There are several types of ink marks on the pencil case. 1. The most common one is fountain pens, which are easy to clean after soaking in detergent. 2. The most difficult thing to wash is ballpoint pen stains. It is an organic matter, so it is insoluble in water, and because of its large molecular weight, it has a strong binding ability. Washing powder and detergent can not be cleaned. 3. If the family has a car, get a little gasoline and rinse it after cleaning. If not, use 84 disinfectant, soak for a period of time and then wash by hand. It can also achieve the purpose, but the speed is relatively high. Slow, and very tired 4. Wash with oxalic acid, the effect is very good. 5. There are many ways to remove ink stains. Rinse the floating ink with cold water first, then mix thoroughly with rice grains and detergent solution, and rub it on the ink repeatedly. Use 1 part of alcohol and 2 parts of soap to scrub repeatedly. Use glutinous rice grains or toothpaste to scrub the stained area repeatedly. Brush with 4% baking soda. Mash the almond pinellia and egg into a puree, apply it to the stained area, and let it wash for 3 to 5 minutes. 6. Dip the red ink, soak the new traces with a warm water detergent solution for a while and then scrub; wash the old traces with detergent first, and then scrub with 10% alcohol. 7. When stained with blue ink, new traces can be scrubbed with general detergent; old traces can be soaked in 2% oxalic acid solution for a few minutes and then scrubbed.