“…Albite or orthoclase are usually used as flux and contain high sodium or potassium oxide content, respectively [1,2]. Less common raw materials used as fluxes include phyllite, pegmatites, and, more recently, phonolites, soda-lime scrap-glass and slag [3][4][5][6][7][8][9][10][11]. However, different types and proportions of fluxes can modify the firing temperature and final mechanical resistance of the products.…”