Part II: Closing the Cotton Loop
In Part I: The Cotton Loop, we shared insights into the production of cotton and what happens to cotton seeds after cotton is ginned.
This second part “closes the loop” by spotlighting:
- the cotton fiber
- how it develops within the plant
- and how it becomes cotton fabric
The Cotton Fiber
While cotton is growing, like most plants, it develops a seed. And like some other seeds, specialized cells grow out of the seed coat like hairs. They are generally referred to as fibers, though in a strict anatomical sense, they are technically trichomes. And cotton has the most impressive trichomes in the world!
Figure 1. The structure of cotton
Developing Within the Plant
Each hair is a single, unbranched cell, high in cellulose…but unlike other forms of cellulose (think wood pulp), its structure is multilayered, densely packed, and uniquely parallel. The individual strand looks like a flat, tightly twirled ribbon, tapered on the leading edge and “fuzzy” where separated from the seed. This gives cotton unparalleled softness, especially when compared to synthetics with their sharply cut ends. No wonder cotton is the #1 fabric in the world!
After being separated from seeds at the gin, the fiber is cleaned, dried and compressed into massive bales, ready for a textile mill or other downstream use. Before sale it is classified by specialists for quality, using factors such as staple (average fiber length), color, and cleanliness.
Figure 2. The process of developing cotton fabric
How Cotton Becomes a Fabric
If you look around your home, you can find cotton everywhere: swabs and cotton balls, bandages, books, and even money…but mostly in the form of fabric. The bales from the gin (1) are blended and fluffed to make the most uniform starting material possible (2), spread out into a thin web over rollers (3) to be cleaned and aligned. The material is then fed through a trumpet (4) to form sliver (pronounced sly-ver)(5).
Multiple slivers are drawn together (6), twisted and spun to form cotton yarn (7) wound onto spindles or bobbins. Those bobbins are mounted on machines to be woven or knitted into fabric. To get an idea of the difference, weaving yarn on a loom produces a tight, structured fabric (like denim). Using needles to knit yarns results in a stretchier feel (like jersey).
The next time you put on your comfiest T-shirt, swab your ears, or slide a dollar into a vending machine, we hope you’ll have a deeper appreciation of the cotton used to make these items.