opal glass are opaque due to light scattering resulting from either liquid-liquid or liquid-solid phase separation.
compositions in the lithium borosilicate system may spontaneously from opal glass due to the coarse scale of liquid-liquid phase separation.
other opal glasses are formed by addition of a few percent of NaF or CaF2 to the composition.
formation of many small crystals can occur spontaneously during cooling, or during subsequent reheating of and initially clear glass.
the between the phases, the volume of the lesser phase, and the morphology of the composite.
these glasses are used for decorative glass products such as vases and dinnerware.