The surface finish of the paper machine is treated in multiple steps to achieve good surface quality. Most of the paper is calendered by a mechanical calender after the paper machine to make the paper surface flat. The mechanical calender is made up of several cold cast iron rolls that flatten the paper surface with the weight of each roll or another pressurization. If higher surface smoothness is required, it should be calendered with a super calender. It is generally composed of a stack of paper rolls and cold cast iron rolls. Depending on the application requirements, some varieties are surface sized to improve surface quality; some are surface coated to improve appearance quality or print quality. Surface sizing and coating can be processed by paper machine outside the paper machine through a size press and a coater, or the size press and coating equipment can be combined in a paper machine for in-machine processing.