Cotton is a fabric we use every day, and one which many of us take for granted. But where does cotton come from? How is it made? Why is it so comfortable to wear and so versatile to use?
This is the first in a series of educational articles designed to help those who work in the textile industry better understand how their products are manufactured and the tradeoffs inherent in choices of raw materials, processing, and construction. Knowledge is the key to selecting the best and most appropriate options for your business and your customers.
You likely know that cotton is a plant-based textile. It is derived from the fibers surrounding the cotton seeds, housed inside a protective leathery boll—the fruit of the cotton plant. In the past, cotton bolls were picked by hand. Today, cotton is harvested using large machines called, appropriately, cotton pickers. Harvested cotton is sent to a cotton gin mill for initial processing.
Processing Cotton Fibers
At the gin mill, the cotton fibers are separated from the cotton seeds. Depending on the length of the fibers, the cotton is processed using either a saw gin (for shorter fibers) or a roller gin (for longer fibers). The ginned fiber is then pressed into bales and sent to the textile mill.
At the textile mill the bales are opened, and raw cotton fibers are pulled and stretched and further separated from extraneous plant material. Machines disentangle and pull the fibers into parallel strands in a process called carding. These strands are combined to make long, continuous rope-like slivers (pronounced sly-ver). A combing machine refines the slivers by eliminating fibers that are too short and any remaining impurities. The slivers are then wound onto bobbins in preparation for spinning.
Spinning Cotton to Make Yarn
Spinning takes strands of cotton fibers and turns them into yarn using twisting and tension. Open end spinning produces a lower quality, lesser refined yarn, but is also least expensive. Ring spinning generates a softer, more durable, but more expensive cotton. And air jet spinning yields the highest quality, most refined, and most consistent yarn; but it’s also the most expensive.
Each type of spinning can create different qualities of yarn in various yarn counts. The smaller the number, the thicker the yarn. As an example, size 1 yarn is commonly used for string mops, size 6 to 8 yarns are used for blankets, size 10 to 18 yarns for terry towels, and size 80 for fine dress shirts.
Weaving Cotton Yarns into Fabrics
Weaving takes place on a loom, interlacing warp and weft yarns to form fabric. Warp refers to the yarns that run lengthwise in the woven fabric; weft are the yarns that run crosswise. In some products, such as towels, a third dimension—pile—is intertwined into the warp and weft of the fabric for extra absorbency. The end product of weaving cotton yarns is a natural-colored fabric called greige.
Three major types of looms are used to weave cotton textiles: the power loom, the oldest form of loom technology, uses mechanical force to send a shuttle bearing weft yarn across and through the warp yarns; the rapier loom employs an arm, rather than a shuttle; the shuttleless loom uses air or water to propel the yarn across—this is the fastest technology and the most consistent, producing the highest quality product.
The Truth About Thread Count
When we talk about thread count in sheets, we’re talking about the number of warp yarns and weft yarns in one square inch of fabric. For instance, in a perfectly balanced T250 thread count sheet you’ll find 125 warp and 125 weft yarns in a given inch.
You can make the same T250 thread count sheet with 77 yarns in the warp and 48 yarns in the weft, but those would be plied yarns. Plying is the process of taking one yarn and doubling or tripling it by twisting multiple yarns together.
Consumer perception is that the higher the thread count the better. However, the most important thing about your sheets is the yarn quality. Some manufacturers claim their sheet is a 500 or even a 1,000 thread count, but in fact they are achieving this by plying yarns. This reduces the overall durability of the sheet and misrepresents the true thread count.
Knowing more about how your sheets are constructed will help you to be aware of these situations, allowing you to make more informed decisions — for your business and your customers — about the products you purchase. Remember that while some sheets will boast more yarns per square inch, it is most important to take into consideration the softness and durability of the fabric — not just thread count.
Polyester—a man-made fiber—can be added to cotton at any of several stages, including spinning and weaving. If added early on when the cotton is being pulled into the long sliver strands, a superior quality cotton/poly yarn can be produced. The stage at which the fibers are mixed affects strength, dyeability, and moisture retention/wicking.
The ratio in cotton/poly blends—valued for their versatility and durability—varies, with 65% cotton and 35% polyester being the most common; 50/50 blends are also popular.
In its fresh-from-the-loom state, greige fabric retains the natural light khaki color of cotton. For cotton fabrics that require bleaching, a variety of processes can be used, each of which will have an effect on the overall softness and appearance of the final product.
Similarly, there several types of dyeing processes, each of which affects the end product differently. In yarn dyeing, the strands are dyed first and then woven into the finished product. With lot dyeing, the fabric is dyed before it is cut and sewn. And in piece dyeing, pieces of the final product are dyed individually.
The success of dying depends on the reaction between the fibers and the dyes. Reactive dying is the most common and the least expensive process, a good fit with the natural fibers of cotton. Vat dyeing, on the other hand, is more expensive but will keep colors from fading. Cotton fabrics that are vat dyed can withstand higher temperatures and even a low percentage of bleach. Vat-dyed towels are often a good choice because there tends to be less fading.
Stitching of Cotton Products
When cotton fabric is cut and sewn, two types of stitches are used: a lock stitch in which two threads are used to interlock together (so that if you pull one stitch out only one stitch is affected); and a chain stitch using one continuous thread to sew (the downside: if a stitch breaks the entire chain can unravel).
Understanding the basics of how a textile such as cotton is made, and how it is turned into the fabric we use in so many applications on a daily basis, can enhance your decision-making for your textile-based business. Watch for further articles in this series on textile manufacturing and the implications for businesses. And, for a more interactive and visual experience, check out Calderon’s video content hosted on www.calderontextiles.com. The more you know, the better you can serve your customers and enhance your business.