Dyeing fastness refers to the ability of dyes or pigments to maintain their original color under the influence of various external factors during the use of dyed products or during the processing after dyeing. It is also a quality requirement for dyed and printed fabrics. Because the dyed fabric will fade or change color due to light, sweat, friction, washing, ironing and other reasons during wearing and storage, which will affect the appearance of the fabric or clothing. The nature or degree of variation of dyeing state can be expressed by dyeing fastness. The dyeing fastness of fabric is related to fiber type, yarn structure, fabric structure, dyeing method, dye type and external force. It can be divided into sun fastness, washing or soap fastness, friction fastness, perspiration fastness, ironing fastness and sublimation fastness.

1 Fastness to sunlight

Sun fastness refers to the degree to which a colored fabric is discolored by the action of sunlight. The test method can be used both sunlight and sunlight, the degree of fading of the sample after exposure to sunlight is compared with the standard color sample, the rating standard has two kinds of wool blue label and gray card, the national standard and the European standard are divided into 8 levels, 8 is the best, 1 is the worst; The US standard is divided into 5 levels, 5 is the best, 1 is the worst. Fabrics with poor sun fastness should not be exposed to the sun for a long time, and should be dried in a ventilated place. Xenon lamp is generally used for 24 hours of testing.

2 Washing fastness

Washing or soaping fastness refers to the degree of color change of dyed fabric after washing with washing liquid. Usually the gray grading sample card is used as the evaluation standard, that is, the color difference between the original and the sample after fading is used to judge. Washing fastness is divided into 5 levels, 5 is the best, 1 is the worst. Fabrics with poor washing fastness should be dry cleaned, if wet washing, you need to pay more attention to the washing conditions, such as washing temperature can not be too high, the time can not be too long. Washing fastness is divided into two indexes, original change and white cloth staining, white cloth staining is divided into cotton, nylon, polyester, wool, acrylic, acetate six kinds of fibers. The test temperature is 40/50/60/95 degrees, the general silk and wool using 40 degrees standard, cellulose fiber using 60 degrees.

3 Rubbing fastness

Friction fastness refers to the degree of color loss of dyed fabric after friction, which can be divided into dry friction and wet friction. The friction fastness is evaluated by the degree of white cloth staining, which is divided into 5 levels (1-5). The larger the value, the better the friction fastness.

4 Fastness to perspiration

Perspiration fastness refers to the degree of discoloration of dyed fabric after immersion in sweat. Perspiration fastness Because the composition of artificially prepared sweat is not the same, it is generally measured separately and combined with other color fastness. Perspiration fastness is divided into 1 to 5 levels, the higher the better. European standard and national standard, perspiration fastness is divided into acid sweat fastness, alkali sweat fastness.

5 Ironing fastness

Ironing fastness refers to the degree of discoloration or fading of dyed fabric during ironing. The degree of discoloration and fading is assessed by the color of other fabrics with the iron at the same time. Ironing fastness is divided into 1 to 5 grades, 5 is the best, 1 is the worst. When testing the ironing fastness of different fabrics, the ironing temperature used in the test should be selected.

6 Sublimation fastness

Sublimation fastness refers to the degree of sublimation that occurs in dyed fabric during storage. Sublimation fastness The degree of discoloration, fading and staining of white cloth after dry hot pressing treatment is evaluated by grey grading sample card. There are 5 grades, 1 is the worst, 5 is the best. This test is generally used for disperse dyes dyed polyester fabrics.

7 Chlorine fastness

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

8 Fastness to sweating light

Some fabrics have been tested for perspiration fastness and sun fastness are very good, but in the actual use of the process, especially in the summer, sweat soaking and sun exposure is easy to fade, which puts forward a new requirement, at the same time, a new standard has been produced.

9 Fastness to peroxide

Most of the washing powder now adds peroxides and some activators like peracetic acid, resulting in textiles being oxidized and faded during the washing process. Therefore, the color fastness of textiles should have a certain tolerance to peroxide.

The dyeing fastness of normal fabrics is generally required to reach 3 to 4 levels in order to meet the needs of wearing.

Others are weather fastness, color fastness, saliva fastness, blister fastness, dry cleaning fastness, etc. These fastness put forward higher and higher requirements for textile printing and dyeing processing.