How to improve the two-sidedness of paper?

Two-sidedness of colored paper sheet is where one side of paper sheet is darker while it is lighter on the other side. This normally occurs where fillers in sheet are used and the dyed filler accumulates on the vacuum side of the sheet resulting in darker color.

To reduce the two-sidedness of paper, the following points need to be done: 

Correct selection of dyes and pigments; Check amount of filler; The foils and vacuum system should be adjusted to improve wet line; 

Check addition point and sequence, the use of fixing agent, color fixing agent or other dyeing auxiliaries, and the surface dyeing together.