During firing of a ceramic body, the formation of a liquid phase that upon cooling becomes a glass-bonding matrix.
Vitrification (from Latin vitreum, "glass" via French vitrifier) is the transformation of a substance into a glass. Usually, it is achieved by rapidly cooling a liquid through the glass transition. Certain chemical reactions also result in glasses. An important application is the vitrification of an antifreeze-like liquid in cryopreservation.
Vitrification is characteristic for amorphous materials or disordered systems and occurs when bonding between elementary particles (atoms, molecules, forming blocks) becomes higher than a certain threshold value. Thermal fluctuations break the bonds therefore the lower the temperature the higher the degree of connectivity. Because of that amorphous materials have a characteristic threshold temperature termed glass transition temperature (Tg): below Tg amorphous materials are glassy whereas above Tg they are molten.
In a wider sense, the embedding of material in a glassy matrix is also called vitrification. An important application is the vitrification of radioactive waste to obtain a stable compound that is suitable for ultimate disposal.