Silica is silicon dioxide, the main glass-forming ingredient in glazes and a major part of every clay. As fine dust it is a serious health hazard, because breathing crystalline silica can cause silicosis and lung cancer.
What Is Silica?
In glazes, silica is what forms the glass; fluxes help it melt at kiln temperatures, and alumina keeps it from running. In clay bodies, silica forms part of the structure that holds the fired clay together, and its quartz form undergoes sudden volume changes during firing, which is behind dunting.
Potters buy it as a fine white powder, sometimes called flint or quartz, and it is also present in clay, feldspar and many other materials.
The safety side matters as much as the chemistry. WorkSafe Victoria and SafeWork NSW warn that respirable crystalline silica can cause silicosis, a permanent lung disease, and lung cancer. In a pottery studio, the dust comes from dry clay, glaze powders, sanding, sweeping and scraping kiln shelves.
Good habits keep exposure low: mix dry materials with a P2 or better respirator and good ventilation, sand only damp clay, wet-mop and sponge surfaces instead of sweeping, and wash studio clothes often.
This pottery glossary entry from Le Studio Art Space is general educational content. Always follow the clay, glaze and kiln makers’ data for your own materials and equipment.