Colour Fastness

Colour fastness is a term used in the dyeing of textile materials, meaning resistance of the material's colour to fading or running. The term is usually used in the context of clothes. The first known use of the word colorfast was in 1916. In general, clothing should be tested for colourfastness before using bleach or other cleaning products.

Color Fastness:

Color 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 color. Color fastness refers to the resistance of color 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 color fastness.

General Principle:

A specimen of the textile to be tested, with the adjacent fabric attached is subjected to washing under specified conditions. The extent of any change in color and that of the staining of the adjacent fabric are assessed and the rating is expressed in fastness numbers.

There are two types of adjacent fabrics; (1) single fibre fabric and multiple fibre fabric. In the case of multi-fibre fabric only one specimen is required and in the of single fiber fabric two adjacent fabric are required.

Standards of Color Fastness: 

1. AATCC (American Association of Textile Chemists and Colorists) technical manual:
Describes 66 numbers of different color fastness tests.

2. SDC (Society of Dyers and Colorists):
In 1927, SDC (Europe) made fastness test committee.

3. ISO(International Organization for Standardization):
In 1947, ISO made color sub committee. ISO also grades the fastness:
For light fastness: 1~8
For other fastness: 1~5

Factors Affecting the Color Fastness Properties: 

1.     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.

2.     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.

3.     The manner in which the dye is bonded to the fiber or the physical form present.

4.     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.

5.     The presence of other chemicals in the material.

6.     The actual conditions prevailing during exposure.

If the color removes itself from the garment onto the cloth, you should not use the cleaning product on the clothing. Important color fastness tests are given below:

1.     Color Fastness to Washing

2.     Color Fastness to light

3.     Color Fastness to perspiration

4.     Color Fastness to Water

5.     Color Fastness to Rubbing

6.     Color Fastness to Crocking

Color Fastness to Washing

In the test, change in color of the textile and also staining of color on the adjacent fabric are assessed. A 10 x 4 cm swatch of the coloured fabric is taken and is sandwitched between two adjacent fabrics and stitched, the sample and the adjacent fabric are washed together. Five different types of washing are specified as different washing methods.

The solution for washing should be prepared to the required temperature of washing. The liquor material ratio is 50:1 . After soaping treatment, remove the speciment, rinse twice in cold water and then in running cold water under a tap. Squeeze it and air dry at a temperture not exceeding 60°C. The change in color and staining is evaluated with the help of grey scales.

Color Fastness to light

The purpose of Color fastness to light test is to determine how much the color will fade when exposed to a known light source. It is an off line quality assurance system. Generally man wears the fabric and goes outside of the home for doing their job. In day; sun light fall on the fabric surface. So it needs to know how much protection ability have a fabric to sun light. It is determined by an experiment called color fastness to light. To measure the color fastness a blue scale is used. After completing the test, sample is compared with the blue scale.

Principle of Color Fastness to Light: 

This test measures the resistance to fading of dyed textile when exposed to day light. The test sample is exposed to light for a certain time which is about 24 hours to 72 hours or by customer/buyer demand and compare the change with original unexposed sample the changes are assessed by Blue Scales.

Light Fastness Grades:

Color Fastness to Perspiration:

The garments a\which come into contact with the body where perspiration is heavy may suffer serious local discoloration. This test is intended to determine the resistance of color of dyed textile to the action of acidic and alkaline perspiration. Before knowing about the Color Fastness to perspiration you must have to know about Color Fastness to Wash and Color Fastness to Rubbing.

Color Fastness to Water 

Color fastness to water is designed to measure the resistance to water of dyed, printed, or otherwise colored textile yarns and fabrics.The test method by which this test is carried out is AATCC 107-1991 or ISO 105 E01. This method is to assess the degree of cross staining which may occur when garments are left in contact when damp. The test measures the resistance to water of any colored textiles. 

Color Fastness to Rubbing

This test is designed to determine the degree of color which may be transferred from the surface of a colored fabric to a specify test cloth for rubbing (which could be dry and Wet).

There are two test methods for rubbing fastness.

1.ISO-105-X12
2.AATCC-08

In ISO-105-X12 the wet pickup of the rubbing cloth is 100% .While in AATCC-08 the wet Pickup of the rubbing cloth is 65%.We check rubbing by Dry and Wet methods. In wet rubbing we wet the rubbing cloth according to test method and give rating by comparing the Staining with the gray scale.

Similarly for dry rubbing we check the rubbing with dry rubbing cloth and compare the staining With gray scale for ratings.Color Fastness to rubbing is a main test which is always required for every colored fabric either it is Printed or dyed.

If the color fastness to rubbing is good then its other properties like Washing fastness and durability etc improves automatically because the rubbing is a method to check the fixation of the color on the fabric. So if the fixation is good its washing properties will be good.

Rubbing Fastness depends on: 

Nature of the Color
Depth of the Shade
Construction of the FabricNature of the color Each color either it is pigment ,Reactive ,Disperse or direct has its own fastness properties to rubbing. There are some colors like black, Red ,Burgundy ,Navy blue which have poor Color fastness properties because of their chemical structure.

Like Black color is a carbon base color and the particle size of carbon is large than the other colors that's why its rubbing properties are poor. Similarly red and blue are in the same case. So to improve the color fastness we add more binder to improve the fastness properties of these colors. It doesn't mean that we can not achieve the best results with these colors. The required results can achieve but production cost will be increase. On the other hand the construction of the fabric also effects the fastness properties.

If the rubbing fastness on 100.80/40.40 is 3 on the gray scale it will be 2-3 on 52.52/22.22 with the same printing parameters. So always keep in mind these effects during finalize the required parameters with your customer. 

Color Fastness for Crocking

Crocking is simply the transfer of color from a fabric onto another white test fabric. The more color is transferred, the more the fabric "crocks". Crocking determines the amount of color transferred from the surface of colored textile material to other surfaces by rubbing.