Cotton: cultivation, processing, properties and uses
Cotton is a seed-hair cellulose fibre grown in warm climates. It is absorbent, cool and strong when wet but creases easily, which suits Indian summers and hospital use.
Draw it: from boll to bale
Cultivation and processing
- 1Growing: cotton needs a long, warm, frost-free season, moderate rain and bright sun. The moisture-holding black cotton soil of the Deccan suits it. Most Indian cotton today is Bt cotton, approved in 2002.
- 2Bolls: after the flower drops, a green boll grows. Fibres grow out from the seed coat, first lengthening, then thickening as cellulose is laid down inside.
- 3Picking: ripe bolls burst open and are picked, in India mostly by hand, in several rounds.
- 4★Ginning: the gin separates the lint (fibre) from the seed. Roller gins are gentle and suit long staple; saw gins are faster for short staple.
- 5By-products: short fuzz left on the seed (linters) goes into rayon, paper and other cellulose products; the seed gives cottonseed oil and oilcake.
- 6Baling and grading: lint is pressed into bales and graded by staple length, fineness, colour and trash. Long-staple types (Egyptian, Sea Island, Indian Suvin) give the finest yarn. Spinning follows (Unit II).
★ one-way, controls the pace
Properties of cotton
| Property | Cotton | So in use |
|---|---|---|
| Structure | Flat, twisted ribbon (convolutions) with a central lumen; kidney-shaped cross-section | Twists help spinning; dull look unless mercerised |
| Strength | Good, and stronger when wet | Survives repeated washing and boiling |
| Absorbency | High (regain about 8.5%); conducts heat away | Cool and comfortable; soaks up sweat |
| Elasticity and resiliency | Low | Creases easily; needs ironing or a resin finish |
| Heat | Takes a hot iron; scorches and burns but never melts | Does not stick to skin, but loose or napped cotton catches fire easily |
| Chemicals | Resists alkalis; weakened by acids and strong chlorine bleach | Can be boiled with soda; rinse acid stains at once |
| Biological | Mildew grows on damp cotton; silverfish attack starched cotton | Dry fully before storage |
| Sunlight | Slowly weakens and yellows | Line curtains to protect them |
Uses of cotton
- Clothing: saris, shirts, kurtas, innerwear, baby clothes, nightwear, school uniforms (often blended with polyester).
- Household: bedsheets, towels, kitchen dusters, curtains, table linen.
- Medical: absorbent (surgical) cotton, bandages, gauze and hospital linen, which can be boiled and sterilised.
- Industrial: canvas, tarpaulins, sewing thread, hose and belt fabrics.
- Indian heritage: khadi (hand-spun and hand-woven, the cloth of the freedom movement), fine mulmul, and handloom saris such as Chettinad and Venkatagiri.
Cotton and linen
Both are cellulose, so they share the same burning test and chemical behaviour.
Cotton is the first choice for kitchen aprons, hospital linen and baby clothes: it absorbs sweat, can be boiled or hot-washed to kill germs, and does not melt onto skin. The same crop gives cottonseed oil (refined to remove the toxic pigment gossypol) and oilcake for cattle.
2 marks: “What is ginning?” Ginning separates cotton lint from the seed, using roller gins (long staple) or saw gins (short staple).
5 marks: “List the properties of cotton.” Structure (convolutions, lumen), strength (stronger wet), absorbency, low resiliency, heat, acids and alkalis, mildew, sunlight; one use for each.
10 marks: “Describe the cultivation, properties and uses of cotton.” Climate and soil, bolls, picking, ginning, linters, baling and grading; properties in a table; uses in clothing, home, medicine and industry; Indian examples.
Cotton loves water and heat (stronger wet, takes a hot iron, can be boiled) but hates acid and mildew.