1. Appearance: if the paper is very white, it indicates that the protective coating and thermal coating of the paper are unreasonable, too much phosphor is added, and the better paper should be slightly green. The paper finish is not high or looks uneven, indicating that the paper coating is uneven. If the paper looks very strong reflected light, too much phosphor is added, and the quality is not very good.

2. Fire baking: the method of fire baking is also very simple. Heat the back of the paper with a lighter. If the color on the paper is brown after heating, it indicates that the thermal formula is unreasonable and the storage time may be relatively short. If there are small stripes or uneven color blocks on the black part of the paper, it indicates that the coating is uneven. The paper with good quality should be dark green (with a little green) after heating, and the color block is uniform, and the color gradually fades from the center to the periphery.