“Jet black” is exactly the opposite of “snow white”. In terms of color brightness, “snow white” needs to be extremely light, and the reflectivity of the fabric must be as large as possible;
And “Jet black” requires to be extremely dark, and the reflectivity of the fabric must be as small as possible.
In layman’s terms, “snow white” requires “pure and clean”; while “black” requires “mixed and dark”.
In other words: “Snow white” is like Cantonese cuisine, which emphasizes “purity” and original flavor; while “black” is like Sichuan cuisine, which emphasizes “purity”. “Heavy flavor”; the other colors are Hubei dishes, each with its own “taste” but no special characteristics.
In actual production, what our colorists are most happy to do is “black”. In fact, the “black” they dye can only be classified as “black” in a strict sense. It is classified as a “color” with relatively low brightness, but there is still a considerable gap between it and the true “black”. It is indeed difficult to dye black to a “jet black” color.
What is “jet black”
Most of the black we see every day has low reflectivity Therefore, red light black and cyan light black are often used to describe the color characteristics of a certain black. This description of the characteristics of black is actually a negation of black.
From the perspective of color science definition, the definition of black is: the lightness value (L) is very low, the purity value (C) is close to zero, that is, the chroma value is very small . When several characteristic values of the fabric color meet this requirement, the characteristic of the fabric color is “black”.
Pre-treatment of fabrics
Grey fabric preparation: When processing general black, the requirements for gray fabric can be A little lower, as long as there is no mildew, there will be no problem with gray fabrics that do not contain polypropylene and polyester yarns. However, if the fabric is dyed “black”, the requirements for the gray fabric will be higher. The cotton content of the gray fabric will be higher. The fiber maturity must be high, so that the color absorption rate of the processed fabric will be improved.
Singeing process: There are no special requirements for the singeing process, but the singeing process is clean and there must be no slurry contamination. This is the most basic requirement for the singeing process. As a black dyeing This should also be noted for semi-finished fabrics.
③Desizing and scouring process: The requirements for desizing and scouring black fabric semi-finished products are that the desizing should be as uniform and clean as possible, and the scouring alkali concentration should be as high as possible , the cooking temperature should be higher and the cooking time should be longer.
④ Bleaching process: The whiteness requirements of black fabric semi-finished products are not very high, but the whiteness must be uniform. Therefore, the concentration of hydrogen peroxide can be relatively low. The concentration of hydrogen peroxide can be relatively low. It can be controlled at around 4g/L.
⑤Acid washing: Although the metal salts on the fabric have no obvious adverse effects on dyeing black, it is still necessary to pickle the fabric after desizing. Acid washing can ensure that the fabric does not contain alkali before entering the bleaching solution, preventing pH fluctuations in the bleaching solution from affecting the consistency of whiteness, while pickling after mercerization can ensure the stability and consistency of the fabric during the dyeing process. , to prevent color difference caused by inconsistent alkali on the fabric due to incomplete mercerization.
⑥Mercerization process: The requirement for mercerization of black fabrics is that the mercerization alkali concentration should be high. The concentration of caustic soda in the alkali rolling tank should be controlled at about 250g/L. The mercerization tension can be smaller. Dealkalization should be uniform and clean.
Dye screening
①Dye Characteristics: Conduct spectral analysis of existing dyes, and measure the reflected light curves of the dyes in the visible light region under different light sources at deep, medium and shallow concentrations to provide information for dye selection.
②Dye ratio: Based on the light source and order requirements specified by the customer, based on black dye, the dye with the best matching performance is selected among similar dyes based on the dyeing characteristics of the dye. and dosage. Under normal circumstances, suppliers will adjust the color of black dye to blue and slightly green, which makes it easier to adjust the shade during the dyeing process. It is rare to adjust the color of black dye to yellow or red. If we want to For fabrics to be dyed “black”, the blue and green light in the black dye must be reduced, which can quickly increase the black depth. Therefore, when dyeing black, it is generally customary to add some red and yellow dyes for this reason. In order to improve vision When adjusting the depth, red and yellow dyes tend to be heavier.
③Recipe correction: Theoretically, equal amounts of the three primary colors of red, yellow, and blue can be mixed to produce black, but Since the dye saturation used in actual production is not enough, the color produced by mixing this impure primary color has a complex shade. It is impossible to mix the ideal black with equal amounts of these three primary colors. How to master the black mixing The optimal mixing quantity of dyes needs to be carefully selected through small sample tests.
Any dye has a dye uptake rate. When the amount of dye reaches a certain concentration, thenIncreasing the amount of dye will not increase the depth of the color. When dyeing black, there is a serious waste of dye usage. This waste is manifested in three aspects: first, there is a waste of fl in the entire visible light band; second, there is a waste of dye usage in individual bands in the visible light band. The third problem is the waste of dye usage under a certain light source.
The waste phenomenon in the first situation is relatively rare and easy to grasp; the waste phenomenon caused by the second and third situations is very common and receives little attention. Black is a special color. Firstly, the amount of dye is high. Secondly, black dye accounts for a large proportion. Other dyes are just adjustments and supplements for a color light and depth within a certain interval. During the dyeing process, the color The change pattern is mainly determined by the black dye, and changes in other dyes will not cause substantial changes in the overall color of the fabric.
When dyeing black, there is a serious waste of dye usage. This waste is manifested in three aspects: First, there is a waste of dye usage in the entire visible light band; The second is the problem of waste of dye usage in individual bands in the visible light band; the third is the problem of waste of dye usage under a certain specified light source. The waste phenomenon in the first situation is relatively rare and easy to control; the waste phenomenon caused by the second and third situations is very common and receives little attention.
Black is a special color. One is that the amount of dye is high, and the other is that black dye accounts for a large proportion. Other dyes are only one color and a certain range. Adjustment and supplementation of depth. During the dyeing process, the color change pattern is mainly determined by the black dye. Changes in other dyes will not cause substantial changes in the overall color of the fabric. Therefore, when dyeing black, don’t be limited to the matching and adjustment of three dyes, and don’t use simple red, yellow, blue, and green to judge the characteristics of the color, but conduct a full-band color light analysis of the color in the visible light band. and adjust the reflected light curve as much as possible to a “straight line”.
Process Control
① During steam fixation, the pH of the fixation solution can be controlled at Around 12, the steaming time should be controlled at around 75 seconds, and the full cold water rinse at the outlet of the steamer should be strengthened.
② Soaping should be sufficient. 1~2g/L chelating dispersant should be added to the soaping liquid, and the fabric should be washed thoroughly. The fabric should not be too alkaline.
③ In addition to the normal addition of various additives to the tenter finishing fluid, 2g/L of Swire oil can also be added.
④ When shrink-proofing, the front side of the fabric should be in contact with the rubber blanket to prevent laser marks. </p
