Color Fastness Affecting Underwear Quality

Many friends have experienced varying degrees of color fading during the daily washing of underwear. The occurrence of discoloration in underwear is closely related to the color fastness, and will also manifest differently in different temperatures and physical or chemical environments.

What is color fastness?

Color fastness refers to the degree of fading of dyed fabric under external factors (extrusion, friction, washing, rain, exposure, light, seawater immersion, saliva immersion, water stains, sweat stains, etc.) during use or processing, and is an important indicator of fabric. The most commonly used items are washing resistance, light resistance, friction resistance and sweat stain resistance, ironing resistance, weather resistance and so on.

In actual work, testing items are mainly determined based on the final use of the product and product standards. For example, the wool textile product standards stipulate that the color fastness to sunlight must be tested. Knitted underwear must of course be tested for perspiration fastness, while outdoor textiles (such as parasols, light box cloth, canopy materials), of course, their color fastness to weather must be tested.

Including: color fastness to soaping (sample), color 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), and color fastness to perspiration, color fastness to water, color fastness to light, color fastness to sea water, color fastness to saliva.

In terms of color fastness of underwear fabrics, there are several aspects that determine whether it is good or bad, as follows:

1. Washing fastness refers to the degree of color change of the finished fabric after being washed with water or washed with washing powder and detergent. It is divided into wash water fading and staining. Fading refers to the degree of color falling off after washing, and staining refers to mix fabrics of other colors stain after being washed together. The wash fastness of normal fabrics is generally very high. Otherwise, the condition of the finished garments will be very bad after being washed, the color will not fade well, and the washing water will be dyed. For example, after washing black clothes, the water will turn black and the color of the clothes will become lighter; staining will not be possible. Well, for example, if white clothes and black clothes are washed together, the white clothes will turn black. These two points are easy for ordinary consumers to discover, so the wash fastness must be good, otherwise it will affect the brand image and actual sales. Level 4 is generally required.

​2. Rubbing fastness is divided into dry rubbing and wet rubbing. It refers to rubbing the tested cloth with a dry white cloth and a wet white cloth to see the staining of the white cloth after rubbing. Wet and dry rub is difficult in the production of dark fabrics, especially black fabrics, which is a common problem in the industry. Brand owners, even top brands, will lower their requirements. Dark colors require level 3, and black will accept a half-level reduction.

3. Light fastness refers to the color change under sunlight. Sunlight fastness is basically no problem for medium-colored and dark-colored fabrics, but it is somewhat difficult for light colors, especially white. Especially white fabrics will appear fading when exposed to sunlight for a long time. In the case of yellow, it is generally required to reach level 3 or above.

4. Perspiration fastness refers to the discoloration and staining of fabrics when the human body sweats (several pieces of clothing are worn together). The requirements for sports bras in this regard are relatively higher, generally requiring 3-4 level (equal to level 3.5).

5. Light-perspiration composite fastness refers to the discoloration and staining of fabrics under the dual influence of sunlight and sweat stains. Generally, it requires level 3 or 3.5.

There are many factors that affect the dye fastness of textile underwear fabrics. For internal factors, all production processes must be in place to ensure that the product has excellent color fastness indicators and meets the requirements for daily use and reprocessing; for external factors Generally speaking, you must follow the product's usage requirements, pay attention to factors such as washing temperature, detergent and washing method, as well as friction intensity, exposure time and other factors that can reduce color fastness, so that the product can be used better.

Specific underwear laundry recommendations:

1. Do not soak for a long time, especially new black underwear.

2. Do not wash dark and light colored underwear together in the early stage, especially black and white.

3. Do not leave it in the sun for a long time, especially light-colored and white underwear.

4. Wash your underwear promptly after it becomes dirty. Sweat stains will cause color changes.

5. If you buy black underwear, it is recommended to wash it separately once or twice before washing it with other items.

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