Reference
How to write a yarn specification
Most sourcing problems start with an incomplete specification. If you state only the count, the mill decides everything else — fibre, spin, twist, finish — and you find out what it decided when the fabric comes off the machine.
This page sets out what a complete yarn specification contains, with a worked example you can copy.
The six things every specification must state
Leave any of these open and someone else makes the decision for you.
| # | Parameter | Example | Why it matters |
|---|---|---|---|
| 1 | Count | 30s Ne | Sets fabric weight and hand |
| 2 | Fibre and blend ratio | 100% cotton, or PC 65/35 | Drives cost, dyeing route and performance |
| 3 | Spin type | Combed ring-spun | Determines evenness, strength and price |
| 4 | Twist | TM 3.4 (approx 18.6 TPI) | Controls handle, strength and spirality |
| 5 | Fold | Single, or 2-ply | Changes strength, evenness and cost |
| 6 | Finish | Grey / RFD / dyed to shade | Decides what processing is still needed |
The parameters that separate a good spec from a vague one
The six above make a spec workable. These make it enforceable.
| Parameter | What it controls | Typical ask |
|---|---|---|
| Count CV% | Shade banding after dyeing | Under 2% between lots |
| CSP or RKM | Yarn strength | CSP 2,300+ for combed warp |
| Evenness U% / CV% | Fabric appearance | CV% 10–12 for 30s combed |
| IPI | Visible faults per km | 80–160 for 30s combed |
| Hairiness (H) | Pilling and surface finish | Lower for compact yarn |
| Moisture regain | Invoiced weight | 8.5% standard for cotton |
| Shade tolerance | Colour continuity | Grey scale 4–5 or better |
You do not need every one of these on every order. But if a parameter is not on the specification, it will not be on the test report — and if it is not on the test report, it was not tested.
A complete worked example
This is a full specification for a knitting yarn. Copy the structure and change the values.
| Field | Specification |
|---|---|
| Product | Cotton hosiery yarn |
| Count | 30s Ne, single |
| Fibre | 100% cotton, combed |
| Spin | Ring-spun, combed |
| Twist | TM 3.4, approx. 18.6 TPI |
| Count CV% | Max 2.0% between lots |
| Evenness CV% | Max 12.0% |
| IPI | Max 160 per km |
| CSP | Min 2,300 |
| Finish | Grey (undyed) |
| Winding | Cone, 1.89 kg net |
| Packing | 12 cones per carton, 22.7 kg net |
| Quantity | 5,000 kg |
| Delivery | Single lot, ex-Delhi |
| Testing | Mill test report per lot, covering count, CV%, IPI and CSP |
What to say about testing
State how many tests, against which parameters, and what happens if a lot fails. A specification without a test clause is a wish list.
We can provide mill test reports for the yarn we supply. Tell us at enquiry stage which parameters you want covered, so the report you receive matches the specification you wrote rather than whatever the mill routinely prints.
Commercial terms that belong on the spec
Technical parameters describe the yarn. These describe the deal, and leaving them vague causes as many problems.
Lot size and whether the full quantity comes from one lot. Delivery schedule and whether staged call-offs are allowed. Packing configuration. Shade continuity across the programme. Basis of weight — conditioned or actual.
Shade continuity is the one most often forgotten and most often regretted. A second lot dyed weeks later will rarely match the first.
Six common specification mistakes
1. Count only. Everything else gets decided for you.
2. “Best quality”. Not a specification. It means nothing on an invoice and less in a dispute.
3. Copying a spec written for a different spin type. Carded tolerances applied to combed yarn, or ring-spun figures applied to open-end.
4. Omitting whether GSM or weight is greige or finished. The single most common cause of inspection disputes.
5. No shade continuity clause. Then discovering the second delivery does not match the first.
6. Specifying tolerances tighter than the process can hold. You will pay for them and still get rejections.
Frequently asked questions
What information do you need to quote yarn?
Count, fibre and blend ratio, spin type, twist, single or folded, finish, quantity and delivery city. Anything else you specify we will quote against.
What is a good CV% for cotton yarn?
Around 10 to 12 per cent for 30s combed and 13 to 15 per cent for 30s carded. Compact yarn runs lower.
Should I specify TM or TPI?
Either works. TM is more portable because it holds across counts; TPI is absolute. If you give one we will confirm the other.
How many tests should be run per lot?
Enough to show consistency between machines, not just an average. Ask how many frames were sampled, not only how many tests.
Can you supply against our own specification sheet?
Yes. Send your spec sheet and we will quote against it and confirm which parameters we can meet before you commit.
Do you provide test reports?
We can provide mill test reports for the yarn we supply. Tell us which parameters to cover when you enquire.
Need this quoted?
Send your count, blend and quantity and we will come back with firm pricing ex-Delhi and a lead time, within one working day.
Get a quote