1, soak it in washing powder water, wash it clean, then dilute the water with pure blue ink, put the schoolbag in and soak it for a while, and then take it out and wash it clean. This is suitable for white schoolbags and can have some effects. 2. If the schoolbag is stained, wrap it with sanitary towel after washing and cover the whole schoolbag bit by bit. Don't miss the corner. Pay attention to the wet toilet paper, stick it on the bag completely, and then dry it. Sanitary napkins can absorb yellow stains on schoolbags. However, these methods are only applicable to bags made of pure white cloth. Just try it.