Material preparation: laundry detergent, toothpaste, clear water and a basin of clear water.
Step 1: Pour a proper amount of laundry detergent into the basin (the laundry detergent has good cleaning and decontamination ability, and can clean the black ink on the pencil case).
Step 2: Then squeeze a proper amount of toothpaste into the basin (toothpaste contains detergent, which can decompose the black ink dirt on the pencil case).
Step 3: Put the pencil box stained with black ink into the basin.
Step 4: Then carefully scrub the black ink dirt on the pencil case by hand.
Step 5: Rinse the residual laundry detergent and toothpaste on the pencil case with clear water.
Step 6: The black ink on the pencil box has been removed.