Write the fibre spec from your count programme
Staple, micronaire, strength, grade and trash for cotton; denier, cut length and tenacity for polyester and viscose. The tonnes decided by the counts you spin, not by what is on offer.
A quotation for something unspecified is a quotation for the cheapest thing the words cover. The vocabulary below defines every line of the spec; the blank sheet turns it into a form you can send, so every supplier prices the same stated thing and the quotes compare.
The words a supplier will use at you, and what each one costs you 11 terms
Cotton is not one product. Six measured properties decide what it can be spun into and what it is worth, and every one of them is on the classing report that comes with the bale. A quotation without them is a quotation for something unspecified.
- Staple length
- The length of the fibre, in millimetres or in thirty seconds of an inch. It sets the finest count that can be spun at all, by degrees rather than at one cut-off: 28 mm upland spins comfortably to about 30s, good combed upland reaches the 40s and 50s, and from roughly 60s upward a mill will start asking for extra long staple, which is not optional at 80s and above. Where exactly the line falls depends on the spinning system and the quality you want. Longer fibre also gives a stronger, smoother, less hairy yarn at the same count.
- Micronaire
- Fineness and maturity in one reading, from an air flow test. The premium band is about 3.5 to 4.9. Below it the fibre is immature and takes dye unevenly, which is where barré and shade patches come from. Above it the fibre is coarse, so fewer fibres sit in the yarn cross section and the yarn is weaker for the same count.
- Strength
- Grams per tex on the classing instrument. Around 28 to 30 is ordinary upland; above 30 is strong. It carries straight through into yarn strength and into how often the spinning frame breaks, which is a cost the mill pays and prices in.
- Uniformity and short fibre content
- How much of the sample is much shorter than the rest. A high short fibre content means waste at every stage, more neps, a weaker and hairier yarn, and it is the property most often quietly out of line in a cheap lot.
- Colour grade
- Reflectance and yellowness, reported as a grade. It decides whether the cotton can go into a white or a pale pastel at all. A yellow lot can be bleached, but bleaching costs money and takes strength out of the fibre.
- Trash and leaf
- Non lint matter: leaf, bark, seed coat. It comes out in cleaning, and everything that comes out was paid for by weight. Two lots at the same price per pound are not the same price per pound of usable fibre.
- Contamination
- Polypropylene from bale wrapping, jute, hair, cloth. Not graded, not on the report, and the single most expensive fault in cotton, because a contaminated bale is only discovered as a fault in the finished fabric after every conversion cost has already been spent.
- Moisture regain
- Cotton is settled at 8.5 per cent commercial regain. It is a trade convention for weighing, not a measurement of the bale in front of you, and a lot arriving wetter than that is a lot you are paying for water on.
- Polyester staple: denier and cut length
- The two numbers that decide what it can be blended with. Denier is the fibre fineness; cut length is chosen to suit the spinning system, typically around 38 mm for a cotton system blend. A mismatch to the cotton it is blended with shows up as unevenness.
- Polyester staple: bright, semi dull or dull
- How much titanium dioxide is in the fibre. It changes the look of the finished cloth and it is not adjustable later, so it belongs on the order rather than in a conversation.
- Virgin or recycled polyester
- Recycled staple made from bottle flake behaves differently: shorter effective length, more variation between lots, and a shade that is harder to hold. If a certification such as GRS is being claimed, the certificate is the thing to ask for, not the claim.
What to put on the order for a bale of fibre
Every line below is one you can be given a straight answer on. A supplier who will not put one of them in writing is telling you something, and it is usually the most useful thing you will learn in the negotiation.
- Origin and crop year, because a two year old bale is not the same fibre.
- Staple length, micronaire, strength, uniformity and colour grade, as a range with a minimum, not a single target figure.
- The maximum short fibre content and trash content you will accept.
- A contamination clause, and who pays when contamination is found downstream.
- The weight basis: at what regain, and weighed where.
- For polyester: denier, cut length, lustre, tenacity, shrinkage, and virgin or recycled with the certificate named.
Cotton properties as measured by high volume instrument classing, which is the basis USDA and most origins report on. Ranges above are typical published values for orientation, not a specification.
These are standard trade definitions and typical published ranges, compiled by VeriMills for orientation. They are not a specification, they do not replace a test report, and where a figure here differs from your contract, your contract is the one that binds.
Buying polyester or viscose staple instead of cotton? The twelve steps hold, but the spec words and the price sources change: the man-made fibre section carries both, with the live prices.
Take it with you a blank specification sheet for a bale of fibre: a calculator with live formulas , with its sources, its licence and a sheet explaining every column inside the file.
Tools for this step
- Natural fibre properties
Check a claim about staple length, micronaire, tenacity or regain against the published range before it becomes a contract specification.
- Man-made fibre properties
Look up the melt temperature, regain and wet strength of a synthetic before deciding whether your blend survives the finish you want.
Every tool for this guide, grouped by what you are trying to do, is on the tools page.
