First, let us remind
you how this method works: it all starts with the preforming of rough ruby to eliminate
matrix and other impurities. Then, depending on the ruby type, the rough is heated up to
900° - 1,400°C. After this first treatment, the red preforms from the previous steps are
now packed in a crucible with lead and silica-rich oxide powders, and heated another
time to temperatures around 900° to 1000°C.