The Most Complete Guide to Color Fastness

 

Definition of colour fastness

The so-called color fastness refers to the degree of fading of dyed fabric under the action of external factors (extrusion, friction, washing, rain, exposure, light, seawater impregnation, saliva impregnation, water stains, sweat stains, etc.) during use or processing. It is an important index of fabric.
Color fastness refers to the resistance of the color of a textile to various effects during processing and use. The fastness grade is evaluated according to the discoloration of the sample and the stain of the undyed lining fabric. The colour fastness test of textiles is a routine item in the intrinsic quality test of textiles.
Textiles will be subjected to various external effects such as lighting, washing, ironing, sweat stains, friction and chemical agents during their use. Some printed and dyed textiles have also undergone special finishing processing, such as resin finishing, flame retardant finishing, sand washing, wool grinding, etc., which requires the color and color of printed and dyed textiles to maintain a certain fastness.

Types of color fastness

Color fastness includes colour fastness to soap washing (sample), colour fastness to rubbing, color fastness to chlorine water, color fastness to non-chlorine bleaching, color fastness to dry cleaning, color fastness to actual washing (garments, fabrics), colour fastness to sweat stains, color fastness to water, color fastness to light, colour fastness to sea water, colour fastness to saliva, etc.
Introduction to common color fastness
Color fastness to washing: The sample is stitched together with the standard lining fabric, washed, cleaned and dried, and washed at the right temperature, alkalinity, bleaching and friction conditions to obtain test results in a relatively short time. The friction action in between is completed by small bath ratio and the appropriate number of stainless steel beads rolling, impact, with gray card rating, get the test results.Different test methods have different temperature, alkalinity, bleaching and friction conditions and sample size, specific to the test standards and customer requirements to choose. General washing colour fastness is poor color green orchid, bright blue, black red, navy blue, etc.
Color fastness to dry cleaning: Same as color fastness to washing.
Rubbing colour fastness: Put the sample on the rubbing fastness tester, and rub the standard rubbing white cloth against it for a certain number of times at a certain pressure. Each group of samples shall be tested for dry and wet rubbing colour fastness.The color on a standard friction white cloth is rated by a gray card. The resulting series is the measured colour fastness. The colour fastness of friction requires both dry and wet rubbing tests, and all colors on the sample should be rubbed to.
Colour fastness to sunlight: Textiles are usually exposed to light when they are used, which can damage the dye and lead to the well-known “fading”, so that colored textiles change color, generally become lighter and darker, and some will also change color light. Therefore, it is necessary to test the color fastness. That is, the sample and blue wool standard cloth with different levels of fastness are placed together under specified conditions for solar exposure, and the sample is compared with blue wool cloth to evaluate the color fastness to light. The higher the level of blue wool standard cloth, the more light fastness.
Color fastness to perspiration: The sample is stitched together with the standard paste lining fabric, placed in the perspiration liquid, clamped on the colour fastness to perspiration, placed in the oven at constant temperature, and then dried, rated with gray card, test results. Different test methods have different perspiration liquid ratio, different sample size, different test temperature and time.
Colour fastness to water stains: Test samples treated with water as above.
Chlorine bleaching fastness: After the fabric is washed in chlorine bleaching solution under certain conditions, the degree of color change is assessed. This is chlorine bleaching fastness.
Non-chlorine bleaching fastness: After the fabric is washed in the washing condition with non-chlorine bleaching, the degree of color change is assessed. This is the non-chlorine bleaching fastness.
Pressing color fastness: After the dry sample is covered with cotton lining fabric, it is pressed in the heating device of specified temperature and pressure for a certain period of time, and then the color change of the sample and the colour touch of the lining fabric are evaluated with a gray sample card. The colour fastness of hot pressing includes dry pressing, damp pressing and wet pressing. The test method should be selected according to different customer requirements and test standards.
Color fastness to saliva: the sample and the specified lining fabric are bonded together, placed in artificial saliva for treatment, the test liquid is removed, placed between two plates in the test device and the specified pressure is applied, and then the sample and the lining fabric are dried respectively, and the color change of the sample and the stain of the lining fabric are evaluated with gray card.

The importance of color fastness

Good or poor color fastness is directly related to human health and safety. When products with poor colour fastness encounter rain or sweat during wearing, the pigments on the fabric will fall off and fade, and the dye molecules and heavy metal ions may be absorbed by the skin and harm the health of human skin. On the other hand, it will affect the coloring of other clothes worn on the body. Or stain other clothes when washing with other clothes.
Due to the great difference in the processing and use of fabrics, the requirements are different, so most of the current test methods are based on the environment and conditions of the simulation test or comprehensive test, so the test methods of color fastness are quite extensive. However, throughout the International Standards Organization (ISO), American Society of Dyers and Chemists (AATCC), Japanese (JIS), British (BS) and many other standards, the most commonly used are washing resistance, light resistance, friction and sweat resistance, ironing resistance, weather resistance and so on. In practice, the test items are mainly determined according to the end use and product standards of the products. For example, wool textile product standards specify that the colour fastness to sun exposure must be tested, knitted underwear must be tested for sweat stain fastness, and outdoor textiles (such as sunshade, light box cloth, canopy material) must be tested for colour fastness to weather.

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