Quartz

Quartz is crystalline silica, SiO₂. Added to a ceramic body as sand or flour, it does not soften at firing temperature and acts as a filler: it limits shrinkage and deformation while the clays and feldspars around it sinter and melt.

Quartz changes its crystal form at 573 °C with a small change in volume. Kilns pass through this point carefully, above all during cooling, to avoid cracks.

Dust from cutting or grinding fired ceramics contains respirable crystalline silica. Wet cutting and dust extraction are the normal precautions.