by Ariyah Chambers April, EMGV intern
Extension Master Gardener Volunteers commit to spreading research-based gardening practices within our communities. One of the ways we share knowledge is by teaching kids (grades K through 5) in afterschool 4-H programs across Durham County.
I spent most of my own grade school years in South Carolina. Teachers took us on field trips to nearby cotton fields to learn about the state’s socio-political and agricultural histories. Holding cotton stalks in my young hands—gently, because we all know what happens if not—my appreciation developed for the intense drudgery required to pick and process cotton before modern machinery became widespread.
It occurred to me to create a cotton lesson for the local 4-H kids, replete with actual cotton stalks, bolls, and fiber samples (after all, show-and-tell is much better received than a PowerPoint presentation… no matter the age group). A few email exchanges later with the North Carolina State University Textiles Building staff, I drove out to Raleigh to pick up some samples they kindly offered to fortify my cotton lesson.
NCSU’s Zeis Textiles Extension (ZTE) manages five world-class “TexLabs,” all critical to the textile and apparel industries by enabling cutting-edge research and product development. Experienced professionals and faculty at each lab assist students and industry partners in reaching their academic or industry goals.
The Spinning Lab—one of ZTE’s five TexLabs—is designed to help meet the needs of the textile industry in applied research. The lab’s state-of-the-art machinery converts cotton fibers (less than 65mm) into spun yarn. Lab services include evaluating the processability of various fibers and running trials to determine optimum machine settings and speeds.
I recently joined Senior Lab Operations Manager Tim Pleasants for a tour of the Spinning Lab. Our time together provided the opportunity to reflect on the major changes modernization has made to the U.S. textile industry. Tech advancement has streamlined equipment, fully automated much of cotton processing operations, and tremendously increased machine speeds. Tim is both an expert and an enthusiast when it comes to cotton, hailing from a Durham-based cotton family himself.
So what are the steps of modern cotton processing, from boll to yarn?
Step 1: Ginning is the opening, cleaning, and carding of cotton bolls. The opening of cotton bales at most mills is fully automated. Lint from several bales is mixed and blended together to provide a uniform blend of fiber properties. To ensure that the new high-speed automated feeding equipment performs at peak efficiency, and that fiber properties are consistent, computers group the bales for production/feeding according to fiber properties.
The blended lint is blown by air from the feeder through chutes into cleaning and carding machines that separate and align the fibers into a thin web. Carding machines can process cotton in excess of 400 pounds per hour.
The web of fibers at the front of the card is then drawn through a funnel-shaped device called a trumpet, providing a soft, rope-like strand called a sliver (pronounced SLY-ver).
STEP 2: Drawing, or sliver processing, is when as many as eight strands of sliver are blended together. Drawing speeds have increased dramatically over the past few years and now can exceed 40,000 feet per minute.
STEP 3: Combing makes cotton fibers nice by making strands more parallel and removing short fibers. This process can add light crimping for more surface cohesion of fibers.
STEP 4: Spinning, or yarn making, can happen in one of several ways:
Ring spinning is slower than more modern spinning systems—and the end resulting bobbins don’t hold a lot of yarn in comparison to the output of other spinner types—but is a dependable process for producing high quality yarn. Ring spinning first requires roving, which draws the slivers out even more thinly and adds a gentle twist; this process makes the fiber tighter and thinner until it reaches the yarn thickness (or count) needed for weaving or knitting fabric. The yarns can be twisted many times per inch.
Open-end or rotor spinning uses rotors that, totally automated, can spin 10 times as fast as a ring spinning machine. Rotor spinning is becoming more widespread as it eliminates the roving process; yarn is produced directly from sliver, saving time. The result is a cone of yarn that goes on to create cotton fabric that is coarser than yarn from ring spinning creates.
Air Jet & Vortex spinning (not pictured) eliminate the need for roving, similar to rotor/open-end spinning. Air jet and vortex spinning also address the key limitation of both ring and open-end spinning: mechanical twisting. This method uses compressed air currents to stabilize the yarn, faster and more productive than any other short-staple spinning system. The Vortex spinner at NCSU is its newest spinner and became commercially available in the 2000s.
STAGE 5: Twisting happens after spinning, when the yarns are tightly wound around bobbins or tubes and are ready for fabric forming. In case you’re wondering, ply yarns are two or more single yarns twisted together, while cord is plied yarn twisted together.
You can see this and more machinery in action on the Spinning Lab’s website. The equipment’s humming brings a Zen-type comfort that the resulting cotton fiber does, too.
For the 4-H cotton lesson, Tim Pleasants kindly gave me sliver and other samples representing the different phases of cotton processing. I have no doubt these samples, held in the hands of the students, will awaken them to the complexity of textile production. It’s not simply magic that the cotton cultivated in fields turns into their sweatshirts and jeans—it’s thanks to necessity, technology, and human ingenuity we have the cotton to create everything from dollar bills to baseballs.
All photos were taken by Ariyah April.
Resources & Further Reading
Tim Pleasants, Senior Lab Operations Manager for Zeis Textiles Extension at NCSU