"Jet Black" is the opposite of "Snow White". In terms of color brightness, "Snow White" requires lightness to the extreme, and the reflectivity of the fabric should be as large as possible;
The "Jet Black" requires the extreme depth, and the reflectivity of the fabric should be as small as possible.
In actual production, what our colorists are most happy to do is "black". In fact, the "black" they dye can only be classified as a "color" with a relatively low brightness in a strict sense, which is different from real In the sense of "black", there is still a considerable gap. It is really difficult to dye black to "Jet Black".
(1) What is "Jet Black": The blacks we see daily are mostly colors with relatively low light reflectivity. Therefore, red light black and cyan light black are often used to describe the color characteristics of a certain black. This characteristic of black The description is actually a negation of black.
From the perspective of the definition of color science, the definition of black is: the lightness value (L) is very low, and the purity value (C) is close to zero, that is, the chroma value is very small. When several characteristic values of fabric color meet this requirement, the characteristic of fabric color is "Jet Black".
(2) Pretreatment of fabric:
① Grey fabric preparation: When processing general black, the requirements for grey fabric can be slightly lower. As long as there is no mildew, there will be no problem with grey fabrics that do not contain polypropylene and polyester filaments, but if the fabric is dyed "Jet Black" At this time, the requirements for the grey cloth should be higher, and the maturity of the cotton fiber of the grey cloth should be higher, so that the color absorption rate of the processed fabric can be improved.
② Singeing process: There are no special requirements for the singeing process, but the singeing process is clean and free of slurry contamination. This is the most basic requirement for the singeing process. It is also necessary to pay attention to this as a semi-finished product dyed with black fabric.
③Desizing and scouring process: The requirements of black fabric for the desizing and scouring of semi-products are that the desizing should be as uniform and clean as possible, the concentration of scouring alkali should be as high as possible, the scouring temperature should be higher, and the scouring time should be biased. long.
④ Bleaching process: The whiteness of black fabric semi-products is not very demanding, but the whiteness must be uniform. Therefore, the concentration of hydrogen peroxide can be relatively low, and the concentration of hydrogen peroxide can be controlled at about 4g/L.
⑤Pickling: Although the metal salt on the fabric does not have any obvious adverse effect on dyeing black, it is still necessary to pickle the fabric. Pickling after desizing can ensure that the fabric does not carry alkali before entering the bleaching solution. , To prevent the consistency of whiteness from being affected by the fluctuation of pH in the bleaching solution, and the acid washing after mercerizing can ensure the stability and consistency of the fabric during the dyeing process, and prevent the fabric from being inconsistent with alkali due to unclean mercerizing. Produce chromatic aberration.
⑥ Mercerizing process: The black fabric requires high mercerizing alkali concentration, the caustic soda concentration in the caustic soda tank is controlled at about 250g/L, the mercerizing tension can be smaller, and the mercerizing dealkalization should be uniform and clean.
(3) Dye screening:
① Dye characteristics: Perform spectral analysis of existing dyes, and measure the reflected light curve of the dye in the visible light region under different light sources with multiple concentrations of deep, medium and shallow, providing information for selecting dyes.
② Dye ratio: According to the customer's specified light source and order requirements, based on black dyes, among similar dyes, the dyes with the best matching performance are selected and combined according to their dyeing characteristics. Under normal circumstances, suppliers will adjust the shade of black dye to blue and greenish, so that it is convenient to adjust the shade during the dyeing process. It is rare to adjust the shade of black dye to yellow or red. If we want to When the fabric is dyed with a "black" effect, it is necessary to reduce the blue and green light in the black dye, which can increase the black depth quickly. Therefore, when dyeing black, it is generally used to add red and yellow dyes, in order to improve the vision When adjusting the depth, red and yellow dyes tend to be heavier.
③Formulation correction: In theory, equal amounts of the three primary colors of red, yellow, and blue can be mixed to produce black, but due to insufficient dye saturation in actual production, the mixed color of this impure primary color is other The shade is more complicated, and the ideal black cannot be mixed with equal amounts of these three primary colors. How to grasp the best compatibility of black mixed dyes needs to be carefully selected through a sample test.
Any dye has a dye uptake rate. When the amount of dye reaches a certain concentration, increasing the amount of dye will not increase the depth of its color. When dyeing black, the waste of the dye amount is more serious. This waste is manifested in three aspects: one is the waste of fl in the entire visible light band; the other is the waste of dye in individual wavelengths in the visible light band Problem: The third is the waste of dye consumption under a certain specified light source.
The waste phenomenon in the first case is relatively rare and easy to grasp; the waste caused by the second and third cases is very common and rarely gets attention. As a special color, black has a high amount of dye, and a large proportion of black dye. Other dyes are just a shade and depth adjustment and supplement in a certain range. During the dyeing process, its color The change rule is mainly determined by black dyes, and the changes of other dyes will not cause substantial changes to the overall color of the fabric.
When dyeing black, the waste of the amount of dye is more serious. This waste is manifested in three aspects: one is the waste of the entire visible light band; the other is the waste of the amount of dye in the visible light band. The third is the waste of dye consumption under a certain specified light source. The waste phenomenon in the first case is relatively rare and easy to grasp; the waste caused by the second and third cases is very common and rarely receives attention.
Black is a special color. One is that the amount of dye is high, and the other is that the proportion of black dye is large. Other dyes are just a shade and the adjustment and supplement of the depth in a certain interval. During the dyeing process, its color The law of change is mainly determined by black dyes, and the changes of other dyes will not cause substantial changes to the overall color of the fabric. Therefore, when dyeing black, do not limit the matching and adjustment of the three dyes, and do not use simple red, yellow, blue, and green to judge the characteristics of the color, but perform a full-band color light analysis of the color in the visible light band. And adjust, adjust its reflected light curve as a "straight line" as much as possible.
(4) Process control:
① When steaming and fixing, the pH of the fixing solution can be controlled at about 12, the steaming time is controlled at about 75s, and the full-width cold water rinsing at the outlet of the steamer should be strengthened.
②The soaping should be sufficient. Add 1~2g/L chelating dispersant to the soaping solution, wash thoroughly, and the fabric should not be alkaline.
③In addition to the normal addition of various additives, 2g/L of Taikoo oil can be added to the stenter finishing solution.
④ When shrink-proof, the front of the fabric should be in contact with the rubber blanket to prevent laser printing.