Password whitewashing: one of the methods of forging questions. The so-called washing is to wash away the words of the original author, without cutting, digging or mending.
This kind of fraud is rare, because calligraphers used to pay attention to wrist strength, and books often penetrated the back of the paper and went straight to the subject. In other words, the pen is heavy and the strokes are solid, and the ink seeps through the back of the paper.