Colour Fastness to Perspiration: ISO 105-E04, AATCC 15 and Which Edition to Cite

1. What does a colour fastness to perspiration test actually measure?

Colour fastness, spelled color fastness in US usage and the same property either way, means the resistance of a colour to a defined stress: light, washing, rubbing, or in this case perspiration. The result is not a concentration, it is a grade. A specimen is exposed under controlled conditions and then read against a reference: the grey scale for change in shade of the specimen itself, and a second grey scale for staining of the undyed adjacent fabric held against it. Both are scored 1 to 5, where 5 is no perceptible change.

Two consequences follow, and both surprise people arriving from chemical testing. First, the number is ordinal: a 4 is better than a 3, but the interval between them is not a quantity. Second, the adjacent fabric matters as much as the specimen. A dye that holds its own shade perfectly and transfers heavily onto the multifibre strip has failed the test that matters commercially, because in wear that transfer lands on someone's skin or on the garment underneath.

Which stress is named matters, because the grades do not transfer. Colour fastness to washing (the ISO 105-C series) exposes the specimen to detergent, temperature and mechanical action; colour fastness to perspiration (ISO 105-E04) exposes it to a sweat solution under a load at body temperature. A dye can grade 4-5 to washing and 2 to perspiration, and a report that names the wrong one is not a near miss, it answers a different question.

2. Why does ISO 105-E04 need both an acid and an alkaline bath?

Human perspiration is not a single pH. It is acidic when fresh and drifts alkaline as it ages and as bacteria act on it, and dyes do not behave identically across that range: a dye can be perfectly fast in acid and bleed in alkali. That is why ISO 105-E04 runs an acid solution and an alkaline solution as a matched pair, and why a report that cites the standard and shows one bath is incomplete rather than merely brief.

This is the practical reason the two solutions are supplied as a kit rather than as separate bottles. A laboratory that runs the acid bath from one batch and the alkaline bath from another, prepared weeks apart, has introduced a variable into a comparison that is supposed to isolate the dye. The volumes match because the specimens are the same size in both baths.

3. Can an AATCC 15 result be reported against ISO 105-E04?

Both are perspiration colour fastness, both use an artificial sweat, and they are routinely treated as interchangeable by people specifying a test from a purchase order. They are not. The clearest difference for ordering purposes is that AATCC 15, the North American method, works with a single acid solution, at a lower pH than the ISO acid bath, while ISO 105-E04 requires the acid and alkaline pair described above.

The consequence is commercial rather than scientific. A buyer supplying both the European and the US market needs both fluids, and a laboratory that has only the ISO kit cannot produce an AATCC 15 report by using half of it. Where the two methods differ beyond the solution, in specimen assembly, in the load applied and in the conditioning, we would rather point you at your testing laboratory than paraphrase two documents we do not publish.

4. Which edition of the standard are you citing?

This comes up often enough to be worth stating plainly: check the edition before the audit, not during it. ISO 105-E04 has been revised, and a technical file that cites a withdrawn edition invites a question that costs more to answer than to prevent. The same applies to the national adoptions. BS EN ISO 105-E04, NF EN ISO 105-E04 and DIN EN ISO 105-E04 are the British, French and German publications of the same European text: one fluid serves all three, and the prefix tells you which national catalogue the copy came from and nothing else.

The version of this we are asked most often is whether ISO 105-E04:2013 is the one to cite. We will not answer that here with a year, and the reason is the point: whichever year we printed would be right until it was not, and a supplier page is the worst possible place to learn that a standard moved. Check the entry in your national body's catalogue, or ask the laboratory that will sign the report, and record the answer in the file with the date you checked it.

We deliberately do not publish a current edition number on this page. Editions move, a page does not, and a supplier stating the wrong one is worse than a supplier stating none. Your standards body or your testing laboratory holds the answer that is true today.