Basic methods of printing
Basic methods of printing
1. Direct printing
Direct printing is printing directly on white fabric or on fabric that has been pre-dyed. The latter is called overprinting. , 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 from the back than the front, then we can determine that it is a directly printed fabric (note: due to the strong penetration of printing color paste, it is suitable for light and thin products. Fabrics cannot be judged by this method).
If the background color of the fabric is the same on the front and back (due to piece dyeing), and the printed pattern is much darker than the background color, then this is an overprinted fabric.
2. Discharge printing
Discharge printing is carried out in two steps. The first step is to dye the fabric pieces into a solid color. The second step is to print the pattern on the fabric.
The printing paste in the second step contains strong bleaching agents that can destroy the background dye. Therefore, this method can produce floral cloth with a blue background and white polka dot pattern. This process is called whitening. Discharge printing can be done when bleach is mixed in the same color paste with dyes that do not react with it (vat dyes are of this type). Therefore, when a suitable yellow dye (such as a vat dye) is mixed with a colored bleach, a yellow dot pattern can be printed on a blue background fabric.
Because the background color of discharge printing is first dyed using piece dyeing method, if compared with all-over printing where the background color is printed on, the color of the background color is much richer and deeper. This is the main purpose of using discharge printing.
Discharge printed fabrics can be printed by roller printing and screen printing, but not by heat transfer printing. Because discharge-printed fabrics are very expensive to produce compared to direct printing, the use of the reducing agents required must also be very carefully and accurately controlled. Fabrics printed in this way have better sales and higher price levels. Sometimes, the reducing agents used in this process can cause damage or damage to the fabric in the printed pattern.
If the background color on both sides of the fabric is the same (because it is piece dyeing), and the pattern is white or a different color from the background, it can be confirmed that it is a discharge-dyed printed fabric; carefully check the reverse side of the pattern to see if Traces of the original background color are revealed (the reason for this phenomenon is that the chemicals that destroy the dye cannot fully penetrate into the reverse side of the fabric).
3. Resist dye printing
Resist dye printing includes a two-stage process:
(1) Print chemicals or waxy resin on white fabric that can prevent or prevent dyes from penetrating into the fabric;
(2) Piece dyed fabrics. The purpose is to dye the base color to bring out the white pattern. Note that the results are the same as for discharge-printed fabrics, however the method of achieving this result is the opposite of discharge printing.
The resist printing method is not commonly used and is generally used when the background color cannot be discharged. Compared with large-scale production basis, most resist printing is achieved through methods such as handicraft or manual printing (such as wax resist printing).
Because discharge printing and resist printing produce the same printing effect, they often cannot be distinguished through naked eye observation.
4. Pigment printing
The use of paints rather than dyes to produce printed fabrics became so widespread that it began to be considered a separate form of printing. Pigment printing is direct printing with paint. This process is usually called dry printing to distinguish it from wet printing (or dye printing).
Pigment printing and dye printing can be distinguished by comparing the hardness difference between the printed and unprinted parts of the same piece of fabric. The paint-printed areas will feel slightly harder and perhaps a bit thicker than the unprinted areas. If the fabric is printed with dye, there will be no significant difference in hardness between the printed and unprinted areas.
Dark pigment prints are likely to feel harder and less flexible than lighter or lighter colors. When inspecting a piece of fabric for a paint print, be sure to check all colors, as both dye and paint may be present on the same piece of fabric. White paint is also used for printing, this factor should not be ignored.
Pigment printing is a cheap printing method in printing production, because the printing of paint is relatively simple, requires few processes, and usually does not require steaming and washing. The coatings are available in bright, rich colors and can be used on all textile fibers. Their light fastness and dry cleaning fastness are good or even excellent, so they are widely used in decorative fabrics, curtain fabrics and clothing fabrics that require dry cleaning. In addition, the paint will hardly produce large color differences on different batches of fabrics, and the coverage of the base color during overprinting is also very good.
With constant washing or dry cleaning, paint prints will gradually fade and become lighter in color. This is due to the resin binder gradually falling off due to constant turning and stirring during the cleaning process. Generally, after 20-30 times of cleaning, this kind of printed cloth will show obvious fading. Color fastness is improved due to the application of resins and silicone softeners to the fabric during the finishing process. It’s worth noting that dark colors fade more easily than light or pastel colors.
The paint makes the printed parts of the fabric feel stiff, which is less noticeable in light colors but very prominent in dark colors. The paint isn’t particularly hard-wearing, especially dark colors. Dark paints should be especially avoided in fabrics such as furniture upholstery. S0aRBf0d
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