Colour Fastness Test Protocols: What ISO 105 and AATCC Ratings Mean

What exactly does colour fastness measure and why does it appear on my report?

For a B2B buyer, colour fastness is measurable proof of how the shipped batch will behave once it reaches the end user. The colour achieved in the dyehouse to a target of ΔE<1 is washed, rubbed and exposed to sunlight during use; fastness tests reproduce exactly these real-life scenarios under laboratory conditions.

Fastness assessment is read along two separate axes. The first is colour change: how much the specimen's own colour has faded or shifted in hue after the test. The second is staining: how much the adjacent (accompanying) fabrics in contact with the specimen have been coloured by the bleeding dye. These two ratings are usually reported separately; for example, "colour change 4-5, acrylic staining 4".

There are two major standard families. The ISO 105 series is the reference for the European and global market; each letter denotes a different agent (C: washing, X: miscellaneous, B: light, E: water/perspiration). AATCC is a North American method family that uses numbered test methods. The two systems measure similar principles, but the conditions (temperature, detergent, number of cycles) are not identical; the results are therefore not regarded as directly equivalent.

How are grey scale and blue wool scale ratings read?

The grey scale assessment is visual and standardised. The grey scale used for colour change references the contrast between the original and the tested specimen; the staining grey scale references the colouration of the white accompanying fabric. Half-step ratings (such as 4-5, 3-4) are used for intermediate distinctions.

The practical meaning of the ratings can be summarised as follows:

Light fastness falls outside this pattern. Here the specimen is exposed under a controlled light source alongside blue wool references numbered 1-8; the number corresponding to the blue wool reference that fades to the same degree as the specimen is given as the rating. 8 represents the highest durability and 1 the lowest. It is therefore incorrect to compare a light rating with a wash rating as if they were on the same scale.

Wash fastness: what is the difference between ISO 105-C06 and AATCC 61?

Wash (laundering) fastness is the most frequently requested test for a knitted fabric, because it is an agent repeated many times over the product's life. Both standards reproduce the effect of real washes by accelerating them in a controlled vessel using high temperature, mechanical abrasion (steel balls) and a standard detergent.

ISO 105-C06 has several variants defined by letter-number combinations (such as A1S, B2S, C2S) that represent different temperatures and chemical intensities. AATCC 61 likewise includes numbered conditions such as 1A, 2A, 3A; each condition is designed to correspond to a given number of home washes. Although the two standards serve the same purpose, they should not be converted one-to-one because the temperature, cycle duration and detergent formulation differ.

The result is reported with two components: the specimen's own colour change and the staining on the multifibre accompanying strip used during the test. The multifibre strip combines acetate, cotton, nylon, polyester, acrylic and wool in a single strip, so that the fibre to which the colour tends to migrate can be seen in a single test. In reactive dyeing, residual hydrolysed dyestuff after inadequate washing (soaping) is one of the most common causes of poor wash fastness.

Rub (crocking) fastness: what do ISO 105-X12 and AATCC 8 / 116 say?

Rub fastness measures the transfer of colour when the fabric surface rubs against another surface (for example sitting, bag contact, contact with unwashed denim). The test is carried out on a device called a crockmeter, in which a standard-sized white cotton test cloth is moved over the specimen with controlled force and stroke. The colouration on the white cloth is rated against the grey scale.

Two conditions are reported separately: dry crocking and wet crocking. Wet rubbing almost always gives a lower rating, because moisture makes it easier for the dyestuff to detach from the surface. Dark shades, pigment dyeing and especially surface-bonded dyes such as indigo/woad are prone to a low wet rub rating.

How are light fastness (ISO 105-B02 / AATCC 16) and perspiration fastness assessed?

In the light fastness test, the specimen is exposed under a standardised light source such as a xenon arc lamp, alongside blue wool reference strips numbered 1-8. Exposure continues until a certain degree of fading is reached in the references. The number of the blue wool reference whose fading matches the fading of the specimen becomes the light fastness rating. A high light rating is critical for outdoor textiles and curtain fabrics; for underwear the expectation may be lower.

Perspiration fastness is important for garments that remain in prolonged contact with the skin. The test is carried out with two separate artificial perspiration solutions, acidic and alkaline; the specimen is immersed in the solution, pressed together with the accompanying fabric and held at a set temperature. Both the colour change and the staining on the accompanying fibre are rated. In disperse dyeing, inadequate reduction clearing after fixation can lower perspiration and wash fastness together.

Water fastness, with ISO 105-E01 and AATCC 107, measures the tendency of the colour to bleed and stain adjacent fabric after dripping or immersion; separate variants exist for sea water (ISO 105-E02). These tests are usually requested as a package together with perspiration fastness.

What should the acceptance threshold be and against which standard is the target set?

The most common mistake here is to look for a single figure for "good fastness". In reality, the acceptance threshold depends on three variables: the product's end use (underwear, outerwear, home textiles), the depth of the colour (dark shades are always more challenging) and the buyer's own brand specification. Each buyer's technical specification should therefore be taken as the reference, with the sector norm viewed as a general starting point.

Colour depth is especially decisive. In shades with a high dyestuff load such as deep navy, black and vivid red, wet rub and wash staining ratings are naturally lower; many specifications therefore define separate, more tolerant thresholds for dark shades. For pale and pastel shades, where even slight staining is visible, the threshold rises.

Fastness results are not an isolated laboratory step; they are part of a chain that runs from lab-dip approval through to production. If fastness targets are defined from the outset at recipe approval, the risk of an unexpected rejection after production is reduced. Because finishing and finishing treatment processes (for example the choice of softener) can affect some fastness ratings, the test protocol should be run on the final finished fabric. To see the relationship between test standards and acceptance criteria as a whole, see our quality and testing guide, and for shrinkage behaviour see the dimensional stability page.

Can ISO and AATCC results be used interchangeably?

In practice, many buyers choose a standard according to their target market: European and global brands generally require the ISO 105 series, while North American buyers frequently require AATCC methods. Certification and compliance documentation also influences this choice. If there are multiple export markets, it is common for the same fabric to be tested under both standard families.

When interpreting a result, three pieces of information must be read together: which standard and variant was used, under which condition (temperature/cycle) it was run, and whether the rating is colour change or staining. Without this trio, a "4" rating on its own is incomplete information. A valid comparison is made only between results obtained under the same standard and the same condition.

Within our knitting, dyeing and printing processes, fastness is a target addressed at the start of recipe design; achieving the colour (the relationship between colour fastness and ΔE) and achieving the fastness are two sides of the same process. The choice of reactive and disperse dyeing directly determines the targeted fastness profile.

Frequently asked questions

Are colour fastness ratings on a 1-5 or a 1-8 scale? Which one applies to which test?

Both are in use. For wash, rubbing (crocking), perspiration and water fastness, colour change and staining are rated against a calibrated grey scale from 1 (poor) to 5 (excellent), where 5 = no difference. Light fastness, by contrast, follows a different logic and is graded on the 8-step blue wool scale, where 8 is the most durable. This is why it is wrong to compare a light rating as though it were on the same scale as a wash rating.

Why do I see two separate ratings on a fastness report instead of a single number?

Because fastness is read on two distinct axes: colour change (fading or shade shift of the specimen's own colour) and staining (the marking of the adjacent accompanying (multifibre) fabrics in contact with the specimen). These are usually reported separately, for example 'colour change 4-5, acrylic staining 4'. In the rubbing (crocking) test, only a staining rating is given, reported separately for dry and wet.

Are ISO 105-C06 and AATCC 61 results treated as identical?

No. Both standards simulate the effect of laundering in an accelerated way using steel balls, elevated temperature and a reference detergent; ISO 105-C06 includes variants such as A1S, B2S, C2S, while AATCC 61 includes conditions such as 1A, 2A, 3A. However, because the temperature, cycle time and detergent formulation differ, they must not be converted one-to-one. A comparison is only meaningful within the same standard and the same condition.

Why does the wet rubbing (crocking) rating come out lower than the dry rubbing and the other tests?

Wet rubbing almost always gives a lower rating because moisture makes it easier for the dye to lift off the fabric surface. Dark shades, pigment dyeing and especially surface-held dyes such as indigo/woad are prone to this item; this is why wet rubbing is generally the most critical and lowest-scoring item. For rubbing fastness, ISO 105-X12 / AATCC 8 assess the crockmeter, while AATCC 116 assesses rotary rubbing.

What should our acceptance threshold be? Is there a single valid figure?

There is no universal single figure; the threshold depends on three variables: the product's end use, the depth of the shade and the buyer's brand specification. As a typical starting point, for wash and perspiration fastness a lower limit between 3-4 and 4-5 is expected, and for rubbing around dry 4 / wet 3. In dark navy, black and vivid red shades the staining ratings naturally fall; most specifications define a separate, more tolerant threshold for these shades.

On which fabric and at which stage of the process should fastness testing be performed?

Testing should be carried out on the final finished fabric, because finishing and after-treatment processes (for example the choice of softener) can affect certain fastness ratings. Fastness is not an isolated lab step but part of the chain running from lab-dip approval to production; if the targets are defined up front at recipe approval, the risk of a post-production rejection surprise is reduced. The choice of reactive or disperse dye also directly determines the targeted fastness profile.