How to identify the front and back of the cleanroom paper?
cleanroom paper is a thin paper, and the front and back are not well analyzed. Let's take a look at the summary method.
1. Tear method: Hold the test piece in hand, make the longitudinal direction parallel to the line of sight, level with the surface of the test piece, and pull the paper up with the other hand, so that it is first torn in the longitudinal direction. The direction of the tearing paper is then gradually turned to the lateral direction, and the outer edge of the paper is torn off and turned over the paper. On the other side, the paper is still torn according to the above method, and the paper hair on the two tear lines is compared, and one line is more obvious than the other. Especially in the longitudinal direction of the curve, the paper hair is obviously the mesh surface. When the net is facing up. The burrs of cleanroom paper are even worse.
2, intuitive method: Fold a test piece, observe the relative smoothness of one side, the diamond indentation from the paper net can often recognize the net surface. When the time is horizontal, the person shoots light at a 45° angle to the paper surface, and the line of sight is also at an angle of 45° to the paper surface to observe the web marks on the paper surface. It is also possible to observe the paper surface under a microscope to help identify the mesh surface.
3. Wetting method: Dip the dust-free cleanroom paper surface with water or dilute sodium hydroxide solution, drain the excess liquid, leave it for a few minutes, observe both sides, if there is a clear screen printing, it is the reverse side.