Optical brightener is a fluorescent dye and a complex organic compound. Its characteristic is that it can produce blue fluorescence, which can make the substances visible to the naked eye become very white.

Test whether the mask contains fluorescent whitening agent, unpack the mask, and then put it under ZF-C three-purpose uv analyzer, and irradiate the mask with ultraviolet rays to see if it will emit bright blue light. If yes, the mask contains fluorescent agent. If you don't have an ultraviolet analyzer, you can use an ultraviolet flashlight, an ultraviolet money detector/pen, etc.

The mask containing fluorescent agent shows a very large area of bright blue under ultraviolet irradiation. A little contact with the mask liquid will attach the fluorescent agent component, and the hand holding the mask will also have fluorescence. After washing your hands with clear water for three times, the fluorescent agent on your hands still emits strong bright blue light under ultraviolet irradiation, which can hardly be washed off. After washing with hand sanitizer for 3 times, the hand also emits blue light after irradiation, but the effect is slightly better than that of clear water. Cleaning with facial cleanser has the same effect as hand sanitizer, and it can't completely clean the residual fluorescence on your hands. ...