What Is Cotton?

How is cotton made?

Cotton is made by harvesting the fibre that grows in the seed bolls of the cotton plant, separating it from the seed, then spinning it into yarn that is woven or knitted into cloth. EU law defines it simply as fibre “obtained from the bolls of the cotton plant (Gossypium)”.

1. Growing. Cotton comes from several species. Upland (Gossypium hirsutum) is native to Mexico and Central America. Pima (G. barbadense) is of early South American origin. The Old World species, G. arboreum and G. herbaceum, are native to India and Eastern Asia according to Cotton Incorporated’s classing handbook, though its CottonWorks guide places G. herbaceum in sub-Saharan Africa and Arabia.
2. Ginning. A gin separates the fibre from the seed. Upland is saw ginned. Pima is roller ginned, which leaves it looking less smooth.
3. Classing. Practically all cotton grown in the United States is classed by the US Department of Agriculture (USDA), which measures fibre length, strength, fineness and colour.
4. Spinning and fabric making. The fibre is spun into yarn, then woven into cloths such as poplin, twill, canvas and denim, or knitted into jersey.
5. Finishing. The cloth is dyed or printed and may be finished, for example by mercerising. Mills can also compact knits to reduce the shrinkage left in them.

What are the properties of cotton?

Cotton’s behaviour in a garment depends on a few measurable fibre traits and on how the yarn and cloth are built from them. Cotton Incorporated’s classing handbook links each trait to what ends up in the shop:

• Length. Fibre length affects yarn strength, yarn evenness and how fine a yarn can be spun. Cotton with a wide spread of fibre lengths is likely to produce low-quality yarn.
• Strength. Fibre strength and yarn strength are highly correlated.
• Fineness and maturity. Micronaire, an airflow test, measures both. The more mature the fibre, the better it absorbs and holds dye. Very fine, low-micronaire cotton needs slower processing to avoid fibre damage.
• Colour. Raw American Pima cotton is a deeper yellow than American upland.
• Shrinkage. How much a cotton cloth shrinks depends on how much its yarns bend and how much open space the fabric has. Knits are more open than wovens and more prone to shrink.

How is cotton graded?

Cotton is graded on fibre length, length uniformity, strength, micronaire, colour, leaf (plant debris) and other trash content, and in the United States these are measured by the USDA.

Length is the average length of the longer half of the fibres, called the upper half mean length. It is reported in hundredths and in 32nds of an inch. Strength is reported in grams per tex; one tex is the weight in grams of 1,000 metres of fibre.

The names you see on labels mostly describe species or origin, and only some of them tell you about length:

Sources differ slightly on where Pima starts. Cotton Incorporated’s CottonWorks guide gives 1⅜ inches or more, while its USDA-based classing handbook gives a Pima range starting at 1¼ inches. The handbook also gives upland a wider range, starting below 1 inch. “Egyptian cotton” is simply cotton from Egypt, where both upland and Pima are grown, so the name alone says nothing about staple length.

How does cotton appear on a clothing label?

Cotton appears on a label under its legal generic name, “cotton”, with its percentage by fibre weight; in both the US and the EU, fibres are listed from the largest share to the smallest.

United States

• Fibres under 5% may be grouped as “other fiber” or “other fibers”, except wool, which must always be named.
• Labels have a 3% tolerance for fibre content, but none when the label claims a single fibre. A blouse deliberately made 97% silk and 3% polyester cannot be sold as “100% silk”, and the same applies to “100% cotton”.
• “All cotton” may be used instead of “100% cotton”.
• “100% Pima Cotton” is allowed only if every fibre is Pima. Under Federal Trade Commission (FTC) guidance, “100% Cotton, Pima Blend” without the Pima percentage is unacceptable.
• Advertising that mentions a premium cotton, such as Pima or Egyptian, must not suggest the product is made only of it unless that is true. A fibre trademark must not imply a product is made entirely of one fibre if it is not.

European Union

• “Cotton” is the name listed for this fibre in Regulation (EU) No 1007/2011.
• “100 %”, “pure” or “all” may be used only for products made exclusively of one fibre. Up to 2% by weight of extraneous fibres is allowed (5% for carded products), but only when technically unavoidable and not added routinely.
• Blends must state every fibre and its percentage by weight, in descending order.
• The label must be in the official language or languages of the member state where the garment is sold, unless that state allows otherwise.

The order is quickest to read. On “polyester 60%, cotton 40%”, polyester is the main fibre by weight.

How do you tell good cotton from poor cotton?

Good cotton shows in an even, firm yarn, uniform colour and a label that states exactly what is in it; all three can be checked in a shop.

1. Read the fibre-content label first. “Pima” on a blend must come with its percentage. “Pima blend” with no figure is a red flag under FTC guidance.
2. Treat “Egyptian” as a place, not a grade. Both species grow in Egypt, so the word does not promise extra-long staple fibre.
3. Hold the cloth up to the light and look along the yarns. Fibre length and length uniformity drive yarn evenness, so frequent thick and thin places in a plain cloth can point to poorer fibre or spinning. Slub fabrics are uneven on purpose.
4. Check how open the fabric is. The more open space a cloth has, the more it can shrink. A loose T-shirt jersey you can easily see through is a shrinkage risk.
5. Look at a solid colour in daylight. Dye uptake depends on fibre maturity. Streaky or patchy colour on a piece meant to be one shade is a warning sign.
6. Check after the first wash. Seam puckering and skew are among the shrinkage-related changes Cotton Incorporated’s quality guide lists. If they appear after a wash at the care-label setting, the garment still held residual shrinkage.

How do you care for cotton?

Care for cotton by following the garment’s permanent care label, which US rules require on clothing, and by expecting knits to shrink more than wovens.

Mills reduce the shrinkage left in cotton with relaxation dryers, compactors or crosslinking agents. Compaction is used mainly on knits such as underwear fabrics and tubular goods. How much a garment changes still depends on how it is washed and dried, so the care label is the instruction to follow.

Is cotton sustainable?

Cotton is neither automatically sustainable nor automatically harmful: its footprint depends heavily on where and how it is grown, and global water figures are averages that hide large differences between countries.

• Scale. Textile Exchange reports 24.4 million tonnes of cotton produced in 2023, out of 124 million tonnes of all fibres: about a fifth. Polyester made up 57%.
• Programmes. In 2023, 28% of all cotton was produced under sustainability programmes, according to Textile Exchange.
• Organic. Organic cotton describes the farming method, not the species or the fibre quality. Any species can be grown organically.
• Water. A 2005 UNESCO-IHE study put the global average at 9,359 cubic metres of water per tonne of finished cotton textile, using 1997–2001 data. Roughly half was rainfall used by the crop, and half was surface and groundwater. The study counted water needed to dilute processing pollution separately.
• Origin matters. The same study found the figure per tonne of textile ranged from 5,404 cubic metres for China to 21,563 for India.

So a single water figure says little about a specific shirt. The useful questions are where the cotton was grown and under which programme or certification.