The basic ways of printing include direct printing, discharge printing and resist printing.
Direct Printing
Direct printing is a kind of printing directly on white fabric or on pre-dyed fabric. The latter is called overprint. Of course the color of the printing pattern is much darker than the background 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 printing pattern looks lighter from the back than from the front, then we can determine that this is a directly printed fabric (note: this method coul dnot be used for light and thin fabric for the strong penertration of the printing paste.)
If the background color of the fabric is the same (due to matching dyeing), and the printing pattern is much darker than the background color, then this is the overprint fabric.
Discharge Printing
Discharge printing is carried out in two steps: the first step is to dye the fabric into a monochrome color, and the second step is to print the pattern on the fabric.
The printing paste in the second step contains a strong bleach that can destroy the background dye, so this method can be used to produce a flower cloth with a blue background and white dot pattern, a process called bleaching. Color discharge printing can be carried out when the bleach is mixed with dyes that will not react with it in the same paste (vat dyes belong to this type). Therefore, when a suitable yellow dye (such as vat dye) is mixed with the bleach of the color, the yellow dot pattern can be printed on the blue fabric.
Because the background color of discharge printing is first dyed by matching dyeing, if compared with the blotch printing on which the background color is printed, the background color is much richer and much darker. This is the main purpose of discharge printing.
Discharge printing fabrics can be printed by drum printing and screen printing, but not by heat transfer printing. Because compared with direct printing, the production cost of discharge-printed fabric is very high, and the use of reducing agent must be carefully and accurately controlled.
Resist Printing
Resist printing consists of two stages:
(1) Printing on white fabrics with chemicals or waxy resins that can prevent or prevent dyes from penetrating into the fabric.
(2) match dyed fabric. Its purpose is to dye the background color to set off the white pattern. Note that the result is the same as that of discharge printing, but the method to achieve this result is the opposite of discharge printing.
The application of dye-proof printing is not common, and it will only be used when the background color can not be dyed. Compared with large-scale production basis, most resist printing is achieved through methods such as handicrafts or manual printing (such as wax printing).
Because discharge printing and resist printing produce the same printing effect, it is often impossible to identify through naked eye observation.
Pigment Printing
The use of paint instead of dyes to produce printed fabric has become so widespread that it has begun to be regarded as a separate method of printing. Pigment printing is direct printing with paint, which is usually called dry printing to distinguish it from wet printing (or dye printing).
By comparing the hardness difference between printed and unprinted parts on the same fabric, pigment printing and dye printing can be distinguished. Pigment printing areas than unprinted areas feel a little harder, perhaps a little thicker. If the fabric is printed with dyes, there is no significant difference in hardness between printed and unprinted parts.
Dark pigment printing is more likely to feel harder and less flexible than light or light colors. When inspecting a fabric with pigment printing, be sure to check all colors, as the same fabric may contain both dye and paint. White paint is also used for printing, this factor should not be ignored.
Pigment printing is the cheapest printing method in printing production, because paint printing is relatively simple, requires the least process, and usually does not need steaming and washing. The paint has bright and rich colors and can be used in all textile fibers. They have good fastness to light and dry cleaning, even excellent, so they are widely used in decorative fabrics, curtain fabrics and clothing fabrics that need dry cleaning. In addition, the paint almost does not produce a large color difference on different batches of fabric, and has a good coverage of the background color during overprinting.
With continuous washing or dry cleaning, pigment printing will gradually fade and the color will be lighter and lighter. This is due to the gradual shedding of the resin adhesive due to continuous rotation and stirring in the cleaning process. Generally, this kind of printed fabric will fade obviously after 30 times of cleaning. Due to the application of 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.
Paint makes the fabric printing parts feel hard, this situation is not obvious in light color, but very prominent in dark color. The paint is not particularly wear-resistant, especially dark. Dark paints should be especially avoided in decorative fabrics such as furniture.