Cotton Lint

Each lint fibre is a single elongated cell that grew out of the cotton seed coat and then dried into a flat, twisted ribbon. That natural twist — the convolution — is why cotton fibres grip one another when drawn and twisted, and therefore why cotton spins at all. The commodity is a mass of these cells, cleaned of seed and most trash, and pressed into a bale dense enough to ship economically.

Lint is not homogeneous across the crop. Upland cotton accounts for the bulk of world supply; extra-long staple types, ginned on roller gins rather than saw gins, occupy a distinct and higher-priced segment. The species and type determine the range of fibre properties available, and no amount of processing at the gin can lengthen a staple that the plant did not grow.

Lint quality is described by a group of measured attributes, most of them now determined instrumentally rather than by eye. They are not interchangeable and a bale is not summarised by one number: a spinner reads them together, because they describe different things about what the fibre will do on a machine.

Staple length

The length of the fibres in the sample. It sets the yarn counts a lint can be spun to and is one of the strongest drivers of price.

Micronaire

An airflow measurement reflecting fibre fineness and maturity together. Both very low and very high readings are discounted, so it is a value with a preferred range rather than a "more is better" attribute.

Strength and uniformity

Fibre bundle strength, and how consistent fibre length is within the sample. Low uniformity means more short fibre and more waste in spinning.

Colour and leaf grade

Reflectance and yellowness, and the amount of leaf trash left after ginning. Both affect appearance and dyeing, and both reflect weathering and gin cleaning.

Classing systems and their grade names are national and versioned, and the same bale can be described differently under different systems. AgricultureID reproduces no thresholds or grade tables: those belong to the issuing standard and to the contract that invokes it.

Some lint faults originate in the field and the weather — weathered, spotted, or grey cotton, and immature fibre that reads low on micronaire. Others are made at the gin: seed-coat fragments carried through with the fibre, neps, and fibre breakage from over-aggressive cleaning of over-dry cotton. Stickiness, caused by insect honeydew deposited on the fibre before harvest, is a particular commercial problem because it fouls spinning machinery and is not visible in a sample.

Contamination is the defect the modern lint trade cares about most. Fragments of polypropylene twine, module wrap, plastic sheeting, hair, or jute enter with the seed cotton, survive ginning, and are only discovered when they appear as a flaw in dyed fabric — by which point the cost is enormous relative to the bale. The response is preventive, and it runs backwards from the spinner through the merchant to the gin and the field, since nothing at the gin reliably removes what should never have entered.

Lint leaves the gin as a pressed bale, wrapped and strapped, carrying a permanent identification that ties it to its classing data throughout its life. Bales are stored dry and under cover: lint takes up and gives off moisture with the air, and both very dry and damp bales are problems — the first because dry fibre is brittle and static-prone, the second because damp lint yellows, moulds, and, in a warehouse full of compressed fibre, presents a fire risk that dominates storage design.

Not all fibre on the seed leaves with the lint. The saw gin takes the long fibres and leaves a layer of short fuzz still attached to the seed; those short fibres are recovered separately, downstream, as linters. They are a residual stream of the ginning chain rather than a second grade of lint, and they are treated as a by-product here.