easier to see and follow.
Carding
Carding partly aligns the fibers and forms them into a thin web that is gathered into a soft, very weak rope of fibers called a carded sliver. A sliver is a ropelike strand of fibers. The carding machine uses a revolving cylinder and an outer belt covered with fine, short wire teeth that remove trash and neps, or tangled clumps of short, undeveloped, or underdeveloped fibers.
Drawing
Drawing increases fiber parallelism and combines several carded or combed slivers into one drawn sliver. This blending step helps create better yarn uniformity. Drawing is carried out by sets of rollers, each set moving faster than the one before it. As slivers are combined, their size is reduced.
The drawing step is repeated once more for carded slivers. At this stage, fibers from different generic types are often combined into a blended drawn sliver. Because each fiber has different physical properties, the carding and initial drawing conditions differ for each fiber in a blend. Blending during drawing also removes mixed wastes.
Combing
If long-staple fibers are to be spun, one more step is added. Combing produces a yarn that is superior to carded yarn in smoothness, fineness, evenness, and strength. It aligns the fibers in a more parallel arrangement and removes short fibers so the combed sliver is more uniform in length.
Combing is costly, and long-staple fibers are costly as well. As much as one-fourth of the fiber may be combed out as waste and reprocessed into short-staple carded yarns. Carded yarns made from short-staple fibers have more protruding fiber ends than combed yarns made from long-staple fibers. Those protruding ends add comfort and warmth, but they also produce dull luster, a fuzzy appearance, lint shedding from broken fiber ends, and surface pills. Fiber ends can be removed from the fabric surface by singeing.
When working with cotton or cotton blends, the term combed yarn is used. When working with wool or wool blends, the term worsted yarn is used. Yarns that have not received this process are called carded yarns for cotton and cotton blends, or woolen yarns for wool and wool blends. Combed yarns are drawn once before combing and two more times after combing.
Roving
The roving step reduces the drawn sliver, increases fiber parallel alignment, and inserts a small amount of twist into the strand, which is then called roving. It is a softly twisted strand of fibers about the size of a pencil.
Other Spinning Systems
In the woolen system, oil is added to wool fibers to help processing. A condenser divides the carded web into strips, and a small amount of twist is inserted. Ring spinning is usually used to produce bulky, soft, and fuzzy yarns.
In the worsted system, longer wool and manufactured fibers pass several times through gill boxes, which ensure even fiber distribution in the sliver and make the fibers more parallel. After gilling, the slivers are combed, gilled again, drawn, and spun into compact, smooth, strong yarns.
In the flax system, a hackling machine with a revolving belt fitted with embedded pins removes short and tangled fibers as well as nonfibrous matter. Yarns made from shorter and less parallel fibers are tow or hackled yarns; yarns made from longer and more parallel fibers are line or well-hackled yarns. The fibers are processed either wet or dry, depending on the desired yarn. Wet-processed yarns are the finest, smoothest, and strongest ones available.
Spinning Methods
Most spun yarns are made by either ring spinning or open-end spinning. These are the two basic systems, although several alternate methods are also used.
Ring Spinning
Ring or conventional spinning is a series of operations designed to clean and make staple fibers parallel, draw them into a fine strand, and twist them so they stay together and gain strength. It is the most important spinning method for short staple fibers and remains the standard by which spun yarns are judged. Even with continuous spinning, higher speeds, and automation, it is still a long and expensive process.
Ring-spun yarns are finer, smoother, more uniform, and better in quality, and they create fewer problems during fabrication. Ring spinning is also more versatile than alternate spinning systems, which is why many fine-spun yarns are made this way. Spinning adds yarn twist, and a spinning frame holds a number of individual units. Ring spinning draws, twists, and winds in one continuous operation. The traveler carries the yarn as it slides around the ring, which inserts the twist.
Ring spinning is slow, with rates of 25,000 to 30,000 rpm, compared with speeds up to 150,000 rpm for open-end spinning. Ring-spun yarns are preferred for knits and fine blends of polyester and cotton because they have a more comfortable hand. Blending can also take place during roving or spinning, since several fiber strands are combined in those stages, and it is usually done there to achieve a color blend. For woolen yarns, ring-frame spinning, which is similar to ring spinning for cotton yarns, is commonly used.
Open-End Spinning
Open-end rotor spinning eliminates the roving stage. Knots are eliminated, larger yarn packages are formed, less operator supervision is needed, and production speeds are about four times those of ring spinning. Open-end yarns have a harsher hand and are weaker and more sensitive to abrasion, but they are more uniform and more opaque in appearance. While moderately thin yarns are possible, ring spinning is still used to make thinner yarns. Open-end yarns are preferred for toweling, other pile yarn fabrics, denim, sheeting, and base fabrics for laminated fabrics.
Rotor Spinning
In the more commonly used rotor-air-jet spinning process, sliver is separated so that individual fibers are fed by an air stream and deposited on the inner surface of a high-speed rotor. As the fibers are drawn off, twist is inserted by the rotation of the rotor, making a yarn. Rotor-spun yarns have a higher twist at the center of the yarn.
Friction Spinning
Friction spinning is another type of open-end spinning that combines rotor and air techniques. The sliver is separated into fibers that are spread into carding or combing rolls and delivered by air to two cylinders rotating in the same direction, which pull the fibers into a yarn. The feed angle into the cylinder controls fiber alignment. Friction-spun yarns are more even, freer of lint and other debris, and loftier, but they are weaker than conventional yarns. Friction spinning may be used to process very-short-waste staple fiber into yarns.
Air-Jet Spinning
In air-jet spinning, a narrow sliver is fed into a machine with two nozzles facing in opposite directions. Each nozzle blows air against the sliver, forcing the outermost fibers to wrap around it and produce a yarn. Air-jet yarns are less elastic, weaker, and rougher than either ring- or rotor-spun yarns.
Direct Spinning
Direct spinning eliminates the roving step and uses the ring-spinning device to insert twist. The sliver is fed directly to the spinning frame. These heavier yarns are used for pile fabrics and carpets.
Compact Spinning
Compact spinning is a variation of ring spinning that condenses the roving before final twist insertion and creates a smoother, compact, or condensed yarn. Compact spun yarns are considered superior to ring-spun yarns. They are smaller, stronger, better in elongation, and lower in hairiness. They also show better fiber alignment and fewer defects.
Because of their smoothness and compact structure, they cause fewer yarn breakages in weaving and improve weaving efficiency. Their use is growing, although it is still limited by their relative newness and the higher technology demands of the equipment.
Vortex Spinning
Vortex spinning produces a yarn with an outer layer of fibers wrapped around a center of parallel fibers. High speeds are possible, but the sliver must contain clean, strong fibers of uniform length. After the sliver reaches the desired fineness, high-speed vortex air currents wrap the fibers around a hollow stationary spindle. Yarn twist develops as the fibers swirl around the spindle before they are pulled through the hollow center. Shorter fibers are removed in the process.
Twistless Spinning
Twistless spinning removes the twisting step altogether. A roving is wetted, drawn out, sprayed with sizing or adhesive, wound on a package, and steamed so the fibers bond together. The yarns are ribbonlike and stiff because of the sizing. They lack strength as individual yarns, but they gain strength in the fabric from the pressure within the fabric components.
The absence of twist gives the yarn a soft hand, good luster, and opacity after the sizing is removed. These yarns are easy to dye and have good durability, but they are not suitable for very open fabric structures.
Self-Twist Spinning
In self-twist spinning, two strands of roving are carried between two rollers, which draw out the roving and insert twist. The yarns have areas of S-twist and areas of Z-twist. When the two twisted yarns are brought together, they intermesh and entangle, and when pressure is released, the yarns ply over one another. This process can be used to combine staple strands, filament strands, or a mix of staple and filament strands.
Types of Spun Yarns
Different spinning paths produce different yarn types, and the length and alignment of the fibers play a major role in how the yarn behaves in fabric.
Carded Yarn
Yarns made from carded sliver are called carded yarns. They are made from fibers that have been partially aligned but not combed. Carded yarns generally have more protruding fiber ends than combed yarns, which gives them a less smooth surface.
Combed Yarn
Yarns made from combed sliver are called combed yarns. Combing removes short fibers and leaves the remaining fibers more parallel and more uniform in length. Fine-combed cotton yarns are made from fibers that are more than 1⅛ inches long.
Woolen Yarn
Carded sliver made from short wool fibers becomes woolen yarn, and the fabrics are called woolen fabrics. The term woolen refers to yarn type and is not another word for wool. Woolen yarns are usually bulky, soft, and fuzzy.
Worsted Yarn
With wool, combed sliver is called top, and yarns made from top are called worsted yarns. The short fibers removed in combing are called noils, and they are a source of fibers for woolen yarns. Worsted yarns are compact, smooth, and strong.
Flax Yarns
In the flax system, tow or hackled yarns are made from shorter and less parallel fibers, while line or well-hackled yarns are made from longer and more parallel fibers. Wet-processed flax yarns are the finest, smoothest, and strongest ones available.
Tow-to-Top and Tow-to-Yarn Spinning
Filament tow of any manufactured fiber can be made into spun yarns by direct spinning without disrupting the continuity of the strand. The two systems are tow-to-top and tow-to-yarn.
Tow-to-Top System
The tow-to-top system skips the opening, picking, and carding steps used in conventional spinning. In this system, filament tow is reduced to staple and formed into sliver, or top, by either diagonal cutting or break stretching. The sliver is then made into regular spun yarn by conventional spinning.
The diagonal-cutting stapler changes tow into staple of equal or variable lengths and forms it into a crimped sliver. In the break-stretch process, the tow is stretched and the fibers break at their weakest points without disrupting the continuity of the strand. The resulting staple fibers vary in length.
Tow-to-Yarn System
Tow-to-yarn spinning is carried out by a machine called a direct spinner. Light tow of 4,400 denier passes between two pairs of nip rolls. The second pair of nip rolls breaks the fibers at their weakest points. The resulting staple-fiber strand is drawn to yarn size, twisted, and wound on a bobbin.
High-Bulk Yarns
High-bulk yarns are spun yarns that are essentially free from stretch. Some of the staple fibers have taken on a relatively high random crimp caused by shrinkage of low-crimp fibers.
Some fibers can be made with latent shrinkage potential and can retain their bulk indefinitely at room temperature. Latent-shrinkage fibers are produced by heating, stretching, and then cooling them while they are still stretched. These heat-stretched fibers are called high-shrinkage fibers, and they are combined with nonshrinkage fibers in the same yarn before the product is made. Heat treatment of the product causes the high-shrinkage fibers to relax or shrink, which forces the nonshrinkage fibers to bulk. This is how high-bulk sweaters, knitting yarns, and other products are made.
High-shrinkage fibers migrate to the center of the yarn. If fine-denier nonshrinkage fibers are combined with coarse-denier high-shrinkage fibers, the fine-denier fibers end up concentrated on the outer surface of the yarn. The bulk can be controlled by regulating the heat stretching. This high-bulk principle can also be used to create guard hairs in synthetic furs and sculptured high-low carpets. Higher-density carpet pile or fur-like fabrics can be made by using a high-shrinkage fiber for the ground yarns, since shrinking brings the fibers much closer together.
Conclusion
Spun yarns are defined by their fiber structure, their twist behavior, and the way they perform in fabric. Their comfort, warmth, strength, and surface character all depend on how the fibers are opened, aligned, twisted, or otherwise held together. Different spinning systems suit different fibers, and each one produces a yarn with its own balance of texture, uniformity, and performance. As spinning technology keeps becoming faster and more automated, spun yarns will remain important in both everyday textiles and technical fabrics.
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor to Wikipedia.
