They are fundamentally glasses and constitute the main base of glazes. Frits are produced by mixing various raw materials in the form of powder. When introduced into suitable fusion furnaces, where they decompose, react with each other, and transform into viscous liquid masses, they are rapidly cooled by water or air to assume the form of sheets or vitreous grains. Typically, a frit, mixed with others and/or with appropriate amounts of non-vitrified raw materials, has the ability to melt again, incorporating the additive elements into its structure, ultimately forming a homogeneous glass with characteristics different from the original. This property allows, with a limited number of frits and raw materials, the creation of many different glazes.