The indigenous species was Gossypium hirsutum , which is today the most widely planted species of cotton in the world, constituting about 89.9% of all production worldwide. The greatest diversity of wild cotton species is found in Mexico, followed by Australia and Africa.
"Cotton has been spun, woven, and dyed since prehistoric times. It clothed the people of ancient India, Egypt, and China. Hundreds of years before the Christian era cotton textiles were woven in India with matchless skill, and their use spread to the Mediterranean countries. In the 1st cent. Arab traders brought fine muslin and calico to Italy and Spain. The Moors introduced the cultivation of cotton into Spain in the 9th cent. Fustians and dimities were woven there and in the 14th cent. in Venice and Milan, at first with a linen warp. Little cotton cloth was imported to England before the 15th cent., although small amounts were obtained chiefly for candlewicks. By the 17th century the East India Company was bringing rare fabrics from India. Native Americans skillfully spun and wove cotton into fine garments and dyed tapestries. Cotton fabrics found in Peruvian tombs are said to belong to a pre-Inca culture. In color and texture the ancient Peruvian and Mexican textiles resemble those found in Egyptian tombs."
Cotton fibers looked at with a Scanning Electron Microscope Prisoners farming cotton under the trusty system in Mississippi - 1911 Picking cotton in Georgia , United States, in 1943 Cotton exhibit at the Louisiana State Exhibit Museum in Shreveport . Louisiana has been a major cotton produce
Nitragenous manures are applied during the early stages of growth and later on phosphatic manures to cause early and uniform ripening of the CAPSULES or BOLLS……….
The bolls are ripe about 50 – 60 days after the flower has fallen and they dehisce by 3 – 5 valves,exposing the seeds which are contained in a similar number of LOCULI.
Each boll contains about 36 seeds ………
The “ COTTON” as the seeds with the trichomes attached are termed technically,is picked by hand at a time when there is neither rain nor dew and is carefully dried in the shade on hurdles until the seeds can be cracked between the teeth
The seeds are then transferred to a “ GIN” which is a machine for separating the trichomes or LINT from the seeds .
In this machine the seeds are fed by a hopper on to a cylinder formed of a set of finely toothed circular saws placed side by side ,these drag the hairs from the seeds and the hairs are removed from the saws by a cylinder of rotating brushes and drawn up an inclined collecting shaft to pass between 2 rollers which compress them in to a felt.
This felted “ lint ” is made in to bales by hydraulic pressure …
Hairs which are rejected by certain machinery during the preperation of cotton for spinning ,usually it is the “ COMBER WASTE ” of American and Egyptian cottons.
The “ COMBER WASTE “ is loosened by machinery and then heated with Dil.Caustic soda and Soda ash solution at a pressure of 1 – 3 atm for 10 -15 hrs.
This removes much of the fatty cuticle & renders the trichome wall absorbent .
It is then well washed with water,bleached with Sodium hypochlorite solution & treated with very Dil.HCL .
After washing & drying it is in a mattened condition and is there fore opened by machines & then scutched this is converted in to a continous sheeet of fairly even thickness with the fibres loosened ready for the carding machine .
The carding machine effects a combing operation & forms a thin continous film of cotton wool.
Several such films are superimposed on one another , interrelated with paper & packed in rolls.
This treatment removes the cuticle which consists of fatty matter composed of wax with stearic and palmitic acids .
Cotton had to be picked several times in the season because bolls of cotton do not all ripen at the same time.
The cotton gin, created by American inventor Eli Whitney (1765–1825) in 1793, mechanized the process of separating seeds from fibers, revolutionizing the cotton industry.
Before going to the gin, harvested cotton is dried and put through cleaning equipment that removes leaves, dirt, twigs, and other unwanted material.
After cleaning, the long fibers are separated from the seeds with a cotton gin and then packed tightly into 500-pound (225-kilogram) bales.
Cotton is classified according to its staple (length of fiber), grade (color), and character (smoothness).
At a textile mill, cotton fibers are spun into yarn and then woven or knitted into cloth. At an oil mill, cottonseed oil is extracted from cotton seeds for use in cooking oil, shortening, soaps, and cosmetics.
The plant Cotton plants can grow into shrubs 6 to 20 m high, although they are usually much smaller in cultivation . Leaves – broad and have three to five (or even seven) lobes. Fruits – creamy-white flowers are produced that later turn deep pink and fall off, leaving seed pods called 'cotton bolls'. Inside the bolls are seeds surrounded by fibres which are spun into thread for cloth. These cotton fibres are used to make 40% of the world's textiles . Absorbent cotton Raw cotton Absorbent cotton wool is a loosely felted mass of delicate filaments , soft to touch & WHITE in colour . This sinks in water. Raw cotton has a slight brownish tint, a colour is due to dried remains of protoplasm & cell contents the wall of trichomes being quite transparent & colour less. Non absorbent & floats on water Due to fatty substance in cuticle.
Cotton consists of trichomes which are tubular and flattened and show numerous twists ,which may be in either direction or may change direction in the same trichome .
The edges of the flattened trichome are rounded and show the thickness of the wall as a distinct margin occupying about one sixth of diameter on each side.
The wall consists of cellulose and the layer lining the lumen has a firmer consistence than the remainder and often shows ,when treated with reagents ,a double spiral structure .
The apex is rounded and has often a very strongly thickened wall ocasionally it is solid .
The width of the trichomes is 10 – 16 -30 – 40 microns and length from 30 – 40 mm in absorbent cotton wool the “staple” as the length of trichomes is termed technically, should not be less than 16 mm .
The standard staple Is comparatively short because absorbent cotton is made from “waste”. which consists of short fragments of trichomes.
Raw cotton can be distinguished microscopically from absorbent cotton by its behaviour towards “CUOXAM”.
When trichomes are soaked in aqueous Ruthenium red (8 mg in 10 ml), the excess reagent removed and cuoxam added,the cuticle is stained red & can be shrinking to form constricting bands while the inner layers of the wall swell to form globular enlargements .
This indicates that the cutin is distributed throughout the primary wall which contains pectic substances.
The trichomes as they exist in the capsules before dehiscence , are quite cylindrical and exbhit no twists ,the flatness and twists arise during drying in the air & sun.
The twists are due to the variation in density of the different parts of the wall ,especially to the presence of the denser part lining the lumen and to the strains producedby the contraction of the cuticle .
Twists are more numerous in the finest cotton from about 150 in Indian Surat cotton to 300 in Sea island cotton.
It is to the twists that cotton owes the property of being suitable for spinning in to a thred ,a property that is not possessed by trichomes of other plants ,such as bombax,which are cylindrical and devoid of twists.
27–54 27–54 Wood pulp 10–14 22–27 Rayon (regular) 30–54 27–45 Cotton Wet Dry Fiber Table 6 Dry and wet strengths of fibers (g/tex)
The chemical composition of Raw cotton is as follows: cellulose 91.00% water 7.85% fatty substances 0.40% mineral salts 0.20% pectins 0.55% protoplasm & other cell contents 0.6% Moisture 7.8% , waxes . Raw cotton Absorbent cotton The chemical composition of Absorbent cotton is as follows: Purified absorbent cotton is almost pure cellulose , Moisture 6 – 7 % & yields 0.1 – 0.3 % of ash .
Cellobiose- note the 1,4 linkage between the glucose residues. Below is cellobiose in relation to the glucose chain, n subunits (typically 25k to 250k) constitute a single chain.
On ignition ,which should be done both by advancing the fibre towards a flame & by heating on porcelain , cotton burns with a flame ,gives very little odour or fumes ,does not produce a bead, and leaves a small white ash.
Moisten with N/50 Iodine and , when nearly dry , add 80% w/w Sulphuric acid , a blue colour is produced.
With Ammonical copper oxide solution , Raw cotton dissolves with ballooning ,leaving a few fragements of cuticle . Absorbent cotton dissolves completely with uniform swelling .
From the lint (the fiber separated from the seed) come the major products, chiefly textile and yarn goods, cordage, automobile-tire cord, and plastic reinforcing.
The linters (short, cut ends removed from the seed after ginning) are a valuable source of cellulose .
Cotton hulls are used for fertilizer, fuel, and packing; fiber from the stalk is used for pressed paper and cardboard.
The short fibres from cotton are used to make ice cream. Vegetable lambs In the Middle Ages many believed cotton came from 'vegetable lambs' dangling from trees in India. Fake cotton lambs made their way into museums. Cotton is used as a filtering medium. Chief constituent of many surgical dressings. It is an insulating material. STORAGE
Bacteria & fungi can not attack cotton if the moisture content is below 0.9%.
Bacterial damage makes cotton fibres brittle & friable so that the cotton wool
becomes dusty .
Heat renders absorbent cotton non absorbent .
Absorbent cotton should be wrapped in paper in such a way as to exclude