For manufacturing specific optical devices, the pitch polishing pad (polisher), which has been in use for 300 years, is utilized with mesh grooves on its surface. The effect of mesh grooves is similar to the pores in the polyurethane pad (polisher). Concerning the pitch polisher, its surface roughened by the work surface holds abrasives that make both pad/polisher and work surfaces smooth as polishing advances.
The wear and softness of the pad/polisher can cause deterioration of geometric accuracy, such as flatness, and generation of turned-down edges. The correct selection of a polishing machine and its operation is important to satisfy the requirements for high-precision polishing.