Ceramic frits are obtained by fusing raw materials in a melting kiln at high temperature (1350 ºC – 1550 ºC). The melt is cooled quickly, either by a laminating process or by quenching in water, which transforms it into a fragmented solid that is practically insoluble in water and in the most commonly used acids and bases.
The most important group of compounds that give rise to glasses is that of the oxides, since these include the main glass formers of technical and industrial interest, as is the case of ceramic frits, in which the main oxides are SiO2 and the B2O3. These have the ability not only to form glasses separately, but also, when they are mixed with many other metallic oxides, such as the alkalines, alkaline earths and alumina, which by themselves are not able to reach the glassy state, to react with these and form a continuous glassy phase.
On the other hand, in the European Inventory of Existing Commercial Chemical Substances (EINECS) ceramic frits are described under No. EINECS 266-047-6, and in the Information Service on Chemical Substances (CAS) of the American Chemical Society under No. CAS 65997-18-4, they are defined as ‘a mixture of inorganic chemical substances produced by rapidly quenching a molten, complex combination of materials, confining the chemical substances thus manufactured as non-migratory components of glassy solid flakes or granules’.