Principle

Colour fastness is an important demand and refers to the resistance of colour to fade or bleed of a dyed or printed textile materials to various types of influences including water, light, rubbing, washing, perspiration, etc. to which they are normally exposed during textile manufacturing and in daily use.

Colour fastness may be affected by Fastness Properties:

  • The chemical nature of the fibre. For example, cellulosic fibres dyed with reactive or vat dyes will show good fastness properties. Protein fibres dyed with acid mordant and reactive dyes will achieve good fastness properties and so on. In other words: dyes and fibres have to be compatible.
  • The molecular structure (e.g.) of a dye molecule: If the dye molecule is larger in size, it will be tightly entrapped inside the inter-polymer chain space of a fibre and thus result in a better colour fastness.
  • The manner in which the dye is bonded to the fibre.
  • The amount of dye in the fibre i.e. depth of shade. A deep (darker) shade will have a lesser fastness than a pale or light shade.
  • The presence of other chemicals in the material.
  • The conditions during exposure to light and other influences (sweat, water, ...).

Standard test methods: a few examples

Colour fastness to light

  • ISO 105-B01:2014 specifies a method intended for determining the resistance of the colour of textiles of all kinds and in all forms to the action of daylight.
  • ISO 105-B02:2013 specifies a method intended for determining the effect on the colour of textiles of all kinds and in all forms to the action of an artificial light source representative of natural daylight (D65). The method is also applicable to white (bleached or optically brightened) textiles. 

Colour fastness to laundering

  • ISO 105-C06:2010 specifies methods intended for determining the resistance of the colour of textiles of all kinds and in all forms to domestic or commercial laundering procedures used for normal household articles using a reference detergent. Industrial and hospital articles may be subjected to special laundering procedures which may be more severe in some aspects. The colour loss and staining resulting from desorption and/or abrasive action in one single (S) test closely approximates to one commercial or domestic laundering. The results of one multiple (M) test may in some cases be approximated by the results of up to five domestic or commercial launderings at temperatures not exceeding 70 °C. The M tests are more severe than the S tests because of an increase in mechanical action.

Colour fastness to human perspiration and saliva

  • ISO 105-E04:2013 specifies a method for determining the resistance of the colour of textiles of all kinds and in all forms to the action of human perspiration.
  • ISO 20701 | IUF 427:2017 specifies a method for determining the colour fastness to saliva of all kinds of leathers, independent of the colouring procedure applied. The method uses an artificial saliva solution to simulate whether colouring materials can migrate from leather to the mouth or to the mucous membranes. 

Colour fastness to rubbing

  • ISO 105-X12:2016 specifies a method for determining the resistance of the colour of textiles of all kinds, including textile floor coverings and other pile fabrics, to rubbing off and staining other materials. The method is applicable to textiles made from all kinds of fibres in the form of yarn or fabric, including textile floor coverings, whether dyed or printed. Two tests may be made, one with a dry rubbing cloth and one with a wet rubbing cloth.

Example of how a test is performed

Colour fastness to Chlorinated Water (Chlorine)

The test is carried out according to ISO 105-E03:2010 -- Textiles -- Tests for colour fastness -- Part E03: Colour fastness to chlorinated water (swimming-pool water).

This part of ISO 105 specifies a method for determining the resistance of the colour of textiles of all kinds and in all forms to the action of active chlorine in concentrations such as are used to disinfect swimming-pool water (break-point chlorination). Three alternative test conditions are specified. The active chlorine concentrations of 50 mg/l and 100 mg/l are intended for swimwear. The active chlorine concentration of 20 mg/l is intended for accessories such as beach robes and towels.

A specimen of the textile is treated with a weak chlorine solution of a given concentration and dried. The change in colour of the specimen is assessed by comparison with the grey scale or instrumentally. Three alternative test conditions are specified.

Apparatus

  1. Suitable mechanical device, consisting of a water bath containing a rotatable shaft which supports, radially, glass or stainless steel containers with a diameter of (75 ± 5) mm and a height of (125 ± 10) mm of (550 ± 50) ml capacity, the bottom of the containers being (45 ± 10) mm from the centre of the shaft. The shaft/container assembly is rotated at a frequency of (40 ± 2) min−1. The temperature of the water bath is thermostatically controlled to maintain the test solution at the prescribed temperature ±2 °C. Other mechanical devices may be used for the test, provided that the results are identical to those obtained in the apparatus described above.
  2. pH-meter, having an accuracy of 0,02 units.
  3. Grey scale for assessing change in colour, complying with ISO 105-A02.
  4. Spectrophotometer or colorimeter for assessing change in colour, complying with ISO 105-A05.
  5. Analytical balance, accurate to ± 0,01 g (see ISO 105-A01).

Reagents

  • Sodium hypochlorite (NaOCl) in different compositions
  • Potassium dihydrogenphosphate (KH2PO4)
  • Disodium hydrogenphosphate dihydrate (Na2HPO42H2O), or disodium hydrogenphosphate dodecahydrate (Na2 HPO 4⋅12H2O).
  • Grade 3 water, complying with ISO 3696.

Test specimen

  • If the textile to be tested is fabric, use a specimen measuring (40 ± 2) mm × (100 ± 2) mm.
  • If the textile to be tested is yarn, knit it into fabric and use a specimen measuring (40 ± 2) mm × (100 ± 2) mm, or make a wick of parallel lengths, (100 ± 2) mm long and about (5 ± 2) mm in diameter, tied near both ends. 
  • If the textile to be tested is loose fibre, comb and compress enough of it to form a sheet measuring (40 ± 2) mm × (100 ± 2) mm. Determine the mass of the fibre and sew it onto a piece of polyester or polypropylene cloth to support the fibre. The liquor ratio (see 7.1) shall be based on the mass of fibre only.

Procedure

  • Each specimen shall be tested in a separate container in the mechanical device. Immerse the specimen in the sodium hypochlorite solution, ensuring that the specimen is thoroughly wetted. Close the container and agitate at (27 ± 2) °C for 1 h in darkness.
  • Remove the specimen from the container, squeeze or hydroextract it, and dry it by hanging it in air at room temperature in subdued light.
  • Assess the change in colour of each specimen with reference to the original specimen by comparison with the grey scale and/or instrumentally.
     

Test report

The test report shall include the following information:

  1. a reference to this part of ISO 105 (ISO 105-E03:2010);
  2. all details necessary for the identification of the sample tested;
  3. the numerical grey scale ratings and/or instrument assessment for the change in colour of each specimen;
  4. the concentration of active chlorine used (see 5.2, 5.3 and 5.4.);
  5. any deviation, by agreement or otherwise, from the procedure specified.