1. Appearance: If the thermal paper is very white, it means that the protective coating and thermal coating of the paper are unreasonable, and too much phosphor is added. The better paper should be slightly green. The paper is not smooth or looks uneven, indicating that the paper coating is uneven. If the paper seems to reflect very strong light, too much phosphor is added, and the quality is not good.
2. Fire roasting: The method of roasting with fire is also very simple. Use a lighter to heat the back of the thermal paper. If the color that appears on the thermal paper is brown after heating, it means that the heat-sensitive formula is not reasonable and the storage time may be relatively short. The black part of the paper has small streaks or uneven color blocks, indicating that the coating is uneven. Good quality paper should be black and green (with a little green) after heating, and the color blocks should be uniform, and the color should gradually fade from the center to the periphery.
3. Comparison of sunlight exposure: smear the printed paper with a highlighter and put it in the sun (this can accelerate the reaction of the thermal coating to light), which paper turns black fastest, indicating the shorter the storage time .
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