Paper base paper is made of high-quality reel newsprint or offset printing paper, and high-grade copperplate paper is made of special base paper. The surface coating firmly adheres to the base paper. The paper surface is then supercalendered, the coating is firm, no bubbles, no streaks, high gloss, and high smoothness. The smoothness of coated paper is generally more than 600s, more than 10 times higher than offset paper. In this way, the coated paper can be brought into close contact with the printing plate, and dots can be printed clearly. The pH of the coated paper is about 7 and it has no adverse effect on the lithographic wetting liquid, and has no adverse effect on the ink drying process. In the coated paper, the ink adheres fast and dry quickly. After drying, it can bring out the gloss, the dot reproducibility is good, the ink layer is thin, the image is clear, and the dots are smooth and clean. The dimensional stability of coated paper is also better than that of offset paper. Printing on coated paper can meet the precise requirements of overprinting. The tensile strength and surface strength of the coated paper are also high enough to resist the large pulling force generated by the more viscous ink ink film used. As a result of the above points, it is common to use coated paper to print high-grade prints.