29 Apr | Fact check: Cotton’s Share of Worldwide Pesticide Use
Cotton is not the largest user of agricultural pesticides – it’s actually one of (…)Read more
People have been wearing cotton textiles now for many millennia. This has been shown for example by the remains of cotton bolls and cotton textiles discovered in a cave near Tehuacán in Mexico and dated at 5800 BC. In the Old World, the oldest finds of cotton fabrics and cotton cords (around 3000 BC) come from the area of present-day Pakistan. The Indus Delta is also thought to be the area where the first cotton fields were laid out.
Cotton belongs to the mallow family. The cotton fibre is the seed hair of the Gossypium plant. Its blossom looks very similar to that of our native hollyhock and the hibiscus. After blossoming, the ovary in the chalice turns into an egg-shaped capsule that springs open and oozes out the seed hairs. A cotton boll contains about 30 seeds, on each of which sit 2,000 to 7,000 seed hairs. Depending on the type, climate and growing method, the cotton plant reaches a height of 25 cm to more than 2 m. It is grown mainly as a shrub-high annual plant. Only in a few areas (Peru and northern Brazil) is cotton still grown on perennial shrubs.
The period from sowing to maturity ranges from 175 – 225 days. The plant needs a lot of moisture at sowing and a lot of warmth at the stage of maturity. The harvested cotton is stored to mature and dry for about 30 days and is then brought to the gins, where the fibres are separated from the seed grains. About 35 kg of fibre can be obtained from 100 kg of seed cotton.
Raw cotton is traded on colour, purity, fibre length (staple), fineness, strength and uniformity. Some varieties are hard and rough to the touch, while others are silky soft. In terms of colour, raw cotton is classified as “white”, “creamy” (slightly yellow), “light spotted” (slightly stained) and “spotted” (blotchy). There are also varieties that appear brownish yellow, and coloured growths in green and brown tones. An important quality feature is the staple length.
The finest and longest cotton fibres have the greatest strength in relation to their cross-section, a property which is very valuable for spinning the finest cotton yarns. The cotton fibre can be stretched by 8-10% in both the dry and wet state, with its wet strength being higher than the dry strength.