How denim is made: A Guide to Denim Fabric Manufacturing

Introduction

Cotton is the most significant textile fiber and one of the most plentiful agricultural raw resources. Cotton fiber is a natural, cellulosic, monocellular, staple fiber with a high cellulose content of up to 95%. Cotton is derived from Arabic and is pronounced ‘kutan,’ as well as ‘qutn,’ ‘qutun,’ and so on (Gohl and Vilenksy, 1983). Cotton is assumed to have existed for roughly 7000 years, yet no one knows for certain when cotton was found. Since its inception thousands of years ago, cotton has established itself as one of the most versatile and commonly used fibers. Cotton is cultivated in warm regions, and around 20 million tonnes of cotton are produced each year. Despite the fact that it is cultivated in around 90 nations, China, the United States, India, Pakistan, Uzbekistan, and West Africa account for more than 75% of world output. Brazil and Turkey are two more important cotton growing nations.

The majority of this fiber’s output goes into garments, with denim pants being one of the most prominent applications. Cotton processing procedures have remained mostly unchanged to this day; what has changed is the technology and scientific understanding that has allowed this fiber to become one of the most widely used and prized textile materials. Cotton is processed into short staple yarns, and the finished yarns or textiles are subjected to finishing operations to enhance their final qualities. It is also frequently mixed with polyester and other synthetic fibers, notably spandex (lycra), and is utilized in a variety of applications, including the production of denim (Anon., 1997). Denim is said to have been invented in the sixteenth century in the French city of Nimes, which was famous for weaving an off-white cotton fabric recognized for its resilience. Gradually, the artisans started to color the cloth blue with indigo before sending it to Italy, where jeans (denim sailor trousers) were first manufactured. The term “jeans” is said to be originated from the name of the Italian port city of Genoa. Cotton fibers, which are robust, pleasant, and breathable, were the primary fibers utilized in the production of this material, and the production of denim textiles using cotton fibers continues to this day (Paul and Malanker, 1997).

Cotton cultivars

Cotton comes in a wide range of sorts and types. Their properties influence the utilization of cotton and hence its value. Cotton belongs to the order Malvales, the family Malvaceae, and the genus Gossypium. The genus Gossypium has 50 wild and cultivated species, only four of which are farmed commercially throughout the globe. Upland cotton, Gossypium hirsutum, is endemic to Central America, Mexico, the Caribbean, and southern Florida, and accounts for 90% of global output. The staple lengths of upland strains may vary, although they are often treated to uniformity, resulting in a tougher, less elastic fabric. Upland cotton is said to be most suitable for making denim fabric. Gossypium barbadense, often known as pima cotton, is endemic to South America and accounts for 8% of global output. Both of these kinds are known as New World species, and they contribute for around 98% of global output. Old World or Asiatic cottons, Gossypium arboreum and Gossypium herbaceum, are produced commercially in India, Pakistan, and areas of Southeast Asia, accounting for roughly 2% of global output.

Harvesting and growing

Cotton is a costly fiber to manufacture, and it requires a lot of sunshine, low humidity, and excellent soil with a decent irrigation system to thrive. Cotton is mostly produced on self-mulching, cracked clay soils found on floodplains near rivers. Cotton farmers evaluate the soil a few months before planting to determine nutrient levels and how much fertilizer is needed. Cotton may be planted in a variety of ways, the most common of which is directly into the stubble of a previous harvest. Cotton farmers that use traditional tillage plow or list the ground into rows, providing solid seed beds for sowing. Planting using no-till or conservation tillage techniques requires the use of specific machinery intended to push the seed through the litter that covers the soil surface. Seeding is done using mechanized planters that may cover up to 24 rows at a time. The planter digs a tiny trench or furrow in each row, puts in the appropriate quantity of seed, then covers and packs the ground on top. Cultivators are used to remove weeds and grass that compete with cotton plants for soil nutrients, sunshine, and water. Cotton plants produce flower buds known as “squares” around two months after planting. The blooms will unfold in three weeks. The petals progress from creamy white to yellow, pink, and eventually dark crimson. They wither and fall after three days, leaving green pods known as cotton bolls. Moist fibers sprout and push out from freshly created seeds within the boll, which is shaped like a little football. The boll becomes dark as it ripens. Under the warm sun, the fibers continue to develop until they rip the boll apart and the fluffy cotton pours out. As depicted in Figure 2.1, the cotton fiber begins its path towards denim manufacture from the cotton boll (The Textile Institute). Depending on how hot it is and how well the plant grows, the cotton plant will need to be watered many times while it is growing. More than 20,000 liters of water may be required to create 1 kilogram of cotton, which is comparable to a single T-shirt and a pair of pants. Irrigated land accounts for about 73% of the worldwide cotton yield. Other elements that influence its development include pests such as insects, and the pesticides used to kill these insects are harmful to the environment and may impair the quality of the cotton fiber.

A cotton ball growing on a cotton plant Cotton is said to account for just 3% of global crop production but 15% of global pesticide spraying. Unsafe agricultural pesticide usage has serious health consequences for field workers and ecosystems that absorb excess dosages from farms. Unsustainable cotton growing, with its vast inputs of water and pesticides, has already resulted in the loss of large-scale ecosystems and the deterioration of people’s health and livelihoods. Cotton harvesting is done either manually or using machinery. Hand harvesting accounts for around 70% of the over 100 million bales of cotton produced worldwide. Cotton harvesting is totally mechanized in several nations, including the United States, Australia, and Israel. Modern cotton harvesting equipment, which comprises a picker or a stripper, is intended to reap cotton with little structural damage. If the plant height is more than 1.2 m for picked cotton and 0.9 m for stripped cotton, too much foreign matter will be gathered. Cotton picking machines use spindles to separate the seed cotton from the burrs adhering to the plant stems. The cotton is subsequently removed from the spindles by doffers and knocked into the conveying system. Traditional cotton stripping machines employ rollers with alternating bats and brushes to break open bolls from plants onto a conveyor. A second kind of stripper employs a broadcast attachment that resembles a grain header. All cotton harvesting techniques employ air to transport and lift the cotton into a storage receptacle known as a basket. The stored seed cotton is emptied into a bole buggy, trailer, or module builder after the basket is full.

Fibre properties

The cotton fiber consists of a cuticle, a primary wall, a secondary wall, and a lumen. The cuticle is a few molecules thick and covers the primary wall with a waxy film. The wax is a mixture of fats, waxes, and resins. The primary wall consists of numerous fibrils spiraling around the fiber axis. Fibrils are simply packs of cellulose chains. The secondary wall has several layers of spiraling fibers, which make up most of the weight of 18 structure of cellulose polymer. of the cotton fiber The lumen, located within the secondary wall, is a hollow canal that carries nutrients during growth. It also contains the dried out remains of the protoplasm and nucleus when the cotton boll’s development is complete. Cotton fiber is about 95% cellulose, and the rest of the materials are waxes, pertinacious substances, and nitrogenous matter, which are primarily located in the primary wall and some in the lumen. The fiber has natural twists along its entire length, called convolutions. The convolutions help the fibers interlock when they are spun into yarn. Long fibers have about 300 convolutions per inch, and short fibers have 200 or less. Layers of the secondary wall also contain fibrils that are arranged spirally and reverse direction at regular intervals. These reverse spirals help the cotton fiber have better elasticity and twist. Also beneath the primary wall is the winding layer, which has a single layer of fibrillar bundles that are at about a 70° angle around the fiber axis. This winding layer is also a layer of the secondary wall. Cotton is basically a linear cellulose polymer, and the repeating unit is cellobiose, which consists of two glucose units. The cotton polymer system consists of about 5000 cellobiose units, which means its degree of polymerization is about 5000. Cotton is a crystalline fiber, and its polymer system is about 65–70% crystalline and about 35–30% amorphous. Figure 2.2 (The Textile Institute) shows the structure of cellulose polymer. Compared to other major fibers like wool, silk, viscose, and polyester, cotton has many interesting properties. Table 2.1 gives a comparative analysis of the physical and mechanical properties of cotton with these fibers (Zupin and Dimitrovski, 2010). The fiber length is an important property of any fiber, and it is referred to as the staple length. Cotton with longer staple lengths tends to produce softer and hairier fabrics than those with shorter ones. Based on their staple length, cotton fibers can be classified into three groups. The first group of fibers has a staple length ranging from 25 to 65 mm. These are fine, lustrous fibers of the highest quality. Examples of these fibers include Egyptian, Sea Island, and pima cottons. These fibers are the most difficult to grow, making them the most costly to produce, and they are used in products for the high quality end of the market. The term commonly used to describe these fibers is “long staple cotton.” The next group is medium staple and is commonly produced in the United States (upland cotton). The staple length can be within a range of 13–35 mm. The third and final group, originating from Asia, has short staple fibers with a staple length between 10 and 20 mm. These would be used in the production of lower quality carpets and blankets, as well as for coarse and inexpensive fabrics and blends with other fibers. So in general, cotton fiber length can range from 10 to 65 mm, and the fineness values are in the range of 1–3 dtex. The average moisture regain of cotton is about 8.5%, and the density lies between 1.50 and 1.54 g/cm3. Another property of the fiber that plays a major role during processing is its maturity. The maturity degree depends on the provenance and the harvesting year. Values for the maturity degree are frequently between 75 and 85%. The maturity determines the dye uptake in further processes like indigo dyeing in the case of denim. Micronaire is another important characteristic of cotton fiber (Heap, 2000). It is an indicator of air permeability and is regarded as an indication of both fineness (linear density) and maturity (degree of cell wall development). For a given type of cotton, a relatively low micronaire has been used as a predictor of problems when processing, but a low micronaire may also indicate fine fibers with a low maturity (Montalvo, 2005). A high micronaire value indicates fibers that are coarse, which makes them less desirable for spinning and also gives greater yarn unevenness. In order to produce a finer denim warp yarn, fine fibers with long staple lengths are needed. This will ultimately result in a denim fabric that is smoother and aesthetically more pleasing to the eye. It will be more comfortable to wear and is likely to last longer, and the manufacturing of garments from the fabric will be more efficient. In general, denim fabric manufacture requires cotton fibers with a minimum staple length of approximately 28 mm, short fiber content under 40%, and micronaire of 4.0–4.5. Some other interesting properties of cotton are the following:

· It is one of the few fibers that gets stronger when it is wet, enabling a smoother manufacturing process when woven into denim fabric. It is a relatively strong fiber due to its polymer structure and its crystalline nature. • It is relatively inelastic due to its crystalline nature.

· Cotton is a hydrophilic fiber due to its amorphous regions and can absorb up to 50% moisture when wet. It has the ability to conduct heat energy, minimizing any destructive heat accumulation, and so can withstand very hot ironing temperatures. Cotton fibers are resistant to cold, weak acids but disintegrate in strong acids.

Cotton fiber processing

Most of the seeds (cotton seed) are separated from the fibers by a process known as ginning. In the countries where cotton is hand picked as well as in the countries where mechanical harvesting is done, ginning is the first important mechanical processing that cotton undergoes. This process separates cotton seeds from fiber, making cotton usable for textile mills and other applications. By the time cotton enters the gin, its quality in terms of fiber properties such as length, strength, maturity, and fineness has already been decided. It is only the ginning practices and conditions at the ginning factory that can maintain the quality of the fiber, with very limited scope for improvement by the cleaning process and baling parameters. Once the cotton has been ginned, it is then shipped in bales to the cotton textile mills for further processing. Cotton is a rather dirty fiber due to its natural origin in the fields. Most of the trash, like leaves, plant parts, immature bolls, small stones, dust, sand, etc., gets collected with cotton. The transportation from the fields or market yards to ginning factories, as well as the further transportation of bales to textile mills, also add to the contamination. The storage of cotton in open areas full of dust and other contaminants may further contribute to fiber contamination (Bajaj and Sharma, 1999). In order to bring the cotton material to a level where it can be used commercially for manufacturing denim yarns, it needs to be cleaned thoroughly and processed through several stages. Figure 2.3 schematically shows all the main processes involved.

Opening, cleaning and blending

The opening process divides the compressed bales of raw cotton progressively into smaller clumps or tufts, which can then be fed to the carding machine for final subdivision into individual fibres. The production of tufts is a traditional process for storing and transporting material between the opening line and the card. It has now largely been replaced by direct feeding, where the opened material is transported directly to the card by a ducted air flow and then consolidated into a sheet of fibre in a chute. A unique feature of the opening line is the inclusion of such a chute mounted on top of the scutcher. The opening action creates new fibre surfaces, which may expose impurities or trash adhering to the fibres or buried within the larger clumps. These impurities may then be removed by a simultaneous cleaning action, heavy impurities being ejected below the machines, lighter impurities being carried away in an air flow for subsequent filtering. To assess the effectiveness of opening and cleaning lines, it is possible to determine the tuft size (difficult) and the amount of trash removed (relatively easy). Four important factors associated with cleaning are the following:

· Amount of trash in the raw cotton.

· Amount of fibre that is removed along with the trash, as this increases costs. • Levels of fine trash (dust) in raw cotton, as this is both hazardous and causes a spinning fault called a moiré (an undesirable fault that occurs in fabric from yarns that have a rippled appearance) in rotor spun yarns. • Cleaning efficiency of the opening line. Further, the action of the opening machine breaks up and redistributes the fibres, which results in a blending action that may be enhanced by specific machine

Opening and cleaning line. configurations. The blending is the mixing of fibrous tufts from opened bales to produce a homogeneous mass for consistent yarn properties. A typical opening and cleaning line is shown in Figure 2.4.

Carding

Carding is one of the most significant activities in cotton fiber processing since it directly impacts the yarn’s final characteristics. Aside from the elimination of trash and neps (tiny bundles of superfluous fibers), the degree of fiber individualization and the fiber hook configurations in the sliver are essential features of the carding process in terms of yarn quality and spinning performance. The general goal of carding may be summarized as follows:

· Fibre separation into separate states • Parallelization and fiber orientation • mass/unit length reduction • Disentangling neps and removing short fibers • fiber blending • Extraction of any leftover contaminants from the cotton The carding process achieves complete fiber separation via the use of opposing wire points, or teeth. The following elements are deemed crucial in order to achieve the appropriate degree of fiber separation: The wire points must be capable of grabbing individual fibers and pulling them back or forward. These wire points must be in excellent shape, and there must be a large tooth population in relation to the quantity of fibers supplied, resulting in more points than fibers. Carding may be done using spinning flat carding action, fixed tops, roller and clearer methods. The rotating flat card is the most popular machine used in the processing of cotton fibers. Throughout the years, countless

a standard carding machine. With the carding machine, things have changed. The primary spinning components may operate at much greater speeds as manufacturing rates improve. Triple intake rollers and redesigned feed systems are used; more carding segments are installed for more effective fiber opening; and enhanced wire clothing profiles have been devised for increased carding action. Electronic advancements have greatly enhanced monitoring and process control. The majority of these advancements have resulted in improved cotton fiber cleaning, decreased nappiness of the card web, and improved silver uniformity. Toyoda’s current carding machine is shown in Figure 2.5.

Combing

Combing is an additional procedure that improves the quality of the sliver that comes out of the card. It results in the removal of short fibers, improved fiber parallelization, straightening curls, and the removal of neps. As a result, the combing process increases the evenness, cleanness, smoothness, look, and twist level of the yarn. The comber must conduct the following actions in order to increase fiber quality:

· Remove a certain number of short fibers. • Get rid of any leftover contaminants. • Get rid of the majority of the neps. • Cut a very straight sliver. The comb is an uncommon element among cotton processing machines since its mode of operation is discontinuous and requires a sequence of synchronized operations to achieve the intended result. The combing cycle refers to these activities and the sequence in which they occur. The method of combing varies depending on the fiber type; however, rectilinear combing is the most often employed technique for both long and short staple fibers. The fibers must be supplied to the comber in the form of a sheet or lam to be combed on a typical combing machine. transformed into a web In the case of short staple fibers, many of these webs are condensed into slivers, which are then joined in a draw box to make the final combed sliver. Combing is often employed in the creation of medium fine to fine yarns in the 5–16 tex range. The waste from combing ranges from 12 to 25%, depending on the final product grade. A typical combing machine is shown in Figure 2.6.

Draw frame

The draw frame combines the drafting (mass reduction per unit length) and doubling actions (combining two or more ends to produce a single end). Draft is a critical machine variable that can influence sliver regularity. On a machine, the total draft is the ratio of input to output mass per unit length, and it has no units. The total draft is divided between pairs of rollers that grip the fibers and rotate to provide different surface speeds, with the speeds increasing from the back to the front of the machine. Major drafting is always taking place in a drafting zone where the roller design and configuration can grip and accelerate fibers to allow for relatively high drafts. Doubling is the process of creating a single sliver from several slivers fed to the draw frame. The primary goals of doubling are to eliminate mass variation in the delivery slice and to blend fibers. The draw frame combines drafting and doubling to achieve process goals such as improved sliver regularity, fiber alignment with the material axis, and improved fiber blending. Sliver regularity is difficult to detect, but it is critical to the efficiency of subsequent processes and the final yarn quality. The variation in mass per unit length along the length of the sliver is measured as regularity (thick and thin places). The dielectric properties of a textile material are directly related to its mass, which can be used to measure variations in mass along the length of a moving sample.

Draw a cotton processing frame. These measurements can be taken live on the machine or remotely in offline mode. By comparing the appearance of the slivers before and after drawing, the improvement in fiber alignment can be seen. As a result of the improved fiber orientation, the sliver appears to be more lustrous. Fiber blending can be observed by processing slivers of dissimilar fibers; the resulting sliver will be a combination of the fibers fed to the machine. Figure 2.7 depicts a typical draw frame used in cotton processing.

Speed frame

The speed frame is an unavoidable byproduct of the ring spun yarn manufacturing process. A drawn sliver has all of the properties necessary for the production of yarn. It’s a neat, ordered strand of fibers that runs along the material’s axis. However, there is an intermediary step of roving production between the drawing and spinning processes, which employs expensive equipment, has poor productivity, introduces defects, and generates a product that is sensitive to both winding and unwinding. One of the key reasons for its employment is the overall decrease in linear density needed between the sliver and the yarn, which may be in the range of 100 to 500. The draw frame’s roller drafting methods cannot impose drawings of this scale in a single step and are restricted to a maximum draft of roughly 50. The second reason is that draw frame cans cannot be transported or presented to the ring spinning machine. As a result, the primary goal of the speed frame is to lower the linear density of the sliver. Because the resultant strand is so thin, it lacks coherence, so a modest degree of protective twist is added to keep it together. Finally, the twisted strand must be coiled onto the ring frame to make a package appropriate for transit, storage, and processing. The speed frame is a sophisticated piece of equipment due to the eventual goal of winding and package manufacturing. Efforts were made to remove these obstacles, but none were effective, and cotton processing needed a speed frame. the development of advanced spinning technologies such as rotor spinning to remove the speed frame and immediately convert sliver to yarn. Figure 2.8 depicts a typical speed frame used in cotton processing.

spinning of denim yarns

Spinning is a centuries-old process that transforms natural fibers such as cotton into yarns that are then woven into fabrics. This time-honored procedure includes the following steps:

· Drawing, to thin the fibers and lower the material’s density. • Adding twist to produce yarn and give it strength • winding yarn packets in preparation for warping on a warping beam. These methods are still used in sophisticated gear that manufactures denim warp yarns with varying properties and qualities. Ring spinning, compact spinning, and rotor spinning are the most prevalent methods for spinning cotton fibers. Currently, all of these processes are used to spin cotton warp yarns for denim production. In order to ensure problem-free warping, dyeing, and weaving processes, the denim warp yarn should have certain characteristics, such as volume, low curling tendency, and hairiness. These yarns typically have counts ranging from Ne 4.0 to Ne 4.0.

Ring spinning

The ring frame can spin extremely fine yarns that are regular along the yarn axis at high speeds. These machines’ capacity to create high-quality warp yarns

Figure 2.9: Schematic illustration of the ring spinning process This results in smoother, higher-quality denim. Figure 2.9 depicts a schematic perspective of the ring spinning process (Wulfhorst et al., 2006), while Figure 2.10 depicts a typical ring spinning machine. Using a double apron drafting technique, the roving is first attenuated to obtain a fibrous bundle that matches the yarn fineness (draw ratios of about 10–40). The untwisted fibrous bundle escapes the drafting field and is twisted by the ring’s rotation, which produces the twist. With each revolution of the ring traveler, the yarn is twisted once. The twist formation progresses to the spinning triangle, the shape of which is dictated by the equilibrium of the yarn’s torsional moment and the opposing movement of the loose fibrous bundle. Because of the trailing of the traveler, the twist of the yarn is somewhat lower than the twist created only by the rotating policemen. The ring and traveler mechanism allows for not just yarn twisting but also yarn wrapping on the bobbin. The ring spinning technique twists the fibers from the outside to the interior of the spinning triangle, such that the fibers in the center of the spinning triangle are relatively parallel and the outside fibers are twisted around them. The highest ring spinning output is limited by the maximum velocity of the traveler, which is around 40 m/s, creating local temperatures of up to 450 °C on the traveler. The use of fiber material or the proportion of fibers in a modern ring spinning machine With ring yarns, the compound yarn that sustains the tensile loads of the yarn is roughly 30–65%. Ring spinning generates the finest and strongest yarns, which are ideally suited for denim since this value is much greater than with other spinning technologies such as rotor spinning.

Compact spinning

The presence of hairy yarn structures has been identified as one of the major challenges faced by ring spinning technology over the years, and this is avoided in compact spinning. Figure 2.11 compares the ring and compact spinning technologies. This is accomplished by condensing the fibers after the main draft with a perforated roller and a suction unit. When compared to ring spun yarns, the hairiness of the yarn is reduced and the tenacity is increased. The evenness of the yarn is also significantly improved. ring and compact spinning comparison Various techniques can be used to achieve compact spinning. The following are the traditional techniques:

· The delivery roller is replaced by a suction-powered, perforated bottom roller. The roller aids in the gathering of all the fibers before they are spun into yarn. A perforated apron wound around a roller and spacer bar with a suction zone is another method for compaction of fibers. Another technology is mechanical fiber compacting, which uses guides that act as condensers to control the spinning triangle and does not use suction.

Rotor spinning

Rotor spun yarns were formerly solely used as weft but are now widely utilized as denim warp. When compared to ring spinning, rotor spinning delivers more productivity and hence lower manufacturing costs. Because the pace is faster than ring spinning, the yarns produced are coarser than ring spun yarns. Because there is a distinct interruption in the fiber flow prior to yarn generation, the rotor spinning machine is referred to as “open end spinning.” Figure 2.12 depicts a schematic depiction of the rotor spinning process (Alagirusamy and Das, 2010), whereas Figure 2.13 depicts a typical rotor spinning machine. The rotor spinning process is fully automated since it includes three production processes: speed framing, ring spinning, and winding. In rotor spinning, the process sequence involves feeding the input sliver, opening the fibers to the individual stage, transporting the fibers up to the rotor groove, insertion of twist, and yarn winding (Alagirusamy and Das, 2010). A sliver is fed into the machine by either a combing machine or a draw frame. The sliver is transported to the opening roller by a feed roller or feed plate unit. The opening roller revolves at a circumferential speed of 5000–8000 rpm, or 20–30 m/s, resulting in intensive combing and separation of the rotor spinning process.

contemporary rotor spinning machine. Table 2.2 compares the fibers of ring spun and rotor spun yarns. With the help of an air stream, the fibers are separated from the roller clothes and propelled through a conical transport channel. This duct leads to a rotor that can spin at up to 200,000 rpm. The fibers slide along the exterior of the rotor wall and create a ring-like structure in the rotor groove due to centrifugal force. The fibers’ location in the rotor groove is mainly straightened since they are continually accelerated throughout this operation. When an open yarn end is fed into the rotor through a pull off pipe and nozzle, a fresh yarn is spun. As the yarn spins in the rotor groove, fibers in the groove connect to the yarn end. A continuous spinning process is started by pulling the yarn through the nozzle and the uptake pipe. A minimum of 70–100 fibers in the yarn cross section is required for rotor spinning. Rotor yarns cannot be spun as fine as ring yarns due to the inherent limitations of this process. Rotor yarns have lower tenacity than comparable ring yarns. Because the rotor spinning is fully automated, it produces cross wound bobbins that are ready for further processing without the need for any additional winding. The rotor groove also has a significant impact on yarn properties. Rotors with diameters of 40 or 46 mm and rotor grooves in the shape of T, U, or S are commonly used in the production of both warp and weft denim yarns. Rotor spun yarns have a two-part structure that includes a central core similar to ring spun yarns and an outer sheath (wrapper) with a random disarray of fibers. The outer sheath is formed while the fibers are still being fed into the yarn after it has been formed. Denim warp yarns typically have a metric twist factor of 140, while weft yarns typically have a factor of 130. Table 2.2 compares the yarns produced by the ring and rotor spinning methods used in denim production.

Warping yarns

Unlike traditional woven fabrics, the cotton warp yarn used in denim production is specially prepared. Before it is placed on the weaving machine, the yarn goes through several stages of processing. Weft yarn, unlike warp yarn, is packaged and delivered directly to the weaving machine, where it is inserted into the fabric without further preparation. The process of transferring multiple yarns from individual yarn packages onto a single package assembly is known as warping. The yarns are brought together and condensed into a rope before being wound onto a relatively short cylindrical barrel or shell with no end flanges for ball warp denim. The yarns are collected in a sheet form, parallel to each other and in the same plane, onto a beam, which is a cylindrical barrel with side flanges, in beam warping. The supply yarn packages are placed on spindles in both cases, which are housed in a framework known as a creel.

During ball warping

250–400 yarn ends are pulled from the creel. The yarns are then passed through a comb-like device (also known as a hack or reed) that maintains each warp yarn distinct and parallel to the ends of its neighbors. A lease string is put across the sheet of warp yarns at intervals of 1000 or 2000 m to enable yarn separation for the subsequent re-beaming procedure. The strands are then sent through a trumpet or condenser, which compresses and condenses the sheet of yarn into rope form. This mechanism is positioned at the warper head’s base and moves back and forth, directing the freshly created yarn rope onto a log. To prevent the strands from tangling, the rope must be coiled at a consistent tension. In the rope dyeing range, the ropes are then dyed with indigo.

warping of beams

Beam warping keeps the yarns open in a sheet and wraps them parallel to one another onto a slightly broader flanged beam. These yarns will not be colored with indigo rope, but instead will be slasher dyed or undyed fabric that may be piece dyed, garment dyed, or left natural. Another possibility is to dye the yarns with a dye other than indigo (Anon., 2004).

Cotton developments for denim

Cotton farmers are always battling for a fair price for their crop. Cotton producers should now be paid a fair price for their product as there is a shift toward fair trade practices. In this regard, there is a growing trend toward organic cotton cultivation and production for denim manufacturing. Cotton that is not genetically engineered and grows without the use of synthetic agricultural chemicals, such as fertilizers and pesticides, is often referred to as “organic cotton.” Organic cotton cultivation and commerce are also marketed as a more feasible and long-term alternative to traditional cotton production. Cotton producers, on the other hand, often do not embrace new production methods until they are lucrative. Organic cotton yields are usually lower than conventional cotton yields and may even be lower than what is acceptable given decreased production costs. Nonetheless, some customers are willing to pay a premium for denim manufactured from certified organic cotton fiber and labeled as such. Despite fast growth in organic cotton production, conventional cotton still accounts for around 99.9% of total global output. Because of its eco-friendliness, naturally colored cotton has grown in popularity in recent years for denim. Cotton comes in a variety of colors, including creamy white, brown, green, blue, and pink. Color is a genetically determined trait, and pigment deposition in the fiber lumen begins before boll rupture. The full manifestation of color, however, occurs only after the boll breaks open and the fiber is exposed to sunlight. It takes approximately a week for the fiber to fully acquire its natural color. It is worth noting that, although sunshine is necessary for the formation of color, prolonged exposure causes color fading. Some genotypes’ colors may fade with time and washing, while others may not. Some genotypes’ brown color may deepen after multiple washings. Naturally colored cotton has certain intrinsic limitations, including poor yield potential, short fiber length, restricted colors, and color instability. It also requires specialized harvesting methods and infrastructure, increasing the cost of harvesting white cotton. Because the fiber length is short, spinning is more difficult than with white cotton.

Despite the fact that brands such as Levi Strauss have shown interest in naturally colored cotton, the market for colored cotton is generally regarded as a niche sector. Another area of research and development is genetically modified cotton, which has been developed to be insect resistant or herbicide tolerant. Bacillus thuringiensis (Bt) cotton is a commercial variety that is resistant to bollworms. Bacillus thuringiensis is a common soil bacteria capable of generating crystal proteins with insecticidal properties. These proteins are poisonous to particular kinds of cotton-attacking insects (moths such as bollworms), and the activity is exclusive to those insects. For the protein to be effective, the target insect must consume it. BT cotton was first planted commercially in Australia and the United States in 1996. Genetically modified cotton has been legally authorized for commercial distribution in certain countries, and research is ongoing in others. Monsanto, based in the United States, has a strong position and owns around 80% of commercially farmed genetically modified cotton (Joseph and Paul, 2007; Paul and Joseph, 2003). Numerous scientific investigations have also been conducted in order to transform cotton fiber into new and unique denim textile materials. In this regard, experimental research was conducted in order to improve the physical look by employing low torque ring spun yarns (Hua et al., 2013). The residual weft torque in cotton yarn was minimized in this study. On a modified ring spinning machine, low torque cotton yarns of 84 and 58 tex linear density with different twist levels were produced. The study’s findings revealed that low torque yarns had fewer yarn snarling turns. Denim was able to improve its smoothness and appearance as a result of this. Many other studies on the cotton fiber used in denim production are being conducted. These include modified rotor spinning of denim warp yarns, physical property testing of various denim textiles, and enzyme treatments on denim goods (Biermann and Schmidt, 2002; Miettinen-Oinonen et al., 1996; Rathod and Kolhatkar, 2013). Cotton is frequently blended with other fibers, such as lycra, to achieve desired denim effects. This gives the yarn used in denim a high degree of extensibility, allowing for the production of tightly fitting garments. These are primarily used in the production of ladies’ denim jeans. By combining cotton fiber with DuPont T400 polyester, the fabric becomes more bleach resistant and can tolerate chlorine more efficiently. DuPont has also developed Veloflex, a knitted stretch denim made of 96% cotton and 4% lycra. The fabric is said to have a smooth feel and to be supple, allowing designers to construct thin cut jeans that give comfort and flexibility of movement. The advancements in mixing cotton fibers with lycra have also resulted in several prominent firms working to increase denim stretch fabric performance (Anon., 2013). Invista, the owner of the Lycra brand, and Lenzing AG, a prominent manufacturer of man-made cellulosics, collaborated to enhance the aesthetic performance of stretch textiles. The results included the introduction of novel solutions to the denim sector via the combination of Invista’s proprietary lycra dualFX fabric technology and Lenzing’s lyocell fiber for the enhancement of stretch cellulosic fabrics and the reinvention of lyocell fiber. Stay True Cotton, one of Cotton Inc. USA’s revolutionary cotton finishing technologies, helps indigo-colored denim keep its natural color for longer.

A very minimal amount of color is discharged during the home laundry of these clothes, giving them an eco-friendly appearance. Wicking Windows is a cotton moisture management technique that moves moisture away from the body while also decreasing absorbent capacity for speedier drying. Fabrics treated with this method outperform untreated cotton by 1400% in one-way moisture transfer to the outside of the garment. Cotton fabrics with TransDRY technology provide the softness and comfort of cotton while remaining dry, keeping the wearer cooler and more comfortable. Storm Denim is a highly resistant finish that protects the user from mild rain, snow, and damp situations while retaining cotton’s inherent comfort and breathability (Crumbley, 2008). There are also studies underway to replace cotton in denim with more environmentally friendly fibers. In this regard, researchers at the Herriot-Watt School of Textiles and Design in the United Kingdom have produced jeans that use a fiber manufactured from sustainable wood instead of cotton, and it is believed that this might be the key to decreasing carbon emissions in the global denim jeans sector. The created jeans feature cotton-like properties but utilize one-fifth of the water and energy required to produce traditional jeans.

Future developments

Cotton farmers are always battling for a fair price for their crop. Cotton producers should now be paid a fair price for their product as there is a shift toward fair trade practices. In this regard, there is a growing trend toward organic cotton cultivation and production for denim manufacturing. Cotton that is not genetically engineered and grows without the use of synthetic agricultural chemicals, such as fertilizers and pesticides, is often referred to as “organic cotton.” Organic cotton cultivation and commerce are also marketed as a more feasible and long-term alternative to traditional cotton production. Cotton producers, on the other hand, often do not embrace new production methods until they are lucrative. Organic cotton yields are usually lower than conventional cotton yields and may even be lower than what is acceptable given decreased production costs. Nonetheless, some customers are willing to pay a premium for denim manufactured from certified organic cotton fiber and labeled as such. Despite fast growth in organic cotton production, conventional cotton still accounts for around 99.9% of total global output. Because of its eco-friendliness, naturally colored cotton has grown in popularity in recent years for denim. Cotton comes in a variety of colors, including creamy white, brown, green, blue, and pink. Color is a genetically determined trait, and pigment deposition in the fiber lumen begins before boll rupture. The full manifestation of color, however, occurs only after the boll breaks open and the fiber is exposed to sunlight. It takes approximately a week for the fiber to fully acquire its natural color. It is worth noting that, although sunshine is necessary for the formation of color, prolonged exposure causes color fading. Some genotypes’ colors may fade with time and washing, while others may not. Some genotypes’ brown color may deepen after multiple washings. Naturally colored cotton has certain intrinsic limitations, including poor yield potential, short fiber length, restricted colors, and color instability. It also requires specialized harvesting methods and infrastructure, increasing the cost of harvesting white cotton. Because the fiber length is short, spinning is more difficult than with white cotton.

Despite the fact that brands such as Levi Strauss have shown interest in naturally colored cotton, the market for colored cotton is generally regarded as a niche sector. Another area of research and development is genetically modified cotton, which has been developed to be insect resistant or herbicide tolerant. Bacillus thuringiensis (Bt) cotton is a commercial variety that is resistant to bollworms. Bacillus thuringiensis is a common soil bacteria capable of generating crystal proteins with insecticidal properties. These proteins are poisonous to particular kinds of cotton-attacking insects (moths such as bollworms), and the activity is exclusive to those insects. For the protein to be effective, the target insect must consume it. BT cotton was first planted commercially in Australia and the United States in 1996. Genetically modified cotton has been legally authorized for commercial distribution in certain countries, and research is ongoing in others. Monsanto, based in the United States, has a strong position and owns around 80% of commercially farmed genetically modified cotton (Joseph and Paul, 2007; Paul and Joseph, 2003). Numerous scientific investigations have also been conducted in order to transform cotton fiber into new and unique denim textile materials. In this regard, experimental research was conducted in order to improve the physical look by employing low torque ring spun yarns (Hua et al., 2013). The residual weft torque in cotton yarn was minimized in this study. On a modified ring spinning machine, low torque cotton yarns of 84 and 58 tex linear density with variable twist levels were spun. The study’s findings revealed that low torque yarns had fewer yarn snarling turns. Denim was able to increase its smoothness and look as a result of this. Many further investigations on the cotton fiber used in denim manufacture are being conducted. These include modified rotor spinning of denim warp yarns, physical property testing of various denim textiles, and enzyme treatments on denim goods (Biermann and Schmidt, 2002; Miettinen-Oinonen et al., 1996; Rathod and Kolhatkar, 2013). Cotton is often combined with other fibers, such as lycra, to achieve desirable denim characteristics. This gives the yarn used in denim a high degree of elasticity, allowing for the production of clothes that fit closely. These are mostly utilized in the production of women’s denim jeans. By combining cotton fiber with DuPont T400 polyester, the fabric becomes more bleach resistant and can tolerate chlorine more efficiently. DuPont has also developed Veloflex, a knitted stretch denim made of 96% cotton and 4% lycra. The fabric is said to have a smooth feel and to be supple, allowing designers to construct thin cut jeans that give comfort and flexibility of movement. The advancements in mixing cotton fibers with lycra have also resulted in several prominent firms working to increase denim stretch fabric performance (Anon., 2013). Invista, the owner of the Lycra brand, and Lenzing AG, a prominent manufacturer of man-made cellulosics, collaborated to enhance the aesthetic performance of stretch textiles. The results included the introduction of novel solutions to the denim sector via the combination of Invista’s proprietary lycra dualFX fabric technology and Lenzing’s lyocell fiber for the enhancement of stretch cellulosic fabrics and the reinvention of lyocell fiber. Stay True Cotton, one of Cotton Inc. USA’s revolutionary cotton finishing technologies, helps indigo-colored denim keep its natural color for longer.

A very minimal amount of color is discharged during the home laundry of these clothes, giving them an eco-friendly appearance. Wicking Windows is a cotton moisture management technique that moves moisture away from the body while also decreasing absorbent capacity for speedier drying. Fabrics treated with this method outperform untreated cotton by 1400% in one-way moisture transfer to the outside of the garment. Cotton textiles with TransDRY technology provide the softness and comfort of cotton while remaining dry, keeping the user cooler and more comfortable. Storm denim is a highly resistant finish that protects the user from mild rain, snow, and damp situations while retaining cotton’s inherent comfort and breathability (Crumbley, 2008). There is also research underway to substitute cotton in denim with more environmentally friendly fibers. In this regard, researchers at the Herriot-Watt School of Textiles and Design in the United Kingdom have produced jeans that use a fiber manufactured from sustainable wood instead of cotton, and it is believed that this might be the key to decreasing carbon emissions in the global denim jeans sector. The created jeans feature cotton-like properties but utilize one-fifth of the water and energy required to produce traditional jeans.

How denim fabrics are made – The process from start to finish

Denim is one of the hottest clothing items in fashion right now, but the process by which jeans are made is often hidden from view. Watch this video to learn about the science behind denim production.

Conclusion

Denim would not be denim without the cotton fibre, and the whole process begins from a plant grown in a field in some country in the world. Most of the cotton processing techniques have not changed during the years, and the general principles outlined in this chapter are followed for denim manufacture. Apart from ring spinning, rotor spinning is becoming more important in denim production. Weaving a combination of ring spun and rotor spun yarns can help to reduce fabric costs while still maintaining some favourable ring spun fabric characteristics. As the cotton fibre is spun into a yarn and that yarn is woven into denim material, the cycle of manufacturing a wearable product has begun. From work wear to busi- ness attire, denim has become a universal material in apparel. It is used in almost every type of garment from jeans and jackets to skirts, dresses and even evening wear. This phenomenon shows no signs of abating, meeting the market demands and fash- ion needs. Manufacturers are constantly developing denim materials using new fibre blends, weights and finishes. Even with all of the new developments in fibre blending, full cotton denim still remains as the eternal favourite of the masses.