Many products – such as textiles, inks/paints/coatings, plastics and paper – are coloured with dyes and pigments. These colours can change and fade over time due to the effects of various environmental factors such as water, light, rubbing, washing and perspiration. Colour fastness is a measure of a dyed fabric’s ability to retain its original colour and not bleed or transfer onto other materials or objects.
There are a number of tests that can be performed to determine the degree to which a fabric’s colour is resistant to fading, bleeding or running. These include the abrasion test (ISO 105 E04), the perspiration test (ISO 105 E05), the light fastness test (ISO 105 L1) and the rubbing/crocking test (DIN EN 20105-A03). Other tests can be performed to determine a fabric’s resistance to ironing, bleaching and weathering.
Fading is a common problem that can occur in fabrics, particularly with polyester, silk, wool and cotton. These fibres can become weakened by repeated washing and rubbing, and this can cause the dyes to break down and run or transfer to other fabrics and surfaces. Fading can also occur in light-coloured fabrics due to sunlight or artificial lighting and is often more noticeable on lighter shades of garments.
To assess a fabric’s light fastness, a sample of the product is placed in a light box and subjected to a standard machine which emits artificial daylight. A standardized grey scale is then used to evaluate the level of colour deterioration. A fabric with a high light fastness rating will have little to no fading.
When a coloured fabric is exposed to rubbing or crocking, it can lose its colour and bleed into other materials such as cotton. The rubbing/crocking test (DIN ISO 105-E04 or AATCC 15) is a test that evaluates the level of colour deterioration and staining of a dyed and non-dyed sample of the fabric against a set of grey cards. A fabric with a good rubbing/crocking test rating will have minimal to no colour deterioration or fading, and it will not bleed onto the grey card.
This type of testing is usually carried out by a professional testing laboratory such as SGS or Bureau Veritas(BV). Alternatively, a fabric manufacturer can carry out its own in-house rubbing/crocking and wash resistance tests. However, this can be a costly exercise and is best left to a third party, which can ensure the results are impartial and accurate. A good rubbing/crocking and wash test can prevent unnecessary returns from disgruntled customers and protect a brand’s reputation.