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United States Department of Agriculture

Agricultural Research Service

A New Spin on Naturally Colored Cottons

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A New Spin on Naturally Colored Cottons

Imagine cotton-fields—not with their usual fluffy white bolls of fiber—but with ones of olive green, or pumpkin, or deep russet. Imagine bolls so soft that they seem to melt on your fingertips.

This is not a fantasy from the Wizard of Oz. It's naturally colored cotton, and it grows worldwide in a variety of' earth tones, eliminating the need for dyes.

But these colorful fibers also tend to be shorter and weaker than while varieties, which limits their commercial prospects.

Naturally colored cotton is indigenous to many countries—from Russia to Peru. Many farming communities worldwide use the colored cottons to make blankets, curtains, and clothing. Historically, artisans have spun the fibers into yarn by hand to make cloth, including long-time Louisiana residents who have cultivated the plant for generations.

Louisiana also happens to be the place where Agricultural Research Service textile engineer Linda B. Kimmel is adapting patented yam-making technology to enhance the strength and versatility of naturally colored cotton fabrics.

And this could help the market for colored cotton grow.

"Commercial processing of naturally colored cotton was not practical until breeders began improving the plants," says Kimmel. "Although geneticists continue to improve their properties, the fibers remain comparatively short and weak."

As a result, spinning colored cotton yarn is difficult unless the colored fibers are mixed with white cotton. This kind of blending helps textile makers to process the fiber and strengthen the yams, but it also reduces color intensity.

Yet colored cotton is still finding its way in the commercial world. While some previous ventures have failed, its novelty and softness keep a steady hold on niche markets. Today, its woodsy hues show up at rock conceits in the form of organic, earth-friendly, undyed T-shirts in muted color blends.

The future of colored cotton depends on a combination of successful plant breeding for enhanced fiber strength and the development of suitable manufacturing methods.

Kimmel, who is in the Cotton Textile Engineering Research Unit at ARS' Southern Regional Research Center (SRRC), is working cooperatively with Harvey Campbell of B.C. Cotton in Bakersfield, California, to develop improved colored cotton yarns and fabrics. Campbell is one of a handful of people in the United States who breed and grow colored cotton. His success depends on finding companies that want to produce colored cotton products.

"Naturally colored cotton has a wonderful hand," says Campbell. "That's an industry term for how it feels to the touch, and in this case it means almost irresistible." Campbell had heard about research at New Orleans where Kimmel and other scientists had developed several pioneering yarn spinning methods. The two met at a conference and decided to see what technology could do to improve colored cotton.

Kimmel is using two ARS-patented methods, staple-core and filament-core spinning, to produce composite yarns. Yarns made this way contain an outer layer of naturally colored fiber and an inner core of stronger white cotton or synthetic fibers. The result: a bicomponent yarn that contains two types of fibers that are securely sandwiched—instead of merely twisted—together. Consequently, the fabrics look and feel like solid colored cotton but are stronger than those made from the same fibers on typical machines.

The words ''staple" and "filament" refer to the kind of core used. Staple is short fibers; filament is a long, continuous fiber. Polyester is usually used in the core for its tenacity and easy-care properties. But fiberglass shows promise for industrial applications, because of its fire resistance.

The methods were developed with the guidance of cotton technologist A. Paul S. Sawhney, working with Kimmel, and with the mechanical engineering support of technician Craig L. Folk.

"The goal of this technology is to maintain desirable attributes of cotton, such as comfort and style, while deriving, benefit from the fibers hidden in the center of the yarn." says Kimmel.

"It's only natural that Campbell would be drawn to the SRRC-considering our reputation," says center director J. Patrick Jordan. "Our scientists have a 50-year tradition of enhancing the quality and use of cotton."

Among SRRC achievements that Jordan cites are wrinkle-free and flame-resistant finishes and high-performance fabrics for the military.

Sawhney and Kimmel are presently experimenting with a variety of synthetic core fibers to achieve improved fabric appearance and durability for cottons in general. When heat-set, these fabrics would allow clothing to hold its shape better after laundering, with fewer chemicals.

"Right now we make towels, blankets, and T-shirts with colored cotton," says Campbell. "With a stronger yarn we could make items such as khaki trousers and skirts."

Kimmel adds that while currently available colored cotton fabrics contain as little as 25 percent in blends with while fibers, the new products can have pure colored cotton on the outside in rich, vibrant colors.

One advantage of the ARS-developed techniques is that they are easily adapted to conventional spinning frames. Both staple-core and filament-core spinning methods use special devices to control the fibers and direct them to their proper positions in the yarn. The core fibers, which give the yam strength, are held in the center by a carefully engineered groove, while the colored fibers converge from both sides, interlocking around them.

"I have already produced staple-core yarns from red, green, brown, and mocha-colored cottons with great success," says Kimmel. "Experimental yarns containing pure colored cotton surfaces are up to 50 percent stronger than pure colored yarns spun by traditional methods. They are also 20 to 30 percent stronger than yarns made from currently available blends of while and colored fibers, and the colors are much richer."

While colored cotton can he a risky proposition for growers, its rewards can be considerable.

For example, white cotton produces 2 to 2-½ bales per acre, and some colored cottons yield barely half that much. But the white brings in around 80 cents per pound to colored cotton's 3 or 4 dollars.

And colored cotton has to be isolated from while varieties to prevent contamination of the fiber or seeds. But colored plants resist pests and drought better, so they are more adaptable to dryland farming. Current estimates are that colored cotton is being grown on 5,000 to 7,000 acres, mainly in Texas, California, and Arizona. In 1995, total U.S. cotton acreage was nearly 16 million acres.

Furthermore, "The ecological benefits and cost advantage of not having to chemically dye colored cotton should offer an incentive to commercialize the fibers using our patented spinning technologies," says Kimmel. "But higher harvesting, processing, and fiber costs do presently reduce its price advantage."

Though there may be some obstacles to overcome, colored cotton's supporters are banking that with the help of science, this velvet-smooth fiber's future will be rosy. — By Jill Lee ARS.

Linda B. Kimmel is in the USDA-ARS Cotton Textile Engineering Research Unit, Southern Regional Research Center, Room 1213, 1100 Robert E. Lee Boulevard, New Orleans, LA; phone: (504) 286-4335 ext. 335.

"A New Spin on Naturally Colored Cottons" was published in the April 1996 issue of Agricultural Research magazine.

Last Modified: 8/23/2007
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