What Is Color Fastness ?

1. About Color Fastness.

Color fastness refers to the resistance of a fabric’s color to fading or running. It measures how well a fabric retains its color when subjected to various conditions such as washing, exposure to sunlight, rubbing, perspiration, and environmental factors. High color fastness means the fabric maintains its original color for a long time, while low color fastness means the color fades or bleeds easily.

2. Is the Color Fastness of Fabrics Very Important?

It is very important to know the color fastness of your fabric. First, the design of the clothes may have different colors of fabrics stitching, such as white and black, which are contrasting colors. We need to ensure that the light colors will not be stained by dark colors after washing. Second, knowing the color fastness can correctly mark the care instructions on the label, such as washing temperature, washing with clothes of the same color, etc. Third, ensure quality. If the clothes are complained by customers or even accumulated negative reviews due to color fastness issues after they are made, it will affect the reputation of the brand or company.

3. Common Color Fastness Test Standards.

Color Fastness to Washing: ISO 105 C06 and AATCC61 are the most common color fastness test standards for measuring fabrics after home washing. The fabric will be washed with six-fiber strips in a special washing color fastness machine at a specific temperature, and then taken out and dried to determine the degree of fading and transfer to the six-fiber strips.Each test standard has specified washing temperature, water volume, amount of detergent or agent, and washing time. In addition, some test standards will also add small steel balls to simulate the fading caused by friction between fabrics and other clothing or accessories in the washing machine. For example, AATCC61-2A is a very common washing simulation test. Its 45-minute test with steel balls is intended to simulate the results after five home washes. Generally, if the fabric can pass the self-color change (fading) level 4 and the transfer dyeing to the six-fiber strands level 4, it is of very good quality. However, sometimes there will be differences in color depth and brightness, and not all colors can reach such a level.

Color Fastness to Water: ISO 105 E01 and AATCC 107 are the most common water fastness test standards used to determine whether the color of fabrics will change or transfer due to immersion in water during the washing process.

Color Fastness to Light: ISO 105 B02 and AATCC 16 Option 3 are the most common test standards for color fastness to sunlight, which are used to test the color fastness of fabrics exposed to sunlight or fluorescent lights. The test fabrics will be placed in a machine that simulates sunlight. The AATCC 16 Option 3 test method is to place the fabric in a fading instrument and irradiate it with high-intensity ultraviolet light with a wavelength similar to that of sunlight for 40 hours to measure the degree of fading. Such tests are particularly important for outdoor clothing, or to test whether daily wear can fade after being exposed to sunlight.

Color Fastness to Crocking (Rubbing) : AATCC 8 and ISO 105 X12 are the most common rubbing color fastness test standards, which are used to test the degree of transfer of dyes to other fabrics after fabrics are rubbed. For example, if we put on a dark coat over a white T-shirt, the fabrics may transfer dyes due to mutual friction all day long. The rubbing color fastness will test the transfer of dyes by rubbing dry fabrics and wet fabrics – the test fabric will be rubbed back and forth with a fixed force and frequency on a non-dyed fabric in a dry or wet state using a special machine for testing friction. Finally, the degree of transfer of dyes to the non-dyed fabric is observed. If it can reach level 4 for dry friction and level 3-3.5 for wet friction, the quality is very good.

Color Fastness to Sweat: ISO 105 E04 and AATCC 15 are the most common perspiration fastness test standards, and are often used on sports fabrics. The test uses a six-fiber strip to test whether the color of the fabric will transfer to other fabrics through wet sweat. AATCC 15 tests acid perspiration color fastness, while ISO 105 E04 tests acid and alkaline perspiration color fastness. Human sweat is usually acidic, but it can become alkaline at high temperatures or due to bacteria.

Other Common Fastness Test: chlorine water fastness test and seawater fastness test.

4. How to Improve Color Fastness?

Sometimes dyeing factories will find that the color fastness required by the brand is not good, so they will use fixing agents in the process to ensure color fastness. But the fixing agent cannot make the color fastness reach level 5. The color of the fabric itself is a very important factor. For example, the color fastness of light colors in sunlight is worse than that of dark colors. The color fastness of neon colors, brighter colors, and darker colors is generally poor, and it is also more prone to color staining. If the fabric itself is ordinary polyester fiber (Polyester), it can also be replaced by CD yarn (Cationic Polyester) to improve the color fastness of washing. However, it should be noted that switching to CD yarn still cannot improve the color fastness in sunlight, and the cost will increase as a result. Brands sometimes have to compromise on the choice of color or design in order to achieve the required color fastness.