1. Appearance: if the paper is very white, it indicates that too much phosphor is added to the protective coating and thermal coating of the paper, and the better paper should be slightly green.
2. Fire baking: heat the front of the paper with a lighter. If the color on the paper is brown after heating, it indicates that the thermal formula is not reasonable, and the good thermal paper is black or green.
3. Comparison and identification of sunlight exposure: after smearing the printed paper with a fluorescent pen and drying it in the sun, which paper blackens fastest indicates that the shorter the storage time.
