Basic knowledge of dyeing and proofing – Preparation of proofing gray fabric Information on composite fabrics

Basic knowledge of dyeing and proofing–Preparation of proofing gray fabric
　1. Keeping the cloth used for small samples and large samples consistent is the basic condition for improving the accuracy of small samples.
For pure cotton fabrics, the effects will be different due to different varieties, origins or maturity of cotton fibers, different warp and weft densities and tissue specifications of the fabrics, as well as different pre-treatment methods and pre-treatment levels of the fabrics. For chemical fiber fabrics and blended fabrics, such as pure polyester or polyester-cotton, polyester-viscose and other blended fabrics, due to the different raw materials and process operations used in making synthetic fibers, differences in fiber microstructure will directly result in different manufacturers and different brands. Polyester with different batch numbers and specifications has different color absorption properties when dyed.
In view of the above and many other factors, when selecting the gray fabric for proofing, you must use the semi-finished gray fabric used in mass production. If you proof the sample in advance and the semi-finished gray fabric used in mass production is not available in time, you can choose a similar semi-finished gray fabric. For the first sample, the basic material prescription should be worked out in advance. After the semi-finished gray fabric used for mass production comes out, a duplicate sample will be made. If it does not match the standard color light, the materials used will be adjusted until the duplicate sample matches the village sample. To sum up, only by ensuring that the cloth used for small and large samples is consistent can we avoid differences in large and small samples due to differences in fiber quality, blending ratio, tissue specifications, whiteness, gloss, moisture absorption properties, etc., and improve the accuracy of small and large samples.
　2. Requirements for gray fabric pre-treatment are based on the dyeing color and dyeing materials:
Since the dyeing color depth and brightness are different, the requirements for gray fabric processing are also different. For example, a light bright color dyed with reactive dyes will It is required that the gray fabric be carefully bleached to make it have better whiteness and wool effect; for dark and dark colors, it can be semi-bleached or not bleached.
In addition, because some dyes have special properties, they also put forward some special requirements for the pre-treatment process. For example: when dyeing with reactive dyes, since the dyes are reactive dyes and are relatively sensitive to the chemical environment they are exposed to, the gray fabric is required to be pre-treated:
1) Boiling and bleaching must be even and thorough to avoid the waste of reactive dyes;
2) Do not use chlorine. Most reactive dyes have poor resistance to chlorine bleaching. If there are residual chlorine or bleaching powder stains on the cloth, most reactive dyes will be destroyed and the color will become lighter and darker; 3) After pre-treatment, the cloth surface appears neutral. Because the cloth surface contains alkali, it is easy to cause uneven dyeing. The acid content on the cloth surface will affect the dye and make it light in color. The pre-treatment has a good capillary effect. The pH value of the cloth surface is uniform, with a PH value of 6~7.
In short, the quality of the gray fabric for dyeing and the choice of pre-treatment process have a certain impact on dyeing proofing and dyeing quality. Therefore, the preparation of gray fabric before dyeing and proofing is an important task that cannot be ignored.

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