Ink absorption can be considered from the perspective of pore size. After the ink fills in the pores, the capillary tube in the paper absorbs the binder in the ink. If the pores between the fibers of the paper are small, the capillary action of the fibers is destroyed, and the ink absorption performance is poor. Large, ink absorption is too strong, when the viscosity of the printing ink is low, the capillary not only absorbs the binder, but also absorbs the pigment, it will cause the ink to penetrate to the back of the paper, the phenomenon of through-printing, and the thickness of the ink layer after drying, The imprint can not show the proper color saturation on the paper, which affects the quality of the print.

The permeation amount in the pressure permeation stage and the free permeation stage has a great relationship with the absorption performance of the paper, especially the free permeation is more prominent. Therefore, the stronger the ink absorbency of the paper, the faster the paper absorbs the ink binder, and the faster the ink dries. The ink absorption of paper has a great relationship with the quality of printed matter. Many printing failures are caused by the mismatch between the ink absorption of paper and the printing conditions used.

  1. Paper is too absorbent

(1) Matte and powder

In printing, the paper mainly absorbs the binder in the ink. If the paper's ability to absorb the ink is too strong, the binder is excessively absorbed into the paper layer or coating, resulting in a lack of binder in the ink layer on the paper. The pigment particles are suspended on the paper surface. After the conjunctiva is dried, the prints have faded or tarnished, and even if some prints are rubbed, the pigments will peel off in a granular form, causing pulverization. When the powdering is serious, during the overprinting process, the ink layer of the previous color will be peeled off from the paper when the next color is printed.

The solution is as follows

① Replace the appropriate paper.

② Use a thickener to increase the viscosity of the ink, or add a high-viscosity ink with a resin content in the ink.

③ Humidify the paper.

(2) through printing

Ink viscosity is low. When the printing pressure is too high, the paper is too absorbent to the ink. The binder penetrates into the internal pores of the paper, replacing some of the air in the pores of the paper, causing air-fiber, air-filler, and air-coating scattering. Decreasing the interface reduces the light scattering ability of the paper and increases the transparency, which may lead to the occurrence of through-printing.

The solution is as follows

① Replace the appropriate paper.

② Reduce printing pressure.

③ Increase the viscosity of the ink.

(3) The density of the ink layer decreases, and the hue changes.

When printing on paper with large pores, part of the pigment and binder will penetrate into the paper together (the pores of the paper fibers are larger than the pigment particles). Excessive penetration of the binder will dry up the print and reduce the tinting power of the ink The saturation of the layer is reduced, which significantly reduces the color density of the print. At the same time, the obvious reduction in the color density of printed matter will also change the hue of printed matter and affect the correct reproduction of gray balance.

The solution is as follows:

① Replace the appropriate paper.

② Retest the gray balance data for this kind of paper.

  2. Paper is too weak to absorb ink

The paper's ink absorption is too weak, and the speed of absorbing ink is too slow. Although a colorful ink layer can be obtained in the printing process, it affects the penetration and fixation of the ink and oxidative polymerization, resulting in a reduction in the fixing speed of the ink and the transfer of ink to the paper It cannot be absorbed by the paper soon after being applied, so that the wet ink will be transferred to the back of another paper covered by it, causing stickiness, and in severe cases, adhesion will also occur.

The solution is as follows:

① Replace the appropriate paper.

② Increase printing pressure appropriately.

③ Reduce ink viscosity.

④ Reduce printing speed.