There are two parts of ATM printing paper roll, its front is felt side and the back is that contacts with copper net of sand paper machine, it is also called wire side, ATM printing paper roll with worse quality will have more obvious difference between front and back, it is hard to distinguish when its quality good. There are many ways to distinguish the front and back:

1. Observe their surface shapes or structures of two sides of ATM printing paper roll with eyes, if you can see wire mark of paper machine, that is wire side, you can use magnifying glass when you can't see it clearly.

2. Put carbon tissue on the face of paper with a mark, mark of carbon tissue will be left on the paper, it can be drawn  a black mark whose width is 13mm and length is 51-76mm for distinguishing front and back, it should be put on the smooth surface ( like flat glass).

3.For indistinguishable SC-paper, using water and  aqueous sodium hydroxide to soak surface of paper for a few seconds, using absorbent paper to remove unnecessary liquid, after few minutes, fiber of paper will slack and return to origin structure, at this time, the side with wire mark is the back of paper.

4. Fold the paper to keep both sides on the same plane and use coins to draw marks on both sides, marks on wire side are not easy to see because its little padding, that is to say, which side with light mark must be the back of paper. This way is suitable for distinguishing paper with xylene oxide filler and coated side of one-side coated paper.

5. Put ATM printing paper roll in oven to observe its curl direction, which crimping to inside is wire side.