The process temperatures of between 500 °C and 700 °C arising during hot glass forming and the optical quality standards involved mean that the mold material must fulfill extremely demanding specifications. Only a few, mostly monocrystalline or amorphous materials are suitable, e.g. monocrystalline silicon. This, in turn, increases the demands placed on the micro-cutting process. In order to machine to the required surface quality in just a few processing stages, the separation cracks generated during cutting may only be created in the removed silicon and not in the remaining raw material. Single-grain diamond cutting makes this type of ductile surface treatment possible.