Cov khoom siv tseem ceeb siv rau cov iav raj yog silicate iav, uas yog tsim los ntawm melting raw khoom-xws li silica xuab zeb (nws lub ntsiab yog silicon dioxide), dej qab zib tshauv (sodium carbonate), thiab limestone (calcium carbonate)- ntawm qhov kub thiab txias. Cov ntaub ntawv nyoos no tau muab sib xyaw rau hauv ib qho kev faib ua feem thiab, tom qab tau yaj hauv qhov kub siab - qhov cub kub, tsim cov pob tshab lossis cov khoom siv pob tshab hu ua silicate iav.
Cov iav kuaj cov raj feem ntau yog tsim los ntawm silicate iav. Silicate iav yog ib qho inorganic, tsis yog -cov khoom siv hlau ua los ntawm qhov siab - kub melting ntawm raw cov ntaub ntawv xws li silica xuab zeb, dej qab zib tshauv, thiab limestone. Silica xuab zeb ua cov khoom siv tseem ceeb rau kev tsim iav, nrog silicon dioxide yog nws cov khoom tseem ceeb. Soda tshauv thiab limestone muaj nuj nqi ua cov tshuaj fluxing thiab stabilizers, pab txo qhov melting point ntawm iav thiab txhim khu nws cov tshuaj stability.