Quartz glass machining

Fused Silica is a hard, high purity glass with high use temperature and near zero thermal expansion, and so is extremely thermal shock resistant. It is also chemically inert to most substances except for a few substances including hydrofluoric acid and hot potassium hydroxide. Borosilicate glasses such as Tempax and Pyrex contain approximately 80% silica, and so are less thermally stable than fused silica. Compared to ordinary glasses however, they exhibit much lower thermal expansion and so is more thermal shock resistant. Both fused silica glass and borosilicate glass have excellent thermal and chemical stability, and they are also lower in cost for both material and machining compared to ceramic materials. They are even available in large bulk forms unlike some ceramic materials. These hard glasses can be lapped or polished for high quality surface finishes to produce optically smooth surface, or to make it UV / infrared transparent.