In principle, the pen oil of an oil-based pen is soluble in organic solvents, such as alcohol. Generally, what is written on the whiteboard cannot be washed off with water, but it is easy to wash off with alcohol.

Therefore, first of all, the best choice is to clean with alcohol. If the fiber is infiltrated for a long time, it is difficult for alcohol to be thoroughly cleaned.

Secondly, wash with baking soda and oxalic acid.

Third, finally wash with 84.

The combination of the three methods can generally solve the problem.

I hope the above answers can help you!