The front side of the paper: the felt side, which is relatively smooth and tight.
The reverse side of the paper: the mesh surface, in the paper sheet forming process, contact with the mesh surface to produce screen printing on the paper surface, so the reverse side is always rough and relatively loose.
The difference between the front side and the back side of the paper is called two-sided difference.
Causes of poor paper on both sides:
① The fiber orientation arrangement is different along the thickness direction of the paper;
② The sorting and scrubbing effect of paper material in the forming process;
③ The proportion of pulp;
④ The concentration of fine fibers that are easy to be highly colored on the front side of the paper is relatively large, causing the color difference between the two sides of the paper.
Ways to reduce the difference between two sides of the paper:
① Use fine mesh, smoother fabric net as much as possible;
② Use smooth press, back press, size press, facing roll and calender to calender;
③ Add retention aids to the paper stock;
④ For the cylinder paper machine, adopt an improved cylinder mesh slot;
⑤ For Fourdrinier paper machines, use grooved table rolls and chopping boards instead of table rolls to reasonably control the vacuum degree of the vacuum box;
⑥ Adding carbon amide and phenolic resin to the paper material can reduce the color difference of colored paper on both sides;
⑦ Adopting the mesh former.