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Cotton, a long journey from India
The textile use of cotton fibre is attested in the oldest civilizations. Archaeologists have found fragments of cotton fabrics 8,000 years old in the Indus Valley in present Pakistan and 7,200 years old in Mexico. It is from India that the art of cotton fabrics is exported to the Old World.
Already, in 445 before our era, the Greek Herodotus wrote about India: “one finds there trees growing in the wild state, whose fruit is better and more beautiful wool than that of sheep”.
From the 7th century, the Arab conquests spread the use of cotton in North Africa and Europe. Trade between Europe and India took on a new dimension, thanks in particular to the opening of the route to India by Vasco da Gama in 1497. Spinning and weaving are then perfected.
In industrialized countries, cotton clothing, even the finest, is now accessible to everyone. It is the invention of saw gin that will be at the origin of the development of cotton growing in the United States.
At the start of the 20th century, 90% of the world cotton trade was in the hands of Europeans and the supply of raw cotton was ensured above all by the United States, India and Egypt. Today, cotton is grown on five continents, and in around a hundred countries. And India has some of the top rated cotton exporters
From Plants to Textiles
Man has always used textile fibres of plant, animal, mineral or chemical origin (artificial or synthetic), for the manufacture of clothing.
Two parameters have led man to use certain plant organs in the form of fibres, first allowing the manufacture of threads, strings and cords, then, thanks to increasingly sophisticated technological means (hand weaving, knitting, weaving by machine) the manufacture of manufactured fabrics for clothing, household linen, furniture and decoration:
1 – wealth in cellulose, a polymer of glucose very long chain, naturally structured in micro-fibrils
2 – the distribution of these micro-fibrils in elongated cells (plant fibres), used by the plant as support elements and m ore or less easily extractable.
The simplest fibre, consisting of almost pure cellulose, is cotton fibre. The other fibres (linen and hemp) are more complex and less pure. From cellulose extracted from wood, it is possible to regenerate fibres and thus manufacture derived textiles such as viscose and then rayon.
Cotton, and Cotton Fibre
The cotton plant (genus Gossypium, family Malvaceae) is a shrub native to India, grown in many hot countries for the fibres that surround the seeds when the fruit matures. Depending on the country, the plant is more or less tree-like, but it is the herbaceous cotton plant (50-60 cm) that gives the finest fibres.
The flowers have corollas of the colour pink then ivory with five petals. The fruits are ovoid capsules with four or five compartments, each containing six to twelve seeds.
The seeds are covered with long unicellular hairs (up to thirty to forty millimetres) of silky appearance which begin to grow from fertilization and constitute the cotton fibres formed from cellulose almost pure. These fibres are used for the manufacture of cotton hydrophilic thread or cloth.
The cotton plant is budding, gate flowers and fruits at the same time, so the harvest lasts several months. Fibre has the shape of a 15 to 40 mm tube attached to the seed by a foot and tapering in shape towards its end.
- A thin outer primary wall (0.1 µm thick) composed of cellulose, waxes, lipids and pectin is the fibre sheath;
- A thicker internal secondary wall (0.4 µm thick) formed of three cellulosic layers forming a spiral;
- A channel or lumen occupies the centre of the fibre which contains the cellular constituents.
- The young cotton hair is cylindrical then when mature the cytoplasm central disappears, the lumen flattens and the hairs twist, which facilitates the twist fibres for making yarn solid.
From raw cotton to thread, then to fabric
After the harvest, the seed cotton is transported by truck to the ginning factory. It is cleaned by machines which rid it of large impurities (leaves, stems, capsules). Then it is shelled, that is, the fibre is separated from the seed. The fibre is cleaned by machines that remove small impurities.
At the end of the warp, the cotton fibres are clean. They are packed and compressed to form bales of kilos. Modern factories produce one bale per minute, or more than a thousand bales a day!
Spinning consists of transforming masses of cotton fibres delivered in bales of different origins into linear textiles. From a strongly disorganized state, we pass to a very organized state which is the thread.
The fibres are first prepared, that is to say, cleaned, disentangled and individualized. Several operations then follow:
Special treatments applied to cotton give it a different look or feel (satin) or new properties: stain-resistant, anti-microbial, anti-UV, wrinkle-resistant, waterproof, flame-retardant (resistance to combustion). Some of these properties can also be obtained by mixing cotton with synthetic fibres with the appropriate characteristics.
The fabric or the knit can undergo finishing operations, depending on the use for which it is intended:
- Buckling: the fabric is burnt superficially to remove all the small fibres that protrude, otherwise the fabric would be fluffy.
- Scraping: Conversely, it is scraped to obtain a “peach skin” effect.
- Boiling and bleaching: the strip of fabric is passed through a bath made up of water and soda which removes the natural wax, swells the fibres and makes the cotton hydrophilic. A second bath, in hydrogen peroxide, will turn the fabric white. It will be able to “take” the dye
- Mercerizing: the yarn or fabric is soaked in an alkaline bath. The fibres swell, round out and take on a lustrous appearance. Their dye retention power increases. Mercerized fabrics are more compact and more resistant than those that have not undergone this operation dyeing (passing the fabric through a dye bath) or printing (creation of a monochrome or polychrome pattern) have a purpose aesthetic and decorative. However, the yarn can be dyed directly before weaving or knitting in order to obtain special effects.
The main outlets for cotton yarn are clothing (clothing (60%), furniture (35%), and professional clothing (5%). Cotton also finds applications in medicine and hygiene.
It is used in the manufacture of absorbent cotton (wadding), compresses, gauze bandages, sanitary tampons, and cotton swabs. In the field of cotton wool, the variety Gossypium herbaceum is the most used, because it produces short and thick fibres.