The origins of cotton

The cotton plant | The Cotton fruit | The cultivation of cotton | The morphology of cotton 

The properties of cotton | Egyptian cotton | The cotton of the United States | The cotton of the West Indies or Sea Island | Chinese cotton

The main processes of the working of cotton | Yarn count number | The twisting of cotton | The main principles of ennobling cotton

The origins of cotton

Certainly, the most important and widespread vegetable textile fibre, cotton derives its name from the Arabic al-qutu. Known for more than five thousand years (as testified by the finds uncovered at Mohenjo-Daro, in current Pakistan and Tehuacan in Mexico), depicted in antique Egyptian hieroglyphics (3.000 AC-30 AC), quoted by Herodotus in the V century AC and widely known to the Aztecs in America during the Pre-Columbian period, which reached Europe during the Middle Ages but affirmed itself only in 1600.
The commerce of cotton textiles made India, of exceptional fineness and quality, co-involved the counties of the Mediterranean already during the time of Alexander the Great (356-323 AC), who had established the commercial routes towards the Orient. Alessandria thereby became the main centre of distribution of these goods. Several centuries later, the force of the City State of Venice was founded, largely, on the same commerce of textile cottons originating from India.
The Islamic world initiated the West in the use of cotton textiles, starting from the know how of the techniques of weaving. In fact, already in the VIII century the Arabs had introduced in to Spain the cultivation of cotton and the fabrication of cloth, which prospered until the “witch-hunt of the Moors “initiated with the edict of 1609. Subsequently, the opening of the maritime routes towards India saw the rise and affirmation of Portugal as the main supplier of textiles in cotton.
During the course of the XVII century, the experience of the production of textiles and the maritime power began to be concentrated in England, which thus became the main centre of the production of textiles. In fact cotton became one of the main wheels of the English Industrial revolution (1760-1830) taken as an example by France, where despite the ostracism decreed by the crown on painted textiles (1686-1759), cotton became a fashion phenomenon already starting from 1650, also through "calico" (white muslin and dyed linen imported from India) called indiennes and subsequently printed also in France.
In the meantime, the cultivation of cotton had extended to North America and the Caribbean. These trends were consolidated with the invention of the first "cotton gin" (cotton engines) invented in 1794 by the American Eli Whitney (1765-1825), which were perfect as machines for the spinning and weaving of textiles. These machines allowed quickly and easily separating the cotton fibres from the seeds, thereby accelerating the production cycle.


The cotton plant

Belonging to the Malvacee family (Gossypium irsutum, barbadense, herbaceum, arboreum) the cotton plant can have an annual cycle, so-called “weed“ with a height between 25/50 and 150/200 cm, or many years so-called “wooden“ that can grow to between 200 and 500 cm. The first species is the most common, the second mainly cultivated in South America and the Caribbean. Each plant produces between 200 to 500 fruits equivalent to approximately 2/5 kg of rough fibre.


The Cotton fruit

Three months after sowing in rows, the plant begins to flower. After fecundation the flowers turn into capsules (bolls) composed of 3/5 pods, that contain from six to eight seeds, that harden as they grow. Inside, around the seeds, there begin to form downy fibres that turn into spirals and remain well compressed within the capsule. The biological cycle ends with the opening of the capsules burst open revealing the white fibres of cotton (flakes or cotton wool) composed of essentially pure cellulose. The cotton wool is of two types, linter that is shorter and attached to the seeds, which is mainly used to produce artificial fibre, and lint, which is the longer fibre and is used to produce the proper spun cotton (yarn).


The cultivation of cotton

Native to tropical and sub-tropical countries the cotton plant is today widespread in more than eighty countries. The main producers are China (5 million tons per year), the United states (4 million tons per year), India (2.5 million tons per year) and following them, with lower quotas, Egypt, Pakistan, Uzbekistan, Turkey, Australia, Argentina, Brazil, Greece, Sub Sahara Africa and South America. The cultivation of the so-called American Upland cotton now widespread in all continents, takes its name from the Uplands of the United States where, thanks to the exploitation of the slave labour, it experienced a huge expansion. Today this quality represents the highest quota of production in the world. The long ed extra long staple (Gossypium Hyrsutum, Gossypium Barbadense) that occupy a much lower percentage quota, are mainly cultivated in Egypt, United States (California and New Mexico), China and India. Lesser quantities and much more valued are present in Peru (Pima), Israel (Israeli Pima), Sudan (Barakat), India (Suvin) and West Indies (Sea Island Cotton).


The morphology of cotton 

The fibres of cotton appear ribbon-like spirally twisted which are frequent and regular in fibres of good quality. Observed sideways the filaments are divided into four parts "Cuticle" (a very thin non-cellulose natural external membrane); the “Primary wall“ formed of fine threads (fibrils of minute fibre) of cellulose that entwined with each other; the “Secondary wall“ composed of cellulose and spirally twisted fibrils and lumen which is a void central canal of fibre (non-cellulose) and of narrow form. Its composition is made up of 85% by cellulose, 10% by humidity and the remaining 5% by other substances (protein, inorganic matter, mineral salts).


The properties of cotton

The fundamental property of cotton is represented by its marked tenacity or tensile strength (resistance to breakage when a forced is applied along the length of the fibre) due to its crystalline structure, especially in a humid environment, where the force of the cotton fibres increases up to 15%. However it is relatively inelastic, though superior to all other vegetable fibres. The optimum hygroscopicity (that is the capacity to absorb quickly molecules of water present in the atmosphere surrounding it) is combined with an average level of insulation (thermal conductivity). Morbid and pleasant to the touch, it has a dull sheen, good resistance to wear and tear and abrasion, and well tolerated by the skin thanks to its so-called "skin loving touch". Cotton is preferred to synthetic fibres by 64% of consumers in the world (Global Lifestyle Monitor according to research done by the Cotton Council International and Cotton Incorporated) who have declared that they are willing to "pay more" for clothes made of natural fibres such as cotton.


Egyptian cotton

Egypt, due to its particular climatic conditions, the fertility of the earth close the Nile and the zone south of the delta, favours the production of the best cotton. The abundant rainfall that develops between October and April, the relative humidity level of 60-70% and the winds coming from the North guarantee few variations of temperature thereby creating an ideal microclimate. These conditions make Egypt the main historical producer and current world leader in the production of long and extra long staple cotton. The LS long staple cotton includes the quality Giza 86/89/90 (the city of Giza is situated approx. 20 km from Cairo and called the “City Of The Gods” as it guards, through its most famous and prominent monuments, the mysteries of Egyptian civilization). The cottons of the LS long staple quality reach a fibre length of around 33 mm and a micronaire of 4.3/4.9 (a system of measurement obtained by analysing the resistance of a "plug of cotton" to airflow in certain given conditions to determine its cleanliness, efficiency, force and uniformity; through the measurement of the permeability of air one obtains a value which is an index of the fineness in that, the thinner the fibres the more smaller are the gaps between them and therefore higher the level of resistance to air. A finer fibre corresponds to a lower micronaire value) is used to produce yarn count range NE 50/1, 70/1. ELS cotton or extra long staple comprises an even higher quality of cotton such as Giza 45/87/88 capable of generating very fine yarn count range and resistant at the same time, with an average micronaire value of 2.95.


The cotton of the United States

The lack of pollution in the fibres, a vast system of irrigation and a mild climate distinguish the production of American cotton, which is cultivated in a vast zone of the country that is justly called the Cotton Belt. This area comprises some 17 States, from North Carolina until California, from the East Coast to the West Coast. The production is differentiated into two main qualities, Upland (that represents approximately 97% of the production) and Pima cotton that belongs to the category of the ELS, extra long staple and is cultivated mainly in the states of Arizona, New Mexico, Texas and California, and represents the remaining 3%. The characteristics of Pima cotton (or Supima) are controlled and guaranteed by the Supima Association of the same name, which verifies the production process at all the different levels. The wide use of automated technology and the industrial large-scale harvesting, permits huge plantations, avoids the contamination of the foreign fibres and makes this type of yarn ideal for the production of cloth for white shirts, with count range up to NE 100/2, 120/2. It also offers particular resistance and is not subject to pilling (a physical process that can occur on the surface of cloth which leads to the formation of small irregular balls of fibre that are called pills).


The cotton of the West Indies or Sea Island

The cotton produced in the West Indies, in particular in Barbados, is highly valued: the fibres reach up to 39 mm in length - the longest in the world - and is counter-distinguished for its pureness and resistance. This production detains a quota equal to 0.0004% of the world production with a micronaire value between 2.9 and 3.2. The process of harvesting is done completely by hand and the product is worked with great skill so as to avoid damaging the fibres, this procedure is justified by the high value of the Sea Island cotton and monitored by WISICA (West Indian Sea Island Cotton Association).


Chinese cotton

The Xinjiang Cotton is an ELS extra long staple cultivated in the region of the same name. The fires reach a length that varies between 36/37mm and a micronaire value that oscillates between 3.5 and 4.0. It is a product with a good cleanliness destined exclusively for the internal market.
China, though being one of the major producers of cotton (approx. 5 million tons per year) is also one of the most important importers (more than 4 million tons per year) having an internal consumption that is approximately double their current production (data supplied by the United States Ministry of Agriculture in 2005).


The main processes of the working of cotton

After harvesting, generally done by machines, with the exception of certain highly valued qualities of cotton (see Sea Island Cotton), it is dried, to remove its moisture, as it is very humid when harvested; this process is done by using hot air dryers. It is then de-seeded using appropriate husking machines (gin), which separate the fibre from the seeds. In this phase the linters (the shortest fibres, between 1-4 mm) remain attached to the seeds and constitute the primary material for the production of the cellulose fibres, artificial and paper, while seeds with linters, are used for new planting and/or for the production of cotton oil. 100 kg of seed cotton yields approximately 35 kg of fibre, 62 kg of seeds and 3 kg of waste. The dried and de-seeded cotton is the pressed into bales. During the first phase of spinning the bales are opened and the fibres pulled apart. During the so-called "blending" phase various grades of cotton are blended together after which it is cleaned and carded. The process of carding the flecks of cotton (wads) is to draw (pull) the fibres into parallel alignment with the carder (wire toothed rollers) so as to form a thin web or fleece of fibres that is condensed into a continuous, untwisted, rope-like strand which is then used for the carding of thicker yarns (maximum length 3 cm) or for combing for finer yarns (minimum length 3 cm). The carding is done in three steps: the pairing and drawing, pre-spinning, which consists in a second drawing of the bands to give them a slight twist and to transform them into slivers. The spinning is done on ring or open-end machines (machines that produces a yarn directly from a sliver of fibre, the sliver is split into in single fibres in the separating cylinder; the fibres are then fed into a rotary spinner and spun directly, thereby eliminating the preliminary preparation of the slivers. The yarns are then pulled and wound). During the process of combing, an additional step is performed as well as all the steps described for the carding. The carded bands after pairing and drawing are combed which eliminates fibres that are very short and occurs before the pre-spinning.


Yarn count number

The yarn count determines the count or number of single or spun yarn. As it is not possible to directly measure the section of a fibre as it is easily deformed and very often not circular, a yarn count is used, that is the relationship between the weight and the length of the yarn. The value of the length (L) and the value of the weight (W) are put into relationship between each other and produce the value of the count (C), in the direct count or the number (N), in the indirect count. Therefore there are two methods for the count: Direct System where length is fixed (C=W/L) (used for all yarns manufactured with continuous fibres such as silk, rayon, nylon, etc.) and the Indirect System where weight is fixed (N=L/W) (used for all yarns manufactured with discontinuous fibres such as wool, cotton, rayon, etc.

The denomination in the direct system is:
- Tex (Tt) indicates the weight of yarn in gm present in 1000-meter length
- Decitex (dtex) indicates the weight in grams of 10 000 metres of yarn or filament
- Denier System (Td) – the weight in grams of 9000 metres of yarn or filament

The denomination in the indirect system is:
- The metric number (Nm), the number of meters in 1 gram of yarn. For example: Nm 80 indicates that a yarn weighs 1 gr
- The number in kilograms (Nkgm) indicates how many metres of yarn there are in 1000 gr. (This number is used mainly for the count of thick yarns, such as "Pratese" and "Biellese")
- The number of English cotton count (Ne – Nec – Ne cotton) indicates number of a hank of 840 yards (768,096 m) of yarn in one English or American lb (453.5924 grams). For example: Ne 1 means that a hank of yarn of 768.096 metres weighs 453.5924 grams
 - The number Pratese (Np) indicates the hank of 583 metres (equivalent to 1.000 Tuscan arms)

There are 339.50 grams (equivalent to a Tuscan pound). The conversion of number Nm in number Ne is obtained as follows: Nec x 1.693 = Nm


The twisting of cotton

The twisting of cotton increases the resistance to breakage and rubbing, and reduces the effect of pilling, as well as obtaining greater surface regularity and uniformity. The letters (S) and (Z) indicates the direction of the twist of the fibre, which corresponds to the direction of the oblique line of the letter, that form spirals when the yarn is held vertically. Simple twists are composed of two or more single-ply yarns, joined by a single twist operation; complex yarns are formed by two or more single-ply twisted yarns joined by a single or several twist operations.


The main principles of ennobling cotton

Mercerizing consists of treating cotton yarn in a solution of caustic soda (sodium hydroxide NaOH) to make the section of the yarn more circular, thereby making it more shiny and strong. The crease resistant finish, improves the elasticity of cotton through synthetic resins but compromising its strength the capacity to absorb although reducing the drying time. The anti-shrink finish is an additional methodology that prevents the shrinking of the textile. With a waterproof finish, the textiles are impregnated with special chemical products (silicones) so as to render them less permeable to humidity.