wash with strong acid or alkali. And physical methods. Such as mortar spraying, mechanical scraping, pneumatic nozzles or ultrasonic waves. Among them, strong acid or strong alkali is the best, but different decoloring agents should be selected according to different materials. In addition, an optical decolourant can also be used to remove the color on the color carving. These optical decolorants have certain chemical properties and specific photosensitive materials (such as chloride, fluoride, hydrochloride, etc.), and different optical decolorants can be selected according to different applications, so as to completely decolor the graphics and characters on the surface.