Textile Colorfastness: Why Do Your Clothes Fade?

Textile Colorfastness: Why Do Your Clothes Fade?

When we excitedly put on new clothes, only to see a basin of "colored water" after washing, the disappointment is unmistakable. In textile terminology, this phenomenon is referred to as poor colorfastness. In simple terms, colorfastness is the "resistance" of a textile's color to various external factors during processing and use. It directly determines whether garments remain looking new over time and also relates to our health and safety during wear.

Main Types of Colorfastness and Their Testing

The colorfastness family is extensive, with numerous test items. The following categories are the most relevant to our daily lives:

1. Colorfastness to Light (Lightfastness)

This refers to the ability of colored fabrics to resist fading under sunlight exposure. Ultraviolet (UV) rays in sunlight act as "killers" to dye molecules, triggering photochemical reactions that cause fading. The test method typically involves exposing the specimen alongside a set of blue wool reference standards to an artificial light source (e.g., xenon arc lamp) and assessing the color change against the standards. Lightfastness is rated on an 8-grade scale, with Grade 1 being the poorest and Grade 8 the best. Lighter shades are generally more susceptible to fading from sunlight than darker shades.

2. Colorfastness to Washing (Colorfastness to Soap Washing)

This assesses the ability of textiles to retain their color during laundering with detergents and water. The test method involves stitching the specimen together with standard adjacent fabrics and washing them under specified conditions of temperature, time, and detergent. The results are then evaluated based on the color change of the specimen and the degree of staining on the adjacent fabrics. Colorfastness to washing is rated on a 5-grade scale, with Grade 5 being the best and Grade 1 the poorest. Test temperatures range from 40°C to 95°C, depending on the intended end-use of the product.

3. Colorfastness to Rubbing (Crocking)

This directly affects whether clothing will stain other items. It is divided into dry rubbing fastness and wet rubbing fastness. The test method involves placing the specimen on a crockmeter, where a standard white cloth rubs against the specimen under a pressure of 9N for 10 reciprocating cycles. The degree of staining on the white cloth is then assessed. This is also rated on a 5-grade scale, with higher grades indicating less color transfer. For deep-colored cellulose fiber products such as cotton and linen, achieving ideal wet rubbing fastness often remains a challenge.

4. Colorfastness to Perspiration, Water, and Saliva

These tests simulate actual wearing scenarios for the human body. Garments for infants and young children must undergo colorfastness to saliva testing to prevent dyes from being absorbed by infants through saliva, which could pose health risks. The test methods involve treating the specimen with adjacent fabrics in prepared artificial perspiration, water, or saliva solutions, placing them in a constant-temperature oven, and then assessing color change and staining. Colorfastness to perspiration, water, and saliva are all rated on a 5-grade scale.

In addition to the above, there are standards for colorfastness to dry cleaning, chlorine bleaching, and hot pressing (ironing), which together form a comprehensive colorfastness testing system. Internationally recognized standards include the ISO 105 series, the US AATCC standards, and China's GB/T series.

Colorfastness is not only a matter of aesthetics but is also directly linked to health and safety. Understanding this knowledge helps us make more informed choices when purchasing and caring for our clothes, allowing us to avoid the hassle of color bleeding.