The initial step in creating a primary or master grating is selecting the substrate material, typically glass or copper. The substrate is polished to a high degree of flatness and coated with a thin layer of aluminum. Adjusting the parallelism and equidistant spacing of the scribing lines requires a lengthy process, potentially taking several days to set up and test before actual scribing. The scribing machine must be able to retract the diamond tip along a precise path after each scribing, scribing the substrate according to a predetermined amount. The parallelism and displacement of the scribing lines must be precisely controlled.