Reference
Yarn faults and defects
Every spun yarn carries faults. The question is not whether they exist but whether there are few enough, and small enough, that they never reach the finished garment.
This page covers the main faults, what causes them, what they cost downstream, and which tolerances are worth writing into an order.
Why yarn faults are a commercial problem, not a technical one
A fault that costs a rupee or two per kilogram to avoid at the spinning stage can cost hundreds of rupees per garment at final inspection — and considerably more if it reaches the customer.
The asymmetry is the point. Yarn is the cheapest place in the chain to fix a quality problem and the most expensive place to ignore one. A fault in a cone becomes a fault in a fabric roll, then a fault in a cut panel, then a rejected garment with all the value already added.
The main yarn faults
| Fault | What it looks like | Usual cause | Remedy |
|---|---|---|---|
| Slub | Abnormally thick, low-twist lump | Fly and fluff accumulation, poor carding, defective drafting, bad piecing | Clean machine surfaces, check roller clearers, retrain piecing |
| Neps | Small tangled knots of fibre | Immature or short-staple cotton, over-beating in blowroom, worn card clothing | Better cotton selection, gentler opening, card clothing maintenance |
| Thick places | Localised increase in diameter | Drafting irregularity, worn or eccentric top rollers | Roller setting, replacement schedule |
| Thin places | Localised reduction in diameter | Uneven drafting, roving weight variation | Check roving evenness and draft settings |
| Snarls | Yarn kinking and twisting on itself | Excess twist, insufficient setting | Reduce twist multiplier or steam-set the yarn |
| Soft or weak yarn | Low strength, frequent breaks | Slack spindle tapes, low twist, poor traveller clearing | Check tapes, twist level, replace worn rings and travellers |
| Hairiness | Protruding fibre ends | Short fibre content, high spindle speed, poor traveller condition | Fibre selection, compact spinning, traveller change |
| Oil stains | Discoloured patches on the package | Lubrication contamination | Lubrication discipline and guard maintenance |
| Foreign matter | Coloured fibre, jute, hair, plastic | Contaminated cotton, poor manual picking | Contamination sorting, better cotton source |
| Count variation | Weight per unit length drifts | Roving variation, frame-to-frame differences, mixing errors | Frame audit, mixing discipline, count checks per shift |
How faults are measured
Evenness testing on Uster or equivalent equipment is the industry standard. Four numbers matter most:
U% and CV% describe mass variation along the yarn. CV% is the more useful of the two, and lower is better. IPI is the combined count of thin places, thick places and neps per kilometre. Hairiness (H) describes protruding fibre. CSP gives strength normalised for count — use the CSP calculator to work it out.
A single test on a large lot tells you very little. Ask how many tests were run and across how many machines — consistency between frames is usually what causes trouble, not the average.
Realistic tolerances by count
These are working ranges for ring-spun cotton. Open-end yarn runs differently and should be judged against open-end benchmarks.
| Count | CV% (good) | IPI (good) | Notes |
|---|---|---|---|
| 20s carded | 12 – 14 | 200 – 350 | Weft, coarse knits, towels |
| 30s carded | 13 – 15 | 250 – 400 | Standard commodity yarn |
| 30s combed | 10 – 12 | 80 – 160 | Warp and quality knitwear |
| 40s combed | 11 – 13 | 100 – 200 | Fine shirting, premium tees |
| 60s combed | 12 – 14 | 150 – 280 | Voile and fine counts |
| 30s compact | 9 – 11 | 50 – 120 | Premium; lowest hairiness |
The faults that only appear after dyeing
Some problems are invisible in the cone and obvious in the finished fabric. These are the expensive ones.
Barré is horizontal shade banding, usually caused by count variation or by mixing yarn from different lots or frames. Shade variation across a programme comes from lots dyed at different times. Contamination shows as coloured specks that only appear once the ground is dyed.
All three are avoidable by buying the full programme quantity in a single lot. It is almost always cheaper to carry a small surplus than to re-dye.
What to ask your supplier for
Ask for the mill test report against your specification, and state which parameters you will judge on before the lot ships. We can provide mill test reports for the yarn we supply.
If a parameter is not on the report, it was not tested. “Best quality” on an order is not a specification — see our guide to writing a yarn specification.
Frequently asked questions
What causes slubs in yarn?
Usually fly and fluff accumulating on machine parts, poor carding, defective ring frame drafting or bad piecing. Clean surfaces and functioning roller clearers prevent most of them.
What are neps in yarn?
Small tangled knots of fibre, generally caused by immature or short-staple cotton, over-aggressive opening in the blowroom, or worn card clothing.
What is a good CV% for cotton yarn?
Roughly 10 to 12 per cent for 30s combed and 13 to 15 per cent for 30s carded. Lower is better, and compact yarn goes lower still.
What are IPI values?
The combined count of thin places, thick places and neps per kilometre of yarn. Good 30s combed runs around 80 to 160.
What causes barré in fabric?
Most often count variation or mixing yarn from different lots or spinning frames. It shows as horizontal shade banding after dyeing.
Do you supply yarn with test reports?
Yes. We can provide mill test reports against your specification. Tell us which parameters you want covered 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