Colour Fastness:
Colour fastness is the resistance of the material to its change in its colour properties, to transfer its colourants to the other material. Besides, colour fastness is one of the important factors in case of buyers demand. The outstandingly important property of a dyed material is the fastness of the shade of colour. Colourfastness refers to the resistance of colour to fade or bleed of a dyed or printed textile materials to various types of influences e.g. water, light, rubbing, washing, perspiration etc. to which they are normally exposed in textile manufacturing and in daily use. We have written a lot of articles on colour fastness.
Domestic consumers needs to be assured that purchased goods will be fit for their intended purpose. Colour fastness test helps them to choose appropriate products.
The colour fastness tests are developed under the following main concepts and rules (ISO 105 Part A01, 2010):
- The tests have to be concordant, i.e. the results obtained in the laboratory tests must be as close as possible to those that would be obtained under real conditions during manufacture or use.
- The tests have to be reproducible, i.e. the same results must be obtained independently whenever and wherever the test is repeated.
- The tests have to be as simple as possible. All of the elements (materials, products, devices, etc.) which are needed for the test must be, as far as possible, simple and easy to obtain.
In order to fulfill these criteria, several types of test method have been proposed for assessing textile color fastness.
Different Types of Colour Fastness Test:
- Colour fastness to washing
- Colour fastness to laundering
- Colour fastness test to water
- Colour fastness to rubbing/crocking
- Colour fastness to perspiration
- Colour fastness to light
- Colour fastness test to sea water
- Colour fastness to chlorinated water
- Colourfastness to hot pressing
- Colourfastness to dry cleaning
- Colourfastness to heat treatments
- Colourfastness to bleaching agents
- Colour fastness to atmospheric contaminants
- Colour fastness to potting
- Colourfastness to decatizing
- Colourfastness to steaming
- Colourfastness to milling
Standards of Colour Fastness:
1. AATCC (American Association of Textile Chemists and Colourists) technical manual:
Describes 66 numbers of different colour fastness tests.
2. SDC (Society of Dyers and Colourists):
In 1927, SDC (Europe) made fastness test committee.
3. ISO (International Organization for Standardization):
In 1947, ISO made colour subcommittee. ISO also grades the fastness:
- For light fastness: 1~8
- For other fastness: 1~5
Factors Affecting the Colour Fastness Properties:
The fastness of a dyed material to various agencies may be caused either by a chemical breakdown of the dye or by removal of the dye from the fabric, or by both. In general terms, fastness properties depend on factors such as the chemical structure of the dye, the state of the dye in the fibre, the depth of shade and the presence of chemicals in the fibre.
Fastness assessments are also affected by the fineness of fibres, simply because a given amount of dye on a fine fibre, in contrast to coarse fibre, is spread over a larger surface area. The compactness of the yarn or fabric structure can have a bearing on how easily the dye fades or can be removed during washing treatments. The nature of the fibre itself can also markedly affect fastness to light: the fastness to light of basic dyes, for example, is very poor on cotton and wool, but excellent on acrylic fibers. Crease‐resist finishes or dye‐fixing agents applied to some dyed cotton also adversely affect the fastness to light of some dyes.
Further influences originate from the state of the dye in the fibre. Insoluble pigments trapped mechanically inside the fibre, or dyes that have formed a strong chemical linkage with the fibre, will obviously be more resistant to removal by wet treatments than dyes that are more loosely attached. The crystallinity and state of aggregation of the dye will also influence its fastness.
In general, the deeper the shade, the better the fastness properties, although a deep dyeing of a dye with poor wash fastness will release more dye into the water than a paler dyeing. During washing this dye may well stain other fibres or fabrics.
Below factors affecting the colour fastness properties:
- The chemical nature of the fiber. For example, cellulosic fibers dyed with reactive or vat dyes will show good fastness properties. Protein fibers dyed with acid mordant and reactive dyes will achieve good fastness properties and so on. That is to say compatibility of dye with the fiber is very important.
- 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 fiber. Thus the fastness will be better.
- The manner in which the dye is bonded to the fiber or the physical form present.
- The amount of dye present in the fiber i.e. depth of shade. A deep shade will be less fast than a pale or light shade.
- The presence of other chemicals in the material.
- The actual conditions prevailing during exposure.
You may also like:
- Various Fastness Methods Given to the Dyed Material
- How to Determine Color Fastness to Wash
- Light Fastness of Textiles: Factors Affecting and Control Measures
- Color Fastness to Laundering Test
- Factors Affecting the Rubbing Fastness of Textile Materials
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
