Zircon opacifier. See zirconium silicate. Toxic in inhalation.

Common flaw in plaster or bisque molds, where the clay or casting catches and will not pull free without breaking or distorting.

Process of applying any decoration to the bare, (usually bisque-fired) clay surface directly before glazing.

Under glaze pigments in pencil form, excellent for marking wares and test-tiles, and for "pencil-drawn" decorative effects.

Colored slips formulated to have low drying shrinkage, allowing application to bone-dry or bisque-fired surface before glazing. Commercial under glazes are available in a wide palette of colors primarily for low-fire, but many will survive high-fire.

A formula generated by glaze calculation, which lists all glaze oxides present in separate columns for fluxes, refractories, and glass-formers.

Kiln in which exhaust gases exit through flue in the roof of the kiln.