Colorfastness Detection Reveals the Lie: Color Will Last Longer After Few Wash

Colorfastness detection reveals the lie: color will last longer after few wash! When we wash new clothes at the very 1st time, we found the water becomes colored. We know the clothes color will fading. We only know that clothes are fading, but never know what causing the discoloring. The reason is the color fastness too low, colorfastness test failed or unqualified product quality, which you shall maintain your rights.

Textile dyeing fastness includes a broad range of tests. Now we briefly introduce what the content of textile color fastness detection is.

Dyeing fastness refers to the dyed products in use or the dyeing process, dyes, and pigments in a variety of external factors under the influence of whether the original color cannot fade, do not change the ability. It is one of the important indicators to measure product quality.

For example, some dyed fabric after several wash or exposure for a long time will show a significant fade phenomenon, which indicates the low quality of color fastness. If after few more wash and long exposure to the sun and there is no significant fading phenomenon, which indicates the high quality of color fastness. Dyeing fastness is mainly resistant to sun, weather, soap wash, perspiration, abrasion, ironing, chlorine bleaching and smoke. Different dyes have different color fastness on the fabric. This is primarily determined by the chemical structure of the dye, in addition to the state of the dye on the fiber, such as the degree of dye dispersion and the combination of dye and fiber. The same dye on different fibers will have very different color fastness. Such as indigo in cotton after the resistance to light fastness is only about 3, and dying in the wool fabric on its resistance to light fastness, up to 7 to 8 level to carry out a quality inspection of the product, the textile business sector will reference to the taking of textiles to develop a set of color fastness test methods and standards. General requirements for the color fastness to the fabric are the following.

1. Resistant to light fastness

Dyeing fabric resistant to light fastness, refers to the fabric after dyeing in the long-term sunlight under the fade, discoloration degree.
Sun fade, discoloration is a complex process. In the role of sunlight, the dye absorbs light energy. Molecules in the excited state, very unstable must be obtained in different forms of energy released in order to become stable state. One form is that the dye receives light and decomposes it directly and fades. The same dyestuffs have different fading mechanisms on different fibers. For example, the fading of azo dyes on cellulosic fibers is oxidation, and fading on protein fibers is a reducing effect. The resistance to light fastness of the dye is also related to its molecular structure. Such as anthracene awake, phthalocyanine, metal complex dyes resistant to high fastness, insoluble azo dyes between the resistances to light fastness difference between the larger. If the molecular structure contains more amino, hydroxyl and it’s easy to absorb light energy and not resistant to oxidation, resistance to poor light fastness. The resistance to light fastness is also related to the dye concentration at the time of dyeing. The general concentration is high resistance to light fastness with low concentration of sun fastness is relatively good. Resistance to light fastness assessment is based on “blue standard” as the basis. The so-called “blue standard” refers to the use of the specified dye in a certain concentration of blue wool fabric. The exposure time required for the sun to fade under the prescribed conditions is roughly doubled.

2. Soap clean fastness

Resistant wash fastness means the degree to which the dyed fabric is discolored after soaping in a soap solution under prescribed conditions. It includes both faded and white cloth stains. The fade is the fade of the fabric before and after soaping.
White cloth is stained with white cloth and dyed fabric stitched together, after soaping, because the dyed fabric faded white cloth caused by the situation. The cleanliness of soap resistance is related to the chemical structure of the dye. Water-soluble dyes containing hydrophilic groups have a higher wash fastness than those without hydrophilic groups. Such as acid dyes direct dyes, due to contain more hydrophilic groups, resistance to soap and wash fastness, and the reduction of dyes, sulfur dyes, insoluble azo dyes and so does not contain hydrophilic groups. The wash ability is also related to the combination of dye and fiber. Such as acid mordant dyes and direct copper salt dyes, due to dye and metal ions chelate, dye molecules increased, water solubility decreased, soap washing fastness and thus increased. Reactive dyes and fiber covalent bond, dyes and fiber into one, so the soap wash fastness is also better. The same dye in different fibers on the soap-washing fastness is different, such as disperse dyes in the polyester on the soap-washing fastness than in the nylon to be high. This is because the structure of polyester is stronger than nylon closes, hydrophobic. Soaping fastness and dyeing process related. Dye is bad, the floating color is not clean, will lead to decreased resistance to soaping fastness. The temperature, pH and agitation of the soap solution are also affected. The dyeing density also has an effect on the color fastness, and sometimes the color fastness is higher than the dark color. The method of washing the washing fastness is to treat the fabric under the specified conditions. After the treatment, the paper will be evaluated with the ministerial “color fastness fading card” or “color fastness coloring card”. Resistant wash fastness is divided into five levels. Level 1 is the worst, level 5 is the best. Color fastness is also divided into five levels.

3. Friction fastness

The friction fastness of the dyed fabric is divided into dry friction fastness and wet friction fastness. Dry friction fastness is reflected in the dry cloth after the white cloth stains, wet friction fastness is reflected with the water content of 95% to 100% of the white cloth after the friction of the situation. General wet friction fastness is lower than dry friction fastness. The frictional fastness of the fabric depends on the amount of the float and the combination of the dye and the fiber, the permeability of the dye, and so on. Such as reactive dyes and fibers covalently bonded, dry friction fastness is very good. The higher the dyeing concentration is, the lower the friction fastness is. The friction fastness test was carried out on a friction fastness tester, and the “friction fastness stained gray card” was rated as levels 5. Level 1 is the worst, serious staining, level 5 is the best.

4. Perspiration fastness

Perspiration fastness refers to the simulation of human sweat under the conditions of dyeing fabric dyeing and color fastness performance indicators. The test solution is alkaline and acidic two. Fastness is also divided into five levels. Level 1 is the worst, serious staining, level 5 is the best. In addition to the above four major fastness indicators are resistant to chlorine bleach fastness, sublimation fastness, etc., are have ministerial standards and generally 5 grading level.


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