Color fastness is the quality requirement for colored and printed fabrics. Because dyed fabrics will fade or change color due to wear, sweat, friction, washing, ironing, etc. during wearing and storage, which will affect the appearance of the fabric or workwear. The nature or degree of the variation of the coloring state can be expressed by the color fastness. The color fastness of the fabric is related to the structure of the spinning yarn, the structure of the fabric, the printing and dyeing method, the type of dye and the size of the external force. It can be divided into light fastness, washing or soaping fastness, rubbing fastness, perspiration fastness, ironing fastness and sublimation fastness.
1. Light fastness
Light fastness refers to the degree of discoloration of colored fabrics under the influence of the sun. The test method can adopt either the sun-burning or the sun-burning machine. The fading degree of the sample after the sun-burning is compared with the standard color sample, and it is divided into 8 grades, grade 8 is better, and grade 1 is worse. Fabrics with poor light fastness should not be exposed to the sun for a long time, and should be placed in a ventilated place to dry in the shade.
2. Washing fastness
Washing or soaping fastness refers to the degree of color change of colored fabrics after washing with cleaning liquid. Generally, the gray graded sample card is used as the evaluation standard, that is, the color difference between the original sample and the sample after the fade is used for the judgment. The washing fastness is divided into 5 grades, grade 5 is better and grade 1 is worse. The fabrics with poor washing fastness should be dry-cleaned. If they are wet-washed, the washing conditions should be paid extra attention, such as the washing temperature should not be too high and the time should not be too long.
3. Rubbing fastness
Rubbing fastness refers to the degree of discoloration of colored fabrics after rubbing, which can be divided into dry rubbing and wet rubbing. The rubbing fastness is evaluated based on the degree of white cloth staining, and it is divided into 5 levels (1~5). The larger the value, the better the rubbing fastness. The service life of fabrics with poor rubbing fastness is limited.
4. Perspiration fastness
Perspiration fastness refers to the degree of color fading of colored fabrics after being soaked in sweat. The perspiration fastness is not completely the same in the artificially prepared sweat, so it is generally evaluated in combination with other dye fastnesses in addition to a separate measurement. The perspiration fastness is divided into 1 to 5 grades, the larger the value, the better.
5. Ironing fastness
Ironing fastness refers to the degree of discoloration or fading of colored fabrics during ironing. The degree of this discoloration and fading is evaluated by the iron's staining of other fabrics at the same time. Ironing fastness is divided into grades 1 to 5, with grade 5 being better and grade 1 being worse. When testing the ironing fastness of different fabrics, the temperature of the iron used for the test should be selected.
6. Sublimation fastness
Sublimation fastness refers to the degree of sublimation phenomenon that occurs in the storage of colored fabrics. The sublimation fastness is evaluated by a gray graded sample card for the degree of discoloration, fading and staining of white cloth after dry hot pressing. There are 5 grades, 1 is poor, and 5 is better.
The color fastness of normal fabrics is generally required to reach level 3~4 to meet the requirements of wearing.