Appearance: If the paper is very white, the protective coating and thermal coating of the paper are unreasonable, too much phosphor is added. The better paper should be slightly green. The paper is not as smooth as it looks uneven, which indicates that the paper coating is uneven. If the paper looks very reflective, it is also too much phosphor added, the quality is not very good.

Fire roasting: The method of roasting with fire is also very simple, You can use a lighter on the back of the paper to heat, the color on the paper is brown after heating, then the heat-sensitive formula is not very reasonable, the storage time may be relatively short. If the black part of the paper has fine stripes or uneven color blocks, the coating is uneven. Better quality paper 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 periphery.

Sunlight exposure comparison identification: the printed paper is coated with a highlighter and placed under the sun to dry (this can accelerate the reaction of the thermal coating to light), which paper turns black faster, the shorter the storage time it will be.