Glass ceramic is a family of materials that combines the benefits of both: they are formed like conventional glass (such as pressing, bending and blowing) and crystallised to behave like high performance ceramic. This gives them unique advantages, such as transparency combined with superior thermal shock resistance; or machinability combined with near zero thermal expansion. They are expensive and typically only used for the most demanding applications in aerospace, manufacturing, astronomical telescopes and spacecraft.

These super high performance materials have found their way into our domestic environment as a result of their hard smooth surface, thermal resistance, dielectric strength and dimensional stability. Examples include cookware that can go from freezer to hob, as well as the cooktop itself.

Their unique properties are the result of a parent glass (of which there are many options) and the method of crystallisation. Typically, crystal formation is initiated by a nucleating agent, such as at a specific temperature (heat treatment). This method of forming a polycrystalline material, from a homogenous vitreous parent phase, results in a harmonious crystal structure made up of fine, uniform, randomly orientated interlocking crystals. This near ideal structure yields a material with little or no porosity and optimum mechanical properties. Surface polishing enhances mechanical properties further by reducing imperfections that act as stress concentrators.