If it is a stubborn water stain or stain, find a glass plate larger than the work and wipe it clean. Spread the paper flat, soak it with a clean white towel (preferably new), twist it half dry, roll it into a roll, then roll it on the paper like a roller, press it again, and wash the towel with clear water; In this way, you can wash the roll over and over again, and then rinse it with clear water after washing away the water stains.
The washed works should be picked out with a straight and smooth stick (such as a stainless steel tube with a diameter of two or three centimeters), dried, and then supported or mounted.