According to the mask bag manufacturer's packaging, the ink activity of mask bags is an important point in the production of mask packaging bags. In the production process of ink, a certain amount of active agents are generally added. The plate cylinder also has certain activity after chrome plating. If the activity of the ink and plate cylinder is too high, the active substance will adhere firmly to the cylinder during printing, and it is difficult for the scraper to clean it, thus forming a knife line. At this time, the plate cylinder is cleaned to remove the active substances on its surface, and the active retarder is added to the ink to eliminate the knife line.