Cotton is considered the most important and widely used fiber in our society. From clothing to salad dressing, cotton provides many products for human and animal consumption.
Cotton has been cultivated for centuries. Currently, there are five prominent types of cotton being grown commercially around the world. They are Egyptian, Sea Island, American Pima, Asiatic and Upland. The largest producers of cotton are the United States, China, India, and Pakistan. Brazil, Australia, Egypt, and Argentina produce significant, but lesser amounts.
The strength and quality of cotton thread is often measured by the length of the staple. Egyptian long staple cotton has staples of 1.25 inches. Egyptian extra-long staple has a minimum of 1.37 inch staples.
From planting to maturity, it takes 140 days to produce a cotton crop. As the plant matures, the fibers within the cotton boll grow and thicken with their primary growth substance, cellulose. An average boll is about two inches in diameter and contains 500,000 fibers of cotton. Each plant may bear up to 100 bolls.
In processing cotton, the cotton fiber is first separated from the cotton seed. The fiber is then dried to reduce moisture and improve the fiber quality. It is then cleaned to remove leaf trash, sticks and other foreign matter. The raw fiber, called lint, is then compressed into bales, sampled for classification, wrapped and shipped to textile mills. The mills produce cotton yarn and cloth by first carding the cotton. Carding is the process of pulling the fibers into parallel alignment to form a thin web. The web is then combed, which removes impurities and makes the fibers smoother. The final step is spinning the fibers to make uniform strands.
Further processing may done to make a mercerized, glazed, or gassed thread.
Mercerizing is a process of treating cotton thread with an alkali solution, causing the fibers to swell. This process allows the dye to better penetrate the fibers, thereby increasing the luster. Mercerizing increases the strength of the thread and reduces the amount of lint.
Glazing involves heating the thread and then coating it with waxes, starches, and other chemicals. The thread is then polished to a high luster. Glazing results in a glossy thread with a hard finish. Glazed thread is often stiffer than unglazed thread. Most professionals do not recommend glazed threads for machine work as the glaze rubs off and gums up the machine.
Gassing refers to passing a cotton thread at high speed through a flame, burning off the excess fuzz in order to create a higher sheen.