Color fastness(Dyeing)

Dyeing fastness is the quality requirement for dyed and printed fabrics. Because dyed fabrics will be discolored or discolored due to light, sweat, friction, washing, ironing, etc. during wearing and storage, which will affect the appearance of the fabric or clothing. The nature or degree of the variation of the dyeing state can be expressed by the color fastness. The dye fastness of the fabric is related to the fiber type, yarn structure, fabric structure, printing and dyeing method, dye type and external force. It can be divided into light fastness, washing or soaping fastness, rubbing fastness, perspiration fastness, ironing fastness and sublimation fastness, etc.

1. Light fastness

Light fastness refers to the degree of discoloration of colored fabrics by sunlight. The test method can be either in sunlight or in a daylight machine. The degree of fading of the sample after exposure is compared with the standard color sample, and it is divided into 8 levels, 8 is the best, and 1 is the worst. 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 dyed fabrics after washing with washing liquid. Usually, the gray graded sample card is used as the evaluation standard, that is, the color difference between the original sample and the faded sample is used for judgment. The washing fastness is divided into 5 grades, grade 5 is the best and grade 1 is the worst. The fabrics with poor washing fastness should be dry-cleaned. If they are wet-washed, the washing conditions should be paid more attention to, 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 dyed 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 discoloration of dyed fabrics after being immersed in sweat. The perspiration fastness is not the same as the artificially prepared sweat composition, so it is generally evaluated in combination with other color fastnesses in addition to a separate measurement. The perspiration fastness is divided into 1~5 grades, the larger the value, the better.

5. Ironing fastness

Ironing fastness refers to the degree of discoloration or fading of dyed fabrics during ironing. The degree of 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 the best and grade 1 being the worst. 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 of dyed fabrics in storage. The sublimation fastness is evaluated by the gray graded sample card for the degree of discoloration, fading and staining of the white cloth after the dry hot pressing treatment. There are 5 grades, 1 is the worst, and 5 is the best.

The dye fastness of normal fabrics is generally required to reach level 3~4 to meet the requirements of wearing.