Knowledge

1. Direct printing

Direct printing is a kind of printing directly on white fabric or on pre-dyed fabric. The latter is called an overprint. , Of course, the color of the printed pattern is much darker than the dyed base color. A large number of common printing methods are direct printing.

If the background color of the fabric is white or mostly white, and the printed pattern looks lighter than the front color from the back, then we can determine that it is a direct printed fabric (Note: Because the printing paste has a strong penetrating power, it is suitable for light and thin The fabric cannot be judged by this method).

If the fabric background color is the same on the front and back (because it is piece dyed), and the printed pattern is much darker than the background color, then this is an overprint fabric.

2. Discharge printing

Discharge printing is carried out in two steps. In the first step, the fabric is piece-dyed into a single color, and in the second step, the pattern is printed on the fabric. The printing paste in the second step contains a strong bleaching agent that can destroy the background dye. Therefore, this method can produce a pattern of blue and white dots. This process is called whitening. When the bleaching agent and the dyes that do not react with it are mixed in the same color paste (Vat dyes belong to this type), color discharge printing can be carried out. Therefore, when a suitable yellow dye (such as a vat dye) is mixed with a colored bleaching agent, a yellow dot pattern can be printed on the blue fabric.

Discharge printing fabrics can be printed by roller printing and screen printing, but not by thermal transfer printing. Because the production cost of discharging fabrics is very high compared with direct printing, it is necessary to carefully and accurately control the use of reducing agents. The fabrics printed in this way have better sales and higher prices.　Because the background color of discharge printing is first dyed by piece dyeing, if the background color is printed on the whole floor, the color of the background color is much richer and darker.

If the background color of the front and back of the fabric is the same color (because it is piece dyed), and the pattern is white or a color different from the background color, it can be confirmed that it is a discharge printed fabric; check the reverse side of the pattern carefully, it will Reveal the traces of the original background color (the reason for this phenomenon is that the chemical agent that destroys the dye cannot fully penetrate the reverse side of the fabric).

Three, anti-dye printing

Anti-dye printing includes two stages:

(1) Print on white fabrics chemical agents or waxy resins that can prevent or prevent dyes from penetrating into the fabrics;

(2) Piece dyed fabric. The purpose is to dye the base color to bring out the white pattern. Note that the result is the same as that of discharge printing fabric, but the method to achieve this result is the opposite of discharge printing.

Because discharge printing and anti-dye printing produce the same printing effect, they are often not distinguished by naked eye observation. The application of anti-dyeing printing method is not universal, and it is generally used when the background color cannot be discharged. Compared with the basis of large-scale production, most of the anti-dye printing is achieved through methods such as handicraft or manual printing (such as wax anti-printing).

Fourth, paint printing

The use of paint instead of dyes to produce printed cloth has been so widespread that it has begun to be regarded as an independent printing method. Pigment printing is direct printing with paint. This process is usually called dry printing to distinguish it from wet printing (or dye printing).

Dark pigment printing is likely to feel harder and less flexible than light or light colors. When inspecting a fabric with pigment printing, make sure to check all colors, because the same fabric may contain both dyes and paints. White paint is also used for printing, this factor should not be ignored.

Pigment printing is the cheapest printing method in printing production, because the printing of paint is relatively simple, requires the least process, and usually does not require steaming and washing. The paint has bright and rich colors and can be used for all textile fibers. Their light fastness and dry-cleaning fastness are good, even excellent, so they are widely used in decorative fabrics, curtain fabrics and clothing fabrics that require dry cleaning. In addition, the paint hardly produces large color differences on fabrics of different batches, and the coverage of the base color during overprinting is also very good.

With continuous washing or dry cleaning, the pigment printing will gradually fade and the color will become lighter and lighter. This is due to the gradual fall off of the resin binder due to constant rotation and stirring during the cleaning process. Generally after 20-30 times of washing, this kind of printed cloth will show obvious fading phenomenon. As the fabric is treated with resin and silicon softener in the finishing process, the color fastness is improved. It is worth noting that dark colors fade more easily than light or light colors.