Paper ink absorption is not only related to the loose degree and capillary state of paper, but also related to the surface properties of paper fiber, the content of filler, pigment, glue, the composition and characteristics of ink, printing method, printing pressure and other factors.In actual printing, the absorption of ink can be divided into two stages.
The first stage is the pressing moment of the printing press, relying on the action of printing pressure, part of the ink transferred to the surface of the paper into the larger pores, that is, the whole ink (including the pigment in the ink) into the paper pores. This process is generally called the pressure infiltration stage. At this stage, the paper absorption of the ink mainly depends on the size of the printing pressure, the structure of the paper and the ink viscosity and other factors.
The second stage is from the paper from the imprint area until the ink is completely dry. This stage mainly depends on the capillary action of the paper to absorb the ink, called the free infiltration stage. At this stage, the link separates from the ink bulk and enters the paper interior rather slowly through the small pores and the rough surface of the paper fibers.
Paper is a porous material, and there are many different size gaps between fiber and fiber, and between fiber and filler, which are equivalent to many capillaries. Under the action of these capillaries, the connecting material in the ink can be absorbed, and the thicker the diameter of the capillary, the faster the ink absorption rate.Therefore, the pore structure of the paper determines its absorption of the ink. The looser the paper, the larger the pores, and the stronger the ink absorption.