1. Appearance: If the paper is very white, it shows that the protective coating and thermal coating of the paper are unreasonable, and excessive phosphor is added, the better paper should be slightly greenish. Paper finish is not high or looks uneven, indicating that the paper coating is not uniform. If the paper looks very reflective, it also adds too much phosphor, the quality is not good.
2. Fire-baking: The method of fire-baking is also very simple. The lighter is used to heat the back of the paper. If the color on the paper is brown after heating, it means that the heat-sensitive formula is not reasonable, and the storage time may be shorter. If the black part of the paper has fine stripes or uneven color blocks, it means that the coating is not uniform. The paper of better quality should be black-green (with a little green) after heating, and the color block is uniform, and the color gradually fades from the center to the surrounding.
3. Contrastive identification of sunshine exposure: The printed paper is smeared with a fluorescent pen and then sunned in the sun (which can accelerate the reaction of the thermal coating to light). Which kind of paper darkens the fastest, indicating the shorter the storage time.