Pilling is one of the most disputed tests in textile quality control. Same fabric, same standard, two laboratories — two different grades. The buyer rejects the lot, the supplier objects, and nobody can prove who is right.
In most cases the instrument is not the problem. The disagreement comes from five details in ISO 12945-2 that are easy to overlook and that each move the grade in a predictable direction.
1. Conditioning is skipped
This is the most common one. ISO 139 requires the specimen to rest at 20 ± 2 °C and 65 ± 4 % relative humidity for at least 24 hours before testing. An unconditioned specimen — especially cotton or viscose — enters the test with a different moisture content.
Moist fibre is softer. Surface fibres lift more easily but break less readily, so they stay on the surface and roll into pills. The practical consequence: the same fabric graded in winter and in summer gives different results. If your test room is not conditioned, your results depend on the weather.
Quick check: keep a thermohygrometer log and record temperature and humidity at the time of test on the report. In a dispute this is the first thing that will be asked for.
2. The wrong abradant is used
In ISO 12945-2 the abradant is the fabric itself — specimen rubs against specimen. Some product specifications instead call for the box method (ISO 12945-1) or for a standard abradant fabric.
These methods do not give the same grade and there is no conversion between them. If the specification does not state the method explicitly, ask the customer before you start. Discovering afterwards that they expected the box method means running the test again.
3. Load and cycle counts are mixed up
ISO 12945-2 uses a nominal pressure of 155 g/cm² or 415 g/cm² for pilling, with assessment at defined intervals: 125, 500, 1000, 2000, 5000 and 7000 rubs.
A frequent mistake is applying the abrasion load to a pilling test. The Martindale instrument performs both tests, but the loads and specimen holders differ. Too much load wears the fabric faster than the method intends and typically costs one to two grades.
| Test | Standard | Load | Assessment |
|---|---|---|---|
| Pilling | ISO 12945-2 | 155 or 415 g/cm² | 5-step visual grade |
| Abrasion | ISO 12947-2 | 9 or 12 kPa | Cycles to yarn breakdown |
4. Assessment lighting is not controlled
The pilling grade is assigned visually, by comparing the specimen with reference photographs. That assessment must be made under directional lighting — light arriving across the fabric surface so that pills cast shadows and become visible.
Under flat overhead office lighting the same specimen looks roughly one grade better. Assess in a standard viewing cabinet, with the same geometry every time.
5. A single specimen decides the result
The standard requires at least three specimens and the reported result is their median. A grade based on one specimen may reflect the fabric direction or a local defect rather than the lot.
Cut specimens from different areas of the fabric, at least 10 cm in from the selvedge, and avoid repeating the same set of yarns across specimens.
Checklist before you report
- Was the specimen conditioned for 24 hours, and were temperature and humidity recorded?
- Which method does the specification require — ISO 12945-1 or 12945-2?
- Was the load chosen for pilling, not for abrasion?
- Was the grade assigned under directional lighting?
- Is the reported value the median of at least three specimens?
Two laboratories that control these five points usually agree within half a grade on the same fabric. Laboratories that do not can differ by two grades — which is the difference between acceptance and rejection.