Opacifier

An opacifier is a substance added to a material in order to make the ensuing system opaque.

Conversely, clarity may be achieved in a system by choosing components with very similar refractive indices.

Opaque yellow glasses contained crystals of lead antimonate; bindheimite mineral may have been used as the additive.

From 2nd century BC tin oxide appears in use as opacifier, likely in the form of cassiterite mineral.

The opacifiers also prevent sub-surface overheating and localized premature ignition in the grains where imperfections absorbing the thermal radiation are present.