Color fastness refers to the ability of dye or pigment to maintain its original color under the influence of various external factors during the use or finishing process of dyed products. It is also the quality requirement for colored and printed fabrics. Because the dyed fabric will fade or discolor due to wear, sweat, friction, cleaning, ironing and other reasons during wearing and storage, which will affect the aesthetic appearance of the fabric or work clothes. The nature or degree of the variation of the color state can be expressed by the color fastness. The color 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.

1. Light fastness
The light fastness refers to the degree of discoloration of colored fabrics under the effect of daily finishing. The test method can be either day-end exposure or day-end exposure. The fading degree of the sample after exposure is compared with the standard color sample. There are two rating standards: wool blue standard and gray card. The national standard and European standard are divided into 8 grades, 8 grades are good, and 1 grade is poor; American standard is divided into five grades, five grades are good and one grade is poor. Fabrics with poor light fastness should not be exposed to the sun for a long time, and should be put in a ventilated place to dry in the shade. The xenon lamp is generally used for 24-hour test.

2. Cleaning fastness
Water washing or soaping fastness refers to the degree of color change of colored fabrics after washing with detergent. Generally, the gray grading sample card is adopted as the evaluation standard, that is, the evaluation is based on the color difference between the original sample and the sample after fading. Cleaning fastness is divided into five grades, five grades are good and one grade is poor. The fabrics with poor cleaning fastness should be dry-cleaned. If wet cleaning is carried out, double attention should be paid to the cleaning conditions, such as the cleaning temperature should not be too high and the time should not be too long. The washing fastness is divided into two indexes, the change of the original sample and the staining of white cloth. The staining of white cloth is divided into six kinds of fibers: cotton, nylon, polyester, wool, polyacrylonitrile fiber and acetate. The test temperature is 40/50/60/95 ℃. Generally, 40 ℃ is adopted for silk and wool, and 60 ℃ is adopted for cellulose fiber.

3. Friction fastness
Friction fastness refers to the degree of color loss of colored fabrics after friction, which can be divided into dry friction and wet friction. The rubbing fastness is evaluated based on the degree of staining of white cloth, which is divided into five levels (1-5). The higher the value, the better the rubbing fastness.

4. Sweat fastness
The color fastness to perspiration refers to the color fading degree of the dyed fabric after being soaked in sweat. Due to the different components of the perspiration solution prepared manually, the perspiration fastness is generally tested in combination with other dyeing fastness in addition to being measured separately. The perspiration fastness is divided into 1-5 grades, the higher the grade, the better. In European and national standards, perspiration fastness is divided into acid perspiration fastness and alkali perspiration fastness.

5. Ironing fastness
Ironing fastness refers to the degree of discoloration or discoloration of colored fabrics during ironing. The degree of discoloration and fading is evaluated by the staining of the iron on other fabrics at the same time. Ironing fastness is divided into 1~5 grades, 5 grades are good, and 1 grade is poor. When testing the ironing fastness of different fabrics, the ironing temperature for the test should be selected.

6. Sublimation fastness
Sublimation fastness refers to the degree of sublimation of colored fabrics during storage. Sublimation fastness The degree of discoloration, discoloration and staining of white cloth after dry-hot press treatment is evaluated by grey grading sample card, which is divided into 5 grades, 1 grade is poor, and 5 grade is good. This test is generally used for dyeing polyester fabrics with disperse dyes.

7. Chlorine immersion fastness
The chlorine immersion fastness is generally aimed at some swimming suits, because the seawater contains chlorine, which is easy to fade the fabric. At present, urban tap water also contains available chlorine, and some hospital and hotel supplies need to be disinfected with chlorine-containing detergent, so higher and higher requirements are put forward for the fastness to chlorine bleaching.

8. Sweat fastness
Some fabrics are tested to have good fastness to perspiration and sunlight, but in the actual use process, especially in summer, perspiration and sunlight are easy to fade, which puts forward a new requirement. At the same time, a new standard is also produced.

9. Fastness to peroxide
Most of the washing powder now contains peroxides such as peracetic acid and some activators, which cause the fabric to be oxidized and faded during cleaning. Therefore, the dyeing fastness of fabric should have a positive tolerance to peroxide.