What is Color Fastness?
Color fastness is one of the important indicators to measure product quality. During production and usage, textiles can be subjected to considerable stresses, resulting in color changes. Both color intake (bleeding into) and color loss (bleeding) are common. These effects are normally unwanted; hence it is of crucial importance to determine the colorfastness of textiles at an early stage.
Color fastness can be defined as the ability of the original color of the finished textile to resist any challenges that it may normally encounter during its working lifetime. High colorfastness is an essential property of all textile materials to render them fit for purpose. For apparel, the most common “challenges” are exposure to light, loss of dye during laundering, rub fastness, which measures whether color is lost from the fabric surface after mechanical rubbing, perspiration fastness, and thermal stability, at temperatures that may be experienced during ironing, for example.
We can also define color fastness as, having color that will not run or fade with washing or wear. That means characterizes a material’s color’s resistance to fading or running. Clothing is colorfast if its colors and dyes do not bleed or run from the clothing. Clothing should be tested for colorfastness before using any type of bleach or bleaching solution, or strong cleaning product. Colorfastness is very important factor for buyer. Colourfastness properties of textiles are an important measure of quality of a product.
To test for color fastness, find a hidden seam of the garment or an hidden spot. Apply the cleaner to the garment and then dab the area with a clean cotton cloth.
If the color removes itself from the garment onto the cloth, you should not use the cleaning product on the clothing.
Important Terms and Definitions on Color Fastness:
Colorfastness: The resistance of color against outer influences is called colorfastness. It is distinguished between production colorfastness and usage colorfastness.
Change of color: During colorfastness tests, the change of the color within the visible spectrum between treated and untreated sample is measured. The color change can be caused by changes in color shade as well as color purity.
Bleeding: This term is used to describe the visible color difference between an undyed and untreated control fabric and a similar but treated fabric specimen. The difference is caused by dyestuff migrating from the treated fabric into the control fabric. Here, it is not important whether the dyestuff was exchanged via the aqueous solution or through direct contact between the fabrics.
Gray scale: Gray scales are photo standards with which color change can be assessed by comparing the contrasts between control fabrics and treated fabrics. Gray scales for the assessment of color changes according to DIN EN 20 105-A02 consist of five pairs of standardized, dull, gray panels with different contrast. The first panel of each pair is of neutral gray color. The second field of each panel is of increasing brightness, resulting in an increasing contrast. By comparing the contrast of the untreated and treated samples with those pairs, the panel with the most similar contrast can be determined. That panel number is then the value for the color change.
The gray scale for the assessment of bleeding (DIN EN 20 105-A03) also consists of five pairs of standardized, dull color panels. The first panel of each pair is always white; the second field becomes brighter with each fastness level. The fastness level 1 represents the biggest color distance, which means the highest degree of bleeding.
You may also like: Gray Scale for Color Change and Color Staining
Blue scale: For the assessment of light fastness, a special scale is used: the so called blue scale. It must be prepared a new every time before it is used according to DIN 54 003 and DIN 54 004. It consists of eight standardized color panels (different blue dyes), sorted according to their lightfastness. For the assessment, both the specimen and the blue-scale panels are subjected to defined light conditions. After a certain time, the contrast between the exposed and unexposed sample is compared to the contrast between the exposed and unexposed colored panels. The most similar pair determines the degree of lightfastness. This method can also be used to assess washing fastness and resistance to perspiration.
Different Types of Color Fastness:
There are various types of color fastness test for fabric. Important color fastness tests are given below:
- Color fastness to washing
- Color fastness to light
- Color fastness to perspiration
- Color fastness to water
- Color fastness to rubbing
- Color fastness to sea water
- Color fastness to hot pressing
- Color fastness to chlorinated water
- Color fastness to laundering
We have also published a comprehensive article on Different Types of Colour Fastness Test.
How to Improve Color Fastness?
Under the term color fastness, a complex pattern of properties is summarized, including fastness to water, sweat, washing, crocking and rubbing, light, peroxide, chlorine and combinations, for example, weather fastness. In fact, many fastness properties are defined by the chemical principle of the dyestuff system used and by the molecular structure and stability of the respective dye.
Thus, the improvement of color fastness often concentrates on aspects where the chemical principle of the dyeing allows the dye to achieve mobility and re-equilibration. Establishment of a new exhaust equilibration leads to desorption of dyestuff molecules during conditions of use and care.
Polycationic compounds: Water fastness of direct dyeing and reactive dyeing can be improved by deposition of polycationic compounds. Polydadmac polydiallyl-dimethylammonium chloride is a representative compound. The polycation forms insoluble ionic compounds with the anionic dyes and thus contributes to improved dyestuff fixation.
Direct dyes adhere to the fiber only through Van der Waals forces and hydrogen bonds; thus, establishing a new dissolution equilibrium under wet conditions is prevented.
In the case of reactive dyes, the dyes are bound covalently to the fiber; thus, the use of such a treatment does not seem necessary. However, both the presence of substantial amounts of adsorbed hydrolysate and slow hydrolysis of the anchor bonding lead to mobile dyestuff molecules, which then have to be kept attached to the fiber surface. Such polycationic additives also are used in the washing of darker reactive dyeing to shorten the process, as the full release of absorbed hydrolysate can require considerable time during technical rinsing operations.
The presence of such chemicals also influences other properties of the dyed product and can lead to the reduction of light fastness, color change, greying, increased soil uptake and reduced uptake of softeners.
Syntans – condensation products of aromatic sulphonates: Syntans (synthetic tannins) are used in dyeings of polyamide fibres. Acid dyes and metal complex dyes used for polyamide dyeing exhibit a negative charge. Thus, the mechanism of these anionic polymers is different. Representative formulas for such compounds are shown in Figure 2.
The function of these products is explained by different mechanisms. The negatively charged polymer forms a film on the surface of the fiber that prevents diffusion of negatively charged dye from inside of the fiber into the wash solution. Another explanation is based on aromatic interactions between the polymer and the chromophore of the dyestuff, thus strengthening the binding of the dye to the fiber.
Importance of Color Fastness:
Textile fabric has many properties. Color fastness property is one of the most important properties of them. The ability of the fabric to maintain primary color is one of the most important properties of textiles. It is a property of a colorant which allows it to retain its different characteristics despite degradation conditions such as exposure to light and dry cleaning. Product performance and evaluation to determine if the fabric is suitable for the intended end use. It is a identity for fabric. If colorfastness is good then fabric quality high and if poor fastness property then fabric quality is bad. So, colorfastness is the important factor for the buyer to justify which fabric is bad and which is better.
You may also like:
- Various Fastness Methods Given to the Dyed Material
- How to Determine Colour Fastness to Wash
- Gray Scale for Color Change and Color Staining
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.