How do I read colour fastness ratings on the grey scale?

Main answer

Colour fastness is reported as grades for colour change and for staining, tested separately for washing, rubbing, perspiration and light, and each test has its own method and scale. Ask the supplier which tests matter for your product, what method and grade each one reached, and set a minimum grade for each in the quotation. Reports also state the fibre of the adjacent cloth used for staining, which affects the result.

One colour, several tests

A colour that survives washing may still rub off or fade in light, so fastness is not one number. ISO 105-C06 covers colour fastness to domestic and commercial laundering. ISO 105-X12 covers rubbing, tested dry and wet. ISO 105-E04 covers perspiration. ISO 105-B02 covers artificial light using a xenon arc lamp. AATCC publishes comparable methods, such as TM15 for perspiration.

The scales

Colour change and staining are assessed visually or instrumentally against grey scales, where a higher grade means less change or staining. Light fastness uses blue wool references instead, with a different numbering. The rubbing method assesses staining on the white cotton cloth with a grey scale. Always read which scale applies to which result in the report.

Which tests matter for your product

Activewear needs perspiration and washing. Dark cotton hoodies need washing and rubbing. Items displayed or worn in strong sun need light fastness. Contrast panels need staining on adjacent fabric. Choose the tests by use and not by a generic checklist, and ask for results on your exact colours, since fastness differs by shade.

Setting minimum grades

Decide a grade for each test with your customer’s expectations and any retailer requirements in mind. Ask the supplier to confirm it can meet them before you order, and who pays if a lot fails. Keep reports by lot. See options on sportswear and hoodies.