A specification says "wash fastness to ISO 105-C06: 4". The supplier tests and reports 4–5 for colour change. The buyer's lab reports 3 for staining on the nylon stripe. Both reports carry the same standard number.
In most of these cases nobody has made a mistake with the machine. They have run different tests, because "ISO 105-C06" on its own does not define a test. The test code does.
The code is the test
ISO 105-C06 contains a table of test procedures, each with a short code such as A1S, A2S, B2S or C2S. Each code fixes the temperature, the liquor volume, the number of steel balls, whether bleach is added, the pH and the time. Read the code in three parts:
| Part of the code | What it tells you |
|---|---|
| Letter (A, B, C, D, E) | Temperature band — A is the 40 °C test, C is the 60 °C test, and the series climbs towards the 95 °C tests |
| Number (1 or 2) | Without (1) or with (2) sodium perborate as the bleach component |
| Last letter (S or M) | Single (S) or multiple (M) test |
The standard's scope explains S and M plainly: one S test closely approximates one domestic or commercial laundering, while one M test may in some cases be approximated by up to five launderings at temperatures not exceeding 70 °C. M tests are more severe because the mechanical action is increased.
So "C06, grade 4" is meaningless until somebody writes the code next to it. If the specification is incomplete, ask before testing — a 40 °C result and a 60 °C result for the same fabric are not comparable.
Mechanical action comes from liquor and balls, not only from heat
The standard states that the abrasive action is produced by a low liquor ratio and an appropriate number of steel balls. This is why the codes differ in more than temperature. In the commonly quoted conditions, A2S runs in 150 ml of liquor with 10 steel balls, while C2S runs in only 50 ml with 25 balls — far more mechanical action on the specimen.
Two habits break this:
- Counting balls by eye. Ten and twenty-five look similar in a palm. Use a dedicated counting tray or pre-counted pots per code.
- Topping up liquor "to cover the specimen". The volume is part of the test. More liquor means a higher liquor ratio and gentler action.
The apparatus itself is also specified: stainless steel containers of about 550 ml capacity on a shaft rotating at (40 ± 2) min⁻¹ in a thermostatically controlled bath, with stainless steel balls of approximately 6 mm diameter. If your rotation speed has never been checked with a stopwatch, check it.
Detergent: two references, not "any powder"
ISO 105-C06:2010 allows two reference detergents, both without optical brightener (WOB): the AATCC 1993 Standard Reference Detergent WOB, or the ECE Reference Detergent with Phosphates. The standard also asks for at least one litre of detergent solution to be prepared at a time, because the powder may not be homogeneous.
Common errors:
- A supermarket detergent "because it is closer to real life". It is not the test, and its brightener will make whites look better than they are.
- Weighing 0.6 g of powder for a single pot instead of making a litre of solution.
- Mixing up the two references between runs. Report which one you used.
Bleach: perborate is not optional on a "2" code
On codes with a 2, sodium perborate tetrahydrate is part of the liquor. Perborate loses strength in storage and in solution, so prepare it fresh. Where a test requires pH adjustment, the standard provides sodium carbonate for that purpose — measure the pH, do not assume it.
If a "2" code result is suspiciously good on a reactive dye known to be sensitive to oxidation, check the perborate first.
Choosing the right multifibre
The standard lets you use either a multifibre adjacent fabric to ISO 105-F10 or two single-fibre adjacent fabrics. The multifibre choice depends on temperature:
| Multifibre type | Contains | Use in ISO 105-C06 |
|---|---|---|
| DW | Diacetate and wool | Tests at 40 °C and 50 °C; in some cases at 60 °C if stated in the report |
| TV | Triacetate and viscose, no wool or acetate | Some tests at 60 °C, all tests at 70 °C and 95 °C |
The standard warns that perborate at 60 °C can damage the wool stripe. A damaged wool stripe cannot be graded honestly, so a C2S run on DW multifibre produces a staining result nobody should sign.
Single-fibre adjacent fabrics follow a pairing table: for a cotton specimen, the second piece is wool in the A and B tests but viscose in the C, D and E tests. Write down which option you used — the report has to.
Rinsing, drying, grading
After the wash, rinse and dry the composite as the method describes, with the parts touching only at the stitching. Then grade colour change with the ISO 105-A02 grey scale and staining with the ISO 105-A03 grey scale, in a viewing cabinet rather than under the ceiling lights. A grade read under office fluorescent light is a different grade.
Grade every stripe of the multifibre separately. "Staining 4" with no fibre named tells the buyer nothing about the nylon, which is usually the stripe that fails.
Before you report
- Is the test code written on the report, not just "ISO 105-C06"?
- Were the ball count and liquor volume the ones the code requires?
- Which reference detergent was used, and was the solution made in at least one litre?
- On a "2" code, was the perborate fresh?
- Is the multifibre type (DW or TV) right for the temperature?
- Were all stripes graded in a light cabinet?
Two laboratories that agree on these six points rarely differ by more than half a grade. TLI-TexLabInstruments builds its washing fastness tester in its own workshop in Istanbul; the grey scales and light cabinet needed to grade the result are in the same catalogue.