A calender is a series of hard pressure rollers used to form or smooth a sheet of material such as paper or plastic film. In a principal paper application, the calender is located at the end of a papermaking process (on-line). Those that are used separately from the process (off-line) are also called supercalenders. The purpose of a calender is to make the paper smooth and glossy for printing and writing, as well as of a consistent thickness for capacitors that use paper as their dielectric membrane.